1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2023 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{} 1988-2023 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) 1988-2023 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 @value{GDBN}
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The @value{GDBN} Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: @value{GDBN} trace file format
186 * Index Section Format:: .gdb_index section format
187 * Debuginfod:: Download debugging resources with @code{debuginfod}
188 * Man Pages:: Manual pages
189 * Copying:: GNU General Public License says
190 how you can copy and share @value{GDBN}
191 * GNU Free Documentation License:: The license for this documentation
192 * Concept Index:: Index of @value{GDBN} concepts
193 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
194 functions, and Python data types
202 @unnumbered Summary of @value{GDBN}
204 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
205 going on ``inside'' another program while it executes---or what another
206 program was doing at the moment it crashed.
208 @value{GDBN} can do four main kinds of things (plus other things in support of
209 these) to help you catch bugs in the act:
213 Start your program, specifying anything that might affect its behavior.
216 Make your program stop on specified conditions.
219 Examine what has happened, when your program has stopped.
222 Change things in your program, so you can experiment with correcting the
223 effects of one bug and go on to learn about another.
226 You can use @value{GDBN} to debug programs written in C and C@t{++}.
227 For more information, see @ref{Supported Languages,,Supported Languages}.
228 For more information, see @ref{C,,C and C++}.
230 Support for D is partial. For information on D, see
234 Support for Modula-2 is partial. For information on Modula-2, see
235 @ref{Modula-2,,Modula-2}.
237 Support for OpenCL C is partial. For information on OpenCL C, see
238 @ref{OpenCL C,,OpenCL C}.
241 Debugging Pascal programs which use sets, subranges, file variables, or
242 nested functions does not currently work. @value{GDBN} does not support
243 entering expressions, printing values, or similar features using Pascal
247 @value{GDBN} can be used to debug programs written in Fortran, although
248 it may be necessary to refer to some variables with a trailing
251 @value{GDBN} can be used to debug programs written in Objective-C,
252 using either the Apple/NeXT or the GNU Objective-C runtime.
255 * Free Software:: Freely redistributable software
256 * Free Documentation:: Free Software Needs Free Documentation
257 * Contributors:: Contributors to GDB
261 @unnumberedsec Free Software
263 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
264 General Public License
265 (GPL). The GPL gives you the freedom to copy or adapt a licensed
266 program---but every person getting a copy also gets with it the
267 freedom to modify that copy (which means that they must get access to
268 the source code), and the freedom to distribute further copies.
269 Typical software companies use copyrights to limit your freedoms; the
270 Free Software Foundation uses the GPL to preserve these freedoms.
272 Fundamentally, the General Public License is a license which says that
273 you have these freedoms and that you cannot take these freedoms away
276 @node Free Documentation
277 @unnumberedsec Free Software Needs Free Documentation
279 The biggest deficiency in the free software community today is not in
280 the software---it is the lack of good free documentation that we can
281 include with the free software. Many of our most important
282 programs do not come with free reference manuals and free introductory
283 texts. Documentation is an essential part of any software package;
284 when an important free software package does not come with a free
285 manual and a free tutorial, that is a major gap. We have many such
288 Consider Perl, for instance. The tutorial manuals that people
289 normally use are non-free. How did this come about? Because the
290 authors of those manuals published them with restrictive terms---no
291 copying, no modification, source files not available---which exclude
292 them from the free software world.
294 That wasn't the first time this sort of thing happened, and it was far
295 from the last. Many times we have heard a GNU user eagerly describe a
296 manual that he is writing, his intended contribution to the community,
297 only to learn that he had ruined everything by signing a publication
298 contract to make it non-free.
300 Free documentation, like free software, is a matter of freedom, not
301 price. The problem with the non-free manual is not that publishers
302 charge a price for printed copies---that in itself is fine. (The Free
303 Software Foundation sells printed copies of manuals, too.) The
304 problem is the restrictions on the use of the manual. Free manuals
305 are available in source code form, and give you permission to copy and
306 modify. Non-free manuals do not allow this.
308 The criteria of freedom for a free manual are roughly the same as for
309 free software. Redistribution (including the normal kinds of
310 commercial redistribution) must be permitted, so that the manual can
311 accompany every copy of the program, both on-line and on paper.
313 Permission for modification of the technical content is crucial too.
314 When people modify the software, adding or changing features, if they
315 are conscientious they will change the manual too---so they can
316 provide accurate and clear documentation for the modified program. A
317 manual that leaves you no choice but to write a new manual to document
318 a changed version of the program is not really available to our
321 Some kinds of limits on the way modification is handled are
322 acceptable. For example, requirements to preserve the original
323 author's copyright notice, the distribution terms, or the list of
324 authors, are ok. It is also no problem to require modified versions
325 to include notice that they were modified. Even entire sections that
326 may not be deleted or changed are acceptable, as long as they deal
327 with nontechnical topics (like this one). These kinds of restrictions
328 are acceptable because they don't obstruct the community's normal use
331 However, it must be possible to modify all the @emph{technical}
332 content of the manual, and then distribute the result in all the usual
333 media, through all the usual channels. Otherwise, the restrictions
334 obstruct the use of the manual, it is not free, and we need another
335 manual to replace it.
337 Please spread the word about this issue. Our community continues to
338 lose manuals to proprietary publishing. If we spread the word that
339 free software needs free reference manuals and free tutorials, perhaps
340 the next person who wants to contribute by writing documentation will
341 realize, before it is too late, that only free manuals contribute to
342 the free software community.
344 If you are writing documentation, please insist on publishing it under
345 the GNU Free Documentation License or another free documentation
346 license. Remember that this decision requires your approval---you
347 don't have to let the publisher decide. Some commercial publishers
348 will use a free license if you insist, but they will not propose the
349 option; it is up to you to raise the issue and say firmly that this is
350 what you want. If the publisher you are dealing with refuses, please
351 try other publishers. If you're not sure whether a proposed license
352 is free, write to @email{licensing@@gnu.org}.
354 You can encourage commercial publishers to sell more free, copylefted
355 manuals and tutorials by buying them, and particularly by buying
356 copies from the publishers that paid for their writing or for major
357 improvements. Meanwhile, try to avoid buying non-free documentation
358 at all. Check the distribution terms of a manual before you buy it,
359 and insist that whoever seeks your business must respect your freedom.
360 Check the history of the book, and try to reward the publishers that
361 have paid or pay the authors to work on it.
363 The Free Software Foundation maintains a list of free documentation
364 published by other publishers, at
365 @url{http://www.fsf.org/doc/other-free-books.html}.
368 @unnumberedsec Contributors to @value{GDBN}
370 Richard Stallman was the original author of @value{GDBN}, and of many
371 other @sc{gnu} programs. Many others have contributed to its
372 development. This section attempts to credit major contributors. One
373 of the virtues of free software is that everyone is free to contribute
374 to it; with regret, we cannot actually acknowledge everyone here. The
375 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
376 blow-by-blow account.
378 Changes much prior to version 2.0 are lost in the mists of time.
381 @emph{Plea:} Additions to this section are particularly welcome. If you
382 or your friends (or enemies, to be evenhanded) have been unfairly
383 omitted from this list, we would like to add your names!
386 So that they may not regard their many labors as thankless, we
387 particularly thank those who shepherded @value{GDBN} through major
389 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
390 Jim Blandy (release 4.18);
391 Jason Molenda (release 4.17);
392 Stan Shebs (release 4.14);
393 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
394 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
395 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
396 Jim Kingdon (releases 3.5, 3.4, and 3.3);
397 and Randy Smith (releases 3.2, 3.1, and 3.0).
399 Richard Stallman, assisted at various times by Peter TerMaat, Chris
400 Hanson, and Richard Mlynarik, handled releases through 2.8.
402 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
403 in @value{GDBN}, with significant additional contributions from Per
404 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
405 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
406 much general update work leading to release 3.0).
408 @value{GDBN} uses the BFD subroutine library to examine multiple
409 object-file formats; BFD was a joint project of David V.
410 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
412 David Johnson wrote the original COFF support; Pace Willison did
413 the original support for encapsulated COFF.
415 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
417 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
418 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
420 Jean-Daniel Fekete contributed Sun 386i support.
421 Chris Hanson improved the HP9000 support.
422 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
423 David Johnson contributed Encore Umax support.
424 Jyrki Kuoppala contributed Altos 3068 support.
425 Jeff Law contributed HP PA and SOM support.
426 Keith Packard contributed NS32K support.
427 Doug Rabson contributed Acorn Risc Machine support.
428 Bob Rusk contributed Harris Nighthawk CX-UX support.
429 Chris Smith contributed Convex support (and Fortran debugging).
430 Jonathan Stone contributed Pyramid support.
431 Michael Tiemann contributed SPARC support.
432 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
433 Pace Willison contributed Intel 386 support.
434 Jay Vosburgh contributed Symmetry support.
435 Marko Mlinar contributed OpenRISC 1000 support.
437 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
439 Rich Schaefer and Peter Schauer helped with support of SunOS shared
442 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
443 about several machine instruction sets.
445 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
446 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
447 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
448 and RDI targets, respectively.
450 Brian Fox is the author of the readline libraries providing
451 command-line editing and command history.
453 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
454 Modula-2 support, and contributed the Languages chapter of this manual.
456 Fred Fish wrote most of the support for Unix System Vr4.
457 He also enhanced the command-completion support to cover C@t{++} overloaded
460 Hitachi America (now Renesas America), Ltd. sponsored the support for
461 H8/300, H8/500, and Super-H processors.
463 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
465 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
468 Toshiba sponsored the support for the TX39 Mips processor.
470 Matsushita sponsored the support for the MN10200 and MN10300 processors.
472 Fujitsu sponsored the support for SPARClite and FR30 processors.
474 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
477 Michael Snyder added support for tracepoints.
479 Stu Grossman wrote gdbserver.
481 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
482 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
484 The following people at the Hewlett-Packard Company contributed
485 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
486 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
487 compiler, and the Text User Interface (nee Terminal User Interface):
488 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
489 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
490 provided HP-specific information in this manual.
492 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
493 Robert Hoehne made significant contributions to the DJGPP port.
495 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
496 development since 1991. Cygnus engineers who have worked on @value{GDBN}
497 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
498 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
499 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
500 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
501 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
502 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
503 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
504 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
505 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
506 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
507 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
508 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
509 Zuhn have made contributions both large and small.
511 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
512 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
514 Jim Blandy added support for preprocessor macros, while working for Red
517 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
518 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
519 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
520 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
521 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
522 with the migration of old architectures to this new framework.
524 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
525 unwinder framework, this consisting of a fresh new design featuring
526 frame IDs, independent frame sniffers, and the sentinel frame. Mark
527 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
528 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
529 trad unwinders. The architecture-specific changes, each involving a
530 complete rewrite of the architecture's frame code, were carried out by
531 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
532 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
533 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
534 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
537 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
538 Tensilica, Inc.@: contributed support for Xtensa processors. Others
539 who have worked on the Xtensa port of @value{GDBN} in the past include
540 Steve Tjiang, John Newlin, and Scott Foehner.
542 Michael Eager and staff of Xilinx, Inc., contributed support for the
543 Xilinx MicroBlaze architecture.
545 Initial support for the FreeBSD/mips target and native configuration
546 was developed by SRI International and the University of Cambridge
547 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
548 ("CTSRD"), as part of the DARPA CRASH research programme.
550 Initial support for the FreeBSD/riscv target and native configuration
551 was developed by SRI International and the University of Cambridge
552 Computer Laboratory (Department of Computer Science and Technology)
553 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
554 SSITH research programme.
556 The original port to the OpenRISC 1000 is believed to be due to
557 Alessandro Forin and Per Bothner. More recent ports have been the work
558 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 Weimin Pan, David Faust and Jose E. Marchesi contributed support for
562 the Linux kernel BPF virtual architecture. This work was sponsored by
566 @chapter A Sample @value{GDBN} Session
568 You can use this manual at your leisure to read all about @value{GDBN}.
569 However, a handful of commands are enough to get started using the
570 debugger. This chapter illustrates those commands.
573 In this sample session, we emphasize user input like this: @b{input},
574 to make it easier to pick out from the surrounding output.
577 @c FIXME: this example may not be appropriate for some configs, where
578 @c FIXME...primary interest is in remote use.
580 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
581 processor) exhibits the following bug: sometimes, when we change its
582 quote strings from the default, the commands used to capture one macro
583 definition within another stop working. In the following short @code{m4}
584 session, we define a macro @code{foo} which expands to @code{0000}; we
585 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
586 same thing. However, when we change the open quote string to
587 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
588 procedure fails to define a new synonym @code{baz}:
597 @b{define(bar,defn(`foo'))}
601 @b{changequote(<QUOTE>,<UNQUOTE>)}
603 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
606 m4: End of input: 0: fatal error: EOF in string
610 Let us use @value{GDBN} to try to see what is going on.
613 $ @b{@value{GDBP} m4}
614 @c FIXME: this falsifies the exact text played out, to permit smallbook
615 @c FIXME... format to come out better.
616 @value{GDBN} is free software and you are welcome to distribute copies
617 of it under certain conditions; type "show copying" to see
619 There is absolutely no warranty for @value{GDBN}; type "show warranty"
622 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
627 @value{GDBN} reads only enough symbol data to know where to find the
628 rest when needed; as a result, the first prompt comes up very quickly.
629 We now tell @value{GDBN} to use a narrower display width than usual, so
630 that examples fit in this manual.
633 (@value{GDBP}) @b{set width 70}
637 We need to see how the @code{m4} built-in @code{changequote} works.
638 Having looked at the source, we know the relevant subroutine is
639 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
640 @code{break} command.
643 (@value{GDBP}) @b{break m4_changequote}
644 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
648 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
649 control; as long as control does not reach the @code{m4_changequote}
650 subroutine, the program runs as usual:
653 (@value{GDBP}) @b{run}
654 Starting program: /work/Editorial/gdb/gnu/m4/m4
662 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
663 suspends execution of @code{m4}, displaying information about the
664 context where it stops.
667 @b{changequote(<QUOTE>,<UNQUOTE>)}
669 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
671 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
675 Now we use the command @code{n} (@code{next}) to advance execution to
676 the next line of the current function.
680 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
685 @code{set_quotes} looks like a promising subroutine. We can go into it
686 by using the command @code{s} (@code{step}) instead of @code{next}.
687 @code{step} goes to the next line to be executed in @emph{any}
688 subroutine, so it steps into @code{set_quotes}.
692 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
694 530 if (lquote != def_lquote)
698 The display that shows the subroutine where @code{m4} is now
699 suspended (and its arguments) is called a stack frame display. It
700 shows a summary of the stack. We can use the @code{backtrace}
701 command (which can also be spelled @code{bt}), to see where we are
702 in the stack as a whole: the @code{backtrace} command displays a
703 stack frame for each active subroutine.
706 (@value{GDBP}) @b{bt}
707 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
709 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
711 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
712 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
714 #4 0x79dc in expand_input () at macro.c:40
715 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
719 We step through a few more lines to see what happens. The first two
720 times, we can use @samp{s}; the next two times we use @code{n} to avoid
721 falling into the @code{xstrdup} subroutine.
725 0x3b5c 532 if (rquote != def_rquote)
727 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
728 def_lquote : xstrdup(lq);
730 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
733 538 len_lquote = strlen(rquote);
737 The last line displayed looks a little odd; we can examine the variables
738 @code{lquote} and @code{rquote} to see if they are in fact the new left
739 and right quotes we specified. We use the command @code{p}
740 (@code{print}) to see their values.
743 (@value{GDBP}) @b{p lquote}
744 $1 = 0x35d40 "<QUOTE>"
745 (@value{GDBP}) @b{p rquote}
746 $2 = 0x35d50 "<UNQUOTE>"
750 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
751 To look at some context, we can display ten lines of source
752 surrounding the current line with the @code{l} (@code{list}) command.
758 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
760 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
763 538 len_lquote = strlen(rquote);
764 539 len_rquote = strlen(lquote);
771 Let us step past the two lines that set @code{len_lquote} and
772 @code{len_rquote}, and then examine the values of those variables.
776 539 len_rquote = strlen(lquote);
779 (@value{GDBP}) @b{p len_lquote}
781 (@value{GDBP}) @b{p len_rquote}
786 That certainly looks wrong, assuming @code{len_lquote} and
787 @code{len_rquote} are meant to be the lengths of @code{lquote} and
788 @code{rquote} respectively. We can set them to better values using
789 the @code{p} command, since it can print the value of
790 any expression---and that expression can include subroutine calls and
794 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
796 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
801 Is that enough to fix the problem of using the new quotes with the
802 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
803 executing with the @code{c} (@code{continue}) command, and then try the
804 example that caused trouble initially:
810 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
817 Success! The new quotes now work just as well as the default ones. The
818 problem seems to have been just the two typos defining the wrong
819 lengths. We allow @code{m4} exit by giving it an EOF as input:
823 Program exited normally.
827 The message @samp{Program exited normally.} is from @value{GDBN}; it
828 indicates @code{m4} has finished executing. We can end our @value{GDBN}
829 session with the @value{GDBN} @code{quit} command.
832 (@value{GDBP}) @b{quit}
836 @chapter Getting In and Out of @value{GDBN}
838 This chapter discusses how to start @value{GDBN}, and how to get out of it.
842 type @samp{@value{GDBP}} to start @value{GDBN}.
844 type @kbd{quit}, @kbd{exit} or @kbd{Ctrl-d} to exit.
848 * Invoking GDB:: How to start @value{GDBN}
849 * Quitting GDB:: How to quit @value{GDBN}
850 * Shell Commands:: How to use shell commands inside @value{GDBN}
851 * Logging Output:: How to log @value{GDBN}'s output to a file
855 @section Invoking @value{GDBN}
857 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
858 @value{GDBN} reads commands from the terminal until you tell it to exit.
860 You can also run @code{@value{GDBP}} with a variety of arguments and options,
861 to specify more of your debugging environment at the outset.
863 The command-line options described here are designed
864 to cover a variety of situations; in some environments, some of these
865 options may effectively be unavailable.
867 The most usual way to start @value{GDBN} is with one argument,
868 specifying an executable program:
871 @value{GDBP} @var{program}
875 You can also start with both an executable program and a core file
879 @value{GDBP} @var{program} @var{core}
882 You can, instead, specify a process ID as a second argument or use option
883 @code{-p}, if you want to debug a running process:
886 @value{GDBP} @var{program} 1234
891 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
892 can omit the @var{program} filename.
894 Taking advantage of the second command-line argument requires a fairly
895 complete operating system; when you use @value{GDBN} as a remote
896 debugger attached to a bare board, there may not be any notion of
897 ``process'', and there is often no way to get a core dump. @value{GDBN}
898 will warn you if it is unable to attach or to read core dumps.
900 You can optionally have @code{@value{GDBP}} pass any arguments after the
901 executable file to the inferior using @code{--args}. This option stops
904 @value{GDBP} --args gcc -O2 -c foo.c
906 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
907 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
909 You can run @code{@value{GDBP}} without printing the front material, which describes
910 @value{GDBN}'s non-warranty, by specifying @code{--silent}
911 (or @code{-q}/@code{--quiet}):
914 @value{GDBP} --silent
918 You can further control how @value{GDBN} starts up by using command-line
919 options. @value{GDBN} itself can remind you of the options available.
929 to display all available options and briefly describe their use
930 (@samp{@value{GDBP} -h} is a shorter equivalent).
932 All options and command line arguments you give are processed
933 in sequential order. The order makes a difference when the
934 @samp{-x} option is used.
938 * File Options:: Choosing files
939 * Mode Options:: Choosing modes
940 * Startup:: What @value{GDBN} does during startup
941 * Initialization Files:: Initialization Files
945 @subsection Choosing Files
947 When @value{GDBN} starts, it reads any arguments other than options as
948 specifying an executable file and core file (or process ID). This is
949 the same as if the arguments were specified by the @samp{-se} and
950 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
951 first argument that does not have an associated option flag as
952 equivalent to the @samp{-se} option followed by that argument; and the
953 second argument that does not have an associated option flag, if any, as
954 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
955 If the second argument begins with a decimal digit, @value{GDBN} will
956 first attempt to attach to it as a process, and if that fails, attempt
957 to open it as a corefile. If you have a corefile whose name begins with
958 a digit, you can prevent @value{GDBN} from treating it as a pid by
959 prefixing it with @file{./}, e.g.@: @file{./12345}.
961 If @value{GDBN} has not been configured to included core file support,
962 such as for most embedded targets, then it will complain about a second
963 argument and ignore it.
965 For the @samp{-s}, @samp{-e}, and @samp{-se} options, and their long
966 form equivalents, the method used to search the file system for the
967 symbol and/or executable file is the same as that used by the
968 @code{file} command. @xref{Files, ,file}.
970 Many options have both long and short forms; both are shown in the
971 following list. @value{GDBN} also recognizes the long forms if you truncate
972 them, so long as enough of the option is present to be unambiguous.
973 (If you prefer, you can flag option arguments with @samp{--} rather
974 than @samp{-}, though we illustrate the more usual convention.)
976 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
977 @c way, both those who look for -foo and --foo in the index, will find
981 @item -symbols @var{file}
983 @cindex @code{--symbols}
985 Read symbol table from file @var{file}.
987 @item -exec @var{file}
989 @cindex @code{--exec}
991 Use file @var{file} as the executable file to execute when appropriate,
992 and for examining pure data in conjunction with a core dump.
996 Read symbol table from file @var{file} and use it as the executable
999 @item -core @var{file}
1000 @itemx -c @var{file}
1001 @cindex @code{--core}
1003 Use file @var{file} as a core dump to examine.
1005 @item -pid @var{number}
1006 @itemx -p @var{number}
1007 @cindex @code{--pid}
1009 Connect to process ID @var{number}, as with the @code{attach} command.
1011 @item -command @var{file}
1012 @itemx -x @var{file}
1013 @cindex @code{--command}
1015 Execute commands from file @var{file}. The contents of this file is
1016 evaluated exactly as the @code{source} command would.
1017 @xref{Command Files,, Command files}.
1019 @item -eval-command @var{command}
1020 @itemx -ex @var{command}
1021 @cindex @code{--eval-command}
1023 Execute a single @value{GDBN} command.
1025 This option may be used multiple times to call multiple commands. It may
1026 also be interleaved with @samp{-command} as required.
1029 @value{GDBP} -ex 'target sim' -ex 'load' \
1030 -x setbreakpoints -ex 'run' a.out
1033 @item -init-command @var{file}
1034 @itemx -ix @var{file}
1035 @cindex @code{--init-command}
1037 Execute commands from file @var{file} before loading the inferior (but
1038 after loading gdbinit files).
1041 @item -init-eval-command @var{command}
1042 @itemx -iex @var{command}
1043 @cindex @code{--init-eval-command}
1045 Execute a single @value{GDBN} command before loading the inferior (but
1046 after loading gdbinit files).
1049 @item -early-init-command @var{file}
1050 @itemx -eix @var{file}
1051 @cindex @code{--early-init-command}
1053 Execute commands from @var{file} very early in the initialization
1054 process, before any output is produced. @xref{Startup}.
1056 @item -early-init-eval-command @var{command}
1057 @itemx -eiex @var{command}
1058 @cindex @code{--early-init-eval-command}
1059 @cindex @code{-eiex}
1060 Execute a single @value{GDBN} command very early in the initialization
1061 process, before any output is produced.
1063 @item -directory @var{directory}
1064 @itemx -d @var{directory}
1065 @cindex @code{--directory}
1067 Add @var{directory} to the path to search for source and script files.
1071 @cindex @code{--readnow}
1073 Read each symbol file's entire symbol table immediately, rather than
1074 the default, which is to read it incrementally as it is needed.
1075 This makes startup slower, but makes future operations faster.
1078 @anchor{--readnever}
1079 @cindex @code{--readnever}, command-line option
1080 Do not read each symbol file's symbolic debug information. This makes
1081 startup faster but at the expense of not being able to perform
1082 symbolic debugging. DWARF unwind information is also not read,
1083 meaning backtraces may become incomplete or inaccurate. One use of
1084 this is when a user simply wants to do the following sequence: attach,
1085 dump core, detach. Loading the debugging information in this case is
1086 an unnecessary cause of delay.
1090 @subsection Choosing Modes
1092 You can run @value{GDBN} in various alternative modes---for example, in
1093 batch mode or quiet mode.
1101 Do not execute commands found in any initialization files
1102 (@pxref{Initialization Files}).
1107 Do not execute commands found in any home directory initialization
1108 file (@pxref{Initialization Files,,Home directory initialization
1109 file}). The system wide and current directory initialization files
1115 @cindex @code{--quiet}
1116 @cindex @code{--silent}
1118 ``Quiet''. Do not print the introductory and copyright messages. These
1119 messages are also suppressed in batch mode.
1121 @kindex set startup-quietly
1122 @kindex show startup-quietly
1123 This can also be enabled using @code{set startup-quietly on}. The
1124 default is @code{off}. Use @code{show startup-quietly} to see the
1125 current setting. Place @code{set startup-quietly on} into your early
1126 initialization file (@pxref{Initialization Files,,Initialization
1127 Files}) to have future @value{GDBN} sessions startup quietly.
1130 @cindex @code{--batch}
1131 Run in batch mode. Exit with status @code{0} after processing all the
1132 command files specified with @samp{-x} (and all commands from
1133 initialization files, if not inhibited with @samp{-n}). Exit with
1134 nonzero status if an error occurs in executing the @value{GDBN} commands
1135 in the command files. Batch mode also disables pagination, sets unlimited
1136 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1137 off} were in effect (@pxref{Messages/Warnings}).
1139 Batch mode may be useful for running @value{GDBN} as a filter, for
1140 example to download and run a program on another computer; in order to
1141 make this more useful, the message
1144 Program exited normally.
1148 (which is ordinarily issued whenever a program running under
1149 @value{GDBN} control terminates) is not issued when running in batch
1153 @cindex @code{--batch-silent}
1154 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1155 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1156 unaffected). This is much quieter than @samp{-silent} and would be useless
1157 for an interactive session.
1159 This is particularly useful when using targets that give @samp{Loading section}
1160 messages, for example.
1162 Note that targets that give their output via @value{GDBN}, as opposed to
1163 writing directly to @code{stdout}, will also be made silent.
1165 @item -return-child-result
1166 @cindex @code{--return-child-result}
1167 The return code from @value{GDBN} will be the return code from the child
1168 process (the process being debugged), with the following exceptions:
1172 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1173 internal error. In this case the exit code is the same as it would have been
1174 without @samp{-return-child-result}.
1176 The user quits with an explicit value. E.g., @samp{quit 1}.
1178 The child process never runs, or is not allowed to terminate, in which case
1179 the exit code will be -1.
1182 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1183 when @value{GDBN} is being used as a remote program loader or simulator
1188 @cindex @code{--nowindows}
1190 ``No windows''. If @value{GDBN} comes with a graphical user interface
1191 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1192 interface. If no GUI is available, this option has no effect.
1196 @cindex @code{--windows}
1198 If @value{GDBN} includes a GUI, then this option requires it to be
1201 @item -cd @var{directory}
1203 Run @value{GDBN} using @var{directory} as its working directory,
1204 instead of the current directory.
1206 @item -data-directory @var{directory}
1207 @itemx -D @var{directory}
1208 @cindex @code{--data-directory}
1210 Run @value{GDBN} using @var{directory} as its data directory.
1211 The data directory is where @value{GDBN} searches for its
1212 auxiliary files. @xref{Data Files}.
1216 @cindex @code{--fullname}
1218 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1219 subprocess. It tells @value{GDBN} to output the full file name and line
1220 number in a standard, recognizable fashion each time a stack frame is
1221 displayed (which includes each time your program stops). This
1222 recognizable format looks like two @samp{\032} characters, followed by
1223 the file name, line number and character position separated by colons,
1224 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1225 @samp{\032} characters as a signal to display the source code for the
1228 @item -annotate @var{level}
1229 @cindex @code{--annotate}
1230 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1231 effect is identical to using @samp{set annotate @var{level}}
1232 (@pxref{Annotations}). The annotation @var{level} controls how much
1233 information @value{GDBN} prints together with its prompt, values of
1234 expressions, source lines, and other types of output. Level 0 is the
1235 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1236 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1237 that control @value{GDBN}, and level 2 has been deprecated.
1239 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1243 @cindex @code{--args}
1244 Change interpretation of command line so that arguments following the
1245 executable file are passed as command line arguments to the inferior.
1246 This option stops option processing.
1248 @item -baud @var{bps}
1250 @cindex @code{--baud}
1252 Set the line speed (baud rate or bits per second) of any serial
1253 interface used by @value{GDBN} for remote debugging.
1255 @item -l @var{timeout}
1257 Set the timeout (in seconds) of any communication used by @value{GDBN}
1258 for remote debugging.
1260 @item -tty @var{device}
1261 @itemx -t @var{device}
1262 @cindex @code{--tty}
1264 Run using @var{device} for your program's standard input and output.
1265 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1267 @c resolve the situation of these eventually
1269 @cindex @code{--tui}
1270 Activate the @dfn{Text User Interface} when starting. The Text User
1271 Interface manages several text windows on the terminal, showing
1272 source, assembly, registers and @value{GDBN} command outputs
1273 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1274 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1275 Using @value{GDBN} under @sc{gnu} Emacs}).
1277 @item -interpreter @var{interp}
1278 @cindex @code{--interpreter}
1279 Use the interpreter @var{interp} for interface with the controlling
1280 program or device. This option is meant to be set by programs which
1281 communicate with @value{GDBN} using it as a back end.
1282 @xref{Interpreters, , Command Interpreters}.
1284 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1285 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1286 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1287 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1288 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1289 interfaces are no longer supported.
1292 @cindex @code{--write}
1293 Open the executable and core files for both reading and writing. This
1294 is equivalent to the @samp{set write on} command inside @value{GDBN}
1298 @cindex @code{--statistics}
1299 This option causes @value{GDBN} to print statistics about time and
1300 memory usage after it completes each command and returns to the prompt.
1303 @cindex @code{--version}
1304 This option causes @value{GDBN} to print its version number and
1305 no-warranty blurb, and exit.
1307 @item -configuration
1308 @cindex @code{--configuration}
1309 This option causes @value{GDBN} to print details about its build-time
1310 configuration parameters, and then exit. These details can be
1311 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1316 @subsection What @value{GDBN} Does During Startup
1317 @cindex @value{GDBN} startup
1319 Here's the description of what @value{GDBN} does during session startup:
1324 Performs minimal setup required to initialize basic internal state.
1327 @cindex early initialization file
1328 Reads commands from the early initialization file (if any) in your
1329 home directory. Only a restricted set of commands can be placed into
1330 an early initialization file, see @ref{Initialization Files}, for
1334 Executes commands and command files specified by the @samp{-eiex} and
1335 @samp{-eix} command line options in their specified order. Only a
1336 restricted set of commands can be used with @samp{-eiex} and
1337 @samp{eix}, see @ref{Initialization Files}, for details.
1340 Sets up the command interpreter as specified by the command line
1341 (@pxref{Mode Options, interpreter}).
1345 Reads the system wide initialization file and the files from the
1346 system wide initialization directory, @pxref{System Wide Init Files}.
1349 Reads the initialization file (if any) in your home directory and
1350 executes all the commands in that file, @pxref{Home Directory Init
1353 @anchor{Option -init-eval-command}
1355 Executes commands and command files specified by the @samp{-iex} and
1356 @samp{-ix} options in their specified order. Usually you should use the
1357 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1358 settings before @value{GDBN} init files get executed and before inferior
1362 Processes command line options and operands.
1365 Reads and executes the commands from the initialization file (if any)
1366 in the current working directory as long as @samp{set auto-load
1367 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1368 Directory}). This is only done if the current directory is different
1369 from your home directory. Thus, you can have more than one init file,
1370 one generic in your home directory, and another, specific to the
1371 program you are debugging, in the directory where you invoke
1372 @value{GDBN}. @xref{Init File in the Current Directory during
1376 If the command line specified a program to debug, or a process to
1377 attach to, or a core file, @value{GDBN} loads any auto-loaded
1378 scripts provided for the program or for its loaded shared libraries.
1379 @xref{Auto-loading}.
1381 If you wish to disable the auto-loading during startup,
1382 you must do something like the following:
1385 $ gdb -iex "set auto-load python-scripts off" myprogram
1388 Option @samp{-ex} does not work because the auto-loading is then turned
1392 Executes commands and command files specified by the @samp{-ex} and
1393 @samp{-x} options in their specified order. @xref{Command Files}, for
1394 more details about @value{GDBN} command files.
1397 Reads the command history recorded in the @dfn{history file}.
1398 @xref{Command History}, for more details about the command history and the
1399 files where @value{GDBN} records it.
1402 @node Initialization Files
1403 @subsection Initialization Files
1404 @cindex init file name
1406 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1407 from several initialization files. These initialization files use the
1408 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1409 processed by @value{GDBN} in the same way.
1411 To display the list of initialization files loaded by @value{GDBN} at
1412 startup, in the order they will be loaded, you can use @kbd{gdb
1415 @cindex early initialization
1416 The @dfn{early initialization} file is loaded very early in
1417 @value{GDBN}'s initialization process, before the interpreter
1418 (@pxref{Interpreters}) has been initialized, and before the default
1419 target (@pxref{Targets}) is initialized. Only @code{set} or
1420 @code{source} commands should be placed into an early initialization
1421 file, and the only @code{set} commands that can be used are those that
1422 control how @value{GDBN} starts up.
1424 Commands that can be placed into an early initialization file will be
1425 documented as such throughout this manual. Any command that is not
1426 documented as being suitable for an early initialization file should
1427 instead be placed into a general initialization file. Command files
1428 passed to @code{--early-init-command} or @code{-eix} are also early
1429 initialization files, with the same command restrictions. Only
1430 commands that can appear in an early initialization file should be
1431 passed to @code{--early-init-eval-command} or @code{-eiex}.
1433 @cindex general initialization
1434 In contrast, the @dfn{general initialization} files are processed
1435 later, after @value{GDBN} has finished its own internal initialization
1436 process, any valid command can be used in these files.
1438 @cindex initialization file
1439 Throughout the rest of this document the term @dfn{initialization
1440 file} refers to one of the general initialization files, not the early
1441 initialization file. Any discussion of the early initialization file
1442 will specifically mention that it is the early initialization file
1445 As the system wide and home directory initialization files are
1446 processed before most command line options, changes to settings
1447 (e.g.@: @samp{set complaints}) can affect subsequent processing of
1448 command line options and operands.
1450 The following sections describe where @value{GDBN} looks for the early
1451 initialization and initialization files, and the order that the files
1454 @subsubsection Home directory early initialization files
1456 @value{GDBN} initially looks for an early initialization file in the
1457 users home directory@footnote{On DOS/Windows systems, the home
1458 directory is the one pointed to by the @env{HOME} environment
1459 variable.}. There are a number of locations that @value{GDBN} will
1460 search in the home directory, these locations are searched in order
1461 and @value{GDBN} will load the first file that it finds, and
1462 subsequent locations will not be checked.
1464 On non-macOS hosts the locations searched are:
1467 The file @file{gdb/gdbearlyinit} within the directory pointed to by the
1468 environment variable @env{XDG_CONFIG_HOME}, if it is defined.
1470 The file @file{.config/gdb/gdbearlyinit} within the directory pointed to
1471 by the environment variable @env{HOME}, if it is defined.
1473 The file @file{.gdbearlyinit} within the directory pointed to by the
1474 environment variable @env{HOME}, if it is defined.
1477 By contrast, on macOS hosts the locations searched are:
1480 The file @file{Library/Preferences/gdb/gdbearlyinit} within the
1481 directory pointed to by the environment variable @env{HOME}, if it is
1484 The file @file{.gdbearlyinit} within the directory pointed to by the
1485 environment variable @env{HOME}, if it is defined.
1488 It is possible to prevent the home directory early initialization file
1489 from being loaded using the @samp{-nx} or @samp{-nh} command line
1490 options, @pxref{Mode Options,,Choosing Modes}.
1492 @anchor{System Wide Init Files}
1493 @subsubsection System wide initialization files
1495 There are two locations that are searched for system wide
1496 initialization files. Both of these locations are always checked:
1500 @item @file{system.gdbinit}
1501 This is a single system-wide initialization file. Its location is
1502 specified with the @code{--with-system-gdbinit} configure option
1503 (@pxref{System-wide configuration}). It is loaded first when
1504 @value{GDBN} starts, before command line options have been processed.
1506 @item @file{system.gdbinit.d}
1507 This is the system-wide initialization directory. Its location is
1508 specified with the @code{--with-system-gdbinit-dir} configure option
1509 (@pxref{System-wide configuration}). Files in this directory are
1510 loaded in alphabetical order immediately after @file{system.gdbinit}
1511 (if enabled) when @value{GDBN} starts, before command line options
1512 have been processed. Files need to have a recognized scripting
1513 language extension (@file{.py}/@file{.scm}) or be named with a
1514 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1515 commands. @value{GDBN} will not recurse into any subdirectories of
1520 It is possible to prevent the system wide initialization files from
1521 being loaded using the @samp{-nx} command line option, @pxref{Mode
1522 Options,,Choosing Modes}.
1524 @anchor{Home Directory Init File}
1525 @subsubsection Home directory initialization file
1526 @cindex @file{gdbinit}
1527 @cindex @file{.gdbinit}
1528 @cindex @file{gdb.ini}
1530 After loading the system wide initialization files @value{GDBN} will
1531 look for an initialization file in the users home
1532 directory@footnote{On DOS/Windows systems, the home directory is the
1533 one pointed to by the @env{HOME} environment variable.}. There are a
1534 number of locations that @value{GDBN} will search in the home
1535 directory, these locations are searched in order and @value{GDBN} will
1536 load the first file that it finds, and subsequent locations will not
1539 On non-Apple hosts the locations searched are:
1541 @item $XDG_CONFIG_HOME/gdb/gdbinit
1542 @item $HOME/.config/gdb/gdbinit
1543 @item $HOME/.gdbinit
1546 While on Apple hosts the locations searched are:
1548 @item $HOME/Library/Preferences/gdb/gdbinit
1549 @item $HOME/.gdbinit
1552 It is possible to prevent the home directory initialization file from
1553 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1554 @pxref{Mode Options,,Choosing Modes}.
1556 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1557 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1558 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1559 uses the standard name, but if it finds a @file{gdb.ini} file in your
1560 home directory, it warns you about that and suggests to rename the
1561 file to the standard name.
1563 @anchor{Init File in the Current Directory during Startup}
1564 @subsubsection Local directory initialization file
1566 @value{GDBN} will check the current directory for a file called
1567 @file{.gdbinit}. It is loaded last, after command line options
1568 other than @samp{-x} and @samp{-ex} have been processed. The command
1569 line options @samp{-x} and @samp{-ex} are processed last, after
1570 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1573 If the file in the current directory was already loaded as the home
1574 directory initialization file then it will not be loaded a second
1577 It is possible to prevent the local directory initialization file from
1578 being loaded using the @samp{-nx} command line option, @pxref{Mode
1579 Options,,Choosing Modes}.
1582 @section Quitting @value{GDBN}
1583 @cindex exiting @value{GDBN}
1584 @cindex leaving @value{GDBN}
1587 @kindex quit @r{[}@var{expression}@r{]}
1588 @kindex exit @r{[}@var{expression}@r{]}
1589 @kindex q @r{(@code{quit})}
1590 @item quit @r{[}@var{expression}@r{]}
1591 @itemx exit @r{[}@var{expression}@r{]}
1593 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1594 @code{q}), the @code{exit} command, or type an end-of-file
1595 character (usually @kbd{Ctrl-d}). If you do not supply @var{expression},
1596 @value{GDBN} will terminate normally; otherwise it will terminate using
1597 the result of @var{expression} as the error code.
1601 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1602 terminates the action of any @value{GDBN} command that is in progress and
1603 returns to @value{GDBN} command level. It is safe to type the interrupt
1604 character at any time because @value{GDBN} does not allow it to take effect
1605 until a time when it is safe.
1607 If you have been using @value{GDBN} to control an attached process or
1608 device, you can release it with the @code{detach} command
1609 (@pxref{Attach, ,Debugging an Already-running Process}).
1611 @node Shell Commands
1612 @section Shell Commands
1614 If you need to execute occasional shell commands during your
1615 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1616 just use the @code{shell} command.
1621 @cindex shell escape
1622 @item shell @var{command-string}
1623 @itemx !@var{command-string}
1624 Invoke a standard shell to execute @var{command-string}.
1625 Note that no space is needed between @code{!} and @var{command-string}.
1626 On GNU and Unix systems, the environment variable @env{SHELL}, if it
1627 exists, determines which shell to run. Otherwise @value{GDBN} uses
1628 the default shell (@file{/bin/sh} on GNU and Unix systems,
1629 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1632 The utility @code{make} is often needed in development environments.
1633 You do not have to use the @code{shell} command for this purpose in
1638 @cindex calling make
1639 @item make @var{make-args}
1640 Execute the @code{make} program with the specified
1641 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1647 @cindex send the output of a gdb command to a shell command
1649 @item pipe [@var{command}] | @var{shell_command}
1650 @itemx | [@var{command}] | @var{shell_command}
1651 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1652 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1653 Executes @var{command} and sends its output to @var{shell_command}.
1654 Note that no space is needed around @code{|}.
1655 If no @var{command} is provided, the last command executed is repeated.
1657 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1658 can be used to specify an alternate delimiter string @var{delim} that separates
1659 the @var{command} from the @var{shell_command}.
1664 (@value{GDBP}) p var
1674 (@value{GDBP}) pipe p var|wc
1676 (@value{GDBP}) |p var|wc -l
1680 (@value{GDBP}) p /x var
1688 (@value{GDBP}) ||grep red
1692 (@value{GDBP}) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1693 this contains a PIPE char
1694 (@value{GDBP}) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1695 this contains a PIPE char!
1701 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1702 can be used to examine the exit status of the last shell command launched
1703 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1704 @xref{Convenience Vars,, Convenience Variables}.
1706 @node Logging Output
1707 @section Logging Output
1708 @cindex logging @value{GDBN} output
1709 @cindex save @value{GDBN} output to a file
1711 You may want to save the output of @value{GDBN} commands to a file.
1712 There are several commands to control @value{GDBN}'s logging.
1715 @kindex set logging enabled
1716 @item set logging enabled [on|off]
1717 Enable or disable logging.
1718 @cindex logging file name
1719 @item set logging file @var{file}
1720 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1721 @item set logging overwrite [on|off]
1722 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1723 you want @code{set logging enabled on} to overwrite the logfile instead.
1724 @item set logging redirect [on|off]
1725 By default, @value{GDBN} output will go to both the terminal and the logfile.
1726 Set @code{redirect} if you want output to go only to the log file.
1727 @item set logging debugredirect [on|off]
1728 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1729 Set @code{debugredirect} if you want debug output to go only to the log file.
1730 @kindex show logging
1732 Show the current values of the logging settings.
1735 You can also redirect the output of a @value{GDBN} command to a
1736 shell command. @xref{pipe}.
1738 @chapter @value{GDBN} Commands
1740 You can abbreviate a @value{GDBN} command to the first few letters of the command
1741 name, if that abbreviation is unambiguous; and you can repeat certain
1742 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1743 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1744 show you the alternatives available, if there is more than one possibility).
1747 * Command Syntax:: How to give commands to @value{GDBN}
1748 * Command Settings:: How to change default behavior of commands
1749 * Completion:: Command completion
1750 * Command Options:: Command options
1751 * Help:: How to ask @value{GDBN} for help
1754 @node Command Syntax
1755 @section Command Syntax
1757 A @value{GDBN} command is a single line of input. There is no limit on
1758 how long it can be. It starts with a command name, which is followed by
1759 arguments whose meaning depends on the command name. For example, the
1760 command @code{step} accepts an argument which is the number of times to
1761 step, as in @samp{step 5}. You can also use the @code{step} command
1762 with no arguments. Some commands do not allow any arguments.
1764 @cindex abbreviation
1765 @value{GDBN} command names may always be truncated if that abbreviation is
1766 unambiguous. Other possible command abbreviations are listed in the
1767 documentation for individual commands. In some cases, even ambiguous
1768 abbreviations are allowed; for example, @code{s} is specially defined as
1769 equivalent to @code{step} even though there are other commands whose
1770 names start with @code{s}. You can test abbreviations by using them as
1771 arguments to the @code{help} command.
1773 @cindex repeating commands
1774 @kindex RET @r{(repeat last command)}
1775 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1776 repeat the previous command. Certain commands (for example, @code{run})
1777 will not repeat this way; these are commands whose unintentional
1778 repetition might cause trouble and which you are unlikely to want to
1779 repeat. User-defined commands can disable this feature; see
1780 @ref{Define, dont-repeat}.
1782 The @code{list} and @code{x} commands, when you repeat them with
1783 @key{RET}, construct new arguments rather than repeating
1784 exactly as typed. This permits easy scanning of source or memory.
1786 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1787 output, in a way similar to the common utility @code{more}
1788 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1789 @key{RET} too many in this situation, @value{GDBN} disables command
1790 repetition after any command that generates this sort of display.
1792 @kindex # @r{(a comment)}
1794 Any text from a @kbd{#} to the end of the line is a comment; it does
1795 nothing. This is useful mainly in command files (@pxref{Command
1796 Files,,Command Files}).
1798 @cindex repeating command sequences
1799 @kindex Ctrl-o @r{(operate-and-get-next)}
1800 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1801 commands. This command accepts the current line, like @key{RET}, and
1802 then fetches the next line relative to the current line from the history
1806 @node Command Settings
1807 @section Command Settings
1808 @cindex default behavior of commands, changing
1809 @cindex default settings, changing
1811 Many commands change their behavior according to command-specific
1812 variables or settings. These settings can be changed with the
1813 @code{set} subcommands. For example, the @code{print} command
1814 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1815 settings changeable with the commands @code{set print elements
1816 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1818 You can change these settings to your preference in the gdbinit files
1819 loaded at @value{GDBN} startup. @xref{Startup}.
1821 The settings can also be changed interactively during the debugging
1822 session. For example, to change the limit of array elements to print,
1823 you can do the following:
1825 (@value{GDBP}) set print elements 10
1826 (@value{GDBP}) print some_array
1827 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1830 The above @code{set print elements 10} command changes the number of
1831 elements to print from the default of 200 to 10. If you only intend
1832 this limit of 10 to be used for printing @code{some_array}, then you
1833 must restore the limit back to 200, with @code{set print elements
1836 Some commands allow overriding settings with command options. For
1837 example, the @code{print} command supports a number of options that
1838 allow overriding relevant global print settings as set by @code{set
1839 print} subcommands. @xref{print options}. The example above could be
1842 (@value{GDBP}) print -elements 10 -- some_array
1843 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1846 Alternatively, you can use the @code{with} command to change a setting
1847 temporarily, for the duration of a command invocation.
1850 @kindex with command
1851 @kindex w @r{(@code{with})}
1853 @cindex temporarily change settings
1854 @item with @var{setting} [@var{value}] [-- @var{command}]
1855 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1856 Temporarily set @var{setting} to @var{value} for the duration of
1859 @var{setting} is any setting you can change with the @code{set}
1860 subcommands. @var{value} is the value to assign to @code{setting}
1861 while running @code{command}.
1863 If no @var{command} is provided, the last command executed is
1866 If a @var{command} is provided, it must be preceded by a double dash
1867 (@code{--}) separator. This is required because some settings accept
1868 free-form arguments, such as expressions or filenames.
1870 For example, the command
1872 (@value{GDBP}) with print array on -- print some_array
1875 is equivalent to the following 3 commands:
1877 (@value{GDBP}) set print array on
1878 (@value{GDBP}) print some_array
1879 (@value{GDBP}) set print array off
1882 The @code{with} command is particularly useful when you want to
1883 override a setting while running user-defined commands, or commands
1884 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1887 (@value{GDBP}) with print pretty on -- my_complex_command
1890 To change several settings for the same command, you can nest
1891 @code{with} commands. For example, @code{with language ada -- with
1892 print elements 10} temporarily changes the language to Ada and sets a
1893 limit of 10 elements to print for arrays and strings.
1898 @section Command Completion
1901 @cindex word completion
1902 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1903 only one possibility; it can also show you what the valid possibilities
1904 are for the next word in a command, at any time. This works for @value{GDBN}
1905 commands, @value{GDBN} subcommands, command options, and the names of symbols
1908 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1909 of a word. If there is only one possibility, @value{GDBN} fills in the
1910 word, and waits for you to finish the command (or press @key{RET} to
1911 enter it). For example, if you type
1913 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1914 @c complete accuracy in these examples; space introduced for clarity.
1915 @c If texinfo enhancements make it unnecessary, it would be nice to
1916 @c replace " @key" by "@key" in the following...
1918 (@value{GDBP}) info bre@key{TAB}
1922 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1923 the only @code{info} subcommand beginning with @samp{bre}:
1926 (@value{GDBP}) info breakpoints
1930 You can either press @key{RET} at this point, to run the @code{info
1931 breakpoints} command, or backspace and enter something else, if
1932 @samp{breakpoints} does not look like the command you expected. (If you
1933 were sure you wanted @code{info breakpoints} in the first place, you
1934 might as well just type @key{RET} immediately after @samp{info bre},
1935 to exploit command abbreviations rather than command completion).
1937 If there is more than one possibility for the next word when you press
1938 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1939 characters and try again, or just press @key{TAB} a second time;
1940 @value{GDBN} displays all the possible completions for that word. For
1941 example, you might want to set a breakpoint on a subroutine whose name
1942 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1943 just sounds the bell. Typing @key{TAB} again displays all the
1944 function names in your program that begin with those characters, for
1948 (@value{GDBP}) b make_@key{TAB}
1949 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1950 make_a_section_from_file make_environ
1951 make_abs_section make_function_type
1952 make_blockvector make_pointer_type
1953 make_cleanup make_reference_type
1954 make_command make_symbol_completion_list
1955 (@value{GDBP}) b make_
1959 After displaying the available possibilities, @value{GDBN} copies your
1960 partial input (@samp{b make_} in the example) so you can finish the
1963 If the command you are trying to complete expects either a keyword or a
1964 number to follow, then @samp{NUMBER} will be shown among the available
1965 completions, for example:
1968 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
1970 (@value{GDBP}) print -elements@tie{}
1974 Here, the option expects a number (e.g., @code{100}), not literal
1975 @code{NUMBER}. Such metasyntactical arguments are always presented in
1978 If you just want to see the list of alternatives in the first place, you
1979 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1980 means @kbd{@key{META} ?}. You can type this either by holding down a
1981 key designated as the @key{META} shift on your keyboard (if there is
1982 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1984 If the number of possible completions is large, @value{GDBN} will
1985 print as much of the list as it has collected, as well as a message
1986 indicating that the list may be truncated.
1989 (@value{GDBP}) b m@key{TAB}@key{TAB}
1991 <... the rest of the possible completions ...>
1992 *** List may be truncated, max-completions reached. ***
1997 This behavior can be controlled with the following commands:
2000 @kindex set max-completions
2001 @item set max-completions @var{limit}
2002 @itemx set max-completions unlimited
2003 Set the maximum number of completion candidates. @value{GDBN} will
2004 stop looking for more completions once it collects this many candidates.
2005 This is useful when completing on things like function names as collecting
2006 all the possible candidates can be time consuming.
2007 The default value is 200. A value of zero disables tab-completion.
2008 Note that setting either no limit or a very large limit can make
2010 @kindex show max-completions
2011 @item show max-completions
2012 Show the maximum number of candidates that @value{GDBN} will collect and show
2016 @cindex quotes in commands
2017 @cindex completion of quoted strings
2018 Sometimes the string you need, while logically a ``word'', may contain
2019 parentheses or other characters that @value{GDBN} normally excludes from
2020 its notion of a word. To permit word completion to work in this
2021 situation, you may enclose words in @code{'} (single quote marks) in
2022 @value{GDBN} commands.
2024 A likely situation where you might need this is in typing an
2025 expression that involves a C@t{++} symbol name with template
2026 parameters. This is because when completing expressions, GDB treats
2027 the @samp{<} character as word delimiter, assuming that it's the
2028 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
2031 For example, when you want to call a C@t{++} template function
2032 interactively using the @code{print} or @code{call} commands, you may
2033 need to distinguish whether you mean the version of @code{name} that
2034 was specialized for @code{int}, @code{name<int>()}, or the version
2035 that was specialized for @code{float}, @code{name<float>()}. To use
2036 the word-completion facilities in this situation, type a single quote
2037 @code{'} at the beginning of the function name. This alerts
2038 @value{GDBN} that it may need to consider more information than usual
2039 when you press @key{TAB} or @kbd{M-?} to request word completion:
2042 (@value{GDBP}) p 'func<@kbd{M-?}
2043 func<int>() func<float>()
2044 (@value{GDBP}) p 'func<
2047 When setting breakpoints however (@pxref{Location Specifications}), you don't
2048 usually need to type a quote before the function name, because
2049 @value{GDBN} understands that you want to set a breakpoint on a
2053 (@value{GDBP}) b func<@kbd{M-?}
2054 func<int>() func<float>()
2055 (@value{GDBP}) b func<
2058 This is true even in the case of typing the name of C@t{++} overloaded
2059 functions (multiple definitions of the same function, distinguished by
2060 argument type). For example, when you want to set a breakpoint you
2061 don't need to distinguish whether you mean the version of @code{name}
2062 that takes an @code{int} parameter, @code{name(int)}, or the version
2063 that takes a @code{float} parameter, @code{name(float)}.
2066 (@value{GDBP}) b bubble(@kbd{M-?}
2067 bubble(int) bubble(double)
2068 (@value{GDBP}) b bubble(dou@kbd{M-?}
2072 See @ref{quoting names} for a description of other scenarios that
2075 For more information about overloaded functions, see @ref{C Plus Plus
2076 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
2077 overload-resolution off} to disable overload resolution;
2078 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
2080 @cindex completion of structure field names
2081 @cindex structure field name completion
2082 @cindex completion of union field names
2083 @cindex union field name completion
2084 When completing in an expression which looks up a field in a
2085 structure, @value{GDBN} also tries@footnote{The completer can be
2086 confused by certain kinds of invalid expressions. Also, it only
2087 examines the static type of the expression, not the dynamic type.} to
2088 limit completions to the field names available in the type of the
2092 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
2093 magic to_fputs to_rewind
2094 to_data to_isatty to_write
2095 to_delete to_put to_write_async_safe
2100 This is because the @code{gdb_stdout} is a variable of the type
2101 @code{struct ui_file} that is defined in @value{GDBN} sources as
2108 ui_file_flush_ftype *to_flush;
2109 ui_file_write_ftype *to_write;
2110 ui_file_write_async_safe_ftype *to_write_async_safe;
2111 ui_file_fputs_ftype *to_fputs;
2112 ui_file_read_ftype *to_read;
2113 ui_file_delete_ftype *to_delete;
2114 ui_file_isatty_ftype *to_isatty;
2115 ui_file_rewind_ftype *to_rewind;
2116 ui_file_put_ftype *to_put;
2121 @node Command Options
2122 @section Command options
2124 @cindex command options
2125 Some commands accept options starting with a leading dash. For
2126 example, @code{print -pretty}. Similarly to command names, you can
2127 abbreviate a @value{GDBN} option to the first few letters of the
2128 option name, if that abbreviation is unambiguous, and you can also use
2129 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2130 in an option (or to show you the alternatives available, if there is
2131 more than one possibility).
2133 @cindex command options, raw input
2134 Some commands take raw input as argument. For example, the print
2135 command processes arbitrary expressions in any of the languages
2136 supported by @value{GDBN}. With such commands, because raw input may
2137 start with a leading dash that would be confused with an option or any
2138 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2139 -pretty} or printing negative @code{p}?), if you specify any command
2140 option, then you must use a double-dash (@code{--}) delimiter to
2141 indicate the end of options.
2143 @cindex command options, boolean
2145 Some options are described as accepting an argument which can be
2146 either @code{on} or @code{off}. These are known as @dfn{boolean
2147 options}. Similarly to boolean settings commands---@code{on} and
2148 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2149 @code{enable} can also be used as ``true'' value, and any of @code{0},
2150 @code{no} and @code{disable} can also be used as ``false'' value. You
2151 can also omit a ``true'' value, as it is implied by default.
2153 For example, these are equivalent:
2156 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2157 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2160 You can discover the set of options some command accepts by completing
2161 on @code{-} after the command name. For example:
2164 (@value{GDBP}) print -@key{TAB}@key{TAB}
2165 -address -max-depth -object -static-members
2166 -array -memory-tag-violations -pretty -symbol
2167 -array-indexes -nibbles -raw-values -union
2168 -elements -null-stop -repeats -vtbl
2171 Completion will in some cases guide you with a suggestion of what kind
2172 of argument an option expects. For example:
2175 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2180 Here, the option expects a number (e.g., @code{100}), not literal
2181 @code{NUMBER}. Such metasyntactical arguments are always presented in
2184 (For more on using the @code{print} command, see @ref{Data, ,Examining
2188 @section Getting Help
2189 @cindex online documentation
2192 You can always ask @value{GDBN} itself for information on its commands,
2193 using the command @code{help}.
2196 @kindex h @r{(@code{help})}
2199 You can use @code{help} (abbreviated @code{h}) with no arguments to
2200 display a short list of named classes of commands:
2204 List of classes of commands:
2206 aliases -- User-defined aliases of other commands
2207 breakpoints -- Making program stop at certain points
2208 data -- Examining data
2209 files -- Specifying and examining files
2210 internals -- Maintenance commands
2211 obscure -- Obscure features
2212 running -- Running the program
2213 stack -- Examining the stack
2214 status -- Status inquiries
2215 support -- Support facilities
2216 tracepoints -- Tracing of program execution without
2217 stopping the program
2218 user-defined -- User-defined commands
2220 Type "help" followed by a class name for a list of
2221 commands in that class.
2222 Type "help" followed by command name for full
2224 Command name abbreviations are allowed if unambiguous.
2227 @c the above line break eliminates huge line overfull...
2229 @item help @var{class}
2230 Using one of the general help classes as an argument, you can get a
2231 list of the individual commands in that class. If a command has
2232 aliases, the aliases are given after the command name, separated by
2233 commas. If an alias has default arguments, the full definition of
2234 the alias is given after the first line.
2235 For example, here is the help display for the class @code{status}:
2238 (@value{GDBP}) help status
2243 @c Line break in "show" line falsifies real output, but needed
2244 @c to fit in smallbook page size.
2245 info, inf, i -- Generic command for showing things
2246 about the program being debugged
2247 info address, iamain -- Describe where symbol SYM is stored.
2248 alias iamain = info address main
2249 info all-registers -- List of all registers and their contents,
2250 for selected stack frame.
2252 show, info set -- Generic command for showing things
2255 Type "help" followed by command name for full
2257 Command name abbreviations are allowed if unambiguous.
2261 @item help @var{command}
2262 With a command name as @code{help} argument, @value{GDBN} displays a
2263 short paragraph on how to use that command. If that command has
2264 one or more aliases, @value{GDBN} will display a first line with
2265 the command name and all its aliases separated by commas.
2266 This first line will be followed by the full definition of all aliases
2267 having default arguments.
2268 When asking the help for an alias, the documentation for the aliased
2271 A user-defined alias can optionally be documented using the
2272 @code{document} command (@pxref{Define, document}). @value{GDBN} then
2273 considers this alias as different from the aliased command: this alias
2274 is not listed in the aliased command help output, and asking help for
2275 this alias will show the documentation provided for the alias instead of
2276 the documentation of the aliased command.
2279 @item apropos [-v] @var{regexp}
2280 The @code{apropos} command searches through all of the @value{GDBN}
2281 commands and aliases, and their documentation, for the regular expression specified in
2282 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2283 which stands for @samp{verbose}, indicates to output the full documentation
2284 of the matching commands and highlight the parts of the documentation
2285 matching @var{regexp}. For example:
2296 alias -- Define a new command that is an alias of an existing command
2297 aliases -- User-defined aliases of other commands
2305 apropos -v cut.*thread apply
2309 results in the below output, where @samp{cut for 'thread apply}
2310 is highlighted if styling is enabled.
2314 taas -- Apply a command to all threads (ignoring errors
2317 shortcut for 'thread apply all -s COMMAND'
2319 tfaas -- Apply a command to all frames of all threads
2320 (ignoring errors and empty output).
2321 Usage: tfaas COMMAND
2322 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2327 @item complete @var{args}
2328 The @code{complete @var{args}} command lists all the possible completions
2329 for the beginning of a command. Use @var{args} to specify the beginning of the
2330 command you want completed. For example:
2336 @noindent results in:
2347 @noindent This is intended for use by @sc{gnu} Emacs.
2350 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2351 and @code{show} to inquire about the state of your program, or the state
2352 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2353 manual introduces each of them in the appropriate context. The listings
2354 under @code{info} and under @code{show} in the Command, Variable, and
2355 Function Index point to all the sub-commands. @xref{Command and Variable
2361 @kindex i @r{(@code{info})}
2363 This command (abbreviated @code{i}) is for describing the state of your
2364 program. For example, you can show the arguments passed to a function
2365 with @code{info args}, list the registers currently in use with @code{info
2366 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2367 You can get a complete list of the @code{info} sub-commands with
2368 @w{@code{help info}}.
2372 You can assign the result of an expression to an environment variable with
2373 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2374 @code{set prompt $}.
2378 In contrast to @code{info}, @code{show} is for describing the state of
2379 @value{GDBN} itself.
2380 You can change most of the things you can @code{show}, by using the
2381 related command @code{set}; for example, you can control what number
2382 system is used for displays with @code{set radix}, or simply inquire
2383 which is currently in use with @code{show radix}.
2386 To display all the settable parameters and their current
2387 values, you can use @code{show} with no arguments; you may also use
2388 @code{info set}. Both commands produce the same display.
2389 @c FIXME: "info set" violates the rule that "info" is for state of
2390 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2391 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2395 Here are several miscellaneous @code{show} subcommands, all of which are
2396 exceptional in lacking corresponding @code{set} commands:
2399 @kindex show version
2400 @cindex @value{GDBN} version number
2402 Show what version of @value{GDBN} is running. You should include this
2403 information in @value{GDBN} bug-reports. If multiple versions of
2404 @value{GDBN} are in use at your site, you may need to determine which
2405 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2406 commands are introduced, and old ones may wither away. Also, many
2407 system vendors ship variant versions of @value{GDBN}, and there are
2408 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2409 The version number is the same as the one announced when you start
2412 @kindex show copying
2413 @kindex info copying
2414 @cindex display @value{GDBN} copyright
2417 Display information about permission for copying @value{GDBN}.
2419 @kindex show warranty
2420 @kindex info warranty
2422 @itemx info warranty
2423 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2424 if your version of @value{GDBN} comes with one.
2426 @kindex show configuration
2427 @item show configuration
2428 Display detailed information about the way @value{GDBN} was configured
2429 when it was built. This displays the optional arguments passed to the
2430 @file{configure} script and also configuration parameters detected
2431 automatically by @command{configure}. When reporting a @value{GDBN}
2432 bug (@pxref{GDB Bugs}), it is important to include this information in
2438 @chapter Running Programs Under @value{GDBN}
2440 When you run a program under @value{GDBN}, you must first generate
2441 debugging information when you compile it.
2443 You may start @value{GDBN} with its arguments, if any, in an environment
2444 of your choice. If you are doing native debugging, you may redirect
2445 your program's input and output, debug an already running process, or
2446 kill a child process.
2449 * Compilation:: Compiling for debugging
2450 * Starting:: Starting your program
2451 * Arguments:: Your program's arguments
2452 * Environment:: Your program's environment
2454 * Working Directory:: Your program's working directory
2455 * Input/Output:: Your program's input and output
2456 * Attach:: Debugging an already-running process
2457 * Kill Process:: Killing the child process
2458 * Inferiors Connections and Programs:: Debugging multiple inferiors
2459 connections and programs
2460 * Threads:: Debugging programs with multiple threads
2461 * Forks:: Debugging forks
2462 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2466 @section Compiling for Debugging
2468 In order to debug a program effectively, you need to generate
2469 debugging information when you compile it. This debugging information
2470 is stored in the object file; it describes the data type of each
2471 variable or function and the correspondence between source line numbers
2472 and addresses in the executable code.
2474 To request debugging information, specify the @samp{-g} option when you run
2477 Programs that are to be shipped to your customers are compiled with
2478 optimizations, using the @samp{-O} compiler option. However, some
2479 compilers are unable to handle the @samp{-g} and @samp{-O} options
2480 together. Using those compilers, you cannot generate optimized
2481 executables containing debugging information.
2483 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2484 without @samp{-O}, making it possible to debug optimized code. We
2485 recommend that you @emph{always} use @samp{-g} whenever you compile a
2486 program. You may think your program is correct, but there is no sense
2487 in pushing your luck. For more information, see @ref{Optimized Code}.
2489 Older versions of the @sc{gnu} C compiler permitted a variant option
2490 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2491 format; if your @sc{gnu} C compiler has this option, do not use it.
2493 @value{GDBN} knows about preprocessor macros and can show you their
2494 expansion (@pxref{Macros}). Most compilers do not include information
2495 about preprocessor macros in the debugging information if you specify
2496 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2497 the @sc{gnu} C compiler, provides macro information if you are using
2498 the DWARF debugging format, and specify the option @option{-g3}.
2500 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2501 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2502 information on @value{NGCC} options affecting debug information.
2504 You will have the best debugging experience if you use the latest
2505 version of the DWARF debugging format that your compiler supports.
2506 DWARF is currently the most expressive and best supported debugging
2507 format in @value{GDBN}.
2511 @section Starting your Program
2517 @kindex r @r{(@code{run})}
2520 Use the @code{run} command to start your program under @value{GDBN}.
2521 You must first specify the program name with an argument to
2522 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2523 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2524 command (@pxref{Files, ,Commands to Specify Files}).
2528 If you are running your program in an execution environment that
2529 supports processes, @code{run} creates an inferior process and makes
2530 that process run your program. In some environments without processes,
2531 @code{run} jumps to the start of your program. Other targets,
2532 like @samp{remote}, are always running. If you get an error
2533 message like this one:
2536 The "remote" target does not support "run".
2537 Try "help target" or "continue".
2541 then use @code{continue} to run your program. You may need @code{load}
2542 first (@pxref{load}).
2544 The execution of a program is affected by certain information it
2545 receives from its superior. @value{GDBN} provides ways to specify this
2546 information, which you must do @emph{before} starting your program. (You
2547 can change it after starting your program, but such changes only affect
2548 your program the next time you start it.) This information may be
2549 divided into four categories:
2552 @item The @emph{arguments.}
2553 Specify the arguments to give your program as the arguments of the
2554 @code{run} command. If a shell is available on your target, the shell
2555 is used to pass the arguments, so that you may use normal conventions
2556 (such as wildcard expansion or variable substitution) in describing
2558 In Unix systems, you can control which shell is used with the
2559 @env{SHELL} environment variable. If you do not define @env{SHELL},
2560 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2561 use of any shell with the @code{set startup-with-shell} command (see
2564 @item The @emph{environment.}
2565 Your program normally inherits its environment from @value{GDBN}, but you can
2566 use the @value{GDBN} commands @code{set environment} and @code{unset
2567 environment} to change parts of the environment that affect
2568 your program. @xref{Environment, ,Your Program's Environment}.
2570 @item The @emph{working directory.}
2571 You can set your program's working directory with the command
2572 @kbd{set cwd}. If you do not set any working directory with this
2573 command, your program will inherit @value{GDBN}'s working directory if
2574 native debugging, or the remote server's working directory if remote
2575 debugging. @xref{Working Directory, ,Your Program's Working
2578 @item The @emph{standard input and output.}
2579 Your program normally uses the same device for standard input and
2580 standard output as @value{GDBN} is using. You can redirect input and output
2581 in the @code{run} command line, or you can use the @code{tty} command to
2582 set a different device for your program.
2583 @xref{Input/Output, ,Your Program's Input and Output}.
2586 @emph{Warning:} While input and output redirection work, you cannot use
2587 pipes to pass the output of the program you are debugging to another
2588 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2592 When you issue the @code{run} command, your program begins to execute
2593 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2594 of how to arrange for your program to stop. Once your program has
2595 stopped, you may call functions in your program, using the @code{print}
2596 or @code{call} commands. @xref{Data, ,Examining Data}.
2598 If the modification time of your symbol file has changed since the last
2599 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2600 table, and reads it again. When it does this, @value{GDBN} tries to retain
2601 your current breakpoints.
2606 @cindex run to main procedure
2607 The name of the main procedure can vary from language to language.
2608 With C or C@t{++}, the main procedure name is always @code{main}, but
2609 other languages such as Ada do not require a specific name for their
2610 main procedure. The debugger provides a convenient way to start the
2611 execution of the program and to stop at the beginning of the main
2612 procedure, depending on the language used.
2614 The @samp{start} command does the equivalent of setting a temporary
2615 breakpoint at the beginning of the main procedure and then invoking
2616 the @samp{run} command.
2618 @cindex elaboration phase
2619 Some programs contain an @dfn{elaboration} phase where some startup code is
2620 executed before the main procedure is called. This depends on the
2621 languages used to write your program. In C@t{++}, for instance,
2622 constructors for static and global objects are executed before
2623 @code{main} is called. It is therefore possible that the debugger stops
2624 before reaching the main procedure. However, the temporary breakpoint
2625 will remain to halt execution.
2627 Specify the arguments to give to your program as arguments to the
2628 @samp{start} command. These arguments will be given verbatim to the
2629 underlying @samp{run} command. Note that the same arguments will be
2630 reused if no argument is provided during subsequent calls to
2631 @samp{start} or @samp{run}.
2633 It is sometimes necessary to debug the program during elaboration. In
2634 these cases, using the @code{start} command would stop the execution
2635 of your program too late, as the program would have already completed
2636 the elaboration phase. Under these circumstances, either insert
2637 breakpoints in your elaboration code before running your program or
2638 use the @code{starti} command.
2642 @cindex run to first instruction
2643 The @samp{starti} command does the equivalent of setting a temporary
2644 breakpoint at the first instruction of a program's execution and then
2645 invoking the @samp{run} command. For programs containing an
2646 elaboration phase, the @code{starti} command will stop execution at
2647 the start of the elaboration phase.
2649 @anchor{set exec-wrapper}
2650 @kindex set exec-wrapper
2651 @item set exec-wrapper @var{wrapper}
2652 @itemx show exec-wrapper
2653 @itemx unset exec-wrapper
2654 When @samp{exec-wrapper} is set, the specified wrapper is used to
2655 launch programs for debugging. @value{GDBN} starts your program
2656 with a shell command of the form @kbd{exec @var{wrapper}
2657 @var{program}}. Quoting is added to @var{program} and its
2658 arguments, but not to @var{wrapper}, so you should add quotes if
2659 appropriate for your shell. The wrapper runs until it executes
2660 your program, and then @value{GDBN} takes control.
2662 You can use any program that eventually calls @code{execve} with
2663 its arguments as a wrapper. Several standard Unix utilities do
2664 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2665 with @code{exec "$@@"} will also work.
2667 For example, you can use @code{env} to pass an environment variable to
2668 the debugged program, without setting the variable in your shell's
2672 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2676 This command is available when debugging locally on most targets, excluding
2677 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2679 @kindex set startup-with-shell
2680 @anchor{set startup-with-shell}
2681 @item set startup-with-shell
2682 @itemx set startup-with-shell on
2683 @itemx set startup-with-shell off
2684 @itemx show startup-with-shell
2685 On Unix systems, by default, if a shell is available on your target,
2686 @value{GDBN}) uses it to start your program. Arguments of the
2687 @code{run} command are passed to the shell, which does variable
2688 substitution, expands wildcard characters and performs redirection of
2689 I/O. In some circumstances, it may be useful to disable such use of a
2690 shell, for example, when debugging the shell itself or diagnosing
2691 startup failures such as:
2695 Starting program: ./a.out
2696 During startup program terminated with signal SIGSEGV, Segmentation fault.
2700 which indicates the shell or the wrapper specified with
2701 @samp{exec-wrapper} crashed, not your program. Most often, this is
2702 caused by something odd in your shell's non-interactive mode
2703 initialization file---such as @file{.cshrc} for C-shell,
2704 $@file{.zshenv} for the Z shell, or the file specified in the
2705 @env{BASH_ENV} environment variable for BASH.
2707 @anchor{set auto-connect-native-target}
2708 @kindex set auto-connect-native-target
2709 @item set auto-connect-native-target
2710 @itemx set auto-connect-native-target on
2711 @itemx set auto-connect-native-target off
2712 @itemx show auto-connect-native-target
2714 By default, if the current inferior is not connected to any target yet
2715 (e.g., with @code{target remote}), the @code{run} command starts your
2716 program as a native process under @value{GDBN}, on your local machine.
2717 If you're sure you don't want to debug programs on your local machine,
2718 you can tell @value{GDBN} to not connect to the native target
2719 automatically with the @code{set auto-connect-native-target off}
2722 If @code{on}, which is the default, and if the current inferior is not
2723 connected to a target already, the @code{run} command automaticaly
2724 connects to the native target, if one is available.
2726 If @code{off}, and if the current inferior is not connected to a
2727 target already, the @code{run} command fails with an error:
2731 Don't know how to run. Try "help target".
2734 If the current inferior is already connected to a target, @value{GDBN}
2735 always uses it with the @code{run} command.
2737 In any case, you can explicitly connect to the native target with the
2738 @code{target native} command. For example,
2741 (@value{GDBP}) set auto-connect-native-target off
2743 Don't know how to run. Try "help target".
2744 (@value{GDBP}) target native
2746 Starting program: ./a.out
2747 [Inferior 1 (process 10421) exited normally]
2750 In case you connected explicitly to the @code{native} target,
2751 @value{GDBN} remains connected even if all inferiors exit, ready for
2752 the next @code{run} command. Use the @code{disconnect} command to
2755 Examples of other commands that likewise respect the
2756 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2757 proc}, @code{info os}.
2759 @kindex set disable-randomization
2760 @item set disable-randomization
2761 @itemx set disable-randomization on
2762 This option (enabled by default in @value{GDBN}) will turn off the native
2763 randomization of the virtual address space of the started program. This option
2764 is useful for multiple debugging sessions to make the execution better
2765 reproducible and memory addresses reusable across debugging sessions.
2767 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2768 On @sc{gnu}/Linux you can get the same behavior using
2771 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2774 @item set disable-randomization off
2775 Leave the behavior of the started executable unchanged. Some bugs rear their
2776 ugly heads only when the program is loaded at certain addresses. If your bug
2777 disappears when you run the program under @value{GDBN}, that might be because
2778 @value{GDBN} by default disables the address randomization on platforms, such
2779 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2780 disable-randomization off} to try to reproduce such elusive bugs.
2782 On targets where it is available, virtual address space randomization
2783 protects the programs against certain kinds of security attacks. In these
2784 cases the attacker needs to know the exact location of a concrete executable
2785 code. Randomizing its location makes it impossible to inject jumps misusing
2786 a code at its expected addresses.
2788 Prelinking shared libraries provides a startup performance advantage but it
2789 makes addresses in these libraries predictable for privileged processes by
2790 having just unprivileged access at the target system. Reading the shared
2791 library binary gives enough information for assembling the malicious code
2792 misusing it. Still even a prelinked shared library can get loaded at a new
2793 random address just requiring the regular relocation process during the
2794 startup. Shared libraries not already prelinked are always loaded at
2795 a randomly chosen address.
2797 Position independent executables (PIE) contain position independent code
2798 similar to the shared libraries and therefore such executables get loaded at
2799 a randomly chosen address upon startup. PIE executables always load even
2800 already prelinked shared libraries at a random address. You can build such
2801 executable using @command{gcc -fPIE -pie}.
2803 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2804 (as long as the randomization is enabled).
2806 @item show disable-randomization
2807 Show the current setting of the explicit disable of the native randomization of
2808 the virtual address space of the started program.
2813 @section Your Program's Arguments
2815 @cindex arguments (to your program)
2816 The arguments to your program can be specified by the arguments of the
2818 They are passed to a shell, which expands wildcard characters and
2819 performs redirection of I/O, and thence to your program. Your
2820 @env{SHELL} environment variable (if it exists) specifies what shell
2821 @value{GDBN} uses. If you do not define @env{SHELL}, @value{GDBN} uses
2822 the default shell (@file{/bin/sh} on Unix).
2824 On non-Unix systems, the program is usually invoked directly by
2825 @value{GDBN}, which emulates I/O redirection via the appropriate system
2826 calls, and the wildcard characters are expanded by the startup code of
2827 the program, not by the shell.
2829 @code{run} with no arguments uses the same arguments used by the previous
2830 @code{run}, or those set by the @code{set args} command.
2835 Specify the arguments to be used the next time your program is run. If
2836 @code{set args} has no arguments, @code{run} executes your program
2837 with no arguments. Once you have run your program with arguments,
2838 using @code{set args} before the next @code{run} is the only way to run
2839 it again without arguments.
2843 Show the arguments to give your program when it is started.
2847 @section Your Program's Environment
2849 @cindex environment (of your program)
2850 The @dfn{environment} consists of a set of environment variables and
2851 their values. Environment variables conventionally record such things as
2852 your user name, your home directory, your terminal type, and your search
2853 path for programs to run. Usually you set up environment variables with
2854 the shell and they are inherited by all the other programs you run. When
2855 debugging, it can be useful to try running your program with a modified
2856 environment without having to start @value{GDBN} over again.
2860 @item path @var{directory}
2861 Add @var{directory} to the front of the @env{PATH} environment variable
2862 (the search path for executables) that will be passed to your program.
2863 The value of @env{PATH} used by @value{GDBN} does not change.
2864 You may specify several directory names, separated by whitespace or by a
2865 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2866 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2867 is moved to the front, so it is searched sooner.
2869 You can use the string @samp{$cwd} to refer to whatever is the current
2870 working directory at the time @value{GDBN} searches the path. If you
2871 use @samp{.} instead, it refers to the directory where you executed the
2872 @code{path} command. @value{GDBN} replaces @samp{.} in the
2873 @var{directory} argument (with the current path) before adding
2874 @var{directory} to the search path.
2875 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2876 @c document that, since repeating it would be a no-op.
2880 Display the list of search paths for executables (the @env{PATH}
2881 environment variable).
2883 @kindex show environment
2884 @item show environment @r{[}@var{varname}@r{]}
2885 Print the value of environment variable @var{varname} to be given to
2886 your program when it starts. If you do not supply @var{varname},
2887 print the names and values of all environment variables to be given to
2888 your program. You can abbreviate @code{environment} as @code{env}.
2890 @kindex set environment
2891 @anchor{set environment}
2892 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2893 Set environment variable @var{varname} to @var{value}. The value
2894 changes for your program (and the shell @value{GDBN} uses to launch
2895 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2896 values of environment variables are just strings, and any
2897 interpretation is supplied by your program itself. The @var{value}
2898 parameter is optional; if it is eliminated, the variable is set to a
2900 @c "any string" here does not include leading, trailing
2901 @c blanks. Gnu asks: does anyone care?
2903 For example, this command:
2910 tells the debugged program, when subsequently run, that its user is named
2911 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2912 are not actually required.)
2914 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2915 which also inherits the environment set with @code{set environment}.
2916 If necessary, you can avoid that by using the @samp{env} program as a
2917 wrapper instead of using @code{set environment}. @xref{set
2918 exec-wrapper}, for an example doing just that.
2920 Environment variables that are set by the user are also transmitted to
2921 @command{gdbserver} to be used when starting the remote inferior.
2922 @pxref{QEnvironmentHexEncoded}.
2924 @kindex unset environment
2925 @anchor{unset environment}
2926 @item unset environment @var{varname}
2927 Remove variable @var{varname} from the environment to be passed to your
2928 program. This is different from @samp{set env @var{varname} =};
2929 @code{unset environment} removes the variable from the environment,
2930 rather than assigning it an empty value.
2932 Environment variables that are unset by the user are also unset on
2933 @command{gdbserver} when starting the remote inferior.
2934 @pxref{QEnvironmentUnset}.
2937 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2938 the shell indicated by your @env{SHELL} environment variable if it
2939 exists (or @code{/bin/sh} if not). If your @env{SHELL} variable
2940 names a shell that runs an initialization file when started
2941 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2942 for the Z shell, or the file specified in the @env{BASH_ENV}
2943 environment variable for BASH---any variables you set in that file
2944 affect your program. You may wish to move setting of environment
2945 variables to files that are only run when you sign on, such as
2946 @file{.login} or @file{.profile}.
2948 @node Working Directory
2949 @section Your Program's Working Directory
2951 @cindex working directory (of your program)
2952 Each time you start your program with @code{run}, the inferior will be
2953 initialized with the current working directory specified by the
2954 @kbd{set cwd} command. If no directory has been specified by this
2955 command, then the inferior will inherit @value{GDBN}'s current working
2956 directory as its working directory if native debugging, or it will
2957 inherit the remote server's current working directory if remote
2962 @cindex change inferior's working directory
2963 @anchor{set cwd command}
2964 @item set cwd @r{[}@var{directory}@r{]}
2965 Set the inferior's working directory to @var{directory}, which will be
2966 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2967 argument has been specified, the command clears the setting and resets
2968 it to an empty state. This setting has no effect on @value{GDBN}'s
2969 working directory, and it only takes effect the next time you start
2970 the inferior. The @file{~} in @var{directory} is a short for the
2971 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2972 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2973 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2976 You can also change @value{GDBN}'s current working directory by using
2977 the @code{cd} command.
2981 @cindex show inferior's working directory
2983 Show the inferior's working directory. If no directory has been
2984 specified by @kbd{set cwd}, then the default inferior's working
2985 directory is the same as @value{GDBN}'s working directory.
2988 @cindex change @value{GDBN}'s working directory
2990 @item cd @r{[}@var{directory}@r{]}
2991 Set the @value{GDBN} working directory to @var{directory}. If not
2992 given, @var{directory} uses @file{'~'}.
2994 The @value{GDBN} working directory serves as a default for the
2995 commands that specify files for @value{GDBN} to operate on.
2996 @xref{Files, ,Commands to Specify Files}.
2997 @xref{set cwd command}.
3001 Print the @value{GDBN} working directory.
3004 It is generally impossible to find the current working directory of
3005 the process being debugged (since a program can change its directory
3006 during its run). If you work on a system where @value{GDBN} supports
3007 the @code{info proc} command (@pxref{Process Information}), you can
3008 use the @code{info proc} command to find out the
3009 current working directory of the debuggee.
3012 @section Your Program's Input and Output
3017 By default, the program you run under @value{GDBN} does input and output to
3018 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
3019 to its own terminal modes to interact with you, but it records the terminal
3020 modes your program was using and switches back to them when you continue
3021 running your program.
3024 @kindex info terminal
3026 Displays information recorded by @value{GDBN} about the terminal modes your
3030 You can redirect your program's input and/or output using shell
3031 redirection with the @code{run} command. For example,
3038 starts your program, diverting its output to the file @file{outfile}.
3041 @cindex controlling terminal
3042 Another way to specify where your program should do input and output is
3043 with the @code{tty} command. This command accepts a file name as
3044 argument, and causes this file to be the default for future @code{run}
3045 commands. It also resets the controlling terminal for the child
3046 process, for future @code{run} commands. For example,
3053 directs that processes started with subsequent @code{run} commands
3054 default to do input and output on the terminal @file{/dev/ttyb} and have
3055 that as their controlling terminal.
3057 An explicit redirection in @code{run} overrides the @code{tty} command's
3058 effect on the input/output device, but not its effect on the controlling
3061 When you use the @code{tty} command or redirect input in the @code{run}
3062 command, only the input @emph{for your program} is affected. The input
3063 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
3064 for @code{set inferior-tty}.
3066 @cindex inferior tty
3067 @cindex set inferior controlling terminal
3068 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
3069 display the name of the terminal that will be used for future runs of your
3073 @item set inferior-tty [ @var{tty} ]
3074 @kindex set inferior-tty
3075 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
3076 restores the default behavior, which is to use the same terminal as
3079 @item show inferior-tty
3080 @kindex show inferior-tty
3081 Show the current tty for the program being debugged.
3085 @section Debugging an Already-running Process
3090 @item attach @var{process-id}
3091 This command attaches to a running process---one that was started
3092 outside @value{GDBN}. (@code{info files} shows your active
3093 targets.) The command takes as argument a process ID. The usual way to
3094 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
3095 or with the @samp{jobs -l} shell command.
3097 @code{attach} does not repeat if you press @key{RET} a second time after
3098 executing the command.
3101 To use @code{attach}, your program must be running in an environment
3102 which supports processes; for example, @code{attach} does not work for
3103 programs on bare-board targets that lack an operating system. You must
3104 also have permission to send the process a signal.
3106 When you use @code{attach}, the debugger finds the program running in
3107 the process first by looking in the current working directory, then (if
3108 the program is not found) by using the source file search path
3109 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3110 the @code{file} command to load the program. @xref{Files, ,Commands to
3113 @anchor{set exec-file-mismatch}
3114 If the debugger can determine that the executable file running in the
3115 process it is attaching to does not match the current exec-file loaded
3116 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3117 handle the mismatch. @value{GDBN} tries to compare the files by
3118 comparing their build IDs (@pxref{build ID}), if available.
3121 @kindex exec-file-mismatch
3122 @cindex set exec-file-mismatch
3123 @item set exec-file-mismatch @samp{ask|warn|off}
3125 Whether to detect mismatch between the current executable file loaded
3126 by @value{GDBN} and the executable file used to start the process. If
3127 @samp{ask}, the default, display a warning and ask the user whether to
3128 load the process executable file; if @samp{warn}, just display a
3129 warning; if @samp{off}, don't attempt to detect a mismatch.
3130 If the user confirms loading the process executable file, then its symbols
3131 will be loaded as well.
3133 @cindex show exec-file-mismatch
3134 @item show exec-file-mismatch
3135 Show the current value of @code{exec-file-mismatch}.
3139 The first thing @value{GDBN} does after arranging to debug the specified
3140 process is to stop it. You can examine and modify an attached process
3141 with all the @value{GDBN} commands that are ordinarily available when
3142 you start processes with @code{run}. You can insert breakpoints; you
3143 can step and continue; you can modify storage. If you would rather the
3144 process continue running, you may use the @code{continue} command after
3145 attaching @value{GDBN} to the process.
3150 When you have finished debugging the attached process, you can use the
3151 @code{detach} command to release it from @value{GDBN} control. Detaching
3152 the process continues its execution. After the @code{detach} command,
3153 that process and @value{GDBN} become completely independent once more, and you
3154 are ready to @code{attach} another process or start one with @code{run}.
3155 @code{detach} does not repeat if you press @key{RET} again after
3156 executing the command.
3159 If you exit @value{GDBN} while you have an attached process, you detach
3160 that process. If you use the @code{run} command, you kill that process.
3161 By default, @value{GDBN} asks for confirmation if you try to do either of these
3162 things; you can control whether or not you need to confirm by using the
3163 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3167 @section Killing the Child Process
3172 Kill the child process in which your program is running under @value{GDBN}.
3175 This command is useful if you wish to debug a core dump instead of a
3176 running process. @value{GDBN} ignores any core dump file while your program
3179 On some operating systems, a program cannot be executed outside @value{GDBN}
3180 while you have breakpoints set on it inside @value{GDBN}. You can use the
3181 @code{kill} command in this situation to permit running your program
3182 outside the debugger.
3184 The @code{kill} command is also useful if you wish to recompile and
3185 relink your program, since on many systems it is impossible to modify an
3186 executable file while it is running in a process. In this case, when you
3187 next type @code{run}, @value{GDBN} notices that the file has changed, and
3188 reads the symbol table again (while trying to preserve your current
3189 breakpoint settings).
3191 @node Inferiors Connections and Programs
3192 @section Debugging Multiple Inferiors Connections and Programs
3194 @value{GDBN} lets you run and debug multiple programs in a single
3195 session. In addition, @value{GDBN} on some systems may let you run
3196 several programs simultaneously (otherwise you have to exit from one
3197 before starting another). On some systems @value{GDBN} may even let
3198 you debug several programs simultaneously on different remote systems.
3199 In the most general case, you can have multiple threads of execution
3200 in each of multiple processes, launched from multiple executables,
3201 running on different machines.
3204 @value{GDBN} represents the state of each program execution with an
3205 object called an @dfn{inferior}. An inferior typically corresponds to
3206 a process, but is more general and applies also to targets that do not
3207 have processes. Inferiors may be created before a process runs, and
3208 may be retained after a process exits. Inferiors have unique
3209 identifiers that are different from process ids. Usually each
3210 inferior will also have its own distinct address space, although some
3211 embedded targets may have several inferiors running in different parts
3212 of a single address space. Each inferior may in turn have multiple
3213 threads running in it.
3215 To find out what inferiors exist at any moment, use @w{@code{info
3219 @kindex info inferiors [ @var{id}@dots{} ]
3220 @item info inferiors
3221 Print a list of all inferiors currently being managed by @value{GDBN}.
3222 By default all inferiors are printed, but the argument @var{id}@dots{}
3223 -- a space separated list of inferior numbers -- can be used to limit
3224 the display to just the requested inferiors.
3226 @value{GDBN} displays for each inferior (in this order):
3230 the inferior number assigned by @value{GDBN}
3233 the target system's inferior identifier
3236 the target connection the inferior is bound to, including the unique
3237 connection number assigned by @value{GDBN}, and the protocol used by
3241 the name of the executable the inferior is running.
3246 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3247 indicates the current inferior.
3251 @c end table here to get a little more width for example
3254 (@value{GDBP}) info inferiors
3255 Num Description Connection Executable
3256 * 1 process 3401 1 (native) goodbye
3257 2 process 2307 2 (extended-remote host:10000) hello
3260 To get informations about the current inferior, use @code{inferior}:
3265 Shows information about the current inferior.
3269 @c end table here to get a little more width for example
3272 (@value{GDBP}) inferior
3273 [Current inferior is 1 [process 3401] (helloworld)]
3276 To find out what open target connections exist at any moment, use
3277 @w{@code{info connections}}:
3280 @kindex info connections [ @var{id}@dots{} ]
3281 @item info connections
3282 Print a list of all open target connections currently being managed by
3283 @value{GDBN}. By default all connections are printed, but the
3284 argument @var{id}@dots{} -- a space separated list of connections
3285 numbers -- can be used to limit the display to just the requested
3288 @value{GDBN} displays for each connection (in this order):
3292 the connection number assigned by @value{GDBN}.
3295 the protocol used by the connection.
3298 a textual description of the protocol used by the connection.
3303 An asterisk @samp{*} preceding the connection number indicates the
3304 connection of the current inferior.
3308 @c end table here to get a little more width for example
3311 (@value{GDBP}) info connections
3312 Num What Description
3313 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3314 2 native Native process
3315 3 core Local core dump file
3318 To switch focus between inferiors, use the @code{inferior} command:
3321 @kindex inferior @var{infno}
3322 @item inferior @var{infno}
3323 Make inferior number @var{infno} the current inferior. The argument
3324 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3325 in the first field of the @samp{info inferiors} display.
3328 @vindex $_inferior@r{, convenience variable}
3329 The debugger convenience variable @samp{$_inferior} contains the
3330 number of the current inferior. You may find this useful in writing
3331 breakpoint conditional expressions, command scripts, and so forth.
3332 @xref{Convenience Vars,, Convenience Variables}, for general
3333 information on convenience variables.
3335 You can get multiple executables into a debugging session via the
3336 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3337 systems @value{GDBN} can add inferiors to the debug session
3338 automatically by following calls to @code{fork} and @code{exec}. To
3339 remove inferiors from the debugging session use the
3340 @w{@code{remove-inferiors}} command.
3343 @anchor{add_inferior_cli}
3344 @kindex add-inferior
3345 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3346 Adds @var{n} inferiors to be run using @var{executable} as the
3347 executable; @var{n} defaults to 1. If no executable is specified,
3348 the inferiors begins empty, with no program. You can still assign or
3349 change the program assigned to the inferior at any time by using the
3350 @code{file} command with the executable name as its argument.
3352 By default, the new inferior begins connected to the same target
3353 connection as the current inferior. For example, if the current
3354 inferior was connected to @code{gdbserver} with @code{target remote},
3355 then the new inferior will be connected to the same @code{gdbserver}
3356 instance. The @samp{-no-connection} option starts the new inferior
3357 with no connection yet. You can then for example use the @code{target
3358 remote} command to connect to some other @code{gdbserver} instance,
3359 use @code{run} to spawn a local program, etc.
3361 @kindex clone-inferior
3362 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3363 Adds @var{n} inferiors ready to execute the same program as inferior
3364 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3365 number of the current inferior. This command copies the values of the
3366 @var{args}, @w{@var{inferior-tty}} and @var{cwd} properties from the
3367 current inferior to the new one. It also propagates changes the user
3368 made to environment variables using the @w{@code{set environment}} and
3369 @w{@code{unset environment}} commands. This is a convenient command
3370 when you want to run another instance of the inferior you are debugging.
3373 (@value{GDBP}) info inferiors
3374 Num Description Connection Executable
3375 * 1 process 29964 1 (native) helloworld
3376 (@value{GDBP}) clone-inferior
3379 (@value{GDBP}) info inferiors
3380 Num Description Connection Executable
3381 * 1 process 29964 1 (native) helloworld
3382 2 <null> 1 (native) helloworld
3385 You can now simply switch focus to inferior 2 and run it.
3387 @kindex remove-inferiors
3388 @item remove-inferiors @var{infno}@dots{}
3389 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3390 possible to remove an inferior that is running with this command. For
3391 those, use the @code{kill} or @code{detach} command first.
3395 To quit debugging one of the running inferiors that is not the current
3396 inferior, you can either detach from it by using the @w{@code{detach
3397 inferior}} command (allowing it to run independently), or kill it
3398 using the @w{@code{kill inferiors}} command:
3401 @kindex detach inferiors @var{infno}@dots{}
3402 @item detach inferior @var{infno}@dots{}
3403 Detach from the inferior or inferiors identified by @value{GDBN}
3404 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3405 still stays on the list of inferiors shown by @code{info inferiors},
3406 but its Description will show @samp{<null>}.
3408 @kindex kill inferiors @var{infno}@dots{}
3409 @item kill inferiors @var{infno}@dots{}
3410 Kill the inferior or inferiors identified by @value{GDBN} inferior
3411 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3412 stays on the list of inferiors shown by @code{info inferiors}, but its
3413 Description will show @samp{<null>}.
3416 After the successful completion of a command such as @code{detach},
3417 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3418 a normal process exit, the inferior is still valid and listed with
3419 @code{info inferiors}, ready to be restarted.
3422 To be notified when inferiors are started or exit under @value{GDBN}'s
3423 control use @w{@code{set print inferior-events}}:
3426 @kindex set print inferior-events
3427 @cindex print messages on inferior start and exit
3428 @item set print inferior-events
3429 @itemx set print inferior-events on
3430 @itemx set print inferior-events off
3431 The @code{set print inferior-events} command allows you to enable or
3432 disable printing of messages when @value{GDBN} notices that new
3433 inferiors have started or that inferiors have exited or have been
3434 detached. By default, these messages will be printed.
3436 @kindex show print inferior-events
3437 @item show print inferior-events
3438 Show whether messages will be printed when @value{GDBN} detects that
3439 inferiors have started, exited or have been detached.
3442 Many commands will work the same with multiple programs as with a
3443 single program: e.g., @code{print myglobal} will simply display the
3444 value of @code{myglobal} in the current inferior.
3447 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3448 get more info about the relationship of inferiors, programs, address
3449 spaces in a debug session. You can do that with the @w{@code{maint
3450 info program-spaces}} command.
3453 @kindex maint info program-spaces
3454 @item maint info program-spaces
3455 Print a list of all program spaces currently being managed by
3458 @value{GDBN} displays for each program space (in this order):
3462 the program space number assigned by @value{GDBN}
3465 the name of the executable loaded into the program space, with e.g.,
3466 the @code{file} command.
3469 the name of the core file loaded into the program space, with e.g.,
3470 the @code{core-file} command.
3475 An asterisk @samp{*} preceding the @value{GDBN} program space number
3476 indicates the current program space.
3478 In addition, below each program space line, @value{GDBN} prints extra
3479 information that isn't suitable to display in tabular form. For
3480 example, the list of inferiors bound to the program space.
3483 (@value{GDBP}) maint info program-spaces
3484 Id Executable Core File
3487 Bound inferiors: ID 1 (process 21561)
3490 Here we can see that no inferior is running the program @code{hello},
3491 while @code{process 21561} is running the program @code{goodbye}. On
3492 some targets, it is possible that multiple inferiors are bound to the
3493 same program space. The most common example is that of debugging both
3494 the parent and child processes of a @code{vfork} call. For example,
3497 (@value{GDBP}) maint info program-spaces
3498 Id Executable Core File
3500 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3503 Here, both inferior 2 and inferior 1 are running in the same program
3504 space as a result of inferior 1 having executed a @code{vfork} call.
3508 @section Debugging Programs with Multiple Threads
3510 @cindex threads of execution
3511 @cindex multiple threads
3512 @cindex switching threads
3513 In some operating systems, such as GNU/Linux and Solaris, a single program
3514 may have more than one @dfn{thread} of execution. The precise semantics
3515 of threads differ from one operating system to another, but in general
3516 the threads of a single program are akin to multiple processes---except
3517 that they share one address space (that is, they can all examine and
3518 modify the same variables). On the other hand, each thread has its own
3519 registers and execution stack, and perhaps private memory.
3521 @value{GDBN} provides these facilities for debugging multi-thread
3525 @item automatic notification of new threads
3526 @item @samp{thread @var{thread-id}}, a command to switch among threads
3527 @item @samp{info threads}, a command to inquire about existing threads
3528 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3529 a command to apply a command to a list of threads
3530 @item thread-specific breakpoints
3531 @item @samp{set print thread-events}, which controls printing of
3532 messages on thread start and exit.
3533 @item @samp{set libthread-db-search-path @var{path}}, which lets
3534 the user specify which @code{libthread_db} to use if the default choice
3535 isn't compatible with the program.
3538 @cindex focus of debugging
3539 @cindex current thread
3540 The @value{GDBN} thread debugging facility allows you to observe all
3541 threads while your program runs---but whenever @value{GDBN} takes
3542 control, one thread in particular is always the focus of debugging.
3543 This thread is called the @dfn{current thread}. Debugging commands show
3544 program information from the perspective of the current thread.
3546 @cindex @code{New} @var{systag} message
3547 @cindex thread identifier (system)
3548 @c FIXME-implementors!! It would be more helpful if the [New...] message
3549 @c included GDB's numeric thread handle, so you could just go to that
3550 @c thread without first checking `info threads'.
3551 Whenever @value{GDBN} detects a new thread in your program, it displays
3552 the target system's identification for the thread with a message in the
3553 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3554 whose form varies depending on the particular system. For example, on
3555 @sc{gnu}/Linux, you might see
3558 [New Thread 0x41e02940 (LWP 25582)]
3562 when @value{GDBN} notices a new thread. In contrast, on other systems,
3563 the @var{systag} is simply something like @samp{process 368}, with no
3566 @c FIXME!! (1) Does the [New...] message appear even for the very first
3567 @c thread of a program, or does it only appear for the
3568 @c second---i.e.@: when it becomes obvious we have a multithread
3570 @c (2) *Is* there necessarily a first thread always? Or do some
3571 @c multithread systems permit starting a program with multiple
3572 @c threads ab initio?
3574 @anchor{thread numbers}
3575 @cindex thread number, per inferior
3576 @cindex thread identifier (GDB)
3577 For debugging purposes, @value{GDBN} associates its own thread number
3578 ---always a single integer---with each thread of an inferior. This
3579 number is unique between all threads of an inferior, but not unique
3580 between threads of different inferiors.
3582 @cindex qualified thread ID
3583 You can refer to a given thread in an inferior using the qualified
3584 @var{inferior-num}.@var{thread-num} syntax, also known as
3585 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3586 number and @var{thread-num} being the thread number of the given
3587 inferior. For example, thread @code{2.3} refers to thread number 3 of
3588 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3589 then @value{GDBN} infers you're referring to a thread of the current
3592 Until you create a second inferior, @value{GDBN} does not show the
3593 @var{inferior-num} part of thread IDs, even though you can always use
3594 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3595 of inferior 1, the initial inferior.
3597 @anchor{thread ID lists}
3598 @cindex thread ID lists
3599 Some commands accept a space-separated @dfn{thread ID list} as
3600 argument. A list element can be:
3604 A thread ID as shown in the first field of the @samp{info threads}
3605 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3609 A range of thread numbers, again with or without an inferior
3610 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3611 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3614 All threads of an inferior, specified with a star wildcard, with or
3615 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3616 @samp{1.*}) or @code{*}. The former refers to all threads of the
3617 given inferior, and the latter form without an inferior qualifier
3618 refers to all threads of the current inferior.
3622 For example, if the current inferior is 1, and inferior 7 has one
3623 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3624 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3625 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3626 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3630 @anchor{global thread numbers}
3631 @cindex global thread number
3632 @cindex global thread identifier (GDB)
3633 In addition to a @emph{per-inferior} number, each thread is also
3634 assigned a unique @emph{global} number, also known as @dfn{global
3635 thread ID}, a single integer. Unlike the thread number component of
3636 the thread ID, no two threads have the same global ID, even when
3637 you're debugging multiple inferiors.
3639 From @value{GDBN}'s perspective, a process always has at least one
3640 thread. In other words, @value{GDBN} assigns a thread number to the
3641 program's ``main thread'' even if the program is not multi-threaded.
3643 @vindex $_thread@r{, convenience variable}
3644 @vindex $_gthread@r{, convenience variable}
3645 The debugger convenience variables @samp{$_thread} and
3646 @samp{$_gthread} contain, respectively, the per-inferior thread number
3647 and the global thread number of the current thread. You may find this
3648 useful in writing breakpoint conditional expressions, command scripts,
3649 and so forth. The convenience variable @samp{$_inferior_thread_count}
3650 contains the number of live threads in the current inferior.
3651 @xref{Convenience Vars,, Convenience Variables}, for general
3652 information on convenience variables.
3654 When running in non-stop mode (@pxref{Non-Stop Mode}), where new
3655 threads can be created, and existing threads exit, at any time,
3656 @samp{$_inferior_thread_count} could return a different value each
3657 time it is evaluated.
3659 If @value{GDBN} detects the program is multi-threaded, it augments the
3660 usual message about stopping at a breakpoint with the ID and name of
3661 the thread that hit the breakpoint.
3664 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3667 Likewise when the program receives a signal:
3670 Thread 1 "main" received signal SIGINT, Interrupt.
3674 @anchor{info_threads}
3675 @kindex info threads
3676 @item info threads @r{[}@var{thread-id-list}@r{]}
3678 Display information about one or more threads. With no arguments
3679 displays information about all threads. You can specify the list of
3680 threads that you want to display using the thread ID list syntax
3681 (@pxref{thread ID lists}).
3683 @value{GDBN} displays for each thread (in this order):
3687 the per-inferior thread number assigned by @value{GDBN}
3690 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3691 option was specified
3694 the target system's thread identifier (@var{systag})
3697 the thread's name, if one is known. A thread can either be named by
3698 the user (see @code{thread name}, below), or, in some cases, by the
3702 the current stack frame summary for that thread
3706 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3707 indicates the current thread.
3711 @c end table here to get a little more width for example
3714 (@value{GDBP}) info threads
3716 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3717 2 process 35 thread 23 0x34e5 in sigpause ()
3718 3 process 35 thread 27 0x34e5 in sigpause ()
3722 If you're debugging multiple inferiors, @value{GDBN} displays thread
3723 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3724 Otherwise, only @var{thread-num} is shown.
3726 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3727 indicating each thread's global thread ID:
3730 (@value{GDBP}) info threads
3731 Id GId Target Id Frame
3732 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3733 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3734 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3735 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3738 On Solaris, you can display more information about user threads with a
3739 Solaris-specific command:
3742 @item maint info sol-threads
3743 @kindex maint info sol-threads
3744 @cindex thread info (Solaris)
3745 Display info on Solaris user threads.
3749 @kindex thread @var{thread-id}
3750 @item thread @var{thread-id}
3751 Make thread ID @var{thread-id} the current thread. The command
3752 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3753 the first field of the @samp{info threads} display, with or without an
3754 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3756 @value{GDBN} responds by displaying the system identifier of the
3757 thread you selected, and its current stack frame summary:
3760 (@value{GDBP}) thread 2
3761 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3762 #0 some_function (ignore=0x0) at example.c:8
3763 8 printf ("hello\n");
3767 As with the @samp{[New @dots{}]} message, the form of the text after
3768 @samp{Switching to} depends on your system's conventions for identifying
3771 @anchor{thread apply all}
3772 @kindex thread apply
3773 @cindex apply command to several threads
3774 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3775 The @code{thread apply} command allows you to apply the named
3776 @var{command} to one or more threads. Specify the threads that you
3777 want affected using the thread ID list syntax (@pxref{thread ID
3778 lists}), or specify @code{all} to apply to all threads. To apply a
3779 command to all threads in descending order, type @kbd{thread apply all
3780 @var{command}}. To apply a command to all threads in ascending order,
3781 type @kbd{thread apply all -ascending @var{command}}.
3783 The @var{flag} arguments control what output to produce and how to handle
3784 errors raised when applying @var{command} to a thread. @var{flag}
3785 must start with a @code{-} directly followed by one letter in
3786 @code{qcs}. If several flags are provided, they must be given
3787 individually, such as @code{-c -q}.
3789 By default, @value{GDBN} displays some thread information before the
3790 output produced by @var{command}, and an error raised during the
3791 execution of a @var{command} will abort @code{thread apply}. The
3792 following flags can be used to fine-tune this behavior:
3796 The flag @code{-c}, which stands for @samp{continue}, causes any
3797 errors in @var{command} to be displayed, and the execution of
3798 @code{thread apply} then continues.
3800 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3801 or empty output produced by a @var{command} to be silently ignored.
3802 That is, the execution continues, but the thread information and errors
3805 The flag @code{-q} (@samp{quiet}) disables printing the thread
3809 Flags @code{-c} and @code{-s} cannot be used together.
3812 @cindex apply command to all threads (ignoring errors and empty output)
3813 @item taas [@var{option}]@dots{} @var{command}
3814 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3815 Applies @var{command} on all threads, ignoring errors and empty output.
3817 The @code{taas} command accepts the same options as the @code{thread
3818 apply all} command. @xref{thread apply all}.
3821 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3822 @item tfaas [@var{option}]@dots{} @var{command}
3823 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3824 Applies @var{command} on all frames of all threads, ignoring errors
3825 and empty output. Note that the flag @code{-s} is specified twice:
3826 The first @code{-s} ensures that @code{thread apply} only shows the thread
3827 information of the threads for which @code{frame apply} produces
3828 some output. The second @code{-s} is needed to ensure that @code{frame
3829 apply} shows the frame information of a frame only if the
3830 @var{command} successfully produced some output.
3832 It can for example be used to print a local variable or a function
3833 argument without knowing the thread or frame where this variable or argument
3836 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3839 The @code{tfaas} command accepts the same options as the @code{frame
3840 apply} command. @xref{Frame Apply,,frame apply}.
3843 @cindex name a thread
3844 @item thread name [@var{name}]
3845 This command assigns a name to the current thread. If no argument is
3846 given, any existing user-specified name is removed. The thread name
3847 appears in the @samp{info threads} display.
3849 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3850 determine the name of the thread as given by the OS. On these
3851 systems, a name specified with @samp{thread name} will override the
3852 system-give name, and removing the user-specified name will cause
3853 @value{GDBN} to once again display the system-specified name.
3856 @cindex search for a thread
3857 @item thread find [@var{regexp}]
3858 Search for and display thread ids whose name or @var{systag}
3859 matches the supplied regular expression.
3861 As well as being the complement to the @samp{thread name} command,
3862 this command also allows you to identify a thread by its target
3863 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3867 (@value{GDBP}) thread find 26688
3868 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3869 (@value{GDBP}) info thread 4
3871 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3874 @kindex set print thread-events
3875 @cindex print messages on thread start and exit
3876 @item set print thread-events
3877 @itemx set print thread-events on
3878 @itemx set print thread-events off
3879 The @code{set print thread-events} command allows you to enable or
3880 disable printing of messages when @value{GDBN} notices that new threads have
3881 started or that threads have exited. By default, these messages will
3882 be printed if detection of these events is supported by the target.
3883 Note that these messages cannot be disabled on all targets.
3885 @kindex show print thread-events
3886 @item show print thread-events
3887 Show whether messages will be printed when @value{GDBN} detects that threads
3888 have started and exited.
3891 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3892 more information about how @value{GDBN} behaves when you stop and start
3893 programs with multiple threads.
3895 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3896 watchpoints in programs with multiple threads.
3898 @anchor{set libthread-db-search-path}
3900 @kindex set libthread-db-search-path
3901 @cindex search path for @code{libthread_db}
3902 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3903 If this variable is set, @var{path} is a colon-separated list of
3904 directories @value{GDBN} will use to search for @code{libthread_db}.
3905 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3906 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3907 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3910 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3911 @code{libthread_db} library to obtain information about threads in the
3912 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3913 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3914 specific thread debugging library loading is enabled
3915 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3917 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3918 refers to the default system directories that are
3919 normally searched for loading shared libraries. The @samp{$sdir} entry
3920 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3921 (@pxref{libthread_db.so.1 file}).
3923 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3924 refers to the directory from which @code{libpthread}
3925 was loaded in the inferior process.
3927 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3928 @value{GDBN} attempts to initialize it with the current inferior process.
3929 If this initialization fails (which could happen because of a version
3930 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3931 will unload @code{libthread_db}, and continue with the next directory.
3932 If none of @code{libthread_db} libraries initialize successfully,
3933 @value{GDBN} will issue a warning and thread debugging will be disabled.
3935 Setting @code{libthread-db-search-path} is currently implemented
3936 only on some platforms.
3938 @kindex show libthread-db-search-path
3939 @item show libthread-db-search-path
3940 Display current libthread_db search path.
3942 @kindex set debug libthread-db
3943 @kindex show debug libthread-db
3944 @cindex debugging @code{libthread_db}
3945 @item set debug libthread-db
3946 @itemx show debug libthread-db
3947 Turns on or off display of @code{libthread_db}-related events.
3948 Use @code{1} to enable, @code{0} to disable.
3950 @kindex set debug threads
3951 @kindex show debug threads
3952 @cindex debugging @code{threads}
3953 @item set debug threads @r{[}on@r{|}off@r{]}
3954 @itemx show debug threads
3955 When @samp{on} @value{GDBN} will print additional messages when
3956 threads are created and deleted.
3960 @section Debugging Forks
3962 @cindex fork, debugging programs which call
3963 @cindex multiple processes
3964 @cindex processes, multiple
3965 On most systems, @value{GDBN} has no special support for debugging
3966 programs which create additional processes using the @code{fork}
3967 function. When a program forks, @value{GDBN} will continue to debug the
3968 parent process and the child process will run unimpeded. If you have
3969 set a breakpoint in any code which the child then executes, the child
3970 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3971 will cause it to terminate.
3973 However, if you want to debug the child process there is a workaround
3974 which isn't too painful. Put a call to @code{sleep} in the code which
3975 the child process executes after the fork. It may be useful to sleep
3976 only if a certain environment variable is set, or a certain file exists,
3977 so that the delay need not occur when you don't want to run @value{GDBN}
3978 on the child. While the child is sleeping, use the @code{ps} program to
3979 get its process ID. Then tell @value{GDBN} (a new invocation of
3980 @value{GDBN} if you are also debugging the parent process) to attach to
3981 the child process (@pxref{Attach}). From that point on you can debug
3982 the child process just like any other process which you attached to.
3984 On some systems, @value{GDBN} provides support for debugging programs
3985 that create additional processes using the @code{fork} or @code{vfork}
3986 functions. On @sc{gnu}/Linux platforms, this feature is supported
3987 with kernel version 2.5.46 and later.
3989 The fork debugging commands are supported in native mode and when
3990 connected to @code{gdbserver} in either @code{target remote} mode or
3991 @code{target extended-remote} mode.
3993 By default, when a program forks, @value{GDBN} will continue to debug
3994 the parent process and the child process will run unimpeded.
3996 If you want to follow the child process instead of the parent process,
3997 use the command @w{@code{set follow-fork-mode}}.
4000 @kindex set follow-fork-mode
4001 @item set follow-fork-mode @var{mode}
4002 Set the debugger response to a program call of @code{fork} or
4003 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
4004 process. The @var{mode} argument can be:
4008 The original process is debugged after a fork. The child process runs
4009 unimpeded. This is the default.
4012 The new process is debugged after a fork. The parent process runs
4017 @kindex show follow-fork-mode
4018 @item show follow-fork-mode
4019 Display the current debugger response to a @code{fork} or @code{vfork} call.
4022 @cindex debugging multiple processes
4023 On Linux, if you want to debug both the parent and child processes, use the
4024 command @w{@code{set detach-on-fork}}.
4027 @kindex set detach-on-fork
4028 @item set detach-on-fork @var{mode}
4029 Tells gdb whether to detach one of the processes after a fork, or
4030 retain debugger control over them both.
4034 The child process (or parent process, depending on the value of
4035 @code{follow-fork-mode}) will be detached and allowed to run
4036 independently. This is the default.
4039 Both processes will be held under the control of @value{GDBN}.
4040 One process (child or parent, depending on the value of
4041 @code{follow-fork-mode}) is debugged as usual, while the other
4046 @kindex show detach-on-fork
4047 @item show detach-on-fork
4048 Show whether detach-on-fork mode is on/off.
4051 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
4052 will retain control of all forked processes (including nested forks).
4053 You can list the forked processes under the control of @value{GDBN} by
4054 using the @w{@code{info inferiors}} command, and switch from one fork
4055 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4056 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4058 To quit debugging one of the forked processes, you can either detach
4059 from it by using the @w{@code{detach inferiors}} command (allowing it
4060 to run independently), or kill it using the @w{@code{kill inferiors}}
4061 command. @xref{Inferiors Connections and Programs, ,Debugging
4062 Multiple Inferiors Connections and Programs}.
4064 If you ask to debug a child process and a @code{vfork} is followed by an
4065 @code{exec}, @value{GDBN} executes the new target up to the first
4066 breakpoint in the new target. If you have a breakpoint set on
4067 @code{main} in your original program, the breakpoint will also be set on
4068 the child process's @code{main}.
4070 On some systems, when a child process is spawned by @code{vfork}, you
4071 cannot debug the child or parent until an @code{exec} call completes.
4073 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4074 call executes, the new target restarts. To restart the parent
4075 process, use the @code{file} command with the parent executable name
4076 as its argument. By default, after an @code{exec} call executes,
4077 @value{GDBN} discards the symbols of the previous executable image.
4078 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4082 @kindex set follow-exec-mode
4083 @item set follow-exec-mode @var{mode}
4085 Set debugger response to a program call of @code{exec}. An
4086 @code{exec} call replaces the program image of a process.
4088 @code{follow-exec-mode} can be:
4092 @value{GDBN} creates a new inferior and rebinds the process to this
4093 new inferior. The program the process was running before the
4094 @code{exec} call can be restarted afterwards by restarting the
4100 (@value{GDBP}) info inferiors
4101 (@value{GDBP}) info inferior
4102 Id Description Executable
4105 process 12020 is executing new program: prog2
4106 Program exited normally.
4107 (@value{GDBP}) info inferiors
4108 Id Description Executable
4114 @value{GDBN} keeps the process bound to the same inferior. The new
4115 executable image replaces the previous executable loaded in the
4116 inferior. Restarting the inferior after the @code{exec} call, with
4117 e.g., the @code{run} command, restarts the executable the process was
4118 running after the @code{exec} call. This is the default mode.
4123 (@value{GDBP}) info inferiors
4124 Id Description Executable
4127 process 12020 is executing new program: prog2
4128 Program exited normally.
4129 (@value{GDBP}) info inferiors
4130 Id Description Executable
4137 @code{follow-exec-mode} is supported in native mode and
4138 @code{target extended-remote} mode.
4140 You can use the @code{catch} command to make @value{GDBN} stop whenever
4141 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4142 Catchpoints, ,Setting Catchpoints}.
4144 @node Checkpoint/Restart
4145 @section Setting a @emph{Bookmark} to Return to Later
4150 @cindex snapshot of a process
4151 @cindex rewind program state
4153 On certain operating systems@footnote{Currently, only
4154 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4155 program's state, called a @dfn{checkpoint}, and come back to it
4158 Returning to a checkpoint effectively undoes everything that has
4159 happened in the program since the @code{checkpoint} was saved. This
4160 includes changes in memory, registers, and even (within some limits)
4161 system state. Effectively, it is like going back in time to the
4162 moment when the checkpoint was saved.
4164 Thus, if you're stepping thru a program and you think you're
4165 getting close to the point where things go wrong, you can save
4166 a checkpoint. Then, if you accidentally go too far and miss
4167 the critical statement, instead of having to restart your program
4168 from the beginning, you can just go back to the checkpoint and
4169 start again from there.
4171 This can be especially useful if it takes a lot of time or
4172 steps to reach the point where you think the bug occurs.
4174 To use the @code{checkpoint}/@code{restart} method of debugging:
4179 Save a snapshot of the debugged program's current execution state.
4180 The @code{checkpoint} command takes no arguments, but each checkpoint
4181 is assigned a small integer id, similar to a breakpoint id.
4183 @kindex info checkpoints
4184 @item info checkpoints
4185 List the checkpoints that have been saved in the current debugging
4186 session. For each checkpoint, the following information will be
4193 @item Source line, or label
4196 @kindex restart @var{checkpoint-id}
4197 @item restart @var{checkpoint-id}
4198 Restore the program state that was saved as checkpoint number
4199 @var{checkpoint-id}. All program variables, registers, stack frames
4200 etc.@: will be returned to the values that they had when the checkpoint
4201 was saved. In essence, gdb will ``wind back the clock'' to the point
4202 in time when the checkpoint was saved.
4204 Note that breakpoints, @value{GDBN} variables, command history etc.
4205 are not affected by restoring a checkpoint. In general, a checkpoint
4206 only restores things that reside in the program being debugged, not in
4209 @kindex delete checkpoint @var{checkpoint-id}
4210 @item delete checkpoint @var{checkpoint-id}
4211 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4215 Returning to a previously saved checkpoint will restore the user state
4216 of the program being debugged, plus a significant subset of the system
4217 (OS) state, including file pointers. It won't ``un-write'' data from
4218 a file, but it will rewind the file pointer to the previous location,
4219 so that the previously written data can be overwritten. For files
4220 opened in read mode, the pointer will also be restored so that the
4221 previously read data can be read again.
4223 Of course, characters that have been sent to a printer (or other
4224 external device) cannot be ``snatched back'', and characters received
4225 from eg.@: a serial device can be removed from internal program buffers,
4226 but they cannot be ``pushed back'' into the serial pipeline, ready to
4227 be received again. Similarly, the actual contents of files that have
4228 been changed cannot be restored (at this time).
4230 However, within those constraints, you actually can ``rewind'' your
4231 program to a previously saved point in time, and begin debugging it
4232 again --- and you can change the course of events so as to debug a
4233 different execution path this time.
4235 @cindex checkpoints and process id
4236 Finally, there is one bit of internal program state that will be
4237 different when you return to a checkpoint --- the program's process
4238 id. Each checkpoint will have a unique process id (or @var{pid}),
4239 and each will be different from the program's original @var{pid}.
4240 If your program has saved a local copy of its process id, this could
4241 potentially pose a problem.
4243 @subsection A Non-obvious Benefit of Using Checkpoints
4245 On some systems such as @sc{gnu}/Linux, address space randomization
4246 is performed on new processes for security reasons. This makes it
4247 difficult or impossible to set a breakpoint, or watchpoint, on an
4248 absolute address if you have to restart the program, since the
4249 absolute location of a symbol will change from one execution to the
4252 A checkpoint, however, is an @emph{identical} copy of a process.
4253 Therefore if you create a checkpoint at (eg.@:) the start of main,
4254 and simply return to that checkpoint instead of restarting the
4255 process, you can avoid the effects of address randomization and
4256 your symbols will all stay in the same place.
4259 @chapter Stopping and Continuing
4261 The principal purposes of using a debugger are so that you can stop your
4262 program before it terminates; or so that, if your program runs into
4263 trouble, you can investigate and find out why.
4265 Inside @value{GDBN}, your program may stop for any of several reasons,
4266 such as a signal, a breakpoint, or reaching a new line after a
4267 @value{GDBN} command such as @code{step}. You may then examine and
4268 change variables, set new breakpoints or remove old ones, and then
4269 continue execution. Usually, the messages shown by @value{GDBN} provide
4270 ample explanation of the status of your program---but you can also
4271 explicitly request this information at any time.
4274 @kindex info program
4276 Display information about the status of your program: whether it is
4277 running or not, what process it is, and why it stopped.
4281 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4282 * Continuing and Stepping:: Resuming execution
4283 * Skipping Over Functions and Files::
4284 Skipping over functions and files
4286 * Thread Stops:: Stopping and starting multi-thread programs
4290 @section Breakpoints, Watchpoints, and Catchpoints
4293 A @dfn{breakpoint} makes your program stop whenever a certain point in
4294 the program is reached. For each breakpoint, you can add conditions to
4295 control in finer detail whether your program stops. You can set
4296 breakpoints with the @code{break} command and its variants (@pxref{Set
4297 Breaks, ,Setting Breakpoints}), to specify the place where your program
4298 should stop by line number, function name or exact address in the
4301 On some systems, you can set breakpoints in shared libraries before
4302 the executable is run.
4305 @cindex data breakpoints
4306 @cindex memory tracing
4307 @cindex breakpoint on memory address
4308 @cindex breakpoint on variable modification
4309 A @dfn{watchpoint} is a special breakpoint that stops your program
4310 when the value of an expression changes. The expression may be a value
4311 of a variable, or it could involve values of one or more variables
4312 combined by operators, such as @samp{a + b}. This is sometimes called
4313 @dfn{data breakpoints}. You must use a different command to set
4314 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4315 from that, you can manage a watchpoint like any other breakpoint: you
4316 enable, disable, and delete both breakpoints and watchpoints using the
4319 You can arrange to have values from your program displayed automatically
4320 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4324 @cindex breakpoint on events
4325 A @dfn{catchpoint} is another special breakpoint that stops your program
4326 when a certain kind of event occurs, such as the throwing of a C@t{++}
4327 exception or the loading of a library. As with watchpoints, you use a
4328 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4329 Catchpoints}), but aside from that, you can manage a catchpoint like any
4330 other breakpoint. (To stop when your program receives a signal, use the
4331 @code{handle} command; see @ref{Signals, ,Signals}.)
4333 @cindex breakpoint numbers
4334 @cindex numbers for breakpoints
4335 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4336 catchpoint when you create it; these numbers are successive integers
4337 starting with one. In many of the commands for controlling various
4338 features of breakpoints you use the breakpoint number to say which
4339 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4340 @dfn{disabled}; if disabled, it has no effect on your program until you
4343 @cindex breakpoint ranges
4344 @cindex breakpoint lists
4345 @cindex ranges of breakpoints
4346 @cindex lists of breakpoints
4347 Some @value{GDBN} commands accept a space-separated list of breakpoints
4348 on which to operate. A list element can be either a single breakpoint number,
4349 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4350 When a breakpoint list is given to a command, all breakpoints in that list
4354 * Set Breaks:: Setting breakpoints
4355 * Set Watchpoints:: Setting watchpoints
4356 * Set Catchpoints:: Setting catchpoints
4357 * Delete Breaks:: Deleting breakpoints
4358 * Disabling:: Disabling breakpoints
4359 * Conditions:: Break conditions
4360 * Break Commands:: Breakpoint command lists
4361 * Dynamic Printf:: Dynamic printf
4362 * Save Breakpoints:: How to save breakpoints in a file
4363 * Static Probe Points:: Listing static probe points
4364 * Error in Breakpoints:: ``Cannot insert breakpoints''
4365 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4369 @subsection Setting Breakpoints
4371 @c FIXME LMB what does GDB do if no code on line of breakpt?
4372 @c consider in particular declaration with/without initialization.
4374 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4377 @kindex b @r{(@code{break})}
4378 @vindex $bpnum@r{, convenience variable}
4379 @cindex latest breakpoint
4380 Breakpoints are set with the @code{break} command (abbreviated
4381 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4382 number of the breakpoint you've set most recently:
4385 Breakpoint 1 at 0x11c6: file zeoes.c, line 24.
4390 A breakpoint may be mapped to multiple code locations for example with
4391 inlined functions, Ada generics, C@t{++} templates or overloaded function names.
4392 @value{GDBN} then indicates the number of code locations in the breakpoint
4396 Breakpoint 2 at 0x1179: some_func. (3 locations)
4402 @vindex $_hit_bpnum@r{, convenience variable}
4403 @vindex $_hit_locno@r{, convenience variable}
4404 When your program stops on a breakpoint, the convenience variables
4405 @samp{$_hit_bpnum} and @samp{$_hit_locno} are respectively set to the number of
4406 the encountered breakpoint and the number of the breakpoint's code location:
4408 Thread 1 "zeoes" hit Breakpoint 2.1, some_func () at zeoes.c:8
4409 8 printf("some func\n");
4417 Note that @samp{$_hit_bpnum} and @samp{$bpnum} are not equivalent:
4418 @samp{$_hit_bpnum} is set to the breakpoint number @b{last hit}, while
4419 @samp{$bpnum} is set to the breakpoint number @b{last set}.
4422 If the encountered breakpoint has only one code location, @samp{$_hit_locno}
4425 Breakpoint 1, main (argc=1, argv=0x7fffffffe018) at zeoes.c:24
4434 The @samp{$_hit_bpnum} and @samp{$_hit_locno} variables can typically be used
4435 in a breakpoint command list.
4436 (@pxref{Break Commands, ,Breakpoint Command Lists}). For example, as
4437 part of the breakpoint command list, you can disable completely the
4438 encountered breakpoint using @kbd{disable $_hit_bpnum} or disable the
4439 specific encountered breakpoint location using
4440 @kbd{disable $_hit_bpnum.$_hit_locno}.
4441 If a breakpoint has only one location, @samp{$_hit_locno} is set to 1
4442 and the commands @kbd{disable $_hit_bpnum} and
4443 @kbd{disable $_hit_bpnum.$_hit_locno} both disable the breakpoint.
4445 You can also define aliases to easily disable the last hit location or
4446 last hit breakpoint:
4448 (gdb) alias lld = disable $_hit_bpnum.$_hit_locno
4449 (gdb) alias lbd = disable $_hit_bpnum
4453 @item break @var{locspec}
4454 Set a breakpoint at all the code locations in your program that result
4455 from resolving the given @var{locspec}. @var{locspec} can specify a
4456 function name, a line number, an address of an instruction, and more.
4457 @xref{Location Specifications}, for the various forms of
4458 @var{locspec}. The breakpoint will stop your program just before it
4459 executes the instruction at the address of any of the breakpoint's
4462 When using source languages that permit overloading of symbols, such
4463 as C@t{++}, a function name may refer to more than one symbol, and
4464 thus more than one place to break. @xref{Ambiguous
4465 Expressions,,Ambiguous Expressions}, for a discussion of that
4468 It is also possible to insert a breakpoint that will stop the program
4469 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4470 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4473 When called without any arguments, @code{break} sets a breakpoint at
4474 the next instruction to be executed in the selected stack frame
4475 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4476 innermost, this makes your program stop as soon as control
4477 returns to that frame. This is similar to the effect of a
4478 @code{finish} command in the frame inside the selected frame---except
4479 that @code{finish} does not leave an active breakpoint. If you use
4480 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4481 the next time it reaches the current location; this may be useful
4484 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4485 least one instruction has been executed. If it did not do this, you
4486 would be unable to proceed past a breakpoint without first disabling the
4487 breakpoint. This rule applies whether or not the breakpoint already
4488 existed when your program stopped.
4490 @item break @dots{} if @var{cond}
4491 Set a breakpoint with condition @var{cond}; evaluate the expression
4492 @var{cond} each time the breakpoint is reached, and stop only if the
4493 value is nonzero---that is, if @var{cond} evaluates as true.
4494 @samp{@dots{}} stands for one of the possible arguments described
4495 above (or no argument) specifying where to break. @xref{Conditions,
4496 ,Break Conditions}, for more information on breakpoint conditions.
4498 The breakpoint may be mapped to multiple locations. If the breakpoint
4499 condition @var{cond} is invalid at some but not all of the locations,
4500 the locations for which the condition is invalid are disabled. For
4501 example, @value{GDBN} reports below that two of the three locations
4505 (@value{GDBP}) break func if a == 10
4506 warning: failed to validate condition at location 0x11ce, disabling:
4507 No symbol "a" in current context.
4508 warning: failed to validate condition at location 0x11b6, disabling:
4509 No symbol "a" in current context.
4510 Breakpoint 1 at 0x11b6: func. (3 locations)
4513 Locations that are disabled because of the condition are denoted by an
4514 uppercase @code{N} in the output of the @code{info breakpoints}
4518 (@value{GDBP}) info breakpoints
4519 Num Type Disp Enb Address What
4520 1 breakpoint keep y <MULTIPLE>
4521 stop only if a == 10
4522 1.1 N* 0x00000000000011b6 in ...
4523 1.2 y 0x00000000000011c2 in ...
4524 1.3 N* 0x00000000000011ce in ...
4525 (*): Breakpoint condition is invalid at this location.
4528 If the breakpoint condition @var{cond} is invalid in the context of
4529 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4530 define the breakpoint. For example, if variable @code{foo} is an
4534 (@value{GDBP}) break func if foo
4535 No symbol "foo" in current context.
4538 @item break @dots{} -force-condition if @var{cond}
4539 There may be cases where the condition @var{cond} is invalid at all
4540 the current locations, but the user knows that it will be valid at a
4541 future location; for example, because of a library load. In such
4542 cases, by using the @code{-force-condition} keyword before @samp{if},
4543 @value{GDBN} can be forced to define the breakpoint with the given
4544 condition expression instead of refusing it.
4547 (@value{GDBP}) break func -force-condition if foo
4548 warning: failed to validate condition at location 1, disabling:
4549 No symbol "foo" in current context.
4550 warning: failed to validate condition at location 2, disabling:
4551 No symbol "foo" in current context.
4552 warning: failed to validate condition at location 3, disabling:
4553 No symbol "foo" in current context.
4554 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4557 This causes all the present locations where the breakpoint would
4558 otherwise be inserted, to be disabled, as seen in the example above.
4559 However, if there exist locations at which the condition is valid, the
4560 @code{-force-condition} keyword has no effect.
4563 @item tbreak @var{args}
4564 Set a breakpoint enabled only for one stop. The @var{args} are the
4565 same as for the @code{break} command, and the breakpoint is set in the same
4566 way, but the breakpoint is automatically deleted after the first time your
4567 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4570 @cindex hardware breakpoints
4571 @item hbreak @var{args}
4572 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4573 @code{break} command and the breakpoint is set in the same way, but the
4574 breakpoint requires hardware support and some target hardware may not
4575 have this support. The main purpose of this is EPROM/ROM code
4576 debugging, so you can set a breakpoint at an instruction without
4577 changing the instruction. This can be used with the new trap-generation
4578 provided by SPARClite DSU and most x86-based targets. These targets
4579 will generate traps when a program accesses some data or instruction
4580 address that is assigned to the debug registers. However the hardware
4581 breakpoint registers can take a limited number of breakpoints. For
4582 example, on the DSU, only two data breakpoints can be set at a time, and
4583 @value{GDBN} will reject this command if more than two are used. Delete
4584 or disable unused hardware breakpoints before setting new ones
4585 (@pxref{Disabling, ,Disabling Breakpoints}).
4586 @xref{Conditions, ,Break Conditions}.
4587 For remote targets, you can restrict the number of hardware
4588 breakpoints @value{GDBN} will use, see @ref{set remote
4589 hardware-breakpoint-limit}.
4592 @item thbreak @var{args}
4593 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4594 are the same as for the @code{hbreak} command and the breakpoint is set in
4595 the same way. However, like the @code{tbreak} command,
4596 the breakpoint is automatically deleted after the
4597 first time your program stops there. Also, like the @code{hbreak}
4598 command, the breakpoint requires hardware support and some target hardware
4599 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4600 See also @ref{Conditions, ,Break Conditions}.
4603 @cindex regular expression
4604 @cindex breakpoints at functions matching a regexp
4605 @cindex set breakpoints in many functions
4606 @item rbreak @var{regex}
4607 Set breakpoints on all functions matching the regular expression
4608 @var{regex}. This command sets an unconditional breakpoint on all
4609 matches, printing a list of all breakpoints it set. Once these
4610 breakpoints are set, they are treated just like the breakpoints set with
4611 the @code{break} command. You can delete them, disable them, or make
4612 them conditional the same way as any other breakpoint.
4614 In programs using different languages, @value{GDBN} chooses the syntax
4615 to print the list of all breakpoints it sets according to the
4616 @samp{set language} value: using @samp{set language auto}
4617 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4618 language of the breakpoint's function, other values mean to use
4619 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4621 The syntax of the regular expression is the standard one used with tools
4622 like @file{grep}. Note that this is different from the syntax used by
4623 shells, so for instance @code{foo*} matches all functions that include
4624 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4625 @code{.*} leading and trailing the regular expression you supply, so to
4626 match only functions that begin with @code{foo}, use @code{^foo}.
4628 @cindex non-member C@t{++} functions, set breakpoint in
4629 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4630 breakpoints on overloaded functions that are not members of any special
4633 @cindex set breakpoints on all functions
4634 The @code{rbreak} command can be used to set breakpoints in
4635 @strong{all} the functions in a program, like this:
4638 (@value{GDBP}) rbreak .
4641 @item rbreak @var{file}:@var{regex}
4642 If @code{rbreak} is called with a filename qualification, it limits
4643 the search for functions matching the given regular expression to the
4644 specified @var{file}. This can be used, for example, to set breakpoints on
4645 every function in a given file:
4648 (@value{GDBP}) rbreak file.c:.
4651 The colon separating the filename qualifier from the regex may
4652 optionally be surrounded by spaces.
4654 @kindex info breakpoints
4655 @cindex @code{$_} and @code{info breakpoints}
4656 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4657 @itemx info break @r{[}@var{list}@dots{}@r{]}
4658 Print a table of all breakpoints, watchpoints, and catchpoints set and
4659 not deleted. Optional argument @var{n} means print information only
4660 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4661 For each breakpoint, following columns are printed:
4664 @item Breakpoint Numbers
4666 Breakpoint, watchpoint, or catchpoint.
4668 Whether the breakpoint is marked to be disabled or deleted when hit.
4669 @item Enabled or Disabled
4670 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4671 that are not enabled.
4673 Where the breakpoint is in your program, as a memory address. For a
4674 pending breakpoint whose address is not yet known, this field will
4675 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4676 library that has the symbol or line referred by breakpoint is loaded.
4677 See below for details. A breakpoint with several locations will
4678 have @samp{<MULTIPLE>} in this field---see below for details.
4680 Where the breakpoint is in the source for your program, as a file and
4681 line number. For a pending breakpoint, the original string passed to
4682 the breakpoint command will be listed as it cannot be resolved until
4683 the appropriate shared library is loaded in the future.
4687 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4688 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4689 @value{GDBN} on the host's side. If it is ``target'', then the condition
4690 is evaluated by the target. The @code{info break} command shows
4691 the condition on the line following the affected breakpoint, together with
4692 its condition evaluation mode in between parentheses.
4694 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4695 allowed to have a condition specified for it. The condition is not parsed for
4696 validity until a shared library is loaded that allows the pending
4697 breakpoint to resolve to a valid location.
4700 @code{info break} with a breakpoint
4701 number @var{n} as argument lists only that breakpoint. The
4702 convenience variable @code{$_} and the default examining-address for
4703 the @code{x} command are set to the address of the last breakpoint
4704 listed (@pxref{Memory, ,Examining Memory}).
4707 @code{info break} displays a count of the number of times the breakpoint
4708 has been hit. This is especially useful in conjunction with the
4709 @code{ignore} command. You can ignore a large number of breakpoint
4710 hits, look at the breakpoint info to see how many times the breakpoint
4711 was hit, and then run again, ignoring one less than that number. This
4712 will get you quickly to the last hit of that breakpoint.
4715 For a breakpoints with an enable count (xref) greater than 1,
4716 @code{info break} also displays that count.
4720 @value{GDBN} allows you to set any number of breakpoints at the same place in
4721 your program. There is nothing silly or meaningless about this. When
4722 the breakpoints are conditional, this is even useful
4723 (@pxref{Conditions, ,Break Conditions}).
4725 @cindex multiple locations, breakpoints
4726 @cindex breakpoints, multiple locations
4727 It is possible that a single logical breakpoint is set at several code
4728 locations in your program. @xref{Location Specifications}, for
4731 A breakpoint with multiple code locations is displayed in the
4732 breakpoint table using several rows---one header row, followed by one
4733 row for each code location. The header row has @samp{<MULTIPLE>} in
4734 the address column. Each code location row contains the actual
4735 address, source file, source line and function of its code location.
4736 The number column for a code location is of the form
4737 @var{breakpoint-number}.@var{location-number}.
4742 Num Type Disp Enb Address What
4743 1 breakpoint keep y <MULTIPLE>
4745 breakpoint already hit 1 time
4746 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4747 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4750 You cannot delete the individual locations from a breakpoint. However,
4751 each location can be individually enabled or disabled by passing
4752 @var{breakpoint-number}.@var{location-number} as argument to the
4753 @code{enable} and @code{disable} commands. It's also possible to
4754 @code{enable} and @code{disable} a range of @var{location-number}
4755 locations using a @var{breakpoint-number} and two @var{location-number}s,
4756 in increasing order, separated by a hyphen, like
4757 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4758 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4759 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4760 all of the locations that belong to that breakpoint.
4762 Locations that are enabled while their parent breakpoint is disabled
4763 won't trigger a break, and are denoted by @code{y-} in the @code{Enb}
4764 column. For example:
4767 (@value{GDBP}) info breakpoints
4768 Num Type Disp Enb Address What
4769 1 breakpoint keep n <MULTIPLE>
4770 1.1 y- 0x00000000000011b6 in ...
4771 1.2 y- 0x00000000000011c2 in ...
4772 1.3 n 0x00000000000011ce in ...
4775 @cindex pending breakpoints
4776 It's quite common to have a breakpoint inside a shared library.
4777 Shared libraries can be loaded and unloaded explicitly,
4778 and possibly repeatedly, as the program is executed. To support
4779 this use case, @value{GDBN} updates breakpoint locations whenever
4780 any shared library is loaded or unloaded. Typically, you would
4781 set a breakpoint in a shared library at the beginning of your
4782 debugging session, when the library is not loaded, and when the
4783 symbols from the library are not available. When you try to set
4784 breakpoint, @value{GDBN} will ask you if you want to set
4785 a so called @dfn{pending breakpoint}---breakpoint whose address
4786 is not yet resolved.
4788 After the program is run, whenever a new shared library is loaded,
4789 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4790 shared library contains the symbol or line referred to by some
4791 pending breakpoint, that breakpoint is resolved and becomes an
4792 ordinary breakpoint. When a library is unloaded, all breakpoints
4793 that refer to its symbols or source lines become pending again.
4795 This logic works for breakpoints with multiple locations, too. For
4796 example, if you have a breakpoint in a C@t{++} template function, and
4797 a newly loaded shared library has an instantiation of that template,
4798 a new location is added to the list of locations for the breakpoint.
4800 Except for having unresolved address, pending breakpoints do not
4801 differ from regular breakpoints. You can set conditions or commands,
4802 enable and disable them and perform other breakpoint operations.
4804 @value{GDBN} provides some additional commands for controlling what
4805 happens when the @samp{break} command cannot resolve the location spec
4806 to any code location in your program (@pxref{Location
4809 @kindex set breakpoint pending
4810 @kindex show breakpoint pending
4812 @item set breakpoint pending auto
4813 This is the default behavior. When @value{GDBN} cannot resolve the
4814 location spec, it queries you whether a pending breakpoint should be
4817 @item set breakpoint pending on
4818 This indicates that when @value{GDBN} cannot resolve the location
4819 spec, it should create a pending breakpoint without confirmation.
4821 @item set breakpoint pending off
4822 This indicates that pending breakpoints are not to be created. If
4823 @value{GDBN} cannot resolve the location spec, it aborts the
4824 breakpoint creation with an error. This setting does not affect any
4825 pending breakpoints previously created.
4827 @item show breakpoint pending
4828 Show the current behavior setting for creating pending breakpoints.
4831 The settings above only affect the @code{break} command and its
4832 variants. Once a breakpoint is set, it will be automatically updated
4833 as shared libraries are loaded and unloaded.
4835 @cindex automatic hardware breakpoints
4836 For some targets, @value{GDBN} can automatically decide if hardware or
4837 software breakpoints should be used, depending on whether the
4838 breakpoint address is read-only or read-write. This applies to
4839 breakpoints set with the @code{break} command as well as to internal
4840 breakpoints set by commands like @code{next} and @code{finish}. For
4841 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4844 You can control this automatic behaviour with the following commands:
4846 @kindex set breakpoint auto-hw
4847 @kindex show breakpoint auto-hw
4849 @item set breakpoint auto-hw on
4850 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4851 will try to use the target memory map to decide if software or hardware
4852 breakpoint must be used.
4854 @item set breakpoint auto-hw off
4855 This indicates @value{GDBN} should not automatically select breakpoint
4856 type. If the target provides a memory map, @value{GDBN} will warn when
4857 trying to set software breakpoint at a read-only address.
4860 @value{GDBN} normally implements breakpoints by replacing the program code
4861 at the breakpoint address with a special instruction, which, when
4862 executed, given control to the debugger. By default, the program
4863 code is so modified only when the program is resumed. As soon as
4864 the program stops, @value{GDBN} restores the original instructions. This
4865 behaviour guards against leaving breakpoints inserted in the
4866 target should gdb abrubptly disconnect. However, with slow remote
4867 targets, inserting and removing breakpoint can reduce the performance.
4868 This behavior can be controlled with the following commands::
4870 @kindex set breakpoint always-inserted
4871 @kindex show breakpoint always-inserted
4873 @item set breakpoint always-inserted off
4874 All breakpoints, including newly added by the user, are inserted in
4875 the target only when the target is resumed. All breakpoints are
4876 removed from the target when it stops. This is the default mode.
4878 @item set breakpoint always-inserted on
4879 Causes all breakpoints to be inserted in the target at all times. If
4880 the user adds a new breakpoint, or changes an existing breakpoint, the
4881 breakpoints in the target are updated immediately. A breakpoint is
4882 removed from the target only when breakpoint itself is deleted.
4885 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4886 when a breakpoint breaks. If the condition is true, then the process being
4887 debugged stops, otherwise the process is resumed.
4889 If the target supports evaluating conditions on its end, @value{GDBN} may
4890 download the breakpoint, together with its conditions, to it.
4892 This feature can be controlled via the following commands:
4894 @kindex set breakpoint condition-evaluation
4895 @kindex show breakpoint condition-evaluation
4897 @item set breakpoint condition-evaluation host
4898 This option commands @value{GDBN} to evaluate the breakpoint
4899 conditions on the host's side. Unconditional breakpoints are sent to
4900 the target which in turn receives the triggers and reports them back to GDB
4901 for condition evaluation. This is the standard evaluation mode.
4903 @item set breakpoint condition-evaluation target
4904 This option commands @value{GDBN} to download breakpoint conditions
4905 to the target at the moment of their insertion. The target
4906 is responsible for evaluating the conditional expression and reporting
4907 breakpoint stop events back to @value{GDBN} whenever the condition
4908 is true. Due to limitations of target-side evaluation, some conditions
4909 cannot be evaluated there, e.g., conditions that depend on local data
4910 that is only known to the host. Examples include
4911 conditional expressions involving convenience variables, complex types
4912 that cannot be handled by the agent expression parser and expressions
4913 that are too long to be sent over to the target, specially when the
4914 target is a remote system. In these cases, the conditions will be
4915 evaluated by @value{GDBN}.
4917 @item set breakpoint condition-evaluation auto
4918 This is the default mode. If the target supports evaluating breakpoint
4919 conditions on its end, @value{GDBN} will download breakpoint conditions to
4920 the target (limitations mentioned previously apply). If the target does
4921 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4922 to evaluating all these conditions on the host's side.
4926 @cindex negative breakpoint numbers
4927 @cindex internal @value{GDBN} breakpoints
4928 @value{GDBN} itself sometimes sets breakpoints in your program for
4929 special purposes, such as proper handling of @code{longjmp} (in C
4930 programs). These internal breakpoints are assigned negative numbers,
4931 starting with @code{-1}; @samp{info breakpoints} does not display them.
4932 You can see these breakpoints with the @value{GDBN} maintenance command
4933 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4936 @node Set Watchpoints
4937 @subsection Setting Watchpoints
4939 @cindex setting watchpoints
4940 You can use a watchpoint to stop execution whenever the value of an
4941 expression changes, without having to predict a particular place where
4942 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4943 The expression may be as simple as the value of a single variable, or
4944 as complex as many variables combined by operators. Examples include:
4948 A reference to the value of a single variable.
4951 An address cast to an appropriate data type. For example,
4952 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4953 address (assuming an @code{int} occupies 4 bytes).
4956 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4957 expression can use any operators valid in the program's native
4958 language (@pxref{Languages}).
4961 You can set a watchpoint on an expression even if the expression can
4962 not be evaluated yet. For instance, you can set a watchpoint on
4963 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4964 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4965 the expression produces a valid value. If the expression becomes
4966 valid in some other way than changing a variable (e.g.@: if the memory
4967 pointed to by @samp{*global_ptr} becomes readable as the result of a
4968 @code{malloc} call), @value{GDBN} may not stop until the next time
4969 the expression changes.
4971 @cindex software watchpoints
4972 @cindex hardware watchpoints
4973 Depending on your system, watchpoints may be implemented in software or
4974 hardware. @value{GDBN} does software watchpointing by single-stepping your
4975 program and testing the variable's value each time, which is hundreds of
4976 times slower than normal execution. (But this may still be worth it, to
4977 catch errors where you have no clue what part of your program is the
4980 On some systems, such as most PowerPC or x86-based targets,
4981 @value{GDBN} includes support for hardware watchpoints, which do not
4982 slow down the running of your program.
4986 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]} @r{[}task @var{task-id}@r{]}
4987 Set a watchpoint for an expression. @value{GDBN} will break when the
4988 expression @var{expr} is written into by the program and its value
4989 changes. The simplest (and the most popular) use of this command is
4990 to watch the value of a single variable:
4993 (@value{GDBP}) watch foo
4996 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4997 argument, @value{GDBN} breaks only when the thread identified by
4998 @var{thread-id} changes the value of @var{expr}. If any other threads
4999 change the value of @var{expr}, @value{GDBN} will not break. Note
5000 that watchpoints restricted to a single thread in this way only work
5001 with Hardware Watchpoints.
5003 Similarly, if the @code{task} argument is given, then the watchpoint
5004 will be specific to the indicated Ada task (@pxref{Ada Tasks}).
5006 Ordinarily a watchpoint respects the scope of variables in @var{expr}
5007 (see below). The @code{-location} argument tells @value{GDBN} to
5008 instead watch the memory referred to by @var{expr}. In this case,
5009 @value{GDBN} will evaluate @var{expr}, take the address of the result,
5010 and watch the memory at that address. The type of the result is used
5011 to determine the size of the watched memory. If the expression's
5012 result does not have an address, then @value{GDBN} will print an
5015 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
5016 of masked watchpoints, if the current architecture supports this
5017 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
5018 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
5019 to an address to watch. The mask specifies that some bits of an address
5020 (the bits which are reset in the mask) should be ignored when matching
5021 the address accessed by the inferior against the watchpoint address.
5022 Thus, a masked watchpoint watches many addresses simultaneously---those
5023 addresses whose unmasked bits are identical to the unmasked bits in the
5024 watchpoint address. The @code{mask} argument implies @code{-location}.
5028 (@value{GDBP}) watch foo mask 0xffff00ff
5029 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
5033 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
5034 Set a watchpoint that will break when the value of @var{expr} is read
5038 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
5039 Set a watchpoint that will break when @var{expr} is either read from
5040 or written into by the program.
5042 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
5043 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
5044 This command prints a list of watchpoints, using the same format as
5045 @code{info break} (@pxref{Set Breaks}).
5048 If you watch for a change in a numerically entered address you need to
5049 dereference it, as the address itself is just a constant number which will
5050 never change. @value{GDBN} refuses to create a watchpoint that watches
5051 a never-changing value:
5054 (@value{GDBP}) watch 0x600850
5055 Cannot watch constant value 0x600850.
5056 (@value{GDBP}) watch *(int *) 0x600850
5057 Watchpoint 1: *(int *) 6293584
5060 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
5061 watchpoints execute very quickly, and the debugger reports a change in
5062 value at the exact instruction where the change occurs. If @value{GDBN}
5063 cannot set a hardware watchpoint, it sets a software watchpoint, which
5064 executes more slowly and reports the change in value at the next
5065 @emph{statement}, not the instruction, after the change occurs.
5067 @cindex use only software watchpoints
5068 You can force @value{GDBN} to use only software watchpoints with the
5069 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
5070 zero, @value{GDBN} will never try to use hardware watchpoints, even if
5071 the underlying system supports them. (Note that hardware-assisted
5072 watchpoints that were set @emph{before} setting
5073 @code{can-use-hw-watchpoints} to zero will still use the hardware
5074 mechanism of watching expression values.)
5077 @item set can-use-hw-watchpoints
5078 @kindex set can-use-hw-watchpoints
5079 Set whether or not to use hardware watchpoints.
5081 @item show can-use-hw-watchpoints
5082 @kindex show can-use-hw-watchpoints
5083 Show the current mode of using hardware watchpoints.
5086 For remote targets, you can restrict the number of hardware
5087 watchpoints @value{GDBN} will use, see @ref{set remote
5088 hardware-breakpoint-limit}.
5090 When you issue the @code{watch} command, @value{GDBN} reports
5093 Hardware watchpoint @var{num}: @var{expr}
5097 if it was able to set a hardware watchpoint.
5099 Currently, the @code{awatch} and @code{rwatch} commands can only set
5100 hardware watchpoints, because accesses to data that don't change the
5101 value of the watched expression cannot be detected without examining
5102 every instruction as it is being executed, and @value{GDBN} does not do
5103 that currently. If @value{GDBN} finds that it is unable to set a
5104 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
5105 will print a message like this:
5108 Expression cannot be implemented with read/access watchpoint.
5111 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
5112 data type of the watched expression is wider than what a hardware
5113 watchpoint on the target machine can handle. For example, some systems
5114 can only watch regions that are up to 4 bytes wide; on such systems you
5115 cannot set hardware watchpoints for an expression that yields a
5116 double-precision floating-point number (which is typically 8 bytes
5117 wide). As a work-around, it might be possible to break the large region
5118 into a series of smaller ones and watch them with separate watchpoints.
5120 If you set too many hardware watchpoints, @value{GDBN} might be unable
5121 to insert all of them when you resume the execution of your program.
5122 Since the precise number of active watchpoints is unknown until such
5123 time as the program is about to be resumed, @value{GDBN} might not be
5124 able to warn you about this when you set the watchpoints, and the
5125 warning will be printed only when the program is resumed:
5128 Hardware watchpoint @var{num}: Could not insert watchpoint
5132 If this happens, delete or disable some of the watchpoints.
5134 Watching complex expressions that reference many variables can also
5135 exhaust the resources available for hardware-assisted watchpoints.
5136 That's because @value{GDBN} needs to watch every variable in the
5137 expression with separately allocated resources.
5139 If you call a function interactively using @code{print} or @code{call},
5140 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5141 kind of breakpoint or the call completes.
5143 @value{GDBN} automatically deletes watchpoints that watch local
5144 (automatic) variables, or expressions that involve such variables, when
5145 they go out of scope, that is, when the execution leaves the block in
5146 which these variables were defined. In particular, when the program
5147 being debugged terminates, @emph{all} local variables go out of scope,
5148 and so only watchpoints that watch global variables remain set. If you
5149 rerun the program, you will need to set all such watchpoints again. One
5150 way of doing that would be to set a code breakpoint at the entry to the
5151 @code{main} function and when it breaks, set all the watchpoints.
5153 @cindex watchpoints and threads
5154 @cindex threads and watchpoints
5155 In multi-threaded programs, watchpoints will detect changes to the
5156 watched expression from every thread.
5159 @emph{Warning:} In multi-threaded programs, software watchpoints
5160 have only limited usefulness. If @value{GDBN} creates a software
5161 watchpoint, it can only watch the value of an expression @emph{in a
5162 single thread}. If you are confident that the expression can only
5163 change due to the current thread's activity (and if you are also
5164 confident that no other thread can become current), then you can use
5165 software watchpoints as usual. However, @value{GDBN} may not notice
5166 when a non-current thread's activity changes the expression. (Hardware
5167 watchpoints, in contrast, watch an expression in all threads.)
5170 @xref{set remote hardware-watchpoint-limit}.
5172 @node Set Catchpoints
5173 @subsection Setting Catchpoints
5174 @cindex catchpoints, setting
5175 @cindex exception handlers
5176 @cindex event handling
5178 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5179 kinds of program events, such as C@t{++} exceptions or the loading of a
5180 shared library. Use the @code{catch} command to set a catchpoint.
5184 @item catch @var{event}
5185 Stop when @var{event} occurs. The @var{event} can be any of the following:
5188 @item throw @r{[}@var{regexp}@r{]}
5189 @itemx rethrow @r{[}@var{regexp}@r{]}
5190 @itemx catch @r{[}@var{regexp}@r{]}
5192 @kindex catch rethrow
5194 @cindex stop on C@t{++} exceptions
5195 The throwing, re-throwing, or catching of a C@t{++} exception.
5197 If @var{regexp} is given, then only exceptions whose type matches the
5198 regular expression will be caught.
5200 @vindex $_exception@r{, convenience variable}
5201 The convenience variable @code{$_exception} is available at an
5202 exception-related catchpoint, on some systems. This holds the
5203 exception being thrown.
5205 There are currently some limitations to C@t{++} exception handling in
5210 The support for these commands is system-dependent. Currently, only
5211 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5215 The regular expression feature and the @code{$_exception} convenience
5216 variable rely on the presence of some SDT probes in @code{libstdc++}.
5217 If these probes are not present, then these features cannot be used.
5218 These probes were first available in the GCC 4.8 release, but whether
5219 or not they are available in your GCC also depends on how it was
5223 The @code{$_exception} convenience variable is only valid at the
5224 instruction at which an exception-related catchpoint is set.
5227 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5228 location in the system library which implements runtime exception
5229 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5230 (@pxref{Selection}) to get to your code.
5233 If you call a function interactively, @value{GDBN} normally returns
5234 control to you when the function has finished executing. If the call
5235 raises an exception, however, the call may bypass the mechanism that
5236 returns control to you and cause your program either to abort or to
5237 simply continue running until it hits a breakpoint, catches a signal
5238 that @value{GDBN} is listening for, or exits. This is the case even if
5239 you set a catchpoint for the exception; catchpoints on exceptions are
5240 disabled within interactive calls. @xref{Calling}, for information on
5241 controlling this with @code{set unwind-on-terminating-exception}.
5244 You cannot raise an exception interactively.
5247 You cannot install an exception handler interactively.
5250 @item exception @r{[}@var{name}@r{]}
5251 @kindex catch exception
5252 @cindex Ada exception catching
5253 @cindex catch Ada exceptions
5254 An Ada exception being raised. If an exception name is specified
5255 at the end of the command (eg @code{catch exception Program_Error}),
5256 the debugger will stop only when this specific exception is raised.
5257 Otherwise, the debugger stops execution when any Ada exception is raised.
5259 When inserting an exception catchpoint on a user-defined exception whose
5260 name is identical to one of the exceptions defined by the language, the
5261 fully qualified name must be used as the exception name. Otherwise,
5262 @value{GDBN} will assume that it should stop on the pre-defined exception
5263 rather than the user-defined one. For instance, assuming an exception
5264 called @code{Constraint_Error} is defined in package @code{Pck}, then
5265 the command to use to catch such exceptions is @kbd{catch exception
5266 Pck.Constraint_Error}.
5268 @vindex $_ada_exception@r{, convenience variable}
5269 The convenience variable @code{$_ada_exception} holds the address of
5270 the exception being thrown. This can be useful when setting a
5271 condition for such a catchpoint.
5273 @item exception unhandled
5274 @kindex catch exception unhandled
5275 An exception that was raised but is not handled by the program. The
5276 convenience variable @code{$_ada_exception} is set as for @code{catch
5279 @item handlers @r{[}@var{name}@r{]}
5280 @kindex catch handlers
5281 @cindex Ada exception handlers catching
5282 @cindex catch Ada exceptions when handled
5283 An Ada exception being handled. If an exception name is
5284 specified at the end of the command
5285 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5286 only when this specific exception is handled.
5287 Otherwise, the debugger stops execution when any Ada exception is handled.
5289 When inserting a handlers catchpoint on a user-defined
5290 exception whose name is identical to one of the exceptions
5291 defined by the language, the fully qualified name must be used
5292 as the exception name. Otherwise, @value{GDBN} will assume that it
5293 should stop on the pre-defined exception rather than the
5294 user-defined one. For instance, assuming an exception called
5295 @code{Constraint_Error} is defined in package @code{Pck}, then the
5296 command to use to catch such exceptions handling is
5297 @kbd{catch handlers Pck.Constraint_Error}.
5299 The convenience variable @code{$_ada_exception} is set as for
5300 @code{catch exception}.
5303 @kindex catch assert
5304 A failed Ada assertion. Note that the convenience variable
5305 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5309 @cindex break on fork/exec
5310 A call to @code{exec}.
5312 @anchor{catch syscall}
5314 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5315 @kindex catch syscall
5316 @cindex break on a system call.
5317 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5318 syscall is a mechanism for application programs to request a service
5319 from the operating system (OS) or one of the OS system services.
5320 @value{GDBN} can catch some or all of the syscalls issued by the
5321 debuggee, and show the related information for each syscall. If no
5322 argument is specified, calls to and returns from all system calls
5325 @var{name} can be any system call name that is valid for the
5326 underlying OS. Just what syscalls are valid depends on the OS. On
5327 GNU and Unix systems, you can find the full list of valid syscall
5328 names on @file{/usr/include/asm/unistd.h}.
5330 @c For MS-Windows, the syscall names and the corresponding numbers
5331 @c can be found, e.g., on this URL:
5332 @c http://www.metasploit.com/users/opcode/syscalls.html
5333 @c but we don't support Windows syscalls yet.
5335 Normally, @value{GDBN} knows in advance which syscalls are valid for
5336 each OS, so you can use the @value{GDBN} command-line completion
5337 facilities (@pxref{Completion,, command completion}) to list the
5340 You may also specify the system call numerically. A syscall's
5341 number is the value passed to the OS's syscall dispatcher to
5342 identify the requested service. When you specify the syscall by its
5343 name, @value{GDBN} uses its database of syscalls to convert the name
5344 into the corresponding numeric code, but using the number directly
5345 may be useful if @value{GDBN}'s database does not have the complete
5346 list of syscalls on your system (e.g., because @value{GDBN} lags
5347 behind the OS upgrades).
5349 You may specify a group of related syscalls to be caught at once using
5350 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5351 instance, on some platforms @value{GDBN} allows you to catch all
5352 network related syscalls, by passing the argument @code{group:network}
5353 to @code{catch syscall}. Note that not all syscall groups are
5354 available in every system. You can use the command completion
5355 facilities (@pxref{Completion,, command completion}) to list the
5356 syscall groups available on your environment.
5358 The example below illustrates how this command works if you don't provide
5362 (@value{GDBP}) catch syscall
5363 Catchpoint 1 (syscall)
5365 Starting program: /tmp/catch-syscall
5367 Catchpoint 1 (call to syscall 'close'), \
5368 0xffffe424 in __kernel_vsyscall ()
5372 Catchpoint 1 (returned from syscall 'close'), \
5373 0xffffe424 in __kernel_vsyscall ()
5377 Here is an example of catching a system call by name:
5380 (@value{GDBP}) catch syscall chroot
5381 Catchpoint 1 (syscall 'chroot' [61])
5383 Starting program: /tmp/catch-syscall
5385 Catchpoint 1 (call to syscall 'chroot'), \
5386 0xffffe424 in __kernel_vsyscall ()
5390 Catchpoint 1 (returned from syscall 'chroot'), \
5391 0xffffe424 in __kernel_vsyscall ()
5395 An example of specifying a system call numerically. In the case
5396 below, the syscall number has a corresponding entry in the XML
5397 file, so @value{GDBN} finds its name and prints it:
5400 (@value{GDBP}) catch syscall 252
5401 Catchpoint 1 (syscall(s) 'exit_group')
5403 Starting program: /tmp/catch-syscall
5405 Catchpoint 1 (call to syscall 'exit_group'), \
5406 0xffffe424 in __kernel_vsyscall ()
5410 Program exited normally.
5414 Here is an example of catching a syscall group:
5417 (@value{GDBP}) catch syscall group:process
5418 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5419 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5420 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5422 Starting program: /tmp/catch-syscall
5424 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5425 from /lib64/ld-linux-x86-64.so.2
5431 However, there can be situations when there is no corresponding name
5432 in XML file for that syscall number. In this case, @value{GDBN} prints
5433 a warning message saying that it was not able to find the syscall name,
5434 but the catchpoint will be set anyway. See the example below:
5437 (@value{GDBP}) catch syscall 764
5438 warning: The number '764' does not represent a known syscall.
5439 Catchpoint 2 (syscall 764)
5443 If you configure @value{GDBN} using the @samp{--without-expat} option,
5444 it will not be able to display syscall names. Also, if your
5445 architecture does not have an XML file describing its system calls,
5446 you will not be able to see the syscall names. It is important to
5447 notice that these two features are used for accessing the syscall
5448 name database. In either case, you will see a warning like this:
5451 (@value{GDBP}) catch syscall
5452 warning: Could not open "syscalls/i386-linux.xml"
5453 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5454 GDB will not be able to display syscall names.
5455 Catchpoint 1 (syscall)
5459 Of course, the file name will change depending on your architecture and system.
5461 Still using the example above, you can also try to catch a syscall by its
5462 number. In this case, you would see something like:
5465 (@value{GDBP}) catch syscall 252
5466 Catchpoint 1 (syscall(s) 252)
5469 Again, in this case @value{GDBN} would not be able to display syscall's names.
5473 A call to @code{fork}.
5477 A call to @code{vfork}.
5479 @item load @r{[}@var{regexp}@r{]}
5480 @itemx unload @r{[}@var{regexp}@r{]}
5482 @kindex catch unload
5483 The loading or unloading of a shared library. If @var{regexp} is
5484 given, then the catchpoint will stop only if the regular expression
5485 matches one of the affected libraries.
5487 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5488 @kindex catch signal
5489 The delivery of a signal.
5491 With no arguments, this catchpoint will catch any signal that is not
5492 used internally by @value{GDBN}, specifically, all signals except
5493 @samp{SIGTRAP} and @samp{SIGINT}.
5495 With the argument @samp{all}, all signals, including those used by
5496 @value{GDBN}, will be caught. This argument cannot be used with other
5499 Otherwise, the arguments are a list of signal names as given to
5500 @code{handle} (@pxref{Signals}). Only signals specified in this list
5503 One reason that @code{catch signal} can be more useful than
5504 @code{handle} is that you can attach commands and conditions to the
5507 When a signal is caught by a catchpoint, the signal's @code{stop} and
5508 @code{print} settings, as specified by @code{handle}, are ignored.
5509 However, whether the signal is still delivered to the inferior depends
5510 on the @code{pass} setting; this can be changed in the catchpoint's
5515 @item tcatch @var{event}
5517 Set a catchpoint that is enabled only for one stop. The catchpoint is
5518 automatically deleted after the first time the event is caught.
5522 Use the @code{info break} command to list the current catchpoints.
5526 @subsection Deleting Breakpoints
5528 @cindex clearing breakpoints, watchpoints, catchpoints
5529 @cindex deleting breakpoints, watchpoints, catchpoints
5530 It is often necessary to eliminate a breakpoint, watchpoint, or
5531 catchpoint once it has done its job and you no longer want your program
5532 to stop there. This is called @dfn{deleting} the breakpoint. A
5533 breakpoint that has been deleted no longer exists; it is forgotten.
5535 With the @code{clear} command you can delete breakpoints according to
5536 where they are in your program. With the @code{delete} command you can
5537 delete individual breakpoints, watchpoints, or catchpoints by specifying
5538 their breakpoint numbers.
5540 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5541 automatically ignores breakpoints on the first instruction to be executed
5542 when you continue execution without changing the execution address.
5547 Delete any breakpoints at the next instruction to be executed in the
5548 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5549 the innermost frame is selected, this is a good way to delete a
5550 breakpoint where your program just stopped.
5552 @item clear @var{locspec}
5553 Delete any breakpoint with a code location that corresponds to
5554 @var{locspec}. @xref{Location Specifications}, for the various forms
5555 of @var{locspec}. Which code locations correspond to @var{locspec}
5556 depends on the form used in the location specification @var{locspec}:
5560 @itemx @var{filename}:@var{linenum}
5561 @itemx -line @var{linenum}
5562 @itemx -source @var{filename} -line @var{linenum}
5563 If @var{locspec} specifies a line number, with or without a file name,
5564 the command deletes any breakpoint with a code location that is at or
5565 within the specified line @var{linenum} in files that match the
5566 specified @var{filename}. If @var{filename} is omitted, it defaults
5567 to the current source file.
5569 @item *@var{address}
5570 If @var{locspec} specifies an address, the command deletes any
5571 breakpoint with a code location that is at the given @var{address}.
5573 @item @var{function}
5574 @itemx -function @var{function}
5575 If @var{locspec} specifies a function, the command deletes any
5576 breakpoint with a code location that is at the entry to any function
5577 whose name matches @var{function}.
5580 Ambiguity in names of files and functions can be resolved as described
5581 in @ref{Location Specifications}.
5583 @cindex delete breakpoints
5585 @kindex d @r{(@code{delete})}
5586 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5587 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5588 list specified as argument. If no argument is specified, delete all
5589 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5590 confirm off}). You can abbreviate this command as @code{d}.
5594 @subsection Disabling Breakpoints
5596 @cindex enable/disable a breakpoint
5597 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5598 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5599 it had been deleted, but remembers the information on the breakpoint so
5600 that you can @dfn{enable} it again later.
5602 You disable and enable breakpoints, watchpoints, and catchpoints with
5603 the @code{enable} and @code{disable} commands, optionally specifying
5604 one or more breakpoint numbers as arguments. Use @code{info break} to
5605 print a list of all breakpoints, watchpoints, and catchpoints if you
5606 do not know which numbers to use.
5608 Disabling and enabling a breakpoint that has multiple locations
5609 affects all of its locations.
5611 A breakpoint, watchpoint, or catchpoint can have any of several
5612 different states of enablement:
5616 Enabled. The breakpoint stops your program. A breakpoint set
5617 with the @code{break} command starts out in this state.
5619 Disabled. The breakpoint has no effect on your program.
5621 Enabled once. The breakpoint stops your program, but then becomes
5624 Enabled for a count. The breakpoint stops your program for the next
5625 N times, then becomes disabled.
5627 Enabled for deletion. The breakpoint stops your program, but
5628 immediately after it does so it is deleted permanently. A breakpoint
5629 set with the @code{tbreak} command starts out in this state.
5632 You can use the following commands to enable or disable breakpoints,
5633 watchpoints, and catchpoints:
5637 @kindex dis @r{(@code{disable})}
5638 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5639 Disable the specified breakpoints---or all breakpoints, if none are
5640 listed. A disabled breakpoint has no effect but is not forgotten. All
5641 options such as ignore-counts, conditions and commands are remembered in
5642 case the breakpoint is enabled again later. You may abbreviate
5643 @code{disable} as @code{dis}.
5646 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5647 Enable the specified breakpoints (or all defined breakpoints). They
5648 become effective once again in stopping your program.
5650 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5651 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5652 of these breakpoints immediately after stopping your program.
5654 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5655 Enable the specified breakpoints temporarily. @value{GDBN} records
5656 @var{count} with each of the specified breakpoints, and decrements a
5657 breakpoint's count when it is hit. When any count reaches 0,
5658 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5659 count (@pxref{Conditions, ,Break Conditions}), that will be
5660 decremented to 0 before @var{count} is affected.
5662 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5663 Enable the specified breakpoints to work once, then die. @value{GDBN}
5664 deletes any of these breakpoints as soon as your program stops there.
5665 Breakpoints set by the @code{tbreak} command start out in this state.
5668 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5669 @c confusing: tbreak is also initially enabled.
5670 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5671 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5672 subsequently, they become disabled or enabled only when you use one of
5673 the commands above. (The command @code{until} can set and delete a
5674 breakpoint of its own, but it does not change the state of your other
5675 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5679 @subsection Break Conditions
5680 @cindex conditional breakpoints
5681 @cindex breakpoint conditions
5683 @c FIXME what is scope of break condition expr? Context where wanted?
5684 @c in particular for a watchpoint?
5685 The simplest sort of breakpoint breaks every time your program reaches a
5686 specified place. You can also specify a @dfn{condition} for a
5687 breakpoint. A condition is just a Boolean expression in your
5688 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5689 a condition evaluates the expression each time your program reaches it,
5690 and your program stops only if the condition is @emph{true}.
5692 This is the converse of using assertions for program validation; in that
5693 situation, you want to stop when the assertion is violated---that is,
5694 when the condition is false. In C, if you want to test an assertion expressed
5695 by the condition @var{assert}, you should set the condition
5696 @samp{! @var{assert}} on the appropriate breakpoint.
5698 Conditions are also accepted for watchpoints; you may not need them,
5699 since a watchpoint is inspecting the value of an expression anyhow---but
5700 it might be simpler, say, to just set a watchpoint on a variable name,
5701 and specify a condition that tests whether the new value is an interesting
5704 Break conditions can have side effects, and may even call functions in
5705 your program. This can be useful, for example, to activate functions
5706 that log program progress, or to use your own print functions to
5707 format special data structures. The effects are completely predictable
5708 unless there is another enabled breakpoint at the same address. (In
5709 that case, @value{GDBN} might see the other breakpoint first and stop your
5710 program without checking the condition of this one.) Note that
5711 breakpoint commands are usually more convenient and flexible than break
5713 purpose of performing side effects when a breakpoint is reached
5714 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5716 Breakpoint conditions can also be evaluated on the target's side if
5717 the target supports it. Instead of evaluating the conditions locally,
5718 @value{GDBN} encodes the expression into an agent expression
5719 (@pxref{Agent Expressions}) suitable for execution on the target,
5720 independently of @value{GDBN}. Global variables become raw memory
5721 locations, locals become stack accesses, and so forth.
5723 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5724 when its condition evaluates to true. This mechanism may provide faster
5725 response times depending on the performance characteristics of the target
5726 since it does not need to keep @value{GDBN} informed about
5727 every breakpoint trigger, even those with false conditions.
5729 Break conditions can be specified when a breakpoint is set, by using
5730 @samp{if} in the arguments to the @code{break} command. @xref{Set
5731 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5732 with the @code{condition} command.
5734 You can also use the @code{if} keyword with the @code{watch} command.
5735 The @code{catch} command does not recognize the @code{if} keyword;
5736 @code{condition} is the only way to impose a further condition on a
5741 @item condition @var{bnum} @var{expression}
5742 Specify @var{expression} as the break condition for breakpoint,
5743 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5744 breakpoint @var{bnum} stops your program only if the value of
5745 @var{expression} is true (nonzero, in C). When you use
5746 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5747 syntactic correctness, and to determine whether symbols in it have
5748 referents in the context of your breakpoint. If @var{expression} uses
5749 symbols not referenced in the context of the breakpoint, @value{GDBN}
5750 prints an error message:
5753 No symbol "foo" in current context.
5758 not actually evaluate @var{expression} at the time the @code{condition}
5759 command (or a command that sets a breakpoint with a condition, like
5760 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5762 @item condition -force @var{bnum} @var{expression}
5763 When the @code{-force} flag is used, define the condition even if
5764 @var{expression} is invalid at all the current locations of breakpoint
5765 @var{bnum}. This is similar to the @code{-force-condition} option
5766 of the @code{break} command.
5768 @item condition @var{bnum}
5769 Remove the condition from breakpoint number @var{bnum}. It becomes
5770 an ordinary unconditional breakpoint.
5773 @cindex ignore count (of breakpoint)
5774 A special case of a breakpoint condition is to stop only when the
5775 breakpoint has been reached a certain number of times. This is so
5776 useful that there is a special way to do it, using the @dfn{ignore
5777 count} of the breakpoint. Every breakpoint has an ignore count, which
5778 is an integer. Most of the time, the ignore count is zero, and
5779 therefore has no effect. But if your program reaches a breakpoint whose
5780 ignore count is positive, then instead of stopping, it just decrements
5781 the ignore count by one and continues. As a result, if the ignore count
5782 value is @var{n}, the breakpoint does not stop the next @var{n} times
5783 your program reaches it.
5787 @item ignore @var{bnum} @var{count}
5788 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5789 The next @var{count} times the breakpoint is reached, your program's
5790 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5793 To make the breakpoint stop the next time it is reached, specify
5796 When you use @code{continue} to resume execution of your program from a
5797 breakpoint, you can specify an ignore count directly as an argument to
5798 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5799 Stepping,,Continuing and Stepping}.
5801 If a breakpoint has a positive ignore count and a condition, the
5802 condition is not checked. Once the ignore count reaches zero,
5803 @value{GDBN} resumes checking the condition.
5805 You could achieve the effect of the ignore count with a condition such
5806 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5807 is decremented each time. @xref{Convenience Vars, ,Convenience
5811 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5814 @node Break Commands
5815 @subsection Breakpoint Command Lists
5817 @cindex breakpoint commands
5818 You can give any breakpoint (or watchpoint or catchpoint) a series of
5819 commands to execute when your program stops due to that breakpoint. For
5820 example, you might want to print the values of certain expressions, or
5821 enable other breakpoints.
5825 @kindex end@r{ (breakpoint commands)}
5826 @item commands @r{[}@var{list}@dots{}@r{]}
5827 @itemx @dots{} @var{command-list} @dots{}
5829 Specify a list of commands for the given breakpoints. The commands
5830 themselves appear on the following lines. Type a line containing just
5831 @code{end} to terminate the commands.
5833 To remove all commands from a breakpoint, type @code{commands} and
5834 follow it immediately with @code{end}; that is, give no commands.
5836 With no argument, @code{commands} refers to the last breakpoint,
5837 watchpoint, or catchpoint set (not to the breakpoint most recently
5838 encountered). If the most recent breakpoints were set with a single
5839 command, then the @code{commands} will apply to all the breakpoints
5840 set by that command. This applies to breakpoints set by
5841 @code{rbreak}, and also applies when a single @code{break} command
5842 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5846 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5847 disabled within a @var{command-list}.
5849 Inside a command list, you can use the command
5850 @kbd{disable $_hit_bpnum} to disable the encountered breakpoint.
5852 If your breakpoint has several code locations, the command
5853 @kbd{disable $_hit_bpnum.$_hit_locno} will disable the specific breakpoint
5854 code location encountered. If the breakpoint has only one location,
5855 this command will disable the encountered breakpoint.
5857 You can use breakpoint commands to start your program up again. Simply
5858 use the @code{continue} command, or @code{step}, or any other command
5859 that resumes execution.
5861 Any other commands in the command list, after a command that resumes
5862 execution, are ignored. This is because any time you resume execution
5863 (even with a simple @code{next} or @code{step}), you may encounter
5864 another breakpoint---which could have its own command list, leading to
5865 ambiguities about which list to execute.
5868 If the first command you specify in a command list is @code{silent}, the
5869 usual message about stopping at a breakpoint is not printed. This may
5870 be desirable for breakpoints that are to print a specific message and
5871 then continue. If none of the remaining commands print anything, you
5872 see no sign that the breakpoint was reached. @code{silent} is
5873 meaningful only at the beginning of a breakpoint command list.
5875 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5876 print precisely controlled output, and are often useful in silent
5877 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5879 For example, here is how you could use breakpoint commands to print the
5880 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5886 printf "x is %d\n",x
5891 One application for breakpoint commands is to compensate for one bug so
5892 you can test for another. Put a breakpoint just after the erroneous line
5893 of code, give it a condition to detect the case in which something
5894 erroneous has been done, and give it commands to assign correct values
5895 to any variables that need them. End with the @code{continue} command
5896 so that your program does not stop, and start with the @code{silent}
5897 command so that no output is produced. Here is an example:
5908 @node Dynamic Printf
5909 @subsection Dynamic Printf
5911 @cindex dynamic printf
5913 The dynamic printf command @code{dprintf} combines a breakpoint with
5914 formatted printing of your program's data to give you the effect of
5915 inserting @code{printf} calls into your program on-the-fly, without
5916 having to recompile it.
5918 In its most basic form, the output goes to the GDB console. However,
5919 you can set the variable @code{dprintf-style} for alternate handling.
5920 For instance, you can ask to format the output by calling your
5921 program's @code{printf} function. This has the advantage that the
5922 characters go to the program's output device, so they can recorded in
5923 redirects to files and so forth.
5925 If you are doing remote debugging with a stub or agent, you can also
5926 ask to have the printf handled by the remote agent. In addition to
5927 ensuring that the output goes to the remote program's device along
5928 with any other output the program might produce, you can also ask that
5929 the dprintf remain active even after disconnecting from the remote
5930 target. Using the stub/agent is also more efficient, as it can do
5931 everything without needing to communicate with @value{GDBN}.
5935 @item dprintf @var{locspec},@var{template},@var{expression}[,@var{expression}@dots{}]
5936 Whenever execution reaches a code location that results from resolving
5937 @var{locspec}, print the values of one or more @var{expressions} under
5938 the control of the string @var{template}. To print several values,
5939 separate them with commas.
5941 @item set dprintf-style @var{style}
5942 Set the dprintf output to be handled in one of several different
5943 styles enumerated below. A change of style affects all existing
5944 dynamic printfs immediately. (If you need individual control over the
5945 print commands, simply define normal breakpoints with
5946 explicitly-supplied command lists.)
5950 @kindex dprintf-style gdb
5951 Handle the output using the @value{GDBN} @code{printf} command.
5954 @kindex dprintf-style call
5955 Handle the output by calling a function in your program (normally
5959 @kindex dprintf-style agent
5960 Have the remote debugging agent (such as @code{gdbserver}) handle
5961 the output itself. This style is only available for agents that
5962 support running commands on the target.
5965 @item set dprintf-function @var{function}
5966 Set the function to call if the dprintf style is @code{call}. By
5967 default its value is @code{printf}. You may set it to any expression.
5968 that @value{GDBN} can evaluate to a function, as per the @code{call}
5971 @item set dprintf-channel @var{channel}
5972 Set a ``channel'' for dprintf. If set to a non-empty value,
5973 @value{GDBN} will evaluate it as an expression and pass the result as
5974 a first argument to the @code{dprintf-function}, in the manner of
5975 @code{fprintf} and similar functions. Otherwise, the dprintf format
5976 string will be the first argument, in the manner of @code{printf}.
5978 As an example, if you wanted @code{dprintf} output to go to a logfile
5979 that is a standard I/O stream assigned to the variable @code{mylog},
5980 you could do the following:
5983 (@value{GDBP}) set dprintf-style call
5984 (@value{GDBP}) set dprintf-function fprintf
5985 (@value{GDBP}) set dprintf-channel mylog
5986 (@value{GDBP}) dprintf 25,"at line 25, glob=%d\n",glob
5987 Dprintf 1 at 0x123456: file main.c, line 25.
5988 (@value{GDBP}) info break
5989 1 dprintf keep y 0x00123456 in main at main.c:25
5990 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5995 Note that the @code{info break} displays the dynamic printf commands
5996 as normal breakpoint commands; you can thus easily see the effect of
5997 the variable settings.
5999 @item set disconnected-dprintf on
6000 @itemx set disconnected-dprintf off
6001 @kindex set disconnected-dprintf
6002 Choose whether @code{dprintf} commands should continue to run if
6003 @value{GDBN} has disconnected from the target. This only applies
6004 if the @code{dprintf-style} is @code{agent}.
6006 @item show disconnected-dprintf off
6007 @kindex show disconnected-dprintf
6008 Show the current choice for disconnected @code{dprintf}.
6012 @value{GDBN} does not check the validity of function and channel,
6013 relying on you to supply values that are meaningful for the contexts
6014 in which they are being used. For instance, the function and channel
6015 may be the values of local variables, but if that is the case, then
6016 all enabled dynamic prints must be at locations within the scope of
6017 those locals. If evaluation fails, @value{GDBN} will report an error.
6019 @node Save Breakpoints
6020 @subsection How to save breakpoints to a file
6022 To save breakpoint definitions to a file use the @w{@code{save
6023 breakpoints}} command.
6026 @kindex save breakpoints
6027 @cindex save breakpoints to a file for future sessions
6028 @item save breakpoints [@var{filename}]
6029 This command saves all current breakpoint definitions together with
6030 their commands and ignore counts, into a file @file{@var{filename}}
6031 suitable for use in a later debugging session. This includes all
6032 types of breakpoints (breakpoints, watchpoints, catchpoints,
6033 tracepoints). To read the saved breakpoint definitions, use the
6034 @code{source} command (@pxref{Command Files}). Note that watchpoints
6035 with expressions involving local variables may fail to be recreated
6036 because it may not be possible to access the context where the
6037 watchpoint is valid anymore. Because the saved breakpoint definitions
6038 are simply a sequence of @value{GDBN} commands that recreate the
6039 breakpoints, you can edit the file in your favorite editing program,
6040 and remove the breakpoint definitions you're not interested in, or
6041 that can no longer be recreated.
6044 @node Static Probe Points
6045 @subsection Static Probe Points
6047 @cindex static probe point, SystemTap
6048 @cindex static probe point, DTrace
6049 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
6050 for Statically Defined Tracing, and the probes are designed to have a tiny
6051 runtime code and data footprint, and no dynamic relocations.
6053 Currently, the following types of probes are supported on
6054 ELF-compatible systems:
6058 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
6059 @acronym{SDT} probes@footnote{See
6060 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
6061 for more information on how to add @code{SystemTap} @acronym{SDT}
6062 probes in your applications.}. @code{SystemTap} probes are usable
6063 from assembly, C and C@t{++} languages@footnote{See
6064 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
6065 for a good reference on how the @acronym{SDT} probes are implemented.}.
6067 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
6068 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
6072 @cindex semaphores on static probe points
6073 Some @code{SystemTap} probes have an associated semaphore variable;
6074 for instance, this happens automatically if you defined your probe
6075 using a DTrace-style @file{.d} file. If your probe has a semaphore,
6076 @value{GDBN} will automatically enable it when you specify a
6077 breakpoint using the @samp{-probe-stap} notation. But, if you put a
6078 breakpoint at a probe's location by some other method (e.g.,
6079 @code{break file:line}), then @value{GDBN} will not automatically set
6080 the semaphore. @code{DTrace} probes do not support semaphores.
6082 You can examine the available static static probes using @code{info
6083 probes}, with optional arguments:
6087 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6088 If given, @var{type} is either @code{stap} for listing
6089 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
6090 probes. If omitted all probes are listed regardless of their types.
6092 If given, @var{provider} is a regular expression used to match against provider
6093 names when selecting which probes to list. If omitted, probes by all
6094 probes from all providers are listed.
6096 If given, @var{name} is a regular expression to match against probe names
6097 when selecting which probes to list. If omitted, probe names are not
6098 considered when deciding whether to display them.
6100 If given, @var{objfile} is a regular expression used to select which
6101 object files (executable or shared libraries) to examine. If not
6102 given, all object files are considered.
6104 @item info probes all
6105 List the available static probes, from all types.
6108 @cindex enabling and disabling probes
6109 Some probe points can be enabled and/or disabled. The effect of
6110 enabling or disabling a probe depends on the type of probe being
6111 handled. Some @code{DTrace} probes can be enabled or
6112 disabled, but @code{SystemTap} probes cannot be disabled.
6114 You can enable (or disable) one or more probes using the following
6115 commands, with optional arguments:
6117 @anchor{enable probes}
6119 @kindex enable probes
6120 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6121 If given, @var{provider} is a regular expression used to match against
6122 provider names when selecting which probes to enable. If omitted,
6123 all probes from all providers are enabled.
6125 If given, @var{name} is a regular expression to match against probe
6126 names when selecting which probes to enable. If omitted, probe names
6127 are not considered when deciding whether to enable them.
6129 If given, @var{objfile} is a regular expression used to select which
6130 object files (executable or shared libraries) to examine. If not
6131 given, all object files are considered.
6133 @kindex disable probes
6134 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6135 See the @code{enable probes} command above for a description of the
6136 optional arguments accepted by this command.
6139 @vindex $_probe_arg@r{, convenience variable}
6140 A probe may specify up to twelve arguments. These are available at the
6141 point at which the probe is defined---that is, when the current PC is
6142 at the probe's location. The arguments are available using the
6143 convenience variables (@pxref{Convenience Vars})
6144 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
6145 probes each probe argument is an integer of the appropriate size;
6146 types are not preserved. In @code{DTrace} probes types are preserved
6147 provided that they are recognized as such by @value{GDBN}; otherwise
6148 the value of the probe argument will be a long integer. The
6149 convenience variable @code{$_probe_argc} holds the number of arguments
6150 at the current probe point.
6152 These variables are always available, but attempts to access them at
6153 any location other than a probe point will cause @value{GDBN} to give
6157 @c @ifclear BARETARGET
6158 @node Error in Breakpoints
6159 @subsection ``Cannot insert breakpoints''
6161 If you request too many active hardware-assisted breakpoints and
6162 watchpoints, you will see this error message:
6164 @c FIXME: the precise wording of this message may change; the relevant
6165 @c source change is not committed yet (Sep 3, 1999).
6167 Stopped; cannot insert breakpoints.
6168 You may have requested too many hardware breakpoints and watchpoints.
6172 This message is printed when you attempt to resume the program, since
6173 only then @value{GDBN} knows exactly how many hardware breakpoints and
6174 watchpoints it needs to insert.
6176 When this message is printed, you need to disable or remove some of the
6177 hardware-assisted breakpoints and watchpoints, and then continue.
6179 @node Breakpoint-related Warnings
6180 @subsection ``Breakpoint address adjusted...''
6181 @cindex breakpoint address adjusted
6183 Some processor architectures place constraints on the addresses at
6184 which breakpoints may be placed. For architectures thus constrained,
6185 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6186 with the constraints dictated by the architecture.
6188 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6189 a VLIW architecture in which a number of RISC-like instructions may be
6190 bundled together for parallel execution. The FR-V architecture
6191 constrains the location of a breakpoint instruction within such a
6192 bundle to the instruction with the lowest address. @value{GDBN}
6193 honors this constraint by adjusting a breakpoint's address to the
6194 first in the bundle.
6196 It is not uncommon for optimized code to have bundles which contain
6197 instructions from different source statements, thus it may happen that
6198 a breakpoint's address will be adjusted from one source statement to
6199 another. Since this adjustment may significantly alter @value{GDBN}'s
6200 breakpoint related behavior from what the user expects, a warning is
6201 printed when the breakpoint is first set and also when the breakpoint
6204 A warning like the one below is printed when setting a breakpoint
6205 that's been subject to address adjustment:
6208 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6211 Such warnings are printed both for user settable and @value{GDBN}'s
6212 internal breakpoints. If you see one of these warnings, you should
6213 verify that a breakpoint set at the adjusted address will have the
6214 desired affect. If not, the breakpoint in question may be removed and
6215 other breakpoints may be set which will have the desired behavior.
6216 E.g., it may be sufficient to place the breakpoint at a later
6217 instruction. A conditional breakpoint may also be useful in some
6218 cases to prevent the breakpoint from triggering too often.
6220 @value{GDBN} will also issue a warning when stopping at one of these
6221 adjusted breakpoints:
6224 warning: Breakpoint 1 address previously adjusted from 0x00010414
6228 When this warning is encountered, it may be too late to take remedial
6229 action except in cases where the breakpoint is hit earlier or more
6230 frequently than expected.
6232 @node Continuing and Stepping
6233 @section Continuing and Stepping
6237 @cindex resuming execution
6238 @dfn{Continuing} means resuming program execution until your program
6239 completes normally. In contrast, @dfn{stepping} means executing just
6240 one more ``step'' of your program, where ``step'' may mean either one
6241 line of source code, or one machine instruction (depending on what
6242 particular command you use). Either when continuing or when stepping,
6243 your program may stop even sooner, due to a breakpoint or a signal. (If
6244 it stops due to a signal, you may want to use @code{handle}, or use
6245 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6246 or you may step into the signal's handler (@pxref{stepping and signal
6251 @kindex c @r{(@code{continue})}
6252 @kindex fg @r{(resume foreground execution)}
6253 @item continue @r{[}@var{ignore-count}@r{]}
6254 @itemx c @r{[}@var{ignore-count}@r{]}
6255 @itemx fg @r{[}@var{ignore-count}@r{]}
6256 Resume program execution, at the address where your program last stopped;
6257 any breakpoints set at that address are bypassed. The optional argument
6258 @var{ignore-count} allows you to specify a further number of times to
6259 ignore a breakpoint at this location; its effect is like that of
6260 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6262 The argument @var{ignore-count} is meaningful only when your program
6263 stopped due to a breakpoint. At other times, the argument to
6264 @code{continue} is ignored.
6266 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6267 debugged program is deemed to be the foreground program) are provided
6268 purely for convenience, and have exactly the same behavior as
6272 To resume execution at a different place, you can use @code{return}
6273 (@pxref{Returning, ,Returning from a Function}) to go back to the
6274 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6275 Different Address}) to go to an arbitrary location in your program.
6277 A typical technique for using stepping is to set a breakpoint
6278 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6279 beginning of the function or the section of your program where a problem
6280 is believed to lie, run your program until it stops at that breakpoint,
6281 and then step through the suspect area, examining the variables that are
6282 interesting, until you see the problem happen.
6286 @kindex s @r{(@code{step})}
6288 Continue running your program until control reaches a different source
6289 line, then stop it and return control to @value{GDBN}. This command is
6290 abbreviated @code{s}.
6293 @c "without debugging information" is imprecise; actually "without line
6294 @c numbers in the debugging information". (gcc -g1 has debugging info but
6295 @c not line numbers). But it seems complex to try to make that
6296 @c distinction here.
6297 @emph{Warning:} If you use the @code{step} command while control is
6298 within a function that was compiled without debugging information,
6299 execution proceeds until control reaches a function that does have
6300 debugging information. Likewise, it will not step into a function which
6301 is compiled without debugging information. To step through functions
6302 without debugging information, use the @code{stepi} command, described
6306 The @code{step} command only stops at the first instruction of a source
6307 line. This prevents the multiple stops that could otherwise occur in
6308 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6309 to stop if a function that has debugging information is called within
6310 the line. In other words, @code{step} @emph{steps inside} any functions
6311 called within the line.
6313 Also, the @code{step} command only enters a function if there is line
6314 number information for the function. Otherwise it acts like the
6315 @code{next} command. This avoids problems when using @code{cc -gl}
6316 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6317 was any debugging information about the routine.
6319 @item step @var{count}
6320 Continue running as in @code{step}, but do so @var{count} times. If a
6321 breakpoint is reached, or a signal not related to stepping occurs before
6322 @var{count} steps, stepping stops right away.
6325 @kindex n @r{(@code{next})}
6326 @item next @r{[}@var{count}@r{]}
6327 Continue to the next source line in the current (innermost) stack frame.
6328 This is similar to @code{step}, but function calls that appear within
6329 the line of code are executed without stopping. Execution stops when
6330 control reaches a different line of code at the original stack level
6331 that was executing when you gave the @code{next} command. This command
6332 is abbreviated @code{n}.
6334 An argument @var{count} is a repeat count, as for @code{step}.
6337 @c FIX ME!! Do we delete this, or is there a way it fits in with
6338 @c the following paragraph? --- Vctoria
6340 @c @code{next} within a function that lacks debugging information acts like
6341 @c @code{step}, but any function calls appearing within the code of the
6342 @c function are executed without stopping.
6344 The @code{next} command only stops at the first instruction of a
6345 source line. This prevents multiple stops that could otherwise occur in
6346 @code{switch} statements, @code{for} loops, etc.
6348 @kindex set step-mode
6350 @cindex functions without line info, and stepping
6351 @cindex stepping into functions with no line info
6352 @itemx set step-mode on
6353 The @code{set step-mode on} command causes the @code{step} command to
6354 stop at the first instruction of a function which contains no debug line
6355 information rather than stepping over it.
6357 This is useful in cases where you may be interested in inspecting the
6358 machine instructions of a function which has no symbolic info and do not
6359 want @value{GDBN} to automatically skip over this function.
6361 @item set step-mode off
6362 Causes the @code{step} command to step over any functions which contains no
6363 debug information. This is the default.
6365 @item show step-mode
6366 Show whether @value{GDBN} will stop in or step over functions without
6367 source line debug information.
6370 @kindex fin @r{(@code{finish})}
6372 Continue running until just after function in the selected stack frame
6373 returns. Print the returned value (if any). This command can be
6374 abbreviated as @code{fin}.
6376 Contrast this with the @code{return} command (@pxref{Returning,
6377 ,Returning from a Function}).
6379 @kindex set print finish
6380 @kindex show print finish
6381 @item set print finish @r{[}on|off@r{]}
6382 @itemx show print finish
6383 By default the @code{finish} command will show the value that is
6384 returned by the function. This can be disabled using @code{set print
6385 finish off}. When disabled, the value is still entered into the value
6386 history (@pxref{Value History}), but not displayed.
6389 @kindex u @r{(@code{until})}
6390 @cindex run until specified location
6393 Continue running until a source line past the current line, in the
6394 current stack frame, is reached. This command is used to avoid single
6395 stepping through a loop more than once. It is like the @code{next}
6396 command, except that when @code{until} encounters a jump, it
6397 automatically continues execution until the program counter is greater
6398 than the address of the jump.
6400 This means that when you reach the end of a loop after single stepping
6401 though it, @code{until} makes your program continue execution until it
6402 exits the loop. In contrast, a @code{next} command at the end of a loop
6403 simply steps back to the beginning of the loop, which forces you to step
6404 through the next iteration.
6406 @code{until} always stops your program if it attempts to exit the current
6409 @code{until} may produce somewhat counterintuitive results if the order
6410 of machine code does not match the order of the source lines. For
6411 example, in the following excerpt from a debugging session, the @code{f}
6412 (@code{frame}) command shows that execution is stopped at line
6413 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6417 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6419 (@value{GDBP}) until
6420 195 for ( ; argc > 0; NEXTARG) @{
6423 This happened because, for execution efficiency, the compiler had
6424 generated code for the loop closure test at the end, rather than the
6425 start, of the loop---even though the test in a C @code{for}-loop is
6426 written before the body of the loop. The @code{until} command appeared
6427 to step back to the beginning of the loop when it advanced to this
6428 expression; however, it has not really gone to an earlier
6429 statement---not in terms of the actual machine code.
6431 @code{until} with no argument works by means of single
6432 instruction stepping, and hence is slower than @code{until} with an
6435 @item until @var{locspec}
6436 @itemx u @var{locspec}
6437 Continue running your program until either it reaches a code location
6438 that results from resolving @var{locspec}, or the current stack frame
6439 returns. @var{locspec} is any of the forms described in @ref{Location
6441 This form of the command uses temporary breakpoints, and
6442 hence is quicker than @code{until} without an argument. The specified
6443 location is actually reached only if it is in the current frame. This
6444 implies that @code{until} can be used to skip over recursive function
6445 invocations. For instance in the code below, if the current location is
6446 line @code{96}, issuing @code{until 99} will execute the program up to
6447 line @code{99} in the same invocation of factorial, i.e., after the inner
6448 invocations have returned.
6451 94 int factorial (int value)
6453 96 if (value > 1) @{
6454 97 value *= factorial (value - 1);
6461 @kindex advance @var{locspec}
6462 @item advance @var{locspec}
6463 Continue running your program until either it reaches a code location
6464 that results from resolving @var{locspec}, or the current stack frame
6465 returns. @var{locspec} is any of the forms described in @ref{Location
6466 Specifications}. This command is similar to @code{until}, but
6467 @code{advance} will not skip over recursive function calls, and the
6468 target code location doesn't have to be in the same frame as the
6473 @kindex si @r{(@code{stepi})}
6475 @itemx stepi @var{arg}
6477 Execute one machine instruction, then stop and return to the debugger.
6479 It is often useful to do @samp{display/i $pc} when stepping by machine
6480 instructions. This makes @value{GDBN} automatically display the next
6481 instruction to be executed, each time your program stops. @xref{Auto
6482 Display,, Automatic Display}.
6484 An argument is a repeat count, as in @code{step}.
6488 @kindex ni @r{(@code{nexti})}
6490 @itemx nexti @var{arg}
6492 Execute one machine instruction, but if it is a function call,
6493 proceed until the function returns.
6495 An argument is a repeat count, as in @code{next}.
6499 @anchor{range stepping}
6500 @cindex range stepping
6501 @cindex target-assisted range stepping
6502 By default, and if available, @value{GDBN} makes use of
6503 target-assisted @dfn{range stepping}. In other words, whenever you
6504 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6505 tells the target to step the corresponding range of instruction
6506 addresses instead of issuing multiple single-steps. This speeds up
6507 line stepping, particularly for remote targets. Ideally, there should
6508 be no reason you would want to turn range stepping off. However, it's
6509 possible that a bug in the debug info, a bug in the remote stub (for
6510 remote targets), or even a bug in @value{GDBN} could make line
6511 stepping behave incorrectly when target-assisted range stepping is
6512 enabled. You can use the following command to turn off range stepping
6516 @kindex set range-stepping
6517 @kindex show range-stepping
6518 @item set range-stepping
6519 @itemx show range-stepping
6520 Control whether range stepping is enabled.
6522 If @code{on}, and the target supports it, @value{GDBN} tells the
6523 target to step a range of addresses itself, instead of issuing
6524 multiple single-steps. If @code{off}, @value{GDBN} always issues
6525 single-steps, even if range stepping is supported by the target. The
6526 default is @code{on}.
6530 @node Skipping Over Functions and Files
6531 @section Skipping Over Functions and Files
6532 @cindex skipping over functions and files
6534 The program you are debugging may contain some functions which are
6535 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6536 skip a function, all functions in a file or a particular function in
6537 a particular file when stepping.
6539 For example, consider the following C function:
6550 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6551 are not interested in stepping through @code{boring}. If you run @code{step}
6552 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6553 step over both @code{foo} and @code{boring}!
6555 One solution is to @code{step} into @code{boring} and use the @code{finish}
6556 command to immediately exit it. But this can become tedious if @code{boring}
6557 is called from many places.
6559 A more flexible solution is to execute @kbd{skip boring}. This instructs
6560 @value{GDBN} never to step into @code{boring}. Now when you execute
6561 @code{step} at line 103, you'll step over @code{boring} and directly into
6564 Functions may be skipped by providing either a function name, linespec
6565 (@pxref{Location Specifications}), regular expression that matches the function's
6566 name, file name or a @code{glob}-style pattern that matches the file name.
6568 On Posix systems the form of the regular expression is
6569 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6570 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6571 expression is whatever is provided by the @code{regcomp} function of
6572 the underlying system.
6573 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6574 description of @code{glob}-style patterns.
6578 @item skip @r{[}@var{options}@r{]}
6579 The basic form of the @code{skip} command takes zero or more options
6580 that specify what to skip.
6581 The @var{options} argument is any useful combination of the following:
6584 @item -file @var{file}
6585 @itemx -fi @var{file}
6586 Functions in @var{file} will be skipped over when stepping.
6588 @item -gfile @var{file-glob-pattern}
6589 @itemx -gfi @var{file-glob-pattern}
6590 @cindex skipping over files via glob-style patterns
6591 Functions in files matching @var{file-glob-pattern} will be skipped
6595 (@value{GDBP}) skip -gfi utils/*.c
6598 @item -function @var{linespec}
6599 @itemx -fu @var{linespec}
6600 Functions named by @var{linespec} or the function containing the line
6601 named by @var{linespec} will be skipped over when stepping.
6602 @xref{Location Specifications}.
6604 @item -rfunction @var{regexp}
6605 @itemx -rfu @var{regexp}
6606 @cindex skipping over functions via regular expressions
6607 Functions whose name matches @var{regexp} will be skipped over when stepping.
6609 This form is useful for complex function names.
6610 For example, there is generally no need to step into C@t{++} @code{std::string}
6611 constructors or destructors. Plus with C@t{++} templates it can be hard to
6612 write out the full name of the function, and often it doesn't matter what
6613 the template arguments are. Specifying the function to be skipped as a
6614 regular expression makes this easier.
6617 (@value{GDBP}) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6620 If you want to skip every templated C@t{++} constructor and destructor
6621 in the @code{std} namespace you can do:
6624 (@value{GDBP}) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6628 If no options are specified, the function you're currently debugging
6631 @kindex skip function
6632 @item skip function @r{[}@var{linespec}@r{]}
6633 After running this command, the function named by @var{linespec} or the
6634 function containing the line named by @var{linespec} will be skipped over when
6635 stepping. @xref{Location Specifications}.
6637 If you do not specify @var{linespec}, the function you're currently debugging
6640 (If you have a function called @code{file} that you want to skip, use
6641 @kbd{skip function file}.)
6644 @item skip file @r{[}@var{filename}@r{]}
6645 After running this command, any function whose source lives in @var{filename}
6646 will be skipped over when stepping.
6649 (@value{GDBP}) skip file boring.c
6650 File boring.c will be skipped when stepping.
6653 If you do not specify @var{filename}, functions whose source lives in the file
6654 you're currently debugging will be skipped.
6657 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6658 These are the commands for managing your list of skips:
6662 @item info skip @r{[}@var{range}@r{]}
6663 Print details about the specified skip(s). If @var{range} is not specified,
6664 print a table with details about all functions and files marked for skipping.
6665 @code{info skip} prints the following information about each skip:
6669 A number identifying this skip.
6670 @item Enabled or Disabled
6671 Enabled skips are marked with @samp{y}.
6672 Disabled skips are marked with @samp{n}.
6674 If the file name is a @samp{glob} pattern this is @samp{y}.
6675 Otherwise it is @samp{n}.
6677 The name or @samp{glob} pattern of the file to be skipped.
6678 If no file is specified this is @samp{<none>}.
6680 If the function name is a @samp{regular expression} this is @samp{y}.
6681 Otherwise it is @samp{n}.
6683 The name or regular expression of the function to skip.
6684 If no function is specified this is @samp{<none>}.
6688 @item skip delete @r{[}@var{range}@r{]}
6689 Delete the specified skip(s). If @var{range} is not specified, delete all
6693 @item skip enable @r{[}@var{range}@r{]}
6694 Enable the specified skip(s). If @var{range} is not specified, enable all
6697 @kindex skip disable
6698 @item skip disable @r{[}@var{range}@r{]}
6699 Disable the specified skip(s). If @var{range} is not specified, disable all
6702 @kindex set debug skip
6703 @item set debug skip @r{[}on|off@r{]}
6704 Set whether to print the debug output about skipping files and functions.
6706 @kindex show debug skip
6707 @item show debug skip
6708 Show whether the debug output about skipping files and functions is printed.
6716 A signal is an asynchronous event that can happen in a program. The
6717 operating system defines the possible kinds of signals, and gives each
6718 kind a name and a number. For example, in Unix @code{SIGINT} is the
6719 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6720 @code{SIGSEGV} is the signal a program gets from referencing a place in
6721 memory far away from all the areas in use; @code{SIGALRM} occurs when
6722 the alarm clock timer goes off (which happens only if your program has
6723 requested an alarm).
6725 @cindex fatal signals
6726 Some signals, including @code{SIGALRM}, are a normal part of the
6727 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6728 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6729 program has not specified in advance some other way to handle the signal.
6730 @code{SIGINT} does not indicate an error in your program, but it is normally
6731 fatal so it can carry out the purpose of the interrupt: to kill the program.
6733 @value{GDBN} has the ability to detect any occurrence of a signal in your
6734 program. You can tell @value{GDBN} in advance what to do for each kind of
6737 @cindex handling signals
6738 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6739 @code{SIGALRM} be silently passed to your program
6740 (so as not to interfere with their role in the program's functioning)
6741 but to stop your program immediately whenever an error signal happens.
6742 You can change these settings with the @code{handle} command.
6745 @kindex info signals
6749 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6750 handle each one. You can use this to see the signal numbers of all
6751 the defined types of signals.
6753 @item info signals @var{sig}
6754 Similar, but print information only about the specified signal number.
6756 @code{info handle} is an alias for @code{info signals}.
6758 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6759 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6760 for details about this command.
6763 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6764 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6765 can be the number of a signal or its name (with or without the
6766 @samp{SIG} at the beginning); a list of signal numbers of the form
6767 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6768 known signals. Optional arguments @var{keywords}, described below,
6769 say what change to make.
6773 The keywords allowed by the @code{handle} command can be abbreviated.
6774 Their full names are:
6778 @value{GDBN} should not stop your program when this signal happens. It may
6779 still print a message telling you that the signal has come in.
6782 @value{GDBN} should stop your program when this signal happens. This implies
6783 the @code{print} keyword as well.
6786 @value{GDBN} should print a message when this signal happens.
6789 @value{GDBN} should not mention the occurrence of the signal at all. This
6790 implies the @code{nostop} keyword as well.
6794 @value{GDBN} should allow your program to see this signal; your program
6795 can handle the signal, or else it may terminate if the signal is fatal
6796 and not handled. @code{pass} and @code{noignore} are synonyms.
6800 @value{GDBN} should not allow your program to see this signal.
6801 @code{nopass} and @code{ignore} are synonyms.
6805 When a signal stops your program, the signal is not visible to the
6807 continue. Your program sees the signal then, if @code{pass} is in
6808 effect for the signal in question @emph{at that time}. In other words,
6809 after @value{GDBN} reports a signal, you can use the @code{handle}
6810 command with @code{pass} or @code{nopass} to control whether your
6811 program sees that signal when you continue.
6813 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6814 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6815 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6818 You can also use the @code{signal} command to prevent your program from
6819 seeing a signal, or cause it to see a signal it normally would not see,
6820 or to give it any signal at any time. For example, if your program stopped
6821 due to some sort of memory reference error, you might store correct
6822 values into the erroneous variables and continue, hoping to see more
6823 execution; but your program would probably terminate immediately as
6824 a result of the fatal signal once it saw the signal. To prevent this,
6825 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6828 @cindex stepping and signal handlers
6829 @anchor{stepping and signal handlers}
6831 @value{GDBN} optimizes for stepping the mainline code. If a signal
6832 that has @code{handle nostop} and @code{handle pass} set arrives while
6833 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6834 in progress, @value{GDBN} lets the signal handler run and then resumes
6835 stepping the mainline code once the signal handler returns. In other
6836 words, @value{GDBN} steps over the signal handler. This prevents
6837 signals that you've specified as not interesting (with @code{handle
6838 nostop}) from changing the focus of debugging unexpectedly. Note that
6839 the signal handler itself may still hit a breakpoint, stop for another
6840 signal that has @code{handle stop} in effect, or for any other event
6841 that normally results in stopping the stepping command sooner. Also
6842 note that @value{GDBN} still informs you that the program received a
6843 signal if @code{handle print} is set.
6845 @anchor{stepping into signal handlers}
6847 If you set @code{handle pass} for a signal, and your program sets up a
6848 handler for it, then issuing a stepping command, such as @code{step}
6849 or @code{stepi}, when your program is stopped due to the signal will
6850 step @emph{into} the signal handler (if the target supports that).
6852 Likewise, if you use the @code{queue-signal} command to queue a signal
6853 to be delivered to the current thread when execution of the thread
6854 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6855 stepping command will step into the signal handler.
6857 Here's an example, using @code{stepi} to step to the first instruction
6858 of @code{SIGUSR1}'s handler:
6861 (@value{GDBP}) handle SIGUSR1
6862 Signal Stop Print Pass to program Description
6863 SIGUSR1 Yes Yes Yes User defined signal 1
6867 Program received signal SIGUSR1, User defined signal 1.
6868 main () sigusr1.c:28
6871 sigusr1_handler () at sigusr1.c:9
6875 The same, but using @code{queue-signal} instead of waiting for the
6876 program to receive the signal first:
6881 (@value{GDBP}) queue-signal SIGUSR1
6883 sigusr1_handler () at sigusr1.c:9
6888 @cindex extra signal information
6889 @anchor{extra signal information}
6891 On some targets, @value{GDBN} can inspect extra signal information
6892 associated with the intercepted signal, before it is actually
6893 delivered to the program being debugged. This information is exported
6894 by the convenience variable @code{$_siginfo}, and consists of data
6895 that is passed by the kernel to the signal handler at the time of the
6896 receipt of a signal. The data type of the information itself is
6897 target dependent. You can see the data type using the @code{ptype
6898 $_siginfo} command. On Unix systems, it typically corresponds to the
6899 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6902 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6903 referenced address that raised a segmentation fault.
6907 (@value{GDBP}) continue
6908 Program received signal SIGSEGV, Segmentation fault.
6909 0x0000000000400766 in main ()
6911 (@value{GDBP}) ptype $_siginfo
6918 struct @{...@} _kill;
6919 struct @{...@} _timer;
6921 struct @{...@} _sigchld;
6922 struct @{...@} _sigfault;
6923 struct @{...@} _sigpoll;
6926 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6930 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6931 $1 = (void *) 0x7ffff7ff7000
6935 Depending on target support, @code{$_siginfo} may also be writable.
6937 @cindex Intel MPX boundary violations
6938 @cindex boundary violations, Intel MPX
6939 On some targets, a @code{SIGSEGV} can be caused by a boundary
6940 violation, i.e., accessing an address outside of the allowed range.
6941 In those cases @value{GDBN} may displays additional information,
6942 depending on how @value{GDBN} has been told to handle the signal.
6943 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6944 kind: "Upper" or "Lower", the memory address accessed and the
6945 bounds, while with @code{handle nostop SIGSEGV} no additional
6946 information is displayed.
6948 The usual output of a segfault is:
6950 Program received signal SIGSEGV, Segmentation fault
6951 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6952 68 value = *(p + len);
6955 While a bound violation is presented as:
6957 Program received signal SIGSEGV, Segmentation fault
6958 Upper bound violation while accessing address 0x7fffffffc3b3
6959 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6960 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6961 68 value = *(p + len);
6965 @section Stopping and Starting Multi-thread Programs
6967 @cindex stopped threads
6968 @cindex threads, stopped
6970 @cindex continuing threads
6971 @cindex threads, continuing
6973 @value{GDBN} supports debugging programs with multiple threads
6974 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6975 are two modes of controlling execution of your program within the
6976 debugger. In the default mode, referred to as @dfn{all-stop mode},
6977 when any thread in your program stops (for example, at a breakpoint
6978 or while being stepped), all other threads in the program are also stopped by
6979 @value{GDBN}. On some targets, @value{GDBN} also supports
6980 @dfn{non-stop mode}, in which other threads can continue to run freely while
6981 you examine the stopped thread in the debugger.
6984 * All-Stop Mode:: All threads stop when GDB takes control
6985 * Non-Stop Mode:: Other threads continue to execute
6986 * Background Execution:: Running your program asynchronously
6987 * Thread-Specific Breakpoints:: Controlling breakpoints
6988 * Interrupted System Calls:: GDB may interfere with system calls
6989 * Observer Mode:: GDB does not alter program behavior
6993 @subsection All-Stop Mode
6995 @cindex all-stop mode
6997 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6998 @emph{all} threads of execution stop, not just the current thread. This
6999 allows you to examine the overall state of the program, including
7000 switching between threads, without worrying that things may change
7003 Conversely, whenever you restart the program, @emph{all} threads start
7004 executing. @emph{This is true even when single-stepping} with commands
7005 like @code{step} or @code{next}.
7007 In particular, @value{GDBN} cannot single-step all threads in lockstep.
7008 Since thread scheduling is up to your debugging target's operating
7009 system (not controlled by @value{GDBN}), other threads may
7010 execute more than one statement while the current thread completes a
7011 single step. Moreover, in general other threads stop in the middle of a
7012 statement, rather than at a clean statement boundary, when the program
7015 You might even find your program stopped in another thread after
7016 continuing or even single-stepping. This happens whenever some other
7017 thread runs into a breakpoint, a signal, or an exception before the
7018 first thread completes whatever you requested.
7020 @cindex automatic thread selection
7021 @cindex switching threads automatically
7022 @cindex threads, automatic switching
7023 Whenever @value{GDBN} stops your program, due to a breakpoint or a
7024 signal, it automatically selects the thread where that breakpoint or
7025 signal happened. @value{GDBN} alerts you to the context switch with a
7026 message such as @samp{[Switching to Thread @var{n}]} to identify the
7029 On some OSes, you can modify @value{GDBN}'s default behavior by
7030 locking the OS scheduler to allow only a single thread to run.
7033 @item set scheduler-locking @var{mode}
7034 @cindex scheduler locking mode
7035 @cindex lock scheduler
7036 Set the scheduler locking mode. It applies to normal execution,
7037 record mode, and replay mode. @var{mode} can be one of
7042 There is no locking and any thread may run at any time.
7045 Only the current thread may run when the inferior is resumed.
7048 Behaves like @code{on} when stepping, and @code{off} otherwise.
7049 Threads other than the current never get a chance to run when you
7050 step, and they are completely free to run when you use commands like
7051 @samp{continue}, @samp{until}, or @samp{finish}.
7053 This mode optimizes for single-stepping; it prevents other threads
7054 from preempting the current thread while you are stepping, so that the
7055 focus of debugging does not change unexpectedly. However, unless
7056 another thread hits a breakpoint during its timeslice, @value{GDBN}
7057 does not change the current thread away from the thread that you are
7061 Behaves like @code{on} in replay mode, and @code{off} in either record
7062 mode or during normal execution. This is the default mode.
7065 @item show scheduler-locking
7066 Display the current scheduler locking mode.
7069 @cindex resume threads of multiple processes simultaneously
7070 By default, when you issue one of the execution commands such as
7071 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
7072 threads of the current inferior to run. For example, if @value{GDBN}
7073 is attached to two inferiors, each with two threads, the
7074 @code{continue} command resumes only the two threads of the current
7075 inferior. This is useful, for example, when you debug a program that
7076 forks and you want to hold the parent stopped (so that, for instance,
7077 it doesn't run to exit), while you debug the child. In other
7078 situations, you may not be interested in inspecting the current state
7079 of any of the processes @value{GDBN} is attached to, and you may want
7080 to resume them all until some breakpoint is hit. In the latter case,
7081 you can instruct @value{GDBN} to allow all threads of all the
7082 inferiors to run with the @w{@code{set schedule-multiple}} command.
7085 @kindex set schedule-multiple
7086 @item set schedule-multiple
7087 Set the mode for allowing threads of multiple processes to be resumed
7088 when an execution command is issued. When @code{on}, all threads of
7089 all processes are allowed to run. When @code{off}, only the threads
7090 of the current process are resumed. The default is @code{off}. The
7091 @code{scheduler-locking} mode takes precedence when set to @code{on},
7092 or while you are stepping and set to @code{step}.
7094 @item show schedule-multiple
7095 Display the current mode for resuming the execution of threads of
7100 @subsection Non-Stop Mode
7102 @cindex non-stop mode
7104 @c This section is really only a place-holder, and needs to be expanded
7105 @c with more details.
7107 For some multi-threaded targets, @value{GDBN} supports an optional
7108 mode of operation in which you can examine stopped program threads in
7109 the debugger while other threads continue to execute freely. This
7110 minimizes intrusion when debugging live systems, such as programs
7111 where some threads have real-time constraints or must continue to
7112 respond to external events. This is referred to as @dfn{non-stop} mode.
7114 In non-stop mode, when a thread stops to report a debugging event,
7115 @emph{only} that thread is stopped; @value{GDBN} does not stop other
7116 threads as well, in contrast to the all-stop mode behavior. Additionally,
7117 execution commands such as @code{continue} and @code{step} apply by default
7118 only to the current thread in non-stop mode, rather than all threads as
7119 in all-stop mode. This allows you to control threads explicitly in
7120 ways that are not possible in all-stop mode --- for example, stepping
7121 one thread while allowing others to run freely, stepping
7122 one thread while holding all others stopped, or stepping several threads
7123 independently and simultaneously.
7125 To enter non-stop mode, use this sequence of commands before you run
7126 or attach to your program:
7129 # If using the CLI, pagination breaks non-stop.
7132 # Finally, turn it on!
7136 You can use these commands to manipulate the non-stop mode setting:
7139 @kindex set non-stop
7140 @item set non-stop on
7141 Enable selection of non-stop mode.
7142 @item set non-stop off
7143 Disable selection of non-stop mode.
7144 @kindex show non-stop
7146 Show the current non-stop enablement setting.
7149 Note these commands only reflect whether non-stop mode is enabled,
7150 not whether the currently-executing program is being run in non-stop mode.
7151 In particular, the @code{set non-stop} preference is only consulted when
7152 @value{GDBN} starts or connects to the target program, and it is generally
7153 not possible to switch modes once debugging has started. Furthermore,
7154 since not all targets support non-stop mode, even when you have enabled
7155 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
7158 In non-stop mode, all execution commands apply only to the current thread
7159 by default. That is, @code{continue} only continues one thread.
7160 To continue all threads, issue @code{continue -a} or @code{c -a}.
7162 You can use @value{GDBN}'s background execution commands
7163 (@pxref{Background Execution}) to run some threads in the background
7164 while you continue to examine or step others from @value{GDBN}.
7165 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7166 always executed asynchronously in non-stop mode.
7168 Suspending execution is done with the @code{interrupt} command when
7169 running in the background, or @kbd{Ctrl-c} during foreground execution.
7170 In all-stop mode, this stops the whole process;
7171 but in non-stop mode the interrupt applies only to the current thread.
7172 To stop the whole program, use @code{interrupt -a}.
7174 Other execution commands do not currently support the @code{-a} option.
7176 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7177 that thread current, as it does in all-stop mode. This is because the
7178 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7179 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7180 changed to a different thread just as you entered a command to operate on the
7181 previously current thread.
7183 @node Background Execution
7184 @subsection Background Execution
7186 @cindex foreground execution
7187 @cindex background execution
7188 @cindex asynchronous execution
7189 @cindex execution, foreground, background and asynchronous
7191 @value{GDBN}'s execution commands have two variants: the normal
7192 foreground (synchronous) behavior, and a background
7193 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7194 the program to report that some thread has stopped before prompting for
7195 another command. In background execution, @value{GDBN} immediately gives
7196 a command prompt so that you can issue other commands while your program runs.
7198 If the target doesn't support async mode, @value{GDBN} issues an error
7199 message if you attempt to use the background execution commands.
7201 @cindex @code{&}, background execution of commands
7202 To specify background execution, add a @code{&} to the command. For example,
7203 the background form of the @code{continue} command is @code{continue&}, or
7204 just @code{c&}. The execution commands that accept background execution
7210 @xref{Starting, , Starting your Program}.
7214 @xref{Attach, , Debugging an Already-running Process}.
7218 @xref{Continuing and Stepping, step}.
7222 @xref{Continuing and Stepping, stepi}.
7226 @xref{Continuing and Stepping, next}.
7230 @xref{Continuing and Stepping, nexti}.
7234 @xref{Continuing and Stepping, continue}.
7238 @xref{Continuing and Stepping, finish}.
7242 @xref{Continuing and Stepping, until}.
7246 Background execution is especially useful in conjunction with non-stop
7247 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7248 However, you can also use these commands in the normal all-stop mode with
7249 the restriction that you cannot issue another execution command until the
7250 previous one finishes. Examples of commands that are valid in all-stop
7251 mode while the program is running include @code{help} and @code{info break}.
7253 You can interrupt your program while it is running in the background by
7254 using the @code{interrupt} command.
7261 Suspend execution of the running program. In all-stop mode,
7262 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7263 only the current thread. To stop the whole program in non-stop mode,
7264 use @code{interrupt -a}.
7267 @node Thread-Specific Breakpoints
7268 @subsection Thread-Specific Breakpoints
7270 When your program has multiple threads (@pxref{Threads,, Debugging
7271 Programs with Multiple Threads}), you can choose whether to set
7272 breakpoints on all threads, or on a particular thread.
7275 @cindex breakpoints and threads
7276 @cindex thread breakpoints
7277 @kindex break @dots{} thread @var{thread-id}
7278 @item break @var{locspec} thread @var{thread-id}
7279 @itemx break @var{locspec} thread @var{thread-id} if @dots{}
7280 @var{locspec} specifies a code location or locations in your program.
7281 @xref{Location Specifications}, for details.
7283 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7284 to specify that you only want @value{GDBN} to stop the program when a
7285 particular thread reaches this breakpoint. The @var{thread-id} specifier
7286 is one of the thread identifiers assigned by @value{GDBN}, shown
7287 in the first column of the @samp{info threads} display.
7289 If you do not specify @samp{thread @var{thread-id}} when you set a
7290 breakpoint, the breakpoint applies to @emph{all} threads of your
7293 You can use the @code{thread} qualifier on conditional breakpoints as
7294 well; in this case, place @samp{thread @var{thread-id}} before or
7295 after the breakpoint condition, like this:
7298 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7303 Thread-specific breakpoints are automatically deleted when
7304 @value{GDBN} detects the corresponding thread is no longer in the
7305 thread list. For example:
7309 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7312 There are several ways for a thread to disappear, such as a regular
7313 thread exit, but also when you detach from the process with the
7314 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7315 Process}), or if @value{GDBN} loses the remote connection
7316 (@pxref{Remote Debugging}), etc. Note that with some targets,
7317 @value{GDBN} is only able to detect a thread has exited when the user
7318 explictly asks for the thread list with the @code{info threads}
7321 @node Interrupted System Calls
7322 @subsection Interrupted System Calls
7324 @cindex thread breakpoints and system calls
7325 @cindex system calls and thread breakpoints
7326 @cindex premature return from system calls
7327 There is an unfortunate side effect when using @value{GDBN} to debug
7328 multi-threaded programs. If one thread stops for a
7329 breakpoint, or for some other reason, and another thread is blocked in a
7330 system call, then the system call may return prematurely. This is a
7331 consequence of the interaction between multiple threads and the signals
7332 that @value{GDBN} uses to implement breakpoints and other events that
7335 To handle this problem, your program should check the return value of
7336 each system call and react appropriately. This is good programming
7339 For example, do not write code like this:
7345 The call to @code{sleep} will return early if a different thread stops
7346 at a breakpoint or for some other reason.
7348 Instead, write this:
7353 unslept = sleep (unslept);
7356 A system call is allowed to return early, so the system is still
7357 conforming to its specification. But @value{GDBN} does cause your
7358 multi-threaded program to behave differently than it would without
7361 Also, @value{GDBN} uses internal breakpoints in the thread library to
7362 monitor certain events such as thread creation and thread destruction.
7363 When such an event happens, a system call in another thread may return
7364 prematurely, even though your program does not appear to stop.
7367 @subsection Observer Mode
7369 If you want to build on non-stop mode and observe program behavior
7370 without any chance of disruption by @value{GDBN}, you can set
7371 variables to disable all of the debugger's attempts to modify state,
7372 whether by writing memory, inserting breakpoints, etc. These operate
7373 at a low level, intercepting operations from all commands.
7375 When all of these are set to @code{off}, then @value{GDBN} is said to
7376 be @dfn{observer mode}. As a convenience, the variable
7377 @code{observer} can be set to disable these, plus enable non-stop
7380 Note that @value{GDBN} will not prevent you from making nonsensical
7381 combinations of these settings. For instance, if you have enabled
7382 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7383 then breakpoints that work by writing trap instructions into the code
7384 stream will still not be able to be placed.
7389 @item set observer on
7390 @itemx set observer off
7391 When set to @code{on}, this disables all the permission variables
7392 below (except for @code{insert-fast-tracepoints}), plus enables
7393 non-stop debugging. Setting this to @code{off} switches back to
7394 normal debugging, though remaining in non-stop mode.
7397 Show whether observer mode is on or off.
7399 @kindex may-write-registers
7400 @item set may-write-registers on
7401 @itemx set may-write-registers off
7402 This controls whether @value{GDBN} will attempt to alter the values of
7403 registers, such as with assignment expressions in @code{print}, or the
7404 @code{jump} command. It defaults to @code{on}.
7406 @item show may-write-registers
7407 Show the current permission to write registers.
7409 @kindex may-write-memory
7410 @item set may-write-memory on
7411 @itemx set may-write-memory off
7412 This controls whether @value{GDBN} will attempt to alter the contents
7413 of memory, such as with assignment expressions in @code{print}. It
7414 defaults to @code{on}.
7416 @item show may-write-memory
7417 Show the current permission to write memory.
7419 @kindex may-insert-breakpoints
7420 @item set may-insert-breakpoints on
7421 @itemx set may-insert-breakpoints off
7422 This controls whether @value{GDBN} will attempt to insert breakpoints.
7423 This affects all breakpoints, including internal breakpoints defined
7424 by @value{GDBN}. It defaults to @code{on}.
7426 @item show may-insert-breakpoints
7427 Show the current permission to insert breakpoints.
7429 @kindex may-insert-tracepoints
7430 @item set may-insert-tracepoints on
7431 @itemx set may-insert-tracepoints off
7432 This controls whether @value{GDBN} will attempt to insert (regular)
7433 tracepoints at the beginning of a tracing experiment. It affects only
7434 non-fast tracepoints, fast tracepoints being under the control of
7435 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7437 @item show may-insert-tracepoints
7438 Show the current permission to insert tracepoints.
7440 @kindex may-insert-fast-tracepoints
7441 @item set may-insert-fast-tracepoints on
7442 @itemx set may-insert-fast-tracepoints off
7443 This controls whether @value{GDBN} will attempt to insert fast
7444 tracepoints at the beginning of a tracing experiment. It affects only
7445 fast tracepoints, regular (non-fast) tracepoints being under the
7446 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7448 @item show may-insert-fast-tracepoints
7449 Show the current permission to insert fast tracepoints.
7451 @kindex may-interrupt
7452 @item set may-interrupt on
7453 @itemx set may-interrupt off
7454 This controls whether @value{GDBN} will attempt to interrupt or stop
7455 program execution. When this variable is @code{off}, the
7456 @code{interrupt} command will have no effect, nor will
7457 @kbd{Ctrl-c}. It defaults to @code{on}.
7459 @item show may-interrupt
7460 Show the current permission to interrupt or stop the program.
7464 @node Reverse Execution
7465 @chapter Running programs backward
7466 @cindex reverse execution
7467 @cindex running programs backward
7469 When you are debugging a program, it is not unusual to realize that
7470 you have gone too far, and some event of interest has already happened.
7471 If the target environment supports it, @value{GDBN} can allow you to
7472 ``rewind'' the program by running it backward.
7474 A target environment that supports reverse execution should be able
7475 to ``undo'' the changes in machine state that have taken place as the
7476 program was executing normally. Variables, registers etc.@: should
7477 revert to their previous values. Obviously this requires a great
7478 deal of sophistication on the part of the target environment; not
7479 all target environments can support reverse execution.
7481 When a program is executed in reverse, the instructions that
7482 have most recently been executed are ``un-executed'', in reverse
7483 order. The program counter runs backward, following the previous
7484 thread of execution in reverse. As each instruction is ``un-executed'',
7485 the values of memory and/or registers that were changed by that
7486 instruction are reverted to their previous states. After executing
7487 a piece of source code in reverse, all side effects of that code
7488 should be ``undone'', and all variables should be returned to their
7489 prior values@footnote{
7490 Note that some side effects are easier to undo than others. For instance,
7491 memory and registers are relatively easy, but device I/O is hard. Some
7492 targets may be able undo things like device I/O, and some may not.
7494 The contract between @value{GDBN} and the reverse executing target
7495 requires only that the target do something reasonable when
7496 @value{GDBN} tells it to execute backwards, and then report the
7497 results back to @value{GDBN}. Whatever the target reports back to
7498 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7499 assumes that the memory and registers that the target reports are in a
7500 consistent state, but @value{GDBN} accepts whatever it is given.
7503 On some platforms, @value{GDBN} has built-in support for reverse
7504 execution, activated with the @code{record} or @code{record btrace}
7505 commands. @xref{Process Record and Replay}. Some remote targets,
7506 typically full system emulators, support reverse execution directly
7507 without requiring any special command.
7509 If you are debugging in a target environment that supports
7510 reverse execution, @value{GDBN} provides the following commands.
7513 @kindex reverse-continue
7514 @kindex rc @r{(@code{reverse-continue})}
7515 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7516 @itemx rc @r{[}@var{ignore-count}@r{]}
7517 Beginning at the point where your program last stopped, start executing
7518 in reverse. Reverse execution will stop for breakpoints and synchronous
7519 exceptions (signals), just like normal execution. Behavior of
7520 asynchronous signals depends on the target environment.
7522 @kindex reverse-step
7523 @kindex rs @r{(@code{step})}
7524 @item reverse-step @r{[}@var{count}@r{]}
7525 Run the program backward until control reaches the start of a
7526 different source line; then stop it, and return control to @value{GDBN}.
7528 Like the @code{step} command, @code{reverse-step} will only stop
7529 at the beginning of a source line. It ``un-executes'' the previously
7530 executed source line. If the previous source line included calls to
7531 debuggable functions, @code{reverse-step} will step (backward) into
7532 the called function, stopping at the beginning of the @emph{last}
7533 statement in the called function (typically a return statement).
7535 Also, as with the @code{step} command, if non-debuggable functions are
7536 called, @code{reverse-step} will run thru them backward without stopping.
7538 @kindex reverse-stepi
7539 @kindex rsi @r{(@code{reverse-stepi})}
7540 @item reverse-stepi @r{[}@var{count}@r{]}
7541 Reverse-execute one machine instruction. Note that the instruction
7542 to be reverse-executed is @emph{not} the one pointed to by the program
7543 counter, but the instruction executed prior to that one. For instance,
7544 if the last instruction was a jump, @code{reverse-stepi} will take you
7545 back from the destination of the jump to the jump instruction itself.
7547 @kindex reverse-next
7548 @kindex rn @r{(@code{reverse-next})}
7549 @item reverse-next @r{[}@var{count}@r{]}
7550 Run backward to the beginning of the previous line executed in
7551 the current (innermost) stack frame. If the line contains function
7552 calls, they will be ``un-executed'' without stopping. Starting from
7553 the first line of a function, @code{reverse-next} will take you back
7554 to the caller of that function, @emph{before} the function was called,
7555 just as the normal @code{next} command would take you from the last
7556 line of a function back to its return to its caller
7557 @footnote{Unless the code is too heavily optimized.}.
7559 @kindex reverse-nexti
7560 @kindex rni @r{(@code{reverse-nexti})}
7561 @item reverse-nexti @r{[}@var{count}@r{]}
7562 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7563 in reverse, except that called functions are ``un-executed'' atomically.
7564 That is, if the previously executed instruction was a return from
7565 another function, @code{reverse-nexti} will continue to execute
7566 in reverse until the call to that function (from the current stack
7569 @kindex reverse-finish
7570 @item reverse-finish
7571 Just as the @code{finish} command takes you to the point where the
7572 current function returns, @code{reverse-finish} takes you to the point
7573 where it was called. Instead of ending up at the end of the current
7574 function invocation, you end up at the beginning.
7576 @kindex set exec-direction
7577 @item set exec-direction
7578 Set the direction of target execution.
7579 @item set exec-direction reverse
7580 @cindex execute forward or backward in time
7581 @value{GDBN} will perform all execution commands in reverse, until the
7582 exec-direction mode is changed to ``forward''. Affected commands include
7583 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7584 command cannot be used in reverse mode.
7585 @item set exec-direction forward
7586 @value{GDBN} will perform all execution commands in the normal fashion.
7587 This is the default.
7591 @node Process Record and Replay
7592 @chapter Recording Inferior's Execution and Replaying It
7593 @cindex process record and replay
7594 @cindex recording inferior's execution and replaying it
7596 On some platforms, @value{GDBN} provides a special @dfn{process record
7597 and replay} target that can record a log of the process execution, and
7598 replay it later with both forward and reverse execution commands.
7601 When this target is in use, if the execution log includes the record
7602 for the next instruction, @value{GDBN} will debug in @dfn{replay
7603 mode}. In the replay mode, the inferior does not really execute code
7604 instructions. Instead, all the events that normally happen during
7605 code execution are taken from the execution log. While code is not
7606 really executed in replay mode, the values of registers (including the
7607 program counter register) and the memory of the inferior are still
7608 changed as they normally would. Their contents are taken from the
7612 If the record for the next instruction is not in the execution log,
7613 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7614 inferior executes normally, and @value{GDBN} records the execution log
7617 The process record and replay target supports reverse execution
7618 (@pxref{Reverse Execution}), even if the platform on which the
7619 inferior runs does not. However, the reverse execution is limited in
7620 this case by the range of the instructions recorded in the execution
7621 log. In other words, reverse execution on platforms that don't
7622 support it directly can only be done in the replay mode.
7624 When debugging in the reverse direction, @value{GDBN} will work in
7625 replay mode as long as the execution log includes the record for the
7626 previous instruction; otherwise, it will work in record mode, if the
7627 platform supports reverse execution, or stop if not.
7629 Currently, process record and replay is supported on ARM, Aarch64,
7630 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7631 GNU/Linux. Process record and replay can be used both when native
7632 debugging, and when remote debugging via @code{gdbserver}.
7634 For architecture environments that support process record and replay,
7635 @value{GDBN} provides the following commands:
7638 @kindex target record
7639 @kindex target record-full
7640 @kindex target record-btrace
7643 @kindex record btrace
7644 @kindex record btrace bts
7645 @kindex record btrace pt
7651 @kindex rec btrace bts
7652 @kindex rec btrace pt
7655 @item record @var{method}
7656 This command starts the process record and replay target. The
7657 recording method can be specified as parameter. Without a parameter
7658 the command uses the @code{full} recording method. The following
7659 recording methods are available:
7663 Full record/replay recording using @value{GDBN}'s software record and
7664 replay implementation. This method allows replaying and reverse
7667 @item btrace @var{format}
7668 Hardware-supported instruction recording, supported on Intel
7669 processors. This method does not record data. Further, the data is
7670 collected in a ring buffer so old data will be overwritten when the
7671 buffer is full. It allows limited reverse execution. Variables and
7672 registers are not available during reverse execution. In remote
7673 debugging, recording continues on disconnect. Recorded data can be
7674 inspected after reconnecting. The recording may be stopped using
7677 The recording format can be specified as parameter. Without a parameter
7678 the command chooses the recording format. The following recording
7679 formats are available:
7683 @cindex branch trace store
7684 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7685 this format, the processor stores a from/to record for each executed
7686 branch in the btrace ring buffer.
7689 @cindex Intel Processor Trace
7690 Use the @dfn{Intel Processor Trace} recording format. In this
7691 format, the processor stores the execution trace in a compressed form
7692 that is afterwards decoded by @value{GDBN}.
7694 The trace can be recorded with very low overhead. The compressed
7695 trace format also allows small trace buffers to already contain a big
7696 number of instructions compared to @acronym{BTS}.
7698 Decoding the recorded execution trace, on the other hand, is more
7699 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7700 increased number of instructions to process. You should increase the
7701 buffer-size with care.
7704 Not all recording formats may be available on all processors.
7707 The process record and replay target can only debug a process that is
7708 already running. Therefore, you need first to start the process with
7709 the @kbd{run} or @kbd{start} commands, and then start the recording
7710 with the @kbd{record @var{method}} command.
7712 @cindex displaced stepping, and process record and replay
7713 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7714 will be automatically disabled when process record and replay target
7715 is started. That's because the process record and replay target
7716 doesn't support displaced stepping.
7718 @cindex non-stop mode, and process record and replay
7719 @cindex asynchronous execution, and process record and replay
7720 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7721 the asynchronous execution mode (@pxref{Background Execution}), not
7722 all recording methods are available. The @code{full} recording method
7723 does not support these two modes.
7728 Stop the process record and replay target. When process record and
7729 replay target stops, the entire execution log will be deleted and the
7730 inferior will either be terminated, or will remain in its final state.
7732 When you stop the process record and replay target in record mode (at
7733 the end of the execution log), the inferior will be stopped at the
7734 next instruction that would have been recorded. In other words, if
7735 you record for a while and then stop recording, the inferior process
7736 will be left in the same state as if the recording never happened.
7738 On the other hand, if the process record and replay target is stopped
7739 while in replay mode (that is, not at the end of the execution log,
7740 but at some earlier point), the inferior process will become ``live''
7741 at that earlier state, and it will then be possible to continue the
7742 usual ``live'' debugging of the process from that state.
7744 When the inferior process exits, or @value{GDBN} detaches from it,
7745 process record and replay target will automatically stop itself.
7749 Go to a specific location in the execution log. There are several
7750 ways to specify the location to go to:
7753 @item record goto begin
7754 @itemx record goto start
7755 Go to the beginning of the execution log.
7757 @item record goto end
7758 Go to the end of the execution log.
7760 @item record goto @var{n}
7761 Go to instruction number @var{n} in the execution log.
7765 @item record save @var{filename}
7766 Save the execution log to a file @file{@var{filename}}.
7767 Default filename is @file{gdb_record.@var{process_id}}, where
7768 @var{process_id} is the process ID of the inferior.
7770 This command may not be available for all recording methods.
7772 @kindex record restore
7773 @item record restore @var{filename}
7774 Restore the execution log from a file @file{@var{filename}}.
7775 File must have been created with @code{record save}.
7777 @kindex set record full
7778 @item set record full insn-number-max @var{limit}
7779 @itemx set record full insn-number-max unlimited
7780 Set the limit of instructions to be recorded for the @code{full}
7781 recording method. Default value is 200000.
7783 If @var{limit} is a positive number, then @value{GDBN} will start
7784 deleting instructions from the log once the number of the record
7785 instructions becomes greater than @var{limit}. For every new recorded
7786 instruction, @value{GDBN} will delete the earliest recorded
7787 instruction to keep the number of recorded instructions at the limit.
7788 (Since deleting recorded instructions loses information, @value{GDBN}
7789 lets you control what happens when the limit is reached, by means of
7790 the @code{stop-at-limit} option, described below.)
7792 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7793 delete recorded instructions from the execution log. The number of
7794 recorded instructions is limited only by the available memory.
7796 @kindex show record full
7797 @item show record full insn-number-max
7798 Show the limit of instructions to be recorded with the @code{full}
7801 @item set record full stop-at-limit
7802 Control the behavior of the @code{full} recording method when the
7803 number of recorded instructions reaches the limit. If ON (the
7804 default), @value{GDBN} will stop when the limit is reached for the
7805 first time and ask you whether you want to stop the inferior or
7806 continue running it and recording the execution log. If you decide
7807 to continue recording, each new recorded instruction will cause the
7808 oldest one to be deleted.
7810 If this option is OFF, @value{GDBN} will automatically delete the
7811 oldest record to make room for each new one, without asking.
7813 @item show record full stop-at-limit
7814 Show the current setting of @code{stop-at-limit}.
7816 @item set record full memory-query
7817 Control the behavior when @value{GDBN} is unable to record memory
7818 changes caused by an instruction for the @code{full} recording method.
7819 If ON, @value{GDBN} will query whether to stop the inferior in that
7822 If this option is OFF (the default), @value{GDBN} will automatically
7823 ignore the effect of such instructions on memory. Later, when
7824 @value{GDBN} replays this execution log, it will mark the log of this
7825 instruction as not accessible, and it will not affect the replay
7828 @item show record full memory-query
7829 Show the current setting of @code{memory-query}.
7831 @kindex set record btrace
7832 The @code{btrace} record target does not trace data. As a
7833 convenience, when replaying, @value{GDBN} reads read-only memory off
7834 the live program directly, assuming that the addresses of the
7835 read-only areas don't change. This for example makes it possible to
7836 disassemble code while replaying, but not to print variables.
7837 In some cases, being able to inspect variables might be useful.
7838 You can use the following command for that:
7840 @item set record btrace replay-memory-access
7841 Control the behavior of the @code{btrace} recording method when
7842 accessing memory during replay. If @code{read-only} (the default),
7843 @value{GDBN} will only allow accesses to read-only memory.
7844 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7845 and to read-write memory. Beware that the accessed memory corresponds
7846 to the live target and not necessarily to the current replay
7849 @item set record btrace cpu @var{identifier}
7850 Set the processor to be used for enabling workarounds for processor
7851 errata when decoding the trace.
7853 Processor errata are defects in processor operation, caused by its
7854 design or manufacture. They can cause a trace not to match the
7855 specification. This, in turn, may cause trace decode to fail.
7856 @value{GDBN} can detect erroneous trace packets and correct them, thus
7857 avoiding the decoding failures. These corrections are known as
7858 @dfn{errata workarounds}, and are enabled based on the processor on
7859 which the trace was recorded.
7861 By default, @value{GDBN} attempts to detect the processor
7862 automatically, and apply the necessary workarounds for it. However,
7863 you may need to specify the processor if @value{GDBN} does not yet
7864 support it. This command allows you to do that, and also allows to
7865 disable the workarounds.
7867 The argument @var{identifier} identifies the @sc{cpu} and is of the
7868 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7869 there are two special identifiers, @code{none} and @code{auto}
7872 The following vendor identifiers and corresponding processor
7873 identifiers are currently supported:
7875 @multitable @columnfractions .1 .9
7878 @tab @var{family}/@var{model}[/@var{stepping}]
7882 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7883 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7885 If @var{identifier} is @code{auto}, enable errata workarounds for the
7886 processor on which the trace was recorded. If @var{identifier} is
7887 @code{none}, errata workarounds are disabled.
7889 For example, when using an old @value{GDBN} on a new system, decode
7890 may fail because @value{GDBN} does not support the new processor. It
7891 often suffices to specify an older processor that @value{GDBN}
7895 (@value{GDBP}) info record
7896 Active record target: record-btrace
7897 Recording format: Intel Processor Trace.
7899 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7900 (@value{GDBP}) set record btrace cpu intel:6/158
7901 (@value{GDBP}) info record
7902 Active record target: record-btrace
7903 Recording format: Intel Processor Trace.
7905 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7908 @kindex show record btrace
7909 @item show record btrace replay-memory-access
7910 Show the current setting of @code{replay-memory-access}.
7912 @item show record btrace cpu
7913 Show the processor to be used for enabling trace decode errata
7916 @kindex set record btrace bts
7917 @item set record btrace bts buffer-size @var{size}
7918 @itemx set record btrace bts buffer-size unlimited
7919 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7920 format. Default is 64KB.
7922 If @var{size} is a positive number, then @value{GDBN} will try to
7923 allocate a buffer of at least @var{size} bytes for each new thread
7924 that uses the btrace recording method and the @acronym{BTS} format.
7925 The actually obtained buffer size may differ from the requested
7926 @var{size}. Use the @code{info record} command to see the actual
7927 buffer size for each thread that uses the btrace recording method and
7928 the @acronym{BTS} format.
7930 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7931 allocate a buffer of 4MB.
7933 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7934 also need longer to process the branch trace data before it can be used.
7936 @item show record btrace bts buffer-size @var{size}
7937 Show the current setting of the requested ring buffer size for branch
7938 tracing in @acronym{BTS} format.
7940 @kindex set record btrace pt
7941 @item set record btrace pt buffer-size @var{size}
7942 @itemx set record btrace pt buffer-size unlimited
7943 Set the requested ring buffer size for branch tracing in Intel
7944 Processor Trace format. Default is 16KB.
7946 If @var{size} is a positive number, then @value{GDBN} will try to
7947 allocate a buffer of at least @var{size} bytes for each new thread
7948 that uses the btrace recording method and the Intel Processor Trace
7949 format. The actually obtained buffer size may differ from the
7950 requested @var{size}. Use the @code{info record} command to see the
7951 actual buffer size for each thread.
7953 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7954 allocate a buffer of 4MB.
7956 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7957 also need longer to process the branch trace data before it can be used.
7959 @item show record btrace pt buffer-size @var{size}
7960 Show the current setting of the requested ring buffer size for branch
7961 tracing in Intel Processor Trace format.
7965 Show various statistics about the recording depending on the recording
7970 For the @code{full} recording method, it shows the state of process
7971 record and its in-memory execution log buffer, including:
7975 Whether in record mode or replay mode.
7977 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7979 Highest recorded instruction number.
7981 Current instruction about to be replayed (if in replay mode).
7983 Number of instructions contained in the execution log.
7985 Maximum number of instructions that may be contained in the execution log.
7989 For the @code{btrace} recording method, it shows:
7995 Number of instructions that have been recorded.
7997 Number of blocks of sequential control-flow formed by the recorded
8000 Whether in record mode or replay mode.
8003 For the @code{bts} recording format, it also shows:
8006 Size of the perf ring buffer.
8009 For the @code{pt} recording format, it also shows:
8012 Size of the perf ring buffer.
8016 @kindex record delete
8019 When record target runs in replay mode (``in the past''), delete the
8020 subsequent execution log and begin to record a new execution log starting
8021 from the current address. This means you will abandon the previously
8022 recorded ``future'' and begin recording a new ``future''.
8024 @kindex record instruction-history
8025 @kindex rec instruction-history
8026 @item record instruction-history
8027 Disassembles instructions from the recorded execution log. By
8028 default, ten instructions are disassembled. This can be changed using
8029 the @code{set record instruction-history-size} command. Instructions
8030 are printed in execution order.
8032 It can also print mixed source+disassembly if you specify the the
8033 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
8034 as well as in symbolic form by specifying the @code{/r} or @code{/b}
8035 modifier. The behaviour of the @code{/m}, @code{/s}, @code{/r}, and
8036 @code{/b} modifiers are the same as for the @kbd{disassemble} command
8037 (@pxref{disassemble,,@kbd{disassemble}}).
8039 The current position marker is printed for the instruction at the
8040 current program counter value. This instruction can appear multiple
8041 times in the trace and the current position marker will be printed
8042 every time. To omit the current position marker, specify the
8045 To better align the printed instructions when the trace contains
8046 instructions from more than one function, the function name may be
8047 omitted by specifying the @code{/f} modifier.
8049 Speculatively executed instructions are prefixed with @samp{?}. This
8050 feature is not available for all recording formats.
8052 There are several ways to specify what part of the execution log to
8056 @item record instruction-history @var{insn}
8057 Disassembles ten instructions starting from instruction number
8060 @item record instruction-history @var{insn}, +/-@var{n}
8061 Disassembles @var{n} instructions around instruction number
8062 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
8063 @var{n} instructions after instruction number @var{insn}. If
8064 @var{n} is preceded with @code{-}, disassembles @var{n}
8065 instructions before instruction number @var{insn}.
8067 @item record instruction-history
8068 Disassembles ten more instructions after the last disassembly.
8070 @item record instruction-history -
8071 Disassembles ten more instructions before the last disassembly.
8073 @item record instruction-history @var{begin}, @var{end}
8074 Disassembles instructions beginning with instruction number
8075 @var{begin} until instruction number @var{end}. The instruction
8076 number @var{end} is included.
8079 This command may not be available for all recording methods.
8082 @item set record instruction-history-size @var{size}
8083 @itemx set record instruction-history-size unlimited
8084 Define how many instructions to disassemble in the @code{record
8085 instruction-history} command. The default value is 10.
8086 A @var{size} of @code{unlimited} means unlimited instructions.
8089 @item show record instruction-history-size
8090 Show how many instructions to disassemble in the @code{record
8091 instruction-history} command.
8093 @kindex record function-call-history
8094 @kindex rec function-call-history
8095 @item record function-call-history
8096 Prints the execution history at function granularity. For each sequence
8097 of instructions that belong to the same function, it prints the name of
8098 that function, the source lines for this instruction sequence (if the
8099 @code{/l} modifier is specified), and the instructions numbers that form
8100 the sequence (if the @code{/i} modifier is specified). The function names
8101 are indented to reflect the call stack depth if the @code{/c} modifier is
8102 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
8106 (@value{GDBP}) @b{list 1, 10}
8117 (@value{GDBP}) @b{record function-call-history /ilc}
8118 1 bar inst 1,4 at foo.c:6,8
8119 2 foo inst 5,10 at foo.c:2,3
8120 3 bar inst 11,13 at foo.c:9,10
8123 By default, ten functions are printed. This can be changed using the
8124 @code{set record function-call-history-size} command. Functions are
8125 printed in execution order. There are several ways to specify what
8129 @item record function-call-history @var{func}
8130 Prints ten functions starting from function number @var{func}.
8132 @item record function-call-history @var{func}, +/-@var{n}
8133 Prints @var{n} functions around function number @var{func}. If
8134 @var{n} is preceded with @code{+}, prints @var{n} functions after
8135 function number @var{func}. If @var{n} is preceded with @code{-},
8136 prints @var{n} functions before function number @var{func}.
8138 @item record function-call-history
8139 Prints ten more functions after the last ten-function print.
8141 @item record function-call-history -
8142 Prints ten more functions before the last ten-function print.
8144 @item record function-call-history @var{begin}, @var{end}
8145 Prints functions beginning with function number @var{begin} until
8146 function number @var{end}. The function number @var{end} is included.
8149 This command may not be available for all recording methods.
8151 @item set record function-call-history-size @var{size}
8152 @itemx set record function-call-history-size unlimited
8153 Define how many functions to print in the
8154 @code{record function-call-history} command. The default value is 10.
8155 A size of @code{unlimited} means unlimited functions.
8157 @item show record function-call-history-size
8158 Show how many functions to print in the
8159 @code{record function-call-history} command.
8164 @chapter Examining the Stack
8166 When your program has stopped, the first thing you need to know is where it
8167 stopped and how it got there.
8170 Each time your program performs a function call, information about the call
8172 That information includes the location of the call in your program,
8173 the arguments of the call,
8174 and the local variables of the function being called.
8175 The information is saved in a block of data called a @dfn{stack frame}.
8176 The stack frames are allocated in a region of memory called the @dfn{call
8179 When your program stops, the @value{GDBN} commands for examining the
8180 stack allow you to see all of this information.
8182 @cindex selected frame
8183 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8184 @value{GDBN} commands refer implicitly to the selected frame. In
8185 particular, whenever you ask @value{GDBN} for the value of a variable in
8186 your program, the value is found in the selected frame. There are
8187 special @value{GDBN} commands to select whichever frame you are
8188 interested in. @xref{Selection, ,Selecting a Frame}.
8190 When your program stops, @value{GDBN} automatically selects the
8191 currently executing frame and describes it briefly, similar to the
8192 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8195 * Frames:: Stack frames
8196 * Backtrace:: Backtraces
8197 * Selection:: Selecting a frame
8198 * Frame Info:: Information on a frame
8199 * Frame Apply:: Applying a command to several frames
8200 * Frame Filter Management:: Managing frame filters
8205 @section Stack Frames
8207 @cindex frame, definition
8209 The call stack is divided up into contiguous pieces called @dfn{stack
8210 frames}, or @dfn{frames} for short; each frame is the data associated
8211 with one call to one function. The frame contains the arguments given
8212 to the function, the function's local variables, and the address at
8213 which the function is executing.
8215 @cindex initial frame
8216 @cindex outermost frame
8217 @cindex innermost frame
8218 When your program is started, the stack has only one frame, that of the
8219 function @code{main}. This is called the @dfn{initial} frame or the
8220 @dfn{outermost} frame. Each time a function is called, a new frame is
8221 made. Each time a function returns, the frame for that function invocation
8222 is eliminated. If a function is recursive, there can be many frames for
8223 the same function. The frame for the function in which execution is
8224 actually occurring is called the @dfn{innermost} frame. This is the most
8225 recently created of all the stack frames that still exist.
8227 @cindex frame pointer
8228 Inside your program, stack frames are identified by their addresses. A
8229 stack frame consists of many bytes, each of which has its own address; each
8230 kind of computer has a convention for choosing one byte whose
8231 address serves as the address of the frame. Usually this address is kept
8232 in a register called the @dfn{frame pointer register}
8233 (@pxref{Registers, $fp}) while execution is going on in that frame.
8236 @cindex frame number
8237 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8238 number that is zero for the innermost frame, one for the frame that
8239 called it, and so on upward. These level numbers give you a way of
8240 designating stack frames in @value{GDBN} commands. The terms
8241 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8242 describe this number.
8244 @c The -fomit-frame-pointer below perennially causes hbox overflow
8245 @c underflow problems.
8246 @cindex frameless execution
8247 Some compilers provide a way to compile functions so that they operate
8248 without stack frames. (For example, the @value{NGCC} option
8250 @samp{-fomit-frame-pointer}
8252 generates functions without a frame.)
8253 This is occasionally done with heavily used library functions to save
8254 the frame setup time. @value{GDBN} has limited facilities for dealing
8255 with these function invocations. If the innermost function invocation
8256 has no stack frame, @value{GDBN} nevertheless regards it as though
8257 it had a separate frame, which is numbered zero as usual, allowing
8258 correct tracing of the function call chain. However, @value{GDBN} has
8259 no provision for frameless functions elsewhere in the stack.
8265 @cindex call stack traces
8266 A backtrace is a summary of how your program got where it is. It shows one
8267 line per frame, for many frames, starting with the currently executing
8268 frame (frame zero), followed by its caller (frame one), and on up the
8271 @anchor{backtrace-command}
8273 @kindex bt @r{(@code{backtrace})}
8274 To print a backtrace of the entire stack, use the @code{backtrace}
8275 command, or its alias @code{bt}. This command will print one line per
8276 frame for frames in the stack. By default, all stack frames are
8277 printed. You can stop the backtrace at any time by typing the system
8278 interrupt character, normally @kbd{Ctrl-c}.
8281 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8282 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8283 Print the backtrace of the entire stack.
8285 The optional @var{count} can be one of the following:
8290 Print only the innermost @var{n} frames, where @var{n} is a positive
8295 Print only the outermost @var{n} frames, where @var{n} is a positive
8303 Print the values of the local variables also. This can be combined
8304 with the optional @var{count} to limit the number of frames shown.
8307 Do not run Python frame filters on this backtrace. @xref{Frame
8308 Filter API}, for more information. Additionally use @ref{disable
8309 frame-filter all} to turn off all frame filters. This is only
8310 relevant when @value{GDBN} has been configured with @code{Python}
8314 A Python frame filter might decide to ``elide'' some frames. Normally
8315 such elided frames are still printed, but they are indented relative
8316 to the filtered frames that cause them to be elided. The @code{-hide}
8317 option causes elided frames to not be printed at all.
8320 The @code{backtrace} command also supports a number of options that
8321 allow overriding relevant global print settings as set by @code{set
8322 backtrace} and @code{set print} subcommands:
8325 @item -past-main [@code{on}|@code{off}]
8326 Set whether backtraces should continue past @code{main}. Related setting:
8327 @ref{set backtrace past-main}.
8329 @item -past-entry [@code{on}|@code{off}]
8330 Set whether backtraces should continue past the entry point of a program.
8331 Related setting: @ref{set backtrace past-entry}.
8333 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8334 Set printing of function arguments at function entry.
8335 Related setting: @ref{set print entry-values}.
8337 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8338 Set printing of non-scalar frame arguments.
8339 Related setting: @ref{set print frame-arguments}.
8341 @item -raw-frame-arguments [@code{on}|@code{off}]
8342 Set whether to print frame arguments in raw form.
8343 Related setting: @ref{set print raw-frame-arguments}.
8345 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8346 Set printing of frame information.
8347 Related setting: @ref{set print frame-info}.
8350 The optional @var{qualifier} is maintained for backward compatibility.
8351 It can be one of the following:
8355 Equivalent to the @code{-full} option.
8358 Equivalent to the @code{-no-filters} option.
8361 Equivalent to the @code{-hide} option.
8368 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8369 are additional aliases for @code{backtrace}.
8371 @cindex multiple threads, backtrace
8372 In a multi-threaded program, @value{GDBN} by default shows the
8373 backtrace only for the current thread. To display the backtrace for
8374 several or all of the threads, use the command @code{thread apply}
8375 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8376 apply all backtrace}, @value{GDBN} will display the backtrace for all
8377 the threads; this is handy when you debug a core dump of a
8378 multi-threaded program.
8380 Each line in the backtrace shows the frame number and the function name.
8381 The program counter value is also shown---unless you use @code{set
8382 print address off}. The backtrace also shows the source file name and
8383 line number, as well as the arguments to the function. The program
8384 counter value is omitted if it is at the beginning of the code for that
8387 Here is an example of a backtrace. It was made with the command
8388 @samp{bt 3}, so it shows the innermost three frames.
8392 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8394 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8395 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8397 (More stack frames follow...)
8402 The display for frame zero does not begin with a program counter
8403 value, indicating that your program has stopped at the beginning of the
8404 code for line @code{993} of @code{builtin.c}.
8407 The value of parameter @code{data} in frame 1 has been replaced by
8408 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8409 only if it is a scalar (integer, pointer, enumeration, etc). See command
8410 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8411 on how to configure the way function parameter values are printed.
8412 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8413 what frame information is printed.
8415 @cindex optimized out, in backtrace
8416 @cindex function call arguments, optimized out
8417 If your program was compiled with optimizations, some compilers will
8418 optimize away arguments passed to functions if those arguments are
8419 never used after the call. Such optimizations generate code that
8420 passes arguments through registers, but doesn't store those arguments
8421 in the stack frame. @value{GDBN} has no way of displaying such
8422 arguments in stack frames other than the innermost one. Here's what
8423 such a backtrace might look like:
8427 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8429 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8430 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8432 (More stack frames follow...)
8437 The values of arguments that were not saved in their stack frames are
8438 shown as @samp{<optimized out>}.
8440 If you need to display the values of such optimized-out arguments,
8441 either deduce that from other variables whose values depend on the one
8442 you are interested in, or recompile without optimizations.
8444 @cindex backtrace beyond @code{main} function
8445 @cindex program entry point
8446 @cindex startup code, and backtrace
8447 Most programs have a standard user entry point---a place where system
8448 libraries and startup code transition into user code. For C this is
8449 @code{main}@footnote{
8450 Note that embedded programs (the so-called ``free-standing''
8451 environment) are not required to have a @code{main} function as the
8452 entry point. They could even have multiple entry points.}.
8453 When @value{GDBN} finds the entry function in a backtrace
8454 it will terminate the backtrace, to avoid tracing into highly
8455 system-specific (and generally uninteresting) code.
8457 If you need to examine the startup code, or limit the number of levels
8458 in a backtrace, you can change this behavior:
8461 @item set backtrace past-main
8462 @itemx set backtrace past-main on
8463 @anchor{set backtrace past-main}
8464 @kindex set backtrace
8465 Backtraces will continue past the user entry point.
8467 @item set backtrace past-main off
8468 Backtraces will stop when they encounter the user entry point. This is the
8471 @item show backtrace past-main
8472 @kindex show backtrace
8473 Display the current user entry point backtrace policy.
8475 @item set backtrace past-entry
8476 @itemx set backtrace past-entry on
8477 @anchor{set backtrace past-entry}
8478 Backtraces will continue past the internal entry point of an application.
8479 This entry point is encoded by the linker when the application is built,
8480 and is likely before the user entry point @code{main} (or equivalent) is called.
8482 @item set backtrace past-entry off
8483 Backtraces will stop when they encounter the internal entry point of an
8484 application. This is the default.
8486 @item show backtrace past-entry
8487 Display the current internal entry point backtrace policy.
8489 @item set backtrace limit @var{n}
8490 @itemx set backtrace limit 0
8491 @itemx set backtrace limit unlimited
8492 @anchor{set backtrace limit}
8493 @cindex backtrace limit
8494 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8495 or zero means unlimited levels.
8497 @item show backtrace limit
8498 Display the current limit on backtrace levels.
8501 You can control how file names are displayed.
8504 @item set filename-display
8505 @itemx set filename-display relative
8506 @cindex filename-display
8507 Display file names relative to the compilation directory. This is the default.
8509 @item set filename-display basename
8510 Display only basename of a filename.
8512 @item set filename-display absolute
8513 Display an absolute filename.
8515 @item show filename-display
8516 Show the current way to display filenames.
8520 @section Selecting a Frame
8522 Most commands for examining the stack and other data in your program work on
8523 whichever stack frame is selected at the moment. Here are the commands for
8524 selecting a stack frame; all of them finish by printing a brief description
8525 of the stack frame just selected.
8528 @kindex frame@r{, selecting}
8529 @kindex f @r{(@code{frame})}
8530 @item frame @r{[} @var{frame-selection-spec} @r{]}
8531 @item f @r{[} @var{frame-selection-spec} @r{]}
8532 The @command{frame} command allows different stack frames to be
8533 selected. The @var{frame-selection-spec} can be any of the following:
8538 @item level @var{num}
8539 Select frame level @var{num}. Recall that frame zero is the innermost
8540 (currently executing) frame, frame one is the frame that called the
8541 innermost one, and so on. The highest level frame is usually the one
8544 As this is the most common method of navigating the frame stack, the
8545 string @command{level} can be omitted. For example, the following two
8546 commands are equivalent:
8549 (@value{GDBP}) frame 3
8550 (@value{GDBP}) frame level 3
8553 @kindex frame address
8554 @item address @var{stack-address}
8555 Select the frame with stack address @var{stack-address}. The
8556 @var{stack-address} for a frame can be seen in the output of
8557 @command{info frame}, for example:
8560 (@value{GDBP}) info frame
8561 Stack level 1, frame at 0x7fffffffda30:
8562 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8563 tail call frame, caller of frame at 0x7fffffffda30
8564 source language c++.
8565 Arglist at unknown address.
8566 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8569 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8570 indicated by the line:
8573 Stack level 1, frame at 0x7fffffffda30:
8576 @kindex frame function
8577 @item function @var{function-name}
8578 Select the stack frame for function @var{function-name}. If there are
8579 multiple stack frames for function @var{function-name} then the inner
8580 most stack frame is selected.
8583 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8584 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8585 viewed has stack address @var{stack-addr}, and optionally, a program
8586 counter address of @var{pc-addr}.
8588 This is useful mainly if the chaining of stack frames has been
8589 damaged by a bug, making it impossible for @value{GDBN} to assign
8590 numbers properly to all frames. In addition, this can be useful
8591 when your program has multiple stacks and switches between them.
8593 When viewing a frame outside the current backtrace using
8594 @command{frame view} then you can always return to the original
8595 stack using one of the previous stack frame selection instructions,
8596 for example @command{frame level 0}.
8602 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8603 numbers @var{n}, this advances toward the outermost frame, to higher
8604 frame numbers, to frames that have existed longer.
8607 @kindex do @r{(@code{down})}
8609 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8610 positive numbers @var{n}, this advances toward the innermost frame, to
8611 lower frame numbers, to frames that were created more recently.
8612 You may abbreviate @code{down} as @code{do}.
8615 All of these commands end by printing two lines of output describing the
8616 frame. The first line shows the frame number, the function name, the
8617 arguments, and the source file and line number of execution in that
8618 frame. The second line shows the text of that source line.
8626 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8628 10 read_input_file (argv[i]);
8632 After such a printout, the @code{list} command with no arguments
8633 prints ten lines centered on the point of execution in the frame.
8634 You can also edit the program at the point of execution with your favorite
8635 editing program by typing @code{edit}.
8636 @xref{List, ,Printing Source Lines},
8640 @kindex select-frame
8641 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8642 The @code{select-frame} command is a variant of @code{frame} that does
8643 not display the new frame after selecting it. This command is
8644 intended primarily for use in @value{GDBN} command scripts, where the
8645 output might be unnecessary and distracting. The
8646 @var{frame-selection-spec} is as for the @command{frame} command
8647 described in @ref{Selection, ,Selecting a Frame}.
8649 @kindex down-silently
8651 @item up-silently @var{n}
8652 @itemx down-silently @var{n}
8653 These two commands are variants of @code{up} and @code{down},
8654 respectively; they differ in that they do their work silently, without
8655 causing display of the new frame. They are intended primarily for use
8656 in @value{GDBN} command scripts, where the output might be unnecessary and
8661 @section Information About a Frame
8663 There are several other commands to print information about the selected
8669 When used without any argument, this command does not change which
8670 frame is selected, but prints a brief description of the currently
8671 selected stack frame. It can be abbreviated @code{f}. With an
8672 argument, this command is used to select a stack frame.
8673 @xref{Selection, ,Selecting a Frame}.
8676 @kindex info f @r{(@code{info frame})}
8679 This command prints a verbose description of the selected stack frame,
8684 the address of the frame
8686 the address of the next frame down (called by this frame)
8688 the address of the next frame up (caller of this frame)
8690 the language in which the source code corresponding to this frame is written
8692 the address of the frame's arguments
8694 the address of the frame's local variables
8696 the program counter saved in it (the address of execution in the caller frame)
8698 which registers were saved in the frame
8701 @noindent The verbose description is useful when
8702 something has gone wrong that has made the stack format fail to fit
8703 the usual conventions.
8705 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8706 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8707 Print a verbose description of the frame selected by
8708 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8709 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8710 a Frame}). The selected frame remains unchanged by this command.
8713 @item info args [-q]
8714 Print the arguments of the selected frame, each on a separate line.
8716 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8717 printing header information and messages explaining why no argument
8720 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8721 Like @kbd{info args}, but only print the arguments selected
8722 with the provided regexp(s).
8724 If @var{regexp} is provided, print only the arguments whose names
8725 match the regular expression @var{regexp}.
8727 If @var{type_regexp} is provided, print only the arguments whose
8728 types, as printed by the @code{whatis} command, match
8729 the regular expression @var{type_regexp}.
8730 If @var{type_regexp} contains space(s), it should be enclosed in
8731 quote characters. If needed, use backslash to escape the meaning
8732 of special characters or quotes.
8734 If both @var{regexp} and @var{type_regexp} are provided, an argument
8735 is printed only if its name matches @var{regexp} and its type matches
8738 @item info locals [-q]
8740 Print the local variables of the selected frame, each on a separate
8741 line. These are all variables (declared either static or automatic)
8742 accessible at the point of execution of the selected frame.
8744 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8745 printing header information and messages explaining why no local variables
8748 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8749 Like @kbd{info locals}, but only print the local variables selected
8750 with the provided regexp(s).
8752 If @var{regexp} is provided, print only the local variables whose names
8753 match the regular expression @var{regexp}.
8755 If @var{type_regexp} is provided, print only the local variables whose
8756 types, as printed by the @code{whatis} command, match
8757 the regular expression @var{type_regexp}.
8758 If @var{type_regexp} contains space(s), it should be enclosed in
8759 quote characters. If needed, use backslash to escape the meaning
8760 of special characters or quotes.
8762 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8763 is printed only if its name matches @var{regexp} and its type matches
8766 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8767 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8768 For example, your program might use Resource Acquisition Is
8769 Initialization types (RAII) such as @code{lock_something_t}: each
8770 local variable of type @code{lock_something_t} automatically places a
8771 lock that is destroyed when the variable goes out of scope. You can
8772 then list all acquired locks in your program by doing
8774 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8777 or the equivalent shorter form
8779 tfaas i lo -q -t lock_something_t
8785 @section Applying a Command to Several Frames.
8787 @cindex apply command to several frames
8789 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8790 The @code{frame apply} command allows you to apply the named
8791 @var{command} to one or more frames.
8795 Specify @code{all} to apply @var{command} to all frames.
8798 Use @var{count} to apply @var{command} to the innermost @var{count}
8799 frames, where @var{count} is a positive number.
8802 Use @var{-count} to apply @var{command} to the outermost @var{count}
8803 frames, where @var{count} is a positive number.
8806 Use @code{level} to apply @var{command} to the set of frames identified
8807 by the @var{level} list. @var{level} is a frame level or a range of frame
8808 levels as @var{level1}-@var{level2}. The frame level is the number shown
8809 in the first field of the @samp{backtrace} command output.
8810 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8811 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8815 Note that the frames on which @code{frame apply} applies a command are
8816 also influenced by the @code{set backtrace} settings such as @code{set
8817 backtrace past-main} and @code{set backtrace limit N}.
8818 @xref{Backtrace,,Backtraces}.
8820 The @code{frame apply} command also supports a number of options that
8821 allow overriding relevant @code{set backtrace} settings:
8824 @item -past-main [@code{on}|@code{off}]
8825 Whether backtraces should continue past @code{main}.
8826 Related setting: @ref{set backtrace past-main}.
8828 @item -past-entry [@code{on}|@code{off}]
8829 Whether backtraces should continue past the entry point of a program.
8830 Related setting: @ref{set backtrace past-entry}.
8833 By default, @value{GDBN} displays some frame information before the
8834 output produced by @var{command}, and an error raised during the
8835 execution of a @var{command} will abort @code{frame apply}. The
8836 following options can be used to fine-tune these behaviors:
8840 The flag @code{-c}, which stands for @samp{continue}, causes any
8841 errors in @var{command} to be displayed, and the execution of
8842 @code{frame apply} then continues.
8844 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8845 or empty output produced by a @var{command} to be silently ignored.
8846 That is, the execution continues, but the frame information and errors
8849 The flag @code{-q} (@samp{quiet}) disables printing the frame
8853 The following example shows how the flags @code{-c} and @code{-s} are
8854 working when applying the command @code{p j} to all frames, where
8855 variable @code{j} can only be successfully printed in the outermost
8856 @code{#1 main} frame.
8860 (@value{GDBP}) frame apply all p j
8861 #0 some_function (i=5) at fun.c:4
8862 No symbol "j" in current context.
8863 (@value{GDBP}) frame apply all -c p j
8864 #0 some_function (i=5) at fun.c:4
8865 No symbol "j" in current context.
8866 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8868 (@value{GDBP}) frame apply all -s p j
8869 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8875 By default, @samp{frame apply}, prints the frame location
8876 information before the command output:
8880 (@value{GDBP}) frame apply all p $sp
8881 #0 some_function (i=5) at fun.c:4
8882 $4 = (void *) 0xffffd1e0
8883 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8884 $5 = (void *) 0xffffd1f0
8889 If the flag @code{-q} is given, no frame information is printed:
8892 (@value{GDBP}) frame apply all -q p $sp
8893 $12 = (void *) 0xffffd1e0
8894 $13 = (void *) 0xffffd1f0
8904 @cindex apply a command to all frames (ignoring errors and empty output)
8905 @item faas @var{command}
8906 Shortcut for @code{frame apply all -s @var{command}}.
8907 Applies @var{command} on all frames, ignoring errors and empty output.
8909 It can for example be used to print a local variable or a function
8910 argument without knowing the frame where this variable or argument
8913 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8916 The @code{faas} command accepts the same options as the @code{frame
8917 apply} command. @xref{Frame Apply,,frame apply}.
8919 Note that the command @code{tfaas @var{command}} applies @var{command}
8920 on all frames of all threads. See @xref{Threads,,Threads}.
8924 @node Frame Filter Management
8925 @section Management of Frame Filters.
8926 @cindex managing frame filters
8928 Frame filters are Python based utilities to manage and decorate the
8929 output of frames. @xref{Frame Filter API}, for further information.
8931 Managing frame filters is performed by several commands available
8932 within @value{GDBN}, detailed here.
8935 @kindex info frame-filter
8936 @item info frame-filter
8937 Print a list of installed frame filters from all dictionaries, showing
8938 their name, priority and enabled status.
8940 @kindex disable frame-filter
8941 @anchor{disable frame-filter all}
8942 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8943 Disable a frame filter in the dictionary matching
8944 @var{filter-dictionary} and @var{filter-name}. The
8945 @var{filter-dictionary} may be @code{all}, @code{global},
8946 @code{progspace}, or the name of the object file where the frame filter
8947 dictionary resides. When @code{all} is specified, all frame filters
8948 across all dictionaries are disabled. The @var{filter-name} is the name
8949 of the frame filter and is used when @code{all} is not the option for
8950 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8951 may be enabled again later.
8953 @kindex enable frame-filter
8954 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8955 Enable a frame filter in the dictionary matching
8956 @var{filter-dictionary} and @var{filter-name}. The
8957 @var{filter-dictionary} may be @code{all}, @code{global},
8958 @code{progspace} or the name of the object file where the frame filter
8959 dictionary resides. When @code{all} is specified, all frame filters across
8960 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8961 filter and is used when @code{all} is not the option for
8962 @var{filter-dictionary}.
8967 (@value{GDBP}) info frame-filter
8969 global frame-filters:
8970 Priority Enabled Name
8971 1000 No PrimaryFunctionFilter
8974 progspace /build/test frame-filters:
8975 Priority Enabled Name
8976 100 Yes ProgspaceFilter
8978 objfile /build/test frame-filters:
8979 Priority Enabled Name
8980 999 Yes BuildProgramFilter
8982 (@value{GDBP}) disable frame-filter /build/test BuildProgramFilter
8983 (@value{GDBP}) info frame-filter
8985 global frame-filters:
8986 Priority Enabled Name
8987 1000 No PrimaryFunctionFilter
8990 progspace /build/test frame-filters:
8991 Priority Enabled Name
8992 100 Yes ProgspaceFilter
8994 objfile /build/test frame-filters:
8995 Priority Enabled Name
8996 999 No BuildProgramFilter
8998 (@value{GDBP}) enable frame-filter global PrimaryFunctionFilter
8999 (@value{GDBP}) info frame-filter
9001 global frame-filters:
9002 Priority Enabled Name
9003 1000 Yes PrimaryFunctionFilter
9006 progspace /build/test frame-filters:
9007 Priority Enabled Name
9008 100 Yes ProgspaceFilter
9010 objfile /build/test frame-filters:
9011 Priority Enabled Name
9012 999 No BuildProgramFilter
9015 @kindex set frame-filter priority
9016 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
9017 Set the @var{priority} of a frame filter in the dictionary matching
9018 @var{filter-dictionary}, and the frame filter name matching
9019 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
9020 @code{progspace} or the name of the object file where the frame filter
9021 dictionary resides. The @var{priority} is an integer.
9023 @kindex show frame-filter priority
9024 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
9025 Show the @var{priority} of a frame filter in the dictionary matching
9026 @var{filter-dictionary}, and the frame filter name matching
9027 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
9028 @code{progspace} or the name of the object file where the frame filter
9034 (@value{GDBP}) info frame-filter
9036 global frame-filters:
9037 Priority Enabled Name
9038 1000 Yes PrimaryFunctionFilter
9041 progspace /build/test frame-filters:
9042 Priority Enabled Name
9043 100 Yes ProgspaceFilter
9045 objfile /build/test frame-filters:
9046 Priority Enabled Name
9047 999 No BuildProgramFilter
9049 (@value{GDBP}) set frame-filter priority global Reverse 50
9050 (@value{GDBP}) info frame-filter
9052 global frame-filters:
9053 Priority Enabled Name
9054 1000 Yes PrimaryFunctionFilter
9057 progspace /build/test frame-filters:
9058 Priority Enabled Name
9059 100 Yes ProgspaceFilter
9061 objfile /build/test frame-filters:
9062 Priority Enabled Name
9063 999 No BuildProgramFilter
9068 @chapter Examining Source Files
9070 @value{GDBN} can print parts of your program's source, since the debugging
9071 information recorded in the program tells @value{GDBN} what source files were
9072 used to build it. When your program stops, @value{GDBN} spontaneously prints
9073 the line where it stopped. Likewise, when you select a stack frame
9074 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
9075 execution in that frame has stopped. You can print other portions of
9076 source files by explicit command.
9078 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
9079 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
9080 @value{GDBN} under @sc{gnu} Emacs}.
9083 * List:: Printing source lines
9084 * Location Specifications:: How to specify code locations
9085 * Edit:: Editing source files
9086 * Search:: Searching source files
9087 * Source Path:: Specifying source directories
9088 * Machine Code:: Source and machine code
9089 * Disable Reading Source:: Disable Reading Source Code
9093 @section Printing Source Lines
9096 @kindex l @r{(@code{list})}
9097 To print lines from a source file, use the @code{list} command
9098 (abbreviated @code{l}). By default, ten lines are printed.
9099 There are several ways to specify what part of the file you want to
9100 print; see @ref{Location Specifications}, for the full list.
9102 Here are the forms of the @code{list} command most commonly used:
9105 @item list @var{linenum}
9106 Print lines centered around line number @var{linenum} in the
9107 current source file.
9109 @item list @var{function}
9110 Print lines centered around the beginning of function
9114 Print more lines. If the last lines printed were printed with a
9115 @code{list} command, this prints lines following the last lines
9116 printed; however, if the last line printed was a solitary line printed
9117 as part of displaying a stack frame (@pxref{Stack, ,Examining the
9118 Stack}), this prints lines centered around that line.
9121 Print lines just before the lines last printed.
9124 @cindex @code{list}, how many lines to display
9125 By default, @value{GDBN} prints ten source lines with any of these forms of
9126 the @code{list} command. You can change this using @code{set listsize}:
9129 @kindex set listsize
9130 @item set listsize @var{count}
9131 @itemx set listsize unlimited
9132 Make the @code{list} command display @var{count} source lines (unless
9133 the @code{list} argument explicitly specifies some other number).
9134 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
9136 @kindex show listsize
9138 Display the number of lines that @code{list} prints.
9141 Repeating a @code{list} command with @key{RET} discards the argument,
9142 so it is equivalent to typing just @code{list}. This is more useful
9143 than listing the same lines again. An exception is made for an
9144 argument of @samp{-}; that argument is preserved in repetition so that
9145 each repetition moves up in the source file.
9147 In general, the @code{list} command expects you to supply zero, one or
9148 two location specs. These location specs are interpreted to resolve
9149 to source code lines; there are several ways of writing them
9150 (@pxref{Location Specifications}), but the effect is always to resolve
9151 to some source lines to display.
9153 Here is a complete description of the possible arguments for @code{list}:
9156 @item list @var{locspec}
9157 Print lines centered around the line or lines of all the code
9158 locations that result from resolving @var{locspec}.
9160 @item list @var{first},@var{last}
9161 Print lines from @var{first} to @var{last}. Both arguments are
9162 location specs. When a @code{list} command has two location specs,
9163 and the source file of the second location spec is omitted, this
9164 refers to the same source file as the first location spec. If either
9165 @var{first} or @var{last} resolve to more than one source line in the
9166 program, then the list command shows the list of resolved source
9167 lines and does not proceed with the source code listing.
9169 @item list ,@var{last}
9170 Print lines ending with @var{last}.
9172 Likewise, if @var{last} resolves to more than one source line in the
9173 program, then the list command prints the list of resolved source
9174 lines and does not proceed with the source code listing.
9176 @item list @var{first},
9177 Print lines starting with @var{first}.
9180 Print lines just after the lines last printed.
9183 Print lines just before the lines last printed.
9186 As described in the preceding table.
9189 @node Location Specifications
9190 @section Location Specifications
9191 @cindex specifying location
9193 @cindex source location
9194 @cindex code location
9196 @cindex location spec
9197 Several @value{GDBN} commands accept arguments that specify a location
9198 or locations of your program's code. Many times locations are
9199 specified using a source line number, but they can also be specified
9200 by a function name, an address, a label, etc. The different
9201 forms of specifying a location that @value{GDBN} recognizes are
9202 collectively known as forms of @dfn{location specification}, or
9203 @dfn{location spec}. This section documents the forms of specifying
9204 locations that @value{GDBN} recognizes.
9206 @cindex location resolution
9207 @cindex resolution of location spec
9208 When you specify a location, @value{GDBN} needs to find the place in
9209 your program, known as @dfn{code location}, that corresponds to the
9210 given location spec. We call this process of finding actual code
9211 locations corresponding to a location spec @dfn{location resolution}.
9213 A concrete code location in your program is uniquely identifiable by a
9214 set of several attributes: its source line number, the name of its
9215 source file, the fully-qualified and prototyped function in which it
9216 is defined, and an instruction address. Because each inferior has its
9217 own address space, the inferior number is also a necessary part of
9220 By contrast, location specs you type will many times omit some of
9221 these attributes. For example, it is customary to specify just the
9222 source line number to mean a line in the current source file, or
9223 specify just the basename of the file, omitting its directories. In
9224 other words, a location spec is usually incomplete, a kind of
9225 blueprint, and @value{GDBN} needs to complete the missing attributes
9226 by using the implied defaults, and by considering the source code and
9227 the debug information available to it. This is what location
9228 resolution is about.
9230 The resolution of an incomplete location spec can produce more than a
9231 single code location, if the spec doesn't allow distinguishing between
9232 them. Here are some examples of situations that result in a location
9233 spec matching multiple code locations in your program:
9237 The location spec specifies a function name, and there are several
9238 functions in the program which have that name. (To distinguish
9239 between them, you can specify a fully-qualified and prototyped
9240 function name, such as @code{A::func(int)} instead of just
9244 The location spec specifies a source file name, and there are several
9245 source files in the program that share the same name, for example
9246 several files with the same basename in different subdirectories. (To
9247 distinguish between them, specify enough leading directories with the
9251 For a C@t{++} constructor, the @value{NGCC} compiler generates several
9252 instances of the function body, used in different cases, but their
9253 source-level names are identical.
9256 For a C@t{++} template function, a given line in the function can
9257 correspond to any number of instantiations.
9260 For an inlined function, a given source line can correspond to several
9261 actual code locations with that function's inlined code.
9264 Resolution of a location spec can also fail to produce a complete code
9265 location, or even fail to produce any code location. Here are some
9266 examples of such situations:
9270 Some parts of the program lack detailed enough debug info, so the
9271 resolved code location lacks some attributes, like source file name
9272 and line number, leaving just the instruction address and perhaps also
9273 a function name. Such an incomplete code location is only usable in
9274 contexts that work with addresses and/or function names. Some
9275 commands can only work with complete code locations.
9278 The location spec specifies a function name, and there are no
9279 functions in the program by that name, or they only exist in a
9280 yet-unloaded shared library.
9283 The location spec specifies a source file name, and there are no
9284 source files in the program by that name, or they only exist in a
9285 yet-unloaded shared library.
9288 The location spec specifies both a source file name and a source line
9289 number, and even though there are source files in the program that
9290 match the file name, none of those files has the specified line
9294 Locations may be specified using three different formats: linespec
9295 locations, explicit locations, or address locations. The following
9296 subsections describe these formats.
9299 * Linespec Locations:: Linespec locations
9300 * Explicit Locations:: Explicit locations
9301 * Address Locations:: Address locations
9304 @node Linespec Locations
9305 @subsection Linespec Locations
9306 @cindex linespec locations
9308 A @dfn{linespec} is a colon-separated list of source location parameters such
9309 as file name, function name, etc. Here are all the different ways of
9310 specifying a linespec:
9314 Specifies the line number @var{linenum} of the current source file.
9317 @itemx +@var{offset}
9318 Specifies the line @var{offset} lines before or after the @dfn{current
9319 line}. For the @code{list} command, the current line is the last one
9320 printed; for the breakpoint commands, this is the line at which
9321 execution stopped in the currently selected @dfn{stack frame}
9322 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9323 used as the second of the two linespecs in a @code{list} command,
9324 this specifies the line @var{offset} lines up or down from the first
9327 @item @var{filename}:@var{linenum}
9328 Specifies the line @var{linenum} in the source file @var{filename}.
9329 If @var{filename} is a relative file name, then it will match any
9330 source file name with the same trailing components. For example, if
9331 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9332 name of @file{/build/trunk/gcc/expr.c}, but not
9333 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9335 @item @var{function}
9336 Specifies the line that begins the body of the function @var{function}.
9337 For example, in C, this is the line with the open brace.
9339 By default, in C@t{++} and Ada, @var{function} is interpreted as
9340 specifying all functions named @var{function} in all scopes. For
9341 C@t{++}, this means in all namespaces and classes. For Ada, this
9342 means in all packages.
9344 For example, assuming a program with C@t{++} symbols named
9345 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9346 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9348 Commands that accept a linespec let you override this with the
9349 @code{-qualified} option. For example, @w{@kbd{break -qualified
9350 func}} sets a breakpoint on a free-function named @code{func} ignoring
9351 any C@t{++} class methods and namespace functions called @code{func}.
9353 @xref{Explicit Locations}.
9355 @item @var{function}:@var{label}
9356 Specifies the line where @var{label} appears in @var{function}.
9358 @item @var{filename}:@var{function}
9359 Specifies the line that begins the body of the function @var{function}
9360 in the file @var{filename}. You only need the file name with a
9361 function name to avoid ambiguity when there are identically named
9362 functions in different source files.
9365 Specifies the line at which the label named @var{label} appears
9366 in the function corresponding to the currently selected stack frame.
9367 If there is no current selected stack frame (for instance, if the inferior
9368 is not running), then @value{GDBN} will not search for a label.
9370 @cindex breakpoint at static probe point
9371 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9372 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9373 applications to embed static probes. @xref{Static Probe Points}, for more
9374 information on finding and using static probes. This form of linespec
9375 specifies the location of such a static probe.
9377 If @var{objfile} is given, only probes coming from that shared library
9378 or executable matching @var{objfile} as a regular expression are considered.
9379 If @var{provider} is given, then only probes from that provider are considered.
9380 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9381 each one of those probes.
9384 @node Explicit Locations
9385 @subsection Explicit Locations
9386 @cindex explicit locations
9388 @dfn{Explicit locations} allow the user to directly specify the source
9389 location's parameters using option-value pairs.
9391 Explicit locations are useful when several functions, labels, or
9392 file names have the same name (base name for files) in the program's
9393 sources. In these cases, explicit locations point to the source
9394 line you meant more accurately and unambiguously. Also, using
9395 explicit locations might be faster in large programs.
9397 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9398 defined in the file named @file{foo} or the label @code{bar} in a function
9399 named @code{foo}. @value{GDBN} must search either the file system or
9400 the symbol table to know.
9402 The list of valid explicit location options is summarized in the
9406 @item -source @var{filename}
9407 The value specifies the source file name. To differentiate between
9408 files with the same base name, prepend as many directories as is necessary
9409 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9410 @value{GDBN} will use the first file it finds with the given base
9411 name. This option requires the use of either @code{-function} or @code{-line}.
9413 @item -function @var{function}
9414 The value specifies the name of a function. Operations
9415 on function locations unmodified by other options (such as @code{-label}
9416 or @code{-line}) refer to the line that begins the body of the function.
9417 In C, for example, this is the line with the open brace.
9419 By default, in C@t{++} and Ada, @var{function} is interpreted as
9420 specifying all functions named @var{function} in all scopes. For
9421 C@t{++}, this means in all namespaces and classes. For Ada, this
9422 means in all packages.
9424 For example, assuming a program with C@t{++} symbols named
9425 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9426 -function func}} and @w{@kbd{break -function B::func}} set a
9427 breakpoint on both symbols.
9429 You can use the @kbd{-qualified} flag to override this (see below).
9433 This flag makes @value{GDBN} interpret a function name specified with
9434 @kbd{-function} as a complete fully-qualified name.
9436 For example, assuming a C@t{++} program with symbols named
9437 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9438 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9440 (Note: the @kbd{-qualified} option can precede a linespec as well
9441 (@pxref{Linespec Locations}), so the particular example above could be
9442 simplified as @w{@kbd{break -qualified B::func}}.)
9444 @item -label @var{label}
9445 The value specifies the name of a label. When the function
9446 name is not specified, the label is searched in the function of the currently
9447 selected stack frame.
9449 @item -line @var{number}
9450 The value specifies a line offset for the location. The offset may either
9451 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9452 the command. When specified without any other options, the line offset is
9453 relative to the current line.
9456 Explicit location options may be abbreviated by omitting any non-unique
9457 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9459 @node Address Locations
9460 @subsection Address Locations
9461 @cindex address locations
9463 @dfn{Address locations} indicate a specific program address. They have
9464 the generalized form *@var{address}.
9466 For line-oriented commands, such as @code{list} and @code{edit}, this
9467 specifies a source line that contains @var{address}. For @code{break} and
9468 other breakpoint-oriented commands, this can be used to set breakpoints in
9469 parts of your program which do not have debugging information or
9472 Here @var{address} may be any expression valid in the current working
9473 language (@pxref{Languages, working language}) that specifies a code
9474 address. In addition, as a convenience, @value{GDBN} extends the
9475 semantics of expressions used in locations to cover several situations
9476 that frequently occur during debugging. Here are the various forms
9480 @item @var{expression}
9481 Any expression valid in the current working language.
9483 @item @var{funcaddr}
9484 An address of a function or procedure derived from its name. In C,
9485 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9486 simply the function's name @var{function} (and actually a special case
9487 of a valid expression). In Pascal and Modula-2, this is
9488 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9489 (although the Pascal form also works).
9491 This form specifies the address of the function's first instruction,
9492 before the stack frame and arguments have been set up.
9494 @item '@var{filename}':@var{funcaddr}
9495 Like @var{funcaddr} above, but also specifies the name of the source
9496 file explicitly. This is useful if the name of the function does not
9497 specify the function unambiguously, e.g., if there are several
9498 functions with identical names in different source files.
9502 @section Editing Source Files
9503 @cindex editing source files
9506 @kindex e @r{(@code{edit})}
9507 To edit the lines in a source file, use the @code{edit} command.
9508 The editing program of your choice
9509 is invoked with the current line set to
9510 the active line in the program.
9511 Alternatively, there are several ways to specify what part of the file you
9512 want to print if you want to see other parts of the program:
9515 @item edit @var{locspec}
9516 Edit the source file of the code location that results from resolving
9517 @code{locspec}. Editing starts at the source file and source line
9518 @code{locspec} resolves to.
9519 @xref{Location Specifications}, for all the possible forms of the
9520 @var{locspec} argument.
9522 If @code{locspec} resolves to more than one source line in your
9523 program, then the command prints the list of resolved source lines and
9524 does not proceed with the editing.
9526 Here are the forms of the @code{edit} command most commonly used:
9529 @item edit @var{number}
9530 Edit the current source file with @var{number} as the active line number.
9532 @item edit @var{function}
9533 Edit the file containing @var{function} at the beginning of its definition.
9538 @subsection Choosing your Editor
9539 You can customize @value{GDBN} to use any editor you want
9541 The only restriction is that your editor (say @code{ex}), recognizes the
9542 following command-line syntax:
9544 ex +@var{number} file
9546 The optional numeric value +@var{number} specifies the number of the line in
9547 the file where to start editing.}.
9548 By default, it is @file{@value{EDITOR}}, but you can change this
9549 by setting the environment variable @env{EDITOR} before using
9550 @value{GDBN}. For example, to configure @value{GDBN} to use the
9551 @code{vi} editor, you could use these commands with the @code{sh} shell:
9557 or in the @code{csh} shell,
9559 setenv EDITOR /usr/bin/vi
9564 @section Searching Source Files
9565 @cindex searching source files
9567 There are two commands for searching through the current source file for a
9572 @kindex forward-search
9573 @kindex fo @r{(@code{forward-search})}
9574 @item forward-search @var{regexp}
9575 @itemx search @var{regexp}
9576 The command @samp{forward-search @var{regexp}} checks each line,
9577 starting with the one following the last line listed, for a match for
9578 @var{regexp}. It lists the line that is found. You can use the
9579 synonym @samp{search @var{regexp}} or abbreviate the command name as
9582 @kindex reverse-search
9583 @item reverse-search @var{regexp}
9584 The command @samp{reverse-search @var{regexp}} checks each line, starting
9585 with the one before the last line listed and going backward, for a match
9586 for @var{regexp}. It lists the line that is found. You can abbreviate
9587 this command as @code{rev}.
9591 @section Specifying Source Directories
9594 @cindex directories for source files
9595 Executable programs sometimes do not record the directories of the source
9596 files from which they were compiled, just the names. Even when they do,
9597 the directories could be moved between the compilation and your debugging
9598 session. @value{GDBN} has a list of directories to search for source files;
9599 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9600 it tries all the directories in the list, in the order they are present
9601 in the list, until it finds a file with the desired name.
9603 For example, suppose an executable references the file
9604 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9605 directory, and the @dfn{source path} is @file{/mnt/cross}.
9606 @value{GDBN} would look for the source file in the following
9611 @item @file{/usr/src/foo-1.0/lib/foo.c}
9612 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9613 @item @file{/mnt/cross/foo.c}
9617 If the source file is not present at any of the above locations then
9618 an error is printed. @value{GDBN} does not look up the parts of the
9619 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9620 Likewise, the subdirectories of the source path are not searched: if
9621 the source path is @file{/mnt/cross}, and the binary refers to
9622 @file{foo.c}, @value{GDBN} would not find it under
9623 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9625 Plain file names, relative file names with leading directories, file
9626 names containing dots, etc.@: are all treated as described above,
9627 except that non-absolute file names are not looked up literally. If
9628 the @dfn{source path} is @file{/mnt/cross}, the source file is
9629 recorded as @file{../lib/foo.c}, and no compilation directory is
9630 recorded, then @value{GDBN} will search in the following locations:
9634 @item @file{/mnt/cross/../lib/foo.c}
9635 @item @file{/mnt/cross/foo.c}
9641 @vindex $cdir@r{, convenience variable}
9642 @vindex $cwd@r{, convenience variable}
9643 @cindex compilation directory
9644 @cindex current directory
9645 @cindex working directory
9646 @cindex directory, current
9647 @cindex directory, compilation
9648 The @dfn{source path} will always include two special entries
9649 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9650 (if one is recorded) and the current working directory respectively.
9652 @samp{$cdir} causes @value{GDBN} to search within the compilation
9653 directory, if one is recorded in the debug information. If no
9654 compilation directory is recorded in the debug information then
9655 @samp{$cdir} is ignored.
9657 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9658 current working directory as it changes during your @value{GDBN}
9659 session, while the latter is immediately expanded to the current
9660 directory at the time you add an entry to the source path.
9662 If a compilation directory is recorded in the debug information, and
9663 @value{GDBN} has not found the source file after the first search
9664 using @dfn{source path}, then @value{GDBN} will combine the
9665 compilation directory and the filename, and then search for the source
9666 file again using the @dfn{source path}.
9668 For example, if the executable records the source file as
9669 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9670 recorded as @file{/project/build}, and the @dfn{source path} is
9671 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9672 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9673 search for the source file in the following locations:
9677 @item @file{/usr/src/foo-1.0/lib/foo.c}
9678 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9679 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9680 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9681 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9682 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9683 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9684 @item @file{/mnt/cross/foo.c}
9685 @item @file{/project/build/foo.c}
9686 @item @file{/home/user/foo.c}
9690 If the file name in the previous example had been recorded in the
9691 executable as a relative path rather than an absolute path, then the
9692 first look up would not have occurred, but all of the remaining steps
9695 When searching for source files on MS-DOS and MS-Windows, where
9696 absolute paths start with a drive letter (e.g.@:
9697 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9698 from the file name before appending it to a search directory from
9699 @dfn{source path}; for instance if the executable references the
9700 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9701 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9702 locations for the source file:
9706 @item @file{C:/project/foo.c}
9707 @item @file{D:/mnt/cross/project/foo.c}
9708 @item @file{D:/mnt/cross/foo.c}
9712 Note that the executable search path is @emph{not} used to locate the
9715 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9716 any information it has cached about where source files are found and where
9717 each line is in the file.
9721 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9722 and @samp{$cwd}, in that order.
9723 To add other directories, use the @code{directory} command.
9725 The search path is used to find both program source files and @value{GDBN}
9726 script files (read using the @samp{-command} option and @samp{source} command).
9728 In addition to the source path, @value{GDBN} provides a set of commands
9729 that manage a list of source path substitution rules. A @dfn{substitution
9730 rule} specifies how to rewrite source directories stored in the program's
9731 debug information in case the sources were moved to a different
9732 directory between compilation and debugging. A rule is made of
9733 two strings, the first specifying what needs to be rewritten in
9734 the path, and the second specifying how it should be rewritten.
9735 In @ref{set substitute-path}, we name these two parts @var{from} and
9736 @var{to} respectively. @value{GDBN} does a simple string replacement
9737 of @var{from} with @var{to} at the start of the directory part of the
9738 source file name, and uses that result instead of the original file
9739 name to look up the sources.
9741 Using the previous example, suppose the @file{foo-1.0} tree has been
9742 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9743 @value{GDBN} to replace @file{/usr/src} in all source path names with
9744 @file{/mnt/cross}. The first lookup will then be
9745 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9746 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9747 substitution rule, use the @code{set substitute-path} command
9748 (@pxref{set substitute-path}).
9750 To avoid unexpected substitution results, a rule is applied only if the
9751 @var{from} part of the directory name ends at a directory separator.
9752 For instance, a rule substituting @file{/usr/source} into
9753 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9754 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9755 is applied only at the beginning of the directory name, this rule will
9756 not be applied to @file{/root/usr/source/baz.c} either.
9758 In many cases, you can achieve the same result using the @code{directory}
9759 command. However, @code{set substitute-path} can be more efficient in
9760 the case where the sources are organized in a complex tree with multiple
9761 subdirectories. With the @code{directory} command, you need to add each
9762 subdirectory of your project. If you moved the entire tree while
9763 preserving its internal organization, then @code{set substitute-path}
9764 allows you to direct the debugger to all the sources with one single
9767 @code{set substitute-path} is also more than just a shortcut command.
9768 The source path is only used if the file at the original location no
9769 longer exists. On the other hand, @code{set substitute-path} modifies
9770 the debugger behavior to look at the rewritten location instead. So, if
9771 for any reason a source file that is not relevant to your executable is
9772 located at the original location, a substitution rule is the only
9773 method available to point @value{GDBN} at the new location.
9775 @cindex @samp{--with-relocated-sources}
9776 @cindex default source path substitution
9777 You can configure a default source path substitution rule by
9778 configuring @value{GDBN} with the
9779 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9780 should be the name of a directory under @value{GDBN}'s configured
9781 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9782 directory names in debug information under @var{dir} will be adjusted
9783 automatically if the installed @value{GDBN} is moved to a new
9784 location. This is useful if @value{GDBN}, libraries or executables
9785 with debug information and corresponding source code are being moved
9789 @item directory @var{dirname} @dots{}
9790 @item dir @var{dirname} @dots{}
9791 Add directory @var{dirname} to the front of the source path. Several
9792 directory names may be given to this command, separated by @samp{:}
9793 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9794 part of absolute file names) or
9795 whitespace. You may specify a directory that is already in the source
9796 path; this moves it forward, so @value{GDBN} searches it sooner.
9798 The special strings @samp{$cdir} (to refer to the compilation
9799 directory, if one is recorded), and @samp{$cwd} (to refer to the
9800 current working directory) can also be included in the list of
9801 directories @var{dirname}. Though these will already be in the source
9802 path they will be moved forward in the list so @value{GDBN} searches
9806 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9808 @c RET-repeat for @code{directory} is explicitly disabled, but since
9809 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9811 @item set directories @var{path-list}
9812 @kindex set directories
9813 Set the source path to @var{path-list}.
9814 @samp{$cdir:$cwd} are added if missing.
9816 @item show directories
9817 @kindex show directories
9818 Print the source path: show which directories it contains.
9820 @anchor{set substitute-path}
9821 @item set substitute-path @var{from} @var{to}
9822 @kindex set substitute-path
9823 Define a source path substitution rule, and add it at the end of the
9824 current list of existing substitution rules. If a rule with the same
9825 @var{from} was already defined, then the old rule is also deleted.
9827 For example, if the file @file{/foo/bar/baz.c} was moved to
9828 @file{/mnt/cross/baz.c}, then the command
9831 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9835 will tell @value{GDBN} to replace @samp{/foo/bar} with
9836 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9837 @file{baz.c} even though it was moved.
9839 In the case when more than one substitution rule have been defined,
9840 the rules are evaluated one by one in the order where they have been
9841 defined. The first one matching, if any, is selected to perform
9844 For instance, if we had entered the following commands:
9847 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9848 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9852 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9853 @file{/mnt/include/defs.h} by using the first rule. However, it would
9854 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9855 @file{/mnt/src/lib/foo.c}.
9858 @item unset substitute-path [path]
9859 @kindex unset substitute-path
9860 If a path is specified, search the current list of substitution rules
9861 for a rule that would rewrite that path. Delete that rule if found.
9862 A warning is emitted by the debugger if no rule could be found.
9864 If no path is specified, then all substitution rules are deleted.
9866 @item show substitute-path [path]
9867 @kindex show substitute-path
9868 If a path is specified, then print the source path substitution rule
9869 which would rewrite that path, if any.
9871 If no path is specified, then print all existing source path substitution
9876 If your source path is cluttered with directories that are no longer of
9877 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9878 versions of source. You can correct the situation as follows:
9882 Use @code{directory} with no argument to reset the source path to its default value.
9885 Use @code{directory} with suitable arguments to reinstall the
9886 directories you want in the source path. You can add all the
9887 directories in one command.
9891 @section Source and Machine Code
9892 @cindex source line and its code address
9894 You can use the command @code{info line} to map source lines to program
9895 addresses (and vice versa), and the command @code{disassemble} to display
9896 a range of addresses as machine instructions. You can use the command
9897 @code{set disassemble-next-line} to set whether to disassemble next
9898 source line when execution stops. When run under @sc{gnu} Emacs
9899 mode, the @code{info line} command causes the arrow to point to the
9900 line specified. Also, @code{info line} prints addresses in symbolic form as
9906 @itemx info line @var{locspec}
9907 Print the starting and ending addresses of the compiled code for the
9908 source lines of the code locations that result from resolving
9909 @var{locspec}. @xref{Location Specifications}, for the various forms
9911 With no @var{locspec}, information about the current source line is
9915 For example, we can use @code{info line} to discover the location of
9916 the object code for the first line of function
9917 @code{m4_changequote}:
9920 (@value{GDBP}) info line m4_changequote
9921 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9922 ends at 0x6350 <m4_changequote+4>.
9926 @cindex code address and its source line
9927 We can also inquire, using @code{*@var{addr}} as the form for
9928 @var{locspec}, what source line covers a particular address
9931 (@value{GDBP}) info line *0x63ff
9932 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9933 ends at 0x6404 <m4_changequote+184>.
9936 @cindex @code{$_} and @code{info line}
9937 @cindex @code{x} command, default address
9938 @kindex x@r{(examine), and} info line
9939 After @code{info line}, the default address for the @code{x} command
9940 is changed to the starting address of the line, so that @samp{x/i} is
9941 sufficient to begin examining the machine code (@pxref{Memory,
9942 ,Examining Memory}). Also, this address is saved as the value of the
9943 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9946 @cindex info line, repeated calls
9947 After @code{info line}, using @code{info line} again without
9948 specifying a location will display information about the next source
9951 @anchor{disassemble}
9954 @cindex assembly instructions
9955 @cindex instructions, assembly
9956 @cindex machine instructions
9957 @cindex listing machine instructions
9959 @itemx disassemble /m
9960 @itemx disassemble /s
9961 @itemx disassemble /r
9962 @itemx disassemble /b
9963 This specialized command dumps a range of memory as machine
9964 instructions. It can also print mixed source+disassembly by specifying
9965 the @code{/m} or @code{/s} modifier and print the raw instructions in
9966 hex as well as in symbolic form by specifying the @code{/r} or @code{/b}
9967 modifier. The default memory range is the function surrounding the
9968 program counter of the selected frame. A single argument to this
9969 command is a program counter value; @value{GDBN} dumps the function
9970 surrounding this value. When two arguments are given, they should be
9971 separated by a comma, possibly surrounded by whitespace. The arguments
9972 specify a range of addresses to dump, in one of two forms:
9975 @item @var{start},@var{end}
9976 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9977 @item @var{start},+@var{length}
9978 the addresses from @var{start} (inclusive) to
9979 @code{@var{start}+@var{length}} (exclusive).
9983 When 2 arguments are specified, the name of the function is also
9984 printed (since there could be several functions in the given range).
9986 The argument(s) can be any expression yielding a numeric value, such as
9987 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9989 If the range of memory being disassembled contains current program counter,
9990 the instruction at that location is shown with a @code{=>} marker.
9993 The following example shows the disassembly of a range of addresses of
9994 HP PA-RISC 2.0 code:
9997 (@value{GDBP}) disas 0x32c4, 0x32e4
9998 Dump of assembler code from 0x32c4 to 0x32e4:
9999 0x32c4 <main+204>: addil 0,dp
10000 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
10001 0x32cc <main+212>: ldil 0x3000,r31
10002 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
10003 0x32d4 <main+220>: ldo 0(r31),rp
10004 0x32d8 <main+224>: addil -0x800,dp
10005 0x32dc <main+228>: ldo 0x588(r1),r26
10006 0x32e0 <main+232>: ldil 0x3000,r31
10007 End of assembler dump.
10010 The following two examples are for RISC-V, and demonstrates the
10011 difference between the @code{/r} and @code{/b} modifiers. First with
10012 @code{/b}, the bytes of the instruction are printed, in hex, in memory
10016 (@value{GDBP}) disassemble /b 0x00010150,0x0001015c
10017 Dump of assembler code from 0x10150 to 0x1015c:
10018 0x00010150 <call_me+4>: 22 dc sw s0,56(sp)
10019 0x00010152 <call_me+6>: 80 00 addi s0,sp,64
10020 0x00010154 <call_me+8>: 23 26 a4 fe sw a0,-20(s0)
10021 0x00010158 <call_me+12>: 23 24 b4 fe sw a1,-24(s0)
10022 End of assembler dump.
10025 In contrast, with @code{/r} the bytes of the instruction are displayed
10026 in the instruction order, for RISC-V this means that the bytes have been
10027 swapped to little-endian order:
10030 (@value{GDBP}) disassemble /r 0x00010150,0x0001015c
10031 Dump of assembler code from 0x10150 to 0x1015c:
10032 0x00010150 <call_me+4>: dc22 sw s0,56(sp)
10033 0x00010152 <call_me+6>: 0080 addi s0,sp,64
10034 0x00010154 <call_me+8>: fea42623 sw a0,-20(s0)
10035 0x00010158 <call_me+12>: feb42423 sw a1,-24(s0)
10036 End of assembler dump.
10039 Here is an example showing mixed source+assembly for Intel x86
10040 with @code{/m} or @code{/s}, when the program is stopped just after
10041 function prologue in a non-optimized function with no inline code.
10044 (@value{GDBP}) disas /m main
10045 Dump of assembler code for function main:
10047 0x08048330 <+0>: push %ebp
10048 0x08048331 <+1>: mov %esp,%ebp
10049 0x08048333 <+3>: sub $0x8,%esp
10050 0x08048336 <+6>: and $0xfffffff0,%esp
10051 0x08048339 <+9>: sub $0x10,%esp
10053 6 printf ("Hello.\n");
10054 => 0x0804833c <+12>: movl $0x8048440,(%esp)
10055 0x08048343 <+19>: call 0x8048284 <puts@@plt>
10059 0x08048348 <+24>: mov $0x0,%eax
10060 0x0804834d <+29>: leave
10061 0x0804834e <+30>: ret
10063 End of assembler dump.
10066 The @code{/m} option is deprecated as its output is not useful when
10067 there is either inlined code or re-ordered code.
10068 The @code{/s} option is the preferred choice.
10069 Here is an example for AMD x86-64 showing the difference between
10070 @code{/m} output and @code{/s} output.
10071 This example has one inline function defined in a header file,
10072 and the code is compiled with @samp{-O2} optimization.
10073 Note how the @code{/m} output is missing the disassembly of
10074 several instructions that are present in the @code{/s} output.
10104 (@value{GDBP}) disas /m main
10105 Dump of assembler code for function main:
10109 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
10110 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
10114 0x000000000040041d <+29>: xor %eax,%eax
10115 0x000000000040041f <+31>: retq
10116 0x0000000000400420 <+32>: add %eax,%eax
10117 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
10119 End of assembler dump.
10120 (@value{GDBP}) disas /s main
10121 Dump of assembler code for function main:
10125 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
10129 0x0000000000400406 <+6>: test %eax,%eax
10130 0x0000000000400408 <+8>: js 0x400420 <main+32>
10135 0x000000000040040a <+10>: lea 0xa(%rax),%edx
10136 0x000000000040040d <+13>: test %eax,%eax
10137 0x000000000040040f <+15>: mov $0x1,%eax
10138 0x0000000000400414 <+20>: cmovne %edx,%eax
10142 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
10146 0x000000000040041d <+29>: xor %eax,%eax
10147 0x000000000040041f <+31>: retq
10151 0x0000000000400420 <+32>: add %eax,%eax
10152 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
10153 End of assembler dump.
10156 Here is another example showing raw instructions in hex for AMD x86-64,
10159 (@value{GDBP}) disas /r 0x400281,+10
10160 Dump of assembler code from 0x400281 to 0x40028b:
10161 0x0000000000400281: 38 36 cmp %dh,(%rsi)
10162 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
10163 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
10164 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
10165 End of assembler dump.
10168 Note that the @samp{disassemble} command's address arguments are
10169 specified using expressions in your programming language
10170 (@pxref{Expressions, ,Expressions}), not location specs
10171 (@pxref{Location Specifications}). So, for example, if you want to
10172 disassemble function @code{bar} in file @file{foo.c}, you must type
10173 @samp{disassemble 'foo.c'::bar} and not @samp{disassemble foo.c:bar}.
10175 Some architectures have more than one commonly-used set of instruction
10176 mnemonics or other syntax.
10178 For programs that were dynamically linked and use shared libraries,
10179 instructions that call functions or branch to locations in the shared
10180 libraries might show a seemingly bogus location---it's actually a
10181 location of the relocation table. On some architectures, @value{GDBN}
10182 might be able to resolve these to actual function names.
10185 @kindex set disassembler-options
10186 @cindex disassembler options
10187 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
10188 This command controls the passing of target specific information to
10189 the disassembler. For a list of valid options, please refer to the
10190 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
10191 manual and/or the output of @kbd{objdump --help}
10192 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
10193 The default value is the empty string.
10195 If it is necessary to specify more than one disassembler option, then
10196 multiple options can be placed together into a comma separated list.
10197 Currently this command is only supported on targets ARC, ARM, MIPS,
10200 @kindex show disassembler-options
10201 @item show disassembler-options
10202 Show the current setting of the disassembler options.
10206 @kindex set disassembly-flavor
10207 @cindex Intel disassembly flavor
10208 @cindex AT&T disassembly flavor
10209 @item set disassembly-flavor @var{instruction-set}
10210 Select the instruction set to use when disassembling the
10211 program via the @code{disassemble} or @code{x/i} commands.
10213 Currently this command is only defined for the Intel x86 family. You
10214 can set @var{instruction-set} to either @code{intel} or @code{att}.
10215 The default is @code{att}, the AT&T flavor used by default by Unix
10216 assemblers for x86-based targets.
10218 @kindex show disassembly-flavor
10219 @item show disassembly-flavor
10220 Show the current setting of the disassembly flavor.
10224 @kindex set disassemble-next-line
10225 @kindex show disassemble-next-line
10226 @item set disassemble-next-line
10227 @itemx show disassemble-next-line
10228 Control whether or not @value{GDBN} will disassemble the next source
10229 line or instruction when execution stops. If ON, @value{GDBN} will
10230 display disassembly of the next source line when execution of the
10231 program being debugged stops. This is @emph{in addition} to
10232 displaying the source line itself, which @value{GDBN} always does if
10233 possible. If the next source line cannot be displayed for some reason
10234 (e.g., if @value{GDBN} cannot find the source file, or there's no line
10235 info in the debug info), @value{GDBN} will display disassembly of the
10236 next @emph{instruction} instead of showing the next source line. If
10237 AUTO, @value{GDBN} will display disassembly of next instruction only
10238 if the source line cannot be displayed. This setting causes
10239 @value{GDBN} to display some feedback when you step through a function
10240 with no line info or whose source file is unavailable. The default is
10241 OFF, which means never display the disassembly of the next line or
10245 @node Disable Reading Source
10246 @section Disable Reading Source Code
10247 @cindex source code, disable access
10249 In some cases it can be desirable to prevent @value{GDBN} from
10250 accessing source code files. One case where this might be desirable
10251 is if the source code files are located over a slow network
10254 The following command can be used to control whether @value{GDBN}
10255 should access source code files or not:
10258 @kindex set source open
10259 @kindex show source open
10260 @item set source open @r{[}on@r{|}off@r{]}
10261 @itemx show source open
10262 When this option is @code{on}, which is the default, @value{GDBN} will
10263 access source code files when needed, for example to print source
10264 lines when @value{GDBN} stops, or in response to the @code{list}
10267 When this option is @code{off}, @value{GDBN} will not access source
10272 @chapter Examining Data
10274 @cindex printing data
10275 @cindex examining data
10278 The usual way to examine data in your program is with the @code{print}
10279 command (abbreviated @code{p}), or its synonym @code{inspect}. It
10280 evaluates and prints the value of an expression of the language your
10281 program is written in (@pxref{Languages, ,Using @value{GDBN} with
10282 Different Languages}). It may also print the expression using a
10283 Python-based pretty-printer (@pxref{Pretty Printing}).
10286 @item print [[@var{options}] --] @var{expr}
10287 @itemx print [[@var{options}] --] /@var{f} @var{expr}
10288 @var{expr} is an expression (in the source language). By default the
10289 value of @var{expr} is printed in a format appropriate to its data type;
10290 you can choose a different format by specifying @samp{/@var{f}}, where
10291 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
10294 @anchor{print options}
10295 The @code{print} command supports a number of options that allow
10296 overriding relevant global print settings as set by @code{set print}
10300 @item -address [@code{on}|@code{off}]
10301 Set printing of addresses.
10302 Related setting: @ref{set print address}.
10304 @item -array [@code{on}|@code{off}]
10305 Pretty formatting of arrays.
10306 Related setting: @ref{set print array}.
10308 @item -array-indexes [@code{on}|@code{off}]
10309 Set printing of array indexes.
10310 Related setting: @ref{set print array-indexes}.
10312 @item -characters @var{number-of-characters}|@code{elements}|@code{unlimited}
10313 Set limit on string characters to print. The value @code{elements}
10314 causes the limit on array elements to print to be used. The value
10315 @code{unlimited} causes there to be no limit. Related setting:
10316 @ref{set print characters}.
10318 @item -elements @var{number-of-elements}|@code{unlimited}
10319 Set limit on array elements and optionally string characters to print.
10320 See @ref{set print characters}, and the @code{-characters} option above
10321 for when this option applies to strings. The value @code{unlimited}
10322 causes there to be no limit. @xref{set print elements}, for a related
10325 @item -max-depth @var{depth}|@code{unlimited}
10326 Set the threshold after which nested structures are replaced with
10327 ellipsis. Related setting: @ref{set print max-depth}.
10329 @item -nibbles [@code{on}|@code{off}]
10330 Set whether to print binary values in groups of four bits, known
10331 as ``nibbles''. @xref{set print nibbles}.
10333 @item -memory-tag-violations [@code{on}|@code{off}]
10334 Set printing of additional information about memory tag violations.
10335 @xref{set print memory-tag-violations}.
10337 @item -null-stop [@code{on}|@code{off}]
10338 Set printing of char arrays to stop at first null char. Related
10339 setting: @ref{set print null-stop}.
10341 @item -object [@code{on}|@code{off}]
10342 Set printing C@t{++} virtual function tables. Related setting:
10343 @ref{set print object}.
10345 @item -pretty [@code{on}|@code{off}]
10346 Set pretty formatting of structures. Related setting: @ref{set print
10349 @item -raw-values [@code{on}|@code{off}]
10350 Set whether to print values in raw form, bypassing any
10351 pretty-printers for that value. Related setting: @ref{set print
10354 @item -repeats @var{number-of-repeats}|@code{unlimited}
10355 Set threshold for repeated print elements. @code{unlimited} causes
10356 all elements to be individually printed. Related setting: @ref{set
10359 @item -static-members [@code{on}|@code{off}]
10360 Set printing C@t{++} static members. Related setting: @ref{set print
10363 @item -symbol [@code{on}|@code{off}]
10364 Set printing of symbol names when printing pointers. Related setting:
10365 @ref{set print symbol}.
10367 @item -union [@code{on}|@code{off}]
10368 Set printing of unions interior to structures. Related setting:
10369 @ref{set print union}.
10371 @item -vtbl [@code{on}|@code{off}]
10372 Set printing of C++ virtual function tables. Related setting:
10373 @ref{set print vtbl}.
10376 Because the @code{print} command accepts arbitrary expressions which
10377 may look like options (including abbreviations), if you specify any
10378 command option, then you must use a double dash (@code{--}) to mark
10379 the end of option processing.
10381 For example, this prints the value of the @code{-p} expression:
10384 (@value{GDBP}) print -p
10387 While this repeats the last value in the value history (see below)
10388 with the @code{-pretty} option in effect:
10391 (@value{GDBP}) print -p --
10394 Here is an example including both on option and an expression:
10398 (@value{GDBP}) print -pretty -- *myptr
10410 @item print [@var{options}]
10411 @itemx print [@var{options}] /@var{f}
10412 @cindex reprint the last value
10413 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10414 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10415 conveniently inspect the same value in an alternative format.
10418 If the architecture supports memory tagging, the @code{print} command will
10419 display pointer/memory tag mismatches if what is being printed is a pointer
10420 or reference type. @xref{Memory Tagging}.
10422 A more low-level way of examining data is with the @code{x} command.
10423 It examines data in memory at a specified address and prints it in a
10424 specified format. @xref{Memory, ,Examining Memory}.
10426 If you are interested in information about types, or about how the
10427 fields of a struct or a class are declared, use the @code{ptype @var{expr}}
10428 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10431 @cindex exploring hierarchical data structures
10433 Another way of examining values of expressions and type information is
10434 through the Python extension command @code{explore} (available only if
10435 the @value{GDBN} build is configured with @code{--with-python}). It
10436 offers an interactive way to start at the highest level (or, the most
10437 abstract level) of the data type of an expression (or, the data type
10438 itself) and explore all the way down to leaf scalar values/fields
10439 embedded in the higher level data types.
10442 @item explore @var{arg}
10443 @var{arg} is either an expression (in the source language), or a type
10444 visible in the current context of the program being debugged.
10447 The working of the @code{explore} command can be illustrated with an
10448 example. If a data type @code{struct ComplexStruct} is defined in your
10452 struct SimpleStruct
10458 struct ComplexStruct
10460 struct SimpleStruct *ss_p;
10466 followed by variable declarations as
10469 struct SimpleStruct ss = @{ 10, 1.11 @};
10470 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10474 then, the value of the variable @code{cs} can be explored using the
10475 @code{explore} command as follows.
10478 (@value{GDBP}) explore cs
10479 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10480 the following fields:
10482 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10483 arr = <Enter 1 to explore this field of type `int [10]'>
10485 Enter the field number of choice:
10489 Since the fields of @code{cs} are not scalar values, you are being
10490 prompted to chose the field you want to explore. Let's say you choose
10491 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10492 pointer, you will be asked if it is pointing to a single value. From
10493 the declaration of @code{cs} above, it is indeed pointing to a single
10494 value, hence you enter @code{y}. If you enter @code{n}, then you will
10495 be asked if it were pointing to an array of values, in which case this
10496 field will be explored as if it were an array.
10499 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10500 Continue exploring it as a pointer to a single value [y/n]: y
10501 The value of `*(cs.ss_p)' is a struct/class of type `struct
10502 SimpleStruct' with the following fields:
10504 i = 10 .. (Value of type `int')
10505 d = 1.1100000000000001 .. (Value of type `double')
10507 Press enter to return to parent value:
10511 If the field @code{arr} of @code{cs} was chosen for exploration by
10512 entering @code{1} earlier, then since it is as array, you will be
10513 prompted to enter the index of the element in the array that you want
10517 `cs.arr' is an array of `int'.
10518 Enter the index of the element you want to explore in `cs.arr': 5
10520 `(cs.arr)[5]' is a scalar value of type `int'.
10524 Press enter to return to parent value:
10527 In general, at any stage of exploration, you can go deeper towards the
10528 leaf values by responding to the prompts appropriately, or hit the
10529 return key to return to the enclosing data structure (the @i{higher}
10530 level data structure).
10532 Similar to exploring values, you can use the @code{explore} command to
10533 explore types. Instead of specifying a value (which is typically a
10534 variable name or an expression valid in the current context of the
10535 program being debugged), you specify a type name. If you consider the
10536 same example as above, your can explore the type
10537 @code{struct ComplexStruct} by passing the argument
10538 @code{struct ComplexStruct} to the @code{explore} command.
10541 (@value{GDBP}) explore struct ComplexStruct
10545 By responding to the prompts appropriately in the subsequent interactive
10546 session, you can explore the type @code{struct ComplexStruct} in a
10547 manner similar to how the value @code{cs} was explored in the above
10550 The @code{explore} command also has two sub-commands,
10551 @code{explore value} and @code{explore type}. The former sub-command is
10552 a way to explicitly specify that value exploration of the argument is
10553 being invoked, while the latter is a way to explicitly specify that type
10554 exploration of the argument is being invoked.
10557 @item explore value @var{expr}
10558 @cindex explore value
10559 This sub-command of @code{explore} explores the value of the
10560 expression @var{expr} (if @var{expr} is an expression valid in the
10561 current context of the program being debugged). The behavior of this
10562 command is identical to that of the behavior of the @code{explore}
10563 command being passed the argument @var{expr}.
10565 @item explore type @var{arg}
10566 @cindex explore type
10567 This sub-command of @code{explore} explores the type of @var{arg} (if
10568 @var{arg} is a type visible in the current context of program being
10569 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10570 is an expression valid in the current context of the program being
10571 debugged). If @var{arg} is a type, then the behavior of this command is
10572 identical to that of the @code{explore} command being passed the
10573 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10574 this command will be identical to that of the @code{explore} command
10575 being passed the type of @var{arg} as the argument.
10579 * Expressions:: Expressions
10580 * Ambiguous Expressions:: Ambiguous Expressions
10581 * Variables:: Program variables
10582 * Arrays:: Artificial arrays
10583 * Output Formats:: Output formats
10584 * Memory:: Examining memory
10585 * Memory Tagging:: Memory Tagging
10586 * Auto Display:: Automatic display
10587 * Print Settings:: Print settings
10588 * Pretty Printing:: Python pretty printing
10589 * Value History:: Value history
10590 * Convenience Vars:: Convenience variables
10591 * Convenience Funs:: Convenience functions
10592 * Registers:: Registers
10593 * Floating Point Hardware:: Floating point hardware
10594 * Vector Unit:: Vector Unit
10595 * OS Information:: Auxiliary data provided by operating system
10596 * Memory Region Attributes:: Memory region attributes
10597 * Dump/Restore Files:: Copy between memory and a file
10598 * Core File Generation:: Cause a program dump its core
10599 * Character Sets:: Debugging programs that use a different
10600 character set than GDB does
10601 * Caching Target Data:: Data caching for targets
10602 * Searching Memory:: Searching memory for a sequence of bytes
10603 * Value Sizes:: Managing memory allocated for values
10607 @section Expressions
10609 @cindex expressions
10610 @code{print} and many other @value{GDBN} commands accept an expression and
10611 compute its value. Any kind of constant, variable or operator defined
10612 by the programming language you are using is valid in an expression in
10613 @value{GDBN}. This includes conditional expressions, function calls,
10614 casts, and string constants. It also includes preprocessor macros, if
10615 you compiled your program to include this information; see
10618 @cindex arrays in expressions
10619 @value{GDBN} supports array constants in expressions input by
10620 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10621 you can use the command @code{print @{1, 2, 3@}} to create an array
10622 of three integers. If you pass an array to a function or assign it
10623 to a program variable, @value{GDBN} copies the array to memory that
10624 is @code{malloc}ed in the target program.
10626 Because C is so widespread, most of the expressions shown in examples in
10627 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10628 Languages}, for information on how to use expressions in other
10631 In this section, we discuss operators that you can use in @value{GDBN}
10632 expressions regardless of your programming language.
10634 @cindex casts, in expressions
10635 Casts are supported in all languages, not just in C, because it is so
10636 useful to cast a number into a pointer in order to examine a structure
10637 at that address in memory.
10638 @c FIXME: casts supported---Mod2 true?
10640 @value{GDBN} supports these operators, in addition to those common
10641 to programming languages:
10645 @samp{@@} is a binary operator for treating parts of memory as arrays.
10646 @xref{Arrays, ,Artificial Arrays}, for more information.
10649 @samp{::} allows you to specify a variable in terms of the file or
10650 function where it is defined. @xref{Variables, ,Program Variables}.
10652 @cindex @{@var{type}@}
10653 @cindex type casting memory
10654 @cindex memory, viewing as typed object
10655 @cindex casts, to view memory
10656 @item @{@var{type}@} @var{addr}
10657 Refers to an object of type @var{type} stored at address @var{addr} in
10658 memory. The address @var{addr} may be any expression whose value is
10659 an integer or pointer (but parentheses are required around binary
10660 operators, just as in a cast). This construct is allowed regardless
10661 of what kind of data is normally supposed to reside at @var{addr}.
10664 @node Ambiguous Expressions
10665 @section Ambiguous Expressions
10666 @cindex ambiguous expressions
10668 Expressions can sometimes contain some ambiguous elements. For instance,
10669 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10670 a single function name to be defined several times, for application in
10671 different contexts. This is called @dfn{overloading}. Another example
10672 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10673 templates and is typically instantiated several times, resulting in
10674 the same function name being defined in different contexts.
10676 In some cases and depending on the language, it is possible to adjust
10677 the expression to remove the ambiguity. For instance in C@t{++}, you
10678 can specify the signature of the function you want to break on, as in
10679 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10680 qualified name of your function often makes the expression unambiguous
10683 When an ambiguity that needs to be resolved is detected, the debugger
10684 has the capability to display a menu of numbered choices for each
10685 possibility, and then waits for the selection with the prompt @samp{>}.
10686 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10687 aborts the current command. If the command in which the expression was
10688 used allows more than one choice to be selected, the next option in the
10689 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10692 For example, the following session excerpt shows an attempt to set a
10693 breakpoint at the overloaded symbol @code{String::after}.
10694 We choose three particular definitions of that function name:
10696 @c FIXME! This is likely to change to show arg type lists, at least
10699 (@value{GDBP}) b String::after
10702 [2] file:String.cc; line number:867
10703 [3] file:String.cc; line number:860
10704 [4] file:String.cc; line number:875
10705 [5] file:String.cc; line number:853
10706 [6] file:String.cc; line number:846
10707 [7] file:String.cc; line number:735
10709 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10710 Breakpoint 2 at 0xb344: file String.cc, line 875.
10711 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10712 Multiple breakpoints were set.
10713 Use the "delete" command to delete unwanted
10720 @kindex set multiple-symbols
10721 @item set multiple-symbols @var{mode}
10722 @cindex multiple-symbols menu
10724 This option allows you to adjust the debugger behavior when an expression
10727 By default, @var{mode} is set to @code{all}. If the command with which
10728 the expression is used allows more than one choice, then @value{GDBN}
10729 automatically selects all possible choices. For instance, inserting
10730 a breakpoint on a function using an ambiguous name results in a breakpoint
10731 inserted on each possible match. However, if a unique choice must be made,
10732 then @value{GDBN} uses the menu to help you disambiguate the expression.
10733 For instance, printing the address of an overloaded function will result
10734 in the use of the menu.
10736 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10737 when an ambiguity is detected.
10739 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10740 an error due to the ambiguity and the command is aborted.
10742 @kindex show multiple-symbols
10743 @item show multiple-symbols
10744 Show the current value of the @code{multiple-symbols} setting.
10748 @section Program Variables
10750 The most common kind of expression to use is the name of a variable
10753 Variables in expressions are understood in the selected stack frame
10754 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10758 global (or file-static)
10765 visible according to the scope rules of the
10766 programming language from the point of execution in that frame
10769 @noindent This means that in the function
10784 you can examine and use the variable @code{a} whenever your program is
10785 executing within the function @code{foo}, but you can only use or
10786 examine the variable @code{b} while your program is executing inside
10787 the block where @code{b} is declared.
10789 @cindex variable name conflict
10790 There is an exception: you can refer to a variable or function whose
10791 scope is a single source file even if the current execution point is not
10792 in this file. But it is possible to have more than one such variable or
10793 function with the same name (in different source files). If that
10794 happens, referring to that name has unpredictable effects. If you wish,
10795 you can specify a static variable in a particular function or file by
10796 using the colon-colon (@code{::}) notation:
10798 @cindex colon-colon, context for variables/functions
10800 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10801 @cindex @code{::}, context for variables/functions
10804 @var{file}::@var{variable}
10805 @var{function}::@var{variable}
10809 Here @var{file} or @var{function} is the name of the context for the
10810 static @var{variable}. In the case of file names, you can use quotes to
10811 make sure @value{GDBN} parses the file name as a single word---for example,
10812 to print a global value of @code{x} defined in @file{f2.c}:
10815 (@value{GDBP}) p 'f2.c'::x
10818 The @code{::} notation is normally used for referring to
10819 static variables, since you typically disambiguate uses of local variables
10820 in functions by selecting the appropriate frame and using the
10821 simple name of the variable. However, you may also use this notation
10822 to refer to local variables in frames enclosing the selected frame:
10831 process (a); /* Stop here */
10842 For example, if there is a breakpoint at the commented line,
10843 here is what you might see
10844 when the program stops after executing the call @code{bar(0)}:
10849 (@value{GDBP}) p bar::a
10851 (@value{GDBP}) up 2
10852 #2 0x080483d0 in foo (a=5) at foobar.c:12
10855 (@value{GDBP}) p bar::a
10859 @cindex C@t{++} scope resolution
10860 These uses of @samp{::} are very rarely in conflict with the very
10861 similar use of the same notation in C@t{++}. When they are in
10862 conflict, the C@t{++} meaning takes precedence; however, this can be
10863 overridden by quoting the file or function name with single quotes.
10865 For example, suppose the program is stopped in a method of a class
10866 that has a field named @code{includefile}, and there is also an
10867 include file named @file{includefile} that defines a variable,
10868 @code{some_global}.
10871 (@value{GDBP}) p includefile
10873 (@value{GDBP}) p includefile::some_global
10874 A syntax error in expression, near `'.
10875 (@value{GDBP}) p 'includefile'::some_global
10879 @cindex wrong values
10880 @cindex variable values, wrong
10881 @cindex function entry/exit, wrong values of variables
10882 @cindex optimized code, wrong values of variables
10884 @emph{Warning:} Occasionally, a local variable may appear to have the
10885 wrong value at certain points in a function---just after entry to a new
10886 scope, and just before exit.
10888 You may see this problem when you are stepping by machine instructions.
10889 This is because, on most machines, it takes more than one instruction to
10890 set up a stack frame (including local variable definitions); if you are
10891 stepping by machine instructions, variables may appear to have the wrong
10892 values until the stack frame is completely built. On exit, it usually
10893 also takes more than one machine instruction to destroy a stack frame;
10894 after you begin stepping through that group of instructions, local
10895 variable definitions may be gone.
10897 This may also happen when the compiler does significant optimizations.
10898 To be sure of always seeing accurate values, turn off all optimization
10901 @cindex ``No symbol "foo" in current context''
10902 Another possible effect of compiler optimizations is to optimize
10903 unused variables out of existence, or assign variables to registers (as
10904 opposed to memory addresses). Depending on the support for such cases
10905 offered by the debug info format used by the compiler, @value{GDBN}
10906 might not be able to display values for such local variables. If that
10907 happens, @value{GDBN} will print a message like this:
10910 No symbol "foo" in current context.
10913 To solve such problems, either recompile without optimizations, or use a
10914 different debug info format, if the compiler supports several such
10915 formats. @xref{Compilation}, for more information on choosing compiler
10916 options. @xref{C, ,C and C@t{++}}, for more information about debug
10917 info formats that are best suited to C@t{++} programs.
10919 If you ask to print an object whose contents are unknown to
10920 @value{GDBN}, e.g., because its data type is not completely specified
10921 by the debug information, @value{GDBN} will say @samp{<incomplete
10922 type>}. @xref{Symbols, incomplete type}, for more about this.
10924 @cindex no debug info variables
10925 If you try to examine or use the value of a (global) variable for
10926 which @value{GDBN} has no type information, e.g., because the program
10927 includes no debug information, @value{GDBN} displays an error message.
10928 @xref{Symbols, unknown type}, for more about unknown types. If you
10929 cast the variable to its declared type, @value{GDBN} gets the
10930 variable's value using the cast-to type as the variable's type. For
10931 example, in a C program:
10934 (@value{GDBP}) p var
10935 'var' has unknown type; cast it to its declared type
10936 (@value{GDBP}) p (float) var
10940 If you append @kbd{@@entry} string to a function parameter name you get its
10941 value at the time the function got called. If the value is not available an
10942 error message is printed. Entry values are available only with some compilers.
10943 Entry values are normally also printed at the function parameter list according
10944 to @ref{set print entry-values}.
10947 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10949 (@value{GDBP}) next
10951 (@value{GDBP}) print i
10953 (@value{GDBP}) print i@@entry
10957 Strings are identified as arrays of @code{char} values without specified
10958 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10959 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10960 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10961 defines literal string type @code{"char"} as @code{char} without a sign.
10966 signed char var1[] = "A";
10969 You get during debugging
10971 (@value{GDBP}) print var0
10973 (@value{GDBP}) print var1
10974 $2 = @{65 'A', 0 '\0'@}
10978 @section Artificial Arrays
10980 @cindex artificial array
10982 @kindex @@@r{, referencing memory as an array}
10983 It is often useful to print out several successive objects of the
10984 same type in memory; a section of an array, or an array of
10985 dynamically determined size for which only a pointer exists in the
10988 You can do this by referring to a contiguous span of memory as an
10989 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10990 operand of @samp{@@} should be the first element of the desired array
10991 and be an individual object. The right operand should be the desired length
10992 of the array. The result is an array value whose elements are all of
10993 the type of the left argument. The first element is actually the left
10994 argument; the second element comes from bytes of memory immediately
10995 following those that hold the first element, and so on. Here is an
10996 example. If a program says
10999 int *array = (int *) malloc (len * sizeof (int));
11003 you can print the contents of @code{array} with
11009 The left operand of @samp{@@} must reside in memory. Array values made
11010 with @samp{@@} in this way behave just like other arrays in terms of
11011 subscripting, and are coerced to pointers when used in expressions.
11012 Artificial arrays most often appear in expressions via the value history
11013 (@pxref{Value History, ,Value History}), after printing one out.
11015 Another way to create an artificial array is to use a cast.
11016 This re-interprets a value as if it were an array.
11017 The value need not be in memory:
11019 (@value{GDBP}) p/x (short[2])0x12345678
11020 $1 = @{0x1234, 0x5678@}
11023 As a convenience, if you leave the array length out (as in
11024 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
11025 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
11027 (@value{GDBP}) p/x (short[])0x12345678
11028 $2 = @{0x1234, 0x5678@}
11031 Sometimes the artificial array mechanism is not quite enough; in
11032 moderately complex data structures, the elements of interest may not
11033 actually be adjacent---for example, if you are interested in the values
11034 of pointers in an array. One useful work-around in this situation is
11035 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
11036 Variables}) as a counter in an expression that prints the first
11037 interesting value, and then repeat that expression via @key{RET}. For
11038 instance, suppose you have an array @code{dtab} of pointers to
11039 structures, and you are interested in the values of a field @code{fv}
11040 in each structure. Here is an example of what you might type:
11050 @node Output Formats
11051 @section Output Formats
11053 @cindex formatted output
11054 @cindex output formats
11055 By default, @value{GDBN} prints a value according to its data type. Sometimes
11056 this is not what you want. For example, you might want to print a number
11057 in hex, or a pointer in decimal. Or you might want to view data in memory
11058 at a certain address as a character string or as an instruction. To do
11059 these things, specify an @dfn{output format} when you print a value.
11061 The simplest use of output formats is to say how to print a value
11062 already computed. This is done by starting the arguments of the
11063 @code{print} command with a slash and a format letter. The format
11064 letters supported are:
11068 Print the binary representation of the value in hexadecimal.
11071 Print the binary representation of the value in decimal.
11074 Print the binary representation of the value as an decimal, as if it
11078 Print the binary representation of the value in octal.
11081 Print the binary representation of the value in binary. The letter
11082 @samp{t} stands for ``two''. @footnote{@samp{b} cannot be used
11083 because these format letters are also used with the @code{x} command,
11084 where @samp{b} stands for ``byte''; see @ref{Memory,,Examining
11088 @cindex unknown address, locating
11089 @cindex locate address
11090 Print as an address, both absolute in hexadecimal and as an offset from
11091 the nearest preceding symbol. You can use this format used to discover
11092 where (in what function) an unknown address is located:
11095 (@value{GDBP}) p/a 0x54320
11096 $3 = 0x54320 <_initialize_vx+396>
11100 The command @code{info symbol 0x54320} yields similar results.
11101 @xref{Symbols, info symbol}.
11104 Cast the value to an integer (unlike other formats, this does not just
11105 reinterpret the underlying bits) and print it as a character constant.
11106 This prints both the numerical value and its character representation.
11107 The character representation is replaced with the octal escape
11108 @samp{\nnn} for characters outside the 7-bit @sc{ascii} range.
11110 Without this format, @value{GDBN} displays @code{char},
11111 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
11112 constants. Single-byte members of vectors are displayed as integer
11116 Regard the bits of the value as a floating point number and print
11117 using typical floating point syntax.
11120 @cindex printing strings
11121 @cindex printing byte arrays
11122 Regard as a string, if possible. With this format, pointers to single-byte
11123 data are displayed as null-terminated strings and arrays of single-byte data
11124 are displayed as fixed-length strings. Other values are displayed in their
11127 Without this format, @value{GDBN} displays pointers to and arrays of
11128 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
11129 strings. Single-byte members of a vector are displayed as an integer
11133 Like @samp{x} formatting, the value is treated as an integer and
11134 printed as hexadecimal, but leading zeros are printed to pad the value
11135 to the size of the integer type.
11138 @cindex raw printing
11139 Print using the @samp{raw} formatting. By default, @value{GDBN} will
11140 use a Python-based pretty-printer, if one is available (@pxref{Pretty
11141 Printing}). This typically results in a higher-level display of the
11142 value's contents. The @samp{r} format bypasses any Python
11143 pretty-printer which might exist.
11146 For example, to print the program counter in hex (@pxref{Registers}), type
11153 Note that no space is required before the slash; this is because command
11154 names in @value{GDBN} cannot contain a slash.
11156 To reprint the last value in the value history with a different format,
11157 you can use the @code{print} command with just a format and no
11158 expression. For example, @samp{p/x} reprints the last value in hex.
11161 @section Examining Memory
11163 You can use the command @code{x} (for ``examine'') to examine memory in
11164 any of several formats, independently of your program's data types.
11166 @cindex examining memory
11168 @kindex x @r{(examine memory)}
11169 @item x/@var{nfu} @var{addr}
11170 @itemx x @var{addr}
11172 Use the @code{x} command to examine memory.
11175 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
11176 much memory to display and how to format it; @var{addr} is an
11177 expression giving the address where you want to start displaying memory.
11178 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
11179 Several commands set convenient defaults for @var{addr}.
11182 @item @var{n}, the repeat count
11183 The repeat count is a decimal integer; the default is 1. It specifies
11184 how much memory (counting by units @var{u}) to display. If a negative
11185 number is specified, memory is examined backward from @var{addr}.
11186 @c This really is **decimal**; unaffected by 'set radix' as of GDB
11189 @item @var{f}, the display format
11190 The display format is one of the formats used by @code{print}
11191 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
11192 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
11193 @samp{m} (for displaying memory tags).
11194 The default is @samp{x} (hexadecimal) initially. The default changes
11195 each time you use either @code{x} or @code{print}.
11197 @item @var{u}, the unit size
11198 The unit size is any of
11204 Halfwords (two bytes).
11206 Words (four bytes). This is the initial default.
11208 Giant words (eight bytes).
11211 Each time you specify a unit size with @code{x}, that size becomes the
11212 default unit the next time you use @code{x}. For the @samp{i} format,
11213 the unit size is ignored and is normally not written. For the @samp{s} format,
11214 the unit size defaults to @samp{b}, unless it is explicitly given.
11215 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
11216 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
11217 Note that the results depend on the programming language of the
11218 current compilation unit. If the language is C, the @samp{s}
11219 modifier will use the UTF-16 encoding while @samp{w} will use
11220 UTF-32. The encoding is set by the programming language and cannot
11223 @item @var{addr}, starting display address
11224 @var{addr} is the address where you want @value{GDBN} to begin displaying
11225 memory. The expression need not have a pointer value (though it may);
11226 it is always interpreted as an integer address of a byte of memory.
11227 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
11228 @var{addr} is usually just after the last address examined---but several
11229 other commands also set the default address: @code{info breakpoints} (to
11230 the address of the last breakpoint listed), @code{info line} (to the
11231 starting address of a line), and @code{print} (if you use it to display
11232 a value from memory).
11235 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
11236 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
11237 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
11238 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
11239 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
11241 You can also specify a negative repeat count to examine memory backward
11242 from the given address. For example, @samp{x/-3uh 0x54320} prints three
11243 halfwords (@code{h}) at @code{0x5431a}, @code{0x5431c}, and @code{0x5431e}.
11245 Since the letters indicating unit sizes are all distinct from the
11246 letters specifying output formats, you do not have to remember whether
11247 unit size or format comes first; either order works. The output
11248 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
11249 (However, the count @var{n} must come first; @samp{wx4} does not work.)
11251 Even though the unit size @var{u} is ignored for the formats @samp{s}
11252 and @samp{i}, you might still want to use a count @var{n}; for example,
11253 @samp{3i} specifies that you want to see three machine instructions,
11254 including any operands. For convenience, especially when used with
11255 the @code{display} command, the @samp{i} format also prints branch delay
11256 slot instructions, if any, beyond the count specified, which immediately
11257 follow the last instruction that is within the count. The command
11258 @code{disassemble} gives an alternative way of inspecting machine
11259 instructions; see @ref{Machine Code,,Source and Machine Code}.
11261 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
11262 the command displays null-terminated strings or instructions before the given
11263 address as many as the absolute value of the given number. For the @samp{i}
11264 format, we use line number information in the debug info to accurately locate
11265 instruction boundaries while disassembling backward. If line info is not
11266 available, the command stops examining memory with an error message.
11268 All the defaults for the arguments to @code{x} are designed to make it
11269 easy to continue scanning memory with minimal specifications each time
11270 you use @code{x}. For example, after you have inspected three machine
11271 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
11272 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
11273 the repeat count @var{n} is used again; the other arguments default as
11274 for successive uses of @code{x}.
11276 When examining machine instructions, the instruction at current program
11277 counter is shown with a @code{=>} marker. For example:
11280 (@value{GDBP}) x/5i $pc-6
11281 0x804837f <main+11>: mov %esp,%ebp
11282 0x8048381 <main+13>: push %ecx
11283 0x8048382 <main+14>: sub $0x4,%esp
11284 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
11285 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
11288 If the architecture supports memory tagging, the tags can be displayed by
11289 using @samp{m}. @xref{Memory Tagging}.
11291 The information will be displayed once per granule size
11292 (the amount of bytes a particular memory tag covers). For example, AArch64
11293 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
11295 Due to the way @value{GDBN} prints information with the @code{x} command (not
11296 aligned to a particular boundary), the tag information will refer to the
11297 initial address displayed on a particular line. If a memory tag boundary
11298 is crossed in the middle of a line displayed by the @code{x} command, it
11299 will be displayed on the next line.
11301 The @samp{m} format doesn't affect any other specified formats that were
11302 passed to the @code{x} command.
11304 @cindex @code{$_}, @code{$__}, and value history
11305 The addresses and contents printed by the @code{x} command are not saved
11306 in the value history because there is often too much of them and they
11307 would get in the way. Instead, @value{GDBN} makes these values available for
11308 subsequent use in expressions as values of the convenience variables
11309 @code{$_} and @code{$__}. After an @code{x} command, the last address
11310 examined is available for use in expressions in the convenience variable
11311 @code{$_}. The contents of that address, as examined, are available in
11312 the convenience variable @code{$__}.
11314 If the @code{x} command has a repeat count, the address and contents saved
11315 are from the last memory unit printed; this is not the same as the last
11316 address printed if several units were printed on the last line of output.
11318 @anchor{addressable memory unit}
11319 @cindex addressable memory unit
11320 Most targets have an addressable memory unit size of 8 bits. This means
11321 that to each memory address are associated 8 bits of data. Some
11322 targets, however, have other addressable memory unit sizes.
11323 Within @value{GDBN} and this document, the term
11324 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
11325 when explicitly referring to a chunk of data of that size. The word
11326 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
11327 the addressable memory unit size of the target. For most systems,
11328 addressable memory unit is a synonym of byte.
11330 @cindex remote memory comparison
11331 @cindex target memory comparison
11332 @cindex verify remote memory image
11333 @cindex verify target memory image
11334 When you are debugging a program running on a remote target machine
11335 (@pxref{Remote Debugging}), you may wish to verify the program's image
11336 in the remote machine's memory against the executable file you
11337 downloaded to the target. Or, on any target, you may want to check
11338 whether the program has corrupted its own read-only sections. The
11339 @code{compare-sections} command is provided for such situations.
11342 @kindex compare-sections
11343 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
11344 Compare the data of a loadable section @var{section-name} in the
11345 executable file of the program being debugged with the same section in
11346 the target machine's memory, and report any mismatches. With no
11347 arguments, compares all loadable sections. With an argument of
11348 @code{-r}, compares all loadable read-only sections.
11350 Note: for remote targets, this command can be accelerated if the
11351 target supports computing the CRC checksum of a block of memory
11352 (@pxref{qCRC packet}).
11355 @node Memory Tagging
11356 @section Memory Tagging
11358 Memory tagging is a memory protection technology that uses a pair of tags to
11359 validate memory accesses through pointers. The tags are integer values
11360 usually comprised of a few bits, depending on the architecture.
11362 There are two types of tags that are used in this setup: logical and
11363 allocation. A logical tag is stored in the pointers themselves, usually at the
11364 higher bits of the pointers. An allocation tag is the tag associated
11365 with particular ranges of memory in the physical address space, against which
11366 the logical tags from pointers are compared.
11368 The pointer tag (logical tag) must match the memory tag (allocation tag)
11369 for the memory access to be valid. If the logical tag does not match the
11370 allocation tag, that will raise a memory violation.
11372 Allocation tags cover multiple contiguous bytes of physical memory. This
11373 range of bytes is called a memory tag granule and is architecture-specific.
11374 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11375 tag spans 16 bytes of memory.
11377 If the underlying architecture supports memory tagging, like AArch64 MTE
11378 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11379 against memory allocation tags.
11381 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11382 display tag information when appropriate, and a command prefix of
11383 @code{memory-tag} gives access to the various memory tagging commands.
11385 The @code{memory-tag} commands are the following:
11388 @kindex memory-tag print-logical-tag
11389 @item memory-tag print-logical-tag @var{pointer_expression}
11390 Print the logical tag stored in @var{pointer_expression}.
11391 @kindex memory-tag with-logical-tag
11392 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11393 Print the pointer given by @var{pointer_expression}, augmented with a logical
11394 tag of @var{tag_bytes}.
11395 @kindex memory-tag print-allocation-tag
11396 @item memory-tag print-allocation-tag @var{address_expression}
11397 Print the allocation tag associated with the memory address given by
11398 @var{address_expression}.
11399 @kindex memory-tag setatag
11400 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11401 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11402 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11403 @kindex memory-tag check
11404 @item memory-tag check @var{pointer_expression}
11405 Check if the logical tag in the pointer given by @var{pointer_expression}
11406 matches the allocation tag for the memory referenced by the pointer.
11408 This essentially emulates the hardware validation that is done when tagged
11409 memory is accessed through a pointer, but does not cause a memory fault as
11410 it would during hardware validation.
11412 It can be used to inspect potential memory tagging violations in the running
11413 process, before any faults get triggered.
11417 @section Automatic Display
11418 @cindex automatic display
11419 @cindex display of expressions
11421 If you find that you want to print the value of an expression frequently
11422 (to see how it changes), you might want to add it to the @dfn{automatic
11423 display list} so that @value{GDBN} prints its value each time your program stops.
11424 Each expression added to the list is given a number to identify it;
11425 to remove an expression from the list, you specify that number.
11426 The automatic display looks like this:
11430 3: bar[5] = (struct hack *) 0x3804
11434 This display shows item numbers, expressions and their current values. As with
11435 displays you request manually using @code{x} or @code{print}, you can
11436 specify the output format you prefer; in fact, @code{display} decides
11437 whether to use @code{print} or @code{x} depending your format
11438 specification---it uses @code{x} if you specify either the @samp{i}
11439 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11443 @item display @var{expr}
11444 Add the expression @var{expr} to the list of expressions to display
11445 each time your program stops. @xref{Expressions, ,Expressions}.
11447 @code{display} does not repeat if you press @key{RET} again after using it.
11449 @item display/@var{fmt} @var{expr}
11450 For @var{fmt} specifying only a display format and not a size or
11451 count, add the expression @var{expr} to the auto-display list but
11452 arrange to display it each time in the specified format @var{fmt}.
11453 @xref{Output Formats,,Output Formats}.
11455 @item display/@var{fmt} @var{addr}
11456 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11457 number of units, add the expression @var{addr} as a memory address to
11458 be examined each time your program stops. Examining means in effect
11459 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11462 For example, @samp{display/i $pc} can be helpful, to see the machine
11463 instruction about to be executed each time execution stops (@samp{$pc}
11464 is a common name for the program counter; @pxref{Registers, ,Registers}).
11467 @kindex delete display
11469 @item undisplay @var{dnums}@dots{}
11470 @itemx delete display @var{dnums}@dots{}
11471 Remove items from the list of expressions to display. Specify the
11472 numbers of the displays that you want affected with the command
11473 argument @var{dnums}. It can be a single display number, one of the
11474 numbers shown in the first field of the @samp{info display} display;
11475 or it could be a range of display numbers, as in @code{2-4}.
11477 @code{undisplay} does not repeat if you press @key{RET} after using it.
11478 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11480 @kindex disable display
11481 @item disable display @var{dnums}@dots{}
11482 Disable the display of item numbers @var{dnums}. A disabled display
11483 item is not printed automatically, but is not forgotten. It may be
11484 enabled again later. Specify the numbers of the displays that you
11485 want affected with the command argument @var{dnums}. It can be a
11486 single display number, one of the numbers shown in the first field of
11487 the @samp{info display} display; or it could be a range of display
11488 numbers, as in @code{2-4}.
11490 @kindex enable display
11491 @item enable display @var{dnums}@dots{}
11492 Enable display of item numbers @var{dnums}. It becomes effective once
11493 again in auto display of its expression, until you specify otherwise.
11494 Specify the numbers of the displays that you want affected with the
11495 command argument @var{dnums}. It can be a single display number, one
11496 of the numbers shown in the first field of the @samp{info display}
11497 display; or it could be a range of display numbers, as in @code{2-4}.
11500 Display the current values of the expressions on the list, just as is
11501 done when your program stops.
11503 @kindex info display
11505 Print the list of expressions previously set up to display
11506 automatically, each one with its item number, but without showing the
11507 values. This includes disabled expressions, which are marked as such.
11508 It also includes expressions which would not be displayed right now
11509 because they refer to automatic variables not currently available.
11512 @cindex display disabled out of scope
11513 If a display expression refers to local variables, then it does not make
11514 sense outside the lexical context for which it was set up. Such an
11515 expression is disabled when execution enters a context where one of its
11516 variables is not defined. For example, if you give the command
11517 @code{display last_char} while inside a function with an argument
11518 @code{last_char}, @value{GDBN} displays this argument while your program
11519 continues to stop inside that function. When it stops elsewhere---where
11520 there is no variable @code{last_char}---the display is disabled
11521 automatically. The next time your program stops where @code{last_char}
11522 is meaningful, you can enable the display expression once again.
11524 @node Print Settings
11525 @section Print Settings
11527 @cindex format options
11528 @cindex print settings
11529 @value{GDBN} provides the following ways to control how arrays, structures,
11530 and symbols are printed.
11533 These settings are useful for debugging programs in any language:
11537 @anchor{set print address}
11538 @item set print address
11539 @itemx set print address on
11540 @cindex print/don't print memory addresses
11541 @value{GDBN} prints memory addresses showing the location of stack
11542 traces, structure values, pointer values, breakpoints, and so forth,
11543 even when it also displays the contents of those addresses. The default
11544 is @code{on}. For example, this is what a stack frame display looks like with
11545 @code{set print address on}:
11550 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11552 530 if (lquote != def_lquote)
11556 @item set print address off
11557 Do not print addresses when displaying their contents. For example,
11558 this is the same stack frame displayed with @code{set print address off}:
11562 (@value{GDBP}) set print addr off
11564 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11565 530 if (lquote != def_lquote)
11569 You can use @samp{set print address off} to eliminate all machine
11570 dependent displays from the @value{GDBN} interface. For example, with
11571 @code{print address off}, you should get the same text for backtraces on
11572 all machines---whether or not they involve pointer arguments.
11575 @item show print address
11576 Show whether or not addresses are to be printed.
11579 When @value{GDBN} prints a symbolic address, it normally prints the
11580 closest earlier symbol plus an offset. If that symbol does not uniquely
11581 identify the address (for example, it is a name whose scope is a single
11582 source file), you may need to clarify. One way to do this is with
11583 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11584 you can set @value{GDBN} to print the source file and line number when
11585 it prints a symbolic address:
11588 @item set print symbol-filename on
11589 @cindex source file and line of a symbol
11590 @cindex symbol, source file and line
11591 Tell @value{GDBN} to print the source file name and line number of a
11592 symbol in the symbolic form of an address.
11594 @item set print symbol-filename off
11595 Do not print source file name and line number of a symbol. This is the
11598 @item show print symbol-filename
11599 Show whether or not @value{GDBN} will print the source file name and
11600 line number of a symbol in the symbolic form of an address.
11603 Another situation where it is helpful to show symbol filenames and line
11604 numbers is when disassembling code; @value{GDBN} shows you the line
11605 number and source file that corresponds to each instruction.
11607 Also, you may wish to see the symbolic form only if the address being
11608 printed is reasonably close to the closest earlier symbol:
11611 @item set print max-symbolic-offset @var{max-offset}
11612 @itemx set print max-symbolic-offset unlimited
11613 @cindex maximum value for offset of closest symbol
11614 Tell @value{GDBN} to only display the symbolic form of an address if the
11615 offset between the closest earlier symbol and the address is less than
11616 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11617 to always print the symbolic form of an address if any symbol precedes
11618 it. Zero is equivalent to @code{unlimited}.
11620 @item show print max-symbolic-offset
11621 Ask how large the maximum offset is that @value{GDBN} prints in a
11625 @cindex wild pointer, interpreting
11626 @cindex pointer, finding referent
11627 If you have a pointer and you are not sure where it points, try
11628 @samp{set print symbol-filename on}. Then you can determine the name
11629 and source file location of the variable where it points, using
11630 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11631 For example, here @value{GDBN} shows that a variable @code{ptt} points
11632 at another variable @code{t}, defined in @file{hi2.c}:
11635 (@value{GDBP}) set print symbol-filename on
11636 (@value{GDBP}) p/a ptt
11637 $4 = 0xe008 <t in hi2.c>
11641 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11642 does not show the symbol name and filename of the referent, even with
11643 the appropriate @code{set print} options turned on.
11646 You can also enable @samp{/a}-like formatting all the time using
11647 @samp{set print symbol on}:
11649 @anchor{set print symbol}
11651 @item set print symbol on
11652 Tell @value{GDBN} to print the symbol corresponding to an address, if
11655 @item set print symbol off
11656 Tell @value{GDBN} not to print the symbol corresponding to an
11657 address. In this mode, @value{GDBN} will still print the symbol
11658 corresponding to pointers to functions. This is the default.
11660 @item show print symbol
11661 Show whether @value{GDBN} will display the symbol corresponding to an
11665 Other settings control how different kinds of objects are printed:
11668 @anchor{set print array}
11669 @item set print array
11670 @itemx set print array on
11671 @cindex pretty print arrays
11672 Pretty print arrays. This format is more convenient to read,
11673 but uses more space. The default is off.
11675 @item set print array off
11676 Return to compressed format for arrays.
11678 @item show print array
11679 Show whether compressed or pretty format is selected for displaying
11682 @cindex print array indexes
11683 @anchor{set print array-indexes}
11684 @item set print array-indexes
11685 @itemx set print array-indexes on
11686 Print the index of each element when displaying arrays. May be more
11687 convenient to locate a given element in the array or quickly find the
11688 index of a given element in that printed array. The default is off.
11690 @item set print array-indexes off
11691 Stop printing element indexes when displaying arrays.
11693 @item show print array-indexes
11694 Show whether the index of each element is printed when displaying
11697 @anchor{set print nibbles}
11698 @item set print nibbles
11699 @itemx set print nibbles on
11700 @cindex print binary values in groups of four bits
11701 Print binary values in groups of four bits, known as @dfn{nibbles},
11702 when using the print command of @value{GDBN} with the option @samp{/t}.
11703 For example, this is what it looks like with @code{set print nibbles on}:
11707 (@value{GDBP}) print val_flags
11709 (@value{GDBP}) print/t val_flags
11710 $2 = 0100 1100 1110
11714 @item set print nibbles off
11715 Don't printing binary values in groups. This is the default.
11717 @item show print nibbles
11718 Show whether to print binary values in groups of four bits.
11720 @anchor{set print characters}
11721 @item set print characters @var{number-of-characters}
11722 @itemx set print characters elements
11723 @itemx set print characters unlimited
11724 @cindex number of string characters to print
11725 @cindex limit on number of printed string characters
11726 Set a limit on how many characters of a string @value{GDBN} will print.
11727 If @value{GDBN} is printing a large string, it stops printing after it
11728 has printed the number of characters set by the @code{set print
11729 characters} command. This equally applies to multi-byte and wide
11730 character strings, that is for strings whose character type is
11731 @code{wchar_t}, @code{char16_t}, or @code{char32_t} it is the number of
11732 actual characters rather than underlying bytes the encoding uses that
11733 this setting controls.
11734 Setting @var{number-of-characters} to @code{elements} means that the
11735 limit on the number of characters to print follows one for array
11736 elements; see @ref{set print elements}.
11737 Setting @var{number-of-characters} to @code{unlimited} means that the
11738 number of characters to print is unlimited.
11739 When @value{GDBN} starts, this limit is set to @code{elements}.
11741 @item show print characters
11742 Display the number of characters of a large string that @value{GDBN}
11745 @anchor{set print elements}
11746 @item set print elements @var{number-of-elements}
11747 @itemx set print elements unlimited
11748 @cindex number of array elements to print
11749 @cindex limit on number of printed array elements
11750 Set a limit on how many elements of an array @value{GDBN} will print.
11751 If @value{GDBN} is printing a large array, it stops printing after it has
11752 printed the number of elements set by the @code{set print elements} command.
11753 By default this limit also applies to the display of strings; see
11754 @ref{set print characters}.
11755 When @value{GDBN} starts, this limit is set to 200.
11756 Setting @var{number-of-elements} to @code{unlimited} or zero means
11757 that the number of elements to print is unlimited.
11759 @item show print elements
11760 Display the number of elements of a large array that @value{GDBN} will print.
11762 @anchor{set print frame-arguments}
11763 @item set print frame-arguments @var{value}
11764 @kindex set print frame-arguments
11765 @cindex printing frame argument values
11766 @cindex print all frame argument values
11767 @cindex print frame argument values for scalars only
11768 @cindex do not print frame arguments
11769 This command allows to control how the values of arguments are printed
11770 when the debugger prints a frame (@pxref{Frames}). The possible
11775 The values of all arguments are printed.
11778 Print the value of an argument only if it is a scalar. The value of more
11779 complex arguments such as arrays, structures, unions, etc, is replaced
11780 by @code{@dots{}}. This is the default. Here is an example where
11781 only scalar arguments are shown:
11784 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11789 None of the argument values are printed. Instead, the value of each argument
11790 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11793 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11798 Only the presence of arguments is indicated by @code{@dots{}}.
11799 The @code{@dots{}} are not printed for function without any arguments.
11800 None of the argument names and values are printed.
11801 In this case, the example above now becomes:
11804 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11809 By default, only scalar arguments are printed. This command can be used
11810 to configure the debugger to print the value of all arguments, regardless
11811 of their type. However, it is often advantageous to not print the value
11812 of more complex parameters. For instance, it reduces the amount of
11813 information printed in each frame, making the backtrace more readable.
11814 Also, it improves performance when displaying Ada frames, because
11815 the computation of large arguments can sometimes be CPU-intensive,
11816 especially in large applications. Setting @code{print frame-arguments}
11817 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11818 this computation, thus speeding up the display of each Ada frame.
11820 @item show print frame-arguments
11821 Show how the value of arguments should be displayed when printing a frame.
11823 @anchor{set print raw-frame-arguments}
11824 @item set print raw-frame-arguments on
11825 Print frame arguments in raw, non pretty-printed, form.
11827 @item set print raw-frame-arguments off
11828 Print frame arguments in pretty-printed form, if there is a pretty-printer
11829 for the value (@pxref{Pretty Printing}),
11830 otherwise print the value in raw form.
11831 This is the default.
11833 @item show print raw-frame-arguments
11834 Show whether to print frame arguments in raw form.
11836 @anchor{set print entry-values}
11837 @item set print entry-values @var{value}
11838 @kindex set print entry-values
11839 Set printing of frame argument values at function entry. In some cases
11840 @value{GDBN} can determine the value of function argument which was passed by
11841 the function caller, even if the value was modified inside the called function
11842 and therefore is different. With optimized code, the current value could be
11843 unavailable, but the entry value may still be known.
11845 The default value is @code{default} (see below for its description). Older
11846 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11847 this feature will behave in the @code{default} setting the same way as with the
11850 This functionality is currently supported only by DWARF 2 debugging format and
11851 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11852 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11855 The @var{value} parameter can be one of the following:
11859 Print only actual parameter values, never print values from function entry
11863 #0 different (val=6)
11864 #0 lost (val=<optimized out>)
11866 #0 invalid (val=<optimized out>)
11870 Print only parameter values from function entry point. The actual parameter
11871 values are never printed.
11873 #0 equal (val@@entry=5)
11874 #0 different (val@@entry=5)
11875 #0 lost (val@@entry=5)
11876 #0 born (val@@entry=<optimized out>)
11877 #0 invalid (val@@entry=<optimized out>)
11881 Print only parameter values from function entry point. If value from function
11882 entry point is not known while the actual value is known, print the actual
11883 value for such parameter.
11885 #0 equal (val@@entry=5)
11886 #0 different (val@@entry=5)
11887 #0 lost (val@@entry=5)
11889 #0 invalid (val@@entry=<optimized out>)
11893 Print actual parameter values. If actual parameter value is not known while
11894 value from function entry point is known, print the entry point value for such
11898 #0 different (val=6)
11899 #0 lost (val@@entry=5)
11901 #0 invalid (val=<optimized out>)
11905 Always print both the actual parameter value and its value from function entry
11906 point, even if values of one or both are not available due to compiler
11909 #0 equal (val=5, val@@entry=5)
11910 #0 different (val=6, val@@entry=5)
11911 #0 lost (val=<optimized out>, val@@entry=5)
11912 #0 born (val=10, val@@entry=<optimized out>)
11913 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11917 Print the actual parameter value if it is known and also its value from
11918 function entry point if it is known. If neither is known, print for the actual
11919 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11920 values are known and identical, print the shortened
11921 @code{param=param@@entry=VALUE} notation.
11923 #0 equal (val=val@@entry=5)
11924 #0 different (val=6, val@@entry=5)
11925 #0 lost (val@@entry=5)
11927 #0 invalid (val=<optimized out>)
11931 Always print the actual parameter value. Print also its value from function
11932 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11933 if both values are known and identical, print the shortened
11934 @code{param=param@@entry=VALUE} notation.
11936 #0 equal (val=val@@entry=5)
11937 #0 different (val=6, val@@entry=5)
11938 #0 lost (val=<optimized out>, val@@entry=5)
11940 #0 invalid (val=<optimized out>)
11944 For analysis messages on possible failures of frame argument values at function
11945 entry resolution see @ref{set debug entry-values}.
11947 @item show print entry-values
11948 Show the method being used for printing of frame argument values at function
11951 @anchor{set print frame-info}
11952 @item set print frame-info @var{value}
11953 @kindex set print frame-info
11954 @cindex printing frame information
11955 @cindex frame information, printing
11956 This command allows to control the information printed when
11957 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11958 for a general explanation about frames and frame information.
11959 Note that some other settings (such as @code{set print frame-arguments}
11960 and @code{set print address}) are also influencing if and how some frame
11961 information is displayed. In particular, the frame program counter is never
11962 printed if @code{set print address} is off.
11964 The possible values for @code{set print frame-info} are:
11966 @item short-location
11967 Print the frame level, the program counter (if not at the
11968 beginning of the location source line), the function, the function
11971 Same as @code{short-location} but also print the source file and source line
11973 @item location-and-address
11974 Same as @code{location} but print the program counter even if located at the
11975 beginning of the location source line.
11977 Print the program counter (if not at the beginning of the location
11978 source line), the line number and the source line.
11979 @item source-and-location
11980 Print what @code{location} and @code{source-line} are printing.
11982 The information printed for a frame is decided automatically
11983 by the @value{GDBN} command that prints a frame.
11984 For example, @code{frame} prints the information printed by
11985 @code{source-and-location} while @code{stepi} will switch between
11986 @code{source-line} and @code{source-and-location} depending on the program
11988 The default value is @code{auto}.
11991 @anchor{set print repeats}
11992 @item set print repeats @var{number-of-repeats}
11993 @itemx set print repeats unlimited
11994 @cindex repeated array elements
11995 Set the threshold for suppressing display of repeated array
11996 elements. When the number of consecutive identical elements of an
11997 array exceeds the threshold, @value{GDBN} prints the string
11998 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11999 identical repetitions, instead of displaying the identical elements
12000 themselves. Setting the threshold to @code{unlimited} or zero will
12001 cause all elements to be individually printed. The default threshold
12004 @item show print repeats
12005 Display the current threshold for printing repeated identical
12008 @anchor{set print max-depth}
12009 @item set print max-depth @var{depth}
12010 @item set print max-depth unlimited
12011 @cindex printing nested structures
12012 Set the threshold after which nested structures are replaced with
12013 ellipsis, this can make visualising deeply nested structures easier.
12015 For example, given this C code
12018 typedef struct s1 @{ int a; @} s1;
12019 typedef struct s2 @{ s1 b; @} s2;
12020 typedef struct s3 @{ s2 c; @} s3;
12021 typedef struct s4 @{ s3 d; @} s4;
12023 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
12026 The following table shows how different values of @var{depth} will
12027 effect how @code{var} is printed by @value{GDBN}:
12029 @multitable @columnfractions .3 .7
12030 @headitem @var{depth} setting @tab Result of @samp{p var}
12032 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
12034 @tab @code{$1 = @{...@}}
12036 @tab @code{$1 = @{d = @{...@}@}}
12038 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
12040 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
12042 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
12045 To see the contents of structures that have been hidden the user can
12046 either increase the print max-depth, or they can print the elements of
12047 the structure that are visible, for example
12050 (@value{GDBP}) set print max-depth 2
12051 (@value{GDBP}) p var
12052 $1 = @{d = @{c = @{...@}@}@}
12053 (@value{GDBP}) p var.d
12054 $2 = @{c = @{b = @{...@}@}@}
12055 (@value{GDBP}) p var.d.c
12056 $3 = @{b = @{a = 3@}@}
12059 The pattern used to replace nested structures varies based on
12060 language, for most languages @code{@{...@}} is used, but Fortran uses
12063 @item show print max-depth
12064 Display the current threshold after which nested structures are
12065 replaces with ellipsis.
12067 @anchor{set print memory-tag-violations}
12068 @cindex printing memory tag violation information
12069 @item set print memory-tag-violations
12070 @itemx set print memory-tag-violations on
12071 Cause @value{GDBN} to display additional information about memory tag violations
12072 when printing pointers and addresses.
12074 @item set print memory-tag-violations off
12075 Stop printing memory tag violation information.
12077 @item show print memory-tag-violations
12078 Show whether memory tag violation information is displayed when printing
12079 pointers and addresses.
12081 @anchor{set print null-stop}
12082 @item set print null-stop
12083 @cindex @sc{null} elements in arrays
12084 Cause @value{GDBN} to stop printing the characters of an array when the first
12085 @sc{null} is encountered. This is useful when large arrays actually
12086 contain only short strings.
12087 The default is off.
12089 @item show print null-stop
12090 Show whether @value{GDBN} stops printing an array on the first
12091 @sc{null} character.
12093 @anchor{set print pretty}
12094 @item set print pretty on
12095 @cindex print structures in indented form
12096 @cindex indentation in structure display
12097 Cause @value{GDBN} to print structures in an indented format with one member
12098 per line, like this:
12113 @item set print pretty off
12114 Cause @value{GDBN} to print structures in a compact format, like this:
12118 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
12119 meat = 0x54 "Pork"@}
12124 This is the default format.
12126 @item show print pretty
12127 Show which format @value{GDBN} is using to print structures.
12129 @anchor{set print raw-values}
12130 @item set print raw-values on
12131 Print values in raw form, without applying the pretty
12132 printers for the value.
12134 @item set print raw-values off
12135 Print values in pretty-printed form, if there is a pretty-printer
12136 for the value (@pxref{Pretty Printing}),
12137 otherwise print the value in raw form.
12139 The default setting is ``off''.
12141 @item show print raw-values
12142 Show whether to print values in raw form.
12144 @item set print sevenbit-strings on
12145 @cindex eight-bit characters in strings
12146 @cindex octal escapes in strings
12147 Print using only seven-bit characters; if this option is set,
12148 @value{GDBN} displays any eight-bit characters (in strings or
12149 character values) using the notation @code{\}@var{nnn}. This setting is
12150 best if you are working in English (@sc{ascii}) and you use the
12151 high-order bit of characters as a marker or ``meta'' bit.
12153 @item set print sevenbit-strings off
12154 Print full eight-bit characters. This allows the use of more
12155 international character sets, and is the default.
12157 @item show print sevenbit-strings
12158 Show whether or not @value{GDBN} is printing only seven-bit characters.
12160 @anchor{set print union}
12161 @item set print union on
12162 @cindex unions in structures, printing
12163 Tell @value{GDBN} to print unions which are contained in structures
12164 and other unions. This is the default setting.
12166 @item set print union off
12167 Tell @value{GDBN} not to print unions which are contained in
12168 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
12171 @item show print union
12172 Ask @value{GDBN} whether or not it will print unions which are contained in
12173 structures and other unions.
12175 For example, given the declarations
12178 typedef enum @{Tree, Bug@} Species;
12179 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
12180 typedef enum @{Caterpillar, Cocoon, Butterfly@}
12191 struct thing foo = @{Tree, @{Acorn@}@};
12195 with @code{set print union on} in effect @samp{p foo} would print
12198 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
12202 and with @code{set print union off} in effect it would print
12205 $1 = @{it = Tree, form = @{...@}@}
12209 @code{set print union} affects programs written in C-like languages
12215 These settings are of interest when debugging C@t{++} programs:
12218 @cindex demangling C@t{++} names
12219 @item set print demangle
12220 @itemx set print demangle on
12221 Print C@t{++} names in their source form rather than in the encoded
12222 (``mangled'') form passed to the assembler and linker for type-safe
12223 linkage. The default is on.
12225 @item show print demangle
12226 Show whether C@t{++} names are printed in mangled or demangled form.
12228 @item set print asm-demangle
12229 @itemx set print asm-demangle on
12230 Print C@t{++} names in their source form rather than their mangled form, even
12231 in assembler code printouts such as instruction disassemblies.
12232 The default is off.
12234 @item show print asm-demangle
12235 Show whether C@t{++} names in assembly listings are printed in mangled
12238 @cindex C@t{++} symbol decoding style
12239 @cindex symbol decoding style, C@t{++}
12240 @kindex set demangle-style
12241 @item set demangle-style @var{style}
12242 Choose among several encoding schemes used by different compilers to represent
12243 C@t{++} names. If you omit @var{style}, you will see a list of possible
12244 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
12245 decoding style by inspecting your program.
12247 @item show demangle-style
12248 Display the encoding style currently in use for decoding C@t{++} symbols.
12250 @anchor{set print object}
12251 @item set print object
12252 @itemx set print object on
12253 @cindex derived type of an object, printing
12254 @cindex display derived types
12255 When displaying a pointer to an object, identify the @emph{actual}
12256 (derived) type of the object rather than the @emph{declared} type, using
12257 the virtual function table. Note that the virtual function table is
12258 required---this feature can only work for objects that have run-time
12259 type identification; a single virtual method in the object's declared
12260 type is sufficient. Note that this setting is also taken into account when
12261 working with variable objects via MI (@pxref{GDB/MI}).
12263 @item set print object off
12264 Display only the declared type of objects, without reference to the
12265 virtual function table. This is the default setting.
12267 @item show print object
12268 Show whether actual, or declared, object types are displayed.
12270 @anchor{set print static-members}
12271 @item set print static-members
12272 @itemx set print static-members on
12273 @cindex static members of C@t{++} objects
12274 Print static members when displaying a C@t{++} object. The default is on.
12276 @item set print static-members off
12277 Do not print static members when displaying a C@t{++} object.
12279 @item show print static-members
12280 Show whether C@t{++} static members are printed or not.
12282 @item set print pascal_static-members
12283 @itemx set print pascal_static-members on
12284 @cindex static members of Pascal objects
12285 @cindex Pascal objects, static members display
12286 Print static members when displaying a Pascal object. The default is on.
12288 @item set print pascal_static-members off
12289 Do not print static members when displaying a Pascal object.
12291 @item show print pascal_static-members
12292 Show whether Pascal static members are printed or not.
12294 @c These don't work with HP ANSI C++ yet.
12295 @anchor{set print vtbl}
12296 @item set print vtbl
12297 @itemx set print vtbl on
12298 @cindex pretty print C@t{++} virtual function tables
12299 @cindex virtual functions (C@t{++}) display
12300 @cindex VTBL display
12301 Pretty print C@t{++} virtual function tables. The default is off.
12302 (The @code{vtbl} commands do not work on programs compiled with the HP
12303 ANSI C@t{++} compiler (@code{aCC}).)
12305 @item set print vtbl off
12306 Do not pretty print C@t{++} virtual function tables.
12308 @item show print vtbl
12309 Show whether C@t{++} virtual function tables are pretty printed, or not.
12312 @node Pretty Printing
12313 @section Pretty Printing
12315 @value{GDBN} provides a mechanism to allow pretty-printing of values using
12316 Python code. It greatly simplifies the display of complex objects. This
12317 mechanism works for both MI and the CLI.
12320 * Pretty-Printer Introduction:: Introduction to pretty-printers
12321 * Pretty-Printer Example:: An example pretty-printer
12322 * Pretty-Printer Commands:: Pretty-printer commands
12325 @node Pretty-Printer Introduction
12326 @subsection Pretty-Printer Introduction
12328 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
12329 registered for the value. If there is then @value{GDBN} invokes the
12330 pretty-printer to print the value. Otherwise the value is printed normally.
12332 Pretty-printers are normally named. This makes them easy to manage.
12333 The @samp{info pretty-printer} command will list all the installed
12334 pretty-printers with their names.
12335 If a pretty-printer can handle multiple data types, then its
12336 @dfn{subprinters} are the printers for the individual data types.
12337 Each such subprinter has its own name.
12338 The format of the name is @var{printer-name};@var{subprinter-name}.
12340 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
12341 Typically they are automatically loaded and registered when the corresponding
12342 debug information is loaded, thus making them available without having to
12343 do anything special.
12345 There are three places where a pretty-printer can be registered.
12349 Pretty-printers registered globally are available when debugging
12353 Pretty-printers registered with a program space are available only
12354 when debugging that program.
12355 @xref{Progspaces In Python}, for more details on program spaces in Python.
12358 Pretty-printers registered with an objfile are loaded and unloaded
12359 with the corresponding objfile (e.g., shared library).
12360 @xref{Objfiles In Python}, for more details on objfiles in Python.
12363 @xref{Selecting Pretty-Printers}, for further information on how
12364 pretty-printers are selected,
12366 @xref{Writing a Pretty-Printer}, for implementing pretty printers
12369 @node Pretty-Printer Example
12370 @subsection Pretty-Printer Example
12372 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
12375 (@value{GDBP}) print s
12377 static npos = 4294967295,
12379 <std::allocator<char>> = @{
12380 <__gnu_cxx::new_allocator<char>> = @{
12381 <No data fields>@}, <No data fields>
12383 members of std::basic_string<char, std::char_traits<char>,
12384 std::allocator<char> >::_Alloc_hider:
12385 _M_p = 0x804a014 "abcd"
12390 With a pretty-printer for @code{std::string} only the contents are printed:
12393 (@value{GDBP}) print s
12397 @node Pretty-Printer Commands
12398 @subsection Pretty-Printer Commands
12399 @cindex pretty-printer commands
12402 @kindex info pretty-printer
12403 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12404 Print the list of installed pretty-printers.
12405 This includes disabled pretty-printers, which are marked as such.
12407 @var{object-regexp} is a regular expression matching the objects
12408 whose pretty-printers to list.
12409 Objects can be @code{global}, the program space's file
12410 (@pxref{Progspaces In Python}),
12411 and the object files within that program space (@pxref{Objfiles In Python}).
12412 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12413 looks up a printer from these three objects.
12415 @var{name-regexp} is a regular expression matching the name of the printers
12418 @kindex disable pretty-printer
12419 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12420 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12421 A disabled pretty-printer is not forgotten, it may be enabled again later.
12423 @kindex enable pretty-printer
12424 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12425 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12430 Suppose we have three pretty-printers installed: one from library1.so
12431 named @code{foo} that prints objects of type @code{foo}, and
12432 another from library2.so named @code{bar} that prints two types of objects,
12433 @code{bar1} and @code{bar2}.
12437 (@value{GDBP}) info pretty-printer
12446 (@value{GDBP}) info pretty-printer library2
12453 (@value{GDBP}) disable pretty-printer library1
12455 2 of 3 printers enabled
12456 (@value{GDBP}) info pretty-printer
12465 (@value{GDBP}) disable pretty-printer library2 bar;bar1
12467 1 of 3 printers enabled
12468 (@value{GDBP}) info pretty-printer library2
12475 (@value{GDBP}) disable pretty-printer library2 bar
12477 0 of 3 printers enabled
12478 (@value{GDBP}) info pretty-printer
12488 Note that for @code{bar} the entire printer can be disabled,
12489 as can each individual subprinter.
12491 Printing values and frame arguments is done by default using
12492 the enabled pretty printers.
12494 The print option @code{-raw-values} and @value{GDBN} setting
12495 @code{set print raw-values} (@pxref{set print raw-values}) can be
12496 used to print values without applying the enabled pretty printers.
12498 Similarly, the backtrace option @code{-raw-frame-arguments} and
12499 @value{GDBN} setting @code{set print raw-frame-arguments}
12500 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12501 enabled pretty printers when printing frame argument values.
12503 @node Value History
12504 @section Value History
12506 @cindex value history
12507 @cindex history of values printed by @value{GDBN}
12508 Values printed by the @code{print} command are saved in the @value{GDBN}
12509 @dfn{value history}. This allows you to refer to them in other expressions.
12510 Values are kept until the symbol table is re-read or discarded
12511 (for example with the @code{file} or @code{symbol-file} commands).
12512 When the symbol table changes, the value history is discarded,
12513 since the values may contain pointers back to the types defined in the
12518 @cindex history number
12519 The values printed are given @dfn{history numbers} by which you can
12520 refer to them. These are successive integers starting with one.
12521 @code{print} shows you the history number assigned to a value by
12522 printing @samp{$@var{num} = } before the value; here @var{num} is the
12525 To refer to any previous value, use @samp{$} followed by the value's
12526 history number. The way @code{print} labels its output is designed to
12527 remind you of this. Just @code{$} refers to the most recent value in
12528 the history, and @code{$$} refers to the value before that.
12529 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12530 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12531 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12533 For example, suppose you have just printed a pointer to a structure and
12534 want to see the contents of the structure. It suffices to type
12540 If you have a chain of structures where the component @code{next} points
12541 to the next one, you can print the contents of the next one with this:
12548 You can print successive links in the chain by repeating this
12549 command---which you can do by just typing @key{RET}.
12551 Note that the history records values, not expressions. If the value of
12552 @code{x} is 4 and you type these commands:
12560 then the value recorded in the value history by the @code{print} command
12561 remains 4 even though the value of @code{x} has changed.
12564 @kindex show values
12566 Print the last ten values in the value history, with their item numbers.
12567 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12568 values} does not change the history.
12570 @item show values @var{n}
12571 Print ten history values centered on history item number @var{n}.
12573 @item show values +
12574 Print ten history values just after the values last printed. If no more
12575 values are available, @code{show values +} produces no display.
12578 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12579 same effect as @samp{show values +}.
12581 @node Convenience Vars
12582 @section Convenience Variables
12584 @cindex convenience variables
12585 @cindex user-defined variables
12586 @value{GDBN} provides @dfn{convenience variables} that you can use within
12587 @value{GDBN} to hold on to a value and refer to it later. These variables
12588 exist entirely within @value{GDBN}; they are not part of your program, and
12589 setting a convenience variable has no direct effect on further execution
12590 of your program. That is why you can use them freely.
12592 Convenience variables are prefixed with @samp{$}. Any name preceded by
12593 @samp{$} can be used for a convenience variable, unless it is one of
12594 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12595 (Value history references, in contrast, are @emph{numbers} preceded
12596 by @samp{$}. @xref{Value History, ,Value History}.)
12598 You can save a value in a convenience variable with an assignment
12599 expression, just as you would set a variable in your program.
12603 set $foo = *object_ptr
12607 would save in @code{$foo} the value contained in the object pointed to by
12610 Using a convenience variable for the first time creates it, but its
12611 value is @code{void} until you assign a new value. You can alter the
12612 value with another assignment at any time.
12614 Convenience variables have no fixed types. You can assign a convenience
12615 variable any type of value, including structures and arrays, even if
12616 that variable already has a value of a different type. The convenience
12617 variable, when used as an expression, has the type of its current value.
12620 @kindex show convenience
12621 @cindex show all user variables and functions
12622 @item show convenience
12623 Print a list of convenience variables used so far, and their values,
12624 as well as a list of the convenience functions.
12625 Abbreviated @code{show conv}.
12627 @kindex init-if-undefined
12628 @cindex convenience variables, initializing
12629 @item init-if-undefined $@var{variable} = @var{expression}
12630 Set a convenience variable if it has not already been set. This is useful
12631 for user-defined commands that keep some state. It is similar, in concept,
12632 to using local static variables with initializers in C (except that
12633 convenience variables are global). It can also be used to allow users to
12634 override default values used in a command script.
12636 If the variable is already defined then the expression is not evaluated so
12637 any side-effects do not occur.
12640 One of the ways to use a convenience variable is as a counter to be
12641 incremented or a pointer to be advanced. For example, to print
12642 a field from successive elements of an array of structures:
12646 print bar[$i++]->contents
12650 Repeat that command by typing @key{RET}.
12652 Some convenience variables are created automatically by @value{GDBN} and given
12653 values likely to be useful.
12656 @vindex $_@r{, convenience variable}
12658 The variable @code{$_} is automatically set by the @code{x} command to
12659 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12660 commands which provide a default address for @code{x} to examine also
12661 set @code{$_} to that address; these commands include @code{info line}
12662 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12663 except when set by the @code{x} command, in which case it is a pointer
12664 to the type of @code{$__}.
12666 @vindex $__@r{, convenience variable}
12668 The variable @code{$__} is automatically set by the @code{x} command
12669 to the value found in the last address examined. Its type is chosen
12670 to match the format in which the data was printed.
12673 @vindex $_exitcode@r{, convenience variable}
12674 When the program being debugged terminates normally, @value{GDBN}
12675 automatically sets this variable to the exit code of the program, and
12676 resets @code{$_exitsignal} to @code{void}.
12679 @vindex $_exitsignal@r{, convenience variable}
12680 When the program being debugged dies due to an uncaught signal,
12681 @value{GDBN} automatically sets this variable to that signal's number,
12682 and resets @code{$_exitcode} to @code{void}.
12684 To distinguish between whether the program being debugged has exited
12685 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12686 @code{$_exitsignal} is not @code{void}), the convenience function
12687 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12688 Functions}). For example, considering the following source code:
12691 #include <signal.h>
12694 main (int argc, char *argv[])
12701 A valid way of telling whether the program being debugged has exited
12702 or signalled would be:
12705 (@value{GDBP}) define has_exited_or_signalled
12706 Type commands for definition of ``has_exited_or_signalled''.
12707 End with a line saying just ``end''.
12708 >if $_isvoid ($_exitsignal)
12709 >echo The program has exited\n
12711 >echo The program has signalled\n
12717 Program terminated with signal SIGALRM, Alarm clock.
12718 The program no longer exists.
12719 (@value{GDBP}) has_exited_or_signalled
12720 The program has signalled
12723 As can be seen, @value{GDBN} correctly informs that the program being
12724 debugged has signalled, since it calls @code{raise} and raises a
12725 @code{SIGALRM} signal. If the program being debugged had not called
12726 @code{raise}, then @value{GDBN} would report a normal exit:
12729 (@value{GDBP}) has_exited_or_signalled
12730 The program has exited
12734 The variable @code{$_exception} is set to the exception object being
12735 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12737 @item $_ada_exception
12738 The variable @code{$_ada_exception} is set to the address of the
12739 exception being caught or thrown at an Ada exception-related
12740 catchpoint. @xref{Set Catchpoints}.
12743 @itemx $_probe_arg0@dots{}$_probe_arg11
12744 Arguments to a static probe. @xref{Static Probe Points}.
12747 @vindex $_sdata@r{, inspect, convenience variable}
12748 The variable @code{$_sdata} contains extra collected static tracepoint
12749 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12750 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12751 if extra static tracepoint data has not been collected.
12754 @vindex $_siginfo@r{, convenience variable}
12755 The variable @code{$_siginfo} contains extra signal information
12756 (@pxref{extra signal information}). Note that @code{$_siginfo}
12757 could be empty, if the application has not yet received any signals.
12758 For example, it will be empty before you execute the @code{run} command.
12761 @vindex $_tlb@r{, convenience variable}
12762 The variable @code{$_tlb} is automatically set when debugging
12763 applications running on MS-Windows in native mode or connected to
12764 gdbserver that supports the @code{qGetTIBAddr} request.
12765 @xref{General Query Packets}.
12766 This variable contains the address of the thread information block.
12769 The number of the current inferior. @xref{Inferiors Connections and
12770 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12773 The thread number of the current thread. @xref{thread numbers}.
12776 The global number of the current thread. @xref{global thread numbers}.
12778 @item $_inferior_thread_count
12779 The number of live threads in the current inferior. @xref{Threads}.
12783 @vindex $_gdb_major@r{, convenience variable}
12784 @vindex $_gdb_minor@r{, convenience variable}
12785 The major and minor version numbers of the running @value{GDBN}.
12786 Development snapshots and pretest versions have their minor version
12787 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12788 the value 12 for @code{$_gdb_minor}. These variables allow you to
12789 write scripts that work with different versions of @value{GDBN}
12790 without errors caused by features unavailable in some of those
12793 @item $_shell_exitcode
12794 @itemx $_shell_exitsignal
12795 @vindex $_shell_exitcode@r{, convenience variable}
12796 @vindex $_shell_exitsignal@r{, convenience variable}
12797 @cindex shell command, exit code
12798 @cindex shell command, exit signal
12799 @cindex exit status of shell commands
12800 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12801 shell commands. When a launched command terminates, @value{GDBN}
12802 automatically maintains the variables @code{$_shell_exitcode}
12803 and @code{$_shell_exitsignal} according to the exit status of the last
12804 launched command. These variables are set and used similarly to
12805 the variables @code{$_exitcode} and @code{$_exitsignal}.
12809 @node Convenience Funs
12810 @section Convenience Functions
12812 @cindex convenience functions
12813 @value{GDBN} also supplies some @dfn{convenience functions}. These
12814 have a syntax similar to convenience variables. A convenience
12815 function can be used in an expression just like an ordinary function;
12816 however, a convenience function is implemented internally to
12819 These functions do not require @value{GDBN} to be configured with
12820 @code{Python} support, which means that they are always available.
12824 @item $_isvoid (@var{expr})
12825 @findex $_isvoid@r{, convenience function}
12826 Return one if the expression @var{expr} is @code{void}. Otherwise it
12829 A @code{void} expression is an expression where the type of the result
12830 is @code{void}. For example, you can examine a convenience variable
12831 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12835 (@value{GDBP}) print $_exitcode
12837 (@value{GDBP}) print $_isvoid ($_exitcode)
12840 Starting program: ./a.out
12841 [Inferior 1 (process 29572) exited normally]
12842 (@value{GDBP}) print $_exitcode
12844 (@value{GDBP}) print $_isvoid ($_exitcode)
12848 In the example above, we used @code{$_isvoid} to check whether
12849 @code{$_exitcode} is @code{void} before and after the execution of the
12850 program being debugged. Before the execution there is no exit code to
12851 be examined, therefore @code{$_exitcode} is @code{void}. After the
12852 execution the program being debugged returned zero, therefore
12853 @code{$_exitcode} is zero, which means that it is not @code{void}
12856 The @code{void} expression can also be a call of a function from the
12857 program being debugged. For example, given the following function:
12866 The result of calling it inside @value{GDBN} is @code{void}:
12869 (@value{GDBP}) print foo ()
12871 (@value{GDBP}) print $_isvoid (foo ())
12873 (@value{GDBP}) set $v = foo ()
12874 (@value{GDBP}) print $v
12876 (@value{GDBP}) print $_isvoid ($v)
12880 @item $_gdb_setting_str (@var{setting})
12881 @findex $_gdb_setting_str@r{, convenience function}
12882 Return the value of the @value{GDBN} @var{setting} as a string.
12883 @var{setting} is any setting that can be used in a @code{set} or
12884 @code{show} command (@pxref{Controlling GDB}).
12887 (@value{GDBP}) show print frame-arguments
12888 Printing of non-scalar frame arguments is "scalars".
12889 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12891 (@value{GDBP}) p $_gdb_setting_str("height")
12896 @item $_gdb_setting (@var{setting})
12897 @findex $_gdb_setting@r{, convenience function}
12898 Return the value of the @value{GDBN} @var{setting}.
12899 The type of the returned value depends on the setting.
12901 The value type for boolean and auto boolean settings is @code{int}.
12902 The boolean values @code{off} and @code{on} are converted to
12903 the integer values @code{0} and @code{1}. The value @code{auto} is
12904 converted to the value @code{-1}.
12906 The value type for integer settings is either @code{unsigned int}
12907 or @code{int}, depending on the setting.
12909 Some integer settings accept an @code{unlimited} value.
12910 Depending on the setting, the @code{set} command also accepts
12911 the value @code{0} or the value @code{@minus{}1} as a synonym for
12913 For example, @code{set height unlimited} is equivalent to
12914 @code{set height 0}.
12916 Some other settings that accept the @code{unlimited} value
12917 use the value @code{0} to literally mean zero.
12918 For example, @code{set history size 0} indicates to not
12919 record any @value{GDBN} commands in the command history.
12920 For such settings, @code{@minus{}1} is the synonym
12921 for @code{unlimited}.
12923 See the documentation of the corresponding @code{set} command for
12924 the numerical value equivalent to @code{unlimited}.
12926 The @code{$_gdb_setting} function converts the unlimited value
12927 to a @code{0} or a @code{@minus{}1} value according to what the
12928 @code{set} command uses.
12932 (@value{GDBP}) p $_gdb_setting_str("height")
12934 (@value{GDBP}) p $_gdb_setting("height")
12936 (@value{GDBP}) set height unlimited
12937 (@value{GDBP}) p $_gdb_setting_str("height")
12939 (@value{GDBP}) p $_gdb_setting("height")
12943 (@value{GDBP}) p $_gdb_setting_str("history size")
12945 (@value{GDBP}) p $_gdb_setting("history size")
12947 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12949 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12955 Other setting types (enum, filename, optional filename, string, string noescape)
12956 are returned as string values.
12959 @item $_gdb_maint_setting_str (@var{setting})
12960 @findex $_gdb_maint_setting_str@r{, convenience function}
12961 Like the @code{$_gdb_setting_str} function, but works with
12962 @code{maintenance set} variables.
12964 @item $_gdb_maint_setting (@var{setting})
12965 @findex $_gdb_maint_setting@r{, convenience function}
12966 Like the @code{$_gdb_setting} function, but works with
12967 @code{maintenance set} variables.
12971 The following functions require @value{GDBN} to be configured with
12972 @code{Python} support.
12976 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12977 @findex $_memeq@r{, convenience function}
12978 Returns one if the @var{length} bytes at the addresses given by
12979 @var{buf1} and @var{buf2} are equal.
12980 Otherwise it returns zero.
12982 @item $_regex(@var{str}, @var{regex})
12983 @findex $_regex@r{, convenience function}
12984 Returns one if the string @var{str} matches the regular expression
12985 @var{regex}. Otherwise it returns zero.
12986 The syntax of the regular expression is that specified by @code{Python}'s
12987 regular expression support.
12989 @item $_streq(@var{str1}, @var{str2})
12990 @findex $_streq@r{, convenience function}
12991 Returns one if the strings @var{str1} and @var{str2} are equal.
12992 Otherwise it returns zero.
12994 @item $_strlen(@var{str})
12995 @findex $_strlen@r{, convenience function}
12996 Returns the length of string @var{str}.
12998 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12999 @findex $_caller_is@r{, convenience function}
13000 Returns one if the calling function's name is equal to @var{name}.
13001 Otherwise it returns zero.
13003 If the optional argument @var{number_of_frames} is provided,
13004 it is the number of frames up in the stack to look.
13010 (@value{GDBP}) backtrace
13012 at testsuite/gdb.python/py-caller-is.c:21
13013 #1 0x00000000004005a0 in middle_func ()
13014 at testsuite/gdb.python/py-caller-is.c:27
13015 #2 0x00000000004005ab in top_func ()
13016 at testsuite/gdb.python/py-caller-is.c:33
13017 #3 0x00000000004005b6 in main ()
13018 at testsuite/gdb.python/py-caller-is.c:39
13019 (@value{GDBP}) print $_caller_is ("middle_func")
13021 (@value{GDBP}) print $_caller_is ("top_func", 2)
13025 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
13026 @findex $_caller_matches@r{, convenience function}
13027 Returns one if the calling function's name matches the regular expression
13028 @var{regexp}. Otherwise it returns zero.
13030 If the optional argument @var{number_of_frames} is provided,
13031 it is the number of frames up in the stack to look.
13034 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
13035 @findex $_any_caller_is@r{, convenience function}
13036 Returns one if any calling function's name is equal to @var{name}.
13037 Otherwise it returns zero.
13039 If the optional argument @var{number_of_frames} is provided,
13040 it is the number of frames up in the stack to look.
13043 This function differs from @code{$_caller_is} in that this function
13044 checks all stack frames from the immediate caller to the frame specified
13045 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
13046 frame specified by @var{number_of_frames}.
13048 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
13049 @findex $_any_caller_matches@r{, convenience function}
13050 Returns one if any calling function's name matches the regular expression
13051 @var{regexp}. Otherwise it returns zero.
13053 If the optional argument @var{number_of_frames} is provided,
13054 it is the number of frames up in the stack to look.
13057 This function differs from @code{$_caller_matches} in that this function
13058 checks all stack frames from the immediate caller to the frame specified
13059 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
13060 frame specified by @var{number_of_frames}.
13062 @item $_as_string(@var{value})
13063 @findex $_as_string@r{, convenience function}
13064 Return the string representation of @var{value}.
13066 This function is useful to obtain the textual label (enumerator) of an
13067 enumeration value. For example, assuming the variable @var{node} is of
13068 an enumerated type:
13071 (@value{GDBP}) printf "Visiting node of type %s\n", $_as_string(node)
13072 Visiting node of type NODE_INTEGER
13075 @item $_cimag(@var{value})
13076 @itemx $_creal(@var{value})
13077 @findex $_cimag@r{, convenience function}
13078 @findex $_creal@r{, convenience function}
13079 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
13080 the complex number @var{value}.
13082 The type of the imaginary or real part depends on the type of the
13083 complex number, e.g., using @code{$_cimag} on a @code{float complex}
13084 will return an imaginary part of type @code{float}.
13088 @value{GDBN} provides the ability to list and get help on
13089 convenience functions.
13092 @item help function
13093 @kindex help function
13094 @cindex show all convenience functions
13095 Print a list of all convenience functions.
13102 You can refer to machine register contents, in expressions, as variables
13103 with names starting with @samp{$}. The names of registers are different
13104 for each machine; use @code{info registers} to see the names used on
13108 @kindex info registers
13109 @item info registers
13110 Print the names and values of all registers except floating-point
13111 and vector registers (in the selected stack frame).
13113 @kindex info all-registers
13114 @cindex floating point registers
13115 @item info all-registers
13116 Print the names and values of all registers, including floating-point
13117 and vector registers (in the selected stack frame).
13119 @anchor{info_registers_reggroup}
13120 @item info registers @var{reggroup} @dots{}
13121 Print the name and value of the registers in each of the specified
13122 @var{reggroup}s. The @var{reggroup} can be any of those returned by
13123 @code{maint print reggroups} (@pxref{Maintenance Commands}).
13125 @item info registers @var{regname} @dots{}
13126 Print the @dfn{relativized} value of each specified register @var{regname}.
13127 As discussed in detail below, register values are normally relative to
13128 the selected stack frame. The @var{regname} may be any register name valid on
13129 the machine you are using, with or without the initial @samp{$}.
13132 @anchor{standard registers}
13133 @cindex stack pointer register
13134 @cindex program counter register
13135 @cindex process status register
13136 @cindex frame pointer register
13137 @cindex standard registers
13138 @value{GDBN} has four ``standard'' register names that are available (in
13139 expressions) on most machines---whenever they do not conflict with an
13140 architecture's canonical mnemonics for registers. The register names
13141 @code{$pc} and @code{$sp} are used for the program counter register and
13142 the stack pointer. @code{$fp} is used for a register that contains a
13143 pointer to the current stack frame, and @code{$ps} is used for a
13144 register that contains the processor status. For example,
13145 you could print the program counter in hex with
13152 or print the instruction to be executed next with
13159 or add four to the stack pointer@footnote{This is a way of removing
13160 one word from the stack, on machines where stacks grow downward in
13161 memory (most machines, nowadays). This assumes that the innermost
13162 stack frame is selected; setting @code{$sp} is not allowed when other
13163 stack frames are selected. To pop entire frames off the stack,
13164 regardless of machine architecture, use @code{return};
13165 see @ref{Returning, ,Returning from a Function}.} with
13171 Whenever possible, these four standard register names are available on
13172 your machine even though the machine has different canonical mnemonics,
13173 so long as there is no conflict. The @code{info registers} command
13174 shows the canonical names. For example, on the SPARC, @code{info
13175 registers} displays the processor status register as @code{$psr} but you
13176 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
13177 is an alias for the @sc{eflags} register.
13179 @value{GDBN} always considers the contents of an ordinary register as an
13180 integer when the register is examined in this way. Some machines have
13181 special registers which can hold nothing but floating point; these
13182 registers are considered to have floating point values. There is no way
13183 to refer to the contents of an ordinary register as floating point value
13184 (although you can @emph{print} it as a floating point value with
13185 @samp{print/f $@var{regname}}).
13187 Some registers have distinct ``raw'' and ``virtual'' data formats. This
13188 means that the data format in which the register contents are saved by
13189 the operating system is not the same one that your program normally
13190 sees. For example, the registers of the 68881 floating point
13191 coprocessor are always saved in ``extended'' (raw) format, but all C
13192 programs expect to work with ``double'' (virtual) format. In such
13193 cases, @value{GDBN} normally works with the virtual format only (the format
13194 that makes sense for your program), but the @code{info registers} command
13195 prints the data in both formats.
13197 @cindex SSE registers (x86)
13198 @cindex MMX registers (x86)
13199 Some machines have special registers whose contents can be interpreted
13200 in several different ways. For example, modern x86-based machines
13201 have SSE and MMX registers that can hold several values packed
13202 together in several different formats. @value{GDBN} refers to such
13203 registers in @code{struct} notation:
13206 (@value{GDBP}) print $xmm1
13208 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
13209 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
13210 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
13211 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
13212 v4_int32 = @{0, 20657912, 11, 13@},
13213 v2_int64 = @{88725056443645952, 55834574859@},
13214 uint128 = 0x0000000d0000000b013b36f800000000
13219 To set values of such registers, you need to tell @value{GDBN} which
13220 view of the register you wish to change, as if you were assigning
13221 value to a @code{struct} member:
13224 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
13227 Normally, register values are relative to the selected stack frame
13228 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
13229 value that the register would contain if all stack frames farther in
13230 were exited and their saved registers restored. In order to see the
13231 true contents of hardware registers, you must select the innermost
13232 frame (with @samp{frame 0}).
13234 @cindex caller-saved registers
13235 @cindex call-clobbered registers
13236 @cindex volatile registers
13237 @cindex <not saved> values
13238 Usually ABIs reserve some registers as not needed to be saved by the
13239 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
13240 registers). It may therefore not be possible for @value{GDBN} to know
13241 the value a register had before the call (in other words, in the outer
13242 frame), if the register value has since been changed by the callee.
13243 @value{GDBN} tries to deduce where the inner frame saved
13244 (``callee-saved'') registers, from the debug info, unwind info, or the
13245 machine code generated by your compiler. If some register is not
13246 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
13247 its own knowledge of the ABI, or because the debug/unwind info
13248 explicitly says the register's value is undefined), @value{GDBN}
13249 displays @w{@samp{<not saved>}} as the register's value. With targets
13250 that @value{GDBN} has no knowledge of the register saving convention,
13251 if a register was not saved by the callee, then its value and location
13252 in the outer frame are assumed to be the same of the inner frame.
13253 This is usually harmless, because if the register is call-clobbered,
13254 the caller either does not care what is in the register after the
13255 call, or has code to restore the value that it does care about. Note,
13256 however, that if you change such a register in the outer frame, you
13257 may also be affecting the inner frame. Also, the more ``outer'' the
13258 frame is you're looking at, the more likely a call-clobbered
13259 register's value is to be wrong, in the sense that it doesn't actually
13260 represent the value the register had just before the call.
13262 @node Floating Point Hardware
13263 @section Floating Point Hardware
13264 @cindex floating point
13266 Depending on the configuration, @value{GDBN} may be able to give
13267 you more information about the status of the floating point hardware.
13272 Display hardware-dependent information about the floating
13273 point unit. The exact contents and layout vary depending on the
13274 floating point chip. Currently, @samp{info float} is supported on
13275 the ARM and x86 machines.
13279 @section Vector Unit
13280 @cindex vector unit
13282 Depending on the configuration, @value{GDBN} may be able to give you
13283 more information about the status of the vector unit.
13286 @kindex info vector
13288 Display information about the vector unit. The exact contents and
13289 layout vary depending on the hardware.
13292 @node OS Information
13293 @section Operating System Auxiliary Information
13294 @cindex OS information
13296 @value{GDBN} provides interfaces to useful OS facilities that can help
13297 you debug your program.
13299 @cindex auxiliary vector
13300 @cindex vector, auxiliary
13301 Some operating systems supply an @dfn{auxiliary vector} to programs at
13302 startup. This is akin to the arguments and environment that you
13303 specify for a program, but contains a system-dependent variety of
13304 binary values that tell system libraries important details about the
13305 hardware, operating system, and process. Each value's purpose is
13306 identified by an integer tag; the meanings are well-known but system-specific.
13307 Depending on the configuration and operating system facilities,
13308 @value{GDBN} may be able to show you this information. For remote
13309 targets, this functionality may further depend on the remote stub's
13310 support of the @samp{qXfer:auxv:read} packet, see
13311 @ref{qXfer auxiliary vector read}.
13316 Display the auxiliary vector of the inferior, which can be either a
13317 live process or a core dump file. @value{GDBN} prints each tag value
13318 numerically, and also shows names and text descriptions for recognized
13319 tags. Some values in the vector are numbers, some bit masks, and some
13320 pointers to strings or other data. @value{GDBN} displays each value in the
13321 most appropriate form for a recognized tag, and in hexadecimal for
13322 an unrecognized tag.
13325 On some targets, @value{GDBN} can access operating system-specific
13326 information and show it to you. The types of information available
13327 will differ depending on the type of operating system running on the
13328 target. The mechanism used to fetch the data is described in
13329 @ref{Operating System Information}. For remote targets, this
13330 functionality depends on the remote stub's support of the
13331 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
13335 @item info os @var{infotype}
13337 Display OS information of the requested type.
13339 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
13341 @anchor{linux info os infotypes}
13343 @kindex info os cpus
13345 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
13346 the available fields from /proc/cpuinfo. For each supported architecture
13347 different fields are available. Two common entries are processor which gives
13348 CPU number and bogomips; a system constant that is calculated during
13349 kernel initialization.
13351 @kindex info os files
13353 Display the list of open file descriptors on the target. For each
13354 file descriptor, @value{GDBN} prints the identifier of the process
13355 owning the descriptor, the command of the owning process, the value
13356 of the descriptor, and the target of the descriptor.
13358 @kindex info os modules
13360 Display the list of all loaded kernel modules on the target. For each
13361 module, @value{GDBN} prints the module name, the size of the module in
13362 bytes, the number of times the module is used, the dependencies of the
13363 module, the status of the module, and the address of the loaded module
13366 @kindex info os msg
13368 Display the list of all System V message queues on the target. For each
13369 message queue, @value{GDBN} prints the message queue key, the message
13370 queue identifier, the access permissions, the current number of bytes
13371 on the queue, the current number of messages on the queue, the processes
13372 that last sent and received a message on the queue, the user and group
13373 of the owner and creator of the message queue, the times at which a
13374 message was last sent and received on the queue, and the time at which
13375 the message queue was last changed.
13377 @kindex info os processes
13379 Display the list of processes on the target. For each process,
13380 @value{GDBN} prints the process identifier, the name of the user, the
13381 command corresponding to the process, and the list of processor cores
13382 that the process is currently running on. (To understand what these
13383 properties mean, for this and the following info types, please consult
13384 the general @sc{gnu}/Linux documentation.)
13386 @kindex info os procgroups
13388 Display the list of process groups on the target. For each process,
13389 @value{GDBN} prints the identifier of the process group that it belongs
13390 to, the command corresponding to the process group leader, the process
13391 identifier, and the command line of the process. The list is sorted
13392 first by the process group identifier, then by the process identifier,
13393 so that processes belonging to the same process group are grouped together
13394 and the process group leader is listed first.
13396 @kindex info os semaphores
13398 Display the list of all System V semaphore sets on the target. For each
13399 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
13400 set identifier, the access permissions, the number of semaphores in the
13401 set, the user and group of the owner and creator of the semaphore set,
13402 and the times at which the semaphore set was operated upon and changed.
13404 @kindex info os shm
13406 Display the list of all System V shared-memory regions on the target.
13407 For each shared-memory region, @value{GDBN} prints the region key,
13408 the shared-memory identifier, the access permissions, the size of the
13409 region, the process that created the region, the process that last
13410 attached to or detached from the region, the current number of live
13411 attaches to the region, and the times at which the region was last
13412 attached to, detach from, and changed.
13414 @kindex info os sockets
13416 Display the list of Internet-domain sockets on the target. For each
13417 socket, @value{GDBN} prints the address and port of the local and
13418 remote endpoints, the current state of the connection, the creator of
13419 the socket, the IP address family of the socket, and the type of the
13422 @kindex info os threads
13424 Display the list of threads running on the target. For each thread,
13425 @value{GDBN} prints the identifier of the process that the thread
13426 belongs to, the command of the process, the thread identifier, and the
13427 processor core that it is currently running on. The main thread of a
13428 process is not listed.
13432 If @var{infotype} is omitted, then list the possible values for
13433 @var{infotype} and the kind of OS information available for each
13434 @var{infotype}. If the target does not return a list of possible
13435 types, this command will report an error.
13438 @node Memory Region Attributes
13439 @section Memory Region Attributes
13440 @cindex memory region attributes
13442 @dfn{Memory region attributes} allow you to describe special handling
13443 required by regions of your target's memory. @value{GDBN} uses
13444 attributes to determine whether to allow certain types of memory
13445 accesses; whether to use specific width accesses; and whether to cache
13446 target memory. By default the description of memory regions is
13447 fetched from the target (if the current target supports this), but the
13448 user can override the fetched regions.
13450 Defined memory regions can be individually enabled and disabled. When a
13451 memory region is disabled, @value{GDBN} uses the default attributes when
13452 accessing memory in that region. Similarly, if no memory regions have
13453 been defined, @value{GDBN} uses the default attributes when accessing
13456 When a memory region is defined, it is given a number to identify it;
13457 to enable, disable, or remove a memory region, you specify that number.
13461 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13462 Define a memory region bounded by @var{lower} and @var{upper} with
13463 attributes @var{attributes}@dots{}, and add it to the list of regions
13464 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13465 case: it is treated as the target's maximum memory address.
13466 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13469 Discard any user changes to the memory regions and use target-supplied
13470 regions, if available, or no regions if the target does not support.
13473 @item delete mem @var{nums}@dots{}
13474 Remove memory regions @var{nums}@dots{} from the list of regions
13475 monitored by @value{GDBN}.
13477 @kindex disable mem
13478 @item disable mem @var{nums}@dots{}
13479 Disable monitoring of memory regions @var{nums}@dots{}.
13480 A disabled memory region is not forgotten.
13481 It may be enabled again later.
13484 @item enable mem @var{nums}@dots{}
13485 Enable monitoring of memory regions @var{nums}@dots{}.
13489 Print a table of all defined memory regions, with the following columns
13493 @item Memory Region Number
13494 @item Enabled or Disabled.
13495 Enabled memory regions are marked with @samp{y}.
13496 Disabled memory regions are marked with @samp{n}.
13499 The address defining the inclusive lower bound of the memory region.
13502 The address defining the exclusive upper bound of the memory region.
13505 The list of attributes set for this memory region.
13510 @subsection Attributes
13512 @subsubsection Memory Access Mode
13513 The access mode attributes set whether @value{GDBN} may make read or
13514 write accesses to a memory region.
13516 While these attributes prevent @value{GDBN} from performing invalid
13517 memory accesses, they do nothing to prevent the target system, I/O DMA,
13518 etc.@: from accessing memory.
13522 Memory is read only.
13524 Memory is write only.
13526 Memory is read/write. This is the default.
13529 @subsubsection Memory Access Size
13530 The access size attribute tells @value{GDBN} to use specific sized
13531 accesses in the memory region. Often memory mapped device registers
13532 require specific sized accesses. If no access size attribute is
13533 specified, @value{GDBN} may use accesses of any size.
13537 Use 8 bit memory accesses.
13539 Use 16 bit memory accesses.
13541 Use 32 bit memory accesses.
13543 Use 64 bit memory accesses.
13546 @c @subsubsection Hardware/Software Breakpoints
13547 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13548 @c will use hardware or software breakpoints for the internal breakpoints
13549 @c used by the step, next, finish, until, etc. commands.
13553 @c Always use hardware breakpoints
13554 @c @item swbreak (default)
13557 @subsubsection Data Cache
13558 The data cache attributes set whether @value{GDBN} will cache target
13559 memory. While this generally improves performance by reducing debug
13560 protocol overhead, it can lead to incorrect results because @value{GDBN}
13561 does not know about volatile variables or memory mapped device
13566 Enable @value{GDBN} to cache target memory.
13568 Disable @value{GDBN} from caching target memory. This is the default.
13571 @subsection Memory Access Checking
13572 @value{GDBN} can be instructed to refuse accesses to memory that is
13573 not explicitly described. This can be useful if accessing such
13574 regions has undesired effects for a specific target, or to provide
13575 better error checking. The following commands control this behaviour.
13578 @kindex set mem inaccessible-by-default
13579 @item set mem inaccessible-by-default [on|off]
13580 If @code{on} is specified, make @value{GDBN} treat memory not
13581 explicitly described by the memory ranges as non-existent and refuse accesses
13582 to such memory. The checks are only performed if there's at least one
13583 memory range defined. If @code{off} is specified, make @value{GDBN}
13584 treat the memory not explicitly described by the memory ranges as RAM.
13585 The default value is @code{on}.
13586 @kindex show mem inaccessible-by-default
13587 @item show mem inaccessible-by-default
13588 Show the current handling of accesses to unknown memory.
13592 @c @subsubsection Memory Write Verification
13593 @c The memory write verification attributes set whether @value{GDBN}
13594 @c will re-reads data after each write to verify the write was successful.
13598 @c @item noverify (default)
13601 @node Dump/Restore Files
13602 @section Copy Between Memory and a File
13603 @cindex dump/restore files
13604 @cindex append data to a file
13605 @cindex dump data to a file
13606 @cindex restore data from a file
13608 You can use the commands @code{dump}, @code{append}, and
13609 @code{restore} to copy data between target memory and a file. The
13610 @code{dump} and @code{append} commands write data to a file, and the
13611 @code{restore} command reads data from a file back into the inferior's
13612 memory. Files may be in binary, Motorola S-record, Intel hex,
13613 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13614 append to binary files, and cannot read from Verilog Hex files.
13619 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13620 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13621 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13622 or the value of @var{expr}, to @var{filename} in the given format.
13624 The @var{format} parameter may be any one of:
13631 Motorola S-record format.
13633 Tektronix Hex format.
13635 Verilog Hex format.
13638 @value{GDBN} uses the same definitions of these formats as the
13639 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13640 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13644 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13645 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13646 Append the contents of memory from @var{start_addr} to @var{end_addr},
13647 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13648 (@value{GDBN} can only append data to files in raw binary form.)
13651 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13652 Restore the contents of file @var{filename} into memory. The
13653 @code{restore} command can automatically recognize any known @sc{bfd}
13654 file format, except for raw binary. To restore a raw binary file you
13655 must specify the optional keyword @code{binary} after the filename.
13657 If @var{bias} is non-zero, its value will be added to the addresses
13658 contained in the file. Binary files always start at address zero, so
13659 they will be restored at address @var{bias}. Other bfd files have
13660 a built-in location; they will be restored at offset @var{bias}
13661 from that location.
13663 If @var{start} and/or @var{end} are non-zero, then only data between
13664 file offset @var{start} and file offset @var{end} will be restored.
13665 These offsets are relative to the addresses in the file, before
13666 the @var{bias} argument is applied.
13670 @node Core File Generation
13671 @section How to Produce a Core File from Your Program
13672 @cindex dump core from inferior
13674 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13675 image of a running process and its process status (register values
13676 etc.). Its primary use is post-mortem debugging of a program that
13677 crashed while it ran outside a debugger. A program that crashes
13678 automatically produces a core file, unless this feature is disabled by
13679 the user. @xref{Files}, for information on invoking @value{GDBN} in
13680 the post-mortem debugging mode.
13682 Occasionally, you may wish to produce a core file of the program you
13683 are debugging in order to preserve a snapshot of its state.
13684 @value{GDBN} has a special command for that.
13688 @kindex generate-core-file
13689 @item generate-core-file [@var{file}]
13690 @itemx gcore [@var{file}]
13691 Produce a core dump of the inferior process. The optional argument
13692 @var{file} specifies the file name where to put the core dump. If not
13693 specified, the file name defaults to @file{core.@var{pid}}, where
13694 @var{pid} is the inferior process ID.
13696 Note that this command is implemented only for some systems (as of
13697 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13699 On @sc{gnu}/Linux, this command can take into account the value of the
13700 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13701 dump (@pxref{set use-coredump-filter}), and by default honors the
13702 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13703 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13705 @kindex set use-coredump-filter
13706 @anchor{set use-coredump-filter}
13707 @item set use-coredump-filter on
13708 @itemx set use-coredump-filter off
13709 Enable or disable the use of the file
13710 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13711 files. This file is used by the Linux kernel to decide what types of
13712 memory mappings will be dumped or ignored when generating a core dump
13713 file. @var{pid} is the process ID of a currently running process.
13715 To make use of this feature, you have to write in the
13716 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13717 which is a bit mask representing the memory mapping types. If a bit
13718 is set in the bit mask, then the memory mappings of the corresponding
13719 types will be dumped; otherwise, they will be ignored. This
13720 configuration is inherited by child processes. For more information
13721 about the bits that can be set in the
13722 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13723 manpage of @code{core(5)}.
13725 By default, this option is @code{on}. If this option is turned
13726 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13727 and instead uses the same default value as the Linux kernel in order
13728 to decide which pages will be dumped in the core dump file. This
13729 value is currently @code{0x33}, which means that bits @code{0}
13730 (anonymous private mappings), @code{1} (anonymous shared mappings),
13731 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13732 This will cause these memory mappings to be dumped automatically.
13734 @kindex set dump-excluded-mappings
13735 @anchor{set dump-excluded-mappings}
13736 @item set dump-excluded-mappings on
13737 @itemx set dump-excluded-mappings off
13738 If @code{on} is specified, @value{GDBN} will dump memory mappings
13739 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13740 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13742 The default value is @code{off}.
13745 @node Character Sets
13746 @section Character Sets
13747 @cindex character sets
13749 @cindex translating between character sets
13750 @cindex host character set
13751 @cindex target character set
13753 If the program you are debugging uses a different character set to
13754 represent characters and strings than the one @value{GDBN} uses itself,
13755 @value{GDBN} can automatically translate between the character sets for
13756 you. The character set @value{GDBN} uses we call the @dfn{host
13757 character set}; the one the inferior program uses we call the
13758 @dfn{target character set}.
13760 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13761 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13762 remote protocol (@pxref{Remote Debugging}) to debug a program
13763 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13764 then the host character set is Latin-1, and the target character set is
13765 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13766 target-charset EBCDIC-US}, then @value{GDBN} translates between
13767 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13768 character and string literals in expressions.
13770 @value{GDBN} has no way to automatically recognize which character set
13771 the inferior program uses; you must tell it, using the @code{set
13772 target-charset} command, described below.
13774 Here are the commands for controlling @value{GDBN}'s character set
13778 @item set target-charset @var{charset}
13779 @kindex set target-charset
13780 Set the current target character set to @var{charset}. To display the
13781 list of supported target character sets, type
13782 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13784 @item set host-charset @var{charset}
13785 @kindex set host-charset
13786 Set the current host character set to @var{charset}.
13788 By default, @value{GDBN} uses a host character set appropriate to the
13789 system it is running on; you can override that default using the
13790 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13791 automatically determine the appropriate host character set. In this
13792 case, @value{GDBN} uses @samp{UTF-8}.
13794 @value{GDBN} can only use certain character sets as its host character
13795 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13796 @value{GDBN} will list the host character sets it supports.
13798 @item set charset @var{charset}
13799 @kindex set charset
13800 Set the current host and target character sets to @var{charset}. As
13801 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13802 @value{GDBN} will list the names of the character sets that can be used
13803 for both host and target.
13806 @kindex show charset
13807 Show the names of the current host and target character sets.
13809 @item show host-charset
13810 @kindex show host-charset
13811 Show the name of the current host character set.
13813 @item show target-charset
13814 @kindex show target-charset
13815 Show the name of the current target character set.
13817 @item set target-wide-charset @var{charset}
13818 @kindex set target-wide-charset
13819 Set the current target's wide character set to @var{charset}. This is
13820 the character set used by the target's @code{wchar_t} type. To
13821 display the list of supported wide character sets, type
13822 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13824 @item show target-wide-charset
13825 @kindex show target-wide-charset
13826 Show the name of the current target's wide character set.
13829 Here is an example of @value{GDBN}'s character set support in action.
13830 Assume that the following source code has been placed in the file
13831 @file{charset-test.c}:
13837 = @{72, 101, 108, 108, 111, 44, 32, 119,
13838 111, 114, 108, 100, 33, 10, 0@};
13839 char ibm1047_hello[]
13840 = @{200, 133, 147, 147, 150, 107, 64, 166,
13841 150, 153, 147, 132, 90, 37, 0@};
13845 printf ("Hello, world!\n");
13849 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13850 containing the string @samp{Hello, world!} followed by a newline,
13851 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13853 We compile the program, and invoke the debugger on it:
13856 $ gcc -g charset-test.c -o charset-test
13857 $ gdb -nw charset-test
13858 GNU gdb 2001-12-19-cvs
13859 Copyright 2001 Free Software Foundation, Inc.
13864 We can use the @code{show charset} command to see what character sets
13865 @value{GDBN} is currently using to interpret and display characters and
13869 (@value{GDBP}) show charset
13870 The current host and target character set is `ISO-8859-1'.
13874 For the sake of printing this manual, let's use @sc{ascii} as our
13875 initial character set:
13877 (@value{GDBP}) set charset ASCII
13878 (@value{GDBP}) show charset
13879 The current host and target character set is `ASCII'.
13883 Let's assume that @sc{ascii} is indeed the correct character set for our
13884 host system --- in other words, let's assume that if @value{GDBN} prints
13885 characters using the @sc{ascii} character set, our terminal will display
13886 them properly. Since our current target character set is also
13887 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13890 (@value{GDBP}) print ascii_hello
13891 $1 = 0x401698 "Hello, world!\n"
13892 (@value{GDBP}) print ascii_hello[0]
13897 @value{GDBN} uses the target character set for character and string
13898 literals you use in expressions:
13901 (@value{GDBP}) print '+'
13906 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13909 @value{GDBN} relies on the user to tell it which character set the
13910 target program uses. If we print @code{ibm1047_hello} while our target
13911 character set is still @sc{ascii}, we get jibberish:
13914 (@value{GDBP}) print ibm1047_hello
13915 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13916 (@value{GDBP}) print ibm1047_hello[0]
13921 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13922 @value{GDBN} tells us the character sets it supports:
13925 (@value{GDBP}) set target-charset
13926 ASCII EBCDIC-US IBM1047 ISO-8859-1
13927 (@value{GDBP}) set target-charset
13930 We can select @sc{ibm1047} as our target character set, and examine the
13931 program's strings again. Now the @sc{ascii} string is wrong, but
13932 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13933 target character set, @sc{ibm1047}, to the host character set,
13934 @sc{ascii}, and they display correctly:
13937 (@value{GDBP}) set target-charset IBM1047
13938 (@value{GDBP}) show charset
13939 The current host character set is `ASCII'.
13940 The current target character set is `IBM1047'.
13941 (@value{GDBP}) print ascii_hello
13942 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13943 (@value{GDBP}) print ascii_hello[0]
13945 (@value{GDBP}) print ibm1047_hello
13946 $8 = 0x4016a8 "Hello, world!\n"
13947 (@value{GDBP}) print ibm1047_hello[0]
13952 As above, @value{GDBN} uses the target character set for character and
13953 string literals you use in expressions:
13956 (@value{GDBP}) print '+'
13961 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13964 @node Caching Target Data
13965 @section Caching Data of Targets
13966 @cindex caching data of targets
13968 @value{GDBN} caches data exchanged between the debugger and a target.
13969 Each cache is associated with the address space of the inferior.
13970 @xref{Inferiors Connections and Programs}, about inferior and address space.
13971 Such caching generally improves performance in remote debugging
13972 (@pxref{Remote Debugging}), because it reduces the overhead of the
13973 remote protocol by bundling memory reads and writes into large chunks.
13974 Unfortunately, simply caching everything would lead to incorrect results,
13975 since @value{GDBN} does not necessarily know anything about volatile
13976 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13977 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13979 Therefore, by default, @value{GDBN} only caches data
13980 known to be on the stack@footnote{In non-stop mode, it is moderately
13981 rare for a running thread to modify the stack of a stopped thread
13982 in a way that would interfere with a backtrace, and caching of
13983 stack reads provides a significant speed up of remote backtraces.} or
13984 in the code segment.
13985 Other regions of memory can be explicitly marked as
13986 cacheable; @pxref{Memory Region Attributes}.
13989 @kindex set remotecache
13990 @item set remotecache on
13991 @itemx set remotecache off
13992 This option no longer does anything; it exists for compatibility
13995 @kindex show remotecache
13996 @item show remotecache
13997 Show the current state of the obsolete remotecache flag.
13999 @kindex set stack-cache
14000 @item set stack-cache on
14001 @itemx set stack-cache off
14002 Enable or disable caching of stack accesses. When @code{on}, use
14003 caching. By default, this option is @code{on}.
14005 @kindex show stack-cache
14006 @item show stack-cache
14007 Show the current state of data caching for memory accesses.
14009 @kindex set code-cache
14010 @item set code-cache on
14011 @itemx set code-cache off
14012 Enable or disable caching of code segment accesses. When @code{on},
14013 use caching. By default, this option is @code{on}. This improves
14014 performance of disassembly in remote debugging.
14016 @kindex show code-cache
14017 @item show code-cache
14018 Show the current state of target memory cache for code segment
14021 @kindex info dcache
14022 @item info dcache @r{[}line@r{]}
14023 Print the information about the performance of data cache of the
14024 current inferior's address space. The information displayed
14025 includes the dcache width and depth, and for each cache line, its
14026 number, address, and how many times it was referenced. This
14027 command is useful for debugging the data cache operation.
14029 If a line number is specified, the contents of that line will be
14032 @item set dcache size @var{size}
14033 @cindex dcache size
14034 @kindex set dcache size
14035 Set maximum number of entries in dcache (dcache depth above).
14037 @item set dcache line-size @var{line-size}
14038 @cindex dcache line-size
14039 @kindex set dcache line-size
14040 Set number of bytes each dcache entry caches (dcache width above).
14041 Must be a power of 2.
14043 @item show dcache size
14044 @kindex show dcache size
14045 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
14047 @item show dcache line-size
14048 @kindex show dcache line-size
14049 Show default size of dcache lines.
14051 @item maint flush dcache
14052 @cindex dcache, flushing
14053 @kindex maint flush dcache
14054 Flush the contents (if any) of the dcache. This maintainer command is
14055 useful when debugging the dcache implementation.
14059 @node Searching Memory
14060 @section Search Memory
14061 @cindex searching memory
14063 Memory can be searched for a particular sequence of bytes with the
14064 @code{find} command.
14068 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
14069 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
14070 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
14071 etc. The search begins at address @var{start_addr} and continues for either
14072 @var{len} bytes or through to @var{end_addr} inclusive.
14075 @var{s} and @var{n} are optional parameters.
14076 They may be specified in either order, apart or together.
14079 @item @var{s}, search query size
14080 The size of each search query value.
14086 halfwords (two bytes)
14090 giant words (eight bytes)
14093 All values are interpreted in the current language.
14094 This means, for example, that if the current source language is C/C@t{++}
14095 then searching for the string ``hello'' includes the trailing '\0'.
14096 The null terminator can be removed from searching by using casts,
14097 e.g.: @samp{@{char[5]@}"hello"}.
14099 If the value size is not specified, it is taken from the
14100 value's type in the current language.
14101 This is useful when one wants to specify the search
14102 pattern as a mixture of types.
14103 Note that this means, for example, that in the case of C-like languages
14104 a search for an untyped 0x42 will search for @samp{(int) 0x42}
14105 which is typically four bytes.
14107 @item @var{n}, maximum number of finds
14108 The maximum number of matches to print. The default is to print all finds.
14111 You can use strings as search values. Quote them with double-quotes
14113 The string value is copied into the search pattern byte by byte,
14114 regardless of the endianness of the target and the size specification.
14116 The address of each match found is printed as well as a count of the
14117 number of matches found.
14119 The address of the last value found is stored in convenience variable
14121 A count of the number of matches is stored in @samp{$numfound}.
14123 For example, if stopped at the @code{printf} in this function:
14129 static char hello[] = "hello-hello";
14130 static struct @{ char c; short s; int i; @}
14131 __attribute__ ((packed)) mixed
14132 = @{ 'c', 0x1234, 0x87654321 @};
14133 printf ("%s\n", hello);
14138 you get during debugging:
14141 (@value{GDBP}) find &hello[0], +sizeof(hello), "hello"
14142 0x804956d <hello.1620+6>
14144 (@value{GDBP}) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
14145 0x8049567 <hello.1620>
14146 0x804956d <hello.1620+6>
14148 (@value{GDBP}) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
14149 0x8049567 <hello.1620>
14150 0x804956d <hello.1620+6>
14152 (@value{GDBP}) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
14153 0x8049567 <hello.1620>
14155 (@value{GDBP}) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
14156 0x8049560 <mixed.1625>
14158 (@value{GDBP}) print $numfound
14160 (@value{GDBP}) print $_
14161 $2 = (void *) 0x8049560
14165 @section Value Sizes
14167 Whenever @value{GDBN} prints a value memory will be allocated within
14168 @value{GDBN} to hold the contents of the value. It is possible in
14169 some languages with dynamic typing systems, that an invalid program
14170 may indicate a value that is incorrectly large, this in turn may cause
14171 @value{GDBN} to try and allocate an overly large amount of memory.
14174 @kindex set max-value-size
14175 @item set max-value-size @var{bytes}
14176 @itemx set max-value-size unlimited
14177 Set the maximum size of memory that @value{GDBN} will allocate for the
14178 contents of a value to @var{bytes}, trying to display a value that
14179 requires more memory than that will result in an error.
14181 Setting this variable does not effect values that have already been
14182 allocated within @value{GDBN}, only future allocations.
14184 There's a minimum size that @code{max-value-size} can be set to in
14185 order that @value{GDBN} can still operate correctly, this minimum is
14186 currently 16 bytes.
14188 The limit applies to the results of some subexpressions as well as to
14189 complete expressions. For example, an expression denoting a simple
14190 integer component, such as @code{x.y.z}, may fail if the size of
14191 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
14192 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
14193 @var{A} is an array variable with non-constant size, will generally
14194 succeed regardless of the bounds on @var{A}, as long as the component
14195 size is less than @var{bytes}.
14197 The default value of @code{max-value-size} is currently 64k.
14199 @kindex show max-value-size
14200 @item show max-value-size
14201 Show the maximum size of memory, in bytes, that @value{GDBN} will
14202 allocate for the contents of a value.
14205 @node Optimized Code
14206 @chapter Debugging Optimized Code
14207 @cindex optimized code, debugging
14208 @cindex debugging optimized code
14210 Almost all compilers support optimization. With optimization
14211 disabled, the compiler generates assembly code that corresponds
14212 directly to your source code, in a simplistic way. As the compiler
14213 applies more powerful optimizations, the generated assembly code
14214 diverges from your original source code. With help from debugging
14215 information generated by the compiler, @value{GDBN} can map from
14216 the running program back to constructs from your original source.
14218 @value{GDBN} is more accurate with optimization disabled. If you
14219 can recompile without optimization, it is easier to follow the
14220 progress of your program during debugging. But, there are many cases
14221 where you may need to debug an optimized version.
14223 When you debug a program compiled with @samp{-g -O}, remember that the
14224 optimizer has rearranged your code; the debugger shows you what is
14225 really there. Do not be too surprised when the execution path does not
14226 exactly match your source file! An extreme example: if you define a
14227 variable, but never use it, @value{GDBN} never sees that
14228 variable---because the compiler optimizes it out of existence.
14230 Some things do not work as well with @samp{-g -O} as with just
14231 @samp{-g}, particularly on machines with instruction scheduling. If in
14232 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
14233 please report it to us as a bug (including a test case!).
14234 @xref{Variables}, for more information about debugging optimized code.
14237 * Inline Functions:: How @value{GDBN} presents inlining
14238 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
14241 @node Inline Functions
14242 @section Inline Functions
14243 @cindex inline functions, debugging
14245 @dfn{Inlining} is an optimization that inserts a copy of the function
14246 body directly at each call site, instead of jumping to a shared
14247 routine. @value{GDBN} displays inlined functions just like
14248 non-inlined functions. They appear in backtraces. You can view their
14249 arguments and local variables, step into them with @code{step}, skip
14250 them with @code{next}, and escape from them with @code{finish}.
14251 You can check whether a function was inlined by using the
14252 @code{info frame} command.
14254 For @value{GDBN} to support inlined functions, the compiler must
14255 record information about inlining in the debug information ---
14256 @value{NGCC} using the @sc{dwarf 2} format does this, and several
14257 other compilers do also. @value{GDBN} only supports inlined functions
14258 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
14259 do not emit two required attributes (@samp{DW_AT_call_file} and
14260 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
14261 function calls with earlier versions of @value{NGCC}. It instead
14262 displays the arguments and local variables of inlined functions as
14263 local variables in the caller.
14265 The body of an inlined function is directly included at its call site;
14266 unlike a non-inlined function, there are no instructions devoted to
14267 the call. @value{GDBN} still pretends that the call site and the
14268 start of the inlined function are different instructions. Stepping to
14269 the call site shows the call site, and then stepping again shows
14270 the first line of the inlined function, even though no additional
14271 instructions are executed.
14273 This makes source-level debugging much clearer; you can see both the
14274 context of the call and then the effect of the call. Only stepping by
14275 a single instruction using @code{stepi} or @code{nexti} does not do
14276 this; single instruction steps always show the inlined body.
14278 There are some ways that @value{GDBN} does not pretend that inlined
14279 function calls are the same as normal calls:
14283 Setting breakpoints at the call site of an inlined function may not
14284 work, because the call site does not contain any code. @value{GDBN}
14285 may incorrectly move the breakpoint to the next line of the enclosing
14286 function, after the call. This limitation will be removed in a future
14287 version of @value{GDBN}; until then, set a breakpoint on an earlier line
14288 or inside the inlined function instead.
14291 @value{GDBN} cannot locate the return value of inlined calls after
14292 using the @code{finish} command. This is a limitation of compiler-generated
14293 debugging information; after @code{finish}, you can step to the next line
14294 and print a variable where your program stored the return value.
14298 @node Tail Call Frames
14299 @section Tail Call Frames
14300 @cindex tail call frames, debugging
14302 Function @code{B} can call function @code{C} in its very last statement. In
14303 unoptimized compilation the call of @code{C} is immediately followed by return
14304 instruction at the end of @code{B} code. Optimizing compiler may replace the
14305 call and return in function @code{B} into one jump to function @code{C}
14306 instead. Such use of a jump instruction is called @dfn{tail call}.
14308 During execution of function @code{C}, there will be no indication in the
14309 function call stack frames that it was tail-called from @code{B}. If function
14310 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
14311 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
14312 some cases @value{GDBN} can determine that @code{C} was tail-called from
14313 @code{B}, and it will then create fictitious call frame for that, with the
14314 return address set up as if @code{B} called @code{C} normally.
14316 This functionality is currently supported only by DWARF 2 debugging format and
14317 the compiler has to produce @samp{DW_TAG_call_site} tags. With
14318 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
14321 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
14322 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
14325 (@value{GDBP}) x/i $pc - 2
14326 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
14327 (@value{GDBP}) info frame
14328 Stack level 1, frame at 0x7fffffffda30:
14329 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
14330 tail call frame, caller of frame at 0x7fffffffda30
14331 source language c++.
14332 Arglist at unknown address.
14333 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
14336 The detection of all the possible code path executions can find them ambiguous.
14337 There is no execution history stored (possible @ref{Reverse Execution} is never
14338 used for this purpose) and the last known caller could have reached the known
14339 callee by multiple different jump sequences. In such case @value{GDBN} still
14340 tries to show at least all the unambiguous top tail callers and all the
14341 unambiguous bottom tail calees, if any.
14344 @anchor{set debug entry-values}
14345 @item set debug entry-values
14346 @kindex set debug entry-values
14347 When set to on, enables printing of analysis messages for both frame argument
14348 values at function entry and tail calls. It will show all the possible valid
14349 tail calls code paths it has considered. It will also print the intersection
14350 of them with the final unambiguous (possibly partial or even empty) code path
14353 @item show debug entry-values
14354 @kindex show debug entry-values
14355 Show the current state of analysis messages printing for both frame argument
14356 values at function entry and tail calls.
14359 The analysis messages for tail calls can for example show why the virtual tail
14360 call frame for function @code{c} has not been recognized (due to the indirect
14361 reference by variable @code{x}):
14364 static void __attribute__((noinline, noclone)) c (void);
14365 void (*x) (void) = c;
14366 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14367 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
14368 int main (void) @{ x (); return 0; @}
14370 Breakpoint 1, DW_OP_entry_value resolving cannot find
14371 DW_TAG_call_site 0x40039a in main
14373 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14376 #1 0x000000000040039a in main () at t.c:5
14379 Another possibility is an ambiguous virtual tail call frames resolution:
14383 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
14384 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
14385 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
14386 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
14387 static void __attribute__((noinline, noclone)) b (void)
14388 @{ if (i) c (); else e (); @}
14389 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
14390 int main (void) @{ a (); return 0; @}
14392 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
14393 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
14394 tailcall: reduced: 0x4004d2(a) |
14397 #1 0x00000000004004d2 in a () at t.c:8
14398 #2 0x0000000000400395 in main () at t.c:9
14401 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
14402 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
14404 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
14405 @ifset HAVE_MAKEINFO_CLICK
14406 @set ARROW @click{}
14407 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
14408 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
14410 @ifclear HAVE_MAKEINFO_CLICK
14412 @set CALLSEQ1B @value{CALLSEQ1A}
14413 @set CALLSEQ2B @value{CALLSEQ2A}
14416 Frames #0 and #2 are real, #1 is a virtual tail call frame.
14417 The code can have possible execution paths @value{CALLSEQ1B} or
14418 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14420 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14421 has found. It then finds another possible calling sequence - that one is
14422 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14423 printed as the @code{reduced:} calling sequence. That one could have many
14424 further @code{compare:} and @code{reduced:} statements as long as there remain
14425 any non-ambiguous sequence entries.
14427 For the frame of function @code{b} in both cases there are different possible
14428 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14429 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14430 therefore this one is displayed to the user while the ambiguous frames are
14433 There can be also reasons why printing of frame argument values at function
14438 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14439 static void __attribute__((noinline, noclone)) a (int i);
14440 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14441 static void __attribute__((noinline, noclone)) a (int i)
14442 @{ if (i) b (i - 1); else c (0); @}
14443 int main (void) @{ a (5); return 0; @}
14446 #0 c (i=i@@entry=0) at t.c:2
14447 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14448 function "a" at 0x400420 can call itself via tail calls
14449 i=<optimized out>) at t.c:6
14450 #2 0x000000000040036e in main () at t.c:7
14453 @value{GDBN} cannot find out from the inferior state if and how many times did
14454 function @code{a} call itself (via function @code{b}) as these calls would be
14455 tail calls. Such tail calls would modify the @code{i} variable, therefore
14456 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14457 prints @code{<optimized out>} instead.
14460 @chapter C Preprocessor Macros
14462 Some languages, such as C and C@t{++}, provide a way to define and invoke
14463 ``preprocessor macros'' which expand into strings of tokens.
14464 @value{GDBN} can evaluate expressions containing macro invocations, show
14465 the result of macro expansion, and show a macro's definition, including
14466 where it was defined.
14468 You may need to compile your program specially to provide @value{GDBN}
14469 with information about preprocessor macros. Most compilers do not
14470 include macros in their debugging information, even when you compile
14471 with the @option{-g} flag. @xref{Compilation}.
14473 A program may define a macro at one point, remove that definition later,
14474 and then provide a different definition after that. Thus, at different
14475 points in the program, a macro may have different definitions, or have
14476 no definition at all. If there is a current stack frame, @value{GDBN}
14477 uses the macros in scope at that frame's source code line. Otherwise,
14478 @value{GDBN} uses the macros in scope at the current listing location;
14481 Whenever @value{GDBN} evaluates an expression, it always expands any
14482 macro invocations present in the expression. @value{GDBN} also provides
14483 the following commands for working with macros explicitly.
14487 @kindex macro expand
14488 @cindex macro expansion, showing the results of preprocessor
14489 @cindex preprocessor macro expansion, showing the results of
14490 @cindex expanding preprocessor macros
14491 @item macro expand @var{expression}
14492 @itemx macro exp @var{expression}
14493 Show the results of expanding all preprocessor macro invocations in
14494 @var{expression}. Since @value{GDBN} simply expands macros, but does
14495 not parse the result, @var{expression} need not be a valid expression;
14496 it can be any string of tokens.
14499 @item macro expand-once @var{expression}
14500 @itemx macro exp1 @var{expression}
14501 @cindex expand macro once
14502 @i{(This command is not yet implemented.)} Show the results of
14503 expanding those preprocessor macro invocations that appear explicitly in
14504 @var{expression}. Macro invocations appearing in that expansion are
14505 left unchanged. This command allows you to see the effect of a
14506 particular macro more clearly, without being confused by further
14507 expansions. Since @value{GDBN} simply expands macros, but does not
14508 parse the result, @var{expression} need not be a valid expression; it
14509 can be any string of tokens.
14512 @cindex macro definition, showing
14513 @cindex definition of a macro, showing
14514 @cindex macros, from debug info
14515 @item info macro [-a|-all] [--] @var{macro}
14516 Show the current definition or all definitions of the named @var{macro},
14517 and describe the source location or compiler command-line where that
14518 definition was established. The optional double dash is to signify the end of
14519 argument processing and the beginning of @var{macro} for non C-like macros where
14520 the macro may begin with a hyphen.
14522 @kindex info macros
14523 @item info macros @var{locspec}
14524 Show all macro definitions that are in effect at the source line of
14525 the code location that results from resolving @var{locspec}, and
14526 describe the source location or compiler command-line where those
14527 definitions were established.
14529 @kindex macro define
14530 @cindex user-defined macros
14531 @cindex defining macros interactively
14532 @cindex macros, user-defined
14533 @item macro define @var{macro} @var{replacement-list}
14534 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14535 Introduce a definition for a preprocessor macro named @var{macro},
14536 invocations of which are replaced by the tokens given in
14537 @var{replacement-list}. The first form of this command defines an
14538 ``object-like'' macro, which takes no arguments; the second form
14539 defines a ``function-like'' macro, which takes the arguments given in
14542 A definition introduced by this command is in scope in every
14543 expression evaluated in @value{GDBN}, until it is removed with the
14544 @code{macro undef} command, described below. The definition overrides
14545 all definitions for @var{macro} present in the program being debugged,
14546 as well as any previous user-supplied definition.
14548 @kindex macro undef
14549 @item macro undef @var{macro}
14550 Remove any user-supplied definition for the macro named @var{macro}.
14551 This command only affects definitions provided with the @code{macro
14552 define} command, described above; it cannot remove definitions present
14553 in the program being debugged.
14557 List all the macros defined using the @code{macro define} command.
14560 @cindex macros, example of debugging with
14561 Here is a transcript showing the above commands in action. First, we
14562 show our source files:
14567 #include "sample.h"
14570 #define ADD(x) (M + x)
14575 printf ("Hello, world!\n");
14577 printf ("We're so creative.\n");
14579 printf ("Goodbye, world!\n");
14586 Now, we compile the program using the @sc{gnu} C compiler,
14587 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14588 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14589 and @option{-gdwarf-4}; we recommend always choosing the most recent
14590 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14591 includes information about preprocessor macros in the debugging
14595 $ gcc -gdwarf-2 -g3 sample.c -o sample
14599 Now, we start @value{GDBN} on our sample program:
14603 GNU gdb 2002-05-06-cvs
14604 Copyright 2002 Free Software Foundation, Inc.
14605 GDB is free software, @dots{}
14609 We can expand macros and examine their definitions, even when the
14610 program is not running. @value{GDBN} uses the current listing position
14611 to decide which macro definitions are in scope:
14614 (@value{GDBP}) list main
14617 5 #define ADD(x) (M + x)
14622 10 printf ("Hello, world!\n");
14624 12 printf ("We're so creative.\n");
14625 (@value{GDBP}) info macro ADD
14626 Defined at /home/jimb/gdb/macros/play/sample.c:5
14627 #define ADD(x) (M + x)
14628 (@value{GDBP}) info macro Q
14629 Defined at /home/jimb/gdb/macros/play/sample.h:1
14630 included at /home/jimb/gdb/macros/play/sample.c:2
14632 (@value{GDBP}) macro expand ADD(1)
14633 expands to: (42 + 1)
14634 (@value{GDBP}) macro expand-once ADD(1)
14635 expands to: once (M + 1)
14639 In the example above, note that @code{macro expand-once} expands only
14640 the macro invocation explicit in the original text --- the invocation of
14641 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14642 which was introduced by @code{ADD}.
14644 Once the program is running, @value{GDBN} uses the macro definitions in
14645 force at the source line of the current stack frame:
14648 (@value{GDBP}) break main
14649 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14651 Starting program: /home/jimb/gdb/macros/play/sample
14653 Breakpoint 1, main () at sample.c:10
14654 10 printf ("Hello, world!\n");
14658 At line 10, the definition of the macro @code{N} at line 9 is in force:
14661 (@value{GDBP}) info macro N
14662 Defined at /home/jimb/gdb/macros/play/sample.c:9
14664 (@value{GDBP}) macro expand N Q M
14665 expands to: 28 < 42
14666 (@value{GDBP}) print N Q M
14671 As we step over directives that remove @code{N}'s definition, and then
14672 give it a new definition, @value{GDBN} finds the definition (or lack
14673 thereof) in force at each point:
14676 (@value{GDBP}) next
14678 12 printf ("We're so creative.\n");
14679 (@value{GDBP}) info macro N
14680 The symbol `N' has no definition as a C/C++ preprocessor macro
14681 at /home/jimb/gdb/macros/play/sample.c:12
14682 (@value{GDBP}) next
14684 14 printf ("Goodbye, world!\n");
14685 (@value{GDBP}) info macro N
14686 Defined at /home/jimb/gdb/macros/play/sample.c:13
14688 (@value{GDBP}) macro expand N Q M
14689 expands to: 1729 < 42
14690 (@value{GDBP}) print N Q M
14695 In addition to source files, macros can be defined on the compilation command
14696 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14697 such a way, @value{GDBN} displays the location of their definition as line zero
14698 of the source file submitted to the compiler.
14701 (@value{GDBP}) info macro __STDC__
14702 Defined at /home/jimb/gdb/macros/play/sample.c:0
14709 @chapter Tracepoints
14710 @c This chapter is based on the documentation written by Michael
14711 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14713 @cindex tracepoints
14714 In some applications, it is not feasible for the debugger to interrupt
14715 the program's execution long enough for the developer to learn
14716 anything helpful about its behavior. If the program's correctness
14717 depends on its real-time behavior, delays introduced by a debugger
14718 might cause the program to change its behavior drastically, or perhaps
14719 fail, even when the code itself is correct. It is useful to be able
14720 to observe the program's behavior without interrupting it.
14722 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14723 specify locations in the program, called @dfn{tracepoints}, and
14724 arbitrary expressions to evaluate when those tracepoints are reached.
14725 Later, using the @code{tfind} command, you can examine the values
14726 those expressions had when the program hit the tracepoints. The
14727 expressions may also denote objects in memory---structures or arrays,
14728 for example---whose values @value{GDBN} should record; while visiting
14729 a particular tracepoint, you may inspect those objects as if they were
14730 in memory at that moment. However, because @value{GDBN} records these
14731 values without interacting with you, it can do so quickly and
14732 unobtrusively, hopefully not disturbing the program's behavior.
14734 The tracepoint facility is currently available only for remote
14735 targets. @xref{Targets}. In addition, your remote target must know
14736 how to collect trace data. This functionality is implemented in the
14737 remote stub; however, none of the stubs distributed with @value{GDBN}
14738 support tracepoints as of this writing. The format of the remote
14739 packets used to implement tracepoints are described in @ref{Tracepoint
14742 It is also possible to get trace data from a file, in a manner reminiscent
14743 of corefiles; you specify the filename, and use @code{tfind} to search
14744 through the file. @xref{Trace Files}, for more details.
14746 This chapter describes the tracepoint commands and features.
14749 * Set Tracepoints::
14750 * Analyze Collected Data::
14751 * Tracepoint Variables::
14755 @node Set Tracepoints
14756 @section Commands to Set Tracepoints
14758 Before running such a @dfn{trace experiment}, an arbitrary number of
14759 tracepoints can be set. A tracepoint is actually a special type of
14760 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14761 standard breakpoint commands. For instance, as with breakpoints,
14762 tracepoint numbers are successive integers starting from one, and many
14763 of the commands associated with tracepoints take the tracepoint number
14764 as their argument, to identify which tracepoint to work on.
14766 For each tracepoint, you can specify, in advance, some arbitrary set
14767 of data that you want the target to collect in the trace buffer when
14768 it hits that tracepoint. The collected data can include registers,
14769 local variables, or global data. Later, you can use @value{GDBN}
14770 commands to examine the values these data had at the time the
14771 tracepoint was hit.
14773 Tracepoints do not support every breakpoint feature. Ignore counts on
14774 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14775 commands when they are hit. Tracepoints may not be thread-specific
14778 @cindex fast tracepoints
14779 Some targets may support @dfn{fast tracepoints}, which are inserted in
14780 a different way (such as with a jump instead of a trap), that is
14781 faster but possibly restricted in where they may be installed.
14783 @cindex static tracepoints
14784 @cindex markers, static tracepoints
14785 @cindex probing markers, static tracepoints
14786 Regular and fast tracepoints are dynamic tracing facilities, meaning
14787 that they can be used to insert tracepoints at (almost) any location
14788 in the target. Some targets may also support controlling @dfn{static
14789 tracepoints} from @value{GDBN}. With static tracing, a set of
14790 instrumentation points, also known as @dfn{markers}, are embedded in
14791 the target program, and can be activated or deactivated by name or
14792 address. These are usually placed at locations which facilitate
14793 investigating what the target is actually doing. @value{GDBN}'s
14794 support for static tracing includes being able to list instrumentation
14795 points, and attach them with @value{GDBN} defined high level
14796 tracepoints that expose the whole range of convenience of
14797 @value{GDBN}'s tracepoints support. Namely, support for collecting
14798 registers values and values of global or local (to the instrumentation
14799 point) variables; tracepoint conditions and trace state variables.
14800 The act of installing a @value{GDBN} static tracepoint on an
14801 instrumentation point, or marker, is referred to as @dfn{probing} a
14802 static tracepoint marker.
14804 @code{gdbserver} supports tracepoints on some target systems.
14805 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14807 This section describes commands to set tracepoints and associated
14808 conditions and actions.
14811 * Create and Delete Tracepoints::
14812 * Enable and Disable Tracepoints::
14813 * Tracepoint Passcounts::
14814 * Tracepoint Conditions::
14815 * Trace State Variables::
14816 * Tracepoint Actions::
14817 * Listing Tracepoints::
14818 * Listing Static Tracepoint Markers::
14819 * Starting and Stopping Trace Experiments::
14820 * Tracepoint Restrictions::
14823 @node Create and Delete Tracepoints
14824 @subsection Create and Delete Tracepoints
14827 @cindex set tracepoint
14829 @item trace @var{locspec}
14830 The @code{trace} command is very similar to the @code{break} command.
14831 Its argument @var{locspec} can be any valid location specification.
14832 @xref{Location Specifications}. The @code{trace} command defines a tracepoint,
14833 which is a point in the target program where the debugger will briefly stop,
14834 collect some data, and then allow the program to continue. Setting a tracepoint
14835 or changing its actions takes effect immediately if the remote stub
14836 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14838 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14839 these changes don't take effect until the next @code{tstart}
14840 command, and once a trace experiment is running, further changes will
14841 not have any effect until the next trace experiment starts. In addition,
14842 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14843 address is not yet resolved. (This is similar to pending breakpoints.)
14844 Pending tracepoints are not downloaded to the target and not installed
14845 until they are resolved. The resolution of pending tracepoints requires
14846 @value{GDBN} support---when debugging with the remote target, and
14847 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14848 tracing}), pending tracepoints can not be resolved (and downloaded to
14849 the remote stub) while @value{GDBN} is disconnected.
14851 Here are some examples of using the @code{trace} command:
14854 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14856 (@value{GDBP}) @b{trace +2} // 2 lines forward
14858 (@value{GDBP}) @b{trace my_function} // first source line of function
14860 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14862 (@value{GDBP}) @b{trace *0x2117c4} // an address
14866 You can abbreviate @code{trace} as @code{tr}.
14868 @item trace @var{locspec} if @var{cond}
14869 Set a tracepoint with condition @var{cond}; evaluate the expression
14870 @var{cond} each time the tracepoint is reached, and collect data only
14871 if the value is nonzero---that is, if @var{cond} evaluates as true.
14872 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14873 information on tracepoint conditions.
14875 @item ftrace @var{locspec} [ if @var{cond} ]
14876 @cindex set fast tracepoint
14877 @cindex fast tracepoints, setting
14879 The @code{ftrace} command sets a fast tracepoint. For targets that
14880 support them, fast tracepoints will use a more efficient but possibly
14881 less general technique to trigger data collection, such as a jump
14882 instruction instead of a trap, or some sort of hardware support. It
14883 may not be possible to create a fast tracepoint at the desired
14884 location, in which case the command will exit with an explanatory
14887 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14890 On 32-bit x86-architecture systems, fast tracepoints normally need to
14891 be placed at an instruction that is 5 bytes or longer, but can be
14892 placed at 4-byte instructions if the low 64K of memory of the target
14893 program is available to install trampolines. Some Unix-type systems,
14894 such as @sc{gnu}/Linux, exclude low addresses from the program's
14895 address space; but for instance with the Linux kernel it is possible
14896 to let @value{GDBN} use this area by doing a @command{sysctl} command
14897 to set the @code{mmap_min_addr} kernel parameter, as in
14900 sudo sysctl -w vm.mmap_min_addr=32768
14904 which sets the low address to 32K, which leaves plenty of room for
14905 trampolines. The minimum address should be set to a page boundary.
14907 @item strace [@var{locspec} | -m @var{marker}] [ if @var{cond} ]
14908 @cindex set static tracepoint
14909 @cindex static tracepoints, setting
14910 @cindex probe static tracepoint marker
14912 The @code{strace} command sets a static tracepoint. For targets that
14913 support it, setting a static tracepoint probes a static
14914 instrumentation point, or marker, found at the code locations that
14915 result from resolving @var{locspec}. It may not be possible to set a
14916 static tracepoint at the desired code location, in which case the
14917 command will exit with an explanatory message.
14919 @value{GDBN} handles arguments to @code{strace} exactly as for
14920 @code{trace}, with the addition that the user can also specify
14921 @code{-m @var{marker}} instead of a location spec. This probes the marker
14922 identified by the @var{marker} string identifier. This identifier
14923 depends on the static tracepoint backend library your program is
14924 using. You can find all the marker identifiers in the @samp{ID} field
14925 of the @code{info static-tracepoint-markers} command output.
14926 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14927 Markers}. For example, in the following small program using the UST
14933 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14938 the marker id is composed of joining the first two arguments to the
14939 @code{trace_mark} call with a slash, which translates to:
14942 (@value{GDBP}) info static-tracepoint-markers
14943 Cnt Enb ID Address What
14944 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14950 so you may probe the marker above with:
14953 (@value{GDBP}) strace -m ust/bar33
14956 Static tracepoints accept an extra collect action --- @code{collect
14957 $_sdata}. This collects arbitrary user data passed in the probe point
14958 call to the tracing library. In the UST example above, you'll see
14959 that the third argument to @code{trace_mark} is a printf-like format
14960 string. The user data is then the result of running that formatting
14961 string against the following arguments. Note that @code{info
14962 static-tracepoint-markers} command output lists that format string in
14963 the @samp{Data:} field.
14965 You can inspect this data when analyzing the trace buffer, by printing
14966 the $_sdata variable like any other variable available to
14967 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14970 @cindex last tracepoint number
14971 @cindex recent tracepoint number
14972 @cindex tracepoint number
14973 The convenience variable @code{$tpnum} records the tracepoint number
14974 of the most recently set tracepoint.
14976 @kindex delete tracepoint
14977 @cindex tracepoint deletion
14978 @item delete tracepoint @r{[}@var{num}@r{]}
14979 Permanently delete one or more tracepoints. With no argument, the
14980 default is to delete all tracepoints. Note that the regular
14981 @code{delete} command can remove tracepoints also.
14986 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14988 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14992 You can abbreviate this command as @code{del tr}.
14995 @node Enable and Disable Tracepoints
14996 @subsection Enable and Disable Tracepoints
14998 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
15001 @kindex disable tracepoint
15002 @item disable tracepoint @r{[}@var{num}@r{]}
15003 Disable tracepoint @var{num}, or all tracepoints if no argument
15004 @var{num} is given. A disabled tracepoint will have no effect during
15005 a trace experiment, but it is not forgotten. You can re-enable
15006 a disabled tracepoint using the @code{enable tracepoint} command.
15007 If the command is issued during a trace experiment and the debug target
15008 has support for disabling tracepoints during a trace experiment, then the
15009 change will be effective immediately. Otherwise, it will be applied to the
15010 next trace experiment.
15012 @kindex enable tracepoint
15013 @item enable tracepoint @r{[}@var{num}@r{]}
15014 Enable tracepoint @var{num}, or all tracepoints. If this command is
15015 issued during a trace experiment and the debug target supports enabling
15016 tracepoints during a trace experiment, then the enabled tracepoints will
15017 become effective immediately. Otherwise, they will become effective the
15018 next time a trace experiment is run.
15021 @node Tracepoint Passcounts
15022 @subsection Tracepoint Passcounts
15026 @cindex tracepoint pass count
15027 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
15028 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
15029 automatically stop a trace experiment. If a tracepoint's passcount is
15030 @var{n}, then the trace experiment will be automatically stopped on
15031 the @var{n}'th time that tracepoint is hit. If the tracepoint number
15032 @var{num} is not specified, the @code{passcount} command sets the
15033 passcount of the most recently defined tracepoint. If no passcount is
15034 given, the trace experiment will run until stopped explicitly by the
15040 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
15041 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
15043 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
15044 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
15045 (@value{GDBP}) @b{trace foo}
15046 (@value{GDBP}) @b{pass 3}
15047 (@value{GDBP}) @b{trace bar}
15048 (@value{GDBP}) @b{pass 2}
15049 (@value{GDBP}) @b{trace baz}
15050 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
15051 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
15052 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
15053 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
15057 @node Tracepoint Conditions
15058 @subsection Tracepoint Conditions
15059 @cindex conditional tracepoints
15060 @cindex tracepoint conditions
15062 The simplest sort of tracepoint collects data every time your program
15063 reaches a specified place. You can also specify a @dfn{condition} for
15064 a tracepoint. A condition is just a Boolean expression in your
15065 programming language (@pxref{Expressions, ,Expressions}). A
15066 tracepoint with a condition evaluates the expression each time your
15067 program reaches it, and data collection happens only if the condition
15070 Tracepoint conditions can be specified when a tracepoint is set, by
15071 using @samp{if} in the arguments to the @code{trace} command.
15072 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
15073 also be set or changed at any time with the @code{condition} command,
15074 just as with breakpoints.
15076 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
15077 the conditional expression itself. Instead, @value{GDBN} encodes the
15078 expression into an agent expression (@pxref{Agent Expressions})
15079 suitable for execution on the target, independently of @value{GDBN}.
15080 Global variables become raw memory locations, locals become stack
15081 accesses, and so forth.
15083 For instance, suppose you have a function that is usually called
15084 frequently, but should not be called after an error has occurred. You
15085 could use the following tracepoint command to collect data about calls
15086 of that function that happen while the error code is propagating
15087 through the program; an unconditional tracepoint could end up
15088 collecting thousands of useless trace frames that you would have to
15092 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
15095 @node Trace State Variables
15096 @subsection Trace State Variables
15097 @cindex trace state variables
15099 A @dfn{trace state variable} is a special type of variable that is
15100 created and managed by target-side code. The syntax is the same as
15101 that for GDB's convenience variables (a string prefixed with ``$''),
15102 but they are stored on the target. They must be created explicitly,
15103 using a @code{tvariable} command. They are always 64-bit signed
15106 Trace state variables are remembered by @value{GDBN}, and downloaded
15107 to the target along with tracepoint information when the trace
15108 experiment starts. There are no intrinsic limits on the number of
15109 trace state variables, beyond memory limitations of the target.
15111 @cindex convenience variables, and trace state variables
15112 Although trace state variables are managed by the target, you can use
15113 them in print commands and expressions as if they were convenience
15114 variables; @value{GDBN} will get the current value from the target
15115 while the trace experiment is running. Trace state variables share
15116 the same namespace as other ``$'' variables, which means that you
15117 cannot have trace state variables with names like @code{$23} or
15118 @code{$pc}, nor can you have a trace state variable and a convenience
15119 variable with the same name.
15123 @item tvariable $@var{name} [ = @var{expression} ]
15125 The @code{tvariable} command creates a new trace state variable named
15126 @code{$@var{name}}, and optionally gives it an initial value of
15127 @var{expression}. The @var{expression} is evaluated when this command is
15128 entered; the result will be converted to an integer if possible,
15129 otherwise @value{GDBN} will report an error. A subsequent
15130 @code{tvariable} command specifying the same name does not create a
15131 variable, but instead assigns the supplied initial value to the
15132 existing variable of that name, overwriting any previous initial
15133 value. The default initial value is 0.
15135 @item info tvariables
15136 @kindex info tvariables
15137 List all the trace state variables along with their initial values.
15138 Their current values may also be displayed, if the trace experiment is
15141 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
15142 @kindex delete tvariable
15143 Delete the given trace state variables, or all of them if no arguments
15148 @node Tracepoint Actions
15149 @subsection Tracepoint Action Lists
15153 @cindex tracepoint actions
15154 @item actions @r{[}@var{num}@r{]}
15155 This command will prompt for a list of actions to be taken when the
15156 tracepoint is hit. If the tracepoint number @var{num} is not
15157 specified, this command sets the actions for the one that was most
15158 recently defined (so that you can define a tracepoint and then say
15159 @code{actions} without bothering about its number). You specify the
15160 actions themselves on the following lines, one action at a time, and
15161 terminate the actions list with a line containing just @code{end}. So
15162 far, the only defined actions are @code{collect}, @code{teval}, and
15163 @code{while-stepping}.
15165 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
15166 Commands, ,Breakpoint Command Lists}), except that only the defined
15167 actions are allowed; any other @value{GDBN} command is rejected.
15169 @cindex remove actions from a tracepoint
15170 To remove all actions from a tracepoint, type @samp{actions @var{num}}
15171 and follow it immediately with @samp{end}.
15174 (@value{GDBP}) @b{collect @var{data}} // collect some data
15176 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
15178 (@value{GDBP}) @b{end} // signals the end of actions.
15181 In the following example, the action list begins with @code{collect}
15182 commands indicating the things to be collected when the tracepoint is
15183 hit. Then, in order to single-step and collect additional data
15184 following the tracepoint, a @code{while-stepping} command is used,
15185 followed by the list of things to be collected after each step in a
15186 sequence of single steps. The @code{while-stepping} command is
15187 terminated by its own separate @code{end} command. Lastly, the action
15188 list is terminated by an @code{end} command.
15191 (@value{GDBP}) @b{trace foo}
15192 (@value{GDBP}) @b{actions}
15193 Enter actions for tracepoint 1, one per line:
15196 > while-stepping 12
15197 > collect $pc, arr[i]
15202 @kindex collect @r{(tracepoints)}
15203 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
15204 Collect values of the given expressions when the tracepoint is hit.
15205 This command accepts a comma-separated list of any valid expressions.
15206 In addition to global, static, or local variables, the following
15207 special arguments are supported:
15211 Collect all registers.
15214 Collect all function arguments.
15217 Collect all local variables.
15220 Collect the return address. This is helpful if you want to see more
15223 @emph{Note:} The return address location can not always be reliably
15224 determined up front, and the wrong address / registers may end up
15225 collected instead. On some architectures the reliability is higher
15226 for tracepoints at function entry, while on others it's the opposite.
15227 When this happens, backtracing will stop because the return address is
15228 found unavailable (unless another collect rule happened to match it).
15231 Collects the number of arguments from the static probe at which the
15232 tracepoint is located.
15233 @xref{Static Probe Points}.
15235 @item $_probe_arg@var{n}
15236 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
15237 from the static probe at which the tracepoint is located.
15238 @xref{Static Probe Points}.
15241 @vindex $_sdata@r{, collect}
15242 Collect static tracepoint marker specific data. Only available for
15243 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
15244 Lists}. On the UST static tracepoints library backend, an
15245 instrumentation point resembles a @code{printf} function call. The
15246 tracing library is able to collect user specified data formatted to a
15247 character string using the format provided by the programmer that
15248 instrumented the program. Other backends have similar mechanisms.
15249 Here's an example of a UST marker call:
15252 const char master_name[] = "$your_name";
15253 trace_mark(channel1, marker1, "hello %s", master_name)
15256 In this case, collecting @code{$_sdata} collects the string
15257 @samp{hello $yourname}. When analyzing the trace buffer, you can
15258 inspect @samp{$_sdata} like any other variable available to
15262 You can give several consecutive @code{collect} commands, each one
15263 with a single argument, or one @code{collect} command with several
15264 arguments separated by commas; the effect is the same.
15266 The optional @var{mods} changes the usual handling of the arguments.
15267 @code{s} requests that pointers to chars be handled as strings, in
15268 particular collecting the contents of the memory being pointed at, up
15269 to the first zero. The upper bound is by default the value of the
15270 @code{print characters} variable; if @code{s} is followed by a decimal
15271 number, that is the upper bound instead. So for instance
15272 @samp{collect/s25 mystr} collects as many as 25 characters at
15275 The command @code{info scope} (@pxref{Symbols, info scope}) is
15276 particularly useful for figuring out what data to collect.
15278 @kindex teval @r{(tracepoints)}
15279 @item teval @var{expr1}, @var{expr2}, @dots{}
15280 Evaluate the given expressions when the tracepoint is hit. This
15281 command accepts a comma-separated list of expressions. The results
15282 are discarded, so this is mainly useful for assigning values to trace
15283 state variables (@pxref{Trace State Variables}) without adding those
15284 values to the trace buffer, as would be the case if the @code{collect}
15287 @kindex while-stepping @r{(tracepoints)}
15288 @item while-stepping @var{n}
15289 Perform @var{n} single-step instruction traces after the tracepoint,
15290 collecting new data after each step. The @code{while-stepping}
15291 command is followed by the list of what to collect while stepping
15292 (followed by its own @code{end} command):
15295 > while-stepping 12
15296 > collect $regs, myglobal
15302 Note that @code{$pc} is not automatically collected by
15303 @code{while-stepping}; you need to explicitly collect that register if
15304 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
15307 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
15308 @kindex set default-collect
15309 @cindex default collection action
15310 This variable is a list of expressions to collect at each tracepoint
15311 hit. It is effectively an additional @code{collect} action prepended
15312 to every tracepoint action list. The expressions are parsed
15313 individually for each tracepoint, so for instance a variable named
15314 @code{xyz} may be interpreted as a global for one tracepoint, and a
15315 local for another, as appropriate to the tracepoint's location.
15317 @item show default-collect
15318 @kindex show default-collect
15319 Show the list of expressions that are collected by default at each
15324 @node Listing Tracepoints
15325 @subsection Listing Tracepoints
15328 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
15329 @kindex info tp @r{[}@var{n}@dots{}@r{]}
15330 @cindex information about tracepoints
15331 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
15332 Display information about the tracepoint @var{num}. If you don't
15333 specify a tracepoint number, displays information about all the
15334 tracepoints defined so far. The format is similar to that used for
15335 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
15336 command, simply restricting itself to tracepoints.
15338 A tracepoint's listing may include additional information specific to
15343 its passcount as given by the @code{passcount @var{n}} command
15346 the state about installed on target of each location
15350 (@value{GDBP}) @b{info trace}
15351 Num Type Disp Enb Address What
15352 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
15354 collect globfoo, $regs
15359 2 tracepoint keep y <MULTIPLE>
15361 2.1 y 0x0804859c in func4 at change-loc.h:35
15362 installed on target
15363 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
15364 installed on target
15365 2.3 y <PENDING> set_tracepoint
15366 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
15367 not installed on target
15372 This command can be abbreviated @code{info tp}.
15375 @node Listing Static Tracepoint Markers
15376 @subsection Listing Static Tracepoint Markers
15379 @kindex info static-tracepoint-markers
15380 @cindex information about static tracepoint markers
15381 @item info static-tracepoint-markers
15382 Display information about all static tracepoint markers defined in the
15385 For each marker, the following columns are printed:
15389 An incrementing counter, output to help readability. This is not a
15392 The marker ID, as reported by the target.
15393 @item Enabled or Disabled
15394 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
15395 that are not enabled.
15397 Where the marker is in your program, as a memory address.
15399 Where the marker is in the source for your program, as a file and line
15400 number. If the debug information included in the program does not
15401 allow @value{GDBN} to locate the source of the marker, this column
15402 will be left blank.
15406 In addition, the following information may be printed for each marker:
15410 User data passed to the tracing library by the marker call. In the
15411 UST backend, this is the format string passed as argument to the
15413 @item Static tracepoints probing the marker
15414 The list of static tracepoints attached to the marker.
15418 (@value{GDBP}) info static-tracepoint-markers
15419 Cnt ID Enb Address What
15420 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15421 Data: number1 %d number2 %d
15422 Probed by static tracepoints: #2
15423 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15429 @node Starting and Stopping Trace Experiments
15430 @subsection Starting and Stopping Trace Experiments
15433 @kindex tstart [ @var{notes} ]
15434 @cindex start a new trace experiment
15435 @cindex collected data discarded
15437 This command starts the trace experiment, and begins collecting data.
15438 It has the side effect of discarding all the data collected in the
15439 trace buffer during the previous trace experiment. If any arguments
15440 are supplied, they are taken as a note and stored with the trace
15441 experiment's state. The notes may be arbitrary text, and are
15442 especially useful with disconnected tracing in a multi-user context;
15443 the notes can explain what the trace is doing, supply user contact
15444 information, and so forth.
15446 @kindex tstop [ @var{notes} ]
15447 @cindex stop a running trace experiment
15449 This command stops the trace experiment. If any arguments are
15450 supplied, they are recorded with the experiment as a note. This is
15451 useful if you are stopping a trace started by someone else, for
15452 instance if the trace is interfering with the system's behavior and
15453 needs to be stopped quickly.
15455 @strong{Note}: a trace experiment and data collection may stop
15456 automatically if any tracepoint's passcount is reached
15457 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15460 @cindex status of trace data collection
15461 @cindex trace experiment, status of
15463 This command displays the status of the current trace data
15467 Here is an example of the commands we described so far:
15470 (@value{GDBP}) @b{trace gdb_c_test}
15471 (@value{GDBP}) @b{actions}
15472 Enter actions for tracepoint #1, one per line.
15473 > collect $regs,$locals,$args
15474 > while-stepping 11
15478 (@value{GDBP}) @b{tstart}
15479 [time passes @dots{}]
15480 (@value{GDBP}) @b{tstop}
15483 @anchor{disconnected tracing}
15484 @cindex disconnected tracing
15485 You can choose to continue running the trace experiment even if
15486 @value{GDBN} disconnects from the target, voluntarily or
15487 involuntarily. For commands such as @code{detach}, the debugger will
15488 ask what you want to do with the trace. But for unexpected
15489 terminations (@value{GDBN} crash, network outage), it would be
15490 unfortunate to lose hard-won trace data, so the variable
15491 @code{disconnected-tracing} lets you decide whether the trace should
15492 continue running without @value{GDBN}.
15495 @item set disconnected-tracing on
15496 @itemx set disconnected-tracing off
15497 @kindex set disconnected-tracing
15498 Choose whether a tracing run should continue to run if @value{GDBN}
15499 has disconnected from the target. Note that @code{detach} or
15500 @code{quit} will ask you directly what to do about a running trace no
15501 matter what this variable's setting, so the variable is mainly useful
15502 for handling unexpected situations, such as loss of the network.
15504 @item show disconnected-tracing
15505 @kindex show disconnected-tracing
15506 Show the current choice for disconnected tracing.
15510 When you reconnect to the target, the trace experiment may or may not
15511 still be running; it might have filled the trace buffer in the
15512 meantime, or stopped for one of the other reasons. If it is running,
15513 it will continue after reconnection.
15515 Upon reconnection, the target will upload information about the
15516 tracepoints in effect. @value{GDBN} will then compare that
15517 information to the set of tracepoints currently defined, and attempt
15518 to match them up, allowing for the possibility that the numbers may
15519 have changed due to creation and deletion in the meantime. If one of
15520 the target's tracepoints does not match any in @value{GDBN}, the
15521 debugger will create a new tracepoint, so that you have a number with
15522 which to specify that tracepoint. This matching-up process is
15523 necessarily heuristic, and it may result in useless tracepoints being
15524 created; you may simply delete them if they are of no use.
15526 @cindex circular trace buffer
15527 If your target agent supports a @dfn{circular trace buffer}, then you
15528 can run a trace experiment indefinitely without filling the trace
15529 buffer; when space runs out, the agent deletes already-collected trace
15530 frames, oldest first, until there is enough room to continue
15531 collecting. This is especially useful if your tracepoints are being
15532 hit too often, and your trace gets terminated prematurely because the
15533 buffer is full. To ask for a circular trace buffer, simply set
15534 @samp{circular-trace-buffer} to on. You can set this at any time,
15535 including during tracing; if the agent can do it, it will change
15536 buffer handling on the fly, otherwise it will not take effect until
15540 @item set circular-trace-buffer on
15541 @itemx set circular-trace-buffer off
15542 @kindex set circular-trace-buffer
15543 Choose whether a tracing run should use a linear or circular buffer
15544 for trace data. A linear buffer will not lose any trace data, but may
15545 fill up prematurely, while a circular buffer will discard old trace
15546 data, but it will have always room for the latest tracepoint hits.
15548 @item show circular-trace-buffer
15549 @kindex show circular-trace-buffer
15550 Show the current choice for the trace buffer. Note that this may not
15551 match the agent's current buffer handling, nor is it guaranteed to
15552 match the setting that might have been in effect during a past run,
15553 for instance if you are looking at frames from a trace file.
15558 @item set trace-buffer-size @var{n}
15559 @itemx set trace-buffer-size unlimited
15560 @kindex set trace-buffer-size
15561 Request that the target use a trace buffer of @var{n} bytes. Not all
15562 targets will honor the request; they may have a compiled-in size for
15563 the trace buffer, or some other limitation. Set to a value of
15564 @code{unlimited} or @code{-1} to let the target use whatever size it
15565 likes. This is also the default.
15567 @item show trace-buffer-size
15568 @kindex show trace-buffer-size
15569 Show the current requested size for the trace buffer. Note that this
15570 will only match the actual size if the target supports size-setting,
15571 and was able to handle the requested size. For instance, if the
15572 target can only change buffer size between runs, this variable will
15573 not reflect the change until the next run starts. Use @code{tstatus}
15574 to get a report of the actual buffer size.
15578 @item set trace-user @var{text}
15579 @kindex set trace-user
15581 @item show trace-user
15582 @kindex show trace-user
15584 @item set trace-notes @var{text}
15585 @kindex set trace-notes
15586 Set the trace run's notes.
15588 @item show trace-notes
15589 @kindex show trace-notes
15590 Show the trace run's notes.
15592 @item set trace-stop-notes @var{text}
15593 @kindex set trace-stop-notes
15594 Set the trace run's stop notes. The handling of the note is as for
15595 @code{tstop} arguments; the set command is convenient way to fix a
15596 stop note that is mistaken or incomplete.
15598 @item show trace-stop-notes
15599 @kindex show trace-stop-notes
15600 Show the trace run's stop notes.
15604 @node Tracepoint Restrictions
15605 @subsection Tracepoint Restrictions
15607 @cindex tracepoint restrictions
15608 There are a number of restrictions on the use of tracepoints. As
15609 described above, tracepoint data gathering occurs on the target
15610 without interaction from @value{GDBN}. Thus the full capabilities of
15611 the debugger are not available during data gathering, and then at data
15612 examination time, you will be limited by only having what was
15613 collected. The following items describe some common problems, but it
15614 is not exhaustive, and you may run into additional difficulties not
15620 Tracepoint expressions are intended to gather objects (lvalues). Thus
15621 the full flexibility of GDB's expression evaluator is not available.
15622 You cannot call functions, cast objects to aggregate types, access
15623 convenience variables or modify values (except by assignment to trace
15624 state variables). Some language features may implicitly call
15625 functions (for instance Objective-C fields with accessors), and therefore
15626 cannot be collected either.
15629 Collection of local variables, either individually or in bulk with
15630 @code{$locals} or @code{$args}, during @code{while-stepping} may
15631 behave erratically. The stepping action may enter a new scope (for
15632 instance by stepping into a function), or the location of the variable
15633 may change (for instance it is loaded into a register). The
15634 tracepoint data recorded uses the location information for the
15635 variables that is correct for the tracepoint location. When the
15636 tracepoint is created, it is not possible, in general, to determine
15637 where the steps of a @code{while-stepping} sequence will advance the
15638 program---particularly if a conditional branch is stepped.
15641 Collection of an incompletely-initialized or partially-destroyed object
15642 may result in something that @value{GDBN} cannot display, or displays
15643 in a misleading way.
15646 When @value{GDBN} displays a pointer to character it automatically
15647 dereferences the pointer to also display characters of the string
15648 being pointed to. However, collecting the pointer during tracing does
15649 not automatically collect the string. You need to explicitly
15650 dereference the pointer and provide size information if you want to
15651 collect not only the pointer, but the memory pointed to. For example,
15652 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15656 It is not possible to collect a complete stack backtrace at a
15657 tracepoint. Instead, you may collect the registers and a few hundred
15658 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15659 (adjust to use the name of the actual stack pointer register on your
15660 target architecture, and the amount of stack you wish to capture).
15661 Then the @code{backtrace} command will show a partial backtrace when
15662 using a trace frame. The number of stack frames that can be examined
15663 depends on the sizes of the frames in the collected stack. Note that
15664 if you ask for a block so large that it goes past the bottom of the
15665 stack, the target agent may report an error trying to read from an
15669 If you do not collect registers at a tracepoint, @value{GDBN} can
15670 infer that the value of @code{$pc} must be the same as the address of
15671 the tracepoint and use that when you are looking at a trace frame
15672 for that tracepoint. However, this cannot work if the tracepoint has
15673 multiple locations (for instance if it was set in a function that was
15674 inlined), or if it has a @code{while-stepping} loop. In those cases
15675 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15680 @node Analyze Collected Data
15681 @section Using the Collected Data
15683 After the tracepoint experiment ends, you use @value{GDBN} commands
15684 for examining the trace data. The basic idea is that each tracepoint
15685 collects a trace @dfn{snapshot} every time it is hit and another
15686 snapshot every time it single-steps. All these snapshots are
15687 consecutively numbered from zero and go into a buffer, and you can
15688 examine them later. The way you examine them is to @dfn{focus} on a
15689 specific trace snapshot. When the remote stub is focused on a trace
15690 snapshot, it will respond to all @value{GDBN} requests for memory and
15691 registers by reading from the buffer which belongs to that snapshot,
15692 rather than from @emph{real} memory or registers of the program being
15693 debugged. This means that @strong{all} @value{GDBN} commands
15694 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15695 behave as if we were currently debugging the program state as it was
15696 when the tracepoint occurred. Any requests for data that are not in
15697 the buffer will fail.
15700 * tfind:: How to select a trace snapshot
15701 * tdump:: How to display all data for a snapshot
15702 * save tracepoints:: How to save tracepoints for a future run
15706 @subsection @code{tfind @var{n}}
15709 @cindex select trace snapshot
15710 @cindex find trace snapshot
15711 The basic command for selecting a trace snapshot from the buffer is
15712 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15713 counting from zero. If no argument @var{n} is given, the next
15714 snapshot is selected.
15716 Here are the various forms of using the @code{tfind} command.
15720 Find the first snapshot in the buffer. This is a synonym for
15721 @code{tfind 0} (since 0 is the number of the first snapshot).
15724 Stop debugging trace snapshots, resume @emph{live} debugging.
15727 Same as @samp{tfind none}.
15730 No argument means find the next trace snapshot or find the first
15731 one if no trace snapshot is selected.
15734 Find the previous trace snapshot before the current one. This permits
15735 retracing earlier steps.
15737 @item tfind tracepoint @var{num}
15738 Find the next snapshot associated with tracepoint @var{num}. Search
15739 proceeds forward from the last examined trace snapshot. If no
15740 argument @var{num} is given, it means find the next snapshot collected
15741 for the same tracepoint as the current snapshot.
15743 @item tfind pc @var{addr}
15744 Find the next snapshot associated with the value @var{addr} of the
15745 program counter. Search proceeds forward from the last examined trace
15746 snapshot. If no argument @var{addr} is given, it means find the next
15747 snapshot with the same value of PC as the current snapshot.
15749 @item tfind outside @var{addr1}, @var{addr2}
15750 Find the next snapshot whose PC is outside the given range of
15751 addresses (exclusive).
15753 @item tfind range @var{addr1}, @var{addr2}
15754 Find the next snapshot whose PC is between @var{addr1} and
15755 @var{addr2} (inclusive).
15757 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15758 Find the next snapshot associated with the source line @var{n}. If
15759 the optional argument @var{file} is given, refer to line @var{n} in
15760 that source file. Search proceeds forward from the last examined
15761 trace snapshot. If no argument @var{n} is given, it means find the
15762 next line other than the one currently being examined; thus saying
15763 @code{tfind line} repeatedly can appear to have the same effect as
15764 stepping from line to line in a @emph{live} debugging session.
15767 The default arguments for the @code{tfind} commands are specifically
15768 designed to make it easy to scan through the trace buffer. For
15769 instance, @code{tfind} with no argument selects the next trace
15770 snapshot, and @code{tfind -} with no argument selects the previous
15771 trace snapshot. So, by giving one @code{tfind} command, and then
15772 simply hitting @key{RET} repeatedly you can examine all the trace
15773 snapshots in order. Or, by saying @code{tfind -} and then hitting
15774 @key{RET} repeatedly you can examine the snapshots in reverse order.
15775 The @code{tfind line} command with no argument selects the snapshot
15776 for the next source line executed. The @code{tfind pc} command with
15777 no argument selects the next snapshot with the same program counter
15778 (PC) as the current frame. The @code{tfind tracepoint} command with
15779 no argument selects the next trace snapshot collected by the same
15780 tracepoint as the current one.
15782 In addition to letting you scan through the trace buffer manually,
15783 these commands make it easy to construct @value{GDBN} scripts that
15784 scan through the trace buffer and print out whatever collected data
15785 you are interested in. Thus, if we want to examine the PC, FP, and SP
15786 registers from each trace frame in the buffer, we can say this:
15789 (@value{GDBP}) @b{tfind start}
15790 (@value{GDBP}) @b{while ($trace_frame != -1)}
15791 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15792 $trace_frame, $pc, $sp, $fp
15796 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15797 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15798 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15799 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15800 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15801 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15802 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15803 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15804 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15805 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15806 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15809 Or, if we want to examine the variable @code{X} at each source line in
15813 (@value{GDBP}) @b{tfind start}
15814 (@value{GDBP}) @b{while ($trace_frame != -1)}
15815 > printf "Frame %d, X == %d\n", $trace_frame, X
15825 @subsection @code{tdump}
15827 @cindex dump all data collected at tracepoint
15828 @cindex tracepoint data, display
15830 This command takes no arguments. It prints all the data collected at
15831 the current trace snapshot.
15834 (@value{GDBP}) @b{trace 444}
15835 (@value{GDBP}) @b{actions}
15836 Enter actions for tracepoint #2, one per line:
15837 > collect $regs, $locals, $args, gdb_long_test
15840 (@value{GDBP}) @b{tstart}
15842 (@value{GDBP}) @b{tfind line 444}
15843 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15845 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15847 (@value{GDBP}) @b{tdump}
15848 Data collected at tracepoint 2, trace frame 1:
15849 d0 0xc4aa0085 -995491707
15853 d4 0x71aea3d 119204413
15856 d7 0x380035 3670069
15857 a0 0x19e24a 1696330
15858 a1 0x3000668 50333288
15860 a3 0x322000 3284992
15861 a4 0x3000698 50333336
15862 a5 0x1ad3cc 1758156
15863 fp 0x30bf3c 0x30bf3c
15864 sp 0x30bf34 0x30bf34
15866 pc 0x20b2c8 0x20b2c8
15870 p = 0x20e5b4 "gdb-test"
15877 gdb_long_test = 17 '\021'
15882 @code{tdump} works by scanning the tracepoint's current collection
15883 actions and printing the value of each expression listed. So
15884 @code{tdump} can fail, if after a run, you change the tracepoint's
15885 actions to mention variables that were not collected during the run.
15887 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15888 uses the collected value of @code{$pc} to distinguish between trace
15889 frames that were collected at the tracepoint hit, and frames that were
15890 collected while stepping. This allows it to correctly choose whether
15891 to display the basic list of collections, or the collections from the
15892 body of the while-stepping loop. However, if @code{$pc} was not collected,
15893 then @code{tdump} will always attempt to dump using the basic collection
15894 list, and may fail if a while-stepping frame does not include all the
15895 same data that is collected at the tracepoint hit.
15896 @c This is getting pretty arcane, example would be good.
15898 @node save tracepoints
15899 @subsection @code{save tracepoints @var{filename}}
15900 @kindex save tracepoints
15901 @kindex save-tracepoints
15902 @cindex save tracepoints for future sessions
15904 This command saves all current tracepoint definitions together with
15905 their actions and passcounts, into a file @file{@var{filename}}
15906 suitable for use in a later debugging session. To read the saved
15907 tracepoint definitions, use the @code{source} command (@pxref{Command
15908 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15909 alias for @w{@code{save tracepoints}}
15911 @node Tracepoint Variables
15912 @section Convenience Variables for Tracepoints
15913 @cindex tracepoint variables
15914 @cindex convenience variables for tracepoints
15917 @vindex $trace_frame
15918 @item (int) $trace_frame
15919 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15920 snapshot is selected.
15922 @vindex $tracepoint
15923 @item (int) $tracepoint
15924 The tracepoint for the current trace snapshot.
15926 @vindex $trace_line
15927 @item (int) $trace_line
15928 The line number for the current trace snapshot.
15930 @vindex $trace_file
15931 @item (char []) $trace_file
15932 The source file for the current trace snapshot.
15934 @vindex $trace_func
15935 @item (char []) $trace_func
15936 The name of the function containing @code{$tracepoint}.
15939 Note: @code{$trace_file} is not suitable for use in @code{printf},
15940 use @code{output} instead.
15942 Here's a simple example of using these convenience variables for
15943 stepping through all the trace snapshots and printing some of their
15944 data. Note that these are not the same as trace state variables,
15945 which are managed by the target.
15948 (@value{GDBP}) @b{tfind start}
15950 (@value{GDBP}) @b{while $trace_frame != -1}
15951 > output $trace_file
15952 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15958 @section Using Trace Files
15959 @cindex trace files
15961 In some situations, the target running a trace experiment may no
15962 longer be available; perhaps it crashed, or the hardware was needed
15963 for a different activity. To handle these cases, you can arrange to
15964 dump the trace data into a file, and later use that file as a source
15965 of trace data, via the @code{target tfile} command.
15970 @item tsave [ -r ] @var{filename}
15971 @itemx tsave [-ctf] @var{dirname}
15972 Save the trace data to @var{filename}. By default, this command
15973 assumes that @var{filename} refers to the host filesystem, so if
15974 necessary @value{GDBN} will copy raw trace data up from the target and
15975 then save it. If the target supports it, you can also supply the
15976 optional argument @code{-r} (``remote'') to direct the target to save
15977 the data directly into @var{filename} in its own filesystem, which may be
15978 more efficient if the trace buffer is very large. (Note, however, that
15979 @code{target tfile} can only read from files accessible to the host.)
15980 By default, this command will save trace frame in tfile format.
15981 You can supply the optional argument @code{-ctf} to save data in CTF
15982 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15983 that can be shared by multiple debugging and tracing tools. Please go to
15984 @indicateurl{http://www.efficios.com/ctf} to get more information.
15986 @kindex target tfile
15990 @item target tfile @var{filename}
15991 @itemx target ctf @var{dirname}
15992 Use the file named @var{filename} or directory named @var{dirname} as
15993 a source of trace data. Commands that examine data work as they do with
15994 a live target, but it is not possible to run any new trace experiments.
15995 @code{tstatus} will report the state of the trace run at the moment
15996 the data was saved, as well as the current trace frame you are examining.
15997 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
16001 (@value{GDBP}) target ctf ctf.ctf
16002 (@value{GDBP}) tfind
16003 Found trace frame 0, tracepoint 2
16004 39 ++a; /* set tracepoint 1 here */
16005 (@value{GDBP}) tdump
16006 Data collected at tracepoint 2, trace frame 0:
16010 c = @{"123", "456", "789", "123", "456", "789"@}
16011 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
16019 @chapter Debugging Programs That Use Overlays
16022 If your program is too large to fit completely in your target system's
16023 memory, you can sometimes use @dfn{overlays} to work around this
16024 problem. @value{GDBN} provides some support for debugging programs that
16028 * How Overlays Work:: A general explanation of overlays.
16029 * Overlay Commands:: Managing overlays in @value{GDBN}.
16030 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
16031 mapped by asking the inferior.
16032 * Overlay Sample Program:: A sample program using overlays.
16035 @node How Overlays Work
16036 @section How Overlays Work
16037 @cindex mapped overlays
16038 @cindex unmapped overlays
16039 @cindex load address, overlay's
16040 @cindex mapped address
16041 @cindex overlay area
16043 Suppose you have a computer whose instruction address space is only 64
16044 kilobytes long, but which has much more memory which can be accessed by
16045 other means: special instructions, segment registers, or memory
16046 management hardware, for example. Suppose further that you want to
16047 adapt a program which is larger than 64 kilobytes to run on this system.
16049 One solution is to identify modules of your program which are relatively
16050 independent, and need not call each other directly; call these modules
16051 @dfn{overlays}. Separate the overlays from the main program, and place
16052 their machine code in the larger memory. Place your main program in
16053 instruction memory, but leave at least enough space there to hold the
16054 largest overlay as well.
16056 Now, to call a function located in an overlay, you must first copy that
16057 overlay's machine code from the large memory into the space set aside
16058 for it in the instruction memory, and then jump to its entry point
16061 @c NB: In the below the mapped area's size is greater or equal to the
16062 @c size of all overlays. This is intentional to remind the developer
16063 @c that overlays don't necessarily need to be the same size.
16067 Data Instruction Larger
16068 Address Space Address Space Address Space
16069 +-----------+ +-----------+ +-----------+
16071 +-----------+ +-----------+ +-----------+<-- overlay 1
16072 | program | | main | .----| overlay 1 | load address
16073 | variables | | program | | +-----------+
16074 | and heap | | | | | |
16075 +-----------+ | | | +-----------+<-- overlay 2
16076 | | +-----------+ | | | load address
16077 +-----------+ | | | .-| overlay 2 |
16079 mapped --->+-----------+ | | +-----------+
16080 address | | | | | |
16081 | overlay | <-' | | |
16082 | area | <---' +-----------+<-- overlay 3
16083 | | <---. | | load address
16084 +-----------+ `--| overlay 3 |
16091 @anchor{A code overlay}A code overlay
16095 The diagram (@pxref{A code overlay}) shows a system with separate data
16096 and instruction address spaces. To map an overlay, the program copies
16097 its code from the larger address space to the instruction address space.
16098 Since the overlays shown here all use the same mapped address, only one
16099 may be mapped at a time. For a system with a single address space for
16100 data and instructions, the diagram would be similar, except that the
16101 program variables and heap would share an address space with the main
16102 program and the overlay area.
16104 An overlay loaded into instruction memory and ready for use is called a
16105 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
16106 instruction memory. An overlay not present (or only partially present)
16107 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
16108 is its address in the larger memory. The mapped address is also called
16109 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
16110 called the @dfn{load memory address}, or @dfn{LMA}.
16112 Unfortunately, overlays are not a completely transparent way to adapt a
16113 program to limited instruction memory. They introduce a new set of
16114 global constraints you must keep in mind as you design your program:
16119 Before calling or returning to a function in an overlay, your program
16120 must make sure that overlay is actually mapped. Otherwise, the call or
16121 return will transfer control to the right address, but in the wrong
16122 overlay, and your program will probably crash.
16125 If the process of mapping an overlay is expensive on your system, you
16126 will need to choose your overlays carefully to minimize their effect on
16127 your program's performance.
16130 The executable file you load onto your system must contain each
16131 overlay's instructions, appearing at the overlay's load address, not its
16132 mapped address. However, each overlay's instructions must be relocated
16133 and its symbols defined as if the overlay were at its mapped address.
16134 You can use GNU linker scripts to specify different load and relocation
16135 addresses for pieces of your program; see @ref{Overlay Description,,,
16136 ld.info, Using ld: the GNU linker}.
16139 The procedure for loading executable files onto your system must be able
16140 to load their contents into the larger address space as well as the
16141 instruction and data spaces.
16145 The overlay system described above is rather simple, and could be
16146 improved in many ways:
16151 If your system has suitable bank switch registers or memory management
16152 hardware, you could use those facilities to make an overlay's load area
16153 contents simply appear at their mapped address in instruction space.
16154 This would probably be faster than copying the overlay to its mapped
16155 area in the usual way.
16158 If your overlays are small enough, you could set aside more than one
16159 overlay area, and have more than one overlay mapped at a time.
16162 You can use overlays to manage data, as well as instructions. In
16163 general, data overlays are even less transparent to your design than
16164 code overlays: whereas code overlays only require care when you call or
16165 return to functions, data overlays require care every time you access
16166 the data. Also, if you change the contents of a data overlay, you
16167 must copy its contents back out to its load address before you can copy a
16168 different data overlay into the same mapped area.
16173 @node Overlay Commands
16174 @section Overlay Commands
16176 To use @value{GDBN}'s overlay support, each overlay in your program must
16177 correspond to a separate section of the executable file. The section's
16178 virtual memory address and load memory address must be the overlay's
16179 mapped and load addresses. Identifying overlays with sections allows
16180 @value{GDBN} to determine the appropriate address of a function or
16181 variable, depending on whether the overlay is mapped or not.
16183 @value{GDBN}'s overlay commands all start with the word @code{overlay};
16184 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
16189 Disable @value{GDBN}'s overlay support. When overlay support is
16190 disabled, @value{GDBN} assumes that all functions and variables are
16191 always present at their mapped addresses. By default, @value{GDBN}'s
16192 overlay support is disabled.
16194 @item overlay manual
16195 @cindex manual overlay debugging
16196 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
16197 relies on you to tell it which overlays are mapped, and which are not,
16198 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
16199 commands described below.
16201 @item overlay map-overlay @var{overlay}
16202 @itemx overlay map @var{overlay}
16203 @cindex map an overlay
16204 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
16205 be the name of the object file section containing the overlay. When an
16206 overlay is mapped, @value{GDBN} assumes it can find the overlay's
16207 functions and variables at their mapped addresses. @value{GDBN} assumes
16208 that any other overlays whose mapped ranges overlap that of
16209 @var{overlay} are now unmapped.
16211 @item overlay unmap-overlay @var{overlay}
16212 @itemx overlay unmap @var{overlay}
16213 @cindex unmap an overlay
16214 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
16215 must be the name of the object file section containing the overlay.
16216 When an overlay is unmapped, @value{GDBN} assumes it can find the
16217 overlay's functions and variables at their load addresses.
16220 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
16221 consults a data structure the overlay manager maintains in the inferior
16222 to see which overlays are mapped. For details, see @ref{Automatic
16223 Overlay Debugging}.
16225 @item overlay load-target
16226 @itemx overlay load
16227 @cindex reloading the overlay table
16228 Re-read the overlay table from the inferior. Normally, @value{GDBN}
16229 re-reads the table @value{GDBN} automatically each time the inferior
16230 stops, so this command should only be necessary if you have changed the
16231 overlay mapping yourself using @value{GDBN}. This command is only
16232 useful when using automatic overlay debugging.
16234 @item overlay list-overlays
16235 @itemx overlay list
16236 @cindex listing mapped overlays
16237 Display a list of the overlays currently mapped, along with their mapped
16238 addresses, load addresses, and sizes.
16242 Normally, when @value{GDBN} prints a code address, it includes the name
16243 of the function the address falls in:
16246 (@value{GDBP}) print main
16247 $3 = @{int ()@} 0x11a0 <main>
16250 When overlay debugging is enabled, @value{GDBN} recognizes code in
16251 unmapped overlays, and prints the names of unmapped functions with
16252 asterisks around them. For example, if @code{foo} is a function in an
16253 unmapped overlay, @value{GDBN} prints it this way:
16256 (@value{GDBP}) overlay list
16257 No sections are mapped.
16258 (@value{GDBP}) print foo
16259 $5 = @{int (int)@} 0x100000 <*foo*>
16262 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
16266 (@value{GDBP}) overlay list
16267 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
16268 mapped at 0x1016 - 0x104a
16269 (@value{GDBP}) print foo
16270 $6 = @{int (int)@} 0x1016 <foo>
16273 When overlay debugging is enabled, @value{GDBN} can find the correct
16274 address for functions and variables in an overlay, whether or not the
16275 overlay is mapped. This allows most @value{GDBN} commands, like
16276 @code{break} and @code{disassemble}, to work normally, even on unmapped
16277 code. However, @value{GDBN}'s breakpoint support has some limitations:
16281 @cindex breakpoints in overlays
16282 @cindex overlays, setting breakpoints in
16283 You can set breakpoints in functions in unmapped overlays, as long as
16284 @value{GDBN} can write to the overlay at its load address.
16286 @value{GDBN} can not set hardware or simulator-based breakpoints in
16287 unmapped overlays. However, if you set a breakpoint at the end of your
16288 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
16289 you are using manual overlay management), @value{GDBN} will re-set its
16290 breakpoints properly.
16294 @node Automatic Overlay Debugging
16295 @section Automatic Overlay Debugging
16296 @cindex automatic overlay debugging
16298 @value{GDBN} can automatically track which overlays are mapped and which
16299 are not, given some simple co-operation from the overlay manager in the
16300 inferior. If you enable automatic overlay debugging with the
16301 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
16302 looks in the inferior's memory for certain variables describing the
16303 current state of the overlays.
16305 Here are the variables your overlay manager must define to support
16306 @value{GDBN}'s automatic overlay debugging:
16310 @item @code{_ovly_table}:
16311 This variable must be an array of the following structures:
16316 /* The overlay's mapped address. */
16319 /* The size of the overlay, in bytes. */
16320 unsigned long size;
16322 /* The overlay's load address. */
16325 /* Non-zero if the overlay is currently mapped;
16327 unsigned long mapped;
16331 @item @code{_novlys}:
16332 This variable must be a four-byte signed integer, holding the total
16333 number of elements in @code{_ovly_table}.
16337 To decide whether a particular overlay is mapped or not, @value{GDBN}
16338 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
16339 @code{lma} members equal the VMA and LMA of the overlay's section in the
16340 executable file. When @value{GDBN} finds a matching entry, it consults
16341 the entry's @code{mapped} member to determine whether the overlay is
16344 In addition, your overlay manager may define a function called
16345 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
16346 will silently set a breakpoint there. If the overlay manager then
16347 calls this function whenever it has changed the overlay table, this
16348 will enable @value{GDBN} to accurately keep track of which overlays
16349 are in program memory, and update any breakpoints that may be set
16350 in overlays. This will allow breakpoints to work even if the
16351 overlays are kept in ROM or other non-writable memory while they
16352 are not being executed.
16354 @node Overlay Sample Program
16355 @section Overlay Sample Program
16356 @cindex overlay example program
16358 When linking a program which uses overlays, you must place the overlays
16359 at their load addresses, while relocating them to run at their mapped
16360 addresses. To do this, you must write a linker script (@pxref{Overlay
16361 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
16362 since linker scripts are specific to a particular host system, target
16363 architecture, and target memory layout, this manual cannot provide
16364 portable sample code demonstrating @value{GDBN}'s overlay support.
16366 However, the @value{GDBN} source distribution does contain an overlaid
16367 program, with linker scripts for a few systems, as part of its test
16368 suite. The program consists of the following files from
16369 @file{gdb/testsuite/gdb.base}:
16373 The main program file.
16375 A simple overlay manager, used by @file{overlays.c}.
16380 Overlay modules, loaded and used by @file{overlays.c}.
16383 Linker scripts for linking the test program on the @code{d10v-elf}
16384 and @code{m32r-elf} targets.
16387 You can build the test program using the @code{d10v-elf} GCC
16388 cross-compiler like this:
16391 $ d10v-elf-gcc -g -c overlays.c
16392 $ d10v-elf-gcc -g -c ovlymgr.c
16393 $ d10v-elf-gcc -g -c foo.c
16394 $ d10v-elf-gcc -g -c bar.c
16395 $ d10v-elf-gcc -g -c baz.c
16396 $ d10v-elf-gcc -g -c grbx.c
16397 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
16398 baz.o grbx.o -Wl,-Td10v.ld -o overlays
16401 The build process is identical for any other architecture, except that
16402 you must substitute the appropriate compiler and linker script for the
16403 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
16407 @chapter Using @value{GDBN} with Different Languages
16410 Although programming languages generally have common aspects, they are
16411 rarely expressed in the same manner. For instance, in ANSI C,
16412 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
16413 Modula-2, it is accomplished by @code{p^}. Values can also be
16414 represented (and displayed) differently. Hex numbers in C appear as
16415 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
16417 @cindex working language
16418 Language-specific information is built into @value{GDBN} for some languages,
16419 allowing you to express operations like the above in your program's
16420 native language, and allowing @value{GDBN} to output values in a manner
16421 consistent with the syntax of your program's native language. The
16422 language you use to build expressions is called the @dfn{working
16426 * Setting:: Switching between source languages
16427 * Show:: Displaying the language
16428 * Checks:: Type and range checks
16429 * Supported Languages:: Supported languages
16430 * Unsupported Languages:: Unsupported languages
16434 @section Switching Between Source Languages
16436 There are two ways to control the working language---either have @value{GDBN}
16437 set it automatically, or select it manually yourself. You can use the
16438 @code{set language} command for either purpose. On startup, @value{GDBN}
16439 defaults to setting the language automatically. The working language is
16440 used to determine how expressions you type are interpreted, how values
16443 In addition to the working language, every source file that
16444 @value{GDBN} knows about has its own working language. For some object
16445 file formats, the compiler might indicate which language a particular
16446 source file is in. However, most of the time @value{GDBN} infers the
16447 language from the name of the file. The language of a source file
16448 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16449 show each frame appropriately for its own language. There is no way to
16450 set the language of a source file from within @value{GDBN}, but you can
16451 set the language associated with a filename extension. @xref{Show, ,
16452 Displaying the Language}.
16454 This is most commonly a problem when you use a program, such
16455 as @code{cfront} or @code{f2c}, that generates C but is written in
16456 another language. In that case, make the
16457 program use @code{#line} directives in its C output; that way
16458 @value{GDBN} will know the correct language of the source code of the original
16459 program, and will display that source code, not the generated C code.
16462 * Filenames:: Filename extensions and languages.
16463 * Manually:: Setting the working language manually
16464 * Automatically:: Having @value{GDBN} infer the source language
16468 @subsection List of Filename Extensions and Languages
16470 If a source file name ends in one of the following extensions, then
16471 @value{GDBN} infers that its language is the one indicated.
16489 C@t{++} source file
16495 Objective-C source file
16499 Fortran source file
16502 Modula-2 source file
16506 Assembler source file. This actually behaves almost like C, but
16507 @value{GDBN} does not skip over function prologues when stepping.
16510 In addition, you may set the language associated with a filename
16511 extension. @xref{Show, , Displaying the Language}.
16514 @subsection Setting the Working Language
16516 If you allow @value{GDBN} to set the language automatically,
16517 expressions are interpreted the same way in your debugging session and
16520 @kindex set language
16521 If you wish, you may set the language manually. To do this, issue the
16522 command @samp{set language @var{lang}}, where @var{lang} is the name of
16523 a language, such as
16524 @code{c} or @code{modula-2}.
16525 For a list of the supported languages, type @samp{set language}.
16527 Setting the language manually prevents @value{GDBN} from updating the working
16528 language automatically. This can lead to confusion if you try
16529 to debug a program when the working language is not the same as the
16530 source language, when an expression is acceptable to both
16531 languages---but means different things. For instance, if the current
16532 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16540 might not have the effect you intended. In C, this means to add
16541 @code{b} and @code{c} and place the result in @code{a}. The result
16542 printed would be the value of @code{a}. In Modula-2, this means to compare
16543 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16545 @node Automatically
16546 @subsection Having @value{GDBN} Infer the Source Language
16548 To have @value{GDBN} set the working language automatically, use
16549 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16550 then infers the working language. That is, when your program stops in a
16551 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16552 working language to the language recorded for the function in that
16553 frame. If the language for a frame is unknown (that is, if the function
16554 or block corresponding to the frame was defined in a source file that
16555 does not have a recognized extension), the current working language is
16556 not changed, and @value{GDBN} issues a warning.
16558 This may not seem necessary for most programs, which are written
16559 entirely in one source language. However, program modules and libraries
16560 written in one source language can be used by a main program written in
16561 a different source language. Using @samp{set language auto} in this
16562 case frees you from having to set the working language manually.
16565 @section Displaying the Language
16567 The following commands help you find out which language is the
16568 working language, and also what language source files were written in.
16571 @item show language
16572 @anchor{show language}
16573 @kindex show language
16574 Display the current working language. This is the
16575 language you can use with commands such as @code{print} to
16576 build and compute expressions that may involve variables in your program.
16579 @kindex info frame@r{, show the source language}
16580 Display the source language for this frame. This language becomes the
16581 working language if you use an identifier from this frame.
16582 @xref{Frame Info, ,Information about a Frame}, to identify the other
16583 information listed here.
16586 @kindex info source@r{, show the source language}
16587 Display the source language of this source file.
16588 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16589 information listed here.
16592 In unusual circumstances, you may have source files with extensions
16593 not in the standard list. You can then set the extension associated
16594 with a language explicitly:
16597 @item set extension-language @var{ext} @var{language}
16598 @kindex set extension-language
16599 Tell @value{GDBN} that source files with extension @var{ext} are to be
16600 assumed as written in the source language @var{language}.
16602 @item info extensions
16603 @kindex info extensions
16604 List all the filename extensions and the associated languages.
16608 @section Type and Range Checking
16610 Some languages are designed to guard you against making seemingly common
16611 errors through a series of compile- and run-time checks. These include
16612 checking the type of arguments to functions and operators and making
16613 sure mathematical overflows are caught at run time. Checks such as
16614 these help to ensure a program's correctness once it has been compiled
16615 by eliminating type mismatches and providing active checks for range
16616 errors when your program is running.
16618 By default @value{GDBN} checks for these errors according to the
16619 rules of the current source language. Although @value{GDBN} does not check
16620 the statements in your program, it can check expressions entered directly
16621 into @value{GDBN} for evaluation via the @code{print} command, for example.
16624 * Type Checking:: An overview of type checking
16625 * Range Checking:: An overview of range checking
16628 @cindex type checking
16629 @cindex checks, type
16630 @node Type Checking
16631 @subsection An Overview of Type Checking
16633 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16634 arguments to operators and functions have to be of the correct type,
16635 otherwise an error occurs. These checks prevent type mismatch
16636 errors from ever causing any run-time problems. For example,
16639 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16641 (@value{GDBP}) print obj.my_method (0)
16644 (@value{GDBP}) print obj.my_method (0x1234)
16645 Cannot resolve method klass::my_method to any overloaded instance
16648 The second example fails because in C@t{++} the integer constant
16649 @samp{0x1234} is not type-compatible with the pointer parameter type.
16651 For the expressions you use in @value{GDBN} commands, you can tell
16652 @value{GDBN} to not enforce strict type checking or
16653 to treat any mismatches as errors and abandon the expression;
16654 When type checking is disabled, @value{GDBN} successfully evaluates
16655 expressions like the second example above.
16657 Even if type checking is off, there may be other reasons
16658 related to type that prevent @value{GDBN} from evaluating an expression.
16659 For instance, @value{GDBN} does not know how to add an @code{int} and
16660 a @code{struct foo}. These particular type errors have nothing to do
16661 with the language in use and usually arise from expressions which make
16662 little sense to evaluate anyway.
16664 @value{GDBN} provides some additional commands for controlling type checking:
16666 @kindex set check type
16667 @kindex show check type
16669 @item set check type on
16670 @itemx set check type off
16671 Set strict type checking on or off. If any type mismatches occur in
16672 evaluating an expression while type checking is on, @value{GDBN} prints a
16673 message and aborts evaluation of the expression.
16675 @item show check type
16676 Show the current setting of type checking and whether @value{GDBN}
16677 is enforcing strict type checking rules.
16680 @cindex range checking
16681 @cindex checks, range
16682 @node Range Checking
16683 @subsection An Overview of Range Checking
16685 In some languages (such as Modula-2), it is an error to exceed the
16686 bounds of a type; this is enforced with run-time checks. Such range
16687 checking is meant to ensure program correctness by making sure
16688 computations do not overflow, or indices on an array element access do
16689 not exceed the bounds of the array.
16691 For expressions you use in @value{GDBN} commands, you can tell
16692 @value{GDBN} to treat range errors in one of three ways: ignore them,
16693 always treat them as errors and abandon the expression, or issue
16694 warnings but evaluate the expression anyway.
16696 A range error can result from numerical overflow, from exceeding an
16697 array index bound, or when you type a constant that is not a member
16698 of any type. Some languages, however, do not treat overflows as an
16699 error. In many implementations of C, mathematical overflow causes the
16700 result to ``wrap around'' to lower values---for example, if @var{m} is
16701 the largest integer value, and @var{s} is the smallest, then
16704 @var{m} + 1 @result{} @var{s}
16707 This, too, is specific to individual languages, and in some cases
16708 specific to individual compilers or machines. @xref{Supported Languages, ,
16709 Supported Languages}, for further details on specific languages.
16711 @value{GDBN} provides some additional commands for controlling the range checker:
16713 @kindex set check range
16714 @kindex show check range
16716 @item set check range auto
16717 Set range checking on or off based on the current working language.
16718 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16721 @item set check range on
16722 @itemx set check range off
16723 Set range checking on or off, overriding the default setting for the
16724 current working language. A warning is issued if the setting does not
16725 match the language default. If a range error occurs and range checking is on,
16726 then a message is printed and evaluation of the expression is aborted.
16728 @item set check range warn
16729 Output messages when the @value{GDBN} range checker detects a range error,
16730 but attempt to evaluate the expression anyway. Evaluating the
16731 expression may still be impossible for other reasons, such as accessing
16732 memory that the process does not own (a typical example from many Unix
16735 @item show check range
16736 Show the current setting of the range checker, and whether or not it is
16737 being set automatically by @value{GDBN}.
16740 @node Supported Languages
16741 @section Supported Languages
16743 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16744 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16745 @c This is false ...
16746 Some @value{GDBN} features may be used in expressions regardless of the
16747 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16748 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16749 ,Expressions}) can be used with the constructs of any supported
16752 The following sections detail to what degree each source language is
16753 supported by @value{GDBN}. These sections are not meant to be language
16754 tutorials or references, but serve only as a reference guide to what the
16755 @value{GDBN} expression parser accepts, and what input and output
16756 formats should look like for different languages. There are many good
16757 books written on each of these languages; please look to these for a
16758 language reference or tutorial.
16761 * C:: C and C@t{++}
16764 * Objective-C:: Objective-C
16765 * OpenCL C:: OpenCL C
16766 * Fortran:: Fortran
16769 * Modula-2:: Modula-2
16774 @subsection C and C@t{++}
16776 @cindex C and C@t{++}
16777 @cindex expressions in C or C@t{++}
16779 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16780 to both languages. Whenever this is the case, we discuss those languages
16784 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16785 @cindex @sc{gnu} C@t{++}
16786 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16787 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16788 effectively, you must compile your C@t{++} programs with a supported
16789 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16790 compiler (@code{aCC}).
16793 * C Operators:: C and C@t{++} operators
16794 * C Constants:: C and C@t{++} constants
16795 * C Plus Plus Expressions:: C@t{++} expressions
16796 * C Defaults:: Default settings for C and C@t{++}
16797 * C Checks:: C and C@t{++} type and range checks
16798 * Debugging C:: @value{GDBN} and C
16799 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16800 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16804 @subsubsection C and C@t{++} Operators
16806 @cindex C and C@t{++} operators
16808 Operators must be defined on values of specific types. For instance,
16809 @code{+} is defined on numbers, but not on structures. Operators are
16810 often defined on groups of types.
16812 For the purposes of C and C@t{++}, the following definitions hold:
16817 @emph{Integral types} include @code{int} with any of its storage-class
16818 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16821 @emph{Floating-point types} include @code{float}, @code{double}, and
16822 @code{long double} (if supported by the target platform).
16825 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16828 @emph{Scalar types} include all of the above.
16833 The following operators are supported. They are listed here
16834 in order of increasing precedence:
16838 The comma or sequencing operator. Expressions in a comma-separated list
16839 are evaluated from left to right, with the result of the entire
16840 expression being the last expression evaluated.
16843 Assignment. The value of an assignment expression is the value
16844 assigned. Defined on scalar types.
16847 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16848 and translated to @w{@code{@var{a} = @var{a op b}}}.
16849 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16850 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16851 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16854 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16855 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16856 should be of an integral type.
16859 Logical @sc{or}. Defined on integral types.
16862 Logical @sc{and}. Defined on integral types.
16865 Bitwise @sc{or}. Defined on integral types.
16868 Bitwise exclusive-@sc{or}. Defined on integral types.
16871 Bitwise @sc{and}. Defined on integral types.
16874 Equality and inequality. Defined on scalar types. The value of these
16875 expressions is 0 for false and non-zero for true.
16877 @item <@r{, }>@r{, }<=@r{, }>=
16878 Less than, greater than, less than or equal, greater than or equal.
16879 Defined on scalar types. The value of these expressions is 0 for false
16880 and non-zero for true.
16883 left shift, and right shift. Defined on integral types.
16886 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16889 Addition and subtraction. Defined on integral types, floating-point types and
16892 @item *@r{, }/@r{, }%
16893 Multiplication, division, and modulus. Multiplication and division are
16894 defined on integral and floating-point types. Modulus is defined on
16898 Increment and decrement. When appearing before a variable, the
16899 operation is performed before the variable is used in an expression;
16900 when appearing after it, the variable's value is used before the
16901 operation takes place.
16904 Pointer dereferencing. Defined on pointer types. Same precedence as
16908 Address operator. Defined on variables. Same precedence as @code{++}.
16910 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16911 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16912 to examine the address
16913 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16917 Negative. Defined on integral and floating-point types. Same
16918 precedence as @code{++}.
16921 Logical negation. Defined on integral types. Same precedence as
16925 Bitwise complement operator. Defined on integral types. Same precedence as
16930 Structure member, and pointer-to-structure member. For convenience,
16931 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16932 pointer based on the stored type information.
16933 Defined on @code{struct} and @code{union} data.
16936 Dereferences of pointers to members.
16939 Array indexing. @code{@var{a}[@var{i}]} is defined as
16940 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16943 Function parameter list. Same precedence as @code{->}.
16946 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16947 and @code{class} types.
16950 Doubled colons also represent the @value{GDBN} scope operator
16951 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16955 If an operator is redefined in the user code, @value{GDBN} usually
16956 attempts to invoke the redefined version instead of using the operator's
16957 predefined meaning.
16960 @subsubsection C and C@t{++} Constants
16962 @cindex C and C@t{++} constants
16964 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16969 Integer constants are a sequence of digits. Octal constants are
16970 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16971 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16972 @samp{l}, specifying that the constant should be treated as a
16976 Floating point constants are a sequence of digits, followed by a decimal
16977 point, followed by a sequence of digits, and optionally followed by an
16978 exponent. An exponent is of the form:
16979 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16980 sequence of digits. The @samp{+} is optional for positive exponents.
16981 A floating-point constant may also end with a letter @samp{f} or
16982 @samp{F}, specifying that the constant should be treated as being of
16983 the @code{float} (as opposed to the default @code{double}) type; or with
16984 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16988 Enumerated constants consist of enumerated identifiers, or their
16989 integral equivalents.
16992 Character constants are a single character surrounded by single quotes
16993 (@code{'}), or a number---the ordinal value of the corresponding character
16994 (usually its @sc{ascii} value). Within quotes, the single character may
16995 be represented by a letter or by @dfn{escape sequences}, which are of
16996 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16997 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16998 @samp{@var{x}} is a predefined special character---for example,
16999 @samp{\n} for newline.
17001 Wide character constants can be written by prefixing a character
17002 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
17003 form of @samp{x}. The target wide character set is used when
17004 computing the value of this constant (@pxref{Character Sets}).
17007 String constants are a sequence of character constants surrounded by
17008 double quotes (@code{"}). Any valid character constant (as described
17009 above) may appear. Double quotes within the string must be preceded by
17010 a backslash, so for instance @samp{"a\"b'c"} is a string of five
17013 Wide string constants can be written by prefixing a string constant
17014 with @samp{L}, as in C. The target wide character set is used when
17015 computing the value of this constant (@pxref{Character Sets}).
17018 Pointer constants are an integral value. You can also write pointers
17019 to constants using the C operator @samp{&}.
17022 Array constants are comma-separated lists surrounded by braces @samp{@{}
17023 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
17024 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
17025 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
17028 @node C Plus Plus Expressions
17029 @subsubsection C@t{++} Expressions
17031 @cindex expressions in C@t{++}
17032 @value{GDBN} expression handling can interpret most C@t{++} expressions.
17034 @cindex debugging C@t{++} programs
17035 @cindex C@t{++} compilers
17036 @cindex debug formats and C@t{++}
17037 @cindex @value{NGCC} and C@t{++}
17039 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
17040 the proper compiler and the proper debug format. Currently,
17041 @value{GDBN} works best when debugging C@t{++} code that is compiled
17042 with the most recent version of @value{NGCC} possible. The DWARF
17043 debugging format is preferred; @value{NGCC} defaults to this on most
17044 popular platforms. Other compilers and/or debug formats are likely to
17045 work badly or not at all when using @value{GDBN} to debug C@t{++}
17046 code. @xref{Compilation}.
17051 @cindex member functions
17053 Member function calls are allowed; you can use expressions like
17056 count = aml->GetOriginal(x, y)
17059 @vindex this@r{, inside C@t{++} member functions}
17060 @cindex namespace in C@t{++}
17062 While a member function is active (in the selected stack frame), your
17063 expressions have the same namespace available as the member function;
17064 that is, @value{GDBN} allows implicit references to the class instance
17065 pointer @code{this} following the same rules as C@t{++}. @code{using}
17066 declarations in the current scope are also respected by @value{GDBN}.
17068 @cindex call overloaded functions
17069 @cindex overloaded functions, calling
17070 @cindex type conversions in C@t{++}
17072 You can call overloaded functions; @value{GDBN} resolves the function
17073 call to the right definition, with some restrictions. @value{GDBN} does not
17074 perform overload resolution involving user-defined type conversions,
17075 calls to constructors, or instantiations of templates that do not exist
17076 in the program. It also cannot handle ellipsis argument lists or
17079 It does perform integral conversions and promotions, floating-point
17080 promotions, arithmetic conversions, pointer conversions, conversions of
17081 class objects to base classes, and standard conversions such as those of
17082 functions or arrays to pointers; it requires an exact match on the
17083 number of function arguments.
17085 Overload resolution is always performed, unless you have specified
17086 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
17087 ,@value{GDBN} Features for C@t{++}}.
17089 You must specify @code{set overload-resolution off} in order to use an
17090 explicit function signature to call an overloaded function, as in
17092 p 'foo(char,int)'('x', 13)
17095 The @value{GDBN} command-completion facility can simplify this;
17096 see @ref{Completion, ,Command Completion}.
17098 @cindex reference declarations
17100 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
17101 references; you can use them in expressions just as you do in C@t{++}
17102 source---they are automatically dereferenced.
17104 In the parameter list shown when @value{GDBN} displays a frame, the values of
17105 reference variables are not displayed (unlike other variables); this
17106 avoids clutter, since references are often used for large structures.
17107 The @emph{address} of a reference variable is always shown, unless
17108 you have specified @samp{set print address off}.
17111 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
17112 expressions can use it just as expressions in your program do. Since
17113 one scope may be defined in another, you can use @code{::} repeatedly if
17114 necessary, for example in an expression like
17115 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
17116 resolving name scope by reference to source files, in both C and C@t{++}
17117 debugging (@pxref{Variables, ,Program Variables}).
17120 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
17125 @subsubsection C and C@t{++} Defaults
17127 @cindex C and C@t{++} defaults
17129 If you allow @value{GDBN} to set range checking automatically, it
17130 defaults to @code{off} whenever the working language changes to
17131 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
17132 selects the working language.
17134 If you allow @value{GDBN} to set the language automatically, it
17135 recognizes source files whose names end with @file{.c}, @file{.C}, or
17136 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
17137 these files, it sets the working language to C or C@t{++}.
17138 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
17139 for further details.
17142 @subsubsection C and C@t{++} Type and Range Checks
17144 @cindex C and C@t{++} checks
17146 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
17147 checking is used. However, if you turn type checking off, @value{GDBN}
17148 will allow certain non-standard conversions, such as promoting integer
17149 constants to pointers.
17151 Range checking, if turned on, is done on mathematical operations. Array
17152 indices are not checked, since they are often used to index a pointer
17153 that is not itself an array.
17156 @subsubsection @value{GDBN} and C
17158 The @code{set print union} and @code{show print union} commands apply to
17159 the @code{union} type. When set to @samp{on}, any @code{union} that is
17160 inside a @code{struct} or @code{class} is also printed. Otherwise, it
17161 appears as @samp{@{...@}}.
17163 The @code{@@} operator aids in the debugging of dynamic arrays, formed
17164 with pointers and a memory allocation function. @xref{Expressions,
17167 @node Debugging C Plus Plus
17168 @subsubsection @value{GDBN} Features for C@t{++}
17170 @cindex commands for C@t{++}
17172 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
17173 designed specifically for use with C@t{++}. Here is a summary:
17176 @cindex break in overloaded functions
17177 @item @r{breakpoint menus}
17178 When you want a breakpoint in a function whose name is overloaded,
17179 @value{GDBN} has the capability to display a menu of possible breakpoint
17180 locations to help you specify which function definition you want.
17181 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
17183 @cindex overloading in C@t{++}
17184 @item rbreak @var{regex}
17185 Setting breakpoints using regular expressions is helpful for setting
17186 breakpoints on overloaded functions that are not members of any special
17188 @xref{Set Breaks, ,Setting Breakpoints}.
17190 @cindex C@t{++} exception handling
17192 @itemx catch rethrow
17194 Debug C@t{++} exception handling using these commands. @xref{Set
17195 Catchpoints, , Setting Catchpoints}.
17197 @cindex inheritance
17198 @item ptype @var{typename}
17199 Print inheritance relationships as well as other information for type
17201 @xref{Symbols, ,Examining the Symbol Table}.
17203 @item info vtbl @var{expression}.
17204 The @code{info vtbl} command can be used to display the virtual
17205 method tables of the object computed by @var{expression}. This shows
17206 one entry per virtual table; there may be multiple virtual tables when
17207 multiple inheritance is in use.
17209 @cindex C@t{++} demangling
17210 @item demangle @var{name}
17211 Demangle @var{name}.
17212 @xref{Symbols}, for a more complete description of the @code{demangle} command.
17214 @cindex C@t{++} symbol display
17215 @item set print demangle
17216 @itemx show print demangle
17217 @itemx set print asm-demangle
17218 @itemx show print asm-demangle
17219 Control whether C@t{++} symbols display in their source form, both when
17220 displaying code as C@t{++} source and when displaying disassemblies.
17221 @xref{Print Settings, ,Print Settings}.
17223 @item set print object
17224 @itemx show print object
17225 Choose whether to print derived (actual) or declared types of objects.
17226 @xref{Print Settings, ,Print Settings}.
17228 @item set print vtbl
17229 @itemx show print vtbl
17230 Control the format for printing virtual function tables.
17231 @xref{Print Settings, ,Print Settings}.
17232 (The @code{vtbl} commands do not work on programs compiled with the HP
17233 ANSI C@t{++} compiler (@code{aCC}).)
17235 @kindex set overload-resolution
17236 @cindex overloaded functions, overload resolution
17237 @item set overload-resolution on
17238 Enable overload resolution for C@t{++} expression evaluation. The default
17239 is on. For overloaded functions, @value{GDBN} evaluates the arguments
17240 and searches for a function whose signature matches the argument types,
17241 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
17242 Expressions, ,C@t{++} Expressions}, for details).
17243 If it cannot find a match, it emits a message.
17245 @item set overload-resolution off
17246 Disable overload resolution for C@t{++} expression evaluation. For
17247 overloaded functions that are not class member functions, @value{GDBN}
17248 chooses the first function of the specified name that it finds in the
17249 symbol table, whether or not its arguments are of the correct type. For
17250 overloaded functions that are class member functions, @value{GDBN}
17251 searches for a function whose signature @emph{exactly} matches the
17254 @kindex show overload-resolution
17255 @item show overload-resolution
17256 Show the current setting of overload resolution.
17258 @item @r{Overloaded symbol names}
17259 You can specify a particular definition of an overloaded symbol, using
17260 the same notation that is used to declare such symbols in C@t{++}: type
17261 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
17262 also use the @value{GDBN} command-line word completion facilities to list the
17263 available choices, or to finish the type list for you.
17264 @xref{Completion,, Command Completion}, for details on how to do this.
17266 @item @r{Breakpoints in template functions}
17268 Similar to how overloaded symbols are handled, @value{GDBN} will ignore
17269 template parameter lists when it encounters a symbol which includes a
17270 C@t{++} template. This permits setting breakpoints on families of template functions
17271 or functions whose parameters include template types.
17273 The @kbd{-qualified} flag may be used to override this behavior, causing
17274 @value{GDBN} to search for a specific function or type.
17276 The @value{GDBN} command-line word completion facility also understands
17277 template parameters and may be used to list available choices or finish
17278 template parameter lists for you. @xref{Completion,, Command Completion}, for
17279 details on how to do this.
17281 @item @r{Breakpoints in functions with ABI tags}
17283 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
17284 correspond to changes in the ABI of a type, function, or variable that
17285 would not otherwise be reflected in a mangled name. See
17286 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
17289 The ABI tags are visible in C@t{++} demangled names. For example, a
17290 function that returns a std::string:
17293 std::string function(int);
17297 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
17298 tag, and @value{GDBN} displays the symbol like this:
17301 function[abi:cxx11](int)
17304 You can set a breakpoint on such functions simply as if they had no
17308 (@value{GDBP}) b function(int)
17309 Breakpoint 2 at 0x40060d: file main.cc, line 10.
17310 (@value{GDBP}) info breakpoints
17311 Num Type Disp Enb Address What
17312 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
17316 On the rare occasion you need to disambiguate between different ABI
17317 tags, you can do so by simply including the ABI tag in the function
17321 (@value{GDBP}) b ambiguous[abi:other_tag](int)
17325 @node Decimal Floating Point
17326 @subsubsection Decimal Floating Point format
17327 @cindex decimal floating point format
17329 @value{GDBN} can examine, set and perform computations with numbers in
17330 decimal floating point format, which in the C language correspond to the
17331 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
17332 specified by the extension to support decimal floating-point arithmetic.
17334 There are two encodings in use, depending on the architecture: BID (Binary
17335 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
17336 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
17339 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
17340 to manipulate decimal floating point numbers, it is not possible to convert
17341 (using a cast, for example) integers wider than 32-bit to decimal float.
17343 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
17344 point computations, error checking in decimal float operations ignores
17345 underflow, overflow and divide by zero exceptions.
17347 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
17348 to inspect @code{_Decimal128} values stored in floating point registers.
17349 See @ref{PowerPC,,PowerPC} for more details.
17355 @value{GDBN} can be used to debug programs written in D and compiled with
17356 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
17357 specific feature --- dynamic arrays.
17362 @cindex Go (programming language)
17363 @value{GDBN} can be used to debug programs written in Go and compiled with
17364 @file{gccgo} or @file{6g} compilers.
17366 Here is a summary of the Go-specific features and restrictions:
17369 @cindex current Go package
17370 @item The current Go package
17371 The name of the current package does not need to be specified when
17372 specifying global variables and functions.
17374 For example, given the program:
17378 var myglob = "Shall we?"
17384 When stopped inside @code{main} either of these work:
17387 (@value{GDBP}) p myglob
17388 (@value{GDBP}) p main.myglob
17391 @cindex builtin Go types
17392 @item Builtin Go types
17393 The @code{string} type is recognized by @value{GDBN} and is printed
17396 @cindex builtin Go functions
17397 @item Builtin Go functions
17398 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
17399 function and handles it internally.
17401 @cindex restrictions on Go expressions
17402 @item Restrictions on Go expressions
17403 All Go operators are supported except @code{&^}.
17404 The Go @code{_} ``blank identifier'' is not supported.
17405 Automatic dereferencing of pointers is not supported.
17409 @subsection Objective-C
17411 @cindex Objective-C
17412 This section provides information about some commands and command
17413 options that are useful for debugging Objective-C code. See also
17414 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
17415 few more commands specific to Objective-C support.
17418 * Method Names in Commands::
17419 * The Print Command with Objective-C::
17422 @node Method Names in Commands
17423 @subsubsection Method Names in Commands
17425 The following commands have been extended to accept Objective-C method
17426 names as line specifications:
17428 @kindex clear@r{, and Objective-C}
17429 @kindex break@r{, and Objective-C}
17430 @kindex info line@r{, and Objective-C}
17431 @kindex jump@r{, and Objective-C}
17432 @kindex list@r{, and Objective-C}
17436 @item @code{info line}
17441 A fully qualified Objective-C method name is specified as
17444 -[@var{Class} @var{methodName}]
17447 where the minus sign is used to indicate an instance method and a
17448 plus sign (not shown) is used to indicate a class method. The class
17449 name @var{Class} and method name @var{methodName} are enclosed in
17450 brackets, similar to the way messages are specified in Objective-C
17451 source code. For example, to set a breakpoint at the @code{create}
17452 instance method of class @code{Fruit} in the program currently being
17456 break -[Fruit create]
17459 To list ten program lines around the @code{initialize} class method,
17463 list +[NSText initialize]
17466 In the current version of @value{GDBN}, the plus or minus sign is
17467 required. In future versions of @value{GDBN}, the plus or minus
17468 sign will be optional, but you can use it to narrow the search. It
17469 is also possible to specify just a method name:
17475 You must specify the complete method name, including any colons. If
17476 your program's source files contain more than one @code{create} method,
17477 you'll be presented with a numbered list of classes that implement that
17478 method. Indicate your choice by number, or type @samp{0} to exit if
17481 As another example, to clear a breakpoint established at the
17482 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17485 clear -[NSWindow makeKeyAndOrderFront:]
17488 @node The Print Command with Objective-C
17489 @subsubsection The Print Command With Objective-C
17490 @cindex Objective-C, print objects
17491 @kindex print-object
17492 @kindex po @r{(@code{print-object})}
17494 The print command has also been extended to accept methods. For example:
17497 print -[@var{object} hash]
17500 @cindex print an Objective-C object description
17501 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17503 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17504 and print the result. Also, an additional command has been added,
17505 @code{print-object} or @code{po} for short, which is meant to print
17506 the description of an object. However, this command may only work
17507 with certain Objective-C libraries that have a particular hook
17508 function, @code{_NSPrintForDebugger}, defined.
17511 @subsection OpenCL C
17514 This section provides information about @value{GDBN}s OpenCL C support.
17517 * OpenCL C Datatypes::
17518 * OpenCL C Expressions::
17519 * OpenCL C Operators::
17522 @node OpenCL C Datatypes
17523 @subsubsection OpenCL C Datatypes
17525 @cindex OpenCL C Datatypes
17526 @value{GDBN} supports the builtin scalar and vector datatypes specified
17527 by OpenCL 1.1. In addition the half- and double-precision floating point
17528 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17529 extensions are also known to @value{GDBN}.
17531 @node OpenCL C Expressions
17532 @subsubsection OpenCL C Expressions
17534 @cindex OpenCL C Expressions
17535 @value{GDBN} supports accesses to vector components including the access as
17536 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17537 supported by @value{GDBN} can be used as well.
17539 @node OpenCL C Operators
17540 @subsubsection OpenCL C Operators
17542 @cindex OpenCL C Operators
17543 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17547 @subsection Fortran
17548 @cindex Fortran-specific support in @value{GDBN}
17550 @value{GDBN} can be used to debug programs written in Fortran. Note, that not
17551 all Fortran language features are available yet.
17553 @cindex trailing underscore, in Fortran symbols
17554 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17555 among them) append an underscore to the names of variables and
17556 functions. When you debug programs compiled by those compilers, you
17557 will need to refer to variables and functions with a trailing
17560 @cindex Fortran Defaults
17561 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17562 default uses case-insensitive matching for Fortran symbols. You can
17563 change that with the @samp{set case-insensitive} command, see
17564 @ref{Symbols}, for the details.
17567 * Fortran Types:: Fortran builtin types
17568 * Fortran Operators:: Fortran operators and expressions
17569 * Fortran Intrinsics:: Fortran intrinsic functions
17570 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17573 @node Fortran Types
17574 @subsubsection Fortran Types
17576 @cindex Fortran Types
17578 In Fortran the primitive data-types have an associated @code{KIND} type
17579 parameter, written as @samp{@var{type}*@var{kindparam}},
17580 @samp{@var{type}*@var{kindparam}}, or in the @value{GDBN}-only dialect
17581 @samp{@var{type}_@var{kindparam}}. A concrete example would be
17582 @samp{@code{Real*4}}, @samp{@code{Real(kind=4)}}, and @samp{@code{Real_4}}.
17583 The kind of a type can be retrieved by using the intrinsic function
17584 @code{KIND}, see @ref{Fortran Intrinsics}.
17586 Generally, the actual implementation of the @code{KIND} type parameter is
17587 compiler specific. In @value{GDBN} the kind parameter is implemented in
17588 accordance with its use in the @sc{gnu} @command{gfortran} compiler. Here, the
17589 kind parameter for a given @var{type} specifies its size in memory --- a
17590 Fortran @code{Integer*4} or @code{Integer(kind=4)} would be an integer type
17591 occupying 4 bytes of memory. An exception to this rule is the @code{Complex}
17592 type for which the kind of the type does not specify its entire size, but
17593 the size of each of the two @code{Real}'s it is composed of. A
17594 @code{Complex*4} would thus consist of two @code{Real*4}s and occupy 8 bytes
17597 For every type there is also a default kind associated with it, e.g.@
17598 @code{Integer} in @value{GDBN} will internally be an @code{Integer*4} (see the
17599 table below for default types). The default types are the same as in @sc{gnu}
17600 compilers but note, that the @sc{gnu} default types can actually be changed by
17601 compiler flags such as @option{-fdefault-integer-8} and
17602 @option{-fdefault-real-8}.
17604 Not every kind parameter is valid for every type and in @value{GDBN} the
17605 following type kinds are available.
17609 @code{Integer*1}, @code{Integer*2}, @code{Integer*4}, @code{Integer*8}, and
17610 @code{Integer} = @code{Integer*4}.
17613 @code{Logical*1}, @code{Logical*2}, @code{Logical*4}, @code{Logical*8}, and
17614 @code{Logical} = @code{Logical*4}.
17617 @code{Real*4}, @code{Real*8}, @code{Real*16}, and @code{Real} = @code{Real*4}.
17620 @code{Complex*4}, @code{Complex*8}, @code{Complex*16}, and @code{Complex} =
17625 @node Fortran Operators
17626 @subsubsection Fortran Operators and Expressions
17628 @cindex Fortran operators and expressions
17630 Operators must be defined on values of specific types. For instance,
17631 @code{+} is defined on numbers, but not on characters or other non-
17632 arithmetic types. Operators are often defined on groups of types.
17636 The exponentiation operator. It raises the first operand to the power
17640 The range operator. Normally used in the form of array(low:high) to
17641 represent a section of array.
17644 The access component operator. Normally used to access elements in derived
17645 types. Also suitable for unions. As unions aren't part of regular Fortran,
17646 this can only happen when accessing a register that uses a gdbarch-defined
17649 The scope operator. Normally used to access variables in modules or
17650 to set breakpoints on subroutines nested in modules or in other
17651 subroutines (internal subroutines).
17654 @node Fortran Intrinsics
17655 @subsubsection Fortran Intrinsics
17657 @cindex Fortran Intrinsics
17659 Fortran provides a large set of intrinsic procedures. @value{GDBN} implements
17660 an incomplete subset of those procedures and their overloads. Some of these
17661 procedures take an optional @code{KIND} parameter, see @ref{Fortran Types}.
17665 Computes the absolute value of its argument @var{a}. Currently not supported
17666 for @code{Complex} arguments.
17668 @item ALLOCATE(@var{array})
17669 Returns whether @var{array} is allocated or not.
17671 @item ASSOCIATED(@var{pointer} [, @var{target}])
17672 Returns the association status of the pointer @var{pointer} or, if @var{target}
17673 is present, whether @var{pointer} is associated with the target @var{target}.
17675 @item CEILING(@var{a} [, @var{kind}])
17676 Computes the least integer greater than or equal to @var{a}. The optional
17677 parameter @var{kind} specifies the kind of the return type
17678 @code{Integer(@var{kind})}.
17680 @item CMPLX(@var{x} [, @var{y} [, @var{kind}]])
17681 Returns a complex number where @var{x} is converted to the real component. If
17682 @var{y} is present it is converted to the imaginary component. If @var{y} is
17683 not present then the imaginary component is set to @code{0.0} except if @var{x}
17684 itself is of @code{Complex} type. The optional parameter @var{kind} specifies
17685 the kind of the return type @code{Complex(@var{kind})}.
17687 @item FLOOR(@var{a} [, @var{kind}])
17688 Computes the greatest integer less than or equal to @var{a}. The optional
17689 parameter @var{kind} specifies the kind of the return type
17690 @code{Integer(@var{kind})}.
17692 @item KIND(@var{a})
17693 Returns the kind value of the argument @var{a}, see @ref{Fortran Types}.
17695 @item LBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17696 Returns the lower bounds of an @var{array}, or a single lower bound along the
17697 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17698 the kind of the return type @code{Integer(@var{kind})}.
17701 Returns the address of @var{x} as an @code{Integer}.
17703 @item MOD(@var{a}, @var{p})
17704 Computes the remainder of the division of @var{a} by @var{p}.
17706 @item MODULO(@var{a}, @var{p})
17707 Computes the @var{a} modulo @var{p}.
17709 @item RANK(@var{a})
17710 Returns the rank of a scalar or array (scalars have rank @code{0}).
17712 @item SHAPE(@var{a})
17713 Returns the shape of a scalar or array (scalars have shape @samp{()}).
17715 @item SIZE(@var{array}[, @var{dim} [, @var{kind}]])
17716 Returns the extent of @var{array} along a specified dimension @var{dim}, or the
17717 total number of elements in @var{array} if @var{dim} is absent. The optional
17718 parameter @var{kind} specifies the kind of the return type
17719 @code{Integer(@var{kind})}.
17721 @item UBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17722 Returns the upper bounds of an @var{array}, or a single upper bound along the
17723 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17724 the kind of the return type @code{Integer(@var{kind})}.
17728 @node Special Fortran Commands
17729 @subsubsection Special Fortran Commands
17731 @cindex Special Fortran commands
17733 @value{GDBN} has some commands to support Fortran-specific features,
17734 such as displaying common blocks.
17737 @cindex @code{COMMON} blocks, Fortran
17738 @kindex info common
17739 @item info common @r{[}@var{common-name}@r{]}
17740 This command prints the values contained in the Fortran @code{COMMON}
17741 block whose name is @var{common-name}. With no argument, the names of
17742 all @code{COMMON} blocks visible at the current program location are
17744 @cindex arrays slices (Fortran)
17745 @kindex set fortran repack-array-slices
17746 @kindex show fortran repack-array-slices
17747 @item set fortran repack-array-slices [on|off]
17748 @item show fortran repack-array-slices
17749 When taking a slice from an array, a Fortran compiler can choose to
17750 either produce an array descriptor that describes the slice in place,
17751 or it may repack the slice, copying the elements of the slice into a
17752 new region of memory.
17754 When this setting is on, then @value{GDBN} will also repack array
17755 slices in some situations. When this setting is off, then
17756 @value{GDBN} will create array descriptors for slices that reference
17757 the original data in place.
17759 @value{GDBN} will never repack an array slice if the data for the
17760 slice is contiguous within the original array.
17762 @value{GDBN} will always repack string slices if the data for the
17763 slice is non-contiguous within the original string as @value{GDBN}
17764 does not support printing non-contiguous strings.
17766 The default for this setting is @code{off}.
17772 @cindex Pascal support in @value{GDBN}, limitations
17773 Debugging Pascal programs which use sets, subranges, file variables, or
17774 nested functions does not currently work. @value{GDBN} does not support
17775 entering expressions, printing values, or similar features using Pascal
17778 The Pascal-specific command @code{set print pascal_static-members}
17779 controls whether static members of Pascal objects are displayed.
17780 @xref{Print Settings, pascal_static-members}.
17785 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17786 Programming Language}. Type- and value-printing, and expression
17787 parsing, are reasonably complete. However, there are a few
17788 peculiarities and holes to be aware of.
17792 Linespecs (@pxref{Location Specifications}) are never relative to the
17793 current crate. Instead, they act as if there were a global namespace
17794 of crates, somewhat similar to the way @code{extern crate} behaves.
17796 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17797 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17798 to set a breakpoint in a function named @samp{f} in a crate named
17801 As a consequence of this approach, linespecs also cannot refer to
17802 items using @samp{self::} or @samp{super::}.
17805 Because @value{GDBN} implements Rust name-lookup semantics in
17806 expressions, it will sometimes prepend the current crate to a name.
17807 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17808 @samp{K}, then @code{print ::x::y} will try to find the symbol
17811 However, since it is useful to be able to refer to other crates when
17812 debugging, @value{GDBN} provides the @code{extern} extension to
17813 circumvent this. To use the extension, just put @code{extern} before
17814 a path expression to refer to the otherwise unavailable ``global''
17817 In the above example, if you wanted to refer to the symbol @samp{y} in
17818 the crate @samp{x}, you would use @code{print extern x::y}.
17821 The Rust expression evaluator does not support ``statement-like''
17822 expressions such as @code{if} or @code{match}, or lambda expressions.
17825 Tuple expressions are not implemented.
17828 The Rust expression evaluator does not currently implement the
17829 @code{Drop} trait. Objects that may be created by the evaluator will
17830 never be destroyed.
17833 @value{GDBN} does not implement type inference for generics. In order
17834 to call generic functions or otherwise refer to generic items, you
17835 will have to specify the type parameters manually.
17838 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17839 cases this does not cause any problems. However, in an expression
17840 context, completing a generic function name will give syntactically
17841 invalid results. This happens because Rust requires the @samp{::}
17842 operator between the function name and its generic arguments. For
17843 example, @value{GDBN} might provide a completion like
17844 @code{crate::f<u32>}, where the parser would require
17845 @code{crate::f::<u32>}.
17848 As of this writing, the Rust compiler (version 1.8) has a few holes in
17849 the debugging information it generates. These holes prevent certain
17850 features from being implemented by @value{GDBN}:
17854 Method calls cannot be made via traits.
17857 Operator overloading is not implemented.
17860 When debugging in a monomorphized function, you cannot use the generic
17864 The type @code{Self} is not available.
17867 @code{use} statements are not available, so some names may not be
17868 available in the crate.
17873 @subsection Modula-2
17875 @cindex Modula-2, @value{GDBN} support
17877 The extensions made to @value{GDBN} to support Modula-2 only support
17878 output from the @sc{gnu} Modula-2 compiler (which is currently being
17879 developed). Other Modula-2 compilers are not currently supported, and
17880 attempting to debug executables produced by them is most likely
17881 to give an error as @value{GDBN} reads in the executable's symbol
17884 @cindex expressions in Modula-2
17886 * M2 Operators:: Built-in operators
17887 * Built-In Func/Proc:: Built-in functions and procedures
17888 * M2 Constants:: Modula-2 constants
17889 * M2 Types:: Modula-2 types
17890 * M2 Defaults:: Default settings for Modula-2
17891 * Deviations:: Deviations from standard Modula-2
17892 * M2 Checks:: Modula-2 type and range checks
17893 * M2 Scope:: The scope operators @code{::} and @code{.}
17894 * GDB/M2:: @value{GDBN} and Modula-2
17898 @subsubsection Operators
17899 @cindex Modula-2 operators
17901 Operators must be defined on values of specific types. For instance,
17902 @code{+} is defined on numbers, but not on structures. Operators are
17903 often defined on groups of types. For the purposes of Modula-2, the
17904 following definitions hold:
17909 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17913 @emph{Character types} consist of @code{CHAR} and its subranges.
17916 @emph{Floating-point types} consist of @code{REAL}.
17919 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17923 @emph{Scalar types} consist of all of the above.
17926 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17929 @emph{Boolean types} consist of @code{BOOLEAN}.
17933 The following operators are supported, and appear in order of
17934 increasing precedence:
17938 Function argument or array index separator.
17941 Assignment. The value of @var{var} @code{:=} @var{value} is
17945 Less than, greater than on integral, floating-point, or enumerated
17949 Less than or equal to, greater than or equal to
17950 on integral, floating-point and enumerated types, or set inclusion on
17951 set types. Same precedence as @code{<}.
17953 @item =@r{, }<>@r{, }#
17954 Equality and two ways of expressing inequality, valid on scalar types.
17955 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17956 available for inequality, since @code{#} conflicts with the script
17960 Set membership. Defined on set types and the types of their members.
17961 Same precedence as @code{<}.
17964 Boolean disjunction. Defined on boolean types.
17967 Boolean conjunction. Defined on boolean types.
17970 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17973 Addition and subtraction on integral and floating-point types, or union
17974 and difference on set types.
17977 Multiplication on integral and floating-point types, or set intersection
17981 Division on floating-point types, or symmetric set difference on set
17982 types. Same precedence as @code{*}.
17985 Integer division and remainder. Defined on integral types. Same
17986 precedence as @code{*}.
17989 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17992 Pointer dereferencing. Defined on pointer types.
17995 Boolean negation. Defined on boolean types. Same precedence as
17999 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
18000 precedence as @code{^}.
18003 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
18006 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
18010 @value{GDBN} and Modula-2 scope operators.
18014 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
18015 treats the use of the operator @code{IN}, or the use of operators
18016 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
18017 @code{<=}, and @code{>=} on sets as an error.
18021 @node Built-In Func/Proc
18022 @subsubsection Built-in Functions and Procedures
18023 @cindex Modula-2 built-ins
18025 Modula-2 also makes available several built-in procedures and functions.
18026 In describing these, the following metavariables are used:
18031 represents an @code{ARRAY} variable.
18034 represents a @code{CHAR} constant or variable.
18037 represents a variable or constant of integral type.
18040 represents an identifier that belongs to a set. Generally used in the
18041 same function with the metavariable @var{s}. The type of @var{s} should
18042 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
18045 represents a variable or constant of integral or floating-point type.
18048 represents a variable or constant of floating-point type.
18054 represents a variable.
18057 represents a variable or constant of one of many types. See the
18058 explanation of the function for details.
18061 All Modula-2 built-in procedures also return a result, described below.
18065 Returns the absolute value of @var{n}.
18068 If @var{c} is a lower case letter, it returns its upper case
18069 equivalent, otherwise it returns its argument.
18072 Returns the character whose ordinal value is @var{i}.
18075 Decrements the value in the variable @var{v} by one. Returns the new value.
18077 @item DEC(@var{v},@var{i})
18078 Decrements the value in the variable @var{v} by @var{i}. Returns the
18081 @item EXCL(@var{m},@var{s})
18082 Removes the element @var{m} from the set @var{s}. Returns the new
18085 @item FLOAT(@var{i})
18086 Returns the floating point equivalent of the integer @var{i}.
18088 @item HIGH(@var{a})
18089 Returns the index of the last member of @var{a}.
18092 Increments the value in the variable @var{v} by one. Returns the new value.
18094 @item INC(@var{v},@var{i})
18095 Increments the value in the variable @var{v} by @var{i}. Returns the
18098 @item INCL(@var{m},@var{s})
18099 Adds the element @var{m} to the set @var{s} if it is not already
18100 there. Returns the new set.
18103 Returns the maximum value of the type @var{t}.
18106 Returns the minimum value of the type @var{t}.
18109 Returns boolean TRUE if @var{i} is an odd number.
18112 Returns the ordinal value of its argument. For example, the ordinal
18113 value of a character is its @sc{ascii} value (on machines supporting
18114 the @sc{ascii} character set). The argument @var{x} must be of an
18115 ordered type, which include integral, character and enumerated types.
18117 @item SIZE(@var{x})
18118 Returns the size of its argument. The argument @var{x} can be a
18119 variable or a type.
18121 @item TRUNC(@var{r})
18122 Returns the integral part of @var{r}.
18124 @item TSIZE(@var{x})
18125 Returns the size of its argument. The argument @var{x} can be a
18126 variable or a type.
18128 @item VAL(@var{t},@var{i})
18129 Returns the member of the type @var{t} whose ordinal value is @var{i}.
18133 @emph{Warning:} Sets and their operations are not yet supported, so
18134 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
18138 @cindex Modula-2 constants
18140 @subsubsection Constants
18142 @value{GDBN} allows you to express the constants of Modula-2 in the following
18148 Integer constants are simply a sequence of digits. When used in an
18149 expression, a constant is interpreted to be type-compatible with the
18150 rest of the expression. Hexadecimal integers are specified by a
18151 trailing @samp{H}, and octal integers by a trailing @samp{B}.
18154 Floating point constants appear as a sequence of digits, followed by a
18155 decimal point and another sequence of digits. An optional exponent can
18156 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
18157 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
18158 digits of the floating point constant must be valid decimal (base 10)
18162 Character constants consist of a single character enclosed by a pair of
18163 like quotes, either single (@code{'}) or double (@code{"}). They may
18164 also be expressed by their ordinal value (their @sc{ascii} value, usually)
18165 followed by a @samp{C}.
18168 String constants consist of a sequence of characters enclosed by a
18169 pair of like quotes, either single (@code{'}) or double (@code{"}).
18170 Escape sequences in the style of C are also allowed. @xref{C
18171 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
18175 Enumerated constants consist of an enumerated identifier.
18178 Boolean constants consist of the identifiers @code{TRUE} and
18182 Pointer constants consist of integral values only.
18185 Set constants are not yet supported.
18189 @subsubsection Modula-2 Types
18190 @cindex Modula-2 types
18192 Currently @value{GDBN} can print the following data types in Modula-2
18193 syntax: array types, record types, set types, pointer types, procedure
18194 types, enumerated types, subrange types and base types. You can also
18195 print the contents of variables declared using these type.
18196 This section gives a number of simple source code examples together with
18197 sample @value{GDBN} sessions.
18199 The first example contains the following section of code:
18208 and you can request @value{GDBN} to interrogate the type and value of
18209 @code{r} and @code{s}.
18212 (@value{GDBP}) print s
18214 (@value{GDBP}) ptype s
18216 (@value{GDBP}) print r
18218 (@value{GDBP}) ptype r
18223 Likewise if your source code declares @code{s} as:
18227 s: SET ['A'..'Z'] ;
18231 then you may query the type of @code{s} by:
18234 (@value{GDBP}) ptype s
18235 type = SET ['A'..'Z']
18239 Note that at present you cannot interactively manipulate set
18240 expressions using the debugger.
18242 The following example shows how you might declare an array in Modula-2
18243 and how you can interact with @value{GDBN} to print its type and contents:
18247 s: ARRAY [-10..10] OF CHAR ;
18251 (@value{GDBP}) ptype s
18252 ARRAY [-10..10] OF CHAR
18255 Note that the array handling is not yet complete and although the type
18256 is printed correctly, expression handling still assumes that all
18257 arrays have a lower bound of zero and not @code{-10} as in the example
18260 Here are some more type related Modula-2 examples:
18264 colour = (blue, red, yellow, green) ;
18265 t = [blue..yellow] ;
18273 The @value{GDBN} interaction shows how you can query the data type
18274 and value of a variable.
18277 (@value{GDBP}) print s
18279 (@value{GDBP}) ptype t
18280 type = [blue..yellow]
18284 In this example a Modula-2 array is declared and its contents
18285 displayed. Observe that the contents are written in the same way as
18286 their @code{C} counterparts.
18290 s: ARRAY [1..5] OF CARDINAL ;
18296 (@value{GDBP}) print s
18297 $1 = @{1, 0, 0, 0, 0@}
18298 (@value{GDBP}) ptype s
18299 type = ARRAY [1..5] OF CARDINAL
18302 The Modula-2 language interface to @value{GDBN} also understands
18303 pointer types as shown in this example:
18307 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
18314 and you can request that @value{GDBN} describes the type of @code{s}.
18317 (@value{GDBP}) ptype s
18318 type = POINTER TO ARRAY [1..5] OF CARDINAL
18321 @value{GDBN} handles compound types as we can see in this example.
18322 Here we combine array types, record types, pointer types and subrange
18333 myarray = ARRAY myrange OF CARDINAL ;
18334 myrange = [-2..2] ;
18336 s: POINTER TO ARRAY myrange OF foo ;
18340 and you can ask @value{GDBN} to describe the type of @code{s} as shown
18344 (@value{GDBP}) ptype s
18345 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
18348 f3 : ARRAY [-2..2] OF CARDINAL;
18353 @subsubsection Modula-2 Defaults
18354 @cindex Modula-2 defaults
18356 If type and range checking are set automatically by @value{GDBN}, they
18357 both default to @code{on} whenever the working language changes to
18358 Modula-2. This happens regardless of whether you or @value{GDBN}
18359 selected the working language.
18361 If you allow @value{GDBN} to set the language automatically, then entering
18362 code compiled from a file whose name ends with @file{.mod} sets the
18363 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
18364 Infer the Source Language}, for further details.
18367 @subsubsection Deviations from Standard Modula-2
18368 @cindex Modula-2, deviations from
18370 A few changes have been made to make Modula-2 programs easier to debug.
18371 This is done primarily via loosening its type strictness:
18375 Unlike in standard Modula-2, pointer constants can be formed by
18376 integers. This allows you to modify pointer variables during
18377 debugging. (In standard Modula-2, the actual address contained in a
18378 pointer variable is hidden from you; it can only be modified
18379 through direct assignment to another pointer variable or expression that
18380 returned a pointer.)
18383 C escape sequences can be used in strings and characters to represent
18384 non-printable characters. @value{GDBN} prints out strings with these
18385 escape sequences embedded. Single non-printable characters are
18386 printed using the @samp{CHR(@var{nnn})} format.
18389 The assignment operator (@code{:=}) returns the value of its right-hand
18393 All built-in procedures both modify @emph{and} return their argument.
18397 @subsubsection Modula-2 Type and Range Checks
18398 @cindex Modula-2 checks
18401 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
18404 @c FIXME remove warning when type/range checks added
18406 @value{GDBN} considers two Modula-2 variables type equivalent if:
18410 They are of types that have been declared equivalent via a @code{TYPE
18411 @var{t1} = @var{t2}} statement
18414 They have been declared on the same line. (Note: This is true of the
18415 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
18418 As long as type checking is enabled, any attempt to combine variables
18419 whose types are not equivalent is an error.
18421 Range checking is done on all mathematical operations, assignment, array
18422 index bounds, and all built-in functions and procedures.
18425 @subsubsection The Scope Operators @code{::} and @code{.}
18427 @cindex @code{.}, Modula-2 scope operator
18428 @cindex colon, doubled as scope operator
18430 @vindex colon-colon@r{, in Modula-2}
18431 @c Info cannot handle :: but TeX can.
18434 @vindex ::@r{, in Modula-2}
18437 There are a few subtle differences between the Modula-2 scope operator
18438 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
18443 @var{module} . @var{id}
18444 @var{scope} :: @var{id}
18448 where @var{scope} is the name of a module or a procedure,
18449 @var{module} the name of a module, and @var{id} is any declared
18450 identifier within your program, except another module.
18452 Using the @code{::} operator makes @value{GDBN} search the scope
18453 specified by @var{scope} for the identifier @var{id}. If it is not
18454 found in the specified scope, then @value{GDBN} searches all scopes
18455 enclosing the one specified by @var{scope}.
18457 Using the @code{.} operator makes @value{GDBN} search the current scope for
18458 the identifier specified by @var{id} that was imported from the
18459 definition module specified by @var{module}. With this operator, it is
18460 an error if the identifier @var{id} was not imported from definition
18461 module @var{module}, or if @var{id} is not an identifier in
18465 @subsubsection @value{GDBN} and Modula-2
18467 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
18468 Five subcommands of @code{set print} and @code{show print} apply
18469 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
18470 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
18471 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
18472 analogue in Modula-2.
18474 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
18475 with any language, is not useful with Modula-2. Its
18476 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
18477 created in Modula-2 as they can in C or C@t{++}. However, because an
18478 address can be specified by an integral constant, the construct
18479 @samp{@{@var{type}@}@var{adrexp}} is still useful.
18481 @cindex @code{#} in Modula-2
18482 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
18483 interpreted as the beginning of a comment. Use @code{<>} instead.
18489 The extensions made to @value{GDBN} for Ada only support
18490 output from the @sc{gnu} Ada (GNAT) compiler.
18491 Other Ada compilers are not currently supported, and
18492 attempting to debug executables produced by them is most likely
18496 @cindex expressions in Ada
18498 * Ada Mode Intro:: General remarks on the Ada syntax
18499 and semantics supported by Ada mode
18501 * Omissions from Ada:: Restrictions on the Ada expression syntax.
18502 * Additions to Ada:: Extensions of the Ada expression syntax.
18503 * Overloading support for Ada:: Support for expressions involving overloaded
18505 * Stopping Before Main Program:: Debugging the program during elaboration.
18506 * Ada Exceptions:: Ada Exceptions
18507 * Ada Tasks:: Listing and setting breakpoints in tasks.
18508 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
18509 * Ravenscar Profile:: Tasking Support when using the Ravenscar
18511 * Ada Source Character Set:: Character set of Ada source files.
18512 * Ada Glitches:: Known peculiarities of Ada mode.
18515 @node Ada Mode Intro
18516 @subsubsection Introduction
18517 @cindex Ada mode, general
18519 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
18520 syntax, with some extensions.
18521 The philosophy behind the design of this subset is
18525 That @value{GDBN} should provide basic literals and access to operations for
18526 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18527 leaving more sophisticated computations to subprograms written into the
18528 program (which therefore may be called from @value{GDBN}).
18531 That type safety and strict adherence to Ada language restrictions
18532 are not particularly important to the @value{GDBN} user.
18535 That brevity is important to the @value{GDBN} user.
18538 Thus, for brevity, the debugger acts as if all names declared in
18539 user-written packages are directly visible, even if they are not visible
18540 according to Ada rules, thus making it unnecessary to fully qualify most
18541 names with their packages, regardless of context. Where this causes
18542 ambiguity, @value{GDBN} asks the user's intent.
18544 The debugger will start in Ada mode if it detects an Ada main program.
18545 As for other languages, it will enter Ada mode when stopped in a program that
18546 was translated from an Ada source file.
18548 While in Ada mode, you may use `@t{--}' for comments. This is useful
18549 mostly for documenting command files. The standard @value{GDBN} comment
18550 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
18551 middle (to allow based literals).
18553 @node Omissions from Ada
18554 @subsubsection Omissions from Ada
18555 @cindex Ada, omissions from
18557 Here are the notable omissions from the subset:
18561 Only a subset of the attributes are supported:
18565 @t{'First}, @t{'Last}, and @t{'Length}
18566 on array objects (not on types and subtypes).
18569 @t{'Min} and @t{'Max}.
18572 @t{'Pos} and @t{'Val}.
18578 @t{'Range} on array objects (not subtypes), but only as the right
18579 operand of the membership (@code{in}) operator.
18582 @t{'Access}, @t{'Unchecked_Access}, and
18583 @t{'Unrestricted_Access} (a GNAT extension).
18590 The names in @code{Characters.Latin_1} are not available.
18593 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18594 equality of representations. They will generally work correctly
18595 for strings and arrays whose elements have integer or enumeration types.
18596 They may not work correctly for arrays whose element
18597 types have user-defined equality, for arrays of real values
18598 (in particular, IEEE-conformant floating point, because of negative
18599 zeroes and NaNs), and for arrays whose elements contain unused bits with
18600 indeterminate values.
18603 The other component-by-component array operations (@code{and}, @code{or},
18604 @code{xor}, @code{not}, and relational tests other than equality)
18605 are not implemented.
18608 @cindex array aggregates (Ada)
18609 @cindex record aggregates (Ada)
18610 @cindex aggregates (Ada)
18611 There is limited support for array and record aggregates. They are
18612 permitted only on the right sides of assignments, as in these examples:
18615 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18616 (@value{GDBP}) set An_Array := (1, others => 0)
18617 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18618 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18619 (@value{GDBP}) set A_Record := (1, "Peter", True);
18620 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18624 discriminant's value by assigning an aggregate has an
18625 undefined effect if that discriminant is used within the record.
18626 However, you can first modify discriminants by directly assigning to
18627 them (which normally would not be allowed in Ada), and then performing an
18628 aggregate assignment. For example, given a variable @code{A_Rec}
18629 declared to have a type such as:
18632 type Rec (Len : Small_Integer := 0) is record
18634 Vals : IntArray (1 .. Len);
18638 you can assign a value with a different size of @code{Vals} with two
18642 (@value{GDBP}) set A_Rec.Len := 4
18643 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18646 As this example also illustrates, @value{GDBN} is very loose about the usual
18647 rules concerning aggregates. You may leave out some of the
18648 components of an array or record aggregate (such as the @code{Len}
18649 component in the assignment to @code{A_Rec} above); they will retain their
18650 original values upon assignment. You may freely use dynamic values as
18651 indices in component associations. You may even use overlapping or
18652 redundant component associations, although which component values are
18653 assigned in such cases is not defined.
18656 Calls to dispatching subprograms are not implemented.
18659 The overloading algorithm is much more limited (i.e., less selective)
18660 than that of real Ada. It makes only limited use of the context in
18661 which a subexpression appears to resolve its meaning, and it is much
18662 looser in its rules for allowing type matches. As a result, some
18663 function calls will be ambiguous, and the user will be asked to choose
18664 the proper resolution.
18667 The @code{new} operator is not implemented.
18670 Entry calls are not implemented.
18673 Aside from printing, arithmetic operations on the native VAX floating-point
18674 formats are not supported.
18677 It is not possible to slice a packed array.
18680 The names @code{True} and @code{False}, when not part of a qualified name,
18681 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18683 Should your program
18684 redefine these names in a package or procedure (at best a dubious practice),
18685 you will have to use fully qualified names to access their new definitions.
18688 Based real literals are not implemented.
18691 @node Additions to Ada
18692 @subsubsection Additions to Ada
18693 @cindex Ada, deviations from
18695 As it does for other languages, @value{GDBN} makes certain generic
18696 extensions to Ada (@pxref{Expressions}):
18700 If the expression @var{E} is a variable residing in memory (typically
18701 a local variable or array element) and @var{N} is a positive integer,
18702 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18703 @var{N}-1 adjacent variables following it in memory as an array. In
18704 Ada, this operator is generally not necessary, since its prime use is
18705 in displaying parts of an array, and slicing will usually do this in
18706 Ada. However, there are occasional uses when debugging programs in
18707 which certain debugging information has been optimized away.
18710 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18711 appears in function or file @var{B}.'' When @var{B} is a file name,
18712 you must typically surround it in single quotes.
18715 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18716 @var{type} that appears at address @var{addr}.''
18719 A name starting with @samp{$} is a convenience variable
18720 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18723 In addition, @value{GDBN} provides a few other shortcuts and outright
18724 additions specific to Ada:
18728 The assignment statement is allowed as an expression, returning
18729 its right-hand operand as its value. Thus, you may enter
18732 (@value{GDBP}) set x := y + 3
18733 (@value{GDBP}) print A(tmp := y + 1)
18737 The semicolon is allowed as an ``operator,'' returning as its value
18738 the value of its right-hand operand.
18739 This allows, for example,
18740 complex conditional breaks:
18743 (@value{GDBP}) break f
18744 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18748 An extension to based literals can be used to specify the exact byte
18749 contents of a floating-point literal. After the base, you can use
18750 from zero to two @samp{l} characters, followed by an @samp{f}. The
18751 number of @samp{l} characters controls the width of the resulting real
18752 constant: zero means @code{Float} is used, one means
18753 @code{Long_Float}, and two means @code{Long_Long_Float}.
18756 (@value{GDBP}) print 16f#41b80000#
18761 Rather than use catenation and symbolic character names to introduce special
18762 characters into strings, one may instead use a special bracket notation,
18763 which is also used to print strings. A sequence of characters of the form
18764 @samp{["@var{XX}"]} within a string or character literal denotes the
18765 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18766 sequence of characters @samp{["""]} also denotes a single quotation mark
18767 in strings. For example,
18769 "One line.["0a"]Next line.["0a"]"
18772 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18776 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18777 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18781 (@value{GDBP}) print 'max(x, y)
18785 When printing arrays, @value{GDBN} uses positional notation when the
18786 array has a lower bound of 1, and uses a modified named notation otherwise.
18787 For example, a one-dimensional array of three integers with a lower bound
18788 of 3 might print as
18795 That is, in contrast to valid Ada, only the first component has a @code{=>}
18799 You may abbreviate attributes in expressions with any unique,
18800 multi-character subsequence of
18801 their names (an exact match gets preference).
18802 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18803 in place of @t{a'length}.
18806 @cindex quoting Ada internal identifiers
18807 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18808 to lower case. The GNAT compiler uses upper-case characters for
18809 some of its internal identifiers, which are normally of no interest to users.
18810 For the rare occasions when you actually have to look at them,
18811 enclose them in angle brackets to avoid the lower-case mapping.
18814 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18818 Printing an object of class-wide type or dereferencing an
18819 access-to-class-wide value will display all the components of the object's
18820 specific type (as indicated by its run-time tag). Likewise, component
18821 selection on such a value will operate on the specific type of the
18826 @node Overloading support for Ada
18827 @subsubsection Overloading support for Ada
18828 @cindex overloading, Ada
18830 The debugger supports limited overloading. Given a subprogram call in which
18831 the function symbol has multiple definitions, it will use the number of
18832 actual parameters and some information about their types to attempt to narrow
18833 the set of definitions. It also makes very limited use of context, preferring
18834 procedures to functions in the context of the @code{call} command, and
18835 functions to procedures elsewhere.
18837 If, after narrowing, the set of matching definitions still contains more than
18838 one definition, @value{GDBN} will display a menu to query which one it should
18842 (@value{GDBP}) print f(1)
18843 Multiple matches for f
18845 [1] foo.f (integer) return boolean at foo.adb:23
18846 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18850 In this case, just select one menu entry either to cancel expression evaluation
18851 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18852 instance (type the corresponding number and press @key{RET}).
18854 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18859 @kindex set ada print-signatures
18860 @item set ada print-signatures
18861 Control whether parameter types and return types are displayed in overloads
18862 selection menus. It is @code{on} by default.
18863 @xref{Overloading support for Ada}.
18865 @kindex show ada print-signatures
18866 @item show ada print-signatures
18867 Show the current setting for displaying parameter types and return types in
18868 overloads selection menu.
18869 @xref{Overloading support for Ada}.
18873 @node Stopping Before Main Program
18874 @subsubsection Stopping at the Very Beginning
18876 @cindex breakpointing Ada elaboration code
18877 It is sometimes necessary to debug the program during elaboration, and
18878 before reaching the main procedure.
18879 As defined in the Ada Reference
18880 Manual, the elaboration code is invoked from a procedure called
18881 @code{adainit}. To run your program up to the beginning of
18882 elaboration, simply use the following two commands:
18883 @code{tbreak adainit} and @code{run}.
18885 @node Ada Exceptions
18886 @subsubsection Ada Exceptions
18888 A command is provided to list all Ada exceptions:
18891 @kindex info exceptions
18892 @item info exceptions
18893 @itemx info exceptions @var{regexp}
18894 The @code{info exceptions} command allows you to list all Ada exceptions
18895 defined within the program being debugged, as well as their addresses.
18896 With a regular expression, @var{regexp}, as argument, only those exceptions
18897 whose names match @var{regexp} are listed.
18900 Below is a small example, showing how the command can be used, first
18901 without argument, and next with a regular expression passed as an
18905 (@value{GDBP}) info exceptions
18906 All defined Ada exceptions:
18907 constraint_error: 0x613da0
18908 program_error: 0x613d20
18909 storage_error: 0x613ce0
18910 tasking_error: 0x613ca0
18911 const.aint_global_e: 0x613b00
18912 (@value{GDBP}) info exceptions const.aint
18913 All Ada exceptions matching regular expression "const.aint":
18914 constraint_error: 0x613da0
18915 const.aint_global_e: 0x613b00
18918 It is also possible to ask @value{GDBN} to stop your program's execution
18919 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18922 @subsubsection Extensions for Ada Tasks
18923 @cindex Ada, tasking
18925 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18926 @value{GDBN} provides the following task-related commands:
18931 This command shows a list of current Ada tasks, as in the following example:
18938 (@value{GDBP}) info tasks
18939 ID TID P-ID Pri State Name
18940 1 8088000 0 15 Child Activation Wait main_task
18941 2 80a4000 1 15 Accept Statement b
18942 3 809a800 1 15 Child Activation Wait a
18943 * 4 80ae800 3 15 Runnable c
18948 In this listing, the asterisk before the last task indicates it to be the
18949 task currently being inspected.
18953 Represents @value{GDBN}'s internal task number.
18959 The parent's task ID (@value{GDBN}'s internal task number).
18962 The base priority of the task.
18965 Current state of the task.
18969 The task has been created but has not been activated. It cannot be
18973 The task is not blocked for any reason known to Ada. (It may be waiting
18974 for a mutex, though.) It is conceptually "executing" in normal mode.
18977 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18978 that were waiting on terminate alternatives have been awakened and have
18979 terminated themselves.
18981 @item Child Activation Wait
18982 The task is waiting for created tasks to complete activation.
18984 @item Accept or Select Term
18985 The task is waiting on an accept or selective wait statement.
18987 @item Waiting on entry call
18988 The task is waiting on an entry call.
18990 @item Async Select Wait
18991 The task is waiting to start the abortable part of an asynchronous
18995 The task is waiting on a select statement with only a delay
18998 @item Child Termination Wait
18999 The task is sleeping having completed a master within itself, and is
19000 waiting for the tasks dependent on that master to become terminated or
19001 waiting on a terminate Phase.
19003 @item Wait Child in Term Alt
19004 The task is sleeping waiting for tasks on terminate alternatives to
19005 finish terminating.
19007 @item Asynchronous Hold
19008 The task has been held by @code{Ada.Asynchronous_Task_Control.Hold_Task}.
19011 The task has been created and is being made runnable.
19013 @item Selective Wait
19014 The task is waiting in a selective wait statement.
19016 @item Accepting RV with @var{taskno}
19017 The task is accepting a rendez-vous with the task @var{taskno}.
19019 @item Waiting on RV with @var{taskno}
19020 The task is waiting for a rendez-vous with the task @var{taskno}.
19024 Name of the task in the program.
19028 @kindex info task @var{taskno}
19029 @item info task @var{taskno}
19030 This command shows detailed informations on the specified task, as in
19031 the following example:
19036 (@value{GDBP}) info tasks
19037 ID TID P-ID Pri State Name
19038 1 8077880 0 15 Child Activation Wait main_task
19039 * 2 807c468 1 15 Runnable task_1
19040 (@value{GDBP}) info task 2
19041 Ada Task: 0x807c468
19045 Parent: 1 ("main_task")
19051 @kindex task@r{ (Ada)}
19052 @cindex current Ada task ID
19053 This command prints the ID and name of the current task.
19059 (@value{GDBP}) info tasks
19060 ID TID P-ID Pri State Name
19061 1 8077870 0 15 Child Activation Wait main_task
19062 * 2 807c458 1 15 Runnable some_task
19063 (@value{GDBP}) task
19064 [Current task is 2 "some_task"]
19067 @item task @var{taskno}
19068 @cindex Ada task switching
19069 This command is like the @code{thread @var{thread-id}}
19070 command (@pxref{Threads}). It switches the context of debugging
19071 from the current task to the given task.
19077 (@value{GDBP}) info tasks
19078 ID TID P-ID Pri State Name
19079 1 8077870 0 15 Child Activation Wait main_task
19080 * 2 807c458 1 15 Runnable some_task
19081 (@value{GDBP}) task 1
19082 [Switching to task 1 "main_task"]
19083 #0 0x8067726 in pthread_cond_wait ()
19085 #0 0x8067726 in pthread_cond_wait ()
19086 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
19087 #2 0x805cb63 in system.task_primitives.operations.sleep ()
19088 #3 0x806153e in system.tasking.stages.activate_tasks ()
19089 #4 0x804aacc in un () at un.adb:5
19092 @item task apply [@var{task-id-list} | all] [@var{flag}]@dots{} @var{command}
19093 The @code{task apply} command is the Ada tasking analogue of
19094 @code{thread apply} (@pxref{Threads}). It allows you to apply the
19095 named @var{command} to one or more tasks. Specify the tasks that you
19096 want affected using a list of task IDs, or specify @code{all} to apply
19099 The @var{flag} arguments control what output to produce and how to
19100 handle errors raised when applying @var{command} to a task.
19101 @var{flag} must start with a @code{-} directly followed by one letter
19102 in @code{qcs}. If several flags are provided, they must be given
19103 individually, such as @code{-c -q}.
19105 By default, @value{GDBN} displays some task information before the
19106 output produced by @var{command}, and an error raised during the
19107 execution of a @var{command} will abort @code{task apply}. The
19108 following flags can be used to fine-tune this behavior:
19112 The flag @code{-c}, which stands for @samp{continue}, causes any
19113 errors in @var{command} to be displayed, and the execution of
19114 @code{task apply} then continues.
19116 The flag @code{-s}, which stands for @samp{silent}, causes any errors
19117 or empty output produced by a @var{command} to be silently ignored.
19118 That is, the execution continues, but the task information and errors
19121 The flag @code{-q} (@samp{quiet}) disables printing the task
19125 Flags @code{-c} and @code{-s} cannot be used together.
19127 @item break @var{locspec} task @var{taskno}
19128 @itemx break @var{locspec} task @var{taskno} if @dots{}
19129 @cindex breakpoints and tasks, in Ada
19130 @cindex task breakpoints, in Ada
19131 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
19132 These commands are like the @code{break @dots{} thread @dots{}}
19133 command (@pxref{Thread Stops}). @xref{Location Specifications}, for
19134 the various forms of @var{locspec}.
19136 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
19137 to specify that you only want @value{GDBN} to stop the program when a
19138 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
19139 numeric task identifiers assigned by @value{GDBN}, shown in the first
19140 column of the @samp{info tasks} display.
19142 If you do not specify @samp{task @var{taskno}} when you set a
19143 breakpoint, the breakpoint applies to @emph{all} tasks of your
19146 You can use the @code{task} qualifier on conditional breakpoints as
19147 well; in this case, place @samp{task @var{taskno}} before the
19148 breakpoint condition (before the @code{if}).
19156 (@value{GDBP}) info tasks
19157 ID TID P-ID Pri State Name
19158 1 140022020 0 15 Child Activation Wait main_task
19159 2 140045060 1 15 Accept/Select Wait t2
19160 3 140044840 1 15 Runnable t1
19161 * 4 140056040 1 15 Runnable t3
19162 (@value{GDBP}) b 15 task 2
19163 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
19164 (@value{GDBP}) cont
19169 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
19171 (@value{GDBP}) info tasks
19172 ID TID P-ID Pri State Name
19173 1 140022020 0 15 Child Activation Wait main_task
19174 * 2 140045060 1 15 Runnable t2
19175 3 140044840 1 15 Runnable t1
19176 4 140056040 1 15 Delay Sleep t3
19180 @node Ada Tasks and Core Files
19181 @subsubsection Tasking Support when Debugging Core Files
19182 @cindex Ada tasking and core file debugging
19184 When inspecting a core file, as opposed to debugging a live program,
19185 tasking support may be limited or even unavailable, depending on
19186 the platform being used.
19187 For instance, on x86-linux, the list of tasks is available, but task
19188 switching is not supported.
19190 On certain platforms, the debugger needs to perform some
19191 memory writes in order to provide Ada tasking support. When inspecting
19192 a core file, this means that the core file must be opened with read-write
19193 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
19194 Under these circumstances, you should make a backup copy of the core
19195 file before inspecting it with @value{GDBN}.
19197 @node Ravenscar Profile
19198 @subsubsection Tasking Support when using the Ravenscar Profile
19199 @cindex Ravenscar Profile
19201 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
19202 specifically designed for systems with safety-critical real-time
19206 @kindex set ravenscar task-switching on
19207 @cindex task switching with program using Ravenscar Profile
19208 @item set ravenscar task-switching on
19209 Allows task switching when debugging a program that uses the Ravenscar
19210 Profile. This is the default.
19212 @kindex set ravenscar task-switching off
19213 @item set ravenscar task-switching off
19214 Turn off task switching when debugging a program that uses the Ravenscar
19215 Profile. This is mostly intended to disable the code that adds support
19216 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
19217 the Ravenscar runtime is preventing @value{GDBN} from working properly.
19218 To be effective, this command should be run before the program is started.
19220 @kindex show ravenscar task-switching
19221 @item show ravenscar task-switching
19222 Show whether it is possible to switch from task to task in a program
19223 using the Ravenscar Profile.
19227 @cindex Ravenscar thread
19228 When Ravenscar task-switching is enabled, Ravenscar tasks are
19229 announced by @value{GDBN} as if they were threads:
19233 [New Ravenscar Thread 0x2b8f0]
19236 Both Ravenscar tasks and the underlying CPU threads will show up in
19237 the output of @code{info threads}:
19242 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
19243 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
19244 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
19245 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
19246 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
19247 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
19250 One known limitation of the Ravenscar support in @value{GDBN} is that
19251 it isn't currently possible to single-step through the runtime
19252 initialization sequence. If you need to debug this code, you should
19253 use @code{set ravenscar task-switching off}.
19255 @node Ada Source Character Set
19256 @subsubsection Ada Source Character Set
19257 @cindex Ada, source character set
19259 The GNAT compiler supports a number of character sets for source
19260 files. @xref{Character Set Control, , Character Set Control,
19261 gnat_ugn}. @value{GDBN} includes support for this as well.
19264 @item set ada source-charset @var{charset}
19265 @kindex set ada source-charset
19266 Set the source character set for Ada. The character set must be
19267 supported by GNAT. Because this setting affects the decoding of
19268 symbols coming from the debug information in your program, the setting
19269 should be set as early as possible. The default is @code{ISO-8859-1},
19270 because that is also GNAT's default.
19272 @item show ada source-charset
19273 @kindex show ada source-charset
19274 Show the current source character set for Ada.
19278 @subsubsection Known Peculiarities of Ada Mode
19279 @cindex Ada, problems
19281 Besides the omissions listed previously (@pxref{Omissions from Ada}),
19282 we know of several problems with and limitations of Ada mode in
19284 some of which will be fixed with planned future releases of the debugger
19285 and the GNU Ada compiler.
19289 Static constants that the compiler chooses not to materialize as objects in
19290 storage are invisible to the debugger.
19293 Named parameter associations in function argument lists are ignored (the
19294 argument lists are treated as positional).
19297 Many useful library packages are currently invisible to the debugger.
19300 Fixed-point arithmetic, conversions, input, and output is carried out using
19301 floating-point arithmetic, and may give results that only approximate those on
19305 The GNAT compiler never generates the prefix @code{Standard} for any of
19306 the standard symbols defined by the Ada language. @value{GDBN} knows about
19307 this: it will strip the prefix from names when you use it, and will never
19308 look for a name you have so qualified among local symbols, nor match against
19309 symbols in other packages or subprograms. If you have
19310 defined entities anywhere in your program other than parameters and
19311 local variables whose simple names match names in @code{Standard},
19312 GNAT's lack of qualification here can cause confusion. When this happens,
19313 you can usually resolve the confusion
19314 by qualifying the problematic names with package
19315 @code{Standard} explicitly.
19318 Older versions of the compiler sometimes generate erroneous debugging
19319 information, resulting in the debugger incorrectly printing the value
19320 of affected entities. In some cases, the debugger is able to work
19321 around an issue automatically. In other cases, the debugger is able
19322 to work around the issue, but the work-around has to be specifically
19325 @kindex set ada trust-PAD-over-XVS
19326 @kindex show ada trust-PAD-over-XVS
19329 @item set ada trust-PAD-over-XVS on
19330 Configure GDB to strictly follow the GNAT encoding when computing the
19331 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
19332 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
19333 a complete description of the encoding used by the GNAT compiler).
19334 This is the default.
19336 @item set ada trust-PAD-over-XVS off
19337 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
19338 sometimes prints the wrong value for certain entities, changing @code{ada
19339 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
19340 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
19341 @code{off}, but this incurs a slight performance penalty, so it is
19342 recommended to leave this setting to @code{on} unless necessary.
19346 @cindex GNAT descriptive types
19347 @cindex GNAT encoding
19348 Internally, the debugger also relies on the compiler following a number
19349 of conventions known as the @samp{GNAT Encoding}, all documented in
19350 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
19351 how the debugging information should be generated for certain types.
19352 In particular, this convention makes use of @dfn{descriptive types},
19353 which are artificial types generated purely to help the debugger.
19355 These encodings were defined at a time when the debugging information
19356 format used was not powerful enough to describe some of the more complex
19357 types available in Ada. Since DWARF allows us to express nearly all
19358 Ada features, the long-term goal is to slowly replace these descriptive
19359 types by their pure DWARF equivalent. To facilitate that transition,
19360 a new maintenance option is available to force the debugger to ignore
19361 those descriptive types. It allows the user to quickly evaluate how
19362 well @value{GDBN} works without them.
19366 @kindex maint ada set ignore-descriptive-types
19367 @item maintenance ada set ignore-descriptive-types [on|off]
19368 Control whether the debugger should ignore descriptive types.
19369 The default is not to ignore descriptives types (@code{off}).
19371 @kindex maint ada show ignore-descriptive-types
19372 @item maintenance ada show ignore-descriptive-types
19373 Show if descriptive types are ignored by @value{GDBN}.
19377 @node Unsupported Languages
19378 @section Unsupported Languages
19380 @cindex unsupported languages
19381 @cindex minimal language
19382 In addition to the other fully-supported programming languages,
19383 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
19384 It does not represent a real programming language, but provides a set
19385 of capabilities close to what the C or assembly languages provide.
19386 This should allow most simple operations to be performed while debugging
19387 an application that uses a language currently not supported by @value{GDBN}.
19389 If the language is set to @code{auto}, @value{GDBN} will automatically
19390 select this language if the current frame corresponds to an unsupported
19394 @chapter Examining the Symbol Table
19396 The commands described in this chapter allow you to inquire about the
19397 symbols (names of variables, functions and types) defined in your
19398 program. This information is inherent in the text of your program and
19399 does not change as your program executes. @value{GDBN} finds it in your
19400 program's symbol table, in the file indicated when you started @value{GDBN}
19401 (@pxref{File Options, ,Choosing Files}), or by one of the
19402 file-management commands (@pxref{Files, ,Commands to Specify Files}).
19404 @cindex symbol names
19405 @cindex names of symbols
19406 @cindex quoting names
19407 @anchor{quoting names}
19408 Occasionally, you may need to refer to symbols that contain unusual
19409 characters, which @value{GDBN} ordinarily treats as word delimiters. The
19410 most frequent case is in referring to static variables in other
19411 source files (@pxref{Variables,,Program Variables}). File names
19412 are recorded in object files as debugging symbols, but @value{GDBN} would
19413 ordinarily parse a typical file name, like @file{foo.c}, as the three words
19414 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
19415 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
19422 looks up the value of @code{x} in the scope of the file @file{foo.c}.
19425 @cindex case-insensitive symbol names
19426 @cindex case sensitivity in symbol names
19427 @kindex set case-sensitive
19428 @item set case-sensitive on
19429 @itemx set case-sensitive off
19430 @itemx set case-sensitive auto
19431 Normally, when @value{GDBN} looks up symbols, it matches their names
19432 with case sensitivity determined by the current source language.
19433 Occasionally, you may wish to control that. The command @code{set
19434 case-sensitive} lets you do that by specifying @code{on} for
19435 case-sensitive matches or @code{off} for case-insensitive ones. If
19436 you specify @code{auto}, case sensitivity is reset to the default
19437 suitable for the source language. The default is case-sensitive
19438 matches for all languages except for Fortran, for which the default is
19439 case-insensitive matches.
19441 @kindex show case-sensitive
19442 @item show case-sensitive
19443 This command shows the current setting of case sensitivity for symbols
19446 @kindex set print type methods
19447 @item set print type methods
19448 @itemx set print type methods on
19449 @itemx set print type methods off
19450 Normally, when @value{GDBN} prints a class, it displays any methods
19451 declared in that class. You can control this behavior either by
19452 passing the appropriate flag to @code{ptype}, or using @command{set
19453 print type methods}. Specifying @code{on} will cause @value{GDBN} to
19454 display the methods; this is the default. Specifying @code{off} will
19455 cause @value{GDBN} to omit the methods.
19457 @kindex show print type methods
19458 @item show print type methods
19459 This command shows the current setting of method display when printing
19462 @kindex set print type nested-type-limit
19463 @item set print type nested-type-limit @var{limit}
19464 @itemx set print type nested-type-limit unlimited
19465 Set the limit of displayed nested types that the type printer will
19466 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
19467 nested definitions. By default, the type printer will not show any nested
19468 types defined in classes.
19470 @kindex show print type nested-type-limit
19471 @item show print type nested-type-limit
19472 This command shows the current display limit of nested types when
19475 @kindex set print type typedefs
19476 @item set print type typedefs
19477 @itemx set print type typedefs on
19478 @itemx set print type typedefs off
19480 Normally, when @value{GDBN} prints a class, it displays any typedefs
19481 defined in that class. You can control this behavior either by
19482 passing the appropriate flag to @code{ptype}, or using @command{set
19483 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
19484 display the typedef definitions; this is the default. Specifying
19485 @code{off} will cause @value{GDBN} to omit the typedef definitions.
19486 Note that this controls whether the typedef definition itself is
19487 printed, not whether typedef names are substituted when printing other
19490 @kindex show print type typedefs
19491 @item show print type typedefs
19492 This command shows the current setting of typedef display when
19495 @kindex set print type hex
19496 @item set print type hex
19497 @itemx set print type hex on
19498 @itemx set print type hex off
19500 When @value{GDBN} prints sizes and offsets of struct members, it can use
19501 either the decimal or hexadecimal notation. You can select one or the
19502 other either by passing the appropriate flag to @code{ptype}, or by using
19503 the @command{set print type hex} command.
19505 @kindex show print type hex
19506 @item show print type hex
19507 This command shows whether the sizes and offsets of struct members are
19508 printed in decimal or hexadecimal notation.
19510 @kindex info address
19511 @cindex address of a symbol
19512 @item info address @var{symbol}
19513 Describe where the data for @var{symbol} is stored. For a register
19514 variable, this says which register it is kept in. For a non-register
19515 local variable, this prints the stack-frame offset at which the variable
19518 Note the contrast with @samp{print &@var{symbol}}, which does not work
19519 at all for a register variable, and for a stack local variable prints
19520 the exact address of the current instantiation of the variable.
19522 @kindex info symbol
19523 @cindex symbol from address
19524 @cindex closest symbol and offset for an address
19525 @item info symbol @var{addr}
19526 Print the name of a symbol which is stored at the address @var{addr}.
19527 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
19528 nearest symbol and an offset from it:
19531 (@value{GDBP}) info symbol 0x54320
19532 _initialize_vx + 396 in section .text
19536 This is the opposite of the @code{info address} command. You can use
19537 it to find out the name of a variable or a function given its address.
19539 For dynamically linked executables, the name of executable or shared
19540 library containing the symbol is also printed:
19543 (@value{GDBP}) info symbol 0x400225
19544 _start + 5 in section .text of /tmp/a.out
19545 (@value{GDBP}) info symbol 0x2aaaac2811cf
19546 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
19551 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
19552 Demangle @var{name}.
19553 If @var{language} is provided it is the name of the language to demangle
19554 @var{name} in. Otherwise @var{name} is demangled in the current language.
19556 The @samp{--} option specifies the end of options,
19557 and is useful when @var{name} begins with a dash.
19559 The parameter @code{demangle-style} specifies how to interpret the kind
19560 of mangling used. @xref{Print Settings}.
19563 @item whatis[/@var{flags}] [@var{arg}]
19564 Print the data type of @var{arg}, which can be either an expression
19565 or a name of a data type. With no argument, print the data type of
19566 @code{$}, the last value in the value history.
19568 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
19569 is not actually evaluated, and any side-effecting operations (such as
19570 assignments or function calls) inside it do not take place.
19572 If @var{arg} is a variable or an expression, @code{whatis} prints its
19573 literal type as it is used in the source code. If the type was
19574 defined using a @code{typedef}, @code{whatis} will @emph{not} print
19575 the data type underlying the @code{typedef}. If the type of the
19576 variable or the expression is a compound data type, such as
19577 @code{struct} or @code{class}, @code{whatis} never prints their
19578 fields or methods. It just prints the @code{struct}/@code{class}
19579 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
19580 such a compound data type, use @code{ptype}.
19582 If @var{arg} is a type name that was defined using @code{typedef},
19583 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
19584 Unrolling means that @code{whatis} will show the underlying type used
19585 in the @code{typedef} declaration of @var{arg}. However, if that
19586 underlying type is also a @code{typedef}, @code{whatis} will not
19589 For C code, the type names may also have the form @samp{class
19590 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
19591 @var{union-tag}} or @samp{enum @var{enum-tag}}.
19593 @var{flags} can be used to modify how the type is displayed.
19594 Available flags are:
19598 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
19599 parameters and typedefs defined in a class when printing the class'
19600 members. The @code{/r} flag disables this.
19603 Do not print methods defined in the class.
19606 Print methods defined in the class. This is the default, but the flag
19607 exists in case you change the default with @command{set print type methods}.
19610 Do not print typedefs defined in the class. Note that this controls
19611 whether the typedef definition itself is printed, not whether typedef
19612 names are substituted when printing other types.
19615 Print typedefs defined in the class. This is the default, but the flag
19616 exists in case you change the default with @command{set print type typedefs}.
19619 Print the offsets and sizes of fields in a struct, similar to what the
19620 @command{pahole} tool does. This option implies the @code{/tm} flags.
19623 Use hexadecimal notation when printing offsets and sizes of fields in a
19627 Use decimal notation when printing offsets and sizes of fields in a
19630 For example, given the following declarations:
19666 Issuing a @kbd{ptype /o struct tuv} command would print:
19669 (@value{GDBP}) ptype /o struct tuv
19670 /* offset | size */ type = struct tuv @{
19671 /* 0 | 4 */ int a1;
19672 /* XXX 4-byte hole */
19673 /* 8 | 8 */ char *a2;
19674 /* 16 | 4 */ int a3;
19676 /* total size (bytes): 24 */
19680 Notice the format of the first column of comments. There, you can
19681 find two parts separated by the @samp{|} character: the @emph{offset},
19682 which indicates where the field is located inside the struct, in
19683 bytes, and the @emph{size} of the field. Another interesting line is
19684 the marker of a @emph{hole} in the struct, indicating that it may be
19685 possible to pack the struct and make it use less space by reorganizing
19688 It is also possible to print offsets inside an union:
19691 (@value{GDBP}) ptype /o union qwe
19692 /* offset | size */ type = union qwe @{
19693 /* 24 */ struct tuv @{
19694 /* 0 | 4 */ int a1;
19695 /* XXX 4-byte hole */
19696 /* 8 | 8 */ char *a2;
19697 /* 16 | 4 */ int a3;
19699 /* total size (bytes): 24 */
19701 /* 40 */ struct xyz @{
19702 /* 0 | 4 */ int f1;
19703 /* 4 | 1 */ char f2;
19704 /* XXX 3-byte hole */
19705 /* 8 | 8 */ void *f3;
19706 /* 16 | 24 */ struct tuv @{
19707 /* 16 | 4 */ int a1;
19708 /* XXX 4-byte hole */
19709 /* 24 | 8 */ char *a2;
19710 /* 32 | 4 */ int a3;
19712 /* total size (bytes): 24 */
19715 /* total size (bytes): 40 */
19718 /* total size (bytes): 40 */
19722 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19723 same space (because we are dealing with an union), the offset is not
19724 printed for them. However, you can still examine the offset of each
19725 of these structures' fields.
19727 Another useful scenario is printing the offsets of a struct containing
19731 (@value{GDBP}) ptype /o struct tyu
19732 /* offset | size */ type = struct tyu @{
19733 /* 0:31 | 4 */ int a1 : 1;
19734 /* 0:28 | 4 */ int a2 : 3;
19735 /* 0: 5 | 4 */ int a3 : 23;
19736 /* 3: 3 | 1 */ signed char a4 : 2;
19737 /* XXX 3-bit hole */
19738 /* XXX 4-byte hole */
19739 /* 8 | 8 */ int64_t a5;
19740 /* 16: 0 | 4 */ int a6 : 5;
19741 /* 16: 5 | 8 */ int64_t a7 : 3;
19742 /* XXX 7-byte padding */
19744 /* total size (bytes): 24 */
19748 Note how the offset information is now extended to also include the
19749 first bit of the bitfield.
19753 @item ptype[/@var{flags}] [@var{arg}]
19754 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19755 detailed description of the type, instead of just the name of the type.
19756 @xref{Expressions, ,Expressions}.
19758 Contrary to @code{whatis}, @code{ptype} always unrolls any
19759 @code{typedef}s in its argument declaration, whether the argument is
19760 a variable, expression, or a data type. This means that @code{ptype}
19761 of a variable or an expression will not print literally its type as
19762 present in the source code---use @code{whatis} for that. @code{typedef}s at
19763 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19764 fields, methods and inner @code{class typedef}s of @code{struct}s,
19765 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19767 For example, for this variable declaration:
19770 typedef double real_t;
19771 struct complex @{ real_t real; double imag; @};
19772 typedef struct complex complex_t;
19774 real_t *real_pointer_var;
19778 the two commands give this output:
19782 (@value{GDBP}) whatis var
19784 (@value{GDBP}) ptype var
19785 type = struct complex @{
19789 (@value{GDBP}) whatis complex_t
19790 type = struct complex
19791 (@value{GDBP}) whatis struct complex
19792 type = struct complex
19793 (@value{GDBP}) ptype struct complex
19794 type = struct complex @{
19798 (@value{GDBP}) whatis real_pointer_var
19800 (@value{GDBP}) ptype real_pointer_var
19806 As with @code{whatis}, using @code{ptype} without an argument refers to
19807 the type of @code{$}, the last value in the value history.
19809 @cindex incomplete type
19810 Sometimes, programs use opaque data types or incomplete specifications
19811 of complex data structure. If the debug information included in the
19812 program does not allow @value{GDBN} to display a full declaration of
19813 the data type, it will say @samp{<incomplete type>}. For example,
19814 given these declarations:
19818 struct foo *fooptr;
19822 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19825 (@value{GDBP}) ptype foo
19826 $1 = <incomplete type>
19830 ``Incomplete type'' is C terminology for data types that are not
19831 completely specified.
19833 @cindex unknown type
19834 Othertimes, information about a variable's type is completely absent
19835 from the debug information included in the program. This most often
19836 happens when the program or library where the variable is defined
19837 includes no debug information at all. @value{GDBN} knows the variable
19838 exists from inspecting the linker/loader symbol table (e.g., the ELF
19839 dynamic symbol table), but such symbols do not contain type
19840 information. Inspecting the type of a (global) variable for which
19841 @value{GDBN} has no type information shows:
19844 (@value{GDBP}) ptype var
19845 type = <data variable, no debug info>
19848 @xref{Variables, no debug info variables}, for how to print the values
19852 @item info types [-q] [@var{regexp}]
19853 Print a brief description of all types whose names match the regular
19854 expression @var{regexp} (or all types in your program, if you supply
19855 no argument). Each complete typename is matched as though it were a
19856 complete line; thus, @samp{i type value} gives information on all
19857 types in your program whose names include the string @code{value}, but
19858 @samp{i type ^value$} gives information only on types whose complete
19859 name is @code{value}.
19861 In programs using different languages, @value{GDBN} chooses the syntax
19862 to print the type description according to the
19863 @samp{set language} value: using @samp{set language auto}
19864 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19865 language of the type, other values mean to use
19866 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19868 This command differs from @code{ptype} in two ways: first, like
19869 @code{whatis}, it does not print a detailed description; second, it
19870 lists all source files and line numbers where a type is defined.
19872 The output from @samp{into types} is proceeded with a header line
19873 describing what types are being listed. The optional flag @samp{-q},
19874 which stands for @samp{quiet}, disables printing this header
19877 @kindex info type-printers
19878 @item info type-printers
19879 Versions of @value{GDBN} that ship with Python scripting enabled may
19880 have ``type printers'' available. When using @command{ptype} or
19881 @command{whatis}, these printers are consulted when the name of a type
19882 is needed. @xref{Type Printing API}, for more information on writing
19885 @code{info type-printers} displays all the available type printers.
19887 @kindex enable type-printer
19888 @kindex disable type-printer
19889 @item enable type-printer @var{name}@dots{}
19890 @item disable type-printer @var{name}@dots{}
19891 These commands can be used to enable or disable type printers.
19894 @cindex local variables
19895 @item info scope @var{locspec}
19896 List all the variables local to the lexical scope of the code location
19897 that results from resolving @var{locspec}. @xref{Location
19898 Specifications}, for details about supported forms of @var{locspec}.
19902 (@value{GDBP}) @b{info scope command_line_handler}
19903 Scope for command_line_handler:
19904 Symbol rl is an argument at stack/frame offset 8, length 4.
19905 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19906 Symbol linelength is in static storage at address 0x150a1c, length 4.
19907 Symbol p is a local variable in register $esi, length 4.
19908 Symbol p1 is a local variable in register $ebx, length 4.
19909 Symbol nline is a local variable in register $edx, length 4.
19910 Symbol repeat is a local variable at frame offset -8, length 4.
19914 This command is especially useful for determining what data to collect
19915 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19918 @kindex info source
19920 Show information about the current source file---that is, the source file for
19921 the function containing the current point of execution:
19924 the name of the source file, and the directory containing it,
19926 the directory it was compiled in,
19928 its length, in lines,
19930 which programming language it is written in,
19932 if the debug information provides it, the program that compiled the file
19933 (which may include, e.g., the compiler version and command line arguments),
19935 whether the executable includes debugging information for that file, and
19936 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19938 whether the debugging information includes information about
19939 preprocessor macros.
19943 @kindex info sources
19944 @item info sources @r{[}-dirname | -basename@r{]} @r{[}--@r{]} @r{[}@var{regexp}@r{]}
19947 With no options @samp{info sources} prints the names of all source
19948 files in your program for which there is debugging information. The
19949 source files are presented based on a list of object files
19950 (executables and libraries) currently loaded into @value{GDBN}. For
19951 each object file all of the associated source files are listed.
19953 Each source file will only be printed once for each object file, but a
19954 single source file can be repeated in the output if it is part of
19955 multiple object files.
19957 If the optional @var{regexp} is provided, then only source files that
19958 match the regular expression will be printed. The matching is
19959 case-sensitive, except on operating systems that have case-insensitive
19960 filesystem (e.g., MS-Windows). @samp{--} can be used before
19961 @var{regexp} to prevent @value{GDBN} interpreting @var{regexp} as a
19962 command option (e.g. if @var{regexp} starts with @samp{-}).
19964 By default, the @var{regexp} is used to match anywhere in the
19965 filename. If @code{-dirname}, only files having a dirname matching
19966 @var{regexp} are shown. If @code{-basename}, only files having a
19967 basename matching @var{regexp} are shown.
19969 It is possible that an object file may be printed in the list with no
19970 associated source files. This can happen when either no source files
19971 match @var{regexp}, or, the object file was compiled without debug
19972 information and so @value{GDBN} is unable to find any source file
19975 @kindex info functions
19976 @item info functions [-q] [-n]
19977 Print the names and data types of all defined functions.
19978 Similarly to @samp{info types}, this command groups its output by source
19979 files and annotates each function definition with its source line
19982 In programs using different languages, @value{GDBN} chooses the syntax
19983 to print the function name and type according to the
19984 @samp{set language} value: using @samp{set language auto}
19985 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19986 language of the function, other values mean to use
19987 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19989 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19990 results. A non-debugging symbol is a symbol that comes from the
19991 executable's symbol table, not from the debug information (for
19992 example, DWARF) associated with the executable.
19994 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19995 printing header information and messages explaining why no functions
19998 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19999 Like @samp{info functions}, but only print the names and data types
20000 of the functions selected with the provided regexp(s).
20002 If @var{regexp} is provided, print only the functions whose names
20003 match the regular expression @var{regexp}.
20004 Thus, @samp{info fun step} finds all functions whose
20005 names include @code{step}; @samp{info fun ^step} finds those whose names
20006 start with @code{step}. If a function name contains characters that
20007 conflict with the regular expression language (e.g.@:
20008 @samp{operator*()}), they may be quoted with a backslash.
20010 If @var{type_regexp} is provided, print only the functions whose
20011 types, as printed by the @code{whatis} command, match
20012 the regular expression @var{type_regexp}.
20013 If @var{type_regexp} contains space(s), it should be enclosed in
20014 quote characters. If needed, use backslash to escape the meaning
20015 of special characters or quotes.
20016 Thus, @samp{info fun -t '^int ('} finds the functions that return
20017 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
20018 have an argument type containing int; @samp{info fun -t '^int (' ^step}
20019 finds the functions whose names start with @code{step} and that return
20022 If both @var{regexp} and @var{type_regexp} are provided, a function
20023 is printed only if its name matches @var{regexp} and its type matches
20027 @kindex info variables
20028 @item info variables [-q] [-n]
20029 Print the names and data types of all variables that are defined
20030 outside of functions (i.e.@: excluding local variables).
20031 The printed variables are grouped by source files and annotated with
20032 their respective source line numbers.
20034 In programs using different languages, @value{GDBN} chooses the syntax
20035 to print the variable name and type according to the
20036 @samp{set language} value: using @samp{set language auto}
20037 (see @ref{Automatically, ,Set Language Automatically}) means to use the
20038 language of the variable, other values mean to use
20039 the manually specified language (see @ref{Manually, ,Set Language Manually}).
20041 The @samp{-n} flag excludes non-debugging symbols from the results.
20043 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
20044 printing header information and messages explaining why no variables
20047 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
20048 Like @kbd{info variables}, but only print the variables selected
20049 with the provided regexp(s).
20051 If @var{regexp} is provided, print only the variables whose names
20052 match the regular expression @var{regexp}.
20054 If @var{type_regexp} is provided, print only the variables whose
20055 types, as printed by the @code{whatis} command, match
20056 the regular expression @var{type_regexp}.
20057 If @var{type_regexp} contains space(s), it should be enclosed in
20058 quote characters. If needed, use backslash to escape the meaning
20059 of special characters or quotes.
20061 If both @var{regexp} and @var{type_regexp} are provided, an argument
20062 is printed only if its name matches @var{regexp} and its type matches
20065 @kindex info modules
20067 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
20068 List all Fortran modules in the program, or all modules matching the
20069 optional regular expression @var{regexp}.
20071 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
20072 printing header information and messages explaining why no modules
20075 @kindex info module
20076 @cindex Fortran modules, information about
20077 @cindex functions and variables by Fortran module
20078 @cindex module functions and variables
20079 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
20080 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
20081 List all functions or variables within all Fortran modules. The set
20082 of functions or variables listed can be limited by providing some or
20083 all of the optional regular expressions. If @var{module-regexp} is
20084 provided, then only Fortran modules matching @var{module-regexp} will
20085 be searched. Only functions or variables whose type matches the
20086 optional regular expression @var{type-regexp} will be listed. And
20087 only functions or variables whose name matches the optional regular
20088 expression @var{regexp} will be listed.
20090 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
20091 printing header information and messages explaining why no functions
20092 or variables have been printed.
20094 @kindex info classes
20095 @cindex Objective-C, classes and selectors
20097 @itemx info classes @var{regexp}
20098 Display all Objective-C classes in your program, or
20099 (with the @var{regexp} argument) all those matching a particular regular
20102 @kindex info selectors
20103 @item info selectors
20104 @itemx info selectors @var{regexp}
20105 Display all Objective-C selectors in your program, or
20106 (with the @var{regexp} argument) all those matching a particular regular
20110 This was never implemented.
20111 @kindex info methods
20113 @itemx info methods @var{regexp}
20114 The @code{info methods} command permits the user to examine all defined
20115 methods within C@t{++} program, or (with the @var{regexp} argument) a
20116 specific set of methods found in the various C@t{++} classes. Many
20117 C@t{++} classes provide a large number of methods. Thus, the output
20118 from the @code{ptype} command can be overwhelming and hard to use. The
20119 @code{info-methods} command filters the methods, printing only those
20120 which match the regular-expression @var{regexp}.
20123 @cindex opaque data types
20124 @kindex set opaque-type-resolution
20125 @item set opaque-type-resolution on
20126 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
20127 declared as a pointer to a @code{struct}, @code{class}, or
20128 @code{union}---for example, @code{struct MyType *}---that is used in one
20129 source file although the full declaration of @code{struct MyType} is in
20130 another source file. The default is on.
20132 A change in the setting of this subcommand will not take effect until
20133 the next time symbols for a file are loaded.
20135 @item set opaque-type-resolution off
20136 Tell @value{GDBN} not to resolve opaque types. In this case, the type
20137 is printed as follows:
20139 @{<no data fields>@}
20142 @kindex show opaque-type-resolution
20143 @item show opaque-type-resolution
20144 Show whether opaque types are resolved or not.
20146 @kindex set print symbol-loading
20147 @cindex print messages when symbols are loaded
20148 @item set print symbol-loading
20149 @itemx set print symbol-loading full
20150 @itemx set print symbol-loading brief
20151 @itemx set print symbol-loading off
20152 The @code{set print symbol-loading} command allows you to control the
20153 printing of messages when @value{GDBN} loads symbol information.
20154 By default a message is printed for the executable and one for each
20155 shared library, and normally this is what you want. However, when
20156 debugging apps with large numbers of shared libraries these messages
20158 When set to @code{brief} a message is printed for each executable,
20159 and when @value{GDBN} loads a collection of shared libraries at once
20160 it will only print one message regardless of the number of shared
20161 libraries. When set to @code{off} no messages are printed.
20163 @kindex show print symbol-loading
20164 @item show print symbol-loading
20165 Show whether messages will be printed when a @value{GDBN} command
20166 entered from the keyboard causes symbol information to be loaded.
20168 @kindex maint print symbols
20169 @cindex symbol dump
20170 @kindex maint print psymbols
20171 @cindex partial symbol dump
20172 @kindex maint print msymbols
20173 @cindex minimal symbol dump
20174 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
20175 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20176 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20177 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20178 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
20179 Write a dump of debugging symbol data into the file @var{filename} or
20180 the terminal if @var{filename} is unspecified.
20181 If @code{-objfile @var{objfile}} is specified, only dump symbols for
20183 If @code{-pc @var{address}} is specified, only dump symbols for the file
20184 with code at that address. Note that @var{address} may be a symbol like
20186 If @code{-source @var{source}} is specified, only dump symbols for that
20189 These commands are used to debug the @value{GDBN} symbol-reading code.
20190 These commands do not modify internal @value{GDBN} state, therefore
20191 @samp{maint print symbols} will only print symbols for already expanded symbol
20193 You can use the command @code{info sources} to find out which files these are.
20194 If you use @samp{maint print psymbols} instead, the dump shows information
20195 about symbols that @value{GDBN} only knows partially---that is, symbols
20196 defined in files that @value{GDBN} has skimmed, but not yet read completely.
20197 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
20200 @xref{Files, ,Commands to Specify Files}, for a discussion of how
20201 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
20203 @kindex maint info symtabs
20204 @kindex maint info psymtabs
20205 @cindex listing @value{GDBN}'s internal symbol tables
20206 @cindex symbol tables, listing @value{GDBN}'s internal
20207 @cindex full symbol tables, listing @value{GDBN}'s internal
20208 @cindex partial symbol tables, listing @value{GDBN}'s internal
20209 @item maint info symtabs @r{[} @var{regexp} @r{]}
20210 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
20212 List the @code{struct symtab} or @code{struct partial_symtab}
20213 structures whose names match @var{regexp}. If @var{regexp} is not
20214 given, list them all. The output includes expressions which you can
20215 copy into a @value{GDBN} debugging this one to examine a particular
20216 structure in more detail. For example:
20219 (@value{GDBP}) maint info psymtabs dwarf2read
20220 @{ objfile /home/gnu/build/gdb/gdb
20221 ((struct objfile *) 0x82e69d0)
20222 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
20223 ((struct partial_symtab *) 0x8474b10)
20226 text addresses 0x814d3c8 -- 0x8158074
20227 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
20228 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
20229 dependencies (none)
20232 (@value{GDBP}) maint info symtabs
20236 We see that there is one partial symbol table whose filename contains
20237 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
20238 and we see that @value{GDBN} has not read in any symtabs yet at all.
20239 If we set a breakpoint on a function, that will cause @value{GDBN} to
20240 read the symtab for the compilation unit containing that function:
20243 (@value{GDBP}) break dwarf2_psymtab_to_symtab
20244 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
20246 (@value{GDBP}) maint info symtabs
20247 @{ objfile /home/gnu/build/gdb/gdb
20248 ((struct objfile *) 0x82e69d0)
20249 @{ symtab /home/gnu/src/gdb/dwarf2read.c
20250 ((struct symtab *) 0x86c1f38)
20253 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
20254 linetable ((struct linetable *) 0x8370fa0)
20255 debugformat DWARF 2
20261 @kindex maint info line-table
20262 @cindex listing @value{GDBN}'s internal line tables
20263 @cindex line tables, listing @value{GDBN}'s internal
20264 @item maint info line-table @r{[} @var{regexp} @r{]}
20266 List the @code{struct linetable} from all @code{struct symtab}
20267 instances whose name matches @var{regexp}. If @var{regexp} is not
20268 given, list the @code{struct linetable} from all @code{struct symtab}.
20272 (@value{GDBP}) maint info line-table
20273 objfile: /home/gnu/build/a.out ((struct objfile *) 0x6120000e0d40)
20274 compunit_symtab: simple.cpp ((struct compunit_symtab *) 0x6210000ff450)
20275 symtab: /home/gnu/src/simple.cpp ((struct symtab *) 0x6210000ff4d0)
20276 linetable: ((struct linetable *) 0x62100012b760):
20277 INDEX LINE ADDRESS IS-STMT PROLOGUE-END
20278 0 3 0x0000000000401110 Y
20279 1 4 0x0000000000401114 Y Y
20280 2 9 0x0000000000401120 Y
20281 3 10 0x0000000000401124 Y Y
20282 4 10 0x0000000000401129
20283 5 15 0x0000000000401130 Y
20284 6 16 0x0000000000401134 Y Y
20285 7 16 0x0000000000401139
20286 8 21 0x0000000000401140 Y
20287 9 22 0x000000000040114f Y Y
20288 10 22 0x0000000000401154
20289 11 END 0x000000000040115a Y
20292 The @samp{IS-STMT} column indicates if the address is a recommended breakpoint
20293 location to represent a line or a statement. The @samp{PROLOGUE-END} column
20294 indicates that a given address is an adequate place to set a breakpoint at the
20295 first instruction following a function prologue.
20297 @kindex maint set symbol-cache-size
20298 @cindex symbol cache size
20299 @item maint set symbol-cache-size @var{size}
20300 Set the size of the symbol cache to @var{size}.
20301 The default size is intended to be good enough for debugging
20302 most applications. This option exists to allow for experimenting
20303 with different sizes.
20305 @kindex maint show symbol-cache-size
20306 @item maint show symbol-cache-size
20307 Show the size of the symbol cache.
20309 @kindex maint print symbol-cache
20310 @cindex symbol cache, printing its contents
20311 @item maint print symbol-cache
20312 Print the contents of the symbol cache.
20313 This is useful when debugging symbol cache issues.
20315 @kindex maint print symbol-cache-statistics
20316 @cindex symbol cache, printing usage statistics
20317 @item maint print symbol-cache-statistics
20318 Print symbol cache usage statistics.
20319 This helps determine how well the cache is being utilized.
20321 @kindex maint flush symbol-cache
20322 @kindex maint flush-symbol-cache
20323 @cindex symbol cache, flushing
20324 @item maint flush symbol-cache
20325 @itemx maint flush-symbol-cache
20326 Flush the contents of the symbol cache, all entries are removed. This
20327 command is useful when debugging the symbol cache. It is also useful
20328 when collecting performance data. The command @code{maint
20329 flush-symbol-cache} is deprecated in favor of @code{maint flush
20332 @kindex maint set ignore-prologue-end-flag
20333 @cindex prologue-end
20334 @item maint set ignore-prologue-end-flag [on|off]
20335 Enable or disable the use of the @samp{PROLOGUE-END} flag from the line-table.
20336 When @samp{off} (the default), @value{GDBN} uses the @samp{PROLOGUE-END} flag
20337 to place breakpoints past the end of a function prologue. When @samp{on},
20338 @value{GDBN} ignores the flag and relies on prologue analyzers to skip function
20341 @kindex maint show ignore-prologue-end-flag
20342 @item maint show ignore-prologue-end-flag
20343 Show whether @value{GDBN} will ignore the @samp{PROLOGUE-END} flag.
20348 @chapter Altering Execution
20350 Once you think you have found an error in your program, you might want to
20351 find out for certain whether correcting the apparent error would lead to
20352 correct results in the rest of the run. You can find the answer by
20353 experiment, using the @value{GDBN} features for altering execution of the
20356 For example, you can store new values into variables or memory
20357 locations, give your program a signal, restart it at a different
20358 address, or even return prematurely from a function.
20361 * Assignment:: Assignment to variables
20362 * Jumping:: Continuing at a different address
20363 * Signaling:: Giving your program a signal
20364 * Returning:: Returning from a function
20365 * Calling:: Calling your program's functions
20366 * Patching:: Patching your program
20367 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
20371 @section Assignment to Variables
20374 @cindex setting variables
20375 To alter the value of a variable, evaluate an assignment expression.
20376 @xref{Expressions, ,Expressions}. For example,
20383 stores the value 4 into the variable @code{x}, and then prints the
20384 value of the assignment expression (which is 4).
20385 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
20386 information on operators in supported languages.
20388 @kindex set variable
20389 @cindex variables, setting
20390 If you are not interested in seeing the value of the assignment, use the
20391 @code{set} command instead of the @code{print} command. @code{set} is
20392 really the same as @code{print} except that the expression's value is
20393 not printed and is not put in the value history (@pxref{Value History,
20394 ,Value History}). The expression is evaluated only for its effects.
20396 If the beginning of the argument string of the @code{set} command
20397 appears identical to a @code{set} subcommand, use the @code{set
20398 variable} command instead of just @code{set}. This command is identical
20399 to @code{set} except for its lack of subcommands. For example, if your
20400 program has a variable @code{width}, you get an error if you try to set
20401 a new value with just @samp{set width=13}, because @value{GDBN} has the
20402 command @code{set width}:
20405 (@value{GDBP}) whatis width
20407 (@value{GDBP}) p width
20409 (@value{GDBP}) set width=47
20410 Invalid syntax in expression.
20414 The invalid expression, of course, is @samp{=47}. In
20415 order to actually set the program's variable @code{width}, use
20418 (@value{GDBP}) set var width=47
20421 Because the @code{set} command has many subcommands that can conflict
20422 with the names of program variables, it is a good idea to use the
20423 @code{set variable} command instead of just @code{set}. For example, if
20424 your program has a variable @code{g}, you run into problems if you try
20425 to set a new value with just @samp{set g=4}, because @value{GDBN} has
20426 the command @code{set gnutarget}, abbreviated @code{set g}:
20430 (@value{GDBP}) whatis g
20434 (@value{GDBP}) set g=4
20438 The program being debugged has been started already.
20439 Start it from the beginning? (y or n) y
20440 Starting program: /home/smith/cc_progs/a.out
20441 "/home/smith/cc_progs/a.out": can't open to read symbols:
20442 Invalid bfd target.
20443 (@value{GDBP}) show g
20444 The current BFD target is "=4".
20449 The program variable @code{g} did not change, and you silently set the
20450 @code{gnutarget} to an invalid value. In order to set the variable
20454 (@value{GDBP}) set var g=4
20457 @value{GDBN} allows more implicit conversions in assignments than C; you can
20458 freely store an integer value into a pointer variable or vice versa,
20459 and you can convert any structure to any other structure that is the
20460 same length or shorter.
20461 @comment FIXME: how do structs align/pad in these conversions?
20462 @comment /doc@cygnus.com 18dec1990
20464 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
20465 construct to generate a value of specified type at a specified address
20466 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
20467 to memory location @code{0x83040} as an integer (which implies a certain size
20468 and representation in memory), and
20471 set @{int@}0x83040 = 4
20475 stores the value 4 into that memory location.
20478 @section Continuing at a Different Address
20480 Ordinarily, when you continue your program, you do so at the place where
20481 it stopped, with the @code{continue} command. You can instead continue at
20482 an address of your own choosing, with the following commands:
20486 @kindex j @r{(@code{jump})}
20487 @item jump @var{locspec}
20488 @itemx j @var{locspec}
20489 Resume execution at the address of the code location that results from
20490 resolving @var{locspec}.
20491 @xref{Location Specifications}, for a description of the different
20492 forms of @var{locspec}. If @var{locspec} resolves to more than one
20493 address, the command aborts before jumping.
20494 Execution stops again immediately if there is a breakpoint there. It
20495 is common practice to use the @code{tbreak} command in conjunction
20496 with @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
20498 The @code{jump} command does not change the current stack frame, or
20499 the stack pointer, or the contents of any memory location or any
20500 register other than the program counter. If @var{locspec} resolves to
20501 an address in a different function from the one currently executing, the
20502 results may be bizarre if the two functions expect different patterns
20503 of arguments or of local variables. For this reason, the @code{jump}
20504 command requests confirmation if the jump address is not in the
20505 function currently executing. However, even bizarre results are
20506 predictable if you are well acquainted with the machine-language code
20510 On many systems, you can get much the same effect as the @code{jump}
20511 command by storing a new value into the register @code{$pc}. The
20512 difference is that this does not start your program running; it only
20513 changes the address of where it @emph{will} run when you continue. For
20521 makes the next @code{continue} command or stepping command execute at
20522 address @code{0x485}, rather than at the address where your program stopped.
20523 @xref{Continuing and Stepping, ,Continuing and Stepping}.
20525 The most common occasion to use the @code{jump} command is to back
20526 up---perhaps with more breakpoints set---over a portion of a program
20527 that has already executed, in order to examine its execution in more
20532 @section Giving your Program a Signal
20533 @cindex deliver a signal to a program
20537 @item signal @var{signal}
20538 Resume execution where your program is stopped, but immediately give it the
20539 signal @var{signal}. The @var{signal} can be the name or the number of a
20540 signal. For example, on many systems @code{signal 2} and @code{signal
20541 SIGINT} are both ways of sending an interrupt signal.
20543 Alternatively, if @var{signal} is zero, continue execution without
20544 giving a signal. This is useful when your program stopped on account of
20545 a signal and would ordinarily see the signal when resumed with the
20546 @code{continue} command; @samp{signal 0} causes it to resume without a
20549 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
20550 delivered to the currently selected thread, not the thread that last
20551 reported a stop. This includes the situation where a thread was
20552 stopped due to a signal. So if you want to continue execution
20553 suppressing the signal that stopped a thread, you should select that
20554 same thread before issuing the @samp{signal 0} command. If you issue
20555 the @samp{signal 0} command with another thread as the selected one,
20556 @value{GDBN} detects that and asks for confirmation.
20558 Invoking the @code{signal} command is not the same as invoking the
20559 @code{kill} utility from the shell. Sending a signal with @code{kill}
20560 causes @value{GDBN} to decide what to do with the signal depending on
20561 the signal handling tables (@pxref{Signals}). The @code{signal} command
20562 passes the signal directly to your program.
20564 @code{signal} does not repeat when you press @key{RET} a second time
20565 after executing the command.
20567 @kindex queue-signal
20568 @item queue-signal @var{signal}
20569 Queue @var{signal} to be delivered immediately to the current thread
20570 when execution of the thread resumes. The @var{signal} can be the name or
20571 the number of a signal. For example, on many systems @code{signal 2} and
20572 @code{signal SIGINT} are both ways of sending an interrupt signal.
20573 The handling of the signal must be set to pass the signal to the program,
20574 otherwise @value{GDBN} will report an error.
20575 You can control the handling of signals from @value{GDBN} with the
20576 @code{handle} command (@pxref{Signals}).
20578 Alternatively, if @var{signal} is zero, any currently queued signal
20579 for the current thread is discarded and when execution resumes no signal
20580 will be delivered. This is useful when your program stopped on account
20581 of a signal and would ordinarily see the signal when resumed with the
20582 @code{continue} command.
20584 This command differs from the @code{signal} command in that the signal
20585 is just queued, execution is not resumed. And @code{queue-signal} cannot
20586 be used to pass a signal whose handling state has been set to @code{nopass}
20591 @xref{stepping into signal handlers}, for information on how stepping
20592 commands behave when the thread has a signal queued.
20595 @section Returning from a Function
20598 @cindex returning from a function
20601 @itemx return @var{expression}
20602 You can cancel execution of a function call with the @code{return}
20603 command. If you give an
20604 @var{expression} argument, its value is used as the function's return
20608 When you use @code{return}, @value{GDBN} discards the selected stack frame
20609 (and all frames within it). You can think of this as making the
20610 discarded frame return prematurely. If you wish to specify a value to
20611 be returned, give that value as the argument to @code{return}.
20613 This pops the selected stack frame (@pxref{Selection, ,Selecting a
20614 Frame}), and any other frames inside of it, leaving its caller as the
20615 innermost remaining frame. That frame becomes selected. The
20616 specified value is stored in the registers used for returning values
20619 The @code{return} command does not resume execution; it leaves the
20620 program stopped in the state that would exist if the function had just
20621 returned. In contrast, the @code{finish} command (@pxref{Continuing
20622 and Stepping, ,Continuing and Stepping}) resumes execution until the
20623 selected stack frame returns naturally.
20625 @value{GDBN} needs to know how the @var{expression} argument should be set for
20626 the inferior. The concrete registers assignment depends on the OS ABI and the
20627 type being returned by the selected stack frame. For example it is common for
20628 OS ABI to return floating point values in FPU registers while integer values in
20629 CPU registers. Still some ABIs return even floating point values in CPU
20630 registers. Larger integer widths (such as @code{long long int}) also have
20631 specific placement rules. @value{GDBN} already knows the OS ABI from its
20632 current target so it needs to find out also the type being returned to make the
20633 assignment into the right register(s).
20635 Normally, the selected stack frame has debug info. @value{GDBN} will always
20636 use the debug info instead of the implicit type of @var{expression} when the
20637 debug info is available. For example, if you type @kbd{return -1}, and the
20638 function in the current stack frame is declared to return a @code{long long
20639 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
20640 into a @code{long long int}:
20643 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
20645 (@value{GDBP}) return -1
20646 Make func return now? (y or n) y
20647 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
20648 43 printf ("result=%lld\n", func ());
20652 However, if the selected stack frame does not have a debug info, e.g., if the
20653 function was compiled without debug info, @value{GDBN} has to find out the type
20654 to return from user. Specifying a different type by mistake may set the value
20655 in different inferior registers than the caller code expects. For example,
20656 typing @kbd{return -1} with its implicit type @code{int} would set only a part
20657 of a @code{long long int} result for a debug info less function (on 32-bit
20658 architectures). Therefore the user is required to specify the return type by
20659 an appropriate cast explicitly:
20662 Breakpoint 2, 0x0040050b in func ()
20663 (@value{GDBP}) return -1
20664 Return value type not available for selected stack frame.
20665 Please use an explicit cast of the value to return.
20666 (@value{GDBP}) return (long long int) -1
20667 Make selected stack frame return now? (y or n) y
20668 #0 0x00400526 in main ()
20673 @section Calling Program Functions
20676 @cindex calling functions
20677 @cindex inferior functions, calling
20678 @item print @var{expr}
20679 Evaluate the expression @var{expr} and display the resulting value.
20680 The expression may include calls to functions in the program being
20684 @item call @var{expr}
20685 Evaluate the expression @var{expr} without displaying @code{void}
20688 You can use this variant of the @code{print} command if you want to
20689 execute a function from your program that does not return anything
20690 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20691 with @code{void} returned values that @value{GDBN} will otherwise
20692 print. If the result is not void, it is printed and saved in the
20696 It is possible for the function you call via the @code{print} or
20697 @code{call} command to generate a signal (e.g., if there's a bug in
20698 the function, or if you passed it incorrect arguments). What happens
20699 in that case is controlled by the @code{set unwindonsignal} command.
20701 Similarly, with a C@t{++} program it is possible for the function you
20702 call via the @code{print} or @code{call} command to generate an
20703 exception that is not handled due to the constraints of the dummy
20704 frame. In this case, any exception that is raised in the frame, but has
20705 an out-of-frame exception handler will not be found. GDB builds a
20706 dummy-frame for the inferior function call, and the unwinder cannot
20707 seek for exception handlers outside of this dummy-frame. What happens
20708 in that case is controlled by the
20709 @code{set unwind-on-terminating-exception} command.
20712 @item set unwindonsignal
20713 @kindex set unwindonsignal
20714 @cindex unwind stack in called functions
20715 @cindex call dummy stack unwinding
20716 Set unwinding of the stack if a signal is received while in a function
20717 that @value{GDBN} called in the program being debugged. If set to on,
20718 @value{GDBN} unwinds the stack it created for the call and restores
20719 the context to what it was before the call. If set to off (the
20720 default), @value{GDBN} stops in the frame where the signal was
20723 @item show unwindonsignal
20724 @kindex show unwindonsignal
20725 Show the current setting of stack unwinding in the functions called by
20728 @item set unwind-on-terminating-exception
20729 @kindex set unwind-on-terminating-exception
20730 @cindex unwind stack in called functions with unhandled exceptions
20731 @cindex call dummy stack unwinding on unhandled exception.
20732 Set unwinding of the stack if a C@t{++} exception is raised, but left
20733 unhandled while in a function that @value{GDBN} called in the program being
20734 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20735 it created for the call and restores the context to what it was before
20736 the call. If set to off, @value{GDBN} the exception is delivered to
20737 the default C@t{++} exception handler and the inferior terminated.
20739 @item show unwind-on-terminating-exception
20740 @kindex show unwind-on-terminating-exception
20741 Show the current setting of stack unwinding in the functions called by
20744 @item set may-call-functions
20745 @kindex set may-call-functions
20746 @cindex disabling calling functions in the program
20747 @cindex calling functions in the program, disabling
20748 Set permission to call functions in the program.
20749 This controls whether @value{GDBN} will attempt to call functions in
20750 the program, such as with expressions in the @code{print} command. It
20751 defaults to @code{on}.
20753 To call a function in the program, @value{GDBN} has to temporarily
20754 modify the state of the inferior. This has potentially undesired side
20755 effects. Also, having @value{GDBN} call nested functions is likely to
20756 be erroneous and may even crash the program being debugged. You can
20757 avoid such hazards by forbidding @value{GDBN} from calling functions
20758 in the program being debugged. If calling functions in the program
20759 is forbidden, GDB will throw an error when a command (such as printing
20760 an expression) starts a function call in the program.
20762 @item show may-call-functions
20763 @kindex show may-call-functions
20764 Show permission to call functions in the program.
20768 @subsection Calling functions with no debug info
20770 @cindex no debug info functions
20771 Sometimes, a function you wish to call is missing debug information.
20772 In such case, @value{GDBN} does not know the type of the function,
20773 including the types of the function's parameters. To avoid calling
20774 the inferior function incorrectly, which could result in the called
20775 function functioning erroneously and even crash, @value{GDBN} refuses
20776 to call the function unless you tell it the type of the function.
20778 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
20779 to do that. The simplest is to cast the call to the function's
20780 declared return type. For example:
20783 (@value{GDBP}) p getenv ("PATH")
20784 'getenv' has unknown return type; cast the call to its declared return type
20785 (@value{GDBP}) p (char *) getenv ("PATH")
20786 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
20789 Casting the return type of a no-debug function is equivalent to
20790 casting the function to a pointer to a prototyped function that has a
20791 prototype that matches the types of the passed-in arguments, and
20792 calling that. I.e., the call above is equivalent to:
20795 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
20799 and given this prototyped C or C++ function with float parameters:
20802 float multiply (float v1, float v2) @{ return v1 * v2; @}
20806 these calls are equivalent:
20809 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
20810 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
20813 If the function you wish to call is declared as unprototyped (i.e.@:
20814 old K&R style), you must use the cast-to-function-pointer syntax, so
20815 that @value{GDBN} knows that it needs to apply default argument
20816 promotions (promote float arguments to double). @xref{ABI, float
20817 promotion}. For example, given this unprototyped C function with
20818 float parameters, and no debug info:
20822 multiply_noproto (v1, v2)
20830 you call it like this:
20833 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
20837 @section Patching Programs
20839 @cindex patching binaries
20840 @cindex writing into executables
20841 @cindex writing into corefiles
20843 By default, @value{GDBN} opens the file containing your program's
20844 executable code (or the corefile) read-only. This prevents accidental
20845 alterations to machine code; but it also prevents you from intentionally
20846 patching your program's binary.
20848 If you'd like to be able to patch the binary, you can specify that
20849 explicitly with the @code{set write} command. For example, you might
20850 want to turn on internal debugging flags, or even to make emergency
20856 @itemx set write off
20857 If you specify @samp{set write on}, @value{GDBN} opens executable and
20858 core files for both reading and writing; if you specify @kbd{set write
20859 off} (the default), @value{GDBN} opens them read-only.
20861 If you have already loaded a file, you must load it again (using the
20862 @code{exec-file} or @code{core-file} command) after changing @code{set
20863 write}, for your new setting to take effect.
20867 Display whether executable files and core files are opened for writing
20868 as well as reading.
20871 @node Compiling and Injecting Code
20872 @section Compiling and injecting code in @value{GDBN}
20873 @cindex injecting code
20874 @cindex writing into executables
20875 @cindex compiling code
20877 @value{GDBN} supports on-demand compilation and code injection into
20878 programs running under @value{GDBN}. GCC 5.0 or higher built with
20879 @file{libcc1.so} must be installed for this functionality to be enabled.
20880 This functionality is implemented with the following commands.
20883 @kindex compile code
20884 @item compile code @var{source-code}
20885 @itemx compile code -raw @var{--} @var{source-code}
20886 Compile @var{source-code} with the compiler language found as the current
20887 language in @value{GDBN} (@pxref{Languages}). If compilation and
20888 injection is not supported with the current language specified in
20889 @value{GDBN}, or the compiler does not support this feature, an error
20890 message will be printed. If @var{source-code} compiles and links
20891 successfully, @value{GDBN} will load the object-code emitted,
20892 and execute it within the context of the currently selected inferior.
20893 It is important to note that the compiled code is executed immediately.
20894 After execution, the compiled code is removed from @value{GDBN} and any
20895 new types or variables you have defined will be deleted.
20897 The command allows you to specify @var{source-code} in two ways.
20898 The simplest method is to provide a single line of code to the command.
20902 compile code printf ("hello world\n");
20905 If you specify options on the command line as well as source code, they
20906 may conflict. The @samp{--} delimiter can be used to separate options
20907 from actual source code. E.g.:
20910 compile code -r -- printf ("hello world\n");
20913 Alternatively you can enter source code as multiple lines of text. To
20914 enter this mode, invoke the @samp{compile code} command without any text
20915 following the command. This will start the multiple-line editor and
20916 allow you to type as many lines of source code as required. When you
20917 have completed typing, enter @samp{end} on its own line to exit the
20922 >printf ("hello\n");
20923 >printf ("world\n");
20927 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20928 provided @var{source-code} in a callable scope. In this case, you must
20929 specify the entry point of the code by defining a function named
20930 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20931 inferior. Using @samp{-raw} option may be needed for example when
20932 @var{source-code} requires @samp{#include} lines which may conflict with
20933 inferior symbols otherwise.
20935 @kindex compile file
20936 @item compile file @var{filename}
20937 @itemx compile file -raw @var{filename}
20938 Like @code{compile code}, but take the source code from @var{filename}.
20941 compile file /home/user/example.c
20946 @item compile print [[@var{options}] --] @var{expr}
20947 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20948 Compile and execute @var{expr} with the compiler language found as the
20949 current language in @value{GDBN} (@pxref{Languages}). By default the
20950 value of @var{expr} is printed in a format appropriate to its data type;
20951 you can choose a different format by specifying @samp{/@var{f}}, where
20952 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20953 Formats}. The @code{compile print} command accepts the same options
20954 as the @code{print} command; see @ref{print options}.
20956 @item compile print [[@var{options}] --]
20957 @itemx compile print [[@var{options}] --] /@var{f}
20958 @cindex reprint the last value
20959 Alternatively you can enter the expression (source code producing it) as
20960 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20961 command without any text following the command. This will start the
20962 multiple-line editor.
20966 The process of compiling and injecting the code can be inspected using:
20969 @anchor{set debug compile}
20970 @item set debug compile
20971 @cindex compile command debugging info
20972 Turns on or off display of @value{GDBN} process of compiling and
20973 injecting the code. The default is off.
20975 @item show debug compile
20976 Displays the current state of displaying @value{GDBN} process of
20977 compiling and injecting the code.
20979 @anchor{set debug compile-cplus-types}
20980 @item set debug compile-cplus-types
20981 @cindex compile C@t{++} type conversion
20982 Turns on or off the display of C@t{++} type conversion debugging information.
20983 The default is off.
20985 @item show debug compile-cplus-types
20986 Displays the current state of displaying debugging information for
20987 C@t{++} type conversion.
20990 @subsection Compilation options for the @code{compile} command
20992 @value{GDBN} needs to specify the right compilation options for the code
20993 to be injected, in part to make its ABI compatible with the inferior
20994 and in part to make the injected code compatible with @value{GDBN}'s
20998 The options used, in increasing precedence:
21001 @item target architecture and OS options (@code{gdbarch})
21002 These options depend on target processor type and target operating
21003 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
21004 (@code{-m64}) compilation option.
21006 @item compilation options recorded in the target
21007 @value{NGCC} (since version 4.7) stores the options used for compilation
21008 into @code{DW_AT_producer} part of DWARF debugging information according
21009 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
21010 explicitly specify @code{-g} during inferior compilation otherwise
21011 @value{NGCC} produces no DWARF. This feature is only relevant for
21012 platforms where @code{-g} produces DWARF by default, otherwise one may
21013 try to enforce DWARF by using @code{-gdwarf-4}.
21015 @item compilation options set by @code{set compile-args}
21019 You can override compilation options using the following command:
21022 @item set compile-args
21023 @cindex compile command options override
21024 Set compilation options used for compiling and injecting code with the
21025 @code{compile} commands. These options override any conflicting ones
21026 from the target architecture and/or options stored during inferior
21029 @item show compile-args
21030 Displays the current state of compilation options override.
21031 This does not show all the options actually used during compilation,
21032 use @ref{set debug compile} for that.
21035 @subsection Caveats when using the @code{compile} command
21037 There are a few caveats to keep in mind when using the @code{compile}
21038 command. As the caveats are different per language, the table below
21039 highlights specific issues on a per language basis.
21042 @item C code examples and caveats
21043 When the language in @value{GDBN} is set to @samp{C}, the compiler will
21044 attempt to compile the source code with a @samp{C} compiler. The source
21045 code provided to the @code{compile} command will have much the same
21046 access to variables and types as it normally would if it were part of
21047 the program currently being debugged in @value{GDBN}.
21049 Below is a sample program that forms the basis of the examples that
21050 follow. This program has been compiled and loaded into @value{GDBN},
21051 much like any other normal debugging session.
21054 void function1 (void)
21057 printf ("function 1\n");
21060 void function2 (void)
21075 For the purposes of the examples in this section, the program above has
21076 been compiled, loaded into @value{GDBN}, stopped at the function
21077 @code{main}, and @value{GDBN} is awaiting input from the user.
21079 To access variables and types for any program in @value{GDBN}, the
21080 program must be compiled and packaged with debug information. The
21081 @code{compile} command is not an exception to this rule. Without debug
21082 information, you can still use the @code{compile} command, but you will
21083 be very limited in what variables and types you can access.
21085 So with that in mind, the example above has been compiled with debug
21086 information enabled. The @code{compile} command will have access to
21087 all variables and types (except those that may have been optimized
21088 out). Currently, as @value{GDBN} has stopped the program in the
21089 @code{main} function, the @code{compile} command would have access to
21090 the variable @code{k}. You could invoke the @code{compile} command
21091 and type some source code to set the value of @code{k}. You can also
21092 read it, or do anything with that variable you would normally do in
21093 @code{C}. Be aware that changes to inferior variables in the
21094 @code{compile} command are persistent. In the following example:
21097 compile code k = 3;
21101 the variable @code{k} is now 3. It will retain that value until
21102 something else in the example program changes it, or another
21103 @code{compile} command changes it.
21105 Normal scope and access rules apply to source code compiled and
21106 injected by the @code{compile} command. In the example, the variables
21107 @code{j} and @code{k} are not accessible yet, because the program is
21108 currently stopped in the @code{main} function, where these variables
21109 are not in scope. Therefore, the following command
21112 compile code j = 3;
21116 will result in a compilation error message.
21118 Once the program is continued, execution will bring these variables in
21119 scope, and they will become accessible; then the code you specify via
21120 the @code{compile} command will be able to access them.
21122 You can create variables and types with the @code{compile} command as
21123 part of your source code. Variables and types that are created as part
21124 of the @code{compile} command are not visible to the rest of the program for
21125 the duration of its run. This example is valid:
21128 compile code int ff = 5; printf ("ff is %d\n", ff);
21131 However, if you were to type the following into @value{GDBN} after that
21132 command has completed:
21135 compile code printf ("ff is %d\n'', ff);
21139 a compiler error would be raised as the variable @code{ff} no longer
21140 exists. Object code generated and injected by the @code{compile}
21141 command is removed when its execution ends. Caution is advised
21142 when assigning to program variables values of variables created by the
21143 code submitted to the @code{compile} command. This example is valid:
21146 compile code int ff = 5; k = ff;
21149 The value of the variable @code{ff} is assigned to @code{k}. The variable
21150 @code{k} does not require the existence of @code{ff} to maintain the value
21151 it has been assigned. However, pointers require particular care in
21152 assignment. If the source code compiled with the @code{compile} command
21153 changed the address of a pointer in the example program, perhaps to a
21154 variable created in the @code{compile} command, that pointer would point
21155 to an invalid location when the command exits. The following example
21156 would likely cause issues with your debugged program:
21159 compile code int ff = 5; p = &ff;
21162 In this example, @code{p} would point to @code{ff} when the
21163 @code{compile} command is executing the source code provided to it.
21164 However, as variables in the (example) program persist with their
21165 assigned values, the variable @code{p} would point to an invalid
21166 location when the command exists. A general rule should be followed
21167 in that you should either assign @code{NULL} to any assigned pointers,
21168 or restore a valid location to the pointer before the command exits.
21170 Similar caution must be exercised with any structs, unions, and typedefs
21171 defined in @code{compile} command. Types defined in the @code{compile}
21172 command will no longer be available in the next @code{compile} command.
21173 Therefore, if you cast a variable to a type defined in the
21174 @code{compile} command, care must be taken to ensure that any future
21175 need to resolve the type can be achieved.
21178 (@value{GDBP}) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
21179 (@value{GDBP}) compile code printf ("%d\n", ((struct a *) argv)->a);
21180 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
21181 Compilation failed.
21182 (@value{GDBP}) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
21186 Variables that have been optimized away by the compiler are not
21187 accessible to the code submitted to the @code{compile} command.
21188 Access to those variables will generate a compiler error which @value{GDBN}
21189 will print to the console.
21192 @subsection Compiler search for the @code{compile} command
21194 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
21195 which may not be obvious for remote targets of different architecture
21196 than where @value{GDBN} is running. Environment variable @env{PATH} on
21197 @value{GDBN} host is searched for @value{NGCC} binary matching the
21198 target architecture and operating system. This search can be overriden
21199 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
21200 taken from shell that executed @value{GDBN}, it is not the value set by
21201 @value{GDBN} command @code{set environment}). @xref{Environment}.
21204 Specifically @env{PATH} is searched for binaries matching regular expression
21205 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
21206 debugged. @var{arch} is processor name --- multiarch is supported, so for
21207 example both @code{i386} and @code{x86_64} targets look for pattern
21208 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
21209 for pattern @code{s390x?}. @var{os} is currently supported only for
21210 pattern @code{linux(-gnu)?}.
21212 On Posix hosts the compiler driver @value{GDBN} needs to find also
21213 shared library @file{libcc1.so} from the compiler. It is searched in
21214 default shared library search path (overridable with usual environment
21215 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
21216 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
21217 according to the installation of the found compiler --- as possibly
21218 specified by the @code{set compile-gcc} command.
21221 @item set compile-gcc
21222 @cindex compile command driver filename override
21223 Set compilation command used for compiling and injecting code with the
21224 @code{compile} commands. If this option is not set (it is set to
21225 an empty string), the search described above will occur --- that is the
21228 @item show compile-gcc
21229 Displays the current compile command @value{NGCC} driver filename.
21230 If set, it is the main command @command{gcc}, found usually for example
21231 under name @file{x86_64-linux-gnu-gcc}.
21235 @chapter @value{GDBN} Files
21237 @value{GDBN} needs to know the file name of the program to be debugged,
21238 both in order to read its symbol table and in order to start your
21239 program. To debug a core dump of a previous run, you must also tell
21240 @value{GDBN} the name of the core dump file.
21243 * Files:: Commands to specify files
21244 * File Caching:: Information about @value{GDBN}'s file caching
21245 * Separate Debug Files:: Debugging information in separate files
21246 * MiniDebugInfo:: Debugging information in a special section
21247 * Index Files:: Index files speed up GDB
21248 * Symbol Errors:: Errors reading symbol files
21249 * Data Files:: GDB data files
21253 @section Commands to Specify Files
21255 @cindex symbol table
21256 @cindex core dump file
21258 You may want to specify executable and core dump file names. The usual
21259 way to do this is at start-up time, using the arguments to
21260 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
21261 Out of @value{GDBN}}).
21263 Occasionally it is necessary to change to a different file during a
21264 @value{GDBN} session. Or you may run @value{GDBN} and forget to
21265 specify a file you want to use. Or you are debugging a remote target
21266 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
21267 Program}). In these situations the @value{GDBN} commands to specify
21268 new files are useful.
21271 @cindex executable file
21273 @item file @var{filename}
21274 Use @var{filename} as the program to be debugged. It is read for its
21275 symbols and for the contents of pure memory. It is also the program
21276 executed when you use the @code{run} command. If you do not specify a
21277 directory and the file is not found in the @value{GDBN} working directory,
21278 @value{GDBN} uses the environment variable @env{PATH} as a list of
21279 directories to search, just as the shell does when looking for a program
21280 to run. You can change the value of this variable, for both @value{GDBN}
21281 and your program, using the @code{path} command.
21283 @cindex unlinked object files
21284 @cindex patching object files
21285 You can load unlinked object @file{.o} files into @value{GDBN} using
21286 the @code{file} command. You will not be able to ``run'' an object
21287 file, but you can disassemble functions and inspect variables. Also,
21288 if the underlying BFD functionality supports it, you could use
21289 @kbd{gdb -write} to patch object files using this technique. Note
21290 that @value{GDBN} can neither interpret nor modify relocations in this
21291 case, so branches and some initialized variables will appear to go to
21292 the wrong place. But this feature is still handy from time to time.
21295 @code{file} with no argument makes @value{GDBN} discard any information it
21296 has on both executable file and the symbol table.
21299 @item exec-file @r{[} @var{filename} @r{]}
21300 Specify that the program to be run (but not the symbol table) is found
21301 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
21302 if necessary to locate your program. Omitting @var{filename} means to
21303 discard information on the executable file.
21305 @kindex symbol-file
21306 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
21307 Read symbol table information from file @var{filename}. @env{PATH} is
21308 searched when necessary. Use the @code{file} command to get both symbol
21309 table and program to run from the same file.
21311 If an optional @var{offset} is specified, it is added to the start
21312 address of each section in the symbol file. This is useful if the
21313 program is relocated at runtime, such as the Linux kernel with kASLR
21316 @code{symbol-file} with no argument clears out @value{GDBN} information on your
21317 program's symbol table.
21319 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
21320 some breakpoints and auto-display expressions. This is because they may
21321 contain pointers to the internal data recording symbols and data types,
21322 which are part of the old symbol table data being discarded inside
21325 @code{symbol-file} does not repeat if you press @key{RET} again after
21328 When @value{GDBN} is configured for a particular environment, it
21329 understands debugging information in whatever format is the standard
21330 generated for that environment; you may use either a @sc{gnu} compiler, or
21331 other compilers that adhere to the local conventions.
21332 Best results are usually obtained from @sc{gnu} compilers; for example,
21333 using @code{@value{NGCC}} you can generate debugging information for
21336 For most kinds of object files, with the exception of old SVR3 systems
21337 using COFF, the @code{symbol-file} command does not normally read the
21338 symbol table in full right away. Instead, it scans the symbol table
21339 quickly to find which source files and which symbols are present. The
21340 details are read later, one source file at a time, as they are needed.
21342 The purpose of this two-stage reading strategy is to make @value{GDBN}
21343 start up faster. For the most part, it is invisible except for
21344 occasional pauses while the symbol table details for a particular source
21345 file are being read. (The @code{set verbose} command can turn these
21346 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
21347 Warnings and Messages}.)
21349 We have not implemented the two-stage strategy for COFF yet. When the
21350 symbol table is stored in COFF format, @code{symbol-file} reads the
21351 symbol table data in full right away. Note that ``stabs-in-COFF''
21352 still does the two-stage strategy, since the debug info is actually
21356 @cindex reading symbols immediately
21357 @cindex symbols, reading immediately
21358 @item symbol-file @r{[} -readnow @r{]} @var{filename}
21359 @itemx file @r{[} -readnow @r{]} @var{filename}
21360 You can override the @value{GDBN} two-stage strategy for reading symbol
21361 tables by using the @samp{-readnow} option with any of the commands that
21362 load symbol table information, if you want to be sure @value{GDBN} has the
21363 entire symbol table available.
21365 @cindex @code{-readnever}, option for symbol-file command
21366 @cindex never read symbols
21367 @cindex symbols, never read
21368 @item symbol-file @r{[} -readnever @r{]} @var{filename}
21369 @itemx file @r{[} -readnever @r{]} @var{filename}
21370 You can instruct @value{GDBN} to never read the symbolic information
21371 contained in @var{filename} by using the @samp{-readnever} option.
21372 @xref{--readnever}.
21374 @c FIXME: for now no mention of directories, since this seems to be in
21375 @c flux. 13mar1992 status is that in theory GDB would look either in
21376 @c current dir or in same dir as myprog; but issues like competing
21377 @c GDB's, or clutter in system dirs, mean that in practice right now
21378 @c only current dir is used. FFish says maybe a special GDB hierarchy
21379 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
21383 @item core-file @r{[}@var{filename}@r{]}
21385 Specify the whereabouts of a core dump file to be used as the ``contents
21386 of memory''. Traditionally, core files contain only some parts of the
21387 address space of the process that generated them; @value{GDBN} can access the
21388 executable file itself for other parts.
21390 @code{core-file} with no argument specifies that no core file is
21393 Note that the core file is ignored when your program is actually running
21394 under @value{GDBN}. So, if you have been running your program and you
21395 wish to debug a core file instead, you must kill the subprocess in which
21396 the program is running. To do this, use the @code{kill} command
21397 (@pxref{Kill Process, ,Killing the Child Process}).
21399 @kindex add-symbol-file
21400 @cindex dynamic linking
21401 @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{]}
21402 The @code{add-symbol-file} command reads additional symbol table
21403 information from the file @var{filename}. You would use this command
21404 when @var{filename} has been dynamically loaded (by some other means)
21405 into the program that is running. The @var{textaddress} parameter gives
21406 the memory address at which the file's text section has been loaded.
21407 You can additionally specify the base address of other sections using
21408 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
21409 If a section is omitted, @value{GDBN} will use its default addresses
21410 as found in @var{filename}. Any @var{address} or @var{textaddress}
21411 can be given as an expression.
21413 If an optional @var{offset} is specified, it is added to the start
21414 address of each section, except those for which the address was
21415 specified explicitly.
21417 The symbol table of the file @var{filename} is added to the symbol table
21418 originally read with the @code{symbol-file} command. You can use the
21419 @code{add-symbol-file} command any number of times; the new symbol data
21420 thus read is kept in addition to the old.
21422 Changes can be reverted using the command @code{remove-symbol-file}.
21424 @cindex relocatable object files, reading symbols from
21425 @cindex object files, relocatable, reading symbols from
21426 @cindex reading symbols from relocatable object files
21427 @cindex symbols, reading from relocatable object files
21428 @cindex @file{.o} files, reading symbols from
21429 Although @var{filename} is typically a shared library file, an
21430 executable file, or some other object file which has been fully
21431 relocated for loading into a process, you can also load symbolic
21432 information from relocatable @file{.o} files, as long as:
21436 the file's symbolic information refers only to linker symbols defined in
21437 that file, not to symbols defined by other object files,
21439 every section the file's symbolic information refers to has actually
21440 been loaded into the inferior, as it appears in the file, and
21442 you can determine the address at which every section was loaded, and
21443 provide these to the @code{add-symbol-file} command.
21447 Some embedded operating systems, like Sun Chorus and VxWorks, can load
21448 relocatable files into an already running program; such systems
21449 typically make the requirements above easy to meet. However, it's
21450 important to recognize that many native systems use complex link
21451 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
21452 assembly, for example) that make the requirements difficult to meet. In
21453 general, one cannot assume that using @code{add-symbol-file} to read a
21454 relocatable object file's symbolic information will have the same effect
21455 as linking the relocatable object file into the program in the normal
21458 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
21460 @kindex remove-symbol-file
21461 @item remove-symbol-file @var{filename}
21462 @item remove-symbol-file -a @var{address}
21463 Remove a symbol file added via the @code{add-symbol-file} command. The
21464 file to remove can be identified by its @var{filename} or by an @var{address}
21465 that lies within the boundaries of this symbol file in memory. Example:
21468 (@value{GDBP}) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
21469 add symbol table from file "/home/user/gdb/mylib.so" at
21470 .text_addr = 0x7ffff7ff9480
21472 Reading symbols from /home/user/gdb/mylib.so...
21473 (@value{GDBP}) remove-symbol-file -a 0x7ffff7ff9480
21474 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
21479 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
21481 @kindex add-symbol-file-from-memory
21482 @cindex @code{syscall DSO}
21483 @cindex load symbols from memory
21484 @item add-symbol-file-from-memory @var{address}
21485 Load symbols from the given @var{address} in a dynamically loaded
21486 object file whose image is mapped directly into the inferior's memory.
21487 For example, the Linux kernel maps a @code{syscall DSO} into each
21488 process's address space; this DSO provides kernel-specific code for
21489 some system calls. The argument can be any expression whose
21490 evaluation yields the address of the file's shared object file header.
21491 For this command to work, you must have used @code{symbol-file} or
21492 @code{exec-file} commands in advance.
21495 @item section @var{section} @var{addr}
21496 The @code{section} command changes the base address of the named
21497 @var{section} of the exec file to @var{addr}. This can be used if the
21498 exec file does not contain section addresses, (such as in the
21499 @code{a.out} format), or when the addresses specified in the file
21500 itself are wrong. Each section must be changed separately. The
21501 @code{info files} command, described below, lists all the sections and
21505 @kindex info target
21508 @code{info files} and @code{info target} are synonymous; both print the
21509 current target (@pxref{Targets, ,Specifying a Debugging Target}),
21510 including the names of the executable and core dump files currently in
21511 use by @value{GDBN}, and the files from which symbols were loaded. The
21512 command @code{help target} lists all possible targets rather than
21515 @kindex maint info sections
21516 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
21517 Another command that can give you extra information about program sections
21518 is @code{maint info sections}. In addition to the section information
21519 displayed by @code{info files}, this command displays the flags and file
21520 offset of each section in the executable and core dump files.
21522 When @samp{-all-objects} is passed then sections from all loaded object
21523 files, including shared libraries, are printed.
21525 The optional @var{filter-list} is a space separated list of filter
21526 keywords. Sections that match any one of the filter criteria will be
21527 printed. There are two types of filter:
21530 @item @var{section-name}
21531 Display information about any section named @var{section-name}.
21532 @item @var{section-flag}
21533 Display information for any section with @var{section-flag}. The
21534 section flags that @value{GDBN} currently knows about are:
21537 Section will have space allocated in the process when loaded.
21538 Set for all sections except those containing debug information.
21540 Section will be loaded from the file into the child process memory.
21541 Set for pre-initialized code and data, clear for @code{.bss} sections.
21543 Section needs to be relocated before loading.
21545 Section cannot be modified by the child process.
21547 Section contains executable code only.
21549 Section contains data only (no executable code).
21551 Section will reside in ROM.
21553 Section contains data for constructor/destructor lists.
21555 Section is not empty.
21557 An instruction to the linker to not output the section.
21558 @item COFF_SHARED_LIBRARY
21559 A notification to the linker that the section contains
21560 COFF shared library information.
21562 Section contains common symbols.
21566 @kindex maint info target-sections
21567 @item maint info target-sections
21568 This command prints @value{GDBN}'s internal section table. For each
21569 target @value{GDBN} maintains a table containing the allocatable
21570 sections from all currently mapped objects, along with information
21571 about where the section is mapped.
21573 @kindex set trust-readonly-sections
21574 @cindex read-only sections
21575 @item set trust-readonly-sections on
21576 Tell @value{GDBN} that readonly sections in your object file
21577 really are read-only (i.e.@: that their contents will not change).
21578 In that case, @value{GDBN} can fetch values from these sections
21579 out of the object file, rather than from the target program.
21580 For some targets (notably embedded ones), this can be a significant
21581 enhancement to debugging performance.
21583 The default is off.
21585 @item set trust-readonly-sections off
21586 Tell @value{GDBN} not to trust readonly sections. This means that
21587 the contents of the section might change while the program is running,
21588 and must therefore be fetched from the target when needed.
21590 @item show trust-readonly-sections
21591 Show the current setting of trusting readonly sections.
21594 All file-specifying commands allow both absolute and relative file names
21595 as arguments. @value{GDBN} always converts the file name to an absolute file
21596 name and remembers it that way.
21598 @cindex shared libraries
21599 @anchor{Shared Libraries}
21600 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
21601 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
21602 DSBT (TIC6X) shared libraries.
21604 On MS-Windows @value{GDBN} must be linked with the Expat library to support
21605 shared libraries. @xref{Expat}.
21607 @value{GDBN} automatically loads symbol definitions from shared libraries
21608 when you use the @code{run} command, or when you examine a core file.
21609 (Before you issue the @code{run} command, @value{GDBN} does not understand
21610 references to a function in a shared library, however---unless you are
21611 debugging a core file).
21613 @c FIXME: some @value{GDBN} release may permit some refs to undef
21614 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
21615 @c FIXME...lib; check this from time to time when updating manual
21617 There are times, however, when you may wish to not automatically load
21618 symbol definitions from shared libraries, such as when they are
21619 particularly large or there are many of them.
21621 To control the automatic loading of shared library symbols, use the
21625 @kindex set auto-solib-add
21626 @item set auto-solib-add @var{mode}
21627 If @var{mode} is @code{on}, symbols from all shared object libraries
21628 will be loaded automatically when the inferior begins execution, you
21629 attach to an independently started inferior, or when the dynamic linker
21630 informs @value{GDBN} that a new library has been loaded. If @var{mode}
21631 is @code{off}, symbols must be loaded manually, using the
21632 @code{sharedlibrary} command. The default value is @code{on}.
21634 @cindex memory used for symbol tables
21635 If your program uses lots of shared libraries with debug info that
21636 takes large amounts of memory, you can decrease the @value{GDBN}
21637 memory footprint by preventing it from automatically loading the
21638 symbols from shared libraries. To that end, type @kbd{set
21639 auto-solib-add off} before running the inferior, then load each
21640 library whose debug symbols you do need with @kbd{sharedlibrary
21641 @var{regexp}}, where @var{regexp} is a regular expression that matches
21642 the libraries whose symbols you want to be loaded.
21644 @kindex show auto-solib-add
21645 @item show auto-solib-add
21646 Display the current autoloading mode.
21649 @cindex load shared library
21650 To explicitly load shared library symbols, use the @code{sharedlibrary}
21654 @kindex info sharedlibrary
21656 @item info share @var{regex}
21657 @itemx info sharedlibrary @var{regex}
21658 Print the names of the shared libraries which are currently loaded
21659 that match @var{regex}. If @var{regex} is omitted then print
21660 all shared libraries that are loaded.
21663 @item info dll @var{regex}
21664 This is an alias of @code{info sharedlibrary}.
21666 @kindex sharedlibrary
21668 @item sharedlibrary @var{regex}
21669 @itemx share @var{regex}
21670 Load shared object library symbols for files matching a
21671 Unix regular expression.
21672 As with files loaded automatically, it only loads shared libraries
21673 required by your program for a core file or after typing @code{run}. If
21674 @var{regex} is omitted all shared libraries required by your program are
21677 @item nosharedlibrary
21678 @kindex nosharedlibrary
21679 @cindex unload symbols from shared libraries
21680 Unload all shared object library symbols. This discards all symbols
21681 that have been loaded from all shared libraries. Symbols from shared
21682 libraries that were loaded by explicit user requests are not
21686 Sometimes you may wish that @value{GDBN} stops and gives you control
21687 when any of shared library events happen. The best way to do this is
21688 to use @code{catch load} and @code{catch unload} (@pxref{Set
21691 @value{GDBN} also supports the @code{set stop-on-solib-events}
21692 command for this. This command exists for historical reasons. It is
21693 less useful than setting a catchpoint, because it does not allow for
21694 conditions or commands as a catchpoint does.
21697 @item set stop-on-solib-events
21698 @kindex set stop-on-solib-events
21699 This command controls whether @value{GDBN} should give you control
21700 when the dynamic linker notifies it about some shared library event.
21701 The most common event of interest is loading or unloading of a new
21704 @item show stop-on-solib-events
21705 @kindex show stop-on-solib-events
21706 Show whether @value{GDBN} stops and gives you control when shared
21707 library events happen.
21710 Shared libraries are also supported in many cross or remote debugging
21711 configurations. @value{GDBN} needs to have access to the target's libraries;
21712 this can be accomplished either by providing copies of the libraries
21713 on the host system, or by asking @value{GDBN} to automatically retrieve the
21714 libraries from the target. If copies of the target libraries are
21715 provided, they need to be the same as the target libraries, although the
21716 copies on the target can be stripped as long as the copies on the host are
21719 @cindex where to look for shared libraries
21720 For remote debugging, you need to tell @value{GDBN} where the target
21721 libraries are, so that it can load the correct copies---otherwise, it
21722 may try to load the host's libraries. @value{GDBN} has two variables
21723 to specify the search directories for target libraries.
21726 @cindex prefix for executable and shared library file names
21727 @cindex system root, alternate
21728 @kindex set solib-absolute-prefix
21729 @kindex set sysroot
21730 @item set sysroot @var{path}
21731 Use @var{path} as the system root for the program being debugged. Any
21732 absolute shared library paths will be prefixed with @var{path}; many
21733 runtime loaders store the absolute paths to the shared library in the
21734 target program's memory. When starting processes remotely, and when
21735 attaching to already-running processes (local or remote), their
21736 executable filenames will be prefixed with @var{path} if reported to
21737 @value{GDBN} as absolute by the operating system. If you use
21738 @code{set sysroot} to find executables and shared libraries, they need
21739 to be laid out in the same way that they are on the target, with
21740 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21743 If @var{path} starts with the sequence @file{target:} and the target
21744 system is remote then @value{GDBN} will retrieve the target binaries
21745 from the remote system. This is only supported when using a remote
21746 target that supports the @code{remote get} command (@pxref{File
21747 Transfer,,Sending files to a remote system}). The part of @var{path}
21748 following the initial @file{target:} (if present) is used as system
21749 root prefix on the remote file system. If @var{path} starts with the
21750 sequence @file{remote:} this is converted to the sequence
21751 @file{target:} by @code{set sysroot}@footnote{Historically the
21752 functionality to retrieve binaries from the remote system was
21753 provided by prefixing @var{path} with @file{remote:}}. If you want
21754 to specify a local system root using a directory that happens to be
21755 named @file{target:} or @file{remote:}, you need to use some
21756 equivalent variant of the name like @file{./target:}.
21758 For targets with an MS-DOS based filesystem, such as MS-Windows,
21759 @value{GDBN} tries prefixing a few variants of the target
21760 absolute file name with @var{path}. But first, on Unix hosts,
21761 @value{GDBN} converts all backslash directory separators into forward
21762 slashes, because the backslash is not a directory separator on Unix:
21765 c:\foo\bar.dll @result{} c:/foo/bar.dll
21768 Then, @value{GDBN} attempts prefixing the target file name with
21769 @var{path}, and looks for the resulting file name in the host file
21773 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
21776 If that does not find the binary, @value{GDBN} tries removing
21777 the @samp{:} character from the drive spec, both for convenience, and,
21778 for the case of the host file system not supporting file names with
21782 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
21785 This makes it possible to have a system root that mirrors a target
21786 with more than one drive. E.g., you may want to setup your local
21787 copies of the target system shared libraries like so (note @samp{c} vs
21791 @file{/path/to/sysroot/c/sys/bin/foo.dll}
21792 @file{/path/to/sysroot/c/sys/bin/bar.dll}
21793 @file{/path/to/sysroot/z/sys/bin/bar.dll}
21797 and point the system root at @file{/path/to/sysroot}, so that
21798 @value{GDBN} can find the correct copies of both
21799 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
21801 If that still does not find the binary, @value{GDBN} tries
21802 removing the whole drive spec from the target file name:
21805 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
21808 This last lookup makes it possible to not care about the drive name,
21809 if you don't want or need to.
21811 The @code{set solib-absolute-prefix} command is an alias for @code{set
21814 @cindex default system root
21815 @cindex @samp{--with-sysroot}
21816 You can set the default system root by using the configure-time
21817 @samp{--with-sysroot} option. If the system root is inside
21818 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21819 @samp{--exec-prefix}), then the default system root will be updated
21820 automatically if the installed @value{GDBN} is moved to a new
21823 @kindex show sysroot
21825 Display the current executable and shared library prefix.
21827 @kindex set solib-search-path
21828 @item set solib-search-path @var{path}
21829 If this variable is set, @var{path} is a colon-separated list of
21830 directories to search for shared libraries. @samp{solib-search-path}
21831 is used after @samp{sysroot} fails to locate the library, or if the
21832 path to the library is relative instead of absolute. If you want to
21833 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
21834 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
21835 finding your host's libraries. @samp{sysroot} is preferred; setting
21836 it to a nonexistent directory may interfere with automatic loading
21837 of shared library symbols.
21839 @kindex show solib-search-path
21840 @item show solib-search-path
21841 Display the current shared library search path.
21843 @cindex DOS file-name semantics of file names.
21844 @kindex set target-file-system-kind (unix|dos-based|auto)
21845 @kindex show target-file-system-kind
21846 @item set target-file-system-kind @var{kind}
21847 Set assumed file system kind for target reported file names.
21849 Shared library file names as reported by the target system may not
21850 make sense as is on the system @value{GDBN} is running on. For
21851 example, when remote debugging a target that has MS-DOS based file
21852 system semantics, from a Unix host, the target may be reporting to
21853 @value{GDBN} a list of loaded shared libraries with file names such as
21854 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
21855 drive letters, so the @samp{c:\} prefix is not normally understood as
21856 indicating an absolute file name, and neither is the backslash
21857 normally considered a directory separator character. In that case,
21858 the native file system would interpret this whole absolute file name
21859 as a relative file name with no directory components. This would make
21860 it impossible to point @value{GDBN} at a copy of the remote target's
21861 shared libraries on the host using @code{set sysroot}, and impractical
21862 with @code{set solib-search-path}. Setting
21863 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
21864 to interpret such file names similarly to how the target would, and to
21865 map them to file names valid on @value{GDBN}'s native file system
21866 semantics. The value of @var{kind} can be @code{"auto"}, in addition
21867 to one of the supported file system kinds. In that case, @value{GDBN}
21868 tries to determine the appropriate file system variant based on the
21869 current target's operating system (@pxref{ABI, ,Configuring the
21870 Current ABI}). The supported file system settings are:
21874 Instruct @value{GDBN} to assume the target file system is of Unix
21875 kind. Only file names starting the forward slash (@samp{/}) character
21876 are considered absolute, and the directory separator character is also
21880 Instruct @value{GDBN} to assume the target file system is DOS based.
21881 File names starting with either a forward slash, or a drive letter
21882 followed by a colon (e.g., @samp{c:}), are considered absolute, and
21883 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
21884 considered directory separators.
21887 Instruct @value{GDBN} to use the file system kind associated with the
21888 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
21889 This is the default.
21893 @cindex file name canonicalization
21894 @cindex base name differences
21895 When processing file names provided by the user, @value{GDBN}
21896 frequently needs to compare them to the file names recorded in the
21897 program's debug info. Normally, @value{GDBN} compares just the
21898 @dfn{base names} of the files as strings, which is reasonably fast
21899 even for very large programs. (The base name of a file is the last
21900 portion of its name, after stripping all the leading directories.)
21901 This shortcut in comparison is based upon the assumption that files
21902 cannot have more than one base name. This is usually true, but
21903 references to files that use symlinks or similar filesystem
21904 facilities violate that assumption. If your program records files
21905 using such facilities, or if you provide file names to @value{GDBN}
21906 using symlinks etc., you can set @code{basenames-may-differ} to
21907 @code{true} to instruct @value{GDBN} to completely canonicalize each
21908 pair of file names it needs to compare. This will make file-name
21909 comparisons accurate, but at a price of a significant slowdown.
21912 @item set basenames-may-differ
21913 @kindex set basenames-may-differ
21914 Set whether a source file may have multiple base names.
21916 @item show basenames-may-differ
21917 @kindex show basenames-may-differ
21918 Show whether a source file may have multiple base names.
21922 @section File Caching
21923 @cindex caching of opened files
21924 @cindex caching of bfd objects
21926 To speed up file loading, and reduce memory usage, @value{GDBN} will
21927 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21928 BFD, bfd, The Binary File Descriptor Library}. The following commands
21929 allow visibility and control of the caching behavior.
21932 @kindex maint info bfds
21933 @item maint info bfds
21934 This prints information about each @code{bfd} object that is known to
21937 @kindex maint set bfd-sharing
21938 @kindex maint show bfd-sharing
21939 @kindex bfd caching
21940 @item maint set bfd-sharing
21941 @item maint show bfd-sharing
21942 Control whether @code{bfd} objects can be shared. When sharing is
21943 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21944 than reopening the same file. Turning sharing off does not cause
21945 already shared @code{bfd} objects to be unshared, but all future files
21946 that are opened will create a new @code{bfd} object. Similarly,
21947 re-enabling sharing does not cause multiple existing @code{bfd}
21948 objects to be collapsed into a single shared @code{bfd} object.
21950 @kindex set debug bfd-cache @var{level}
21951 @kindex bfd caching
21952 @item set debug bfd-cache @var{level}
21953 Turns on debugging of the bfd cache, setting the level to @var{level}.
21955 @kindex show debug bfd-cache
21956 @kindex bfd caching
21957 @item show debug bfd-cache
21958 Show the current debugging level of the bfd cache.
21961 @node Separate Debug Files
21962 @section Debugging Information in Separate Files
21963 @cindex separate debugging information files
21964 @cindex debugging information in separate files
21965 @cindex @file{.debug} subdirectories
21966 @cindex debugging information directory, global
21967 @cindex global debugging information directories
21968 @cindex build ID, and separate debugging files
21969 @cindex @file{.build-id} directory
21971 @value{GDBN} allows you to put a program's debugging information in a
21972 file separate from the executable itself, in a way that allows
21973 @value{GDBN} to find and load the debugging information automatically.
21974 Since debugging information can be very large---sometimes larger
21975 than the executable code itself---some systems distribute debugging
21976 information for their executables in separate files, which users can
21977 install only when they need to debug a problem.
21979 @value{GDBN} supports two ways of specifying the separate debug info
21984 The executable contains a @dfn{debug link} that specifies the name of
21985 the separate debug info file. The separate debug file's name is
21986 usually @file{@var{executable}.debug}, where @var{executable} is the
21987 name of the corresponding executable file without leading directories
21988 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21989 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21990 checksum for the debug file, which @value{GDBN} uses to validate that
21991 the executable and the debug file came from the same build.
21995 The executable contains a @dfn{build ID}, a unique bit string that is
21996 also present in the corresponding debug info file. (This is supported
21997 only on some operating systems, when using the ELF or PE file formats
21998 for binary files and the @sc{gnu} Binutils.) For more details about
21999 this feature, see the description of the @option{--build-id}
22000 command-line option in @ref{Options, , Command Line Options, ld,
22001 The GNU Linker}. The debug info file's name is not specified
22002 explicitly by the build ID, but can be computed from the build ID, see
22006 Depending on the way the debug info file is specified, @value{GDBN}
22007 uses two different methods of looking for the debug file:
22011 For the ``debug link'' method, @value{GDBN} looks up the named file in
22012 the directory of the executable file, then in a subdirectory of that
22013 directory named @file{.debug}, and finally under each one of the
22014 global debug directories, in a subdirectory whose name is identical to
22015 the leading directories of the executable's absolute file name. (On
22016 MS-Windows/MS-DOS, the drive letter of the executable's leading
22017 directories is converted to a one-letter subdirectory, i.e.@:
22018 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
22019 filesystems disallow colons in file names.)
22022 For the ``build ID'' method, @value{GDBN} looks in the
22023 @file{.build-id} subdirectory of each one of the global debug directories for
22024 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
22025 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
22026 are the rest of the bit string. (Real build ID strings are 32 or more
22027 hex characters, not 10.) @value{GDBN} can automatically query
22028 @code{debuginfod} servers using build IDs in order to download separate debug
22029 files that cannot be found locally. For more information see @ref{Debuginfod}.
22032 So, for example, suppose you ask @value{GDBN} to debug
22033 @file{/usr/bin/ls}, which has a debug link that specifies the
22034 file @file{ls.debug}, and a build ID whose value in hex is
22035 @code{abcdef1234}. If the list of the global debug directories includes
22036 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
22037 debug information files, in the indicated order:
22041 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
22043 @file{/usr/bin/ls.debug}
22045 @file{/usr/bin/.debug/ls.debug}
22047 @file{/usr/lib/debug/usr/bin/ls.debug}.
22050 If the debug file still has not been found and @code{debuginfod}
22051 (@pxref{Debuginfod}) is enabled, @value{GDBN} will attempt to download the
22052 file from @code{debuginfod} servers.
22054 @anchor{debug-file-directory}
22055 Global debugging info directories default to what is set by @value{GDBN}
22056 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
22057 you can also set the global debugging info directories, and view the list
22058 @value{GDBN} is currently using.
22062 @kindex set debug-file-directory
22063 @item set debug-file-directory @var{directories}
22064 Set the directories which @value{GDBN} searches for separate debugging
22065 information files to @var{directory}. Multiple path components can be set
22066 concatenating them by a path separator.
22068 @kindex show debug-file-directory
22069 @item show debug-file-directory
22070 Show the directories @value{GDBN} searches for separate debugging
22075 @cindex @code{.gnu_debuglink} sections
22076 @cindex debug link sections
22077 A debug link is a special section of the executable file named
22078 @code{.gnu_debuglink}. The section must contain:
22082 A filename, with any leading directory components removed, followed by
22085 zero to three bytes of padding, as needed to reach the next four-byte
22086 boundary within the section, and
22088 a four-byte CRC checksum, stored in the same endianness used for the
22089 executable file itself. The checksum is computed on the debugging
22090 information file's full contents by the function given below, passing
22091 zero as the @var{crc} argument.
22094 Any executable file format can carry a debug link, as long as it can
22095 contain a section named @code{.gnu_debuglink} with the contents
22098 @cindex @code{.note.gnu.build-id} sections
22099 @cindex build ID sections
22100 The build ID is a special section in the executable file (and in other
22101 ELF binary files that @value{GDBN} may consider). This section is
22102 often named @code{.note.gnu.build-id}, but that name is not mandatory.
22103 It contains unique identification for the built files---the ID remains
22104 the same across multiple builds of the same build tree. The default
22105 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
22106 content for the build ID string. The same section with an identical
22107 value is present in the original built binary with symbols, in its
22108 stripped variant, and in the separate debugging information file.
22110 The debugging information file itself should be an ordinary
22111 executable, containing a full set of linker symbols, sections, and
22112 debugging information. The sections of the debugging information file
22113 should have the same names, addresses, and sizes as the original file,
22114 but they need not contain any data---much like a @code{.bss} section
22115 in an ordinary executable.
22117 The @sc{gnu} binary utilities (Binutils) package includes the
22118 @samp{objcopy} utility that can produce
22119 the separated executable / debugging information file pairs using the
22120 following commands:
22123 @kbd{objcopy --only-keep-debug foo foo.debug}
22128 These commands remove the debugging
22129 information from the executable file @file{foo} and place it in the file
22130 @file{foo.debug}. You can use the first, second or both methods to link the
22135 The debug link method needs the following additional command to also leave
22136 behind a debug link in @file{foo}:
22139 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
22142 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
22143 a version of the @code{strip} command such that the command @kbd{strip foo -f
22144 foo.debug} has the same functionality as the two @code{objcopy} commands and
22145 the @code{ln -s} command above, together.
22148 Build ID gets embedded into the main executable using @code{ld --build-id} or
22149 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
22150 compatibility fixes for debug files separation are present in @sc{gnu} binary
22151 utilities (Binutils) package since version 2.18.
22156 @cindex CRC algorithm definition
22157 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
22158 IEEE 802.3 using the polynomial:
22160 @c TexInfo requires naked braces for multi-digit exponents for Tex
22161 @c output, but this causes HTML output to barf. HTML has to be set using
22162 @c raw commands. So we end up having to specify this equation in 2
22167 <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>
22168 + <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
22174 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
22175 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
22179 The function is computed byte at a time, taking the least
22180 significant bit of each byte first. The initial pattern
22181 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
22182 the final result is inverted to ensure trailing zeros also affect the
22185 @emph{Note:} This is the same CRC polynomial as used in handling the
22186 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
22187 However in the case of the Remote Serial Protocol, the CRC is computed
22188 @emph{most} significant bit first, and the result is not inverted, so
22189 trailing zeros have no effect on the CRC value.
22191 To complete the description, we show below the code of the function
22192 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
22193 initially supplied @code{crc} argument means that an initial call to
22194 this function passing in zero will start computing the CRC using
22197 @kindex gnu_debuglink_crc32
22200 gnu_debuglink_crc32 (unsigned long crc,
22201 unsigned char *buf, size_t len)
22203 static const unsigned long crc32_table[256] =
22205 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
22206 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
22207 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
22208 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
22209 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
22210 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
22211 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
22212 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
22213 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
22214 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
22215 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
22216 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
22217 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
22218 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
22219 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
22220 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
22221 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
22222 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
22223 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
22224 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
22225 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
22226 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
22227 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
22228 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
22229 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
22230 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
22231 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
22232 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
22233 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
22234 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
22235 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
22236 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
22237 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
22238 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
22239 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
22240 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
22241 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
22242 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
22243 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
22244 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
22245 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
22246 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
22247 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
22248 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
22249 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
22250 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
22251 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
22252 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
22253 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
22254 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
22255 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
22258 unsigned char *end;
22260 crc = ~crc & 0xffffffff;
22261 for (end = buf + len; buf < end; ++buf)
22262 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
22263 return ~crc & 0xffffffff;
22268 This computation does not apply to the ``build ID'' method.
22270 @node MiniDebugInfo
22271 @section Debugging information in a special section
22272 @cindex separate debug sections
22273 @cindex @samp{.gnu_debugdata} section
22275 Some systems ship pre-built executables and libraries that have a
22276 special @samp{.gnu_debugdata} section. This feature is called
22277 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
22278 is used to supply extra symbols for backtraces.
22280 The intent of this section is to provide extra minimal debugging
22281 information for use in simple backtraces. It is not intended to be a
22282 replacement for full separate debugging information (@pxref{Separate
22283 Debug Files}). The example below shows the intended use; however,
22284 @value{GDBN} does not currently put restrictions on what sort of
22285 debugging information might be included in the section.
22287 @value{GDBN} has support for this extension. If the section exists,
22288 then it is used provided that no other source of debugging information
22289 can be found, and that @value{GDBN} was configured with LZMA support.
22291 This section can be easily created using @command{objcopy} and other
22292 standard utilities:
22295 # Extract the dynamic symbols from the main binary, there is no need
22296 # to also have these in the normal symbol table.
22297 nm -D @var{binary} --format=posix --defined-only \
22298 | awk '@{ print $1 @}' | sort > dynsyms
22300 # Extract all the text (i.e. function) symbols from the debuginfo.
22301 # (Note that we actually also accept "D" symbols, for the benefit
22302 # of platforms like PowerPC64 that use function descriptors.)
22303 nm @var{binary} --format=posix --defined-only \
22304 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
22307 # Keep all the function symbols not already in the dynamic symbol
22309 comm -13 dynsyms funcsyms > keep_symbols
22311 # Separate full debug info into debug binary.
22312 objcopy --only-keep-debug @var{binary} debug
22314 # Copy the full debuginfo, keeping only a minimal set of symbols and
22315 # removing some unnecessary sections.
22316 objcopy -S --remove-section .gdb_index --remove-section .comment \
22317 --keep-symbols=keep_symbols debug mini_debuginfo
22319 # Drop the full debug info from the original binary.
22320 strip --strip-all -R .comment @var{binary}
22322 # Inject the compressed data into the .gnu_debugdata section of the
22325 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
22329 @section Index Files Speed Up @value{GDBN}
22330 @cindex index files
22331 @cindex @samp{.gdb_index} section
22333 When @value{GDBN} finds a symbol file, it scans the symbols in the
22334 file in order to construct an internal symbol table. This lets most
22335 @value{GDBN} operations work quickly---at the cost of a delay early
22336 on. For large programs, this delay can be quite lengthy, so
22337 @value{GDBN} provides a way to build an index, which speeds up
22340 For convenience, @value{GDBN} comes with a program,
22341 @command{gdb-add-index}, which can be used to add the index to a
22342 symbol file. It takes the symbol file as its only argument:
22345 $ gdb-add-index symfile
22348 @xref{gdb-add-index}.
22350 It is also possible to do the work manually. Here is what
22351 @command{gdb-add-index} does behind the curtains.
22353 The index is stored as a section in the symbol file. @value{GDBN} can
22354 write the index to a file, then you can put it into the symbol file
22355 using @command{objcopy}.
22357 To create an index file, use the @code{save gdb-index} command:
22360 @item save gdb-index [-dwarf-5] @var{directory}
22361 @kindex save gdb-index
22362 Create index files for all symbol files currently known by
22363 @value{GDBN}. For each known @var{symbol-file}, this command by
22364 default creates it produces a single file
22365 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
22366 the @option{-dwarf-5} option, it produces 2 files:
22367 @file{@var{symbol-file}.debug_names} and
22368 @file{@var{symbol-file}.debug_str}. The files are created in the
22369 given @var{directory}.
22372 Once you have created an index file you can merge it into your symbol
22373 file, here named @file{symfile}, using @command{objcopy}:
22376 $ objcopy --add-section .gdb_index=symfile.gdb-index \
22377 --set-section-flags .gdb_index=readonly symfile symfile
22380 Or for @code{-dwarf-5}:
22383 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
22384 $ cat symfile.debug_str >>symfile.debug_str.new
22385 $ objcopy --add-section .debug_names=symfile.gdb-index \
22386 --set-section-flags .debug_names=readonly \
22387 --update-section .debug_str=symfile.debug_str.new symfile symfile
22390 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
22391 sections that have been deprecated. Usually they are deprecated because
22392 they are missing a new feature or have performance issues.
22393 To tell @value{GDBN} to use a deprecated index section anyway
22394 specify @code{set use-deprecated-index-sections on}.
22395 The default is @code{off}.
22396 This can speed up startup, but may result in some functionality being lost.
22397 @xref{Index Section Format}.
22399 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
22400 must be done before gdb reads the file. The following will not work:
22403 $ gdb -ex "set use-deprecated-index-sections on" <program>
22406 Instead you must do, for example,
22409 $ gdb -iex "set use-deprecated-index-sections on" <program>
22412 Indices only work when using DWARF debugging information, not stabs.
22414 @subsection Automatic symbol index cache
22416 @cindex automatic symbol index cache
22417 It is possible for @value{GDBN} to automatically save a copy of this index in a
22418 cache on disk and retrieve it from there when loading the same binary in the
22419 future. This feature can be turned on with @kbd{set index-cache enabled on}.
22420 The following commands can be used to tweak the behavior of the index cache.
22424 @kindex set index-cache
22425 @item set index-cache enabled on
22426 @itemx set index-cache enabled off
22427 Enable or disable the use of the symbol index cache.
22429 @item set index-cache directory @var{directory}
22430 @kindex show index-cache
22431 @itemx show index-cache directory
22432 Set/show the directory where index files will be saved.
22434 The default value for this directory depends on the host platform. On
22435 most systems, the index is cached in the @file{gdb} subdirectory of
22436 the directory pointed to by the @env{XDG_CACHE_HOME} environment
22437 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
22438 of your home directory. However, on some systems, the default may
22439 differ according to local convention.
22441 There is no limit on the disk space used by index cache. It is perfectly safe
22442 to delete the content of that directory to free up disk space.
22444 @item show index-cache stats
22445 Print the number of cache hits and misses since the launch of @value{GDBN}.
22449 @node Symbol Errors
22450 @section Errors Reading Symbol Files
22452 While reading a symbol file, @value{GDBN} occasionally encounters problems,
22453 such as symbol types it does not recognize, or known bugs in compiler
22454 output. By default, @value{GDBN} does not notify you of such problems, since
22455 they are relatively common and primarily of interest to people
22456 debugging compilers. If you are interested in seeing information
22457 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
22458 only one message about each such type of problem, no matter how many
22459 times the problem occurs; or you can ask @value{GDBN} to print more messages,
22460 to see how many times the problems occur, with the @code{set
22461 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
22464 The messages currently printed, and their meanings, include:
22467 @item inner block not inside outer block in @var{symbol}
22469 The symbol information shows where symbol scopes begin and end
22470 (such as at the start of a function or a block of statements). This
22471 error indicates that an inner scope block is not fully contained
22472 in its outer scope blocks.
22474 @value{GDBN} circumvents the problem by treating the inner block as if it had
22475 the same scope as the outer block. In the error message, @var{symbol}
22476 may be shown as ``@code{(don't know)}'' if the outer block is not a
22479 @item block at @var{address} out of order
22481 The symbol information for symbol scope blocks should occur in
22482 order of increasing addresses. This error indicates that it does not
22485 @value{GDBN} does not circumvent this problem, and has trouble
22486 locating symbols in the source file whose symbols it is reading. (You
22487 can often determine what source file is affected by specifying
22488 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
22491 @item bad block start address patched
22493 The symbol information for a symbol scope block has a start address
22494 smaller than the address of the preceding source line. This is known
22495 to occur in the SunOS 4.1.1 (and earlier) C compiler.
22497 @value{GDBN} circumvents the problem by treating the symbol scope block as
22498 starting on the previous source line.
22500 @item bad string table offset in symbol @var{n}
22503 Symbol number @var{n} contains a pointer into the string table which is
22504 larger than the size of the string table.
22506 @value{GDBN} circumvents the problem by considering the symbol to have the
22507 name @code{foo}, which may cause other problems if many symbols end up
22510 @item unknown symbol type @code{0x@var{nn}}
22512 The symbol information contains new data types that @value{GDBN} does
22513 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
22514 uncomprehended information, in hexadecimal.
22516 @value{GDBN} circumvents the error by ignoring this symbol information.
22517 This usually allows you to debug your program, though certain symbols
22518 are not accessible. If you encounter such a problem and feel like
22519 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
22520 on @code{complain}, then go up to the function @code{read_dbx_symtab}
22521 and examine @code{*bufp} to see the symbol.
22523 @item stub type has NULL name
22525 @value{GDBN} could not find the full definition for a struct or class.
22527 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
22528 The symbol information for a C@t{++} member function is missing some
22529 information that recent versions of the compiler should have output for
22532 @item info mismatch between compiler and debugger
22534 @value{GDBN} could not parse a type specification output by the compiler.
22539 @section GDB Data Files
22541 @cindex prefix for data files
22542 @value{GDBN} will sometimes read an auxiliary data file. These files
22543 are kept in a directory known as the @dfn{data directory}.
22545 You can set the data directory's name, and view the name @value{GDBN}
22546 is currently using.
22549 @kindex set data-directory
22550 @item set data-directory @var{directory}
22551 Set the directory which @value{GDBN} searches for auxiliary data files
22552 to @var{directory}.
22554 @kindex show data-directory
22555 @item show data-directory
22556 Show the directory @value{GDBN} searches for auxiliary data files.
22559 @cindex default data directory
22560 @cindex @samp{--with-gdb-datadir}
22561 You can set the default data directory by using the configure-time
22562 @samp{--with-gdb-datadir} option. If the data directory is inside
22563 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
22564 @samp{--exec-prefix}), then the default data directory will be updated
22565 automatically if the installed @value{GDBN} is moved to a new
22568 The data directory may also be specified with the
22569 @code{--data-directory} command line option.
22570 @xref{Mode Options}.
22573 @chapter Specifying a Debugging Target
22575 @cindex debugging target
22576 A @dfn{target} is the execution environment occupied by your program.
22578 Often, @value{GDBN} runs in the same host environment as your program;
22579 in that case, the debugging target is specified as a side effect when
22580 you use the @code{file} or @code{core} commands. When you need more
22581 flexibility---for example, running @value{GDBN} on a physically separate
22582 host, or controlling a standalone system over a serial port or a
22583 realtime system over a TCP/IP connection---you can use the @code{target}
22584 command to specify one of the target types configured for @value{GDBN}
22585 (@pxref{Target Commands, ,Commands for Managing Targets}).
22587 @cindex target architecture
22588 It is possible to build @value{GDBN} for several different @dfn{target
22589 architectures}. When @value{GDBN} is built like that, you can choose
22590 one of the available architectures with the @kbd{set architecture}
22594 @kindex set architecture
22595 @kindex show architecture
22596 @item set architecture @var{arch}
22597 This command sets the current target architecture to @var{arch}. The
22598 value of @var{arch} can be @code{"auto"}, in addition to one of the
22599 supported architectures.
22601 @item show architecture
22602 Show the current target architecture.
22604 @item set processor
22606 @kindex set processor
22607 @kindex show processor
22608 These are alias commands for, respectively, @code{set architecture}
22609 and @code{show architecture}.
22613 * Active Targets:: Active targets
22614 * Target Commands:: Commands for managing targets
22615 * Byte Order:: Choosing target byte order
22618 @node Active Targets
22619 @section Active Targets
22621 @cindex stacking targets
22622 @cindex active targets
22623 @cindex multiple targets
22625 There are multiple classes of targets such as: processes, executable files or
22626 recording sessions. Core files belong to the process class, making core file
22627 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
22628 on multiple active targets, one in each class. This allows you to (for
22629 example) start a process and inspect its activity, while still having access to
22630 the executable file after the process finishes. Or if you start process
22631 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
22632 presented a virtual layer of the recording target, while the process target
22633 remains stopped at the chronologically last point of the process execution.
22635 Use the @code{core-file} and @code{exec-file} commands to select a new core
22636 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
22637 specify as a target a process that is already running, use the @code{attach}
22638 command (@pxref{Attach, ,Debugging an Already-running Process}).
22640 @node Target Commands
22641 @section Commands for Managing Targets
22644 @item target @var{type} @var{parameters}
22645 Connects the @value{GDBN} host environment to a target machine or
22646 process. A target is typically a protocol for talking to debugging
22647 facilities. You use the argument @var{type} to specify the type or
22648 protocol of the target machine.
22650 Further @var{parameters} are interpreted by the target protocol, but
22651 typically include things like device names or host names to connect
22652 with, process numbers, and baud rates.
22654 The @code{target} command does not repeat if you press @key{RET} again
22655 after executing the command.
22657 @kindex help target
22659 Displays the names of all targets available. To display targets
22660 currently selected, use either @code{info target} or @code{info files}
22661 (@pxref{Files, ,Commands to Specify Files}).
22663 @item help target @var{name}
22664 Describe a particular target, including any parameters necessary to
22667 @kindex set gnutarget
22668 @item set gnutarget @var{args}
22669 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
22670 knows whether it is reading an @dfn{executable},
22671 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
22672 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22673 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22676 @emph{Warning:} To specify a file format with @code{set gnutarget},
22677 you must know the actual BFD name.
22681 @xref{Files, , Commands to Specify Files}.
22683 @kindex show gnutarget
22684 @item show gnutarget
22685 Use the @code{show gnutarget} command to display what file format
22686 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22687 @value{GDBN} will determine the file format for each file automatically,
22688 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22691 @cindex common targets
22692 Here are some common targets (available, or not, depending on the GDB
22697 @item target exec @var{program}
22698 @cindex executable file target
22699 An executable file. @samp{target exec @var{program}} is the same as
22700 @samp{exec-file @var{program}}.
22702 @item target core @var{filename}
22703 @cindex core dump file target
22704 A core dump file. @samp{target core @var{filename}} is the same as
22705 @samp{core-file @var{filename}}.
22707 @item target remote @var{medium}
22708 @cindex remote target
22709 A remote system connected to @value{GDBN} via a serial line or network
22710 connection. This command tells @value{GDBN} to use its own remote
22711 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22713 For example, if you have a board connected to @file{/dev/ttya} on the
22714 machine running @value{GDBN}, you could say:
22717 target remote /dev/ttya
22720 @code{target remote} supports the @code{load} command. This is only
22721 useful if you have some other way of getting the stub to the target
22722 system, and you can put it somewhere in memory where it won't get
22723 clobbered by the download.
22725 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22726 @cindex built-in simulator target
22727 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22735 works; however, you cannot assume that a specific memory map, device
22736 drivers, or even basic I/O is available, although some simulators do
22737 provide these. For info about any processor-specific simulator details,
22738 see the appropriate section in @ref{Embedded Processors, ,Embedded
22741 @item target native
22742 @cindex native target
22743 Setup for local/native process debugging. Useful to make the
22744 @code{run} command spawn native processes (likewise @code{attach},
22745 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22746 (@pxref{set auto-connect-native-target}).
22750 Different targets are available on different configurations of @value{GDBN};
22751 your configuration may have more or fewer targets.
22753 Many remote targets require you to download the executable's code once
22754 you've successfully established a connection. You may wish to control
22755 various aspects of this process.
22760 @kindex set hash@r{, for remote monitors}
22761 @cindex hash mark while downloading
22762 This command controls whether a hash mark @samp{#} is displayed while
22763 downloading a file to the remote monitor. If on, a hash mark is
22764 displayed after each S-record is successfully downloaded to the
22768 @kindex show hash@r{, for remote monitors}
22769 Show the current status of displaying the hash mark.
22771 @item set debug monitor
22772 @kindex set debug monitor
22773 @cindex display remote monitor communications
22774 Enable or disable display of communications messages between
22775 @value{GDBN} and the remote monitor.
22777 @item show debug monitor
22778 @kindex show debug monitor
22779 Show the current status of displaying communications between
22780 @value{GDBN} and the remote monitor.
22785 @kindex load @var{filename} @var{offset}
22786 @item load @var{filename} @var{offset}
22788 Depending on what remote debugging facilities are configured into
22789 @value{GDBN}, the @code{load} command may be available. Where it exists, it
22790 is meant to make @var{filename} (an executable) available for debugging
22791 on the remote system---by downloading, or dynamic linking, for example.
22792 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
22793 the @code{add-symbol-file} command.
22795 If your @value{GDBN} does not have a @code{load} command, attempting to
22796 execute it gets the error message ``@code{You can't do that when your
22797 target is @dots{}}''
22799 The file is loaded at whatever address is specified in the executable.
22800 For some object file formats, you can specify the load address when you
22801 link the program; for other formats, like a.out, the object file format
22802 specifies a fixed address.
22803 @c FIXME! This would be a good place for an xref to the GNU linker doc.
22805 It is also possible to tell @value{GDBN} to load the executable file at a
22806 specific offset described by the optional argument @var{offset}. When
22807 @var{offset} is provided, @var{filename} must also be provided.
22809 Depending on the remote side capabilities, @value{GDBN} may be able to
22810 load programs into flash memory.
22812 @code{load} does not repeat if you press @key{RET} again after using it.
22817 @kindex flash-erase
22819 @anchor{flash-erase}
22821 Erases all known flash memory regions on the target.
22826 @section Choosing Target Byte Order
22828 @cindex choosing target byte order
22829 @cindex target byte order
22831 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
22832 offer the ability to run either big-endian or little-endian byte
22833 orders. Usually the executable or symbol will include a bit to
22834 designate the endian-ness, and you will not need to worry about
22835 which to use. However, you may still find it useful to adjust
22836 @value{GDBN}'s idea of processor endian-ness manually.
22840 @item set endian big
22841 Instruct @value{GDBN} to assume the target is big-endian.
22843 @item set endian little
22844 Instruct @value{GDBN} to assume the target is little-endian.
22846 @item set endian auto
22847 Instruct @value{GDBN} to use the byte order associated with the
22851 Display @value{GDBN}'s current idea of the target byte order.
22855 If the @code{set endian auto} mode is in effect and no executable has
22856 been selected, then the endianness used is the last one chosen either
22857 by one of the @code{set endian big} and @code{set endian little}
22858 commands or by inferring from the last executable used. If no
22859 endianness has been previously chosen, then the default for this mode
22860 is inferred from the target @value{GDBN} has been built for, and is
22861 @code{little} if the name of the target CPU has an @code{el} suffix
22862 and @code{big} otherwise.
22864 Note that these commands merely adjust interpretation of symbolic
22865 data on the host, and that they have absolutely no effect on the
22869 @node Remote Debugging
22870 @chapter Debugging Remote Programs
22871 @cindex remote debugging
22873 If you are trying to debug a program running on a machine that cannot run
22874 @value{GDBN} in the usual way, it is often useful to use remote debugging.
22875 For example, you might use remote debugging on an operating system kernel,
22876 or on a small system which does not have a general purpose operating system
22877 powerful enough to run a full-featured debugger.
22879 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
22880 to make this work with particular debugging targets. In addition,
22881 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
22882 but not specific to any particular target system) which you can use if you
22883 write the remote stubs---the code that runs on the remote system to
22884 communicate with @value{GDBN}.
22886 Other remote targets may be available in your
22887 configuration of @value{GDBN}; use @code{help target} to list them.
22890 * Connecting:: Connecting to a remote target
22891 * File Transfer:: Sending files to a remote system
22892 * Server:: Using the gdbserver program
22893 * Remote Configuration:: Remote configuration
22894 * Remote Stub:: Implementing a remote stub
22898 @section Connecting to a Remote Target
22899 @cindex remote debugging, connecting
22900 @cindex @code{gdbserver}, connecting
22901 @cindex remote debugging, types of connections
22902 @cindex @code{gdbserver}, types of connections
22903 @cindex @code{gdbserver}, @code{target remote} mode
22904 @cindex @code{gdbserver}, @code{target extended-remote} mode
22906 This section describes how to connect to a remote target, including the
22907 types of connections and their differences, how to set up executable and
22908 symbol files on the host and target, and the commands used for
22909 connecting to and disconnecting from the remote target.
22911 @subsection Types of Remote Connections
22913 @value{GDBN} supports two types of remote connections, @code{target remote}
22914 mode and @code{target extended-remote} mode. Note that many remote targets
22915 support only @code{target remote} mode. There are several major
22916 differences between the two types of connections, enumerated here:
22920 @cindex remote debugging, detach and program exit
22921 @item Result of detach or program exit
22922 @strong{With target remote mode:} When the debugged program exits or you
22923 detach from it, @value{GDBN} disconnects from the target. When using
22924 @code{gdbserver}, @code{gdbserver} will exit.
22926 @strong{With target extended-remote mode:} When the debugged program exits or
22927 you detach from it, @value{GDBN} remains connected to the target, even
22928 though no program is running. You can rerun the program, attach to a
22929 running program, or use @code{monitor} commands specific to the target.
22931 When using @code{gdbserver} in this case, it does not exit unless it was
22932 invoked using the @option{--once} option. If the @option{--once} option
22933 was not used, you can ask @code{gdbserver} to exit using the
22934 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22936 @item Specifying the program to debug
22937 For both connection types you use the @code{file} command to specify the
22938 program on the host system. If you are using @code{gdbserver} there are
22939 some differences in how to specify the location of the program on the
22942 @strong{With target remote mode:} You must either specify the program to debug
22943 on the @code{gdbserver} command line or use the @option{--attach} option
22944 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22946 @cindex @option{--multi}, @code{gdbserver} option
22947 @strong{With target extended-remote mode:} You may specify the program to debug
22948 on the @code{gdbserver} command line, or you can load the program or attach
22949 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22951 @anchor{--multi Option in Types of Remote Connnections}
22952 You can start @code{gdbserver} without supplying an initial command to run
22953 or process ID to attach. To do this, use the @option{--multi} command line
22954 option. Then you can connect using @code{target extended-remote} and start
22955 the program you want to debug (see below for details on using the
22956 @code{run} command in this scenario). Note that the conditions under which
22957 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22958 (@code{target remote} or @code{target extended-remote}). The
22959 @option{--multi} option to @code{gdbserver} has no influence on that.
22961 @item The @code{run} command
22962 @strong{With target remote mode:} The @code{run} command is not
22963 supported. Once a connection has been established, you can use all
22964 the usual @value{GDBN} commands to examine and change data. The
22965 remote program is already running, so you can use commands like
22966 @kbd{step} and @kbd{continue}.
22968 @strong{With target extended-remote mode:} The @code{run} command is
22969 supported. The @code{run} command uses the value set by
22970 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22971 the program to run. Command line arguments are supported, except for
22972 wildcard expansion and I/O redirection (@pxref{Arguments}).
22974 If you specify the program to debug on the command line, then the
22975 @code{run} command is not required to start execution, and you can
22976 resume using commands like @kbd{step} and @kbd{continue} as with
22977 @code{target remote} mode.
22979 @anchor{Attaching in Types of Remote Connections}
22981 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22982 not supported. To attach to a running program using @code{gdbserver}, you
22983 must use the @option{--attach} option (@pxref{Running gdbserver}).
22985 @strong{With target extended-remote mode:} To attach to a running program,
22986 you may use the @code{attach} command after the connection has been
22987 established. If you are using @code{gdbserver}, you may also invoke
22988 @code{gdbserver} using the @option{--attach} option
22989 (@pxref{Running gdbserver}).
22991 Some remote targets allow @value{GDBN} to determine the executable file running
22992 in the process the debugger is attaching to. In such a case, @value{GDBN}
22993 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22994 between the executable file name running in the process and the name of the
22995 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22999 @anchor{Host and target files}
23000 @subsection Host and Target Files
23001 @cindex remote debugging, symbol files
23002 @cindex symbol files, remote debugging
23004 @value{GDBN}, running on the host, needs access to symbol and debugging
23005 information for your program running on the target. This requires
23006 access to an unstripped copy of your program, and possibly any associated
23007 symbol files. Note that this section applies equally to both @code{target
23008 remote} mode and @code{target extended-remote} mode.
23010 Some remote targets (@pxref{qXfer executable filename read}, and
23011 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
23012 the same connection used to communicate with @value{GDBN}. With such a
23013 target, if the remote program is unstripped, the only command you need is
23014 @code{target remote} (or @code{target extended-remote}).
23016 If the remote program is stripped, or the target does not support remote
23017 program file access, start up @value{GDBN} using the name of the local
23018 unstripped copy of your program as the first argument, or use the
23019 @code{file} command. Use @code{set sysroot} to specify the location (on
23020 the host) of target libraries (unless your @value{GDBN} was compiled with
23021 the correct sysroot using @code{--with-sysroot}). Alternatively, you
23022 may use @code{set solib-search-path} to specify how @value{GDBN} locates
23025 The symbol file and target libraries must exactly match the executable
23026 and libraries on the target, with one exception: the files on the host
23027 system should not be stripped, even if the files on the target system
23028 are. Mismatched or missing files will lead to confusing results
23029 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
23030 files may also prevent @code{gdbserver} from debugging multi-threaded
23033 @subsection Remote Connection Commands
23034 @cindex remote connection commands
23035 @value{GDBN} can communicate with the target over a serial line, a
23036 local Unix domain socket, or
23037 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
23038 each case, @value{GDBN} uses the same protocol for debugging your
23039 program; only the medium carrying the debugging packets varies. The
23040 @code{target remote} and @code{target extended-remote} commands
23041 establish a connection to the target. Both commands accept the same
23042 arguments, which indicate the medium to use:
23046 @item target remote @var{serial-device}
23047 @itemx target extended-remote @var{serial-device}
23048 @cindex serial line, @code{target remote}
23049 Use @var{serial-device} to communicate with the target. For example,
23050 to use a serial line connected to the device named @file{/dev/ttyb}:
23053 target remote /dev/ttyb
23056 If you're using a serial line, you may want to give @value{GDBN} the
23057 @samp{--baud} option, or use the @code{set serial baud} command
23058 (@pxref{Remote Configuration, set serial baud}) before the
23059 @code{target} command.
23061 @item target remote @var{local-socket}
23062 @itemx target extended-remote @var{local-socket}
23063 @cindex local socket, @code{target remote}
23064 @cindex Unix domain socket
23065 Use @var{local-socket} to communicate with the target. For example,
23066 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
23069 target remote /tmp/gdb-socket0
23072 Note that this command has the same form as the command to connect
23073 to a serial line. @value{GDBN} will automatically determine which
23074 kind of file you have specified and will make the appropriate kind
23076 This feature is not available if the host system does not support
23077 Unix domain sockets.
23079 @item target remote @code{@var{host}:@var{port}}
23080 @itemx target remote @code{[@var{host}]:@var{port}}
23081 @itemx target remote @code{tcp:@var{host}:@var{port}}
23082 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
23083 @itemx target remote @code{tcp4:@var{host}:@var{port}}
23084 @itemx target remote @code{tcp6:@var{host}:@var{port}}
23085 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
23086 @itemx target extended-remote @code{@var{host}:@var{port}}
23087 @itemx target extended-remote @code{[@var{host}]:@var{port}}
23088 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
23089 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
23090 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
23091 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
23092 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
23093 @cindex @acronym{TCP} port, @code{target remote}
23094 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
23095 The @var{host} may be either a host name, a numeric @acronym{IPv4}
23096 address, or a numeric @acronym{IPv6} address (with or without the
23097 square brackets to separate the address from the port); @var{port}
23098 must be a decimal number. The @var{host} could be the target machine
23099 itself, if it is directly connected to the net, or it might be a
23100 terminal server which in turn has a serial line to the target.
23102 For example, to connect to port 2828 on a terminal server named
23106 target remote manyfarms:2828
23109 To connect to port 2828 on a terminal server whose address is
23110 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
23111 square bracket syntax:
23114 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
23118 or explicitly specify the @acronym{IPv6} protocol:
23121 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
23124 This last example may be confusing to the reader, because there is no
23125 visible separation between the hostname and the port number.
23126 Therefore, we recommend the user to provide @acronym{IPv6} addresses
23127 using square brackets for clarity. However, it is important to
23128 mention that for @value{GDBN} there is no ambiguity: the number after
23129 the last colon is considered to be the port number.
23131 If your remote target is actually running on the same machine as your
23132 debugger session (e.g.@: a simulator for your target running on the
23133 same host), you can omit the hostname. For example, to connect to
23134 port 1234 on your local machine:
23137 target remote :1234
23141 Note that the colon is still required here.
23143 @item target remote @code{udp:@var{host}:@var{port}}
23144 @itemx target remote @code{udp:[@var{host}]:@var{port}}
23145 @itemx target remote @code{udp4:@var{host}:@var{port}}
23146 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
23147 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
23148 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
23149 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
23150 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
23151 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
23152 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
23153 @cindex @acronym{UDP} port, @code{target remote}
23154 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
23155 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
23158 target remote udp:manyfarms:2828
23161 When using a @acronym{UDP} connection for remote debugging, you should
23162 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
23163 can silently drop packets on busy or unreliable networks, which will
23164 cause havoc with your debugging session.
23166 @item target remote | @var{command}
23167 @itemx target extended-remote | @var{command}
23168 @cindex pipe, @code{target remote} to
23169 Run @var{command} in the background and communicate with it using a
23170 pipe. The @var{command} is a shell command, to be parsed and expanded
23171 by the system's command shell, @code{/bin/sh}; it should expect remote
23172 protocol packets on its standard input, and send replies on its
23173 standard output. You could use this to run a stand-alone simulator
23174 that speaks the remote debugging protocol, to make net connections
23175 using programs like @code{ssh}, or for other similar tricks.
23177 If @var{command} closes its standard output (perhaps by exiting),
23178 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
23179 program has already exited, this will have no effect.)
23183 @cindex interrupting remote programs
23184 @cindex remote programs, interrupting
23185 Whenever @value{GDBN} is waiting for the remote program, if you type the
23186 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
23187 program. This may or may not succeed, depending in part on the hardware
23188 and the serial drivers the remote system uses. If you type the
23189 interrupt character once again, @value{GDBN} displays this prompt:
23192 Interrupted while waiting for the program.
23193 Give up (and stop debugging it)? (y or n)
23196 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
23197 the remote debugging session. (If you decide you want to try again later,
23198 you can use @kbd{target remote} again to connect once more.) If you type
23199 @kbd{n}, @value{GDBN} goes back to waiting.
23201 In @code{target extended-remote} mode, typing @kbd{n} will leave
23202 @value{GDBN} connected to the target.
23205 @kindex detach (remote)
23207 When you have finished debugging the remote program, you can use the
23208 @code{detach} command to release it from @value{GDBN} control.
23209 Detaching from the target normally resumes its execution, but the results
23210 will depend on your particular remote stub. After the @code{detach}
23211 command in @code{target remote} mode, @value{GDBN} is free to connect to
23212 another target. In @code{target extended-remote} mode, @value{GDBN} is
23213 still connected to the target.
23217 The @code{disconnect} command closes the connection to the target, and
23218 the target is generally not resumed. It will wait for @value{GDBN}
23219 (this instance or another one) to connect and continue debugging. After
23220 the @code{disconnect} command, @value{GDBN} is again free to connect to
23223 @cindex send command to remote monitor
23224 @cindex extend @value{GDBN} for remote targets
23225 @cindex add new commands for external monitor
23227 @item monitor @var{cmd}
23228 This command allows you to send arbitrary commands directly to the
23229 remote monitor. Since @value{GDBN} doesn't care about the commands it
23230 sends like this, this command is the way to extend @value{GDBN}---you
23231 can add new commands that only the external monitor will understand
23235 @node File Transfer
23236 @section Sending files to a remote system
23237 @cindex remote target, file transfer
23238 @cindex file transfer
23239 @cindex sending files to remote systems
23241 Some remote targets offer the ability to transfer files over the same
23242 connection used to communicate with @value{GDBN}. This is convenient
23243 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
23244 running @code{gdbserver} over a network interface. For other targets,
23245 e.g.@: embedded devices with only a single serial port, this may be
23246 the only way to upload or download files.
23248 Not all remote targets support these commands.
23252 @item remote put @var{hostfile} @var{targetfile}
23253 Copy file @var{hostfile} from the host system (the machine running
23254 @value{GDBN}) to @var{targetfile} on the target system.
23257 @item remote get @var{targetfile} @var{hostfile}
23258 Copy file @var{targetfile} from the target system to @var{hostfile}
23259 on the host system.
23261 @kindex remote delete
23262 @item remote delete @var{targetfile}
23263 Delete @var{targetfile} from the target system.
23268 @section Using the @code{gdbserver} Program
23271 @cindex remote connection without stubs
23272 @code{gdbserver} is a control program for Unix-like systems, which
23273 allows you to connect your program with a remote @value{GDBN} via
23274 @code{target remote} or @code{target extended-remote}---but without
23275 linking in the usual debugging stub.
23277 @code{gdbserver} is not a complete replacement for the debugging stubs,
23278 because it requires essentially the same operating-system facilities
23279 that @value{GDBN} itself does. In fact, a system that can run
23280 @code{gdbserver} to connect to a remote @value{GDBN} could also run
23281 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
23282 because it is a much smaller program than @value{GDBN} itself. It is
23283 also easier to port than all of @value{GDBN}, so you may be able to get
23284 started more quickly on a new system by using @code{gdbserver}.
23285 Finally, if you develop code for real-time systems, you may find that
23286 the tradeoffs involved in real-time operation make it more convenient to
23287 do as much development work as possible on another system, for example
23288 by cross-compiling. You can use @code{gdbserver} to make a similar
23289 choice for debugging.
23291 @value{GDBN} and @code{gdbserver} communicate via either a serial line
23292 or a TCP connection, using the standard @value{GDBN} remote serial
23296 @emph{Warning:} @code{gdbserver} does not have any built-in security.
23297 Do not run @code{gdbserver} connected to any public network; a
23298 @value{GDBN} connection to @code{gdbserver} provides access to the
23299 target system with the same privileges as the user running
23303 @anchor{Running gdbserver}
23304 @subsection Running @code{gdbserver}
23305 @cindex arguments, to @code{gdbserver}
23306 @cindex @code{gdbserver}, command-line arguments
23308 Run @code{gdbserver} on the target system. You need a copy of the
23309 program you want to debug, including any libraries it requires.
23310 @code{gdbserver} does not need your program's symbol table, so you can
23311 strip the program if necessary to save space. @value{GDBN} on the host
23312 system does all the symbol handling.
23314 To use the server, you must tell it how to communicate with @value{GDBN};
23315 the name of your program; and the arguments for your program. The usual
23319 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
23322 @var{comm} is either a device name (to use a serial line), or a TCP
23323 hostname and portnumber, or @code{-} or @code{stdio} to use
23324 stdin/stdout of @code{gdbserver}.
23325 For example, to debug Emacs with the argument
23326 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
23330 target> gdbserver /dev/com1 emacs foo.txt
23333 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
23336 To use a TCP connection instead of a serial line:
23339 target> gdbserver host:2345 emacs foo.txt
23342 The only difference from the previous example is the first argument,
23343 specifying that you are communicating with the host @value{GDBN} via
23344 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
23345 expect a TCP connection from machine @samp{host} to local TCP port 2345.
23346 (Currently, the @samp{host} part is ignored.) You can choose any number
23347 you want for the port number as long as it does not conflict with any
23348 TCP ports already in use on the target system (for example, @code{23} is
23349 reserved for @code{telnet}).@footnote{If you choose a port number that
23350 conflicts with another service, @code{gdbserver} prints an error message
23351 and exits.} You must use the same port number with the host @value{GDBN}
23352 @code{target remote} command.
23354 The @code{stdio} connection is useful when starting @code{gdbserver}
23358 (@value{GDBP}) target remote | ssh -T hostname gdbserver - hello
23361 The @samp{-T} option to ssh is provided because we don't need a remote pty,
23362 and we don't want escape-character handling. Ssh does this by default when
23363 a command is provided, the flag is provided to make it explicit.
23364 You could elide it if you want to.
23366 Programs started with stdio-connected gdbserver have @file{/dev/null} for
23367 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
23368 display through a pipe connected to gdbserver.
23369 Both @code{stdout} and @code{stderr} use the same pipe.
23371 @anchor{Attaching to a program}
23372 @subsubsection Attaching to a Running Program
23373 @cindex attach to a program, @code{gdbserver}
23374 @cindex @option{--attach}, @code{gdbserver} option
23376 On some targets, @code{gdbserver} can also attach to running programs.
23377 This is accomplished via the @code{--attach} argument. The syntax is:
23380 target> gdbserver --attach @var{comm} @var{pid}
23383 @var{pid} is the process ID of a currently running process. It isn't
23384 necessary to point @code{gdbserver} at a binary for the running process.
23386 In @code{target extended-remote} mode, you can also attach using the
23387 @value{GDBN} attach command
23388 (@pxref{Attaching in Types of Remote Connections}).
23391 You can debug processes by name instead of process ID if your target has the
23392 @code{pidof} utility:
23395 target> gdbserver --attach @var{comm} `pidof @var{program}`
23398 In case more than one copy of @var{program} is running, or @var{program}
23399 has multiple threads, most versions of @code{pidof} support the
23400 @code{-s} option to only return the first process ID.
23402 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
23404 This section applies only when @code{gdbserver} is run to listen on a TCP
23407 @code{gdbserver} normally terminates after all of its debugged processes have
23408 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
23409 extended-remote}, @code{gdbserver} stays running even with no processes left.
23410 @value{GDBN} normally terminates the spawned debugged process on its exit,
23411 which normally also terminates @code{gdbserver} in the @kbd{target remote}
23412 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
23413 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
23414 stays running even in the @kbd{target remote} mode.
23416 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
23417 Such reconnecting is useful for features like @ref{disconnected tracing}. For
23418 completeness, at most one @value{GDBN} can be connected at a time.
23420 @cindex @option{--once}, @code{gdbserver} option
23421 By default, @code{gdbserver} keeps the listening TCP port open, so that
23422 subsequent connections are possible. However, if you start @code{gdbserver}
23423 with the @option{--once} option, it will stop listening for any further
23424 connection attempts after connecting to the first @value{GDBN} session. This
23425 means no further connections to @code{gdbserver} will be possible after the
23426 first one. It also means @code{gdbserver} will terminate after the first
23427 connection with remote @value{GDBN} has closed, even for unexpectedly closed
23428 connections and even in the @kbd{target extended-remote} mode. The
23429 @option{--once} option allows reusing the same port number for connecting to
23430 multiple instances of @code{gdbserver} running on the same host, since each
23431 instance closes its port after the first connection.
23433 @anchor{Other Command-Line Arguments for gdbserver}
23434 @subsubsection Other Command-Line Arguments for @code{gdbserver}
23436 You can use the @option{--multi} option to start @code{gdbserver} without
23437 specifying a program to debug or a process to attach to. Then you can
23438 attach in @code{target extended-remote} mode and run or attach to a
23439 program. For more information,
23440 @pxref{--multi Option in Types of Remote Connnections}.
23442 @cindex @option{--debug}, @code{gdbserver} option
23443 The @option{--debug} option tells @code{gdbserver} to display extra
23444 status information about the debugging process.
23445 @cindex @option{--remote-debug}, @code{gdbserver} option
23446 The @option{--remote-debug} option tells @code{gdbserver} to display
23447 remote protocol debug output.
23448 @cindex @option{--debug-file}, @code{gdbserver} option
23449 @cindex @code{gdbserver}, send all debug output to a single file
23450 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
23451 write any debug output to the given @var{filename}. These options are intended
23452 for @code{gdbserver} development and for bug reports to the developers.
23454 @cindex @option{--debug-format}, @code{gdbserver} option
23455 The @option{--debug-format=option1[,option2,...]} option tells
23456 @code{gdbserver} to include additional information in each output.
23457 Possible options are:
23461 Turn off all extra information in debugging output.
23463 Turn on all extra information in debugging output.
23465 Include a timestamp in each line of debugging output.
23468 Options are processed in order. Thus, for example, if @option{none}
23469 appears last then no additional information is added to debugging output.
23471 @cindex @option{--wrapper}, @code{gdbserver} option
23472 The @option{--wrapper} option specifies a wrapper to launch programs
23473 for debugging. The option should be followed by the name of the
23474 wrapper, then any command-line arguments to pass to the wrapper, then
23475 @kbd{--} indicating the end of the wrapper arguments.
23477 @code{gdbserver} runs the specified wrapper program with a combined
23478 command line including the wrapper arguments, then the name of the
23479 program to debug, then any arguments to the program. The wrapper
23480 runs until it executes your program, and then @value{GDBN} gains control.
23482 You can use any program that eventually calls @code{execve} with
23483 its arguments as a wrapper. Several standard Unix utilities do
23484 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
23485 with @code{exec "$@@"} will also work.
23487 For example, you can use @code{env} to pass an environment variable to
23488 the debugged program, without setting the variable in @code{gdbserver}'s
23492 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
23495 @cindex @option{--selftest}
23496 The @option{--selftest} option runs the self tests in @code{gdbserver}:
23499 $ gdbserver --selftest
23500 Ran 2 unit tests, 0 failed
23503 These tests are disabled in release.
23504 @subsection Connecting to @code{gdbserver}
23506 The basic procedure for connecting to the remote target is:
23510 Run @value{GDBN} on the host system.
23513 Make sure you have the necessary symbol files
23514 (@pxref{Host and target files}).
23515 Load symbols for your application using the @code{file} command before you
23516 connect. Use @code{set sysroot} to locate target libraries (unless your
23517 @value{GDBN} was compiled with the correct sysroot using
23518 @code{--with-sysroot}).
23521 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
23522 For TCP connections, you must start up @code{gdbserver} prior to using
23523 the @code{target} command. Otherwise you may get an error whose
23524 text depends on the host system, but which usually looks something like
23525 @samp{Connection refused}. Don't use the @code{load}
23526 command in @value{GDBN} when using @code{target remote} mode, since the
23527 program is already on the target.
23531 @anchor{Monitor Commands for gdbserver}
23532 @subsection Monitor Commands for @code{gdbserver}
23533 @cindex monitor commands, for @code{gdbserver}
23535 During a @value{GDBN} session using @code{gdbserver}, you can use the
23536 @code{monitor} command to send special requests to @code{gdbserver}.
23537 Here are the available commands.
23541 List the available monitor commands.
23543 @item monitor set debug 0
23544 @itemx monitor set debug 1
23545 Disable or enable general debugging messages.
23547 @item monitor set remote-debug 0
23548 @itemx monitor set remote-debug 1
23549 Disable or enable specific debugging messages associated with the remote
23550 protocol (@pxref{Remote Protocol}).
23552 @item monitor set debug-file filename
23553 @itemx monitor set debug-file
23554 Send any debug output to the given file, or to stderr.
23556 @item monitor set debug-format option1@r{[},option2,...@r{]}
23557 Specify additional text to add to debugging messages.
23558 Possible options are:
23562 Turn off all extra information in debugging output.
23564 Turn on all extra information in debugging output.
23566 Include a timestamp in each line of debugging output.
23569 Options are processed in order. Thus, for example, if @option{none}
23570 appears last then no additional information is added to debugging output.
23572 @item monitor set libthread-db-search-path [PATH]
23573 @cindex gdbserver, search path for @code{libthread_db}
23574 When this command is issued, @var{path} is a colon-separated list of
23575 directories to search for @code{libthread_db} (@pxref{Threads,,set
23576 libthread-db-search-path}). If you omit @var{path},
23577 @samp{libthread-db-search-path} will be reset to its default value.
23579 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
23580 not supported in @code{gdbserver}.
23583 Tell gdbserver to exit immediately. This command should be followed by
23584 @code{disconnect} to close the debugging session. @code{gdbserver} will
23585 detach from any attached processes and kill any processes it created.
23586 Use @code{monitor exit} to terminate @code{gdbserver} at the end
23587 of a multi-process mode debug session.
23591 @subsection Tracepoints support in @code{gdbserver}
23592 @cindex tracepoints support in @code{gdbserver}
23594 On some targets, @code{gdbserver} supports tracepoints, fast
23595 tracepoints and static tracepoints.
23597 For fast or static tracepoints to work, a special library called the
23598 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
23599 This library is built and distributed as an integral part of
23600 @code{gdbserver}. In addition, support for static tracepoints
23601 requires building the in-process agent library with static tracepoints
23602 support. At present, the UST (LTTng Userspace Tracer,
23603 @url{http://lttng.org/ust}) tracing engine is supported. This support
23604 is automatically available if UST development headers are found in the
23605 standard include path when @code{gdbserver} is built, or if
23606 @code{gdbserver} was explicitly configured using @option{--with-ust}
23607 to point at such headers. You can explicitly disable the support
23608 using @option{--with-ust=no}.
23610 There are several ways to load the in-process agent in your program:
23613 @item Specifying it as dependency at link time
23615 You can link your program dynamically with the in-process agent
23616 library. On most systems, this is accomplished by adding
23617 @code{-linproctrace} to the link command.
23619 @item Using the system's preloading mechanisms
23621 You can force loading the in-process agent at startup time by using
23622 your system's support for preloading shared libraries. Many Unixes
23623 support the concept of preloading user defined libraries. In most
23624 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
23625 in the environment. See also the description of @code{gdbserver}'s
23626 @option{--wrapper} command line option.
23628 @item Using @value{GDBN} to force loading the agent at run time
23630 On some systems, you can force the inferior to load a shared library,
23631 by calling a dynamic loader function in the inferior that takes care
23632 of dynamically looking up and loading a shared library. On most Unix
23633 systems, the function is @code{dlopen}. You'll use the @code{call}
23634 command for that. For example:
23637 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
23640 Note that on most Unix systems, for the @code{dlopen} function to be
23641 available, the program needs to be linked with @code{-ldl}.
23644 On systems that have a userspace dynamic loader, like most Unix
23645 systems, when you connect to @code{gdbserver} using @code{target
23646 remote}, you'll find that the program is stopped at the dynamic
23647 loader's entry point, and no shared library has been loaded in the
23648 program's address space yet, including the in-process agent. In that
23649 case, before being able to use any of the fast or static tracepoints
23650 features, you need to let the loader run and load the shared
23651 libraries. The simplest way to do that is to run the program to the
23652 main procedure. E.g., if debugging a C or C@t{++} program, start
23653 @code{gdbserver} like so:
23656 $ gdbserver :9999 myprogram
23659 Start GDB and connect to @code{gdbserver} like so, and run to main:
23663 (@value{GDBP}) target remote myhost:9999
23664 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
23665 (@value{GDBP}) b main
23666 (@value{GDBP}) continue
23669 The in-process tracing agent library should now be loaded into the
23670 process; you can confirm it with the @code{info sharedlibrary}
23671 command, which will list @file{libinproctrace.so} as loaded in the
23672 process. You are now ready to install fast tracepoints, list static
23673 tracepoint markers, probe static tracepoints markers, and start
23676 @node Remote Configuration
23677 @section Remote Configuration
23680 @kindex show remote
23681 This section documents the configuration options available when
23682 debugging remote programs. For the options related to the File I/O
23683 extensions of the remote protocol, see @ref{system,
23684 system-call-allowed}.
23687 @item set remoteaddresssize @var{bits}
23688 @cindex address size for remote targets
23689 @cindex bits in remote address
23690 Set the maximum size of address in a memory packet to the specified
23691 number of bits. @value{GDBN} will mask off the address bits above
23692 that number, when it passes addresses to the remote target. The
23693 default value is the number of bits in the target's address.
23695 @item show remoteaddresssize
23696 Show the current value of remote address size in bits.
23698 @item set serial baud @var{n}
23699 @cindex baud rate for remote targets
23700 Set the baud rate for the remote serial I/O to @var{n} baud. The
23701 value is used to set the speed of the serial port used for debugging
23704 @item show serial baud
23705 Show the current speed of the remote connection.
23707 @item set serial parity @var{parity}
23708 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23709 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23711 @item show serial parity
23712 Show the current parity of the serial port.
23714 @item set remotebreak
23715 @cindex interrupt remote programs
23716 @cindex BREAK signal instead of Ctrl-C
23717 @anchor{set remotebreak}
23718 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
23719 when you type @kbd{Ctrl-c} to interrupt the program running
23720 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
23721 character instead. The default is off, since most remote systems
23722 expect to see @samp{Ctrl-C} as the interrupt signal.
23724 @item show remotebreak
23725 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
23726 interrupt the remote program.
23728 @item set remoteflow on
23729 @itemx set remoteflow off
23730 @kindex set remoteflow
23731 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
23732 on the serial port used to communicate to the remote target.
23734 @item show remoteflow
23735 @kindex show remoteflow
23736 Show the current setting of hardware flow control.
23738 @item set remotelogbase @var{base}
23739 Set the base (a.k.a.@: radix) of logging serial protocol
23740 communications to @var{base}. Supported values of @var{base} are:
23741 @code{ascii}, @code{octal}, and @code{hex}. The default is
23744 @item show remotelogbase
23745 Show the current setting of the radix for logging remote serial
23748 @item set remotelogfile @var{file}
23749 @cindex record serial communications on file
23750 Record remote serial communications on the named @var{file}. The
23751 default is not to record at all.
23753 @item show remotelogfile
23754 Show the current setting of the file name on which to record the
23755 serial communications.
23757 @item set remotetimeout @var{num}
23758 @cindex timeout for serial communications
23759 @cindex remote timeout
23760 Set the timeout limit to wait for the remote target to respond to
23761 @var{num} seconds. The default is 2 seconds.
23763 @item show remotetimeout
23764 Show the current number of seconds to wait for the remote target
23767 @cindex limit hardware breakpoints and watchpoints
23768 @cindex remote target, limit break- and watchpoints
23769 @anchor{set remote hardware-watchpoint-limit}
23770 @anchor{set remote hardware-breakpoint-limit}
23771 @item set remote hardware-watchpoint-limit @var{limit}
23772 @itemx set remote hardware-breakpoint-limit @var{limit}
23773 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
23774 or breakpoints. The @var{limit} can be set to 0 to disable hardware
23775 watchpoints or breakpoints, and @code{unlimited} for unlimited
23776 watchpoints or breakpoints.
23778 @item show remote hardware-watchpoint-limit
23779 @itemx show remote hardware-breakpoint-limit
23780 Show the current limit for the number of hardware watchpoints or
23781 breakpoints that @value{GDBN} can use.
23783 @cindex limit hardware watchpoints length
23784 @cindex remote target, limit watchpoints length
23785 @anchor{set remote hardware-watchpoint-length-limit}
23786 @item set remote hardware-watchpoint-length-limit @var{limit}
23787 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
23788 length of a remote hardware watchpoint. A @var{limit} of 0 disables
23789 hardware watchpoints and @code{unlimited} allows watchpoints of any
23792 @item show remote hardware-watchpoint-length-limit
23793 Show the current limit (in bytes) of the maximum length of
23794 a remote hardware watchpoint.
23796 @item set remote exec-file @var{filename}
23797 @itemx show remote exec-file
23798 @anchor{set remote exec-file}
23799 @cindex executable file, for remote target
23800 Select the file used for @code{run} with @code{target
23801 extended-remote}. This should be set to a filename valid on the
23802 target system. If it is not set, the target will use a default
23803 filename (e.g.@: the last program run).
23805 @item set remote interrupt-sequence
23806 @cindex interrupt remote programs
23807 @cindex select Ctrl-C, BREAK or BREAK-g
23808 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
23809 @samp{BREAK-g} as the
23810 sequence to the remote target in order to interrupt the execution.
23811 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
23812 is high level of serial line for some certain time.
23813 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
23814 It is @code{BREAK} signal followed by character @code{g}.
23816 @item show remote interrupt-sequence
23817 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
23818 is sent by @value{GDBN} to interrupt the remote program.
23819 @code{BREAK-g} is BREAK signal followed by @code{g} and
23820 also known as Magic SysRq g.
23822 @item set remote interrupt-on-connect
23823 @cindex send interrupt-sequence on start
23824 Specify whether interrupt-sequence is sent to remote target when
23825 @value{GDBN} connects to it. This is mostly needed when you debug
23826 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
23827 which is known as Magic SysRq g in order to connect @value{GDBN}.
23829 @item show remote interrupt-on-connect
23830 Show whether interrupt-sequence is sent
23831 to remote target when @value{GDBN} connects to it.
23835 @item set tcp auto-retry on
23836 @cindex auto-retry, for remote TCP target
23837 Enable auto-retry for remote TCP connections. This is useful if the remote
23838 debugging agent is launched in parallel with @value{GDBN}; there is a race
23839 condition because the agent may not become ready to accept the connection
23840 before @value{GDBN} attempts to connect. When auto-retry is
23841 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
23842 to establish the connection using the timeout specified by
23843 @code{set tcp connect-timeout}.
23845 @item set tcp auto-retry off
23846 Do not auto-retry failed TCP connections.
23848 @item show tcp auto-retry
23849 Show the current auto-retry setting.
23851 @item set tcp connect-timeout @var{seconds}
23852 @itemx set tcp connect-timeout unlimited
23853 @cindex connection timeout, for remote TCP target
23854 @cindex timeout, for remote target connection
23855 Set the timeout for establishing a TCP connection to the remote target to
23856 @var{seconds}. The timeout affects both polling to retry failed connections
23857 (enabled by @code{set tcp auto-retry on}) and waiting for connections
23858 that are merely slow to complete, and represents an approximate cumulative
23859 value. If @var{seconds} is @code{unlimited}, there is no timeout and
23860 @value{GDBN} will keep attempting to establish a connection forever,
23861 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
23863 @item show tcp connect-timeout
23864 Show the current connection timeout setting.
23867 @cindex remote packets, enabling and disabling
23868 The @value{GDBN} remote protocol autodetects the packets supported by
23869 your debugging stub. If you need to override the autodetection, you
23870 can use these commands to enable or disable individual packets. Each
23871 packet can be set to @samp{on} (the remote target supports this
23872 packet), @samp{off} (the remote target does not support this packet),
23873 or @samp{auto} (detect remote target support for this packet). They
23874 all default to @samp{auto}. For more information about each packet,
23875 see @ref{Remote Protocol}.
23877 During normal use, you should not have to use any of these commands.
23878 If you do, that may be a bug in your remote debugging stub, or a bug
23879 in @value{GDBN}. You may want to report the problem to the
23880 @value{GDBN} developers.
23882 For each packet @var{name}, the command to enable or disable the
23883 packet is @code{set remote @var{name}-packet}. The available settings
23886 @multitable @columnfractions 0.28 0.32 0.25
23889 @tab Related Features
23891 @item @code{fetch-register}
23893 @tab @code{info registers}
23895 @item @code{set-register}
23899 @item @code{binary-download}
23901 @tab @code{load}, @code{set}
23903 @item @code{read-aux-vector}
23904 @tab @code{qXfer:auxv:read}
23905 @tab @code{info auxv}
23907 @item @code{symbol-lookup}
23908 @tab @code{qSymbol}
23909 @tab Detecting multiple threads
23911 @item @code{attach}
23912 @tab @code{vAttach}
23915 @item @code{verbose-resume}
23917 @tab Stepping or resuming multiple threads
23923 @item @code{software-breakpoint}
23927 @item @code{hardware-breakpoint}
23931 @item @code{write-watchpoint}
23935 @item @code{read-watchpoint}
23939 @item @code{access-watchpoint}
23943 @item @code{pid-to-exec-file}
23944 @tab @code{qXfer:exec-file:read}
23945 @tab @code{attach}, @code{run}
23947 @item @code{target-features}
23948 @tab @code{qXfer:features:read}
23949 @tab @code{set architecture}
23951 @item @code{library-info}
23952 @tab @code{qXfer:libraries:read}
23953 @tab @code{info sharedlibrary}
23955 @item @code{memory-map}
23956 @tab @code{qXfer:memory-map:read}
23957 @tab @code{info mem}
23959 @item @code{read-sdata-object}
23960 @tab @code{qXfer:sdata:read}
23961 @tab @code{print $_sdata}
23963 @item @code{read-siginfo-object}
23964 @tab @code{qXfer:siginfo:read}
23965 @tab @code{print $_siginfo}
23967 @item @code{write-siginfo-object}
23968 @tab @code{qXfer:siginfo:write}
23969 @tab @code{set $_siginfo}
23971 @item @code{threads}
23972 @tab @code{qXfer:threads:read}
23973 @tab @code{info threads}
23975 @item @code{get-thread-local-@*storage-address}
23976 @tab @code{qGetTLSAddr}
23977 @tab Displaying @code{__thread} variables
23979 @item @code{get-thread-information-block-address}
23980 @tab @code{qGetTIBAddr}
23981 @tab Display MS-Windows Thread Information Block.
23983 @item @code{search-memory}
23984 @tab @code{qSearch:memory}
23987 @item @code{supported-packets}
23988 @tab @code{qSupported}
23989 @tab Remote communications parameters
23991 @item @code{catch-syscalls}
23992 @tab @code{QCatchSyscalls}
23993 @tab @code{catch syscall}
23995 @item @code{pass-signals}
23996 @tab @code{QPassSignals}
23997 @tab @code{handle @var{signal}}
23999 @item @code{program-signals}
24000 @tab @code{QProgramSignals}
24001 @tab @code{handle @var{signal}}
24003 @item @code{hostio-close-packet}
24004 @tab @code{vFile:close}
24005 @tab @code{remote get}, @code{remote put}
24007 @item @code{hostio-open-packet}
24008 @tab @code{vFile:open}
24009 @tab @code{remote get}, @code{remote put}
24011 @item @code{hostio-pread-packet}
24012 @tab @code{vFile:pread}
24013 @tab @code{remote get}, @code{remote put}
24015 @item @code{hostio-pwrite-packet}
24016 @tab @code{vFile:pwrite}
24017 @tab @code{remote get}, @code{remote put}
24019 @item @code{hostio-unlink-packet}
24020 @tab @code{vFile:unlink}
24021 @tab @code{remote delete}
24023 @item @code{hostio-readlink-packet}
24024 @tab @code{vFile:readlink}
24027 @item @code{hostio-fstat-packet}
24028 @tab @code{vFile:fstat}
24031 @item @code{hostio-setfs-packet}
24032 @tab @code{vFile:setfs}
24035 @item @code{noack-packet}
24036 @tab @code{QStartNoAckMode}
24037 @tab Packet acknowledgment
24039 @item @code{osdata}
24040 @tab @code{qXfer:osdata:read}
24041 @tab @code{info os}
24043 @item @code{query-attached}
24044 @tab @code{qAttached}
24045 @tab Querying remote process attach state.
24047 @item @code{trace-buffer-size}
24048 @tab @code{QTBuffer:size}
24049 @tab @code{set trace-buffer-size}
24051 @item @code{trace-status}
24052 @tab @code{qTStatus}
24053 @tab @code{tstatus}
24055 @item @code{traceframe-info}
24056 @tab @code{qXfer:traceframe-info:read}
24057 @tab Traceframe info
24059 @item @code{install-in-trace}
24060 @tab @code{InstallInTrace}
24061 @tab Install tracepoint in tracing
24063 @item @code{disable-randomization}
24064 @tab @code{QDisableRandomization}
24065 @tab @code{set disable-randomization}
24067 @item @code{startup-with-shell}
24068 @tab @code{QStartupWithShell}
24069 @tab @code{set startup-with-shell}
24071 @item @code{environment-hex-encoded}
24072 @tab @code{QEnvironmentHexEncoded}
24073 @tab @code{set environment}
24075 @item @code{environment-unset}
24076 @tab @code{QEnvironmentUnset}
24077 @tab @code{unset environment}
24079 @item @code{environment-reset}
24080 @tab @code{QEnvironmentReset}
24081 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
24083 @item @code{set-working-dir}
24084 @tab @code{QSetWorkingDir}
24085 @tab @code{set cwd}
24087 @item @code{conditional-breakpoints-packet}
24088 @tab @code{Z0 and Z1}
24089 @tab @code{Support for target-side breakpoint condition evaluation}
24091 @item @code{multiprocess-extensions}
24092 @tab @code{multiprocess extensions}
24093 @tab Debug multiple processes and remote process PID awareness
24095 @item @code{swbreak-feature}
24096 @tab @code{swbreak stop reason}
24099 @item @code{hwbreak-feature}
24100 @tab @code{hwbreak stop reason}
24103 @item @code{fork-event-feature}
24104 @tab @code{fork stop reason}
24107 @item @code{vfork-event-feature}
24108 @tab @code{vfork stop reason}
24111 @item @code{exec-event-feature}
24112 @tab @code{exec stop reason}
24115 @item @code{thread-events}
24116 @tab @code{QThreadEvents}
24117 @tab Tracking thread lifetime.
24119 @item @code{no-resumed-stop-reply}
24120 @tab @code{no resumed thread left stop reply}
24121 @tab Tracking thread lifetime.
24126 @section Implementing a Remote Stub
24128 @cindex debugging stub, example
24129 @cindex remote stub, example
24130 @cindex stub example, remote debugging
24131 The stub files provided with @value{GDBN} implement the target side of the
24132 communication protocol, and the @value{GDBN} side is implemented in the
24133 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
24134 these subroutines to communicate, and ignore the details. (If you're
24135 implementing your own stub file, you can still ignore the details: start
24136 with one of the existing stub files. @file{sparc-stub.c} is the best
24137 organized, and therefore the easiest to read.)
24139 @cindex remote serial debugging, overview
24140 To debug a program running on another machine (the debugging
24141 @dfn{target} machine), you must first arrange for all the usual
24142 prerequisites for the program to run by itself. For example, for a C
24147 A startup routine to set up the C runtime environment; these usually
24148 have a name like @file{crt0}. The startup routine may be supplied by
24149 your hardware supplier, or you may have to write your own.
24152 A C subroutine library to support your program's
24153 subroutine calls, notably managing input and output.
24156 A way of getting your program to the other machine---for example, a
24157 download program. These are often supplied by the hardware
24158 manufacturer, but you may have to write your own from hardware
24162 The next step is to arrange for your program to use a serial port to
24163 communicate with the machine where @value{GDBN} is running (the @dfn{host}
24164 machine). In general terms, the scheme looks like this:
24168 @value{GDBN} already understands how to use this protocol; when everything
24169 else is set up, you can simply use the @samp{target remote} command
24170 (@pxref{Targets,,Specifying a Debugging Target}).
24172 @item On the target,
24173 you must link with your program a few special-purpose subroutines that
24174 implement the @value{GDBN} remote serial protocol. The file containing these
24175 subroutines is called a @dfn{debugging stub}.
24177 On certain remote targets, you can use an auxiliary program
24178 @code{gdbserver} instead of linking a stub into your program.
24179 @xref{Server,,Using the @code{gdbserver} Program}, for details.
24182 The debugging stub is specific to the architecture of the remote
24183 machine; for example, use @file{sparc-stub.c} to debug programs on
24186 @cindex remote serial stub list
24187 These working remote stubs are distributed with @value{GDBN}:
24192 @cindex @file{i386-stub.c}
24195 For Intel 386 and compatible architectures.
24198 @cindex @file{m68k-stub.c}
24199 @cindex Motorola 680x0
24201 For Motorola 680x0 architectures.
24204 @cindex @file{sh-stub.c}
24207 For Renesas SH architectures.
24210 @cindex @file{sparc-stub.c}
24212 For @sc{sparc} architectures.
24214 @item sparcl-stub.c
24215 @cindex @file{sparcl-stub.c}
24218 For Fujitsu @sc{sparclite} architectures.
24222 The @file{README} file in the @value{GDBN} distribution may list other
24223 recently added stubs.
24226 * Stub Contents:: What the stub can do for you
24227 * Bootstrapping:: What you must do for the stub
24228 * Debug Session:: Putting it all together
24231 @node Stub Contents
24232 @subsection What the Stub Can Do for You
24234 @cindex remote serial stub
24235 The debugging stub for your architecture supplies these three
24239 @item set_debug_traps
24240 @findex set_debug_traps
24241 @cindex remote serial stub, initialization
24242 This routine arranges for @code{handle_exception} to run when your
24243 program stops. You must call this subroutine explicitly in your
24244 program's startup code.
24246 @item handle_exception
24247 @findex handle_exception
24248 @cindex remote serial stub, main routine
24249 This is the central workhorse, but your program never calls it
24250 explicitly---the setup code arranges for @code{handle_exception} to
24251 run when a trap is triggered.
24253 @code{handle_exception} takes control when your program stops during
24254 execution (for example, on a breakpoint), and mediates communications
24255 with @value{GDBN} on the host machine. This is where the communications
24256 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
24257 representative on the target machine. It begins by sending summary
24258 information on the state of your program, then continues to execute,
24259 retrieving and transmitting any information @value{GDBN} needs, until you
24260 execute a @value{GDBN} command that makes your program resume; at that point,
24261 @code{handle_exception} returns control to your own code on the target
24265 @cindex @code{breakpoint} subroutine, remote
24266 Use this auxiliary subroutine to make your program contain a
24267 breakpoint. Depending on the particular situation, this may be the only
24268 way for @value{GDBN} to get control. For instance, if your target
24269 machine has some sort of interrupt button, you won't need to call this;
24270 pressing the interrupt button transfers control to
24271 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
24272 simply receiving characters on the serial port may also trigger a trap;
24273 again, in that situation, you don't need to call @code{breakpoint} from
24274 your own program---simply running @samp{target remote} from the host
24275 @value{GDBN} session gets control.
24277 Call @code{breakpoint} if none of these is true, or if you simply want
24278 to make certain your program stops at a predetermined point for the
24279 start of your debugging session.
24282 @node Bootstrapping
24283 @subsection What You Must Do for the Stub
24285 @cindex remote stub, support routines
24286 The debugging stubs that come with @value{GDBN} are set up for a particular
24287 chip architecture, but they have no information about the rest of your
24288 debugging target machine.
24290 First of all you need to tell the stub how to communicate with the
24294 @item int getDebugChar()
24295 @findex getDebugChar
24296 Write this subroutine to read a single character from the serial port.
24297 It may be identical to @code{getchar} for your target system; a
24298 different name is used to allow you to distinguish the two if you wish.
24300 @item void putDebugChar(int)
24301 @findex putDebugChar
24302 Write this subroutine to write a single character to the serial port.
24303 It may be identical to @code{putchar} for your target system; a
24304 different name is used to allow you to distinguish the two if you wish.
24307 @cindex control C, and remote debugging
24308 @cindex interrupting remote targets
24309 If you want @value{GDBN} to be able to stop your program while it is
24310 running, you need to use an interrupt-driven serial driver, and arrange
24311 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
24312 character). That is the character which @value{GDBN} uses to tell the
24313 remote system to stop.
24315 Getting the debugging target to return the proper status to @value{GDBN}
24316 probably requires changes to the standard stub; one quick and dirty way
24317 is to just execute a breakpoint instruction (the ``dirty'' part is that
24318 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
24320 Other routines you need to supply are:
24323 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
24324 @findex exceptionHandler
24325 Write this function to install @var{exception_address} in the exception
24326 handling tables. You need to do this because the stub does not have any
24327 way of knowing what the exception handling tables on your target system
24328 are like (for example, the processor's table might be in @sc{rom},
24329 containing entries which point to a table in @sc{ram}).
24330 The @var{exception_number} specifies the exception which should be changed;
24331 its meaning is architecture-dependent (for example, different numbers
24332 might represent divide by zero, misaligned access, etc). When this
24333 exception occurs, control should be transferred directly to
24334 @var{exception_address}, and the processor state (stack, registers,
24335 and so on) should be just as it is when a processor exception occurs. So if
24336 you want to use a jump instruction to reach @var{exception_address}, it
24337 should be a simple jump, not a jump to subroutine.
24339 For the 386, @var{exception_address} should be installed as an interrupt
24340 gate so that interrupts are masked while the handler runs. The gate
24341 should be at privilege level 0 (the most privileged level). The
24342 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
24343 help from @code{exceptionHandler}.
24345 @item void flush_i_cache()
24346 @findex flush_i_cache
24347 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
24348 instruction cache, if any, on your target machine. If there is no
24349 instruction cache, this subroutine may be a no-op.
24351 On target machines that have instruction caches, @value{GDBN} requires this
24352 function to make certain that the state of your program is stable.
24356 You must also make sure this library routine is available:
24359 @item void *memset(void *, int, int)
24361 This is the standard library function @code{memset} that sets an area of
24362 memory to a known value. If you have one of the free versions of
24363 @code{libc.a}, @code{memset} can be found there; otherwise, you must
24364 either obtain it from your hardware manufacturer, or write your own.
24367 If you do not use the GNU C compiler, you may need other standard
24368 library subroutines as well; this varies from one stub to another,
24369 but in general the stubs are likely to use any of the common library
24370 subroutines which @code{@value{NGCC}} generates as inline code.
24373 @node Debug Session
24374 @subsection Putting it All Together
24376 @cindex remote serial debugging summary
24377 In summary, when your program is ready to debug, you must follow these
24382 Make sure you have defined the supporting low-level routines
24383 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
24385 @code{getDebugChar}, @code{putDebugChar},
24386 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
24390 Insert these lines in your program's startup code, before the main
24391 procedure is called:
24398 On some machines, when a breakpoint trap is raised, the hardware
24399 automatically makes the PC point to the instruction after the
24400 breakpoint. If your machine doesn't do that, you may need to adjust
24401 @code{handle_exception} to arrange for it to return to the instruction
24402 after the breakpoint on this first invocation, so that your program
24403 doesn't keep hitting the initial breakpoint instead of making
24407 For the 680x0 stub only, you need to provide a variable called
24408 @code{exceptionHook}. Normally you just use:
24411 void (*exceptionHook)() = 0;
24415 but if before calling @code{set_debug_traps}, you set it to point to a
24416 function in your program, that function is called when
24417 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
24418 error). The function indicated by @code{exceptionHook} is called with
24419 one parameter: an @code{int} which is the exception number.
24422 Compile and link together: your program, the @value{GDBN} debugging stub for
24423 your target architecture, and the supporting subroutines.
24426 Make sure you have a serial connection between your target machine and
24427 the @value{GDBN} host, and identify the serial port on the host.
24430 @c The "remote" target now provides a `load' command, so we should
24431 @c document that. FIXME.
24432 Download your program to your target machine (or get it there by
24433 whatever means the manufacturer provides), and start it.
24436 Start @value{GDBN} on the host, and connect to the target
24437 (@pxref{Connecting,,Connecting to a Remote Target}).
24441 @node Configurations
24442 @chapter Configuration-Specific Information
24444 While nearly all @value{GDBN} commands are available for all native and
24445 cross versions of the debugger, there are some exceptions. This chapter
24446 describes things that are only available in certain configurations.
24448 There are three major categories of configurations: native
24449 configurations, where the host and target are the same, embedded
24450 operating system configurations, which are usually the same for several
24451 different processor architectures, and bare embedded processors, which
24452 are quite different from each other.
24457 * Embedded Processors::
24464 This section describes details specific to particular native
24468 * BSD libkvm Interface:: Debugging BSD kernel memory images
24469 * Process Information:: Process information
24470 * DJGPP Native:: Features specific to the DJGPP port
24471 * Cygwin Native:: Features specific to the Cygwin port
24472 * Hurd Native:: Features specific to @sc{gnu} Hurd
24473 * Darwin:: Features specific to Darwin
24474 * FreeBSD:: Features specific to FreeBSD
24477 @node BSD libkvm Interface
24478 @subsection BSD libkvm Interface
24481 @cindex kernel memory image
24482 @cindex kernel crash dump
24484 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
24485 interface that provides a uniform interface for accessing kernel virtual
24486 memory images, including live systems and crash dumps. @value{GDBN}
24487 uses this interface to allow you to debug live kernels and kernel crash
24488 dumps on many native BSD configurations. This is implemented as a
24489 special @code{kvm} debugging target. For debugging a live system, load
24490 the currently running kernel into @value{GDBN} and connect to the
24494 (@value{GDBP}) @b{target kvm}
24497 For debugging crash dumps, provide the file name of the crash dump as an
24501 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
24504 Once connected to the @code{kvm} target, the following commands are
24510 Set current context from the @dfn{Process Control Block} (PCB) address.
24513 Set current context from proc address. This command isn't available on
24514 modern FreeBSD systems.
24517 @node Process Information
24518 @subsection Process Information
24520 @cindex examine process image
24521 @cindex process info via @file{/proc}
24523 Some operating systems provide interfaces to fetch additional
24524 information about running processes beyond memory and per-thread
24525 register state. If @value{GDBN} is configured for an operating system
24526 with a supported interface, the command @code{info proc} is available
24527 to report information about the process running your program, or about
24528 any process running on your system.
24530 One supported interface is a facility called @samp{/proc} that can be
24531 used to examine the image of a running process using file-system
24532 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
24535 On FreeBSD and NetBSD systems, system control nodes are used to query
24536 process information.
24538 In addition, some systems may provide additional process information
24539 in core files. Note that a core file may include a subset of the
24540 information available from a live process. Process information is
24541 currently available from cores created on @sc{gnu}/Linux and FreeBSD
24548 @itemx info proc @var{process-id}
24549 Summarize available information about a process. If a
24550 process ID is specified by @var{process-id}, display information about
24551 that process; otherwise display information about the program being
24552 debugged. The summary includes the debugged process ID, the command
24553 line used to invoke it, its current working directory, and its
24554 executable file's absolute file name.
24556 On some systems, @var{process-id} can be of the form
24557 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
24558 within a process. If the optional @var{pid} part is missing, it means
24559 a thread from the process being debugged (the leading @samp{/} still
24560 needs to be present, or else @value{GDBN} will interpret the number as
24561 a process ID rather than a thread ID).
24563 @item info proc cmdline
24564 @cindex info proc cmdline
24565 Show the original command line of the process. This command is
24566 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24568 @item info proc cwd
24569 @cindex info proc cwd
24570 Show the current working directory of the process. This command is
24571 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24573 @item info proc exe
24574 @cindex info proc exe
24575 Show the name of executable of the process. This command is supported
24576 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24578 @item info proc files
24579 @cindex info proc files
24580 Show the file descriptors open by the process. For each open file
24581 descriptor, @value{GDBN} shows its number, type (file, directory,
24582 character device, socket), file pointer offset, and the name of the
24583 resource open on the descriptor. The resource name can be a file name
24584 (for files, directories, and devices) or a protocol followed by socket
24585 address (for network connections). This command is supported on
24588 This example shows the open file descriptors for a process using a
24589 tty for standard input and output as well as two network sockets:
24592 (@value{GDBP}) info proc files 22136
24596 FD Type Offset Flags Name
24597 text file - r-------- /usr/bin/ssh
24598 ctty chr - rw------- /dev/pts/20
24599 cwd dir - r-------- /usr/home/john
24600 root dir - r-------- /
24601 0 chr 0x32933a4 rw------- /dev/pts/20
24602 1 chr 0x32933a4 rw------- /dev/pts/20
24603 2 chr 0x32933a4 rw------- /dev/pts/20
24604 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
24605 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
24608 @item info proc mappings
24609 @cindex memory address space mappings
24610 Report the memory address space ranges accessible in a process. On
24611 Solaris, FreeBSD and NetBSD systems, each memory range includes information
24612 on whether the process has read, write, or execute access rights to each
24613 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
24614 includes the object file which is mapped to that range.
24616 @item info proc stat
24617 @itemx info proc status
24618 @cindex process detailed status information
24619 Show additional process-related information, including the user ID and
24620 group ID; virtual memory usage; the signals that are pending, blocked,
24621 and ignored; its TTY; its consumption of system and user time; its
24622 stack size; its @samp{nice} value; etc. These commands are supported
24623 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24625 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
24626 information (type @kbd{man 5 proc} from your shell prompt).
24628 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
24629 @code{info proc status}.
24631 @item info proc all
24632 Show all the information about the process described under all of the
24633 above @code{info proc} subcommands.
24636 @comment These sub-options of 'info proc' were not included when
24637 @comment procfs.c was re-written. Keep their descriptions around
24638 @comment against the day when someone finds the time to put them back in.
24639 @kindex info proc times
24640 @item info proc times
24641 Starting time, user CPU time, and system CPU time for your program and
24644 @kindex info proc id
24646 Report on the process IDs related to your program: its own process ID,
24647 the ID of its parent, the process group ID, and the session ID.
24650 @item set procfs-trace
24651 @kindex set procfs-trace
24652 @cindex @code{procfs} API calls
24653 This command enables and disables tracing of @code{procfs} API calls.
24655 @item show procfs-trace
24656 @kindex show procfs-trace
24657 Show the current state of @code{procfs} API call tracing.
24659 @item set procfs-file @var{file}
24660 @kindex set procfs-file
24661 Tell @value{GDBN} to write @code{procfs} API trace to the named
24662 @var{file}. @value{GDBN} appends the trace info to the previous
24663 contents of the file. The default is to display the trace on the
24666 @item show procfs-file
24667 @kindex show procfs-file
24668 Show the file to which @code{procfs} API trace is written.
24670 @item proc-trace-entry
24671 @itemx proc-trace-exit
24672 @itemx proc-untrace-entry
24673 @itemx proc-untrace-exit
24674 @kindex proc-trace-entry
24675 @kindex proc-trace-exit
24676 @kindex proc-untrace-entry
24677 @kindex proc-untrace-exit
24678 These commands enable and disable tracing of entries into and exits
24679 from the @code{syscall} interface.
24682 @kindex info pidlist
24683 @cindex process list, QNX Neutrino
24684 For QNX Neutrino only, this command displays the list of all the
24685 processes and all the threads within each process.
24688 @kindex info meminfo
24689 @cindex mapinfo list, QNX Neutrino
24690 For QNX Neutrino only, this command displays the list of all mapinfos.
24694 @subsection Features for Debugging @sc{djgpp} Programs
24695 @cindex @sc{djgpp} debugging
24696 @cindex native @sc{djgpp} debugging
24697 @cindex MS-DOS-specific commands
24700 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
24701 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
24702 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
24703 top of real-mode DOS systems and their emulations.
24705 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
24706 defines a few commands specific to the @sc{djgpp} port. This
24707 subsection describes those commands.
24712 This is a prefix of @sc{djgpp}-specific commands which print
24713 information about the target system and important OS structures.
24716 @cindex MS-DOS system info
24717 @cindex free memory information (MS-DOS)
24718 @item info dos sysinfo
24719 This command displays assorted information about the underlying
24720 platform: the CPU type and features, the OS version and flavor, the
24721 DPMI version, and the available conventional and DPMI memory.
24726 @cindex segment descriptor tables
24727 @cindex descriptor tables display
24729 @itemx info dos ldt
24730 @itemx info dos idt
24731 These 3 commands display entries from, respectively, Global, Local,
24732 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
24733 tables are data structures which store a descriptor for each segment
24734 that is currently in use. The segment's selector is an index into a
24735 descriptor table; the table entry for that index holds the
24736 descriptor's base address and limit, and its attributes and access
24739 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
24740 segment (used for both data and the stack), and a DOS segment (which
24741 allows access to DOS/BIOS data structures and absolute addresses in
24742 conventional memory). However, the DPMI host will usually define
24743 additional segments in order to support the DPMI environment.
24745 @cindex garbled pointers
24746 These commands allow to display entries from the descriptor tables.
24747 Without an argument, all entries from the specified table are
24748 displayed. An argument, which should be an integer expression, means
24749 display a single entry whose index is given by the argument. For
24750 example, here's a convenient way to display information about the
24751 debugged program's data segment:
24754 @exdent @code{(@value{GDBP}) info dos ldt $ds}
24755 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
24759 This comes in handy when you want to see whether a pointer is outside
24760 the data segment's limit (i.e.@: @dfn{garbled}).
24762 @cindex page tables display (MS-DOS)
24764 @itemx info dos pte
24765 These two commands display entries from, respectively, the Page
24766 Directory and the Page Tables. Page Directories and Page Tables are
24767 data structures which control how virtual memory addresses are mapped
24768 into physical addresses. A Page Table includes an entry for every
24769 page of memory that is mapped into the program's address space; there
24770 may be several Page Tables, each one holding up to 4096 entries. A
24771 Page Directory has up to 4096 entries, one each for every Page Table
24772 that is currently in use.
24774 Without an argument, @kbd{info dos pde} displays the entire Page
24775 Directory, and @kbd{info dos pte} displays all the entries in all of
24776 the Page Tables. An argument, an integer expression, given to the
24777 @kbd{info dos pde} command means display only that entry from the Page
24778 Directory table. An argument given to the @kbd{info dos pte} command
24779 means display entries from a single Page Table, the one pointed to by
24780 the specified entry in the Page Directory.
24782 @cindex direct memory access (DMA) on MS-DOS
24783 These commands are useful when your program uses @dfn{DMA} (Direct
24784 Memory Access), which needs physical addresses to program the DMA
24787 These commands are supported only with some DPMI servers.
24789 @cindex physical address from linear address
24790 @item info dos address-pte @var{addr}
24791 This command displays the Page Table entry for a specified linear
24792 address. The argument @var{addr} is a linear address which should
24793 already have the appropriate segment's base address added to it,
24794 because this command accepts addresses which may belong to @emph{any}
24795 segment. For example, here's how to display the Page Table entry for
24796 the page where a variable @code{i} is stored:
24799 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
24800 @exdent @code{Page Table entry for address 0x11a00d30:}
24801 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
24805 This says that @code{i} is stored at offset @code{0xd30} from the page
24806 whose physical base address is @code{0x02698000}, and shows all the
24807 attributes of that page.
24809 Note that you must cast the addresses of variables to a @code{char *},
24810 since otherwise the value of @code{__djgpp_base_address}, the base
24811 address of all variables and functions in a @sc{djgpp} program, will
24812 be added using the rules of C pointer arithmetics: if @code{i} is
24813 declared an @code{int}, @value{GDBN} will add 4 times the value of
24814 @code{__djgpp_base_address} to the address of @code{i}.
24816 Here's another example, it displays the Page Table entry for the
24820 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
24821 @exdent @code{Page Table entry for address 0x29110:}
24822 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
24826 (The @code{+ 3} offset is because the transfer buffer's address is the
24827 3rd member of the @code{_go32_info_block} structure.) The output
24828 clearly shows that this DPMI server maps the addresses in conventional
24829 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
24830 linear (@code{0x29110}) addresses are identical.
24832 This command is supported only with some DPMI servers.
24835 @cindex DOS serial data link, remote debugging
24836 In addition to native debugging, the DJGPP port supports remote
24837 debugging via a serial data link. The following commands are specific
24838 to remote serial debugging in the DJGPP port of @value{GDBN}.
24841 @kindex set com1base
24842 @kindex set com1irq
24843 @kindex set com2base
24844 @kindex set com2irq
24845 @kindex set com3base
24846 @kindex set com3irq
24847 @kindex set com4base
24848 @kindex set com4irq
24849 @item set com1base @var{addr}
24850 This command sets the base I/O port address of the @file{COM1} serial
24853 @item set com1irq @var{irq}
24854 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
24855 for the @file{COM1} serial port.
24857 There are similar commands @samp{set com2base}, @samp{set com3irq},
24858 etc.@: for setting the port address and the @code{IRQ} lines for the
24861 @kindex show com1base
24862 @kindex show com1irq
24863 @kindex show com2base
24864 @kindex show com2irq
24865 @kindex show com3base
24866 @kindex show com3irq
24867 @kindex show com4base
24868 @kindex show com4irq
24869 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
24870 display the current settings of the base address and the @code{IRQ}
24871 lines used by the COM ports.
24874 @kindex info serial
24875 @cindex DOS serial port status
24876 This command prints the status of the 4 DOS serial ports. For each
24877 port, it prints whether it's active or not, its I/O base address and
24878 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
24879 counts of various errors encountered so far.
24883 @node Cygwin Native
24884 @subsection Features for Debugging MS Windows PE Executables
24885 @cindex MS Windows debugging
24886 @cindex native Cygwin debugging
24887 @cindex Cygwin-specific commands
24889 @value{GDBN} supports native debugging of MS Windows programs, including
24890 DLLs with and without symbolic debugging information.
24892 @cindex Ctrl-BREAK, MS-Windows
24893 @cindex interrupt debuggee on MS-Windows
24894 MS-Windows programs that call @code{SetConsoleMode} to switch off the
24895 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
24896 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
24897 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
24898 sequence, which can be used to interrupt the debuggee even if it
24901 There are various additional Cygwin-specific commands, described in
24902 this section. Working with DLLs that have no debugging symbols is
24903 described in @ref{Non-debug DLL Symbols}.
24908 This is a prefix of MS Windows-specific commands which print
24909 information about the target system and important OS structures.
24911 @item info w32 selector
24912 This command displays information returned by
24913 the Win32 API @code{GetThreadSelectorEntry} function.
24914 It takes an optional argument that is evaluated to
24915 a long value to give the information about this given selector.
24916 Without argument, this command displays information
24917 about the six segment registers.
24919 @item info w32 thread-information-block
24920 This command displays thread specific information stored in the
24921 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24922 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24924 @kindex signal-event
24925 @item signal-event @var{id}
24926 This command signals an event with user-provided @var{id}. Used to resume
24927 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24929 To use it, create or edit the following keys in
24930 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24931 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24932 (for x86_64 versions):
24936 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24937 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24938 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24940 The first @code{%ld} will be replaced by the process ID of the
24941 crashing process, the second @code{%ld} will be replaced by the ID of
24942 the event that blocks the crashing process, waiting for @value{GDBN}
24946 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24947 make the system run debugger specified by the Debugger key
24948 automatically, @code{0} will cause a dialog box with ``OK'' and
24949 ``Cancel'' buttons to appear, which allows the user to either
24950 terminate the crashing process (OK) or debug it (Cancel).
24953 @kindex set cygwin-exceptions
24954 @cindex debugging the Cygwin DLL
24955 @cindex Cygwin DLL, debugging
24956 @item set cygwin-exceptions @var{mode}
24957 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24958 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24959 @value{GDBN} will delay recognition of exceptions, and may ignore some
24960 exceptions which seem to be caused by internal Cygwin DLL
24961 ``bookkeeping''. This option is meant primarily for debugging the
24962 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24963 @value{GDBN} users with false @code{SIGSEGV} signals.
24965 @kindex show cygwin-exceptions
24966 @item show cygwin-exceptions
24967 Displays whether @value{GDBN} will break on exceptions that happen
24968 inside the Cygwin DLL itself.
24970 @kindex set new-console
24971 @item set new-console @var{mode}
24972 If @var{mode} is @code{on} the debuggee will
24973 be started in a new console on next start.
24974 If @var{mode} is @code{off}, the debuggee will
24975 be started in the same console as the debugger.
24977 @kindex show new-console
24978 @item show new-console
24979 Displays whether a new console is used
24980 when the debuggee is started.
24982 @kindex set new-group
24983 @item set new-group @var{mode}
24984 This boolean value controls whether the debuggee should
24985 start a new group or stay in the same group as the debugger.
24986 This affects the way the Windows OS handles
24989 @kindex show new-group
24990 @item show new-group
24991 Displays current value of new-group boolean.
24993 @kindex set debugevents
24994 @item set debugevents
24995 This boolean value adds debug output concerning kernel events related
24996 to the debuggee seen by the debugger. This includes events that
24997 signal thread and process creation and exit, DLL loading and
24998 unloading, console interrupts, and debugging messages produced by the
24999 Windows @code{OutputDebugString} API call.
25001 @kindex set debugexec
25002 @item set debugexec
25003 This boolean value adds debug output concerning execute events
25004 (such as resume thread) seen by the debugger.
25006 @kindex set debugexceptions
25007 @item set debugexceptions
25008 This boolean value adds debug output concerning exceptions in the
25009 debuggee seen by the debugger.
25011 @kindex set debugmemory
25012 @item set debugmemory
25013 This boolean value adds debug output concerning debuggee memory reads
25014 and writes by the debugger.
25018 This boolean values specifies whether the debuggee is called
25019 via a shell or directly (default value is on).
25023 Displays if the debuggee will be started with a shell.
25028 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
25031 @node Non-debug DLL Symbols
25032 @subsubsection Support for DLLs without Debugging Symbols
25033 @cindex DLLs with no debugging symbols
25034 @cindex Minimal symbols and DLLs
25036 Very often on windows, some of the DLLs that your program relies on do
25037 not include symbolic debugging information (for example,
25038 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
25039 symbols in a DLL, it relies on the minimal amount of symbolic
25040 information contained in the DLL's export table. This section
25041 describes working with such symbols, known internally to @value{GDBN} as
25042 ``minimal symbols''.
25044 Note that before the debugged program has started execution, no DLLs
25045 will have been loaded. The easiest way around this problem is simply to
25046 start the program --- either by setting a breakpoint or letting the
25047 program run once to completion.
25049 @subsubsection DLL Name Prefixes
25051 In keeping with the naming conventions used by the Microsoft debugging
25052 tools, DLL export symbols are made available with a prefix based on the
25053 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
25054 also entered into the symbol table, so @code{CreateFileA} is often
25055 sufficient. In some cases there will be name clashes within a program
25056 (particularly if the executable itself includes full debugging symbols)
25057 necessitating the use of the fully qualified name when referring to the
25058 contents of the DLL. Use single-quotes around the name to avoid the
25059 exclamation mark (``!'') being interpreted as a language operator.
25061 Note that the internal name of the DLL may be all upper-case, even
25062 though the file name of the DLL is lower-case, or vice-versa. Since
25063 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
25064 some confusion. If in doubt, try the @code{info functions} and
25065 @code{info variables} commands or even @code{maint print msymbols}
25066 (@pxref{Symbols}). Here's an example:
25069 (@value{GDBP}) info function CreateFileA
25070 All functions matching regular expression "CreateFileA":
25072 Non-debugging symbols:
25073 0x77e885f4 CreateFileA
25074 0x77e885f4 KERNEL32!CreateFileA
25078 (@value{GDBP}) info function !
25079 All functions matching regular expression "!":
25081 Non-debugging symbols:
25082 0x6100114c cygwin1!__assert
25083 0x61004034 cygwin1!_dll_crt0@@0
25084 0x61004240 cygwin1!dll_crt0(per_process *)
25088 @subsubsection Working with Minimal Symbols
25090 Symbols extracted from a DLL's export table do not contain very much
25091 type information. All that @value{GDBN} can do is guess whether a symbol
25092 refers to a function or variable depending on the linker section that
25093 contains the symbol. Also note that the actual contents of the memory
25094 contained in a DLL are not available unless the program is running. This
25095 means that you cannot examine the contents of a variable or disassemble
25096 a function within a DLL without a running program.
25098 Variables are generally treated as pointers and dereferenced
25099 automatically. For this reason, it is often necessary to prefix a
25100 variable name with the address-of operator (``&'') and provide explicit
25101 type information in the command. Here's an example of the type of
25105 (@value{GDBP}) print 'cygwin1!__argv'
25106 'cygwin1!__argv' has unknown type; cast it to its declared type
25110 (@value{GDBP}) x 'cygwin1!__argv'
25111 'cygwin1!__argv' has unknown type; cast it to its declared type
25114 And two possible solutions:
25117 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
25118 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
25122 (@value{GDBP}) x/2x &'cygwin1!__argv'
25123 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
25124 (@value{GDBP}) x/x 0x10021608
25125 0x10021608: 0x0022fd98
25126 (@value{GDBP}) x/s 0x0022fd98
25127 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
25130 Setting a break point within a DLL is possible even before the program
25131 starts execution. However, under these circumstances, @value{GDBN} can't
25132 examine the initial instructions of the function in order to skip the
25133 function's frame set-up code. You can work around this by using ``*&''
25134 to set the breakpoint at a raw memory address:
25137 (@value{GDBP}) break *&'python22!PyOS_Readline'
25138 Breakpoint 1 at 0x1e04eff0
25141 The author of these extensions is not entirely convinced that setting a
25142 break point within a shared DLL like @file{kernel32.dll} is completely
25146 @subsection Commands Specific to @sc{gnu} Hurd Systems
25147 @cindex @sc{gnu} Hurd debugging
25149 This subsection describes @value{GDBN} commands specific to the
25150 @sc{gnu} Hurd native debugging.
25155 @kindex set signals@r{, Hurd command}
25156 @kindex set sigs@r{, Hurd command}
25157 This command toggles the state of inferior signal interception by
25158 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
25159 affected by this command. @code{sigs} is a shorthand alias for
25164 @kindex show signals@r{, Hurd command}
25165 @kindex show sigs@r{, Hurd command}
25166 Show the current state of intercepting inferior's signals.
25168 @item set signal-thread
25169 @itemx set sigthread
25170 @kindex set signal-thread
25171 @kindex set sigthread
25172 This command tells @value{GDBN} which thread is the @code{libc} signal
25173 thread. That thread is run when a signal is delivered to a running
25174 process. @code{set sigthread} is the shorthand alias of @code{set
25177 @item show signal-thread
25178 @itemx show sigthread
25179 @kindex show signal-thread
25180 @kindex show sigthread
25181 These two commands show which thread will run when the inferior is
25182 delivered a signal.
25185 @kindex set stopped@r{, Hurd command}
25186 This commands tells @value{GDBN} that the inferior process is stopped,
25187 as with the @code{SIGSTOP} signal. The stopped process can be
25188 continued by delivering a signal to it.
25191 @kindex show stopped@r{, Hurd command}
25192 This command shows whether @value{GDBN} thinks the debuggee is
25195 @item set exceptions
25196 @kindex set exceptions@r{, Hurd command}
25197 Use this command to turn off trapping of exceptions in the inferior.
25198 When exception trapping is off, neither breakpoints nor
25199 single-stepping will work. To restore the default, set exception
25202 @item show exceptions
25203 @kindex show exceptions@r{, Hurd command}
25204 Show the current state of trapping exceptions in the inferior.
25206 @item set task pause
25207 @kindex set task@r{, Hurd commands}
25208 @cindex task attributes (@sc{gnu} Hurd)
25209 @cindex pause current task (@sc{gnu} Hurd)
25210 This command toggles task suspension when @value{GDBN} has control.
25211 Setting it to on takes effect immediately, and the task is suspended
25212 whenever @value{GDBN} gets control. Setting it to off will take
25213 effect the next time the inferior is continued. If this option is set
25214 to off, you can use @code{set thread default pause on} or @code{set
25215 thread pause on} (see below) to pause individual threads.
25217 @item show task pause
25218 @kindex show task@r{, Hurd commands}
25219 Show the current state of task suspension.
25221 @item set task detach-suspend-count
25222 @cindex task suspend count
25223 @cindex detach from task, @sc{gnu} Hurd
25224 This command sets the suspend count the task will be left with when
25225 @value{GDBN} detaches from it.
25227 @item show task detach-suspend-count
25228 Show the suspend count the task will be left with when detaching.
25230 @item set task exception-port
25231 @itemx set task excp
25232 @cindex task exception port, @sc{gnu} Hurd
25233 This command sets the task exception port to which @value{GDBN} will
25234 forward exceptions. The argument should be the value of the @dfn{send
25235 rights} of the task. @code{set task excp} is a shorthand alias.
25237 @item set noninvasive
25238 @cindex noninvasive task options
25239 This command switches @value{GDBN} to a mode that is the least
25240 invasive as far as interfering with the inferior is concerned. This
25241 is the same as using @code{set task pause}, @code{set exceptions}, and
25242 @code{set signals} to values opposite to the defaults.
25244 @item info send-rights
25245 @itemx info receive-rights
25246 @itemx info port-rights
25247 @itemx info port-sets
25248 @itemx info dead-names
25251 @cindex send rights, @sc{gnu} Hurd
25252 @cindex receive rights, @sc{gnu} Hurd
25253 @cindex port rights, @sc{gnu} Hurd
25254 @cindex port sets, @sc{gnu} Hurd
25255 @cindex dead names, @sc{gnu} Hurd
25256 These commands display information about, respectively, send rights,
25257 receive rights, port rights, port sets, and dead names of a task.
25258 There are also shorthand aliases: @code{info ports} for @code{info
25259 port-rights} and @code{info psets} for @code{info port-sets}.
25261 @item set thread pause
25262 @kindex set thread@r{, Hurd command}
25263 @cindex thread properties, @sc{gnu} Hurd
25264 @cindex pause current thread (@sc{gnu} Hurd)
25265 This command toggles current thread suspension when @value{GDBN} has
25266 control. Setting it to on takes effect immediately, and the current
25267 thread is suspended whenever @value{GDBN} gets control. Setting it to
25268 off will take effect the next time the inferior is continued.
25269 Normally, this command has no effect, since when @value{GDBN} has
25270 control, the whole task is suspended. However, if you used @code{set
25271 task pause off} (see above), this command comes in handy to suspend
25272 only the current thread.
25274 @item show thread pause
25275 @kindex show thread@r{, Hurd command}
25276 This command shows the state of current thread suspension.
25278 @item set thread run
25279 This command sets whether the current thread is allowed to run.
25281 @item show thread run
25282 Show whether the current thread is allowed to run.
25284 @item set thread detach-suspend-count
25285 @cindex thread suspend count, @sc{gnu} Hurd
25286 @cindex detach from thread, @sc{gnu} Hurd
25287 This command sets the suspend count @value{GDBN} will leave on a
25288 thread when detaching. This number is relative to the suspend count
25289 found by @value{GDBN} when it notices the thread; use @code{set thread
25290 takeover-suspend-count} to force it to an absolute value.
25292 @item show thread detach-suspend-count
25293 Show the suspend count @value{GDBN} will leave on the thread when
25296 @item set thread exception-port
25297 @itemx set thread excp
25298 Set the thread exception port to which to forward exceptions. This
25299 overrides the port set by @code{set task exception-port} (see above).
25300 @code{set thread excp} is the shorthand alias.
25302 @item set thread takeover-suspend-count
25303 Normally, @value{GDBN}'s thread suspend counts are relative to the
25304 value @value{GDBN} finds when it notices each thread. This command
25305 changes the suspend counts to be absolute instead.
25307 @item set thread default
25308 @itemx show thread default
25309 @cindex thread default settings, @sc{gnu} Hurd
25310 Each of the above @code{set thread} commands has a @code{set thread
25311 default} counterpart (e.g., @code{set thread default pause}, @code{set
25312 thread default exception-port}, etc.). The @code{thread default}
25313 variety of commands sets the default thread properties for all
25314 threads; you can then change the properties of individual threads with
25315 the non-default commands.
25322 @value{GDBN} provides the following commands specific to the Darwin target:
25325 @item set debug darwin @var{num}
25326 @kindex set debug darwin
25327 When set to a non zero value, enables debugging messages specific to
25328 the Darwin support. Higher values produce more verbose output.
25330 @item show debug darwin
25331 @kindex show debug darwin
25332 Show the current state of Darwin messages.
25334 @item set debug mach-o @var{num}
25335 @kindex set debug mach-o
25336 When set to a non zero value, enables debugging messages while
25337 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
25338 file format used on Darwin for object and executable files.) Higher
25339 values produce more verbose output. This is a command to diagnose
25340 problems internal to @value{GDBN} and should not be needed in normal
25343 @item show debug mach-o
25344 @kindex show debug mach-o
25345 Show the current state of Mach-O file messages.
25347 @item set mach-exceptions on
25348 @itemx set mach-exceptions off
25349 @kindex set mach-exceptions
25350 On Darwin, faults are first reported as a Mach exception and are then
25351 mapped to a Posix signal. Use this command to turn on trapping of
25352 Mach exceptions in the inferior. This might be sometimes useful to
25353 better understand the cause of a fault. The default is off.
25355 @item show mach-exceptions
25356 @kindex show mach-exceptions
25357 Show the current state of exceptions trapping.
25361 @subsection FreeBSD
25364 When the ABI of a system call is changed in the FreeBSD kernel, this
25365 is implemented by leaving a compatibility system call using the old
25366 ABI at the existing number and allocating a new system call number for
25367 the version using the new ABI. As a convenience, when a system call
25368 is caught by name (@pxref{catch syscall}), compatibility system calls
25371 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
25372 system call and catching the @code{kevent} system call by name catches
25376 (@value{GDBP}) catch syscall kevent
25377 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
25383 @section Embedded Operating Systems
25385 This section describes configurations involving the debugging of
25386 embedded operating systems that are available for several different
25389 @value{GDBN} includes the ability to debug programs running on
25390 various real-time operating systems.
25392 @node Embedded Processors
25393 @section Embedded Processors
25395 This section goes into details specific to particular embedded
25398 @cindex send command to simulator
25399 Whenever a specific embedded processor has a simulator, @value{GDBN}
25400 allows to send an arbitrary command to the simulator.
25403 @item sim @var{command}
25404 @kindex sim@r{, a command}
25405 Send an arbitrary @var{command} string to the simulator. Consult the
25406 documentation for the specific simulator in use for information about
25407 acceptable commands.
25412 * ARC:: Synopsys ARC
25415 * M68K:: Motorola M68K
25416 * MicroBlaze:: Xilinx MicroBlaze
25417 * MIPS Embedded:: MIPS Embedded
25418 * OpenRISC 1000:: OpenRISC 1000 (or1k)
25419 * PowerPC Embedded:: PowerPC Embedded
25422 * Super-H:: Renesas Super-H
25426 @subsection Synopsys ARC
25427 @cindex Synopsys ARC
25428 @cindex ARC specific commands
25434 @value{GDBN} provides the following ARC-specific commands:
25437 @item set debug arc
25438 @kindex set debug arc
25439 Control the level of ARC specific debug messages. Use 0 for no messages (the
25440 default), 1 for debug messages, and 2 for even more debug messages.
25442 @item show debug arc
25443 @kindex show debug arc
25444 Show the level of ARC specific debugging in operation.
25446 @item maint print arc arc-instruction @var{address}
25447 @kindex maint print arc arc-instruction
25448 Print internal disassembler information about instruction at a given address.
25455 @value{GDBN} provides the following ARM-specific commands:
25458 @item set arm disassembler
25460 This commands selects from a list of disassembly styles. The
25461 @code{"std"} style is the standard style.
25463 @item show arm disassembler
25465 Show the current disassembly style.
25467 @item set arm apcs32
25468 @cindex ARM 32-bit mode
25469 This command toggles ARM operation mode between 32-bit and 26-bit.
25471 @item show arm apcs32
25472 Display the current usage of the ARM 32-bit mode.
25474 @item set arm fpu @var{fputype}
25475 This command sets the ARM floating-point unit (FPU) type. The
25476 argument @var{fputype} can be one of these:
25480 Determine the FPU type by querying the OS ABI.
25482 Software FPU, with mixed-endian doubles on little-endian ARM
25485 GCC-compiled FPA co-processor.
25487 Software FPU with pure-endian doubles.
25493 Show the current type of the FPU.
25496 This command forces @value{GDBN} to use the specified ABI.
25499 Show the currently used ABI.
25501 @item set arm fallback-mode (arm|thumb|auto)
25502 @value{GDBN} uses the symbol table, when available, to determine
25503 whether instructions are ARM or Thumb. This command controls
25504 @value{GDBN}'s default behavior when the symbol table is not
25505 available. The default is @samp{auto}, which causes @value{GDBN} to
25506 use the current execution mode (from the @code{T} bit in the @code{CPSR}
25509 @item show arm fallback-mode
25510 Show the current fallback instruction mode.
25512 @item set arm force-mode (arm|thumb|auto)
25513 This command overrides use of the symbol table to determine whether
25514 instructions are ARM or Thumb. The default is @samp{auto}, which
25515 causes @value{GDBN} to use the symbol table and then the setting
25516 of @samp{set arm fallback-mode}.
25518 @item show arm force-mode
25519 Show the current forced instruction mode.
25521 @item set arm unwind-secure-frames
25522 This command enables unwinding from Non-secure to Secure mode on
25523 Cortex-M with Security extension.
25524 This can trigger security exceptions when unwinding the exception
25526 It is enabled by default.
25528 @item show arm unwind-secure-frames
25529 Show whether unwinding from Non-secure to Secure mode is enabled.
25531 @item set debug arm
25532 Toggle whether to display ARM-specific debugging messages from the ARM
25533 target support subsystem.
25535 @item show debug arm
25536 Show whether ARM-specific debugging messages are enabled.
25540 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25541 The @value{GDBN} ARM simulator accepts the following optional arguments.
25544 @item --swi-support=@var{type}
25545 Tell the simulator which SWI interfaces to support. The argument
25546 @var{type} may be a comma separated list of the following values.
25547 The default value is @code{all}.
25563 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25564 The @value{GDBN} BPF simulator accepts the following optional arguments.
25567 @item --skb-data-offset=@var{offset}
25568 Tell the simulator the offset, measured in bytes, of the
25569 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
25570 This offset is used by some BPF specific-purpose load/store
25571 instructions. Defaults to 0.
25578 The Motorola m68k configuration includes ColdFire support.
25581 @subsection MicroBlaze
25582 @cindex Xilinx MicroBlaze
25583 @cindex XMD, Xilinx Microprocessor Debugger
25585 The MicroBlaze is a soft-core processor supported on various Xilinx
25586 FPGAs, such as Spartan or Virtex series. Boards with these processors
25587 usually have JTAG ports which connect to a host system running the Xilinx
25588 Embedded Development Kit (EDK) or Software Development Kit (SDK).
25589 This host system is used to download the configuration bitstream to
25590 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
25591 communicates with the target board using the JTAG interface and
25592 presents a @code{gdbserver} interface to the board. By default
25593 @code{xmd} uses port @code{1234}. (While it is possible to change
25594 this default port, it requires the use of undocumented @code{xmd}
25595 commands. Contact Xilinx support if you need to do this.)
25597 Use these GDB commands to connect to the MicroBlaze target processor.
25600 @item target remote :1234
25601 Use this command to connect to the target if you are running @value{GDBN}
25602 on the same system as @code{xmd}.
25604 @item target remote @var{xmd-host}:1234
25605 Use this command to connect to the target if it is connected to @code{xmd}
25606 running on a different system named @var{xmd-host}.
25609 Use this command to download a program to the MicroBlaze target.
25611 @item set debug microblaze @var{n}
25612 Enable MicroBlaze-specific debugging messages if non-zero.
25614 @item show debug microblaze @var{n}
25615 Show MicroBlaze-specific debugging level.
25618 @node MIPS Embedded
25619 @subsection @acronym{MIPS} Embedded
25622 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
25625 @item set mipsfpu double
25626 @itemx set mipsfpu single
25627 @itemx set mipsfpu none
25628 @itemx set mipsfpu auto
25629 @itemx show mipsfpu
25630 @kindex set mipsfpu
25631 @kindex show mipsfpu
25632 @cindex @acronym{MIPS} remote floating point
25633 @cindex floating point, @acronym{MIPS} remote
25634 If your target board does not support the @acronym{MIPS} floating point
25635 coprocessor, you should use the command @samp{set mipsfpu none} (if you
25636 need this, you may wish to put the command in your @value{GDBN} init
25637 file). This tells @value{GDBN} how to find the return value of
25638 functions which return floating point values. It also allows
25639 @value{GDBN} to avoid saving the floating point registers when calling
25640 functions on the board. If you are using a floating point coprocessor
25641 with only single precision floating point support, as on the @sc{r4650}
25642 processor, use the command @samp{set mipsfpu single}. The default
25643 double precision floating point coprocessor may be selected using
25644 @samp{set mipsfpu double}.
25646 In previous versions the only choices were double precision or no
25647 floating point, so @samp{set mipsfpu on} will select double precision
25648 and @samp{set mipsfpu off} will select no floating point.
25650 As usual, you can inquire about the @code{mipsfpu} variable with
25651 @samp{show mipsfpu}.
25654 @node OpenRISC 1000
25655 @subsection OpenRISC 1000
25656 @cindex OpenRISC 1000
25659 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
25660 mainly provided as a soft-core which can run on Xilinx, Altera and other
25663 @value{GDBN} for OpenRISC supports the below commands when connecting to
25671 Runs the builtin CPU simulator which can run very basic
25672 programs but does not support most hardware functions like MMU.
25673 For more complex use cases the user is advised to run an external
25674 target, and connect using @samp{target remote}.
25676 Example: @code{target sim}
25678 @item set debug or1k
25679 Toggle whether to display OpenRISC-specific debugging messages from the
25680 OpenRISC target support subsystem.
25682 @item show debug or1k
25683 Show whether OpenRISC-specific debugging messages are enabled.
25686 @node PowerPC Embedded
25687 @subsection PowerPC Embedded
25689 @cindex DVC register
25690 @value{GDBN} supports using the DVC (Data Value Compare) register to
25691 implement in hardware simple hardware watchpoint conditions of the form:
25694 (@value{GDBP}) watch @var{address|variable} \
25695 if @var{address|variable} == @var{constant expression}
25698 The DVC register will be automatically used when @value{GDBN} detects
25699 such pattern in a condition expression, and the created watchpoint uses one
25700 debug register (either the @code{exact-watchpoints} option is on and the
25701 variable is scalar, or the variable has a length of one byte). This feature
25702 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
25705 When running on PowerPC embedded processors, @value{GDBN} automatically uses
25706 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
25707 in which case watchpoints using only one debug register are created when
25708 watching variables of scalar types.
25710 You can create an artificial array to watch an arbitrary memory
25711 region using one of the following commands (@pxref{Expressions}):
25714 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
25715 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
25718 PowerPC embedded processors support masked watchpoints. See the discussion
25719 about the @code{mask} argument in @ref{Set Watchpoints}.
25721 @cindex ranged breakpoint
25722 PowerPC embedded processors support hardware accelerated
25723 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
25724 the inferior whenever it executes an instruction at any address within
25725 the range it was set at. To set a ranged breakpoint in @value{GDBN},
25726 use the @code{break-range} command.
25728 @value{GDBN} provides the following PowerPC-specific commands:
25731 @kindex break-range
25732 @item break-range @var{start-locspec}, @var{end-locspec}
25733 Set a breakpoint for an address range given by @var{start-locspec} and
25734 @var{end-locspec}, which are location specs. @xref{Location
25735 Specifications}, for a list of all the possible forms of location
25736 specs. @value{GDBN} resolves both @var{start-locspec} and
25737 @var{end-locspec}, and uses the addresses of the resolved code
25738 locations as start and end addresses of the range to break at. The
25739 breakpoint will stop execution of the inferior whenever it executes an
25740 instruction at any address between the start and end addresses,
25741 inclusive. If either @var{start-locspec} or @var{end-locspec} resolve
25742 to multiple code locations in the program, then the command aborts
25743 with an error without creating a breakpoint.
25745 @kindex set powerpc
25746 @item set powerpc soft-float
25747 @itemx show powerpc soft-float
25748 Force @value{GDBN} to use (or not use) a software floating point calling
25749 convention. By default, @value{GDBN} selects the calling convention based
25750 on the selected architecture and the provided executable file.
25752 @item set powerpc vector-abi
25753 @itemx show powerpc vector-abi
25754 Force @value{GDBN} to use the specified calling convention for vector
25755 arguments and return values. The valid options are @samp{auto};
25756 @samp{generic}, to avoid vector registers even if they are present;
25757 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
25758 registers. By default, @value{GDBN} selects the calling convention
25759 based on the selected architecture and the provided executable file.
25761 @item set powerpc exact-watchpoints
25762 @itemx show powerpc exact-watchpoints
25763 Allow @value{GDBN} to use only one debug register when watching a variable
25764 of scalar type, thus assuming that the variable is accessed through the
25765 address of its first byte.
25770 @subsection Atmel AVR
25773 When configured for debugging the Atmel AVR, @value{GDBN} supports the
25774 following AVR-specific commands:
25777 @item info io_registers
25778 @kindex info io_registers@r{, AVR}
25779 @cindex I/O registers (Atmel AVR)
25780 This command displays information about the AVR I/O registers. For
25781 each register, @value{GDBN} prints its number and value.
25788 When configured for debugging CRIS, @value{GDBN} provides the
25789 following CRIS-specific commands:
25792 @item set cris-version @var{ver}
25793 @cindex CRIS version
25794 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
25795 The CRIS version affects register names and sizes. This command is useful in
25796 case autodetection of the CRIS version fails.
25798 @item show cris-version
25799 Show the current CRIS version.
25801 @item set cris-dwarf2-cfi
25802 @cindex DWARF-2 CFI and CRIS
25803 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
25804 Change to @samp{off} when using @code{gcc-cris} whose version is below
25807 @item show cris-dwarf2-cfi
25808 Show the current state of using DWARF-2 CFI.
25810 @item set cris-mode @var{mode}
25812 Set the current CRIS mode to @var{mode}. It should only be changed when
25813 debugging in guru mode, in which case it should be set to
25814 @samp{guru} (the default is @samp{normal}).
25816 @item show cris-mode
25817 Show the current CRIS mode.
25821 @subsection Renesas Super-H
25824 For the Renesas Super-H processor, @value{GDBN} provides these
25828 @item set sh calling-convention @var{convention}
25829 @kindex set sh calling-convention
25830 Set the calling-convention used when calling functions from @value{GDBN}.
25831 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
25832 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
25833 convention. If the DWARF-2 information of the called function specifies
25834 that the function follows the Renesas calling convention, the function
25835 is called using the Renesas calling convention. If the calling convention
25836 is set to @samp{renesas}, the Renesas calling convention is always used,
25837 regardless of the DWARF-2 information. This can be used to override the
25838 default of @samp{gcc} if debug information is missing, or the compiler
25839 does not emit the DWARF-2 calling convention entry for a function.
25841 @item show sh calling-convention
25842 @kindex show sh calling-convention
25843 Show the current calling convention setting.
25848 @node Architectures
25849 @section Architectures
25851 This section describes characteristics of architectures that affect
25852 all uses of @value{GDBN} with the architecture, both native and cross.
25859 * HPPA:: HP PA architecture
25867 @subsection AArch64
25868 @cindex AArch64 support
25870 When @value{GDBN} is debugging the AArch64 architecture, it provides the
25871 following special commands:
25874 @item set debug aarch64
25875 @kindex set debug aarch64
25876 This command determines whether AArch64 architecture-specific debugging
25877 messages are to be displayed.
25879 @item show debug aarch64
25880 Show whether AArch64 debugging messages are displayed.
25884 @subsubsection AArch64 SVE.
25885 @cindex AArch64 SVE.
25887 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
25888 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
25889 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
25890 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
25891 @code{$vg} will be provided. This is the vector granule for the current thread
25892 and represents the number of 64-bit chunks in an SVE @code{z} register.
25894 If the vector length changes, then the @code{$vg} register will be updated,
25895 but the lengths of the @code{z} and @code{p} registers will not change. This
25896 is a known limitation of @value{GDBN} and does not affect the execution of the
25899 @subsubsection AArch64 Pointer Authentication.
25900 @cindex AArch64 Pointer Authentication.
25901 @anchor{AArch64 PAC}
25903 When @value{GDBN} is debugging the AArch64 architecture, and the program is
25904 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
25905 register @code{$lr} is pointing to an PAC function its value will be masked.
25906 When GDB prints a backtrace, any addresses that required unmasking will be
25907 postfixed with the marker [PAC]. When using the MI, this is printed as part
25908 of the @code{addr_flags} field.
25910 @subsubsection AArch64 Memory Tagging Extension.
25911 @cindex AArch64 Memory Tagging Extension.
25913 When @value{GDBN} is debugging the AArch64 architecture, the program is
25914 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
25915 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
25916 available for inspection and editing of logical and allocation tags.
25917 @xref{Memory Tagging}.
25919 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
25920 signals are generated as a result of memory tag failures.
25922 If the tag violation is synchronous, the following will be shown:
25925 Program received signal SIGSEGV, Segmentation fault
25926 Memory tag violation while accessing address 0x0500fffff7ff8000
25931 If the tag violation is asynchronous, the fault address is not available.
25932 In this case @value{GDBN} will show the following:
25935 Program received signal SIGSEGV, Segmentation fault
25936 Memory tag violation
25937 Fault address unavailable.
25940 A special register, @code{tag_ctl}, is made available through the
25941 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
25942 options that can be controlled at runtime and emulates the @code{prctl}
25943 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
25944 documentation in the Linux kernel.
25946 @value{GDBN} supports dumping memory tag data to core files through the
25947 @command{gcore} command and reading memory tag data from core files generated
25948 by the @command{gcore} command or the Linux kernel.
25950 When a process uses memory-mapped pages protected by memory tags (for
25951 example, AArch64 MTE), this additional information will be recorded in
25952 the core file in the event of a crash or if @value{GDBN} generates a core file
25953 from the current process state.
25955 The memory tag data will be used so developers can display the memory
25956 tags from a particular memory region (using the @samp{m} modifier to the
25957 @command{x} command, using the @command{print} command or using the various
25958 @command{memory-tag} subcommands.
25960 In the case of a crash, @value{GDBN} will attempt to retrieve the memory tag
25961 information automatically from the core file, and will show one of the above
25962 messages depending on whether the synchronous or asynchronous mode is selected.
25963 @xref{Memory Tagging}. @xref{Memory}.
25966 @subsection x86 Architecture-specific Issues
25969 @item set struct-convention @var{mode}
25970 @kindex set struct-convention
25971 @cindex struct return convention
25972 @cindex struct/union returned in registers
25973 Set the convention used by the inferior to return @code{struct}s and
25974 @code{union}s from functions to @var{mode}. Possible values of
25975 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
25976 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
25977 are returned on the stack, while @code{"reg"} means that a
25978 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
25979 be returned in a register.
25981 @item show struct-convention
25982 @kindex show struct-convention
25983 Show the current setting of the convention to return @code{struct}s
25988 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25989 @cindex Intel Memory Protection Extensions (MPX).
25991 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25992 @footnote{The register named with capital letters represent the architecture
25993 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25994 which are the lower bound and upper bound. Bounds are effective addresses or
25995 memory locations. The upper bounds are architecturally represented in 1's
25996 complement form. A bound having lower bound = 0, and upper bound = 0
25997 (1's complement of all bits set) will allow access to the entire address space.
25999 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
26000 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
26001 display the upper bound performing the complement of one operation on the
26002 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
26003 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
26004 can also be noted that the upper bounds are inclusive.
26006 As an example, assume that the register BND0 holds bounds for a pointer having
26007 access allowed for the range between 0x32 and 0x71. The values present on
26008 bnd0raw and bnd registers are presented as follows:
26011 bnd0raw = @{0x32, 0xffffffff8e@}
26012 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
26015 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
26016 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
26017 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
26018 Python, the display includes the memory size, in bits, accessible to
26021 Bounds can also be stored in bounds tables, which are stored in
26022 application memory. These tables store bounds for pointers by specifying
26023 the bounds pointer's value along with its bounds. Evaluating and changing
26024 bounds located in bound tables is therefore interesting while investigating
26025 bugs on MPX context. @value{GDBN} provides commands for this purpose:
26028 @item show mpx bound @var{pointer}
26029 @kindex show mpx bound
26030 Display bounds of the given @var{pointer}.
26032 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
26033 @kindex set mpx bound
26034 Set the bounds of a pointer in the bound table.
26035 This command takes three parameters: @var{pointer} is the pointers
26036 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
26037 for lower and upper bounds respectively.
26040 When you call an inferior function on an Intel MPX enabled program,
26041 GDB sets the inferior's bound registers to the init (disabled) state
26042 before calling the function. As a consequence, bounds checks for the
26043 pointer arguments passed to the function will always pass.
26045 This is necessary because when you call an inferior function, the
26046 program is usually in the middle of the execution of other function.
26047 Since at that point bound registers are in an arbitrary state, not
26048 clearing them would lead to random bound violations in the called
26051 You can still examine the influence of the bound registers on the
26052 execution of the called function by stopping the execution of the
26053 called function at its prologue, setting bound registers, and
26054 continuing the execution. For example:
26058 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
26059 $ print upper (a, b, c, d, 1)
26060 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
26062 @{lbound = 0x0, ubound = ffffffff@} : size -1
26065 At this last step the value of bnd0 can be changed for investigation of bound
26066 violations caused along the execution of the call. In order to know how to
26067 set the bound registers or bound table for the call consult the ABI.
26072 See the following section.
26075 @subsection @acronym{MIPS}
26077 @cindex stack on Alpha
26078 @cindex stack on @acronym{MIPS}
26079 @cindex Alpha stack
26080 @cindex @acronym{MIPS} stack
26081 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
26082 sometimes requires @value{GDBN} to search backward in the object code to
26083 find the beginning of a function.
26085 @cindex response time, @acronym{MIPS} debugging
26086 To improve response time (especially for embedded applications, where
26087 @value{GDBN} may be restricted to a slow serial line for this search)
26088 you may want to limit the size of this search, using one of these
26092 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
26093 @item set heuristic-fence-post @var{limit}
26094 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
26095 search for the beginning of a function. A value of @var{0} (the
26096 default) means there is no limit. However, except for @var{0}, the
26097 larger the limit the more bytes @code{heuristic-fence-post} must search
26098 and therefore the longer it takes to run. You should only need to use
26099 this command when debugging a stripped executable.
26101 @item show heuristic-fence-post
26102 Display the current limit.
26106 These commands are available @emph{only} when @value{GDBN} is configured
26107 for debugging programs on Alpha or @acronym{MIPS} processors.
26109 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
26113 @item set mips abi @var{arg}
26114 @kindex set mips abi
26115 @cindex set ABI for @acronym{MIPS}
26116 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
26117 values of @var{arg} are:
26121 The default ABI associated with the current binary (this is the
26131 @item show mips abi
26132 @kindex show mips abi
26133 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
26135 @item set mips compression @var{arg}
26136 @kindex set mips compression
26137 @cindex code compression, @acronym{MIPS}
26138 Tell @value{GDBN} which @acronym{MIPS} compressed
26139 @acronym{ISA, Instruction Set Architecture} encoding is used by the
26140 inferior. @value{GDBN} uses this for code disassembly and other
26141 internal interpretation purposes. This setting is only referred to
26142 when no executable has been associated with the debugging session or
26143 the executable does not provide information about the encoding it uses.
26144 Otherwise this setting is automatically updated from information
26145 provided by the executable.
26147 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
26148 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
26149 executables containing @acronym{MIPS16} code frequently are not
26150 identified as such.
26152 This setting is ``sticky''; that is, it retains its value across
26153 debugging sessions until reset either explicitly with this command or
26154 implicitly from an executable.
26156 The compiler and/or assembler typically add symbol table annotations to
26157 identify functions compiled for the @acronym{MIPS16} or
26158 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
26159 are present, @value{GDBN} uses them in preference to the global
26160 compressed @acronym{ISA} encoding setting.
26162 @item show mips compression
26163 @kindex show mips compression
26164 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
26165 @value{GDBN} to debug the inferior.
26168 @itemx show mipsfpu
26169 @xref{MIPS Embedded, set mipsfpu}.
26171 @item set mips mask-address @var{arg}
26172 @kindex set mips mask-address
26173 @cindex @acronym{MIPS} addresses, masking
26174 This command determines whether the most-significant 32 bits of 64-bit
26175 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
26176 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
26177 setting, which lets @value{GDBN} determine the correct value.
26179 @item show mips mask-address
26180 @kindex show mips mask-address
26181 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
26184 @item set remote-mips64-transfers-32bit-regs
26185 @kindex set remote-mips64-transfers-32bit-regs
26186 This command controls compatibility with 64-bit @acronym{MIPS} targets that
26187 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
26188 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
26189 and 64 bits for other registers, set this option to @samp{on}.
26191 @item show remote-mips64-transfers-32bit-regs
26192 @kindex show remote-mips64-transfers-32bit-regs
26193 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
26195 @item set debug mips
26196 @kindex set debug mips
26197 This command turns on and off debugging messages for the @acronym{MIPS}-specific
26198 target code in @value{GDBN}.
26200 @item show debug mips
26201 @kindex show debug mips
26202 Show the current setting of @acronym{MIPS} debugging messages.
26208 @cindex HPPA support
26210 When @value{GDBN} is debugging the HP PA architecture, it provides the
26211 following special commands:
26214 @item set debug hppa
26215 @kindex set debug hppa
26216 This command determines whether HPPA architecture-specific debugging
26217 messages are to be displayed.
26219 @item show debug hppa
26220 Show whether HPPA debugging messages are displayed.
26222 @item maint print unwind @var{address}
26223 @kindex maint print unwind@r{, HPPA}
26224 This command displays the contents of the unwind table entry at the
26225 given @var{address}.
26231 @subsection PowerPC
26232 @cindex PowerPC architecture
26234 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
26235 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
26236 numbers stored in the floating point registers. These values must be stored
26237 in two consecutive registers, always starting at an even register like
26238 @code{f0} or @code{f2}.
26240 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
26241 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
26242 @code{f2} and @code{f3} for @code{$dl1} and so on.
26244 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
26245 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
26248 @subsection Nios II
26249 @cindex Nios II architecture
26251 When @value{GDBN} is debugging the Nios II architecture,
26252 it provides the following special commands:
26256 @item set debug nios2
26257 @kindex set debug nios2
26258 This command turns on and off debugging messages for the Nios II
26259 target code in @value{GDBN}.
26261 @item show debug nios2
26262 @kindex show debug nios2
26263 Show the current setting of Nios II debugging messages.
26267 @subsection Sparc64
26268 @cindex Sparc64 support
26269 @cindex Application Data Integrity
26270 @subsubsection ADI Support
26272 The M7 processor supports an Application Data Integrity (ADI) feature that
26273 detects invalid data accesses. When software allocates memory and enables
26274 ADI on the allocated memory, it chooses a 4-bit version number, sets the
26275 version in the upper 4 bits of the 64-bit pointer to that data, and stores
26276 the 4-bit version in every cacheline of that data. Hardware saves the latter
26277 in spare bits in the cache and memory hierarchy. On each load and store,
26278 the processor compares the upper 4 VA (virtual address) bits to the
26279 cacheline's version. If there is a mismatch, the processor generates a
26280 version mismatch trap which can be either precise or disrupting. The trap
26281 is an error condition which the kernel delivers to the process as a SIGSEGV
26284 Note that only 64-bit applications can use ADI and need to be built with
26287 Values of the ADI version tags, which are in granularity of a
26288 cacheline (64 bytes), can be viewed or modified.
26292 @kindex adi examine
26293 @item adi (examine | x) [ / @var{n} ] @var{addr}
26295 The @code{adi examine} command displays the value of one ADI version tag per
26298 @var{n} is a decimal integer specifying the number in bytes; the default
26299 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
26300 block size, to display.
26302 @var{addr} is the address in user address space where you want @value{GDBN}
26303 to begin displaying the ADI version tags.
26305 Below is an example of displaying ADI versions of variable "shmaddr".
26308 (@value{GDBP}) adi x/100 shmaddr
26309 0xfff800010002c000: 0 0
26313 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
26315 The @code{adi assign} command is used to assign new ADI version tag
26318 @var{n} is a decimal integer specifying the number in bytes;
26319 the default is 1. It specifies how much ADI version information, at the
26320 ratio of 1:ADI block size, to modify.
26322 @var{addr} is the address in user address space where you want @value{GDBN}
26323 to begin modifying the ADI version tags.
26325 @var{tag} is the new ADI version tag.
26327 For example, do the following to modify then verify ADI versions of
26328 variable "shmaddr":
26331 (@value{GDBP}) adi a/100 shmaddr = 7
26332 (@value{GDBP}) adi x/100 shmaddr
26333 0xfff800010002c000: 7 7
26340 @cindex S12Z support
26342 When @value{GDBN} is debugging the S12Z architecture,
26343 it provides the following special command:
26346 @item maint info bdccsr
26347 @kindex maint info bdccsr@r{, S12Z}
26348 This command displays the current value of the microprocessor's
26353 @node Controlling GDB
26354 @chapter Controlling @value{GDBN}
26356 You can alter the way @value{GDBN} interacts with you by using the
26357 @code{set} command. For commands controlling how @value{GDBN} displays
26358 data, see @ref{Print Settings, ,Print Settings}. Other settings are
26363 * Editing:: Command editing
26364 * Command History:: Command history
26365 * Screen Size:: Screen size
26366 * Output Styling:: Output styling
26367 * Numbers:: Numbers
26368 * ABI:: Configuring the current ABI
26369 * Auto-loading:: Automatically loading associated files
26370 * Messages/Warnings:: Optional warnings and messages
26371 * Debugging Output:: Optional messages about internal happenings
26372 * Other Misc Settings:: Other Miscellaneous Settings
26380 @value{GDBN} indicates its readiness to read a command by printing a string
26381 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
26382 can change the prompt string with the @code{set prompt} command. For
26383 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
26384 the prompt in one of the @value{GDBN} sessions so that you can always tell
26385 which one you are talking to.
26387 @emph{Note:} @code{set prompt} does not add a space for you after the
26388 prompt you set. This allows you to set a prompt which ends in a space
26389 or a prompt that does not.
26393 @item set prompt @var{newprompt}
26394 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
26396 @kindex show prompt
26398 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
26401 Versions of @value{GDBN} that ship with Python scripting enabled have
26402 prompt extensions. The commands for interacting with these extensions
26406 @kindex set extended-prompt
26407 @item set extended-prompt @var{prompt}
26408 Set an extended prompt that allows for substitutions.
26409 @xref{gdb.prompt}, for a list of escape sequences that can be used for
26410 substitution. Any escape sequences specified as part of the prompt
26411 string are replaced with the corresponding strings each time the prompt
26417 set extended-prompt Current working directory: \w (@value{GDBP})
26420 Note that when an extended-prompt is set, it takes control of the
26421 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
26423 @kindex show extended-prompt
26424 @item show extended-prompt
26425 Prints the extended prompt. Any escape sequences specified as part of
26426 the prompt string with @code{set extended-prompt}, are replaced with the
26427 corresponding strings each time the prompt is displayed.
26431 @section Command Editing
26433 @cindex command line editing
26435 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
26436 @sc{gnu} library provides consistent behavior for programs which provide a
26437 command line interface to the user. Advantages are @sc{gnu} Emacs-style
26438 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
26439 substitution, and a storage and recall of command history across
26440 debugging sessions.
26442 You may control the behavior of command line editing in @value{GDBN} with the
26443 command @code{set}.
26446 @kindex set editing
26449 @itemx set editing on
26450 Enable command line editing (enabled by default).
26452 @item set editing off
26453 Disable command line editing.
26455 @kindex show editing
26457 Show whether command line editing is enabled.
26460 @ifset SYSTEM_READLINE
26461 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
26463 @ifclear SYSTEM_READLINE
26464 @xref{Command Line Editing},
26466 for more details about the Readline
26467 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
26468 encouraged to read that chapter.
26470 @cindex Readline application name
26471 @value{GDBN} sets the Readline application name to @samp{gdb}. This
26472 is useful for conditions in @file{.inputrc}.
26474 @cindex operate-and-get-next
26475 @value{GDBN} defines a bindable Readline command,
26476 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
26477 This command accepts the current line for execution and fetches the
26478 next line relative to the current line from the history for editing.
26479 Any argument is ignored.
26481 @node Command History
26482 @section Command History
26483 @cindex command history
26485 @value{GDBN} can keep track of the commands you type during your
26486 debugging sessions, so that you can be certain of precisely what
26487 happened. Use these commands to manage the @value{GDBN} command
26490 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
26491 package, to provide the history facility.
26492 @ifset SYSTEM_READLINE
26493 @xref{Using History Interactively, , , history, GNU History Library},
26495 @ifclear SYSTEM_READLINE
26496 @xref{Using History Interactively},
26498 for the detailed description of the History library.
26500 To issue a command to @value{GDBN} without affecting certain aspects of
26501 the state which is seen by users, prefix it with @samp{server }
26502 (@pxref{Server Prefix}). This
26503 means that this command will not affect the command history, nor will it
26504 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
26505 pressed on a line by itself.
26507 @cindex @code{server}, command prefix
26508 The server prefix does not affect the recording of values into the value
26509 history; to print a value without recording it into the value history,
26510 use the @code{output} command instead of the @code{print} command.
26512 Here is the description of @value{GDBN} commands related to command
26516 @cindex history substitution
26517 @cindex history file
26518 @kindex set history filename
26519 @cindex @env{GDBHISTFILE}, environment variable
26520 @item set history filename @r{[}@var{fname}@r{]}
26521 Set the name of the @value{GDBN} command history file to @var{fname}.
26522 This is the file where @value{GDBN} reads an initial command history
26523 list, and where it writes the command history from this session when it
26524 exits. You can access this list through history expansion or through
26525 the history command editing characters listed below. This file defaults
26526 to the value of the environment variable @env{GDBHISTFILE}, or to
26527 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
26530 The @env{GDBHISTFILE} environment variable is read after processing
26531 any @value{GDBN} initialization files (@pxref{Startup}) and after
26532 processing any commands passed using command line options (for
26533 example, @code{-ex}).
26535 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
26536 is the empty string then @value{GDBN} will neither try to load an
26537 existing history file, nor will it try to save the history on exit.
26539 @cindex save command history
26540 @kindex set history save
26541 @item set history save
26542 @itemx set history save on
26543 Record command history in a file, whose name may be specified with the
26544 @code{set history filename} command. By default, this option is
26545 disabled. The command history will be recorded when @value{GDBN}
26546 exits. If @code{set history filename} is set to the empty string then
26547 history saving is disabled, even when @code{set history save} is
26550 @item set history save off
26551 Don't record the command history into the file specified by @code{set
26552 history filename} when @value{GDBN} exits.
26554 @cindex history size
26555 @kindex set history size
26556 @cindex @env{GDBHISTSIZE}, environment variable
26557 @item set history size @var{size}
26558 @itemx set history size unlimited
26559 Set the number of commands which @value{GDBN} keeps in its history list.
26560 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
26561 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
26562 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
26563 either a negative number or the empty string, then the number of commands
26564 @value{GDBN} keeps in the history list is unlimited.
26566 The @env{GDBHISTSIZE} environment variable is read after processing
26567 any @value{GDBN} initialization files (@pxref{Startup}) and after
26568 processing any commands passed using command line options (for
26569 example, @code{-ex}).
26571 @cindex remove duplicate history
26572 @kindex set history remove-duplicates
26573 @item set history remove-duplicates @var{count}
26574 @itemx set history remove-duplicates unlimited
26575 Control the removal of duplicate history entries in the command history list.
26576 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
26577 history entries and remove the first entry that is a duplicate of the current
26578 entry being added to the command history list. If @var{count} is
26579 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
26580 removal of duplicate history entries is disabled.
26582 Only history entries added during the current session are considered for
26583 removal. This option is set to 0 by default.
26587 History expansion assigns special meaning to the character @kbd{!}.
26588 @ifset SYSTEM_READLINE
26589 @xref{Event Designators, , , history, GNU History Library},
26591 @ifclear SYSTEM_READLINE
26592 @xref{Event Designators},
26596 @cindex history expansion, turn on/off
26597 Since @kbd{!} is also the logical not operator in C, history expansion
26598 is off by default. If you decide to enable history expansion with the
26599 @code{set history expansion on} command, you may sometimes need to
26600 follow @kbd{!} (when it is used as logical not, in an expression) with
26601 a space or a tab to prevent it from being expanded. The readline
26602 history facilities do not attempt substitution on the strings
26603 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
26605 The commands to control history expansion are:
26608 @item set history expansion on
26609 @itemx set history expansion
26610 @kindex set history expansion
26611 Enable history expansion. History expansion is off by default.
26613 @item set history expansion off
26614 Disable history expansion.
26617 @kindex show history
26619 @itemx show history filename
26620 @itemx show history save
26621 @itemx show history size
26622 @itemx show history expansion
26623 These commands display the state of the @value{GDBN} history parameters.
26624 @code{show history} by itself displays all four states.
26629 @kindex show commands
26630 @cindex show last commands
26631 @cindex display command history
26632 @item show commands
26633 Display the last ten commands in the command history.
26635 @item show commands @var{n}
26636 Print ten commands centered on command number @var{n}.
26638 @item show commands +
26639 Print ten commands just after the commands last printed.
26643 @section Screen Size
26644 @cindex size of screen
26645 @cindex screen size
26648 @cindex pauses in output
26650 Certain commands to @value{GDBN} may produce large amounts of
26651 information output to the screen. To help you read all of it,
26652 @value{GDBN} pauses and asks you for input at the end of each page of
26653 output. Type @key{RET} when you want to see one more page of output,
26654 @kbd{q} to discard the remaining output, or @kbd{c} to continue
26655 without paging for the rest of the current command. Also, the screen
26656 width setting determines when to wrap lines of output. Depending on
26657 what is being printed, @value{GDBN} tries to break the line at a
26658 readable place, rather than simply letting it overflow onto the
26661 Normally @value{GDBN} knows the size of the screen from the terminal
26662 driver software. For example, on Unix @value{GDBN} uses the termcap data base
26663 together with the value of the @env{TERM} environment variable and the
26664 @code{stty rows} and @code{stty cols} settings. If this is not correct,
26665 you can override it with the @code{set height} and @code{set
26672 @kindex show height
26673 @item set height @var{lpp}
26674 @itemx set height unlimited
26676 @itemx set width @var{cpl}
26677 @itemx set width unlimited
26679 These @code{set} commands specify a screen height of @var{lpp} lines and
26680 a screen width of @var{cpl} characters. The associated @code{show}
26681 commands display the current settings.
26683 If you specify a height of either @code{unlimited} or zero lines,
26684 @value{GDBN} does not pause during output no matter how long the
26685 output is. This is useful if output is to a file or to an editor
26688 Likewise, you can specify @samp{set width unlimited} or @samp{set
26689 width 0} to prevent @value{GDBN} from wrapping its output.
26691 @item set pagination on
26692 @itemx set pagination off
26693 @kindex set pagination
26694 Turn the output pagination on or off; the default is on. Turning
26695 pagination off is the alternative to @code{set height unlimited}. Note that
26696 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
26697 Options, -batch}) also automatically disables pagination.
26699 @item show pagination
26700 @kindex show pagination
26701 Show the current pagination mode.
26704 @node Output Styling
26705 @section Output Styling
26711 @value{GDBN} can style its output on a capable terminal. This is
26712 enabled by default on most systems, but disabled by default when in
26713 batch mode (@pxref{Mode Options}). Various style settings are available;
26714 and styles can also be disabled entirely.
26717 @item set style enabled @samp{on|off}
26718 Enable or disable all styling. The default is host-dependent, with
26719 most hosts defaulting to @samp{on}.
26721 @item show style enabled
26722 Show the current state of styling.
26724 @item set style sources @samp{on|off}
26725 Enable or disable source code styling. This affects whether source
26726 code, such as the output of the @code{list} command, is styled. The
26727 default is @samp{on}. Note that source styling only works if styling
26728 in general is enabled, and if a source highlighting library is
26729 available to @value{GDBN}.
26731 There are two ways that highlighting can be done. First, if
26732 @value{GDBN} was linked with the GNU Source Highlight library, then it
26733 is used. Otherwise, if @value{GDBN} was configured with Python
26734 scripting support, and if the Python Pygments package is available,
26735 then it will be used.
26737 @item show style sources
26738 Show the current state of source code styling.
26740 @item set style tui-current-position @samp{on|off}
26741 Enable or disable styling of the source and assembly code highlighted
26742 by the TUI's current position indicator. The default is @samp{off}.
26743 @xref{TUI, ,@value{GDBN} Text User Interface}.
26745 @item show style tui-current-position
26746 Show whether the source and assembly code highlighted by the TUI's
26747 current position indicator is styled.
26749 @anchor{style_disassembler_enabled}
26750 @item set style disassembler enabled @samp{on|off}
26751 Enable or disable disassembler styling. This affects whether
26752 disassembler output, such as the output of the @code{disassemble}
26753 command, is styled. Disassembler styling only works if styling in
26754 general is enabled (with @code{set style enabled on}), and if a source
26755 highlighting library is available to @value{GDBN}.
26757 The two source highlighting libraries that @value{GDBN} could use to
26758 style disassembler output are; @value{GDBN}'s builtin disassembler, or
26759 the Python Pygments package.
26761 @value{GDBN}'s first choice will be to use the builtin disassembler
26762 for styling, this usually provides better results, being able to style
26763 different types of instruction operands differently. However, the
26764 builtin disassembler is not able to style all architectures.
26766 For architectures that the builtin disassembler is unable to style,
26767 @value{GDBN} will fall back to use the Python Pygments package where
26768 possible. In order to use the Python Pygments package, @value{GDBN}
26769 must be built with Python support, and the Pygments package must be
26772 If neither of these options are available then @value{GDBN} will
26773 produce unstyled disassembler output, even when this setting is
26776 To discover if the current architecture supports styling using the
26777 builtin disassembler library see @ref{maint_libopcodes_styling,,@kbd{maint
26778 show libopcodes-styling enabled}}.
26780 @item show style disassembler enabled
26781 Show the current state of disassembler styling.
26785 Subcommands of @code{set style} control specific forms of styling.
26786 These subcommands all follow the same pattern: each style-able object
26787 can be styled with a foreground color, a background color, and an
26790 For example, the style of file names can be controlled using the
26791 @code{set style filename} group of commands:
26794 @item set style filename background @var{color}
26795 Set the background to @var{color}. Valid colors are @samp{none}
26796 (meaning the terminal's default color), @samp{black}, @samp{red},
26797 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26800 @item set style filename foreground @var{color}
26801 Set the foreground to @var{color}. Valid colors are @samp{none}
26802 (meaning the terminal's default color), @samp{black}, @samp{red},
26803 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26806 @item set style filename intensity @var{value}
26807 Set the intensity to @var{value}. Valid intensities are @samp{normal}
26808 (the default), @samp{bold}, and @samp{dim}.
26811 The @code{show style} command and its subcommands are styling
26812 a style name in their output using its own style.
26813 So, use @command{show style} to see the complete list of styles,
26814 their characteristics and the visual aspect of each style.
26816 The style-able objects are:
26819 Control the styling of file names and URLs. By default, this style's
26820 foreground color is green.
26823 Control the styling of function names. These are managed with the
26824 @code{set style function} family of commands. By default, this
26825 style's foreground color is yellow.
26827 This style is also used for symbol names in styled disassembler output
26828 if @value{GDBN} is using its builtin disassembler library for styling
26829 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26833 Control the styling of variable names. These are managed with the
26834 @code{set style variable} family of commands. By default, this style's
26835 foreground color is cyan.
26838 Control the styling of addresses. These are managed with the
26839 @code{set style address} family of commands. By default, this style's
26840 foreground color is blue.
26842 This style is also used for addresses in styled disassembler output
26843 if @value{GDBN} is using its builtin disassembler library for styling
26844 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26848 Control the styling of @value{GDBN}'s version number text. By
26849 default, this style's foreground color is magenta and it has bold
26850 intensity. The version number is displayed in two places, the output
26851 of @command{show version}, and when @value{GDBN} starts up.
26853 In order to control how @value{GDBN} styles the version number at
26854 startup, add the @code{set style version} family of commands to the
26855 early initialization command file (@pxref{Initialization
26859 Control the styling of titles. These are managed with the
26860 @code{set style title} family of commands. By default, this style's
26861 intensity is bold. Commands are using the title style to improve
26862 the readability of large output. For example, the commands
26863 @command{apropos} and @command{help} are using the title style
26864 for the command names.
26867 Control the styling of highlightings. These are managed with the
26868 @code{set style highlight} family of commands. By default, this style's
26869 foreground color is red. Commands are using the highlight style to draw
26870 the user attention to some specific parts of their output. For example,
26871 the command @command{apropos -v REGEXP} uses the highlight style to
26872 mark the documentation parts matching @var{regexp}.
26875 Control the styling of data annotations added by @value{GDBN} to data
26876 it displays. By default, this style's intensity is dim. Metadata
26877 annotations include the @samp{repeats @var{n} times} annotation for
26878 suppressed display of repeated array elements (@pxref{Print Settings}),
26879 @samp{<unavailable>} and @w{@samp{<error @var{descr}>}} annotations
26880 for errors and @samp{<optimized-out>} annotations for optimized-out
26881 values in displaying stack frame information in backtraces
26882 (@pxref{Backtrace}), etc.
26885 Control the styling of the TUI border. Note that, unlike other
26886 styling options, only the color of the border can be controlled via
26887 @code{set style}. This was done for compatibility reasons, as TUI
26888 controls to set the border's intensity predated the addition of
26889 general styling to @value{GDBN}. @xref{TUI Configuration}.
26891 @item tui-active-border
26892 Control the styling of the active TUI border; that is, the TUI window
26893 that has the focus.
26895 @item disassembler comment
26896 Control the styling of comments in the disassembler output. These are
26897 managed with the @code{set style disassembler comment} family of
26898 commands. This style is only used when @value{GDBN} is styling using
26899 its builtin disassembler library
26900 (@pxref{style_disassembler_enabled,,@kbd{set style disassembler
26901 enabled}}). By default, this style's intensity is dim, and its
26902 foreground color is white.
26904 @item disassembler immediate
26905 Control the styling of numeric operands in the disassembler output.
26906 These are managed with the @code{set style disassembler immediate}
26907 family of commands. This style is not used for instruction operands
26908 that represent addresses, in that case the @samp{disassembler address}
26909 style is used. This style is only used when @value{GDBN} is styling
26910 using its builtin disassembler library. By default, this style's
26911 foreground color is blue.
26913 @item disassembler address
26914 Control the styling of address operands in the disassembler output.
26915 This is an alias for the @samp{address} style.
26917 @item disassembler symbol
26918 Control the styling of symbol names in the disassembler output. This
26919 is an alias for the @samp{function} style.
26921 @item disassembler mnemonic
26922 Control the styling of instruction mnemonics in the disassembler
26923 output. These are managed with the @code{set style disassembler
26924 mnemonic} family of commands. This style is also used for assembler
26925 directives, e.g.@: @code{.byte}, @code{.word}, etc. This style is
26926 only used when @value{GDBN} is styling using its builtin disassembler
26927 library. By default, this style's foreground color is green.
26929 @item disassembler register
26930 Control the styling of register operands in the disassembler output.
26931 These are managed with the @code{set style disassembler register}
26932 family of commands. This style is only used when @value{GDBN} is
26933 styling using its builtin disassembler library. By default, this style's
26934 foreground color is red.
26940 @cindex number representation
26941 @cindex entering numbers
26943 You can always enter numbers in octal, decimal, or hexadecimal in
26944 @value{GDBN} by the usual conventions: octal numbers begin with
26945 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
26946 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
26947 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
26948 10; likewise, the default display for numbers---when no particular
26949 format is specified---is base 10. You can change the default base for
26950 both input and output with the commands described below.
26953 @kindex set input-radix
26954 @item set input-radix @var{base}
26955 Set the default base for numeric input. Supported choices
26956 for @var{base} are decimal 8, 10, or 16. The base must itself be
26957 specified either unambiguously or using the current input radix; for
26961 set input-radix 012
26962 set input-radix 10.
26963 set input-radix 0xa
26967 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
26968 leaves the input radix unchanged, no matter what it was, since
26969 @samp{10}, being without any leading or trailing signs of its base, is
26970 interpreted in the current radix. Thus, if the current radix is 16,
26971 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
26974 @kindex set output-radix
26975 @item set output-radix @var{base}
26976 Set the default base for numeric display. Supported choices
26977 for @var{base} are decimal 8, 10, or 16. The base must itself be
26978 specified either unambiguously or using the current input radix.
26980 @kindex show input-radix
26981 @item show input-radix
26982 Display the current default base for numeric input.
26984 @kindex show output-radix
26985 @item show output-radix
26986 Display the current default base for numeric display.
26988 @item set radix @r{[}@var{base}@r{]}
26992 These commands set and show the default base for both input and output
26993 of numbers. @code{set radix} sets the radix of input and output to
26994 the same base; without an argument, it resets the radix back to its
26995 default value of 10.
27000 @section Configuring the Current ABI
27002 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
27003 application automatically. However, sometimes you need to override its
27004 conclusions. Use these commands to manage @value{GDBN}'s view of the
27010 @cindex Newlib OS ABI and its influence on the longjmp handling
27012 One @value{GDBN} configuration can debug binaries for multiple operating
27013 system targets, either via remote debugging or native emulation.
27014 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
27015 but you can override its conclusion using the @code{set osabi} command.
27016 One example where this is useful is in debugging of binaries which use
27017 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
27018 not have the same identifying marks that the standard C library for your
27021 When @value{GDBN} is debugging the AArch64 architecture, it provides a
27022 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
27023 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
27024 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
27028 Show the OS ABI currently in use.
27031 With no argument, show the list of registered available OS ABI's.
27033 @item set osabi @var{abi}
27034 Set the current OS ABI to @var{abi}.
27037 @cindex float promotion
27039 Generally, the way that an argument of type @code{float} is passed to a
27040 function depends on whether the function is prototyped. For a prototyped
27041 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
27042 according to the architecture's convention for @code{float}. For unprototyped
27043 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
27044 @code{double} and then passed.
27046 Unfortunately, some forms of debug information do not reliably indicate whether
27047 a function is prototyped. If @value{GDBN} calls a function that is not marked
27048 as prototyped, it consults @kbd{set coerce-float-to-double}.
27051 @kindex set coerce-float-to-double
27052 @item set coerce-float-to-double
27053 @itemx set coerce-float-to-double on
27054 Arguments of type @code{float} will be promoted to @code{double} when passed
27055 to an unprototyped function. This is the default setting.
27057 @item set coerce-float-to-double off
27058 Arguments of type @code{float} will be passed directly to unprototyped
27061 @kindex show coerce-float-to-double
27062 @item show coerce-float-to-double
27063 Show the current setting of promoting @code{float} to @code{double}.
27067 @kindex show cp-abi
27068 @value{GDBN} needs to know the ABI used for your program's C@t{++}
27069 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
27070 used to build your application. @value{GDBN} only fully supports
27071 programs with a single C@t{++} ABI; if your program contains code using
27072 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
27073 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
27074 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
27075 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
27076 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
27077 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
27082 Show the C@t{++} ABI currently in use.
27085 With no argument, show the list of supported C@t{++} ABI's.
27087 @item set cp-abi @var{abi}
27088 @itemx set cp-abi auto
27089 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
27093 @section Automatically loading associated files
27094 @cindex auto-loading
27096 @value{GDBN} sometimes reads files with commands and settings automatically,
27097 without being explicitly told so by the user. We call this feature
27098 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
27099 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
27100 results or introduce security risks (e.g., if the file comes from untrusted
27103 There are various kinds of files @value{GDBN} can automatically load.
27104 In addition to these files, @value{GDBN} supports auto-loading code written
27105 in various extension languages. @xref{Auto-loading extensions}.
27107 Note that loading of these associated files (including the local @file{.gdbinit}
27108 file) requires accordingly configured @code{auto-load safe-path}
27109 (@pxref{Auto-loading safe path}).
27111 For these reasons, @value{GDBN} includes commands and options to let you
27112 control when to auto-load files and which files should be auto-loaded.
27115 @anchor{set auto-load off}
27116 @kindex set auto-load off
27117 @item set auto-load off
27118 Globally disable loading of all auto-loaded files.
27119 You may want to use this command with the @samp{-iex} option
27120 (@pxref{Option -init-eval-command}) such as:
27122 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
27125 Be aware that system init file (@pxref{System-wide configuration})
27126 and init files from your home directory (@pxref{Home Directory Init File})
27127 still get read (as they come from generally trusted directories).
27128 To prevent @value{GDBN} from auto-loading even those init files, use the
27129 @option{-nx} option (@pxref{Mode Options}), in addition to
27130 @code{set auto-load no}.
27132 @anchor{show auto-load}
27133 @kindex show auto-load
27134 @item show auto-load
27135 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
27139 (@value{GDBP}) show auto-load
27140 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
27141 libthread-db: Auto-loading of inferior specific libthread_db is on.
27142 local-gdbinit: Auto-loading of .gdbinit script from current directory
27144 python-scripts: Auto-loading of Python scripts is on.
27145 safe-path: List of directories from which it is safe to auto-load files
27146 is $debugdir:$datadir/auto-load.
27147 scripts-directory: List of directories from which to load auto-loaded scripts
27148 is $debugdir:$datadir/auto-load.
27151 @anchor{info auto-load}
27152 @kindex info auto-load
27153 @item info auto-load
27154 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
27158 (@value{GDBP}) info auto-load
27161 Yes /home/user/gdb/gdb-gdb.gdb
27162 libthread-db: No auto-loaded libthread-db.
27163 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
27167 Yes /home/user/gdb/gdb-gdb.py
27171 These are @value{GDBN} control commands for the auto-loading:
27173 @multitable @columnfractions .5 .5
27174 @item @xref{set auto-load off}.
27175 @tab Disable auto-loading globally.
27176 @item @xref{show auto-load}.
27177 @tab Show setting of all kinds of files.
27178 @item @xref{info auto-load}.
27179 @tab Show state of all kinds of files.
27180 @item @xref{set auto-load gdb-scripts}.
27181 @tab Control for @value{GDBN} command scripts.
27182 @item @xref{show auto-load gdb-scripts}.
27183 @tab Show setting of @value{GDBN} command scripts.
27184 @item @xref{info auto-load gdb-scripts}.
27185 @tab Show state of @value{GDBN} command scripts.
27186 @item @xref{set auto-load python-scripts}.
27187 @tab Control for @value{GDBN} Python scripts.
27188 @item @xref{show auto-load python-scripts}.
27189 @tab Show setting of @value{GDBN} Python scripts.
27190 @item @xref{info auto-load python-scripts}.
27191 @tab Show state of @value{GDBN} Python scripts.
27192 @item @xref{set auto-load guile-scripts}.
27193 @tab Control for @value{GDBN} Guile scripts.
27194 @item @xref{show auto-load guile-scripts}.
27195 @tab Show setting of @value{GDBN} Guile scripts.
27196 @item @xref{info auto-load guile-scripts}.
27197 @tab Show state of @value{GDBN} Guile scripts.
27198 @item @xref{set auto-load scripts-directory}.
27199 @tab Control for @value{GDBN} auto-loaded scripts location.
27200 @item @xref{show auto-load scripts-directory}.
27201 @tab Show @value{GDBN} auto-loaded scripts location.
27202 @item @xref{add-auto-load-scripts-directory}.
27203 @tab Add directory for auto-loaded scripts location list.
27204 @item @xref{set auto-load local-gdbinit}.
27205 @tab Control for init file in the current directory.
27206 @item @xref{show auto-load local-gdbinit}.
27207 @tab Show setting of init file in the current directory.
27208 @item @xref{info auto-load local-gdbinit}.
27209 @tab Show state of init file in the current directory.
27210 @item @xref{set auto-load libthread-db}.
27211 @tab Control for thread debugging library.
27212 @item @xref{show auto-load libthread-db}.
27213 @tab Show setting of thread debugging library.
27214 @item @xref{info auto-load libthread-db}.
27215 @tab Show state of thread debugging library.
27216 @item @xref{set auto-load safe-path}.
27217 @tab Control directories trusted for automatic loading.
27218 @item @xref{show auto-load safe-path}.
27219 @tab Show directories trusted for automatic loading.
27220 @item @xref{add-auto-load-safe-path}.
27221 @tab Add directory trusted for automatic loading.
27225 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
27226 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
27228 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
27229 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
27232 @node Init File in the Current Directory
27233 @subsection Automatically loading init file in the current directory
27234 @cindex auto-loading init file in the current directory
27236 By default, @value{GDBN} reads and executes the canned sequences of commands
27237 from init file (if any) in the current working directory,
27238 see @ref{Init File in the Current Directory during Startup}.
27240 Note that loading of this local @file{.gdbinit} file also requires accordingly
27241 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27244 @anchor{set auto-load local-gdbinit}
27245 @kindex set auto-load local-gdbinit
27246 @item set auto-load local-gdbinit [on|off]
27247 Enable or disable the auto-loading of canned sequences of commands
27248 (@pxref{Sequences}) found in init file in the current directory.
27250 @anchor{show auto-load local-gdbinit}
27251 @kindex show auto-load local-gdbinit
27252 @item show auto-load local-gdbinit
27253 Show whether auto-loading of canned sequences of commands from init file in the
27254 current directory is enabled or disabled.
27256 @anchor{info auto-load local-gdbinit}
27257 @kindex info auto-load local-gdbinit
27258 @item info auto-load local-gdbinit
27259 Print whether canned sequences of commands from init file in the
27260 current directory have been auto-loaded.
27263 @node libthread_db.so.1 file
27264 @subsection Automatically loading thread debugging library
27265 @cindex auto-loading libthread_db.so.1
27267 This feature is currently present only on @sc{gnu}/Linux native hosts.
27269 @value{GDBN} reads in some cases thread debugging library from places specific
27270 to the inferior (@pxref{set libthread-db-search-path}).
27272 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
27273 without checking this @samp{set auto-load libthread-db} switch as system
27274 libraries have to be trusted in general. In all other cases of
27275 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
27276 auto-load libthread-db} is enabled before trying to open such thread debugging
27279 Note that loading of this debugging library also requires accordingly configured
27280 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27283 @anchor{set auto-load libthread-db}
27284 @kindex set auto-load libthread-db
27285 @item set auto-load libthread-db [on|off]
27286 Enable or disable the auto-loading of inferior specific thread debugging library.
27288 @anchor{show auto-load libthread-db}
27289 @kindex show auto-load libthread-db
27290 @item show auto-load libthread-db
27291 Show whether auto-loading of inferior specific thread debugging library is
27292 enabled or disabled.
27294 @anchor{info auto-load libthread-db}
27295 @kindex info auto-load libthread-db
27296 @item info auto-load libthread-db
27297 Print the list of all loaded inferior specific thread debugging libraries and
27298 for each such library print list of inferior @var{pid}s using it.
27301 @node Auto-loading safe path
27302 @subsection Security restriction for auto-loading
27303 @cindex auto-loading safe-path
27305 As the files of inferior can come from untrusted source (such as submitted by
27306 an application user) @value{GDBN} does not always load any files automatically.
27307 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
27308 directories trusted for loading files not explicitly requested by user.
27309 Each directory can also be a shell wildcard pattern.
27311 If the path is not set properly you will see a warning and the file will not
27316 Reading symbols from /home/user/gdb/gdb...
27317 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
27318 declined by your `auto-load safe-path' set
27319 to "$debugdir:$datadir/auto-load".
27320 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
27321 declined by your `auto-load safe-path' set
27322 to "$debugdir:$datadir/auto-load".
27326 To instruct @value{GDBN} to go ahead and use the init files anyway,
27327 invoke @value{GDBN} like this:
27330 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
27333 The list of trusted directories is controlled by the following commands:
27336 @anchor{set auto-load safe-path}
27337 @kindex set auto-load safe-path
27338 @item set auto-load safe-path @r{[}@var{directories}@r{]}
27339 Set the list of directories (and their subdirectories) trusted for automatic
27340 loading and execution of scripts. You can also enter a specific trusted file.
27341 Each directory can also be a shell wildcard pattern; wildcards do not match
27342 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
27343 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
27344 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
27345 its default value as specified during @value{GDBN} compilation.
27347 The list of directories uses path separator (@samp{:} on GNU and Unix
27348 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27349 to the @env{PATH} environment variable.
27351 @anchor{show auto-load safe-path}
27352 @kindex show auto-load safe-path
27353 @item show auto-load safe-path
27354 Show the list of directories trusted for automatic loading and execution of
27357 @anchor{add-auto-load-safe-path}
27358 @kindex add-auto-load-safe-path
27359 @item add-auto-load-safe-path
27360 Add an entry (or list of entries) to the list of directories trusted for
27361 automatic loading and execution of scripts. Multiple entries may be delimited
27362 by the host platform path separator in use.
27365 This variable defaults to what @code{--with-auto-load-dir} has been configured
27366 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
27367 substitution applies the same as for @ref{set auto-load scripts-directory}.
27368 The default @code{set auto-load safe-path} value can be also overriden by
27369 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
27371 Setting this variable to @file{/} disables this security protection,
27372 corresponding @value{GDBN} configuration option is
27373 @option{--without-auto-load-safe-path}.
27374 This variable is supposed to be set to the system directories writable by the
27375 system superuser only. Users can add their source directories in init files in
27376 their home directories (@pxref{Home Directory Init File}). See also deprecated
27377 init file in the current directory
27378 (@pxref{Init File in the Current Directory during Startup}).
27380 To force @value{GDBN} to load the files it declined to load in the previous
27381 example, you could use one of the following ways:
27384 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
27385 Specify this trusted directory (or a file) as additional component of the list.
27386 You have to specify also any existing directories displayed by
27387 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
27389 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
27390 Specify this directory as in the previous case but just for a single
27391 @value{GDBN} session.
27393 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
27394 Disable auto-loading safety for a single @value{GDBN} session.
27395 This assumes all the files you debug during this @value{GDBN} session will come
27396 from trusted sources.
27398 @item @kbd{./configure --without-auto-load-safe-path}
27399 During compilation of @value{GDBN} you may disable any auto-loading safety.
27400 This assumes all the files you will ever debug with this @value{GDBN} come from
27404 On the other hand you can also explicitly forbid automatic files loading which
27405 also suppresses any such warning messages:
27408 @item @kbd{gdb -iex "set auto-load no" @dots{}}
27409 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
27411 @item @file{~/.gdbinit}: @samp{set auto-load no}
27412 Disable auto-loading globally for the user
27413 (@pxref{Home Directory Init File}). While it is improbable, you could also
27414 use system init file instead (@pxref{System-wide configuration}).
27417 This setting applies to the file names as entered by user. If no entry matches
27418 @value{GDBN} tries as a last resort to also resolve all the file names into
27419 their canonical form (typically resolving symbolic links) and compare the
27420 entries again. @value{GDBN} already canonicalizes most of the filenames on its
27421 own before starting the comparison so a canonical form of directories is
27422 recommended to be entered.
27424 @node Auto-loading verbose mode
27425 @subsection Displaying files tried for auto-load
27426 @cindex auto-loading verbose mode
27428 For better visibility of all the file locations where you can place scripts to
27429 be auto-loaded with inferior --- or to protect yourself against accidental
27430 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
27431 all the files attempted to be loaded. Both existing and non-existing files may
27434 For example the list of directories from which it is safe to auto-load files
27435 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
27436 may not be too obvious while setting it up.
27439 (@value{GDBP}) set debug auto-load on
27440 (@value{GDBP}) file ~/src/t/true
27441 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
27442 for objfile "/tmp/true".
27443 auto-load: Updating directories of "/usr:/opt".
27444 auto-load: Using directory "/usr".
27445 auto-load: Using directory "/opt".
27446 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
27447 by your `auto-load safe-path' set to "/usr:/opt".
27451 @anchor{set debug auto-load}
27452 @kindex set debug auto-load
27453 @item set debug auto-load [on|off]
27454 Set whether to print the filenames attempted to be auto-loaded.
27456 @anchor{show debug auto-load}
27457 @kindex show debug auto-load
27458 @item show debug auto-load
27459 Show whether printing of the filenames attempted to be auto-loaded is turned
27463 @node Messages/Warnings
27464 @section Optional Warnings and Messages
27466 @cindex verbose operation
27467 @cindex optional warnings
27468 By default, @value{GDBN} is silent about its inner workings. If you are
27469 running on a slow machine, you may want to use the @code{set verbose}
27470 command. This makes @value{GDBN} tell you when it does a lengthy
27471 internal operation, so you will not think it has crashed.
27473 Currently, the messages controlled by @code{set verbose} are those
27474 which announce that the symbol table for a source file is being read;
27475 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
27478 @kindex set verbose
27479 @item set verbose on
27480 Enables @value{GDBN} output of certain informational messages.
27482 @item set verbose off
27483 Disables @value{GDBN} output of certain informational messages.
27485 @kindex show verbose
27487 Displays whether @code{set verbose} is on or off.
27490 By default, if @value{GDBN} encounters bugs in the symbol table of an
27491 object file, it is silent; but if you are debugging a compiler, you may
27492 find this information useful (@pxref{Symbol Errors, ,Errors Reading
27497 @kindex set complaints
27498 @item set complaints @var{limit}
27499 Permits @value{GDBN} to output @var{limit} complaints about each type of
27500 unusual symbols before becoming silent about the problem. Set
27501 @var{limit} to zero to suppress all complaints; set it to a large number
27502 to prevent complaints from being suppressed.
27504 @kindex show complaints
27505 @item show complaints
27506 Displays how many symbol complaints @value{GDBN} is permitted to produce.
27510 @anchor{confirmation requests}
27511 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
27512 lot of stupid questions to confirm certain commands. For example, if
27513 you try to run a program which is already running:
27517 The program being debugged has been started already.
27518 Start it from the beginning? (y or n)
27521 If you are willing to unflinchingly face the consequences of your own
27522 commands, you can disable this ``feature'':
27526 @kindex set confirm
27528 @cindex confirmation
27529 @cindex stupid questions
27530 @item set confirm off
27531 Disables confirmation requests. Note that running @value{GDBN} with
27532 the @option{--batch} option (@pxref{Mode Options, -batch}) also
27533 automatically disables confirmation requests.
27535 @item set confirm on
27536 Enables confirmation requests (the default).
27538 @kindex show confirm
27540 Displays state of confirmation requests.
27544 @cindex command tracing
27545 If you need to debug user-defined commands or sourced files you may find it
27546 useful to enable @dfn{command tracing}. In this mode each command will be
27547 printed as it is executed, prefixed with one or more @samp{+} symbols, the
27548 quantity denoting the call depth of each command.
27551 @kindex set trace-commands
27552 @cindex command scripts, debugging
27553 @item set trace-commands on
27554 Enable command tracing.
27555 @item set trace-commands off
27556 Disable command tracing.
27557 @item show trace-commands
27558 Display the current state of command tracing.
27561 @node Debugging Output
27562 @section Optional Messages about Internal Happenings
27563 @cindex optional debugging messages
27565 @value{GDBN} has commands that enable optional debugging messages from
27566 various @value{GDBN} subsystems; normally these commands are of
27567 interest to @value{GDBN} maintainers, or when reporting a bug. This
27568 section documents those commands.
27571 @kindex set exec-done-display
27572 @item set exec-done-display
27573 Turns on or off the notification of asynchronous commands'
27574 completion. When on, @value{GDBN} will print a message when an
27575 asynchronous command finishes its execution. The default is off.
27576 @kindex show exec-done-display
27577 @item show exec-done-display
27578 Displays the current setting of asynchronous command completion
27582 @cindex ARM AArch64
27583 @item set debug aarch64
27584 Turns on or off display of debugging messages related to ARM AArch64.
27585 The default is off.
27587 @item show debug aarch64
27588 Displays the current state of displaying debugging messages related to
27591 @cindex gdbarch debugging info
27592 @cindex architecture debugging info
27593 @item set debug arch
27594 Turns on or off display of gdbarch debugging info. The default is off
27595 @item show debug arch
27596 Displays the current state of displaying gdbarch debugging info.
27598 @item set debug aix-thread
27599 @cindex AIX threads
27600 Display debugging messages about inner workings of the AIX thread
27602 @item show debug aix-thread
27603 Show the current state of AIX thread debugging info display.
27605 @item set debug check-physname
27607 Check the results of the ``physname'' computation. When reading DWARF
27608 debugging information for C@t{++}, @value{GDBN} attempts to compute
27609 each entity's name. @value{GDBN} can do this computation in two
27610 different ways, depending on exactly what information is present.
27611 When enabled, this setting causes @value{GDBN} to compute the names
27612 both ways and display any discrepancies.
27613 @item show debug check-physname
27614 Show the current state of ``physname'' checking.
27616 @item set debug coff-pe-read
27617 @cindex COFF/PE exported symbols
27618 Control display of debugging messages related to reading of COFF/PE
27619 exported symbols. The default is off.
27620 @item show debug coff-pe-read
27621 Displays the current state of displaying debugging messages related to
27622 reading of COFF/PE exported symbols.
27624 @item set debug dwarf-die
27626 Dump DWARF DIEs after they are read in.
27627 The value is the number of nesting levels to print.
27628 A value of zero turns off the display.
27629 @item show debug dwarf-die
27630 Show the current state of DWARF DIE debugging.
27632 @item set debug dwarf-line
27633 @cindex DWARF Line Tables
27634 Turns on or off display of debugging messages related to reading
27635 DWARF line tables. The default is 0 (off).
27636 A value of 1 provides basic information.
27637 A value greater than 1 provides more verbose information.
27638 @item show debug dwarf-line
27639 Show the current state of DWARF line table debugging.
27641 @item set debug dwarf-read
27642 @cindex DWARF Reading
27643 Turns on or off display of debugging messages related to reading
27644 DWARF debug info. The default is 0 (off).
27645 A value of 1 provides basic information.
27646 A value greater than 1 provides more verbose information.
27647 @item show debug dwarf-read
27648 Show the current state of DWARF reader debugging.
27650 @item set debug displaced
27651 @cindex displaced stepping debugging info
27652 Turns on or off display of @value{GDBN} debugging info for the
27653 displaced stepping support. The default is off.
27654 @item show debug displaced
27655 Displays the current state of displaying @value{GDBN} debugging info
27656 related to displaced stepping.
27658 @item set debug event
27659 @cindex event debugging info
27660 Turns on or off display of @value{GDBN} event debugging info. The
27662 @item show debug event
27663 Displays the current state of displaying @value{GDBN} event debugging
27666 @item set debug event-loop
27667 @cindex event-loop debugging
27668 Controls output of debugging info about the event loop. The possible
27669 values are @samp{off}, @samp{all} (shows all debugging info) and
27670 @samp{all-except-ui} (shows all debugging info except those about
27671 UI-related events).
27672 @item show debug event-loop
27673 Shows the current state of displaying debugging info about the event
27676 @item set debug expression
27677 @cindex expression debugging info
27678 Turns on or off display of debugging info about @value{GDBN}
27679 expression parsing. The default is off.
27680 @item show debug expression
27681 Displays the current state of displaying debugging info about
27682 @value{GDBN} expression parsing.
27684 @item set debug fbsd-lwp
27685 @cindex FreeBSD LWP debug messages
27686 Turns on or off debugging messages from the FreeBSD LWP debug support.
27687 @item show debug fbsd-lwp
27688 Show the current state of FreeBSD LWP debugging messages.
27690 @item set debug fbsd-nat
27691 @cindex FreeBSD native target debug messages
27692 Turns on or off debugging messages from the FreeBSD native target.
27693 @item show debug fbsd-nat
27694 Show the current state of FreeBSD native target debugging messages.
27696 @item set debug fortran-array-slicing
27697 @cindex fortran array slicing debugging info
27698 Turns on or off display of @value{GDBN} Fortran array slicing
27699 debugging info. The default is off.
27701 @item show debug fortran-array-slicing
27702 Displays the current state of displaying @value{GDBN} Fortran array
27703 slicing debugging info.
27705 @item set debug frame
27706 @cindex frame debugging info
27707 Turns on or off display of @value{GDBN} frame debugging info. The
27709 @item show debug frame
27710 Displays the current state of displaying @value{GDBN} frame debugging
27713 @item set debug gnu-nat
27714 @cindex @sc{gnu}/Hurd debug messages
27715 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
27716 @item show debug gnu-nat
27717 Show the current state of @sc{gnu}/Hurd debugging messages.
27719 @item set debug infrun
27720 @cindex inferior debugging info
27721 Turns on or off display of @value{GDBN} debugging info for running the inferior.
27722 The default is off. @file{infrun.c} contains GDB's runtime state machine used
27723 for implementing operations such as single-stepping the inferior.
27724 @item show debug infrun
27725 Displays the current state of @value{GDBN} inferior debugging.
27727 @item set debug infcall
27728 @cindex inferior function call debugging info
27729 Turns on or off display of debugging info related to inferior function
27730 calls made by @value{GDBN}.
27731 @item show debug infcall
27732 Displays the current state of @value{GDBN} inferior function call debugging.
27734 @item set debug jit
27735 @cindex just-in-time compilation, debugging messages
27736 Turn on or off debugging messages from JIT debug support.
27737 @item show debug jit
27738 Displays the current state of @value{GDBN} JIT debugging.
27740 @item set debug linux-nat @r{[}on@r{|}off@r{]}
27741 @cindex @sc{gnu}/Linux native target debug messages
27742 @cindex Linux native targets
27743 Turn on or off debugging messages from the Linux native target debug support.
27744 @item show debug linux-nat
27745 Show the current state of Linux native target debugging messages.
27747 @item set debug linux-namespaces
27748 @cindex @sc{gnu}/Linux namespaces debug messages
27749 Turn on or off debugging messages from the Linux namespaces debug support.
27750 @item show debug linux-namespaces
27751 Show the current state of Linux namespaces debugging messages.
27753 @item set debug mach-o
27754 @cindex Mach-O symbols processing
27755 Control display of debugging messages related to Mach-O symbols
27756 processing. The default is off.
27757 @item show debug mach-o
27758 Displays the current state of displaying debugging messages related to
27759 reading of COFF/PE exported symbols.
27761 @item set debug notification
27762 @cindex remote async notification debugging info
27763 Turn on or off debugging messages about remote async notification.
27764 The default is off.
27765 @item show debug notification
27766 Displays the current state of remote async notification debugging messages.
27768 @item set debug observer
27769 @cindex observer debugging info
27770 Turns on or off display of @value{GDBN} observer debugging. This
27771 includes info such as the notification of observable events.
27772 @item show debug observer
27773 Displays the current state of observer debugging.
27775 @item set debug overload
27776 @cindex C@t{++} overload debugging info
27777 Turns on or off display of @value{GDBN} C@t{++} overload debugging
27778 info. This includes info such as ranking of functions, etc. The default
27780 @item show debug overload
27781 Displays the current state of displaying @value{GDBN} C@t{++} overload
27784 @cindex expression parser, debugging info
27785 @cindex debug expression parser
27786 @item set debug parser
27787 Turns on or off the display of expression parser debugging output.
27788 Internally, this sets the @code{yydebug} variable in the expression
27789 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
27790 details. The default is off.
27791 @item show debug parser
27792 Show the current state of expression parser debugging.
27794 @cindex packets, reporting on stdout
27795 @cindex serial connections, debugging
27796 @cindex debug remote protocol
27797 @cindex remote protocol debugging
27798 @cindex display remote packets
27799 @item set debug remote
27800 Turns on or off display of reports on all packets sent back and forth across
27801 the serial line to the remote machine. The info is printed on the
27802 @value{GDBN} standard output stream. The default is off.
27803 @item show debug remote
27804 Displays the state of display of remote packets.
27806 @item set debug remote-packet-max-chars
27807 Sets the maximum number of characters to display for each remote packet when
27808 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
27809 displaying lengthy remote packets and polluting the console.
27811 The default value is @code{512}, which means @value{GDBN} will truncate each
27812 remote packet after 512 bytes.
27814 Setting this option to @code{unlimited} will disable truncation and will output
27815 the full length of the remote packets.
27816 @item show debug remote-packet-max-chars
27817 Displays the number of bytes to output for remote packet debugging.
27819 @item set debug separate-debug-file
27820 Turns on or off display of debug output about separate debug file search.
27821 @item show debug separate-debug-file
27822 Displays the state of separate debug file search debug output.
27824 @item set debug serial
27825 Turns on or off display of @value{GDBN} serial debugging info. The
27827 @item show debug serial
27828 Displays the current state of displaying @value{GDBN} serial debugging
27831 @item set debug solib
27832 Turns on or off display of debugging messages related to shared libraries.
27833 The default is off.
27834 @item show debug solib
27835 Show the current state of solib debugging messages.
27837 @item set debug symbol-lookup
27838 @cindex symbol lookup
27839 Turns on or off display of debugging messages related to symbol lookup.
27840 The default is 0 (off).
27841 A value of 1 provides basic information.
27842 A value greater than 1 provides more verbose information.
27843 @item show debug symbol-lookup
27844 Show the current state of symbol lookup debugging messages.
27846 @item set debug symfile
27847 @cindex symbol file functions
27848 Turns on or off display of debugging messages related to symbol file functions.
27849 The default is off. @xref{Files}.
27850 @item show debug symfile
27851 Show the current state of symbol file debugging messages.
27853 @item set debug symtab-create
27854 @cindex symbol table creation
27855 Turns on or off display of debugging messages related to symbol table creation.
27856 The default is 0 (off).
27857 A value of 1 provides basic information.
27858 A value greater than 1 provides more verbose information.
27859 @item show debug symtab-create
27860 Show the current state of symbol table creation debugging.
27862 @item set debug target
27863 @cindex target debugging info
27864 Turns on or off display of @value{GDBN} target debugging info. This info
27865 includes what is going on at the target level of GDB, as it happens. The
27866 default is 0. Set it to 1 to track events, and to 2 to also track the
27867 value of large memory transfers.
27868 @item show debug target
27869 Displays the current state of displaying @value{GDBN} target debugging
27872 @item set debug timestamp
27873 @cindex timestamping debugging info
27874 Turns on or off display of timestamps with @value{GDBN} debugging info.
27875 When enabled, seconds and microseconds are displayed before each debugging
27877 @item show debug timestamp
27878 Displays the current state of displaying timestamps with @value{GDBN}
27881 @item set debug varobj
27882 @cindex variable object debugging info
27883 Turns on or off display of @value{GDBN} variable object debugging
27884 info. The default is off.
27885 @item show debug varobj
27886 Displays the current state of displaying @value{GDBN} variable object
27889 @item set debug xml
27890 @cindex XML parser debugging
27891 Turn on or off debugging messages for built-in XML parsers.
27892 @item show debug xml
27893 Displays the current state of XML debugging messages.
27896 @node Other Misc Settings
27897 @section Other Miscellaneous Settings
27898 @cindex miscellaneous settings
27901 @kindex set interactive-mode
27902 @item set interactive-mode
27903 If @code{on}, forces @value{GDBN} to assume that GDB was started
27904 in a terminal. In practice, this means that @value{GDBN} should wait
27905 for the user to answer queries generated by commands entered at
27906 the command prompt. If @code{off}, forces @value{GDBN} to operate
27907 in the opposite mode, and it uses the default answers to all queries.
27908 If @code{auto} (the default), @value{GDBN} tries to determine whether
27909 its standard input is a terminal, and works in interactive-mode if it
27910 is, non-interactively otherwise.
27912 In the vast majority of cases, the debugger should be able to guess
27913 correctly which mode should be used. But this setting can be useful
27914 in certain specific cases, such as running a MinGW @value{GDBN}
27915 inside a cygwin window.
27917 @kindex show interactive-mode
27918 @item show interactive-mode
27919 Displays whether the debugger is operating in interactive mode or not.
27923 @kindex set suppress-cli-notifications
27924 @item set suppress-cli-notifications
27925 If @code{on}, command-line-interface (CLI) notifications that are
27926 printed by @value{GDBN} are suppressed. If @code{off}, the
27927 notifications are printed as usual. The default value is @code{off}.
27928 CLI notifications occur when you change the selected context or when
27929 the program being debugged stops, as detailed below.
27932 @item User-selected context changes:
27933 When you change the selected context (i.e.@: the current inferior,
27934 thread and/or the frame), @value{GDBN} prints information about the
27935 new context. For example, the default behavior is below:
27939 [Switching to inferior 1 [process 634] (/tmp/test)]
27940 [Switching to thread 1 (process 634)]
27941 #0 main () at test.c:3
27946 When the notifications are suppressed, the new context is not printed:
27949 (gdb) set suppress-cli-notifications on
27954 @item The program being debugged stops:
27955 When the program you are debugging stops (e.g.@: because of hitting a
27956 breakpoint, completing source-stepping, an interrupt, etc.),
27957 @value{GDBN} prints information about the stop event. For example,
27958 below is a breakpoint hit:
27961 (gdb) break test.c:3
27962 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27966 Breakpoint 2, main () at test.c:3
27971 When the notifications are suppressed, the output becomes:
27974 (gdb) break test.c:3
27975 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27976 (gdb) set suppress-cli-notifications on
27982 Suppressing CLI notifications may be useful in scripts to obtain a
27983 reduced output from a list of commands.
27986 @kindex show suppress-cli-notifications
27987 @item show suppress-cli-notifications
27988 Displays whether printing CLI notifications is suppressed or not.
27991 @node Extending GDB
27992 @chapter Extending @value{GDBN}
27993 @cindex extending GDB
27995 @value{GDBN} provides several mechanisms for extension.
27996 @value{GDBN} also provides the ability to automatically load
27997 extensions when it reads a file for debugging. This allows the
27998 user to automatically customize @value{GDBN} for the program
28001 To facilitate the use of extension languages, @value{GDBN} is capable
28002 of evaluating the contents of a file. When doing so, @value{GDBN}
28003 can recognize which extension language is being used by looking at
28004 the filename extension. Files with an unrecognized filename extension
28005 are always treated as a @value{GDBN} Command Files.
28006 @xref{Command Files,, Command files}.
28008 You can control how @value{GDBN} evaluates these files with the following
28012 @kindex set script-extension
28013 @kindex show script-extension
28014 @item set script-extension off
28015 All scripts are always evaluated as @value{GDBN} Command Files.
28017 @item set script-extension soft
28018 The debugger determines the scripting language based on filename
28019 extension. If this scripting language is supported, @value{GDBN}
28020 evaluates the script using that language. Otherwise, it evaluates
28021 the file as a @value{GDBN} Command File.
28023 @item set script-extension strict
28024 The debugger determines the scripting language based on filename
28025 extension, and evaluates the script using that language. If the
28026 language is not supported, then the evaluation fails.
28028 @item show script-extension
28029 Display the current value of the @code{script-extension} option.
28033 @ifset SYSTEM_GDBINIT_DIR
28034 This setting is not used for files in the system-wide gdbinit directory.
28035 Files in that directory must have an extension matching their language,
28036 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
28037 commands. @xref{Startup}.
28041 * Sequences:: Canned Sequences of @value{GDBN} Commands
28042 * Aliases:: Command Aliases
28043 * Python:: Extending @value{GDBN} using Python
28044 * Guile:: Extending @value{GDBN} using Guile
28045 * Auto-loading extensions:: Automatically loading extensions
28046 * Multiple Extension Languages:: Working with multiple extension languages
28050 @section Canned Sequences of Commands
28052 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
28053 Command Lists}), @value{GDBN} provides two ways to store sequences of
28054 commands for execution as a unit: user-defined commands and command
28058 * Define:: How to define your own commands
28059 * Hooks:: Hooks for user-defined commands
28060 * Command Files:: How to write scripts of commands to be stored in a file
28061 * Output:: Commands for controlled output
28062 * Auto-loading sequences:: Controlling auto-loaded command files
28066 @subsection User-defined Commands
28068 @cindex user-defined command
28069 @cindex arguments, to user-defined commands
28070 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
28071 which you assign a new name as a command. This is done with the
28072 @code{define} command. User commands may accept an unlimited number of arguments
28073 separated by whitespace. Arguments are accessed within the user command
28074 via @code{$arg0@dots{}$argN}. A trivial example:
28078 print $arg0 + $arg1 + $arg2
28083 To execute the command use:
28090 This defines the command @code{adder}, which prints the sum of
28091 its three arguments. Note the arguments are text substitutions, so they may
28092 reference variables, use complex expressions, or even perform inferior
28095 @cindex argument count in user-defined commands
28096 @cindex how many arguments (user-defined commands)
28097 In addition, @code{$argc} may be used to find out how many arguments have
28103 print $arg0 + $arg1
28106 print $arg0 + $arg1 + $arg2
28111 Combining with the @code{eval} command (@pxref{eval}) makes it easier
28112 to process a variable number of arguments:
28119 eval "set $sum = $sum + $arg%d", $i
28129 @item define @var{commandname}
28130 Define a command named @var{commandname}. If there is already a command
28131 by that name, you are asked to confirm that you want to redefine it.
28132 The argument @var{commandname} may be a bare command name consisting of letters,
28133 numbers, dashes, dots, and underscores. It may also start with any
28134 predefined or user-defined prefix command.
28135 For example, @samp{define target my-target} creates
28136 a user-defined @samp{target my-target} command.
28138 The definition of the command is made up of other @value{GDBN} command lines,
28139 which are given following the @code{define} command. The end of these
28140 commands is marked by a line containing @code{end}.
28143 @kindex end@r{ (user-defined commands)}
28144 @item document @var{commandname}
28145 Document the user-defined command @var{commandname}, so that it can be
28146 accessed by @code{help}. The command @var{commandname} must already be
28147 defined. This command reads lines of documentation just as @code{define}
28148 reads the lines of the command definition, ending with @code{end}.
28149 After the @code{document} command is finished, @code{help} on command
28150 @var{commandname} displays the documentation you have written.
28152 You may use the @code{document} command again to change the
28153 documentation of a command. Redefining the command with @code{define}
28154 does not change the documentation.
28156 It is also possible to document user-defined aliases. The alias documentation
28157 will then be used by the @code{help} and @code{apropos} commands
28158 instead of the documentation of the aliased command.
28159 Documenting a user-defined alias is particularly useful when defining
28160 an alias as a set of nested @code{with} commands
28161 (@pxref{Command aliases default args}).
28163 @kindex define-prefix
28164 @item define-prefix @var{commandname}
28165 Define or mark the command @var{commandname} as a user-defined prefix
28166 command. Once marked, @var{commandname} can be used as prefix command
28167 by the @code{define} command.
28168 Note that @code{define-prefix} can be used with a not yet defined
28169 @var{commandname}. In such a case, @var{commandname} is defined as
28170 an empty user-defined command.
28171 In case you redefine a command that was marked as a user-defined
28172 prefix command, the subcommands of the redefined command are kept
28173 (and @value{GDBN} indicates so to the user).
28177 (@value{GDBP}) define-prefix abc
28178 (@value{GDBP}) define-prefix abc def
28179 (@value{GDBP}) define abc def
28180 Type commands for definition of "abc def".
28181 End with a line saying just "end".
28182 >echo command initial def\n
28184 (@value{GDBP}) define abc def ghi
28185 Type commands for definition of "abc def ghi".
28186 End with a line saying just "end".
28187 >echo command ghi\n
28189 (@value{GDBP}) define abc def
28190 Keeping subcommands of prefix command "def".
28191 Redefine command "def"? (y or n) y
28192 Type commands for definition of "abc def".
28193 End with a line saying just "end".
28194 >echo command def\n
28196 (@value{GDBP}) abc def ghi
28198 (@value{GDBP}) abc def
28203 @kindex dont-repeat
28204 @cindex don't repeat command
28206 Used inside a user-defined command, this tells @value{GDBN} that this
28207 command should not be repeated when the user hits @key{RET}
28208 (@pxref{Command Syntax, repeat last command}).
28210 @kindex help user-defined
28211 @item help user-defined
28212 List all user-defined commands and all python commands defined in class
28213 COMMAND_USER. The first line of the documentation or docstring is
28218 @itemx show user @var{commandname}
28219 Display the @value{GDBN} commands used to define @var{commandname} (but
28220 not its documentation). If no @var{commandname} is given, display the
28221 definitions for all user-defined commands.
28222 This does not work for user-defined python commands.
28224 @cindex infinite recursion in user-defined commands
28225 @kindex show max-user-call-depth
28226 @kindex set max-user-call-depth
28227 @item show max-user-call-depth
28228 @itemx set max-user-call-depth
28229 The value of @code{max-user-call-depth} controls how many recursion
28230 levels are allowed in user-defined commands before @value{GDBN} suspects an
28231 infinite recursion and aborts the command.
28232 This does not apply to user-defined python commands.
28235 In addition to the above commands, user-defined commands frequently
28236 use control flow commands, described in @ref{Command Files}.
28238 When user-defined commands are executed, the
28239 commands of the definition are not printed. An error in any command
28240 stops execution of the user-defined command.
28242 If used interactively, commands that would ask for confirmation proceed
28243 without asking when used inside a user-defined command. Many @value{GDBN}
28244 commands that normally print messages to say what they are doing omit the
28245 messages when used in a user-defined command.
28248 @subsection User-defined Command Hooks
28249 @cindex command hooks
28250 @cindex hooks, for commands
28251 @cindex hooks, pre-command
28254 You may define @dfn{hooks}, which are a special kind of user-defined
28255 command. Whenever you run the command @samp{foo}, if the user-defined
28256 command @samp{hook-foo} exists, it is executed (with no arguments)
28257 before that command.
28259 @cindex hooks, post-command
28261 A hook may also be defined which is run after the command you executed.
28262 Whenever you run the command @samp{foo}, if the user-defined command
28263 @samp{hookpost-foo} exists, it is executed (with no arguments) after
28264 that command. Post-execution hooks may exist simultaneously with
28265 pre-execution hooks, for the same command.
28267 It is valid for a hook to call the command which it hooks. If this
28268 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
28270 @c It would be nice if hookpost could be passed a parameter indicating
28271 @c if the command it hooks executed properly or not. FIXME!
28273 @kindex stop@r{, a pseudo-command}
28274 In addition, a pseudo-command, @samp{stop} exists. Defining
28275 (@samp{hook-stop}) makes the associated commands execute every time
28276 execution stops in your program: before breakpoint commands are run,
28277 displays are printed, or the stack frame is printed.
28279 For example, to ignore @code{SIGALRM} signals while
28280 single-stepping, but treat them normally during normal execution,
28285 handle SIGALRM nopass
28289 handle SIGALRM pass
28292 define hook-continue
28293 handle SIGALRM pass
28297 As a further example, to hook at the beginning and end of the @code{echo}
28298 command, and to add extra text to the beginning and end of the message,
28306 define hookpost-echo
28310 (@value{GDBP}) echo Hello World
28311 <<<---Hello World--->>>
28316 You can define a hook for any single-word command in @value{GDBN}, but
28317 not for command aliases; you should define a hook for the basic command
28318 name, e.g.@: @code{backtrace} rather than @code{bt}.
28319 @c FIXME! So how does Joe User discover whether a command is an alias
28321 You can hook a multi-word command by adding @code{hook-} or
28322 @code{hookpost-} to the last word of the command, e.g.@:
28323 @samp{define target hook-remote} to add a hook to @samp{target remote}.
28325 If an error occurs during the execution of your hook, execution of
28326 @value{GDBN} commands stops and @value{GDBN} issues a prompt
28327 (before the command that you actually typed had a chance to run).
28329 If you try to define a hook which does not match any known command, you
28330 get a warning from the @code{define} command.
28332 @node Command Files
28333 @subsection Command Files
28335 @cindex command files
28336 @cindex scripting commands
28337 A command file for @value{GDBN} is a text file made of lines that are
28338 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
28339 also be included. An empty line in a command file does nothing; it
28340 does not mean to repeat the last command, as it would from the
28343 You can request the execution of a command file with the @code{source}
28344 command. Note that the @code{source} command is also used to evaluate
28345 scripts that are not Command Files. The exact behavior can be configured
28346 using the @code{script-extension} setting.
28347 @xref{Extending GDB,, Extending GDB}.
28351 @cindex execute commands from a file
28352 @item source [-s] [-v] @var{filename}
28353 Execute the command file @var{filename}.
28356 The lines in a command file are generally executed sequentially,
28357 unless the order of execution is changed by one of the
28358 @emph{flow-control commands} described below. The commands are not
28359 printed as they are executed. An error in any command terminates
28360 execution of the command file and control is returned to the console.
28362 @value{GDBN} first searches for @var{filename} in the current directory.
28363 If the file is not found there, and @var{filename} does not specify a
28364 directory, then @value{GDBN} also looks for the file on the source search path
28365 (specified with the @samp{directory} command);
28366 except that @file{$cdir} is not searched because the compilation directory
28367 is not relevant to scripts.
28369 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
28370 on the search path even if @var{filename} specifies a directory.
28371 The search is done by appending @var{filename} to each element of the
28372 search path. So, for example, if @var{filename} is @file{mylib/myscript}
28373 and the search path contains @file{/home/user} then @value{GDBN} will
28374 look for the script @file{/home/user/mylib/myscript}.
28375 The search is also done if @var{filename} is an absolute path.
28376 For example, if @var{filename} is @file{/tmp/myscript} and
28377 the search path contains @file{/home/user} then @value{GDBN} will
28378 look for the script @file{/home/user/tmp/myscript}.
28379 For DOS-like systems, if @var{filename} contains a drive specification,
28380 it is stripped before concatenation. For example, if @var{filename} is
28381 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
28382 will look for the script @file{c:/tmp/myscript}.
28384 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
28385 each command as it is executed. The option must be given before
28386 @var{filename}, and is interpreted as part of the filename anywhere else.
28388 Commands that would ask for confirmation if used interactively proceed
28389 without asking when used in a command file. Many @value{GDBN} commands that
28390 normally print messages to say what they are doing omit the messages
28391 when called from command files.
28393 @value{GDBN} also accepts command input from standard input. In this
28394 mode, normal output goes to standard output and error output goes to
28395 standard error. Errors in a command file supplied on standard input do
28396 not terminate execution of the command file---execution continues with
28400 gdb < cmds > log 2>&1
28403 (The syntax above will vary depending on the shell used.) This example
28404 will execute commands from the file @file{cmds}. All output and errors
28405 would be directed to @file{log}.
28407 Since commands stored on command files tend to be more general than
28408 commands typed interactively, they frequently need to deal with
28409 complicated situations, such as different or unexpected values of
28410 variables and symbols, changes in how the program being debugged is
28411 built, etc. @value{GDBN} provides a set of flow-control commands to
28412 deal with these complexities. Using these commands, you can write
28413 complex scripts that loop over data structures, execute commands
28414 conditionally, etc.
28421 This command allows to include in your script conditionally executed
28422 commands. The @code{if} command takes a single argument, which is an
28423 expression to evaluate. It is followed by a series of commands that
28424 are executed only if the expression is true (its value is nonzero).
28425 There can then optionally be an @code{else} line, followed by a series
28426 of commands that are only executed if the expression was false. The
28427 end of the list is marked by a line containing @code{end}.
28431 This command allows to write loops. Its syntax is similar to
28432 @code{if}: the command takes a single argument, which is an expression
28433 to evaluate, and must be followed by the commands to execute, one per
28434 line, terminated by an @code{end}. These commands are called the
28435 @dfn{body} of the loop. The commands in the body of @code{while} are
28436 executed repeatedly as long as the expression evaluates to true.
28440 This command exits the @code{while} loop in whose body it is included.
28441 Execution of the script continues after that @code{while}s @code{end}
28444 @kindex loop_continue
28445 @item loop_continue
28446 This command skips the execution of the rest of the body of commands
28447 in the @code{while} loop in whose body it is included. Execution
28448 branches to the beginning of the @code{while} loop, where it evaluates
28449 the controlling expression.
28451 @kindex end@r{ (if/else/while commands)}
28453 Terminate the block of commands that are the body of @code{if},
28454 @code{else}, or @code{while} flow-control commands.
28459 @subsection Commands for Controlled Output
28461 During the execution of a command file or a user-defined command, normal
28462 @value{GDBN} output is suppressed; the only output that appears is what is
28463 explicitly printed by the commands in the definition. This section
28464 describes three commands useful for generating exactly the output you
28469 @item echo @var{text}
28470 @c I do not consider backslash-space a standard C escape sequence
28471 @c because it is not in ANSI.
28472 Print @var{text}. Nonprinting characters can be included in
28473 @var{text} using C escape sequences, such as @samp{\n} to print a
28474 newline. @strong{No newline is printed unless you specify one.}
28475 In addition to the standard C escape sequences, a backslash followed
28476 by a space stands for a space. This is useful for displaying a
28477 string with spaces at the beginning or the end, since leading and
28478 trailing spaces are otherwise trimmed from all arguments.
28479 To print @samp{@w{ }and foo =@w{ }}, use the command
28480 @samp{echo \@w{ }and foo = \@w{ }}.
28482 A backslash at the end of @var{text} can be used, as in C, to continue
28483 the command onto subsequent lines. For example,
28486 echo This is some text\n\
28487 which is continued\n\
28488 onto several lines.\n
28491 produces the same output as
28494 echo This is some text\n
28495 echo which is continued\n
28496 echo onto several lines.\n
28500 @item output @var{expression}
28501 Print the value of @var{expression} and nothing but that value: no
28502 newlines, no @samp{$@var{nn} = }. The value is not entered in the
28503 value history either. @xref{Expressions, ,Expressions}, for more information
28506 @item output/@var{fmt} @var{expression}
28507 Print the value of @var{expression} in format @var{fmt}. You can use
28508 the same formats as for @code{print}. @xref{Output Formats,,Output
28509 Formats}, for more information.
28512 @item printf @var{template}, @var{expressions}@dots{}
28513 Print the values of one or more @var{expressions} under the control of
28514 the string @var{template}. To print several values, make
28515 @var{expressions} be a comma-separated list of individual expressions,
28516 which may be either numbers or pointers. Their values are printed as
28517 specified by @var{template}, exactly as a C program would do by
28518 executing the code below:
28521 printf (@var{template}, @var{expressions}@dots{});
28524 As in @code{C} @code{printf}, ordinary characters in @var{template}
28525 are printed verbatim, while @dfn{conversion specification} introduced
28526 by the @samp{%} character cause subsequent @var{expressions} to be
28527 evaluated, their values converted and formatted according to type and
28528 style information encoded in the conversion specifications, and then
28531 For example, you can print two values in hex like this:
28534 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
28537 @code{printf} supports all the standard @code{C} conversion
28538 specifications, including the flags and modifiers between the @samp{%}
28539 character and the conversion letter, with the following exceptions:
28543 The argument-ordering modifiers, such as @samp{2$}, are not supported.
28546 The modifier @samp{*} is not supported for specifying precision or
28550 The @samp{'} flag (for separation of digits into groups according to
28551 @code{LC_NUMERIC'}) is not supported.
28554 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
28558 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
28561 The conversion letters @samp{a} and @samp{A} are not supported.
28565 Note that the @samp{ll} type modifier is supported only if the
28566 underlying @code{C} implementation used to build @value{GDBN} supports
28567 the @code{long long int} type, and the @samp{L} type modifier is
28568 supported only if @code{long double} type is available.
28570 As in @code{C}, @code{printf} supports simple backslash-escape
28571 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
28572 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
28573 single character. Octal and hexadecimal escape sequences are not
28576 Additionally, @code{printf} supports conversion specifications for DFP
28577 (@dfn{Decimal Floating Point}) types using the following length modifiers
28578 together with a floating point specifier.
28583 @samp{H} for printing @code{Decimal32} types.
28586 @samp{D} for printing @code{Decimal64} types.
28589 @samp{DD} for printing @code{Decimal128} types.
28592 If the underlying @code{C} implementation used to build @value{GDBN} has
28593 support for the three length modifiers for DFP types, other modifiers
28594 such as width and precision will also be available for @value{GDBN} to use.
28596 In case there is no such @code{C} support, no additional modifiers will be
28597 available and the value will be printed in the standard way.
28599 Here's an example of printing DFP types using the above conversion letters:
28601 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
28606 @item eval @var{template}, @var{expressions}@dots{}
28607 Convert the values of one or more @var{expressions} under the control of
28608 the string @var{template} to a command line, and call it.
28612 @node Auto-loading sequences
28613 @subsection Controlling auto-loading native @value{GDBN} scripts
28614 @cindex native script auto-loading
28616 When a new object file is read (for example, due to the @code{file}
28617 command, or because the inferior has loaded a shared library),
28618 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
28619 @xref{Auto-loading extensions}.
28621 Auto-loading can be enabled or disabled,
28622 and the list of auto-loaded scripts can be printed.
28625 @anchor{set auto-load gdb-scripts}
28626 @kindex set auto-load gdb-scripts
28627 @item set auto-load gdb-scripts [on|off]
28628 Enable or disable the auto-loading of canned sequences of commands scripts.
28630 @anchor{show auto-load gdb-scripts}
28631 @kindex show auto-load gdb-scripts
28632 @item show auto-load gdb-scripts
28633 Show whether auto-loading of canned sequences of commands scripts is enabled or
28636 @anchor{info auto-load gdb-scripts}
28637 @kindex info auto-load gdb-scripts
28638 @cindex print list of auto-loaded canned sequences of commands scripts
28639 @item info auto-load gdb-scripts [@var{regexp}]
28640 Print the list of all canned sequences of commands scripts that @value{GDBN}
28644 If @var{regexp} is supplied only canned sequences of commands scripts with
28645 matching names are printed.
28648 @section Command Aliases
28649 @cindex aliases for commands
28651 Aliases allow you to define alternate spellings for existing commands.
28652 For example, if a new @value{GDBN} command defined in Python
28653 (@pxref{Python}) has a long name, it is handy to have an abbreviated
28654 version of it that involves less typing.
28656 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28657 of the @samp{step} command even though it is otherwise an ambiguous
28658 abbreviation of other commands like @samp{set} and @samp{show}.
28660 Aliases are also used to provide shortened or more common versions
28661 of multi-word commands. For example, @value{GDBN} provides the
28662 @samp{tty} alias of the @samp{set inferior-tty} command.
28664 You can define a new alias with the @samp{alias} command.
28669 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
28673 @var{alias} specifies the name of the new alias. Each word of
28674 @var{alias} must consist of letters, numbers, dashes and underscores.
28676 @var{command} specifies the name of an existing command
28677 that is being aliased.
28679 @var{command} can also be the name of an existing alias. In this
28680 case, @var{command} cannot be an alias that has default arguments.
28682 The @samp{-a} option specifies that the new alias is an abbreviation
28683 of the command. Abbreviations are not used in command completion.
28685 The @samp{--} option specifies the end of options,
28686 and is useful when @var{alias} begins with a dash.
28688 You can specify @var{default-args} for your alias. These
28689 @var{default-args} will be automatically added before the alias
28690 arguments typed explicitly on the command line.
28692 For example, the below defines an alias @code{btfullall} that shows all local
28693 variables and all frame arguments:
28695 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
28698 For more information about @var{default-args}, see @ref{Command
28699 aliases default args, ,Default Arguments}.
28701 Here is a simple example showing how to make an abbreviation of a
28702 command so that there is less to type. Suppose you were tired of
28703 typing @samp{disas}, the current shortest unambiguous abbreviation of
28704 the @samp{disassemble} command and you wanted an even shorter version
28705 named @samp{di}. The following will accomplish this.
28708 (@value{GDBP}) alias -a di = disas
28711 Note that aliases are different from user-defined commands. With a
28712 user-defined command, you also need to write documentation for it with
28713 the @samp{document} command. An alias automatically picks up the
28714 documentation of the existing command.
28716 Here is an example where we make @samp{elms} an abbreviation of
28717 @samp{elements} in the @samp{set print elements} command.
28718 This is to show that you can make an abbreviation of any part
28722 (@value{GDBP}) alias -a set print elms = set print elements
28723 (@value{GDBP}) alias -a show print elms = show print elements
28724 (@value{GDBP}) set p elms 200
28725 (@value{GDBP}) show p elms
28726 Limit on string chars or array elements to print is 200.
28729 Note that if you are defining an alias of a @samp{set} command,
28730 and you want to have an alias for the corresponding @samp{show}
28731 command, then you need to define the latter separately.
28733 Unambiguously abbreviated commands are allowed in @var{command} and
28734 @var{alias}, just as they are normally.
28737 (@value{GDBP}) alias -a set pr elms = set p ele
28740 Finally, here is an example showing the creation of a one word
28741 alias for a more complex command.
28742 This creates alias @samp{spe} of the command @samp{set print elements}.
28745 (@value{GDBP}) alias spe = set print elements
28746 (@value{GDBP}) spe 20
28750 * Command aliases default args:: Default arguments for aliases
28753 @node Command aliases default args
28754 @subsection Default Arguments
28755 @cindex aliases for commands, default arguments
28757 You can tell @value{GDBN} to always prepend some default arguments to
28758 the list of arguments provided explicitly by the user when using a
28759 user-defined alias.
28761 If you repeatedly use the same arguments or options for a command, you
28762 can define an alias for this command and tell @value{GDBN} to
28763 automatically prepend these arguments or options to the list of
28764 arguments you type explicitly when using the alias@footnote{@value{GDBN}
28765 could easily accept default arguments for pre-defined commands and aliases,
28766 but it was deemed this would be confusing, and so is not allowed.}.
28768 For example, if you often use the command @code{thread apply all}
28769 specifying to work on the threads in ascending order and to continue in case it
28770 encounters an error, you can tell @value{GDBN} to automatically preprend
28771 the @code{-ascending} and @code{-c} options by using:
28774 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
28777 Once you have defined this alias with its default args, any time you type
28778 the @code{thread apply asc-all} followed by @code{some arguments},
28779 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
28781 To have even less to type, you can also define a one word alias:
28783 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
28786 As usual, unambiguous abbreviations can be used for @var{alias}
28787 and @var{default-args}.
28789 The different aliases of a command do not share their default args.
28790 For example, you define a new alias @code{bt_ALL} showing all possible
28791 information and another alias @code{bt_SMALL} showing very limited information
28794 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
28795 -past-main -past-entry -full
28796 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
28797 -past-main off -past-entry off
28800 (For more on using the @code{alias} command, see @ref{Aliases}.)
28802 Default args are not limited to the arguments and options of @var{command},
28803 but can specify nested commands if @var{command} accepts such a nested command
28805 For example, the below defines @code{faalocalsoftype} that lists the
28806 frames having locals of a certain type, together with the matching
28809 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
28810 (@value{GDBP}) faalocalsoftype int
28811 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
28816 This is also very useful to define an alias for a set of nested @code{with}
28817 commands to have a particular combination of temporary settings. For example,
28818 the below defines the alias @code{pp10} that pretty prints an expression
28819 argument, with a maximum of 10 elements if the expression is a string or
28822 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
28824 This defines the alias @code{pp10} as being a sequence of 3 commands.
28825 The first part @code{with print pretty --} temporarily activates the setting
28826 @code{set print pretty}, then launches the command that follows the separator
28828 The command following the first part is also a @code{with} command that
28829 temporarily changes the setting @code{set print elements} to 10, then
28830 launches the command that follows the second separator @code{--}.
28831 The third part @code{print} is the command the @code{pp10} alias will launch,
28832 using the temporary values of the settings and the arguments explicitly given
28834 For more information about the @code{with} command usage,
28835 see @ref{Command Settings}.
28837 By default, asking the help for an alias shows the documentation of
28838 the aliased command. When the alias is a set of nested commands, @code{help}
28839 of an alias shows the documentation of the first command. This help
28840 is not particularly useful for an alias such as @code{pp10}.
28841 For such an alias, it is useful to give a specific documentation
28842 using the @code{document} command (@pxref{Define, document}).
28845 @c Python docs live in a separate file.
28846 @include python.texi
28848 @c Guile docs live in a separate file.
28849 @include guile.texi
28851 @node Auto-loading extensions
28852 @section Auto-loading extensions
28853 @cindex auto-loading extensions
28855 @value{GDBN} provides two mechanisms for automatically loading
28856 extensions when a new object file is read (for example, due to the
28857 @code{file} command, or because the inferior has loaded a shared
28858 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
28859 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
28860 @code{.debug_gdb_scripts} section of modern file formats like ELF
28861 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
28862 section}). For a discussion of the differences between these two
28863 approaches see @ref{Which flavor to choose?}.
28865 The auto-loading feature is useful for supplying application-specific
28866 debugging commands and features.
28868 Auto-loading can be enabled or disabled,
28869 and the list of auto-loaded scripts can be printed.
28870 See the @samp{auto-loading} section of each extension language
28871 for more information.
28872 For @value{GDBN} command files see @ref{Auto-loading sequences}.
28873 For Python files see @ref{Python Auto-loading}.
28875 Note that loading of this script file also requires accordingly configured
28876 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28879 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
28880 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
28881 * Which flavor to choose?:: Choosing between these approaches
28884 @node objfile-gdbdotext file
28885 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
28886 @cindex @file{@var{objfile}-gdb.gdb}
28887 @cindex @file{@var{objfile}-gdb.py}
28888 @cindex @file{@var{objfile}-gdb.scm}
28890 When a new object file is read, @value{GDBN} looks for a file named
28891 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
28892 where @var{objfile} is the object file's name and
28893 where @var{ext} is the file extension for the extension language:
28896 @item @file{@var{objfile}-gdb.gdb}
28897 GDB's own command language
28898 @item @file{@var{objfile}-gdb.py}
28900 @item @file{@var{objfile}-gdb.scm}
28904 @var{script-name} is formed by ensuring that the file name of @var{objfile}
28905 is absolute, following all symlinks, and resolving @code{.} and @code{..}
28906 components, and appending the @file{-gdb.@var{ext}} suffix.
28907 If this file exists and is readable, @value{GDBN} will evaluate it as a
28908 script in the specified extension language.
28910 If this file does not exist, then @value{GDBN} will look for
28911 @var{script-name} file in all of the directories as specified below.
28912 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
28913 directories is converted to a one-letter subdirectory, i.e.@:
28914 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
28915 filesystems disallow colons in file names.)
28917 Note that loading of these files requires an accordingly configured
28918 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28920 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
28921 scripts normally according to its @file{.exe} filename. But if no scripts are
28922 found @value{GDBN} also tries script filenames matching the object file without
28923 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
28924 is attempted on any platform. This makes the script filenames compatible
28925 between Unix and MS-Windows hosts.
28928 @anchor{set auto-load scripts-directory}
28929 @kindex set auto-load scripts-directory
28930 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
28931 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
28932 may be delimited by the host platform path separator in use
28933 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
28935 Each entry here needs to be covered also by the security setting
28936 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
28938 @anchor{with-auto-load-dir}
28939 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
28940 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
28941 configuration option @option{--with-auto-load-dir}.
28943 Any reference to @file{$debugdir} will get replaced by
28944 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
28945 reference to @file{$datadir} will get replaced by @var{data-directory} which is
28946 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
28947 @file{$datadir} must be placed as a directory component --- either alone or
28948 delimited by @file{/} or @file{\} directory separators, depending on the host
28951 The list of directories uses path separator (@samp{:} on GNU and Unix
28952 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28953 to the @env{PATH} environment variable.
28955 @anchor{show auto-load scripts-directory}
28956 @kindex show auto-load scripts-directory
28957 @item show auto-load scripts-directory
28958 Show @value{GDBN} auto-loaded scripts location.
28960 @anchor{add-auto-load-scripts-directory}
28961 @kindex add-auto-load-scripts-directory
28962 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
28963 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
28964 Multiple entries may be delimited by the host platform path separator in use.
28967 @value{GDBN} does not track which files it has already auto-loaded this way.
28968 @value{GDBN} will load the associated script every time the corresponding
28969 @var{objfile} is opened.
28970 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
28971 is evaluated more than once.
28973 @node dotdebug_gdb_scripts section
28974 @subsection The @code{.debug_gdb_scripts} section
28975 @cindex @code{.debug_gdb_scripts} section
28977 For systems using file formats like ELF and COFF,
28978 when @value{GDBN} loads a new object file
28979 it will look for a special section named @code{.debug_gdb_scripts}.
28980 If this section exists, its contents is a list of null-terminated entries
28981 specifying scripts to load. Each entry begins with a non-null prefix byte that
28982 specifies the kind of entry, typically the extension language and whether the
28983 script is in a file or inlined in @code{.debug_gdb_scripts}.
28985 The following entries are supported:
28988 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
28989 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
28990 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
28991 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
28994 @subsubsection Script File Entries
28996 If the entry specifies a file, @value{GDBN} will look for the file first
28997 in the current directory and then along the source search path
28998 (@pxref{Source Path, ,Specifying Source Directories}),
28999 except that @file{$cdir} is not searched, since the compilation
29000 directory is not relevant to scripts.
29002 File entries can be placed in section @code{.debug_gdb_scripts} with,
29003 for example, this GCC macro for Python scripts.
29006 /* Note: The "MS" section flags are to remove duplicates. */
29007 #define DEFINE_GDB_PY_SCRIPT(script_name) \
29009 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
29010 .byte 1 /* Python */\n\
29011 .asciz \"" script_name "\"\n\
29017 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
29018 Then one can reference the macro in a header or source file like this:
29021 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
29024 The script name may include directories if desired.
29026 Note that loading of this script file also requires accordingly configured
29027 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
29029 If the macro invocation is put in a header, any application or library
29030 using this header will get a reference to the specified script,
29031 and with the use of @code{"MS"} attributes on the section, the linker
29032 will remove duplicates.
29034 @subsubsection Script Text Entries
29036 Script text entries allow to put the executable script in the entry
29037 itself instead of loading it from a file.
29038 The first line of the entry, everything after the prefix byte and up to
29039 the first newline (@code{0xa}) character, is the script name, and must not
29040 contain any kind of space character, e.g., spaces or tabs.
29041 The rest of the entry, up to the trailing null byte, is the script to
29042 execute in the specified language. The name needs to be unique among
29043 all script names, as @value{GDBN} executes each script only once based
29046 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
29050 #include "symcat.h"
29051 #include "gdb/section-scripts.h"
29053 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
29054 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
29055 ".ascii \"gdb.inlined-script\\n\"\n"
29056 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
29057 ".ascii \" def __init__ (self):\\n\"\n"
29058 ".ascii \" super (test_cmd, self).__init__ ("
29059 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
29060 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
29061 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
29062 ".ascii \"test_cmd ()\\n\"\n"
29068 Loading of inlined scripts requires a properly configured
29069 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
29070 The path to specify in @code{auto-load safe-path} is the path of the file
29071 containing the @code{.debug_gdb_scripts} section.
29073 @node Which flavor to choose?
29074 @subsection Which flavor to choose?
29076 Given the multiple ways of auto-loading extensions, it might not always
29077 be clear which one to choose. This section provides some guidance.
29080 Benefits of the @file{-gdb.@var{ext}} way:
29084 Can be used with file formats that don't support multiple sections.
29087 Ease of finding scripts for public libraries.
29089 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
29090 in the source search path.
29091 For publicly installed libraries, e.g., @file{libstdc++}, there typically
29092 isn't a source directory in which to find the script.
29095 Doesn't require source code additions.
29099 Benefits of the @code{.debug_gdb_scripts} way:
29103 Works with static linking.
29105 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
29106 trigger their loading. When an application is statically linked the only
29107 objfile available is the executable, and it is cumbersome to attach all the
29108 scripts from all the input libraries to the executable's
29109 @file{-gdb.@var{ext}} script.
29112 Works with classes that are entirely inlined.
29114 Some classes can be entirely inlined, and thus there may not be an associated
29115 shared library to attach a @file{-gdb.@var{ext}} script to.
29118 Scripts needn't be copied out of the source tree.
29120 In some circumstances, apps can be built out of large collections of internal
29121 libraries, and the build infrastructure necessary to install the
29122 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
29123 cumbersome. It may be easier to specify the scripts in the
29124 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
29125 top of the source tree to the source search path.
29128 @node Multiple Extension Languages
29129 @section Multiple Extension Languages
29131 The Guile and Python extension languages do not share any state,
29132 and generally do not interfere with each other.
29133 There are some things to be aware of, however.
29135 @subsection Python comes first
29137 Python was @value{GDBN}'s first extension language, and to avoid breaking
29138 existing behaviour Python comes first. This is generally solved by the
29139 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
29140 extension languages, and when it makes a call to an extension language,
29141 (say to pretty-print a value), it tries each in turn until an extension
29142 language indicates it has performed the request (e.g., has returned the
29143 pretty-printed form of a value).
29144 This extends to errors while performing such requests: If an error happens
29145 while, for example, trying to pretty-print an object then the error is
29146 reported and any following extension languages are not tried.
29149 @chapter Command Interpreters
29150 @cindex command interpreters
29152 @value{GDBN} supports multiple command interpreters, and some command
29153 infrastructure to allow users or user interface writers to switch
29154 between interpreters or run commands in other interpreters.
29156 @value{GDBN} currently supports two command interpreters, the console
29157 interpreter (sometimes called the command-line interpreter or @sc{cli})
29158 and the machine interface interpreter (or @sc{gdb/mi}). This manual
29159 describes both of these interfaces in great detail.
29161 By default, @value{GDBN} will start with the console interpreter.
29162 However, the user may choose to start @value{GDBN} with another
29163 interpreter by specifying the @option{-i} or @option{--interpreter}
29164 startup options. Defined interpreters include:
29168 @cindex console interpreter
29169 The traditional console or command-line interpreter. This is the most often
29170 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
29171 @value{GDBN} will use this interpreter.
29175 @cindex Debugger Adapter Protocol
29176 When @value{GDBN} has been built with Python support, it also supports
29177 the Debugger Adapter Protocol. This protocol can be used by a
29178 debugger GUI or an IDE to communicate with @value{GDBN}. This
29179 protocol is documented at
29180 @url{https://microsoft.github.io/debug-adapter-protocol/}.
29183 @cindex mi interpreter
29184 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
29185 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
29186 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
29190 @cindex mi3 interpreter
29191 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
29194 @cindex mi2 interpreter
29195 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
29199 @cindex invoke another interpreter
29201 @kindex interpreter-exec
29202 You may execute commands in any interpreter from the current
29203 interpreter using the appropriate command. If you are running the
29204 console interpreter, simply use the @code{interpreter-exec} command:
29207 interpreter-exec mi "-data-list-register-names"
29210 @sc{gdb/mi} has a similar command, although it is only available in versions of
29211 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
29213 Note that @code{interpreter-exec} only changes the interpreter for the
29214 duration of the specified command. It does not change the interpreter
29217 @cindex start a new independent interpreter
29219 Although you may only choose a single interpreter at startup, it is
29220 possible to run an independent interpreter on a specified input/output
29221 device (usually a tty).
29223 For example, consider a debugger GUI or IDE that wants to provide a
29224 @value{GDBN} console view. It may do so by embedding a terminal
29225 emulator widget in its GUI, starting @value{GDBN} in the traditional
29226 command-line mode with stdin/stdout/stderr redirected to that
29227 terminal, and then creating an MI interpreter running on a specified
29228 input/output device. The console interpreter created by @value{GDBN}
29229 at startup handles commands the user types in the terminal widget,
29230 while the GUI controls and synchronizes state with @value{GDBN} using
29231 the separate MI interpreter.
29233 To start a new secondary @dfn{user interface} running MI, use the
29234 @code{new-ui} command:
29237 @cindex new user interface
29239 new-ui @var{interpreter} @var{tty}
29242 The @var{interpreter} parameter specifies the interpreter to run.
29243 This accepts the same values as the @code{interpreter-exec} command.
29244 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
29245 @var{tty} parameter specifies the name of the bidirectional file the
29246 interpreter uses for input/output, usually the name of a
29247 pseudoterminal slave on Unix systems. For example:
29250 (@value{GDBP}) new-ui mi /dev/pts/9
29254 runs an MI interpreter on @file{/dev/pts/9}.
29257 @chapter @value{GDBN} Text User Interface
29259 @cindex Text User Interface
29261 The @value{GDBN} Text User Interface (TUI) is a terminal
29262 interface which uses the @code{curses} library to show the source
29263 file, the assembly output, the program registers and @value{GDBN}
29264 commands in separate text windows. The TUI mode is supported only
29265 on platforms where a suitable version of the @code{curses} library
29268 The TUI mode is enabled by default when you invoke @value{GDBN} as
29269 @samp{@value{GDBP} -tui}.
29270 You can also switch in and out of TUI mode while @value{GDBN} runs by
29271 using various TUI commands and key bindings, such as @command{tui
29272 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
29273 @ref{TUI Keys, ,TUI Key Bindings}.
29276 * TUI Overview:: TUI overview
29277 * TUI Keys:: TUI key bindings
29278 * TUI Single Key Mode:: TUI single key mode
29279 * TUI Mouse Support:: TUI mouse support
29280 * TUI Commands:: TUI-specific commands
29281 * TUI Configuration:: TUI configuration variables
29285 @section TUI Overview
29287 In TUI mode, @value{GDBN} can display several text windows:
29291 This window is the @value{GDBN} command window with the @value{GDBN}
29292 prompt and the @value{GDBN} output. The @value{GDBN} input is still
29293 managed using readline.
29296 The source window shows the source file of the program. The current
29297 line and active breakpoints are displayed in this window.
29300 The assembly window shows the disassembly output of the program.
29303 This window shows the processor registers. Registers are highlighted
29304 when their values change.
29307 The source and assembly windows show the current program position by
29308 highlighting the current line and marking it with a @samp{>} marker.
29309 By default, source and assembly code styling is disabled for the
29310 highlighted text, but you can enable it with the @code{set style
29311 tui-current-position on} command. @xref{Output Styling}.
29313 Breakpoints are indicated with two markers. The first marker
29314 indicates the breakpoint type:
29318 Breakpoint which was hit at least once.
29321 Breakpoint which was never hit.
29324 Hardware breakpoint which was hit at least once.
29327 Hardware breakpoint which was never hit.
29330 The second marker indicates whether the breakpoint is enabled or not:
29334 Breakpoint is enabled.
29337 Breakpoint is disabled.
29340 The source, assembly and register windows are updated when the current
29341 thread changes, when the frame changes, or when the program counter
29344 These windows are not all visible at the same time. The command
29345 window is always visible. The others can be arranged in several
29356 source and assembly,
29359 source and registers, or
29362 assembly and registers.
29365 These are the standard layouts, but other layouts can be defined.
29367 A status line above the command window shows the following information:
29371 Indicates the current @value{GDBN} target.
29372 (@pxref{Targets, ,Specifying a Debugging Target}).
29375 Gives the current process or thread number.
29376 When no process is being debugged, this field is set to @code{No process}.
29379 Gives the current function name for the selected frame.
29380 The name is demangled if demangling is turned on (@pxref{Print Settings}).
29381 When there is no symbol corresponding to the current program counter,
29382 the string @code{??} is displayed.
29385 Indicates the current line number for the selected frame.
29386 When the current line number is not known, the string @code{??} is displayed.
29389 Indicates the current program counter address.
29393 @section TUI Key Bindings
29394 @cindex TUI key bindings
29396 The TUI installs several key bindings in the readline keymaps
29397 @ifset SYSTEM_READLINE
29398 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
29400 @ifclear SYSTEM_READLINE
29401 (@pxref{Command Line Editing}).
29403 The following key bindings are installed for both TUI mode and the
29404 @value{GDBN} standard mode.
29413 Enter or leave the TUI mode. When leaving the TUI mode,
29414 the curses window management stops and @value{GDBN} operates using
29415 its standard mode, writing on the terminal directly. When reentering
29416 the TUI mode, control is given back to the curses windows.
29417 The screen is then refreshed.
29419 This key binding uses the bindable Readline function
29420 @code{tui-switch-mode}.
29424 Use a TUI layout with only one window. The layout will
29425 either be @samp{source} or @samp{assembly}. When the TUI mode
29426 is not active, it will switch to the TUI mode.
29428 Think of this key binding as the Emacs @kbd{C-x 1} binding.
29430 This key binding uses the bindable Readline function
29431 @code{tui-delete-other-windows}.
29435 Use a TUI layout with at least two windows. When the current
29436 layout already has two windows, the next layout with two windows is used.
29437 When a new layout is chosen, one window will always be common to the
29438 previous layout and the new one.
29440 Think of it as the Emacs @kbd{C-x 2} binding.
29442 This key binding uses the bindable Readline function
29443 @code{tui-change-windows}.
29447 Change the active window. The TUI associates several key bindings
29448 (like scrolling and arrow keys) with the active window. This command
29449 gives the focus to the next TUI window.
29451 Think of it as the Emacs @kbd{C-x o} binding.
29453 This key binding uses the bindable Readline function
29454 @code{tui-other-window}.
29458 Switch in and out of the TUI SingleKey mode that binds single
29459 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
29461 This key binding uses the bindable Readline function
29462 @code{next-keymap}.
29465 The following key bindings only work in the TUI mode:
29470 Scroll the active window one page up.
29474 Scroll the active window one page down.
29478 Scroll the active window one line up.
29482 Scroll the active window one line down.
29486 Scroll the active window one column left.
29490 Scroll the active window one column right.
29494 Refresh the screen.
29497 Because the arrow keys scroll the active window in the TUI mode, they
29498 are not available for their normal use by readline unless the command
29499 window has the focus. When another window is active, you must use
29500 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
29501 and @kbd{C-f} to control the command window.
29503 @node TUI Single Key Mode
29504 @section TUI Single Key Mode
29505 @cindex TUI single key mode
29507 The TUI also provides a @dfn{SingleKey} mode, which binds several
29508 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
29509 switch into this mode, where the following key bindings are used:
29512 @kindex c @r{(SingleKey TUI key)}
29516 @kindex d @r{(SingleKey TUI key)}
29520 @kindex f @r{(SingleKey TUI key)}
29524 @kindex n @r{(SingleKey TUI key)}
29528 @kindex o @r{(SingleKey TUI key)}
29530 nexti. The shortcut letter @samp{o} stands for ``step Over''.
29532 @kindex q @r{(SingleKey TUI key)}
29534 exit the SingleKey mode.
29536 @kindex r @r{(SingleKey TUI key)}
29540 @kindex s @r{(SingleKey TUI key)}
29544 @kindex i @r{(SingleKey TUI key)}
29546 stepi. The shortcut letter @samp{i} stands for ``step Into''.
29548 @kindex u @r{(SingleKey TUI key)}
29552 @kindex v @r{(SingleKey TUI key)}
29556 @kindex w @r{(SingleKey TUI key)}
29561 Other keys temporarily switch to the @value{GDBN} command prompt.
29562 The key that was pressed is inserted in the editing buffer so that
29563 it is possible to type most @value{GDBN} commands without interaction
29564 with the TUI SingleKey mode. Once the command is entered the TUI
29565 SingleKey mode is restored. The only way to permanently leave
29566 this mode is by typing @kbd{q} or @kbd{C-x s}.
29568 @cindex SingleKey keymap name
29569 If @value{GDBN} was built with Readline 8.0 or later, the TUI
29570 SingleKey keymap will be named @samp{SingleKey}. This can be used in
29571 @file{.inputrc} to add additional bindings to this keymap.
29573 @node TUI Mouse Support
29574 @section TUI Mouse Support
29575 @cindex TUI mouse support
29577 If the curses library supports the mouse, the TUI supports mouse
29580 The mouse wheel scrolls the appropriate window under the mouse cursor.
29582 The TUI itself does not directly support copying/pasting with the
29583 mouse. However, on Unix terminals, you can typically press and hold
29584 the @key{SHIFT} key on your keyboard to temporarily bypass
29585 @value{GDBN}'s TUI and access the terminal's native mouse copy/paste
29586 functionality (commonly, click-drag-release or double-click to select
29587 text, middle-click to paste). This copy/paste works with the
29588 terminal's selection buffer, as opposed to the TUI's buffer.
29591 @section TUI-specific Commands
29592 @cindex TUI commands
29594 The TUI has specific commands to control the text windows.
29595 These commands are always available, even when @value{GDBN} is not in
29596 the TUI mode. When @value{GDBN} is in the standard mode, most
29597 of these commands will automatically switch to the TUI mode.
29599 Note that if @value{GDBN}'s @code{stdout} is not connected to a
29600 terminal, or @value{GDBN} has been started with the machine interface
29601 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
29602 these commands will fail with an error, because it would not be
29603 possible or desirable to enable curses window management.
29608 Activate TUI mode. The last active TUI window layout will be used if
29609 TUI mode has previously been used in the current debugging session,
29610 otherwise a default layout is used.
29613 @kindex tui disable
29614 Disable TUI mode, returning to the console interpreter.
29616 @anchor{info_win_command}
29619 List the names and sizes of all currently displayed windows.
29621 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
29622 @kindex tui new-layout
29623 Create a new TUI layout. The new layout will be named @var{name}, and
29624 can be accessed using the @code{layout} command (see below).
29626 Each @var{window} parameter is either the name of a window to display,
29627 or a window description. The windows will be displayed from top to
29628 bottom in the order listed.
29630 The names of the windows are the same as the ones given to the
29631 @code{focus} command (see below); additional, the @code{status}
29632 window can be specified. Note that, because it is of fixed height,
29633 the weight assigned to the status window is of no importance. It is
29634 conventional to use @samp{0} here.
29636 A window description looks a bit like an invocation of @code{tui
29637 new-layout}, and is of the form
29638 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
29640 This specifies a sub-layout. If @code{-horizontal} is given, the
29641 windows in this description will be arranged side-by-side, rather than
29644 Each @var{weight} is an integer. It is the weight of this window
29645 relative to all the other windows in the layout. These numbers are
29646 used to calculate how much of the screen is given to each window.
29651 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
29654 Here, the new layout is called @samp{example}. It shows the source
29655 and register windows, followed by the status window, and then finally
29656 the command window. The non-status windows all have the same weight,
29657 so the terminal will be split into three roughly equal sections.
29659 Here is a more complex example, showing a horizontal layout:
29662 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
29665 This will result in side-by-side source and assembly windows; with the
29666 status and command window being beneath these, filling the entire
29667 width of the terminal. Because they have weight 2, the source and
29668 assembly windows will be twice the height of the command window.
29672 @item tui layout @var{name}
29673 @itemx layout @var{name}
29674 Changes which TUI windows are displayed. The @var{name} parameter
29675 controls which layout is shown. It can be either one of the built-in
29676 layout names, or the name of a layout defined by the user using
29677 @code{tui new-layout}.
29679 The built-in layouts are as follows:
29683 Display the next layout.
29686 Display the previous layout.
29689 Display the source and command windows.
29692 Display the assembly and command windows.
29695 Display the source, assembly, and command windows.
29698 When in @code{src} layout display the register, source, and command
29699 windows. When in @code{asm} or @code{split} layout display the
29700 register, assembler, and command windows.
29704 @item tui focus @var{name}
29705 @itemx focus @var{name}
29706 Changes which TUI window is currently active for scrolling. The
29707 @var{name} parameter can be any of the following:
29711 Make the next window active for scrolling.
29714 Make the previous window active for scrolling.
29717 Make the source window active for scrolling.
29720 Make the assembly window active for scrolling.
29723 Make the register window active for scrolling.
29726 Make the command window active for scrolling.
29729 @kindex tui refresh
29733 Refresh the screen. This is similar to typing @kbd{C-L}.
29735 @item tui reg @var{group}
29737 Changes the register group displayed in the tui register window to
29738 @var{group}. If the register window is not currently displayed this
29739 command will cause the register window to be displayed. The list of
29740 register groups, as well as their order is target specific. The
29741 following groups are available on most targets:
29744 Repeatedly selecting this group will cause the display to cycle
29745 through all of the available register groups.
29748 Repeatedly selecting this group will cause the display to cycle
29749 through all of the available register groups in the reverse order to
29753 Display the general registers.
29755 Display the floating point registers.
29757 Display the system registers.
29759 Display the vector registers.
29761 Display all registers.
29766 Update the source window and the current execution point.
29768 @kindex tui window height
29770 @item tui window height @var{name} +@var{count}
29771 @itemx tui window height @var{name} -@var{count}
29772 @itemx winheight @var{name} +@var{count}
29773 @itemx winheight @var{name} -@var{count}
29774 Change the height of the window @var{name} by @var{count} lines.
29775 Positive counts increase the height, while negative counts decrease
29776 it. The @var{name} parameter can be the name of any currently visible
29777 window. The names of the currently visible windows can be discovered
29778 using @kbd{info win} (@pxref{info_win_command,,info win}).
29780 The set of currently visible windows must always fill the terminal,
29781 and so, it is only possible to resize on window if there are other
29782 visible windows that can either give or receive the extra terminal
29785 @kindex tui window width
29787 @item tui window width @var{name} +@var{count}
29788 @itemx tui window width @var{name} -@var{count}
29789 @itemx winwidth @var{name} +@var{count}
29790 @itemx winwidth @var{name} -@var{count}
29791 Change the width of the window @var{name} by @var{count} columns.
29792 Positive counts increase the width, while negative counts decrease it.
29793 The @var{name} parameter can be the name of any currently visible
29794 window. The names of the currently visible windows can be discovered
29795 using @code{info win} (@pxref{info_win_command,,info win}).
29797 The set of currently visible windows must always fill the terminal,
29798 and so, it is only possible to resize on window if there are other
29799 visible windows that can either give or receive the extra terminal
29803 @node TUI Configuration
29804 @section TUI Configuration Variables
29805 @cindex TUI configuration variables
29807 Several configuration variables control the appearance of TUI windows.
29810 @item set tui border-kind @var{kind}
29811 @kindex set tui border-kind
29812 Select the border appearance for the source, assembly and register windows.
29813 The possible values are the following:
29816 Use a space character to draw the border.
29819 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
29822 Use the Alternate Character Set to draw the border. The border is
29823 drawn using character line graphics if the terminal supports them.
29826 @item set tui border-mode @var{mode}
29827 @kindex set tui border-mode
29828 @itemx set tui active-border-mode @var{mode}
29829 @kindex set tui active-border-mode
29830 Select the display attributes for the borders of the inactive windows
29831 or the active window. The @var{mode} can be one of the following:
29834 Use normal attributes to display the border.
29840 Use reverse video mode.
29843 Use half bright mode.
29845 @item half-standout
29846 Use half bright and standout mode.
29849 Use extra bright or bold mode.
29851 @item bold-standout
29852 Use extra bright or bold and standout mode.
29855 @item set tui tab-width @var{nchars}
29856 @kindex set tui tab-width
29858 Set the width of tab stops to be @var{nchars} characters. This
29859 setting affects the display of TAB characters in the source and
29862 @item set tui compact-source @r{[}on@r{|}off@r{]}
29863 @kindex set tui compact-source
29864 Set whether the TUI source window is displayed in ``compact'' form.
29865 The default display uses more space for line numbers and starts the
29866 source text at the next tab stop; the compact display uses only as
29867 much space as is needed for the line numbers in the current file, and
29868 only a single space to separate the line numbers from the source.
29870 @kindex set debug tui
29871 @item set debug tui @r{[}on|off@r{]}
29872 Turn on or off display of @value{GDBN} internal debug messages relating
29875 @kindex show debug tui
29876 @item show debug tui
29877 Show the current status of displaying @value{GDBN} internal debug
29878 messages relating to the TUI.
29882 Note that the colors of the TUI borders can be controlled using the
29883 appropriate @code{set style} commands. @xref{Output Styling}.
29886 @chapter Using @value{GDBN} under @sc{gnu} Emacs
29889 @cindex @sc{gnu} Emacs
29890 A special interface allows you to use @sc{gnu} Emacs to view (and
29891 edit) the source files for the program you are debugging with
29894 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
29895 executable file you want to debug as an argument. This command starts
29896 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
29897 created Emacs buffer.
29898 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
29900 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
29905 All ``terminal'' input and output goes through an Emacs buffer, called
29908 This applies both to @value{GDBN} commands and their output, and to the input
29909 and output done by the program you are debugging.
29911 This is useful because it means that you can copy the text of previous
29912 commands and input them again; you can even use parts of the output
29915 All the facilities of Emacs' Shell mode are available for interacting
29916 with your program. In particular, you can send signals the usual
29917 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
29921 @value{GDBN} displays source code through Emacs.
29923 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
29924 source file for that frame and puts an arrow (@samp{=>}) at the
29925 left margin of the current line. Emacs uses a separate buffer for
29926 source display, and splits the screen to show both your @value{GDBN} session
29929 Explicit @value{GDBN} @code{list} or search commands still produce output as
29930 usual, but you probably have no reason to use them from Emacs.
29933 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
29934 a graphical mode, enabled by default, which provides further buffers
29935 that can control the execution and describe the state of your program.
29936 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
29938 If you specify an absolute file name when prompted for the @kbd{M-x
29939 gdb} argument, then Emacs sets your current working directory to where
29940 your program resides. If you only specify the file name, then Emacs
29941 sets your current working directory to the directory associated
29942 with the previous buffer. In this case, @value{GDBN} may find your
29943 program by searching your environment's @env{PATH} variable, but on
29944 some operating systems it might not find the source. So, although the
29945 @value{GDBN} input and output session proceeds normally, the auxiliary
29946 buffer does not display the current source and line of execution.
29948 The initial working directory of @value{GDBN} is printed on the top
29949 line of the GUD buffer and this serves as a default for the commands
29950 that specify files for @value{GDBN} to operate on. @xref{Files,
29951 ,Commands to Specify Files}.
29953 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
29954 need to call @value{GDBN} by a different name (for example, if you
29955 keep several configurations around, with different names) you can
29956 customize the Emacs variable @code{gud-gdb-command-name} to run the
29959 In the GUD buffer, you can use these special Emacs commands in
29960 addition to the standard Shell mode commands:
29964 Describe the features of Emacs' GUD Mode.
29967 Execute to another source line, like the @value{GDBN} @code{step} command; also
29968 update the display window to show the current file and location.
29971 Execute to next source line in this function, skipping all function
29972 calls, like the @value{GDBN} @code{next} command. Then update the display window
29973 to show the current file and location.
29976 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
29977 display window accordingly.
29980 Execute until exit from the selected stack frame, like the @value{GDBN}
29981 @code{finish} command.
29984 Continue execution of your program, like the @value{GDBN} @code{continue}
29988 Go up the number of frames indicated by the numeric argument
29989 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
29990 like the @value{GDBN} @code{up} command.
29993 Go down the number of frames indicated by the numeric argument, like the
29994 @value{GDBN} @code{down} command.
29997 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
29998 tells @value{GDBN} to set a breakpoint on the source line point is on.
30000 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
30001 separate frame which shows a backtrace when the GUD buffer is current.
30002 Move point to any frame in the stack and type @key{RET} to make it
30003 become the current frame and display the associated source in the
30004 source buffer. Alternatively, click @kbd{Mouse-2} to make the
30005 selected frame become the current one. In graphical mode, the
30006 speedbar displays watch expressions.
30008 If you accidentally delete the source-display buffer, an easy way to get
30009 it back is to type the command @code{f} in the @value{GDBN} buffer, to
30010 request a frame display; when you run under Emacs, this recreates
30011 the source buffer if necessary to show you the context of the current
30014 The source files displayed in Emacs are in ordinary Emacs buffers
30015 which are visiting the source files in the usual way. You can edit
30016 the files with these buffers if you wish; but keep in mind that @value{GDBN}
30017 communicates with Emacs in terms of line numbers. If you add or
30018 delete lines from the text, the line numbers that @value{GDBN} knows cease
30019 to correspond properly with the code.
30021 A more detailed description of Emacs' interaction with @value{GDBN} is
30022 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
30026 @chapter The @sc{gdb/mi} Interface
30028 @unnumberedsec Function and Purpose
30030 @cindex @sc{gdb/mi}, its purpose
30031 @sc{gdb/mi} is a line based machine oriented text interface to
30032 @value{GDBN} and is activated by specifying using the
30033 @option{--interpreter} command line option (@pxref{Mode Options}). It
30034 is specifically intended to support the development of systems which
30035 use the debugger as just one small component of a larger system.
30037 This chapter is a specification of the @sc{gdb/mi} interface. It is written
30038 in the form of a reference manual.
30040 Note that @sc{gdb/mi} is still under construction, so some of the
30041 features described below are incomplete and subject to change
30042 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
30044 @unnumberedsec Notation and Terminology
30046 @cindex notational conventions, for @sc{gdb/mi}
30047 This chapter uses the following notation:
30051 @code{|} separates two alternatives.
30054 @code{[ @var{something} ]} indicates that @var{something} is optional:
30055 it may or may not be given.
30058 @code{( @var{group} )*} means that @var{group} inside the parentheses
30059 may repeat zero or more times.
30062 @code{( @var{group} )+} means that @var{group} inside the parentheses
30063 may repeat one or more times.
30066 @code{( @var{group} )} means that @var{group} inside the parentheses
30067 occurs exactly once.
30070 @code{"@var{string}"} means a literal @var{string}.
30074 @heading Dependencies
30078 * GDB/MI General Design::
30079 * GDB/MI Command Syntax::
30080 * GDB/MI Compatibility with CLI::
30081 * GDB/MI Development and Front Ends::
30082 * GDB/MI Output Records::
30083 * GDB/MI Simple Examples::
30084 * GDB/MI Command Description Format::
30085 * GDB/MI Breakpoint Commands::
30086 * GDB/MI Catchpoint Commands::
30087 * GDB/MI Program Context::
30088 * GDB/MI Thread Commands::
30089 * GDB/MI Ada Tasking Commands::
30090 * GDB/MI Program Execution::
30091 * GDB/MI Stack Manipulation::
30092 * GDB/MI Variable Objects::
30093 * GDB/MI Data Manipulation::
30094 * GDB/MI Tracepoint Commands::
30095 * GDB/MI Symbol Query::
30096 * GDB/MI File Commands::
30098 * GDB/MI Kod Commands::
30099 * GDB/MI Memory Overlay Commands::
30100 * GDB/MI Signal Handling Commands::
30102 * GDB/MI Target Manipulation::
30103 * GDB/MI File Transfer Commands::
30104 * GDB/MI Ada Exceptions Commands::
30105 * GDB/MI Support Commands::
30106 * GDB/MI Miscellaneous Commands::
30109 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30110 @node GDB/MI General Design
30111 @section @sc{gdb/mi} General Design
30112 @cindex GDB/MI General Design
30114 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
30115 parts---commands sent to @value{GDBN}, responses to those commands
30116 and notifications. Each command results in exactly one response,
30117 indicating either successful completion of the command, or an error.
30118 For the commands that do not resume the target, the response contains the
30119 requested information. For the commands that resume the target, the
30120 response only indicates whether the target was successfully resumed.
30121 Notifications is the mechanism for reporting changes in the state of the
30122 target, or in @value{GDBN} state, that cannot conveniently be associated with
30123 a command and reported as part of that command response.
30125 The important examples of notifications are:
30129 Exec notifications. These are used to report changes in
30130 target state---when a target is resumed, or stopped. It would not
30131 be feasible to include this information in response of resuming
30132 commands, because one resume commands can result in multiple events in
30133 different threads. Also, quite some time may pass before any event
30134 happens in the target, while a frontend needs to know whether the resuming
30135 command itself was successfully executed.
30138 Console output, and status notifications. Console output
30139 notifications are used to report output of CLI commands, as well as
30140 diagnostics for other commands. Status notifications are used to
30141 report the progress of a long-running operation. Naturally, including
30142 this information in command response would mean no output is produced
30143 until the command is finished, which is undesirable.
30146 General notifications. Commands may have various side effects on
30147 the @value{GDBN} or target state beyond their official purpose. For example,
30148 a command may change the selected thread. Although such changes can
30149 be included in command response, using notification allows for more
30150 orthogonal frontend design.
30154 There's no guarantee that whenever an MI command reports an error,
30155 @value{GDBN} or the target are in any specific state, and especially,
30156 the state is not reverted to the state before the MI command was
30157 processed. Therefore, whenever an MI command results in an error,
30158 we recommend that the frontend refreshes all the information shown in
30159 the user interface.
30163 * Context management::
30164 * Asynchronous and non-stop modes::
30168 @node Context management
30169 @subsection Context management
30171 @subsubsection Threads and Frames
30173 In most cases when @value{GDBN} accesses the target, this access is
30174 done in context of a specific thread and frame (@pxref{Frames}).
30175 Often, even when accessing global data, the target requires that a thread
30176 be specified. The CLI interface maintains the selected thread and frame,
30177 and supplies them to target on each command. This is convenient,
30178 because a command line user would not want to specify that information
30179 explicitly on each command, and because user interacts with
30180 @value{GDBN} via a single terminal, so no confusion is possible as
30181 to what thread and frame are the current ones.
30183 In the case of MI, the concept of selected thread and frame is less
30184 useful. First, a frontend can easily remember this information
30185 itself. Second, a graphical frontend can have more than one window,
30186 each one used for debugging a different thread, and the frontend might
30187 want to access additional threads for internal purposes. This
30188 increases the risk that by relying on implicitly selected thread, the
30189 frontend may be operating on a wrong one. Therefore, each MI command
30190 should explicitly specify which thread and frame to operate on. To
30191 make it possible, each MI command accepts the @samp{--thread} and
30192 @samp{--frame} options, the value to each is @value{GDBN} global
30193 identifier for thread and frame to operate on.
30195 Usually, each top-level window in a frontend allows the user to select
30196 a thread and a frame, and remembers the user selection for further
30197 operations. However, in some cases @value{GDBN} may suggest that the
30198 current thread or frame be changed. For example, when stopping on a
30199 breakpoint it is reasonable to switch to the thread where breakpoint is
30200 hit. For another example, if the user issues the CLI @samp{thread} or
30201 @samp{frame} commands via the frontend, it is desirable to change the
30202 frontend's selection to the one specified by user. @value{GDBN}
30203 communicates the suggestion to change current thread and frame using the
30204 @samp{=thread-selected} notification.
30206 Note that historically, MI shares the selected thread with CLI, so
30207 frontends used the @code{-thread-select} to execute commands in the
30208 right context. However, getting this to work right is cumbersome. The
30209 simplest way is for frontend to emit @code{-thread-select} command
30210 before every command. This doubles the number of commands that need
30211 to be sent. The alternative approach is to suppress @code{-thread-select}
30212 if the selected thread in @value{GDBN} is supposed to be identical to the
30213 thread the frontend wants to operate on. However, getting this
30214 optimization right can be tricky. In particular, if the frontend
30215 sends several commands to @value{GDBN}, and one of the commands changes the
30216 selected thread, then the behaviour of subsequent commands will
30217 change. So, a frontend should either wait for response from such
30218 problematic commands, or explicitly add @code{-thread-select} for
30219 all subsequent commands. No frontend is known to do this exactly
30220 right, so it is suggested to just always pass the @samp{--thread} and
30221 @samp{--frame} options.
30223 @subsubsection Language
30225 The execution of several commands depends on which language is selected.
30226 By default, the current language (@pxref{show language}) is used.
30227 But for commands known to be language-sensitive, it is recommended
30228 to use the @samp{--language} option. This option takes one argument,
30229 which is the name of the language to use while executing the command.
30233 -data-evaluate-expression --language c "sizeof (void*)"
30238 The valid language names are the same names accepted by the
30239 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
30240 @samp{local} or @samp{unknown}.
30242 @node Asynchronous and non-stop modes
30243 @subsection Asynchronous command execution and non-stop mode
30245 On some targets, @value{GDBN} is capable of processing MI commands
30246 even while the target is running. This is called @dfn{asynchronous
30247 command execution} (@pxref{Background Execution}). The frontend may
30248 specify a preference for asynchronous execution using the
30249 @code{-gdb-set mi-async 1} command, which should be emitted before
30250 either running the executable or attaching to the target. After the
30251 frontend has started the executable or attached to the target, it can
30252 find if asynchronous execution is enabled using the
30253 @code{-list-target-features} command.
30256 @cindex foreground execution
30257 @cindex background execution
30258 @cindex asynchronous execution
30259 @cindex execution, foreground, background and asynchronous
30260 @kindex set mi-async
30261 @item -gdb-set mi-async @r{[}on@r{|}off@r{]}
30262 Set whether MI is in asynchronous mode.
30264 When @code{off}, which is the default, MI execution commands (e.g.,
30265 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
30266 for the program to stop before processing further commands.
30268 When @code{on}, MI execution commands are background execution
30269 commands (e.g., @code{-exec-continue} becomes the equivalent of the
30270 @code{c&} CLI command), and so @value{GDBN} is capable of processing
30271 MI commands even while the target is running.
30273 @kindex show mi-async
30274 @item -gdb-show mi-async
30275 Show whether MI asynchronous mode is enabled.
30278 Note: In @value{GDBN} version 7.7 and earlier, this option was called
30279 @code{target-async} instead of @code{mi-async}, and it had the effect
30280 of both putting MI in asynchronous mode and making CLI background
30281 commands possible. CLI background commands are now always possible
30282 ``out of the box'' if the target supports them. The old spelling is
30283 kept as a deprecated alias for backwards compatibility.
30285 Even if @value{GDBN} can accept a command while target is running,
30286 many commands that access the target do not work when the target is
30287 running. Therefore, asynchronous command execution is most useful
30288 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
30289 it is possible to examine the state of one thread, while other threads
30292 When a given thread is running, MI commands that try to access the
30293 target in the context of that thread may not work, or may work only on
30294 some targets. In particular, commands that try to operate on thread's
30295 stack will not work, on any target. Commands that read memory, or
30296 modify breakpoints, may work or not work, depending on the target. Note
30297 that even commands that operate on global state, such as @code{print},
30298 @code{set}, and breakpoint commands, still access the target in the
30299 context of a specific thread, so frontend should try to find a
30300 stopped thread and perform the operation on that thread (using the
30301 @samp{--thread} option).
30303 Which commands will work in the context of a running thread is
30304 highly target dependent. However, the two commands
30305 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
30306 to find the state of a thread, will always work.
30308 @node Thread groups
30309 @subsection Thread groups
30310 @value{GDBN} may be used to debug several processes at the same time.
30311 On some platforms, @value{GDBN} may support debugging of several
30312 hardware systems, each one having several cores with several different
30313 processes running on each core. This section describes the MI
30314 mechanism to support such debugging scenarios.
30316 The key observation is that regardless of the structure of the
30317 target, MI can have a global list of threads, because most commands that
30318 accept the @samp{--thread} option do not need to know what process that
30319 thread belongs to. Therefore, it is not necessary to introduce
30320 neither additional @samp{--process} option, nor an notion of the
30321 current process in the MI interface. The only strictly new feature
30322 that is required is the ability to find how the threads are grouped
30325 To allow the user to discover such grouping, and to support arbitrary
30326 hierarchy of machines/cores/processes, MI introduces the concept of a
30327 @dfn{thread group}. Thread group is a collection of threads and other
30328 thread groups. A thread group always has a string identifier, a type,
30329 and may have additional attributes specific to the type. A new
30330 command, @code{-list-thread-groups}, returns the list of top-level
30331 thread groups, which correspond to processes that @value{GDBN} is
30332 debugging at the moment. By passing an identifier of a thread group
30333 to the @code{-list-thread-groups} command, it is possible to obtain
30334 the members of specific thread group.
30336 To allow the user to easily discover processes, and other objects, he
30337 wishes to debug, a concept of @dfn{available thread group} is
30338 introduced. Available thread group is an thread group that
30339 @value{GDBN} is not debugging, but that can be attached to, using the
30340 @code{-target-attach} command. The list of available top-level thread
30341 groups can be obtained using @samp{-list-thread-groups --available}.
30342 In general, the content of a thread group may be only retrieved only
30343 after attaching to that thread group.
30345 Thread groups are related to inferiors (@pxref{Inferiors Connections and
30346 Programs}). Each inferior corresponds to a thread group of a special
30347 type @samp{process}, and some additional operations are permitted on
30348 such thread groups.
30350 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30351 @node GDB/MI Command Syntax
30352 @section @sc{gdb/mi} Command Syntax
30355 * GDB/MI Input Syntax::
30356 * GDB/MI Output Syntax::
30359 @node GDB/MI Input Syntax
30360 @subsection @sc{gdb/mi} Input Syntax
30362 @cindex input syntax for @sc{gdb/mi}
30363 @cindex @sc{gdb/mi}, input syntax
30365 @item @var{command} @expansion{}
30366 @code{@var{cli-command} | @var{mi-command}}
30368 @item @var{cli-command} @expansion{}
30369 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
30370 @var{cli-command} is any existing @value{GDBN} CLI command.
30372 @item @var{mi-command} @expansion{}
30373 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
30374 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
30376 @item @var{token} @expansion{}
30377 "any sequence of digits"
30379 @item @var{option} @expansion{}
30380 @code{"-" @var{parameter} [ " " @var{parameter} ]}
30382 @item @var{parameter} @expansion{}
30383 @code{@var{non-blank-sequence} | @var{c-string}}
30385 @item @var{operation} @expansion{}
30386 @emph{any of the operations described in this chapter}
30388 @item @var{non-blank-sequence} @expansion{}
30389 @emph{anything, provided it doesn't contain special characters such as
30390 "-", @var{nl}, """ and of course " "}
30392 @item @var{c-string} @expansion{}
30393 @code{""" @var{seven-bit-iso-c-string-content} """}
30395 @item @var{nl} @expansion{}
30404 The CLI commands are still handled by the @sc{mi} interpreter; their
30405 output is described below.
30408 The @code{@var{token}}, when present, is passed back when the command
30412 Some @sc{mi} commands accept optional arguments as part of the parameter
30413 list. Each option is identified by a leading @samp{-} (dash) and may be
30414 followed by an optional argument parameter. Options occur first in the
30415 parameter list and can be delimited from normal parameters using
30416 @samp{--} (this is useful when some parameters begin with a dash).
30423 We want easy access to the existing CLI syntax (for debugging).
30426 We want it to be easy to spot a @sc{mi} operation.
30429 @node GDB/MI Output Syntax
30430 @subsection @sc{gdb/mi} Output Syntax
30432 @cindex output syntax of @sc{gdb/mi}
30433 @cindex @sc{gdb/mi}, output syntax
30434 The output from @sc{gdb/mi} consists of zero or more out-of-band records
30435 followed, optionally, by a single result record. This result record
30436 is for the most recent command. The sequence of output records is
30437 terminated by @samp{(gdb)}.
30439 If an input command was prefixed with a @code{@var{token}} then the
30440 corresponding output for that command will also be prefixed by that same
30444 @item @var{output} @expansion{}
30445 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
30447 @item @var{result-record} @expansion{}
30448 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
30450 @item @var{out-of-band-record} @expansion{}
30451 @code{@var{async-record} | @var{stream-record}}
30453 @item @var{async-record} @expansion{}
30454 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
30456 @item @var{exec-async-output} @expansion{}
30457 @code{[ @var{token} ] "*" @var{async-output nl}}
30459 @item @var{status-async-output} @expansion{}
30460 @code{[ @var{token} ] "+" @var{async-output nl}}
30462 @item @var{notify-async-output} @expansion{}
30463 @code{[ @var{token} ] "=" @var{async-output nl}}
30465 @item @var{async-output} @expansion{}
30466 @code{@var{async-class} ( "," @var{result} )*}
30468 @item @var{result-class} @expansion{}
30469 @code{"done" | "running" | "connected" | "error" | "exit"}
30471 @item @var{async-class} @expansion{}
30472 @code{"stopped" | @var{others}} (where @var{others} will be added
30473 depending on the needs---this is still in development).
30475 @item @var{result} @expansion{}
30476 @code{ @var{variable} "=" @var{value}}
30478 @item @var{variable} @expansion{}
30479 @code{ @var{string} }
30481 @item @var{value} @expansion{}
30482 @code{ @var{const} | @var{tuple} | @var{list} }
30484 @item @var{const} @expansion{}
30485 @code{@var{c-string}}
30487 @item @var{tuple} @expansion{}
30488 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
30490 @item @var{list} @expansion{}
30491 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
30492 @var{result} ( "," @var{result} )* "]" }
30494 @item @var{stream-record} @expansion{}
30495 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
30497 @item @var{console-stream-output} @expansion{}
30498 @code{"~" @var{c-string nl}}
30500 @item @var{target-stream-output} @expansion{}
30501 @code{"@@" @var{c-string nl}}
30503 @item @var{log-stream-output} @expansion{}
30504 @code{"&" @var{c-string nl}}
30506 @item @var{nl} @expansion{}
30509 @item @var{token} @expansion{}
30510 @emph{any sequence of digits}.
30518 All output sequences end in a single line containing a period.
30521 The @code{@var{token}} is from the corresponding request. Note that
30522 for all async output, while the token is allowed by the grammar and
30523 may be output by future versions of @value{GDBN} for select async
30524 output messages, it is generally omitted. Frontends should treat
30525 all async output as reporting general changes in the state of the
30526 target and there should be no need to associate async output to any
30530 @cindex status output in @sc{gdb/mi}
30531 @var{status-async-output} contains on-going status information about the
30532 progress of a slow operation. It can be discarded. All status output is
30533 prefixed by @samp{+}.
30536 @cindex async output in @sc{gdb/mi}
30537 @var{exec-async-output} contains asynchronous state change on the target
30538 (stopped, started, disappeared). All async output is prefixed by
30542 @cindex notify output in @sc{gdb/mi}
30543 @var{notify-async-output} contains supplementary information that the
30544 client should handle (e.g., a new breakpoint information). All notify
30545 output is prefixed by @samp{=}.
30548 @cindex console output in @sc{gdb/mi}
30549 @var{console-stream-output} is output that should be displayed as is in the
30550 console. It is the textual response to a CLI command. All the console
30551 output is prefixed by @samp{~}.
30554 @cindex target output in @sc{gdb/mi}
30555 @var{target-stream-output} is the output produced by the target program.
30556 All the target output is prefixed by @samp{@@}.
30559 @cindex log output in @sc{gdb/mi}
30560 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
30561 instance messages that should be displayed as part of an error log. All
30562 the log output is prefixed by @samp{&}.
30565 @cindex list output in @sc{gdb/mi}
30566 New @sc{gdb/mi} commands should only output @var{lists} containing
30572 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
30573 details about the various output records.
30575 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30576 @node GDB/MI Compatibility with CLI
30577 @section @sc{gdb/mi} Compatibility with CLI
30579 @cindex compatibility, @sc{gdb/mi} and CLI
30580 @cindex @sc{gdb/mi}, compatibility with CLI
30582 For the developers convenience CLI commands can be entered directly,
30583 but there may be some unexpected behaviour. For example, commands
30584 that query the user will behave as if the user replied yes, breakpoint
30585 command lists are not executed and some CLI commands, such as
30586 @code{if}, @code{when} and @code{define}, prompt for further input with
30587 @samp{>}, which is not valid MI output.
30589 This feature may be removed at some stage in the future and it is
30590 recommended that front ends use the @code{-interpreter-exec} command
30591 (@pxref{-interpreter-exec}).
30593 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30594 @node GDB/MI Development and Front Ends
30595 @section @sc{gdb/mi} Development and Front Ends
30596 @cindex @sc{gdb/mi} development
30598 The application which takes the MI output and presents the state of the
30599 program being debugged to the user is called a @dfn{front end}.
30601 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
30602 to the MI interface may break existing usage. This section describes how the
30603 protocol changes and how to request previous version of the protocol when it
30606 Some changes in MI need not break a carefully designed front end, and
30607 for these the MI version will remain unchanged. The following is a
30608 list of changes that may occur within one level, so front ends should
30609 parse MI output in a way that can handle them:
30613 New MI commands may be added.
30616 New fields may be added to the output of any MI command.
30619 The range of values for fields with specified values, e.g.,
30620 @code{in_scope} (@pxref{-var-update}) may be extended.
30622 @c The format of field's content e.g type prefix, may change so parse it
30623 @c at your own risk. Yes, in general?
30625 @c The order of fields may change? Shouldn't really matter but it might
30626 @c resolve inconsistencies.
30629 If the changes are likely to break front ends, the MI version level
30630 will be increased by one. The new versions of the MI protocol are not compatible
30631 with the old versions. Old versions of MI remain available, allowing front ends
30632 to keep using them until they are modified to use the latest MI version.
30634 Since @code{--interpreter=mi} always points to the latest MI version, it is
30635 recommended that front ends request a specific version of MI when launching
30636 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
30637 interpreter with the MI version they expect.
30639 The following table gives a summary of the released versions of the MI
30640 interface: the version number, the version of GDB in which it first appeared
30641 and the breaking changes compared to the previous version.
30643 @multitable @columnfractions .1 .1 .8
30644 @headitem MI version @tab GDB version @tab Breaking changes
30661 The @code{-environment-pwd}, @code{-environment-directory} and
30662 @code{-environment-path} commands now returns values using the MI output
30663 syntax, rather than CLI output syntax.
30666 @code{-var-list-children}'s @code{children} result field is now a list, rather
30670 @code{-var-update}'s @code{changelist} result field is now a list, rather than
30682 The output of information about multi-location breakpoints has changed in the
30683 responses to the @code{-break-insert} and @code{-break-info} commands, as well
30684 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
30685 The multiple locations are now placed in a @code{locations} field, whose value
30697 The syntax of the "script" field in breakpoint output has changed in the
30698 responses to the @code{-break-insert} and @code{-break-info} commands, as
30699 well as the @code{=breakpoint-created} and @code{=breakpoint-modified}
30700 events. The previous output was syntactically invalid. The new output is
30706 If your front end cannot yet migrate to a more recent version of the
30707 MI protocol, you can nevertheless selectively enable specific features
30708 available in those recent MI versions, using the following commands:
30712 @item -fix-multi-location-breakpoint-output
30713 Use the output for multi-location breakpoints which was introduced by
30714 MI 3, even when using MI versions below 3. This command has no
30715 effect when using MI version 3 or later.
30717 @item -fix-breakpoint-script-output
30718 Use the output for the breakpoint "script" field which was introduced by
30719 MI 4, even when using MI versions below 4. This command has no effect when
30720 using MI version 4 or later.
30724 The best way to avoid unexpected changes in MI that might break your front
30725 end is to make your project known to @value{GDBN} developers and
30726 follow development on @email{gdb@@sourceware.org} and
30727 @email{gdb-patches@@sourceware.org}.
30728 @cindex mailing lists
30730 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30731 @node GDB/MI Output Records
30732 @section @sc{gdb/mi} Output Records
30735 * GDB/MI Result Records::
30736 * GDB/MI Stream Records::
30737 * GDB/MI Async Records::
30738 * GDB/MI Breakpoint Information::
30739 * GDB/MI Frame Information::
30740 * GDB/MI Thread Information::
30741 * GDB/MI Ada Exception Information::
30744 @node GDB/MI Result Records
30745 @subsection @sc{gdb/mi} Result Records
30747 @cindex result records in @sc{gdb/mi}
30748 @cindex @sc{gdb/mi}, result records
30749 In addition to a number of out-of-band notifications, the response to a
30750 @sc{gdb/mi} command includes one of the following result indications:
30754 @item "^done" [ "," @var{results} ]
30755 The synchronous operation was successful, @code{@var{results}} are the return
30760 This result record is equivalent to @samp{^done}. Historically, it
30761 was output instead of @samp{^done} if the command has resumed the
30762 target. This behaviour is maintained for backward compatibility, but
30763 all frontends should treat @samp{^done} and @samp{^running}
30764 identically and rely on the @samp{*running} output record to determine
30765 which threads are resumed.
30769 @value{GDBN} has connected to a remote target.
30771 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
30773 The operation failed. The @code{msg=@var{c-string}} variable contains
30774 the corresponding error message.
30776 If present, the @code{code=@var{c-string}} variable provides an error
30777 code on which consumers can rely on to detect the corresponding
30778 error condition. At present, only one error code is defined:
30781 @item "undefined-command"
30782 Indicates that the command causing the error does not exist.
30787 @value{GDBN} has terminated.
30791 @node GDB/MI Stream Records
30792 @subsection @sc{gdb/mi} Stream Records
30794 @cindex @sc{gdb/mi}, stream records
30795 @cindex stream records in @sc{gdb/mi}
30796 @value{GDBN} internally maintains a number of output streams: the console, the
30797 target, and the log. The output intended for each of these streams is
30798 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
30800 Each stream record begins with a unique @dfn{prefix character} which
30801 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
30802 Syntax}). In addition to the prefix, each stream record contains a
30803 @code{@var{string-output}}. This is either raw text (with an implicit new
30804 line) or a quoted C string (which does not contain an implicit newline).
30807 @item "~" @var{string-output}
30808 The console output stream contains text that should be displayed in the
30809 CLI console window. It contains the textual responses to CLI commands.
30811 @item "@@" @var{string-output}
30812 The target output stream contains any textual output from the running
30813 target. This is only present when GDB's event loop is truly
30814 asynchronous, which is currently only the case for remote targets.
30816 @item "&" @var{string-output}
30817 The log stream contains debugging messages being produced by @value{GDBN}'s
30821 @node GDB/MI Async Records
30822 @subsection @sc{gdb/mi} Async Records
30824 @cindex async records in @sc{gdb/mi}
30825 @cindex @sc{gdb/mi}, async records
30826 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
30827 additional changes that have occurred. Those changes can either be a
30828 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
30829 target activity (e.g., target stopped).
30831 The following is the list of possible async records:
30835 @item *running,thread-id="@var{thread}"
30836 The target is now running. The @var{thread} field can be the global
30837 thread ID of the thread that is now running, and it can be
30838 @samp{all} if all threads are running. The frontend should assume
30839 that no interaction with a running thread is possible after this
30840 notification is produced. The frontend should not assume that this
30841 notification is output only once for any command. @value{GDBN} may
30842 emit this notification several times, either for different threads,
30843 because it cannot resume all threads together, or even for a single
30844 thread, if the thread must be stepped though some code before letting
30847 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
30848 The target has stopped. The @var{reason} field can have one of the
30852 @item breakpoint-hit
30853 A breakpoint was reached.
30854 @item watchpoint-trigger
30855 A watchpoint was triggered.
30856 @item read-watchpoint-trigger
30857 A read watchpoint was triggered.
30858 @item access-watchpoint-trigger
30859 An access watchpoint was triggered.
30860 @item function-finished
30861 An -exec-finish or similar CLI command was accomplished.
30862 @item location-reached
30863 An -exec-until or similar CLI command was accomplished.
30864 @item watchpoint-scope
30865 A watchpoint has gone out of scope.
30866 @item end-stepping-range
30867 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
30868 similar CLI command was accomplished.
30869 @item exited-signalled
30870 The inferior exited because of a signal.
30872 The inferior exited.
30873 @item exited-normally
30874 The inferior exited normally.
30875 @item signal-received
30876 A signal was received by the inferior.
30878 The inferior has stopped due to a library being loaded or unloaded.
30879 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
30880 set or when a @code{catch load} or @code{catch unload} catchpoint is
30881 in use (@pxref{Set Catchpoints}).
30883 The inferior has forked. This is reported when @code{catch fork}
30884 (@pxref{Set Catchpoints}) has been used.
30886 The inferior has vforked. This is reported in when @code{catch vfork}
30887 (@pxref{Set Catchpoints}) has been used.
30888 @item syscall-entry
30889 The inferior entered a system call. This is reported when @code{catch
30890 syscall} (@pxref{Set Catchpoints}) has been used.
30891 @item syscall-return
30892 The inferior returned from a system call. This is reported when
30893 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
30895 The inferior called @code{exec}. This is reported when @code{catch exec}
30896 (@pxref{Set Catchpoints}) has been used.
30898 There isn't enough history recorded to continue reverse execution.
30901 The @var{id} field identifies the global thread ID of the thread
30902 that directly caused the stop -- for example by hitting a breakpoint.
30903 Depending on whether all-stop
30904 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
30905 stop all threads, or only the thread that directly triggered the stop.
30906 If all threads are stopped, the @var{stopped} field will have the
30907 value of @code{"all"}. Otherwise, the value of the @var{stopped}
30908 field will be a list of thread identifiers. Presently, this list will
30909 always include a single thread, but frontend should be prepared to see
30910 several threads in the list. The @var{core} field reports the
30911 processor core on which the stop event has happened. This field may be absent
30912 if such information is not available.
30914 @item =thread-group-added,id="@var{id}"
30915 @itemx =thread-group-removed,id="@var{id}"
30916 A thread group was either added or removed. The @var{id} field
30917 contains the @value{GDBN} identifier of the thread group. When a thread
30918 group is added, it generally might not be associated with a running
30919 process. When a thread group is removed, its id becomes invalid and
30920 cannot be used in any way.
30922 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
30923 A thread group became associated with a running program,
30924 either because the program was just started or the thread group
30925 was attached to a program. The @var{id} field contains the
30926 @value{GDBN} identifier of the thread group. The @var{pid} field
30927 contains process identifier, specific to the operating system.
30929 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
30930 A thread group is no longer associated with a running program,
30931 either because the program has exited, or because it was detached
30932 from. The @var{id} field contains the @value{GDBN} identifier of the
30933 thread group. The @var{code} field is the exit code of the inferior; it exists
30934 only when the inferior exited with some code.
30936 @item =thread-created,id="@var{id}",group-id="@var{gid}"
30937 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
30938 A thread either was created, or has exited. The @var{id} field
30939 contains the global @value{GDBN} identifier of the thread. The @var{gid}
30940 field identifies the thread group this thread belongs to.
30942 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
30943 Informs that the selected thread or frame were changed. This notification
30944 is not emitted as result of the @code{-thread-select} or
30945 @code{-stack-select-frame} commands, but is emitted whenever an MI command
30946 that is not documented to change the selected thread and frame actually
30947 changes them. In particular, invoking, directly or indirectly
30948 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
30949 will generate this notification. Changing the thread or frame from another
30950 user interface (see @ref{Interpreters}) will also generate this notification.
30952 The @var{frame} field is only present if the newly selected thread is
30953 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
30955 We suggest that in response to this notification, front ends
30956 highlight the selected thread and cause subsequent commands to apply to
30959 @item =library-loaded,...
30960 Reports that a new library file was loaded by the program. This
30961 notification has 5 fields---@var{id}, @var{target-name},
30962 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
30963 opaque identifier of the library. For remote debugging case,
30964 @var{target-name} and @var{host-name} fields give the name of the
30965 library file on the target, and on the host respectively. For native
30966 debugging, both those fields have the same value. The
30967 @var{symbols-loaded} field is emitted only for backward compatibility
30968 and should not be relied on to convey any useful information. The
30969 @var{thread-group} field, if present, specifies the id of the thread
30970 group in whose context the library was loaded. If the field is
30971 absent, it means the library was loaded in the context of all present
30972 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
30975 @item =library-unloaded,...
30976 Reports that a library was unloaded by the program. This notification
30977 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
30978 the same meaning as for the @code{=library-loaded} notification.
30979 The @var{thread-group} field, if present, specifies the id of the
30980 thread group in whose context the library was unloaded. If the field is
30981 absent, it means the library was unloaded in the context of all present
30984 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
30985 @itemx =traceframe-changed,end
30986 Reports that the trace frame was changed and its new number is
30987 @var{tfnum}. The number of the tracepoint associated with this trace
30988 frame is @var{tpnum}.
30990 @item =tsv-created,name=@var{name},initial=@var{initial}
30991 Reports that the new trace state variable @var{name} is created with
30992 initial value @var{initial}.
30994 @item =tsv-deleted,name=@var{name}
30995 @itemx =tsv-deleted
30996 Reports that the trace state variable @var{name} is deleted or all
30997 trace state variables are deleted.
30999 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
31000 Reports that the trace state variable @var{name} is modified with
31001 the initial value @var{initial}. The current value @var{current} of
31002 trace state variable is optional and is reported if the current
31003 value of trace state variable is known.
31005 @item =breakpoint-created,bkpt=@{...@}
31006 @itemx =breakpoint-modified,bkpt=@{...@}
31007 @itemx =breakpoint-deleted,id=@var{number}
31008 Reports that a breakpoint was created, modified, or deleted,
31009 respectively. Only user-visible breakpoints are reported to the MI
31012 The @var{bkpt} argument is of the same form as returned by the various
31013 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
31014 @var{number} is the ordinal number of the breakpoint.
31016 Note that if a breakpoint is emitted in the result record of a
31017 command, then it will not also be emitted in an async record.
31019 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
31020 @itemx =record-stopped,thread-group="@var{id}"
31021 Execution log recording was either started or stopped on an
31022 inferior. The @var{id} is the @value{GDBN} identifier of the thread
31023 group corresponding to the affected inferior.
31025 The @var{method} field indicates the method used to record execution. If the
31026 method in use supports multiple recording formats, @var{format} will be present
31027 and contain the currently used format. @xref{Process Record and Replay},
31028 for existing method and format values.
31030 @item =cmd-param-changed,param=@var{param},value=@var{value}
31031 Reports that a parameter of the command @code{set @var{param}} is
31032 changed to @var{value}. In the multi-word @code{set} command,
31033 the @var{param} is the whole parameter list to @code{set} command.
31034 For example, In command @code{set check type on}, @var{param}
31035 is @code{check type} and @var{value} is @code{on}.
31037 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
31038 Reports that bytes from @var{addr} to @var{data} + @var{len} were
31039 written in an inferior. The @var{id} is the identifier of the
31040 thread group corresponding to the affected inferior. The optional
31041 @code{type="code"} part is reported if the memory written to holds
31045 @node GDB/MI Breakpoint Information
31046 @subsection @sc{gdb/mi} Breakpoint Information
31048 When @value{GDBN} reports information about a breakpoint, a
31049 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
31054 The breakpoint number.
31057 The type of the breakpoint. For ordinary breakpoints this will be
31058 @samp{breakpoint}, but many values are possible.
31061 If the type of the breakpoint is @samp{catchpoint}, then this
31062 indicates the exact type of catchpoint.
31065 This is the breakpoint disposition---either @samp{del}, meaning that
31066 the breakpoint will be deleted at the next stop, or @samp{keep},
31067 meaning that the breakpoint will not be deleted.
31070 This indicates whether the breakpoint is enabled, in which case the
31071 value is @samp{y}, or disabled, in which case the value is @samp{n}.
31072 Note that this is not the same as the field @code{enable}.
31075 The address of the breakpoint. This may be a hexidecimal number,
31076 giving the address; or the string @samp{<PENDING>}, for a pending
31077 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
31078 multiple locations. This field will not be present if no address can
31079 be determined. For example, a watchpoint does not have an address.
31082 Optional field containing any flags related to the address. These flags are
31083 architecture-dependent; see @ref{Architectures} for their meaning for a
31087 If known, the function in which the breakpoint appears.
31088 If not known, this field is not present.
31091 The name of the source file which contains this function, if known.
31092 If not known, this field is not present.
31095 The full file name of the source file which contains this function, if
31096 known. If not known, this field is not present.
31099 The line number at which this breakpoint appears, if known.
31100 If not known, this field is not present.
31103 If the source file is not known, this field may be provided. If
31104 provided, this holds the address of the breakpoint, possibly followed
31108 If this breakpoint is pending, this field is present and holds the
31109 text used to set the breakpoint, as entered by the user.
31112 Where this breakpoint's condition is evaluated, either @samp{host} or
31116 If this is a thread-specific breakpoint, then this identifies the
31117 thread in which the breakpoint can trigger.
31120 If this breakpoint is restricted to a particular Ada task, then this
31121 field will hold the task identifier.
31124 If the breakpoint is conditional, this is the condition expression.
31127 The ignore count of the breakpoint.
31130 The enable count of the breakpoint.
31132 @item traceframe-usage
31135 @item static-tracepoint-marker-string-id
31136 For a static tracepoint, the name of the static tracepoint marker.
31139 For a masked watchpoint, this is the mask.
31142 A tracepoint's pass count.
31144 @item original-location
31145 The location of the breakpoint as originally specified by the user.
31146 This field is optional.
31149 The number of times the breakpoint has been hit.
31152 This field is only given for tracepoints. This is either @samp{y},
31153 meaning that the tracepoint is installed, or @samp{n}, meaning that it
31157 Some extra data, the exact contents of which are type-dependent.
31160 This field is present if the breakpoint has multiple locations. It is also
31161 exceptionally present if the breakpoint is enabled and has a single, disabled
31164 The value is a list of locations. The format of a location is described below.
31168 A location in a multi-location breakpoint is represented as a tuple with the
31174 The location number as a dotted pair, like @samp{1.2}. The first digit is the
31175 number of the parent breakpoint. The second digit is the number of the
31176 location within that breakpoint.
31179 There are three possible values, with the following meanings:
31182 The location is enabled.
31184 The location is disabled by the user.
31186 The location is disabled because the breakpoint condition is invalid
31191 The address of this location as an hexidecimal number.
31194 Optional field containing any flags related to the address. These flags are
31195 architecture-dependent; see @ref{Architectures} for their meaning for a
31199 If known, the function in which the location appears.
31200 If not known, this field is not present.
31203 The name of the source file which contains this location, if known.
31204 If not known, this field is not present.
31207 The full file name of the source file which contains this location, if
31208 known. If not known, this field is not present.
31211 The line number at which this location appears, if known.
31212 If not known, this field is not present.
31214 @item thread-groups
31215 The thread groups this location is in.
31219 For example, here is what the output of @code{-break-insert}
31220 (@pxref{GDB/MI Breakpoint Commands}) might be:
31223 -> -break-insert main
31224 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31225 enabled="y",addr="0x08048564",func="main",file="myprog.c",
31226 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
31231 @node GDB/MI Frame Information
31232 @subsection @sc{gdb/mi} Frame Information
31234 Response from many MI commands includes an information about stack
31235 frame. This information is a tuple that may have the following
31240 The level of the stack frame. The innermost frame has the level of
31241 zero. This field is always present.
31244 The name of the function corresponding to the frame. This field may
31245 be absent if @value{GDBN} is unable to determine the function name.
31248 The code address for the frame. This field is always present.
31251 Optional field containing any flags related to the address. These flags are
31252 architecture-dependent; see @ref{Architectures} for their meaning for a
31256 The name of the source files that correspond to the frame's code
31257 address. This field may be absent.
31260 The source line corresponding to the frames' code address. This field
31264 The name of the binary file (either executable or shared library) the
31265 corresponds to the frame's code address. This field may be absent.
31269 @node GDB/MI Thread Information
31270 @subsection @sc{gdb/mi} Thread Information
31272 Whenever @value{GDBN} has to report an information about a thread, it
31273 uses a tuple with the following fields. The fields are always present unless
31278 The global numeric id assigned to the thread by @value{GDBN}.
31281 The target-specific string identifying the thread.
31284 Additional information about the thread provided by the target.
31285 It is supposed to be human-readable and not interpreted by the
31286 frontend. This field is optional.
31289 The name of the thread. If the user specified a name using the
31290 @code{thread name} command, then this name is given. Otherwise, if
31291 @value{GDBN} can extract the thread name from the target, then that
31292 name is given. If @value{GDBN} cannot find the thread name, then this
31296 The execution state of the thread, either @samp{stopped} or @samp{running},
31297 depending on whether the thread is presently running.
31300 The stack frame currently executing in the thread. This field is only present
31301 if the thread is stopped. Its format is documented in
31302 @ref{GDB/MI Frame Information}.
31305 The value of this field is an integer number of the processor core the
31306 thread was last seen on. This field is optional.
31309 @node GDB/MI Ada Exception Information
31310 @subsection @sc{gdb/mi} Ada Exception Information
31312 Whenever a @code{*stopped} record is emitted because the program
31313 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
31314 @value{GDBN} provides the name of the exception that was raised via
31315 the @code{exception-name} field. Also, for exceptions that were raised
31316 with an exception message, @value{GDBN} provides that message via
31317 the @code{exception-message} field.
31319 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31320 @node GDB/MI Simple Examples
31321 @section Simple Examples of @sc{gdb/mi} Interaction
31322 @cindex @sc{gdb/mi}, simple examples
31324 This subsection presents several simple examples of interaction using
31325 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
31326 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
31327 the output received from @sc{gdb/mi}.
31329 Note the line breaks shown in the examples are here only for
31330 readability, they don't appear in the real output.
31332 @subheading Setting a Breakpoint
31334 Setting a breakpoint generates synchronous output which contains detailed
31335 information of the breakpoint.
31338 -> -break-insert main
31339 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31340 enabled="y",addr="0x08048564",func="main",file="myprog.c",
31341 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
31346 @subheading Program Execution
31348 Program execution generates asynchronous records and MI gives the
31349 reason that execution stopped.
31355 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31356 frame=@{addr="0x08048564",func="main",
31357 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
31358 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
31359 arch="i386:x86_64"@}
31364 <- *stopped,reason="exited-normally"
31368 @subheading Quitting @value{GDBN}
31370 Quitting @value{GDBN} just prints the result class @samp{^exit}.
31378 Please note that @samp{^exit} is printed immediately, but it might
31379 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
31380 performs necessary cleanups, including killing programs being debugged
31381 or disconnecting from debug hardware, so the frontend should wait till
31382 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
31383 fails to exit in reasonable time.
31385 @subheading A Bad Command
31387 Here's what happens if you pass a non-existent command:
31391 <- ^error,msg="Undefined MI command: rubbish"
31396 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31397 @node GDB/MI Command Description Format
31398 @section @sc{gdb/mi} Command Description Format
31400 The remaining sections describe blocks of commands. Each block of
31401 commands is laid out in a fashion similar to this section.
31403 @subheading Motivation
31405 The motivation for this collection of commands.
31407 @subheading Introduction
31409 A brief introduction to this collection of commands as a whole.
31411 @subheading Commands
31413 For each command in the block, the following is described:
31415 @subsubheading Synopsis
31418 -command @var{args}@dots{}
31421 @subsubheading Result
31423 @subsubheading @value{GDBN} Command
31425 The corresponding @value{GDBN} CLI command(s), if any.
31427 @subsubheading Example
31429 Example(s) formatted for readability. Some of the described commands have
31430 not been implemented yet and these are labeled N.A.@: (not available).
31433 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31434 @node GDB/MI Breakpoint Commands
31435 @section @sc{gdb/mi} Breakpoint Commands
31437 @cindex breakpoint commands for @sc{gdb/mi}
31438 @cindex @sc{gdb/mi}, breakpoint commands
31439 This section documents @sc{gdb/mi} commands for manipulating
31442 @subheading The @code{-break-after} Command
31443 @findex -break-after
31445 @subsubheading Synopsis
31448 -break-after @var{number} @var{count}
31451 The breakpoint number @var{number} is not in effect until it has been
31452 hit @var{count} times. To see how this is reflected in the output of
31453 the @samp{-break-list} command, see the description of the
31454 @samp{-break-list} command below.
31456 @subsubheading @value{GDBN} Command
31458 The corresponding @value{GDBN} command is @samp{ignore}.
31460 @subsubheading Example
31465 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31466 enabled="y",addr="0x000100d0",func="main",file="hello.c",
31467 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
31475 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31476 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31477 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31478 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31479 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31480 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31481 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31482 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31483 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31484 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
31489 @subheading The @code{-break-catch} Command
31490 @findex -break-catch
31493 @subheading The @code{-break-commands} Command
31494 @findex -break-commands
31496 @subsubheading Synopsis
31499 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
31502 Specifies the CLI commands that should be executed when breakpoint
31503 @var{number} is hit. The parameters @var{command1} to @var{commandN}
31504 are the commands. If no command is specified, any previously-set
31505 commands are cleared. @xref{Break Commands}. Typical use of this
31506 functionality is tracing a program, that is, printing of values of
31507 some variables whenever breakpoint is hit and then continuing.
31509 @subsubheading @value{GDBN} Command
31511 The corresponding @value{GDBN} command is @samp{commands}.
31513 @subsubheading Example
31518 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
31519 enabled="y",addr="0x000100d0",func="main",file="hello.c",
31520 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
31523 -break-commands 1 "print v" "continue"
31528 @subheading The @code{-break-condition} Command
31529 @findex -break-condition
31531 @subsubheading Synopsis
31534 -break-condition [ --force ] @var{number} [ @var{expr} ]
31537 Breakpoint @var{number} will stop the program only if the condition in
31538 @var{expr} is true. The condition becomes part of the
31539 @samp{-break-list} output (see the description of the @samp{-break-list}
31540 command below). If the @samp{--force} flag is passed, the condition
31541 is forcibly defined even when it is invalid for all locations of
31542 breakpoint @var{number}. If the @var{expr} argument is omitted,
31543 breakpoint @var{number} becomes unconditional.
31545 @subsubheading @value{GDBN} Command
31547 The corresponding @value{GDBN} command is @samp{condition}.
31549 @subsubheading Example
31553 -break-condition 1 1
31557 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31558 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31559 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31560 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31561 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31562 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31563 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31564 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31565 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31566 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
31570 @subheading The @code{-break-delete} Command
31571 @findex -break-delete
31573 @subsubheading Synopsis
31576 -break-delete ( @var{breakpoint} )+
31579 Delete the breakpoint(s) whose number(s) are specified in the argument
31580 list. This is obviously reflected in the breakpoint list.
31582 @subsubheading @value{GDBN} Command
31584 The corresponding @value{GDBN} command is @samp{delete}.
31586 @subsubheading Example
31594 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31595 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31596 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31597 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31598 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31599 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31600 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31605 @subheading The @code{-break-disable} Command
31606 @findex -break-disable
31608 @subsubheading Synopsis
31611 -break-disable ( @var{breakpoint} )+
31614 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
31615 break list is now set to @samp{n} for the named @var{breakpoint}(s).
31617 @subsubheading @value{GDBN} Command
31619 The corresponding @value{GDBN} command is @samp{disable}.
31621 @subsubheading Example
31629 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31630 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31631 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31632 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31633 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31634 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31635 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31636 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
31637 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31638 line="5",thread-groups=["i1"],times="0"@}]@}
31642 @subheading The @code{-break-enable} Command
31643 @findex -break-enable
31645 @subsubheading Synopsis
31648 -break-enable ( @var{breakpoint} )+
31651 Enable (previously disabled) @var{breakpoint}(s).
31653 @subsubheading @value{GDBN} Command
31655 The corresponding @value{GDBN} command is @samp{enable}.
31657 @subsubheading Example
31665 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31666 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31667 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31668 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31669 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31670 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31671 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31672 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31673 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31674 line="5",thread-groups=["i1"],times="0"@}]@}
31678 @subheading The @code{-break-info} Command
31679 @findex -break-info
31681 @subsubheading Synopsis
31684 -break-info @var{breakpoint}
31688 Get information about a single breakpoint.
31690 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
31691 Information}, for details on the format of each breakpoint in the
31694 @subsubheading @value{GDBN} Command
31696 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
31698 @subsubheading Example
31701 @subheading The @code{-break-insert} Command
31702 @findex -break-insert
31703 @anchor{-break-insert}
31705 @subsubheading Synopsis
31708 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
31709 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
31710 [ -p @var{thread-id} ] [ @var{locspec} ]
31714 If specified, @var{locspec}, can be one of:
31717 @item linespec location
31718 A linespec location. @xref{Linespec Locations}.
31720 @item explicit location
31721 An explicit location. @sc{gdb/mi} explicit locations are
31722 analogous to the CLI's explicit locations using the option names
31723 listed below. @xref{Explicit Locations}.
31726 @item --source @var{filename}
31727 The source file name of the location. This option requires the use
31728 of either @samp{--function} or @samp{--line}.
31730 @item --function @var{function}
31731 The name of a function or method.
31733 @item --label @var{label}
31734 The name of a label.
31736 @item --line @var{lineoffset}
31737 An absolute or relative line offset from the start of the location.
31740 @item address location
31741 An address location, *@var{address}. @xref{Address Locations}.
31745 The possible optional parameters of this command are:
31749 Insert a temporary breakpoint.
31751 Insert a hardware breakpoint.
31753 If @var{locspec} cannot be resolved (for example if it
31754 refers to unknown files or functions), create a pending
31755 breakpoint. Without this flag, @value{GDBN} will report
31756 an error, and won't create a breakpoint, if @var{locspec}
31759 Create a disabled breakpoint.
31761 Create a tracepoint. @xref{Tracepoints}. When this parameter
31762 is used together with @samp{-h}, a fast tracepoint is created.
31763 @item -c @var{condition}
31764 Make the breakpoint conditional on @var{condition}.
31765 @item --force-condition
31766 Forcibly define the breakpoint even if the condition is invalid at
31767 all of the breakpoint locations.
31768 @item -i @var{ignore-count}
31769 Initialize the @var{ignore-count}.
31770 @item -p @var{thread-id}
31771 Restrict the breakpoint to the thread with the specified global
31774 This option makes @value{GDBN} interpret a function name specified as
31775 a complete fully-qualified name.
31778 @subsubheading Result
31780 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31781 resulting breakpoint.
31783 Note: this format is open to change.
31784 @c An out-of-band breakpoint instead of part of the result?
31786 @subsubheading @value{GDBN} Command
31788 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
31789 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
31791 @subsubheading Example
31796 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
31797 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
31800 -break-insert -t foo
31801 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
31802 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
31806 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31807 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31808 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31809 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31810 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31811 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31812 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31813 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31814 addr="0x0001072c", func="main",file="recursive2.c",
31815 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
31817 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
31818 addr="0x00010774",func="foo",file="recursive2.c",
31819 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31824 @subheading The @code{-dprintf-insert} Command
31825 @findex -dprintf-insert
31827 @subsubheading Synopsis
31830 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
31831 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
31832 [ -p @var{thread-id} ] [ @var{locspec} ] [ @var{format} ]
31837 If supplied, @var{locspec} and @code{--qualified} may be specified
31838 the same way as for the @code{-break-insert} command.
31839 @xref{-break-insert}.
31841 The possible optional parameters of this command are:
31845 Insert a temporary breakpoint.
31847 If @var{locspec} cannot be parsed (for example, if it
31848 refers to unknown files or functions), create a pending
31849 breakpoint. Without this flag, @value{GDBN} will report
31850 an error, and won't create a breakpoint, if @var{locspec}
31853 Create a disabled breakpoint.
31854 @item -c @var{condition}
31855 Make the breakpoint conditional on @var{condition}.
31856 @item --force-condition
31857 Forcibly define the breakpoint even if the condition is invalid at
31858 all of the breakpoint locations.
31859 @item -i @var{ignore-count}
31860 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
31861 to @var{ignore-count}.
31862 @item -p @var{thread-id}
31863 Restrict the breakpoint to the thread with the specified global
31867 @subsubheading Result
31869 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31870 resulting breakpoint.
31872 @c An out-of-band breakpoint instead of part of the result?
31874 @subsubheading @value{GDBN} Command
31876 The corresponding @value{GDBN} command is @samp{dprintf}.
31878 @subsubheading Example
31882 4-dprintf-insert foo "At foo entry\n"
31883 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
31884 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
31885 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
31886 times="0",script=["printf \"At foo entry\\n\"","continue"],
31887 original-location="foo"@}
31889 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
31890 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
31891 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
31892 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
31893 times="0",script=["printf \"arg=%d, g=%d\\n\", arg, g","continue"],
31894 original-location="mi-dprintf.c:26"@}
31898 @subheading The @code{-break-list} Command
31899 @findex -break-list
31901 @subsubheading Synopsis
31907 Displays the list of inserted breakpoints, showing the following fields:
31911 number of the breakpoint
31913 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
31915 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
31918 is the breakpoint enabled or no: @samp{y} or @samp{n}
31920 memory location at which the breakpoint is set
31922 logical location of the breakpoint, expressed by function name, file
31924 @item Thread-groups
31925 list of thread groups to which this breakpoint applies
31927 number of times the breakpoint has been hit
31930 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
31931 @code{body} field is an empty list.
31933 @subsubheading @value{GDBN} Command
31935 The corresponding @value{GDBN} command is @samp{info break}.
31937 @subsubheading Example
31942 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31943 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31944 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31945 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31946 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31947 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31948 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31949 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31950 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
31952 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31953 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
31954 line="13",thread-groups=["i1"],times="0"@}]@}
31958 Here's an example of the result when there are no breakpoints:
31963 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31964 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31965 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31966 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31967 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31968 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31969 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31974 @subheading The @code{-break-passcount} Command
31975 @findex -break-passcount
31977 @subsubheading Synopsis
31980 -break-passcount @var{tracepoint-number} @var{passcount}
31983 Set the passcount for tracepoint @var{tracepoint-number} to
31984 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
31985 is not a tracepoint, error is emitted. This corresponds to CLI
31986 command @samp{passcount}.
31988 @subheading The @code{-break-watch} Command
31989 @findex -break-watch
31991 @subsubheading Synopsis
31994 -break-watch [ -a | -r ]
31997 Create a watchpoint. With the @samp{-a} option it will create an
31998 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
31999 read from or on a write to the memory location. With the @samp{-r}
32000 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
32001 trigger only when the memory location is accessed for reading. Without
32002 either of the options, the watchpoint created is a regular watchpoint,
32003 i.e., it will trigger when the memory location is accessed for writing.
32004 @xref{Set Watchpoints, , Setting Watchpoints}.
32006 Note that @samp{-break-list} will report a single list of watchpoints and
32007 breakpoints inserted.
32009 @subsubheading @value{GDBN} Command
32011 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
32014 @subsubheading Example
32016 Setting a watchpoint on a variable in the @code{main} function:
32021 ^done,wpt=@{number="2",exp="x"@}
32026 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
32027 value=@{old="-268439212",new="55"@},
32028 frame=@{func="main",args=[],file="recursive2.c",
32029 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
32033 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
32034 the program execution twice: first for the variable changing value, then
32035 for the watchpoint going out of scope.
32040 ^done,wpt=@{number="5",exp="C"@}
32045 *stopped,reason="watchpoint-trigger",
32046 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
32047 frame=@{func="callee4",args=[],
32048 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32049 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
32050 arch="i386:x86_64"@}
32055 *stopped,reason="watchpoint-scope",wpnum="5",
32056 frame=@{func="callee3",args=[@{name="strarg",
32057 value="0x11940 \"A string argument.\""@}],
32058 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32059 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32060 arch="i386:x86_64"@}
32064 Listing breakpoints and watchpoints, at different points in the program
32065 execution. Note that once the watchpoint goes out of scope, it is
32071 ^done,wpt=@{number="2",exp="C"@}
32074 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
32075 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32076 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32077 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32078 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32079 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32080 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32081 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32082 addr="0x00010734",func="callee4",
32083 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32084 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
32086 bkpt=@{number="2",type="watchpoint",disp="keep",
32087 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
32092 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
32093 value=@{old="-276895068",new="3"@},
32094 frame=@{func="callee4",args=[],
32095 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32096 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
32097 arch="i386:x86_64"@}
32100 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
32101 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32102 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32103 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32104 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32105 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32106 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32107 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32108 addr="0x00010734",func="callee4",
32109 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32110 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
32112 bkpt=@{number="2",type="watchpoint",disp="keep",
32113 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
32117 ^done,reason="watchpoint-scope",wpnum="2",
32118 frame=@{func="callee3",args=[@{name="strarg",
32119 value="0x11940 \"A string argument.\""@}],
32120 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32121 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32122 arch="i386:x86_64"@}
32125 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
32126 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
32127 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
32128 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
32129 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
32130 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
32131 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
32132 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32133 addr="0x00010734",func="callee4",
32134 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32135 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32136 thread-groups=["i1"],times="1"@}]@}
32141 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32142 @node GDB/MI Catchpoint Commands
32143 @section @sc{gdb/mi} Catchpoint Commands
32145 This section documents @sc{gdb/mi} commands for manipulating
32149 * Shared Library GDB/MI Catchpoint Commands::
32150 * Ada Exception GDB/MI Catchpoint Commands::
32151 * C++ Exception GDB/MI Catchpoint Commands::
32154 @node Shared Library GDB/MI Catchpoint Commands
32155 @subsection Shared Library @sc{gdb/mi} Catchpoints
32157 @subheading The @code{-catch-load} Command
32158 @findex -catch-load
32160 @subsubheading Synopsis
32163 -catch-load [ -t ] [ -d ] @var{regexp}
32166 Add a catchpoint for library load events. If the @samp{-t} option is used,
32167 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
32168 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
32169 in a disabled state. The @samp{regexp} argument is a regular
32170 expression used to match the name of the loaded library.
32173 @subsubheading @value{GDBN} Command
32175 The corresponding @value{GDBN} command is @samp{catch load}.
32177 @subsubheading Example
32180 -catch-load -t foo.so
32181 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
32182 what="load of library matching foo.so",catch-type="load",times="0"@}
32187 @subheading The @code{-catch-unload} Command
32188 @findex -catch-unload
32190 @subsubheading Synopsis
32193 -catch-unload [ -t ] [ -d ] @var{regexp}
32196 Add a catchpoint for library unload events. If the @samp{-t} option is
32197 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
32198 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
32199 created in a disabled state. The @samp{regexp} argument is a regular
32200 expression used to match the name of the unloaded library.
32202 @subsubheading @value{GDBN} Command
32204 The corresponding @value{GDBN} command is @samp{catch unload}.
32206 @subsubheading Example
32209 -catch-unload -d bar.so
32210 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
32211 what="load of library matching bar.so",catch-type="unload",times="0"@}
32215 @node Ada Exception GDB/MI Catchpoint Commands
32216 @subsection Ada Exception @sc{gdb/mi} Catchpoints
32218 The following @sc{gdb/mi} commands can be used to create catchpoints
32219 that stop the execution when Ada exceptions are being raised.
32221 @subheading The @code{-catch-assert} Command
32222 @findex -catch-assert
32224 @subsubheading Synopsis
32227 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
32230 Add a catchpoint for failed Ada assertions.
32232 The possible optional parameters for this command are:
32235 @item -c @var{condition}
32236 Make the catchpoint conditional on @var{condition}.
32238 Create a disabled catchpoint.
32240 Create a temporary catchpoint.
32243 @subsubheading @value{GDBN} Command
32245 The corresponding @value{GDBN} command is @samp{catch assert}.
32247 @subsubheading Example
32251 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
32252 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
32253 thread-groups=["i1"],times="0",
32254 original-location="__gnat_debug_raise_assert_failure"@}
32258 @subheading The @code{-catch-exception} Command
32259 @findex -catch-exception
32261 @subsubheading Synopsis
32264 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
32268 Add a catchpoint stopping when Ada exceptions are raised.
32269 By default, the command stops the program when any Ada exception
32270 gets raised. But it is also possible, by using some of the
32271 optional parameters described below, to create more selective
32274 The possible optional parameters for this command are:
32277 @item -c @var{condition}
32278 Make the catchpoint conditional on @var{condition}.
32280 Create a disabled catchpoint.
32281 @item -e @var{exception-name}
32282 Only stop when @var{exception-name} is raised. This option cannot
32283 be used combined with @samp{-u}.
32285 Create a temporary catchpoint.
32287 Stop only when an unhandled exception gets raised. This option
32288 cannot be used combined with @samp{-e}.
32291 @subsubheading @value{GDBN} Command
32293 The corresponding @value{GDBN} commands are @samp{catch exception}
32294 and @samp{catch exception unhandled}.
32296 @subsubheading Example
32299 -catch-exception -e Program_Error
32300 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
32301 enabled="y",addr="0x0000000000404874",
32302 what="`Program_Error' Ada exception", thread-groups=["i1"],
32303 times="0",original-location="__gnat_debug_raise_exception"@}
32307 @subheading The @code{-catch-handlers} Command
32308 @findex -catch-handlers
32310 @subsubheading Synopsis
32313 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
32317 Add a catchpoint stopping when Ada exceptions are handled.
32318 By default, the command stops the program when any Ada exception
32319 gets handled. But it is also possible, by using some of the
32320 optional parameters described below, to create more selective
32323 The possible optional parameters for this command are:
32326 @item -c @var{condition}
32327 Make the catchpoint conditional on @var{condition}.
32329 Create a disabled catchpoint.
32330 @item -e @var{exception-name}
32331 Only stop when @var{exception-name} is handled.
32333 Create a temporary catchpoint.
32336 @subsubheading @value{GDBN} Command
32338 The corresponding @value{GDBN} command is @samp{catch handlers}.
32340 @subsubheading Example
32343 -catch-handlers -e Constraint_Error
32344 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
32345 enabled="y",addr="0x0000000000402f68",
32346 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
32347 times="0",original-location="__gnat_begin_handler"@}
32351 @node C++ Exception GDB/MI Catchpoint Commands
32352 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
32354 The following @sc{gdb/mi} commands can be used to create catchpoints
32355 that stop the execution when C@t{++} exceptions are being throw, rethrown,
32358 @subheading The @code{-catch-throw} Command
32359 @findex -catch-throw
32361 @subsubheading Synopsis
32364 -catch-throw [ -t ] [ -r @var{regexp}]
32367 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
32368 given, then only exceptions whose type matches the regular expression
32371 If @samp{-t} is given, then the catchpoint is enabled only for one
32372 stop, the catchpoint is automatically deleted after stopping once for
32375 @subsubheading @value{GDBN} Command
32377 The corresponding @value{GDBN} commands are @samp{catch throw}
32378 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
32380 @subsubheading Example
32383 -catch-throw -r exception_type
32384 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32385 what="exception throw",catch-type="throw",
32386 thread-groups=["i1"],
32387 regexp="exception_type",times="0"@}
32393 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
32394 in __cxa_throw () from /lib64/libstdc++.so.6\n"
32395 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32396 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
32397 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32398 thread-id="1",stopped-threads="all",core="6"
32402 @subheading The @code{-catch-rethrow} Command
32403 @findex -catch-rethrow
32405 @subsubheading Synopsis
32408 -catch-rethrow [ -t ] [ -r @var{regexp}]
32411 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
32412 then only exceptions whose type matches the regular expression will be
32415 If @samp{-t} is given, then the catchpoint is enabled only for one
32416 stop, the catchpoint is automatically deleted after the first event is
32419 @subsubheading @value{GDBN} Command
32421 The corresponding @value{GDBN} commands are @samp{catch rethrow}
32422 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
32424 @subsubheading Example
32427 -catch-rethrow -r exception_type
32428 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32429 what="exception rethrow",catch-type="rethrow",
32430 thread-groups=["i1"],
32431 regexp="exception_type",times="0"@}
32437 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
32438 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
32439 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32440 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
32441 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32442 thread-id="1",stopped-threads="all",core="6"
32446 @subheading The @code{-catch-catch} Command
32447 @findex -catch-catch
32449 @subsubheading Synopsis
32452 -catch-catch [ -t ] [ -r @var{regexp}]
32455 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
32456 is given, then only exceptions whose type matches the regular
32457 expression will be caught.
32459 If @samp{-t} is given, then the catchpoint is enabled only for one
32460 stop, the catchpoint is automatically deleted after the first event is
32463 @subsubheading @value{GDBN} Command
32465 The corresponding @value{GDBN} commands are @samp{catch catch}
32466 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
32468 @subsubheading Example
32471 -catch-catch -r exception_type
32472 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
32473 what="exception catch",catch-type="catch",
32474 thread-groups=["i1"],
32475 regexp="exception_type",times="0"@}
32481 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
32482 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
32483 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
32484 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
32485 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
32486 thread-id="1",stopped-threads="all",core="6"
32490 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32491 @node GDB/MI Program Context
32492 @section @sc{gdb/mi} Program Context
32494 @subheading The @code{-exec-arguments} Command
32495 @findex -exec-arguments
32498 @subsubheading Synopsis
32501 -exec-arguments @var{args}
32504 Set the inferior program arguments, to be used in the next
32507 @subsubheading @value{GDBN} Command
32509 The corresponding @value{GDBN} command is @samp{set args}.
32511 @subsubheading Example
32515 -exec-arguments -v word
32522 @subheading The @code{-exec-show-arguments} Command
32523 @findex -exec-show-arguments
32525 @subsubheading Synopsis
32528 -exec-show-arguments
32531 Print the arguments of the program.
32533 @subsubheading @value{GDBN} Command
32535 The corresponding @value{GDBN} command is @samp{show args}.
32537 @subsubheading Example
32542 @subheading The @code{-environment-cd} Command
32543 @findex -environment-cd
32545 @subsubheading Synopsis
32548 -environment-cd @var{pathdir}
32551 Set @value{GDBN}'s working directory.
32553 @subsubheading @value{GDBN} Command
32555 The corresponding @value{GDBN} command is @samp{cd}.
32557 @subsubheading Example
32561 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32567 @subheading The @code{-environment-directory} Command
32568 @findex -environment-directory
32570 @subsubheading Synopsis
32573 -environment-directory [ -r ] [ @var{pathdir} ]+
32576 Add directories @var{pathdir} to beginning of search path for source files.
32577 If the @samp{-r} option is used, the search path is reset to the default
32578 search path. If directories @var{pathdir} are supplied in addition to the
32579 @samp{-r} option, the search path is first reset and then addition
32581 Multiple directories may be specified, separated by blanks. Specifying
32582 multiple directories in a single command
32583 results in the directories added to the beginning of the
32584 search path in the same order they were presented in the command.
32585 If blanks are needed as
32586 part of a directory name, double-quotes should be used around
32587 the name. In the command output, the path will show up separated
32588 by the system directory-separator character. The directory-separator
32589 character must not be used
32590 in any directory name.
32591 If no directories are specified, the current search path is displayed.
32593 @subsubheading @value{GDBN} Command
32595 The corresponding @value{GDBN} command is @samp{dir}.
32597 @subsubheading Example
32601 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32602 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32604 -environment-directory ""
32605 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32607 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
32608 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
32610 -environment-directory -r
32611 ^done,source-path="$cdir:$cwd"
32616 @subheading The @code{-environment-path} Command
32617 @findex -environment-path
32619 @subsubheading Synopsis
32622 -environment-path [ -r ] [ @var{pathdir} ]+
32625 Add directories @var{pathdir} to beginning of search path for object files.
32626 If the @samp{-r} option is used, the search path is reset to the original
32627 search path that existed at gdb start-up. If directories @var{pathdir} are
32628 supplied in addition to the
32629 @samp{-r} option, the search path is first reset and then addition
32631 Multiple directories may be specified, separated by blanks. Specifying
32632 multiple directories in a single command
32633 results in the directories added to the beginning of the
32634 search path in the same order they were presented in the command.
32635 If blanks are needed as
32636 part of a directory name, double-quotes should be used around
32637 the name. In the command output, the path will show up separated
32638 by the system directory-separator character. The directory-separator
32639 character must not be used
32640 in any directory name.
32641 If no directories are specified, the current path is displayed.
32644 @subsubheading @value{GDBN} Command
32646 The corresponding @value{GDBN} command is @samp{path}.
32648 @subsubheading Example
32653 ^done,path="/usr/bin"
32655 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
32656 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
32658 -environment-path -r /usr/local/bin
32659 ^done,path="/usr/local/bin:/usr/bin"
32664 @subheading The @code{-environment-pwd} Command
32665 @findex -environment-pwd
32667 @subsubheading Synopsis
32673 Show the current working directory.
32675 @subsubheading @value{GDBN} Command
32677 The corresponding @value{GDBN} command is @samp{pwd}.
32679 @subsubheading Example
32684 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
32688 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32689 @node GDB/MI Thread Commands
32690 @section @sc{gdb/mi} Thread Commands
32693 @subheading The @code{-thread-info} Command
32694 @findex -thread-info
32696 @subsubheading Synopsis
32699 -thread-info [ @var{thread-id} ]
32702 Reports information about either a specific thread, if the
32703 @var{thread-id} parameter is present, or about all threads.
32704 @var{thread-id} is the thread's global thread ID. When printing
32705 information about all threads, also reports the global ID of the
32708 @subsubheading @value{GDBN} Command
32710 The @samp{info thread} command prints the same information
32713 @subsubheading Result
32715 The result contains the following attributes:
32719 A list of threads. The format of the elements of the list is described in
32720 @ref{GDB/MI Thread Information}.
32722 @item current-thread-id
32723 The global id of the currently selected thread. This field is omitted if there
32724 is no selected thread (for example, when the selected inferior is not running,
32725 and therefore has no threads) or if a @var{thread-id} argument was passed to
32730 @subsubheading Example
32735 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32736 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
32737 args=[]@},state="running"@},
32738 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32739 frame=@{level="0",addr="0x0804891f",func="foo",
32740 args=[@{name="i",value="10"@}],
32741 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
32742 state="running"@}],
32743 current-thread-id="1"
32747 @subheading The @code{-thread-list-ids} Command
32748 @findex -thread-list-ids
32750 @subsubheading Synopsis
32756 Produces a list of the currently known global @value{GDBN} thread ids.
32757 At the end of the list it also prints the total number of such
32760 This command is retained for historical reasons, the
32761 @code{-thread-info} command should be used instead.
32763 @subsubheading @value{GDBN} Command
32765 Part of @samp{info threads} supplies the same information.
32767 @subsubheading Example
32772 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32773 current-thread-id="1",number-of-threads="3"
32778 @subheading The @code{-thread-select} Command
32779 @findex -thread-select
32781 @subsubheading Synopsis
32784 -thread-select @var{thread-id}
32787 Make thread with global thread number @var{thread-id} the current
32788 thread. It prints the number of the new current thread, and the
32789 topmost frame for that thread.
32791 This command is deprecated in favor of explicitly using the
32792 @samp{--thread} option to each command.
32794 @subsubheading @value{GDBN} Command
32796 The corresponding @value{GDBN} command is @samp{thread}.
32798 @subsubheading Example
32805 *stopped,reason="end-stepping-range",thread-id="2",line="187",
32806 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
32810 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32811 number-of-threads="3"
32814 ^done,new-thread-id="3",
32815 frame=@{level="0",func="vprintf",
32816 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
32817 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
32821 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32822 @node GDB/MI Ada Tasking Commands
32823 @section @sc{gdb/mi} Ada Tasking Commands
32825 @subheading The @code{-ada-task-info} Command
32826 @findex -ada-task-info
32828 @subsubheading Synopsis
32831 -ada-task-info [ @var{task-id} ]
32834 Reports information about either a specific Ada task, if the
32835 @var{task-id} parameter is present, or about all Ada tasks.
32837 @subsubheading @value{GDBN} Command
32839 The @samp{info tasks} command prints the same information
32840 about all Ada tasks (@pxref{Ada Tasks}).
32842 @subsubheading Result
32844 The result is a table of Ada tasks. The following columns are
32845 defined for each Ada task:
32849 This field exists only for the current thread. It has the value @samp{*}.
32852 The identifier that @value{GDBN} uses to refer to the Ada task.
32855 The identifier that the target uses to refer to the Ada task.
32858 The global thread identifier of the thread corresponding to the Ada
32861 This field should always exist, as Ada tasks are always implemented
32862 on top of a thread. But if @value{GDBN} cannot find this corresponding
32863 thread for any reason, the field is omitted.
32866 This field exists only when the task was created by another task.
32867 In this case, it provides the ID of the parent task.
32870 The base priority of the task.
32873 The current state of the task. For a detailed description of the
32874 possible states, see @ref{Ada Tasks}.
32877 The name of the task.
32881 @subsubheading Example
32885 ^done,tasks=@{nr_rows="3",nr_cols="8",
32886 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
32887 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
32888 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
32889 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
32890 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
32891 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
32892 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
32893 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
32894 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
32895 state="Child Termination Wait",name="main_task"@}]@}
32899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32900 @node GDB/MI Program Execution
32901 @section @sc{gdb/mi} Program Execution
32903 These are the asynchronous commands which generate the out-of-band
32904 record @samp{*stopped}. Currently @value{GDBN} only really executes
32905 asynchronously with remote targets and this interaction is mimicked in
32908 @subheading The @code{-exec-continue} Command
32909 @findex -exec-continue
32911 @subsubheading Synopsis
32914 -exec-continue [--reverse] [--all|--thread-group N]
32917 Resumes the execution of the inferior program, which will continue
32918 to execute until it reaches a debugger stop event. If the
32919 @samp{--reverse} option is specified, execution resumes in reverse until
32920 it reaches a stop event. Stop events may include
32923 breakpoints or watchpoints
32925 signals or exceptions
32927 the end of the process (or its beginning under @samp{--reverse})
32929 the end or beginning of a replay log if one is being used.
32931 In all-stop mode (@pxref{All-Stop
32932 Mode}), may resume only one thread, or all threads, depending on the
32933 value of the @samp{scheduler-locking} variable. If @samp{--all} is
32934 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
32935 ignored in all-stop mode. If the @samp{--thread-group} options is
32936 specified, then all threads in that thread group are resumed.
32938 @subsubheading @value{GDBN} Command
32940 The corresponding @value{GDBN} corresponding is @samp{continue}.
32942 @subsubheading Example
32949 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
32950 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32951 line="13",arch="i386:x86_64"@}
32955 For a @samp{breakpoint-hit} stopped reason, when the breakpoint
32956 encountered has multiple locations, the field @samp{bkptno} is
32957 followed by the field @samp{locno}.
32964 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",locno="3",frame=@{
32965 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32966 line="13",arch="i386:x86_64"@}
32970 @subheading The @code{-exec-finish} Command
32971 @findex -exec-finish
32973 @subsubheading Synopsis
32976 -exec-finish [--reverse]
32979 Resumes the execution of the inferior program until the current
32980 function is exited. Displays the results returned by the function.
32981 If the @samp{--reverse} option is specified, resumes the reverse
32982 execution of the inferior program until the point where current
32983 function was called.
32985 @subsubheading @value{GDBN} Command
32987 The corresponding @value{GDBN} command is @samp{finish}.
32989 @subsubheading Example
32991 Function returning @code{void}.
32998 *stopped,reason="function-finished",frame=@{func="main",args=[],
32999 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
33003 Function returning other than @code{void}. The name of the internal
33004 @value{GDBN} variable storing the result is printed, together with the
33011 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
33012 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
33013 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33014 arch="i386:x86_64"@},
33015 gdb-result-var="$1",return-value="0"
33020 @subheading The @code{-exec-interrupt} Command
33021 @findex -exec-interrupt
33023 @subsubheading Synopsis
33026 -exec-interrupt [--all|--thread-group N]
33029 Interrupts the background execution of the target. Note how the token
33030 associated with the stop message is the one for the execution command
33031 that has been interrupted. The token for the interrupt itself only
33032 appears in the @samp{^done} output. If the user is trying to
33033 interrupt a non-running program, an error message will be printed.
33035 Note that when asynchronous execution is enabled, this command is
33036 asynchronous just like other execution commands. That is, first the
33037 @samp{^done} response will be printed, and the target stop will be
33038 reported after that using the @samp{*stopped} notification.
33040 In non-stop mode, only the context thread is interrupted by default.
33041 All threads (in all inferiors) will be interrupted if the
33042 @samp{--all} option is specified. If the @samp{--thread-group}
33043 option is specified, all threads in that group will be interrupted.
33045 @subsubheading @value{GDBN} Command
33047 The corresponding @value{GDBN} command is @samp{interrupt}.
33049 @subsubheading Example
33060 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
33061 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
33062 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
33067 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
33071 @subheading The @code{-exec-jump} Command
33074 @subsubheading Synopsis
33077 -exec-jump @var{locspec}
33080 Resumes execution of the inferior program at the address to
33081 which @var{locspec} resolves. @xref{Location Specifications},
33082 for a description of the different forms of @var{locspec}.
33084 @subsubheading @value{GDBN} Command
33086 The corresponding @value{GDBN} command is @samp{jump}.
33088 @subsubheading Example
33091 -exec-jump foo.c:10
33092 *running,thread-id="all"
33097 @subheading The @code{-exec-next} Command
33100 @subsubheading Synopsis
33103 -exec-next [--reverse]
33106 Resumes execution of the inferior program, stopping when the beginning
33107 of the next source line is reached.
33109 If the @samp{--reverse} option is specified, resumes reverse execution
33110 of the inferior program, stopping at the beginning of the previous
33111 source line. If you issue this command on the first line of a
33112 function, it will take you back to the caller of that function, to the
33113 source line where the function was called.
33116 @subsubheading @value{GDBN} Command
33118 The corresponding @value{GDBN} command is @samp{next}.
33120 @subsubheading Example
33126 *stopped,reason="end-stepping-range",line="8",file="hello.c"
33131 @subheading The @code{-exec-next-instruction} Command
33132 @findex -exec-next-instruction
33134 @subsubheading Synopsis
33137 -exec-next-instruction [--reverse]
33140 Executes one machine instruction. If the instruction is a function
33141 call, continues until the function returns. If the program stops at an
33142 instruction in the middle of a source line, the address will be
33145 If the @samp{--reverse} option is specified, resumes reverse execution
33146 of the inferior program, stopping at the previous instruction. If the
33147 previously executed instruction was a return from another function,
33148 it will continue to execute in reverse until the call to that function
33149 (from the current stack frame) is reached.
33151 @subsubheading @value{GDBN} Command
33153 The corresponding @value{GDBN} command is @samp{nexti}.
33155 @subsubheading Example
33159 -exec-next-instruction
33163 *stopped,reason="end-stepping-range",
33164 addr="0x000100d4",line="5",file="hello.c"
33169 @subheading The @code{-exec-return} Command
33170 @findex -exec-return
33172 @subsubheading Synopsis
33178 Makes current function return immediately. Doesn't execute the inferior.
33179 Displays the new current frame.
33181 @subsubheading @value{GDBN} Command
33183 The corresponding @value{GDBN} command is @samp{return}.
33185 @subsubheading Example
33189 200-break-insert callee4
33190 200^done,bkpt=@{number="1",addr="0x00010734",
33191 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
33196 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
33197 frame=@{func="callee4",args=[],
33198 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33199 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
33200 arch="i386:x86_64"@}
33206 111^done,frame=@{level="0",func="callee3",
33207 args=[@{name="strarg",
33208 value="0x11940 \"A string argument.\""@}],
33209 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33210 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
33211 arch="i386:x86_64"@}
33216 @subheading The @code{-exec-run} Command
33219 @subsubheading Synopsis
33222 -exec-run [ --all | --thread-group N ] [ --start ]
33225 Starts execution of the inferior from the beginning. The inferior
33226 executes until either a breakpoint is encountered or the program
33227 exits. In the latter case the output will include an exit code, if
33228 the program has exited exceptionally.
33230 When neither the @samp{--all} nor the @samp{--thread-group} option
33231 is specified, the current inferior is started. If the
33232 @samp{--thread-group} option is specified, it should refer to a thread
33233 group of type @samp{process}, and that thread group will be started.
33234 If the @samp{--all} option is specified, then all inferiors will be started.
33236 Using the @samp{--start} option instructs the debugger to stop
33237 the execution at the start of the inferior's main subprogram,
33238 following the same behavior as the @code{start} command
33239 (@pxref{Starting}).
33241 @subsubheading @value{GDBN} Command
33243 The corresponding @value{GDBN} command is @samp{run}.
33245 @subsubheading Examples
33250 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
33255 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
33256 frame=@{func="main",args=[],file="recursive2.c",
33257 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
33262 Program exited normally:
33270 *stopped,reason="exited-normally"
33275 Program exited exceptionally:
33283 *stopped,reason="exited",exit-code="01"
33287 Another way the program can terminate is if it receives a signal such as
33288 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
33292 *stopped,reason="exited-signalled",signal-name="SIGINT",
33293 signal-meaning="Interrupt"
33297 @c @subheading -exec-signal
33300 @subheading The @code{-exec-step} Command
33303 @subsubheading Synopsis
33306 -exec-step [--reverse]
33309 Resumes execution of the inferior program, stopping when the beginning
33310 of the next source line is reached, if the next source line is not a
33311 function call. If it is, stop at the first instruction of the called
33312 function. If the @samp{--reverse} option is specified, resumes reverse
33313 execution of the inferior program, stopping at the beginning of the
33314 previously executed source line.
33316 @subsubheading @value{GDBN} Command
33318 The corresponding @value{GDBN} command is @samp{step}.
33320 @subsubheading Example
33322 Stepping into a function:
33328 *stopped,reason="end-stepping-range",
33329 frame=@{func="foo",args=[@{name="a",value="10"@},
33330 @{name="b",value="0"@}],file="recursive2.c",
33331 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
33341 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
33346 @subheading The @code{-exec-step-instruction} Command
33347 @findex -exec-step-instruction
33349 @subsubheading Synopsis
33352 -exec-step-instruction [--reverse]
33355 Resumes the inferior which executes one machine instruction. If the
33356 @samp{--reverse} option is specified, resumes reverse execution of the
33357 inferior program, stopping at the previously executed instruction.
33358 The output, once @value{GDBN} has stopped, will vary depending on
33359 whether we have stopped in the middle of a source line or not. In the
33360 former case, the address at which the program stopped will be printed
33363 @subsubheading @value{GDBN} Command
33365 The corresponding @value{GDBN} command is @samp{stepi}.
33367 @subsubheading Example
33371 -exec-step-instruction
33375 *stopped,reason="end-stepping-range",
33376 frame=@{func="foo",args=[],file="try.c",
33377 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
33379 -exec-step-instruction
33383 *stopped,reason="end-stepping-range",
33384 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
33385 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
33390 @subheading The @code{-exec-until} Command
33391 @findex -exec-until
33393 @subsubheading Synopsis
33396 -exec-until [ @var{locspec} ]
33399 Executes the inferior until it reaches the address to which
33400 @var{locspec} resolves. If there is no argument, the inferior
33401 executes until it reaches a source line greater than the current one.
33402 The reason for stopping in this case will be @samp{location-reached}.
33404 @subsubheading @value{GDBN} Command
33406 The corresponding @value{GDBN} command is @samp{until}.
33408 @subsubheading Example
33412 -exec-until recursive2.c:6
33416 *stopped,reason="location-reached",frame=@{func="main",args=[],
33417 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
33418 arch="i386:x86_64"@}
33423 @subheading -file-clear
33424 Is this going away????
33427 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33428 @node GDB/MI Stack Manipulation
33429 @section @sc{gdb/mi} Stack Manipulation Commands
33431 @subheading The @code{-enable-frame-filters} Command
33432 @findex -enable-frame-filters
33435 -enable-frame-filters
33438 @value{GDBN} allows Python-based frame filters to affect the output of
33439 the MI commands relating to stack traces. As there is no way to
33440 implement this in a fully backward-compatible way, a front end must
33441 request that this functionality be enabled.
33443 Once enabled, this feature cannot be disabled.
33445 Note that if Python support has not been compiled into @value{GDBN},
33446 this command will still succeed (and do nothing).
33448 @subheading The @code{-stack-info-frame} Command
33449 @findex -stack-info-frame
33451 @subsubheading Synopsis
33457 Get info on the selected frame.
33459 @subsubheading @value{GDBN} Command
33461 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
33462 (without arguments).
33464 @subsubheading Example
33469 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
33470 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33471 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33472 arch="i386:x86_64"@}
33476 @subheading The @code{-stack-info-depth} Command
33477 @findex -stack-info-depth
33479 @subsubheading Synopsis
33482 -stack-info-depth [ @var{max-depth} ]
33485 Return the depth of the stack. If the integer argument @var{max-depth}
33486 is specified, do not count beyond @var{max-depth} frames.
33488 @subsubheading @value{GDBN} Command
33490 There's no equivalent @value{GDBN} command.
33492 @subsubheading Example
33494 For a stack with frame levels 0 through 11:
33501 -stack-info-depth 4
33504 -stack-info-depth 12
33507 -stack-info-depth 11
33510 -stack-info-depth 13
33515 @anchor{-stack-list-arguments}
33516 @subheading The @code{-stack-list-arguments} Command
33517 @findex -stack-list-arguments
33519 @subsubheading Synopsis
33522 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33523 [ @var{low-frame} @var{high-frame} ]
33526 Display a list of the arguments for the frames between @var{low-frame}
33527 and @var{high-frame} (inclusive). If @var{low-frame} and
33528 @var{high-frame} are not provided, list the arguments for the whole
33529 call stack. If the two arguments are equal, show the single frame
33530 at the corresponding level. It is an error if @var{low-frame} is
33531 larger than the actual number of frames. On the other hand,
33532 @var{high-frame} may be larger than the actual number of frames, in
33533 which case only existing frames will be returned.
33535 If @var{print-values} is 0 or @code{--no-values}, print only the names of
33536 the variables; if it is 1 or @code{--all-values}, print also their
33537 values; and if it is 2 or @code{--simple-values}, print the name,
33538 type and value for simple data types, and the name and type for arrays,
33539 structures and unions. If the option @code{--no-frame-filters} is
33540 supplied, then Python frame filters will not be executed.
33542 If the @code{--skip-unavailable} option is specified, arguments that
33543 are not available are not listed. Partially available arguments
33544 are still displayed, however.
33546 Use of this command to obtain arguments in a single frame is
33547 deprecated in favor of the @samp{-stack-list-variables} command.
33549 @subsubheading @value{GDBN} Command
33551 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
33552 @samp{gdb_get_args} command which partially overlaps with the
33553 functionality of @samp{-stack-list-arguments}.
33555 @subsubheading Example
33562 frame=@{level="0",addr="0x00010734",func="callee4",
33563 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33564 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
33565 arch="i386:x86_64"@},
33566 frame=@{level="1",addr="0x0001076c",func="callee3",
33567 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33568 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33569 arch="i386:x86_64"@},
33570 frame=@{level="2",addr="0x0001078c",func="callee2",
33571 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33572 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
33573 arch="i386:x86_64"@},
33574 frame=@{level="3",addr="0x000107b4",func="callee1",
33575 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33576 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
33577 arch="i386:x86_64"@},
33578 frame=@{level="4",addr="0x000107e0",func="main",
33579 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33580 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
33581 arch="i386:x86_64"@}]
33583 -stack-list-arguments 0
33586 frame=@{level="0",args=[]@},
33587 frame=@{level="1",args=[name="strarg"]@},
33588 frame=@{level="2",args=[name="intarg",name="strarg"]@},
33589 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
33590 frame=@{level="4",args=[]@}]
33592 -stack-list-arguments 1
33595 frame=@{level="0",args=[]@},
33597 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33598 frame=@{level="2",args=[
33599 @{name="intarg",value="2"@},
33600 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33601 @{frame=@{level="3",args=[
33602 @{name="intarg",value="2"@},
33603 @{name="strarg",value="0x11940 \"A string argument.\""@},
33604 @{name="fltarg",value="3.5"@}]@},
33605 frame=@{level="4",args=[]@}]
33607 -stack-list-arguments 0 2 2
33608 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
33610 -stack-list-arguments 1 2 2
33611 ^done,stack-args=[frame=@{level="2",
33612 args=[@{name="intarg",value="2"@},
33613 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
33617 @c @subheading -stack-list-exception-handlers
33620 @anchor{-stack-list-frames}
33621 @subheading The @code{-stack-list-frames} Command
33622 @findex -stack-list-frames
33624 @subsubheading Synopsis
33627 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
33630 List the frames currently on the stack. For each frame it displays the
33635 The frame number, 0 being the topmost frame, i.e., the innermost function.
33637 The @code{$pc} value for that frame.
33641 File name of the source file where the function lives.
33642 @item @var{fullname}
33643 The full file name of the source file where the function lives.
33645 Line number corresponding to the @code{$pc}.
33647 The shared library where this function is defined. This is only given
33648 if the frame's function is not known.
33650 Frame's architecture.
33653 If invoked without arguments, this command prints a backtrace for the
33654 whole stack. If given two integer arguments, it shows the frames whose
33655 levels are between the two arguments (inclusive). If the two arguments
33656 are equal, it shows the single frame at the corresponding level. It is
33657 an error if @var{low-frame} is larger than the actual number of
33658 frames. On the other hand, @var{high-frame} may be larger than the
33659 actual number of frames, in which case only existing frames will be
33660 returned. If the option @code{--no-frame-filters} is supplied, then
33661 Python frame filters will not be executed.
33663 @subsubheading @value{GDBN} Command
33665 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
33667 @subsubheading Example
33669 Full stack backtrace:
33675 [frame=@{level="0",addr="0x0001076c",func="foo",
33676 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
33677 arch="i386:x86_64"@},
33678 frame=@{level="1",addr="0x000107a4",func="foo",
33679 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33680 arch="i386:x86_64"@},
33681 frame=@{level="2",addr="0x000107a4",func="foo",
33682 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33683 arch="i386:x86_64"@},
33684 frame=@{level="3",addr="0x000107a4",func="foo",
33685 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33686 arch="i386:x86_64"@},
33687 frame=@{level="4",addr="0x000107a4",func="foo",
33688 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33689 arch="i386:x86_64"@},
33690 frame=@{level="5",addr="0x000107a4",func="foo",
33691 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33692 arch="i386:x86_64"@},
33693 frame=@{level="6",addr="0x000107a4",func="foo",
33694 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33695 arch="i386:x86_64"@},
33696 frame=@{level="7",addr="0x000107a4",func="foo",
33697 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33698 arch="i386:x86_64"@},
33699 frame=@{level="8",addr="0x000107a4",func="foo",
33700 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33701 arch="i386:x86_64"@},
33702 frame=@{level="9",addr="0x000107a4",func="foo",
33703 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33704 arch="i386:x86_64"@},
33705 frame=@{level="10",addr="0x000107a4",func="foo",
33706 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33707 arch="i386:x86_64"@},
33708 frame=@{level="11",addr="0x00010738",func="main",
33709 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
33710 arch="i386:x86_64"@}]
33714 Show frames between @var{low_frame} and @var{high_frame}:
33718 -stack-list-frames 3 5
33720 [frame=@{level="3",addr="0x000107a4",func="foo",
33721 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33722 arch="i386:x86_64"@},
33723 frame=@{level="4",addr="0x000107a4",func="foo",
33724 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33725 arch="i386:x86_64"@},
33726 frame=@{level="5",addr="0x000107a4",func="foo",
33727 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33728 arch="i386:x86_64"@}]
33732 Show a single frame:
33736 -stack-list-frames 3 3
33738 [frame=@{level="3",addr="0x000107a4",func="foo",
33739 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33740 arch="i386:x86_64"@}]
33745 @subheading The @code{-stack-list-locals} Command
33746 @findex -stack-list-locals
33747 @anchor{-stack-list-locals}
33749 @subsubheading Synopsis
33752 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33755 Display the local variable names for the selected frame. If
33756 @var{print-values} is 0 or @code{--no-values}, print only the names of
33757 the variables; if it is 1 or @code{--all-values}, print also their
33758 values; and if it is 2 or @code{--simple-values}, print the name,
33759 type and value for simple data types, and the name and type for arrays,
33760 structures and unions. In this last case, a frontend can immediately
33761 display the value of simple data types and create variable objects for
33762 other data types when the user wishes to explore their values in
33763 more detail. If the option @code{--no-frame-filters} is supplied, then
33764 Python frame filters will not be executed.
33766 If the @code{--skip-unavailable} option is specified, local variables
33767 that are not available are not listed. Partially available local
33768 variables are still displayed, however.
33770 This command is deprecated in favor of the
33771 @samp{-stack-list-variables} command.
33773 @subsubheading @value{GDBN} Command
33775 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
33777 @subsubheading Example
33781 -stack-list-locals 0
33782 ^done,locals=[name="A",name="B",name="C"]
33784 -stack-list-locals --all-values
33785 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
33786 @{name="C",value="@{1, 2, 3@}"@}]
33787 -stack-list-locals --simple-values
33788 ^done,locals=[@{name="A",type="int",value="1"@},
33789 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
33793 @anchor{-stack-list-variables}
33794 @subheading The @code{-stack-list-variables} Command
33795 @findex -stack-list-variables
33797 @subsubheading Synopsis
33800 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33803 Display the names of local variables and function arguments for the selected frame. If
33804 @var{print-values} is 0 or @code{--no-values}, print only the names of
33805 the variables; if it is 1 or @code{--all-values}, print also their
33806 values; and if it is 2 or @code{--simple-values}, print the name,
33807 type and value for simple data types, and the name and type for arrays,
33808 structures and unions. If the option @code{--no-frame-filters} is
33809 supplied, then Python frame filters will not be executed.
33811 If the @code{--skip-unavailable} option is specified, local variables
33812 and arguments that are not available are not listed. Partially
33813 available arguments and local variables are still displayed, however.
33815 @subsubheading Example
33819 -stack-list-variables --thread 1 --frame 0 --all-values
33820 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
33825 @subheading The @code{-stack-select-frame} Command
33826 @findex -stack-select-frame
33828 @subsubheading Synopsis
33831 -stack-select-frame @var{framenum}
33834 Change the selected frame. Select a different frame @var{framenum} on
33837 This command in deprecated in favor of passing the @samp{--frame}
33838 option to every command.
33840 @subsubheading @value{GDBN} Command
33842 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
33843 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
33845 @subsubheading Example
33849 -stack-select-frame 2
33854 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33855 @node GDB/MI Variable Objects
33856 @section @sc{gdb/mi} Variable Objects
33860 @subheading Motivation for Variable Objects in @sc{gdb/mi}
33862 For the implementation of a variable debugger window (locals, watched
33863 expressions, etc.), we are proposing the adaptation of the existing code
33864 used by @code{Insight}.
33866 The two main reasons for that are:
33870 It has been proven in practice (it is already on its second generation).
33873 It will shorten development time (needless to say how important it is
33877 The original interface was designed to be used by Tcl code, so it was
33878 slightly changed so it could be used through @sc{gdb/mi}. This section
33879 describes the @sc{gdb/mi} operations that will be available and gives some
33880 hints about their use.
33882 @emph{Note}: In addition to the set of operations described here, we
33883 expect the @sc{gui} implementation of a variable window to require, at
33884 least, the following operations:
33887 @item @code{-gdb-show} @code{output-radix}
33888 @item @code{-stack-list-arguments}
33889 @item @code{-stack-list-locals}
33890 @item @code{-stack-select-frame}
33895 @subheading Introduction to Variable Objects
33897 @cindex variable objects in @sc{gdb/mi}
33899 Variable objects are "object-oriented" MI interface for examining and
33900 changing values of expressions. Unlike some other MI interfaces that
33901 work with expressions, variable objects are specifically designed for
33902 simple and efficient presentation in the frontend. A variable object
33903 is identified by string name. When a variable object is created, the
33904 frontend specifies the expression for that variable object. The
33905 expression can be a simple variable, or it can be an arbitrary complex
33906 expression, and can even involve CPU registers. After creating a
33907 variable object, the frontend can invoke other variable object
33908 operations---for example to obtain or change the value of a variable
33909 object, or to change display format.
33911 Variable objects have hierarchical tree structure. Any variable object
33912 that corresponds to a composite type, such as structure in C, has
33913 a number of child variable objects, for example corresponding to each
33914 element of a structure. A child variable object can itself have
33915 children, recursively. Recursion ends when we reach
33916 leaf variable objects, which always have built-in types. Child variable
33917 objects are created only by explicit request, so if a frontend
33918 is not interested in the children of a particular variable object, no
33919 child will be created.
33921 For a leaf variable object it is possible to obtain its value as a
33922 string, or set the value from a string. String value can be also
33923 obtained for a non-leaf variable object, but it's generally a string
33924 that only indicates the type of the object, and does not list its
33925 contents. Assignment to a non-leaf variable object is not allowed.
33927 A frontend does not need to read the values of all variable objects each time
33928 the program stops. Instead, MI provides an update command that lists all
33929 variable objects whose values has changed since the last update
33930 operation. This considerably reduces the amount of data that must
33931 be transferred to the frontend. As noted above, children variable
33932 objects are created on demand, and only leaf variable objects have a
33933 real value. As result, gdb will read target memory only for leaf
33934 variables that frontend has created.
33936 The automatic update is not always desirable. For example, a frontend
33937 might want to keep a value of some expression for future reference,
33938 and never update it. For another example, fetching memory is
33939 relatively slow for embedded targets, so a frontend might want
33940 to disable automatic update for the variables that are either not
33941 visible on the screen, or ``closed''. This is possible using so
33942 called ``frozen variable objects''. Such variable objects are never
33943 implicitly updated.
33945 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
33946 fixed variable object, the expression is parsed when the variable
33947 object is created, including associating identifiers to specific
33948 variables. The meaning of expression never changes. For a floating
33949 variable object the values of variables whose names appear in the
33950 expressions are re-evaluated every time in the context of the current
33951 frame. Consider this example:
33956 struct work_state state;
33963 If a fixed variable object for the @code{state} variable is created in
33964 this function, and we enter the recursive call, the variable
33965 object will report the value of @code{state} in the top-level
33966 @code{do_work} invocation. On the other hand, a floating variable
33967 object will report the value of @code{state} in the current frame.
33969 If an expression specified when creating a fixed variable object
33970 refers to a local variable, the variable object becomes bound to the
33971 thread and frame in which the variable object is created. When such
33972 variable object is updated, @value{GDBN} makes sure that the
33973 thread/frame combination the variable object is bound to still exists,
33974 and re-evaluates the variable object in context of that thread/frame.
33976 The following is the complete set of @sc{gdb/mi} operations defined to
33977 access this functionality:
33979 @multitable @columnfractions .4 .6
33980 @item @strong{Operation}
33981 @tab @strong{Description}
33983 @item @code{-enable-pretty-printing}
33984 @tab enable Python-based pretty-printing
33985 @item @code{-var-create}
33986 @tab create a variable object
33987 @item @code{-var-delete}
33988 @tab delete the variable object and/or its children
33989 @item @code{-var-set-format}
33990 @tab set the display format of this variable
33991 @item @code{-var-show-format}
33992 @tab show the display format of this variable
33993 @item @code{-var-info-num-children}
33994 @tab tells how many children this object has
33995 @item @code{-var-list-children}
33996 @tab return a list of the object's children
33997 @item @code{-var-info-type}
33998 @tab show the type of this variable object
33999 @item @code{-var-info-expression}
34000 @tab print parent-relative expression that this variable object represents
34001 @item @code{-var-info-path-expression}
34002 @tab print full expression that this variable object represents
34003 @item @code{-var-show-attributes}
34004 @tab is this variable editable? does it exist here?
34005 @item @code{-var-evaluate-expression}
34006 @tab get the value of this variable
34007 @item @code{-var-assign}
34008 @tab set the value of this variable
34009 @item @code{-var-update}
34010 @tab update the variable and its children
34011 @item @code{-var-set-frozen}
34012 @tab set frozenness attribute
34013 @item @code{-var-set-update-range}
34014 @tab set range of children to display on update
34017 In the next subsection we describe each operation in detail and suggest
34018 how it can be used.
34020 @subheading Description And Use of Operations on Variable Objects
34022 @subheading The @code{-enable-pretty-printing} Command
34023 @findex -enable-pretty-printing
34026 -enable-pretty-printing
34029 @value{GDBN} allows Python-based visualizers to affect the output of the
34030 MI variable object commands. However, because there was no way to
34031 implement this in a fully backward-compatible way, a front end must
34032 request that this functionality be enabled.
34034 Once enabled, this feature cannot be disabled.
34036 Note that if Python support has not been compiled into @value{GDBN},
34037 this command will still succeed (and do nothing).
34039 @subheading The @code{-var-create} Command
34040 @findex -var-create
34042 @subsubheading Synopsis
34045 -var-create @{@var{name} | "-"@}
34046 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
34049 This operation creates a variable object, which allows the monitoring of
34050 a variable, the result of an expression, a memory cell or a CPU
34053 The @var{name} parameter is the string by which the object can be
34054 referenced. It must be unique. If @samp{-} is specified, the varobj
34055 system will generate a string ``varNNNNNN'' automatically. It will be
34056 unique provided that one does not specify @var{name} of that format.
34057 The command fails if a duplicate name is found.
34059 The frame under which the expression should be evaluated can be
34060 specified by @var{frame-addr}. A @samp{*} indicates that the current
34061 frame should be used. A @samp{@@} indicates that a floating variable
34062 object must be created.
34064 @var{expression} is any expression valid on the current language set (must not
34065 begin with a @samp{*}), or one of the following:
34069 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
34072 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
34075 @samp{$@var{regname}} --- a CPU register name
34078 @cindex dynamic varobj
34079 A varobj's contents may be provided by a Python-based pretty-printer. In this
34080 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
34081 have slightly different semantics in some cases. If the
34082 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
34083 will never create a dynamic varobj. This ensures backward
34084 compatibility for existing clients.
34086 @subsubheading Result
34088 This operation returns attributes of the newly-created varobj. These
34093 The name of the varobj.
34096 The number of children of the varobj. This number is not necessarily
34097 reliable for a dynamic varobj. Instead, you must examine the
34098 @samp{has_more} attribute.
34101 The varobj's scalar value. For a varobj whose type is some sort of
34102 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
34103 will not be interesting.
34106 The varobj's type. This is a string representation of the type, as
34107 would be printed by the @value{GDBN} CLI. If @samp{print object}
34108 (@pxref{Print Settings, set print object}) is set to @code{on}, the
34109 @emph{actual} (derived) type of the object is shown rather than the
34110 @emph{declared} one.
34113 If a variable object is bound to a specific thread, then this is the
34114 thread's global identifier.
34117 For a dynamic varobj, this indicates whether there appear to be any
34118 children available. For a non-dynamic varobj, this will be 0.
34121 This attribute will be present and have the value @samp{1} if the
34122 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34123 then this attribute will not be present.
34126 A dynamic varobj can supply a display hint to the front end. The
34127 value comes directly from the Python pretty-printer object's
34128 @code{display_hint} method. @xref{Pretty Printing API}.
34131 Typical output will look like this:
34134 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
34135 has_more="@var{has_more}"
34139 @subheading The @code{-var-delete} Command
34140 @findex -var-delete
34142 @subsubheading Synopsis
34145 -var-delete [ -c ] @var{name}
34148 Deletes a previously created variable object and all of its children.
34149 With the @samp{-c} option, just deletes the children.
34151 Returns an error if the object @var{name} is not found.
34154 @subheading The @code{-var-set-format} Command
34155 @findex -var-set-format
34157 @subsubheading Synopsis
34160 -var-set-format @var{name} @var{format-spec}
34163 Sets the output format for the value of the object @var{name} to be
34166 @anchor{-var-set-format}
34167 The syntax for the @var{format-spec} is as follows:
34170 @var{format-spec} @expansion{}
34171 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
34174 The natural format is the default format choosen automatically
34175 based on the variable type (like decimal for an @code{int}, hex
34176 for pointers, etc.).
34178 The zero-hexadecimal format has a representation similar to hexadecimal
34179 but with padding zeroes to the left of the value. For example, a 32-bit
34180 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
34181 zero-hexadecimal format.
34183 For a variable with children, the format is set only on the
34184 variable itself, and the children are not affected.
34186 @subheading The @code{-var-show-format} Command
34187 @findex -var-show-format
34189 @subsubheading Synopsis
34192 -var-show-format @var{name}
34195 Returns the format used to display the value of the object @var{name}.
34198 @var{format} @expansion{}
34203 @subheading The @code{-var-info-num-children} Command
34204 @findex -var-info-num-children
34206 @subsubheading Synopsis
34209 -var-info-num-children @var{name}
34212 Returns the number of children of a variable object @var{name}:
34218 Note that this number is not completely reliable for a dynamic varobj.
34219 It will return the current number of children, but more children may
34223 @subheading The @code{-var-list-children} Command
34224 @findex -var-list-children
34226 @subsubheading Synopsis
34229 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
34231 @anchor{-var-list-children}
34233 Return a list of the children of the specified variable object and
34234 create variable objects for them, if they do not already exist. With
34235 a single argument or if @var{print-values} has a value of 0 or
34236 @code{--no-values}, print only the names of the variables; if
34237 @var{print-values} is 1 or @code{--all-values}, also print their
34238 values; and if it is 2 or @code{--simple-values} print the name and
34239 value for simple data types and just the name for arrays, structures
34242 @var{from} and @var{to}, if specified, indicate the range of children
34243 to report. If @var{from} or @var{to} is less than zero, the range is
34244 reset and all children will be reported. Otherwise, children starting
34245 at @var{from} (zero-based) and up to and excluding @var{to} will be
34248 If a child range is requested, it will only affect the current call to
34249 @code{-var-list-children}, but not future calls to @code{-var-update}.
34250 For this, you must instead use @code{-var-set-update-range}. The
34251 intent of this approach is to enable a front end to implement any
34252 update approach it likes; for example, scrolling a view may cause the
34253 front end to request more children with @code{-var-list-children}, and
34254 then the front end could call @code{-var-set-update-range} with a
34255 different range to ensure that future updates are restricted to just
34258 For each child the following results are returned:
34263 Name of the variable object created for this child.
34266 The expression to be shown to the user by the front end to designate this child.
34267 For example this may be the name of a structure member.
34269 For a dynamic varobj, this value cannot be used to form an
34270 expression. There is no way to do this at all with a dynamic varobj.
34272 For C/C@t{++} structures there are several pseudo children returned to
34273 designate access qualifiers. For these pseudo children @var{exp} is
34274 @samp{public}, @samp{private}, or @samp{protected}. In this case the
34275 type and value are not present.
34277 A dynamic varobj will not report the access qualifying
34278 pseudo-children, regardless of the language. This information is not
34279 available at all with a dynamic varobj.
34282 Number of children this child has. For a dynamic varobj, this will be
34286 The type of the child. If @samp{print object}
34287 (@pxref{Print Settings, set print object}) is set to @code{on}, the
34288 @emph{actual} (derived) type of the object is shown rather than the
34289 @emph{declared} one.
34292 If values were requested, this is the value.
34295 If this variable object is associated with a thread, this is the
34296 thread's global thread id. Otherwise this result is not present.
34299 If the variable object is frozen, this variable will be present with a value of 1.
34302 A dynamic varobj can supply a display hint to the front end. The
34303 value comes directly from the Python pretty-printer object's
34304 @code{display_hint} method. @xref{Pretty Printing API}.
34307 This attribute will be present and have the value @samp{1} if the
34308 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34309 then this attribute will not be present.
34313 The result may have its own attributes:
34317 A dynamic varobj can supply a display hint to the front end. The
34318 value comes directly from the Python pretty-printer object's
34319 @code{display_hint} method. @xref{Pretty Printing API}.
34322 This is an integer attribute which is nonzero if there are children
34323 remaining after the end of the selected range.
34326 @subsubheading Example
34330 -var-list-children n
34331 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
34332 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
34334 -var-list-children --all-values n
34335 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
34336 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
34340 @subheading The @code{-var-info-type} Command
34341 @findex -var-info-type
34343 @subsubheading Synopsis
34346 -var-info-type @var{name}
34349 Returns the type of the specified variable @var{name}. The type is
34350 returned as a string in the same format as it is output by the
34354 type=@var{typename}
34358 @subheading The @code{-var-info-expression} Command
34359 @findex -var-info-expression
34361 @subsubheading Synopsis
34364 -var-info-expression @var{name}
34367 Returns a string that is suitable for presenting this
34368 variable object in user interface. The string is generally
34369 not valid expression in the current language, and cannot be evaluated.
34371 For example, if @code{a} is an array, and variable object
34372 @code{A} was created for @code{a}, then we'll get this output:
34375 (gdb) -var-info-expression A.1
34376 ^done,lang="C",exp="1"
34380 Here, the value of @code{lang} is the language name, which can be
34381 found in @ref{Supported Languages}.
34383 Note that the output of the @code{-var-list-children} command also
34384 includes those expressions, so the @code{-var-info-expression} command
34387 @subheading The @code{-var-info-path-expression} Command
34388 @findex -var-info-path-expression
34390 @subsubheading Synopsis
34393 -var-info-path-expression @var{name}
34396 Returns an expression that can be evaluated in the current
34397 context and will yield the same value that a variable object has.
34398 Compare this with the @code{-var-info-expression} command, which
34399 result can be used only for UI presentation. Typical use of
34400 the @code{-var-info-path-expression} command is creating a
34401 watchpoint from a variable object.
34403 This command is currently not valid for children of a dynamic varobj,
34404 and will give an error when invoked on one.
34406 For example, suppose @code{C} is a C@t{++} class, derived from class
34407 @code{Base}, and that the @code{Base} class has a member called
34408 @code{m_size}. Assume a variable @code{c} is has the type of
34409 @code{C} and a variable object @code{C} was created for variable
34410 @code{c}. Then, we'll get this output:
34412 (gdb) -var-info-path-expression C.Base.public.m_size
34413 ^done,path_expr=((Base)c).m_size)
34416 @subheading The @code{-var-show-attributes} Command
34417 @findex -var-show-attributes
34419 @subsubheading Synopsis
34422 -var-show-attributes @var{name}
34425 List attributes of the specified variable object @var{name}:
34428 status=@var{attr} [ ( ,@var{attr} )* ]
34432 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
34434 @subheading The @code{-var-evaluate-expression} Command
34435 @findex -var-evaluate-expression
34437 @subsubheading Synopsis
34440 -var-evaluate-expression [-f @var{format-spec}] @var{name}
34443 Evaluates the expression that is represented by the specified variable
34444 object and returns its value as a string. The format of the string
34445 can be specified with the @samp{-f} option. The possible values of
34446 this option are the same as for @code{-var-set-format}
34447 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
34448 the current display format will be used. The current display format
34449 can be changed using the @code{-var-set-format} command.
34455 Note that one must invoke @code{-var-list-children} for a variable
34456 before the value of a child variable can be evaluated.
34458 @subheading The @code{-var-assign} Command
34459 @findex -var-assign
34461 @subsubheading Synopsis
34464 -var-assign @var{name} @var{expression}
34467 Assigns the value of @var{expression} to the variable object specified
34468 by @var{name}. The object must be @samp{editable}. If the variable's
34469 value is altered by the assign, the variable will show up in any
34470 subsequent @code{-var-update} list.
34472 @subsubheading Example
34480 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
34484 @subheading The @code{-var-update} Command
34485 @findex -var-update
34487 @subsubheading Synopsis
34490 -var-update [@var{print-values}] @{@var{name} | "*"@}
34493 Reevaluate the expressions corresponding to the variable object
34494 @var{name} and all its direct and indirect children, and return the
34495 list of variable objects whose values have changed; @var{name} must
34496 be a root variable object. Here, ``changed'' means that the result of
34497 @code{-var-evaluate-expression} before and after the
34498 @code{-var-update} is different. If @samp{*} is used as the variable
34499 object names, all existing variable objects are updated, except
34500 for frozen ones (@pxref{-var-set-frozen}). The option
34501 @var{print-values} determines whether both names and values, or just
34502 names are printed. The possible values of this option are the same
34503 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
34504 recommended to use the @samp{--all-values} option, to reduce the
34505 number of MI commands needed on each program stop.
34507 With the @samp{*} parameter, if a variable object is bound to a
34508 currently running thread, it will not be updated, without any
34511 If @code{-var-set-update-range} was previously used on a varobj, then
34512 only the selected range of children will be reported.
34514 @code{-var-update} reports all the changed varobjs in a tuple named
34517 Each item in the change list is itself a tuple holding:
34521 The name of the varobj.
34524 If values were requested for this update, then this field will be
34525 present and will hold the value of the varobj.
34528 @anchor{-var-update}
34529 This field is a string which may take one of three values:
34533 The variable object's current value is valid.
34536 The variable object does not currently hold a valid value but it may
34537 hold one in the future if its associated expression comes back into
34541 The variable object no longer holds a valid value.
34542 This can occur when the executable file being debugged has changed,
34543 either through recompilation or by using the @value{GDBN} @code{file}
34544 command. The front end should normally choose to delete these variable
34548 In the future new values may be added to this list so the front should
34549 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
34552 This is only present if the varobj is still valid. If the type
34553 changed, then this will be the string @samp{true}; otherwise it will
34556 When a varobj's type changes, its children are also likely to have
34557 become incorrect. Therefore, the varobj's children are automatically
34558 deleted when this attribute is @samp{true}. Also, the varobj's update
34559 range, when set using the @code{-var-set-update-range} command, is
34563 If the varobj's type changed, then this field will be present and will
34566 @item new_num_children
34567 For a dynamic varobj, if the number of children changed, or if the
34568 type changed, this will be the new number of children.
34570 The @samp{numchild} field in other varobj responses is generally not
34571 valid for a dynamic varobj -- it will show the number of children that
34572 @value{GDBN} knows about, but because dynamic varobjs lazily
34573 instantiate their children, this will not reflect the number of
34574 children which may be available.
34576 The @samp{new_num_children} attribute only reports changes to the
34577 number of children known by @value{GDBN}. This is the only way to
34578 detect whether an update has removed children (which necessarily can
34579 only happen at the end of the update range).
34582 The display hint, if any.
34585 This is an integer value, which will be 1 if there are more children
34586 available outside the varobj's update range.
34589 This attribute will be present and have the value @samp{1} if the
34590 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34591 then this attribute will not be present.
34594 If new children were added to a dynamic varobj within the selected
34595 update range (as set by @code{-var-set-update-range}), then they will
34596 be listed in this attribute.
34599 @subsubheading Example
34606 -var-update --all-values var1
34607 ^done,changelist=[@{name="var1",value="3",in_scope="true",
34608 type_changed="false"@}]
34612 @subheading The @code{-var-set-frozen} Command
34613 @findex -var-set-frozen
34614 @anchor{-var-set-frozen}
34616 @subsubheading Synopsis
34619 -var-set-frozen @var{name} @var{flag}
34622 Set the frozenness flag on the variable object @var{name}. The
34623 @var{flag} parameter should be either @samp{1} to make the variable
34624 frozen or @samp{0} to make it unfrozen. If a variable object is
34625 frozen, then neither itself, nor any of its children, are
34626 implicitly updated by @code{-var-update} of
34627 a parent variable or by @code{-var-update *}. Only
34628 @code{-var-update} of the variable itself will update its value and
34629 values of its children. After a variable object is unfrozen, it is
34630 implicitly updated by all subsequent @code{-var-update} operations.
34631 Unfreezing a variable does not update it, only subsequent
34632 @code{-var-update} does.
34634 @subsubheading Example
34638 -var-set-frozen V 1
34643 @subheading The @code{-var-set-update-range} command
34644 @findex -var-set-update-range
34645 @anchor{-var-set-update-range}
34647 @subsubheading Synopsis
34650 -var-set-update-range @var{name} @var{from} @var{to}
34653 Set the range of children to be returned by future invocations of
34654 @code{-var-update}.
34656 @var{from} and @var{to} indicate the range of children to report. If
34657 @var{from} or @var{to} is less than zero, the range is reset and all
34658 children will be reported. Otherwise, children starting at @var{from}
34659 (zero-based) and up to and excluding @var{to} will be reported.
34661 @subsubheading Example
34665 -var-set-update-range V 1 2
34669 @subheading The @code{-var-set-visualizer} command
34670 @findex -var-set-visualizer
34671 @anchor{-var-set-visualizer}
34673 @subsubheading Synopsis
34676 -var-set-visualizer @var{name} @var{visualizer}
34679 Set a visualizer for the variable object @var{name}.
34681 @var{visualizer} is the visualizer to use. The special value
34682 @samp{None} means to disable any visualizer in use.
34684 If not @samp{None}, @var{visualizer} must be a Python expression.
34685 This expression must evaluate to a callable object which accepts a
34686 single argument. @value{GDBN} will call this object with the value of
34687 the varobj @var{name} as an argument (this is done so that the same
34688 Python pretty-printing code can be used for both the CLI and MI).
34689 When called, this object must return an object which conforms to the
34690 pretty-printing interface (@pxref{Pretty Printing API}).
34692 The pre-defined function @code{gdb.default_visualizer} may be used to
34693 select a visualizer by following the built-in process
34694 (@pxref{Selecting Pretty-Printers}). This is done automatically when
34695 a varobj is created, and so ordinarily is not needed.
34697 This feature is only available if Python support is enabled. The MI
34698 command @code{-list-features} (@pxref{GDB/MI Support Commands})
34699 can be used to check this.
34701 @subsubheading Example
34703 Resetting the visualizer:
34707 -var-set-visualizer V None
34711 Reselecting the default (type-based) visualizer:
34715 -var-set-visualizer V gdb.default_visualizer
34719 Suppose @code{SomeClass} is a visualizer class. A lambda expression
34720 can be used to instantiate this class for a varobj:
34724 -var-set-visualizer V "lambda val: SomeClass()"
34728 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34729 @node GDB/MI Data Manipulation
34730 @section @sc{gdb/mi} Data Manipulation
34732 @cindex data manipulation, in @sc{gdb/mi}
34733 @cindex @sc{gdb/mi}, data manipulation
34734 This section describes the @sc{gdb/mi} commands that manipulate data:
34735 examine memory and registers, evaluate expressions, etc.
34737 For details about what an addressable memory unit is,
34738 @pxref{addressable memory unit}.
34740 @c REMOVED FROM THE INTERFACE.
34741 @c @subheading -data-assign
34742 @c Change the value of a program variable. Plenty of side effects.
34743 @c @subsubheading GDB Command
34745 @c @subsubheading Example
34748 @subheading The @code{-data-disassemble} Command
34749 @findex -data-disassemble
34751 @subsubheading Synopsis
34755 ( -s @var{start-addr} -e @var{end-addr}
34757 | -f @var{filename} -l @var{linenum} [ -n @var{lines} ] )
34758 [ --opcodes @var{opcodes-mode} ]
34767 @item @var{start-addr}
34768 is the beginning address (or @code{$pc})
34769 @item @var{end-addr}
34772 is an address anywhere within (or the name of) the function to
34773 disassemble. If an address is specified, the whole function
34774 surrounding that address will be disassembled. If a name is
34775 specified, the whole function with that name will be disassembled.
34776 @item @var{filename}
34777 is the name of the file to disassemble
34778 @item @var{linenum}
34779 is the line number to disassemble around
34781 is the number of disassembly lines to be produced. If it is -1,
34782 the whole function will be disassembled, in case no @var{end-addr} is
34783 specified. If @var{end-addr} is specified as a non-zero value, and
34784 @var{lines} is lower than the number of disassembly lines between
34785 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
34786 displayed; if @var{lines} is higher than the number of lines between
34787 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
34789 @item @var{opcodes-mode}
34790 can only be used with @var{mode} 0, and should be one of the following:
34793 no opcode information will be included in the result.
34796 opcodes will be included in the result, the opcodes will be formatted
34797 as for @kbd{disassemble /b}.
34800 opcodes will be included in the result, the opcodes will be formatted
34801 as for @kbd{disassemble /r}.
34804 the use of @var{mode} is deprecated in favour of using the
34805 @code{--opcodes} and @code{--source} options. When no @var{mode} is
34806 given, @var{mode} 0 will be assumed. However, the @var{mode} is still
34807 available for backward compatibility. The @var{mode} should be one of:
34810 @emph{disassembly only}, this is the default mode if no mode is
34814 @emph{mixed source and disassembly (deprecated)}, it is not possible
34815 to recreate this mode using @code{--opcodes} and @code{--source}
34819 @emph{disassembly with raw opcodes}, this mode is equivalent to using
34820 @var{mode} 0 and passing @code{--opcodes bytes} to the command.
34823 @emph{mixed source and disassembly with raw opcodes (deprecated)}, it
34824 is not possible to recreate this mode using @code{--opcodes} and
34825 @code{--source} options.
34828 @emph{mixed source and disassembly}, this mode is equivalent to using
34829 @var{mode} 0 and passing @code{--source} to the command.
34832 @emph{mixed source and disassembly with raw opcodes}, this mode is
34833 equivalent to using @var{mode} 0 and passing @code{--opcodes bytes}
34834 and @code{--source} to the command.
34836 Modes 1 and 3 are deprecated. The output is ``source centric''
34837 which hasn't proved useful in practice.
34838 @xref{Machine Code}, for a discussion of the difference between
34839 @code{/m} and @code{/s} output of the @code{disassemble} command.
34842 The @code{--source} can only be used with @var{mode} 0. Passing this
34843 option will include the source code in the disassembly result as if
34844 @var{mode} 4 or 5 had been used.
34846 @subsubheading Result
34848 The result of the @code{-data-disassemble} command will be a list named
34849 @samp{asm_insns}, the contents of this list depend on the options used
34850 with the @code{-data-disassemble} command.
34852 For modes 0 and 2, and when the @code{--source} option is not used, the
34853 @samp{asm_insns} list contains tuples with the following fields:
34857 The address at which this instruction was disassembled.
34860 The name of the function this instruction is within.
34863 The decimal offset in bytes from the start of @samp{func-name}.
34866 The text disassembly for this @samp{address}.
34869 This field is only present for modes 2, 3 and 5, or when the
34870 @code{--opcodes} option @samp{bytes} or @samp{display} is used. This
34871 contains the raw opcode bytes for the @samp{inst} field.
34873 When the @samp{--opcodes} option is not passed to
34874 @code{-data-disassemble}, or the @samp{bytes} value is passed to
34875 @samp{--opcodes}, then the bytes are formatted as a series of single
34876 bytes, in hex, in ascending address order, with a single space between
34877 each byte. This format is equivalent to the @samp{/b} option being
34878 used with the @kbd{disassemble} command
34879 (@pxref{disassemble,,@kbd{disassemble}}).
34881 When @samp{--opcodes} is passed the value @samp{display} then the bytes
34882 are formatted in the natural instruction display order. This means
34883 multiple bytes can be grouped together, and the bytes might be
34884 byte-swapped. This format is equivalent to the @samp{/r} option being
34885 used with the @kbd{disassemble} command.
34888 For modes 1, 3, 4 and 5, or when the @code{--source} option is used, the
34889 @samp{asm_insns} list contains tuples named @samp{src_and_asm_line},
34890 each of which has the following fields:
34894 The line number within @samp{file}.
34897 The file name from the compilation unit. This might be an absolute
34898 file name or a relative file name depending on the compile command
34902 Absolute file name of @samp{file}. It is converted to a canonical form
34903 using the source file search path
34904 (@pxref{Source Path, ,Specifying Source Directories})
34905 and after resolving all the symbolic links.
34907 If the source file is not found this field will contain the path as
34908 present in the debug information.
34910 @item line_asm_insn
34911 This is a list of tuples containing the disassembly for @samp{line} in
34912 @samp{file}. The fields of each tuple are the same as for
34913 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
34914 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
34919 Note that whatever included in the @samp{inst} field, is not
34920 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
34923 @subsubheading @value{GDBN} Command
34925 The corresponding @value{GDBN} command is @samp{disassemble}.
34927 @subsubheading Example
34929 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
34933 -data-disassemble -s $pc -e "$pc + 20" -- 0
34936 @{address="0x000107c0",func-name="main",offset="4",
34937 inst="mov 2, %o0"@},
34938 @{address="0x000107c4",func-name="main",offset="8",
34939 inst="sethi %hi(0x11800), %o2"@},
34940 @{address="0x000107c8",func-name="main",offset="12",
34941 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
34942 @{address="0x000107cc",func-name="main",offset="16",
34943 inst="sethi %hi(0x11800), %o2"@},
34944 @{address="0x000107d0",func-name="main",offset="20",
34945 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
34949 Disassemble the whole @code{main} function. Line 32 is part of
34953 -data-disassemble -f basics.c -l 32 -- 0
34955 @{address="0x000107bc",func-name="main",offset="0",
34956 inst="save %sp, -112, %sp"@},
34957 @{address="0x000107c0",func-name="main",offset="4",
34958 inst="mov 2, %o0"@},
34959 @{address="0x000107c4",func-name="main",offset="8",
34960 inst="sethi %hi(0x11800), %o2"@},
34962 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
34963 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
34967 Disassemble 3 instructions from the start of @code{main}:
34971 -data-disassemble -f basics.c -l 32 -n 3 -- 0
34973 @{address="0x000107bc",func-name="main",offset="0",
34974 inst="save %sp, -112, %sp"@},
34975 @{address="0x000107c0",func-name="main",offset="4",
34976 inst="mov 2, %o0"@},
34977 @{address="0x000107c4",func-name="main",offset="8",
34978 inst="sethi %hi(0x11800), %o2"@}]
34982 Disassemble 3 instructions from the start of @code{main} in mixed mode:
34986 -data-disassemble -f basics.c -l 32 -n 3 -- 1
34988 src_and_asm_line=@{line="31",
34989 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34990 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34991 line_asm_insn=[@{address="0x000107bc",
34992 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
34993 src_and_asm_line=@{line="32",
34994 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34995 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34996 line_asm_insn=[@{address="0x000107c0",
34997 func-name="main",offset="4",inst="mov 2, %o0"@},
34998 @{address="0x000107c4",func-name="main",offset="8",
34999 inst="sethi %hi(0x11800), %o2"@}]@}]
35004 @subheading The @code{-data-evaluate-expression} Command
35005 @findex -data-evaluate-expression
35007 @subsubheading Synopsis
35010 -data-evaluate-expression @var{expr}
35013 Evaluate @var{expr} as an expression. The expression could contain an
35014 inferior function call. The function call will execute synchronously.
35015 If the expression contains spaces, it must be enclosed in double quotes.
35017 @subsubheading @value{GDBN} Command
35019 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
35020 @samp{call}. In @code{gdbtk} only, there's a corresponding
35021 @samp{gdb_eval} command.
35023 @subsubheading Example
35025 In the following example, the numbers that precede the commands are the
35026 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
35027 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
35031 211-data-evaluate-expression A
35034 311-data-evaluate-expression &A
35035 311^done,value="0xefffeb7c"
35037 411-data-evaluate-expression A+3
35040 511-data-evaluate-expression "A + 3"
35046 @subheading The @code{-data-list-changed-registers} Command
35047 @findex -data-list-changed-registers
35049 @subsubheading Synopsis
35052 -data-list-changed-registers
35055 Display a list of the registers that have changed.
35057 @subsubheading @value{GDBN} Command
35059 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
35060 has the corresponding command @samp{gdb_changed_register_list}.
35062 @subsubheading Example
35064 On a PPC MBX board:
35072 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
35073 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
35074 line="5",arch="powerpc"@}
35076 -data-list-changed-registers
35077 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
35078 "10","11","13","14","15","16","17","18","19","20","21","22","23",
35079 "24","25","26","27","28","30","31","64","65","66","67","69"]
35084 @subheading The @code{-data-list-register-names} Command
35085 @findex -data-list-register-names
35087 @subsubheading Synopsis
35090 -data-list-register-names [ ( @var{regno} )+ ]
35093 Show a list of register names for the current target. If no arguments
35094 are given, it shows a list of the names of all the registers. If
35095 integer numbers are given as arguments, it will print a list of the
35096 names of the registers corresponding to the arguments. To ensure
35097 consistency between a register name and its number, the output list may
35098 include empty register names.
35100 @subsubheading @value{GDBN} Command
35102 @value{GDBN} does not have a command which corresponds to
35103 @samp{-data-list-register-names}. In @code{gdbtk} there is a
35104 corresponding command @samp{gdb_regnames}.
35106 @subsubheading Example
35108 For the PPC MBX board:
35111 -data-list-register-names
35112 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
35113 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
35114 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
35115 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
35116 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
35117 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
35118 "", "pc","ps","cr","lr","ctr","xer"]
35120 -data-list-register-names 1 2 3
35121 ^done,register-names=["r1","r2","r3"]
35125 @subheading The @code{-data-list-register-values} Command
35126 @findex -data-list-register-values
35128 @subsubheading Synopsis
35131 -data-list-register-values
35132 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
35135 Display the registers' contents. The format according to which the
35136 registers' contents are to be returned is given by @var{fmt}, followed
35137 by an optional list of numbers specifying the registers to display. A
35138 missing list of numbers indicates that the contents of all the
35139 registers must be returned. The @code{--skip-unavailable} option
35140 indicates that only the available registers are to be returned.
35142 Allowed formats for @var{fmt} are:
35159 @subsubheading @value{GDBN} Command
35161 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
35162 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
35164 @subsubheading Example
35166 For a PPC MBX board (note: line breaks are for readability only, they
35167 don't appear in the actual output):
35171 -data-list-register-values r 64 65
35172 ^done,register-values=[@{number="64",value="0xfe00a300"@},
35173 @{number="65",value="0x00029002"@}]
35175 -data-list-register-values x
35176 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
35177 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
35178 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
35179 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
35180 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
35181 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
35182 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
35183 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
35184 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
35185 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
35186 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
35187 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
35188 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
35189 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
35190 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
35191 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
35192 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
35193 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
35194 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
35195 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
35196 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
35197 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
35198 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
35199 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
35200 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
35201 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
35202 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
35203 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
35204 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
35205 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
35206 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
35207 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
35208 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
35209 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
35210 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
35211 @{number="69",value="0x20002b03"@}]
35216 @subheading The @code{-data-read-memory} Command
35217 @findex -data-read-memory
35219 This command is deprecated, use @code{-data-read-memory-bytes} instead.
35221 @subsubheading Synopsis
35224 -data-read-memory [ -o @var{byte-offset} ]
35225 @var{address} @var{word-format} @var{word-size}
35226 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
35233 @item @var{address}
35234 An expression specifying the address of the first memory word to be
35235 read. Complex expressions containing embedded white space should be
35236 quoted using the C convention.
35238 @item @var{word-format}
35239 The format to be used to print the memory words. The notation is the
35240 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
35243 @item @var{word-size}
35244 The size of each memory word in bytes.
35246 @item @var{nr-rows}
35247 The number of rows in the output table.
35249 @item @var{nr-cols}
35250 The number of columns in the output table.
35253 If present, indicates that each row should include an @sc{ascii} dump. The
35254 value of @var{aschar} is used as a padding character when a byte is not a
35255 member of the printable @sc{ascii} character set (printable @sc{ascii}
35256 characters are those whose code is between 32 and 126, inclusively).
35258 @item @var{byte-offset}
35259 An offset to add to the @var{address} before fetching memory.
35262 This command displays memory contents as a table of @var{nr-rows} by
35263 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
35264 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
35265 (returned as @samp{total-bytes}). Should less than the requested number
35266 of bytes be returned by the target, the missing words are identified
35267 using @samp{N/A}. The number of bytes read from the target is returned
35268 in @samp{nr-bytes} and the starting address used to read memory in
35271 The address of the next/previous row or page is available in
35272 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
35275 @subsubheading @value{GDBN} Command
35277 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
35278 @samp{gdb_get_mem} memory read command.
35280 @subsubheading Example
35282 Read six bytes of memory starting at @code{bytes+6} but then offset by
35283 @code{-6} bytes. Format as three rows of two columns. One byte per
35284 word. Display each word in hex.
35288 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
35289 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
35290 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
35291 prev-page="0x0000138a",memory=[
35292 @{addr="0x00001390",data=["0x00","0x01"]@},
35293 @{addr="0x00001392",data=["0x02","0x03"]@},
35294 @{addr="0x00001394",data=["0x04","0x05"]@}]
35298 Read two bytes of memory starting at address @code{shorts + 64} and
35299 display as a single word formatted in decimal.
35303 5-data-read-memory shorts+64 d 2 1 1
35304 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
35305 next-row="0x00001512",prev-row="0x0000150e",
35306 next-page="0x00001512",prev-page="0x0000150e",memory=[
35307 @{addr="0x00001510",data=["128"]@}]
35311 Read thirty two bytes of memory starting at @code{bytes+16} and format
35312 as eight rows of four columns. Include a string encoding with @samp{x}
35313 used as the non-printable character.
35317 4-data-read-memory bytes+16 x 1 8 4 x
35318 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
35319 next-row="0x000013c0",prev-row="0x0000139c",
35320 next-page="0x000013c0",prev-page="0x00001380",memory=[
35321 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
35322 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
35323 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
35324 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
35325 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
35326 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
35327 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
35328 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
35332 @subheading The @code{-data-read-memory-bytes} Command
35333 @findex -data-read-memory-bytes
35335 @subsubheading Synopsis
35338 -data-read-memory-bytes [ -o @var{offset} ]
35339 @var{address} @var{count}
35346 @item @var{address}
35347 An expression specifying the address of the first addressable memory unit
35348 to be read. Complex expressions containing embedded white space should be
35349 quoted using the C convention.
35352 The number of addressable memory units to read. This should be an integer
35356 The offset relative to @var{address} at which to start reading. This
35357 should be an integer literal. This option is provided so that a frontend
35358 is not required to first evaluate address and then perform address
35359 arithmetics itself.
35363 This command attempts to read all accessible memory regions in the
35364 specified range. First, all regions marked as unreadable in the memory
35365 map (if one is defined) will be skipped. @xref{Memory Region
35366 Attributes}. Second, @value{GDBN} will attempt to read the remaining
35367 regions. For each one, if reading full region results in an errors,
35368 @value{GDBN} will try to read a subset of the region.
35370 In general, every single memory unit in the region may be readable or not,
35371 and the only way to read every readable unit is to try a read at
35372 every address, which is not practical. Therefore, @value{GDBN} will
35373 attempt to read all accessible memory units at either beginning or the end
35374 of the region, using a binary division scheme. This heuristic works
35375 well for reading across a memory map boundary. Note that if a region
35376 has a readable range that is neither at the beginning or the end,
35377 @value{GDBN} will not read it.
35379 The result record (@pxref{GDB/MI Result Records}) that is output of
35380 the command includes a field named @samp{memory} whose content is a
35381 list of tuples. Each tuple represent a successfully read memory block
35382 and has the following fields:
35386 The start address of the memory block, as hexadecimal literal.
35389 The end address of the memory block, as hexadecimal literal.
35392 The offset of the memory block, as hexadecimal literal, relative to
35393 the start address passed to @code{-data-read-memory-bytes}.
35396 The contents of the memory block, in hex.
35402 @subsubheading @value{GDBN} Command
35404 The corresponding @value{GDBN} command is @samp{x}.
35406 @subsubheading Example
35410 -data-read-memory-bytes &a 10
35411 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
35413 contents="01000000020000000300"@}]
35418 @subheading The @code{-data-write-memory-bytes} Command
35419 @findex -data-write-memory-bytes
35421 @subsubheading Synopsis
35424 -data-write-memory-bytes @var{address} @var{contents}
35425 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
35432 @item @var{address}
35433 An expression specifying the address of the first addressable memory unit
35434 to be written. Complex expressions containing embedded white space should
35435 be quoted using the C convention.
35437 @item @var{contents}
35438 The hex-encoded data to write. It is an error if @var{contents} does
35439 not represent an integral number of addressable memory units.
35442 Optional argument indicating the number of addressable memory units to be
35443 written. If @var{count} is greater than @var{contents}' length,
35444 @value{GDBN} will repeatedly write @var{contents} until it fills
35445 @var{count} memory units.
35449 @subsubheading @value{GDBN} Command
35451 There's no corresponding @value{GDBN} command.
35453 @subsubheading Example
35457 -data-write-memory-bytes &a "aabbccdd"
35464 -data-write-memory-bytes &a "aabbccdd" 16e
35469 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35470 @node GDB/MI Tracepoint Commands
35471 @section @sc{gdb/mi} Tracepoint Commands
35473 The commands defined in this section implement MI support for
35474 tracepoints. For detailed introduction, see @ref{Tracepoints}.
35476 @subheading The @code{-trace-find} Command
35477 @findex -trace-find
35479 @subsubheading Synopsis
35482 -trace-find @var{mode} [@var{parameters}@dots{}]
35485 Find a trace frame using criteria defined by @var{mode} and
35486 @var{parameters}. The following table lists permissible
35487 modes and their parameters. For details of operation, see @ref{tfind}.
35492 No parameters are required. Stops examining trace frames.
35495 An integer is required as parameter. Selects tracepoint frame with
35498 @item tracepoint-number
35499 An integer is required as parameter. Finds next
35500 trace frame that corresponds to tracepoint with the specified number.
35503 An address is required as parameter. Finds
35504 next trace frame that corresponds to any tracepoint at the specified
35507 @item pc-inside-range
35508 Two addresses are required as parameters. Finds next trace
35509 frame that corresponds to a tracepoint at an address inside the
35510 specified range. Both bounds are considered to be inside the range.
35512 @item pc-outside-range
35513 Two addresses are required as parameters. Finds
35514 next trace frame that corresponds to a tracepoint at an address outside
35515 the specified range. Both bounds are considered to be inside the range.
35518 Location specification is required as parameter. @xref{Location Specifications}.
35519 Finds next trace frame that corresponds to a tracepoint at
35520 the specified location.
35524 If @samp{none} was passed as @var{mode}, the response does not
35525 have fields. Otherwise, the response may have the following fields:
35529 This field has either @samp{0} or @samp{1} as the value, depending
35530 on whether a matching tracepoint was found.
35533 The index of the found traceframe. This field is present iff
35534 the @samp{found} field has value of @samp{1}.
35537 The index of the found tracepoint. This field is present iff
35538 the @samp{found} field has value of @samp{1}.
35541 The information about the frame corresponding to the found trace
35542 frame. This field is present only if a trace frame was found.
35543 @xref{GDB/MI Frame Information}, for description of this field.
35547 @subsubheading @value{GDBN} Command
35549 The corresponding @value{GDBN} command is @samp{tfind}.
35551 @subheading -trace-define-variable
35552 @findex -trace-define-variable
35554 @subsubheading Synopsis
35557 -trace-define-variable @var{name} [ @var{value} ]
35560 Create trace variable @var{name} if it does not exist. If
35561 @var{value} is specified, sets the initial value of the specified
35562 trace variable to that value. Note that the @var{name} should start
35563 with the @samp{$} character.
35565 @subsubheading @value{GDBN} Command
35567 The corresponding @value{GDBN} command is @samp{tvariable}.
35569 @subheading The @code{-trace-frame-collected} Command
35570 @findex -trace-frame-collected
35572 @subsubheading Synopsis
35575 -trace-frame-collected
35576 [--var-print-values @var{var_pval}]
35577 [--comp-print-values @var{comp_pval}]
35578 [--registers-format @var{regformat}]
35579 [--memory-contents]
35582 This command returns the set of collected objects, register names,
35583 trace state variable names, memory ranges and computed expressions
35584 that have been collected at a particular trace frame. The optional
35585 parameters to the command affect the output format in different ways.
35586 See the output description table below for more details.
35588 The reported names can be used in the normal manner to create
35589 varobjs and inspect the objects themselves. The items returned by
35590 this command are categorized so that it is clear which is a variable,
35591 which is a register, which is a trace state variable, which is a
35592 memory range and which is a computed expression.
35594 For instance, if the actions were
35596 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
35597 collect *(int*)0xaf02bef0@@40
35601 the object collected in its entirety would be @code{myVar}. The
35602 object @code{myArray} would be partially collected, because only the
35603 element at index @code{myIndex} would be collected. The remaining
35604 objects would be computed expressions.
35606 An example output would be:
35610 -trace-frame-collected
35612 explicit-variables=[@{name="myVar",value="1"@}],
35613 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
35614 @{name="myObj.field",value="0"@},
35615 @{name="myPtr->field",value="1"@},
35616 @{name="myCount + 2",value="3"@},
35617 @{name="$tvar1 + 1",value="43970027"@}],
35618 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
35619 @{number="1",value="0x0"@},
35620 @{number="2",value="0x4"@},
35622 @{number="125",value="0x0"@}],
35623 tvars=[@{name="$tvar1",current="43970026"@}],
35624 memory=[@{address="0x0000000000602264",length="4"@},
35625 @{address="0x0000000000615bc0",length="4"@}]
35632 @item explicit-variables
35633 The set of objects that have been collected in their entirety (as
35634 opposed to collecting just a few elements of an array or a few struct
35635 members). For each object, its name and value are printed.
35636 The @code{--var-print-values} option affects how or whether the value
35637 field is output. If @var{var_pval} is 0, then print only the names;
35638 if it is 1, print also their values; and if it is 2, print the name,
35639 type and value for simple data types, and the name and type for
35640 arrays, structures and unions.
35642 @item computed-expressions
35643 The set of computed expressions that have been collected at the
35644 current trace frame. The @code{--comp-print-values} option affects
35645 this set like the @code{--var-print-values} option affects the
35646 @code{explicit-variables} set. See above.
35649 The registers that have been collected at the current trace frame.
35650 For each register collected, the name and current value are returned.
35651 The value is formatted according to the @code{--registers-format}
35652 option. See the @command{-data-list-register-values} command for a
35653 list of the allowed formats. The default is @samp{x}.
35656 The trace state variables that have been collected at the current
35657 trace frame. For each trace state variable collected, the name and
35658 current value are returned.
35661 The set of memory ranges that have been collected at the current trace
35662 frame. Its content is a list of tuples. Each tuple represents a
35663 collected memory range and has the following fields:
35667 The start address of the memory range, as hexadecimal literal.
35670 The length of the memory range, as decimal literal.
35673 The contents of the memory block, in hex. This field is only present
35674 if the @code{--memory-contents} option is specified.
35680 @subsubheading @value{GDBN} Command
35682 There is no corresponding @value{GDBN} command.
35684 @subsubheading Example
35686 @subheading -trace-list-variables
35687 @findex -trace-list-variables
35689 @subsubheading Synopsis
35692 -trace-list-variables
35695 Return a table of all defined trace variables. Each element of the
35696 table has the following fields:
35700 The name of the trace variable. This field is always present.
35703 The initial value. This is a 64-bit signed integer. This
35704 field is always present.
35707 The value the trace variable has at the moment. This is a 64-bit
35708 signed integer. This field is absent iff current value is
35709 not defined, for example if the trace was never run, or is
35714 @subsubheading @value{GDBN} Command
35716 The corresponding @value{GDBN} command is @samp{tvariables}.
35718 @subsubheading Example
35722 -trace-list-variables
35723 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
35724 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
35725 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
35726 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
35727 body=[variable=@{name="$trace_timestamp",initial="0"@}
35728 variable=@{name="$foo",initial="10",current="15"@}]@}
35732 @subheading -trace-save
35733 @findex -trace-save
35735 @subsubheading Synopsis
35738 -trace-save [ -r ] [ -ctf ] @var{filename}
35741 Saves the collected trace data to @var{filename}. Without the
35742 @samp{-r} option, the data is downloaded from the target and saved
35743 in a local file. With the @samp{-r} option the target is asked
35744 to perform the save.
35746 By default, this command will save the trace in the tfile format. You can
35747 supply the optional @samp{-ctf} argument to save it the CTF format. See
35748 @ref{Trace Files} for more information about CTF.
35750 @subsubheading @value{GDBN} Command
35752 The corresponding @value{GDBN} command is @samp{tsave}.
35755 @subheading -trace-start
35756 @findex -trace-start
35758 @subsubheading Synopsis
35764 Starts a tracing experiment. The result of this command does not
35767 @subsubheading @value{GDBN} Command
35769 The corresponding @value{GDBN} command is @samp{tstart}.
35771 @subheading -trace-status
35772 @findex -trace-status
35774 @subsubheading Synopsis
35780 Obtains the status of a tracing experiment. The result may include
35781 the following fields:
35786 May have a value of either @samp{0}, when no tracing operations are
35787 supported, @samp{1}, when all tracing operations are supported, or
35788 @samp{file} when examining trace file. In the latter case, examining
35789 of trace frame is possible but new tracing experiement cannot be
35790 started. This field is always present.
35793 May have a value of either @samp{0} or @samp{1} depending on whether
35794 tracing experiement is in progress on target. This field is present
35795 if @samp{supported} field is not @samp{0}.
35798 Report the reason why the tracing was stopped last time. This field
35799 may be absent iff tracing was never stopped on target yet. The
35800 value of @samp{request} means the tracing was stopped as result of
35801 the @code{-trace-stop} command. The value of @samp{overflow} means
35802 the tracing buffer is full. The value of @samp{disconnection} means
35803 tracing was automatically stopped when @value{GDBN} has disconnected.
35804 The value of @samp{passcount} means tracing was stopped when a
35805 tracepoint was passed a maximal number of times for that tracepoint.
35806 This field is present if @samp{supported} field is not @samp{0}.
35808 @item stopping-tracepoint
35809 The number of tracepoint whose passcount as exceeded. This field is
35810 present iff the @samp{stop-reason} field has the value of
35814 @itemx frames-created
35815 The @samp{frames} field is a count of the total number of trace frames
35816 in the trace buffer, while @samp{frames-created} is the total created
35817 during the run, including ones that were discarded, such as when a
35818 circular trace buffer filled up. Both fields are optional.
35822 These fields tell the current size of the tracing buffer and the
35823 remaining space. These fields are optional.
35826 The value of the circular trace buffer flag. @code{1} means that the
35827 trace buffer is circular and old trace frames will be discarded if
35828 necessary to make room, @code{0} means that the trace buffer is linear
35832 The value of the disconnected tracing flag. @code{1} means that
35833 tracing will continue after @value{GDBN} disconnects, @code{0} means
35834 that the trace run will stop.
35837 The filename of the trace file being examined. This field is
35838 optional, and only present when examining a trace file.
35842 @subsubheading @value{GDBN} Command
35844 The corresponding @value{GDBN} command is @samp{tstatus}.
35846 @subheading -trace-stop
35847 @findex -trace-stop
35849 @subsubheading Synopsis
35855 Stops a tracing experiment. The result of this command has the same
35856 fields as @code{-trace-status}, except that the @samp{supported} and
35857 @samp{running} fields are not output.
35859 @subsubheading @value{GDBN} Command
35861 The corresponding @value{GDBN} command is @samp{tstop}.
35864 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35865 @node GDB/MI Symbol Query
35866 @section @sc{gdb/mi} Symbol Query Commands
35870 @subheading The @code{-symbol-info-address} Command
35871 @findex -symbol-info-address
35873 @subsubheading Synopsis
35876 -symbol-info-address @var{symbol}
35879 Describe where @var{symbol} is stored.
35881 @subsubheading @value{GDBN} Command
35883 The corresponding @value{GDBN} command is @samp{info address}.
35885 @subsubheading Example
35889 @subheading The @code{-symbol-info-file} Command
35890 @findex -symbol-info-file
35892 @subsubheading Synopsis
35898 Show the file for the symbol.
35900 @subsubheading @value{GDBN} Command
35902 There's no equivalent @value{GDBN} command. @code{gdbtk} has
35903 @samp{gdb_find_file}.
35905 @subsubheading Example
35909 @subheading The @code{-symbol-info-functions} Command
35910 @findex -symbol-info-functions
35911 @anchor{-symbol-info-functions}
35913 @subsubheading Synopsis
35916 -symbol-info-functions [--include-nondebug]
35917 [--type @var{type_regexp}]
35918 [--name @var{name_regexp}]
35919 [--max-results @var{limit}]
35923 Return a list containing the names and types for all global functions
35924 taken from the debug information. The functions are grouped by source
35925 file, and shown with the line number on which each function is
35928 The @code{--include-nondebug} option causes the output to include
35929 code symbols from the symbol table.
35931 The options @code{--type} and @code{--name} allow the symbols returned
35932 to be filtered based on either the name of the function, or the type
35933 signature of the function.
35935 The option @code{--max-results} restricts the command to return no
35936 more than @var{limit} results. If exactly @var{limit} results are
35937 returned then there might be additional results available if a higher
35940 @subsubheading @value{GDBN} Command
35942 The corresponding @value{GDBN} command is @samp{info functions}.
35944 @subsubheading Example
35948 -symbol-info-functions
35951 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35952 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35953 symbols=[@{line="36", name="f4", type="void (int *)",
35954 description="void f4(int *);"@},
35955 @{line="42", name="main", type="int ()",
35956 description="int main();"@},
35957 @{line="30", name="f1", type="my_int_t (int, int)",
35958 description="static my_int_t f1(int, int);"@}]@},
35959 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35960 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35961 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35962 description="float f2(another_float_t);"@},
35963 @{line="39", name="f3", type="int (another_int_t)",
35964 description="int f3(another_int_t);"@},
35965 @{line="27", name="f1", type="another_float_t (int)",
35966 description="static another_float_t f1(int);"@}]@}]@}
35970 -symbol-info-functions --name f1
35973 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35974 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35975 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
35976 description="static my_int_t f1(int, int);"@}]@},
35977 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35978 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35979 symbols=[@{line="27", name="f1", type="another_float_t (int)",
35980 description="static another_float_t f1(int);"@}]@}]@}
35984 -symbol-info-functions --type void
35987 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35988 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35989 symbols=[@{line="36", name="f4", type="void (int *)",
35990 description="void f4(int *);"@}]@}]@}
35994 -symbol-info-functions --include-nondebug
35997 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35998 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35999 symbols=[@{line="36", name="f4", type="void (int *)",
36000 description="void f4(int *);"@},
36001 @{line="42", name="main", type="int ()",
36002 description="int main();"@},
36003 @{line="30", name="f1", type="my_int_t (int, int)",
36004 description="static my_int_t f1(int, int);"@}]@},
36005 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36006 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36007 symbols=[@{line="33", name="f2", type="float (another_float_t)",
36008 description="float f2(another_float_t);"@},
36009 @{line="39", name="f3", type="int (another_int_t)",
36010 description="int f3(another_int_t);"@},
36011 @{line="27", name="f1", type="another_float_t (int)",
36012 description="static another_float_t f1(int);"@}]@}],
36014 [@{address="0x0000000000400398",name="_init"@},
36015 @{address="0x00000000004003b0",name="_start"@},
36021 @subheading The @code{-symbol-info-module-functions} Command
36022 @findex -symbol-info-module-functions
36023 @anchor{-symbol-info-module-functions}
36025 @subsubheading Synopsis
36028 -symbol-info-module-functions [--module @var{module_regexp}]
36029 [--name @var{name_regexp}]
36030 [--type @var{type_regexp}]
36034 Return a list containing the names of all known functions within all
36035 know Fortran modules. The functions are grouped by source file and
36036 containing module, and shown with the line number on which each
36037 function is defined.
36039 The option @code{--module} only returns results for modules matching
36040 @var{module_regexp}. The option @code{--name} only returns functions
36041 whose name matches @var{name_regexp}, and @code{--type} only returns
36042 functions whose type matches @var{type_regexp}.
36044 @subsubheading @value{GDBN} Command
36046 The corresponding @value{GDBN} command is @samp{info module functions}.
36048 @subsubheading Example
36053 -symbol-info-module-functions
36056 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36057 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36058 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
36059 description="void mod1::check_all(void);"@}]@}]@},
36061 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36062 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36063 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
36064 description="void mod2::check_var_i(void);"@}]@}]@},
36066 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36067 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36068 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
36069 description="void mod3::check_all(void);"@},
36070 @{line="27",name="mod3::check_mod2",type="void (void)",
36071 description="void mod3::check_mod2(void);"@}]@}]@},
36072 @{module="modmany",
36073 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36074 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36075 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
36076 description="void modmany::check_some(void);"@}]@}]@},
36078 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36079 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36080 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
36081 description="void moduse::check_all(void);"@},
36082 @{line="49",name="moduse::check_var_x",type="void (void)",
36083 description="void moduse::check_var_x(void);"@}]@}]@}]
36087 @subheading The @code{-symbol-info-module-variables} Command
36088 @findex -symbol-info-module-variables
36089 @anchor{-symbol-info-module-variables}
36091 @subsubheading Synopsis
36094 -symbol-info-module-variables [--module @var{module_regexp}]
36095 [--name @var{name_regexp}]
36096 [--type @var{type_regexp}]
36100 Return a list containing the names of all known variables within all
36101 know Fortran modules. The variables are grouped by source file and
36102 containing module, and shown with the line number on which each
36103 variable is defined.
36105 The option @code{--module} only returns results for modules matching
36106 @var{module_regexp}. The option @code{--name} only returns variables
36107 whose name matches @var{name_regexp}, and @code{--type} only returns
36108 variables whose type matches @var{type_regexp}.
36110 @subsubheading @value{GDBN} Command
36112 The corresponding @value{GDBN} command is @samp{info module variables}.
36114 @subsubheading Example
36119 -symbol-info-module-variables
36122 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36123 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36124 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
36125 description="integer(kind=4) mod1::var_const;"@},
36126 @{line="17",name="mod1::var_i",type="integer(kind=4)",
36127 description="integer(kind=4) mod1::var_i;"@}]@}]@},
36129 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36130 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36131 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
36132 description="integer(kind=4) mod2::var_i;"@}]@}]@},
36134 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36135 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36136 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
36137 description="integer(kind=4) mod3::mod1;"@},
36138 @{line="17",name="mod3::mod2",type="integer(kind=4)",
36139 description="integer(kind=4) mod3::mod2;"@},
36140 @{line="19",name="mod3::var_i",type="integer(kind=4)",
36141 description="integer(kind=4) mod3::var_i;"@}]@}]@},
36142 @{module="modmany",
36143 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36144 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36145 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
36146 description="integer(kind=4) modmany::var_a;"@},
36147 @{line="33",name="modmany::var_b",type="integer(kind=4)",
36148 description="integer(kind=4) modmany::var_b;"@},
36149 @{line="33",name="modmany::var_c",type="integer(kind=4)",
36150 description="integer(kind=4) modmany::var_c;"@},
36151 @{line="33",name="modmany::var_i",type="integer(kind=4)",
36152 description="integer(kind=4) modmany::var_i;"@}]@}]@},
36154 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36155 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36156 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
36157 description="integer(kind=4) moduse::var_x;"@},
36158 @{line="42",name="moduse::var_y",type="integer(kind=4)",
36159 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
36163 @subheading The @code{-symbol-info-modules} Command
36164 @findex -symbol-info-modules
36165 @anchor{-symbol-info-modules}
36167 @subsubheading Synopsis
36170 -symbol-info-modules [--name @var{name_regexp}]
36171 [--max-results @var{limit}]
36176 Return a list containing the names of all known Fortran modules. The
36177 modules are grouped by source file, and shown with the line number on
36178 which each modules is defined.
36180 The option @code{--name} allows the modules returned to be filtered
36181 based the name of the module.
36183 The option @code{--max-results} restricts the command to return no
36184 more than @var{limit} results. If exactly @var{limit} results are
36185 returned then there might be additional results available if a higher
36188 @subsubheading @value{GDBN} Command
36190 The corresponding @value{GDBN} command is @samp{info modules}.
36192 @subsubheading Example
36196 -symbol-info-modules
36199 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36200 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36201 symbols=[@{line="16",name="mod1"@},
36202 @{line="22",name="mod2"@}]@},
36203 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36204 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36205 symbols=[@{line="16",name="mod3"@},
36206 @{line="22",name="modmany"@},
36207 @{line="26",name="moduse"@}]@}]@}
36211 -symbol-info-modules --name mod[123]
36214 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36215 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
36216 symbols=[@{line="16",name="mod1"@},
36217 @{line="22",name="mod2"@}]@},
36218 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36219 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
36220 symbols=[@{line="16",name="mod3"@}]@}]@}
36224 @subheading The @code{-symbol-info-types} Command
36225 @findex -symbol-info-types
36226 @anchor{-symbol-info-types}
36228 @subsubheading Synopsis
36231 -symbol-info-types [--name @var{name_regexp}]
36232 [--max-results @var{limit}]
36237 Return a list of all defined types. The types are grouped by source
36238 file, and shown with the line number on which each user defined type
36239 is defined. Some base types are not defined in the source code but
36240 are added to the debug information by the compiler, for example
36241 @code{int}, @code{float}, etc.; these types do not have an associated
36244 The option @code{--name} allows the list of types returned to be
36247 The option @code{--max-results} restricts the command to return no
36248 more than @var{limit} results. If exactly @var{limit} results are
36249 returned then there might be additional results available if a higher
36252 @subsubheading @value{GDBN} Command
36254 The corresponding @value{GDBN} command is @samp{info types}.
36256 @subsubheading Example
36263 [@{filename="gdb.mi/mi-sym-info-1.c",
36264 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36265 symbols=[@{name="float"@},
36267 @{line="27",name="typedef int my_int_t;"@}]@},
36268 @{filename="gdb.mi/mi-sym-info-2.c",
36269 fullname="/project/gdb.mi/mi-sym-info-2.c",
36270 symbols=[@{line="24",name="typedef float another_float_t;"@},
36271 @{line="23",name="typedef int another_int_t;"@},
36273 @{name="int"@}]@}]@}
36277 -symbol-info-types --name _int_
36280 [@{filename="gdb.mi/mi-sym-info-1.c",
36281 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36282 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
36283 @{filename="gdb.mi/mi-sym-info-2.c",
36284 fullname="/project/gdb.mi/mi-sym-info-2.c",
36285 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
36289 @subheading The @code{-symbol-info-variables} Command
36290 @findex -symbol-info-variables
36291 @anchor{-symbol-info-variables}
36293 @subsubheading Synopsis
36296 -symbol-info-variables [--include-nondebug]
36297 [--type @var{type_regexp}]
36298 [--name @var{name_regexp}]
36299 [--max-results @var{limit}]
36304 Return a list containing the names and types for all global variables
36305 taken from the debug information. The variables are grouped by source
36306 file, and shown with the line number on which each variable is
36309 The @code{--include-nondebug} option causes the output to include
36310 data symbols from the symbol table.
36312 The options @code{--type} and @code{--name} allow the symbols returned
36313 to be filtered based on either the name of the variable, or the type
36316 The option @code{--max-results} restricts the command to return no
36317 more than @var{limit} results. If exactly @var{limit} results are
36318 returned then there might be additional results available if a higher
36321 @subsubheading @value{GDBN} Command
36323 The corresponding @value{GDBN} command is @samp{info variables}.
36325 @subsubheading Example
36329 -symbol-info-variables
36332 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36333 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36334 symbols=[@{line="25",name="global_f1",type="float",
36335 description="static float global_f1;"@},
36336 @{line="24",name="global_i1",type="int",
36337 description="static int global_i1;"@}]@},
36338 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36339 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36340 symbols=[@{line="21",name="global_f2",type="int",
36341 description="int global_f2;"@},
36342 @{line="20",name="global_i2",type="int",
36343 description="int global_i2;"@},
36344 @{line="19",name="global_f1",type="float",
36345 description="static float global_f1;"@},
36346 @{line="18",name="global_i1",type="int",
36347 description="static int global_i1;"@}]@}]@}
36351 -symbol-info-variables --name f1
36354 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36355 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36356 symbols=[@{line="25",name="global_f1",type="float",
36357 description="static float global_f1;"@}]@},
36358 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36359 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36360 symbols=[@{line="19",name="global_f1",type="float",
36361 description="static float global_f1;"@}]@}]@}
36365 -symbol-info-variables --type float
36368 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36369 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36370 symbols=[@{line="25",name="global_f1",type="float",
36371 description="static float global_f1;"@}]@},
36372 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36373 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36374 symbols=[@{line="19",name="global_f1",type="float",
36375 description="static float global_f1;"@}]@}]@}
36379 -symbol-info-variables --include-nondebug
36382 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36383 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
36384 symbols=[@{line="25",name="global_f1",type="float",
36385 description="static float global_f1;"@},
36386 @{line="24",name="global_i1",type="int",
36387 description="static int global_i1;"@}]@},
36388 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36389 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
36390 symbols=[@{line="21",name="global_f2",type="int",
36391 description="int global_f2;"@},
36392 @{line="20",name="global_i2",type="int",
36393 description="int global_i2;"@},
36394 @{line="19",name="global_f1",type="float",
36395 description="static float global_f1;"@},
36396 @{line="18",name="global_i1",type="int",
36397 description="static int global_i1;"@}]@}],
36399 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
36400 @{address="0x00000000004005d8",name="__dso_handle"@}
36407 @subheading The @code{-symbol-info-line} Command
36408 @findex -symbol-info-line
36410 @subsubheading Synopsis
36416 Show the core addresses of the code for a source line.
36418 @subsubheading @value{GDBN} Command
36420 The corresponding @value{GDBN} command is @samp{info line}.
36421 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
36423 @subsubheading Example
36427 @subheading The @code{-symbol-info-symbol} Command
36428 @findex -symbol-info-symbol
36430 @subsubheading Synopsis
36433 -symbol-info-symbol @var{addr}
36436 Describe what symbol is at location @var{addr}.
36438 @subsubheading @value{GDBN} Command
36440 The corresponding @value{GDBN} command is @samp{info symbol}.
36442 @subsubheading Example
36446 @subheading The @code{-symbol-list-functions} Command
36447 @findex -symbol-list-functions
36449 @subsubheading Synopsis
36452 -symbol-list-functions
36455 List the functions in the executable.
36457 @subsubheading @value{GDBN} Command
36459 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
36460 @samp{gdb_search} in @code{gdbtk}.
36462 @subsubheading Example
36467 @subheading The @code{-symbol-list-lines} Command
36468 @findex -symbol-list-lines
36470 @subsubheading Synopsis
36473 -symbol-list-lines @var{filename}
36476 Print the list of lines that contain code and their associated program
36477 addresses for the given source filename. The entries are sorted in
36478 ascending PC order.
36480 @subsubheading @value{GDBN} Command
36482 There is no corresponding @value{GDBN} command.
36484 @subsubheading Example
36487 -symbol-list-lines basics.c
36488 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
36494 @subheading The @code{-symbol-list-types} Command
36495 @findex -symbol-list-types
36497 @subsubheading Synopsis
36503 List all the type names.
36505 @subsubheading @value{GDBN} Command
36507 The corresponding commands are @samp{info types} in @value{GDBN},
36508 @samp{gdb_search} in @code{gdbtk}.
36510 @subsubheading Example
36514 @subheading The @code{-symbol-list-variables} Command
36515 @findex -symbol-list-variables
36517 @subsubheading Synopsis
36520 -symbol-list-variables
36523 List all the global and static variable names.
36525 @subsubheading @value{GDBN} Command
36527 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
36529 @subsubheading Example
36533 @subheading The @code{-symbol-locate} Command
36534 @findex -symbol-locate
36536 @subsubheading Synopsis
36542 @subsubheading @value{GDBN} Command
36544 @samp{gdb_loc} in @code{gdbtk}.
36546 @subsubheading Example
36550 @subheading The @code{-symbol-type} Command
36551 @findex -symbol-type
36553 @subsubheading Synopsis
36556 -symbol-type @var{variable}
36559 Show type of @var{variable}.
36561 @subsubheading @value{GDBN} Command
36563 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
36564 @samp{gdb_obj_variable}.
36566 @subsubheading Example
36571 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36572 @node GDB/MI File Commands
36573 @section @sc{gdb/mi} File Commands
36575 This section describes the GDB/MI commands to specify executable file names
36576 and to read in and obtain symbol table information.
36578 @subheading The @code{-file-exec-and-symbols} Command
36579 @findex -file-exec-and-symbols
36581 @subsubheading Synopsis
36584 -file-exec-and-symbols @var{file}
36587 Specify the executable file to be debugged. This file is the one from
36588 which the symbol table is also read. If no file is specified, the
36589 command clears the executable and symbol information. If breakpoints
36590 are set when using this command with no arguments, @value{GDBN} will produce
36591 error messages. Otherwise, no output is produced, except a completion
36594 @subsubheading @value{GDBN} Command
36596 The corresponding @value{GDBN} command is @samp{file}.
36598 @subsubheading Example
36602 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36608 @subheading The @code{-file-exec-file} Command
36609 @findex -file-exec-file
36611 @subsubheading Synopsis
36614 -file-exec-file @var{file}
36617 Specify the executable file to be debugged. Unlike
36618 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
36619 from this file. If used without argument, @value{GDBN} clears the information
36620 about the executable file. No output is produced, except a completion
36623 @subsubheading @value{GDBN} Command
36625 The corresponding @value{GDBN} command is @samp{exec-file}.
36627 @subsubheading Example
36631 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36638 @subheading The @code{-file-list-exec-sections} Command
36639 @findex -file-list-exec-sections
36641 @subsubheading Synopsis
36644 -file-list-exec-sections
36647 List the sections of the current executable file.
36649 @subsubheading @value{GDBN} Command
36651 The @value{GDBN} command @samp{info file} shows, among the rest, the same
36652 information as this command. @code{gdbtk} has a corresponding command
36653 @samp{gdb_load_info}.
36655 @subsubheading Example
36660 @subheading The @code{-file-list-exec-source-file} Command
36661 @findex -file-list-exec-source-file
36663 @subsubheading Synopsis
36666 -file-list-exec-source-file
36669 List the line number, the current source file, and the absolute path
36670 to the current source file for the current executable. The macro
36671 information field has a value of @samp{1} or @samp{0} depending on
36672 whether or not the file includes preprocessor macro information.
36674 @subsubheading @value{GDBN} Command
36676 The @value{GDBN} equivalent is @samp{info source}
36678 @subsubheading Example
36682 123-file-list-exec-source-file
36683 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
36688 @subheading The @code{-file-list-exec-source-files} Command
36689 @kindex info sources
36690 @findex -file-list-exec-source-files
36692 @subsubheading Synopsis
36695 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
36696 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
36698 @r{[} @var{regexp} @r{]}
36701 This command returns information about the source files @value{GDBN}
36702 knows about, it will output both the filename and fullname (absolute
36703 file name) of a source file, though the fullname can be elided if this
36704 information is not known to @value{GDBN}.
36706 With no arguments this command returns a list of source files. Each
36707 source file is represented by a tuple with the fields; @var{file},
36708 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
36709 display name for the file, while @var{fullname} is the absolute name
36710 of the file. The @var{fullname} field can be elided if the absolute
36711 name of the source file can't be computed. The field
36712 @var{debug-fully-read} will be a string, either @code{true} or
36713 @code{false}. When @code{true}, this indicates the full debug
36714 information for the compilation unit describing this file has been
36715 read in. When @code{false}, the full debug information has not yet
36716 been read in. While reading in the full debug information it is
36717 possible that @value{GDBN} could become aware of additional source
36720 The optional @var{regexp} can be used to filter the list of source
36721 files returned. The @var{regexp} will be matched against the full
36722 source file name. The matching is case-sensitive, except on operating
36723 systems that have case-insensitive filesystem (e.g.,
36724 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
36725 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
36726 @var{regexp} starts with @samp{-}).
36728 If @code{--dirname} is provided, then @var{regexp} is matched only
36729 against the directory name of each source file. If @code{--basename}
36730 is provided, then @var{regexp} is matched against the basename of each
36731 source file. Only one of @code{--dirname} or @code{--basename} may be
36732 given, and if either is given then @var{regexp} is required.
36734 If @code{--group-by-objfile} is used then the format of the results is
36735 changed. The results will now be a list of tuples, with each tuple
36736 representing an object file (executable or shared library) loaded into
36737 @value{GDBN}. The fields of these tuples are; @var{filename},
36738 @var{debug-info}, and @var{sources}. The @var{filename} is the
36739 absolute name of the object file, @var{debug-info} is a string with
36740 one of the following values:
36744 This object file has no debug information.
36745 @item partially-read
36746 This object file has debug information, but it is not fully read in
36747 yet. When it is read in later, GDB might become aware of additional
36750 This object file has debug information, and this information is fully
36751 read into GDB. The list of source files is complete.
36754 The @var{sources} is a list or tuples, with each tuple describing a
36755 single source file with the same fields as described previously. The
36756 @var{sources} list can be empty for object files that have no debug
36759 @subsubheading @value{GDBN} Command
36761 The @value{GDBN} equivalent is @samp{info sources}.
36762 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
36764 @subsubheading Example
36767 -file-list-exec-source-files
36768 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
36769 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
36770 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
36772 -file-list-exec-source-files
36773 ^done,files=[@{file="test.c",
36774 fullname="/tmp/info-sources/test.c",
36775 debug-fully-read="true"@},
36776 @{file="/usr/include/stdc-predef.h",
36777 fullname="/usr/include/stdc-predef.h",
36778 debug-fully-read="true"@},
36780 fullname="/tmp/info-sources/header.h",
36781 debug-fully-read="true"@},
36783 fullname="/tmp/info-sources/helper.c",
36784 debug-fully-read="true"@}]
36786 -file-list-exec-source-files -- \\.c
36787 ^done,files=[@{file="test.c",
36788 fullname="/tmp/info-sources/test.c",
36789 debug-fully-read="true"@},
36791 fullname="/tmp/info-sources/helper.c",
36792 debug-fully-read="true"@}]
36794 -file-list-exec-source-files --group-by-objfile
36795 ^done,files=[@{filename="/tmp/info-sources/test.x",
36796 debug-info="fully-read",
36797 sources=[@{file="test.c",
36798 fullname="/tmp/info-sources/test.c",
36799 debug-fully-read="true"@},
36800 @{file="/usr/include/stdc-predef.h",
36801 fullname="/usr/include/stdc-predef.h",
36802 debug-fully-read="true"@},
36804 fullname="/tmp/info-sources/header.h",
36805 debug-fully-read="true"@}]@},
36806 @{filename="/lib64/ld-linux-x86-64.so.2",
36809 @{filename="system-supplied DSO at 0x7ffff7fcf000",
36812 @{filename="/tmp/info-sources/libhelper.so",
36813 debug-info="fully-read",
36814 sources=[@{file="helper.c",
36815 fullname="/tmp/info-sources/helper.c",
36816 debug-fully-read="true"@},
36817 @{file="/usr/include/stdc-predef.h",
36818 fullname="/usr/include/stdc-predef.h",
36819 debug-fully-read="true"@},
36821 fullname="/tmp/info-sources/header.h",
36822 debug-fully-read="true"@}]@},
36823 @{filename="/lib64/libc.so.6",
36828 @subheading The @code{-file-list-shared-libraries} Command
36829 @findex -file-list-shared-libraries
36831 @subsubheading Synopsis
36834 -file-list-shared-libraries [ @var{regexp} ]
36837 List the shared libraries in the program.
36838 With a regular expression @var{regexp}, only those libraries whose
36839 names match @var{regexp} are listed.
36841 @subsubheading @value{GDBN} Command
36843 The corresponding @value{GDBN} command is @samp{info shared}. The fields
36844 have a similar meaning to the @code{=library-loaded} notification.
36845 The @code{ranges} field specifies the multiple segments belonging to this
36846 library. Each range has the following fields:
36850 The address defining the inclusive lower bound of the segment.
36852 The address defining the exclusive upper bound of the segment.
36855 @subsubheading Example
36858 -file-list-exec-source-files
36859 ^done,shared-libraries=[
36860 @{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"@}]@},
36861 @{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"@}]@}]
36867 @subheading The @code{-file-list-symbol-files} Command
36868 @findex -file-list-symbol-files
36870 @subsubheading Synopsis
36873 -file-list-symbol-files
36878 @subsubheading @value{GDBN} Command
36880 The corresponding @value{GDBN} command is @samp{info file} (part of it).
36882 @subsubheading Example
36887 @subheading The @code{-file-symbol-file} Command
36888 @findex -file-symbol-file
36890 @subsubheading Synopsis
36893 -file-symbol-file @var{file}
36896 Read symbol table info from the specified @var{file} argument. When
36897 used without arguments, clears @value{GDBN}'s symbol table info. No output is
36898 produced, except for a completion notification.
36900 @subsubheading @value{GDBN} Command
36902 The corresponding @value{GDBN} command is @samp{symbol-file}.
36904 @subsubheading Example
36908 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36914 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36915 @node GDB/MI Memory Overlay Commands
36916 @section @sc{gdb/mi} Memory Overlay Commands
36918 The memory overlay commands are not implemented.
36920 @c @subheading -overlay-auto
36922 @c @subheading -overlay-list-mapping-state
36924 @c @subheading -overlay-list-overlays
36926 @c @subheading -overlay-map
36928 @c @subheading -overlay-off
36930 @c @subheading -overlay-on
36932 @c @subheading -overlay-unmap
36934 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36935 @node GDB/MI Signal Handling Commands
36936 @section @sc{gdb/mi} Signal Handling Commands
36938 Signal handling commands are not implemented.
36940 @c @subheading -signal-handle
36942 @c @subheading -signal-list-handle-actions
36944 @c @subheading -signal-list-signal-types
36948 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36949 @node GDB/MI Target Manipulation
36950 @section @sc{gdb/mi} Target Manipulation Commands
36953 @subheading The @code{-target-attach} Command
36954 @findex -target-attach
36956 @subsubheading Synopsis
36959 -target-attach @var{pid} | @var{gid} | @var{file}
36962 Attach to a process @var{pid} or a file @var{file} outside of
36963 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
36964 group, the id previously returned by
36965 @samp{-list-thread-groups --available} must be used.
36967 @subsubheading @value{GDBN} Command
36969 The corresponding @value{GDBN} command is @samp{attach}.
36971 @subsubheading Example
36975 =thread-created,id="1"
36976 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
36982 @subheading The @code{-target-compare-sections} Command
36983 @findex -target-compare-sections
36985 @subsubheading Synopsis
36988 -target-compare-sections [ @var{section} ]
36991 Compare data of section @var{section} on target to the exec file.
36992 Without the argument, all sections are compared.
36994 @subsubheading @value{GDBN} Command
36996 The @value{GDBN} equivalent is @samp{compare-sections}.
36998 @subsubheading Example
37003 @subheading The @code{-target-detach} Command
37004 @findex -target-detach
37006 @subsubheading Synopsis
37009 -target-detach [ @var{pid} | @var{gid} ]
37012 Detach from the remote target which normally resumes its execution.
37013 If either @var{pid} or @var{gid} is specified, detaches from either
37014 the specified process, or specified thread group. There's no output.
37016 @subsubheading @value{GDBN} Command
37018 The corresponding @value{GDBN} command is @samp{detach}.
37020 @subsubheading Example
37030 @subheading The @code{-target-disconnect} Command
37031 @findex -target-disconnect
37033 @subsubheading Synopsis
37039 Disconnect from the remote target. There's no output and the target is
37040 generally not resumed.
37042 @subsubheading @value{GDBN} Command
37044 The corresponding @value{GDBN} command is @samp{disconnect}.
37046 @subsubheading Example
37056 @subheading The @code{-target-download} Command
37057 @findex -target-download
37059 @subsubheading Synopsis
37065 Loads the executable onto the remote target.
37066 It prints out an update message every half second, which includes the fields:
37070 The name of the section.
37072 The size of what has been sent so far for that section.
37074 The size of the section.
37076 The total size of what was sent so far (the current and the previous sections).
37078 The size of the overall executable to download.
37082 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
37083 @sc{gdb/mi} Output Syntax}).
37085 In addition, it prints the name and size of the sections, as they are
37086 downloaded. These messages include the following fields:
37090 The name of the section.
37092 The size of the section.
37094 The size of the overall executable to download.
37098 At the end, a summary is printed.
37100 @subsubheading @value{GDBN} Command
37102 The corresponding @value{GDBN} command is @samp{load}.
37104 @subsubheading Example
37106 Note: each status message appears on a single line. Here the messages
37107 have been broken down so that they can fit onto a page.
37112 +download,@{section=".text",section-size="6668",total-size="9880"@}
37113 +download,@{section=".text",section-sent="512",section-size="6668",
37114 total-sent="512",total-size="9880"@}
37115 +download,@{section=".text",section-sent="1024",section-size="6668",
37116 total-sent="1024",total-size="9880"@}
37117 +download,@{section=".text",section-sent="1536",section-size="6668",
37118 total-sent="1536",total-size="9880"@}
37119 +download,@{section=".text",section-sent="2048",section-size="6668",
37120 total-sent="2048",total-size="9880"@}
37121 +download,@{section=".text",section-sent="2560",section-size="6668",
37122 total-sent="2560",total-size="9880"@}
37123 +download,@{section=".text",section-sent="3072",section-size="6668",
37124 total-sent="3072",total-size="9880"@}
37125 +download,@{section=".text",section-sent="3584",section-size="6668",
37126 total-sent="3584",total-size="9880"@}
37127 +download,@{section=".text",section-sent="4096",section-size="6668",
37128 total-sent="4096",total-size="9880"@}
37129 +download,@{section=".text",section-sent="4608",section-size="6668",
37130 total-sent="4608",total-size="9880"@}
37131 +download,@{section=".text",section-sent="5120",section-size="6668",
37132 total-sent="5120",total-size="9880"@}
37133 +download,@{section=".text",section-sent="5632",section-size="6668",
37134 total-sent="5632",total-size="9880"@}
37135 +download,@{section=".text",section-sent="6144",section-size="6668",
37136 total-sent="6144",total-size="9880"@}
37137 +download,@{section=".text",section-sent="6656",section-size="6668",
37138 total-sent="6656",total-size="9880"@}
37139 +download,@{section=".init",section-size="28",total-size="9880"@}
37140 +download,@{section=".fini",section-size="28",total-size="9880"@}
37141 +download,@{section=".data",section-size="3156",total-size="9880"@}
37142 +download,@{section=".data",section-sent="512",section-size="3156",
37143 total-sent="7236",total-size="9880"@}
37144 +download,@{section=".data",section-sent="1024",section-size="3156",
37145 total-sent="7748",total-size="9880"@}
37146 +download,@{section=".data",section-sent="1536",section-size="3156",
37147 total-sent="8260",total-size="9880"@}
37148 +download,@{section=".data",section-sent="2048",section-size="3156",
37149 total-sent="8772",total-size="9880"@}
37150 +download,@{section=".data",section-sent="2560",section-size="3156",
37151 total-sent="9284",total-size="9880"@}
37152 +download,@{section=".data",section-sent="3072",section-size="3156",
37153 total-sent="9796",total-size="9880"@}
37154 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
37161 @subheading The @code{-target-exec-status} Command
37162 @findex -target-exec-status
37164 @subsubheading Synopsis
37167 -target-exec-status
37170 Provide information on the state of the target (whether it is running or
37171 not, for instance).
37173 @subsubheading @value{GDBN} Command
37175 There's no equivalent @value{GDBN} command.
37177 @subsubheading Example
37181 @subheading The @code{-target-list-available-targets} Command
37182 @findex -target-list-available-targets
37184 @subsubheading Synopsis
37187 -target-list-available-targets
37190 List the possible targets to connect to.
37192 @subsubheading @value{GDBN} Command
37194 The corresponding @value{GDBN} command is @samp{help target}.
37196 @subsubheading Example
37200 @subheading The @code{-target-list-current-targets} Command
37201 @findex -target-list-current-targets
37203 @subsubheading Synopsis
37206 -target-list-current-targets
37209 Describe the current target.
37211 @subsubheading @value{GDBN} Command
37213 The corresponding information is printed by @samp{info file} (among
37216 @subsubheading Example
37220 @subheading The @code{-target-list-parameters} Command
37221 @findex -target-list-parameters
37223 @subsubheading Synopsis
37226 -target-list-parameters
37232 @subsubheading @value{GDBN} Command
37236 @subsubheading Example
37239 @subheading The @code{-target-flash-erase} Command
37240 @findex -target-flash-erase
37242 @subsubheading Synopsis
37245 -target-flash-erase
37248 Erases all known flash memory regions on the target.
37250 The corresponding @value{GDBN} command is @samp{flash-erase}.
37252 The output is a list of flash regions that have been erased, with starting
37253 addresses and memory region sizes.
37257 -target-flash-erase
37258 ^done,erased-regions=@{address="0x0",size="0x40000"@}
37262 @subheading The @code{-target-select} Command
37263 @findex -target-select
37265 @subsubheading Synopsis
37268 -target-select @var{type} @var{parameters @dots{}}
37271 Connect @value{GDBN} to the remote target. This command takes two args:
37275 The type of target, for instance @samp{remote}, etc.
37276 @item @var{parameters}
37277 Device names, host names and the like. @xref{Target Commands, ,
37278 Commands for Managing Targets}, for more details.
37281 The output is a connection notification, followed by the address at
37282 which the target program is, in the following form:
37285 ^connected,addr="@var{address}",func="@var{function name}",
37286 args=[@var{arg list}]
37289 @subsubheading @value{GDBN} Command
37291 The corresponding @value{GDBN} command is @samp{target}.
37293 @subsubheading Example
37297 -target-select remote /dev/ttya
37298 ^connected,addr="0xfe00a300",func="??",args=[]
37302 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37303 @node GDB/MI File Transfer Commands
37304 @section @sc{gdb/mi} File Transfer Commands
37307 @subheading The @code{-target-file-put} Command
37308 @findex -target-file-put
37310 @subsubheading Synopsis
37313 -target-file-put @var{hostfile} @var{targetfile}
37316 Copy file @var{hostfile} from the host system (the machine running
37317 @value{GDBN}) to @var{targetfile} on the target system.
37319 @subsubheading @value{GDBN} Command
37321 The corresponding @value{GDBN} command is @samp{remote put}.
37323 @subsubheading Example
37327 -target-file-put localfile remotefile
37333 @subheading The @code{-target-file-get} Command
37334 @findex -target-file-get
37336 @subsubheading Synopsis
37339 -target-file-get @var{targetfile} @var{hostfile}
37342 Copy file @var{targetfile} from the target system to @var{hostfile}
37343 on the host system.
37345 @subsubheading @value{GDBN} Command
37347 The corresponding @value{GDBN} command is @samp{remote get}.
37349 @subsubheading Example
37353 -target-file-get remotefile localfile
37359 @subheading The @code{-target-file-delete} Command
37360 @findex -target-file-delete
37362 @subsubheading Synopsis
37365 -target-file-delete @var{targetfile}
37368 Delete @var{targetfile} from the target system.
37370 @subsubheading @value{GDBN} Command
37372 The corresponding @value{GDBN} command is @samp{remote delete}.
37374 @subsubheading Example
37378 -target-file-delete remotefile
37384 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37385 @node GDB/MI Ada Exceptions Commands
37386 @section Ada Exceptions @sc{gdb/mi} Commands
37388 @subheading The @code{-info-ada-exceptions} Command
37389 @findex -info-ada-exceptions
37391 @subsubheading Synopsis
37394 -info-ada-exceptions [ @var{regexp}]
37397 List all Ada exceptions defined within the program being debugged.
37398 With a regular expression @var{regexp}, only those exceptions whose
37399 names match @var{regexp} are listed.
37401 @subsubheading @value{GDBN} Command
37403 The corresponding @value{GDBN} command is @samp{info exceptions}.
37405 @subsubheading Result
37407 The result is a table of Ada exceptions. The following columns are
37408 defined for each exception:
37412 The name of the exception.
37415 The address of the exception.
37419 @subsubheading Example
37422 -info-ada-exceptions aint
37423 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
37424 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
37425 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
37426 body=[@{name="constraint_error",address="0x0000000000613da0"@},
37427 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
37430 @subheading Catching Ada Exceptions
37432 The commands describing how to ask @value{GDBN} to stop when a program
37433 raises an exception are described at @ref{Ada Exception GDB/MI
37434 Catchpoint Commands}.
37437 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37438 @node GDB/MI Support Commands
37439 @section @sc{gdb/mi} Support Commands
37441 Since new commands and features get regularly added to @sc{gdb/mi},
37442 some commands are available to help front-ends query the debugger
37443 about support for these capabilities. Similarly, it is also possible
37444 to query @value{GDBN} about target support of certain features.
37446 @subheading The @code{-info-gdb-mi-command} Command
37447 @cindex @code{-info-gdb-mi-command}
37448 @findex -info-gdb-mi-command
37450 @subsubheading Synopsis
37453 -info-gdb-mi-command @var{cmd_name}
37456 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
37458 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
37459 is technically not part of the command name (@pxref{GDB/MI Input
37460 Syntax}), and thus should be omitted in @var{cmd_name}. However,
37461 for ease of use, this command also accepts the form with the leading
37464 @subsubheading @value{GDBN} Command
37466 There is no corresponding @value{GDBN} command.
37468 @subsubheading Result
37470 The result is a tuple. There is currently only one field:
37474 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
37475 @code{"false"} otherwise.
37479 @subsubheading Example
37481 Here is an example where the @sc{gdb/mi} command does not exist:
37484 -info-gdb-mi-command unsupported-command
37485 ^done,command=@{exists="false"@}
37489 And here is an example where the @sc{gdb/mi} command is known
37493 -info-gdb-mi-command symbol-list-lines
37494 ^done,command=@{exists="true"@}
37497 @subheading The @code{-list-features} Command
37498 @findex -list-features
37499 @cindex supported @sc{gdb/mi} features, list
37501 Returns a list of particular features of the MI protocol that
37502 this version of gdb implements. A feature can be a command,
37503 or a new field in an output of some command, or even an
37504 important bugfix. While a frontend can sometimes detect presence
37505 of a feature at runtime, it is easier to perform detection at debugger
37508 The command returns a list of strings, with each string naming an
37509 available feature. Each returned string is just a name, it does not
37510 have any internal structure. The list of possible feature names
37516 (gdb) -list-features
37517 ^done,result=["feature1","feature2"]
37520 The current list of features is:
37523 @item frozen-varobjs
37524 Indicates support for the @code{-var-set-frozen} command, as well
37525 as possible presence of the @code{frozen} field in the output
37526 of @code{-varobj-create}.
37527 @item pending-breakpoints
37528 Indicates support for the @option{-f} option to the @code{-break-insert}
37531 Indicates Python scripting support, Python-based
37532 pretty-printing commands, and possible presence of the
37533 @samp{display_hint} field in the output of @code{-var-list-children}
37535 Indicates support for the @code{-thread-info} command.
37536 @item data-read-memory-bytes
37537 Indicates support for the @code{-data-read-memory-bytes} and the
37538 @code{-data-write-memory-bytes} commands.
37539 @item breakpoint-notifications
37540 Indicates that changes to breakpoints and breakpoints created via the
37541 CLI will be announced via async records.
37542 @item ada-task-info
37543 Indicates support for the @code{-ada-task-info} command.
37544 @item language-option
37545 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
37546 option (@pxref{Context management}).
37547 @item info-gdb-mi-command
37548 Indicates support for the @code{-info-gdb-mi-command} command.
37549 @item undefined-command-error-code
37550 Indicates support for the "undefined-command" error code in error result
37551 records, produced when trying to execute an undefined @sc{gdb/mi} command
37552 (@pxref{GDB/MI Result Records}).
37553 @item exec-run-start-option
37554 Indicates that the @code{-exec-run} command supports the @option{--start}
37555 option (@pxref{GDB/MI Program Execution}).
37556 @item data-disassemble-a-option
37557 Indicates that the @code{-data-disassemble} command supports the @option{-a}
37558 option (@pxref{GDB/MI Data Manipulation}).
37561 @subheading The @code{-list-target-features} Command
37562 @findex -list-target-features
37564 Returns a list of particular features that are supported by the
37565 target. Those features affect the permitted MI commands, but
37566 unlike the features reported by the @code{-list-features} command, the
37567 features depend on which target GDB is using at the moment. Whenever
37568 a target can change, due to commands such as @code{-target-select},
37569 @code{-target-attach} or @code{-exec-run}, the list of target features
37570 may change, and the frontend should obtain it again.
37574 (gdb) -list-target-features
37575 ^done,result=["async"]
37578 The current list of features is:
37582 Indicates that the target is capable of asynchronous command
37583 execution, which means that @value{GDBN} will accept further commands
37584 while the target is running.
37587 Indicates that the target is capable of reverse execution.
37588 @xref{Reverse Execution}, for more information.
37592 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37593 @node GDB/MI Miscellaneous Commands
37594 @section Miscellaneous @sc{gdb/mi} Commands
37596 @c @subheading -gdb-complete
37598 @subheading The @code{-gdb-exit} Command
37601 @subsubheading Synopsis
37607 Exit @value{GDBN} immediately.
37609 @subsubheading @value{GDBN} Command
37611 Approximately corresponds to @samp{quit}.
37613 @subsubheading Example
37623 @subheading The @code{-exec-abort} Command
37624 @findex -exec-abort
37626 @subsubheading Synopsis
37632 Kill the inferior running program.
37634 @subsubheading @value{GDBN} Command
37636 The corresponding @value{GDBN} command is @samp{kill}.
37638 @subsubheading Example
37643 @subheading The @code{-gdb-set} Command
37646 @subsubheading Synopsis
37652 Set an internal @value{GDBN} variable.
37653 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
37655 @subsubheading @value{GDBN} Command
37657 The corresponding @value{GDBN} command is @samp{set}.
37659 @subsubheading Example
37669 @subheading The @code{-gdb-show} Command
37672 @subsubheading Synopsis
37678 Show the current value of a @value{GDBN} variable.
37680 @subsubheading @value{GDBN} Command
37682 The corresponding @value{GDBN} command is @samp{show}.
37684 @subsubheading Example
37693 @c @subheading -gdb-source
37696 @subheading The @code{-gdb-version} Command
37697 @findex -gdb-version
37699 @subsubheading Synopsis
37705 Show version information for @value{GDBN}. Used mostly in testing.
37707 @subsubheading @value{GDBN} Command
37709 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
37710 default shows this information when you start an interactive session.
37712 @subsubheading Example
37714 @c This example modifies the actual output from GDB to avoid overfull
37720 ~Copyright 2000 Free Software Foundation, Inc.
37721 ~GDB is free software, covered by the GNU General Public License, and
37722 ~you are welcome to change it and/or distribute copies of it under
37723 ~ certain conditions.
37724 ~Type "show copying" to see the conditions.
37725 ~There is absolutely no warranty for GDB. Type "show warranty" for
37727 ~This GDB was configured as
37728 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
37733 @subheading The @code{-list-thread-groups} Command
37734 @findex -list-thread-groups
37736 @subheading Synopsis
37739 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
37742 Lists thread groups (@pxref{Thread groups}). When a single thread
37743 group is passed as the argument, lists the children of that group.
37744 When several thread group are passed, lists information about those
37745 thread groups. Without any parameters, lists information about all
37746 top-level thread groups.
37748 Normally, thread groups that are being debugged are reported.
37749 With the @samp{--available} option, @value{GDBN} reports thread groups
37750 available on the target.
37752 The output of this command may have either a @samp{threads} result or
37753 a @samp{groups} result. The @samp{thread} result has a list of tuples
37754 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
37755 Information}). The @samp{groups} result has a list of tuples as value,
37756 each tuple describing a thread group. If top-level groups are
37757 requested (that is, no parameter is passed), or when several groups
37758 are passed, the output always has a @samp{groups} result. The format
37759 of the @samp{group} result is described below.
37761 To reduce the number of roundtrips it's possible to list thread groups
37762 together with their children, by passing the @samp{--recurse} option
37763 and the recursion depth. Presently, only recursion depth of 1 is
37764 permitted. If this option is present, then every reported thread group
37765 will also include its children, either as @samp{group} or
37766 @samp{threads} field.
37768 In general, any combination of option and parameters is permitted, with
37769 the following caveats:
37773 When a single thread group is passed, the output will typically
37774 be the @samp{threads} result. Because threads may not contain
37775 anything, the @samp{recurse} option will be ignored.
37778 When the @samp{--available} option is passed, limited information may
37779 be available. In particular, the list of threads of a process might
37780 be inaccessible. Further, specifying specific thread groups might
37781 not give any performance advantage over listing all thread groups.
37782 The frontend should assume that @samp{-list-thread-groups --available}
37783 is always an expensive operation and cache the results.
37787 The @samp{groups} result is a list of tuples, where each tuple may
37788 have the following fields:
37792 Identifier of the thread group. This field is always present.
37793 The identifier is an opaque string; frontends should not try to
37794 convert it to an integer, even though it might look like one.
37797 The type of the thread group. At present, only @samp{process} is a
37801 The target-specific process identifier. This field is only present
37802 for thread groups of type @samp{process} and only if the process exists.
37805 The exit code of this group's last exited thread, formatted in octal.
37806 This field is only present for thread groups of type @samp{process} and
37807 only if the process is not running.
37810 The number of children this thread group has. This field may be
37811 absent for an available thread group.
37814 This field has a list of tuples as value, each tuple describing a
37815 thread. It may be present if the @samp{--recurse} option is
37816 specified, and it's actually possible to obtain the threads.
37819 This field is a list of integers, each identifying a core that one
37820 thread of the group is running on. This field may be absent if
37821 such information is not available.
37824 The name of the executable file that corresponds to this thread group.
37825 The field is only present for thread groups of type @samp{process},
37826 and only if there is a corresponding executable file.
37830 @subheading Example
37834 -list-thread-groups
37835 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
37836 -list-thread-groups 17
37837 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
37838 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
37839 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
37840 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
37841 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
37842 -list-thread-groups --available
37843 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
37844 -list-thread-groups --available --recurse 1
37845 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37846 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37847 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
37848 -list-thread-groups --available --recurse 1 17 18
37849 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37850 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37851 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
37854 @subheading The @code{-info-os} Command
37857 @subsubheading Synopsis
37860 -info-os [ @var{type} ]
37863 If no argument is supplied, the command returns a table of available
37864 operating-system-specific information types. If one of these types is
37865 supplied as an argument @var{type}, then the command returns a table
37866 of data of that type.
37868 The types of information available depend on the target operating
37871 @subsubheading @value{GDBN} Command
37873 The corresponding @value{GDBN} command is @samp{info os}.
37875 @subsubheading Example
37877 When run on a @sc{gnu}/Linux system, the output will look something
37883 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
37884 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
37885 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
37886 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
37887 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
37889 item=@{col0="files",col1="Listing of all file descriptors",
37890 col2="File descriptors"@},
37891 item=@{col0="modules",col1="Listing of all loaded kernel modules",
37892 col2="Kernel modules"@},
37893 item=@{col0="msg",col1="Listing of all message queues",
37894 col2="Message queues"@},
37895 item=@{col0="processes",col1="Listing of all processes",
37896 col2="Processes"@},
37897 item=@{col0="procgroups",col1="Listing of all process groups",
37898 col2="Process groups"@},
37899 item=@{col0="semaphores",col1="Listing of all semaphores",
37900 col2="Semaphores"@},
37901 item=@{col0="shm",col1="Listing of all shared-memory regions",
37902 col2="Shared-memory regions"@},
37903 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
37905 item=@{col0="threads",col1="Listing of all threads",
37909 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
37910 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
37911 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
37912 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
37913 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
37914 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
37915 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
37916 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
37918 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
37919 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
37923 (Note that the MI output here includes a @code{"Title"} column that
37924 does not appear in command-line @code{info os}; this column is useful
37925 for MI clients that want to enumerate the types of data, such as in a
37926 popup menu, but is needless clutter on the command line, and
37927 @code{info os} omits it.)
37929 @subheading The @code{-add-inferior} Command
37930 @findex -add-inferior
37932 @subheading Synopsis
37935 -add-inferior [ --no-connection ]
37938 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
37939 inferior is not associated with any executable. Such association may
37940 be established with the @samp{-file-exec-and-symbols} command
37941 (@pxref{GDB/MI File Commands}).
37943 By default, the new inferior begins connected to the same target
37944 connection as the current inferior. For example, if the current
37945 inferior was connected to @code{gdbserver} with @code{target remote},
37946 then the new inferior will be connected to the same @code{gdbserver}
37947 instance. The @samp{--no-connection} option starts the new inferior
37948 with no connection yet. You can then for example use the
37949 @code{-target-select remote} command to connect to some other
37950 @code{gdbserver} instance, use @code{-exec-run} to spawn a local
37953 The command response always has a field, @var{inferior}, whose value
37954 is the identifier of the thread group corresponding to the new
37957 An additional section field, @var{connection}, is optional. This
37958 field will only exist if the new inferior has a target connection. If
37959 this field exists, then its value will be a tuple containing the
37964 The number of the connection used for the new inferior.
37967 The name of the connection type used for the new inferior.
37970 @subheading @value{GDBN} Command
37972 The corresponding @value{GDBN} command is @samp{add-inferior}
37973 (@pxref{add_inferior_cli,,@samp{add-inferior}}).
37975 @subheading Example
37980 ^done,inferior="i3"
37983 @subheading The @code{-interpreter-exec} Command
37984 @findex -interpreter-exec
37986 @subheading Synopsis
37989 -interpreter-exec @var{interpreter} @var{command}
37991 @anchor{-interpreter-exec}
37993 Execute the specified @var{command} in the given @var{interpreter}.
37995 @subheading @value{GDBN} Command
37997 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
37999 @subheading Example
38003 -interpreter-exec console "break main"
38004 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
38005 &"During symbol reading, bad structure-type format.\n"
38006 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
38011 @subheading The @code{-inferior-tty-set} Command
38012 @findex -inferior-tty-set
38014 @subheading Synopsis
38017 -inferior-tty-set /dev/pts/1
38020 Set terminal for future runs of the program being debugged.
38022 @subheading @value{GDBN} Command
38024 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
38026 @subheading Example
38030 -inferior-tty-set /dev/pts/1
38035 @subheading The @code{-inferior-tty-show} Command
38036 @findex -inferior-tty-show
38038 @subheading Synopsis
38044 Show terminal for future runs of program being debugged.
38046 @subheading @value{GDBN} Command
38048 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
38050 @subheading Example
38054 -inferior-tty-set /dev/pts/1
38058 ^done,inferior_tty_terminal="/dev/pts/1"
38062 @subheading The @code{-enable-timings} Command
38063 @findex -enable-timings
38065 @subheading Synopsis
38068 -enable-timings [yes | no]
38071 Toggle the printing of the wallclock, user and system times for an MI
38072 command as a field in its output. This command is to help frontend
38073 developers optimize the performance of their code. No argument is
38074 equivalent to @samp{yes}.
38076 @subheading @value{GDBN} Command
38080 @subheading Example
38088 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
38089 addr="0x080484ed",func="main",file="myprog.c",
38090 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
38092 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
38100 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
38101 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
38102 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
38103 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
38107 @subheading The @code{-complete} Command
38110 @subheading Synopsis
38113 -complete @var{command}
38116 Show a list of completions for partially typed CLI @var{command}.
38118 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
38119 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
38120 because @value{GDBN} is used remotely via a SSH connection.
38124 The result consists of two or three fields:
38128 This field contains the completed @var{command}. If @var{command}
38129 has no known completions, this field is omitted.
38132 This field contains a (possibly empty) array of matches. It is always present.
38134 @item max_completions_reached
38135 This field contains @code{1} if number of known completions is above
38136 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
38137 @code{0}. It is always present.
38141 @subheading @value{GDBN} Command
38143 The corresponding @value{GDBN} command is @samp{complete}.
38145 @subheading Example
38150 ^done,completion="break",
38151 matches=["break","break-range"],
38152 max_completions_reached="0"
38155 ^done,completion="b ma",
38156 matches=["b madvise","b main"],max_completions_reached="0"
38158 -complete "b push_b"
38159 ^done,completion="b push_back(",
38161 "b A::push_back(void*)",
38162 "b std::string::push_back(char)",
38163 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
38164 max_completions_reached="0"
38166 -complete "nonexist"
38167 ^done,matches=[],max_completions_reached="0"
38173 @chapter @value{GDBN} Annotations
38175 This chapter describes annotations in @value{GDBN}. Annotations were
38176 designed to interface @value{GDBN} to graphical user interfaces or other
38177 similar programs which want to interact with @value{GDBN} at a
38178 relatively high level.
38180 The annotation mechanism has largely been superseded by @sc{gdb/mi}
38184 This is Edition @value{EDITION}, @value{DATE}.
38188 * Annotations Overview:: What annotations are; the general syntax.
38189 * Server Prefix:: Issuing a command without affecting user state.
38190 * Prompting:: Annotations marking @value{GDBN}'s need for input.
38191 * Errors:: Annotations for error messages.
38192 * Invalidation:: Some annotations describe things now invalid.
38193 * Annotations for Running::
38194 Whether the program is running, how it stopped, etc.
38195 * Source Annotations:: Annotations describing source code.
38198 @node Annotations Overview
38199 @section What is an Annotation?
38200 @cindex annotations
38202 Annotations start with a newline character, two @samp{control-z}
38203 characters, and the name of the annotation. If there is no additional
38204 information associated with this annotation, the name of the annotation
38205 is followed immediately by a newline. If there is additional
38206 information, the name of the annotation is followed by a space, the
38207 additional information, and a newline. The additional information
38208 cannot contain newline characters.
38210 Any output not beginning with a newline and two @samp{control-z}
38211 characters denotes literal output from @value{GDBN}. Currently there is
38212 no need for @value{GDBN} to output a newline followed by two
38213 @samp{control-z} characters, but if there was such a need, the
38214 annotations could be extended with an @samp{escape} annotation which
38215 means those three characters as output.
38217 The annotation @var{level}, which is specified using the
38218 @option{--annotate} command line option (@pxref{Mode Options}), controls
38219 how much information @value{GDBN} prints together with its prompt,
38220 values of expressions, source lines, and other types of output. Level 0
38221 is for no annotations, level 1 is for use when @value{GDBN} is run as a
38222 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
38223 for programs that control @value{GDBN}, and level 2 annotations have
38224 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
38225 Interface, annotate, GDB's Obsolete Annotations}).
38228 @kindex set annotate
38229 @item set annotate @var{level}
38230 The @value{GDBN} command @code{set annotate} sets the level of
38231 annotations to the specified @var{level}.
38233 @item show annotate
38234 @kindex show annotate
38235 Show the current annotation level.
38238 This chapter describes level 3 annotations.
38240 A simple example of starting up @value{GDBN} with annotations is:
38243 $ @kbd{gdb --annotate=3}
38245 Copyright 2003 Free Software Foundation, Inc.
38246 GDB is free software, covered by the GNU General Public License,
38247 and you are welcome to change it and/or distribute copies of it
38248 under certain conditions.
38249 Type "show copying" to see the conditions.
38250 There is absolutely no warranty for GDB. Type "show warranty"
38252 This GDB was configured as "i386-pc-linux-gnu"
38263 Here @samp{quit} is input to @value{GDBN}; the rest is output from
38264 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
38265 denotes a @samp{control-z} character) are annotations; the rest is
38266 output from @value{GDBN}.
38268 @node Server Prefix
38269 @section The Server Prefix
38270 @cindex server prefix
38272 If you prefix a command with @samp{server } then it will not affect
38273 the command history, nor will it affect @value{GDBN}'s notion of which
38274 command to repeat if @key{RET} is pressed on a line by itself. This
38275 means that commands can be run behind a user's back by a front-end in
38276 a transparent manner.
38278 The @code{server } prefix does not affect the recording of values into
38279 the value history; to print a value without recording it into the
38280 value history, use the @code{output} command instead of the
38281 @code{print} command.
38283 Using this prefix also disables confirmation requests
38284 (@pxref{confirmation requests}).
38287 @section Annotation for @value{GDBN} Input
38289 @cindex annotations for prompts
38290 When @value{GDBN} prompts for input, it annotates this fact so it is possible
38291 to know when to send output, when the output from a given command is
38294 Different kinds of input each have a different @dfn{input type}. Each
38295 input type has three annotations: a @code{pre-} annotation, which
38296 denotes the beginning of any prompt which is being output, a plain
38297 annotation, which denotes the end of the prompt, and then a @code{post-}
38298 annotation which denotes the end of any echo which may (or may not) be
38299 associated with the input. For example, the @code{prompt} input type
38300 features the following annotations:
38308 The input types are
38311 @findex pre-prompt annotation
38312 @findex prompt annotation
38313 @findex post-prompt annotation
38315 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
38317 @findex pre-commands annotation
38318 @findex commands annotation
38319 @findex post-commands annotation
38321 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
38322 command. The annotations are repeated for each command which is input.
38324 @findex pre-overload-choice annotation
38325 @findex overload-choice annotation
38326 @findex post-overload-choice annotation
38327 @item overload-choice
38328 When @value{GDBN} wants the user to select between various overloaded functions.
38330 @findex pre-query annotation
38331 @findex query annotation
38332 @findex post-query annotation
38334 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
38336 @findex pre-prompt-for-continue annotation
38337 @findex prompt-for-continue annotation
38338 @findex post-prompt-for-continue annotation
38339 @item prompt-for-continue
38340 When @value{GDBN} is asking the user to press return to continue. Note: Don't
38341 expect this to work well; instead use @code{set height 0} to disable
38342 prompting. This is because the counting of lines is buggy in the
38343 presence of annotations.
38348 @cindex annotations for errors, warnings and interrupts
38350 @findex quit annotation
38355 This annotation occurs right before @value{GDBN} responds to an interrupt.
38357 @findex error annotation
38362 This annotation occurs right before @value{GDBN} responds to an error.
38364 Quit and error annotations indicate that any annotations which @value{GDBN} was
38365 in the middle of may end abruptly. For example, if a
38366 @code{value-history-begin} annotation is followed by a @code{error}, one
38367 cannot expect to receive the matching @code{value-history-end}. One
38368 cannot expect not to receive it either, however; an error annotation
38369 does not necessarily mean that @value{GDBN} is immediately returning all the way
38372 @findex error-begin annotation
38373 A quit or error annotation may be preceded by
38379 Any output between that and the quit or error annotation is the error
38382 Warning messages are not yet annotated.
38383 @c If we want to change that, need to fix warning(), type_error(),
38384 @c range_error(), and possibly other places.
38387 @section Invalidation Notices
38389 @cindex annotations for invalidation messages
38390 The following annotations say that certain pieces of state may have
38394 @findex frames-invalid annotation
38395 @item ^Z^Zframes-invalid
38397 The frames (for example, output from the @code{backtrace} command) may
38400 @findex breakpoints-invalid annotation
38401 @item ^Z^Zbreakpoints-invalid
38403 The breakpoints may have changed. For example, the user just added or
38404 deleted a breakpoint.
38407 @node Annotations for Running
38408 @section Running the Program
38409 @cindex annotations for running programs
38411 @findex starting annotation
38412 @findex stopping annotation
38413 When the program starts executing due to a @value{GDBN} command such as
38414 @code{step} or @code{continue},
38420 is output. When the program stops,
38426 is output. Before the @code{stopped} annotation, a variety of
38427 annotations describe how the program stopped.
38430 @findex exited annotation
38431 @item ^Z^Zexited @var{exit-status}
38432 The program exited, and @var{exit-status} is the exit status (zero for
38433 successful exit, otherwise nonzero).
38435 @findex signalled annotation
38436 @findex signal-name annotation
38437 @findex signal-name-end annotation
38438 @findex signal-string annotation
38439 @findex signal-string-end annotation
38440 @item ^Z^Zsignalled
38441 The program exited with a signal. After the @code{^Z^Zsignalled}, the
38442 annotation continues:
38448 ^Z^Zsignal-name-end
38452 ^Z^Zsignal-string-end
38457 where @var{name} is the name of the signal, such as @code{SIGILL} or
38458 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
38459 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
38460 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
38461 user's benefit and have no particular format.
38463 @findex signal annotation
38465 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
38466 just saying that the program received the signal, not that it was
38467 terminated with it.
38469 @findex breakpoint annotation
38470 @item ^Z^Zbreakpoint @var{number}
38471 The program hit breakpoint number @var{number}.
38473 @findex watchpoint annotation
38474 @item ^Z^Zwatchpoint @var{number}
38475 The program hit watchpoint number @var{number}.
38478 @node Source Annotations
38479 @section Displaying Source
38480 @cindex annotations for source display
38482 @findex source annotation
38483 The following annotation is used instead of displaying source code:
38486 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
38489 where @var{filename} is an absolute file name indicating which source
38490 file, @var{line} is the line number within that file (where 1 is the
38491 first line in the file), @var{character} is the character position
38492 within the file (where 0 is the first character in the file) (for most
38493 debug formats this will necessarily point to the beginning of a line),
38494 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
38495 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
38496 @var{addr} is the address in the target program associated with the
38497 source which is being displayed. The @var{addr} is in the form @samp{0x}
38498 followed by one or more lowercase hex digits (note that this does not
38499 depend on the language).
38501 @node JIT Interface
38502 @chapter JIT Compilation Interface
38503 @cindex just-in-time compilation
38504 @cindex JIT compilation interface
38506 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
38507 interface. A JIT compiler is a program or library that generates native
38508 executable code at runtime and executes it, usually in order to achieve good
38509 performance while maintaining platform independence.
38511 Programs that use JIT compilation are normally difficult to debug because
38512 portions of their code are generated at runtime, instead of being loaded from
38513 object files, which is where @value{GDBN} normally finds the program's symbols
38514 and debug information. In order to debug programs that use JIT compilation,
38515 @value{GDBN} has an interface that allows the program to register in-memory
38516 symbol files with @value{GDBN} at runtime.
38518 If you are using @value{GDBN} to debug a program that uses this interface, then
38519 it should work transparently so long as you have not stripped the binary. If
38520 you are developing a JIT compiler, then the interface is documented in the rest
38521 of this chapter. At this time, the only known client of this interface is the
38524 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
38525 JIT compiler communicates with @value{GDBN} by writing data into a global
38526 variable and calling a function at a well-known symbol. When @value{GDBN}
38527 attaches, it reads a linked list of symbol files from the global variable to
38528 find existing code, and puts a breakpoint in the function so that it can find
38529 out about additional code.
38532 * Declarations:: Relevant C struct declarations
38533 * Registering Code:: Steps to register code
38534 * Unregistering Code:: Steps to unregister code
38535 * Custom Debug Info:: Emit debug information in a custom format
38539 @section JIT Declarations
38541 These are the relevant struct declarations that a C program should include to
38542 implement the interface:
38552 struct jit_code_entry
38554 struct jit_code_entry *next_entry;
38555 struct jit_code_entry *prev_entry;
38556 const char *symfile_addr;
38557 uint64_t symfile_size;
38560 struct jit_descriptor
38563 /* This type should be jit_actions_t, but we use uint32_t
38564 to be explicit about the bitwidth. */
38565 uint32_t action_flag;
38566 struct jit_code_entry *relevant_entry;
38567 struct jit_code_entry *first_entry;
38570 /* GDB puts a breakpoint in this function. */
38571 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
38573 /* Make sure to specify the version statically, because the
38574 debugger may check the version before we can set it. */
38575 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
38578 If the JIT is multi-threaded, then it is important that the JIT synchronize any
38579 modifications to this global data properly, which can easily be done by putting
38580 a global mutex around modifications to these structures.
38582 @node Registering Code
38583 @section Registering Code
38585 To register code with @value{GDBN}, the JIT should follow this protocol:
38589 Generate an object file in memory with symbols and other desired debug
38590 information. The file must include the virtual addresses of the sections.
38593 Create a code entry for the file, which gives the start and size of the symbol
38597 Add it to the linked list in the JIT descriptor.
38600 Point the relevant_entry field of the descriptor at the entry.
38603 Set @code{action_flag} to @code{JIT_REGISTER} and call
38604 @code{__jit_debug_register_code}.
38607 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
38608 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
38609 new code. However, the linked list must still be maintained in order to allow
38610 @value{GDBN} to attach to a running process and still find the symbol files.
38612 @node Unregistering Code
38613 @section Unregistering Code
38615 If code is freed, then the JIT should use the following protocol:
38619 Remove the code entry corresponding to the code from the linked list.
38622 Point the @code{relevant_entry} field of the descriptor at the code entry.
38625 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
38626 @code{__jit_debug_register_code}.
38629 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
38630 and the JIT will leak the memory used for the associated symbol files.
38632 @node Custom Debug Info
38633 @section Custom Debug Info
38634 @cindex custom JIT debug info
38635 @cindex JIT debug info reader
38637 Generating debug information in platform-native file formats (like ELF
38638 or COFF) may be an overkill for JIT compilers; especially if all the
38639 debug info is used for is displaying a meaningful backtrace. The
38640 issue can be resolved by having the JIT writers decide on a debug info
38641 format and also provide a reader that parses the debug info generated
38642 by the JIT compiler. This section gives a brief overview on writing
38643 such a parser. More specific details can be found in the source file
38644 @file{gdb/jit-reader.in}, which is also installed as a header at
38645 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
38647 The reader is implemented as a shared object (so this functionality is
38648 not available on platforms which don't allow loading shared objects at
38649 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
38650 @code{jit-reader-unload} are provided, to be used to load and unload
38651 the readers from a preconfigured directory. Once loaded, the shared
38652 object is used the parse the debug information emitted by the JIT
38656 * Using JIT Debug Info Readers:: How to use supplied readers correctly
38657 * Writing JIT Debug Info Readers:: Creating a debug-info reader
38660 @node Using JIT Debug Info Readers
38661 @subsection Using JIT Debug Info Readers
38662 @kindex jit-reader-load
38663 @kindex jit-reader-unload
38665 Readers can be loaded and unloaded using the @code{jit-reader-load}
38666 and @code{jit-reader-unload} commands.
38669 @item jit-reader-load @var{reader}
38670 Load the JIT reader named @var{reader}, which is a shared
38671 object specified as either an absolute or a relative file name. In
38672 the latter case, @value{GDBN} will try to load the reader from a
38673 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
38674 system (here @var{libdir} is the system library directory, often
38675 @file{/usr/local/lib}).
38677 Only one reader can be active at a time; trying to load a second
38678 reader when one is already loaded will result in @value{GDBN}
38679 reporting an error. A new JIT reader can be loaded by first unloading
38680 the current one using @code{jit-reader-unload} and then invoking
38681 @code{jit-reader-load}.
38683 @item jit-reader-unload
38684 Unload the currently loaded JIT reader.
38688 @node Writing JIT Debug Info Readers
38689 @subsection Writing JIT Debug Info Readers
38690 @cindex writing JIT debug info readers
38692 As mentioned, a reader is essentially a shared object conforming to a
38693 certain ABI. This ABI is described in @file{jit-reader.h}.
38695 @file{jit-reader.h} defines the structures, macros and functions
38696 required to write a reader. It is installed (along with
38697 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
38698 the system include directory.
38700 Readers need to be released under a GPL compatible license. A reader
38701 can be declared as released under such a license by placing the macro
38702 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
38704 The entry point for readers is the symbol @code{gdb_init_reader},
38705 which is expected to be a function with the prototype
38707 @findex gdb_init_reader
38709 extern struct gdb_reader_funcs *gdb_init_reader (void);
38712 @cindex @code{struct gdb_reader_funcs}
38714 @code{struct gdb_reader_funcs} contains a set of pointers to callback
38715 functions. These functions are executed to read the debug info
38716 generated by the JIT compiler (@code{read}), to unwind stack frames
38717 (@code{unwind}) and to create canonical frame IDs
38718 (@code{get_frame_id}). It also has a callback that is called when the
38719 reader is being unloaded (@code{destroy}). The struct looks like this
38722 struct gdb_reader_funcs
38724 /* Must be set to GDB_READER_INTERFACE_VERSION. */
38725 int reader_version;
38727 /* For use by the reader. */
38730 gdb_read_debug_info *read;
38731 gdb_unwind_frame *unwind;
38732 gdb_get_frame_id *get_frame_id;
38733 gdb_destroy_reader *destroy;
38737 @cindex @code{struct gdb_symbol_callbacks}
38738 @cindex @code{struct gdb_unwind_callbacks}
38740 The callbacks are provided with another set of callbacks by
38741 @value{GDBN} to do their job. For @code{read}, these callbacks are
38742 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
38743 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
38744 @code{struct gdb_symbol_callbacks} has callbacks to create new object
38745 files and new symbol tables inside those object files. @code{struct
38746 gdb_unwind_callbacks} has callbacks to read registers off the current
38747 frame and to write out the values of the registers in the previous
38748 frame. Both have a callback (@code{target_read}) to read bytes off the
38749 target's address space.
38751 @node In-Process Agent
38752 @chapter In-Process Agent
38753 @cindex debugging agent
38754 The traditional debugging model is conceptually low-speed, but works fine,
38755 because most bugs can be reproduced in debugging-mode execution. However,
38756 as multi-core or many-core processors are becoming mainstream, and
38757 multi-threaded programs become more and more popular, there should be more
38758 and more bugs that only manifest themselves at normal-mode execution, for
38759 example, thread races, because debugger's interference with the program's
38760 timing may conceal the bugs. On the other hand, in some applications,
38761 it is not feasible for the debugger to interrupt the program's execution
38762 long enough for the developer to learn anything helpful about its behavior.
38763 If the program's correctness depends on its real-time behavior, delays
38764 introduced by a debugger might cause the program to fail, even when the
38765 code itself is correct. It is useful to be able to observe the program's
38766 behavior without interrupting it.
38768 Therefore, traditional debugging model is too intrusive to reproduce
38769 some bugs. In order to reduce the interference with the program, we can
38770 reduce the number of operations performed by debugger. The
38771 @dfn{In-Process Agent}, a shared library, is running within the same
38772 process with inferior, and is able to perform some debugging operations
38773 itself. As a result, debugger is only involved when necessary, and
38774 performance of debugging can be improved accordingly. Note that
38775 interference with program can be reduced but can't be removed completely,
38776 because the in-process agent will still stop or slow down the program.
38778 The in-process agent can interpret and execute Agent Expressions
38779 (@pxref{Agent Expressions}) during performing debugging operations. The
38780 agent expressions can be used for different purposes, such as collecting
38781 data in tracepoints, and condition evaluation in breakpoints.
38783 @anchor{Control Agent}
38784 You can control whether the in-process agent is used as an aid for
38785 debugging with the following commands:
38788 @kindex set agent on
38790 Causes the in-process agent to perform some operations on behalf of the
38791 debugger. Just which operations requested by the user will be done
38792 by the in-process agent depends on the its capabilities. For example,
38793 if you request to evaluate breakpoint conditions in the in-process agent,
38794 and the in-process agent has such capability as well, then breakpoint
38795 conditions will be evaluated in the in-process agent.
38797 @kindex set agent off
38798 @item set agent off
38799 Disables execution of debugging operations by the in-process agent. All
38800 of the operations will be performed by @value{GDBN}.
38804 Display the current setting of execution of debugging operations by
38805 the in-process agent.
38809 * In-Process Agent Protocol::
38812 @node In-Process Agent Protocol
38813 @section In-Process Agent Protocol
38814 @cindex in-process agent protocol
38816 The in-process agent is able to communicate with both @value{GDBN} and
38817 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
38818 used for communications between @value{GDBN} or GDBserver and the IPA.
38819 In general, @value{GDBN} or GDBserver sends commands
38820 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
38821 in-process agent replies back with the return result of the command, or
38822 some other information. The data sent to in-process agent is composed
38823 of primitive data types, such as 4-byte or 8-byte type, and composite
38824 types, which are called objects (@pxref{IPA Protocol Objects}).
38827 * IPA Protocol Objects::
38828 * IPA Protocol Commands::
38831 @node IPA Protocol Objects
38832 @subsection IPA Protocol Objects
38833 @cindex ipa protocol objects
38835 The commands sent to and results received from agent may contain some
38836 complex data types called @dfn{objects}.
38838 The in-process agent is running on the same machine with @value{GDBN}
38839 or GDBserver, so it doesn't have to handle as much differences between
38840 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
38841 However, there are still some differences of two ends in two processes:
38845 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
38846 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
38848 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
38849 GDBserver is compiled with one, and in-process agent is compiled with
38853 Here are the IPA Protocol Objects:
38857 agent expression object. It represents an agent expression
38858 (@pxref{Agent Expressions}).
38859 @anchor{agent expression object}
38861 tracepoint action object. It represents a tracepoint action
38862 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
38863 memory, static trace data and to evaluate expression.
38864 @anchor{tracepoint action object}
38866 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
38867 @anchor{tracepoint object}
38871 The following table describes important attributes of each IPA protocol
38874 @multitable @columnfractions .30 .20 .50
38875 @headitem Name @tab Size @tab Description
38876 @item @emph{agent expression object} @tab @tab
38877 @item length @tab 4 @tab length of bytes code
38878 @item byte code @tab @var{length} @tab contents of byte code
38879 @item @emph{tracepoint action for collecting memory} @tab @tab
38880 @item 'M' @tab 1 @tab type of tracepoint action
38881 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
38882 address of the lowest byte to collect, otherwise @var{addr} is the offset
38883 of @var{basereg} for memory collecting.
38884 @item len @tab 8 @tab length of memory for collecting
38885 @item basereg @tab 4 @tab the register number containing the starting
38886 memory address for collecting.
38887 @item @emph{tracepoint action for collecting registers} @tab @tab
38888 @item 'R' @tab 1 @tab type of tracepoint action
38889 @item @emph{tracepoint action for collecting static trace data} @tab @tab
38890 @item 'L' @tab 1 @tab type of tracepoint action
38891 @item @emph{tracepoint action for expression evaluation} @tab @tab
38892 @item 'X' @tab 1 @tab type of tracepoint action
38893 @item agent expression @tab length of @tab @ref{agent expression object}
38894 @item @emph{tracepoint object} @tab @tab
38895 @item number @tab 4 @tab number of tracepoint
38896 @item address @tab 8 @tab address of tracepoint inserted on
38897 @item type @tab 4 @tab type of tracepoint
38898 @item enabled @tab 1 @tab enable or disable of tracepoint
38899 @item step_count @tab 8 @tab step
38900 @item pass_count @tab 8 @tab pass
38901 @item numactions @tab 4 @tab number of tracepoint actions
38902 @item hit count @tab 8 @tab hit count
38903 @item trace frame usage @tab 8 @tab trace frame usage
38904 @item compiled_cond @tab 8 @tab compiled condition
38905 @item orig_size @tab 8 @tab orig size
38906 @item condition @tab 4 if condition is NULL otherwise length of
38907 @ref{agent expression object}
38908 @tab zero if condition is NULL, otherwise is
38909 @ref{agent expression object}
38910 @item actions @tab variable
38911 @tab numactions number of @ref{tracepoint action object}
38914 @node IPA Protocol Commands
38915 @subsection IPA Protocol Commands
38916 @cindex ipa protocol commands
38918 The spaces in each command are delimiters to ease reading this commands
38919 specification. They don't exist in real commands.
38923 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
38924 Installs a new fast tracepoint described by @var{tracepoint_object}
38925 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
38926 head of @dfn{jumppad}, which is used to jump to data collection routine
38931 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
38932 @var{target_address} is address of tracepoint in the inferior.
38933 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
38934 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
38935 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
38936 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
38943 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
38944 is about to kill inferiors.
38952 @item probe_marker_at:@var{address}
38953 Asks in-process agent to probe the marker at @var{address}.
38960 @item unprobe_marker_at:@var{address}
38961 Asks in-process agent to unprobe the marker at @var{address}.
38965 @chapter Reporting Bugs in @value{GDBN}
38966 @cindex bugs in @value{GDBN}
38967 @cindex reporting bugs in @value{GDBN}
38969 Your bug reports play an essential role in making @value{GDBN} reliable.
38971 Reporting a bug may help you by bringing a solution to your problem, or it
38972 may not. But in any case the principal function of a bug report is to help
38973 the entire community by making the next version of @value{GDBN} work better. Bug
38974 reports are your contribution to the maintenance of @value{GDBN}.
38976 In order for a bug report to serve its purpose, you must include the
38977 information that enables us to fix the bug.
38980 * Bug Criteria:: Have you found a bug?
38981 * Bug Reporting:: How to report bugs
38985 @section Have You Found a Bug?
38986 @cindex bug criteria
38988 If you are not sure whether you have found a bug, here are some guidelines:
38991 @cindex fatal signal
38992 @cindex debugger crash
38993 @cindex crash of debugger
38995 If the debugger gets a fatal signal, for any input whatever, that is a
38996 @value{GDBN} bug. Reliable debuggers never crash.
38998 @cindex error on valid input
39000 If @value{GDBN} produces an error message for valid input, that is a
39001 bug. (Note that if you're cross debugging, the problem may also be
39002 somewhere in the connection to the target.)
39004 @cindex invalid input
39006 If @value{GDBN} does not produce an error message for invalid input,
39007 that is a bug. However, you should note that your idea of
39008 ``invalid input'' might be our idea of ``an extension'' or ``support
39009 for traditional practice''.
39012 If you are an experienced user of debugging tools, your suggestions
39013 for improvement of @value{GDBN} are welcome in any case.
39016 @node Bug Reporting
39017 @section How to Report Bugs
39018 @cindex bug reports
39019 @cindex @value{GDBN} bugs, reporting
39021 A number of companies and individuals offer support for @sc{gnu} products.
39022 If you obtained @value{GDBN} from a support organization, we recommend you
39023 contact that organization first.
39025 You can find contact information for many support companies and
39026 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
39028 @c should add a web page ref...
39031 @ifset BUGURL_DEFAULT
39032 In any event, we also recommend that you submit bug reports for
39033 @value{GDBN}. The preferred method is to submit them directly using
39034 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
39035 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
39038 @strong{Do not send bug reports to @samp{info-gdb}, or to
39039 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
39040 not want to receive bug reports. Those that do have arranged to receive
39043 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
39044 serves as a repeater. The mailing list and the newsgroup carry exactly
39045 the same messages. Often people think of posting bug reports to the
39046 newsgroup instead of mailing them. This appears to work, but it has one
39047 problem which can be crucial: a newsgroup posting often lacks a mail
39048 path back to the sender. Thus, if we need to ask for more information,
39049 we may be unable to reach you. For this reason, it is better to send
39050 bug reports to the mailing list.
39052 @ifclear BUGURL_DEFAULT
39053 In any event, we also recommend that you submit bug reports for
39054 @value{GDBN} to @value{BUGURL}.
39058 The fundamental principle of reporting bugs usefully is this:
39059 @strong{report all the facts}. If you are not sure whether to state a
39060 fact or leave it out, state it!
39062 Often people omit facts because they think they know what causes the
39063 problem and assume that some details do not matter. Thus, you might
39064 assume that the name of the variable you use in an example does not matter.
39065 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
39066 stray memory reference which happens to fetch from the location where that
39067 name is stored in memory; perhaps, if the name were different, the contents
39068 of that location would fool the debugger into doing the right thing despite
39069 the bug. Play it safe and give a specific, complete example. That is the
39070 easiest thing for you to do, and the most helpful.
39072 Keep in mind that the purpose of a bug report is to enable us to fix the
39073 bug. It may be that the bug has been reported previously, but neither
39074 you nor we can know that unless your bug report is complete and
39077 Sometimes people give a few sketchy facts and ask, ``Does this ring a
39078 bell?'' Those bug reports are useless, and we urge everyone to
39079 @emph{refuse to respond to them} except to chide the sender to report
39082 To enable us to fix the bug, you should include all these things:
39086 The version of @value{GDBN}. @value{GDBN} announces it if you start
39087 with no arguments; you can also print it at any time using @code{show
39090 Without this, we will not know whether there is any point in looking for
39091 the bug in the current version of @value{GDBN}.
39094 The type of machine you are using, and the operating system name and
39098 The details of the @value{GDBN} build-time configuration.
39099 @value{GDBN} shows these details if you invoke it with the
39100 @option{--configuration} command-line option, or if you type
39101 @code{show configuration} at @value{GDBN}'s prompt.
39104 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
39105 ``@value{GCC}--2.8.1''.
39108 What compiler (and its version) was used to compile the program you are
39109 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
39110 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
39111 to get this information; for other compilers, see the documentation for
39115 The command arguments you gave the compiler to compile your example and
39116 observe the bug. For example, did you use @samp{-O}? To guarantee
39117 you will not omit something important, list them all. A copy of the
39118 Makefile (or the output from make) is sufficient.
39120 If we were to try to guess the arguments, we would probably guess wrong
39121 and then we might not encounter the bug.
39124 A complete input script, and all necessary source files, that will
39128 A description of what behavior you observe that you believe is
39129 incorrect. For example, ``It gets a fatal signal.''
39131 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
39132 will certainly notice it. But if the bug is incorrect output, we might
39133 not notice unless it is glaringly wrong. You might as well not give us
39134 a chance to make a mistake.
39136 Even if the problem you experience is a fatal signal, you should still
39137 say so explicitly. Suppose something strange is going on, such as, your
39138 copy of @value{GDBN} is out of synch, or you have encountered a bug in
39139 the C library on your system. (This has happened!) Your copy might
39140 crash and ours would not. If you told us to expect a crash, then when
39141 ours fails to crash, we would know that the bug was not happening for
39142 us. If you had not told us to expect a crash, then we would not be able
39143 to draw any conclusion from our observations.
39146 @cindex recording a session script
39147 To collect all this information, you can use a session recording program
39148 such as @command{script}, which is available on many Unix systems.
39149 Just run your @value{GDBN} session inside @command{script} and then
39150 include the @file{typescript} file with your bug report.
39152 Another way to record a @value{GDBN} session is to run @value{GDBN}
39153 inside Emacs and then save the entire buffer to a file.
39156 If you wish to suggest changes to the @value{GDBN} source, send us context
39157 diffs. If you even discuss something in the @value{GDBN} source, refer to
39158 it by context, not by line number.
39160 The line numbers in our development sources will not match those in your
39161 sources. Your line numbers would convey no useful information to us.
39165 Here are some things that are not necessary:
39169 A description of the envelope of the bug.
39171 Often people who encounter a bug spend a lot of time investigating
39172 which changes to the input file will make the bug go away and which
39173 changes will not affect it.
39175 This is often time consuming and not very useful, because the way we
39176 will find the bug is by running a single example under the debugger
39177 with breakpoints, not by pure deduction from a series of examples.
39178 We recommend that you save your time for something else.
39180 Of course, if you can find a simpler example to report @emph{instead}
39181 of the original one, that is a convenience for us. Errors in the
39182 output will be easier to spot, running under the debugger will take
39183 less time, and so on.
39185 However, simplification is not vital; if you do not want to do this,
39186 report the bug anyway and send us the entire test case you used.
39189 A patch for the bug.
39191 A patch for the bug does help us if it is a good one. But do not omit
39192 the necessary information, such as the test case, on the assumption that
39193 a patch is all we need. We might see problems with your patch and decide
39194 to fix the problem another way, or we might not understand it at all.
39196 Sometimes with a program as complicated as @value{GDBN} it is very hard to
39197 construct an example that will make the program follow a certain path
39198 through the code. If you do not send us the example, we will not be able
39199 to construct one, so we will not be able to verify that the bug is fixed.
39201 And if we cannot understand what bug you are trying to fix, or why your
39202 patch should be an improvement, we will not install it. A test case will
39203 help us to understand.
39206 A guess about what the bug is or what it depends on.
39208 Such guesses are usually wrong. Even we cannot guess right about such
39209 things without first using the debugger to find the facts.
39212 @c The readline documentation is distributed with the readline code
39213 @c and consists of the two following files:
39216 @c Use -I with makeinfo to point to the appropriate directory,
39217 @c environment var TEXINPUTS with TeX.
39218 @ifclear SYSTEM_READLINE
39219 @include rluser.texi
39220 @include hsuser.texi
39224 @appendix In Memoriam
39226 The @value{GDBN} project mourns the loss of the following long-time
39231 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
39232 to Free Software in general. Outside of @value{GDBN}, he was known in
39233 the Amiga world for his series of Fish Disks, and the GeekGadget project.
39235 @item Michael Snyder
39236 Michael was one of the Global Maintainers of the @value{GDBN} project,
39237 with contributions recorded as early as 1996, until 2011. In addition
39238 to his day to day participation, he was a large driving force behind
39239 adding Reverse Debugging to @value{GDBN}.
39242 Beyond their technical contributions to the project, they were also
39243 enjoyable members of the Free Software Community. We will miss them.
39245 @node Formatting Documentation
39246 @appendix Formatting Documentation
39248 @cindex @value{GDBN} reference card
39249 @cindex reference card
39250 The @value{GDBN} 4 release includes an already-formatted reference card, ready
39251 for printing with PostScript or Ghostscript, in the @file{gdb}
39252 subdirectory of the main source directory@footnote{In
39253 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
39254 release.}. If you can use PostScript or Ghostscript with your printer,
39255 you can print the reference card immediately with @file{refcard.ps}.
39257 The release also includes the source for the reference card. You
39258 can format it, using @TeX{}, by typing:
39264 The @value{GDBN} reference card is designed to print in @dfn{landscape}
39265 mode on US ``letter'' size paper;
39266 that is, on a sheet 11 inches wide by 8.5 inches
39267 high. You will need to specify this form of printing as an option to
39268 your @sc{dvi} output program.
39270 @cindex documentation
39272 All the documentation for @value{GDBN} comes as part of the machine-readable
39273 distribution. The documentation is written in Texinfo format, which is
39274 a documentation system that uses a single source file to produce both
39275 on-line information and a printed manual. You can use one of the Info
39276 formatting commands to create the on-line version of the documentation
39277 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
39279 @value{GDBN} includes an already formatted copy of the on-line Info
39280 version of this manual in the @file{gdb} subdirectory. The main Info
39281 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
39282 subordinate files matching @samp{gdb.info*} in the same directory. If
39283 necessary, you can print out these files, or read them with any editor;
39284 but they are easier to read using the @code{info} subsystem in @sc{gnu}
39285 Emacs or the standalone @code{info} program, available as part of the
39286 @sc{gnu} Texinfo distribution.
39288 If you want to format these Info files yourself, you need one of the
39289 Info formatting programs, such as @code{texinfo-format-buffer} or
39292 If you have @code{makeinfo} installed, and are in the top level
39293 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
39294 version @value{GDBVN}), you can make the Info file by typing:
39301 If you want to typeset and print copies of this manual, you need @TeX{},
39302 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
39303 Texinfo definitions file.
39305 @TeX{} is a typesetting program; it does not print files directly, but
39306 produces output files called @sc{dvi} files. To print a typeset
39307 document, you need a program to print @sc{dvi} files. If your system
39308 has @TeX{} installed, chances are it has such a program. The precise
39309 command to use depends on your system; @kbd{lpr -d} is common; another
39310 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
39311 require a file name without any extension or a @samp{.dvi} extension.
39313 @TeX{} also requires a macro definitions file called
39314 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
39315 written in Texinfo format. On its own, @TeX{} cannot either read or
39316 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
39317 and is located in the @file{gdb-@var{version-number}/texinfo}
39320 If you have @TeX{} and a @sc{dvi} printer program installed, you can
39321 typeset and print this manual. First switch to the @file{gdb}
39322 subdirectory of the main source directory (for example, to
39323 @file{gdb-@value{GDBVN}/gdb}) and type:
39329 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
39331 @node Installing GDB
39332 @appendix Installing @value{GDBN}
39333 @cindex installation
39336 * Requirements:: Requirements for building @value{GDBN}
39337 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
39338 * Separate Objdir:: Compiling @value{GDBN} in another directory
39339 * Config Names:: Specifying names for hosts and targets
39340 * Configure Options:: Summary of options for configure
39341 * System-wide configuration:: Having a system-wide init file
39345 @section Requirements for Building @value{GDBN}
39346 @cindex building @value{GDBN}, requirements for
39348 Building @value{GDBN} requires various tools and packages to be available.
39349 Other packages will be used only if they are found.
39351 @heading Tools/Packages Necessary for Building @value{GDBN}
39353 @item C@t{++}11 compiler
39354 @value{GDBN} is written in C@t{++}11. It should be buildable with any
39355 recent C@t{++}11 compiler, e.g.@: GCC.
39358 @value{GDBN}'s build system relies on features only found in the GNU
39359 make program. Other variants of @code{make} will not work.
39361 @item GMP (The GNU Multiple Precision Arithmetic Library)
39362 @value{GDBN} now uses GMP to perform some of its arithmetics.
39363 This library may be included with your operating system distribution;
39364 if it is not, you can get the latest version from
39365 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
39366 you can use the @option{--with-gmp} option or options
39367 @option{--with-gmp-include} and @option{--with-gmp-lib} to specify
39372 @heading Tools/Packages Optional for Building @value{GDBN}
39376 @value{GDBN} can use the Expat XML parsing library. This library may be
39377 included with your operating system distribution; if it is not, you
39378 can get the latest version from @url{http://expat.sourceforge.net}.
39379 The @file{configure} script will search for this library in several
39380 standard locations; if it is installed in an unusual path, you can
39381 use the @option{--with-libexpat-prefix} option to specify its location.
39387 Remote protocol memory maps (@pxref{Memory Map Format})
39389 Target descriptions (@pxref{Target Descriptions})
39391 Remote shared library lists (@xref{Library List Format},
39392 or alternatively @pxref{Library List Format for SVR4 Targets})
39394 MS-Windows shared libraries (@pxref{Shared Libraries})
39396 Traceframe info (@pxref{Traceframe Info Format})
39398 Branch trace (@pxref{Branch Trace Format},
39399 @pxref{Branch Trace Configuration Format})
39403 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
39404 default, @value{GDBN} will be compiled if the Guile libraries are
39405 installed and are found by @file{configure}. You can use the
39406 @code{--with-guile} option to request Guile, and pass either the Guile
39407 version number or the file name of the relevant @code{pkg-config}
39408 program to choose a particular version of Guile.
39411 @value{GDBN}'s features related to character sets (@pxref{Character
39412 Sets}) require a functioning @code{iconv} implementation. If you are
39413 on a GNU system, then this is provided by the GNU C Library. Some
39414 other systems also provide a working @code{iconv}.
39416 If @value{GDBN} is using the @code{iconv} program which is installed
39417 in a non-standard place, you will need to tell @value{GDBN} where to
39418 find it. This is done with @option{--with-iconv-bin} which specifies
39419 the directory that contains the @code{iconv} program. This program is
39420 run in order to make a list of the available character sets.
39422 On systems without @code{iconv}, you can install GNU Libiconv. If
39423 Libiconv is installed in a standard place, @value{GDBN} will
39424 automatically use it if it is needed. If you have previously
39425 installed Libiconv in a non-standard place, you can use the
39426 @option{--with-libiconv-prefix} option to @file{configure}.
39428 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
39429 arrange to build Libiconv if a directory named @file{libiconv} appears
39430 in the top-most source directory. If Libiconv is built this way, and
39431 if the operating system does not provide a suitable @code{iconv}
39432 implementation, then the just-built library will automatically be used
39433 by @value{GDBN}. One easy way to set this up is to download GNU
39434 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
39435 source tree, and then rename the directory holding the Libiconv source
39436 code to @samp{libiconv}.
39439 @value{GDBN} can support debugging sections that are compressed with
39440 the LZMA library. @xref{MiniDebugInfo}. If this library is not
39441 included with your operating system, you can find it in the xz package
39442 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
39443 the usual place, then the @file{configure} script will use it
39444 automatically. If it is installed in an unusual path, you can use the
39445 @option{--with-liblzma-prefix} option to specify its location.
39449 @value{GDBN} now uses the GNU MPFR multiple-precision floating-point
39450 library. This library may be included with your operating system
39451 distribution; if it is not, you can get the latest version from
39452 @url{http://www.mpfr.org}. The @file{configure} script will search
39453 for this library in several standard locations; if it is installed
39454 in an unusual path, you can use the @option{--with-mpfr} option or options
39455 @option{--with-mpfr-include} and @option{--with-mpfr-lib} to specify
39458 GNU MPFR is used to emulate target floating-point arithmetic during
39459 expression evaluation when the target uses different floating-point
39460 formats than the host.
39463 @value{GDBN} can be scripted using Python language. @xref{Python}.
39464 By default, @value{GDBN} will be compiled if the Python libraries are
39465 installed and are found by @file{configure}. You can use the
39466 @code{--with-python} option to request Python, and pass either the
39467 file name of the relevant @code{python} executable, or the name of the
39468 directory in which Python is installed, to choose a particular
39469 installation of Python.
39472 @cindex compressed debug sections
39473 @value{GDBN} will use the @samp{zlib} library, if available, to read
39474 compressed debug sections. Some linkers, such as GNU gold, are capable
39475 of producing binaries with compressed debug sections. If @value{GDBN}
39476 is compiled with @samp{zlib}, it will be able to read the debug
39477 information in such binaries.
39479 The @samp{zlib} library is likely included with your operating system
39480 distribution; if it is not, you can get the latest version from
39481 @url{http://zlib.net}.
39484 @node Running Configure
39485 @section Invoking the @value{GDBN} @file{configure} Script
39486 @cindex configuring @value{GDBN}
39487 @value{GDBN} comes with a @file{configure} script that automates the process
39488 of preparing @value{GDBN} for installation; you can then use @code{make} to
39489 build the @code{gdb} program.
39491 @c irrelevant in info file; it's as current as the code it lives with.
39492 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
39493 look at the @file{README} file in the sources; we may have improved the
39494 installation procedures since publishing this manual.}
39497 The @value{GDBN} distribution includes all the source code you need for
39498 @value{GDBN} in a single directory, whose name is usually composed by
39499 appending the version number to @samp{gdb}.
39501 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
39502 @file{gdb-@value{GDBVN}} directory. That directory contains:
39505 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
39506 script for configuring @value{GDBN} and all its supporting libraries
39508 @item gdb-@value{GDBVN}/gdb
39509 the source specific to @value{GDBN} itself
39511 @item gdb-@value{GDBVN}/bfd
39512 source for the Binary File Descriptor library
39514 @item gdb-@value{GDBVN}/include
39515 @sc{gnu} include files
39517 @item gdb-@value{GDBVN}/libiberty
39518 source for the @samp{-liberty} free software library
39520 @item gdb-@value{GDBVN}/opcodes
39521 source for the library of opcode tables and disassemblers
39523 @item gdb-@value{GDBVN}/readline
39524 source for the @sc{gnu} command-line interface
39527 There may be other subdirectories as well.
39529 The simplest way to configure and build @value{GDBN} is to run @file{configure}
39530 from the @file{gdb-@var{version-number}} source directory, which in
39531 this example is the @file{gdb-@value{GDBVN}} directory.
39533 First switch to the @file{gdb-@var{version-number}} source directory
39534 if you are not already in it; then run @file{configure}. Pass the
39535 identifier for the platform on which @value{GDBN} will run as an
39541 cd gdb-@value{GDBVN}
39546 Running @samp{configure} and then running @code{make} builds the
39547 included supporting libraries, then @code{gdb} itself. The configured
39548 source files, and the binaries, are left in the corresponding source
39552 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
39553 system does not recognize this automatically when you run a different
39554 shell, you may need to run @code{sh} on it explicitly:
39560 You should run the @file{configure} script from the top directory in the
39561 source tree, the @file{gdb-@var{version-number}} directory. If you run
39562 @file{configure} from one of the subdirectories, you will configure only
39563 that subdirectory. That is usually not what you want. In particular,
39564 if you run the first @file{configure} from the @file{gdb} subdirectory
39565 of the @file{gdb-@var{version-number}} directory, you will omit the
39566 configuration of @file{bfd}, @file{readline}, and other sibling
39567 directories of the @file{gdb} subdirectory. This leads to build errors
39568 about missing include files such as @file{bfd/bfd.h}.
39570 You can install @code{@value{GDBN}} anywhere. The best way to do this
39571 is to pass the @code{--prefix} option to @code{configure}, and then
39572 install it with @code{make install}.
39574 @node Separate Objdir
39575 @section Compiling @value{GDBN} in Another Directory
39577 If you want to run @value{GDBN} versions for several host or target machines,
39578 you need a different @code{gdb} compiled for each combination of
39579 host and target. @file{configure} is designed to make this easy by
39580 allowing you to generate each configuration in a separate subdirectory,
39581 rather than in the source directory. If your @code{make} program
39582 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
39583 @code{make} in each of these directories builds the @code{gdb}
39584 program specified there.
39586 To build @code{gdb} in a separate directory, run @file{configure}
39587 with the @samp{--srcdir} option to specify where to find the source.
39588 (You also need to specify a path to find @file{configure}
39589 itself from your working directory. If the path to @file{configure}
39590 would be the same as the argument to @samp{--srcdir}, you can leave out
39591 the @samp{--srcdir} option; it is assumed.)
39593 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
39594 separate directory for a Sun 4 like this:
39598 cd gdb-@value{GDBVN}
39601 ../gdb-@value{GDBVN}/configure
39606 When @file{configure} builds a configuration using a remote source
39607 directory, it creates a tree for the binaries with the same structure
39608 (and using the same names) as the tree under the source directory. In
39609 the example, you'd find the Sun 4 library @file{libiberty.a} in the
39610 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
39611 @file{gdb-sun4/gdb}.
39613 Make sure that your path to the @file{configure} script has just one
39614 instance of @file{gdb} in it. If your path to @file{configure} looks
39615 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
39616 one subdirectory of @value{GDBN}, not the whole package. This leads to
39617 build errors about missing include files such as @file{bfd/bfd.h}.
39619 One popular reason to build several @value{GDBN} configurations in separate
39620 directories is to configure @value{GDBN} for cross-compiling (where
39621 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
39622 programs that run on another machine---the @dfn{target}).
39623 You specify a cross-debugging target by
39624 giving the @samp{--target=@var{target}} option to @file{configure}.
39626 When you run @code{make} to build a program or library, you must run
39627 it in a configured directory---whatever directory you were in when you
39628 called @file{configure} (or one of its subdirectories).
39630 The @code{Makefile} that @file{configure} generates in each source
39631 directory also runs recursively. If you type @code{make} in a source
39632 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
39633 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
39634 will build all the required libraries, and then build GDB.
39636 When you have multiple hosts or targets configured in separate
39637 directories, you can run @code{make} on them in parallel (for example,
39638 if they are NFS-mounted on each of the hosts); they will not interfere
39642 @section Specifying Names for Hosts and Targets
39644 The specifications used for hosts and targets in the @file{configure}
39645 script are based on a three-part naming scheme, but some short predefined
39646 aliases are also supported. The full naming scheme encodes three pieces
39647 of information in the following pattern:
39650 @var{architecture}-@var{vendor}-@var{os}
39653 For example, you can use the alias @code{sun4} as a @var{host} argument,
39654 or as the value for @var{target} in a @code{--target=@var{target}}
39655 option. The equivalent full name is @samp{sparc-sun-sunos4}.
39657 The @file{configure} script accompanying @value{GDBN} does not provide
39658 any query facility to list all supported host and target names or
39659 aliases. @file{configure} calls the Bourne shell script
39660 @code{config.sub} to map abbreviations to full names; you can read the
39661 script, if you wish, or you can use it to test your guesses on
39662 abbreviations---for example:
39665 % sh config.sub i386-linux
39667 % sh config.sub alpha-linux
39668 alpha-unknown-linux-gnu
39669 % sh config.sub hp9k700
39671 % sh config.sub sun4
39672 sparc-sun-sunos4.1.1
39673 % sh config.sub sun3
39674 m68k-sun-sunos4.1.1
39675 % sh config.sub i986v
39676 Invalid configuration `i986v': machine `i986v' not recognized
39680 @code{config.sub} is also distributed in the @value{GDBN} source
39681 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
39683 @node Configure Options
39684 @section @file{configure} Options
39686 Here is a summary of the @file{configure} options and arguments that
39687 are most often useful for building @value{GDBN}. @file{configure}
39688 also has several other options not listed here. @xref{Running
39689 configure Scripts,,,autoconf}, for a full
39690 explanation of @file{configure}.
39693 configure @r{[}--help@r{]}
39694 @r{[}--prefix=@var{dir}@r{]}
39695 @r{[}--exec-prefix=@var{dir}@r{]}
39696 @r{[}--srcdir=@var{dirname}@r{]}
39697 @r{[}--target=@var{target}@r{]}
39701 You may introduce options with a single @samp{-} rather than
39702 @samp{--} if you prefer; but you may abbreviate option names if you use
39707 Display a quick summary of how to invoke @file{configure}.
39709 @item --prefix=@var{dir}
39710 Configure the source to install programs and files under directory
39713 @item --exec-prefix=@var{dir}
39714 Configure the source to install programs under directory
39717 @c avoid splitting the warning from the explanation:
39719 @item --srcdir=@var{dirname}
39720 Use this option to make configurations in directories separate from the
39721 @value{GDBN} source directories. Among other things, you can use this to
39722 build (or maintain) several configurations simultaneously, in separate
39723 directories. @file{configure} writes configuration-specific files in
39724 the current directory, but arranges for them to use the source in the
39725 directory @var{dirname}. @file{configure} creates directories under
39726 the working directory in parallel to the source directories below
39729 @item --target=@var{target}
39730 Configure @value{GDBN} for cross-debugging programs running on the specified
39731 @var{target}. Without this option, @value{GDBN} is configured to debug
39732 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
39734 There is no convenient way to generate a list of all available
39735 targets. Also see the @code{--enable-targets} option, below.
39738 There are many other options that are specific to @value{GDBN}. This
39739 lists just the most common ones; there are some very specialized
39740 options not described here.
39743 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
39744 @itemx --enable-targets=all
39745 Configure @value{GDBN} for cross-debugging programs running on the
39746 specified list of targets. The special value @samp{all} configures
39747 @value{GDBN} for debugging programs running on any target it supports.
39749 @item --with-gdb-datadir=@var{path}
39750 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
39751 here for certain supporting files or scripts. This defaults to the
39752 @file{gdb} subdirectory of @samp{datadir} (which can be set using
39755 @item --with-relocated-sources=@var{dir}
39756 Sets up the default source path substitution rule so that directory
39757 names recorded in debug information will be automatically adjusted for
39758 any directory under @var{dir}. @var{dir} should be a subdirectory of
39759 @value{GDBN}'s configured prefix, the one mentioned in the
39760 @code{--prefix} or @code{--exec-prefix} options to configure. This
39761 option is useful if GDB is supposed to be moved to a different place
39764 @item --enable-64-bit-bfd
39765 Enable 64-bit support in BFD on 32-bit hosts.
39767 @item --disable-gdbmi
39768 Build @value{GDBN} without the GDB/MI machine interface
39772 Build @value{GDBN} with the text-mode full-screen user interface
39773 (TUI). Requires a curses library (ncurses and cursesX are also
39776 @item --with-curses
39777 Use the curses library instead of the termcap library, for text-mode
39778 terminal operations.
39780 @item --with-debuginfod
39781 Build @value{GDBN} with @file{libdebuginfod}, the @code{debuginfod} client
39782 library. Used to automatically fetch ELF, DWARF and source files from
39783 @code{debuginfod} servers using build IDs associated with any missing
39784 files. Enabled by default if @file{libdebuginfod} is installed and found
39785 at configure time. For more information regarding @code{debuginfod} see
39788 @item --with-libunwind-ia64
39789 Use the libunwind library for unwinding function call stack on ia64
39790 target platforms. See http://www.nongnu.org/libunwind/index.html for
39793 @item --with-system-readline
39794 Use the readline library installed on the host, rather than the
39795 library supplied as part of @value{GDBN}. Readline 7 or newer is
39796 required; this is enforced by the build system.
39798 @item --with-system-zlib
39799 Use the zlib library installed on the host, rather than the library
39800 supplied as part of @value{GDBN}.
39803 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
39804 default if libexpat is installed and found at configure time.) This
39805 library is used to read XML files supplied with @value{GDBN}. If it
39806 is unavailable, some features, such as remote protocol memory maps,
39807 target descriptions, and shared library lists, that are based on XML
39808 files, will not be available in @value{GDBN}. If your host does not
39809 have libexpat installed, you can get the latest version from
39810 `http://expat.sourceforge.net'.
39812 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
39814 Build @value{GDBN} with GNU libiconv, a character set encoding
39815 conversion library. This is not done by default, as on GNU systems
39816 the @code{iconv} that is built in to the C library is sufficient. If
39817 your host does not have a working @code{iconv}, you can get the latest
39818 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
39820 @value{GDBN}'s build system also supports building GNU libiconv as
39821 part of the overall build. @xref{Requirements}.
39824 Build @value{GDBN} with LZMA, a compression library. (Done by default
39825 if liblzma is installed and found at configure time.) LZMA is used by
39826 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
39827 platforms using the ELF object file format. If your host does not
39828 have liblzma installed, you can get the latest version from
39829 `https://tukaani.org/xz/'.
39832 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
39833 floating-point computation with correct rounding. (Done by default if
39834 GNU MPFR is installed and found at configure time.) This library is
39835 used to emulate target floating-point arithmetic during expression
39836 evaluation when the target uses different floating-point formats than
39837 the host. If GNU MPFR is not available, @value{GDBN} will fall back
39838 to using host floating-point arithmetic. If your host does not have
39839 GNU MPFR installed, you can get the latest version from
39840 `http://www.mpfr.org'.
39842 @item --with-python@r{[}=@var{python}@r{]}
39843 Build @value{GDBN} with Python scripting support. (Done by default if
39844 libpython is present and found at configure time.) Python makes
39845 @value{GDBN} scripting much more powerful than the restricted CLI
39846 scripting language. If your host does not have Python installed, you
39847 can find it on `http://www.python.org/download/'. The oldest version
39848 of Python supported by GDB is 2.6. The optional argument @var{python}
39849 is used to find the Python headers and libraries. It can be either
39850 the name of a Python executable, or the name of the directory in which
39851 Python is installed.
39853 @item --with-guile[=GUILE]'
39854 Build @value{GDBN} with GNU Guile scripting support. (Done by default
39855 if libguile is present and found at configure time.) If your host
39856 does not have Guile installed, you can find it at
39857 `https://www.gnu.org/software/guile/'. The optional argument GUILE
39858 can be a version number, which will cause @code{configure} to try to
39859 use that version of Guile; or the file name of a @code{pkg-config}
39860 executable, which will be queried to find the information needed to
39861 compile and link against Guile.
39863 @item --without-included-regex
39864 Don't use the regex library included with @value{GDBN} (as part of the
39865 libiberty library). This is the default on hosts with version 2 of
39868 @item --with-sysroot=@var{dir}
39869 Use @var{dir} as the default system root directory for libraries whose
39870 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
39871 @var{dir} can be modified at run time by using the @command{set
39872 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
39873 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
39874 default system root will be automatically adjusted if and when
39875 @value{GDBN} is moved to a different location.
39877 @item --with-system-gdbinit=@var{file}
39878 Configure @value{GDBN} to automatically load a system-wide init file.
39879 @var{file} should be an absolute file name. If @var{file} is in a
39880 directory under the configured prefix, and @value{GDBN} is moved to
39881 another location after being built, the location of the system-wide
39882 init file will be adjusted accordingly.
39884 @item --with-system-gdbinit-dir=@var{directory}
39885 Configure @value{GDBN} to automatically load init files from a
39886 system-wide directory. @var{directory} should be an absolute directory
39887 name. If @var{directory} is in a directory under the configured
39888 prefix, and @value{GDBN} is moved to another location after being
39889 built, the location of the system-wide init directory will be
39890 adjusted accordingly.
39892 @item --enable-build-warnings
39893 When building the @value{GDBN} sources, ask the compiler to warn about
39894 any code which looks even vaguely suspicious. It passes many
39895 different warning flags, depending on the exact version of the
39896 compiler you are using.
39898 @item --enable-werror
39899 Treat compiler warnings as errors. It adds the @code{-Werror} flag
39900 to the compiler, which will fail the compilation if the compiler
39901 outputs any warning messages.
39903 @item --enable-ubsan
39904 Enable the GCC undefined behavior sanitizer. This is disabled by
39905 default, but passing @code{--enable-ubsan=yes} or
39906 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
39907 undefined behavior sanitizer checks for C@t{++} undefined behavior.
39908 It has a performance cost, so if you are looking at @value{GDBN}'s
39909 performance, you should disable it. The undefined behavior sanitizer
39910 was first introduced in GCC 4.9.
39913 @node System-wide configuration
39914 @section System-wide configuration and settings
39915 @cindex system-wide init file
39917 @value{GDBN} can be configured to have a system-wide init file and a
39918 system-wide init file directory; this file and files in that directory
39919 (if they have a recognized file extension) will be read and executed at
39920 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
39922 Here are the corresponding configure options:
39925 @item --with-system-gdbinit=@var{file}
39926 Specify that the default location of the system-wide init file is
39928 @item --with-system-gdbinit-dir=@var{directory}
39929 Specify that the default location of the system-wide init file directory
39930 is @var{directory}.
39933 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
39934 they may be subject to relocation. Two possible cases:
39938 If the default location of this init file/directory contains @file{$prefix},
39939 it will be subject to relocation. Suppose that the configure options
39940 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
39941 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
39942 init file is looked for as @file{$install/etc/gdbinit} instead of
39943 @file{$prefix/etc/gdbinit}.
39946 By contrast, if the default location does not contain the prefix,
39947 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
39948 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
39949 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
39950 wherever @value{GDBN} is installed.
39953 If the configured location of the system-wide init file (as given by the
39954 @option{--with-system-gdbinit} option at configure time) is in the
39955 data-directory (as specified by @option{--with-gdb-datadir} at configure
39956 time) or in one of its subdirectories, then @value{GDBN} will look for the
39957 system-wide init file in the directory specified by the
39958 @option{--data-directory} command-line option.
39959 Note that the system-wide init file is only read once, during @value{GDBN}
39960 initialization. If the data-directory is changed after @value{GDBN} has
39961 started with the @code{set data-directory} command, the file will not be
39964 This applies similarly to the system-wide directory specified in
39965 @option{--with-system-gdbinit-dir}.
39967 Any supported scripting language can be used for these init files, as long
39968 as the file extension matches the scripting language. To be interpreted
39969 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
39973 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
39976 @node System-wide Configuration Scripts
39977 @subsection Installed System-wide Configuration Scripts
39978 @cindex system-wide configuration scripts
39980 The @file{system-gdbinit} directory, located inside the data-directory
39981 (as specified by @option{--with-gdb-datadir} at configure time) contains
39982 a number of scripts which can be used as system-wide init files. To
39983 automatically source those scripts at startup, @value{GDBN} should be
39984 configured with @option{--with-system-gdbinit}. Otherwise, any user
39985 should be able to source them by hand as needed.
39987 The following scripts are currently available:
39990 @item @file{elinos.py}
39992 @cindex ELinOS system-wide configuration script
39993 This script is useful when debugging a program on an ELinOS target.
39994 It takes advantage of the environment variables defined in a standard
39995 ELinOS environment in order to determine the location of the system
39996 shared libraries, and then sets the @samp{solib-absolute-prefix}
39997 and @samp{solib-search-path} variables appropriately.
39999 @item @file{wrs-linux.py}
40000 @pindex wrs-linux.py
40001 @cindex Wind River Linux system-wide configuration script
40002 This script is useful when debugging a program on a target running
40003 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
40004 the host-side sysroot used by the target system.
40008 @node Maintenance Commands
40009 @appendix Maintenance Commands
40010 @cindex maintenance commands
40011 @cindex internal commands
40013 In addition to commands intended for @value{GDBN} users, @value{GDBN}
40014 includes a number of commands intended for @value{GDBN} developers,
40015 that are not documented elsewhere in this manual. These commands are
40016 provided here for reference. (For commands that turn on debugging
40017 messages, see @ref{Debugging Output}.)
40020 @kindex maint agent
40021 @kindex maint agent-eval
40022 @item maint agent @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
40023 @itemx maint agent-eval @r{[}-at @var{linespec}@r{,}@r{]} @var{expression}
40024 Translate the given @var{expression} into remote agent bytecodes.
40025 This command is useful for debugging the Agent Expression mechanism
40026 (@pxref{Agent Expressions}). The @samp{agent} version produces an
40027 expression useful for data collection, such as by tracepoints, while
40028 @samp{maint agent-eval} produces an expression that evaluates directly
40029 to a result. For instance, a collection expression for @code{globa +
40030 globb} will include bytecodes to record four bytes of memory at each
40031 of the addresses of @code{globa} and @code{globb}, while discarding
40032 the result of the addition, while an evaluation expression will do the
40033 addition and return the sum.
40034 If @code{-at} is given, generate remote agent bytecode for all the
40035 addresses to which @var{linespec} resolves (@pxref{Linespec
40037 If not, generate remote agent bytecode for current frame PC address.
40039 @kindex maint agent-printf
40040 @item maint agent-printf @var{format},@var{expr},...
40041 Translate the given format string and list of argument expressions
40042 into remote agent bytecodes and display them as a disassembled list.
40043 This command is useful for debugging the agent version of dynamic
40044 printf (@pxref{Dynamic Printf}).
40046 @kindex maint info breakpoints
40047 @item @anchor{maint info breakpoints}maint info breakpoints
40048 Using the same format as @samp{info breakpoints}, display both the
40049 breakpoints you've set explicitly, and those @value{GDBN} is using for
40050 internal purposes. Internal breakpoints are shown with negative
40051 breakpoint numbers. The type column identifies what kind of breakpoint
40056 Normal, explicitly set breakpoint.
40059 Normal, explicitly set watchpoint.
40062 Internal breakpoint, used to handle correctly stepping through
40063 @code{longjmp} calls.
40065 @item longjmp resume
40066 Internal breakpoint at the target of a @code{longjmp}.
40069 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
40072 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
40075 Shared library events.
40079 @kindex maint info btrace
40080 @item maint info btrace
40081 Pint information about raw branch tracing data.
40083 @kindex maint btrace packet-history
40084 @item maint btrace packet-history
40085 Print the raw branch trace packets that are used to compute the
40086 execution history for the @samp{record btrace} command. Both the
40087 information and the format in which it is printed depend on the btrace
40092 For the BTS recording format, print a list of blocks of sequential
40093 code. For each block, the following information is printed:
40097 Newer blocks have higher numbers. The oldest block has number zero.
40098 @item Lowest @samp{PC}
40099 @item Highest @samp{PC}
40103 For the Intel Processor Trace recording format, print a list of
40104 Intel Processor Trace packets. For each packet, the following
40105 information is printed:
40108 @item Packet number
40109 Newer packets have higher numbers. The oldest packet has number zero.
40111 The packet's offset in the trace stream.
40112 @item Packet opcode and payload
40116 @kindex maint btrace clear-packet-history
40117 @item maint btrace clear-packet-history
40118 Discards the cached packet history printed by the @samp{maint btrace
40119 packet-history} command. The history will be computed again when
40122 @kindex maint btrace clear
40123 @item maint btrace clear
40124 Discard the branch trace data. The data will be fetched anew and the
40125 branch trace will be recomputed when needed.
40127 This implicitly truncates the branch trace to a single branch trace
40128 buffer. When updating branch trace incrementally, the branch trace
40129 available to @value{GDBN} may be bigger than a single branch trace
40132 @kindex maint set btrace pt skip-pad
40133 @item maint set btrace pt skip-pad
40134 @kindex maint show btrace pt skip-pad
40135 @item maint show btrace pt skip-pad
40136 Control whether @value{GDBN} will skip PAD packets when computing the
40139 @kindex maint info jit
40140 @item maint info jit
40141 Print information about JIT code objects loaded in the current inferior.
40143 @anchor{maint info python-disassemblers}
40144 @kindex maint info python-disassemblers
40145 @item maint info python-disassemblers
40146 This command is defined within the @code{gdb.disassembler} Python
40147 module (@pxref{Disassembly In Python}), and will only be present after
40148 that module has been imported. To force the module to be imported do
40152 (@value{GDBP}) python import gdb.disassembler
40155 This command lists all the architectures for which a disassembler is
40156 currently registered, and the name of the disassembler. If a
40157 disassembler is registered for all architectures, then this is listed
40158 last against the @samp{GLOBAL} architecture.
40160 If one of the disassemblers would be selected for the architecture of
40161 the current inferior, then this disassembler will be marked.
40163 The following example shows a situation in which two disassemblers are
40164 registered, initially the @samp{i386} disassembler matches the current
40165 architecture, then the architecture is changed, now the @samp{GLOBAL}
40166 disassembler matches.
40170 (@value{GDBP}) show architecture
40171 The target architecture is set to "auto" (currently "i386").
40172 (@value{GDBP}) maint info python-disassemblers
40173 Architecture Disassember Name
40174 i386 Disassembler_1 (Matches current architecture)
40175 GLOBAL Disassembler_2
40178 (@value{GDBP}) set architecture arm
40179 The target architecture is set to "arm".
40180 (@value{GDBP}) maint info python-disassemblers
40182 Architecture Disassember Name
40183 i386 Disassembler_1
40184 GLOBAL Disassembler_2 (Matches current architecture)
40188 @kindex set displaced-stepping
40189 @kindex show displaced-stepping
40190 @cindex displaced stepping support
40191 @cindex out-of-line single-stepping
40192 @item set displaced-stepping
40193 @itemx show displaced-stepping
40194 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
40195 if the target supports it. Displaced stepping is a way to single-step
40196 over breakpoints without removing them from the inferior, by executing
40197 an out-of-line copy of the instruction that was originally at the
40198 breakpoint location. It is also known as out-of-line single-stepping.
40201 @item set displaced-stepping on
40202 If the target architecture supports it, @value{GDBN} will use
40203 displaced stepping to step over breakpoints.
40205 @item set displaced-stepping off
40206 @value{GDBN} will not use displaced stepping to step over breakpoints,
40207 even if such is supported by the target architecture.
40209 @cindex non-stop mode, and @samp{set displaced-stepping}
40210 @item set displaced-stepping auto
40211 This is the default mode. @value{GDBN} will use displaced stepping
40212 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
40213 architecture supports displaced stepping.
40216 @kindex maint check-psymtabs
40217 @item maint check-psymtabs
40218 Check the consistency of currently expanded psymtabs versus symtabs.
40219 Use this to check, for example, whether a symbol is in one but not the other.
40221 @kindex maint check-symtabs
40222 @item maint check-symtabs
40223 Check the consistency of currently expanded symtabs.
40225 @kindex maint expand-symtabs
40226 @item maint expand-symtabs [@var{regexp}]
40227 Expand symbol tables.
40228 If @var{regexp} is specified, only expand symbol tables for file
40229 names matching @var{regexp}.
40231 @kindex maint set catch-demangler-crashes
40232 @kindex maint show catch-demangler-crashes
40233 @cindex demangler crashes
40234 @item maint set catch-demangler-crashes [on|off]
40235 @itemx maint show catch-demangler-crashes
40236 Control whether @value{GDBN} should attempt to catch crashes in the
40237 symbol name demangler. The default is to attempt to catch crashes.
40238 If enabled, the first time a crash is caught, a core file is created,
40239 the offending symbol is displayed and the user is presented with the
40240 option to terminate the current session.
40242 @kindex maint cplus first_component
40243 @item maint cplus first_component @var{name}
40244 Print the first C@t{++} class/namespace component of @var{name}.
40246 @kindex maint cplus namespace
40247 @item maint cplus namespace
40248 Print the list of possible C@t{++} namespaces.
40250 @kindex maint deprecate
40251 @kindex maint undeprecate
40252 @cindex deprecated commands
40253 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
40254 @itemx maint undeprecate @var{command}
40255 Deprecate or undeprecate the named @var{command}. Deprecated commands
40256 cause @value{GDBN} to issue a warning when you use them. The optional
40257 argument @var{replacement} says which newer command should be used in
40258 favor of the deprecated one; if it is given, @value{GDBN} will mention
40259 the replacement as part of the warning.
40261 @kindex maint dump-me
40262 @item maint dump-me
40263 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
40264 Cause a fatal signal in the debugger and force it to dump its core.
40265 This is supported only on systems which support aborting a program
40266 with the @code{SIGQUIT} signal.
40268 @kindex maint internal-error
40269 @kindex maint internal-warning
40270 @kindex maint demangler-warning
40271 @cindex demangler crashes
40272 @item maint internal-error @r{[}@var{message-text}@r{]}
40273 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
40274 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
40276 Cause @value{GDBN} to call the internal function @code{internal_error},
40277 @code{internal_warning} or @code{demangler_warning} and hence behave
40278 as though an internal problem has been detected. In addition to
40279 reporting the internal problem, these functions give the user the
40280 opportunity to either quit @value{GDBN} or (for @code{internal_error}
40281 and @code{internal_warning}) create a core file of the current
40282 @value{GDBN} session.
40284 These commands take an optional parameter @var{message-text} that is
40285 used as the text of the error or warning message.
40287 Here's an example of using @code{internal-error}:
40290 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
40291 @dots{}/maint.c:121: internal-error: testing, 1, 2
40292 A problem internal to GDB has been detected. Further
40293 debugging may prove unreliable.
40294 Quit this debugging session? (y or n) @kbd{n}
40295 Create a core file? (y or n) @kbd{n}
40299 @cindex @value{GDBN} internal error
40300 @cindex internal errors, control of @value{GDBN} behavior
40301 @cindex demangler crashes
40303 @kindex maint set internal-error
40304 @kindex maint show internal-error
40305 @kindex maint set internal-warning
40306 @kindex maint show internal-warning
40307 @kindex maint set demangler-warning
40308 @kindex maint show demangler-warning
40309 @item maint set internal-error @var{action} [ask|yes|no]
40310 @itemx maint show internal-error @var{action}
40311 @itemx maint set internal-warning @var{action} [ask|yes|no]
40312 @itemx maint show internal-warning @var{action}
40313 @itemx maint set demangler-warning @var{action} [ask|yes|no]
40314 @itemx maint show demangler-warning @var{action}
40315 When @value{GDBN} reports an internal problem (error or warning) it
40316 gives the user the opportunity to both quit @value{GDBN} and create a
40317 core file of the current @value{GDBN} session. These commands let you
40318 override the default behaviour for each particular @var{action},
40319 described in the table below.
40323 You can specify that @value{GDBN} should always (yes) or never (no)
40324 quit. The default is to ask the user what to do.
40327 You can specify that @value{GDBN} should always (yes) or never (no)
40328 create a core file. The default is to ask the user what to do. Note
40329 that there is no @code{corefile} option for @code{demangler-warning}:
40330 demangler warnings always create a core file and this cannot be
40334 @kindex maint set internal-error
40335 @kindex maint show internal-error
40336 @kindex maint set internal-warning
40337 @kindex maint show internal-warning
40338 @item maint set internal-error backtrace @r{[}on|off@r{]}
40339 @itemx maint show internal-error backtrace
40340 @itemx maint set internal-warning backtrace @r{[}on|off@r{]}
40341 @itemx maint show internal-warning backtrace
40342 When @value{GDBN} reports an internal problem (error or warning) it is
40343 possible to have a backtrace of @value{GDBN} printed to the standard
40344 error stream. This is @samp{on} by default for @code{internal-error}
40345 and @samp{off} by default for @code{internal-warning}.
40347 @anchor{maint packet}
40348 @kindex maint packet
40349 @item maint packet @var{text}
40350 If @value{GDBN} is talking to an inferior via the serial protocol,
40351 then this command sends the string @var{text} to the inferior, and
40352 displays the response packet. @value{GDBN} supplies the initial
40353 @samp{$} character, the terminating @samp{#} character, and the
40356 Any non-printable characters in the reply are printed as escaped hex,
40357 e.g. @samp{\x00}, @samp{\x01}, etc.
40359 @kindex maint print architecture
40360 @item maint print architecture @r{[}@var{file}@r{]}
40361 Print the entire architecture configuration. The optional argument
40362 @var{file} names the file where the output goes.
40364 @kindex maint print c-tdesc
40365 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
40366 Print the target description (@pxref{Target Descriptions}) as
40367 a C source file. By default, the target description is for the current
40368 target, but if the optional argument @var{file} is provided, that file
40369 is used to produce the description. The @var{file} should be an XML
40370 document, of the form described in @ref{Target Description Format}.
40371 The created source file is built into @value{GDBN} when @value{GDBN} is
40372 built again. This command is used by developers after they add or
40373 modify XML target descriptions.
40375 When the optional flag @samp{-single-feature} is provided then the
40376 target description being processed (either the default, or from
40377 @var{file}) must only contain a single feature. The source file
40378 produced is different in this case.
40380 @kindex maint print xml-tdesc
40381 @item maint print xml-tdesc @r{[}@var{file}@r{]}
40382 Print the target description (@pxref{Target Descriptions}) as an XML
40383 file. By default print the target description for the current target,
40384 but if the optional argument @var{file} is provided, then that file is
40385 read in by GDB and then used to produce the description. The
40386 @var{file} should be an XML document, of the form described in
40387 @ref{Target Description Format}.
40389 @kindex maint check xml-descriptions
40390 @item maint check xml-descriptions @var{dir}
40391 Check that the target descriptions dynamically created by @value{GDBN}
40392 equal the descriptions created from XML files found in @var{dir}.
40394 @anchor{maint check libthread-db}
40395 @kindex maint check libthread-db
40396 @item maint check libthread-db
40397 Run integrity checks on the current inferior's thread debugging
40398 library. This exercises all @code{libthread_db} functionality used by
40399 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
40400 @code{proc_service} functions provided by @value{GDBN} that
40401 @code{libthread_db} uses. Note that parts of the test may be skipped
40402 on some platforms when debugging core files.
40404 @kindex maint print core-file-backed-mappings
40405 @cindex memory address space mappings
40406 @item maint print core-file-backed-mappings
40407 Print the file-backed mappings which were loaded from a core file note.
40408 This output represents state internal to @value{GDBN} and should be
40409 similar to the mappings displayed by the @code{info proc mappings}
40412 @kindex maint print dummy-frames
40413 @item maint print dummy-frames
40414 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
40417 (@value{GDBP}) @kbd{b add}
40419 (@value{GDBP}) @kbd{print add(2,3)}
40420 Breakpoint 2, add (a=2, b=3) at @dots{}
40422 The program being debugged stopped while in a function called from GDB.
40424 (@value{GDBP}) @kbd{maint print dummy-frames}
40425 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
40429 Takes an optional file parameter.
40431 @kindex maint print frame-id
40432 @item maint print frame-id
40433 @itemx maint print frame-id @var{level}
40434 Print @value{GDBN}'s internal frame-id for the frame at relative
40435 @var{level}, or for the currently selected frame when @var{level} is
40438 If used, @var{level} should be an integer, as displayed in the
40439 @command{backtrace} output.
40442 (@value{GDBP}) maint print frame-id
40443 frame-id for frame #0: @{stack=0x7fffffffac70,code=0x0000000000401106,!special@}
40444 (@value{GDBP}) maint print frame-id 2
40445 frame-id for frame #2: @{stack=0x7fffffffac90,code=0x000000000040111c,!special@}
40448 @kindex maint print registers
40449 @kindex maint print raw-registers
40450 @kindex maint print cooked-registers
40451 @kindex maint print register-groups
40452 @kindex maint print remote-registers
40453 @item maint print registers @r{[}@var{file}@r{]}
40454 @itemx maint print raw-registers @r{[}@var{file}@r{]}
40455 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
40456 @itemx maint print register-groups @r{[}@var{file}@r{]}
40457 @itemx maint print remote-registers @r{[}@var{file}@r{]}
40458 Print @value{GDBN}'s internal register data structures.
40460 The command @code{maint print raw-registers} includes the contents of
40461 the raw register cache; the command @code{maint print
40462 cooked-registers} includes the (cooked) value of all registers,
40463 including registers which aren't available on the target nor visible
40464 to user; the command @code{maint print register-groups} includes the
40465 groups that each register is a member of; and the command @code{maint
40466 print remote-registers} includes the remote target's register numbers
40467 and offsets in the `G' packets.
40469 These commands take an optional parameter, a file name to which to
40470 write the information.
40472 @kindex maint print reggroups
40473 @item maint print reggroups @r{[}@var{file}@r{]}
40474 Print @value{GDBN}'s internal register group data structures. The
40475 optional argument @var{file} tells to what file to write the
40478 The register groups info looks like this:
40481 (@value{GDBP}) @kbd{maint print reggroups}
40492 @kindex maint flush register-cache
40494 @cindex register cache, flushing
40495 @item maint flush register-cache
40497 Flush the contents of the register cache and as a consequence the
40498 frame cache. This command is useful when debugging issues related to
40499 register fetching, or frame unwinding. The command @code{flushregs}
40500 is deprecated in favor of @code{maint flush register-cache}.
40502 @kindex maint flush source-cache
40503 @cindex source code, caching
40504 @item maint flush source-cache
40505 Flush @value{GDBN}'s cache of source code file contents. After
40506 @value{GDBN} reads a source file, and optionally applies styling
40507 (@pxref{Output Styling}), the file contents are cached. This command
40508 clears that cache. The next time @value{GDBN} wants to show lines
40509 from a source file, the content will be re-read.
40511 This command is useful when debugging issues related to source code
40512 styling. After flushing the cache any source code displayed by
40513 @value{GDBN} will be re-read and re-styled.
40515 @kindex maint print objfiles
40516 @cindex info for known object files
40517 @item maint print objfiles @r{[}@var{regexp}@r{]}
40518 Print a dump of all known object files.
40519 If @var{regexp} is specified, only print object files whose names
40520 match @var{regexp}. For each object file, this command prints its name,
40521 address in memory, and all of its psymtabs and symtabs.
40523 @kindex maint print user-registers
40524 @cindex user registers
40525 @item maint print user-registers
40526 List all currently available @dfn{user registers}. User registers
40527 typically provide alternate names for actual hardware registers. They
40528 include the four ``standard'' registers @code{$fp}, @code{$pc},
40529 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
40530 registers can be used in expressions in the same way as the canonical
40531 register names, but only the latter are listed by the @code{info
40532 registers} and @code{maint print registers} commands.
40534 @kindex maint print section-scripts
40535 @cindex info for known .debug_gdb_scripts-loaded scripts
40536 @item maint print section-scripts [@var{regexp}]
40537 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
40538 If @var{regexp} is specified, only print scripts loaded by object files
40539 matching @var{regexp}.
40540 For each script, this command prints its name as specified in the objfile,
40541 and the full path if known.
40542 @xref{dotdebug_gdb_scripts section}.
40544 @kindex maint print statistics
40545 @cindex bcache statistics
40546 @item maint print statistics
40547 This command prints, for each object file in the program, various data
40548 about that object file followed by the byte cache (@dfn{bcache})
40549 statistics for the object file. The objfile data includes the number
40550 of minimal, partial, full, and stabs symbols, the number of types
40551 defined by the objfile, the number of as yet unexpanded psym tables,
40552 the number of line tables and string tables, and the amount of memory
40553 used by the various tables. The bcache statistics include the counts,
40554 sizes, and counts of duplicates of all and unique objects, max,
40555 average, and median entry size, total memory used and its overhead and
40556 savings, and various measures of the hash table size and chain
40559 @kindex maint print target-stack
40560 @cindex target stack description
40561 @item maint print target-stack
40562 A @dfn{target} is an interface between the debugger and a particular
40563 kind of file or process. Targets can be stacked in @dfn{strata},
40564 so that more than one target can potentially respond to a request.
40565 In particular, memory accesses will walk down the stack of targets
40566 until they find a target that is interested in handling that particular
40569 This command prints a short description of each layer that was pushed on
40570 the @dfn{target stack}, starting from the top layer down to the bottom one.
40572 @kindex maint print type
40573 @cindex type chain of a data type
40574 @item maint print type @var{expr}
40575 Print the type chain for a type specified by @var{expr}. The argument
40576 can be either a type name or a symbol. If it is a symbol, the type of
40577 that symbol is described. The type chain produced by this command is
40578 a recursive definition of the data type as stored in @value{GDBN}'s
40579 data structures, including its flags and contained types.
40581 @kindex maint print record-instruction
40582 @item maint print record-instruction
40583 @itemx maint print record-instruction @var{N}
40584 print how GDB recorded a given instruction. If @var{n} is not positive
40585 number, it prints the values stored by the inferior before the @var{n}-th previous
40586 instruction was exectued. If @var{n} is positive, print the values after the @var{n}-th
40587 following instruction is executed. If @var{n} is not given, 0 is assumed.
40589 @kindex maint selftest
40591 @item maint selftest @r{[}-verbose@r{]} @r{[}@var{filter}@r{]}
40592 Run any self tests that were compiled in to @value{GDBN}. This will
40593 print a message showing how many tests were run, and how many failed.
40594 If a @var{filter} is passed, only the tests with @var{filter} in their
40595 name will be ran. If @code{-verbose} is passed, the self tests can be
40598 @kindex maint set selftest verbose
40599 @kindex maint show selftest verbose
40601 @item maint set selftest verbose
40602 @item maint show selftest verbose
40603 Control whether self tests are run verbosely or not.
40605 @kindex maint info selftests
40607 @item maint info selftests
40608 List the selftests compiled in to @value{GDBN}.
40610 @kindex maint set dwarf always-disassemble
40611 @kindex maint show dwarf always-disassemble
40612 @item maint set dwarf always-disassemble
40613 @item maint show dwarf always-disassemble
40614 Control the behavior of @code{info address} when using DWARF debugging
40617 The default is @code{off}, which means that @value{GDBN} should try to
40618 describe a variable's location in an easily readable format. When
40619 @code{on}, @value{GDBN} will instead display the DWARF location
40620 expression in an assembly-like format. Note that some locations are
40621 too complex for @value{GDBN} to describe simply; in this case you will
40622 always see the disassembly form.
40624 Here is an example of the resulting disassembly:
40627 (@value{GDBP}) info addr argc
40628 Symbol "argc" is a complex DWARF expression:
40632 For more information on these expressions, see
40633 @uref{http://www.dwarfstd.org/, the DWARF standard}.
40635 @kindex maint set dwarf max-cache-age
40636 @kindex maint show dwarf max-cache-age
40637 @item maint set dwarf max-cache-age
40638 @itemx maint show dwarf max-cache-age
40639 Control the DWARF compilation unit cache.
40641 @cindex DWARF compilation units cache
40642 In object files with inter-compilation-unit references, such as those
40643 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
40644 reader needs to frequently refer to previously read compilation units.
40645 This setting controls how long a compilation unit will remain in the
40646 cache if it is not referenced. A higher limit means that cached
40647 compilation units will be stored in memory longer, and more total
40648 memory will be used. Setting it to zero disables caching, which will
40649 slow down @value{GDBN} startup, but reduce memory consumption.
40651 @kindex maint set dwarf unwinders
40652 @kindex maint show dwarf unwinders
40653 @item maint set dwarf unwinders
40654 @itemx maint show dwarf unwinders
40655 Control use of the DWARF frame unwinders.
40657 @cindex DWARF frame unwinders
40658 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
40659 frame unwinders to build the backtrace. Many of these targets will
40660 also have a second mechanism for building the backtrace for use in
40661 cases where DWARF information is not available, this second mechanism
40662 is often an analysis of a function's prologue.
40664 In order to extend testing coverage of the second level stack
40665 unwinding mechanisms it is helpful to be able to disable the DWARF
40666 stack unwinders, this can be done with this switch.
40668 In normal use of @value{GDBN} disabling the DWARF unwinders is not
40669 advisable, there are cases that are better handled through DWARF than
40670 prologue analysis, and the debug experience is likely to be better
40671 with the DWARF frame unwinders enabled.
40673 If DWARF frame unwinders are not supported for a particular target
40674 architecture, then enabling this flag does not cause them to be used.
40676 @kindex maint set worker-threads
40677 @kindex maint show worker-threads
40678 @item maint set worker-threads
40679 @item maint show worker-threads
40680 Control the number of worker threads that may be used by @value{GDBN}.
40681 On capable hosts, @value{GDBN} may use multiple threads to speed up
40682 certain CPU-intensive operations, such as demangling symbol names.
40683 While the number of threads used by @value{GDBN} may vary, this
40684 command can be used to set an upper bound on this number. The default
40685 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
40686 number. Note that this only controls worker threads started by
40687 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
40690 @kindex maint set profile
40691 @kindex maint show profile
40692 @cindex profiling GDB
40693 @item maint set profile
40694 @itemx maint show profile
40695 Control profiling of @value{GDBN}.
40697 Profiling will be disabled until you use the @samp{maint set profile}
40698 command to enable it. When you enable profiling, the system will begin
40699 collecting timing and execution count data; when you disable profiling or
40700 exit @value{GDBN}, the results will be written to a log file. Remember that
40701 if you use profiling, @value{GDBN} will overwrite the profiling log file
40702 (often called @file{gmon.out}). If you have a record of important profiling
40703 data in a @file{gmon.out} file, be sure to move it to a safe location.
40705 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
40706 compiled with the @samp{-pg} compiler option.
40708 @kindex maint set show-debug-regs
40709 @kindex maint show show-debug-regs
40710 @cindex hardware debug registers
40711 @item maint set show-debug-regs
40712 @itemx maint show show-debug-regs
40713 Control whether to show variables that mirror the hardware debug
40714 registers. Use @code{on} to enable, @code{off} to disable. If
40715 enabled, the debug registers values are shown when @value{GDBN} inserts or
40716 removes a hardware breakpoint or watchpoint, and when the inferior
40717 triggers a hardware-assisted breakpoint or watchpoint.
40719 @kindex maint set show-all-tib
40720 @kindex maint show show-all-tib
40721 @item maint set show-all-tib
40722 @itemx maint show show-all-tib
40723 Control whether to show all non zero areas within a 1k block starting
40724 at thread local base, when using the @samp{info w32 thread-information-block}
40727 @kindex maint set target-async
40728 @kindex maint show target-async
40729 @item maint set target-async
40730 @itemx maint show target-async
40731 This controls whether @value{GDBN} targets operate in synchronous or
40732 asynchronous mode (@pxref{Background Execution}). Normally the
40733 default is asynchronous, if it is available; but this can be changed
40734 to more easily debug problems occurring only in synchronous mode.
40736 @kindex maint set target-non-stop @var{mode} [on|off|auto]
40737 @kindex maint show target-non-stop
40738 @item maint set target-non-stop
40739 @itemx maint show target-non-stop
40741 This controls whether @value{GDBN} targets always operate in non-stop
40742 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
40743 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
40744 if supported by the target.
40747 @item maint set target-non-stop auto
40748 This is the default mode. @value{GDBN} controls the target in
40749 non-stop mode if the target supports it.
40751 @item maint set target-non-stop on
40752 @value{GDBN} controls the target in non-stop mode even if the target
40753 does not indicate support.
40755 @item maint set target-non-stop off
40756 @value{GDBN} does not control the target in non-stop mode even if the
40757 target supports it.
40760 @kindex maint set tui-resize-message
40761 @kindex maint show tui-resize-message
40762 @item maint set tui-resize-message
40763 @item maint show tui-resize-message
40764 Control whether @value{GDBN} displays a message each time the terminal
40765 is resized when in TUI mode. The default is @code{off}, which means
40766 that @value{GDBN} is silent during resizes. When @code{on},
40767 @value{GDBN} will display a message after a resize is completed; the
40768 message will include a number indicating how many times the terminal
40769 has been resized. This setting is intended for use by the test suite,
40770 where it would otherwise be difficult to determine when a resize and
40771 refresh has been completed.
40773 @kindex maint set per-command
40774 @kindex maint show per-command
40775 @item maint set per-command
40776 @itemx maint show per-command
40777 @cindex resources used by commands
40779 @value{GDBN} can display the resources used by each command.
40780 This is useful in debugging performance problems.
40783 @item maint set per-command space [on|off]
40784 @itemx maint show per-command space
40785 Enable or disable the printing of the memory used by GDB for each command.
40786 If enabled, @value{GDBN} will display how much memory each command
40787 took, following the command's own output.
40788 This can also be requested by invoking @value{GDBN} with the
40789 @option{--statistics} command-line switch (@pxref{Mode Options}).
40791 @item maint set per-command time [on|off]
40792 @itemx maint show per-command time
40793 Enable or disable the printing of the execution time of @value{GDBN}
40795 If enabled, @value{GDBN} will display how much time it
40796 took to execute each command, following the command's own output.
40797 Both CPU time and wallclock time are printed.
40798 Printing both is useful when trying to determine whether the cost is
40799 CPU or, e.g., disk/network latency.
40800 Note that the CPU time printed is for @value{GDBN} only, it does not include
40801 the execution time of the inferior because there's no mechanism currently
40802 to compute how much time was spent by @value{GDBN} and how much time was
40803 spent by the program been debugged.
40804 This can also be requested by invoking @value{GDBN} with the
40805 @option{--statistics} command-line switch (@pxref{Mode Options}).
40807 @item maint set per-command symtab [on|off]
40808 @itemx maint show per-command symtab
40809 Enable or disable the printing of basic symbol table statistics
40811 If enabled, @value{GDBN} will display the following information:
40815 number of symbol tables
40817 number of primary symbol tables
40819 number of blocks in the blockvector
40823 @kindex maint set check-libthread-db
40824 @kindex maint show check-libthread-db
40825 @item maint set check-libthread-db [on|off]
40826 @itemx maint show check-libthread-db
40827 Control whether @value{GDBN} should run integrity checks on inferior
40828 specific thread debugging libraries as they are loaded. The default
40829 is not to perform such checks. If any check fails @value{GDBN} will
40830 unload the library and continue searching for a suitable candidate as
40831 described in @ref{set libthread-db-search-path}. For more information
40832 about the tests, see @ref{maint check libthread-db}.
40834 @kindex maint set gnu-source-highlight enabled
40835 @kindex maint show gnu-source-highlight enabled
40836 @item maint set gnu-source-highlight enabled @r{[}on|off@r{]}
40837 @itemx maint show gnu-source-highlight enabled
40838 Control whether @value{GDBN} should use the GNU Source Highlight
40839 library for applying styling to source code (@pxref{Output Styling}).
40840 This will be @samp{on} by default if the GNU Source Highlight library
40841 is available. If the GNU Source Highlight library is not available,
40842 then this will be @samp{off} by default, and attempting to change this
40843 value to @samp{on} will give an error.
40845 If the GNU Source Highlight library is not being used, then
40846 @value{GDBN} will use the Python Pygments package for source code
40847 styling, if it is available.
40849 This option is useful for debugging @value{GDBN}'s use of the Pygments
40850 library when @value{GDBN} is linked against the GNU Source Highlight
40853 @anchor{maint_libopcodes_styling}
40854 @kindex maint set libopcodes-styling enabled
40855 @kindex maint show libopcodes-styling enabled
40856 @item maint set libopcodes-styling enabled @r{[}on|off@r{]}
40857 @itemx maint show libopcodes-styling enabled
40858 Control whether @value{GDBN} should use its builtin disassembler
40859 (@file{libopcodes}) to style disassembler output (@pxref{Output
40860 Styling}). The builtin disassembler does not support styling for all
40863 When this option is @samp{off} the builtin disassembler will not be
40864 used for styling, @value{GDBN} will fall back to using the Python
40865 Pygments package if possible.
40867 Trying to set this option @samp{on} for an architecture that the
40868 builtin disassembler is unable to style will give an error, otherwise,
40869 the builtin disassembler will be used to style disassembler output.
40871 This option is @samp{on} by default for supported architectures.
40873 This option is useful for debugging @value{GDBN}'s use of the Pygments
40874 library when @value{GDBN} is built for an architecture that supports
40875 styling with the builtin disassembler
40876 @kindex maint space
40877 @cindex memory used by commands
40878 @item maint space @var{value}
40879 An alias for @code{maint set per-command space}.
40880 A non-zero value enables it, zero disables it.
40883 @cindex time of command execution
40884 @item maint time @var{value}
40885 An alias for @code{maint set per-command time}.
40886 A non-zero value enables it, zero disables it.
40888 @kindex maint translate-address
40889 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
40890 Find the symbol stored at the location specified by the address
40891 @var{addr} and an optional section name @var{section}. If found,
40892 @value{GDBN} prints the name of the closest symbol and an offset from
40893 the symbol's location to the specified address. This is similar to
40894 the @code{info address} command (@pxref{Symbols}), except that this
40895 command also allows to find symbols in other sections.
40897 If section was not specified, the section in which the symbol was found
40898 is also printed. For dynamically linked executables, the name of
40899 executable or shared library containing the symbol is printed as well.
40901 @kindex maint test-options
40902 @item maint test-options require-delimiter
40903 @itemx maint test-options unknown-is-error
40904 @itemx maint test-options unknown-is-operand
40905 These commands are used by the testsuite to validate the command
40906 options framework. The @code{require-delimiter} variant requires a
40907 double-dash delimiter to indicate end of options. The
40908 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
40909 @code{unknown-is-error} variant throws an error on unknown option,
40910 while @code{unknown-is-operand} treats unknown options as the start of
40911 the command's operands. When run, the commands output the result of
40912 the processed options. When completed, the commands store the
40913 internal result of completion in a variable exposed by the @code{maint
40914 show test-options-completion-result} command.
40916 @kindex maint show test-options-completion-result
40917 @item maint show test-options-completion-result
40918 Shows the result of completing the @code{maint test-options}
40919 subcommands. This is used by the testsuite to validate completion
40920 support in the command options framework.
40922 @kindex maint set test-settings
40923 @kindex maint show test-settings
40924 @item maint set test-settings @var{kind}
40925 @itemx maint show test-settings @var{kind}
40926 These are representative commands for each @var{kind} of setting type
40927 @value{GDBN} supports. They are used by the testsuite for exercising
40928 the settings infrastructure.
40930 @kindex maint set backtrace-on-fatal-signal
40931 @kindex maint show backtrace-on-fatal-signal
40932 @item maint set backtrace-on-fatal-signal [on|off]
40933 @itemx maint show backtrace-on-fatal-signal
40934 When this setting is @code{on}, if @value{GDBN} itself terminates with
40935 a fatal signal (e.g.@: SIGSEGV), then a limited backtrace will be
40936 printed to the standard error stream. This backtrace can be used to
40937 help diagnose crashes within @value{GDBN} in situations where a user
40938 is unable to share a corefile with the @value{GDBN} developers.
40940 If the functionality to provide this backtrace is not available for
40941 the platform on which GDB is running then this feature will be
40942 @code{off} by default, and attempting to turn this feature on will
40945 For platforms that do support creating the backtrace this feature is
40946 @code{on} by default.
40949 @item maint with @var{setting} [@var{value}] [-- @var{command}]
40950 Like the @code{with} command, but works with @code{maintenance set}
40951 variables. This is used by the testsuite to exercise the @code{with}
40952 command's infrastructure.
40954 @kindex maint ignore-probes
40955 @item maint ignore-probes [@var{-v}|@var{-verbose}] [@var{provider} [@var{name} [@var{objfile}]]]
40956 @itemx maint ignore-probes @var{-reset}
40957 Set or reset the ignore-probes filter. The @var{provider}, @var{name}
40958 and @var{objfile} arguments are as in @code{enable probes} and
40959 @code{disable probes} (@pxref{enable probes}). Only supported for
40962 Here's an example of using @code{maint ignore-probes}:
40964 (gdb) maint ignore-probes -verbose libc ^longjmp$
40965 ignore-probes filter has been set to:
40967 PROBE_NAME: '^longjmp$'
40970 <... more output ...>
40971 Ignoring SystemTap probe libc longjmp in /lib64/libc.so.6.^M
40972 Ignoring SystemTap probe libc longjmp in /lib64/libc.so.6.^M
40973 Ignoring SystemTap probe libc longjmp in /lib64/libc.so.6.^M
40977 The following command is useful for non-interactive invocations of
40978 @value{GDBN}, such as in the test suite.
40981 @item set watchdog @var{nsec}
40982 @kindex set watchdog
40983 @cindex watchdog timer
40984 @cindex timeout for commands
40985 Set the maximum number of seconds @value{GDBN} will wait for the
40986 target operation to finish. If this time expires, @value{GDBN}
40987 reports and error and the command is aborted.
40989 @item show watchdog
40990 Show the current setting of the target wait timeout.
40993 @node Remote Protocol
40994 @appendix @value{GDBN} Remote Serial Protocol
40999 * Stop Reply Packets::
41000 * General Query Packets::
41001 * Architecture-Specific Protocol Details::
41002 * Tracepoint Packets::
41003 * Host I/O Packets::
41005 * Notification Packets::
41006 * Remote Non-Stop::
41007 * Packet Acknowledgment::
41009 * File-I/O Remote Protocol Extension::
41010 * Library List Format::
41011 * Library List Format for SVR4 Targets::
41012 * Memory Map Format::
41013 * Thread List Format::
41014 * Traceframe Info Format::
41015 * Branch Trace Format::
41016 * Branch Trace Configuration Format::
41022 There may be occasions when you need to know something about the
41023 protocol---for example, if there is only one serial port to your target
41024 machine, you might want your program to do something special if it
41025 recognizes a packet meant for @value{GDBN}.
41027 In the examples below, @samp{->} and @samp{<-} are used to indicate
41028 transmitted and received data, respectively.
41030 @cindex protocol, @value{GDBN} remote serial
41031 @cindex serial protocol, @value{GDBN} remote
41032 @cindex remote serial protocol
41033 All @value{GDBN} commands and responses (other than acknowledgments
41034 and notifications, see @ref{Notification Packets}) are sent as a
41035 @var{packet}. A @var{packet} is introduced with the character
41036 @samp{$}, the actual @var{packet-data}, and the terminating character
41037 @samp{#} followed by a two-digit @var{checksum}:
41040 @code{$}@var{packet-data}@code{#}@var{checksum}
41044 @cindex checksum, for @value{GDBN} remote
41046 The two-digit @var{checksum} is computed as the modulo 256 sum of all
41047 characters between the leading @samp{$} and the trailing @samp{#} (an
41048 eight bit unsigned checksum).
41050 Implementors should note that prior to @value{GDBN} 5.0 the protocol
41051 specification also included an optional two-digit @var{sequence-id}:
41054 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
41057 @cindex sequence-id, for @value{GDBN} remote
41059 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
41060 has never output @var{sequence-id}s. Stubs that handle packets added
41061 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
41063 When either the host or the target machine receives a packet, the first
41064 response expected is an acknowledgment: either @samp{+} (to indicate
41065 the package was received correctly) or @samp{-} (to request
41069 -> @code{$}@var{packet-data}@code{#}@var{checksum}
41074 The @samp{+}/@samp{-} acknowledgments can be disabled
41075 once a connection is established.
41076 @xref{Packet Acknowledgment}, for details.
41078 The host (@value{GDBN}) sends @var{command}s, and the target (the
41079 debugging stub incorporated in your program) sends a @var{response}. In
41080 the case of step and continue @var{command}s, the response is only sent
41081 when the operation has completed, and the target has again stopped all
41082 threads in all attached processes. This is the default all-stop mode
41083 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
41084 execution mode; see @ref{Remote Non-Stop}, for details.
41086 @var{packet-data} consists of a sequence of characters with the
41087 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
41090 @cindex remote protocol, field separator
41091 Fields within the packet should be separated using @samp{,} @samp{;} or
41092 @samp{:}. Except where otherwise noted all numbers are represented in
41093 @sc{hex} with leading zeros suppressed.
41095 Implementors should note that prior to @value{GDBN} 5.0, the character
41096 @samp{:} could not appear as the third character in a packet (as it
41097 would potentially conflict with the @var{sequence-id}).
41099 @cindex remote protocol, binary data
41100 @anchor{Binary Data}
41101 Binary data in most packets is encoded either as two hexadecimal
41102 digits per byte of binary data. This allowed the traditional remote
41103 protocol to work over connections which were only seven-bit clean.
41104 Some packets designed more recently assume an eight-bit clean
41105 connection, and use a more efficient encoding to send and receive
41108 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
41109 as an escape character. Any escaped byte is transmitted as the escape
41110 character followed by the original character XORed with @code{0x20}.
41111 For example, the byte @code{0x7d} would be transmitted as the two
41112 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
41113 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
41114 @samp{@}}) must always be escaped. Responses sent by the stub
41115 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
41116 is not interpreted as the start of a run-length encoded sequence
41119 Response @var{data} can be run-length encoded to save space.
41120 Run-length encoding replaces runs of identical characters with one
41121 instance of the repeated character, followed by a @samp{*} and a
41122 repeat count. The repeat count is itself sent encoded, to avoid
41123 binary characters in @var{data}: a value of @var{n} is sent as
41124 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
41125 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
41126 code 32) for a repeat count of 3. (This is because run-length
41127 encoding starts to win for counts 3 or more.) Thus, for example,
41128 @samp{0* } is a run-length encoding of ``0000'': the space character
41129 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
41132 The printable characters @samp{#} and @samp{$} or with a numeric value
41133 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
41134 seven repeats (@samp{$}) can be expanded using a repeat count of only
41135 five (@samp{"}). For example, @samp{00000000} can be encoded as
41138 The error response returned for some packets includes a two character
41139 error number. That number is not well defined.
41141 @cindex empty response, for unsupported packets
41142 For any @var{command} not supported by the stub, an empty response
41143 (@samp{$#00}) should be returned. That way it is possible to extend the
41144 protocol. A newer @value{GDBN} can tell if a packet is supported based
41147 At a minimum, a stub is required to support the @samp{?} command to
41148 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
41149 commands for register access, and the @samp{m} and @samp{M} commands
41150 for memory access. Stubs that only control single-threaded targets
41151 can implement run control with the @samp{c} (continue) command, and if
41152 the target architecture supports hardware-assisted single-stepping,
41153 the @samp{s} (step) command. Stubs that support multi-threading
41154 targets should support the @samp{vCont} command. All other commands
41160 The following table provides a complete list of all currently defined
41161 @var{command}s and their corresponding response @var{data}.
41162 @xref{File-I/O Remote Protocol Extension}, for details about the File
41163 I/O extension of the remote protocol.
41165 Each packet's description has a template showing the packet's overall
41166 syntax, followed by an explanation of the packet's meaning. We
41167 include spaces in some of the templates for clarity; these are not
41168 part of the packet's syntax. No @value{GDBN} packet uses spaces to
41169 separate its components. For example, a template like @samp{foo
41170 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
41171 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
41172 @var{baz}. @value{GDBN} does not transmit a space character between the
41173 @samp{foo} and the @var{bar}, or between the @var{bar} and the
41176 @cindex @var{thread-id}, in remote protocol
41177 @anchor{thread-id syntax}
41178 Several packets and replies include a @var{thread-id} field to identify
41179 a thread. Normally these are positive numbers with a target-specific
41180 interpretation, formatted as big-endian hex strings. A @var{thread-id}
41181 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
41184 In addition, the remote protocol supports a multiprocess feature in
41185 which the @var{thread-id} syntax is extended to optionally include both
41186 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
41187 The @var{pid} (process) and @var{tid} (thread) components each have the
41188 format described above: a positive number with target-specific
41189 interpretation formatted as a big-endian hex string, literal @samp{-1}
41190 to indicate all processes or threads (respectively), or @samp{0} to
41191 indicate an arbitrary process or thread. Specifying just a process, as
41192 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
41193 error to specify all processes but a specific thread, such as
41194 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
41195 for those packets and replies explicitly documented to include a process
41196 ID, rather than a @var{thread-id}.
41198 The multiprocess @var{thread-id} syntax extensions are only used if both
41199 @value{GDBN} and the stub report support for the @samp{multiprocess}
41200 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
41203 Note that all packet forms beginning with an upper- or lower-case
41204 letter, other than those described here, are reserved for future use.
41206 Here are the packet descriptions.
41211 @cindex @samp{!} packet
41212 @anchor{extended mode}
41213 Enable extended mode. In extended mode, the remote server is made
41214 persistent. The @samp{R} packet is used to restart the program being
41220 The remote target both supports and has enabled extended mode.
41224 @cindex @samp{?} packet
41226 This is sent when connection is first established to query the reason
41227 the target halted. The reply is the same as for step and continue.
41228 This packet has a special interpretation when the target is in
41229 non-stop mode; see @ref{Remote Non-Stop}.
41232 @xref{Stop Reply Packets}, for the reply specifications.
41234 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
41235 @cindex @samp{A} packet
41236 Initialized @code{argv[]} array passed into program. @var{arglen}
41237 specifies the number of bytes in the hex encoded byte stream
41238 @var{arg}. See @code{gdbserver} for more details.
41243 The arguments were set.
41249 @cindex @samp{b} packet
41250 (Don't use this packet; its behavior is not well-defined.)
41251 Change the serial line speed to @var{baud}.
41253 JTC: @emph{When does the transport layer state change? When it's
41254 received, or after the ACK is transmitted. In either case, there are
41255 problems if the command or the acknowledgment packet is dropped.}
41257 Stan: @emph{If people really wanted to add something like this, and get
41258 it working for the first time, they ought to modify ser-unix.c to send
41259 some kind of out-of-band message to a specially-setup stub and have the
41260 switch happen "in between" packets, so that from remote protocol's point
41261 of view, nothing actually happened.}
41263 @item B @var{addr},@var{mode}
41264 @cindex @samp{B} packet
41265 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
41266 breakpoint at @var{addr}.
41268 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
41269 (@pxref{insert breakpoint or watchpoint packet}).
41271 @cindex @samp{bc} packet
41274 Backward continue. Execute the target system in reverse. No parameter.
41275 @xref{Reverse Execution}, for more information.
41278 @xref{Stop Reply Packets}, for the reply specifications.
41280 @cindex @samp{bs} packet
41283 Backward single step. Execute one instruction in reverse. No parameter.
41284 @xref{Reverse Execution}, for more information.
41287 @xref{Stop Reply Packets}, for the reply specifications.
41289 @item c @r{[}@var{addr}@r{]}
41290 @cindex @samp{c} packet
41291 Continue at @var{addr}, which is the address to resume. If @var{addr}
41292 is omitted, resume at current address.
41294 This packet is deprecated for multi-threading support. @xref{vCont
41298 @xref{Stop Reply Packets}, for the reply specifications.
41300 @item C @var{sig}@r{[};@var{addr}@r{]}
41301 @cindex @samp{C} packet
41302 Continue with signal @var{sig} (hex signal number). If
41303 @samp{;@var{addr}} is omitted, resume at same address.
41305 This packet is deprecated for multi-threading support. @xref{vCont
41309 @xref{Stop Reply Packets}, for the reply specifications.
41312 @cindex @samp{d} packet
41315 Don't use this packet; instead, define a general set packet
41316 (@pxref{General Query Packets}).
41320 @cindex @samp{D} packet
41321 The first form of the packet is used to detach @value{GDBN} from the
41322 remote system. It is sent to the remote target
41323 before @value{GDBN} disconnects via the @code{detach} command.
41325 The second form, including a process ID, is used when multiprocess
41326 protocol extensions are enabled (@pxref{multiprocess extensions}), to
41327 detach only a specific process. The @var{pid} is specified as a
41328 big-endian hex string.
41338 @item F @var{RC},@var{EE},@var{CF};@var{XX}
41339 @cindex @samp{F} packet
41340 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
41341 This is part of the File-I/O protocol extension. @xref{File-I/O
41342 Remote Protocol Extension}, for the specification.
41345 @anchor{read registers packet}
41346 @cindex @samp{g} packet
41347 Read general registers.
41351 @item @var{XX@dots{}}
41352 Each byte of register data is described by two hex digits. The bytes
41353 with the register are transmitted in target byte order. The size of
41354 each register and their position within the @samp{g} packet are
41355 determined by the @value{GDBN} internal gdbarch functions
41356 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
41358 When reading registers from a trace frame (@pxref{Analyze Collected
41359 Data,,Using the Collected Data}), the stub may also return a string of
41360 literal @samp{x}'s in place of the register data digits, to indicate
41361 that the corresponding register has not been collected, thus its value
41362 is unavailable. For example, for an architecture with 4 registers of
41363 4 bytes each, the following reply indicates to @value{GDBN} that
41364 registers 0 and 2 have not been collected, while registers 1 and 3
41365 have been collected, and both have zero value:
41369 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
41376 @item G @var{XX@dots{}}
41377 @cindex @samp{G} packet
41378 Write general registers. @xref{read registers packet}, for a
41379 description of the @var{XX@dots{}} data.
41389 @item H @var{op} @var{thread-id}
41390 @cindex @samp{H} packet
41391 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
41392 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
41393 should be @samp{c} for step and continue operations (note that this
41394 is deprecated, supporting the @samp{vCont} command is a better
41395 option), and @samp{g} for other operations. The thread designator
41396 @var{thread-id} has the format and interpretation described in
41397 @ref{thread-id syntax}.
41408 @c 'H': How restrictive (or permissive) is the thread model. If a
41409 @c thread is selected and stopped, are other threads allowed
41410 @c to continue to execute? As I mentioned above, I think the
41411 @c semantics of each command when a thread is selected must be
41412 @c described. For example:
41414 @c 'g': If the stub supports threads and a specific thread is
41415 @c selected, returns the register block from that thread;
41416 @c otherwise returns current registers.
41418 @c 'G' If the stub supports threads and a specific thread is
41419 @c selected, sets the registers of the register block of
41420 @c that thread; otherwise sets current registers.
41422 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
41423 @anchor{cycle step packet}
41424 @cindex @samp{i} packet
41425 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
41426 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
41427 step starting at that address.
41430 @cindex @samp{I} packet
41431 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
41435 @cindex @samp{k} packet
41438 The exact effect of this packet is not specified.
41440 For a bare-metal target, it may power cycle or reset the target
41441 system. For that reason, the @samp{k} packet has no reply.
41443 For a single-process target, it may kill that process if possible.
41445 A multiple-process target may choose to kill just one process, or all
41446 that are under @value{GDBN}'s control. For more precise control, use
41447 the vKill packet (@pxref{vKill packet}).
41449 If the target system immediately closes the connection in response to
41450 @samp{k}, @value{GDBN} does not consider the lack of packet
41451 acknowledgment to be an error, and assumes the kill was successful.
41453 If connected using @kbd{target extended-remote}, and the target does
41454 not close the connection in response to a kill request, @value{GDBN}
41455 probes the target state as if a new connection was opened
41456 (@pxref{? packet}).
41458 @item m @var{addr},@var{length}
41459 @cindex @samp{m} packet
41460 Read @var{length} addressable memory units starting at address @var{addr}
41461 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
41462 any particular boundary.
41464 The stub need not use any particular size or alignment when gathering
41465 data from memory for the response; even if @var{addr} is word-aligned
41466 and @var{length} is a multiple of the word size, the stub is free to
41467 use byte accesses, or not. For this reason, this packet may not be
41468 suitable for accessing memory-mapped I/O devices.
41469 @cindex alignment of remote memory accesses
41470 @cindex size of remote memory accesses
41471 @cindex memory, alignment and size of remote accesses
41475 @item @var{XX@dots{}}
41476 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
41477 The reply may contain fewer addressable memory units than requested if the
41478 server was able to read only part of the region of memory.
41483 @item M @var{addr},@var{length}:@var{XX@dots{}}
41484 @cindex @samp{M} packet
41485 Write @var{length} addressable memory units starting at address @var{addr}
41486 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
41487 byte is transmitted as a two-digit hexadecimal number.
41494 for an error (this includes the case where only part of the data was
41499 @cindex @samp{p} packet
41500 Read the value of register @var{n}; @var{n} is in hex.
41501 @xref{read registers packet}, for a description of how the returned
41502 register value is encoded.
41506 @item @var{XX@dots{}}
41507 the register's value
41511 Indicating an unrecognized @var{query}.
41514 @item P @var{n@dots{}}=@var{r@dots{}}
41515 @anchor{write register packet}
41516 @cindex @samp{P} packet
41517 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
41518 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
41519 digits for each byte in the register (target byte order).
41529 @item q @var{name} @var{params}@dots{}
41530 @itemx Q @var{name} @var{params}@dots{}
41531 @cindex @samp{q} packet
41532 @cindex @samp{Q} packet
41533 General query (@samp{q}) and set (@samp{Q}). These packets are
41534 described fully in @ref{General Query Packets}.
41537 @cindex @samp{r} packet
41538 Reset the entire system.
41540 Don't use this packet; use the @samp{R} packet instead.
41543 @cindex @samp{R} packet
41544 Restart the program being debugged. The @var{XX}, while needed, is ignored.
41545 This packet is only available in extended mode (@pxref{extended mode}).
41547 The @samp{R} packet has no reply.
41549 @item s @r{[}@var{addr}@r{]}
41550 @cindex @samp{s} packet
41551 Single step, resuming at @var{addr}. If
41552 @var{addr} is omitted, resume at same address.
41554 This packet is deprecated for multi-threading support. @xref{vCont
41558 @xref{Stop Reply Packets}, for the reply specifications.
41560 @item S @var{sig}@r{[};@var{addr}@r{]}
41561 @anchor{step with signal packet}
41562 @cindex @samp{S} packet
41563 Step with signal. This is analogous to the @samp{C} packet, but
41564 requests a single-step, rather than a normal resumption of execution.
41566 This packet is deprecated for multi-threading support. @xref{vCont
41570 @xref{Stop Reply Packets}, for the reply specifications.
41572 @item t @var{addr}:@var{PP},@var{MM}
41573 @cindex @samp{t} packet
41574 Search backwards starting at address @var{addr} for a match with pattern
41575 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
41576 There must be at least 3 digits in @var{addr}.
41578 @item T @var{thread-id}
41579 @cindex @samp{T} packet
41580 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
41585 thread is still alive
41591 Packets starting with @samp{v} are identified by a multi-letter name,
41592 up to the first @samp{;} or @samp{?} (or the end of the packet).
41594 @item vAttach;@var{pid}
41595 @cindex @samp{vAttach} packet
41596 Attach to a new process with the specified process ID @var{pid}.
41597 The process ID is a
41598 hexadecimal integer identifying the process. In all-stop mode, all
41599 threads in the attached process are stopped; in non-stop mode, it may be
41600 attached without being stopped if that is supported by the target.
41602 @c In non-stop mode, on a successful vAttach, the stub should set the
41603 @c current thread to a thread of the newly-attached process. After
41604 @c attaching, GDB queries for the attached process's thread ID with qC.
41605 @c Also note that, from a user perspective, whether or not the
41606 @c target is stopped on attach in non-stop mode depends on whether you
41607 @c use the foreground or background version of the attach command, not
41608 @c on what vAttach does; GDB does the right thing with respect to either
41609 @c stopping or restarting threads.
41611 This packet is only available in extended mode (@pxref{extended mode}).
41617 @item @r{Any stop packet}
41618 for success in all-stop mode (@pxref{Stop Reply Packets})
41620 for success in non-stop mode (@pxref{Remote Non-Stop})
41623 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
41624 @cindex @samp{vCont} packet
41625 @anchor{vCont packet}
41626 Resume the inferior, specifying different actions for each thread.
41628 For each inferior thread, the leftmost action with a matching
41629 @var{thread-id} is applied. Threads that don't match any action
41630 remain in their current state. Thread IDs are specified using the
41631 syntax described in @ref{thread-id syntax}. If multiprocess
41632 extensions (@pxref{multiprocess extensions}) are supported, actions
41633 can be specified to match all threads in a process by using the
41634 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
41635 @var{thread-id} matches all threads. Specifying no actions is an
41638 Currently supported actions are:
41644 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
41648 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
41651 @item r @var{start},@var{end}
41652 Step once, and then keep stepping as long as the thread stops at
41653 addresses between @var{start} (inclusive) and @var{end} (exclusive).
41654 The remote stub reports a stop reply when either the thread goes out
41655 of the range or is stopped due to an unrelated reason, such as hitting
41656 a breakpoint. @xref{range stepping}.
41658 If the range is empty (@var{start} == @var{end}), then the action
41659 becomes equivalent to the @samp{s} action. In other words,
41660 single-step once, and report the stop (even if the stepped instruction
41661 jumps to @var{start}).
41663 (A stop reply may be sent at any point even if the PC is still within
41664 the stepping range; for example, it is valid to implement this packet
41665 in a degenerate way as a single instruction step operation.)
41669 The optional argument @var{addr} normally associated with the
41670 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
41671 not supported in @samp{vCont}.
41673 The @samp{t} action is only relevant in non-stop mode
41674 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
41675 A stop reply should be generated for any affected thread not already stopped.
41676 When a thread is stopped by means of a @samp{t} action,
41677 the corresponding stop reply should indicate that the thread has stopped with
41678 signal @samp{0}, regardless of whether the target uses some other signal
41679 as an implementation detail.
41681 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
41682 @samp{r} actions for threads that are already running. Conversely,
41683 the server must ignore @samp{t} actions for threads that are already
41686 @emph{Note:} In non-stop mode, a thread is considered running until
41687 @value{GDBN} acknowledges an asynchronous stop notification for it with
41688 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
41690 The stub must support @samp{vCont} if it reports support for
41691 multiprocess extensions (@pxref{multiprocess extensions}).
41694 @xref{Stop Reply Packets}, for the reply specifications.
41697 @cindex @samp{vCont?} packet
41698 Request a list of actions supported by the @samp{vCont} packet.
41702 @item vCont@r{[};@var{action}@dots{}@r{]}
41703 The @samp{vCont} packet is supported. Each @var{action} is a supported
41704 command in the @samp{vCont} packet.
41706 The @samp{vCont} packet is not supported.
41709 @anchor{vCtrlC packet}
41711 @cindex @samp{vCtrlC} packet
41712 Interrupt remote target as if a control-C was pressed on the remote
41713 terminal. This is the equivalent to reacting to the @code{^C}
41714 (@samp{\003}, the control-C character) character in all-stop mode
41715 while the target is running, except this works in non-stop mode.
41716 @xref{interrupting remote targets}, for more info on the all-stop
41727 @item vFile:@var{operation}:@var{parameter}@dots{}
41728 @cindex @samp{vFile} packet
41729 Perform a file operation on the target system. For details,
41730 see @ref{Host I/O Packets}.
41732 @item vFlashErase:@var{addr},@var{length}
41733 @cindex @samp{vFlashErase} packet
41734 Direct the stub to erase @var{length} bytes of flash starting at
41735 @var{addr}. The region may enclose any number of flash blocks, but
41736 its start and end must fall on block boundaries, as indicated by the
41737 flash block size appearing in the memory map (@pxref{Memory Map
41738 Format}). @value{GDBN} groups flash memory programming operations
41739 together, and sends a @samp{vFlashDone} request after each group; the
41740 stub is allowed to delay erase operation until the @samp{vFlashDone}
41741 packet is received.
41751 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
41752 @cindex @samp{vFlashWrite} packet
41753 Direct the stub to write data to flash address @var{addr}. The data
41754 is passed in binary form using the same encoding as for the @samp{X}
41755 packet (@pxref{Binary Data}). The memory ranges specified by
41756 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
41757 not overlap, and must appear in order of increasing addresses
41758 (although @samp{vFlashErase} packets for higher addresses may already
41759 have been received; the ordering is guaranteed only between
41760 @samp{vFlashWrite} packets). If a packet writes to an address that was
41761 neither erased by a preceding @samp{vFlashErase} packet nor by some other
41762 target-specific method, the results are unpredictable.
41770 for vFlashWrite addressing non-flash memory
41776 @cindex @samp{vFlashDone} packet
41777 Indicate to the stub that flash programming operation is finished.
41778 The stub is permitted to delay or batch the effects of a group of
41779 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
41780 @samp{vFlashDone} packet is received. The contents of the affected
41781 regions of flash memory are unpredictable until the @samp{vFlashDone}
41782 request is completed.
41784 @item vKill;@var{pid}
41785 @cindex @samp{vKill} packet
41786 @anchor{vKill packet}
41787 Kill the process with the specified process ID @var{pid}, which is a
41788 hexadecimal integer identifying the process. This packet is used in
41789 preference to @samp{k} when multiprocess protocol extensions are
41790 supported; see @ref{multiprocess extensions}.
41800 @item vMustReplyEmpty
41801 @cindex @samp{vMustReplyEmpty} packet
41802 The correct reply to an unknown @samp{v} packet is to return the empty
41803 string, however, some older versions of @command{gdbserver} would
41804 incorrectly return @samp{OK} for unknown @samp{v} packets.
41806 The @samp{vMustReplyEmpty} is used as a feature test to check how
41807 @command{gdbserver} handles unknown packets, it is important that this
41808 packet be handled in the same way as other unknown @samp{v} packets.
41809 If this packet is handled differently to other unknown @samp{v}
41810 packets then it is possible that @value{GDBN} may run into problems in
41811 other areas, specifically around use of @samp{vFile:setfs:}.
41813 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
41814 @cindex @samp{vRun} packet
41815 Run the program @var{filename}, passing it each @var{argument} on its
41816 command line. The file and arguments are hex-encoded strings. If
41817 @var{filename} is an empty string, the stub may use a default program
41818 (e.g.@: the last program run). The program is created in the stopped
41821 @c FIXME: What about non-stop mode?
41823 This packet is only available in extended mode (@pxref{extended mode}).
41829 @item @r{Any stop packet}
41830 for success (@pxref{Stop Reply Packets})
41834 @cindex @samp{vStopped} packet
41835 @xref{Notification Packets}.
41837 @item X @var{addr},@var{length}:@var{XX@dots{}}
41839 @cindex @samp{X} packet
41840 Write data to memory, where the data is transmitted in binary.
41841 Memory is specified by its address @var{addr} and number of addressable memory
41842 units @var{length} (@pxref{addressable memory unit});
41843 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
41853 @item z @var{type},@var{addr},@var{kind}
41854 @itemx Z @var{type},@var{addr},@var{kind}
41855 @anchor{insert breakpoint or watchpoint packet}
41856 @cindex @samp{z} packet
41857 @cindex @samp{Z} packets
41858 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
41859 watchpoint starting at address @var{address} of kind @var{kind}.
41861 Each breakpoint and watchpoint packet @var{type} is documented
41864 @emph{Implementation notes: A remote target shall return an empty string
41865 for an unrecognized breakpoint or watchpoint packet @var{type}. A
41866 remote target shall support either both or neither of a given
41867 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
41868 avoid potential problems with duplicate packets, the operations should
41869 be implemented in an idempotent way.}
41871 @item z0,@var{addr},@var{kind}
41872 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41873 @cindex @samp{z0} packet
41874 @cindex @samp{Z0} packet
41875 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
41876 @var{addr} of type @var{kind}.
41878 A software breakpoint is implemented by replacing the instruction at
41879 @var{addr} with a software breakpoint or trap instruction. The
41880 @var{kind} is target-specific and typically indicates the size of the
41881 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
41882 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
41883 architectures have additional meanings for @var{kind}
41884 (@pxref{Architecture-Specific Protocol Details}); if no
41885 architecture-specific value is being used, it should be @samp{0}.
41886 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
41887 conditional expressions in bytecode form that should be evaluated on
41888 the target's side. These are the conditions that should be taken into
41889 consideration when deciding if the breakpoint trigger should be
41890 reported back to @value{GDBN}.
41892 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
41893 for how to best report a software breakpoint event to @value{GDBN}.
41895 The @var{cond_list} parameter is comprised of a series of expressions,
41896 concatenated without separators. Each expression has the following form:
41900 @item X @var{len},@var{expr}
41901 @var{len} is the length of the bytecode expression and @var{expr} is the
41902 actual conditional expression in bytecode form.
41906 The optional @var{cmd_list} parameter introduces commands that may be
41907 run on the target, rather than being reported back to @value{GDBN}.
41908 The parameter starts with a numeric flag @var{persist}; if the flag is
41909 nonzero, then the breakpoint may remain active and the commands
41910 continue to be run even when @value{GDBN} disconnects from the target.
41911 Following this flag is a series of expressions concatenated with no
41912 separators. Each expression has the following form:
41916 @item X @var{len},@var{expr}
41917 @var{len} is the length of the bytecode expression and @var{expr} is the
41918 actual commands expression in bytecode form.
41922 @emph{Implementation note: It is possible for a target to copy or move
41923 code that contains software breakpoints (e.g., when implementing
41924 overlays). The behavior of this packet, in the presence of such a
41925 target, is not defined.}
41937 @item z1,@var{addr},@var{kind}
41938 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41939 @cindex @samp{z1} packet
41940 @cindex @samp{Z1} packet
41941 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
41942 address @var{addr}.
41944 A hardware breakpoint is implemented using a mechanism that is not
41945 dependent on being able to modify the target's memory. The
41946 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
41947 same meaning as in @samp{Z0} packets.
41949 @emph{Implementation note: A hardware breakpoint is not affected by code
41962 @item z2,@var{addr},@var{kind}
41963 @itemx Z2,@var{addr},@var{kind}
41964 @cindex @samp{z2} packet
41965 @cindex @samp{Z2} packet
41966 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
41967 The number of bytes to watch is specified by @var{kind}.
41979 @item z3,@var{addr},@var{kind}
41980 @itemx Z3,@var{addr},@var{kind}
41981 @cindex @samp{z3} packet
41982 @cindex @samp{Z3} packet
41983 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
41984 The number of bytes to watch is specified by @var{kind}.
41996 @item z4,@var{addr},@var{kind}
41997 @itemx Z4,@var{addr},@var{kind}
41998 @cindex @samp{z4} packet
41999 @cindex @samp{Z4} packet
42000 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
42001 The number of bytes to watch is specified by @var{kind}.
42015 @node Stop Reply Packets
42016 @section Stop Reply Packets
42017 @cindex stop reply packets
42019 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
42020 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
42021 receive any of the below as a reply. Except for @samp{?}
42022 and @samp{vStopped}, that reply is only returned
42023 when the target halts. In the below the exact meaning of @dfn{signal
42024 number} is defined by the header @file{include/gdb/signals.h} in the
42025 @value{GDBN} source code.
42027 In non-stop mode, the server will simply reply @samp{OK} to commands
42028 such as @samp{vCont}; any stop will be the subject of a future
42029 notification. @xref{Remote Non-Stop}.
42031 As in the description of request packets, we include spaces in the
42032 reply templates for clarity; these are not part of the reply packet's
42033 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
42039 The program received signal number @var{AA} (a two-digit hexadecimal
42040 number). This is equivalent to a @samp{T} response with no
42041 @var{n}:@var{r} pairs.
42043 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
42044 @cindex @samp{T} packet reply
42045 The program received signal number @var{AA} (a two-digit hexadecimal
42046 number). This is equivalent to an @samp{S} response, except that the
42047 @samp{@var{n}:@var{r}} pairs can carry values of important registers
42048 and other information directly in the stop reply packet, reducing
42049 round-trip latency. Single-step and breakpoint traps are reported
42050 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
42054 If @var{n} is a hexadecimal number, it is a register number, and the
42055 corresponding @var{r} gives that register's value. The data @var{r} is a
42056 series of bytes in target byte order, with each byte given by a
42057 two-digit hex number.
42060 If @var{n} is @samp{thread}, then @var{r} is the thread ID of
42061 the stopped thread, as specified in @ref{thread-id syntax}.
42064 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
42065 the core on which the stop event was detected.
42068 If @var{n} is a recognized @dfn{stop reason}, it describes a more
42069 specific event that stopped the target. The currently defined stop
42070 reasons are listed below. The @var{aa} should be @samp{05}, the trap
42071 signal. At most one stop reason should be present.
42074 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
42075 and go on to the next; this allows us to extend the protocol in the
42079 The currently defined stop reasons are:
42085 The packet indicates a watchpoint hit, and @var{r} is the data address, in
42088 @item syscall_entry
42089 @itemx syscall_return
42090 The packet indicates a syscall entry or return, and @var{r} is the
42091 syscall number, in hex.
42093 @cindex shared library events, remote reply
42095 The packet indicates that the loaded libraries have changed.
42096 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
42097 list of loaded libraries. The @var{r} part is ignored.
42099 @cindex replay log events, remote reply
42101 The packet indicates that the target cannot continue replaying
42102 logged execution events, because it has reached the end (or the
42103 beginning when executing backward) of the log. The value of @var{r}
42104 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
42105 for more information.
42108 @anchor{swbreak stop reason}
42109 The packet indicates a software breakpoint instruction was executed,
42110 irrespective of whether it was @value{GDBN} that planted the
42111 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
42112 part must be left empty.
42114 On some architectures, such as x86, at the architecture level, when a
42115 breakpoint instruction executes the program counter points at the
42116 breakpoint address plus an offset. On such targets, the stub is
42117 responsible for adjusting the PC to point back at the breakpoint
42120 This packet should not be sent by default; older @value{GDBN} versions
42121 did not support it. @value{GDBN} requests it, by supplying an
42122 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
42123 remote stub must also supply the appropriate @samp{qSupported} feature
42124 indicating support.
42126 This packet is required for correct non-stop mode operation.
42129 The packet indicates the target stopped for a hardware breakpoint.
42130 The @var{r} part must be left empty.
42132 The same remarks about @samp{qSupported} and non-stop mode above
42135 @cindex fork events, remote reply
42137 The packet indicates that @code{fork} was called, and @var{r} is the
42138 thread ID of the new child process, as specified in @ref{thread-id
42139 syntax}. This packet is only applicable to targets that support fork
42142 This packet should not be sent by default; older @value{GDBN} versions
42143 did not support it. @value{GDBN} requests it, by supplying an
42144 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
42145 remote stub must also supply the appropriate @samp{qSupported} feature
42146 indicating support.
42148 @cindex vfork events, remote reply
42150 The packet indicates that @code{vfork} was called, and @var{r} is the
42151 thread ID of the new child process, as specified in @ref{thread-id
42152 syntax}. This packet is only applicable to targets that support vfork
42155 This packet should not be sent by default; older @value{GDBN} versions
42156 did not support it. @value{GDBN} requests it, by supplying an
42157 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
42158 remote stub must also supply the appropriate @samp{qSupported} feature
42159 indicating support.
42161 @cindex vforkdone events, remote reply
42163 The packet indicates that a child process created by a vfork
42164 has either called @code{exec} or terminated, so that the
42165 address spaces of the parent and child process are no longer
42166 shared. The @var{r} part is ignored. This packet is only
42167 applicable to targets that support vforkdone events.
42169 This packet should not be sent by default; older @value{GDBN} versions
42170 did not support it. @value{GDBN} requests it, by supplying an
42171 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
42172 remote stub must also supply the appropriate @samp{qSupported} feature
42173 indicating support.
42175 @cindex exec events, remote reply
42177 The packet indicates that @code{execve} was called, and @var{r}
42178 is the absolute pathname of the file that was executed, in hex.
42179 This packet is only applicable to targets that support exec events.
42181 This packet should not be sent by default; older @value{GDBN} versions
42182 did not support it. @value{GDBN} requests it, by supplying an
42183 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
42184 remote stub must also supply the appropriate @samp{qSupported} feature
42185 indicating support.
42187 @cindex thread create event, remote reply
42188 @anchor{thread create event}
42190 The packet indicates that the thread was just created. The new thread
42191 is stopped until @value{GDBN} sets it running with a resumption packet
42192 (@pxref{vCont packet}). This packet should not be sent by default;
42193 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
42194 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
42195 @var{r} part is ignored.
42200 @itemx W @var{AA} ; process:@var{pid}
42201 The process exited, and @var{AA} is the exit status. This is only
42202 applicable to certain targets.
42204 The second form of the response, including the process ID of the
42205 exited process, can be used only when @value{GDBN} has reported
42206 support for multiprocess protocol extensions; see @ref{multiprocess
42207 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
42211 @itemx X @var{AA} ; process:@var{pid}
42212 The process terminated with signal @var{AA}.
42214 The second form of the response, including the process ID of the
42215 terminated process, can be used only when @value{GDBN} has reported
42216 support for multiprocess protocol extensions; see @ref{multiprocess
42217 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
42220 @anchor{thread exit event}
42221 @cindex thread exit event, remote reply
42222 @item w @var{AA} ; @var{tid}
42224 The thread exited, and @var{AA} is the exit status. This response
42225 should not be sent by default; @value{GDBN} requests it with the
42226 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
42227 @var{AA} is formatted as a big-endian hex string.
42230 There are no resumed threads left in the target. In other words, even
42231 though the process is alive, the last resumed thread has exited. For
42232 example, say the target process has two threads: thread 1 and thread
42233 2. The client leaves thread 1 stopped, and resumes thread 2, which
42234 subsequently exits. At this point, even though the process is still
42235 alive, and thus no @samp{W} stop reply is sent, no thread is actually
42236 executing either. The @samp{N} stop reply thus informs the client
42237 that it can stop waiting for stop replies. This packet should not be
42238 sent by default; older @value{GDBN} versions did not support it.
42239 @value{GDBN} requests it, by supplying an appropriate
42240 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
42241 also supply the appropriate @samp{qSupported} feature indicating
42244 @item O @var{XX}@dots{}
42245 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
42246 written as the program's console output. This can happen at any time
42247 while the program is running and the debugger should continue to wait
42248 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
42250 @item F @var{call-id},@var{parameter}@dots{}
42251 @var{call-id} is the identifier which says which host system call should
42252 be called. This is just the name of the function. Translation into the
42253 correct system call is only applicable as it's defined in @value{GDBN}.
42254 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
42257 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
42258 this very system call.
42260 The target replies with this packet when it expects @value{GDBN} to
42261 call a host system call on behalf of the target. @value{GDBN} replies
42262 with an appropriate @samp{F} packet and keeps up waiting for the next
42263 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
42264 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
42265 Protocol Extension}, for more details.
42269 @node General Query Packets
42270 @section General Query Packets
42271 @cindex remote query requests
42273 Packets starting with @samp{q} are @dfn{general query packets};
42274 packets starting with @samp{Q} are @dfn{general set packets}. General
42275 query and set packets are a semi-unified form for retrieving and
42276 sending information to and from the stub.
42278 The initial letter of a query or set packet is followed by a name
42279 indicating what sort of thing the packet applies to. For example,
42280 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
42281 definitions with the stub. These packet names follow some
42286 The name must not contain commas, colons or semicolons.
42288 Most @value{GDBN} query and set packets have a leading upper case
42291 The names of custom vendor packets should use a company prefix, in
42292 lower case, followed by a period. For example, packets designed at
42293 the Acme Corporation might begin with @samp{qacme.foo} (for querying
42294 foos) or @samp{Qacme.bar} (for setting bars).
42297 The name of a query or set packet should be separated from any
42298 parameters by a @samp{:}; the parameters themselves should be
42299 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
42300 full packet name, and check for a separator or the end of the packet,
42301 in case two packet names share a common prefix. New packets should not begin
42302 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
42303 packets predate these conventions, and have arguments without any terminator
42304 for the packet name; we suspect they are in widespread use in places that
42305 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
42306 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
42309 Like the descriptions of the other packets, each description here
42310 has a template showing the packet's overall syntax, followed by an
42311 explanation of the packet's meaning. We include spaces in some of the
42312 templates for clarity; these are not part of the packet's syntax. No
42313 @value{GDBN} packet uses spaces to separate its components.
42315 Here are the currently defined query and set packets:
42321 Turn on or off the agent as a helper to perform some debugging operations
42322 delegated from @value{GDBN} (@pxref{Control Agent}).
42324 @item QAllow:@var{op}:@var{val}@dots{}
42325 @cindex @samp{QAllow} packet
42326 Specify which operations @value{GDBN} expects to request of the
42327 target, as a semicolon-separated list of operation name and value
42328 pairs. Possible values for @var{op} include @samp{WriteReg},
42329 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
42330 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
42331 indicating that @value{GDBN} will not request the operation, or 1,
42332 indicating that it may. (The target can then use this to set up its
42333 own internals optimally, for instance if the debugger never expects to
42334 insert breakpoints, it may not need to install its own trap handler.)
42337 @cindex current thread, remote request
42338 @cindex @samp{qC} packet
42339 Return the current thread ID.
42343 @item QC @var{thread-id}
42344 Where @var{thread-id} is a thread ID as documented in
42345 @ref{thread-id syntax}.
42346 @item @r{(anything else)}
42347 Any other reply implies the old thread ID.
42350 @item qCRC:@var{addr},@var{length}
42351 @cindex CRC of memory block, remote request
42352 @cindex @samp{qCRC} packet
42353 @anchor{qCRC packet}
42354 Compute the CRC checksum of a block of memory using CRC-32 defined in
42355 IEEE 802.3. The CRC is computed byte at a time, taking the most
42356 significant bit of each byte first. The initial pattern code
42357 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
42359 @emph{Note:} This is the same CRC used in validating separate debug
42360 files (@pxref{Separate Debug Files, , Debugging Information in Separate
42361 Files}). However the algorithm is slightly different. When validating
42362 separate debug files, the CRC is computed taking the @emph{least}
42363 significant bit of each byte first, and the final result is inverted to
42364 detect trailing zeros.
42369 An error (such as memory fault)
42370 @item C @var{crc32}
42371 The specified memory region's checksum is @var{crc32}.
42374 @item QDisableRandomization:@var{value}
42375 @cindex disable address space randomization, remote request
42376 @cindex @samp{QDisableRandomization} packet
42377 Some target operating systems will randomize the virtual address space
42378 of the inferior process as a security feature, but provide a feature
42379 to disable such randomization, e.g.@: to allow for a more deterministic
42380 debugging experience. On such systems, this packet with a @var{value}
42381 of 1 directs the target to disable address space randomization for
42382 processes subsequently started via @samp{vRun} packets, while a packet
42383 with a @var{value} of 0 tells the target to enable address space
42386 This packet is only available in extended mode (@pxref{extended mode}).
42391 The request succeeded.
42394 An error occurred. The error number @var{nn} is given as hex digits.
42397 An empty reply indicates that @samp{QDisableRandomization} is not supported
42401 This packet is not probed by default; the remote stub must request it,
42402 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42403 This should only be done on targets that actually support disabling
42404 address space randomization.
42406 @item QStartupWithShell:@var{value}
42407 @cindex startup with shell, remote request
42408 @cindex @samp{QStartupWithShell} packet
42409 On UNIX-like targets, it is possible to start the inferior using a
42410 shell program. This is the default behavior on both @value{GDBN} and
42411 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
42412 used to inform @command{gdbserver} whether it should start the
42413 inferior using a shell or not.
42415 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
42416 to start the inferior. If @var{value} is @samp{1},
42417 @command{gdbserver} will use a shell to start the inferior. All other
42418 values are considered an error.
42420 This packet is only available in extended mode (@pxref{extended
42426 The request succeeded.
42429 An error occurred. The error number @var{nn} is given as hex digits.
42432 This packet is not probed by default; the remote stub must request it,
42433 by supplying an appropriate @samp{qSupported} response
42434 (@pxref{qSupported}). This should only be done on targets that
42435 actually support starting the inferior using a shell.
42437 Use of this packet is controlled by the @code{set startup-with-shell}
42438 command; @pxref{set startup-with-shell}.
42440 @item QEnvironmentHexEncoded:@var{hex-value}
42441 @anchor{QEnvironmentHexEncoded}
42442 @cindex set environment variable, remote request
42443 @cindex @samp{QEnvironmentHexEncoded} packet
42444 On UNIX-like targets, it is possible to set environment variables that
42445 will be passed to the inferior during the startup process. This
42446 packet is used to inform @command{gdbserver} of an environment
42447 variable that has been defined by the user on @value{GDBN} (@pxref{set
42450 The packet is composed by @var{hex-value}, an hex encoded
42451 representation of the @var{name=value} format representing an
42452 environment variable. The name of the environment variable is
42453 represented by @var{name}, and the value to be assigned to the
42454 environment variable is represented by @var{value}. If the variable
42455 has no value (i.e., the value is @code{null}), then @var{value} will
42458 This packet is only available in extended mode (@pxref{extended
42464 The request succeeded.
42467 This packet is not probed by default; the remote stub must request it,
42468 by supplying an appropriate @samp{qSupported} response
42469 (@pxref{qSupported}). This should only be done on targets that
42470 actually support passing environment variables to the starting
42473 This packet is related to the @code{set environment} command;
42474 @pxref{set environment}.
42476 @item QEnvironmentUnset:@var{hex-value}
42477 @anchor{QEnvironmentUnset}
42478 @cindex unset environment variable, remote request
42479 @cindex @samp{QEnvironmentUnset} packet
42480 On UNIX-like targets, it is possible to unset environment variables
42481 before starting the inferior in the remote target. This packet is
42482 used to inform @command{gdbserver} of an environment variable that has
42483 been unset by the user on @value{GDBN} (@pxref{unset environment}).
42485 The packet is composed by @var{hex-value}, an hex encoded
42486 representation of the name of the environment variable to be unset.
42488 This packet is only available in extended mode (@pxref{extended
42494 The request succeeded.
42497 This packet is not probed by default; the remote stub must request it,
42498 by supplying an appropriate @samp{qSupported} response
42499 (@pxref{qSupported}). This should only be done on targets that
42500 actually support passing environment variables to the starting
42503 This packet is related to the @code{unset environment} command;
42504 @pxref{unset environment}.
42506 @item QEnvironmentReset
42507 @anchor{QEnvironmentReset}
42508 @cindex reset environment, remote request
42509 @cindex @samp{QEnvironmentReset} packet
42510 On UNIX-like targets, this packet is used to reset the state of
42511 environment variables in the remote target before starting the
42512 inferior. In this context, reset means unsetting all environment
42513 variables that were previously set by the user (i.e., were not
42514 initially present in the environment). It is sent to
42515 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
42516 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
42517 (@pxref{QEnvironmentUnset}) packets.
42519 This packet is only available in extended mode (@pxref{extended
42525 The request succeeded.
42528 This packet is not probed by default; the remote stub must request it,
42529 by supplying an appropriate @samp{qSupported} response
42530 (@pxref{qSupported}). This should only be done on targets that
42531 actually support passing environment variables to the starting
42534 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
42535 @anchor{QSetWorkingDir packet}
42536 @cindex set working directory, remote request
42537 @cindex @samp{QSetWorkingDir} packet
42538 This packet is used to inform the remote server of the intended
42539 current working directory for programs that are going to be executed.
42541 The packet is composed by @var{directory}, an hex encoded
42542 representation of the directory that the remote inferior will use as
42543 its current working directory. If @var{directory} is an empty string,
42544 the remote server should reset the inferior's current working
42545 directory to its original, empty value.
42547 This packet is only available in extended mode (@pxref{extended
42553 The request succeeded.
42557 @itemx qsThreadInfo
42558 @cindex list active threads, remote request
42559 @cindex @samp{qfThreadInfo} packet
42560 @cindex @samp{qsThreadInfo} packet
42561 Obtain a list of all active thread IDs from the target (OS). Since there
42562 may be too many active threads to fit into one reply packet, this query
42563 works iteratively: it may require more than one query/reply sequence to
42564 obtain the entire list of threads. The first query of the sequence will
42565 be the @samp{qfThreadInfo} query; subsequent queries in the
42566 sequence will be the @samp{qsThreadInfo} query.
42568 NOTE: This packet replaces the @samp{qL} query (see below).
42572 @item m @var{thread-id}
42574 @item m @var{thread-id},@var{thread-id}@dots{}
42575 a comma-separated list of thread IDs
42577 (lower case letter @samp{L}) denotes end of list.
42580 In response to each query, the target will reply with a list of one or
42581 more thread IDs, separated by commas.
42582 @value{GDBN} will respond to each reply with a request for more thread
42583 ids (using the @samp{qs} form of the query), until the target responds
42584 with @samp{l} (lower-case ell, for @dfn{last}).
42585 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
42588 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
42589 initial connection with the remote target, and the very first thread ID
42590 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
42591 message. Therefore, the stub should ensure that the first thread ID in
42592 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
42594 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
42595 @cindex get thread-local storage address, remote request
42596 @cindex @samp{qGetTLSAddr} packet
42597 Fetch the address associated with thread local storage specified
42598 by @var{thread-id}, @var{offset}, and @var{lm}.
42600 @var{thread-id} is the thread ID associated with the
42601 thread for which to fetch the TLS address. @xref{thread-id syntax}.
42603 @var{offset} is the (big endian, hex encoded) offset associated with the
42604 thread local variable. (This offset is obtained from the debug
42605 information associated with the variable.)
42607 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
42608 load module associated with the thread local storage. For example,
42609 a @sc{gnu}/Linux system will pass the link map address of the shared
42610 object associated with the thread local storage under consideration.
42611 Other operating environments may choose to represent the load module
42612 differently, so the precise meaning of this parameter will vary.
42616 @item @var{XX}@dots{}
42617 Hex encoded (big endian) bytes representing the address of the thread
42618 local storage requested.
42621 An error occurred. The error number @var{nn} is given as hex digits.
42624 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
42627 @item qGetTIBAddr:@var{thread-id}
42628 @cindex get thread information block address
42629 @cindex @samp{qGetTIBAddr} packet
42630 Fetch address of the Windows OS specific Thread Information Block.
42632 @var{thread-id} is the thread ID associated with the thread.
42636 @item @var{XX}@dots{}
42637 Hex encoded (big endian) bytes representing the linear address of the
42638 thread information block.
42641 An error occured. This means that either the thread was not found, or the
42642 address could not be retrieved.
42645 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
42648 @item qL @var{startflag} @var{threadcount} @var{nextthread}
42649 Obtain thread information from RTOS. Where: @var{startflag} (one hex
42650 digit) is one to indicate the first query and zero to indicate a
42651 subsequent query; @var{threadcount} (two hex digits) is the maximum
42652 number of threads the response packet can contain; and @var{nextthread}
42653 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
42654 returned in the response as @var{argthread}.
42656 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
42660 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
42661 Where: @var{count} (two hex digits) is the number of threads being
42662 returned; @var{done} (one hex digit) is zero to indicate more threads
42663 and one indicates no further threads; @var{argthreadid} (eight hex
42664 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
42665 is a sequence of thread IDs, @var{threadid} (eight hex
42666 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
42669 @item qMemTags:@var{start address},@var{length}:@var{type}
42671 @cindex fetch memory tags
42672 @cindex @samp{qMemTags} packet
42673 Fetch memory tags of type @var{type} from the address range
42674 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
42675 target is responsible for calculating how many tags will be returned, as this
42676 is architecture-specific.
42678 @var{start address} is the starting address of the memory range.
42680 @var{length} is the length, in bytes, of the memory range.
42682 @var{type} is the type of tag the request wants to fetch. The type is a signed
42687 @item @var{mxx}@dots{}
42688 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
42689 tags found in the requested memory range.
42692 An error occured. This means that fetching of memory tags failed for some
42696 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
42697 although this should not happen given @value{GDBN} will only send this packet
42698 if the stub has advertised support for memory tagging via @samp{qSupported}.
42701 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
42703 @cindex store memory tags
42704 @cindex @samp{QMemTags} packet
42705 Store memory tags of type @var{type} to the address range
42706 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
42707 target is responsible for interpreting the type, the tag bytes and modifying
42708 the memory tag granules accordingly, given this is architecture-specific.
42710 The interpretation of how many tags (@var{nt}) should be written to how many
42711 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
42712 implementation-specific, but the following is suggested.
42714 If the number of memory tags, @var{nt}, is greater than or equal to the
42715 number of memory tag granules, @var{ng}, only @var{ng} tags will be
42718 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
42719 and the tag bytes will be used as a pattern that will get repeated until
42720 @var{ng} tags are stored.
42722 @var{start address} is the starting address of the memory range. The address
42723 does not have any restriction on alignment or size.
42725 @var{length} is the length, in bytes, of the memory range.
42727 @var{type} is the type of tag the request wants to fetch. The type is a signed
42730 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
42731 interpreted by the target. Each pair of hex digits is interpreted as a
42737 The request was successful and the memory tag granules were modified
42741 An error occured. This means that modifying the memory tag granules failed
42745 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
42746 although this should not happen given @value{GDBN} will only send this packet
42747 if the stub has advertised support for memory tagging via @samp{qSupported}.
42751 @cindex section offsets, remote request
42752 @cindex @samp{qOffsets} packet
42753 Get section offsets that the target used when relocating the downloaded
42758 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
42759 Relocate the @code{Text} section by @var{xxx} from its original address.
42760 Relocate the @code{Data} section by @var{yyy} from its original address.
42761 If the object file format provides segment information (e.g.@: @sc{elf}
42762 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
42763 segments by the supplied offsets.
42765 @emph{Note: while a @code{Bss} offset may be included in the response,
42766 @value{GDBN} ignores this and instead applies the @code{Data} offset
42767 to the @code{Bss} section.}
42769 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
42770 Relocate the first segment of the object file, which conventionally
42771 contains program code, to a starting address of @var{xxx}. If
42772 @samp{DataSeg} is specified, relocate the second segment, which
42773 conventionally contains modifiable data, to a starting address of
42774 @var{yyy}. @value{GDBN} will report an error if the object file
42775 does not contain segment information, or does not contain at least
42776 as many segments as mentioned in the reply. Extra segments are
42777 kept at fixed offsets relative to the last relocated segment.
42780 @item qP @var{mode} @var{thread-id}
42781 @cindex thread information, remote request
42782 @cindex @samp{qP} packet
42783 Returns information on @var{thread-id}. Where: @var{mode} is a hex
42784 encoded 32 bit mode; @var{thread-id} is a thread ID
42785 (@pxref{thread-id syntax}).
42787 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
42790 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
42794 @cindex non-stop mode, remote request
42795 @cindex @samp{QNonStop} packet
42797 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
42798 @xref{Remote Non-Stop}, for more information.
42803 The request succeeded.
42806 An error occurred. The error number @var{nn} is given as hex digits.
42809 An empty reply indicates that @samp{QNonStop} is not supported by
42813 This packet is not probed by default; the remote stub must request it,
42814 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42815 Use of this packet is controlled by the @code{set non-stop} command;
42816 @pxref{Non-Stop Mode}.
42818 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
42819 @itemx QCatchSyscalls:0
42820 @cindex catch syscalls from inferior, remote request
42821 @cindex @samp{QCatchSyscalls} packet
42822 @anchor{QCatchSyscalls}
42823 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
42824 catching syscalls from the inferior process.
42826 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
42827 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
42828 is listed, every system call should be reported.
42830 Note that if a syscall not in the list is reported, @value{GDBN} will
42831 still filter the event according to its own list from all corresponding
42832 @code{catch syscall} commands. However, it is more efficient to only
42833 report the requested syscalls.
42835 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
42836 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
42838 If the inferior process execs, the state of @samp{QCatchSyscalls} is
42839 kept for the new process too. On targets where exec may affect syscall
42840 numbers, for example with exec between 32 and 64-bit processes, the
42841 client should send a new packet with the new syscall list.
42846 The request succeeded.
42849 An error occurred. @var{nn} are hex digits.
42852 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
42856 Use of this packet is controlled by the @code{set remote catch-syscalls}
42857 command (@pxref{Remote Configuration, set remote catch-syscalls}).
42858 This packet is not probed by default; the remote stub must request it,
42859 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42861 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42862 @cindex pass signals to inferior, remote request
42863 @cindex @samp{QPassSignals} packet
42864 @anchor{QPassSignals}
42865 Each listed @var{signal} should be passed directly to the inferior process.
42866 Signals are numbered identically to continue packets and stop replies
42867 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42868 strictly greater than the previous item. These signals do not need to stop
42869 the inferior, or be reported to @value{GDBN}. All other signals should be
42870 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
42871 combine; any earlier @samp{QPassSignals} list is completely replaced by the
42872 new list. This packet improves performance when using @samp{handle
42873 @var{signal} nostop noprint pass}.
42878 The request succeeded.
42881 An error occurred. The error number @var{nn} is given as hex digits.
42884 An empty reply indicates that @samp{QPassSignals} is not supported by
42888 Use of this packet is controlled by the @code{set remote pass-signals}
42889 command (@pxref{Remote Configuration, set remote pass-signals}).
42890 This packet is not probed by default; the remote stub must request it,
42891 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42893 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42894 @cindex signals the inferior may see, remote request
42895 @cindex @samp{QProgramSignals} packet
42896 @anchor{QProgramSignals}
42897 Each listed @var{signal} may be delivered to the inferior process.
42898 Others should be silently discarded.
42900 In some cases, the remote stub may need to decide whether to deliver a
42901 signal to the program or not without @value{GDBN} involvement. One
42902 example of that is while detaching --- the program's threads may have
42903 stopped for signals that haven't yet had a chance of being reported to
42904 @value{GDBN}, and so the remote stub can use the signal list specified
42905 by this packet to know whether to deliver or ignore those pending
42908 This does not influence whether to deliver a signal as requested by a
42909 resumption packet (@pxref{vCont packet}).
42911 Signals are numbered identically to continue packets and stop replies
42912 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42913 strictly greater than the previous item. Multiple
42914 @samp{QProgramSignals} packets do not combine; any earlier
42915 @samp{QProgramSignals} list is completely replaced by the new list.
42920 The request succeeded.
42923 An error occurred. The error number @var{nn} is given as hex digits.
42926 An empty reply indicates that @samp{QProgramSignals} is not supported
42930 Use of this packet is controlled by the @code{set remote program-signals}
42931 command (@pxref{Remote Configuration, set remote program-signals}).
42932 This packet is not probed by default; the remote stub must request it,
42933 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42935 @anchor{QThreadEvents}
42936 @item QThreadEvents:1
42937 @itemx QThreadEvents:0
42938 @cindex thread create/exit events, remote request
42939 @cindex @samp{QThreadEvents} packet
42941 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
42942 reporting of thread create and exit events. @xref{thread create
42943 event}, for the reply specifications. For example, this is used in
42944 non-stop mode when @value{GDBN} stops a set of threads and
42945 synchronously waits for the their corresponding stop replies. Without
42946 exit events, if one of the threads exits, @value{GDBN} would hang
42947 forever not knowing that it should no longer expect a stop for that
42948 same thread. @value{GDBN} does not enable this feature unless the
42949 stub reports that it supports it by including @samp{QThreadEvents+} in
42950 its @samp{qSupported} reply.
42955 The request succeeded.
42958 An error occurred. The error number @var{nn} is given as hex digits.
42961 An empty reply indicates that @samp{QThreadEvents} is not supported by
42965 Use of this packet is controlled by the @code{set remote thread-events}
42966 command (@pxref{Remote Configuration, set remote thread-events}).
42968 @item qRcmd,@var{command}
42969 @cindex execute remote command, remote request
42970 @cindex @samp{qRcmd} packet
42971 @var{command} (hex encoded) is passed to the local interpreter for
42972 execution. Invalid commands should be reported using the output
42973 string. Before the final result packet, the target may also respond
42974 with a number of intermediate @samp{O@var{output}} console output
42975 packets. @emph{Implementors should note that providing access to a
42976 stubs's interpreter may have security implications}.
42981 A command response with no output.
42983 A command response with the hex encoded output string @var{OUTPUT}.
42985 Indicate a badly formed request. The error number @var{NN} is given as
42988 An empty reply indicates that @samp{qRcmd} is not recognized.
42991 (Note that the @code{qRcmd} packet's name is separated from the
42992 command by a @samp{,}, not a @samp{:}, contrary to the naming
42993 conventions above. Please don't use this packet as a model for new
42996 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
42997 @cindex searching memory, in remote debugging
42999 @cindex @samp{qSearch:memory} packet
43001 @cindex @samp{qSearch memory} packet
43002 @anchor{qSearch memory}
43003 Search @var{length} bytes at @var{address} for @var{search-pattern}.
43004 Both @var{address} and @var{length} are encoded in hex;
43005 @var{search-pattern} is a sequence of bytes, also hex encoded.
43010 The pattern was not found.
43012 The pattern was found at @var{address}.
43014 A badly formed request or an error was encountered while searching memory.
43016 An empty reply indicates that @samp{qSearch:memory} is not recognized.
43019 @item QStartNoAckMode
43020 @cindex @samp{QStartNoAckMode} packet
43021 @anchor{QStartNoAckMode}
43022 Request that the remote stub disable the normal @samp{+}/@samp{-}
43023 protocol acknowledgments (@pxref{Packet Acknowledgment}).
43028 The stub has switched to no-acknowledgment mode.
43029 @value{GDBN} acknowledges this response,
43030 but neither the stub nor @value{GDBN} shall send or expect further
43031 @samp{+}/@samp{-} acknowledgments in the current connection.
43033 An empty reply indicates that the stub does not support no-acknowledgment mode.
43036 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
43037 @cindex supported packets, remote query
43038 @cindex features of the remote protocol
43039 @cindex @samp{qSupported} packet
43040 @anchor{qSupported}
43041 Tell the remote stub about features supported by @value{GDBN}, and
43042 query the stub for features it supports. This packet allows
43043 @value{GDBN} and the remote stub to take advantage of each others'
43044 features. @samp{qSupported} also consolidates multiple feature probes
43045 at startup, to improve @value{GDBN} performance---a single larger
43046 packet performs better than multiple smaller probe packets on
43047 high-latency links. Some features may enable behavior which must not
43048 be on by default, e.g.@: because it would confuse older clients or
43049 stubs. Other features may describe packets which could be
43050 automatically probed for, but are not. These features must be
43051 reported before @value{GDBN} will use them. This ``default
43052 unsupported'' behavior is not appropriate for all packets, but it
43053 helps to keep the initial connection time under control with new
43054 versions of @value{GDBN} which support increasing numbers of packets.
43058 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
43059 The stub supports or does not support each returned @var{stubfeature},
43060 depending on the form of each @var{stubfeature} (see below for the
43063 An empty reply indicates that @samp{qSupported} is not recognized,
43064 or that no features needed to be reported to @value{GDBN}.
43067 The allowed forms for each feature (either a @var{gdbfeature} in the
43068 @samp{qSupported} packet, or a @var{stubfeature} in the response)
43072 @item @var{name}=@var{value}
43073 The remote protocol feature @var{name} is supported, and associated
43074 with the specified @var{value}. The format of @var{value} depends
43075 on the feature, but it must not include a semicolon.
43077 The remote protocol feature @var{name} is supported, and does not
43078 need an associated value.
43080 The remote protocol feature @var{name} is not supported.
43082 The remote protocol feature @var{name} may be supported, and
43083 @value{GDBN} should auto-detect support in some other way when it is
43084 needed. This form will not be used for @var{gdbfeature} notifications,
43085 but may be used for @var{stubfeature} responses.
43088 Whenever the stub receives a @samp{qSupported} request, the
43089 supplied set of @value{GDBN} features should override any previous
43090 request. This allows @value{GDBN} to put the stub in a known
43091 state, even if the stub had previously been communicating with
43092 a different version of @value{GDBN}.
43094 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
43099 This feature indicates whether @value{GDBN} supports multiprocess
43100 extensions to the remote protocol. @value{GDBN} does not use such
43101 extensions unless the stub also reports that it supports them by
43102 including @samp{multiprocess+} in its @samp{qSupported} reply.
43103 @xref{multiprocess extensions}, for details.
43106 This feature indicates that @value{GDBN} supports the XML target
43107 description. If the stub sees @samp{xmlRegisters=} with target
43108 specific strings separated by a comma, it will report register
43112 This feature indicates whether @value{GDBN} supports the
43113 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
43114 instruction reply packet}).
43117 This feature indicates whether @value{GDBN} supports the swbreak stop
43118 reason in stop replies. @xref{swbreak stop reason}, for details.
43121 This feature indicates whether @value{GDBN} supports the hwbreak stop
43122 reason in stop replies. @xref{swbreak stop reason}, for details.
43125 This feature indicates whether @value{GDBN} supports fork event
43126 extensions to the remote protocol. @value{GDBN} does not use such
43127 extensions unless the stub also reports that it supports them by
43128 including @samp{fork-events+} in its @samp{qSupported} reply.
43131 This feature indicates whether @value{GDBN} supports vfork event
43132 extensions to the remote protocol. @value{GDBN} does not use such
43133 extensions unless the stub also reports that it supports them by
43134 including @samp{vfork-events+} in its @samp{qSupported} reply.
43137 This feature indicates whether @value{GDBN} supports exec event
43138 extensions to the remote protocol. @value{GDBN} does not use such
43139 extensions unless the stub also reports that it supports them by
43140 including @samp{exec-events+} in its @samp{qSupported} reply.
43142 @item vContSupported
43143 This feature indicates whether @value{GDBN} wants to know the
43144 supported actions in the reply to @samp{vCont?} packet.
43147 Stubs should ignore any unknown values for
43148 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
43149 packet supports receiving packets of unlimited length (earlier
43150 versions of @value{GDBN} may reject overly long responses). Additional values
43151 for @var{gdbfeature} may be defined in the future to let the stub take
43152 advantage of new features in @value{GDBN}, e.g.@: incompatible
43153 improvements in the remote protocol---the @samp{multiprocess} feature is
43154 an example of such a feature. The stub's reply should be independent
43155 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
43156 describes all the features it supports, and then the stub replies with
43157 all the features it supports.
43159 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
43160 responses, as long as each response uses one of the standard forms.
43162 Some features are flags. A stub which supports a flag feature
43163 should respond with a @samp{+} form response. Other features
43164 require values, and the stub should respond with an @samp{=}
43167 Each feature has a default value, which @value{GDBN} will use if
43168 @samp{qSupported} is not available or if the feature is not mentioned
43169 in the @samp{qSupported} response. The default values are fixed; a
43170 stub is free to omit any feature responses that match the defaults.
43172 Not all features can be probed, but for those which can, the probing
43173 mechanism is useful: in some cases, a stub's internal
43174 architecture may not allow the protocol layer to know some information
43175 about the underlying target in advance. This is especially common in
43176 stubs which may be configured for multiple targets.
43178 These are the currently defined stub features and their properties:
43180 @multitable @columnfractions 0.35 0.2 0.12 0.2
43181 @c NOTE: The first row should be @headitem, but we do not yet require
43182 @c a new enough version of Texinfo (4.7) to use @headitem.
43184 @tab Value Required
43188 @item @samp{PacketSize}
43193 @item @samp{qXfer:auxv:read}
43198 @item @samp{qXfer:btrace:read}
43203 @item @samp{qXfer:btrace-conf:read}
43208 @item @samp{qXfer:exec-file:read}
43213 @item @samp{qXfer:features:read}
43218 @item @samp{qXfer:libraries:read}
43223 @item @samp{qXfer:libraries-svr4:read}
43228 @item @samp{augmented-libraries-svr4-read}
43233 @item @samp{qXfer:memory-map:read}
43238 @item @samp{qXfer:sdata:read}
43243 @item @samp{qXfer:siginfo:read}
43248 @item @samp{qXfer:siginfo:write}
43253 @item @samp{qXfer:threads:read}
43258 @item @samp{qXfer:traceframe-info:read}
43263 @item @samp{qXfer:uib:read}
43268 @item @samp{qXfer:fdpic:read}
43273 @item @samp{Qbtrace:off}
43278 @item @samp{Qbtrace:bts}
43283 @item @samp{Qbtrace:pt}
43288 @item @samp{Qbtrace-conf:bts:size}
43293 @item @samp{Qbtrace-conf:pt:size}
43298 @item @samp{QNonStop}
43303 @item @samp{QCatchSyscalls}
43308 @item @samp{QPassSignals}
43313 @item @samp{QStartNoAckMode}
43318 @item @samp{multiprocess}
43323 @item @samp{ConditionalBreakpoints}
43328 @item @samp{ConditionalTracepoints}
43333 @item @samp{ReverseContinue}
43338 @item @samp{ReverseStep}
43343 @item @samp{TracepointSource}
43348 @item @samp{QAgent}
43353 @item @samp{QAllow}
43358 @item @samp{QDisableRandomization}
43363 @item @samp{EnableDisableTracepoints}
43368 @item @samp{QTBuffer:size}
43373 @item @samp{tracenz}
43378 @item @samp{BreakpointCommands}
43383 @item @samp{swbreak}
43388 @item @samp{hwbreak}
43393 @item @samp{fork-events}
43398 @item @samp{vfork-events}
43403 @item @samp{exec-events}
43408 @item @samp{QThreadEvents}
43413 @item @samp{no-resumed}
43418 @item @samp{memory-tagging}
43425 These are the currently defined stub features, in more detail:
43428 @cindex packet size, remote protocol
43429 @item PacketSize=@var{bytes}
43430 The remote stub can accept packets up to at least @var{bytes} in
43431 length. @value{GDBN} will send packets up to this size for bulk
43432 transfers, and will never send larger packets. This is a limit on the
43433 data characters in the packet, including the frame and checksum.
43434 There is no trailing NUL byte in a remote protocol packet; if the stub
43435 stores packets in a NUL-terminated format, it should allow an extra
43436 byte in its buffer for the NUL. If this stub feature is not supported,
43437 @value{GDBN} guesses based on the size of the @samp{g} packet response.
43439 @item qXfer:auxv:read
43440 The remote stub understands the @samp{qXfer:auxv:read} packet
43441 (@pxref{qXfer auxiliary vector read}).
43443 @item qXfer:btrace:read
43444 The remote stub understands the @samp{qXfer:btrace:read}
43445 packet (@pxref{qXfer btrace read}).
43447 @item qXfer:btrace-conf:read
43448 The remote stub understands the @samp{qXfer:btrace-conf:read}
43449 packet (@pxref{qXfer btrace-conf read}).
43451 @item qXfer:exec-file:read
43452 The remote stub understands the @samp{qXfer:exec-file:read} packet
43453 (@pxref{qXfer executable filename read}).
43455 @item qXfer:features:read
43456 The remote stub understands the @samp{qXfer:features:read} packet
43457 (@pxref{qXfer target description read}).
43459 @item qXfer:libraries:read
43460 The remote stub understands the @samp{qXfer:libraries:read} packet
43461 (@pxref{qXfer library list read}).
43463 @item qXfer:libraries-svr4:read
43464 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
43465 (@pxref{qXfer svr4 library list read}).
43467 @item augmented-libraries-svr4-read
43468 The remote stub understands the augmented form of the
43469 @samp{qXfer:libraries-svr4:read} packet
43470 (@pxref{qXfer svr4 library list read}).
43472 @item qXfer:memory-map:read
43473 The remote stub understands the @samp{qXfer:memory-map:read} packet
43474 (@pxref{qXfer memory map read}).
43476 @item qXfer:sdata:read
43477 The remote stub understands the @samp{qXfer:sdata:read} packet
43478 (@pxref{qXfer sdata read}).
43480 @item qXfer:siginfo:read
43481 The remote stub understands the @samp{qXfer:siginfo:read} packet
43482 (@pxref{qXfer siginfo read}).
43484 @item qXfer:siginfo:write
43485 The remote stub understands the @samp{qXfer:siginfo:write} packet
43486 (@pxref{qXfer siginfo write}).
43488 @item qXfer:threads:read
43489 The remote stub understands the @samp{qXfer:threads:read} packet
43490 (@pxref{qXfer threads read}).
43492 @item qXfer:traceframe-info:read
43493 The remote stub understands the @samp{qXfer:traceframe-info:read}
43494 packet (@pxref{qXfer traceframe info read}).
43496 @item qXfer:uib:read
43497 The remote stub understands the @samp{qXfer:uib:read}
43498 packet (@pxref{qXfer unwind info block}).
43500 @item qXfer:fdpic:read
43501 The remote stub understands the @samp{qXfer:fdpic:read}
43502 packet (@pxref{qXfer fdpic loadmap read}).
43505 The remote stub understands the @samp{QNonStop} packet
43506 (@pxref{QNonStop}).
43508 @item QCatchSyscalls
43509 The remote stub understands the @samp{QCatchSyscalls} packet
43510 (@pxref{QCatchSyscalls}).
43513 The remote stub understands the @samp{QPassSignals} packet
43514 (@pxref{QPassSignals}).
43516 @item QStartNoAckMode
43517 The remote stub understands the @samp{QStartNoAckMode} packet and
43518 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
43521 @anchor{multiprocess extensions}
43522 @cindex multiprocess extensions, in remote protocol
43523 The remote stub understands the multiprocess extensions to the remote
43524 protocol syntax. The multiprocess extensions affect the syntax of
43525 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
43526 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
43527 replies. Note that reporting this feature indicates support for the
43528 syntactic extensions only, not that the stub necessarily supports
43529 debugging of more than one process at a time. The stub must not use
43530 multiprocess extensions in packet replies unless @value{GDBN} has also
43531 indicated it supports them in its @samp{qSupported} request.
43533 @item qXfer:osdata:read
43534 The remote stub understands the @samp{qXfer:osdata:read} packet
43535 ((@pxref{qXfer osdata read}).
43537 @item ConditionalBreakpoints
43538 The target accepts and implements evaluation of conditional expressions
43539 defined for breakpoints. The target will only report breakpoint triggers
43540 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
43542 @item ConditionalTracepoints
43543 The remote stub accepts and implements conditional expressions defined
43544 for tracepoints (@pxref{Tracepoint Conditions}).
43546 @item ReverseContinue
43547 The remote stub accepts and implements the reverse continue packet
43551 The remote stub accepts and implements the reverse step packet
43554 @item TracepointSource
43555 The remote stub understands the @samp{QTDPsrc} packet that supplies
43556 the source form of tracepoint definitions.
43559 The remote stub understands the @samp{QAgent} packet.
43562 The remote stub understands the @samp{QAllow} packet.
43564 @item QDisableRandomization
43565 The remote stub understands the @samp{QDisableRandomization} packet.
43567 @item StaticTracepoint
43568 @cindex static tracepoints, in remote protocol
43569 The remote stub supports static tracepoints.
43571 @item InstallInTrace
43572 @anchor{install tracepoint in tracing}
43573 The remote stub supports installing tracepoint in tracing.
43575 @item EnableDisableTracepoints
43576 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
43577 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
43578 to be enabled and disabled while a trace experiment is running.
43580 @item QTBuffer:size
43581 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
43582 packet that allows to change the size of the trace buffer.
43585 @cindex string tracing, in remote protocol
43586 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
43587 See @ref{Bytecode Descriptions} for details about the bytecode.
43589 @item BreakpointCommands
43590 @cindex breakpoint commands, in remote protocol
43591 The remote stub supports running a breakpoint's command list itself,
43592 rather than reporting the hit to @value{GDBN}.
43595 The remote stub understands the @samp{Qbtrace:off} packet.
43598 The remote stub understands the @samp{Qbtrace:bts} packet.
43601 The remote stub understands the @samp{Qbtrace:pt} packet.
43603 @item Qbtrace-conf:bts:size
43604 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
43606 @item Qbtrace-conf:pt:size
43607 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
43610 The remote stub reports the @samp{swbreak} stop reason for memory
43614 The remote stub reports the @samp{hwbreak} stop reason for hardware
43618 The remote stub reports the @samp{fork} stop reason for fork events.
43621 The remote stub reports the @samp{vfork} stop reason for vfork events
43622 and vforkdone events.
43625 The remote stub reports the @samp{exec} stop reason for exec events.
43627 @item vContSupported
43628 The remote stub reports the supported actions in the reply to
43629 @samp{vCont?} packet.
43631 @item QThreadEvents
43632 The remote stub understands the @samp{QThreadEvents} packet.
43635 The remote stub reports the @samp{N} stop reply.
43638 @item memory-tagging
43639 The remote stub supports and implements the required memory tagging
43640 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
43641 @samp{QMemTags} (@pxref{QMemTags}) packets.
43643 For AArch64 GNU/Linux systems, this feature also requires access to the
43644 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
43645 This is done via the @samp{vFile} requests.
43650 @cindex symbol lookup, remote request
43651 @cindex @samp{qSymbol} packet
43652 Notify the target that @value{GDBN} is prepared to serve symbol lookup
43653 requests. Accept requests from the target for the values of symbols.
43658 The target does not need to look up any (more) symbols.
43659 @item qSymbol:@var{sym_name}
43660 The target requests the value of symbol @var{sym_name} (hex encoded).
43661 @value{GDBN} may provide the value by using the
43662 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
43666 @item qSymbol:@var{sym_value}:@var{sym_name}
43667 Set the value of @var{sym_name} to @var{sym_value}.
43669 @var{sym_name} (hex encoded) is the name of a symbol whose value the
43670 target has previously requested.
43672 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
43673 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
43679 The target does not need to look up any (more) symbols.
43680 @item qSymbol:@var{sym_name}
43681 The target requests the value of a new symbol @var{sym_name} (hex
43682 encoded). @value{GDBN} will continue to supply the values of symbols
43683 (if available), until the target ceases to request them.
43688 @itemx QTDisconnected
43695 @itemx qTMinFTPILen
43697 @xref{Tracepoint Packets}.
43699 @anchor{qThreadExtraInfo}
43700 @item qThreadExtraInfo,@var{thread-id}
43701 @cindex thread attributes info, remote request
43702 @cindex @samp{qThreadExtraInfo} packet
43703 Obtain from the target OS a printable string description of thread
43704 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
43705 for the forms of @var{thread-id}. This
43706 string may contain anything that the target OS thinks is interesting
43707 for @value{GDBN} to tell the user about the thread. The string is
43708 displayed in @value{GDBN}'s @code{info threads} display. Some
43709 examples of possible thread extra info strings are @samp{Runnable}, or
43710 @samp{Blocked on Mutex}.
43714 @item @var{XX}@dots{}
43715 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
43716 comprising the printable string containing the extra information about
43717 the thread's attributes.
43720 (Note that the @code{qThreadExtraInfo} packet's name is separated from
43721 the command by a @samp{,}, not a @samp{:}, contrary to the naming
43722 conventions above. Please don't use this packet as a model for new
43741 @xref{Tracepoint Packets}.
43743 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
43744 @cindex read special object, remote request
43745 @cindex @samp{qXfer} packet
43746 @anchor{qXfer read}
43747 Read uninterpreted bytes from the target's special data area
43748 identified by the keyword @var{object}. Request @var{length} bytes
43749 starting at @var{offset} bytes into the data. The content and
43750 encoding of @var{annex} is specific to @var{object}; it can supply
43751 additional details about what data to access.
43756 Data @var{data} (@pxref{Binary Data}) has been read from the
43757 target. There may be more data at a higher address (although
43758 it is permitted to return @samp{m} even for the last valid
43759 block of data, as long as at least one byte of data was read).
43760 It is possible for @var{data} to have fewer bytes than the @var{length} in the
43764 Data @var{data} (@pxref{Binary Data}) has been read from the target.
43765 There is no more data to be read. It is possible for @var{data} to
43766 have fewer bytes than the @var{length} in the request.
43769 The @var{offset} in the request is at the end of the data.
43770 There is no more data to be read.
43773 The request was malformed, or @var{annex} was invalid.
43776 The offset was invalid, or there was an error encountered reading the data.
43777 The @var{nn} part is a hex-encoded @code{errno} value.
43780 An empty reply indicates the @var{object} string was not recognized by
43781 the stub, or that the object does not support reading.
43784 Here are the specific requests of this form defined so far. All the
43785 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
43786 formats, listed above.
43789 @item qXfer:auxv:read::@var{offset},@var{length}
43790 @anchor{qXfer auxiliary vector read}
43791 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
43792 auxiliary vector}. Note @var{annex} must be empty.
43794 This packet is not probed by default; the remote stub must request it,
43795 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43797 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
43798 @anchor{qXfer btrace read}
43800 Return a description of the current branch trace.
43801 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
43802 packet may have one of the following values:
43806 Returns all available branch trace.
43809 Returns all available branch trace if the branch trace changed since
43810 the last read request.
43813 Returns the new branch trace since the last read request. Adds a new
43814 block to the end of the trace that begins at zero and ends at the source
43815 location of the first branch in the trace buffer. This extra block is
43816 used to stitch traces together.
43818 If the trace buffer overflowed, returns an error indicating the overflow.
43821 This packet is not probed by default; the remote stub must request it
43822 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43824 @item qXfer:btrace-conf:read::@var{offset},@var{length}
43825 @anchor{qXfer btrace-conf read}
43827 Return a description of the current branch trace configuration.
43828 @xref{Branch Trace Configuration Format}.
43830 This packet is not probed by default; the remote stub must request it
43831 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43833 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
43834 @anchor{qXfer executable filename read}
43835 Return the full absolute name of the file that was executed to create
43836 a process running on the remote system. The annex specifies the
43837 numeric process ID of the process to query, encoded as a hexadecimal
43838 number. If the annex part is empty the remote stub should return the
43839 filename corresponding to the currently executing process.
43841 This packet is not probed by default; the remote stub must request it,
43842 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43844 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
43845 @anchor{qXfer target description read}
43846 Access the @dfn{target description}. @xref{Target Descriptions}. The
43847 annex specifies which XML document to access. The main description is
43848 always loaded from the @samp{target.xml} annex.
43850 This packet is not probed by default; the remote stub must request it,
43851 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43853 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
43854 @anchor{qXfer library list read}
43855 Access the target's list of loaded libraries. @xref{Library List Format}.
43856 The annex part of the generic @samp{qXfer} packet must be empty
43857 (@pxref{qXfer read}).
43859 Targets which maintain a list of libraries in the program's memory do
43860 not need to implement this packet; it is designed for platforms where
43861 the operating system manages the list of loaded libraries.
43863 This packet is not probed by default; the remote stub must request it,
43864 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43866 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
43867 @anchor{qXfer svr4 library list read}
43868 Access the target's list of loaded libraries when the target is an SVR4
43869 platform. @xref{Library List Format for SVR4 Targets}. The annex part
43870 of the generic @samp{qXfer} packet must be empty unless the remote
43871 stub indicated it supports the augmented form of this packet
43872 by supplying an appropriate @samp{qSupported} response
43873 (@pxref{qXfer read}, @ref{qSupported}).
43875 This packet is optional for better performance on SVR4 targets.
43876 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
43878 This packet is not probed by default; the remote stub must request it,
43879 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43881 If the remote stub indicates it supports the augmented form of this
43882 packet then the annex part of the generic @samp{qXfer} packet may
43883 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
43884 arguments. The currently supported arguments are:
43887 @item start=@var{address}
43888 A hexadecimal number specifying the address of the @samp{struct
43889 link_map} to start reading the library list from. If unset or zero
43890 then the first @samp{struct link_map} in the library list will be
43891 chosen as the starting point.
43893 @item prev=@var{address}
43894 A hexadecimal number specifying the address of the @samp{struct
43895 link_map} immediately preceding the @samp{struct link_map}
43896 specified by the @samp{start} argument. If unset or zero then
43897 the remote stub will expect that no @samp{struct link_map}
43898 exists prior to the starting point.
43900 @item lmid=@var{lmid}
43901 A hexadecimal number specifying a namespace identifier. This is
43902 currently only used together with @samp{start} to provide the
43903 namespace identifier back to @value{GDBN} in the response.
43904 @value{GDBN} will only provide values that were previously reported to
43905 it. If unset, the response will include @samp{lmid="0x0"}.
43908 Arguments that are not understood by the remote stub will be silently
43911 @item qXfer:memory-map:read::@var{offset},@var{length}
43912 @anchor{qXfer memory map read}
43913 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
43914 annex part of the generic @samp{qXfer} packet must be empty
43915 (@pxref{qXfer read}).
43917 This packet is not probed by default; the remote stub must request it,
43918 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43920 @item qXfer:sdata:read::@var{offset},@var{length}
43921 @anchor{qXfer sdata read}
43923 Read contents of the extra collected static tracepoint marker
43924 information. The annex part of the generic @samp{qXfer} packet must
43925 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
43928 This packet is not probed by default; the remote stub must request it,
43929 by supplying an appropriate @samp{qSupported} response
43930 (@pxref{qSupported}).
43932 @item qXfer:siginfo:read::@var{offset},@var{length}
43933 @anchor{qXfer siginfo read}
43934 Read contents of the extra signal information on the target
43935 system. The annex part of the generic @samp{qXfer} packet must be
43936 empty (@pxref{qXfer read}).
43938 This packet is not probed by default; the remote stub must request it,
43939 by supplying an appropriate @samp{qSupported} response
43940 (@pxref{qSupported}).
43942 @item qXfer:threads:read::@var{offset},@var{length}
43943 @anchor{qXfer threads read}
43944 Access the list of threads on target. @xref{Thread List Format}. The
43945 annex part of the generic @samp{qXfer} packet must be empty
43946 (@pxref{qXfer read}).
43948 This packet is not probed by default; the remote stub must request it,
43949 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43951 @item qXfer:traceframe-info:read::@var{offset},@var{length}
43952 @anchor{qXfer traceframe info read}
43954 Return a description of the current traceframe's contents.
43955 @xref{Traceframe Info Format}. The annex part of the generic
43956 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
43958 This packet is not probed by default; the remote stub must request it,
43959 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43961 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
43962 @anchor{qXfer unwind info block}
43964 Return the unwind information block for @var{pc}. This packet is used
43965 on OpenVMS/ia64 to ask the kernel unwind information.
43967 This packet is not probed by default.
43969 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
43970 @anchor{qXfer fdpic loadmap read}
43971 Read contents of @code{loadmap}s on the target system. The
43972 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
43973 executable @code{loadmap} or interpreter @code{loadmap} to read.
43975 This packet is not probed by default; the remote stub must request it,
43976 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43978 @item qXfer:osdata:read::@var{offset},@var{length}
43979 @anchor{qXfer osdata read}
43980 Access the target's @dfn{operating system information}.
43981 @xref{Operating System Information}.
43985 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
43986 @cindex write data into object, remote request
43987 @anchor{qXfer write}
43988 Write uninterpreted bytes into the target's special data area
43989 identified by the keyword @var{object}, starting at @var{offset} bytes
43990 into the data. The binary-encoded data (@pxref{Binary Data}) to be
43991 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
43992 is specific to @var{object}; it can supply additional details about what data
43998 @var{nn} (hex encoded) is the number of bytes written.
43999 This may be fewer bytes than supplied in the request.
44002 The request was malformed, or @var{annex} was invalid.
44005 The offset was invalid, or there was an error encountered writing the data.
44006 The @var{nn} part is a hex-encoded @code{errno} value.
44009 An empty reply indicates the @var{object} string was not
44010 recognized by the stub, or that the object does not support writing.
44013 Here are the specific requests of this form defined so far. All the
44014 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
44015 formats, listed above.
44018 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
44019 @anchor{qXfer siginfo write}
44020 Write @var{data} to the extra signal information on the target system.
44021 The annex part of the generic @samp{qXfer} packet must be
44022 empty (@pxref{qXfer write}).
44024 This packet is not probed by default; the remote stub must request it,
44025 by supplying an appropriate @samp{qSupported} response
44026 (@pxref{qSupported}).
44029 @item qXfer:@var{object}:@var{operation}:@dots{}
44030 Requests of this form may be added in the future. When a stub does
44031 not recognize the @var{object} keyword, or its support for
44032 @var{object} does not recognize the @var{operation} keyword, the stub
44033 must respond with an empty packet.
44035 @item qAttached:@var{pid}
44036 @cindex query attached, remote request
44037 @cindex @samp{qAttached} packet
44038 Return an indication of whether the remote server attached to an
44039 existing process or created a new process. When the multiprocess
44040 protocol extensions are supported (@pxref{multiprocess extensions}),
44041 @var{pid} is an integer in hexadecimal format identifying the target
44042 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
44043 the query packet will be simplified as @samp{qAttached}.
44045 This query is used, for example, to know whether the remote process
44046 should be detached or killed when a @value{GDBN} session is ended with
44047 the @code{quit} command.
44052 The remote server attached to an existing process.
44054 The remote server created a new process.
44056 A badly formed request or an error was encountered.
44060 Enable branch tracing for the current thread using Branch Trace Store.
44065 Branch tracing has been enabled.
44067 A badly formed request or an error was encountered.
44071 Enable branch tracing for the current thread using Intel Processor Trace.
44076 Branch tracing has been enabled.
44078 A badly formed request or an error was encountered.
44082 Disable branch tracing for the current thread.
44087 Branch tracing has been disabled.
44089 A badly formed request or an error was encountered.
44092 @item Qbtrace-conf:bts:size=@var{value}
44093 Set the requested ring buffer size for new threads that use the
44094 btrace recording method in bts format.
44099 The ring buffer size has been set.
44101 A badly formed request or an error was encountered.
44104 @item Qbtrace-conf:pt:size=@var{value}
44105 Set the requested ring buffer size for new threads that use the
44106 btrace recording method in pt format.
44111 The ring buffer size has been set.
44113 A badly formed request or an error was encountered.
44118 @node Architecture-Specific Protocol Details
44119 @section Architecture-Specific Protocol Details
44121 This section describes how the remote protocol is applied to specific
44122 target architectures. Also see @ref{Standard Target Features}, for
44123 details of XML target descriptions for each architecture.
44126 * ARM-Specific Protocol Details::
44127 * MIPS-Specific Protocol Details::
44130 @node ARM-Specific Protocol Details
44131 @subsection @acronym{ARM}-specific Protocol Details
44134 * ARM Breakpoint Kinds::
44135 * ARM Memory Tag Types::
44138 @node ARM Breakpoint Kinds
44139 @subsubsection @acronym{ARM} Breakpoint Kinds
44140 @cindex breakpoint kinds, @acronym{ARM}
44142 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
44147 16-bit Thumb mode breakpoint.
44150 32-bit Thumb mode (Thumb-2) breakpoint.
44153 32-bit @acronym{ARM} mode breakpoint.
44157 @node ARM Memory Tag Types
44158 @subsubsection @acronym{ARM} Memory Tag Types
44159 @cindex memory tag types, @acronym{ARM}
44161 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
44174 @node MIPS-Specific Protocol Details
44175 @subsection @acronym{MIPS}-specific Protocol Details
44178 * MIPS Register packet Format::
44179 * MIPS Breakpoint Kinds::
44182 @node MIPS Register packet Format
44183 @subsubsection @acronym{MIPS} Register Packet Format
44184 @cindex register packet format, @acronym{MIPS}
44186 The following @code{g}/@code{G} packets have previously been defined.
44187 In the below, some thirty-two bit registers are transferred as
44188 sixty-four bits. Those registers should be zero/sign extended (which?)
44189 to fill the space allocated. Register bytes are transferred in target
44190 byte order. The two nibbles within a register byte are transferred
44191 most-significant -- least-significant.
44196 All registers are transferred as thirty-two bit quantities in the order:
44197 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
44198 registers; fsr; fir; fp.
44201 All registers are transferred as sixty-four bit quantities (including
44202 thirty-two bit registers such as @code{sr}). The ordering is the same
44207 @node MIPS Breakpoint Kinds
44208 @subsubsection @acronym{MIPS} Breakpoint Kinds
44209 @cindex breakpoint kinds, @acronym{MIPS}
44211 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
44216 16-bit @acronym{MIPS16} mode breakpoint.
44219 16-bit @acronym{microMIPS} mode breakpoint.
44222 32-bit standard @acronym{MIPS} mode breakpoint.
44225 32-bit @acronym{microMIPS} mode breakpoint.
44229 @node Tracepoint Packets
44230 @section Tracepoint Packets
44231 @cindex tracepoint packets
44232 @cindex packets, tracepoint
44234 Here we describe the packets @value{GDBN} uses to implement
44235 tracepoints (@pxref{Tracepoints}).
44239 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
44240 @cindex @samp{QTDP} packet
44241 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
44242 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
44243 the tracepoint is disabled. The @var{step} gives the tracepoint's step
44244 count, and @var{pass} gives its pass count. If an @samp{F} is present,
44245 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
44246 the number of bytes that the target should copy elsewhere to make room
44247 for the tracepoint. If an @samp{X} is present, it introduces a
44248 tracepoint condition, which consists of a hexadecimal length, followed
44249 by a comma and hex-encoded bytes, in a manner similar to action
44250 encodings as described below. If the trailing @samp{-} is present,
44251 further @samp{QTDP} packets will follow to specify this tracepoint's
44257 The packet was understood and carried out.
44259 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
44261 The packet was not recognized.
44264 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
44265 Define actions to be taken when a tracepoint is hit. The @var{n} and
44266 @var{addr} must be the same as in the initial @samp{QTDP} packet for
44267 this tracepoint. This packet may only be sent immediately after
44268 another @samp{QTDP} packet that ended with a @samp{-}. If the
44269 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
44270 specifying more actions for this tracepoint.
44272 In the series of action packets for a given tracepoint, at most one
44273 can have an @samp{S} before its first @var{action}. If such a packet
44274 is sent, it and the following packets define ``while-stepping''
44275 actions. Any prior packets define ordinary actions --- that is, those
44276 taken when the tracepoint is first hit. If no action packet has an
44277 @samp{S}, then all the packets in the series specify ordinary
44278 tracepoint actions.
44280 The @samp{@var{action}@dots{}} portion of the packet is a series of
44281 actions, concatenated without separators. Each action has one of the
44287 Collect the registers whose bits are set in @var{mask},
44288 a hexadecimal number whose @var{i}'th bit is set if register number
44289 @var{i} should be collected. (The least significant bit is numbered
44290 zero.) Note that @var{mask} may be any number of digits long; it may
44291 not fit in a 32-bit word.
44293 @item M @var{basereg},@var{offset},@var{len}
44294 Collect @var{len} bytes of memory starting at the address in register
44295 number @var{basereg}, plus @var{offset}. If @var{basereg} is
44296 @samp{-1}, then the range has a fixed address: @var{offset} is the
44297 address of the lowest byte to collect. The @var{basereg},
44298 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
44299 values (the @samp{-1} value for @var{basereg} is a special case).
44301 @item X @var{len},@var{expr}
44302 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
44303 it directs. The agent expression @var{expr} is as described in
44304 @ref{Agent Expressions}. Each byte of the expression is encoded as a
44305 two-digit hex number in the packet; @var{len} is the number of bytes
44306 in the expression (and thus one-half the number of hex digits in the
44311 Any number of actions may be packed together in a single @samp{QTDP}
44312 packet, as long as the packet does not exceed the maximum packet
44313 length (400 bytes, for many stubs). There may be only one @samp{R}
44314 action per tracepoint, and it must precede any @samp{M} or @samp{X}
44315 actions. Any registers referred to by @samp{M} and @samp{X} actions
44316 must be collected by a preceding @samp{R} action. (The
44317 ``while-stepping'' actions are treated as if they were attached to a
44318 separate tracepoint, as far as these restrictions are concerned.)
44323 The packet was understood and carried out.
44325 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
44327 The packet was not recognized.
44330 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
44331 @cindex @samp{QTDPsrc} packet
44332 Specify a source string of tracepoint @var{n} at address @var{addr}.
44333 This is useful to get accurate reproduction of the tracepoints
44334 originally downloaded at the beginning of the trace run. The @var{type}
44335 is the name of the tracepoint part, such as @samp{cond} for the
44336 tracepoint's conditional expression (see below for a list of types), while
44337 @var{bytes} is the string, encoded in hexadecimal.
44339 @var{start} is the offset of the @var{bytes} within the overall source
44340 string, while @var{slen} is the total length of the source string.
44341 This is intended for handling source strings that are longer than will
44342 fit in a single packet.
44343 @c Add detailed example when this info is moved into a dedicated
44344 @c tracepoint descriptions section.
44346 The available string types are @samp{at} for the location,
44347 @samp{cond} for the conditional, and @samp{cmd} for an action command.
44348 @value{GDBN} sends a separate packet for each command in the action
44349 list, in the same order in which the commands are stored in the list.
44351 The target does not need to do anything with source strings except
44352 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
44355 Although this packet is optional, and @value{GDBN} will only send it
44356 if the target replies with @samp{TracepointSource} @xref{General
44357 Query Packets}, it makes both disconnected tracing and trace files
44358 much easier to use. Otherwise the user must be careful that the
44359 tracepoints in effect while looking at trace frames are identical to
44360 the ones in effect during the trace run; even a small discrepancy
44361 could cause @samp{tdump} not to work, or a particular trace frame not
44364 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
44365 @cindex define trace state variable, remote request
44366 @cindex @samp{QTDV} packet
44367 Create a new trace state variable, number @var{n}, with an initial
44368 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
44369 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
44370 the option of not using this packet for initial values of zero; the
44371 target should simply create the trace state variables as they are
44372 mentioned in expressions. The value @var{builtin} should be 1 (one)
44373 if the trace state variable is builtin and 0 (zero) if it is not builtin.
44374 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
44375 @samp{qTsV} packet had it set. The contents of @var{name} is the
44376 hex-encoded name (without the leading @samp{$}) of the trace state
44379 @item QTFrame:@var{n}
44380 @cindex @samp{QTFrame} packet
44381 Select the @var{n}'th tracepoint frame from the buffer, and use the
44382 register and memory contents recorded there to answer subsequent
44383 request packets from @value{GDBN}.
44385 A successful reply from the stub indicates that the stub has found the
44386 requested frame. The response is a series of parts, concatenated
44387 without separators, describing the frame we selected. Each part has
44388 one of the following forms:
44392 The selected frame is number @var{n} in the trace frame buffer;
44393 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
44394 was no frame matching the criteria in the request packet.
44397 The selected trace frame records a hit of tracepoint number @var{t};
44398 @var{t} is a hexadecimal number.
44402 @item QTFrame:pc:@var{addr}
44403 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44404 currently selected frame whose PC is @var{addr};
44405 @var{addr} is a hexadecimal number.
44407 @item QTFrame:tdp:@var{t}
44408 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44409 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
44410 is a hexadecimal number.
44412 @item QTFrame:range:@var{start}:@var{end}
44413 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
44414 currently selected frame whose PC is between @var{start} (inclusive)
44415 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
44418 @item QTFrame:outside:@var{start}:@var{end}
44419 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
44420 frame @emph{outside} the given range of addresses (exclusive).
44423 @cindex @samp{qTMinFTPILen} packet
44424 This packet requests the minimum length of instruction at which a fast
44425 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
44426 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
44427 it depends on the target system being able to create trampolines in
44428 the first 64K of memory, which might or might not be possible for that
44429 system. So the reply to this packet will be 4 if it is able to
44436 The minimum instruction length is currently unknown.
44438 The minimum instruction length is @var{length}, where @var{length}
44439 is a hexadecimal number greater or equal to 1. A reply
44440 of 1 means that a fast tracepoint may be placed on any instruction
44441 regardless of size.
44443 An error has occurred.
44445 An empty reply indicates that the request is not supported by the stub.
44449 @cindex @samp{QTStart} packet
44450 Begin the tracepoint experiment. Begin collecting data from
44451 tracepoint hits in the trace frame buffer. This packet supports the
44452 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
44453 instruction reply packet}).
44456 @cindex @samp{QTStop} packet
44457 End the tracepoint experiment. Stop collecting trace frames.
44459 @item QTEnable:@var{n}:@var{addr}
44461 @cindex @samp{QTEnable} packet
44462 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
44463 experiment. If the tracepoint was previously disabled, then collection
44464 of data from it will resume.
44466 @item QTDisable:@var{n}:@var{addr}
44468 @cindex @samp{QTDisable} packet
44469 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
44470 experiment. No more data will be collected from the tracepoint unless
44471 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
44474 @cindex @samp{QTinit} packet
44475 Clear the table of tracepoints, and empty the trace frame buffer.
44477 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
44478 @cindex @samp{QTro} packet
44479 Establish the given ranges of memory as ``transparent''. The stub
44480 will answer requests for these ranges from memory's current contents,
44481 if they were not collected as part of the tracepoint hit.
44483 @value{GDBN} uses this to mark read-only regions of memory, like those
44484 containing program code. Since these areas never change, they should
44485 still have the same contents they did when the tracepoint was hit, so
44486 there's no reason for the stub to refuse to provide their contents.
44488 @item QTDisconnected:@var{value}
44489 @cindex @samp{QTDisconnected} packet
44490 Set the choice to what to do with the tracing run when @value{GDBN}
44491 disconnects from the target. A @var{value} of 1 directs the target to
44492 continue the tracing run, while 0 tells the target to stop tracing if
44493 @value{GDBN} is no longer in the picture.
44496 @cindex @samp{qTStatus} packet
44497 Ask the stub if there is a trace experiment running right now.
44499 The reply has the form:
44503 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
44504 @var{running} is a single digit @code{1} if the trace is presently
44505 running, or @code{0} if not. It is followed by semicolon-separated
44506 optional fields that an agent may use to report additional status.
44510 If the trace is not running, the agent may report any of several
44511 explanations as one of the optional fields:
44516 No trace has been run yet.
44518 @item tstop[:@var{text}]:0
44519 The trace was stopped by a user-originated stop command. The optional
44520 @var{text} field is a user-supplied string supplied as part of the
44521 stop command (for instance, an explanation of why the trace was
44522 stopped manually). It is hex-encoded.
44525 The trace stopped because the trace buffer filled up.
44527 @item tdisconnected:0
44528 The trace stopped because @value{GDBN} disconnected from the target.
44530 @item tpasscount:@var{tpnum}
44531 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
44533 @item terror:@var{text}:@var{tpnum}
44534 The trace stopped because tracepoint @var{tpnum} had an error. The
44535 string @var{text} is available to describe the nature of the error
44536 (for instance, a divide by zero in the condition expression); it
44540 The trace stopped for some other reason.
44544 Additional optional fields supply statistical and other information.
44545 Although not required, they are extremely useful for users monitoring
44546 the progress of a trace run. If a trace has stopped, and these
44547 numbers are reported, they must reflect the state of the just-stopped
44552 @item tframes:@var{n}
44553 The number of trace frames in the buffer.
44555 @item tcreated:@var{n}
44556 The total number of trace frames created during the run. This may
44557 be larger than the trace frame count, if the buffer is circular.
44559 @item tsize:@var{n}
44560 The total size of the trace buffer, in bytes.
44562 @item tfree:@var{n}
44563 The number of bytes still unused in the buffer.
44565 @item circular:@var{n}
44566 The value of the circular trace buffer flag. @code{1} means that the
44567 trace buffer is circular and old trace frames will be discarded if
44568 necessary to make room, @code{0} means that the trace buffer is linear
44571 @item disconn:@var{n}
44572 The value of the disconnected tracing flag. @code{1} means that
44573 tracing will continue after @value{GDBN} disconnects, @code{0} means
44574 that the trace run will stop.
44578 @item qTP:@var{tp}:@var{addr}
44579 @cindex tracepoint status, remote request
44580 @cindex @samp{qTP} packet
44581 Ask the stub for the current state of tracepoint number @var{tp} at
44582 address @var{addr}.
44586 @item V@var{hits}:@var{usage}
44587 The tracepoint has been hit @var{hits} times so far during the trace
44588 run, and accounts for @var{usage} in the trace buffer. Note that
44589 @code{while-stepping} steps are not counted as separate hits, but the
44590 steps' space consumption is added into the usage number.
44594 @item qTV:@var{var}
44595 @cindex trace state variable value, remote request
44596 @cindex @samp{qTV} packet
44597 Ask the stub for the value of the trace state variable number @var{var}.
44602 The value of the variable is @var{value}. This will be the current
44603 value of the variable if the user is examining a running target, or a
44604 saved value if the variable was collected in the trace frame that the
44605 user is looking at. Note that multiple requests may result in
44606 different reply values, such as when requesting values while the
44607 program is running.
44610 The value of the variable is unknown. This would occur, for example,
44611 if the user is examining a trace frame in which the requested variable
44616 @cindex @samp{qTfP} packet
44618 @cindex @samp{qTsP} packet
44619 These packets request data about tracepoints that are being used by
44620 the target. @value{GDBN} sends @code{qTfP} to get the first piece
44621 of data, and multiple @code{qTsP} to get additional pieces. Replies
44622 to these packets generally take the form of the @code{QTDP} packets
44623 that define tracepoints. (FIXME add detailed syntax)
44626 @cindex @samp{qTfV} packet
44628 @cindex @samp{qTsV} packet
44629 These packets request data about trace state variables that are on the
44630 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
44631 and multiple @code{qTsV} to get additional variables. Replies to
44632 these packets follow the syntax of the @code{QTDV} packets that define
44633 trace state variables.
44639 @cindex @samp{qTfSTM} packet
44640 @cindex @samp{qTsSTM} packet
44641 These packets request data about static tracepoint markers that exist
44642 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
44643 first piece of data, and multiple @code{qTsSTM} to get additional
44644 pieces. Replies to these packets take the following form:
44648 @item m @var{address}:@var{id}:@var{extra}
44650 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
44651 a comma-separated list of markers
44653 (lower case letter @samp{L}) denotes end of list.
44655 An error occurred. The error number @var{nn} is given as hex digits.
44657 An empty reply indicates that the request is not supported by the
44661 The @var{address} is encoded in hex;
44662 @var{id} and @var{extra} are strings encoded in hex.
44664 In response to each query, the target will reply with a list of one or
44665 more markers, separated by commas. @value{GDBN} will respond to each
44666 reply with a request for more markers (using the @samp{qs} form of the
44667 query), until the target responds with @samp{l} (lower-case ell, for
44670 @item qTSTMat:@var{address}
44672 @cindex @samp{qTSTMat} packet
44673 This packets requests data about static tracepoint markers in the
44674 target program at @var{address}. Replies to this packet follow the
44675 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
44676 tracepoint markers.
44678 @item QTSave:@var{filename}
44679 @cindex @samp{QTSave} packet
44680 This packet directs the target to save trace data to the file name
44681 @var{filename} in the target's filesystem. The @var{filename} is encoded
44682 as a hex string; the interpretation of the file name (relative vs
44683 absolute, wild cards, etc) is up to the target.
44685 @item qTBuffer:@var{offset},@var{len}
44686 @cindex @samp{qTBuffer} packet
44687 Return up to @var{len} bytes of the current contents of trace buffer,
44688 starting at @var{offset}. The trace buffer is treated as if it were
44689 a contiguous collection of traceframes, as per the trace file format.
44690 The reply consists as many hex-encoded bytes as the target can deliver
44691 in a packet; it is not an error to return fewer than were asked for.
44692 A reply consisting of just @code{l} indicates that no bytes are
44695 @item QTBuffer:circular:@var{value}
44696 This packet directs the target to use a circular trace buffer if
44697 @var{value} is 1, or a linear buffer if the value is 0.
44699 @item QTBuffer:size:@var{size}
44700 @anchor{QTBuffer-size}
44701 @cindex @samp{QTBuffer size} packet
44702 This packet directs the target to make the trace buffer be of size
44703 @var{size} if possible. A value of @code{-1} tells the target to
44704 use whatever size it prefers.
44706 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
44707 @cindex @samp{QTNotes} packet
44708 This packet adds optional textual notes to the trace run. Allowable
44709 types include @code{user}, @code{notes}, and @code{tstop}, the
44710 @var{text} fields are arbitrary strings, hex-encoded.
44714 @subsection Relocate instruction reply packet
44715 When installing fast tracepoints in memory, the target may need to
44716 relocate the instruction currently at the tracepoint address to a
44717 different address in memory. For most instructions, a simple copy is
44718 enough, but, for example, call instructions that implicitly push the
44719 return address on the stack, and relative branches or other
44720 PC-relative instructions require offset adjustment, so that the effect
44721 of executing the instruction at a different address is the same as if
44722 it had executed in the original location.
44724 In response to several of the tracepoint packets, the target may also
44725 respond with a number of intermediate @samp{qRelocInsn} request
44726 packets before the final result packet, to have @value{GDBN} handle
44727 this relocation operation. If a packet supports this mechanism, its
44728 documentation will explicitly say so. See for example the above
44729 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
44730 format of the request is:
44733 @item qRelocInsn:@var{from};@var{to}
44735 This requests @value{GDBN} to copy instruction at address @var{from}
44736 to address @var{to}, possibly adjusted so that executing the
44737 instruction at @var{to} has the same effect as executing it at
44738 @var{from}. @value{GDBN} writes the adjusted instruction to target
44739 memory starting at @var{to}.
44744 @item qRelocInsn:@var{adjusted_size}
44745 Informs the stub the relocation is complete. The @var{adjusted_size} is
44746 the length in bytes of resulting relocated instruction sequence.
44748 A badly formed request was detected, or an error was encountered while
44749 relocating the instruction.
44752 @node Host I/O Packets
44753 @section Host I/O Packets
44754 @cindex Host I/O, remote protocol
44755 @cindex file transfer, remote protocol
44757 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
44758 operations on the far side of a remote link. For example, Host I/O is
44759 used to upload and download files to a remote target with its own
44760 filesystem. Host I/O uses the same constant values and data structure
44761 layout as the target-initiated File-I/O protocol. However, the
44762 Host I/O packets are structured differently. The target-initiated
44763 protocol relies on target memory to store parameters and buffers.
44764 Host I/O requests are initiated by @value{GDBN}, and the
44765 target's memory is not involved. @xref{File-I/O Remote Protocol
44766 Extension}, for more details on the target-initiated protocol.
44768 The Host I/O request packets all encode a single operation along with
44769 its arguments. They have this format:
44773 @item vFile:@var{operation}: @var{parameter}@dots{}
44774 @var{operation} is the name of the particular request; the target
44775 should compare the entire packet name up to the second colon when checking
44776 for a supported operation. The format of @var{parameter} depends on
44777 the operation. Numbers are always passed in hexadecimal. Negative
44778 numbers have an explicit minus sign (i.e.@: two's complement is not
44779 used). Strings (e.g.@: filenames) are encoded as a series of
44780 hexadecimal bytes. The last argument to a system call may be a
44781 buffer of escaped binary data (@pxref{Binary Data}).
44785 The valid responses to Host I/O packets are:
44789 @item F @var{result} [, @var{errno}] [; @var{attachment}]
44790 @var{result} is the integer value returned by this operation, usually
44791 non-negative for success and -1 for errors. If an error has occured,
44792 @var{errno} will be included in the result specifying a
44793 value defined by the File-I/O protocol (@pxref{Errno Values}). For
44794 operations which return data, @var{attachment} supplies the data as a
44795 binary buffer. Binary buffers in response packets are escaped in the
44796 normal way (@pxref{Binary Data}). See the individual packet
44797 documentation for the interpretation of @var{result} and
44801 An empty response indicates that this operation is not recognized.
44805 These are the supported Host I/O operations:
44808 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
44809 Open a file at @var{filename} and return a file descriptor for it, or
44810 return -1 if an error occurs. The @var{filename} is a string,
44811 @var{flags} is an integer indicating a mask of open flags
44812 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
44813 of mode bits to use if the file is created (@pxref{mode_t Values}).
44814 @xref{open}, for details of the open flags and mode values.
44816 @item vFile:close: @var{fd}
44817 Close the open file corresponding to @var{fd} and return 0, or
44818 -1 if an error occurs.
44820 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
44821 Read data from the open file corresponding to @var{fd}. Up to
44822 @var{count} bytes will be read from the file, starting at @var{offset}
44823 relative to the start of the file. The target may read fewer bytes;
44824 common reasons include packet size limits and an end-of-file
44825 condition. The number of bytes read is returned. Zero should only be
44826 returned for a successful read at the end of the file, or if
44827 @var{count} was zero.
44829 The data read should be returned as a binary attachment on success.
44830 If zero bytes were read, the response should include an empty binary
44831 attachment (i.e.@: a trailing semicolon). The return value is the
44832 number of target bytes read; the binary attachment may be longer if
44833 some characters were escaped.
44835 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
44836 Write @var{data} (a binary buffer) to the open file corresponding
44837 to @var{fd}. Start the write at @var{offset} from the start of the
44838 file. Unlike many @code{write} system calls, there is no
44839 separate @var{count} argument; the length of @var{data} in the
44840 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
44841 which may be shorter than the length of @var{data}, or -1 if an
44844 @item vFile:fstat: @var{fd}
44845 Get information about the open file corresponding to @var{fd}.
44846 On success the information is returned as a binary attachment
44847 and the return value is the size of this attachment in bytes.
44848 If an error occurs the return value is -1. The format of the
44849 returned binary attachment is as described in @ref{struct stat}.
44851 @item vFile:unlink: @var{filename}
44852 Delete the file at @var{filename} on the target. Return 0,
44853 or -1 if an error occurs. The @var{filename} is a string.
44855 @item vFile:readlink: @var{filename}
44856 Read value of symbolic link @var{filename} on the target. Return
44857 the number of bytes read, or -1 if an error occurs.
44859 The data read should be returned as a binary attachment on success.
44860 If zero bytes were read, the response should include an empty binary
44861 attachment (i.e.@: a trailing semicolon). The return value is the
44862 number of target bytes read; the binary attachment may be longer if
44863 some characters were escaped.
44865 @item vFile:setfs: @var{pid}
44866 Select the filesystem on which @code{vFile} operations with
44867 @var{filename} arguments will operate. This is required for
44868 @value{GDBN} to be able to access files on remote targets where
44869 the remote stub does not share a common filesystem with the
44872 If @var{pid} is nonzero, select the filesystem as seen by process
44873 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
44874 the remote stub. Return 0 on success, or -1 if an error occurs.
44875 If @code{vFile:setfs:} indicates success, the selected filesystem
44876 remains selected until the next successful @code{vFile:setfs:}
44882 @section Interrupts
44883 @cindex interrupts (remote protocol)
44884 @anchor{interrupting remote targets}
44886 In all-stop mode, when a program on the remote target is running,
44887 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
44888 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
44889 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
44891 The precise meaning of @code{BREAK} is defined by the transport
44892 mechanism and may, in fact, be undefined. @value{GDBN} does not
44893 currently define a @code{BREAK} mechanism for any of the network
44894 interfaces except for TCP, in which case @value{GDBN} sends the
44895 @code{telnet} BREAK sequence.
44897 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
44898 transport mechanisms. It is represented by sending the single byte
44899 @code{0x03} without any of the usual packet overhead described in
44900 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
44901 transmitted as part of a packet, it is considered to be packet data
44902 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
44903 (@pxref{X packet}), used for binary downloads, may include an unescaped
44904 @code{0x03} as part of its packet.
44906 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
44907 When Linux kernel receives this sequence from serial port,
44908 it stops execution and connects to gdb.
44910 In non-stop mode, because packet resumptions are asynchronous
44911 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
44912 command to the remote stub, even when the target is running. For that
44913 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
44914 packet}) with the usual packet framing instead of the single byte
44917 Stubs are not required to recognize these interrupt mechanisms and the
44918 precise meaning associated with receipt of the interrupt is
44919 implementation defined. If the target supports debugging of multiple
44920 threads and/or processes, it should attempt to interrupt all
44921 currently-executing threads and processes.
44922 If the stub is successful at interrupting the
44923 running program, it should send one of the stop
44924 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
44925 of successfully stopping the program in all-stop mode, and a stop reply
44926 for each stopped thread in non-stop mode.
44927 Interrupts received while the
44928 program is stopped are queued and the program will be interrupted when
44929 it is resumed next time.
44931 @node Notification Packets
44932 @section Notification Packets
44933 @cindex notification packets
44934 @cindex packets, notification
44936 The @value{GDBN} remote serial protocol includes @dfn{notifications},
44937 packets that require no acknowledgment. Both the GDB and the stub
44938 may send notifications (although the only notifications defined at
44939 present are sent by the stub). Notifications carry information
44940 without incurring the round-trip latency of an acknowledgment, and so
44941 are useful for low-impact communications where occasional packet loss
44944 A notification packet has the form @samp{% @var{data} #
44945 @var{checksum}}, where @var{data} is the content of the notification,
44946 and @var{checksum} is a checksum of @var{data}, computed and formatted
44947 as for ordinary @value{GDBN} packets. A notification's @var{data}
44948 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
44949 receiving a notification, the recipient sends no @samp{+} or @samp{-}
44950 to acknowledge the notification's receipt or to report its corruption.
44952 Every notification's @var{data} begins with a name, which contains no
44953 colon characters, followed by a colon character.
44955 Recipients should silently ignore corrupted notifications and
44956 notifications they do not understand. Recipients should restart
44957 timeout periods on receipt of a well-formed notification, whether or
44958 not they understand it.
44960 Senders should only send the notifications described here when this
44961 protocol description specifies that they are permitted. In the
44962 future, we may extend the protocol to permit existing notifications in
44963 new contexts; this rule helps older senders avoid confusing newer
44966 (Older versions of @value{GDBN} ignore bytes received until they see
44967 the @samp{$} byte that begins an ordinary packet, so new stubs may
44968 transmit notifications without fear of confusing older clients. There
44969 are no notifications defined for @value{GDBN} to send at the moment, but we
44970 assume that most older stubs would ignore them, as well.)
44972 Each notification is comprised of three parts:
44974 @item @var{name}:@var{event}
44975 The notification packet is sent by the side that initiates the
44976 exchange (currently, only the stub does that), with @var{event}
44977 carrying the specific information about the notification, and
44978 @var{name} specifying the name of the notification.
44980 The acknowledge sent by the other side, usually @value{GDBN}, to
44981 acknowledge the exchange and request the event.
44984 The purpose of an asynchronous notification mechanism is to report to
44985 @value{GDBN} that something interesting happened in the remote stub.
44987 The remote stub may send notification @var{name}:@var{event}
44988 at any time, but @value{GDBN} acknowledges the notification when
44989 appropriate. The notification event is pending before @value{GDBN}
44990 acknowledges. Only one notification at a time may be pending; if
44991 additional events occur before @value{GDBN} has acknowledged the
44992 previous notification, they must be queued by the stub for later
44993 synchronous transmission in response to @var{ack} packets from
44994 @value{GDBN}. Because the notification mechanism is unreliable,
44995 the stub is permitted to resend a notification if it believes
44996 @value{GDBN} may not have received it.
44998 Specifically, notifications may appear when @value{GDBN} is not
44999 otherwise reading input from the stub, or when @value{GDBN} is
45000 expecting to read a normal synchronous response or a
45001 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
45002 Notification packets are distinct from any other communication from
45003 the stub so there is no ambiguity.
45005 After receiving a notification, @value{GDBN} shall acknowledge it by
45006 sending a @var{ack} packet as a regular, synchronous request to the
45007 stub. Such acknowledgment is not required to happen immediately, as
45008 @value{GDBN} is permitted to send other, unrelated packets to the
45009 stub first, which the stub should process normally.
45011 Upon receiving a @var{ack} packet, if the stub has other queued
45012 events to report to @value{GDBN}, it shall respond by sending a
45013 normal @var{event}. @value{GDBN} shall then send another @var{ack}
45014 packet to solicit further responses; again, it is permitted to send
45015 other, unrelated packets as well which the stub should process
45018 If the stub receives a @var{ack} packet and there are no additional
45019 @var{event} to report, the stub shall return an @samp{OK} response.
45020 At this point, @value{GDBN} has finished processing a notification
45021 and the stub has completed sending any queued events. @value{GDBN}
45022 won't accept any new notifications until the final @samp{OK} is
45023 received . If further notification events occur, the stub shall send
45024 a new notification, @value{GDBN} shall accept the notification, and
45025 the process shall be repeated.
45027 The process of asynchronous notification can be illustrated by the
45030 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
45033 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
45035 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
45040 The following notifications are defined:
45041 @multitable @columnfractions 0.12 0.12 0.38 0.38
45050 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
45051 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
45052 for information on how these notifications are acknowledged by
45054 @tab Report an asynchronous stop event in non-stop mode.
45058 @node Remote Non-Stop
45059 @section Remote Protocol Support for Non-Stop Mode
45061 @value{GDBN}'s remote protocol supports non-stop debugging of
45062 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
45063 supports non-stop mode, it should report that to @value{GDBN} by including
45064 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
45066 @value{GDBN} typically sends a @samp{QNonStop} packet only when
45067 establishing a new connection with the stub. Entering non-stop mode
45068 does not alter the state of any currently-running threads, but targets
45069 must stop all threads in any already-attached processes when entering
45070 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
45071 probe the target state after a mode change.
45073 In non-stop mode, when an attached process encounters an event that
45074 would otherwise be reported with a stop reply, it uses the
45075 asynchronous notification mechanism (@pxref{Notification Packets}) to
45076 inform @value{GDBN}. In contrast to all-stop mode, where all threads
45077 in all processes are stopped when a stop reply is sent, in non-stop
45078 mode only the thread reporting the stop event is stopped. That is,
45079 when reporting a @samp{S} or @samp{T} response to indicate completion
45080 of a step operation, hitting a breakpoint, or a fault, only the
45081 affected thread is stopped; any other still-running threads continue
45082 to run. When reporting a @samp{W} or @samp{X} response, all running
45083 threads belonging to other attached processes continue to run.
45085 In non-stop mode, the target shall respond to the @samp{?} packet as
45086 follows. First, any incomplete stop reply notification/@samp{vStopped}
45087 sequence in progress is abandoned. The target must begin a new
45088 sequence reporting stop events for all stopped threads, whether or not
45089 it has previously reported those events to @value{GDBN}. The first
45090 stop reply is sent as a synchronous reply to the @samp{?} packet, and
45091 subsequent stop replies are sent as responses to @samp{vStopped} packets
45092 using the mechanism described above. The target must not send
45093 asynchronous stop reply notifications until the sequence is complete.
45094 If all threads are running when the target receives the @samp{?} packet,
45095 or if the target is not attached to any process, it shall respond
45098 If the stub supports non-stop mode, it should also support the
45099 @samp{swbreak} stop reason if software breakpoints are supported, and
45100 the @samp{hwbreak} stop reason if hardware breakpoints are supported
45101 (@pxref{swbreak stop reason}). This is because given the asynchronous
45102 nature of non-stop mode, between the time a thread hits a breakpoint
45103 and the time the event is finally processed by @value{GDBN}, the
45104 breakpoint may have already been removed from the target. Due to
45105 this, @value{GDBN} needs to be able to tell whether a trap stop was
45106 caused by a delayed breakpoint event, which should be ignored, as
45107 opposed to a random trap signal, which should be reported to the user.
45108 Note the @samp{swbreak} feature implies that the target is responsible
45109 for adjusting the PC when a software breakpoint triggers, if
45110 necessary, such as on the x86 architecture.
45112 @node Packet Acknowledgment
45113 @section Packet Acknowledgment
45115 @cindex acknowledgment, for @value{GDBN} remote
45116 @cindex packet acknowledgment, for @value{GDBN} remote
45117 By default, when either the host or the target machine receives a packet,
45118 the first response expected is an acknowledgment: either @samp{+} (to indicate
45119 the package was received correctly) or @samp{-} (to request retransmission).
45120 This mechanism allows the @value{GDBN} remote protocol to operate over
45121 unreliable transport mechanisms, such as a serial line.
45123 In cases where the transport mechanism is itself reliable (such as a pipe or
45124 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
45125 It may be desirable to disable them in that case to reduce communication
45126 overhead, or for other reasons. This can be accomplished by means of the
45127 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
45129 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
45130 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
45131 and response format still includes the normal checksum, as described in
45132 @ref{Overview}, but the checksum may be ignored by the receiver.
45134 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
45135 no-acknowledgment mode, it should report that to @value{GDBN}
45136 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
45137 @pxref{qSupported}.
45138 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
45139 disabled via the @code{set remote noack-packet off} command
45140 (@pxref{Remote Configuration}),
45141 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
45142 Only then may the stub actually turn off packet acknowledgments.
45143 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
45144 response, which can be safely ignored by the stub.
45146 Note that @code{set remote noack-packet} command only affects negotiation
45147 between @value{GDBN} and the stub when subsequent connections are made;
45148 it does not affect the protocol acknowledgment state for any current
45150 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
45151 new connection is established,
45152 there is also no protocol request to re-enable the acknowledgments
45153 for the current connection, once disabled.
45158 Example sequence of a target being re-started. Notice how the restart
45159 does not get any direct output:
45164 @emph{target restarts}
45167 <- @code{T001:1234123412341234}
45171 Example sequence of a target being stepped by a single instruction:
45174 -> @code{G1445@dots{}}
45179 <- @code{T001:1234123412341234}
45183 <- @code{1455@dots{}}
45187 @node File-I/O Remote Protocol Extension
45188 @section File-I/O Remote Protocol Extension
45189 @cindex File-I/O remote protocol extension
45192 * File-I/O Overview::
45193 * Protocol Basics::
45194 * The F Request Packet::
45195 * The F Reply Packet::
45196 * The Ctrl-C Message::
45198 * List of Supported Calls::
45199 * Protocol-specific Representation of Datatypes::
45201 * File-I/O Examples::
45204 @node File-I/O Overview
45205 @subsection File-I/O Overview
45206 @cindex file-i/o overview
45208 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
45209 target to use the host's file system and console I/O to perform various
45210 system calls. System calls on the target system are translated into a
45211 remote protocol packet to the host system, which then performs the needed
45212 actions and returns a response packet to the target system.
45213 This simulates file system operations even on targets that lack file systems.
45215 The protocol is defined to be independent of both the host and target systems.
45216 It uses its own internal representation of datatypes and values. Both
45217 @value{GDBN} and the target's @value{GDBN} stub are responsible for
45218 translating the system-dependent value representations into the internal
45219 protocol representations when data is transmitted.
45221 The communication is synchronous. A system call is possible only when
45222 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
45223 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
45224 the target is stopped to allow deterministic access to the target's
45225 memory. Therefore File-I/O is not interruptible by target signals. On
45226 the other hand, it is possible to interrupt File-I/O by a user interrupt
45227 (@samp{Ctrl-C}) within @value{GDBN}.
45229 The target's request to perform a host system call does not finish
45230 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
45231 after finishing the system call, the target returns to continuing the
45232 previous activity (continue, step). No additional continue or step
45233 request from @value{GDBN} is required.
45236 (@value{GDBP}) continue
45237 <- target requests 'system call X'
45238 target is stopped, @value{GDBN} executes system call
45239 -> @value{GDBN} returns result
45240 ... target continues, @value{GDBN} returns to wait for the target
45241 <- target hits breakpoint and sends a Txx packet
45244 The protocol only supports I/O on the console and to regular files on
45245 the host file system. Character or block special devices, pipes,
45246 named pipes, sockets or any other communication method on the host
45247 system are not supported by this protocol.
45249 File I/O is not supported in non-stop mode.
45251 @node Protocol Basics
45252 @subsection Protocol Basics
45253 @cindex protocol basics, file-i/o
45255 The File-I/O protocol uses the @code{F} packet as the request as well
45256 as reply packet. Since a File-I/O system call can only occur when
45257 @value{GDBN} is waiting for a response from the continuing or stepping target,
45258 the File-I/O request is a reply that @value{GDBN} has to expect as a result
45259 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
45260 This @code{F} packet contains all information needed to allow @value{GDBN}
45261 to call the appropriate host system call:
45265 A unique identifier for the requested system call.
45268 All parameters to the system call. Pointers are given as addresses
45269 in the target memory address space. Pointers to strings are given as
45270 pointer/length pair. Numerical values are given as they are.
45271 Numerical control flags are given in a protocol-specific representation.
45275 At this point, @value{GDBN} has to perform the following actions.
45279 If the parameters include pointer values to data needed as input to a
45280 system call, @value{GDBN} requests this data from the target with a
45281 standard @code{m} packet request. This additional communication has to be
45282 expected by the target implementation and is handled as any other @code{m}
45286 @value{GDBN} translates all value from protocol representation to host
45287 representation as needed. Datatypes are coerced into the host types.
45290 @value{GDBN} calls the system call.
45293 It then coerces datatypes back to protocol representation.
45296 If the system call is expected to return data in buffer space specified
45297 by pointer parameters to the call, the data is transmitted to the
45298 target using a @code{M} or @code{X} packet. This packet has to be expected
45299 by the target implementation and is handled as any other @code{M} or @code{X}
45304 Eventually @value{GDBN} replies with another @code{F} packet which contains all
45305 necessary information for the target to continue. This at least contains
45312 @code{errno}, if has been changed by the system call.
45319 After having done the needed type and value coercion, the target continues
45320 the latest continue or step action.
45322 @node The F Request Packet
45323 @subsection The @code{F} Request Packet
45324 @cindex file-i/o request packet
45325 @cindex @code{F} request packet
45327 The @code{F} request packet has the following format:
45330 @item F@var{call-id},@var{parameter@dots{}}
45332 @var{call-id} is the identifier to indicate the host system call to be called.
45333 This is just the name of the function.
45335 @var{parameter@dots{}} are the parameters to the system call.
45336 Parameters are hexadecimal integer values, either the actual values in case
45337 of scalar datatypes, pointers to target buffer space in case of compound
45338 datatypes and unspecified memory areas, or pointer/length pairs in case
45339 of string parameters. These are appended to the @var{call-id} as a
45340 comma-delimited list. All values are transmitted in ASCII
45341 string representation, pointer/length pairs separated by a slash.
45347 @node The F Reply Packet
45348 @subsection The @code{F} Reply Packet
45349 @cindex file-i/o reply packet
45350 @cindex @code{F} reply packet
45352 The @code{F} reply packet has the following format:
45356 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
45358 @var{retcode} is the return code of the system call as hexadecimal value.
45360 @var{errno} is the @code{errno} set by the call, in protocol-specific
45362 This parameter can be omitted if the call was successful.
45364 @var{Ctrl-C flag} is only sent if the user requested a break. In this
45365 case, @var{errno} must be sent as well, even if the call was successful.
45366 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
45373 or, if the call was interrupted before the host call has been performed:
45380 assuming 4 is the protocol-specific representation of @code{EINTR}.
45385 @node The Ctrl-C Message
45386 @subsection The @samp{Ctrl-C} Message
45387 @cindex ctrl-c message, in file-i/o protocol
45389 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
45390 reply packet (@pxref{The F Reply Packet}),
45391 the target should behave as if it had
45392 gotten a break message. The meaning for the target is ``system call
45393 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
45394 (as with a break message) and return to @value{GDBN} with a @code{T02}
45397 It's important for the target to know in which
45398 state the system call was interrupted. There are two possible cases:
45402 The system call hasn't been performed on the host yet.
45405 The system call on the host has been finished.
45409 These two states can be distinguished by the target by the value of the
45410 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
45411 call hasn't been performed. This is equivalent to the @code{EINTR} handling
45412 on POSIX systems. In any other case, the target may presume that the
45413 system call has been finished --- successfully or not --- and should behave
45414 as if the break message arrived right after the system call.
45416 @value{GDBN} must behave reliably. If the system call has not been called
45417 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
45418 @code{errno} in the packet. If the system call on the host has been finished
45419 before the user requests a break, the full action must be finished by
45420 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
45421 The @code{F} packet may only be sent when either nothing has happened
45422 or the full action has been completed.
45425 @subsection Console I/O
45426 @cindex console i/o as part of file-i/o
45428 By default and if not explicitly closed by the target system, the file
45429 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
45430 on the @value{GDBN} console is handled as any other file output operation
45431 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
45432 by @value{GDBN} so that after the target read request from file descriptor
45433 0 all following typing is buffered until either one of the following
45438 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
45440 system call is treated as finished.
45443 The user presses @key{RET}. This is treated as end of input with a trailing
45447 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
45448 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
45452 If the user has typed more characters than fit in the buffer given to
45453 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
45454 either another @code{read(0, @dots{})} is requested by the target, or debugging
45455 is stopped at the user's request.
45458 @node List of Supported Calls
45459 @subsection List of Supported Calls
45460 @cindex list of supported file-i/o calls
45477 @unnumberedsubsubsec open
45478 @cindex open, file-i/o system call
45483 int open(const char *pathname, int flags);
45484 int open(const char *pathname, int flags, mode_t mode);
45488 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
45491 @var{flags} is the bitwise @code{OR} of the following values:
45495 If the file does not exist it will be created. The host
45496 rules apply as far as file ownership and time stamps
45500 When used with @code{O_CREAT}, if the file already exists it is
45501 an error and open() fails.
45504 If the file already exists and the open mode allows
45505 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
45506 truncated to zero length.
45509 The file is opened in append mode.
45512 The file is opened for reading only.
45515 The file is opened for writing only.
45518 The file is opened for reading and writing.
45522 Other bits are silently ignored.
45526 @var{mode} is the bitwise @code{OR} of the following values:
45530 User has read permission.
45533 User has write permission.
45536 Group has read permission.
45539 Group has write permission.
45542 Others have read permission.
45545 Others have write permission.
45549 Other bits are silently ignored.
45552 @item Return value:
45553 @code{open} returns the new file descriptor or -1 if an error
45560 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
45563 @var{pathname} refers to a directory.
45566 The requested access is not allowed.
45569 @var{pathname} was too long.
45572 A directory component in @var{pathname} does not exist.
45575 @var{pathname} refers to a device, pipe, named pipe or socket.
45578 @var{pathname} refers to a file on a read-only filesystem and
45579 write access was requested.
45582 @var{pathname} is an invalid pointer value.
45585 No space on device to create the file.
45588 The process already has the maximum number of files open.
45591 The limit on the total number of files open on the system
45595 The call was interrupted by the user.
45601 @unnumberedsubsubsec close
45602 @cindex close, file-i/o system call
45611 @samp{Fclose,@var{fd}}
45613 @item Return value:
45614 @code{close} returns zero on success, or -1 if an error occurred.
45620 @var{fd} isn't a valid open file descriptor.
45623 The call was interrupted by the user.
45629 @unnumberedsubsubsec read
45630 @cindex read, file-i/o system call
45635 int read(int fd, void *buf, unsigned int count);
45639 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
45641 @item Return value:
45642 On success, the number of bytes read is returned.
45643 Zero indicates end of file. If count is zero, read
45644 returns zero as well. On error, -1 is returned.
45650 @var{fd} is not a valid file descriptor or is not open for
45654 @var{bufptr} is an invalid pointer value.
45657 The call was interrupted by the user.
45663 @unnumberedsubsubsec write
45664 @cindex write, file-i/o system call
45669 int write(int fd, const void *buf, unsigned int count);
45673 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
45675 @item Return value:
45676 On success, the number of bytes written are returned.
45677 Zero indicates nothing was written. On error, -1
45684 @var{fd} is not a valid file descriptor or is not open for
45688 @var{bufptr} is an invalid pointer value.
45691 An attempt was made to write a file that exceeds the
45692 host-specific maximum file size allowed.
45695 No space on device to write the data.
45698 The call was interrupted by the user.
45704 @unnumberedsubsubsec lseek
45705 @cindex lseek, file-i/o system call
45710 long lseek (int fd, long offset, int flag);
45714 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
45716 @var{flag} is one of:
45720 The offset is set to @var{offset} bytes.
45723 The offset is set to its current location plus @var{offset}
45727 The offset is set to the size of the file plus @var{offset}
45731 @item Return value:
45732 On success, the resulting unsigned offset in bytes from
45733 the beginning of the file is returned. Otherwise, a
45734 value of -1 is returned.
45740 @var{fd} is not a valid open file descriptor.
45743 @var{fd} is associated with the @value{GDBN} console.
45746 @var{flag} is not a proper value.
45749 The call was interrupted by the user.
45755 @unnumberedsubsubsec rename
45756 @cindex rename, file-i/o system call
45761 int rename(const char *oldpath, const char *newpath);
45765 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
45767 @item Return value:
45768 On success, zero is returned. On error, -1 is returned.
45774 @var{newpath} is an existing directory, but @var{oldpath} is not a
45778 @var{newpath} is a non-empty directory.
45781 @var{oldpath} or @var{newpath} is a directory that is in use by some
45785 An attempt was made to make a directory a subdirectory
45789 A component used as a directory in @var{oldpath} or new
45790 path is not a directory. Or @var{oldpath} is a directory
45791 and @var{newpath} exists but is not a directory.
45794 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
45797 No access to the file or the path of the file.
45801 @var{oldpath} or @var{newpath} was too long.
45804 A directory component in @var{oldpath} or @var{newpath} does not exist.
45807 The file is on a read-only filesystem.
45810 The device containing the file has no room for the new
45814 The call was interrupted by the user.
45820 @unnumberedsubsubsec unlink
45821 @cindex unlink, file-i/o system call
45826 int unlink(const char *pathname);
45830 @samp{Funlink,@var{pathnameptr}/@var{len}}
45832 @item Return value:
45833 On success, zero is returned. On error, -1 is returned.
45839 No access to the file or the path of the file.
45842 The system does not allow unlinking of directories.
45845 The file @var{pathname} cannot be unlinked because it's
45846 being used by another process.
45849 @var{pathnameptr} is an invalid pointer value.
45852 @var{pathname} was too long.
45855 A directory component in @var{pathname} does not exist.
45858 A component of the path is not a directory.
45861 The file is on a read-only filesystem.
45864 The call was interrupted by the user.
45870 @unnumberedsubsubsec stat/fstat
45871 @cindex fstat, file-i/o system call
45872 @cindex stat, file-i/o system call
45877 int stat(const char *pathname, struct stat *buf);
45878 int fstat(int fd, struct stat *buf);
45882 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
45883 @samp{Ffstat,@var{fd},@var{bufptr}}
45885 @item Return value:
45886 On success, zero is returned. On error, -1 is returned.
45892 @var{fd} is not a valid open file.
45895 A directory component in @var{pathname} does not exist or the
45896 path is an empty string.
45899 A component of the path is not a directory.
45902 @var{pathnameptr} is an invalid pointer value.
45905 No access to the file or the path of the file.
45908 @var{pathname} was too long.
45911 The call was interrupted by the user.
45917 @unnumberedsubsubsec gettimeofday
45918 @cindex gettimeofday, file-i/o system call
45923 int gettimeofday(struct timeval *tv, void *tz);
45927 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
45929 @item Return value:
45930 On success, 0 is returned, -1 otherwise.
45936 @var{tz} is a non-NULL pointer.
45939 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
45945 @unnumberedsubsubsec isatty
45946 @cindex isatty, file-i/o system call
45951 int isatty(int fd);
45955 @samp{Fisatty,@var{fd}}
45957 @item Return value:
45958 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
45964 The call was interrupted by the user.
45969 Note that the @code{isatty} call is treated as a special case: it returns
45970 1 to the target if the file descriptor is attached
45971 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
45972 would require implementing @code{ioctl} and would be more complex than
45977 @unnumberedsubsubsec system
45978 @cindex system, file-i/o system call
45983 int system(const char *command);
45987 @samp{Fsystem,@var{commandptr}/@var{len}}
45989 @item Return value:
45990 If @var{len} is zero, the return value indicates whether a shell is
45991 available. A zero return value indicates a shell is not available.
45992 For non-zero @var{len}, the value returned is -1 on error and the
45993 return status of the command otherwise. Only the exit status of the
45994 command is returned, which is extracted from the host's @code{system}
45995 return value by calling @code{WEXITSTATUS(retval)}. In case
45996 @file{/bin/sh} could not be executed, 127 is returned.
46002 The call was interrupted by the user.
46007 @value{GDBN} takes over the full task of calling the necessary host calls
46008 to perform the @code{system} call. The return value of @code{system} on
46009 the host is simplified before it's returned
46010 to the target. Any termination signal information from the child process
46011 is discarded, and the return value consists
46012 entirely of the exit status of the called command.
46014 Due to security concerns, the @code{system} call is by default refused
46015 by @value{GDBN}. The user has to allow this call explicitly with the
46016 @code{set remote system-call-allowed 1} command.
46019 @item set remote system-call-allowed
46020 @kindex set remote system-call-allowed
46021 Control whether to allow the @code{system} calls in the File I/O
46022 protocol for the remote target. The default is zero (disabled).
46024 @item show remote system-call-allowed
46025 @kindex show remote system-call-allowed
46026 Show whether the @code{system} calls are allowed in the File I/O
46030 @node Protocol-specific Representation of Datatypes
46031 @subsection Protocol-specific Representation of Datatypes
46032 @cindex protocol-specific representation of datatypes, in file-i/o protocol
46035 * Integral Datatypes::
46037 * Memory Transfer::
46042 @node Integral Datatypes
46043 @unnumberedsubsubsec Integral Datatypes
46044 @cindex integral datatypes, in file-i/o protocol
46046 The integral datatypes used in the system calls are @code{int},
46047 @code{unsigned int}, @code{long}, @code{unsigned long},
46048 @code{mode_t}, and @code{time_t}.
46050 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
46051 implemented as 32 bit values in this protocol.
46053 @code{long} and @code{unsigned long} are implemented as 64 bit types.
46055 @xref{Limits}, for corresponding MIN and MAX values (similar to those
46056 in @file{limits.h}) to allow range checking on host and target.
46058 @code{time_t} datatypes are defined as seconds since the Epoch.
46060 All integral datatypes transferred as part of a memory read or write of a
46061 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
46064 @node Pointer Values
46065 @unnumberedsubsubsec Pointer Values
46066 @cindex pointer values, in file-i/o protocol
46068 Pointers to target data are transmitted as they are. An exception
46069 is made for pointers to buffers for which the length isn't
46070 transmitted as part of the function call, namely strings. Strings
46071 are transmitted as a pointer/length pair, both as hex values, e.g.@:
46078 which is a pointer to data of length 18 bytes at position 0x1aaf.
46079 The length is defined as the full string length in bytes, including
46080 the trailing null byte. For example, the string @code{"hello world"}
46081 at address 0x123456 is transmitted as
46087 @node Memory Transfer
46088 @unnumberedsubsubsec Memory Transfer
46089 @cindex memory transfer, in file-i/o protocol
46091 Structured data which is transferred using a memory read or write (for
46092 example, a @code{struct stat}) is expected to be in a protocol-specific format
46093 with all scalar multibyte datatypes being big endian. Translation to
46094 this representation needs to be done both by the target before the @code{F}
46095 packet is sent, and by @value{GDBN} before
46096 it transfers memory to the target. Transferred pointers to structured
46097 data should point to the already-coerced data at any time.
46101 @unnumberedsubsubsec struct stat
46102 @cindex struct stat, in file-i/o protocol
46104 The buffer of type @code{struct stat} used by the target and @value{GDBN}
46105 is defined as follows:
46109 unsigned int st_dev; /* device */
46110 unsigned int st_ino; /* inode */
46111 mode_t st_mode; /* protection */
46112 unsigned int st_nlink; /* number of hard links */
46113 unsigned int st_uid; /* user ID of owner */
46114 unsigned int st_gid; /* group ID of owner */
46115 unsigned int st_rdev; /* device type (if inode device) */
46116 unsigned long st_size; /* total size, in bytes */
46117 unsigned long st_blksize; /* blocksize for filesystem I/O */
46118 unsigned long st_blocks; /* number of blocks allocated */
46119 time_t st_atime; /* time of last access */
46120 time_t st_mtime; /* time of last modification */
46121 time_t st_ctime; /* time of last change */
46125 The integral datatypes conform to the definitions given in the
46126 appropriate section (see @ref{Integral Datatypes}, for details) so this
46127 structure is of size 64 bytes.
46129 The values of several fields have a restricted meaning and/or
46135 A value of 0 represents a file, 1 the console.
46138 No valid meaning for the target. Transmitted unchanged.
46141 Valid mode bits are described in @ref{Constants}. Any other
46142 bits have currently no meaning for the target.
46147 No valid meaning for the target. Transmitted unchanged.
46152 These values have a host and file system dependent
46153 accuracy. Especially on Windows hosts, the file system may not
46154 support exact timing values.
46157 The target gets a @code{struct stat} of the above representation and is
46158 responsible for coercing it to the target representation before
46161 Note that due to size differences between the host, target, and protocol
46162 representations of @code{struct stat} members, these members could eventually
46163 get truncated on the target.
46165 @node struct timeval
46166 @unnumberedsubsubsec struct timeval
46167 @cindex struct timeval, in file-i/o protocol
46169 The buffer of type @code{struct timeval} used by the File-I/O protocol
46170 is defined as follows:
46174 time_t tv_sec; /* second */
46175 long tv_usec; /* microsecond */
46179 The integral datatypes conform to the definitions given in the
46180 appropriate section (see @ref{Integral Datatypes}, for details) so this
46181 structure is of size 8 bytes.
46184 @subsection Constants
46185 @cindex constants, in file-i/o protocol
46187 The following values are used for the constants inside of the
46188 protocol. @value{GDBN} and target are responsible for translating these
46189 values before and after the call as needed.
46200 @unnumberedsubsubsec Open Flags
46201 @cindex open flags, in file-i/o protocol
46203 All values are given in hexadecimal representation.
46215 @node mode_t Values
46216 @unnumberedsubsubsec mode_t Values
46217 @cindex mode_t values, in file-i/o protocol
46219 All values are given in octal representation.
46236 @unnumberedsubsubsec Errno Values
46237 @cindex errno values, in file-i/o protocol
46239 All values are given in decimal representation.
46264 @code{EUNKNOWN} is used as a fallback error value if a host system returns
46265 any error value not in the list of supported error numbers.
46268 @unnumberedsubsubsec Lseek Flags
46269 @cindex lseek flags, in file-i/o protocol
46278 @unnumberedsubsubsec Limits
46279 @cindex limits, in file-i/o protocol
46281 All values are given in decimal representation.
46284 INT_MIN -2147483648
46286 UINT_MAX 4294967295
46287 LONG_MIN -9223372036854775808
46288 LONG_MAX 9223372036854775807
46289 ULONG_MAX 18446744073709551615
46292 @node File-I/O Examples
46293 @subsection File-I/O Examples
46294 @cindex file-i/o examples
46296 Example sequence of a write call, file descriptor 3, buffer is at target
46297 address 0x1234, 6 bytes should be written:
46300 <- @code{Fwrite,3,1234,6}
46301 @emph{request memory read from target}
46304 @emph{return "6 bytes written"}
46308 Example sequence of a read call, file descriptor 3, buffer is at target
46309 address 0x1234, 6 bytes should be read:
46312 <- @code{Fread,3,1234,6}
46313 @emph{request memory write to target}
46314 -> @code{X1234,6:XXXXXX}
46315 @emph{return "6 bytes read"}
46319 Example sequence of a read call, call fails on the host due to invalid
46320 file descriptor (@code{EBADF}):
46323 <- @code{Fread,3,1234,6}
46327 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
46331 <- @code{Fread,3,1234,6}
46336 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
46340 <- @code{Fread,3,1234,6}
46341 -> @code{X1234,6:XXXXXX}
46345 @node Library List Format
46346 @section Library List Format
46347 @cindex library list format, remote protocol
46349 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
46350 same process as your application to manage libraries. In this case,
46351 @value{GDBN} can use the loader's symbol table and normal memory
46352 operations to maintain a list of shared libraries. On other
46353 platforms, the operating system manages loaded libraries.
46354 @value{GDBN} can not retrieve the list of currently loaded libraries
46355 through memory operations, so it uses the @samp{qXfer:libraries:read}
46356 packet (@pxref{qXfer library list read}) instead. The remote stub
46357 queries the target's operating system and reports which libraries
46360 The @samp{qXfer:libraries:read} packet returns an XML document which
46361 lists loaded libraries and their offsets. Each library has an
46362 associated name and one or more segment or section base addresses,
46363 which report where the library was loaded in memory.
46365 For the common case of libraries that are fully linked binaries, the
46366 library should have a list of segments. If the target supports
46367 dynamic linking of a relocatable object file, its library XML element
46368 should instead include a list of allocated sections. The segment or
46369 section bases are start addresses, not relocation offsets; they do not
46370 depend on the library's link-time base addresses.
46372 @value{GDBN} must be linked with the Expat library to support XML
46373 library lists. @xref{Expat}.
46375 A simple memory map, with one loaded library relocated by a single
46376 offset, looks like this:
46380 <library name="/lib/libc.so.6">
46381 <segment address="0x10000000"/>
46386 Another simple memory map, with one loaded library with three
46387 allocated sections (.text, .data, .bss), looks like this:
46391 <library name="sharedlib.o">
46392 <section address="0x10000000"/>
46393 <section address="0x20000000"/>
46394 <section address="0x30000000"/>
46399 The format of a library list is described by this DTD:
46402 <!-- library-list: Root element with versioning -->
46403 <!ELEMENT library-list (library)*>
46404 <!ATTLIST library-list version CDATA #FIXED "1.0">
46405 <!ELEMENT library (segment*, section*)>
46406 <!ATTLIST library name CDATA #REQUIRED>
46407 <!ELEMENT segment EMPTY>
46408 <!ATTLIST segment address CDATA #REQUIRED>
46409 <!ELEMENT section EMPTY>
46410 <!ATTLIST section address CDATA #REQUIRED>
46413 In addition, segments and section descriptors cannot be mixed within a
46414 single library element, and you must supply at least one segment or
46415 section for each library.
46417 @node Library List Format for SVR4 Targets
46418 @section Library List Format for SVR4 Targets
46419 @cindex library list format, remote protocol
46421 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
46422 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
46423 shared libraries. Still a special library list provided by this packet is
46424 more efficient for the @value{GDBN} remote protocol.
46426 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
46427 loaded libraries and their SVR4 linker parameters. For each library on SVR4
46428 target, the following parameters are reported:
46432 @code{name}, the absolute file name from the @code{l_name} field of
46433 @code{struct link_map}.
46435 @code{lm} with address of @code{struct link_map} used for TLS
46436 (Thread Local Storage) access.
46438 @code{l_addr}, the displacement as read from the field @code{l_addr} of
46439 @code{struct link_map}. For prelinked libraries this is not an absolute
46440 memory address. It is a displacement of absolute memory address against
46441 address the file was prelinked to during the library load.
46443 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
46445 @code{lmid}, which is an identifier for a linker namespace, such as
46446 the memory address of the @code{r_debug} object that contains this
46447 namespace's load map or the namespace identifier returned by
46451 Additionally the single @code{main-lm} attribute specifies address of
46452 @code{struct link_map} used for the main executable. This parameter is used
46453 for TLS access and its presence is optional.
46455 @value{GDBN} must be linked with the Expat library to support XML
46456 SVR4 library lists. @xref{Expat}.
46458 A simple memory map, with two loaded libraries (which do not use prelink),
46462 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
46463 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
46464 l_ld="0xe4eefc" lmid="0xfffe0"/>
46465 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
46466 l_ld="0x152350" lmid="0xfffe0"/>
46467 </library-list-svr>
46470 The format of an SVR4 library list is described by this DTD:
46473 <!-- library-list-svr4: Root element with versioning -->
46474 <!ELEMENT library-list-svr4 (library)*>
46475 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
46476 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
46477 <!ELEMENT library EMPTY>
46478 <!ATTLIST library name CDATA #REQUIRED>
46479 <!ATTLIST library lm CDATA #REQUIRED>
46480 <!ATTLIST library l_addr CDATA #REQUIRED>
46481 <!ATTLIST library l_ld CDATA #REQUIRED>
46482 <!ATTLIST library lmid CDATA #IMPLIED>
46485 @node Memory Map Format
46486 @section Memory Map Format
46487 @cindex memory map format
46489 To be able to write into flash memory, @value{GDBN} needs to obtain a
46490 memory map from the target. This section describes the format of the
46493 The memory map is obtained using the @samp{qXfer:memory-map:read}
46494 (@pxref{qXfer memory map read}) packet and is an XML document that
46495 lists memory regions.
46497 @value{GDBN} must be linked with the Expat library to support XML
46498 memory maps. @xref{Expat}.
46500 The top-level structure of the document is shown below:
46503 <?xml version="1.0"?>
46504 <!DOCTYPE memory-map
46505 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
46506 "http://sourceware.org/gdb/gdb-memory-map.dtd">
46512 Each region can be either:
46517 A region of RAM starting at @var{addr} and extending for @var{length}
46521 <memory type="ram" start="@var{addr}" length="@var{length}"/>
46526 A region of read-only memory:
46529 <memory type="rom" start="@var{addr}" length="@var{length}"/>
46534 A region of flash memory, with erasure blocks @var{blocksize}
46538 <memory type="flash" start="@var{addr}" length="@var{length}">
46539 <property name="blocksize">@var{blocksize}</property>
46545 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
46546 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
46547 packets to write to addresses in such ranges.
46549 The formal DTD for memory map format is given below:
46552 <!-- ................................................... -->
46553 <!-- Memory Map XML DTD ................................ -->
46554 <!-- File: memory-map.dtd .............................. -->
46555 <!-- .................................... .............. -->
46556 <!-- memory-map.dtd -->
46557 <!-- memory-map: Root element with versioning -->
46558 <!ELEMENT memory-map (memory)*>
46559 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
46560 <!ELEMENT memory (property)*>
46561 <!-- memory: Specifies a memory region,
46562 and its type, or device. -->
46563 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
46564 start CDATA #REQUIRED
46565 length CDATA #REQUIRED>
46566 <!-- property: Generic attribute tag -->
46567 <!ELEMENT property (#PCDATA | property)*>
46568 <!ATTLIST property name (blocksize) #REQUIRED>
46571 @node Thread List Format
46572 @section Thread List Format
46573 @cindex thread list format
46575 To efficiently update the list of threads and their attributes,
46576 @value{GDBN} issues the @samp{qXfer:threads:read} packet
46577 (@pxref{qXfer threads read}) and obtains the XML document with
46578 the following structure:
46581 <?xml version="1.0"?>
46583 <thread id="id" core="0" name="name">
46584 ... description ...
46589 Each @samp{thread} element must have the @samp{id} attribute that
46590 identifies the thread (@pxref{thread-id syntax}). The
46591 @samp{core} attribute, if present, specifies which processor core
46592 the thread was last executing on. The @samp{name} attribute, if
46593 present, specifies the human-readable name of the thread. The content
46594 of the of @samp{thread} element is interpreted as human-readable
46595 auxiliary information. The @samp{handle} attribute, if present,
46596 is a hex encoded representation of the thread handle.
46599 @node Traceframe Info Format
46600 @section Traceframe Info Format
46601 @cindex traceframe info format
46603 To be able to know which objects in the inferior can be examined when
46604 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
46605 memory ranges, registers and trace state variables that have been
46606 collected in a traceframe.
46608 This list is obtained using the @samp{qXfer:traceframe-info:read}
46609 (@pxref{qXfer traceframe info read}) packet and is an XML document.
46611 @value{GDBN} must be linked with the Expat library to support XML
46612 traceframe info discovery. @xref{Expat}.
46614 The top-level structure of the document is shown below:
46617 <?xml version="1.0"?>
46618 <!DOCTYPE traceframe-info
46619 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
46620 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
46626 Each traceframe block can be either:
46631 A region of collected memory starting at @var{addr} and extending for
46632 @var{length} bytes from there:
46635 <memory start="@var{addr}" length="@var{length}"/>
46639 A block indicating trace state variable numbered @var{number} has been
46643 <tvar id="@var{number}"/>
46648 The formal DTD for the traceframe info format is given below:
46651 <!ELEMENT traceframe-info (memory | tvar)* >
46652 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
46654 <!ELEMENT memory EMPTY>
46655 <!ATTLIST memory start CDATA #REQUIRED
46656 length CDATA #REQUIRED>
46658 <!ATTLIST tvar id CDATA #REQUIRED>
46661 @node Branch Trace Format
46662 @section Branch Trace Format
46663 @cindex branch trace format
46665 In order to display the branch trace of an inferior thread,
46666 @value{GDBN} needs to obtain the list of branches. This list is
46667 represented as list of sequential code blocks that are connected via
46668 branches. The code in each block has been executed sequentially.
46670 This list is obtained using the @samp{qXfer:btrace:read}
46671 (@pxref{qXfer btrace read}) packet and is an XML document.
46673 @value{GDBN} must be linked with the Expat library to support XML
46674 traceframe info discovery. @xref{Expat}.
46676 The top-level structure of the document is shown below:
46679 <?xml version="1.0"?>
46681 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
46682 "http://sourceware.org/gdb/gdb-btrace.dtd">
46691 A block of sequentially executed instructions starting at @var{begin}
46692 and ending at @var{end}:
46695 <block begin="@var{begin}" end="@var{end}"/>
46700 The formal DTD for the branch trace format is given below:
46703 <!ELEMENT btrace (block* | pt) >
46704 <!ATTLIST btrace version CDATA #FIXED "1.0">
46706 <!ELEMENT block EMPTY>
46707 <!ATTLIST block begin CDATA #REQUIRED
46708 end CDATA #REQUIRED>
46710 <!ELEMENT pt (pt-config?, raw?)>
46712 <!ELEMENT pt-config (cpu?)>
46714 <!ELEMENT cpu EMPTY>
46715 <!ATTLIST cpu vendor CDATA #REQUIRED
46716 family CDATA #REQUIRED
46717 model CDATA #REQUIRED
46718 stepping CDATA #REQUIRED>
46720 <!ELEMENT raw (#PCDATA)>
46723 @node Branch Trace Configuration Format
46724 @section Branch Trace Configuration Format
46725 @cindex branch trace configuration format
46727 For each inferior thread, @value{GDBN} can obtain the branch trace
46728 configuration using the @samp{qXfer:btrace-conf:read}
46729 (@pxref{qXfer btrace-conf read}) packet.
46731 The configuration describes the branch trace format and configuration
46732 settings for that format. The following information is described:
46736 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
46739 The size of the @acronym{BTS} ring buffer in bytes.
46742 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
46746 The size of the @acronym{Intel PT} ring buffer in bytes.
46750 @value{GDBN} must be linked with the Expat library to support XML
46751 branch trace configuration discovery. @xref{Expat}.
46753 The formal DTD for the branch trace configuration format is given below:
46756 <!ELEMENT btrace-conf (bts?, pt?)>
46757 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
46759 <!ELEMENT bts EMPTY>
46760 <!ATTLIST bts size CDATA #IMPLIED>
46762 <!ELEMENT pt EMPTY>
46763 <!ATTLIST pt size CDATA #IMPLIED>
46766 @include agentexpr.texi
46768 @node Target Descriptions
46769 @appendix Target Descriptions
46770 @cindex target descriptions
46772 One of the challenges of using @value{GDBN} to debug embedded systems
46773 is that there are so many minor variants of each processor
46774 architecture in use. It is common practice for vendors to start with
46775 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
46776 and then make changes to adapt it to a particular market niche. Some
46777 architectures have hundreds of variants, available from dozens of
46778 vendors. This leads to a number of problems:
46782 With so many different customized processors, it is difficult for
46783 the @value{GDBN} maintainers to keep up with the changes.
46785 Since individual variants may have short lifetimes or limited
46786 audiences, it may not be worthwhile to carry information about every
46787 variant in the @value{GDBN} source tree.
46789 When @value{GDBN} does support the architecture of the embedded system
46790 at hand, the task of finding the correct architecture name to give the
46791 @command{set architecture} command can be error-prone.
46794 To address these problems, the @value{GDBN} remote protocol allows a
46795 target system to not only identify itself to @value{GDBN}, but to
46796 actually describe its own features. This lets @value{GDBN} support
46797 processor variants it has never seen before --- to the extent that the
46798 descriptions are accurate, and that @value{GDBN} understands them.
46800 @value{GDBN} must be linked with the Expat library to support XML
46801 target descriptions. @xref{Expat}.
46804 * Retrieving Descriptions:: How descriptions are fetched from a target.
46805 * Target Description Format:: The contents of a target description.
46806 * Predefined Target Types:: Standard types available for target
46808 * Enum Target Types:: How to define enum target types.
46809 * Standard Target Features:: Features @value{GDBN} knows about.
46812 @node Retrieving Descriptions
46813 @section Retrieving Descriptions
46815 Target descriptions can be read from the target automatically, or
46816 specified by the user manually. The default behavior is to read the
46817 description from the target. @value{GDBN} retrieves it via the remote
46818 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
46819 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
46820 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
46821 XML document, of the form described in @ref{Target Description
46824 Alternatively, you can specify a file to read for the target description.
46825 If a file is set, the target will not be queried. The commands to
46826 specify a file are:
46829 @cindex set tdesc filename
46830 @item set tdesc filename @var{path}
46831 Read the target description from @var{path}.
46833 @cindex unset tdesc filename
46834 @item unset tdesc filename
46835 Do not read the XML target description from a file. @value{GDBN}
46836 will use the description supplied by the current target.
46838 @cindex show tdesc filename
46839 @item show tdesc filename
46840 Show the filename to read for a target description, if any.
46844 @node Target Description Format
46845 @section Target Description Format
46846 @cindex target descriptions, XML format
46848 A target description annex is an @uref{http://www.w3.org/XML/, XML}
46849 document which complies with the Document Type Definition provided in
46850 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
46851 means you can use generally available tools like @command{xmllint} to
46852 check that your feature descriptions are well-formed and valid.
46853 However, to help people unfamiliar with XML write descriptions for
46854 their targets, we also describe the grammar here.
46856 Target descriptions can identify the architecture of the remote target
46857 and (for some architectures) provide information about custom register
46858 sets. They can also identify the OS ABI of the remote target.
46859 @value{GDBN} can use this information to autoconfigure for your
46860 target, or to warn you if you connect to an unsupported target.
46862 Here is a simple target description:
46865 <target version="1.0">
46866 <architecture>i386:x86-64</architecture>
46871 This minimal description only says that the target uses
46872 the x86-64 architecture.
46874 A target description has the following overall form, with [ ] marking
46875 optional elements and @dots{} marking repeatable elements. The elements
46876 are explained further below.
46879 <?xml version="1.0"?>
46880 <!DOCTYPE target SYSTEM "gdb-target.dtd">
46881 <target version="1.0">
46882 @r{[}@var{architecture}@r{]}
46883 @r{[}@var{osabi}@r{]}
46884 @r{[}@var{compatible}@r{]}
46885 @r{[}@var{feature}@dots{}@r{]}
46890 The description is generally insensitive to whitespace and line
46891 breaks, under the usual common-sense rules. The XML version
46892 declaration and document type declaration can generally be omitted
46893 (@value{GDBN} does not require them), but specifying them may be
46894 useful for XML validation tools. The @samp{version} attribute for
46895 @samp{<target>} may also be omitted, but we recommend
46896 including it; if future versions of @value{GDBN} use an incompatible
46897 revision of @file{gdb-target.dtd}, they will detect and report
46898 the version mismatch.
46900 @subsection Inclusion
46901 @cindex target descriptions, inclusion
46904 @cindex <xi:include>
46907 It can sometimes be valuable to split a target description up into
46908 several different annexes, either for organizational purposes, or to
46909 share files between different possible target descriptions. You can
46910 divide a description into multiple files by replacing any element of
46911 the target description with an inclusion directive of the form:
46914 <xi:include href="@var{document}"/>
46918 When @value{GDBN} encounters an element of this form, it will retrieve
46919 the named XML @var{document}, and replace the inclusion directive with
46920 the contents of that document. If the current description was read
46921 using @samp{qXfer}, then so will be the included document;
46922 @var{document} will be interpreted as the name of an annex. If the
46923 current description was read from a file, @value{GDBN} will look for
46924 @var{document} as a file in the same directory where it found the
46925 original description.
46927 @subsection Architecture
46928 @cindex <architecture>
46930 An @samp{<architecture>} element has this form:
46933 <architecture>@var{arch}</architecture>
46936 @var{arch} is one of the architectures from the set accepted by
46937 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46940 @cindex @code{<osabi>}
46942 This optional field was introduced in @value{GDBN} version 7.0.
46943 Previous versions of @value{GDBN} ignore it.
46945 An @samp{<osabi>} element has this form:
46948 <osabi>@var{abi-name}</osabi>
46951 @var{abi-name} is an OS ABI name from the same selection accepted by
46952 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
46954 @subsection Compatible Architecture
46955 @cindex @code{<compatible>}
46957 This optional field was introduced in @value{GDBN} version 7.0.
46958 Previous versions of @value{GDBN} ignore it.
46960 A @samp{<compatible>} element has this form:
46963 <compatible>@var{arch}</compatible>
46966 @var{arch} is one of the architectures from the set accepted by
46967 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46969 A @samp{<compatible>} element is used to specify that the target
46970 is able to run binaries in some other than the main target architecture
46971 given by the @samp{<architecture>} element. For example, on the
46972 Cell Broadband Engine, the main architecture is @code{powerpc:common}
46973 or @code{powerpc:common64}, but the system is able to run binaries
46974 in the @code{spu} architecture as well. The way to describe this
46975 capability with @samp{<compatible>} is as follows:
46978 <architecture>powerpc:common</architecture>
46979 <compatible>spu</compatible>
46982 @subsection Features
46985 Each @samp{<feature>} describes some logical portion of the target
46986 system. Features are currently used to describe available CPU
46987 registers and the types of their contents. A @samp{<feature>} element
46991 <feature name="@var{name}">
46992 @r{[}@var{type}@dots{}@r{]}
46998 Each feature's name should be unique within the description. The name
46999 of a feature does not matter unless @value{GDBN} has some special
47000 knowledge of the contents of that feature; if it does, the feature
47001 should have its standard name. @xref{Standard Target Features}.
47005 Any register's value is a collection of bits which @value{GDBN} must
47006 interpret. The default interpretation is a two's complement integer,
47007 but other types can be requested by name in the register description.
47008 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
47009 Target Types}), and the description can define additional composite
47012 Each type element must have an @samp{id} attribute, which gives
47013 a unique (within the containing @samp{<feature>}) name to the type.
47014 Types must be defined before they are used.
47017 Some targets offer vector registers, which can be treated as arrays
47018 of scalar elements. These types are written as @samp{<vector>} elements,
47019 specifying the array element type, @var{type}, and the number of elements,
47023 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
47027 If a register's value is usefully viewed in multiple ways, define it
47028 with a union type containing the useful representations. The
47029 @samp{<union>} element contains one or more @samp{<field>} elements,
47030 each of which has a @var{name} and a @var{type}:
47033 <union id="@var{id}">
47034 <field name="@var{name}" type="@var{type}"/>
47041 If a register's value is composed from several separate values, define
47042 it with either a structure type or a flags type.
47043 A flags type may only contain bitfields.
47044 A structure type may either contain only bitfields or contain no bitfields.
47045 If the value contains only bitfields, its total size in bytes must be
47048 Non-bitfield values have a @var{name} and @var{type}.
47051 <struct id="@var{id}">
47052 <field name="@var{name}" type="@var{type}"/>
47057 Both @var{name} and @var{type} values are required.
47058 No implicit padding is added.
47060 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
47063 <struct id="@var{id}" size="@var{size}">
47064 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
47070 <flags id="@var{id}" size="@var{size}">
47071 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
47076 The @var{name} value is required.
47077 Bitfield values may be named with the empty string, @samp{""},
47078 in which case the field is ``filler'' and its value is not printed.
47079 Not all bits need to be specified, so ``filler'' fields are optional.
47081 The @var{start} and @var{end} values are required, and @var{type}
47083 The field's @var{start} must be less than or equal to its @var{end},
47084 and zero represents the least significant bit.
47086 The default value of @var{type} is @code{bool} for single bit fields,
47087 and an unsigned integer otherwise.
47089 Which to choose? Structures or flags?
47091 Registers defined with @samp{flags} have these advantages over
47092 defining them with @samp{struct}:
47096 Arithmetic may be performed on them as if they were integers.
47098 They are printed in a more readable fashion.
47101 Registers defined with @samp{struct} have one advantage over
47102 defining them with @samp{flags}:
47106 One can fetch individual fields like in @samp{C}.
47109 (@value{GDBP}) print $my_struct_reg.field3
47115 @subsection Registers
47118 Each register is represented as an element with this form:
47121 <reg name="@var{name}"
47122 bitsize="@var{size}"
47123 @r{[}regnum="@var{num}"@r{]}
47124 @r{[}save-restore="@var{save-restore}"@r{]}
47125 @r{[}type="@var{type}"@r{]}
47126 @r{[}group="@var{group}"@r{]}/>
47130 The components are as follows:
47135 The register's name; it must be unique within the target description.
47138 The register's size, in bits.
47141 The register's number. If omitted, a register's number is one greater
47142 than that of the previous register (either in the current feature or in
47143 a preceding feature); the first register in the target description
47144 defaults to zero. This register number is used to read or write
47145 the register; e.g.@: it is used in the remote @code{p} and @code{P}
47146 packets, and registers appear in the @code{g} and @code{G} packets
47147 in order of increasing register number.
47150 Whether the register should be preserved across inferior function
47151 calls; this must be either @code{yes} or @code{no}. The default is
47152 @code{yes}, which is appropriate for most registers except for
47153 some system control registers; this is not related to the target's
47157 The type of the register. It may be a predefined type, a type
47158 defined in the current feature, or one of the special types @code{int}
47159 and @code{float}. @code{int} is an integer type of the correct size
47160 for @var{bitsize}, and @code{float} is a floating point type (in the
47161 architecture's normal floating point format) of the correct size for
47162 @var{bitsize}. The default is @code{int}.
47165 The register group to which this register belongs. It can be one of the
47166 standard register groups @code{general}, @code{float}, @code{vector} or an
47167 arbitrary string. Group names should be limited to alphanumeric characters.
47168 If a group name is made up of multiple words the words may be separated by
47169 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
47170 @var{group} is specified, @value{GDBN} will not display the register in
47171 @code{info registers}.
47175 @node Predefined Target Types
47176 @section Predefined Target Types
47177 @cindex target descriptions, predefined types
47179 Type definitions in the self-description can build up composite types
47180 from basic building blocks, but can not define fundamental types. Instead,
47181 standard identifiers are provided by @value{GDBN} for the fundamental
47182 types. The currently supported types are:
47187 Boolean type, occupying a single bit.
47195 Signed integer types holding the specified number of bits.
47203 Unsigned integer types holding the specified number of bits.
47207 Pointers to unspecified code and data. The program counter and
47208 any dedicated return address register may be marked as code
47209 pointers; printing a code pointer converts it into a symbolic
47210 address. The stack pointer and any dedicated address registers
47211 may be marked as data pointers.
47214 Half precision IEEE floating point.
47217 Single precision IEEE floating point.
47220 Double precision IEEE floating point.
47223 The 16-bit @dfn{brain floating point} format used e.g.@: by x86 and ARM.
47226 The 12-byte extended precision format used by ARM FPA registers.
47229 The 10-byte extended precision format used by x87 registers.
47232 32bit @sc{eflags} register used by x86.
47235 32bit @sc{mxcsr} register used by x86.
47239 @node Enum Target Types
47240 @section Enum Target Types
47241 @cindex target descriptions, enum types
47243 Enum target types are useful in @samp{struct} and @samp{flags}
47244 register descriptions. @xref{Target Description Format}.
47246 Enum types have a name, size and a list of name/value pairs.
47249 <enum id="@var{id}" size="@var{size}">
47250 <evalue name="@var{name}" value="@var{value}"/>
47255 Enums must be defined before they are used.
47258 <enum id="levels_type" size="4">
47259 <evalue name="low" value="0"/>
47260 <evalue name="high" value="1"/>
47262 <flags id="flags_type" size="4">
47263 <field name="X" start="0"/>
47264 <field name="LEVEL" start="1" end="1" type="levels_type"/>
47266 <reg name="flags" bitsize="32" type="flags_type"/>
47269 Given that description, a value of 3 for the @samp{flags} register
47270 would be printed as:
47273 (@value{GDBP}) info register flags
47274 flags 0x3 [ X LEVEL=high ]
47277 @node Standard Target Features
47278 @section Standard Target Features
47279 @cindex target descriptions, standard features
47281 A target description must contain either no registers or all the
47282 target's registers. If the description contains no registers, then
47283 @value{GDBN} will assume a default register layout, selected based on
47284 the architecture. If the description contains any registers, the
47285 default layout will not be used; the standard registers must be
47286 described in the target description, in such a way that @value{GDBN}
47287 can recognize them.
47289 This is accomplished by giving specific names to feature elements
47290 which contain standard registers. @value{GDBN} will look for features
47291 with those names and verify that they contain the expected registers;
47292 if any known feature is missing required registers, or if any required
47293 feature is missing, @value{GDBN} will reject the target
47294 description. You can add additional registers to any of the
47295 standard features --- @value{GDBN} will display them just as if
47296 they were added to an unrecognized feature.
47298 This section lists the known features and their expected contents.
47299 Sample XML documents for these features are included in the
47300 @value{GDBN} source tree, in the directory @file{gdb/features}.
47302 Names recognized by @value{GDBN} should include the name of the
47303 company or organization which selected the name, and the overall
47304 architecture to which the feature applies; so e.g.@: the feature
47305 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
47307 The names of registers are not case sensitive for the purpose
47308 of recognizing standard features, but @value{GDBN} will only display
47309 registers using the capitalization used in the description.
47312 * AArch64 Features::
47316 * LoongArch Features::
47317 * MicroBlaze Features::
47321 * Nios II Features::
47322 * OpenRISC 1000 Features::
47323 * PowerPC Features::
47324 * RISC-V Features::
47326 * S/390 and System z Features::
47332 @node AArch64 Features
47333 @subsection AArch64 Features
47334 @cindex target descriptions, AArch64 features
47336 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
47337 targets. It should contain registers @samp{x0} through @samp{x30},
47338 @samp{sp}, @samp{pc}, and @samp{cpsr}.
47340 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
47341 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
47344 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
47345 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
47346 through @samp{p15}, @samp{ffr} and @samp{vg}.
47348 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
47349 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
47352 @subsection ARC Features
47353 @cindex target descriptions, ARC Features
47355 ARC processors are so configurable that even core registers and their numbers
47356 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
47357 registers, which are important to @value{GDBN}, are not ``core'' registers in
47358 ARC. Therefore, there are two features that their presence is mandatory:
47359 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
47361 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
47366 @samp{r0} through @samp{r25} for normal register file targets.
47368 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
47369 register file targets.
47371 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
47372 @samp{blink}, @samp{lp_count}, @samp{pcl}.
47375 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
47376 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
47377 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
47378 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
47379 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
47380 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
47381 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
47382 because of their inaccessibility during user space debugging sessions.
47384 Extension core registers @samp{r32} through @samp{r59} are optional and their
47385 existence depends on the configuration. When debugging GNU/Linux applications,
47386 i.e.@: user space debugging, these core registers are not available.
47388 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
47389 is the list of registers pertinent to this feature:
47393 mandatory: @samp{pc} and @samp{status32}.
47395 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
47399 @subsection ARM Features
47400 @cindex target descriptions, ARM features
47402 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
47404 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
47405 @samp{lr}, @samp{pc}, and @samp{cpsr}.
47407 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
47408 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
47409 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
47412 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
47413 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
47415 The @samp{org.gnu.gdb.arm.m-profile-mve} feature is optional. If present, it
47416 must contain register @samp{vpr}.
47418 If the @samp{org.gnu.gdb.arm.m-profile-mve} feature is available, @value{GDBN}
47419 will synthesize the @samp{p0} pseudo register from @samp{vpr} contents.
47421 If the @samp{org.gnu.gdb.arm.vfp} feature is available alongside the
47422 @samp{org.gnu.gdb.arm.m-profile-mve} feature, @value{GDBN} will
47423 synthesize the @samp{q} pseudo registers from @samp{d} register
47426 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
47427 it should contain at least registers @samp{wR0} through @samp{wR15} and
47428 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
47429 @samp{wCSSF}, and @samp{wCASF} registers are optional.
47431 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
47432 should contain at least registers @samp{d0} through @samp{d15}. If
47433 they are present, @samp{d16} through @samp{d31} should also be included.
47434 @value{GDBN} will synthesize the single-precision registers from
47435 halves of the double-precision registers.
47437 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
47438 need to contain registers; it instructs @value{GDBN} to display the
47439 VFP double-precision registers as vectors and to synthesize the
47440 quad-precision registers from pairs of double-precision registers.
47441 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
47442 be present and include 32 double-precision registers.
47444 The @samp{org.gnu.gdb.arm.m-profile-pacbti} feature is optional, and
47445 acknowledges support for the ARMv8.1-m PACBTI extensions. @value{GDBN}
47446 will track return address signing states and will decorate backtraces using
47447 the [PAC] marker, similar to AArch64's PAC extension.
47448 @xref{AArch64 PAC}.
47450 @node i386 Features
47451 @subsection i386 Features
47452 @cindex target descriptions, i386 features
47454 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
47455 targets. It should describe the following registers:
47459 @samp{eax} through @samp{edi} plus @samp{eip} for i386
47461 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
47463 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
47464 @samp{fs}, @samp{gs}
47466 @samp{st0} through @samp{st7}
47468 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
47469 @samp{foseg}, @samp{fooff} and @samp{fop}
47472 The register sets may be different, depending on the target.
47474 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
47475 describe registers:
47479 @samp{xmm0} through @samp{xmm7} for i386
47481 @samp{xmm0} through @samp{xmm15} for amd64
47486 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
47487 @samp{org.gnu.gdb.i386.sse} feature. It should
47488 describe the upper 128 bits of @sc{ymm} registers:
47492 @samp{ymm0h} through @samp{ymm7h} for i386
47494 @samp{ymm0h} through @samp{ymm15h} for amd64
47497 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
47498 Memory Protection Extension (MPX). It should describe the following registers:
47502 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
47504 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
47507 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
47508 describe a single register, @samp{orig_eax}.
47510 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
47511 describe two system registers: @samp{fs_base} and @samp{gs_base}.
47513 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
47514 @samp{org.gnu.gdb.i386.avx} feature. It should
47515 describe additional @sc{xmm} registers:
47519 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
47522 It should describe the upper 128 bits of additional @sc{ymm} registers:
47526 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
47530 describe the upper 256 bits of @sc{zmm} registers:
47534 @samp{zmm0h} through @samp{zmm7h} for i386.
47536 @samp{zmm0h} through @samp{zmm15h} for amd64.
47540 describe the additional @sc{zmm} registers:
47544 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
47547 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
47548 describe a single register, @samp{pkru}. It is a 32-bit register
47549 valid for i386 and amd64.
47551 @node LoongArch Features
47552 @subsection LoongArch Features
47553 @cindex target descriptions, LoongArch Features
47555 The @samp{org.gnu.gdb.loongarch.base} feature is required for LoongArch
47556 targets. It should contain the registers @samp{r0} through @samp{r31},
47557 @samp{pc}, and @samp{badv}. Either the architectural names (@samp{r0},
47558 @samp{r1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra}, etc).
47560 The @samp{org.gnu.gdb.loongarch.fpu} feature is optional. If present,
47561 it should contain registers @samp{f0} through @samp{f31}, @samp{fcc},
47564 @node MicroBlaze Features
47565 @subsection MicroBlaze Features
47566 @cindex target descriptions, MicroBlaze features
47568 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
47569 targets. It should contain registers @samp{r0} through @samp{r31},
47570 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
47571 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
47572 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
47574 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
47575 If present, it should contain registers @samp{rshr} and @samp{rslr}
47577 @node MIPS Features
47578 @subsection @acronym{MIPS} Features
47579 @cindex target descriptions, @acronym{MIPS} features
47581 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
47582 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
47583 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
47586 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
47587 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
47588 registers. They may be 32-bit or 64-bit depending on the target.
47590 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
47591 it may be optional in a future version of @value{GDBN}. It should
47592 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
47593 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
47595 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
47596 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
47597 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
47598 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
47600 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
47601 contain a single register, @samp{restart}, which is used by the
47602 Linux kernel to control restartable syscalls.
47604 @node M68K Features
47605 @subsection M68K Features
47606 @cindex target descriptions, M68K features
47609 @item @samp{org.gnu.gdb.m68k.core}
47610 @itemx @samp{org.gnu.gdb.coldfire.core}
47611 @itemx @samp{org.gnu.gdb.fido.core}
47612 One of those features must be always present.
47613 The feature that is present determines which flavor of m68k is
47614 used. The feature that is present should contain registers
47615 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
47616 @samp{sp}, @samp{ps} and @samp{pc}.
47618 @item @samp{org.gnu.gdb.coldfire.fp}
47619 This feature is optional. If present, it should contain registers
47620 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
47623 Note that, despite the fact that this feature's name says
47624 @samp{coldfire}, it is used to describe any floating point registers.
47625 The size of the registers must match the main m68k flavor; so, for
47626 example, if the primary feature is reported as @samp{coldfire}, then
47627 64-bit floating point registers are required.
47630 @node NDS32 Features
47631 @subsection NDS32 Features
47632 @cindex target descriptions, NDS32 features
47634 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
47635 targets. It should contain at least registers @samp{r0} through
47636 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
47639 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
47640 it should contain 64-bit double-precision floating-point registers
47641 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
47642 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
47644 @emph{Note:} The first sixteen 64-bit double-precision floating-point
47645 registers are overlapped with the thirty-two 32-bit single-precision
47646 floating-point registers. The 32-bit single-precision registers, if
47647 not being listed explicitly, will be synthesized from halves of the
47648 overlapping 64-bit double-precision registers. Listing 32-bit
47649 single-precision registers explicitly is deprecated, and the
47650 support to it could be totally removed some day.
47652 @node Nios II Features
47653 @subsection Nios II Features
47654 @cindex target descriptions, Nios II features
47656 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
47657 targets. It should contain the 32 core registers (@samp{zero},
47658 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
47659 @samp{pc}, and the 16 control registers (@samp{status} through
47662 @node OpenRISC 1000 Features
47663 @subsection Openrisc 1000 Features
47664 @cindex target descriptions, OpenRISC 1000 features
47666 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
47667 targets. It should contain the 32 general purpose registers (@samp{r0}
47668 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
47670 @node PowerPC Features
47671 @subsection PowerPC Features
47672 @cindex target descriptions, PowerPC features
47674 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
47675 targets. It should contain registers @samp{r0} through @samp{r31},
47676 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
47677 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
47679 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
47680 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
47682 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
47683 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
47684 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
47685 through @samp{v31} as aliases for the corresponding @samp{vrX}
47688 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
47689 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
47690 combine these registers with the floating point registers (@samp{f0}
47691 through @samp{f31}) and the altivec registers (@samp{vr0} through
47692 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
47693 @samp{vs63}, the set of vector-scalar registers for POWER7.
47694 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
47695 @samp{org.gnu.gdb.power.altivec}.
47697 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
47698 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
47699 @samp{spefscr}. SPE targets should provide 32-bit registers in
47700 @samp{org.gnu.gdb.power.core} and provide the upper halves in
47701 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
47702 these to present registers @samp{ev0} through @samp{ev31} to the
47705 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
47706 contain the 64-bit register @samp{ppr}.
47708 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
47709 contain the 64-bit register @samp{dscr}.
47711 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
47712 contain the 64-bit register @samp{tar}.
47714 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
47715 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
47718 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
47719 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
47720 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
47721 server PMU registers provided by @sc{gnu}/Linux.
47723 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
47724 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
47727 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
47728 contain the checkpointed general-purpose registers @samp{cr0} through
47729 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
47730 @samp{cctr}. These registers may all be either 32-bit or 64-bit
47731 depending on the target. It should also contain the checkpointed
47732 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
47735 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
47736 contain the checkpointed 64-bit floating-point registers @samp{cf0}
47737 through @samp{cf31}, as well as the checkpointed 64-bit register
47740 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
47741 should contain the checkpointed altivec registers @samp{cvr0} through
47742 @samp{cvr31}, all 128-bit wide. It should also contain the
47743 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
47746 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
47747 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
47748 will combine these registers with the checkpointed floating point
47749 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
47750 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
47751 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
47752 @samp{cvs63}. Therefore, this feature requires both
47753 @samp{org.gnu.gdb.power.htm.altivec} and
47754 @samp{org.gnu.gdb.power.htm.fpu}.
47756 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
47757 contain the 64-bit checkpointed register @samp{cppr}.
47759 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
47760 contain the 64-bit checkpointed register @samp{cdscr}.
47762 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
47763 contain the 64-bit checkpointed register @samp{ctar}.
47766 @node RISC-V Features
47767 @subsection RISC-V Features
47768 @cindex target descriptions, RISC-V Features
47770 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
47771 targets. It should contain the registers @samp{x0} through
47772 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
47773 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
47776 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
47777 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
47778 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
47779 architectural register names, or the ABI names can be used.
47781 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
47782 it should contain registers that are not backed by real registers on
47783 the target, but are instead virtual, where the register value is
47784 derived from other target state. In many ways these are like
47785 @value{GDBN}s pseudo-registers, except implemented by the target.
47786 Currently the only register expected in this set is the one byte
47787 @samp{priv} register that contains the target's privilege level in the
47788 least significant two bits.
47790 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
47791 should contain all of the target's standard CSRs. Standard CSRs are
47792 those defined in the RISC-V specification documents. There is some
47793 overlap between this feature and the fpu feature; the @samp{fflags},
47794 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
47795 expectation is that these registers will be in the fpu feature if the
47796 target has floating point hardware, but can be moved into the csr
47797 feature if the target has the floating point control registers, but no
47798 other floating point hardware.
47800 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
47801 it should contain registers @samp{v0} through @samp{v31}, all of which
47802 must be the same size. These requirements are based on the v0.10
47803 draft vector extension, as the vector extension is not yet final. In
47804 the event that the register set of the vector extension changes for
47805 the final specification, the requirements given here could change for
47806 future releases of @value{GDBN}.
47809 @subsection RX Features
47810 @cindex target descriptions, RX Features
47812 The @samp{org.gnu.gdb.rx.core} feature is required for RX
47813 targets. It should contain the registers @samp{r0} through
47814 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
47815 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
47817 @node S/390 and System z Features
47818 @subsection S/390 and System z Features
47819 @cindex target descriptions, S/390 features
47820 @cindex target descriptions, System z features
47822 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
47823 System z targets. It should contain the PSW and the 16 general
47824 registers. In particular, System z targets should provide the 64-bit
47825 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
47826 S/390 targets should provide the 32-bit versions of these registers.
47827 A System z target that runs in 31-bit addressing mode should provide
47828 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
47829 register's upper halves @samp{r0h} through @samp{r15h}, and their
47830 lower halves @samp{r0l} through @samp{r15l}.
47832 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
47833 contain the 64-bit registers @samp{f0} through @samp{f15}, and
47836 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
47837 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
47839 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
47840 contain the register @samp{orig_r2}, which is 64-bit wide on System z
47841 targets and 32-bit otherwise. In addition, the feature may contain
47842 the @samp{last_break} register, whose width depends on the addressing
47843 mode, as well as the @samp{system_call} register, which is always
47846 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
47847 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
47848 @samp{atia}, and @samp{tr0} through @samp{tr15}.
47850 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
47851 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
47852 combined by @value{GDBN} with the floating point registers @samp{f0}
47853 through @samp{f15} to present the 128-bit wide vector registers
47854 @samp{v0} through @samp{v15}. In addition, this feature should
47855 contain the 128-bit wide vector registers @samp{v16} through
47858 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
47859 the 64-bit wide guarded-storage-control registers @samp{gsd},
47860 @samp{gssm}, and @samp{gsepla}.
47862 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
47863 the 64-bit wide guarded-storage broadcast control registers
47864 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
47866 @node Sparc Features
47867 @subsection Sparc Features
47868 @cindex target descriptions, sparc32 features
47869 @cindex target descriptions, sparc64 features
47870 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
47871 targets. It should describe the following registers:
47875 @samp{g0} through @samp{g7}
47877 @samp{o0} through @samp{o7}
47879 @samp{l0} through @samp{l7}
47881 @samp{i0} through @samp{i7}
47884 They may be 32-bit or 64-bit depending on the target.
47886 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
47887 targets. It should describe the following registers:
47891 @samp{f0} through @samp{f31}
47893 @samp{f32} through @samp{f62} for sparc64
47896 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
47897 targets. It should describe the following registers:
47901 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
47902 @samp{fsr}, and @samp{csr} for sparc32
47904 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
47908 @node TIC6x Features
47909 @subsection TMS320C6x Features
47910 @cindex target descriptions, TIC6x features
47911 @cindex target descriptions, TMS320C6x features
47912 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
47913 targets. It should contain registers @samp{A0} through @samp{A15},
47914 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
47916 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
47917 contain registers @samp{A16} through @samp{A31} and @samp{B16}
47918 through @samp{B31}.
47920 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
47921 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
47923 @node Operating System Information
47924 @appendix Operating System Information
47925 @cindex operating system information
47927 Users of @value{GDBN} often wish to obtain information about the state of
47928 the operating system running on the target---for example the list of
47929 processes, or the list of open files. This section describes the
47930 mechanism that makes it possible. This mechanism is similar to the
47931 target features mechanism (@pxref{Target Descriptions}), but focuses
47932 on a different aspect of target.
47934 Operating system information is retrieved from the target via the
47935 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
47936 read}). The object name in the request should be @samp{osdata}, and
47937 the @var{annex} identifies the data to be fetched.
47944 @appendixsection Process list
47945 @cindex operating system information, process list
47947 When requesting the process list, the @var{annex} field in the
47948 @samp{qXfer} request should be @samp{processes}. The returned data is
47949 an XML document. The formal syntax of this document is defined in
47950 @file{gdb/features/osdata.dtd}.
47952 An example document is:
47955 <?xml version="1.0"?>
47956 <!DOCTYPE target SYSTEM "osdata.dtd">
47957 <osdata type="processes">
47959 <column name="pid">1</column>
47960 <column name="user">root</column>
47961 <column name="command">/sbin/init</column>
47962 <column name="cores">1,2,3</column>
47967 Each item should include a column whose name is @samp{pid}. The value
47968 of that column should identify the process on the target. The
47969 @samp{user} and @samp{command} columns are optional, and will be
47970 displayed by @value{GDBN}. The @samp{cores} column, if present,
47971 should contain a comma-separated list of cores that this process
47972 is running on. Target may provide additional columns,
47973 which @value{GDBN} currently ignores.
47975 @node Trace File Format
47976 @appendix Trace File Format
47977 @cindex trace file format
47979 The trace file comes in three parts: a header, a textual description
47980 section, and a trace frame section with binary data.
47982 The header has the form @code{\x7fTRACE0\n}. The first byte is
47983 @code{0x7f} so as to indicate that the file contains binary data,
47984 while the @code{0} is a version number that may have different values
47987 The description section consists of multiple lines of @sc{ascii} text
47988 separated by newline characters (@code{0xa}). The lines may include a
47989 variety of optional descriptive or context-setting information, such
47990 as tracepoint definitions or register set size. @value{GDBN} will
47991 ignore any line that it does not recognize. An empty line marks the end
47996 Specifies the size of a register block in bytes. This is equal to the
47997 size of a @code{g} packet payload in the remote protocol. @var{size}
47998 is an ascii decimal number. There should be only one such line in
47999 a single trace file.
48001 @item status @var{status}
48002 Trace status. @var{status} has the same format as a @code{qTStatus}
48003 remote packet reply. There should be only one such line in a single trace
48006 @item tp @var{payload}
48007 Tracepoint definition. The @var{payload} has the same format as
48008 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
48009 may take multiple lines of definition, corresponding to the multiple
48012 @item tsv @var{payload}
48013 Trace state variable definition. The @var{payload} has the same format as
48014 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
48015 may take multiple lines of definition, corresponding to the multiple
48018 @item tdesc @var{payload}
48019 Target description in XML format. The @var{payload} is a single line of
48020 the XML file. All such lines should be concatenated together to get
48021 the original XML file. This file is in the same format as @code{qXfer}
48022 @code{features} payload, and corresponds to the main @code{target.xml}
48023 file. Includes are not allowed.
48027 The trace frame section consists of a number of consecutive frames.
48028 Each frame begins with a two-byte tracepoint number, followed by a
48029 four-byte size giving the amount of data in the frame. The data in
48030 the frame consists of a number of blocks, each introduced by a
48031 character indicating its type (at least register, memory, and trace
48032 state variable). The data in this section is raw binary, not a
48033 hexadecimal or other encoding; its endianness matches the target's
48036 @c FIXME bi-arch may require endianness/arch info in description section
48039 @item R @var{bytes}
48040 Register block. The number and ordering of bytes matches that of a
48041 @code{g} packet in the remote protocol. Note that these are the
48042 actual bytes, in target order, not a hexadecimal encoding.
48044 @item M @var{address} @var{length} @var{bytes}...
48045 Memory block. This is a contiguous block of memory, at the 8-byte
48046 address @var{address}, with a 2-byte length @var{length}, followed by
48047 @var{length} bytes.
48049 @item V @var{number} @var{value}
48050 Trace state variable block. This records the 8-byte signed value
48051 @var{value} of trace state variable numbered @var{number}.
48055 Future enhancements of the trace file format may include additional types
48058 @node Index Section Format
48059 @appendix @code{.gdb_index} section format
48060 @cindex .gdb_index section format
48061 @cindex index section format
48063 This section documents the index section that is created by @code{save
48064 gdb-index} (@pxref{Index Files}). The index section is
48065 DWARF-specific; some knowledge of DWARF is assumed in this
48068 The mapped index file format is designed to be directly
48069 @code{mmap}able on any architecture. In most cases, a datum is
48070 represented using a little-endian 32-bit integer value, called an
48071 @code{offset_type}. Big endian machines must byte-swap the values
48072 before using them. Exceptions to this rule are noted. The data is
48073 laid out such that alignment is always respected.
48075 A mapped index consists of several areas, laid out in order.
48079 The file header. This is a sequence of values, of @code{offset_type}
48080 unless otherwise noted:
48084 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
48085 Version 4 uses a different hashing function from versions 5 and 6.
48086 Version 6 includes symbols for inlined functions, whereas versions 4
48087 and 5 do not. Version 7 adds attributes to the CU indices in the
48088 symbol table. Version 8 specifies that symbols from DWARF type units
48089 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
48090 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
48092 @value{GDBN} will only read version 4, 5, or 6 indices
48093 by specifying @code{set use-deprecated-index-sections on}.
48094 GDB has a workaround for potentially broken version 7 indices so it is
48095 currently not flagged as deprecated.
48098 The offset, from the start of the file, of the CU list.
48101 The offset, from the start of the file, of the types CU list. Note
48102 that this area can be empty, in which case this offset will be equal
48103 to the next offset.
48106 The offset, from the start of the file, of the address area.
48109 The offset, from the start of the file, of the symbol table.
48112 The offset, from the start of the file, of the constant pool.
48116 The CU list. This is a sequence of pairs of 64-bit little-endian
48117 values, sorted by the CU offset. The first element in each pair is
48118 the offset of a CU in the @code{.debug_info} section. The second
48119 element in each pair is the length of that CU. References to a CU
48120 elsewhere in the map are done using a CU index, which is just the
48121 0-based index into this table. Note that if there are type CUs, then
48122 conceptually CUs and type CUs form a single list for the purposes of
48126 The types CU list. This is a sequence of triplets of 64-bit
48127 little-endian values. In a triplet, the first value is the CU offset,
48128 the second value is the type offset in the CU, and the third value is
48129 the type signature. The types CU list is not sorted.
48132 The address area. The address area consists of a sequence of address
48133 entries. Each address entry has three elements:
48137 The low address. This is a 64-bit little-endian value.
48140 The high address. This is a 64-bit little-endian value. Like
48141 @code{DW_AT_high_pc}, the value is one byte beyond the end.
48144 The CU index. This is an @code{offset_type} value.
48148 The symbol table. This is an open-addressed hash table. The size of
48149 the hash table is always a power of 2.
48151 Each slot in the hash table consists of a pair of @code{offset_type}
48152 values. The first value is the offset of the symbol's name in the
48153 constant pool. The second value is the offset of the CU vector in the
48156 If both values are 0, then this slot in the hash table is empty. This
48157 is ok because while 0 is a valid constant pool index, it cannot be a
48158 valid index for both a string and a CU vector.
48160 The hash value for a table entry is computed by applying an
48161 iterative hash function to the symbol's name. Starting with an
48162 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
48163 the string is incorporated into the hash using the formula depending on the
48168 The formula is @code{r = r * 67 + c - 113}.
48170 @item Versions 5 to 7
48171 The formula is @code{r = r * 67 + tolower (c) - 113}.
48174 The terminating @samp{\0} is not incorporated into the hash.
48176 The step size used in the hash table is computed via
48177 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
48178 value, and @samp{size} is the size of the hash table. The step size
48179 is used to find the next candidate slot when handling a hash
48182 The names of C@t{++} symbols in the hash table are canonicalized. We
48183 don't currently have a simple description of the canonicalization
48184 algorithm; if you intend to create new index sections, you must read
48188 The constant pool. This is simply a bunch of bytes. It is organized
48189 so that alignment is correct: CU vectors are stored first, followed by
48192 A CU vector in the constant pool is a sequence of @code{offset_type}
48193 values. The first value is the number of CU indices in the vector.
48194 Each subsequent value is the index and symbol attributes of a CU in
48195 the CU list. This element in the hash table is used to indicate which
48196 CUs define the symbol and how the symbol is used.
48197 See below for the format of each CU index+attributes entry.
48199 A string in the constant pool is zero-terminated.
48202 Attributes were added to CU index values in @code{.gdb_index} version 7.
48203 If a symbol has multiple uses within a CU then there is one
48204 CU index+attributes value for each use.
48206 The format of each CU index+attributes entry is as follows
48212 This is the index of the CU in the CU list.
48214 These bits are reserved for future purposes and must be zero.
48216 The kind of the symbol in the CU.
48220 This value is reserved and should not be used.
48221 By reserving zero the full @code{offset_type} value is backwards compatible
48222 with previous versions of the index.
48224 The symbol is a type.
48226 The symbol is a variable or an enum value.
48228 The symbol is a function.
48230 Any other kind of symbol.
48232 These values are reserved.
48236 This bit is zero if the value is global and one if it is static.
48238 The determination of whether a symbol is global or static is complicated.
48239 The authorative reference is the file @file{dwarf2read.c} in
48240 @value{GDBN} sources.
48244 This pseudo-code describes the computation of a symbol's kind and
48245 global/static attributes in the index.
48248 is_external = get_attribute (die, DW_AT_external);
48249 language = get_attribute (cu_die, DW_AT_language);
48252 case DW_TAG_typedef:
48253 case DW_TAG_base_type:
48254 case DW_TAG_subrange_type:
48258 case DW_TAG_enumerator:
48260 is_static = language != CPLUS;
48262 case DW_TAG_subprogram:
48264 is_static = ! (is_external || language == ADA);
48266 case DW_TAG_constant:
48268 is_static = ! is_external;
48270 case DW_TAG_variable:
48272 is_static = ! is_external;
48274 case DW_TAG_namespace:
48278 case DW_TAG_class_type:
48279 case DW_TAG_interface_type:
48280 case DW_TAG_structure_type:
48281 case DW_TAG_union_type:
48282 case DW_TAG_enumeration_type:
48284 is_static = language != CPLUS;
48292 @appendix Download debugging resources with Debuginfod
48295 @code{debuginfod} is an HTTP server for distributing ELF, DWARF and source
48298 With the @code{debuginfod} client library, @file{libdebuginfod}, @value{GDBN}
48299 can query servers using the build IDs associated with missing debug info,
48300 executables and source files in order to download them on demand.
48302 For instructions on building @value{GDBN} with @file{libdebuginfod},
48303 @pxref{Configure Options,,--with-debuginfod}. @code{debuginfod} is packaged
48304 with @code{elfutils}, starting with version 0.178. See
48305 @uref{https://sourceware.org/elfutils/Debuginfod.html} for more information
48306 regarding @code{debuginfod}.
48309 * Debuginfod Settings:: Configuring debuginfod with @value{GDBN}
48312 @node Debuginfod Settings
48313 @section Debuginfod Settings
48315 @value{GDBN} provides the following commands for configuring @code{debuginfod}.
48318 @kindex set debuginfod enabled
48319 @anchor{set debuginfod enabled}
48320 @item set debuginfod enabled
48321 @itemx set debuginfod enabled on
48322 @cindex enable debuginfod
48323 @value{GDBN} will attempt to query @code{debuginfod} servers when missing debug
48324 info or source files.
48326 @item set debuginfod enabled off
48327 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
48328 debug info or source files. By default, @code{debuginfod enabled} is set to
48329 @code{off} for non-interactive sessions.
48331 @item set debuginfod enabled ask
48332 @value{GDBN} will prompt the user to enable or disable @code{debuginfod} before
48333 attempting to perform the next query. By default, @code{debuginfod enabled}
48334 is set to @code{ask} for interactive sessions.
48336 @kindex show debuginfod enabled
48337 @item show debuginfod enabled
48338 Display whether @code{debuginfod enabled} is set to @code{on}, @code{off} or
48341 @kindex set debuginfod urls
48342 @cindex configure debuginfod URLs
48343 @item set debuginfod urls
48344 @itemx set debuginfod urls @var{urls}
48345 Set the space-separated list of URLs that @code{debuginfod} will attempt to
48346 query. Only @code{http://}, @code{https://} and @code{file://} protocols
48347 should be used. The default value of @code{debuginfod urls} is copied from
48348 the @var{DEBUGINFOD_URLS} environment variable.
48350 @kindex show debuginfod urls
48351 @item show debuginfod urls
48352 Display the list of URLs that @code{debuginfod} will attempt to query.
48354 @kindex set debuginfod verbose
48355 @cindex debuginfod verbosity
48356 @item set debuginfod verbose
48357 @itemx set debuginfod verbose @var{n}
48358 Enable or disable @code{debuginfod}-related output. Use a non-zero value
48359 to enable and @code{0} to disable. @code{debuginfod} output is shown by
48362 @kindex show debuginfod verbose
48363 @item show debuginfod verbose
48364 Show the current verbosity setting.
48369 @appendix Manual pages
48373 * gdb man:: The GNU Debugger man page
48374 * gdbserver man:: Remote Server for the GNU Debugger man page
48375 * gcore man:: Generate a core file of a running program
48376 * gdbinit man:: gdbinit scripts
48377 * gdb-add-index man:: Add index files to speed up GDB
48383 @c man title gdb The GNU Debugger
48385 @c man begin SYNOPSIS gdb
48386 gdb [OPTIONS] [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
48389 @c man begin DESCRIPTION gdb
48390 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
48391 going on ``inside'' another program while it executes -- or what another
48392 program was doing at the moment it crashed.
48394 @value{GDBN} can do four main kinds of things (plus other things in support of
48395 these) to help you catch bugs in the act:
48399 Start your program, specifying anything that might affect its behavior.
48402 Make your program stop on specified conditions.
48405 Examine what has happened, when your program has stopped.
48408 Change things in your program, so you can experiment with correcting the
48409 effects of one bug and go on to learn about another.
48412 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
48415 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
48416 commands from the terminal until you tell it to exit with the @value{GDBN}
48417 command @code{quit} or @code{exit}. You can get online help from @value{GDBN} itself
48418 by using the command @code{help}.
48420 You can run @code{gdb} with no arguments or options; but the most
48421 usual way to start @value{GDBN} is with one argument or two, specifying an
48422 executable program as the argument:
48428 You can also start with both an executable program and a core file specified:
48434 You can, instead, specify a process ID as a second argument or use option
48435 @code{-p}, if you want to debug a running process:
48443 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
48444 can omit the @var{program} filename.
48446 Here are some of the most frequently needed @value{GDBN} commands:
48448 @c pod2man highlights the right hand side of the @item lines.
48450 @item break [@var{file}:][@var{function}|@var{line}]
48451 Set a breakpoint at @var{function} or @var{line} (in @var{file}).
48453 @item run [@var{arglist}]
48454 Start your program (with @var{arglist}, if specified).
48457 Backtrace: display the program stack.
48459 @item print @var{expr}
48460 Display the value of an expression.
48463 Continue running your program (after stopping, e.g.@: at a breakpoint).
48466 Execute next program line (after stopping); step @emph{over} any
48467 function calls in the line.
48469 @item edit [@var{file}:]@var{function}
48470 look at the program line where it is presently stopped.
48472 @item list [@var{file}:]@var{function}
48473 type the text of the program in the vicinity of where it is presently stopped.
48476 Execute next program line (after stopping); step @emph{into} any
48477 function calls in the line.
48479 @item help [@var{name}]
48480 Show information about @value{GDBN} command @var{name}, or general information
48481 about using @value{GDBN}.
48485 Exit from @value{GDBN}.
48489 For full details on @value{GDBN},
48490 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48491 by Richard M. Stallman and Roland H. Pesch. The same text is available online
48492 as the @code{gdb} entry in the @code{info} program.
48496 @c man begin OPTIONS gdb
48497 Any arguments other than options specify an executable
48498 file and core file (or process ID); that is, the first argument
48499 encountered with no
48500 associated option flag is equivalent to a @option{--se} option, and the second,
48501 if any, is equivalent to a @option{-c} option if it's the name of a file.
48503 both long and abbreviated forms; both are shown here. The long forms are also
48504 recognized if you truncate them, so long as enough of the option is
48505 present to be unambiguous.
48507 The abbreviated forms are shown here with @samp{-} and long forms are shown
48508 with @samp{--} to reflect how they are shown in @option{--help}. However,
48509 @value{GDBN} recognizes all of the following conventions for most options:
48512 @item --option=@var{value}
48513 @item --option @var{value}
48514 @item -option=@var{value}
48515 @item -option @var{value}
48516 @item --o=@var{value}
48517 @item --o @var{value}
48518 @item -o=@var{value}
48519 @item -o @var{value}
48522 All the options and command line arguments you give are processed
48523 in sequential order. The order makes a difference when the @option{-x}
48529 List all options, with brief explanations.
48531 @item --symbols=@var{file}
48532 @itemx -s @var{file}
48533 Read symbol table from @var{file}.
48536 Enable writing into executable and core files.
48538 @item --exec=@var{file}
48539 @itemx -e @var{file}
48540 Use @var{file} as the executable file to execute when
48541 appropriate, and for examining pure data in conjunction with a core
48544 @item --se=@var{file}
48545 Read symbol table from @var{file} and use it as the executable
48548 @item --core=@var{file}
48549 @itemx -c @var{file}
48550 Use @var{file} as a core dump to examine.
48552 @item --command=@var{file}
48553 @itemx -x @var{file}
48554 Execute @value{GDBN} commands from @var{file}.
48556 @item --eval-command=@var{command}
48557 @item -ex @var{command}
48558 Execute given @value{GDBN} @var{command}.
48560 @item --init-eval-command=@var{command}
48562 Execute @value{GDBN} @var{command} before loading the inferior.
48564 @item --directory=@var{directory}
48565 @itemx -d @var{directory}
48566 Add @var{directory} to the path to search for source files.
48569 Do not execute commands from @file{~/.config/gdb/gdbinit},
48570 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
48571 @file{~/.gdbearlyinit}
48575 Do not execute commands from any @file{.gdbinit} or
48576 @file{.gdbearlyinit} initialization files.
48581 ``Quiet''. Do not print the introductory and copyright messages. These
48582 messages are also suppressed in batch mode.
48585 Run in batch mode. Exit with status @code{0} after processing all the command
48586 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
48587 Exit with nonzero status if an error occurs in executing the @value{GDBN}
48588 commands in the command files.
48590 Batch mode may be useful for running @value{GDBN} as a filter, for example to
48591 download and run a program on another computer; in order to make this
48592 more useful, the message
48595 Program exited normally.
48599 (which is ordinarily issued whenever a program running under @value{GDBN} control
48600 terminates) is not issued when running in batch mode.
48602 @item --batch-silent
48603 Run in batch mode, just like @option{--batch}, but totally silent. All @value{GDBN}
48604 output is supressed (stderr is unaffected). This is much quieter than
48605 @option{--silent} and would be useless for an interactive session.
48607 This is particularly useful when using targets that give @samp{Loading section}
48608 messages, for example.
48610 Note that targets that give their output via @value{GDBN}, as opposed to writing
48611 directly to @code{stdout}, will also be made silent.
48613 @item --args @var{prog} [@var{arglist}]
48614 Change interpretation of command line so that arguments following this
48615 option are passed as arguments to the inferior. As an example, take
48616 the following command:
48623 It would start @value{GDBN} with @option{-q}, not printing the introductory message. On
48624 the other hand, using:
48627 gdb --args ./a.out -q
48631 starts @value{GDBN} with the introductory message, and passes the option to the inferior.
48633 @item --pid=@var{pid}
48634 Attach @value{GDBN} to an already running program, with the PID @var{pid}.
48637 Open the terminal user interface.
48640 Read all symbols from the given symfile on the first access.
48643 Do not read symbol files.
48645 @item --return-child-result
48646 @value{GDBN}'s exit code will be the same as the child's exit code.
48648 @item --configuration
48649 Print details about GDB configuration and then exit.
48652 Print version information and then exit.
48654 @item --cd=@var{directory}
48655 Run @value{GDBN} using @var{directory} as its working directory,
48656 instead of the current directory.
48658 @item --data-directory=@var{directory}
48660 Run @value{GDBN} using @var{directory} as its data directory. The data
48661 directory is where @value{GDBN} searches for its auxiliary files.
48665 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
48666 @value{GDBN} to output the full file name and line number in a standard,
48667 recognizable fashion each time a stack frame is displayed (which
48668 includes each time the program stops). This recognizable format looks
48669 like two @samp{\032} characters, followed by the file name, line number
48670 and character position separated by colons, and a newline. The
48671 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
48672 characters as a signal to display the source code for the frame.
48674 @item -b @var{baudrate}
48675 Set the line speed (baud rate or bits per second) of any serial
48676 interface used by @value{GDBN} for remote debugging.
48678 @item -l @var{timeout}
48679 Set timeout, in seconds, for remote debugging.
48681 @item --tty=@var{device}
48682 Run using @var{device} for your program's standard input and output.
48686 @c man begin SEEALSO gdb
48688 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48689 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48690 documentation are properly installed at your site, the command
48697 should give you access to the complete manual.
48699 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48700 Richard M. Stallman and Roland H. Pesch, July 1991.
48704 @node gdbserver man
48705 @heading gdbserver man
48707 @c man title gdbserver Remote Server for the GNU Debugger
48709 @c man begin SYNOPSIS gdbserver
48710 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48712 gdbserver --attach @var{comm} @var{pid}
48714 gdbserver --multi @var{comm}
48718 @c man begin DESCRIPTION gdbserver
48719 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
48720 than the one which is running the program being debugged.
48723 @subheading Usage (server (target) side)
48726 Usage (server (target) side):
48729 First, you need to have a copy of the program you want to debug put onto
48730 the target system. The program can be stripped to save space if needed, as
48731 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
48732 the @value{GDBN} running on the host system.
48734 To use the server, you log on to the target system, and run the @command{gdbserver}
48735 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
48736 your program, and (c) its arguments. The general syntax is:
48739 target> gdbserver @var{comm} @var{program} [@var{args} ...]
48742 For example, using a serial port, you might say:
48746 @c @file would wrap it as F</dev/com1>.
48747 target> gdbserver /dev/com1 emacs foo.txt
48750 target> gdbserver @file{/dev/com1} emacs foo.txt
48754 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
48755 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
48756 waits patiently for the host @value{GDBN} to communicate with it.
48758 To use a TCP connection, you could say:
48761 target> gdbserver host:2345 emacs foo.txt
48764 This says pretty much the same thing as the last example, except that we are
48765 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
48766 that we are expecting to see a TCP connection from @code{host} to local TCP port
48767 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
48768 want for the port number as long as it does not conflict with any existing TCP
48769 ports on the target system. This same port number must be used in the host
48770 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
48771 you chose a port number that conflicts with another service, @command{gdbserver} will
48772 print an error message and exit.
48774 @command{gdbserver} can also attach to running programs.
48775 This is accomplished via the @option{--attach} argument. The syntax is:
48778 target> gdbserver --attach @var{comm} @var{pid}
48781 @var{pid} is the process ID of a currently running process. It isn't
48782 necessary to point @command{gdbserver} at a binary for the running process.
48784 To start @code{gdbserver} without supplying an initial command to run
48785 or process ID to attach, use the @option{--multi} command line option.
48786 In such case you should connect using @kbd{target extended-remote} to start
48787 the program you want to debug.
48790 target> gdbserver --multi @var{comm}
48794 @subheading Usage (host side)
48800 You need an unstripped copy of the target program on your host system, since
48801 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
48802 would, with the target program as the first argument. (You may need to use the
48803 @option{--baud} option if the serial line is running at anything except 9600 baud.)
48804 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
48805 new command you need to know about is @code{target remote}
48806 (or @code{target extended-remote}). Its argument is either
48807 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
48808 descriptor. For example:
48812 @c @file would wrap it as F</dev/ttyb>.
48813 (@value{GDBP}) target remote /dev/ttyb
48816 (@value{GDBP}) target remote @file{/dev/ttyb}
48821 communicates with the server via serial line @file{/dev/ttyb}, and:
48824 (@value{GDBP}) target remote the-target:2345
48828 communicates via a TCP connection to port 2345 on host `the-target', where
48829 you previously started up @command{gdbserver} with the same port number. Note that for
48830 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
48831 command, otherwise you may get an error that looks something like
48832 `Connection refused'.
48834 @command{gdbserver} can also debug multiple inferiors at once,
48837 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
48838 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
48841 @ref{Inferiors Connections and Programs}.
48843 In such case use the @code{extended-remote} @value{GDBN} command variant:
48846 (@value{GDBP}) target extended-remote the-target:2345
48849 The @command{gdbserver} option @option{--multi} may or may not be used in such
48853 @c man begin OPTIONS gdbserver
48854 There are three different modes for invoking @command{gdbserver}:
48859 Debug a specific program specified by its program name:
48862 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48865 The @var{comm} parameter specifies how should the server communicate
48866 with @value{GDBN}; it is either a device name (to use a serial line),
48867 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
48868 stdin/stdout of @code{gdbserver}. Specify the name of the program to
48869 debug in @var{prog}. Any remaining arguments will be passed to the
48870 program verbatim. When the program exits, @value{GDBN} will close the
48871 connection, and @code{gdbserver} will exit.
48874 Debug a specific program by specifying the process ID of a running
48878 gdbserver --attach @var{comm} @var{pid}
48881 The @var{comm} parameter is as described above. Supply the process ID
48882 of a running program in @var{pid}; @value{GDBN} will do everything
48883 else. Like with the previous mode, when the process @var{pid} exits,
48884 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
48887 Multi-process mode -- debug more than one program/process:
48890 gdbserver --multi @var{comm}
48893 In this mode, @value{GDBN} can instruct @command{gdbserver} which
48894 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
48895 close the connection when a process being debugged exits, so you can
48896 debug several processes in the same session.
48899 In each of the modes you may specify these options:
48904 List all options, with brief explanations.
48907 This option causes @command{gdbserver} to print its version number and exit.
48910 @command{gdbserver} will attach to a running program. The syntax is:
48913 target> gdbserver --attach @var{comm} @var{pid}
48916 @var{pid} is the process ID of a currently running process. It isn't
48917 necessary to point @command{gdbserver} at a binary for the running process.
48920 To start @code{gdbserver} without supplying an initial command to run
48921 or process ID to attach, use this command line option.
48922 Then you can connect using @kbd{target extended-remote} and start
48923 the program you want to debug. The syntax is:
48926 target> gdbserver --multi @var{comm}
48930 Instruct @code{gdbserver} to display extra status information about the debugging
48932 This option is intended for @code{gdbserver} development and for bug reports to
48935 @item --remote-debug
48936 Instruct @code{gdbserver} to display remote protocol debug output.
48937 This option is intended for @code{gdbserver} development and for bug reports to
48940 @item --debug-file=@var{filename}
48941 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
48942 This option is intended for @code{gdbserver} development and for bug reports to
48945 @item --debug-format=option1@r{[},option2,...@r{]}
48946 Instruct @code{gdbserver} to include extra information in each line
48947 of debugging output.
48948 @xref{Other Command-Line Arguments for gdbserver}.
48951 Specify a wrapper to launch programs
48952 for debugging. The option should be followed by the name of the
48953 wrapper, then any command-line arguments to pass to the wrapper, then
48954 @kbd{--} indicating the end of the wrapper arguments.
48957 By default, @command{gdbserver} keeps the listening TCP port open, so that
48958 additional connections are possible. However, if you start @code{gdbserver}
48959 with the @option{--once} option, it will stop listening for any further
48960 connection attempts after connecting to the first @value{GDBN} session.
48962 @c --disable-packet is not documented for users.
48964 @c --disable-randomization and --no-disable-randomization are superseded by
48965 @c QDisableRandomization.
48970 @c man begin SEEALSO gdbserver
48972 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48973 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48974 documentation are properly installed at your site, the command
48980 should give you access to the complete manual.
48982 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48983 Richard M. Stallman and Roland H. Pesch, July 1991.
48990 @c man title gcore Generate a core file of a running program
48993 @c man begin SYNOPSIS gcore
48994 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
48998 @c man begin DESCRIPTION gcore
48999 Generate core dumps of one or more running programs with process IDs
49000 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
49001 is equivalent to one produced by the kernel when the process crashes
49002 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
49003 limit). However, unlike after a crash, after @command{gcore} finishes
49004 its job the program remains running without any change.
49007 @c man begin OPTIONS gcore
49010 Dump all memory mappings. The actual effect of this option depends on
49011 the Operating System. On @sc{gnu}/Linux, it will disable
49012 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
49013 enable @code{dump-excluded-mappings} (@pxref{set
49014 dump-excluded-mappings}).
49016 @item -o @var{prefix}
49017 The optional argument @var{prefix} specifies the prefix to be used
49018 when composing the file names of the core dumps. The file name is
49019 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
49020 process ID of the running program being analyzed by @command{gcore}.
49021 If not specified, @var{prefix} defaults to @var{gcore}.
49025 @c man begin SEEALSO gcore
49027 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
49028 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
49029 documentation are properly installed at your site, the command
49036 should give you access to the complete manual.
49038 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
49039 Richard M. Stallman and Roland H. Pesch, July 1991.
49046 @c man title gdbinit GDB initialization scripts
49049 @c man begin SYNOPSIS gdbinit
49050 @ifset SYSTEM_GDBINIT
49051 @value{SYSTEM_GDBINIT}
49054 @ifset SYSTEM_GDBINIT_DIR
49055 @value{SYSTEM_GDBINIT_DIR}/*
49058 ~/.config/gdb/gdbinit
49066 @c man begin DESCRIPTION gdbinit
49067 These files contain @value{GDBN} commands to automatically execute during
49068 @value{GDBN} startup. The lines of contents are canned sequences of commands,
49071 the @value{GDBN} manual in node @code{Sequences}
49072 -- shell command @code{info -f gdb -n Sequences}.
49078 Please read more in
49080 the @value{GDBN} manual in node @code{Startup}
49081 -- shell command @code{info -f gdb -n Startup}.
49088 @ifset SYSTEM_GDBINIT
49089 @item @value{SYSTEM_GDBINIT}
49091 @ifclear SYSTEM_GDBINIT
49092 @item (not enabled with @code{--with-system-gdbinit} during compilation)
49094 System-wide initialization file. It is executed unless user specified
49095 @value{GDBN} option @code{-nx} or @code{-n}.
49098 the @value{GDBN} manual in node @code{System-wide configuration}
49099 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
49101 @ifset SYSTEM_GDBINIT_DIR
49102 @item @value{SYSTEM_GDBINIT_DIR}
49104 @ifclear SYSTEM_GDBINIT_DIR
49105 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
49107 System-wide initialization directory. All files in this directory are
49108 executed on startup unless user specified @value{GDBN} option @code{-nx} or
49109 @code{-n}, as long as they have a recognized file extension.
49112 the @value{GDBN} manual in node @code{System-wide configuration}
49113 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
49116 @ref{System-wide configuration}.
49119 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
49120 User initialization file. It is executed unless user specified
49121 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
49123 @item @file{.gdbinit}
49124 Initialization file for current directory. It may need to be enabled with
49125 @value{GDBN} security command @code{set auto-load local-gdbinit}.
49128 the @value{GDBN} manual in node @code{Init File in the Current Directory}
49129 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
49132 @ref{Init File in the Current Directory}.
49137 @c man begin SEEALSO gdbinit
49139 gdb(1), @code{info -f gdb -n Startup}
49141 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
49142 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
49143 documentation are properly installed at your site, the command
49149 should give you access to the complete manual.
49151 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
49152 Richard M. Stallman and Roland H. Pesch, July 1991.
49156 @node gdb-add-index man
49157 @heading gdb-add-index
49158 @pindex gdb-add-index
49159 @anchor{gdb-add-index}
49161 @c man title gdb-add-index Add index files to speed up GDB
49163 @c man begin SYNOPSIS gdb-add-index
49164 gdb-add-index @var{filename}
49167 @c man begin DESCRIPTION gdb-add-index
49168 When @value{GDBN} finds a symbol file, it scans the symbols in the
49169 file in order to construct an internal symbol table. This lets most
49170 @value{GDBN} operations work quickly--at the cost of a delay early on.
49171 For large programs, this delay can be quite lengthy, so @value{GDBN}
49172 provides a way to build an index, which speeds up startup.
49174 To determine whether a file contains such an index, use the command
49175 @kbd{readelf -S filename}: the index is stored in a section named
49176 @code{.gdb_index}. The index file can only be produced on systems
49177 which use ELF binaries and DWARF debug information (i.e., sections
49178 named @code{.debug_*}).
49180 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
49181 in the @env{PATH} environment variable. If you want to use different
49182 versions of these programs, you can specify them through the
49183 @env{GDB} and @env{OBJDUMP} environment variables.
49187 the @value{GDBN} manual in node @code{Index Files}
49188 -- shell command @kbd{info -f gdb -n "Index Files"}.
49195 @c man begin SEEALSO gdb-add-index
49197 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
49198 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
49199 documentation are properly installed at your site, the command
49205 should give you access to the complete manual.
49207 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
49208 Richard M. Stallman and Roland H. Pesch, July 1991.
49214 @node GNU Free Documentation License
49215 @appendix GNU Free Documentation License
49218 @node Concept Index
49219 @unnumbered Concept Index
49223 @node Command and Variable Index
49224 @unnumbered Command, Variable, and Function Index
49229 % I think something like @@colophon should be in texinfo. In the
49231 \long\def\colophon{\hbox to0pt{}\vfill
49232 \centerline{The body of this manual is set in}
49233 \centerline{\fontname\tenrm,}
49234 \centerline{with headings in {\bf\fontname\tenbf}}
49235 \centerline{and examples in {\tt\fontname\tentt}.}
49236 \centerline{{\it\fontname\tenit\/},}
49237 \centerline{{\bf\fontname\tenbf}, and}
49238 \centerline{{\sl\fontname\tensl\/}}
49239 \centerline{are used for emphasis.}\vfill}
49241 % Blame: doc@@cygnus.com, 1991.