1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2020 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2020 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2020 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 Initial support for the FreeBSD/riscv target and native configuration
550 was developed by SRI International and the University of Cambridge
551 Computer Laboratory (Department of Computer Science and Technology)
552 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
553 SSITH research programme.
555 The original port to the OpenRISC 1000 is believed to be due to
556 Alessandro Forin and Per Bothner. More recent ports have been the work
557 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
560 Weimin Pan, David Faust and Jose E. Marchesi contributed support for
561 the Linux kernel BPF virtual architecture. This work was sponsored by
565 @chapter A Sample @value{GDBN} Session
567 You can use this manual at your leisure to read all about @value{GDBN}.
568 However, a handful of commands are enough to get started using the
569 debugger. This chapter illustrates those commands.
572 In this sample session, we emphasize user input like this: @b{input},
573 to make it easier to pick out from the surrounding output.
576 @c FIXME: this example may not be appropriate for some configs, where
577 @c FIXME...primary interest is in remote use.
579 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
580 processor) exhibits the following bug: sometimes, when we change its
581 quote strings from the default, the commands used to capture one macro
582 definition within another stop working. In the following short @code{m4}
583 session, we define a macro @code{foo} which expands to @code{0000}; we
584 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
585 same thing. However, when we change the open quote string to
586 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
587 procedure fails to define a new synonym @code{baz}:
596 @b{define(bar,defn(`foo'))}
600 @b{changequote(<QUOTE>,<UNQUOTE>)}
602 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
605 m4: End of input: 0: fatal error: EOF in string
609 Let us use @value{GDBN} to try to see what is going on.
612 $ @b{@value{GDBP} m4}
613 @c FIXME: this falsifies the exact text played out, to permit smallbook
614 @c FIXME... format to come out better.
615 @value{GDBN} is free software and you are welcome to distribute copies
616 of it under certain conditions; type "show copying" to see
618 There is absolutely no warranty for @value{GDBN}; type "show warranty"
621 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
626 @value{GDBN} reads only enough symbol data to know where to find the
627 rest when needed; as a result, the first prompt comes up very quickly.
628 We now tell @value{GDBN} to use a narrower display width than usual, so
629 that examples fit in this manual.
632 (@value{GDBP}) @b{set width 70}
636 We need to see how the @code{m4} built-in @code{changequote} works.
637 Having looked at the source, we know the relevant subroutine is
638 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
639 @code{break} command.
642 (@value{GDBP}) @b{break m4_changequote}
643 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
647 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
648 control; as long as control does not reach the @code{m4_changequote}
649 subroutine, the program runs as usual:
652 (@value{GDBP}) @b{run}
653 Starting program: /work/Editorial/gdb/gnu/m4/m4
661 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
662 suspends execution of @code{m4}, displaying information about the
663 context where it stops.
666 @b{changequote(<QUOTE>,<UNQUOTE>)}
668 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
670 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
674 Now we use the command @code{n} (@code{next}) to advance execution to
675 the next line of the current function.
679 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
684 @code{set_quotes} looks like a promising subroutine. We can go into it
685 by using the command @code{s} (@code{step}) instead of @code{next}.
686 @code{step} goes to the next line to be executed in @emph{any}
687 subroutine, so it steps into @code{set_quotes}.
691 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
693 530 if (lquote != def_lquote)
697 The display that shows the subroutine where @code{m4} is now
698 suspended (and its arguments) is called a stack frame display. It
699 shows a summary of the stack. We can use the @code{backtrace}
700 command (which can also be spelled @code{bt}), to see where we are
701 in the stack as a whole: the @code{backtrace} command displays a
702 stack frame for each active subroutine.
705 (@value{GDBP}) @b{bt}
706 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
708 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
710 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
711 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
713 #4 0x79dc in expand_input () at macro.c:40
714 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
718 We step through a few more lines to see what happens. The first two
719 times, we can use @samp{s}; the next two times we use @code{n} to avoid
720 falling into the @code{xstrdup} subroutine.
724 0x3b5c 532 if (rquote != def_rquote)
726 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
727 def_lquote : xstrdup(lq);
729 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
732 538 len_lquote = strlen(rquote);
736 The last line displayed looks a little odd; we can examine the variables
737 @code{lquote} and @code{rquote} to see if they are in fact the new left
738 and right quotes we specified. We use the command @code{p}
739 (@code{print}) to see their values.
742 (@value{GDBP}) @b{p lquote}
743 $1 = 0x35d40 "<QUOTE>"
744 (@value{GDBP}) @b{p rquote}
745 $2 = 0x35d50 "<UNQUOTE>"
749 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
750 To look at some context, we can display ten lines of source
751 surrounding the current line with the @code{l} (@code{list}) command.
757 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
759 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
762 538 len_lquote = strlen(rquote);
763 539 len_rquote = strlen(lquote);
770 Let us step past the two lines that set @code{len_lquote} and
771 @code{len_rquote}, and then examine the values of those variables.
775 539 len_rquote = strlen(lquote);
778 (@value{GDBP}) @b{p len_lquote}
780 (@value{GDBP}) @b{p len_rquote}
785 That certainly looks wrong, assuming @code{len_lquote} and
786 @code{len_rquote} are meant to be the lengths of @code{lquote} and
787 @code{rquote} respectively. We can set them to better values using
788 the @code{p} command, since it can print the value of
789 any expression---and that expression can include subroutine calls and
793 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
795 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
800 Is that enough to fix the problem of using the new quotes with the
801 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
802 executing with the @code{c} (@code{continue}) command, and then try the
803 example that caused trouble initially:
809 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
816 Success! The new quotes now work just as well as the default ones. The
817 problem seems to have been just the two typos defining the wrong
818 lengths. We allow @code{m4} exit by giving it an EOF as input:
822 Program exited normally.
826 The message @samp{Program exited normally.} is from @value{GDBN}; it
827 indicates @code{m4} has finished executing. We can end our @value{GDBN}
828 session with the @value{GDBN} @code{quit} command.
831 (@value{GDBP}) @b{quit}
835 @chapter Getting In and Out of @value{GDBN}
837 This chapter discusses how to start @value{GDBN}, and how to get out of it.
841 type @samp{@value{GDBP}} to start @value{GDBN}.
843 type @kbd{quit} or @kbd{Ctrl-d} to exit.
847 * Invoking GDB:: How to start @value{GDBN}
848 * Quitting GDB:: How to quit @value{GDBN}
849 * Shell Commands:: How to use shell commands inside @value{GDBN}
850 * Logging Output:: How to log @value{GDBN}'s output to a file
854 @section Invoking @value{GDBN}
856 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
857 @value{GDBN} reads commands from the terminal until you tell it to exit.
859 You can also run @code{@value{GDBP}} with a variety of arguments and options,
860 to specify more of your debugging environment at the outset.
862 The command-line options described here are designed
863 to cover a variety of situations; in some environments, some of these
864 options may effectively be unavailable.
866 The most usual way to start @value{GDBN} is with one argument,
867 specifying an executable program:
870 @value{GDBP} @var{program}
874 You can also start with both an executable program and a core file
878 @value{GDBP} @var{program} @var{core}
881 You can, instead, specify a process ID as a second argument or use option
882 @code{-p}, if you want to debug a running process:
885 @value{GDBP} @var{program} 1234
890 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
891 can omit the @var{program} filename.
893 Taking advantage of the second command-line argument requires a fairly
894 complete operating system; when you use @value{GDBN} as a remote
895 debugger attached to a bare board, there may not be any notion of
896 ``process'', and there is often no way to get a core dump. @value{GDBN}
897 will warn you if it is unable to attach or to read core dumps.
899 You can optionally have @code{@value{GDBP}} pass any arguments after the
900 executable file to the inferior using @code{--args}. This option stops
903 @value{GDBP} --args gcc -O2 -c foo.c
905 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
906 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
908 You can run @code{@value{GDBP}} without printing the front material, which describes
909 @value{GDBN}'s non-warranty, by specifying @code{--silent}
910 (or @code{-q}/@code{--quiet}):
913 @value{GDBP} --silent
917 You can further control how @value{GDBN} starts up by using command-line
918 options. @value{GDBN} itself can remind you of the options available.
928 to display all available options and briefly describe their use
929 (@samp{@value{GDBP} -h} is a shorter equivalent).
931 All options and command line arguments you give are processed
932 in sequential order. The order makes a difference when the
933 @samp{-x} option is used.
937 * File Options:: Choosing files
938 * Mode Options:: Choosing modes
939 * Startup:: What @value{GDBN} does during startup
943 @subsection Choosing Files
945 When @value{GDBN} starts, it reads any arguments other than options as
946 specifying an executable file and core file (or process ID). This is
947 the same as if the arguments were specified by the @samp{-se} and
948 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
949 first argument that does not have an associated option flag as
950 equivalent to the @samp{-se} option followed by that argument; and the
951 second argument that does not have an associated option flag, if any, as
952 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
953 If the second argument begins with a decimal digit, @value{GDBN} will
954 first attempt to attach to it as a process, and if that fails, attempt
955 to open it as a corefile. If you have a corefile whose name begins with
956 a digit, you can prevent @value{GDBN} from treating it as a pid by
957 prefixing it with @file{./}, e.g.@: @file{./12345}.
959 If @value{GDBN} has not been configured to included core file support,
960 such as for most embedded targets, then it will complain about a second
961 argument and ignore it.
963 Many options have both long and short forms; both are shown in the
964 following list. @value{GDBN} also recognizes the long forms if you truncate
965 them, so long as enough of the option is present to be unambiguous.
966 (If you prefer, you can flag option arguments with @samp{--} rather
967 than @samp{-}, though we illustrate the more usual convention.)
969 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
970 @c way, both those who look for -foo and --foo in the index, will find
974 @item -symbols @var{file}
976 @cindex @code{--symbols}
978 Read symbol table from file @var{file}.
980 @item -exec @var{file}
982 @cindex @code{--exec}
984 Use file @var{file} as the executable file to execute when appropriate,
985 and for examining pure data in conjunction with a core dump.
989 Read symbol table from file @var{file} and use it as the executable
992 @item -core @var{file}
994 @cindex @code{--core}
996 Use file @var{file} as a core dump to examine.
998 @item -pid @var{number}
999 @itemx -p @var{number}
1000 @cindex @code{--pid}
1002 Connect to process ID @var{number}, as with the @code{attach} command.
1004 @item -command @var{file}
1005 @itemx -x @var{file}
1006 @cindex @code{--command}
1008 Execute commands from file @var{file}. The contents of this file is
1009 evaluated exactly as the @code{source} command would.
1010 @xref{Command Files,, Command files}.
1012 @item -eval-command @var{command}
1013 @itemx -ex @var{command}
1014 @cindex @code{--eval-command}
1016 Execute a single @value{GDBN} command.
1018 This option may be used multiple times to call multiple commands. It may
1019 also be interleaved with @samp{-command} as required.
1022 @value{GDBP} -ex 'target sim' -ex 'load' \
1023 -x setbreakpoints -ex 'run' a.out
1026 @item -init-command @var{file}
1027 @itemx -ix @var{file}
1028 @cindex @code{--init-command}
1030 Execute commands from file @var{file} before loading the inferior (but
1031 after loading gdbinit files).
1034 @item -init-eval-command @var{command}
1035 @itemx -iex @var{command}
1036 @cindex @code{--init-eval-command}
1038 Execute a single @value{GDBN} command before loading the inferior (but
1039 after loading gdbinit files).
1042 @item -directory @var{directory}
1043 @itemx -d @var{directory}
1044 @cindex @code{--directory}
1046 Add @var{directory} to the path to search for source and script files.
1050 @cindex @code{--readnow}
1052 Read each symbol file's entire symbol table immediately, rather than
1053 the default, which is to read it incrementally as it is needed.
1054 This makes startup slower, but makes future operations faster.
1057 @anchor{--readnever}
1058 @cindex @code{--readnever}, command-line option
1059 Do not read each symbol file's symbolic debug information. This makes
1060 startup faster but at the expense of not being able to perform
1061 symbolic debugging. DWARF unwind information is also not read,
1062 meaning backtraces may become incomplete or inaccurate. One use of
1063 this is when a user simply wants to do the following sequence: attach,
1064 dump core, detach. Loading the debugging information in this case is
1065 an unnecessary cause of delay.
1069 @subsection Choosing Modes
1071 You can run @value{GDBN} in various alternative modes---for example, in
1072 batch mode or quiet mode.
1080 Do not execute commands found in any initialization file.
1081 There are three init files, loaded in the following order:
1084 @item @file{system.gdbinit}
1085 This is the system-wide init file.
1086 Its location is specified with the @code{--with-system-gdbinit}
1087 configure option (@pxref{System-wide configuration}).
1088 It is loaded first when @value{GDBN} starts, before command line options
1089 have been processed.
1090 @item @file{system.gdbinit.d}
1091 This is the system-wide init directory.
1092 Its location is specified with the @code{--with-system-gdbinit-dir}
1093 configure option (@pxref{System-wide configuration}).
1094 Files in this directory are loaded in alphabetical order immediately after
1095 system.gdbinit (if enabled) when @value{GDBN} starts, before command line
1096 options have been processed. Files need to have a recognized scripting
1097 language extension (@file{.py}/@file{.scm}) or be named with a @file{.gdb}
1098 extension to be interpreted as regular @value{GDBN} commands. @value{GDBN}
1099 will not recurse into any subdirectories of this directory.
1100 @item @file{~/.gdbinit}
1101 This is the init file in your home directory.
1102 It is loaded next, after @file{system.gdbinit}, and before
1103 command options have been processed.
1104 @item @file{./.gdbinit}
1105 This is the init file in the current directory.
1106 It is loaded last, after command line options other than @code{-x} and
1107 @code{-ex} have been processed. Command line options @code{-x} and
1108 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1111 For further documentation on startup processing, @xref{Startup}.
1112 For documentation on how to write command files,
1113 @xref{Command Files,,Command Files}.
1118 Do not execute commands found in @file{~/.gdbinit}, the init file
1119 in your home directory.
1125 @cindex @code{--quiet}
1126 @cindex @code{--silent}
1128 ``Quiet''. Do not print the introductory and copyright messages. These
1129 messages are also suppressed in batch mode.
1132 @cindex @code{--batch}
1133 Run in batch mode. Exit with status @code{0} after processing all the
1134 command files specified with @samp{-x} (and all commands from
1135 initialization files, if not inhibited with @samp{-n}). Exit with
1136 nonzero status if an error occurs in executing the @value{GDBN} commands
1137 in the command files. Batch mode also disables pagination, sets unlimited
1138 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1139 off} were in effect (@pxref{Messages/Warnings}).
1141 Batch mode may be useful for running @value{GDBN} as a filter, for
1142 example to download and run a program on another computer; in order to
1143 make this more useful, the message
1146 Program exited normally.
1150 (which is ordinarily issued whenever a program running under
1151 @value{GDBN} control terminates) is not issued when running in batch
1155 @cindex @code{--batch-silent}
1156 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1157 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1158 unaffected). This is much quieter than @samp{-silent} and would be useless
1159 for an interactive session.
1161 This is particularly useful when using targets that give @samp{Loading section}
1162 messages, for example.
1164 Note that targets that give their output via @value{GDBN}, as opposed to
1165 writing directly to @code{stdout}, will also be made silent.
1167 @item -return-child-result
1168 @cindex @code{--return-child-result}
1169 The return code from @value{GDBN} will be the return code from the child
1170 process (the process being debugged), with the following exceptions:
1174 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1175 internal error. In this case the exit code is the same as it would have been
1176 without @samp{-return-child-result}.
1178 The user quits with an explicit value. E.g., @samp{quit 1}.
1180 The child process never runs, or is not allowed to terminate, in which case
1181 the exit code will be -1.
1184 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1185 when @value{GDBN} is being used as a remote program loader or simulator
1190 @cindex @code{--nowindows}
1192 ``No windows''. If @value{GDBN} comes with a graphical user interface
1193 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1194 interface. If no GUI is available, this option has no effect.
1198 @cindex @code{--windows}
1200 If @value{GDBN} includes a GUI, then this option requires it to be
1203 @item -cd @var{directory}
1205 Run @value{GDBN} using @var{directory} as its working directory,
1206 instead of the current directory.
1208 @item -data-directory @var{directory}
1209 @itemx -D @var{directory}
1210 @cindex @code{--data-directory}
1212 Run @value{GDBN} using @var{directory} as its data directory.
1213 The data directory is where @value{GDBN} searches for its
1214 auxiliary files. @xref{Data Files}.
1218 @cindex @code{--fullname}
1220 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1221 subprocess. It tells @value{GDBN} to output the full file name and line
1222 number in a standard, recognizable fashion each time a stack frame is
1223 displayed (which includes each time your program stops). This
1224 recognizable format looks like two @samp{\032} characters, followed by
1225 the file name, line number and character position separated by colons,
1226 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1227 @samp{\032} characters as a signal to display the source code for the
1230 @item -annotate @var{level}
1231 @cindex @code{--annotate}
1232 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1233 effect is identical to using @samp{set annotate @var{level}}
1234 (@pxref{Annotations}). The annotation @var{level} controls how much
1235 information @value{GDBN} prints together with its prompt, values of
1236 expressions, source lines, and other types of output. Level 0 is the
1237 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1238 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1239 that control @value{GDBN}, and level 2 has been deprecated.
1241 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1245 @cindex @code{--args}
1246 Change interpretation of command line so that arguments following the
1247 executable file are passed as command line arguments to the inferior.
1248 This option stops option processing.
1250 @item -baud @var{bps}
1252 @cindex @code{--baud}
1254 Set the line speed (baud rate or bits per second) of any serial
1255 interface used by @value{GDBN} for remote debugging.
1257 @item -l @var{timeout}
1259 Set the timeout (in seconds) of any communication used by @value{GDBN}
1260 for remote debugging.
1262 @item -tty @var{device}
1263 @itemx -t @var{device}
1264 @cindex @code{--tty}
1266 Run using @var{device} for your program's standard input and output.
1267 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1269 @c resolve the situation of these eventually
1271 @cindex @code{--tui}
1272 Activate the @dfn{Text User Interface} when starting. The Text User
1273 Interface manages several text windows on the terminal, showing
1274 source, assembly, registers and @value{GDBN} command outputs
1275 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1276 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1277 Using @value{GDBN} under @sc{gnu} Emacs}).
1279 @item -interpreter @var{interp}
1280 @cindex @code{--interpreter}
1281 Use the interpreter @var{interp} for interface with the controlling
1282 program or device. This option is meant to be set by programs which
1283 communicate with @value{GDBN} using it as a back end.
1284 @xref{Interpreters, , Command Interpreters}.
1286 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1287 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1288 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1289 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1290 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1291 interfaces are no longer supported.
1294 @cindex @code{--write}
1295 Open the executable and core files for both reading and writing. This
1296 is equivalent to the @samp{set write on} command inside @value{GDBN}
1300 @cindex @code{--statistics}
1301 This option causes @value{GDBN} to print statistics about time and
1302 memory usage after it completes each command and returns to the prompt.
1305 @cindex @code{--version}
1306 This option causes @value{GDBN} to print its version number and
1307 no-warranty blurb, and exit.
1309 @item -configuration
1310 @cindex @code{--configuration}
1311 This option causes @value{GDBN} to print details about its build-time
1312 configuration parameters, and then exit. These details can be
1313 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1318 @subsection What @value{GDBN} Does During Startup
1319 @cindex @value{GDBN} startup
1321 Here's the description of what @value{GDBN} does during session startup:
1325 Sets up the command interpreter as specified by the command line
1326 (@pxref{Mode Options, interpreter}).
1330 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1331 used when building @value{GDBN}; @pxref{System-wide configuration,
1332 ,System-wide configuration and settings}) and the files in the system-wide
1333 gdbinit directory (if @option{--with-system-gdbinit-dir} was used) and executes
1334 all the commands in those files. The files need to be named with a @file{.gdb}
1335 extension to be interpreted as @value{GDBN} commands, or they can be written
1336 in a supported scripting language with an appropriate file extension.
1338 @anchor{Home Directory Init File}
1340 Reads the init file (if any) in your home directory@footnote{On
1341 DOS/Windows systems, the home directory is the one pointed to by the
1342 @code{HOME} environment variable.} and executes all the commands in
1345 @anchor{Option -init-eval-command}
1347 Executes commands and command files specified by the @samp{-iex} and
1348 @samp{-ix} options in their specified order. Usually you should use the
1349 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1350 settings before @value{GDBN} init files get executed and before inferior
1354 Processes command line options and operands.
1356 @anchor{Init File in the Current Directory during Startup}
1358 Reads and executes the commands from init file (if any) in the current
1359 working directory as long as @samp{set auto-load local-gdbinit} is set to
1360 @samp{on} (@pxref{Init File in the Current Directory}).
1361 This is only done if the current directory is
1362 different from your home directory. Thus, you can have more than one
1363 init file, one generic in your home directory, and another, specific
1364 to the program you are debugging, in the directory where you invoke
1368 If the command line specified a program to debug, or a process to
1369 attach to, or a core file, @value{GDBN} loads any auto-loaded
1370 scripts provided for the program or for its loaded shared libraries.
1371 @xref{Auto-loading}.
1373 If you wish to disable the auto-loading during startup,
1374 you must do something like the following:
1377 $ gdb -iex "set auto-load python-scripts off" myprogram
1380 Option @samp{-ex} does not work because the auto-loading is then turned
1384 Executes commands and command files specified by the @samp{-ex} and
1385 @samp{-x} options in their specified order. @xref{Command Files}, for
1386 more details about @value{GDBN} command files.
1389 Reads the command history recorded in the @dfn{history file}.
1390 @xref{Command History}, for more details about the command history and the
1391 files where @value{GDBN} records it.
1394 Init files use the same syntax as @dfn{command files} (@pxref{Command
1395 Files}) and are processed by @value{GDBN} in the same way. The init
1396 file in your home directory can set options (such as @samp{set
1397 complaints}) that affect subsequent processing of command line options
1398 and operands. Init files are not executed if you use the @samp{-nx}
1399 option (@pxref{Mode Options, ,Choosing Modes}).
1401 To display the list of init files loaded by gdb at startup, you
1402 can use @kbd{gdb --help}.
1404 @cindex init file name
1405 @cindex @file{.gdbinit}
1406 @cindex @file{gdb.ini}
1407 The @value{GDBN} init files are normally called @file{.gdbinit}.
1408 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1409 the limitations of file names imposed by DOS filesystems. The Windows
1410 port of @value{GDBN} uses the standard name, but if it finds a
1411 @file{gdb.ini} file in your home directory, it warns you about that
1412 and suggests to rename the file to the standard name.
1416 @section Quitting @value{GDBN}
1417 @cindex exiting @value{GDBN}
1418 @cindex leaving @value{GDBN}
1421 @kindex quit @r{[}@var{expression}@r{]}
1422 @kindex q @r{(@code{quit})}
1423 @item quit @r{[}@var{expression}@r{]}
1425 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1426 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1427 do not supply @var{expression}, @value{GDBN} will terminate normally;
1428 otherwise it will terminate using the result of @var{expression} as the
1433 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1434 terminates the action of any @value{GDBN} command that is in progress and
1435 returns to @value{GDBN} command level. It is safe to type the interrupt
1436 character at any time because @value{GDBN} does not allow it to take effect
1437 until a time when it is safe.
1439 If you have been using @value{GDBN} to control an attached process or
1440 device, you can release it with the @code{detach} command
1441 (@pxref{Attach, ,Debugging an Already-running Process}).
1443 @node Shell Commands
1444 @section Shell Commands
1446 If you need to execute occasional shell commands during your
1447 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1448 just use the @code{shell} command.
1453 @cindex shell escape
1454 @item shell @var{command-string}
1455 @itemx !@var{command-string}
1456 Invoke a standard shell to execute @var{command-string}.
1457 Note that no space is needed between @code{!} and @var{command-string}.
1458 On GNU and Unix systems, the environment variable @code{SHELL}, if it
1459 exists, determines which shell to run. Otherwise @value{GDBN} uses
1460 the default shell (@file{/bin/sh} on GNU and Unix systems,
1461 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1464 The utility @code{make} is often needed in development environments.
1465 You do not have to use the @code{shell} command for this purpose in
1470 @cindex calling make
1471 @item make @var{make-args}
1472 Execute the @code{make} program with the specified
1473 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1479 @cindex send the output of a gdb command to a shell command
1481 @item pipe [@var{command}] | @var{shell_command}
1482 @itemx | [@var{command}] | @var{shell_command}
1483 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1484 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1485 Executes @var{command} and sends its output to @var{shell_command}.
1486 Note that no space is needed around @code{|}.
1487 If no @var{command} is provided, the last command executed is repeated.
1489 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1490 can be used to specify an alternate delimiter string @var{delim} that separates
1491 the @var{command} from the @var{shell_command}.
1524 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1525 this contains a PIPE char
1526 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1527 this contains a PIPE char!
1533 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1534 can be used to examine the exit status of the last shell command launched
1535 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1536 @xref{Convenience Vars,, Convenience Variables}.
1538 @node Logging Output
1539 @section Logging Output
1540 @cindex logging @value{GDBN} output
1541 @cindex save @value{GDBN} output to a file
1543 You may want to save the output of @value{GDBN} commands to a file.
1544 There are several commands to control @value{GDBN}'s logging.
1548 @item set logging on
1550 @item set logging off
1552 @cindex logging file name
1553 @item set logging file @var{file}
1554 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1555 @item set logging overwrite [on|off]
1556 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1557 you want @code{set logging on} to overwrite the logfile instead.
1558 @item set logging redirect [on|off]
1559 By default, @value{GDBN} output will go to both the terminal and the logfile.
1560 Set @code{redirect} if you want output to go only to the log file.
1561 @item set logging debugredirect [on|off]
1562 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1563 Set @code{debugredirect} if you want debug output to go only to the log file.
1564 @kindex show logging
1566 Show the current values of the logging settings.
1569 You can also redirect the output of a @value{GDBN} command to a
1570 shell command. @xref{pipe}.
1572 @chapter @value{GDBN} Commands
1574 You can abbreviate a @value{GDBN} command to the first few letters of the command
1575 name, if that abbreviation is unambiguous; and you can repeat certain
1576 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1577 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1578 show you the alternatives available, if there is more than one possibility).
1581 * Command Syntax:: How to give commands to @value{GDBN}
1582 * Command Settings:: How to change default behavior of commands
1583 * Completion:: Command completion
1584 * Command Options:: Command options
1585 * Command aliases default args:: Automatically prepend default arguments to user-defined aliases
1586 * Help:: How to ask @value{GDBN} for help
1589 @node Command Syntax
1590 @section Command Syntax
1592 A @value{GDBN} command is a single line of input. There is no limit on
1593 how long it can be. It starts with a command name, which is followed by
1594 arguments whose meaning depends on the command name. For example, the
1595 command @code{step} accepts an argument which is the number of times to
1596 step, as in @samp{step 5}. You can also use the @code{step} command
1597 with no arguments. Some commands do not allow any arguments.
1599 @cindex abbreviation
1600 @value{GDBN} command names may always be truncated if that abbreviation is
1601 unambiguous. Other possible command abbreviations are listed in the
1602 documentation for individual commands. In some cases, even ambiguous
1603 abbreviations are allowed; for example, @code{s} is specially defined as
1604 equivalent to @code{step} even though there are other commands whose
1605 names start with @code{s}. You can test abbreviations by using them as
1606 arguments to the @code{help} command.
1608 @cindex repeating commands
1609 @kindex RET @r{(repeat last command)}
1610 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1611 repeat the previous command. Certain commands (for example, @code{run})
1612 will not repeat this way; these are commands whose unintentional
1613 repetition might cause trouble and which you are unlikely to want to
1614 repeat. User-defined commands can disable this feature; see
1615 @ref{Define, dont-repeat}.
1617 The @code{list} and @code{x} commands, when you repeat them with
1618 @key{RET}, construct new arguments rather than repeating
1619 exactly as typed. This permits easy scanning of source or memory.
1621 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1622 output, in a way similar to the common utility @code{more}
1623 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1624 @key{RET} too many in this situation, @value{GDBN} disables command
1625 repetition after any command that generates this sort of display.
1627 @kindex # @r{(a comment)}
1629 Any text from a @kbd{#} to the end of the line is a comment; it does
1630 nothing. This is useful mainly in command files (@pxref{Command
1631 Files,,Command Files}).
1633 @cindex repeating command sequences
1634 @kindex Ctrl-o @r{(operate-and-get-next)}
1635 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1636 commands. This command accepts the current line, like @key{RET}, and
1637 then fetches the next line relative to the current line from the history
1641 @node Command Settings
1642 @section Command Settings
1643 @cindex default behavior of commands, changing
1644 @cindex default settings, changing
1646 Many commands change their behavior according to command-specific
1647 variables or settings. These settings can be changed with the
1648 @code{set} subcommands. For example, the @code{print} command
1649 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1650 settings changeable with the commands @code{set print elements
1651 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1653 You can change these settings to your preference in the gdbinit files
1654 loaded at @value{GDBN} startup. @xref{Startup}.
1656 The settings can also be changed interactively during the debugging
1657 session. For example, to change the limit of array elements to print,
1658 you can do the following:
1660 (@value{GDBN}) set print elements 10
1661 (@value{GDBN}) print some_array
1662 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1665 The above @code{set print elements 10} command changes the number of
1666 elements to print from the default of 200 to 10. If you only intend
1667 this limit of 10 to be used for printing @code{some_array}, then you
1668 must restore the limit back to 200, with @code{set print elements
1671 Some commands allow overriding settings with command options. For
1672 example, the @code{print} command supports a number of options that
1673 allow overriding relevant global print settings as set by @code{set
1674 print} subcommands. @xref{print options}. The example above could be
1677 (@value{GDBN}) print -elements 10 -- some_array
1678 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1681 Alternatively, you can use the @code{with} command to change a setting
1682 temporarily, for the duration of a command invocation.
1685 @kindex with command
1686 @kindex w @r{(@code{with})}
1688 @cindex temporarily change settings
1689 @item with @var{setting} [@var{value}] [-- @var{command}]
1690 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1691 Temporarily set @var{setting} to @var{value} for the duration of
1694 @var{setting} is any setting you can change with the @code{set}
1695 subcommands. @var{value} is the value to assign to @code{setting}
1696 while running @code{command}.
1698 If no @var{command} is provided, the last command executed is
1701 If a @var{command} is provided, it must be preceded by a double dash
1702 (@code{--}) separator. This is required because some settings accept
1703 free-form arguments, such as expressions or filenames.
1705 For example, the command
1707 (@value{GDBN}) with print array on -- print some_array
1710 is equivalent to the following 3 commands:
1712 (@value{GDBN}) set print array on
1713 (@value{GDBN}) print some_array
1714 (@value{GDBN}) set print array off
1717 The @code{with} command is particularly useful when you want to
1718 override a setting while running user-defined commands, or commands
1719 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1722 (@value{GDBN}) with print pretty on -- my_complex_command
1725 To change several settings for the same command, you can nest
1726 @code{with} commands. For example, @code{with language ada -- with
1727 print elements 10} temporarily changes the language to Ada and sets a
1728 limit of 10 elements to print for arrays and strings.
1733 @section Command Completion
1736 @cindex word completion
1737 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1738 only one possibility; it can also show you what the valid possibilities
1739 are for the next word in a command, at any time. This works for @value{GDBN}
1740 commands, @value{GDBN} subcommands, command options, and the names of symbols
1743 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1744 of a word. If there is only one possibility, @value{GDBN} fills in the
1745 word, and waits for you to finish the command (or press @key{RET} to
1746 enter it). For example, if you type
1748 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1749 @c complete accuracy in these examples; space introduced for clarity.
1750 @c If texinfo enhancements make it unnecessary, it would be nice to
1751 @c replace " @key" by "@key" in the following...
1753 (@value{GDBP}) info bre @key{TAB}
1757 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1758 the only @code{info} subcommand beginning with @samp{bre}:
1761 (@value{GDBP}) info breakpoints
1765 You can either press @key{RET} at this point, to run the @code{info
1766 breakpoints} command, or backspace and enter something else, if
1767 @samp{breakpoints} does not look like the command you expected. (If you
1768 were sure you wanted @code{info breakpoints} in the first place, you
1769 might as well just type @key{RET} immediately after @samp{info bre},
1770 to exploit command abbreviations rather than command completion).
1772 If there is more than one possibility for the next word when you press
1773 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1774 characters and try again, or just press @key{TAB} a second time;
1775 @value{GDBN} displays all the possible completions for that word. For
1776 example, you might want to set a breakpoint on a subroutine whose name
1777 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1778 just sounds the bell. Typing @key{TAB} again displays all the
1779 function names in your program that begin with those characters, for
1783 (@value{GDBP}) b make_ @key{TAB}
1784 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1785 make_a_section_from_file make_environ
1786 make_abs_section make_function_type
1787 make_blockvector make_pointer_type
1788 make_cleanup make_reference_type
1789 make_command make_symbol_completion_list
1790 (@value{GDBP}) b make_
1794 After displaying the available possibilities, @value{GDBN} copies your
1795 partial input (@samp{b make_} in the example) so you can finish the
1798 If you just want to see the list of alternatives in the first place, you
1799 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1800 means @kbd{@key{META} ?}. You can type this either by holding down a
1801 key designated as the @key{META} shift on your keyboard (if there is
1802 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1804 If the number of possible completions is large, @value{GDBN} will
1805 print as much of the list as it has collected, as well as a message
1806 indicating that the list may be truncated.
1809 (@value{GDBP}) b m@key{TAB}@key{TAB}
1811 <... the rest of the possible completions ...>
1812 *** List may be truncated, max-completions reached. ***
1817 This behavior can be controlled with the following commands:
1820 @kindex set max-completions
1821 @item set max-completions @var{limit}
1822 @itemx set max-completions unlimited
1823 Set the maximum number of completion candidates. @value{GDBN} will
1824 stop looking for more completions once it collects this many candidates.
1825 This is useful when completing on things like function names as collecting
1826 all the possible candidates can be time consuming.
1827 The default value is 200. A value of zero disables tab-completion.
1828 Note that setting either no limit or a very large limit can make
1830 @kindex show max-completions
1831 @item show max-completions
1832 Show the maximum number of candidates that @value{GDBN} will collect and show
1836 @cindex quotes in commands
1837 @cindex completion of quoted strings
1838 Sometimes the string you need, while logically a ``word'', may contain
1839 parentheses or other characters that @value{GDBN} normally excludes from
1840 its notion of a word. To permit word completion to work in this
1841 situation, you may enclose words in @code{'} (single quote marks) in
1842 @value{GDBN} commands.
1844 A likely situation where you might need this is in typing an
1845 expression that involves a C@t{++} symbol name with template
1846 parameters. This is because when completing expressions, GDB treats
1847 the @samp{<} character as word delimiter, assuming that it's the
1848 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1851 For example, when you want to call a C@t{++} template function
1852 interactively using the @code{print} or @code{call} commands, you may
1853 need to distinguish whether you mean the version of @code{name} that
1854 was specialized for @code{int}, @code{name<int>()}, or the version
1855 that was specialized for @code{float}, @code{name<float>()}. To use
1856 the word-completion facilities in this situation, type a single quote
1857 @code{'} at the beginning of the function name. This alerts
1858 @value{GDBN} that it may need to consider more information than usual
1859 when you press @key{TAB} or @kbd{M-?} to request word completion:
1862 (@value{GDBP}) p 'func< @kbd{M-?}
1863 func<int>() func<float>()
1864 (@value{GDBP}) p 'func<
1867 When setting breakpoints however (@pxref{Specify Location}), you don't
1868 usually need to type a quote before the function name, because
1869 @value{GDBN} understands that you want to set a breakpoint on a
1873 (@value{GDBP}) b func< @kbd{M-?}
1874 func<int>() func<float>()
1875 (@value{GDBP}) b func<
1878 This is true even in the case of typing the name of C@t{++} overloaded
1879 functions (multiple definitions of the same function, distinguished by
1880 argument type). For example, when you want to set a breakpoint you
1881 don't need to distinguish whether you mean the version of @code{name}
1882 that takes an @code{int} parameter, @code{name(int)}, or the version
1883 that takes a @code{float} parameter, @code{name(float)}.
1886 (@value{GDBP}) b bubble( @kbd{M-?}
1887 bubble(int) bubble(double)
1888 (@value{GDBP}) b bubble(dou @kbd{M-?}
1892 See @ref{quoting names} for a description of other scenarios that
1895 For more information about overloaded functions, see @ref{C Plus Plus
1896 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1897 overload-resolution off} to disable overload resolution;
1898 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1900 @cindex completion of structure field names
1901 @cindex structure field name completion
1902 @cindex completion of union field names
1903 @cindex union field name completion
1904 When completing in an expression which looks up a field in a
1905 structure, @value{GDBN} also tries@footnote{The completer can be
1906 confused by certain kinds of invalid expressions. Also, it only
1907 examines the static type of the expression, not the dynamic type.} to
1908 limit completions to the field names available in the type of the
1912 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1913 magic to_fputs to_rewind
1914 to_data to_isatty to_write
1915 to_delete to_put to_write_async_safe
1920 This is because the @code{gdb_stdout} is a variable of the type
1921 @code{struct ui_file} that is defined in @value{GDBN} sources as
1928 ui_file_flush_ftype *to_flush;
1929 ui_file_write_ftype *to_write;
1930 ui_file_write_async_safe_ftype *to_write_async_safe;
1931 ui_file_fputs_ftype *to_fputs;
1932 ui_file_read_ftype *to_read;
1933 ui_file_delete_ftype *to_delete;
1934 ui_file_isatty_ftype *to_isatty;
1935 ui_file_rewind_ftype *to_rewind;
1936 ui_file_put_ftype *to_put;
1941 @node Command Options
1942 @section Command options
1944 @cindex command options
1945 Some commands accept options starting with a leading dash. For
1946 example, @code{print -pretty}. Similarly to command names, you can
1947 abbreviate a @value{GDBN} option to the first few letters of the
1948 option name, if that abbreviation is unambiguous, and you can also use
1949 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
1950 in an option (or to show you the alternatives available, if there is
1951 more than one possibility).
1953 @cindex command options, raw input
1954 Some commands take raw input as argument. For example, the print
1955 command processes arbitrary expressions in any of the languages
1956 supported by @value{GDBN}. With such commands, because raw input may
1957 start with a leading dash that would be confused with an option or any
1958 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
1959 -pretty} or printing negative @code{p}?), if you specify any command
1960 option, then you must use a double-dash (@code{--}) delimiter to
1961 indicate the end of options.
1963 @cindex command options, boolean
1965 Some options are described as accepting an argument which can be
1966 either @code{on} or @code{off}. These are known as @dfn{boolean
1967 options}. Similarly to boolean settings commands---@code{on} and
1968 @code{off} are the typical values, but any of @code{1}, @code{yes} and
1969 @code{enable} can also be used as ``true'' value, and any of @code{0},
1970 @code{no} and @code{disable} can also be used as ``false'' value. You
1971 can also omit a ``true'' value, as it is implied by default.
1973 For example, these are equivalent:
1976 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
1977 (@value{GDBP}) p -o -p 0 -e u -- *myptr
1980 You can discover the set of options some command accepts by completing
1981 on @code{-} after the command name. For example:
1984 (@value{GDBP}) print -@key{TAB}@key{TAB}
1985 -address -max-depth -raw-values -union
1986 -array -null-stop -repeats -vtbl
1987 -array-indexes -object -static-members
1988 -elements -pretty -symbol
1991 Completion will in some cases guide you with a suggestion of what kind
1992 of argument an option expects. For example:
1995 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
1999 Here, the option expects a number (e.g., @code{100}), not literal
2000 @code{NUMBER}. Such metasyntactical arguments are always presented in
2003 (For more on using the @code{print} command, see @ref{Data, ,Examining
2006 @node Command aliases default args
2007 @section Automatically prepend default arguments to user-defined aliases
2009 You can tell @value{GDBN} to always prepend some default arguments to
2010 the list of arguments provided explicitly by the user when using a
2013 If you repeatedly use the same arguments or options for a command, you
2014 can define an alias for this command and tell @value{GDBN} to
2015 automatically prepend these arguments or options to the list of
2016 arguments you type explicitly when using the alias@footnote{@value{GDBN}
2017 could easily accept default arguments for pre-defined commands and aliases,
2018 but it was deemed this would be confusing, and so is not allowed.}.
2020 For example, if you often use the command @code{thread apply all}
2021 specifying to work on the threads in ascending order and to continue in case it
2022 encounters an error, you can tell @value{GDBN} to automatically preprend
2023 the @code{-ascending} and @code{-c} options by using:
2026 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
2029 Once you have defined this alias with its default args, any time you type
2030 the @code{thread apply asc-all} followed by @code{some arguments},
2031 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
2033 To have even less to type, you can also define a one word alias:
2035 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
2038 As usual, unambiguous abbreviations can be used for @var{alias}
2039 and @var{default-args}.
2041 The different aliases of a command do not share their default args.
2042 For example, you define a new alias @code{bt_ALL} showing all possible
2043 information and another alias @code{bt_SMALL} showing very limited information
2046 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
2047 -past-main -past-entry -full
2048 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
2049 -past-main off -past-entry off
2052 (For more on using the @code{alias} command, see @ref{Aliases}.)
2054 Default args are not limited to the arguments and options of @var{command},
2055 but can specify nested commands if @var{command} accepts such a nested command
2057 For example, the below defines @code{faalocalsoftype} that lists the
2058 frames having locals of a certain type, together with the matching
2061 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
2062 (@value{GDBP}) faalocalsoftype int
2063 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
2068 This is also very useful to define an alias for a set of nested @code{with}
2069 commands to have a particular combination of temporary settings. For example,
2070 the below defines the alias @code{pp10} that pretty prints an expression
2071 argument, with a maximum of 10 elements if the expression is a string or
2074 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
2076 This defines the alias @code{pp10} as being a sequence of 3 commands.
2077 The first part @code{with print pretty --} temporarily activates the setting
2078 @code{set print pretty}, then launches the command that follows the separator
2080 The command following the first part is also a @code{with} command that
2081 temporarily changes the setting @code{set print elements} to 10, then
2082 launches the command that follows the second separator @code{--}.
2083 The third part @code{print} is the command the @code{pp10} alias will launch,
2084 using the temporary values of the settings and the arguments explicitly given
2086 For more information about the @code{with} command usage,
2087 see @ref{Command Settings}.
2090 @section Getting Help
2091 @cindex online documentation
2094 You can always ask @value{GDBN} itself for information on its commands,
2095 using the command @code{help}.
2098 @kindex h @r{(@code{help})}
2101 You can use @code{help} (abbreviated @code{h}) with no arguments to
2102 display a short list of named classes of commands:
2106 List of classes of commands:
2108 aliases -- User-defined aliases of other commands
2109 breakpoints -- Making program stop at certain points
2110 data -- Examining data
2111 files -- Specifying and examining files
2112 internals -- Maintenance commands
2113 obscure -- Obscure features
2114 running -- Running the program
2115 stack -- Examining the stack
2116 status -- Status inquiries
2117 support -- Support facilities
2118 tracepoints -- Tracing of program execution without
2119 stopping the program
2120 user-defined -- User-defined commands
2122 Type "help" followed by a class name for a list of
2123 commands in that class.
2124 Type "help" followed by command name for full
2126 Command name abbreviations are allowed if unambiguous.
2129 @c the above line break eliminates huge line overfull...
2131 @item help @var{class}
2132 Using one of the general help classes as an argument, you can get a
2133 list of the individual commands in that class. If a command has
2134 aliases, the aliases are given after the command name, separated by
2135 commas. If an alias has default arguments, the full definition of
2136 the alias is given after the first line.
2137 For example, here is the help display for the class @code{status}:
2140 (@value{GDBP}) help status
2145 @c Line break in "show" line falsifies real output, but needed
2146 @c to fit in smallbook page size.
2147 info, inf, i -- Generic command for showing things
2148 about the program being debugged
2149 info address, iamain -- Describe where symbol SYM is stored.
2150 alias iamain = info address main
2151 info all-registers -- List of all registers and their contents,
2152 for selected stack frame.
2154 show, info set -- Generic command for showing things
2157 Type "help" followed by command name for full
2159 Command name abbreviations are allowed if unambiguous.
2163 @item help @var{command}
2164 With a command name as @code{help} argument, @value{GDBN} displays a
2165 short paragraph on how to use that command. If that command has
2166 one or more aliases, @value{GDBN} will display a first line with
2167 the command name and all its aliases separated by commas.
2168 This first line will be followed by the full definition of all aliases
2169 having default arguments.
2172 @item apropos [-v] @var{regexp}
2173 The @code{apropos} command searches through all of the @value{GDBN}
2174 commands, and their documentation, for the regular expression specified in
2175 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2176 which stands for @samp{verbose}, indicates to output the full documentation
2177 of the matching commands and highlight the parts of the documentation
2178 matching @var{regexp}. For example:
2189 alias -- Define a new command that is an alias of an existing command
2190 aliases -- User-defined aliases of other commands
2198 apropos -v cut.*thread apply
2202 results in the below output, where @samp{cut for 'thread apply}
2203 is highlighted if styling is enabled.
2207 taas -- Apply a command to all threads (ignoring errors
2210 shortcut for 'thread apply all -s COMMAND'
2212 tfaas -- Apply a command to all frames of all threads
2213 (ignoring errors and empty output).
2214 Usage: tfaas COMMAND
2215 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2220 @item complete @var{args}
2221 The @code{complete @var{args}} command lists all the possible completions
2222 for the beginning of a command. Use @var{args} to specify the beginning of the
2223 command you want completed. For example:
2229 @noindent results in:
2240 @noindent This is intended for use by @sc{gnu} Emacs.
2243 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2244 and @code{show} to inquire about the state of your program, or the state
2245 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2246 manual introduces each of them in the appropriate context. The listings
2247 under @code{info} and under @code{show} in the Command, Variable, and
2248 Function Index point to all the sub-commands. @xref{Command and Variable
2254 @kindex i @r{(@code{info})}
2256 This command (abbreviated @code{i}) is for describing the state of your
2257 program. For example, you can show the arguments passed to a function
2258 with @code{info args}, list the registers currently in use with @code{info
2259 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2260 You can get a complete list of the @code{info} sub-commands with
2261 @w{@code{help info}}.
2265 You can assign the result of an expression to an environment variable with
2266 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2267 @code{set prompt $}.
2271 In contrast to @code{info}, @code{show} is for describing the state of
2272 @value{GDBN} itself.
2273 You can change most of the things you can @code{show}, by using the
2274 related command @code{set}; for example, you can control what number
2275 system is used for displays with @code{set radix}, or simply inquire
2276 which is currently in use with @code{show radix}.
2279 To display all the settable parameters and their current
2280 values, you can use @code{show} with no arguments; you may also use
2281 @code{info set}. Both commands produce the same display.
2282 @c FIXME: "info set" violates the rule that "info" is for state of
2283 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2284 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2288 Here are several miscellaneous @code{show} subcommands, all of which are
2289 exceptional in lacking corresponding @code{set} commands:
2292 @kindex show version
2293 @cindex @value{GDBN} version number
2295 Show what version of @value{GDBN} is running. You should include this
2296 information in @value{GDBN} bug-reports. If multiple versions of
2297 @value{GDBN} are in use at your site, you may need to determine which
2298 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2299 commands are introduced, and old ones may wither away. Also, many
2300 system vendors ship variant versions of @value{GDBN}, and there are
2301 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2302 The version number is the same as the one announced when you start
2305 @kindex show copying
2306 @kindex info copying
2307 @cindex display @value{GDBN} copyright
2310 Display information about permission for copying @value{GDBN}.
2312 @kindex show warranty
2313 @kindex info warranty
2315 @itemx info warranty
2316 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2317 if your version of @value{GDBN} comes with one.
2319 @kindex show configuration
2320 @item show configuration
2321 Display detailed information about the way @value{GDBN} was configured
2322 when it was built. This displays the optional arguments passed to the
2323 @file{configure} script and also configuration parameters detected
2324 automatically by @command{configure}. When reporting a @value{GDBN}
2325 bug (@pxref{GDB Bugs}), it is important to include this information in
2331 @chapter Running Programs Under @value{GDBN}
2333 When you run a program under @value{GDBN}, you must first generate
2334 debugging information when you compile it.
2336 You may start @value{GDBN} with its arguments, if any, in an environment
2337 of your choice. If you are doing native debugging, you may redirect
2338 your program's input and output, debug an already running process, or
2339 kill a child process.
2342 * Compilation:: Compiling for debugging
2343 * Starting:: Starting your program
2344 * Arguments:: Your program's arguments
2345 * Environment:: Your program's environment
2347 * Working Directory:: Your program's working directory
2348 * Input/Output:: Your program's input and output
2349 * Attach:: Debugging an already-running process
2350 * Kill Process:: Killing the child process
2351 * Inferiors Connections and Programs:: Debugging multiple inferiors
2352 connections and programs
2353 * Threads:: Debugging programs with multiple threads
2354 * Forks:: Debugging forks
2355 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2359 @section Compiling for Debugging
2361 In order to debug a program effectively, you need to generate
2362 debugging information when you compile it. This debugging information
2363 is stored in the object file; it describes the data type of each
2364 variable or function and the correspondence between source line numbers
2365 and addresses in the executable code.
2367 To request debugging information, specify the @samp{-g} option when you run
2370 Programs that are to be shipped to your customers are compiled with
2371 optimizations, using the @samp{-O} compiler option. However, some
2372 compilers are unable to handle the @samp{-g} and @samp{-O} options
2373 together. Using those compilers, you cannot generate optimized
2374 executables containing debugging information.
2376 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2377 without @samp{-O}, making it possible to debug optimized code. We
2378 recommend that you @emph{always} use @samp{-g} whenever you compile a
2379 program. You may think your program is correct, but there is no sense
2380 in pushing your luck. For more information, see @ref{Optimized Code}.
2382 Older versions of the @sc{gnu} C compiler permitted a variant option
2383 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2384 format; if your @sc{gnu} C compiler has this option, do not use it.
2386 @value{GDBN} knows about preprocessor macros and can show you their
2387 expansion (@pxref{Macros}). Most compilers do not include information
2388 about preprocessor macros in the debugging information if you specify
2389 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2390 the @sc{gnu} C compiler, provides macro information if you are using
2391 the DWARF debugging format, and specify the option @option{-g3}.
2393 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2394 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2395 information on @value{NGCC} options affecting debug information.
2397 You will have the best debugging experience if you use the latest
2398 version of the DWARF debugging format that your compiler supports.
2399 DWARF is currently the most expressive and best supported debugging
2400 format in @value{GDBN}.
2404 @section Starting your Program
2410 @kindex r @r{(@code{run})}
2413 Use the @code{run} command to start your program under @value{GDBN}.
2414 You must first specify the program name with an argument to
2415 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2416 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2417 command (@pxref{Files, ,Commands to Specify Files}).
2421 If you are running your program in an execution environment that
2422 supports processes, @code{run} creates an inferior process and makes
2423 that process run your program. In some environments without processes,
2424 @code{run} jumps to the start of your program. Other targets,
2425 like @samp{remote}, are always running. If you get an error
2426 message like this one:
2429 The "remote" target does not support "run".
2430 Try "help target" or "continue".
2434 then use @code{continue} to run your program. You may need @code{load}
2435 first (@pxref{load}).
2437 The execution of a program is affected by certain information it
2438 receives from its superior. @value{GDBN} provides ways to specify this
2439 information, which you must do @emph{before} starting your program. (You
2440 can change it after starting your program, but such changes only affect
2441 your program the next time you start it.) This information may be
2442 divided into four categories:
2445 @item The @emph{arguments.}
2446 Specify the arguments to give your program as the arguments of the
2447 @code{run} command. If a shell is available on your target, the shell
2448 is used to pass the arguments, so that you may use normal conventions
2449 (such as wildcard expansion or variable substitution) in describing
2451 In Unix systems, you can control which shell is used with the
2452 @code{SHELL} environment variable. If you do not define @code{SHELL},
2453 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2454 use of any shell with the @code{set startup-with-shell} command (see
2457 @item The @emph{environment.}
2458 Your program normally inherits its environment from @value{GDBN}, but you can
2459 use the @value{GDBN} commands @code{set environment} and @code{unset
2460 environment} to change parts of the environment that affect
2461 your program. @xref{Environment, ,Your Program's Environment}.
2463 @item The @emph{working directory.}
2464 You can set your program's working directory with the command
2465 @kbd{set cwd}. If you do not set any working directory with this
2466 command, your program will inherit @value{GDBN}'s working directory if
2467 native debugging, or the remote server's working directory if remote
2468 debugging. @xref{Working Directory, ,Your Program's Working
2471 @item The @emph{standard input and output.}
2472 Your program normally uses the same device for standard input and
2473 standard output as @value{GDBN} is using. You can redirect input and output
2474 in the @code{run} command line, or you can use the @code{tty} command to
2475 set a different device for your program.
2476 @xref{Input/Output, ,Your Program's Input and Output}.
2479 @emph{Warning:} While input and output redirection work, you cannot use
2480 pipes to pass the output of the program you are debugging to another
2481 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2485 When you issue the @code{run} command, your program begins to execute
2486 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2487 of how to arrange for your program to stop. Once your program has
2488 stopped, you may call functions in your program, using the @code{print}
2489 or @code{call} commands. @xref{Data, ,Examining Data}.
2491 If the modification time of your symbol file has changed since the last
2492 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2493 table, and reads it again. When it does this, @value{GDBN} tries to retain
2494 your current breakpoints.
2499 @cindex run to main procedure
2500 The name of the main procedure can vary from language to language.
2501 With C or C@t{++}, the main procedure name is always @code{main}, but
2502 other languages such as Ada do not require a specific name for their
2503 main procedure. The debugger provides a convenient way to start the
2504 execution of the program and to stop at the beginning of the main
2505 procedure, depending on the language used.
2507 The @samp{start} command does the equivalent of setting a temporary
2508 breakpoint at the beginning of the main procedure and then invoking
2509 the @samp{run} command.
2511 @cindex elaboration phase
2512 Some programs contain an @dfn{elaboration} phase where some startup code is
2513 executed before the main procedure is called. This depends on the
2514 languages used to write your program. In C@t{++}, for instance,
2515 constructors for static and global objects are executed before
2516 @code{main} is called. It is therefore possible that the debugger stops
2517 before reaching the main procedure. However, the temporary breakpoint
2518 will remain to halt execution.
2520 Specify the arguments to give to your program as arguments to the
2521 @samp{start} command. These arguments will be given verbatim to the
2522 underlying @samp{run} command. Note that the same arguments will be
2523 reused if no argument is provided during subsequent calls to
2524 @samp{start} or @samp{run}.
2526 It is sometimes necessary to debug the program during elaboration. In
2527 these cases, using the @code{start} command would stop the execution
2528 of your program too late, as the program would have already completed
2529 the elaboration phase. Under these circumstances, either insert
2530 breakpoints in your elaboration code before running your program or
2531 use the @code{starti} command.
2535 @cindex run to first instruction
2536 The @samp{starti} command does the equivalent of setting a temporary
2537 breakpoint at the first instruction of a program's execution and then
2538 invoking the @samp{run} command. For programs containing an
2539 elaboration phase, the @code{starti} command will stop execution at
2540 the start of the elaboration phase.
2542 @anchor{set exec-wrapper}
2543 @kindex set exec-wrapper
2544 @item set exec-wrapper @var{wrapper}
2545 @itemx show exec-wrapper
2546 @itemx unset exec-wrapper
2547 When @samp{exec-wrapper} is set, the specified wrapper is used to
2548 launch programs for debugging. @value{GDBN} starts your program
2549 with a shell command of the form @kbd{exec @var{wrapper}
2550 @var{program}}. Quoting is added to @var{program} and its
2551 arguments, but not to @var{wrapper}, so you should add quotes if
2552 appropriate for your shell. The wrapper runs until it executes
2553 your program, and then @value{GDBN} takes control.
2555 You can use any program that eventually calls @code{execve} with
2556 its arguments as a wrapper. Several standard Unix utilities do
2557 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2558 with @code{exec "$@@"} will also work.
2560 For example, you can use @code{env} to pass an environment variable to
2561 the debugged program, without setting the variable in your shell's
2565 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2569 This command is available when debugging locally on most targets, excluding
2570 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2572 @kindex set startup-with-shell
2573 @anchor{set startup-with-shell}
2574 @item set startup-with-shell
2575 @itemx set startup-with-shell on
2576 @itemx set startup-with-shell off
2577 @itemx show startup-with-shell
2578 On Unix systems, by default, if a shell is available on your target,
2579 @value{GDBN}) uses it to start your program. Arguments of the
2580 @code{run} command are passed to the shell, which does variable
2581 substitution, expands wildcard characters and performs redirection of
2582 I/O. In some circumstances, it may be useful to disable such use of a
2583 shell, for example, when debugging the shell itself or diagnosing
2584 startup failures such as:
2588 Starting program: ./a.out
2589 During startup program terminated with signal SIGSEGV, Segmentation fault.
2593 which indicates the shell or the wrapper specified with
2594 @samp{exec-wrapper} crashed, not your program. Most often, this is
2595 caused by something odd in your shell's non-interactive mode
2596 initialization file---such as @file{.cshrc} for C-shell,
2597 $@file{.zshenv} for the Z shell, or the file specified in the
2598 @samp{BASH_ENV} environment variable for BASH.
2600 @anchor{set auto-connect-native-target}
2601 @kindex set auto-connect-native-target
2602 @item set auto-connect-native-target
2603 @itemx set auto-connect-native-target on
2604 @itemx set auto-connect-native-target off
2605 @itemx show auto-connect-native-target
2607 By default, if the current inferior is not connected to any target yet
2608 (e.g., with @code{target remote}), the @code{run} command starts your
2609 program as a native process under @value{GDBN}, on your local machine.
2610 If you're sure you don't want to debug programs on your local machine,
2611 you can tell @value{GDBN} to not connect to the native target
2612 automatically with the @code{set auto-connect-native-target off}
2615 If @code{on}, which is the default, and if the current inferior is not
2616 connected to a target already, the @code{run} command automaticaly
2617 connects to the native target, if one is available.
2619 If @code{off}, and if the current inferior is not connected to a
2620 target already, the @code{run} command fails with an error:
2624 Don't know how to run. Try "help target".
2627 If the current inferior is already connected to a target, @value{GDBN}
2628 always uses it with the @code{run} command.
2630 In any case, you can explicitly connect to the native target with the
2631 @code{target native} command. For example,
2634 (@value{GDBP}) set auto-connect-native-target off
2636 Don't know how to run. Try "help target".
2637 (@value{GDBP}) target native
2639 Starting program: ./a.out
2640 [Inferior 1 (process 10421) exited normally]
2643 In case you connected explicitly to the @code{native} target,
2644 @value{GDBN} remains connected even if all inferiors exit, ready for
2645 the next @code{run} command. Use the @code{disconnect} command to
2648 Examples of other commands that likewise respect the
2649 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2650 proc}, @code{info os}.
2652 @kindex set disable-randomization
2653 @item set disable-randomization
2654 @itemx set disable-randomization on
2655 This option (enabled by default in @value{GDBN}) will turn off the native
2656 randomization of the virtual address space of the started program. This option
2657 is useful for multiple debugging sessions to make the execution better
2658 reproducible and memory addresses reusable across debugging sessions.
2660 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2661 On @sc{gnu}/Linux you can get the same behavior using
2664 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2667 @item set disable-randomization off
2668 Leave the behavior of the started executable unchanged. Some bugs rear their
2669 ugly heads only when the program is loaded at certain addresses. If your bug
2670 disappears when you run the program under @value{GDBN}, that might be because
2671 @value{GDBN} by default disables the address randomization on platforms, such
2672 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2673 disable-randomization off} to try to reproduce such elusive bugs.
2675 On targets where it is available, virtual address space randomization
2676 protects the programs against certain kinds of security attacks. In these
2677 cases the attacker needs to know the exact location of a concrete executable
2678 code. Randomizing its location makes it impossible to inject jumps misusing
2679 a code at its expected addresses.
2681 Prelinking shared libraries provides a startup performance advantage but it
2682 makes addresses in these libraries predictable for privileged processes by
2683 having just unprivileged access at the target system. Reading the shared
2684 library binary gives enough information for assembling the malicious code
2685 misusing it. Still even a prelinked shared library can get loaded at a new
2686 random address just requiring the regular relocation process during the
2687 startup. Shared libraries not already prelinked are always loaded at
2688 a randomly chosen address.
2690 Position independent executables (PIE) contain position independent code
2691 similar to the shared libraries and therefore such executables get loaded at
2692 a randomly chosen address upon startup. PIE executables always load even
2693 already prelinked shared libraries at a random address. You can build such
2694 executable using @command{gcc -fPIE -pie}.
2696 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2697 (as long as the randomization is enabled).
2699 @item show disable-randomization
2700 Show the current setting of the explicit disable of the native randomization of
2701 the virtual address space of the started program.
2706 @section Your Program's Arguments
2708 @cindex arguments (to your program)
2709 The arguments to your program can be specified by the arguments of the
2711 They are passed to a shell, which expands wildcard characters and
2712 performs redirection of I/O, and thence to your program. Your
2713 @code{SHELL} environment variable (if it exists) specifies what shell
2714 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2715 the default shell (@file{/bin/sh} on Unix).
2717 On non-Unix systems, the program is usually invoked directly by
2718 @value{GDBN}, which emulates I/O redirection via the appropriate system
2719 calls, and the wildcard characters are expanded by the startup code of
2720 the program, not by the shell.
2722 @code{run} with no arguments uses the same arguments used by the previous
2723 @code{run}, or those set by the @code{set args} command.
2728 Specify the arguments to be used the next time your program is run. If
2729 @code{set args} has no arguments, @code{run} executes your program
2730 with no arguments. Once you have run your program with arguments,
2731 using @code{set args} before the next @code{run} is the only way to run
2732 it again without arguments.
2736 Show the arguments to give your program when it is started.
2740 @section Your Program's Environment
2742 @cindex environment (of your program)
2743 The @dfn{environment} consists of a set of environment variables and
2744 their values. Environment variables conventionally record such things as
2745 your user name, your home directory, your terminal type, and your search
2746 path for programs to run. Usually you set up environment variables with
2747 the shell and they are inherited by all the other programs you run. When
2748 debugging, it can be useful to try running your program with a modified
2749 environment without having to start @value{GDBN} over again.
2753 @item path @var{directory}
2754 Add @var{directory} to the front of the @code{PATH} environment variable
2755 (the search path for executables) that will be passed to your program.
2756 The value of @code{PATH} used by @value{GDBN} does not change.
2757 You may specify several directory names, separated by whitespace or by a
2758 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2759 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2760 is moved to the front, so it is searched sooner.
2762 You can use the string @samp{$cwd} to refer to whatever is the current
2763 working directory at the time @value{GDBN} searches the path. If you
2764 use @samp{.} instead, it refers to the directory where you executed the
2765 @code{path} command. @value{GDBN} replaces @samp{.} in the
2766 @var{directory} argument (with the current path) before adding
2767 @var{directory} to the search path.
2768 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2769 @c document that, since repeating it would be a no-op.
2773 Display the list of search paths for executables (the @code{PATH}
2774 environment variable).
2776 @kindex show environment
2777 @item show environment @r{[}@var{varname}@r{]}
2778 Print the value of environment variable @var{varname} to be given to
2779 your program when it starts. If you do not supply @var{varname},
2780 print the names and values of all environment variables to be given to
2781 your program. You can abbreviate @code{environment} as @code{env}.
2783 @kindex set environment
2784 @anchor{set environment}
2785 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2786 Set environment variable @var{varname} to @var{value}. The value
2787 changes for your program (and the shell @value{GDBN} uses to launch
2788 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2789 values of environment variables are just strings, and any
2790 interpretation is supplied by your program itself. The @var{value}
2791 parameter is optional; if it is eliminated, the variable is set to a
2793 @c "any string" here does not include leading, trailing
2794 @c blanks. Gnu asks: does anyone care?
2796 For example, this command:
2803 tells the debugged program, when subsequently run, that its user is named
2804 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2805 are not actually required.)
2807 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2808 which also inherits the environment set with @code{set environment}.
2809 If necessary, you can avoid that by using the @samp{env} program as a
2810 wrapper instead of using @code{set environment}. @xref{set
2811 exec-wrapper}, for an example doing just that.
2813 Environment variables that are set by the user are also transmitted to
2814 @command{gdbserver} to be used when starting the remote inferior.
2815 @pxref{QEnvironmentHexEncoded}.
2817 @kindex unset environment
2818 @anchor{unset environment}
2819 @item unset environment @var{varname}
2820 Remove variable @var{varname} from the environment to be passed to your
2821 program. This is different from @samp{set env @var{varname} =};
2822 @code{unset environment} removes the variable from the environment,
2823 rather than assigning it an empty value.
2825 Environment variables that are unset by the user are also unset on
2826 @command{gdbserver} when starting the remote inferior.
2827 @pxref{QEnvironmentUnset}.
2830 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2831 the shell indicated by your @code{SHELL} environment variable if it
2832 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2833 names a shell that runs an initialization file when started
2834 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2835 for the Z shell, or the file specified in the @samp{BASH_ENV}
2836 environment variable for BASH---any variables you set in that file
2837 affect your program. You may wish to move setting of environment
2838 variables to files that are only run when you sign on, such as
2839 @file{.login} or @file{.profile}.
2841 @node Working Directory
2842 @section Your Program's Working Directory
2844 @cindex working directory (of your program)
2845 Each time you start your program with @code{run}, the inferior will be
2846 initialized with the current working directory specified by the
2847 @kbd{set cwd} command. If no directory has been specified by this
2848 command, then the inferior will inherit @value{GDBN}'s current working
2849 directory as its working directory if native debugging, or it will
2850 inherit the remote server's current working directory if remote
2855 @cindex change inferior's working directory
2856 @anchor{set cwd command}
2857 @item set cwd @r{[}@var{directory}@r{]}
2858 Set the inferior's working directory to @var{directory}, which will be
2859 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2860 argument has been specified, the command clears the setting and resets
2861 it to an empty state. This setting has no effect on @value{GDBN}'s
2862 working directory, and it only takes effect the next time you start
2863 the inferior. The @file{~} in @var{directory} is a short for the
2864 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2865 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2866 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2869 You can also change @value{GDBN}'s current working directory by using
2870 the @code{cd} command.
2874 @cindex show inferior's working directory
2876 Show the inferior's working directory. If no directory has been
2877 specified by @kbd{set cwd}, then the default inferior's working
2878 directory is the same as @value{GDBN}'s working directory.
2881 @cindex change @value{GDBN}'s working directory
2883 @item cd @r{[}@var{directory}@r{]}
2884 Set the @value{GDBN} working directory to @var{directory}. If not
2885 given, @var{directory} uses @file{'~'}.
2887 The @value{GDBN} working directory serves as a default for the
2888 commands that specify files for @value{GDBN} to operate on.
2889 @xref{Files, ,Commands to Specify Files}.
2890 @xref{set cwd command}.
2894 Print the @value{GDBN} working directory.
2897 It is generally impossible to find the current working directory of
2898 the process being debugged (since a program can change its directory
2899 during its run). If you work on a system where @value{GDBN} supports
2900 the @code{info proc} command (@pxref{Process Information}), you can
2901 use the @code{info proc} command to find out the
2902 current working directory of the debuggee.
2905 @section Your Program's Input and Output
2910 By default, the program you run under @value{GDBN} does input and output to
2911 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2912 to its own terminal modes to interact with you, but it records the terminal
2913 modes your program was using and switches back to them when you continue
2914 running your program.
2917 @kindex info terminal
2919 Displays information recorded by @value{GDBN} about the terminal modes your
2923 You can redirect your program's input and/or output using shell
2924 redirection with the @code{run} command. For example,
2931 starts your program, diverting its output to the file @file{outfile}.
2934 @cindex controlling terminal
2935 Another way to specify where your program should do input and output is
2936 with the @code{tty} command. This command accepts a file name as
2937 argument, and causes this file to be the default for future @code{run}
2938 commands. It also resets the controlling terminal for the child
2939 process, for future @code{run} commands. For example,
2946 directs that processes started with subsequent @code{run} commands
2947 default to do input and output on the terminal @file{/dev/ttyb} and have
2948 that as their controlling terminal.
2950 An explicit redirection in @code{run} overrides the @code{tty} command's
2951 effect on the input/output device, but not its effect on the controlling
2954 When you use the @code{tty} command or redirect input in the @code{run}
2955 command, only the input @emph{for your program} is affected. The input
2956 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2957 for @code{set inferior-tty}.
2959 @cindex inferior tty
2960 @cindex set inferior controlling terminal
2961 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2962 display the name of the terminal that will be used for future runs of your
2966 @item set inferior-tty [ @var{tty} ]
2967 @kindex set inferior-tty
2968 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2969 restores the default behavior, which is to use the same terminal as
2972 @item show inferior-tty
2973 @kindex show inferior-tty
2974 Show the current tty for the program being debugged.
2978 @section Debugging an Already-running Process
2983 @item attach @var{process-id}
2984 This command attaches to a running process---one that was started
2985 outside @value{GDBN}. (@code{info files} shows your active
2986 targets.) The command takes as argument a process ID. The usual way to
2987 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2988 or with the @samp{jobs -l} shell command.
2990 @code{attach} does not repeat if you press @key{RET} a second time after
2991 executing the command.
2994 To use @code{attach}, your program must be running in an environment
2995 which supports processes; for example, @code{attach} does not work for
2996 programs on bare-board targets that lack an operating system. You must
2997 also have permission to send the process a signal.
2999 When you use @code{attach}, the debugger finds the program running in
3000 the process first by looking in the current working directory, then (if
3001 the program is not found) by using the source file search path
3002 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3003 the @code{file} command to load the program. @xref{Files, ,Commands to
3006 @anchor{set exec-file-mismatch}
3007 If the debugger can determine that the executable file running in the
3008 process it is attaching to does not match the current exec-file loaded
3009 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3010 handle the mismatch. @value{GDBN} tries to compare the files by
3011 comparing their build IDs (@pxref{build ID}), if available.
3014 @kindex exec-file-mismatch
3015 @cindex set exec-file-mismatch
3016 @item set exec-file-mismatch @samp{ask|warn|off}
3018 Whether to detect mismatch between the current executable file loaded
3019 by @value{GDBN} and the executable file used to start the process. If
3020 @samp{ask}, the default, display a warning and ask the user whether to
3021 load the process executable file; if @samp{warn}, just display a
3022 warning; if @samp{off}, don't attempt to detect a mismatch.
3023 If the user confirms loading the process executable file, then its symbols
3024 will be loaded as well.
3026 @cindex show exec-file-mismatch
3027 @item show exec-file-mismatch
3028 Show the current value of @code{exec-file-mismatch}.
3032 The first thing @value{GDBN} does after arranging to debug the specified
3033 process is to stop it. You can examine and modify an attached process
3034 with all the @value{GDBN} commands that are ordinarily available when
3035 you start processes with @code{run}. You can insert breakpoints; you
3036 can step and continue; you can modify storage. If you would rather the
3037 process continue running, you may use the @code{continue} command after
3038 attaching @value{GDBN} to the process.
3043 When you have finished debugging the attached process, you can use the
3044 @code{detach} command to release it from @value{GDBN} control. Detaching
3045 the process continues its execution. After the @code{detach} command,
3046 that process and @value{GDBN} become completely independent once more, and you
3047 are ready to @code{attach} another process or start one with @code{run}.
3048 @code{detach} does not repeat if you press @key{RET} again after
3049 executing the command.
3052 If you exit @value{GDBN} while you have an attached process, you detach
3053 that process. If you use the @code{run} command, you kill that process.
3054 By default, @value{GDBN} asks for confirmation if you try to do either of these
3055 things; you can control whether or not you need to confirm by using the
3056 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3060 @section Killing the Child Process
3065 Kill the child process in which your program is running under @value{GDBN}.
3068 This command is useful if you wish to debug a core dump instead of a
3069 running process. @value{GDBN} ignores any core dump file while your program
3072 On some operating systems, a program cannot be executed outside @value{GDBN}
3073 while you have breakpoints set on it inside @value{GDBN}. You can use the
3074 @code{kill} command in this situation to permit running your program
3075 outside the debugger.
3077 The @code{kill} command is also useful if you wish to recompile and
3078 relink your program, since on many systems it is impossible to modify an
3079 executable file while it is running in a process. In this case, when you
3080 next type @code{run}, @value{GDBN} notices that the file has changed, and
3081 reads the symbol table again (while trying to preserve your current
3082 breakpoint settings).
3084 @node Inferiors Connections and Programs
3085 @section Debugging Multiple Inferiors Connections and Programs
3087 @value{GDBN} lets you run and debug multiple programs in a single
3088 session. In addition, @value{GDBN} on some systems may let you run
3089 several programs simultaneously (otherwise you have to exit from one
3090 before starting another). On some systems @value{GDBN} may even let
3091 you debug several programs simultaneously on different remote systems.
3092 In the most general case, you can have multiple threads of execution
3093 in each of multiple processes, launched from multiple executables,
3094 running on different machines.
3097 @value{GDBN} represents the state of each program execution with an
3098 object called an @dfn{inferior}. An inferior typically corresponds to
3099 a process, but is more general and applies also to targets that do not
3100 have processes. Inferiors may be created before a process runs, and
3101 may be retained after a process exits. Inferiors have unique
3102 identifiers that are different from process ids. Usually each
3103 inferior will also have its own distinct address space, although some
3104 embedded targets may have several inferiors running in different parts
3105 of a single address space. Each inferior may in turn have multiple
3106 threads running in it.
3108 To find out what inferiors exist at any moment, use @w{@code{info
3112 @kindex info inferiors [ @var{id}@dots{} ]
3113 @item info inferiors
3114 Print a list of all inferiors currently being managed by @value{GDBN}.
3115 By default all inferiors are printed, but the argument @var{id}@dots{}
3116 -- a space separated list of inferior numbers -- can be used to limit
3117 the display to just the requested inferiors.
3119 @value{GDBN} displays for each inferior (in this order):
3123 the inferior number assigned by @value{GDBN}
3126 the target system's inferior identifier
3129 the target connection the inferior is bound to, including the unique
3130 connection number assigned by @value{GDBN}, and the protocol used by
3134 the name of the executable the inferior is running.
3139 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3140 indicates the current inferior.
3144 @c end table here to get a little more width for example
3147 (@value{GDBP}) info inferiors
3148 Num Description Connection Executable
3149 * 1 process 3401 1 (native) goodbye
3150 2 process 2307 2 (extended-remote host:10000) hello
3153 To find out what open target connections exist at any moment, use
3154 @w{@code{info connections}}:
3157 @kindex info connections [ @var{id}@dots{} ]
3158 @item info connections
3159 Print a list of all open target connections currently being managed by
3160 @value{GDBN}. By default all connections are printed, but the
3161 argument @var{id}@dots{} -- a space separated list of connections
3162 numbers -- can be used to limit the display to just the requested
3165 @value{GDBN} displays for each connection (in this order):
3169 the connection number assigned by @value{GDBN}.
3172 the protocol used by the connection.
3175 a textual description of the protocol used by the connection.
3180 An asterisk @samp{*} preceding the connection number indicates the
3181 connection of the current inferior.
3185 @c end table here to get a little more width for example
3188 (@value{GDBP}) info connections
3189 Num What Description
3190 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3191 2 native Native process
3192 3 core Local core dump file
3195 To switch focus between inferiors, use the @code{inferior} command:
3198 @kindex inferior @var{infno}
3199 @item inferior @var{infno}
3200 Make inferior number @var{infno} the current inferior. The argument
3201 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3202 in the first field of the @samp{info inferiors} display.
3205 @vindex $_inferior@r{, convenience variable}
3206 The debugger convenience variable @samp{$_inferior} contains the
3207 number of the current inferior. You may find this useful in writing
3208 breakpoint conditional expressions, command scripts, and so forth.
3209 @xref{Convenience Vars,, Convenience Variables}, for general
3210 information on convenience variables.
3212 You can get multiple executables into a debugging session via the
3213 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3214 systems @value{GDBN} can add inferiors to the debug session
3215 automatically by following calls to @code{fork} and @code{exec}. To
3216 remove inferiors from the debugging session use the
3217 @w{@code{remove-inferiors}} command.
3220 @kindex add-inferior
3221 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3222 Adds @var{n} inferiors to be run using @var{executable} as the
3223 executable; @var{n} defaults to 1. If no executable is specified,
3224 the inferiors begins empty, with no program. You can still assign or
3225 change the program assigned to the inferior at any time by using the
3226 @code{file} command with the executable name as its argument.
3228 By default, the new inferior begins connected to the same target
3229 connection as the current inferior. For example, if the current
3230 inferior was connected to @code{gdbserver} with @code{target remote},
3231 then the new inferior will be connected to the same @code{gdbserver}
3232 instance. The @samp{-no-connection} option starts the new inferior
3233 with no connection yet. You can then for example use the @code{target
3234 remote} command to connect to some other @code{gdbserver} instance,
3235 use @code{run} to spawn a local program, etc.
3237 @kindex clone-inferior
3238 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3239 Adds @var{n} inferiors ready to execute the same program as inferior
3240 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3241 number of the current inferior. This is a convenient command when you
3242 want to run another instance of the inferior you are debugging.
3245 (@value{GDBP}) info inferiors
3246 Num Description Connection Executable
3247 * 1 process 29964 1 (native) helloworld
3248 (@value{GDBP}) clone-inferior
3251 (@value{GDBP}) info inferiors
3252 Num Description Connection Executable
3253 * 1 process 29964 1 (native) helloworld
3254 2 <null> 1 (native) helloworld
3257 You can now simply switch focus to inferior 2 and run it.
3259 @kindex remove-inferiors
3260 @item remove-inferiors @var{infno}@dots{}
3261 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3262 possible to remove an inferior that is running with this command. For
3263 those, use the @code{kill} or @code{detach} command first.
3267 To quit debugging one of the running inferiors that is not the current
3268 inferior, you can either detach from it by using the @w{@code{detach
3269 inferior}} command (allowing it to run independently), or kill it
3270 using the @w{@code{kill inferiors}} command:
3273 @kindex detach inferiors @var{infno}@dots{}
3274 @item detach inferior @var{infno}@dots{}
3275 Detach from the inferior or inferiors identified by @value{GDBN}
3276 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3277 still stays on the list of inferiors shown by @code{info inferiors},
3278 but its Description will show @samp{<null>}.
3280 @kindex kill inferiors @var{infno}@dots{}
3281 @item kill inferiors @var{infno}@dots{}
3282 Kill the inferior or inferiors identified by @value{GDBN} inferior
3283 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3284 stays on the list of inferiors shown by @code{info inferiors}, but its
3285 Description will show @samp{<null>}.
3288 After the successful completion of a command such as @code{detach},
3289 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3290 a normal process exit, the inferior is still valid and listed with
3291 @code{info inferiors}, ready to be restarted.
3294 To be notified when inferiors are started or exit under @value{GDBN}'s
3295 control use @w{@code{set print inferior-events}}:
3298 @kindex set print inferior-events
3299 @cindex print messages on inferior start and exit
3300 @item set print inferior-events
3301 @itemx set print inferior-events on
3302 @itemx set print inferior-events off
3303 The @code{set print inferior-events} command allows you to enable or
3304 disable printing of messages when @value{GDBN} notices that new
3305 inferiors have started or that inferiors have exited or have been
3306 detached. By default, these messages will not be printed.
3308 @kindex show print inferior-events
3309 @item show print inferior-events
3310 Show whether messages will be printed when @value{GDBN} detects that
3311 inferiors have started, exited or have been detached.
3314 Many commands will work the same with multiple programs as with a
3315 single program: e.g., @code{print myglobal} will simply display the
3316 value of @code{myglobal} in the current inferior.
3319 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3320 get more info about the relationship of inferiors, programs, address
3321 spaces in a debug session. You can do that with the @w{@code{maint
3322 info program-spaces}} command.
3325 @kindex maint info program-spaces
3326 @item maint info program-spaces
3327 Print a list of all program spaces currently being managed by
3330 @value{GDBN} displays for each program space (in this order):
3334 the program space number assigned by @value{GDBN}
3337 the name of the executable loaded into the program space, with e.g.,
3338 the @code{file} command.
3343 An asterisk @samp{*} preceding the @value{GDBN} program space number
3344 indicates the current program space.
3346 In addition, below each program space line, @value{GDBN} prints extra
3347 information that isn't suitable to display in tabular form. For
3348 example, the list of inferiors bound to the program space.
3351 (@value{GDBP}) maint info program-spaces
3355 Bound inferiors: ID 1 (process 21561)
3358 Here we can see that no inferior is running the program @code{hello},
3359 while @code{process 21561} is running the program @code{goodbye}. On
3360 some targets, it is possible that multiple inferiors are bound to the
3361 same program space. The most common example is that of debugging both
3362 the parent and child processes of a @code{vfork} call. For example,
3365 (@value{GDBP}) maint info program-spaces
3368 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3371 Here, both inferior 2 and inferior 1 are running in the same program
3372 space as a result of inferior 1 having executed a @code{vfork} call.
3376 @section Debugging Programs with Multiple Threads
3378 @cindex threads of execution
3379 @cindex multiple threads
3380 @cindex switching threads
3381 In some operating systems, such as GNU/Linux and Solaris, a single program
3382 may have more than one @dfn{thread} of execution. The precise semantics
3383 of threads differ from one operating system to another, but in general
3384 the threads of a single program are akin to multiple processes---except
3385 that they share one address space (that is, they can all examine and
3386 modify the same variables). On the other hand, each thread has its own
3387 registers and execution stack, and perhaps private memory.
3389 @value{GDBN} provides these facilities for debugging multi-thread
3393 @item automatic notification of new threads
3394 @item @samp{thread @var{thread-id}}, a command to switch among threads
3395 @item @samp{info threads}, a command to inquire about existing threads
3396 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3397 a command to apply a command to a list of threads
3398 @item thread-specific breakpoints
3399 @item @samp{set print thread-events}, which controls printing of
3400 messages on thread start and exit.
3401 @item @samp{set libthread-db-search-path @var{path}}, which lets
3402 the user specify which @code{libthread_db} to use if the default choice
3403 isn't compatible with the program.
3406 @cindex focus of debugging
3407 @cindex current thread
3408 The @value{GDBN} thread debugging facility allows you to observe all
3409 threads while your program runs---but whenever @value{GDBN} takes
3410 control, one thread in particular is always the focus of debugging.
3411 This thread is called the @dfn{current thread}. Debugging commands show
3412 program information from the perspective of the current thread.
3414 @cindex @code{New} @var{systag} message
3415 @cindex thread identifier (system)
3416 @c FIXME-implementors!! It would be more helpful if the [New...] message
3417 @c included GDB's numeric thread handle, so you could just go to that
3418 @c thread without first checking `info threads'.
3419 Whenever @value{GDBN} detects a new thread in your program, it displays
3420 the target system's identification for the thread with a message in the
3421 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3422 whose form varies depending on the particular system. For example, on
3423 @sc{gnu}/Linux, you might see
3426 [New Thread 0x41e02940 (LWP 25582)]
3430 when @value{GDBN} notices a new thread. In contrast, on other systems,
3431 the @var{systag} is simply something like @samp{process 368}, with no
3434 @c FIXME!! (1) Does the [New...] message appear even for the very first
3435 @c thread of a program, or does it only appear for the
3436 @c second---i.e.@: when it becomes obvious we have a multithread
3438 @c (2) *Is* there necessarily a first thread always? Or do some
3439 @c multithread systems permit starting a program with multiple
3440 @c threads ab initio?
3442 @anchor{thread numbers}
3443 @cindex thread number, per inferior
3444 @cindex thread identifier (GDB)
3445 For debugging purposes, @value{GDBN} associates its own thread number
3446 ---always a single integer---with each thread of an inferior. This
3447 number is unique between all threads of an inferior, but not unique
3448 between threads of different inferiors.
3450 @cindex qualified thread ID
3451 You can refer to a given thread in an inferior using the qualified
3452 @var{inferior-num}.@var{thread-num} syntax, also known as
3453 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3454 number and @var{thread-num} being the thread number of the given
3455 inferior. For example, thread @code{2.3} refers to thread number 3 of
3456 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3457 then @value{GDBN} infers you're referring to a thread of the current
3460 Until you create a second inferior, @value{GDBN} does not show the
3461 @var{inferior-num} part of thread IDs, even though you can always use
3462 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3463 of inferior 1, the initial inferior.
3465 @anchor{thread ID lists}
3466 @cindex thread ID lists
3467 Some commands accept a space-separated @dfn{thread ID list} as
3468 argument. A list element can be:
3472 A thread ID as shown in the first field of the @samp{info threads}
3473 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3477 A range of thread numbers, again with or without an inferior
3478 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3479 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3482 All threads of an inferior, specified with a star wildcard, with or
3483 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3484 @samp{1.*}) or @code{*}. The former refers to all threads of the
3485 given inferior, and the latter form without an inferior qualifier
3486 refers to all threads of the current inferior.
3490 For example, if the current inferior is 1, and inferior 7 has one
3491 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3492 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3493 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3494 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3498 @anchor{global thread numbers}
3499 @cindex global thread number
3500 @cindex global thread identifier (GDB)
3501 In addition to a @emph{per-inferior} number, each thread is also
3502 assigned a unique @emph{global} number, also known as @dfn{global
3503 thread ID}, a single integer. Unlike the thread number component of
3504 the thread ID, no two threads have the same global ID, even when
3505 you're debugging multiple inferiors.
3507 From @value{GDBN}'s perspective, a process always has at least one
3508 thread. In other words, @value{GDBN} assigns a thread number to the
3509 program's ``main thread'' even if the program is not multi-threaded.
3511 @vindex $_thread@r{, convenience variable}
3512 @vindex $_gthread@r{, convenience variable}
3513 The debugger convenience variables @samp{$_thread} and
3514 @samp{$_gthread} contain, respectively, the per-inferior thread number
3515 and the global thread number of the current thread. You may find this
3516 useful in writing breakpoint conditional expressions, command scripts,
3517 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3518 general information on convenience variables.
3520 If @value{GDBN} detects the program is multi-threaded, it augments the
3521 usual message about stopping at a breakpoint with the ID and name of
3522 the thread that hit the breakpoint.
3525 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3528 Likewise when the program receives a signal:
3531 Thread 1 "main" received signal SIGINT, Interrupt.
3535 @kindex info threads
3536 @item info threads @r{[}@var{thread-id-list}@r{]}
3538 Display information about one or more threads. With no arguments
3539 displays information about all threads. You can specify the list of
3540 threads that you want to display using the thread ID list syntax
3541 (@pxref{thread ID lists}).
3543 @value{GDBN} displays for each thread (in this order):
3547 the per-inferior thread number assigned by @value{GDBN}
3550 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3551 option was specified
3554 the target system's thread identifier (@var{systag})
3557 the thread's name, if one is known. A thread can either be named by
3558 the user (see @code{thread name}, below), or, in some cases, by the
3562 the current stack frame summary for that thread
3566 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3567 indicates the current thread.
3571 @c end table here to get a little more width for example
3574 (@value{GDBP}) info threads
3576 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3577 2 process 35 thread 23 0x34e5 in sigpause ()
3578 3 process 35 thread 27 0x34e5 in sigpause ()
3582 If you're debugging multiple inferiors, @value{GDBN} displays thread
3583 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3584 Otherwise, only @var{thread-num} is shown.
3586 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3587 indicating each thread's global thread ID:
3590 (@value{GDBP}) info threads
3591 Id GId Target Id Frame
3592 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3593 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3594 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3595 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3598 On Solaris, you can display more information about user threads with a
3599 Solaris-specific command:
3602 @item maint info sol-threads
3603 @kindex maint info sol-threads
3604 @cindex thread info (Solaris)
3605 Display info on Solaris user threads.
3609 @kindex thread @var{thread-id}
3610 @item thread @var{thread-id}
3611 Make thread ID @var{thread-id} the current thread. The command
3612 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3613 the first field of the @samp{info threads} display, with or without an
3614 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3616 @value{GDBN} responds by displaying the system identifier of the
3617 thread you selected, and its current stack frame summary:
3620 (@value{GDBP}) thread 2
3621 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3622 #0 some_function (ignore=0x0) at example.c:8
3623 8 printf ("hello\n");
3627 As with the @samp{[New @dots{}]} message, the form of the text after
3628 @samp{Switching to} depends on your system's conventions for identifying
3631 @anchor{thread apply all}
3632 @kindex thread apply
3633 @cindex apply command to several threads
3634 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3635 The @code{thread apply} command allows you to apply the named
3636 @var{command} to one or more threads. Specify the threads that you
3637 want affected using the thread ID list syntax (@pxref{thread ID
3638 lists}), or specify @code{all} to apply to all threads. To apply a
3639 command to all threads in descending order, type @kbd{thread apply all
3640 @var{command}}. To apply a command to all threads in ascending order,
3641 type @kbd{thread apply all -ascending @var{command}}.
3643 The @var{flag} arguments control what output to produce and how to handle
3644 errors raised when applying @var{command} to a thread. @var{flag}
3645 must start with a @code{-} directly followed by one letter in
3646 @code{qcs}. If several flags are provided, they must be given
3647 individually, such as @code{-c -q}.
3649 By default, @value{GDBN} displays some thread information before the
3650 output produced by @var{command}, and an error raised during the
3651 execution of a @var{command} will abort @code{thread apply}. The
3652 following flags can be used to fine-tune this behavior:
3656 The flag @code{-c}, which stands for @samp{continue}, causes any
3657 errors in @var{command} to be displayed, and the execution of
3658 @code{thread apply} then continues.
3660 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3661 or empty output produced by a @var{command} to be silently ignored.
3662 That is, the execution continues, but the thread information and errors
3665 The flag @code{-q} (@samp{quiet}) disables printing the thread
3669 Flags @code{-c} and @code{-s} cannot be used together.
3672 @cindex apply command to all threads (ignoring errors and empty output)
3673 @item taas [@var{option}]@dots{} @var{command}
3674 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3675 Applies @var{command} on all threads, ignoring errors and empty output.
3677 The @code{taas} command accepts the same options as the @code{thread
3678 apply all} command. @xref{thread apply all}.
3681 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3682 @item tfaas [@var{option}]@dots{} @var{command}
3683 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3684 Applies @var{command} on all frames of all threads, ignoring errors
3685 and empty output. Note that the flag @code{-s} is specified twice:
3686 The first @code{-s} ensures that @code{thread apply} only shows the thread
3687 information of the threads for which @code{frame apply} produces
3688 some output. The second @code{-s} is needed to ensure that @code{frame
3689 apply} shows the frame information of a frame only if the
3690 @var{command} successfully produced some output.
3692 It can for example be used to print a local variable or a function
3693 argument without knowing the thread or frame where this variable or argument
3696 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3699 The @code{tfaas} command accepts the same options as the @code{frame
3700 apply} command. @xref{Frame Apply,,frame apply}.
3703 @cindex name a thread
3704 @item thread name [@var{name}]
3705 This command assigns a name to the current thread. If no argument is
3706 given, any existing user-specified name is removed. The thread name
3707 appears in the @samp{info threads} display.
3709 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3710 determine the name of the thread as given by the OS. On these
3711 systems, a name specified with @samp{thread name} will override the
3712 system-give name, and removing the user-specified name will cause
3713 @value{GDBN} to once again display the system-specified name.
3716 @cindex search for a thread
3717 @item thread find [@var{regexp}]
3718 Search for and display thread ids whose name or @var{systag}
3719 matches the supplied regular expression.
3721 As well as being the complement to the @samp{thread name} command,
3722 this command also allows you to identify a thread by its target
3723 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3727 (@value{GDBN}) thread find 26688
3728 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3729 (@value{GDBN}) info thread 4
3731 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3734 @kindex set print thread-events
3735 @cindex print messages on thread start and exit
3736 @item set print thread-events
3737 @itemx set print thread-events on
3738 @itemx set print thread-events off
3739 The @code{set print thread-events} command allows you to enable or
3740 disable printing of messages when @value{GDBN} notices that new threads have
3741 started or that threads have exited. By default, these messages will
3742 be printed if detection of these events is supported by the target.
3743 Note that these messages cannot be disabled on all targets.
3745 @kindex show print thread-events
3746 @item show print thread-events
3747 Show whether messages will be printed when @value{GDBN} detects that threads
3748 have started and exited.
3751 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3752 more information about how @value{GDBN} behaves when you stop and start
3753 programs with multiple threads.
3755 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3756 watchpoints in programs with multiple threads.
3758 @anchor{set libthread-db-search-path}
3760 @kindex set libthread-db-search-path
3761 @cindex search path for @code{libthread_db}
3762 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3763 If this variable is set, @var{path} is a colon-separated list of
3764 directories @value{GDBN} will use to search for @code{libthread_db}.
3765 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3766 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3767 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3770 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3771 @code{libthread_db} library to obtain information about threads in the
3772 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3773 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3774 specific thread debugging library loading is enabled
3775 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3777 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3778 refers to the default system directories that are
3779 normally searched for loading shared libraries. The @samp{$sdir} entry
3780 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3781 (@pxref{libthread_db.so.1 file}).
3783 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3784 refers to the directory from which @code{libpthread}
3785 was loaded in the inferior process.
3787 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3788 @value{GDBN} attempts to initialize it with the current inferior process.
3789 If this initialization fails (which could happen because of a version
3790 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3791 will unload @code{libthread_db}, and continue with the next directory.
3792 If none of @code{libthread_db} libraries initialize successfully,
3793 @value{GDBN} will issue a warning and thread debugging will be disabled.
3795 Setting @code{libthread-db-search-path} is currently implemented
3796 only on some platforms.
3798 @kindex show libthread-db-search-path
3799 @item show libthread-db-search-path
3800 Display current libthread_db search path.
3802 @kindex set debug libthread-db
3803 @kindex show debug libthread-db
3804 @cindex debugging @code{libthread_db}
3805 @item set debug libthread-db
3806 @itemx show debug libthread-db
3807 Turns on or off display of @code{libthread_db}-related events.
3808 Use @code{1} to enable, @code{0} to disable.
3812 @section Debugging Forks
3814 @cindex fork, debugging programs which call
3815 @cindex multiple processes
3816 @cindex processes, multiple
3817 On most systems, @value{GDBN} has no special support for debugging
3818 programs which create additional processes using the @code{fork}
3819 function. When a program forks, @value{GDBN} will continue to debug the
3820 parent process and the child process will run unimpeded. If you have
3821 set a breakpoint in any code which the child then executes, the child
3822 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3823 will cause it to terminate.
3825 However, if you want to debug the child process there is a workaround
3826 which isn't too painful. Put a call to @code{sleep} in the code which
3827 the child process executes after the fork. It may be useful to sleep
3828 only if a certain environment variable is set, or a certain file exists,
3829 so that the delay need not occur when you don't want to run @value{GDBN}
3830 on the child. While the child is sleeping, use the @code{ps} program to
3831 get its process ID. Then tell @value{GDBN} (a new invocation of
3832 @value{GDBN} if you are also debugging the parent process) to attach to
3833 the child process (@pxref{Attach}). From that point on you can debug
3834 the child process just like any other process which you attached to.
3836 On some systems, @value{GDBN} provides support for debugging programs
3837 that create additional processes using the @code{fork} or @code{vfork}
3838 functions. On @sc{gnu}/Linux platforms, this feature is supported
3839 with kernel version 2.5.46 and later.
3841 The fork debugging commands are supported in native mode and when
3842 connected to @code{gdbserver} in either @code{target remote} mode or
3843 @code{target extended-remote} mode.
3845 By default, when a program forks, @value{GDBN} will continue to debug
3846 the parent process and the child process will run unimpeded.
3848 If you want to follow the child process instead of the parent process,
3849 use the command @w{@code{set follow-fork-mode}}.
3852 @kindex set follow-fork-mode
3853 @item set follow-fork-mode @var{mode}
3854 Set the debugger response to a program call of @code{fork} or
3855 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3856 process. The @var{mode} argument can be:
3860 The original process is debugged after a fork. The child process runs
3861 unimpeded. This is the default.
3864 The new process is debugged after a fork. The parent process runs
3869 @kindex show follow-fork-mode
3870 @item show follow-fork-mode
3871 Display the current debugger response to a @code{fork} or @code{vfork} call.
3874 @cindex debugging multiple processes
3875 On Linux, if you want to debug both the parent and child processes, use the
3876 command @w{@code{set detach-on-fork}}.
3879 @kindex set detach-on-fork
3880 @item set detach-on-fork @var{mode}
3881 Tells gdb whether to detach one of the processes after a fork, or
3882 retain debugger control over them both.
3886 The child process (or parent process, depending on the value of
3887 @code{follow-fork-mode}) will be detached and allowed to run
3888 independently. This is the default.
3891 Both processes will be held under the control of @value{GDBN}.
3892 One process (child or parent, depending on the value of
3893 @code{follow-fork-mode}) is debugged as usual, while the other
3898 @kindex show detach-on-fork
3899 @item show detach-on-fork
3900 Show whether detach-on-fork mode is on/off.
3903 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3904 will retain control of all forked processes (including nested forks).
3905 You can list the forked processes under the control of @value{GDBN} by
3906 using the @w{@code{info inferiors}} command, and switch from one fork
3907 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
3908 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
3910 To quit debugging one of the forked processes, you can either detach
3911 from it by using the @w{@code{detach inferiors}} command (allowing it
3912 to run independently), or kill it using the @w{@code{kill inferiors}}
3913 command. @xref{Inferiors Connections and Programs, ,Debugging
3914 Multiple Inferiors Connections and Programs}.
3916 If you ask to debug a child process and a @code{vfork} is followed by an
3917 @code{exec}, @value{GDBN} executes the new target up to the first
3918 breakpoint in the new target. If you have a breakpoint set on
3919 @code{main} in your original program, the breakpoint will also be set on
3920 the child process's @code{main}.
3922 On some systems, when a child process is spawned by @code{vfork}, you
3923 cannot debug the child or parent until an @code{exec} call completes.
3925 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3926 call executes, the new target restarts. To restart the parent
3927 process, use the @code{file} command with the parent executable name
3928 as its argument. By default, after an @code{exec} call executes,
3929 @value{GDBN} discards the symbols of the previous executable image.
3930 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3934 @kindex set follow-exec-mode
3935 @item set follow-exec-mode @var{mode}
3937 Set debugger response to a program call of @code{exec}. An
3938 @code{exec} call replaces the program image of a process.
3940 @code{follow-exec-mode} can be:
3944 @value{GDBN} creates a new inferior and rebinds the process to this
3945 new inferior. The program the process was running before the
3946 @code{exec} call can be restarted afterwards by restarting the
3952 (@value{GDBP}) info inferiors
3954 Id Description Executable
3957 process 12020 is executing new program: prog2
3958 Program exited normally.
3959 (@value{GDBP}) info inferiors
3960 Id Description Executable
3966 @value{GDBN} keeps the process bound to the same inferior. The new
3967 executable image replaces the previous executable loaded in the
3968 inferior. Restarting the inferior after the @code{exec} call, with
3969 e.g., the @code{run} command, restarts the executable the process was
3970 running after the @code{exec} call. This is the default mode.
3975 (@value{GDBP}) info inferiors
3976 Id Description Executable
3979 process 12020 is executing new program: prog2
3980 Program exited normally.
3981 (@value{GDBP}) info inferiors
3982 Id Description Executable
3989 @code{follow-exec-mode} is supported in native mode and
3990 @code{target extended-remote} mode.
3992 You can use the @code{catch} command to make @value{GDBN} stop whenever
3993 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3994 Catchpoints, ,Setting Catchpoints}.
3996 @node Checkpoint/Restart
3997 @section Setting a @emph{Bookmark} to Return to Later
4002 @cindex snapshot of a process
4003 @cindex rewind program state
4005 On certain operating systems@footnote{Currently, only
4006 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4007 program's state, called a @dfn{checkpoint}, and come back to it
4010 Returning to a checkpoint effectively undoes everything that has
4011 happened in the program since the @code{checkpoint} was saved. This
4012 includes changes in memory, registers, and even (within some limits)
4013 system state. Effectively, it is like going back in time to the
4014 moment when the checkpoint was saved.
4016 Thus, if you're stepping thru a program and you think you're
4017 getting close to the point where things go wrong, you can save
4018 a checkpoint. Then, if you accidentally go too far and miss
4019 the critical statement, instead of having to restart your program
4020 from the beginning, you can just go back to the checkpoint and
4021 start again from there.
4023 This can be especially useful if it takes a lot of time or
4024 steps to reach the point where you think the bug occurs.
4026 To use the @code{checkpoint}/@code{restart} method of debugging:
4031 Save a snapshot of the debugged program's current execution state.
4032 The @code{checkpoint} command takes no arguments, but each checkpoint
4033 is assigned a small integer id, similar to a breakpoint id.
4035 @kindex info checkpoints
4036 @item info checkpoints
4037 List the checkpoints that have been saved in the current debugging
4038 session. For each checkpoint, the following information will be
4045 @item Source line, or label
4048 @kindex restart @var{checkpoint-id}
4049 @item restart @var{checkpoint-id}
4050 Restore the program state that was saved as checkpoint number
4051 @var{checkpoint-id}. All program variables, registers, stack frames
4052 etc.@: will be returned to the values that they had when the checkpoint
4053 was saved. In essence, gdb will ``wind back the clock'' to the point
4054 in time when the checkpoint was saved.
4056 Note that breakpoints, @value{GDBN} variables, command history etc.
4057 are not affected by restoring a checkpoint. In general, a checkpoint
4058 only restores things that reside in the program being debugged, not in
4061 @kindex delete checkpoint @var{checkpoint-id}
4062 @item delete checkpoint @var{checkpoint-id}
4063 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4067 Returning to a previously saved checkpoint will restore the user state
4068 of the program being debugged, plus a significant subset of the system
4069 (OS) state, including file pointers. It won't ``un-write'' data from
4070 a file, but it will rewind the file pointer to the previous location,
4071 so that the previously written data can be overwritten. For files
4072 opened in read mode, the pointer will also be restored so that the
4073 previously read data can be read again.
4075 Of course, characters that have been sent to a printer (or other
4076 external device) cannot be ``snatched back'', and characters received
4077 from eg.@: a serial device can be removed from internal program buffers,
4078 but they cannot be ``pushed back'' into the serial pipeline, ready to
4079 be received again. Similarly, the actual contents of files that have
4080 been changed cannot be restored (at this time).
4082 However, within those constraints, you actually can ``rewind'' your
4083 program to a previously saved point in time, and begin debugging it
4084 again --- and you can change the course of events so as to debug a
4085 different execution path this time.
4087 @cindex checkpoints and process id
4088 Finally, there is one bit of internal program state that will be
4089 different when you return to a checkpoint --- the program's process
4090 id. Each checkpoint will have a unique process id (or @var{pid}),
4091 and each will be different from the program's original @var{pid}.
4092 If your program has saved a local copy of its process id, this could
4093 potentially pose a problem.
4095 @subsection A Non-obvious Benefit of Using Checkpoints
4097 On some systems such as @sc{gnu}/Linux, address space randomization
4098 is performed on new processes for security reasons. This makes it
4099 difficult or impossible to set a breakpoint, or watchpoint, on an
4100 absolute address if you have to restart the program, since the
4101 absolute location of a symbol will change from one execution to the
4104 A checkpoint, however, is an @emph{identical} copy of a process.
4105 Therefore if you create a checkpoint at (eg.@:) the start of main,
4106 and simply return to that checkpoint instead of restarting the
4107 process, you can avoid the effects of address randomization and
4108 your symbols will all stay in the same place.
4111 @chapter Stopping and Continuing
4113 The principal purposes of using a debugger are so that you can stop your
4114 program before it terminates; or so that, if your program runs into
4115 trouble, you can investigate and find out why.
4117 Inside @value{GDBN}, your program may stop for any of several reasons,
4118 such as a signal, a breakpoint, or reaching a new line after a
4119 @value{GDBN} command such as @code{step}. You may then examine and
4120 change variables, set new breakpoints or remove old ones, and then
4121 continue execution. Usually, the messages shown by @value{GDBN} provide
4122 ample explanation of the status of your program---but you can also
4123 explicitly request this information at any time.
4126 @kindex info program
4128 Display information about the status of your program: whether it is
4129 running or not, what process it is, and why it stopped.
4133 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4134 * Continuing and Stepping:: Resuming execution
4135 * Skipping Over Functions and Files::
4136 Skipping over functions and files
4138 * Thread Stops:: Stopping and starting multi-thread programs
4142 @section Breakpoints, Watchpoints, and Catchpoints
4145 A @dfn{breakpoint} makes your program stop whenever a certain point in
4146 the program is reached. For each breakpoint, you can add conditions to
4147 control in finer detail whether your program stops. You can set
4148 breakpoints with the @code{break} command and its variants (@pxref{Set
4149 Breaks, ,Setting Breakpoints}), to specify the place where your program
4150 should stop by line number, function name or exact address in the
4153 On some systems, you can set breakpoints in shared libraries before
4154 the executable is run.
4157 @cindex data breakpoints
4158 @cindex memory tracing
4159 @cindex breakpoint on memory address
4160 @cindex breakpoint on variable modification
4161 A @dfn{watchpoint} is a special breakpoint that stops your program
4162 when the value of an expression changes. The expression may be a value
4163 of a variable, or it could involve values of one or more variables
4164 combined by operators, such as @samp{a + b}. This is sometimes called
4165 @dfn{data breakpoints}. You must use a different command to set
4166 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4167 from that, you can manage a watchpoint like any other breakpoint: you
4168 enable, disable, and delete both breakpoints and watchpoints using the
4171 You can arrange to have values from your program displayed automatically
4172 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4176 @cindex breakpoint on events
4177 A @dfn{catchpoint} is another special breakpoint that stops your program
4178 when a certain kind of event occurs, such as the throwing of a C@t{++}
4179 exception or the loading of a library. As with watchpoints, you use a
4180 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4181 Catchpoints}), but aside from that, you can manage a catchpoint like any
4182 other breakpoint. (To stop when your program receives a signal, use the
4183 @code{handle} command; see @ref{Signals, ,Signals}.)
4185 @cindex breakpoint numbers
4186 @cindex numbers for breakpoints
4187 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4188 catchpoint when you create it; these numbers are successive integers
4189 starting with one. In many of the commands for controlling various
4190 features of breakpoints you use the breakpoint number to say which
4191 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4192 @dfn{disabled}; if disabled, it has no effect on your program until you
4195 @cindex breakpoint ranges
4196 @cindex breakpoint lists
4197 @cindex ranges of breakpoints
4198 @cindex lists of breakpoints
4199 Some @value{GDBN} commands accept a space-separated list of breakpoints
4200 on which to operate. A list element can be either a single breakpoint number,
4201 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4202 When a breakpoint list is given to a command, all breakpoints in that list
4206 * Set Breaks:: Setting breakpoints
4207 * Set Watchpoints:: Setting watchpoints
4208 * Set Catchpoints:: Setting catchpoints
4209 * Delete Breaks:: Deleting breakpoints
4210 * Disabling:: Disabling breakpoints
4211 * Conditions:: Break conditions
4212 * Break Commands:: Breakpoint command lists
4213 * Dynamic Printf:: Dynamic printf
4214 * Save Breakpoints:: How to save breakpoints in a file
4215 * Static Probe Points:: Listing static probe points
4216 * Error in Breakpoints:: ``Cannot insert breakpoints''
4217 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4221 @subsection Setting Breakpoints
4223 @c FIXME LMB what does GDB do if no code on line of breakpt?
4224 @c consider in particular declaration with/without initialization.
4226 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4229 @kindex b @r{(@code{break})}
4230 @vindex $bpnum@r{, convenience variable}
4231 @cindex latest breakpoint
4232 Breakpoints are set with the @code{break} command (abbreviated
4233 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4234 number of the breakpoint you've set most recently; see @ref{Convenience
4235 Vars,, Convenience Variables}, for a discussion of what you can do with
4236 convenience variables.
4239 @item break @var{location}
4240 Set a breakpoint at the given @var{location}, which can specify a
4241 function name, a line number, or an address of an instruction.
4242 (@xref{Specify Location}, for a list of all the possible ways to
4243 specify a @var{location}.) The breakpoint will stop your program just
4244 before it executes any of the code in the specified @var{location}.
4246 When using source languages that permit overloading of symbols, such as
4247 C@t{++}, a function name may refer to more than one possible place to break.
4248 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
4251 It is also possible to insert a breakpoint that will stop the program
4252 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4253 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4256 When called without any arguments, @code{break} sets a breakpoint at
4257 the next instruction to be executed in the selected stack frame
4258 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4259 innermost, this makes your program stop as soon as control
4260 returns to that frame. This is similar to the effect of a
4261 @code{finish} command in the frame inside the selected frame---except
4262 that @code{finish} does not leave an active breakpoint. If you use
4263 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4264 the next time it reaches the current location; this may be useful
4267 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4268 least one instruction has been executed. If it did not do this, you
4269 would be unable to proceed past a breakpoint without first disabling the
4270 breakpoint. This rule applies whether or not the breakpoint already
4271 existed when your program stopped.
4273 @item break @dots{} if @var{cond}
4274 Set a breakpoint with condition @var{cond}; evaluate the expression
4275 @var{cond} each time the breakpoint is reached, and stop only if the
4276 value is nonzero---that is, if @var{cond} evaluates as true.
4277 @samp{@dots{}} stands for one of the possible arguments described
4278 above (or no argument) specifying where to break. @xref{Conditions,
4279 ,Break Conditions}, for more information on breakpoint conditions.
4282 @item tbreak @var{args}
4283 Set a breakpoint enabled only for one stop. The @var{args} are the
4284 same as for the @code{break} command, and the breakpoint is set in the same
4285 way, but the breakpoint is automatically deleted after the first time your
4286 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4289 @cindex hardware breakpoints
4290 @item hbreak @var{args}
4291 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4292 @code{break} command and the breakpoint is set in the same way, but the
4293 breakpoint requires hardware support and some target hardware may not
4294 have this support. The main purpose of this is EPROM/ROM code
4295 debugging, so you can set a breakpoint at an instruction without
4296 changing the instruction. This can be used with the new trap-generation
4297 provided by SPARClite DSU and most x86-based targets. These targets
4298 will generate traps when a program accesses some data or instruction
4299 address that is assigned to the debug registers. However the hardware
4300 breakpoint registers can take a limited number of breakpoints. For
4301 example, on the DSU, only two data breakpoints can be set at a time, and
4302 @value{GDBN} will reject this command if more than two are used. Delete
4303 or disable unused hardware breakpoints before setting new ones
4304 (@pxref{Disabling, ,Disabling Breakpoints}).
4305 @xref{Conditions, ,Break Conditions}.
4306 For remote targets, you can restrict the number of hardware
4307 breakpoints @value{GDBN} will use, see @ref{set remote
4308 hardware-breakpoint-limit}.
4311 @item thbreak @var{args}
4312 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4313 are the same as for the @code{hbreak} command and the breakpoint is set in
4314 the same way. However, like the @code{tbreak} command,
4315 the breakpoint is automatically deleted after the
4316 first time your program stops there. Also, like the @code{hbreak}
4317 command, the breakpoint requires hardware support and some target hardware
4318 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4319 See also @ref{Conditions, ,Break Conditions}.
4322 @cindex regular expression
4323 @cindex breakpoints at functions matching a regexp
4324 @cindex set breakpoints in many functions
4325 @item rbreak @var{regex}
4326 Set breakpoints on all functions matching the regular expression
4327 @var{regex}. This command sets an unconditional breakpoint on all
4328 matches, printing a list of all breakpoints it set. Once these
4329 breakpoints are set, they are treated just like the breakpoints set with
4330 the @code{break} command. You can delete them, disable them, or make
4331 them conditional the same way as any other breakpoint.
4333 In programs using different languages, @value{GDBN} chooses the syntax
4334 to print the list of all breakpoints it sets according to the
4335 @samp{set language} value: using @samp{set language auto}
4336 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4337 language of the breakpoint's function, other values mean to use
4338 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4340 The syntax of the regular expression is the standard one used with tools
4341 like @file{grep}. Note that this is different from the syntax used by
4342 shells, so for instance @code{foo*} matches all functions that include
4343 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4344 @code{.*} leading and trailing the regular expression you supply, so to
4345 match only functions that begin with @code{foo}, use @code{^foo}.
4347 @cindex non-member C@t{++} functions, set breakpoint in
4348 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4349 breakpoints on overloaded functions that are not members of any special
4352 @cindex set breakpoints on all functions
4353 The @code{rbreak} command can be used to set breakpoints in
4354 @strong{all} the functions in a program, like this:
4357 (@value{GDBP}) rbreak .
4360 @item rbreak @var{file}:@var{regex}
4361 If @code{rbreak} is called with a filename qualification, it limits
4362 the search for functions matching the given regular expression to the
4363 specified @var{file}. This can be used, for example, to set breakpoints on
4364 every function in a given file:
4367 (@value{GDBP}) rbreak file.c:.
4370 The colon separating the filename qualifier from the regex may
4371 optionally be surrounded by spaces.
4373 @kindex info breakpoints
4374 @cindex @code{$_} and @code{info breakpoints}
4375 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4376 @itemx info break @r{[}@var{list}@dots{}@r{]}
4377 Print a table of all breakpoints, watchpoints, and catchpoints set and
4378 not deleted. Optional argument @var{n} means print information only
4379 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4380 For each breakpoint, following columns are printed:
4383 @item Breakpoint Numbers
4385 Breakpoint, watchpoint, or catchpoint.
4387 Whether the breakpoint is marked to be disabled or deleted when hit.
4388 @item Enabled or Disabled
4389 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4390 that are not enabled.
4392 Where the breakpoint is in your program, as a memory address. For a
4393 pending breakpoint whose address is not yet known, this field will
4394 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4395 library that has the symbol or line referred by breakpoint is loaded.
4396 See below for details. A breakpoint with several locations will
4397 have @samp{<MULTIPLE>} in this field---see below for details.
4399 Where the breakpoint is in the source for your program, as a file and
4400 line number. For a pending breakpoint, the original string passed to
4401 the breakpoint command will be listed as it cannot be resolved until
4402 the appropriate shared library is loaded in the future.
4406 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4407 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4408 @value{GDBN} on the host's side. If it is ``target'', then the condition
4409 is evaluated by the target. The @code{info break} command shows
4410 the condition on the line following the affected breakpoint, together with
4411 its condition evaluation mode in between parentheses.
4413 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4414 allowed to have a condition specified for it. The condition is not parsed for
4415 validity until a shared library is loaded that allows the pending
4416 breakpoint to resolve to a valid location.
4419 @code{info break} with a breakpoint
4420 number @var{n} as argument lists only that breakpoint. The
4421 convenience variable @code{$_} and the default examining-address for
4422 the @code{x} command are set to the address of the last breakpoint
4423 listed (@pxref{Memory, ,Examining Memory}).
4426 @code{info break} displays a count of the number of times the breakpoint
4427 has been hit. This is especially useful in conjunction with the
4428 @code{ignore} command. You can ignore a large number of breakpoint
4429 hits, look at the breakpoint info to see how many times the breakpoint
4430 was hit, and then run again, ignoring one less than that number. This
4431 will get you quickly to the last hit of that breakpoint.
4434 For a breakpoints with an enable count (xref) greater than 1,
4435 @code{info break} also displays that count.
4439 @value{GDBN} allows you to set any number of breakpoints at the same place in
4440 your program. There is nothing silly or meaningless about this. When
4441 the breakpoints are conditional, this is even useful
4442 (@pxref{Conditions, ,Break Conditions}).
4444 @cindex multiple locations, breakpoints
4445 @cindex breakpoints, multiple locations
4446 It is possible that a breakpoint corresponds to several locations
4447 in your program. Examples of this situation are:
4451 Multiple functions in the program may have the same name.
4454 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4455 instances of the function body, used in different cases.
4458 For a C@t{++} template function, a given line in the function can
4459 correspond to any number of instantiations.
4462 For an inlined function, a given source line can correspond to
4463 several places where that function is inlined.
4466 In all those cases, @value{GDBN} will insert a breakpoint at all
4467 the relevant locations.
4469 A breakpoint with multiple locations is displayed in the breakpoint
4470 table using several rows---one header row, followed by one row for
4471 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4472 address column. The rows for individual locations contain the actual
4473 addresses for locations, and show the functions to which those
4474 locations belong. The number column for a location is of the form
4475 @var{breakpoint-number}.@var{location-number}.
4480 Num Type Disp Enb Address What
4481 1 breakpoint keep y <MULTIPLE>
4483 breakpoint already hit 1 time
4484 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4485 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4488 You cannot delete the individual locations from a breakpoint. However,
4489 each location can be individually enabled or disabled by passing
4490 @var{breakpoint-number}.@var{location-number} as argument to the
4491 @code{enable} and @code{disable} commands. It's also possible to
4492 @code{enable} and @code{disable} a range of @var{location-number}
4493 locations using a @var{breakpoint-number} and two @var{location-number}s,
4494 in increasing order, separated by a hyphen, like
4495 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4496 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4497 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4498 all of the locations that belong to that breakpoint.
4500 @cindex pending breakpoints
4501 It's quite common to have a breakpoint inside a shared library.
4502 Shared libraries can be loaded and unloaded explicitly,
4503 and possibly repeatedly, as the program is executed. To support
4504 this use case, @value{GDBN} updates breakpoint locations whenever
4505 any shared library is loaded or unloaded. Typically, you would
4506 set a breakpoint in a shared library at the beginning of your
4507 debugging session, when the library is not loaded, and when the
4508 symbols from the library are not available. When you try to set
4509 breakpoint, @value{GDBN} will ask you if you want to set
4510 a so called @dfn{pending breakpoint}---breakpoint whose address
4511 is not yet resolved.
4513 After the program is run, whenever a new shared library is loaded,
4514 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4515 shared library contains the symbol or line referred to by some
4516 pending breakpoint, that breakpoint is resolved and becomes an
4517 ordinary breakpoint. When a library is unloaded, all breakpoints
4518 that refer to its symbols or source lines become pending again.
4520 This logic works for breakpoints with multiple locations, too. For
4521 example, if you have a breakpoint in a C@t{++} template function, and
4522 a newly loaded shared library has an instantiation of that template,
4523 a new location is added to the list of locations for the breakpoint.
4525 Except for having unresolved address, pending breakpoints do not
4526 differ from regular breakpoints. You can set conditions or commands,
4527 enable and disable them and perform other breakpoint operations.
4529 @value{GDBN} provides some additional commands for controlling what
4530 happens when the @samp{break} command cannot resolve breakpoint
4531 address specification to an address:
4533 @kindex set breakpoint pending
4534 @kindex show breakpoint pending
4536 @item set breakpoint pending auto
4537 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4538 location, it queries you whether a pending breakpoint should be created.
4540 @item set breakpoint pending on
4541 This indicates that an unrecognized breakpoint location should automatically
4542 result in a pending breakpoint being created.
4544 @item set breakpoint pending off
4545 This indicates that pending breakpoints are not to be created. Any
4546 unrecognized breakpoint location results in an error. This setting does
4547 not affect any pending breakpoints previously created.
4549 @item show breakpoint pending
4550 Show the current behavior setting for creating pending breakpoints.
4553 The settings above only affect the @code{break} command and its
4554 variants. Once breakpoint is set, it will be automatically updated
4555 as shared libraries are loaded and unloaded.
4557 @cindex automatic hardware breakpoints
4558 For some targets, @value{GDBN} can automatically decide if hardware or
4559 software breakpoints should be used, depending on whether the
4560 breakpoint address is read-only or read-write. This applies to
4561 breakpoints set with the @code{break} command as well as to internal
4562 breakpoints set by commands like @code{next} and @code{finish}. For
4563 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4566 You can control this automatic behaviour with the following commands:
4568 @kindex set breakpoint auto-hw
4569 @kindex show breakpoint auto-hw
4571 @item set breakpoint auto-hw on
4572 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4573 will try to use the target memory map to decide if software or hardware
4574 breakpoint must be used.
4576 @item set breakpoint auto-hw off
4577 This indicates @value{GDBN} should not automatically select breakpoint
4578 type. If the target provides a memory map, @value{GDBN} will warn when
4579 trying to set software breakpoint at a read-only address.
4582 @value{GDBN} normally implements breakpoints by replacing the program code
4583 at the breakpoint address with a special instruction, which, when
4584 executed, given control to the debugger. By default, the program
4585 code is so modified only when the program is resumed. As soon as
4586 the program stops, @value{GDBN} restores the original instructions. This
4587 behaviour guards against leaving breakpoints inserted in the
4588 target should gdb abrubptly disconnect. However, with slow remote
4589 targets, inserting and removing breakpoint can reduce the performance.
4590 This behavior can be controlled with the following commands::
4592 @kindex set breakpoint always-inserted
4593 @kindex show breakpoint always-inserted
4595 @item set breakpoint always-inserted off
4596 All breakpoints, including newly added by the user, are inserted in
4597 the target only when the target is resumed. All breakpoints are
4598 removed from the target when it stops. This is the default mode.
4600 @item set breakpoint always-inserted on
4601 Causes all breakpoints to be inserted in the target at all times. If
4602 the user adds a new breakpoint, or changes an existing breakpoint, the
4603 breakpoints in the target are updated immediately. A breakpoint is
4604 removed from the target only when breakpoint itself is deleted.
4607 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4608 when a breakpoint breaks. If the condition is true, then the process being
4609 debugged stops, otherwise the process is resumed.
4611 If the target supports evaluating conditions on its end, @value{GDBN} may
4612 download the breakpoint, together with its conditions, to it.
4614 This feature can be controlled via the following commands:
4616 @kindex set breakpoint condition-evaluation
4617 @kindex show breakpoint condition-evaluation
4619 @item set breakpoint condition-evaluation host
4620 This option commands @value{GDBN} to evaluate the breakpoint
4621 conditions on the host's side. Unconditional breakpoints are sent to
4622 the target which in turn receives the triggers and reports them back to GDB
4623 for condition evaluation. This is the standard evaluation mode.
4625 @item set breakpoint condition-evaluation target
4626 This option commands @value{GDBN} to download breakpoint conditions
4627 to the target at the moment of their insertion. The target
4628 is responsible for evaluating the conditional expression and reporting
4629 breakpoint stop events back to @value{GDBN} whenever the condition
4630 is true. Due to limitations of target-side evaluation, some conditions
4631 cannot be evaluated there, e.g., conditions that depend on local data
4632 that is only known to the host. Examples include
4633 conditional expressions involving convenience variables, complex types
4634 that cannot be handled by the agent expression parser and expressions
4635 that are too long to be sent over to the target, specially when the
4636 target is a remote system. In these cases, the conditions will be
4637 evaluated by @value{GDBN}.
4639 @item set breakpoint condition-evaluation auto
4640 This is the default mode. If the target supports evaluating breakpoint
4641 conditions on its end, @value{GDBN} will download breakpoint conditions to
4642 the target (limitations mentioned previously apply). If the target does
4643 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4644 to evaluating all these conditions on the host's side.
4648 @cindex negative breakpoint numbers
4649 @cindex internal @value{GDBN} breakpoints
4650 @value{GDBN} itself sometimes sets breakpoints in your program for
4651 special purposes, such as proper handling of @code{longjmp} (in C
4652 programs). These internal breakpoints are assigned negative numbers,
4653 starting with @code{-1}; @samp{info breakpoints} does not display them.
4654 You can see these breakpoints with the @value{GDBN} maintenance command
4655 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4658 @node Set Watchpoints
4659 @subsection Setting Watchpoints
4661 @cindex setting watchpoints
4662 You can use a watchpoint to stop execution whenever the value of an
4663 expression changes, without having to predict a particular place where
4664 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4665 The expression may be as simple as the value of a single variable, or
4666 as complex as many variables combined by operators. Examples include:
4670 A reference to the value of a single variable.
4673 An address cast to an appropriate data type. For example,
4674 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4675 address (assuming an @code{int} occupies 4 bytes).
4678 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4679 expression can use any operators valid in the program's native
4680 language (@pxref{Languages}).
4683 You can set a watchpoint on an expression even if the expression can
4684 not be evaluated yet. For instance, you can set a watchpoint on
4685 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4686 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4687 the expression produces a valid value. If the expression becomes
4688 valid in some other way than changing a variable (e.g.@: if the memory
4689 pointed to by @samp{*global_ptr} becomes readable as the result of a
4690 @code{malloc} call), @value{GDBN} may not stop until the next time
4691 the expression changes.
4693 @cindex software watchpoints
4694 @cindex hardware watchpoints
4695 Depending on your system, watchpoints may be implemented in software or
4696 hardware. @value{GDBN} does software watchpointing by single-stepping your
4697 program and testing the variable's value each time, which is hundreds of
4698 times slower than normal execution. (But this may still be worth it, to
4699 catch errors where you have no clue what part of your program is the
4702 On some systems, such as most PowerPC or x86-based targets,
4703 @value{GDBN} includes support for hardware watchpoints, which do not
4704 slow down the running of your program.
4708 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4709 Set a watchpoint for an expression. @value{GDBN} will break when the
4710 expression @var{expr} is written into by the program and its value
4711 changes. The simplest (and the most popular) use of this command is
4712 to watch the value of a single variable:
4715 (@value{GDBP}) watch foo
4718 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4719 argument, @value{GDBN} breaks only when the thread identified by
4720 @var{thread-id} changes the value of @var{expr}. If any other threads
4721 change the value of @var{expr}, @value{GDBN} will not break. Note
4722 that watchpoints restricted to a single thread in this way only work
4723 with Hardware Watchpoints.
4725 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4726 (see below). The @code{-location} argument tells @value{GDBN} to
4727 instead watch the memory referred to by @var{expr}. In this case,
4728 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4729 and watch the memory at that address. The type of the result is used
4730 to determine the size of the watched memory. If the expression's
4731 result does not have an address, then @value{GDBN} will print an
4734 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4735 of masked watchpoints, if the current architecture supports this
4736 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4737 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4738 to an address to watch. The mask specifies that some bits of an address
4739 (the bits which are reset in the mask) should be ignored when matching
4740 the address accessed by the inferior against the watchpoint address.
4741 Thus, a masked watchpoint watches many addresses simultaneously---those
4742 addresses whose unmasked bits are identical to the unmasked bits in the
4743 watchpoint address. The @code{mask} argument implies @code{-location}.
4747 (@value{GDBP}) watch foo mask 0xffff00ff
4748 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4752 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4753 Set a watchpoint that will break when the value of @var{expr} is read
4757 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4758 Set a watchpoint that will break when @var{expr} is either read from
4759 or written into by the program.
4761 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4762 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4763 This command prints a list of watchpoints, using the same format as
4764 @code{info break} (@pxref{Set Breaks}).
4767 If you watch for a change in a numerically entered address you need to
4768 dereference it, as the address itself is just a constant number which will
4769 never change. @value{GDBN} refuses to create a watchpoint that watches
4770 a never-changing value:
4773 (@value{GDBP}) watch 0x600850
4774 Cannot watch constant value 0x600850.
4775 (@value{GDBP}) watch *(int *) 0x600850
4776 Watchpoint 1: *(int *) 6293584
4779 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4780 watchpoints execute very quickly, and the debugger reports a change in
4781 value at the exact instruction where the change occurs. If @value{GDBN}
4782 cannot set a hardware watchpoint, it sets a software watchpoint, which
4783 executes more slowly and reports the change in value at the next
4784 @emph{statement}, not the instruction, after the change occurs.
4786 @cindex use only software watchpoints
4787 You can force @value{GDBN} to use only software watchpoints with the
4788 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4789 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4790 the underlying system supports them. (Note that hardware-assisted
4791 watchpoints that were set @emph{before} setting
4792 @code{can-use-hw-watchpoints} to zero will still use the hardware
4793 mechanism of watching expression values.)
4796 @item set can-use-hw-watchpoints
4797 @kindex set can-use-hw-watchpoints
4798 Set whether or not to use hardware watchpoints.
4800 @item show can-use-hw-watchpoints
4801 @kindex show can-use-hw-watchpoints
4802 Show the current mode of using hardware watchpoints.
4805 For remote targets, you can restrict the number of hardware
4806 watchpoints @value{GDBN} will use, see @ref{set remote
4807 hardware-breakpoint-limit}.
4809 When you issue the @code{watch} command, @value{GDBN} reports
4812 Hardware watchpoint @var{num}: @var{expr}
4816 if it was able to set a hardware watchpoint.
4818 Currently, the @code{awatch} and @code{rwatch} commands can only set
4819 hardware watchpoints, because accesses to data that don't change the
4820 value of the watched expression cannot be detected without examining
4821 every instruction as it is being executed, and @value{GDBN} does not do
4822 that currently. If @value{GDBN} finds that it is unable to set a
4823 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4824 will print a message like this:
4827 Expression cannot be implemented with read/access watchpoint.
4830 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4831 data type of the watched expression is wider than what a hardware
4832 watchpoint on the target machine can handle. For example, some systems
4833 can only watch regions that are up to 4 bytes wide; on such systems you
4834 cannot set hardware watchpoints for an expression that yields a
4835 double-precision floating-point number (which is typically 8 bytes
4836 wide). As a work-around, it might be possible to break the large region
4837 into a series of smaller ones and watch them with separate watchpoints.
4839 If you set too many hardware watchpoints, @value{GDBN} might be unable
4840 to insert all of them when you resume the execution of your program.
4841 Since the precise number of active watchpoints is unknown until such
4842 time as the program is about to be resumed, @value{GDBN} might not be
4843 able to warn you about this when you set the watchpoints, and the
4844 warning will be printed only when the program is resumed:
4847 Hardware watchpoint @var{num}: Could not insert watchpoint
4851 If this happens, delete or disable some of the watchpoints.
4853 Watching complex expressions that reference many variables can also
4854 exhaust the resources available for hardware-assisted watchpoints.
4855 That's because @value{GDBN} needs to watch every variable in the
4856 expression with separately allocated resources.
4858 If you call a function interactively using @code{print} or @code{call},
4859 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4860 kind of breakpoint or the call completes.
4862 @value{GDBN} automatically deletes watchpoints that watch local
4863 (automatic) variables, or expressions that involve such variables, when
4864 they go out of scope, that is, when the execution leaves the block in
4865 which these variables were defined. In particular, when the program
4866 being debugged terminates, @emph{all} local variables go out of scope,
4867 and so only watchpoints that watch global variables remain set. If you
4868 rerun the program, you will need to set all such watchpoints again. One
4869 way of doing that would be to set a code breakpoint at the entry to the
4870 @code{main} function and when it breaks, set all the watchpoints.
4872 @cindex watchpoints and threads
4873 @cindex threads and watchpoints
4874 In multi-threaded programs, watchpoints will detect changes to the
4875 watched expression from every thread.
4878 @emph{Warning:} In multi-threaded programs, software watchpoints
4879 have only limited usefulness. If @value{GDBN} creates a software
4880 watchpoint, it can only watch the value of an expression @emph{in a
4881 single thread}. If you are confident that the expression can only
4882 change due to the current thread's activity (and if you are also
4883 confident that no other thread can become current), then you can use
4884 software watchpoints as usual. However, @value{GDBN} may not notice
4885 when a non-current thread's activity changes the expression. (Hardware
4886 watchpoints, in contrast, watch an expression in all threads.)
4889 @xref{set remote hardware-watchpoint-limit}.
4891 @node Set Catchpoints
4892 @subsection Setting Catchpoints
4893 @cindex catchpoints, setting
4894 @cindex exception handlers
4895 @cindex event handling
4897 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4898 kinds of program events, such as C@t{++} exceptions or the loading of a
4899 shared library. Use the @code{catch} command to set a catchpoint.
4903 @item catch @var{event}
4904 Stop when @var{event} occurs. The @var{event} can be any of the following:
4907 @item throw @r{[}@var{regexp}@r{]}
4908 @itemx rethrow @r{[}@var{regexp}@r{]}
4909 @itemx catch @r{[}@var{regexp}@r{]}
4911 @kindex catch rethrow
4913 @cindex stop on C@t{++} exceptions
4914 The throwing, re-throwing, or catching of a C@t{++} exception.
4916 If @var{regexp} is given, then only exceptions whose type matches the
4917 regular expression will be caught.
4919 @vindex $_exception@r{, convenience variable}
4920 The convenience variable @code{$_exception} is available at an
4921 exception-related catchpoint, on some systems. This holds the
4922 exception being thrown.
4924 There are currently some limitations to C@t{++} exception handling in
4929 The support for these commands is system-dependent. Currently, only
4930 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4934 The regular expression feature and the @code{$_exception} convenience
4935 variable rely on the presence of some SDT probes in @code{libstdc++}.
4936 If these probes are not present, then these features cannot be used.
4937 These probes were first available in the GCC 4.8 release, but whether
4938 or not they are available in your GCC also depends on how it was
4942 The @code{$_exception} convenience variable is only valid at the
4943 instruction at which an exception-related catchpoint is set.
4946 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4947 location in the system library which implements runtime exception
4948 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4949 (@pxref{Selection}) to get to your code.
4952 If you call a function interactively, @value{GDBN} normally returns
4953 control to you when the function has finished executing. If the call
4954 raises an exception, however, the call may bypass the mechanism that
4955 returns control to you and cause your program either to abort or to
4956 simply continue running until it hits a breakpoint, catches a signal
4957 that @value{GDBN} is listening for, or exits. This is the case even if
4958 you set a catchpoint for the exception; catchpoints on exceptions are
4959 disabled within interactive calls. @xref{Calling}, for information on
4960 controlling this with @code{set unwind-on-terminating-exception}.
4963 You cannot raise an exception interactively.
4966 You cannot install an exception handler interactively.
4969 @item exception @r{[}@var{name}@r{]}
4970 @kindex catch exception
4971 @cindex Ada exception catching
4972 @cindex catch Ada exceptions
4973 An Ada exception being raised. If an exception name is specified
4974 at the end of the command (eg @code{catch exception Program_Error}),
4975 the debugger will stop only when this specific exception is raised.
4976 Otherwise, the debugger stops execution when any Ada exception is raised.
4978 When inserting an exception catchpoint on a user-defined exception whose
4979 name is identical to one of the exceptions defined by the language, the
4980 fully qualified name must be used as the exception name. Otherwise,
4981 @value{GDBN} will assume that it should stop on the pre-defined exception
4982 rather than the user-defined one. For instance, assuming an exception
4983 called @code{Constraint_Error} is defined in package @code{Pck}, then
4984 the command to use to catch such exceptions is @kbd{catch exception
4985 Pck.Constraint_Error}.
4987 @vindex $_ada_exception@r{, convenience variable}
4988 The convenience variable @code{$_ada_exception} holds the address of
4989 the exception being thrown. This can be useful when setting a
4990 condition for such a catchpoint.
4992 @item exception unhandled
4993 @kindex catch exception unhandled
4994 An exception that was raised but is not handled by the program. The
4995 convenience variable @code{$_ada_exception} is set as for @code{catch
4998 @item handlers @r{[}@var{name}@r{]}
4999 @kindex catch handlers
5000 @cindex Ada exception handlers catching
5001 @cindex catch Ada exceptions when handled
5002 An Ada exception being handled. If an exception name is
5003 specified at the end of the command
5004 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5005 only when this specific exception is handled.
5006 Otherwise, the debugger stops execution when any Ada exception is handled.
5008 When inserting a handlers catchpoint on a user-defined
5009 exception whose name is identical to one of the exceptions
5010 defined by the language, the fully qualified name must be used
5011 as the exception name. Otherwise, @value{GDBN} will assume that it
5012 should stop on the pre-defined exception rather than the
5013 user-defined one. For instance, assuming an exception called
5014 @code{Constraint_Error} is defined in package @code{Pck}, then the
5015 command to use to catch such exceptions handling is
5016 @kbd{catch handlers Pck.Constraint_Error}.
5018 The convenience variable @code{$_ada_exception} is set as for
5019 @code{catch exception}.
5022 @kindex catch assert
5023 A failed Ada assertion. Note that the convenience variable
5024 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5028 @cindex break on fork/exec
5029 A call to @code{exec}.
5031 @anchor{catch syscall}
5033 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5034 @kindex catch syscall
5035 @cindex break on a system call.
5036 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5037 syscall is a mechanism for application programs to request a service
5038 from the operating system (OS) or one of the OS system services.
5039 @value{GDBN} can catch some or all of the syscalls issued by the
5040 debuggee, and show the related information for each syscall. If no
5041 argument is specified, calls to and returns from all system calls
5044 @var{name} can be any system call name that is valid for the
5045 underlying OS. Just what syscalls are valid depends on the OS. On
5046 GNU and Unix systems, you can find the full list of valid syscall
5047 names on @file{/usr/include/asm/unistd.h}.
5049 @c For MS-Windows, the syscall names and the corresponding numbers
5050 @c can be found, e.g., on this URL:
5051 @c http://www.metasploit.com/users/opcode/syscalls.html
5052 @c but we don't support Windows syscalls yet.
5054 Normally, @value{GDBN} knows in advance which syscalls are valid for
5055 each OS, so you can use the @value{GDBN} command-line completion
5056 facilities (@pxref{Completion,, command completion}) to list the
5059 You may also specify the system call numerically. A syscall's
5060 number is the value passed to the OS's syscall dispatcher to
5061 identify the requested service. When you specify the syscall by its
5062 name, @value{GDBN} uses its database of syscalls to convert the name
5063 into the corresponding numeric code, but using the number directly
5064 may be useful if @value{GDBN}'s database does not have the complete
5065 list of syscalls on your system (e.g., because @value{GDBN} lags
5066 behind the OS upgrades).
5068 You may specify a group of related syscalls to be caught at once using
5069 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5070 instance, on some platforms @value{GDBN} allows you to catch all
5071 network related syscalls, by passing the argument @code{group:network}
5072 to @code{catch syscall}. Note that not all syscall groups are
5073 available in every system. You can use the command completion
5074 facilities (@pxref{Completion,, command completion}) to list the
5075 syscall groups available on your environment.
5077 The example below illustrates how this command works if you don't provide
5081 (@value{GDBP}) catch syscall
5082 Catchpoint 1 (syscall)
5084 Starting program: /tmp/catch-syscall
5086 Catchpoint 1 (call to syscall 'close'), \
5087 0xffffe424 in __kernel_vsyscall ()
5091 Catchpoint 1 (returned from syscall 'close'), \
5092 0xffffe424 in __kernel_vsyscall ()
5096 Here is an example of catching a system call by name:
5099 (@value{GDBP}) catch syscall chroot
5100 Catchpoint 1 (syscall 'chroot' [61])
5102 Starting program: /tmp/catch-syscall
5104 Catchpoint 1 (call to syscall 'chroot'), \
5105 0xffffe424 in __kernel_vsyscall ()
5109 Catchpoint 1 (returned from syscall 'chroot'), \
5110 0xffffe424 in __kernel_vsyscall ()
5114 An example of specifying a system call numerically. In the case
5115 below, the syscall number has a corresponding entry in the XML
5116 file, so @value{GDBN} finds its name and prints it:
5119 (@value{GDBP}) catch syscall 252
5120 Catchpoint 1 (syscall(s) 'exit_group')
5122 Starting program: /tmp/catch-syscall
5124 Catchpoint 1 (call to syscall 'exit_group'), \
5125 0xffffe424 in __kernel_vsyscall ()
5129 Program exited normally.
5133 Here is an example of catching a syscall group:
5136 (@value{GDBP}) catch syscall group:process
5137 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5138 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5139 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5141 Starting program: /tmp/catch-syscall
5143 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5144 from /lib64/ld-linux-x86-64.so.2
5150 However, there can be situations when there is no corresponding name
5151 in XML file for that syscall number. In this case, @value{GDBN} prints
5152 a warning message saying that it was not able to find the syscall name,
5153 but the catchpoint will be set anyway. See the example below:
5156 (@value{GDBP}) catch syscall 764
5157 warning: The number '764' does not represent a known syscall.
5158 Catchpoint 2 (syscall 764)
5162 If you configure @value{GDBN} using the @samp{--without-expat} option,
5163 it will not be able to display syscall names. Also, if your
5164 architecture does not have an XML file describing its system calls,
5165 you will not be able to see the syscall names. It is important to
5166 notice that these two features are used for accessing the syscall
5167 name database. In either case, you will see a warning like this:
5170 (@value{GDBP}) catch syscall
5171 warning: Could not open "syscalls/i386-linux.xml"
5172 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5173 GDB will not be able to display syscall names.
5174 Catchpoint 1 (syscall)
5178 Of course, the file name will change depending on your architecture and system.
5180 Still using the example above, you can also try to catch a syscall by its
5181 number. In this case, you would see something like:
5184 (@value{GDBP}) catch syscall 252
5185 Catchpoint 1 (syscall(s) 252)
5188 Again, in this case @value{GDBN} would not be able to display syscall's names.
5192 A call to @code{fork}.
5196 A call to @code{vfork}.
5198 @item load @r{[}@var{regexp}@r{]}
5199 @itemx unload @r{[}@var{regexp}@r{]}
5201 @kindex catch unload
5202 The loading or unloading of a shared library. If @var{regexp} is
5203 given, then the catchpoint will stop only if the regular expression
5204 matches one of the affected libraries.
5206 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5207 @kindex catch signal
5208 The delivery of a signal.
5210 With no arguments, this catchpoint will catch any signal that is not
5211 used internally by @value{GDBN}, specifically, all signals except
5212 @samp{SIGTRAP} and @samp{SIGINT}.
5214 With the argument @samp{all}, all signals, including those used by
5215 @value{GDBN}, will be caught. This argument cannot be used with other
5218 Otherwise, the arguments are a list of signal names as given to
5219 @code{handle} (@pxref{Signals}). Only signals specified in this list
5222 One reason that @code{catch signal} can be more useful than
5223 @code{handle} is that you can attach commands and conditions to the
5226 When a signal is caught by a catchpoint, the signal's @code{stop} and
5227 @code{print} settings, as specified by @code{handle}, are ignored.
5228 However, whether the signal is still delivered to the inferior depends
5229 on the @code{pass} setting; this can be changed in the catchpoint's
5234 @item tcatch @var{event}
5236 Set a catchpoint that is enabled only for one stop. The catchpoint is
5237 automatically deleted after the first time the event is caught.
5241 Use the @code{info break} command to list the current catchpoints.
5245 @subsection Deleting Breakpoints
5247 @cindex clearing breakpoints, watchpoints, catchpoints
5248 @cindex deleting breakpoints, watchpoints, catchpoints
5249 It is often necessary to eliminate a breakpoint, watchpoint, or
5250 catchpoint once it has done its job and you no longer want your program
5251 to stop there. This is called @dfn{deleting} the breakpoint. A
5252 breakpoint that has been deleted no longer exists; it is forgotten.
5254 With the @code{clear} command you can delete breakpoints according to
5255 where they are in your program. With the @code{delete} command you can
5256 delete individual breakpoints, watchpoints, or catchpoints by specifying
5257 their breakpoint numbers.
5259 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5260 automatically ignores breakpoints on the first instruction to be executed
5261 when you continue execution without changing the execution address.
5266 Delete any breakpoints at the next instruction to be executed in the
5267 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5268 the innermost frame is selected, this is a good way to delete a
5269 breakpoint where your program just stopped.
5271 @item clear @var{location}
5272 Delete any breakpoints set at the specified @var{location}.
5273 @xref{Specify Location}, for the various forms of @var{location}; the
5274 most useful ones are listed below:
5277 @item clear @var{function}
5278 @itemx clear @var{filename}:@var{function}
5279 Delete any breakpoints set at entry to the named @var{function}.
5281 @item clear @var{linenum}
5282 @itemx clear @var{filename}:@var{linenum}
5283 Delete any breakpoints set at or within the code of the specified
5284 @var{linenum} of the specified @var{filename}.
5287 @cindex delete breakpoints
5289 @kindex d @r{(@code{delete})}
5290 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5291 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5292 list specified as argument. If no argument is specified, delete all
5293 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5294 confirm off}). You can abbreviate this command as @code{d}.
5298 @subsection Disabling Breakpoints
5300 @cindex enable/disable a breakpoint
5301 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5302 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5303 it had been deleted, but remembers the information on the breakpoint so
5304 that you can @dfn{enable} it again later.
5306 You disable and enable breakpoints, watchpoints, and catchpoints with
5307 the @code{enable} and @code{disable} commands, optionally specifying
5308 one or more breakpoint numbers as arguments. Use @code{info break} to
5309 print a list of all breakpoints, watchpoints, and catchpoints if you
5310 do not know which numbers to use.
5312 Disabling and enabling a breakpoint that has multiple locations
5313 affects all of its locations.
5315 A breakpoint, watchpoint, or catchpoint can have any of several
5316 different states of enablement:
5320 Enabled. The breakpoint stops your program. A breakpoint set
5321 with the @code{break} command starts out in this state.
5323 Disabled. The breakpoint has no effect on your program.
5325 Enabled once. The breakpoint stops your program, but then becomes
5328 Enabled for a count. The breakpoint stops your program for the next
5329 N times, then becomes disabled.
5331 Enabled for deletion. The breakpoint stops your program, but
5332 immediately after it does so it is deleted permanently. A breakpoint
5333 set with the @code{tbreak} command starts out in this state.
5336 You can use the following commands to enable or disable breakpoints,
5337 watchpoints, and catchpoints:
5341 @kindex dis @r{(@code{disable})}
5342 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5343 Disable the specified breakpoints---or all breakpoints, if none are
5344 listed. A disabled breakpoint has no effect but is not forgotten. All
5345 options such as ignore-counts, conditions and commands are remembered in
5346 case the breakpoint is enabled again later. You may abbreviate
5347 @code{disable} as @code{dis}.
5350 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5351 Enable the specified breakpoints (or all defined breakpoints). They
5352 become effective once again in stopping your program.
5354 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5355 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5356 of these breakpoints immediately after stopping your program.
5358 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5359 Enable the specified breakpoints temporarily. @value{GDBN} records
5360 @var{count} with each of the specified breakpoints, and decrements a
5361 breakpoint's count when it is hit. When any count reaches 0,
5362 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5363 count (@pxref{Conditions, ,Break Conditions}), that will be
5364 decremented to 0 before @var{count} is affected.
5366 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5367 Enable the specified breakpoints to work once, then die. @value{GDBN}
5368 deletes any of these breakpoints as soon as your program stops there.
5369 Breakpoints set by the @code{tbreak} command start out in this state.
5372 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5373 @c confusing: tbreak is also initially enabled.
5374 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5375 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5376 subsequently, they become disabled or enabled only when you use one of
5377 the commands above. (The command @code{until} can set and delete a
5378 breakpoint of its own, but it does not change the state of your other
5379 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5383 @subsection Break Conditions
5384 @cindex conditional breakpoints
5385 @cindex breakpoint conditions
5387 @c FIXME what is scope of break condition expr? Context where wanted?
5388 @c in particular for a watchpoint?
5389 The simplest sort of breakpoint breaks every time your program reaches a
5390 specified place. You can also specify a @dfn{condition} for a
5391 breakpoint. A condition is just a Boolean expression in your
5392 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5393 a condition evaluates the expression each time your program reaches it,
5394 and your program stops only if the condition is @emph{true}.
5396 This is the converse of using assertions for program validation; in that
5397 situation, you want to stop when the assertion is violated---that is,
5398 when the condition is false. In C, if you want to test an assertion expressed
5399 by the condition @var{assert}, you should set the condition
5400 @samp{! @var{assert}} on the appropriate breakpoint.
5402 Conditions are also accepted for watchpoints; you may not need them,
5403 since a watchpoint is inspecting the value of an expression anyhow---but
5404 it might be simpler, say, to just set a watchpoint on a variable name,
5405 and specify a condition that tests whether the new value is an interesting
5408 Break conditions can have side effects, and may even call functions in
5409 your program. This can be useful, for example, to activate functions
5410 that log program progress, or to use your own print functions to
5411 format special data structures. The effects are completely predictable
5412 unless there is another enabled breakpoint at the same address. (In
5413 that case, @value{GDBN} might see the other breakpoint first and stop your
5414 program without checking the condition of this one.) Note that
5415 breakpoint commands are usually more convenient and flexible than break
5417 purpose of performing side effects when a breakpoint is reached
5418 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5420 Breakpoint conditions can also be evaluated on the target's side if
5421 the target supports it. Instead of evaluating the conditions locally,
5422 @value{GDBN} encodes the expression into an agent expression
5423 (@pxref{Agent Expressions}) suitable for execution on the target,
5424 independently of @value{GDBN}. Global variables become raw memory
5425 locations, locals become stack accesses, and so forth.
5427 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5428 when its condition evaluates to true. This mechanism may provide faster
5429 response times depending on the performance characteristics of the target
5430 since it does not need to keep @value{GDBN} informed about
5431 every breakpoint trigger, even those with false conditions.
5433 Break conditions can be specified when a breakpoint is set, by using
5434 @samp{if} in the arguments to the @code{break} command. @xref{Set
5435 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5436 with the @code{condition} command.
5438 You can also use the @code{if} keyword with the @code{watch} command.
5439 The @code{catch} command does not recognize the @code{if} keyword;
5440 @code{condition} is the only way to impose a further condition on a
5445 @item condition @var{bnum} @var{expression}
5446 Specify @var{expression} as the break condition for breakpoint,
5447 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5448 breakpoint @var{bnum} stops your program only if the value of
5449 @var{expression} is true (nonzero, in C). When you use
5450 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5451 syntactic correctness, and to determine whether symbols in it have
5452 referents in the context of your breakpoint. If @var{expression} uses
5453 symbols not referenced in the context of the breakpoint, @value{GDBN}
5454 prints an error message:
5457 No symbol "foo" in current context.
5462 not actually evaluate @var{expression} at the time the @code{condition}
5463 command (or a command that sets a breakpoint with a condition, like
5464 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5466 @item condition @var{bnum}
5467 Remove the condition from breakpoint number @var{bnum}. It becomes
5468 an ordinary unconditional breakpoint.
5471 @cindex ignore count (of breakpoint)
5472 A special case of a breakpoint condition is to stop only when the
5473 breakpoint has been reached a certain number of times. This is so
5474 useful that there is a special way to do it, using the @dfn{ignore
5475 count} of the breakpoint. Every breakpoint has an ignore count, which
5476 is an integer. Most of the time, the ignore count is zero, and
5477 therefore has no effect. But if your program reaches a breakpoint whose
5478 ignore count is positive, then instead of stopping, it just decrements
5479 the ignore count by one and continues. As a result, if the ignore count
5480 value is @var{n}, the breakpoint does not stop the next @var{n} times
5481 your program reaches it.
5485 @item ignore @var{bnum} @var{count}
5486 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5487 The next @var{count} times the breakpoint is reached, your program's
5488 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5491 To make the breakpoint stop the next time it is reached, specify
5494 When you use @code{continue} to resume execution of your program from a
5495 breakpoint, you can specify an ignore count directly as an argument to
5496 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5497 Stepping,,Continuing and Stepping}.
5499 If a breakpoint has a positive ignore count and a condition, the
5500 condition is not checked. Once the ignore count reaches zero,
5501 @value{GDBN} resumes checking the condition.
5503 You could achieve the effect of the ignore count with a condition such
5504 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5505 is decremented each time. @xref{Convenience Vars, ,Convenience
5509 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5512 @node Break Commands
5513 @subsection Breakpoint Command Lists
5515 @cindex breakpoint commands
5516 You can give any breakpoint (or watchpoint or catchpoint) a series of
5517 commands to execute when your program stops due to that breakpoint. For
5518 example, you might want to print the values of certain expressions, or
5519 enable other breakpoints.
5523 @kindex end@r{ (breakpoint commands)}
5524 @item commands @r{[}@var{list}@dots{}@r{]}
5525 @itemx @dots{} @var{command-list} @dots{}
5527 Specify a list of commands for the given breakpoints. The commands
5528 themselves appear on the following lines. Type a line containing just
5529 @code{end} to terminate the commands.
5531 To remove all commands from a breakpoint, type @code{commands} and
5532 follow it immediately with @code{end}; that is, give no commands.
5534 With no argument, @code{commands} refers to the last breakpoint,
5535 watchpoint, or catchpoint set (not to the breakpoint most recently
5536 encountered). If the most recent breakpoints were set with a single
5537 command, then the @code{commands} will apply to all the breakpoints
5538 set by that command. This applies to breakpoints set by
5539 @code{rbreak}, and also applies when a single @code{break} command
5540 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5544 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5545 disabled within a @var{command-list}.
5547 You can use breakpoint commands to start your program up again. Simply
5548 use the @code{continue} command, or @code{step}, or any other command
5549 that resumes execution.
5551 Any other commands in the command list, after a command that resumes
5552 execution, are ignored. This is because any time you resume execution
5553 (even with a simple @code{next} or @code{step}), you may encounter
5554 another breakpoint---which could have its own command list, leading to
5555 ambiguities about which list to execute.
5558 If the first command you specify in a command list is @code{silent}, the
5559 usual message about stopping at a breakpoint is not printed. This may
5560 be desirable for breakpoints that are to print a specific message and
5561 then continue. If none of the remaining commands print anything, you
5562 see no sign that the breakpoint was reached. @code{silent} is
5563 meaningful only at the beginning of a breakpoint command list.
5565 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5566 print precisely controlled output, and are often useful in silent
5567 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5569 For example, here is how you could use breakpoint commands to print the
5570 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5576 printf "x is %d\n",x
5581 One application for breakpoint commands is to compensate for one bug so
5582 you can test for another. Put a breakpoint just after the erroneous line
5583 of code, give it a condition to detect the case in which something
5584 erroneous has been done, and give it commands to assign correct values
5585 to any variables that need them. End with the @code{continue} command
5586 so that your program does not stop, and start with the @code{silent}
5587 command so that no output is produced. Here is an example:
5598 @node Dynamic Printf
5599 @subsection Dynamic Printf
5601 @cindex dynamic printf
5603 The dynamic printf command @code{dprintf} combines a breakpoint with
5604 formatted printing of your program's data to give you the effect of
5605 inserting @code{printf} calls into your program on-the-fly, without
5606 having to recompile it.
5608 In its most basic form, the output goes to the GDB console. However,
5609 you can set the variable @code{dprintf-style} for alternate handling.
5610 For instance, you can ask to format the output by calling your
5611 program's @code{printf} function. This has the advantage that the
5612 characters go to the program's output device, so they can recorded in
5613 redirects to files and so forth.
5615 If you are doing remote debugging with a stub or agent, you can also
5616 ask to have the printf handled by the remote agent. In addition to
5617 ensuring that the output goes to the remote program's device along
5618 with any other output the program might produce, you can also ask that
5619 the dprintf remain active even after disconnecting from the remote
5620 target. Using the stub/agent is also more efficient, as it can do
5621 everything without needing to communicate with @value{GDBN}.
5625 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5626 Whenever execution reaches @var{location}, print the values of one or
5627 more @var{expressions} under the control of the string @var{template}.
5628 To print several values, separate them with commas.
5630 @item set dprintf-style @var{style}
5631 Set the dprintf output to be handled in one of several different
5632 styles enumerated below. A change of style affects all existing
5633 dynamic printfs immediately. (If you need individual control over the
5634 print commands, simply define normal breakpoints with
5635 explicitly-supplied command lists.)
5639 @kindex dprintf-style gdb
5640 Handle the output using the @value{GDBN} @code{printf} command.
5643 @kindex dprintf-style call
5644 Handle the output by calling a function in your program (normally
5648 @kindex dprintf-style agent
5649 Have the remote debugging agent (such as @code{gdbserver}) handle
5650 the output itself. This style is only available for agents that
5651 support running commands on the target.
5654 @item set dprintf-function @var{function}
5655 Set the function to call if the dprintf style is @code{call}. By
5656 default its value is @code{printf}. You may set it to any expression.
5657 that @value{GDBN} can evaluate to a function, as per the @code{call}
5660 @item set dprintf-channel @var{channel}
5661 Set a ``channel'' for dprintf. If set to a non-empty value,
5662 @value{GDBN} will evaluate it as an expression and pass the result as
5663 a first argument to the @code{dprintf-function}, in the manner of
5664 @code{fprintf} and similar functions. Otherwise, the dprintf format
5665 string will be the first argument, in the manner of @code{printf}.
5667 As an example, if you wanted @code{dprintf} output to go to a logfile
5668 that is a standard I/O stream assigned to the variable @code{mylog},
5669 you could do the following:
5672 (gdb) set dprintf-style call
5673 (gdb) set dprintf-function fprintf
5674 (gdb) set dprintf-channel mylog
5675 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5676 Dprintf 1 at 0x123456: file main.c, line 25.
5678 1 dprintf keep y 0x00123456 in main at main.c:25
5679 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5684 Note that the @code{info break} displays the dynamic printf commands
5685 as normal breakpoint commands; you can thus easily see the effect of
5686 the variable settings.
5688 @item set disconnected-dprintf on
5689 @itemx set disconnected-dprintf off
5690 @kindex set disconnected-dprintf
5691 Choose whether @code{dprintf} commands should continue to run if
5692 @value{GDBN} has disconnected from the target. This only applies
5693 if the @code{dprintf-style} is @code{agent}.
5695 @item show disconnected-dprintf off
5696 @kindex show disconnected-dprintf
5697 Show the current choice for disconnected @code{dprintf}.
5701 @value{GDBN} does not check the validity of function and channel,
5702 relying on you to supply values that are meaningful for the contexts
5703 in which they are being used. For instance, the function and channel
5704 may be the values of local variables, but if that is the case, then
5705 all enabled dynamic prints must be at locations within the scope of
5706 those locals. If evaluation fails, @value{GDBN} will report an error.
5708 @node Save Breakpoints
5709 @subsection How to save breakpoints to a file
5711 To save breakpoint definitions to a file use the @w{@code{save
5712 breakpoints}} command.
5715 @kindex save breakpoints
5716 @cindex save breakpoints to a file for future sessions
5717 @item save breakpoints [@var{filename}]
5718 This command saves all current breakpoint definitions together with
5719 their commands and ignore counts, into a file @file{@var{filename}}
5720 suitable for use in a later debugging session. This includes all
5721 types of breakpoints (breakpoints, watchpoints, catchpoints,
5722 tracepoints). To read the saved breakpoint definitions, use the
5723 @code{source} command (@pxref{Command Files}). Note that watchpoints
5724 with expressions involving local variables may fail to be recreated
5725 because it may not be possible to access the context where the
5726 watchpoint is valid anymore. Because the saved breakpoint definitions
5727 are simply a sequence of @value{GDBN} commands that recreate the
5728 breakpoints, you can edit the file in your favorite editing program,
5729 and remove the breakpoint definitions you're not interested in, or
5730 that can no longer be recreated.
5733 @node Static Probe Points
5734 @subsection Static Probe Points
5736 @cindex static probe point, SystemTap
5737 @cindex static probe point, DTrace
5738 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5739 for Statically Defined Tracing, and the probes are designed to have a tiny
5740 runtime code and data footprint, and no dynamic relocations.
5742 Currently, the following types of probes are supported on
5743 ELF-compatible systems:
5747 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5748 @acronym{SDT} probes@footnote{See
5749 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5750 for more information on how to add @code{SystemTap} @acronym{SDT}
5751 probes in your applications.}. @code{SystemTap} probes are usable
5752 from assembly, C and C@t{++} languages@footnote{See
5753 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5754 for a good reference on how the @acronym{SDT} probes are implemented.}.
5756 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5757 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5761 @cindex semaphores on static probe points
5762 Some @code{SystemTap} probes have an associated semaphore variable;
5763 for instance, this happens automatically if you defined your probe
5764 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5765 @value{GDBN} will automatically enable it when you specify a
5766 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5767 breakpoint at a probe's location by some other method (e.g.,
5768 @code{break file:line}), then @value{GDBN} will not automatically set
5769 the semaphore. @code{DTrace} probes do not support semaphores.
5771 You can examine the available static static probes using @code{info
5772 probes}, with optional arguments:
5776 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5777 If given, @var{type} is either @code{stap} for listing
5778 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5779 probes. If omitted all probes are listed regardless of their types.
5781 If given, @var{provider} is a regular expression used to match against provider
5782 names when selecting which probes to list. If omitted, probes by all
5783 probes from all providers are listed.
5785 If given, @var{name} is a regular expression to match against probe names
5786 when selecting which probes to list. If omitted, probe names are not
5787 considered when deciding whether to display them.
5789 If given, @var{objfile} is a regular expression used to select which
5790 object files (executable or shared libraries) to examine. If not
5791 given, all object files are considered.
5793 @item info probes all
5794 List the available static probes, from all types.
5797 @cindex enabling and disabling probes
5798 Some probe points can be enabled and/or disabled. The effect of
5799 enabling or disabling a probe depends on the type of probe being
5800 handled. Some @code{DTrace} probes can be enabled or
5801 disabled, but @code{SystemTap} probes cannot be disabled.
5803 You can enable (or disable) one or more probes using the following
5804 commands, with optional arguments:
5807 @kindex enable probes
5808 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5809 If given, @var{provider} is a regular expression used to match against
5810 provider names when selecting which probes to enable. If omitted,
5811 all probes from all providers are enabled.
5813 If given, @var{name} is a regular expression to match against probe
5814 names when selecting which probes to enable. If omitted, probe names
5815 are not considered when deciding whether to enable them.
5817 If given, @var{objfile} is a regular expression used to select which
5818 object files (executable or shared libraries) to examine. If not
5819 given, all object files are considered.
5821 @kindex disable probes
5822 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5823 See the @code{enable probes} command above for a description of the
5824 optional arguments accepted by this command.
5827 @vindex $_probe_arg@r{, convenience variable}
5828 A probe may specify up to twelve arguments. These are available at the
5829 point at which the probe is defined---that is, when the current PC is
5830 at the probe's location. The arguments are available using the
5831 convenience variables (@pxref{Convenience Vars})
5832 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5833 probes each probe argument is an integer of the appropriate size;
5834 types are not preserved. In @code{DTrace} probes types are preserved
5835 provided that they are recognized as such by @value{GDBN}; otherwise
5836 the value of the probe argument will be a long integer. The
5837 convenience variable @code{$_probe_argc} holds the number of arguments
5838 at the current probe point.
5840 These variables are always available, but attempts to access them at
5841 any location other than a probe point will cause @value{GDBN} to give
5845 @c @ifclear BARETARGET
5846 @node Error in Breakpoints
5847 @subsection ``Cannot insert breakpoints''
5849 If you request too many active hardware-assisted breakpoints and
5850 watchpoints, you will see this error message:
5852 @c FIXME: the precise wording of this message may change; the relevant
5853 @c source change is not committed yet (Sep 3, 1999).
5855 Stopped; cannot insert breakpoints.
5856 You may have requested too many hardware breakpoints and watchpoints.
5860 This message is printed when you attempt to resume the program, since
5861 only then @value{GDBN} knows exactly how many hardware breakpoints and
5862 watchpoints it needs to insert.
5864 When this message is printed, you need to disable or remove some of the
5865 hardware-assisted breakpoints and watchpoints, and then continue.
5867 @node Breakpoint-related Warnings
5868 @subsection ``Breakpoint address adjusted...''
5869 @cindex breakpoint address adjusted
5871 Some processor architectures place constraints on the addresses at
5872 which breakpoints may be placed. For architectures thus constrained,
5873 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5874 with the constraints dictated by the architecture.
5876 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5877 a VLIW architecture in which a number of RISC-like instructions may be
5878 bundled together for parallel execution. The FR-V architecture
5879 constrains the location of a breakpoint instruction within such a
5880 bundle to the instruction with the lowest address. @value{GDBN}
5881 honors this constraint by adjusting a breakpoint's address to the
5882 first in the bundle.
5884 It is not uncommon for optimized code to have bundles which contain
5885 instructions from different source statements, thus it may happen that
5886 a breakpoint's address will be adjusted from one source statement to
5887 another. Since this adjustment may significantly alter @value{GDBN}'s
5888 breakpoint related behavior from what the user expects, a warning is
5889 printed when the breakpoint is first set and also when the breakpoint
5892 A warning like the one below is printed when setting a breakpoint
5893 that's been subject to address adjustment:
5896 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5899 Such warnings are printed both for user settable and @value{GDBN}'s
5900 internal breakpoints. If you see one of these warnings, you should
5901 verify that a breakpoint set at the adjusted address will have the
5902 desired affect. If not, the breakpoint in question may be removed and
5903 other breakpoints may be set which will have the desired behavior.
5904 E.g., it may be sufficient to place the breakpoint at a later
5905 instruction. A conditional breakpoint may also be useful in some
5906 cases to prevent the breakpoint from triggering too often.
5908 @value{GDBN} will also issue a warning when stopping at one of these
5909 adjusted breakpoints:
5912 warning: Breakpoint 1 address previously adjusted from 0x00010414
5916 When this warning is encountered, it may be too late to take remedial
5917 action except in cases where the breakpoint is hit earlier or more
5918 frequently than expected.
5920 @node Continuing and Stepping
5921 @section Continuing and Stepping
5925 @cindex resuming execution
5926 @dfn{Continuing} means resuming program execution until your program
5927 completes normally. In contrast, @dfn{stepping} means executing just
5928 one more ``step'' of your program, where ``step'' may mean either one
5929 line of source code, or one machine instruction (depending on what
5930 particular command you use). Either when continuing or when stepping,
5931 your program may stop even sooner, due to a breakpoint or a signal. (If
5932 it stops due to a signal, you may want to use @code{handle}, or use
5933 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5934 or you may step into the signal's handler (@pxref{stepping and signal
5939 @kindex c @r{(@code{continue})}
5940 @kindex fg @r{(resume foreground execution)}
5941 @item continue @r{[}@var{ignore-count}@r{]}
5942 @itemx c @r{[}@var{ignore-count}@r{]}
5943 @itemx fg @r{[}@var{ignore-count}@r{]}
5944 Resume program execution, at the address where your program last stopped;
5945 any breakpoints set at that address are bypassed. The optional argument
5946 @var{ignore-count} allows you to specify a further number of times to
5947 ignore a breakpoint at this location; its effect is like that of
5948 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5950 The argument @var{ignore-count} is meaningful only when your program
5951 stopped due to a breakpoint. At other times, the argument to
5952 @code{continue} is ignored.
5954 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5955 debugged program is deemed to be the foreground program) are provided
5956 purely for convenience, and have exactly the same behavior as
5960 To resume execution at a different place, you can use @code{return}
5961 (@pxref{Returning, ,Returning from a Function}) to go back to the
5962 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5963 Different Address}) to go to an arbitrary location in your program.
5965 A typical technique for using stepping is to set a breakpoint
5966 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5967 beginning of the function or the section of your program where a problem
5968 is believed to lie, run your program until it stops at that breakpoint,
5969 and then step through the suspect area, examining the variables that are
5970 interesting, until you see the problem happen.
5974 @kindex s @r{(@code{step})}
5976 Continue running your program until control reaches a different source
5977 line, then stop it and return control to @value{GDBN}. This command is
5978 abbreviated @code{s}.
5981 @c "without debugging information" is imprecise; actually "without line
5982 @c numbers in the debugging information". (gcc -g1 has debugging info but
5983 @c not line numbers). But it seems complex to try to make that
5984 @c distinction here.
5985 @emph{Warning:} If you use the @code{step} command while control is
5986 within a function that was compiled without debugging information,
5987 execution proceeds until control reaches a function that does have
5988 debugging information. Likewise, it will not step into a function which
5989 is compiled without debugging information. To step through functions
5990 without debugging information, use the @code{stepi} command, described
5994 The @code{step} command only stops at the first instruction of a source
5995 line. This prevents the multiple stops that could otherwise occur in
5996 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5997 to stop if a function that has debugging information is called within
5998 the line. In other words, @code{step} @emph{steps inside} any functions
5999 called within the line.
6001 Also, the @code{step} command only enters a function if there is line
6002 number information for the function. Otherwise it acts like the
6003 @code{next} command. This avoids problems when using @code{cc -gl}
6004 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6005 was any debugging information about the routine.
6007 @item step @var{count}
6008 Continue running as in @code{step}, but do so @var{count} times. If a
6009 breakpoint is reached, or a signal not related to stepping occurs before
6010 @var{count} steps, stepping stops right away.
6013 @kindex n @r{(@code{next})}
6014 @item next @r{[}@var{count}@r{]}
6015 Continue to the next source line in the current (innermost) stack frame.
6016 This is similar to @code{step}, but function calls that appear within
6017 the line of code are executed without stopping. Execution stops when
6018 control reaches a different line of code at the original stack level
6019 that was executing when you gave the @code{next} command. This command
6020 is abbreviated @code{n}.
6022 An argument @var{count} is a repeat count, as for @code{step}.
6025 @c FIX ME!! Do we delete this, or is there a way it fits in with
6026 @c the following paragraph? --- Vctoria
6028 @c @code{next} within a function that lacks debugging information acts like
6029 @c @code{step}, but any function calls appearing within the code of the
6030 @c function are executed without stopping.
6032 The @code{next} command only stops at the first instruction of a
6033 source line. This prevents multiple stops that could otherwise occur in
6034 @code{switch} statements, @code{for} loops, etc.
6036 @kindex set step-mode
6038 @cindex functions without line info, and stepping
6039 @cindex stepping into functions with no line info
6040 @itemx set step-mode on
6041 The @code{set step-mode on} command causes the @code{step} command to
6042 stop at the first instruction of a function which contains no debug line
6043 information rather than stepping over it.
6045 This is useful in cases where you may be interested in inspecting the
6046 machine instructions of a function which has no symbolic info and do not
6047 want @value{GDBN} to automatically skip over this function.
6049 @item set step-mode off
6050 Causes the @code{step} command to step over any functions which contains no
6051 debug information. This is the default.
6053 @item show step-mode
6054 Show whether @value{GDBN} will stop in or step over functions without
6055 source line debug information.
6058 @kindex fin @r{(@code{finish})}
6060 Continue running until just after function in the selected stack frame
6061 returns. Print the returned value (if any). This command can be
6062 abbreviated as @code{fin}.
6064 Contrast this with the @code{return} command (@pxref{Returning,
6065 ,Returning from a Function}).
6067 @kindex set print finish
6068 @kindex show print finish
6069 @item set print finish @r{[}on|off@r{]}
6070 @itemx show print finish
6071 By default the @code{finish} command will show the value that is
6072 returned by the function. This can be disabled using @code{set print
6073 finish off}. When disabled, the value is still entered into the value
6074 history (@pxref{Value History}), but not displayed.
6077 @kindex u @r{(@code{until})}
6078 @cindex run until specified location
6081 Continue running until a source line past the current line, in the
6082 current stack frame, is reached. This command is used to avoid single
6083 stepping through a loop more than once. It is like the @code{next}
6084 command, except that when @code{until} encounters a jump, it
6085 automatically continues execution until the program counter is greater
6086 than the address of the jump.
6088 This means that when you reach the end of a loop after single stepping
6089 though it, @code{until} makes your program continue execution until it
6090 exits the loop. In contrast, a @code{next} command at the end of a loop
6091 simply steps back to the beginning of the loop, which forces you to step
6092 through the next iteration.
6094 @code{until} always stops your program if it attempts to exit the current
6097 @code{until} may produce somewhat counterintuitive results if the order
6098 of machine code does not match the order of the source lines. For
6099 example, in the following excerpt from a debugging session, the @code{f}
6100 (@code{frame}) command shows that execution is stopped at line
6101 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6105 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6107 (@value{GDBP}) until
6108 195 for ( ; argc > 0; NEXTARG) @{
6111 This happened because, for execution efficiency, the compiler had
6112 generated code for the loop closure test at the end, rather than the
6113 start, of the loop---even though the test in a C @code{for}-loop is
6114 written before the body of the loop. The @code{until} command appeared
6115 to step back to the beginning of the loop when it advanced to this
6116 expression; however, it has not really gone to an earlier
6117 statement---not in terms of the actual machine code.
6119 @code{until} with no argument works by means of single
6120 instruction stepping, and hence is slower than @code{until} with an
6123 @item until @var{location}
6124 @itemx u @var{location}
6125 Continue running your program until either the specified @var{location} is
6126 reached, or the current stack frame returns. The location is any of
6127 the forms described in @ref{Specify Location}.
6128 This form of the command uses temporary breakpoints, and
6129 hence is quicker than @code{until} without an argument. The specified
6130 location is actually reached only if it is in the current frame. This
6131 implies that @code{until} can be used to skip over recursive function
6132 invocations. For instance in the code below, if the current location is
6133 line @code{96}, issuing @code{until 99} will execute the program up to
6134 line @code{99} in the same invocation of factorial, i.e., after the inner
6135 invocations have returned.
6138 94 int factorial (int value)
6140 96 if (value > 1) @{
6141 97 value *= factorial (value - 1);
6148 @kindex advance @var{location}
6149 @item advance @var{location}
6150 Continue running the program up to the given @var{location}. An argument is
6151 required, which should be of one of the forms described in
6152 @ref{Specify Location}.
6153 Execution will also stop upon exit from the current stack
6154 frame. This command is similar to @code{until}, but @code{advance} will
6155 not skip over recursive function calls, and the target location doesn't
6156 have to be in the same frame as the current one.
6160 @kindex si @r{(@code{stepi})}
6162 @itemx stepi @var{arg}
6164 Execute one machine instruction, then stop and return to the debugger.
6166 It is often useful to do @samp{display/i $pc} when stepping by machine
6167 instructions. This makes @value{GDBN} automatically display the next
6168 instruction to be executed, each time your program stops. @xref{Auto
6169 Display,, Automatic Display}.
6171 An argument is a repeat count, as in @code{step}.
6175 @kindex ni @r{(@code{nexti})}
6177 @itemx nexti @var{arg}
6179 Execute one machine instruction, but if it is a function call,
6180 proceed until the function returns.
6182 An argument is a repeat count, as in @code{next}.
6186 @anchor{range stepping}
6187 @cindex range stepping
6188 @cindex target-assisted range stepping
6189 By default, and if available, @value{GDBN} makes use of
6190 target-assisted @dfn{range stepping}. In other words, whenever you
6191 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6192 tells the target to step the corresponding range of instruction
6193 addresses instead of issuing multiple single-steps. This speeds up
6194 line stepping, particularly for remote targets. Ideally, there should
6195 be no reason you would want to turn range stepping off. However, it's
6196 possible that a bug in the debug info, a bug in the remote stub (for
6197 remote targets), or even a bug in @value{GDBN} could make line
6198 stepping behave incorrectly when target-assisted range stepping is
6199 enabled. You can use the following command to turn off range stepping
6203 @kindex set range-stepping
6204 @kindex show range-stepping
6205 @item set range-stepping
6206 @itemx show range-stepping
6207 Control whether range stepping is enabled.
6209 If @code{on}, and the target supports it, @value{GDBN} tells the
6210 target to step a range of addresses itself, instead of issuing
6211 multiple single-steps. If @code{off}, @value{GDBN} always issues
6212 single-steps, even if range stepping is supported by the target. The
6213 default is @code{on}.
6217 @node Skipping Over Functions and Files
6218 @section Skipping Over Functions and Files
6219 @cindex skipping over functions and files
6221 The program you are debugging may contain some functions which are
6222 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6223 skip a function, all functions in a file or a particular function in
6224 a particular file when stepping.
6226 For example, consider the following C function:
6237 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6238 are not interested in stepping through @code{boring}. If you run @code{step}
6239 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6240 step over both @code{foo} and @code{boring}!
6242 One solution is to @code{step} into @code{boring} and use the @code{finish}
6243 command to immediately exit it. But this can become tedious if @code{boring}
6244 is called from many places.
6246 A more flexible solution is to execute @kbd{skip boring}. This instructs
6247 @value{GDBN} never to step into @code{boring}. Now when you execute
6248 @code{step} at line 103, you'll step over @code{boring} and directly into
6251 Functions may be skipped by providing either a function name, linespec
6252 (@pxref{Specify Location}), regular expression that matches the function's
6253 name, file name or a @code{glob}-style pattern that matches the file name.
6255 On Posix systems the form of the regular expression is
6256 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6257 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6258 expression is whatever is provided by the @code{regcomp} function of
6259 the underlying system.
6260 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6261 description of @code{glob}-style patterns.
6265 @item skip @r{[}@var{options}@r{]}
6266 The basic form of the @code{skip} command takes zero or more options
6267 that specify what to skip.
6268 The @var{options} argument is any useful combination of the following:
6271 @item -file @var{file}
6272 @itemx -fi @var{file}
6273 Functions in @var{file} will be skipped over when stepping.
6275 @item -gfile @var{file-glob-pattern}
6276 @itemx -gfi @var{file-glob-pattern}
6277 @cindex skipping over files via glob-style patterns
6278 Functions in files matching @var{file-glob-pattern} will be skipped
6282 (gdb) skip -gfi utils/*.c
6285 @item -function @var{linespec}
6286 @itemx -fu @var{linespec}
6287 Functions named by @var{linespec} or the function containing the line
6288 named by @var{linespec} will be skipped over when stepping.
6289 @xref{Specify Location}.
6291 @item -rfunction @var{regexp}
6292 @itemx -rfu @var{regexp}
6293 @cindex skipping over functions via regular expressions
6294 Functions whose name matches @var{regexp} will be skipped over when stepping.
6296 This form is useful for complex function names.
6297 For example, there is generally no need to step into C@t{++} @code{std::string}
6298 constructors or destructors. Plus with C@t{++} templates it can be hard to
6299 write out the full name of the function, and often it doesn't matter what
6300 the template arguments are. Specifying the function to be skipped as a
6301 regular expression makes this easier.
6304 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6307 If you want to skip every templated C@t{++} constructor and destructor
6308 in the @code{std} namespace you can do:
6311 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6315 If no options are specified, the function you're currently debugging
6318 @kindex skip function
6319 @item skip function @r{[}@var{linespec}@r{]}
6320 After running this command, the function named by @var{linespec} or the
6321 function containing the line named by @var{linespec} will be skipped over when
6322 stepping. @xref{Specify Location}.
6324 If you do not specify @var{linespec}, the function you're currently debugging
6327 (If you have a function called @code{file} that you want to skip, use
6328 @kbd{skip function file}.)
6331 @item skip file @r{[}@var{filename}@r{]}
6332 After running this command, any function whose source lives in @var{filename}
6333 will be skipped over when stepping.
6336 (gdb) skip file boring.c
6337 File boring.c will be skipped when stepping.
6340 If you do not specify @var{filename}, functions whose source lives in the file
6341 you're currently debugging will be skipped.
6344 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6345 These are the commands for managing your list of skips:
6349 @item info skip @r{[}@var{range}@r{]}
6350 Print details about the specified skip(s). If @var{range} is not specified,
6351 print a table with details about all functions and files marked for skipping.
6352 @code{info skip} prints the following information about each skip:
6356 A number identifying this skip.
6357 @item Enabled or Disabled
6358 Enabled skips are marked with @samp{y}.
6359 Disabled skips are marked with @samp{n}.
6361 If the file name is a @samp{glob} pattern this is @samp{y}.
6362 Otherwise it is @samp{n}.
6364 The name or @samp{glob} pattern of the file to be skipped.
6365 If no file is specified this is @samp{<none>}.
6367 If the function name is a @samp{regular expression} this is @samp{y}.
6368 Otherwise it is @samp{n}.
6370 The name or regular expression of the function to skip.
6371 If no function is specified this is @samp{<none>}.
6375 @item skip delete @r{[}@var{range}@r{]}
6376 Delete the specified skip(s). If @var{range} is not specified, delete all
6380 @item skip enable @r{[}@var{range}@r{]}
6381 Enable the specified skip(s). If @var{range} is not specified, enable all
6384 @kindex skip disable
6385 @item skip disable @r{[}@var{range}@r{]}
6386 Disable the specified skip(s). If @var{range} is not specified, disable all
6389 @kindex set debug skip
6390 @item set debug skip @r{[}on|off@r{]}
6391 Set whether to print the debug output about skipping files and functions.
6393 @kindex show debug skip
6394 @item show debug skip
6395 Show whether the debug output about skipping files and functions is printed.
6403 A signal is an asynchronous event that can happen in a program. The
6404 operating system defines the possible kinds of signals, and gives each
6405 kind a name and a number. For example, in Unix @code{SIGINT} is the
6406 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6407 @code{SIGSEGV} is the signal a program gets from referencing a place in
6408 memory far away from all the areas in use; @code{SIGALRM} occurs when
6409 the alarm clock timer goes off (which happens only if your program has
6410 requested an alarm).
6412 @cindex fatal signals
6413 Some signals, including @code{SIGALRM}, are a normal part of the
6414 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6415 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6416 program has not specified in advance some other way to handle the signal.
6417 @code{SIGINT} does not indicate an error in your program, but it is normally
6418 fatal so it can carry out the purpose of the interrupt: to kill the program.
6420 @value{GDBN} has the ability to detect any occurrence of a signal in your
6421 program. You can tell @value{GDBN} in advance what to do for each kind of
6424 @cindex handling signals
6425 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6426 @code{SIGALRM} be silently passed to your program
6427 (so as not to interfere with their role in the program's functioning)
6428 but to stop your program immediately whenever an error signal happens.
6429 You can change these settings with the @code{handle} command.
6432 @kindex info signals
6436 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6437 handle each one. You can use this to see the signal numbers of all
6438 the defined types of signals.
6440 @item info signals @var{sig}
6441 Similar, but print information only about the specified signal number.
6443 @code{info handle} is an alias for @code{info signals}.
6445 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6446 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6447 for details about this command.
6450 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6451 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6452 can be the number of a signal or its name (with or without the
6453 @samp{SIG} at the beginning); a list of signal numbers of the form
6454 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6455 known signals. Optional arguments @var{keywords}, described below,
6456 say what change to make.
6460 The keywords allowed by the @code{handle} command can be abbreviated.
6461 Their full names are:
6465 @value{GDBN} should not stop your program when this signal happens. It may
6466 still print a message telling you that the signal has come in.
6469 @value{GDBN} should stop your program when this signal happens. This implies
6470 the @code{print} keyword as well.
6473 @value{GDBN} should print a message when this signal happens.
6476 @value{GDBN} should not mention the occurrence of the signal at all. This
6477 implies the @code{nostop} keyword as well.
6481 @value{GDBN} should allow your program to see this signal; your program
6482 can handle the signal, or else it may terminate if the signal is fatal
6483 and not handled. @code{pass} and @code{noignore} are synonyms.
6487 @value{GDBN} should not allow your program to see this signal.
6488 @code{nopass} and @code{ignore} are synonyms.
6492 When a signal stops your program, the signal is not visible to the
6494 continue. Your program sees the signal then, if @code{pass} is in
6495 effect for the signal in question @emph{at that time}. In other words,
6496 after @value{GDBN} reports a signal, you can use the @code{handle}
6497 command with @code{pass} or @code{nopass} to control whether your
6498 program sees that signal when you continue.
6500 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6501 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6502 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6505 You can also use the @code{signal} command to prevent your program from
6506 seeing a signal, or cause it to see a signal it normally would not see,
6507 or to give it any signal at any time. For example, if your program stopped
6508 due to some sort of memory reference error, you might store correct
6509 values into the erroneous variables and continue, hoping to see more
6510 execution; but your program would probably terminate immediately as
6511 a result of the fatal signal once it saw the signal. To prevent this,
6512 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6515 @cindex stepping and signal handlers
6516 @anchor{stepping and signal handlers}
6518 @value{GDBN} optimizes for stepping the mainline code. If a signal
6519 that has @code{handle nostop} and @code{handle pass} set arrives while
6520 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6521 in progress, @value{GDBN} lets the signal handler run and then resumes
6522 stepping the mainline code once the signal handler returns. In other
6523 words, @value{GDBN} steps over the signal handler. This prevents
6524 signals that you've specified as not interesting (with @code{handle
6525 nostop}) from changing the focus of debugging unexpectedly. Note that
6526 the signal handler itself may still hit a breakpoint, stop for another
6527 signal that has @code{handle stop} in effect, or for any other event
6528 that normally results in stopping the stepping command sooner. Also
6529 note that @value{GDBN} still informs you that the program received a
6530 signal if @code{handle print} is set.
6532 @anchor{stepping into signal handlers}
6534 If you set @code{handle pass} for a signal, and your program sets up a
6535 handler for it, then issuing a stepping command, such as @code{step}
6536 or @code{stepi}, when your program is stopped due to the signal will
6537 step @emph{into} the signal handler (if the target supports that).
6539 Likewise, if you use the @code{queue-signal} command to queue a signal
6540 to be delivered to the current thread when execution of the thread
6541 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6542 stepping command will step into the signal handler.
6544 Here's an example, using @code{stepi} to step to the first instruction
6545 of @code{SIGUSR1}'s handler:
6548 (@value{GDBP}) handle SIGUSR1
6549 Signal Stop Print Pass to program Description
6550 SIGUSR1 Yes Yes Yes User defined signal 1
6554 Program received signal SIGUSR1, User defined signal 1.
6555 main () sigusr1.c:28
6558 sigusr1_handler () at sigusr1.c:9
6562 The same, but using @code{queue-signal} instead of waiting for the
6563 program to receive the signal first:
6568 (@value{GDBP}) queue-signal SIGUSR1
6570 sigusr1_handler () at sigusr1.c:9
6575 @cindex extra signal information
6576 @anchor{extra signal information}
6578 On some targets, @value{GDBN} can inspect extra signal information
6579 associated with the intercepted signal, before it is actually
6580 delivered to the program being debugged. This information is exported
6581 by the convenience variable @code{$_siginfo}, and consists of data
6582 that is passed by the kernel to the signal handler at the time of the
6583 receipt of a signal. The data type of the information itself is
6584 target dependent. You can see the data type using the @code{ptype
6585 $_siginfo} command. On Unix systems, it typically corresponds to the
6586 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6589 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6590 referenced address that raised a segmentation fault.
6594 (@value{GDBP}) continue
6595 Program received signal SIGSEGV, Segmentation fault.
6596 0x0000000000400766 in main ()
6598 (@value{GDBP}) ptype $_siginfo
6605 struct @{...@} _kill;
6606 struct @{...@} _timer;
6608 struct @{...@} _sigchld;
6609 struct @{...@} _sigfault;
6610 struct @{...@} _sigpoll;
6613 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6617 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6618 $1 = (void *) 0x7ffff7ff7000
6622 Depending on target support, @code{$_siginfo} may also be writable.
6624 @cindex Intel MPX boundary violations
6625 @cindex boundary violations, Intel MPX
6626 On some targets, a @code{SIGSEGV} can be caused by a boundary
6627 violation, i.e., accessing an address outside of the allowed range.
6628 In those cases @value{GDBN} may displays additional information,
6629 depending on how @value{GDBN} has been told to handle the signal.
6630 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6631 kind: "Upper" or "Lower", the memory address accessed and the
6632 bounds, while with @code{handle nostop SIGSEGV} no additional
6633 information is displayed.
6635 The usual output of a segfault is:
6637 Program received signal SIGSEGV, Segmentation fault
6638 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6639 68 value = *(p + len);
6642 While a bound violation is presented as:
6644 Program received signal SIGSEGV, Segmentation fault
6645 Upper bound violation while accessing address 0x7fffffffc3b3
6646 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6647 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6648 68 value = *(p + len);
6652 @section Stopping and Starting Multi-thread Programs
6654 @cindex stopped threads
6655 @cindex threads, stopped
6657 @cindex continuing threads
6658 @cindex threads, continuing
6660 @value{GDBN} supports debugging programs with multiple threads
6661 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6662 are two modes of controlling execution of your program within the
6663 debugger. In the default mode, referred to as @dfn{all-stop mode},
6664 when any thread in your program stops (for example, at a breakpoint
6665 or while being stepped), all other threads in the program are also stopped by
6666 @value{GDBN}. On some targets, @value{GDBN} also supports
6667 @dfn{non-stop mode}, in which other threads can continue to run freely while
6668 you examine the stopped thread in the debugger.
6671 * All-Stop Mode:: All threads stop when GDB takes control
6672 * Non-Stop Mode:: Other threads continue to execute
6673 * Background Execution:: Running your program asynchronously
6674 * Thread-Specific Breakpoints:: Controlling breakpoints
6675 * Interrupted System Calls:: GDB may interfere with system calls
6676 * Observer Mode:: GDB does not alter program behavior
6680 @subsection All-Stop Mode
6682 @cindex all-stop mode
6684 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6685 @emph{all} threads of execution stop, not just the current thread. This
6686 allows you to examine the overall state of the program, including
6687 switching between threads, without worrying that things may change
6690 Conversely, whenever you restart the program, @emph{all} threads start
6691 executing. @emph{This is true even when single-stepping} with commands
6692 like @code{step} or @code{next}.
6694 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6695 Since thread scheduling is up to your debugging target's operating
6696 system (not controlled by @value{GDBN}), other threads may
6697 execute more than one statement while the current thread completes a
6698 single step. Moreover, in general other threads stop in the middle of a
6699 statement, rather than at a clean statement boundary, when the program
6702 You might even find your program stopped in another thread after
6703 continuing or even single-stepping. This happens whenever some other
6704 thread runs into a breakpoint, a signal, or an exception before the
6705 first thread completes whatever you requested.
6707 @cindex automatic thread selection
6708 @cindex switching threads automatically
6709 @cindex threads, automatic switching
6710 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6711 signal, it automatically selects the thread where that breakpoint or
6712 signal happened. @value{GDBN} alerts you to the context switch with a
6713 message such as @samp{[Switching to Thread @var{n}]} to identify the
6716 On some OSes, you can modify @value{GDBN}'s default behavior by
6717 locking the OS scheduler to allow only a single thread to run.
6720 @item set scheduler-locking @var{mode}
6721 @cindex scheduler locking mode
6722 @cindex lock scheduler
6723 Set the scheduler locking mode. It applies to normal execution,
6724 record mode, and replay mode. If it is @code{off}, then there is no
6725 locking and any thread may run at any time. If @code{on}, then only
6726 the current thread may run when the inferior is resumed. The
6727 @code{step} mode optimizes for single-stepping; it prevents other
6728 threads from preempting the current thread while you are stepping, so
6729 that the focus of debugging does not change unexpectedly. Other
6730 threads never get a chance to run when you step, and they are
6731 completely free to run when you use commands like @samp{continue},
6732 @samp{until}, or @samp{finish}. However, unless another thread hits a
6733 breakpoint during its timeslice, @value{GDBN} does not change the
6734 current thread away from the thread that you are debugging. The
6735 @code{replay} mode behaves like @code{off} in record mode and like
6736 @code{on} in replay mode.
6738 @item show scheduler-locking
6739 Display the current scheduler locking mode.
6742 @cindex resume threads of multiple processes simultaneously
6743 By default, when you issue one of the execution commands such as
6744 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6745 threads of the current inferior to run. For example, if @value{GDBN}
6746 is attached to two inferiors, each with two threads, the
6747 @code{continue} command resumes only the two threads of the current
6748 inferior. This is useful, for example, when you debug a program that
6749 forks and you want to hold the parent stopped (so that, for instance,
6750 it doesn't run to exit), while you debug the child. In other
6751 situations, you may not be interested in inspecting the current state
6752 of any of the processes @value{GDBN} is attached to, and you may want
6753 to resume them all until some breakpoint is hit. In the latter case,
6754 you can instruct @value{GDBN} to allow all threads of all the
6755 inferiors to run with the @w{@code{set schedule-multiple}} command.
6758 @kindex set schedule-multiple
6759 @item set schedule-multiple
6760 Set the mode for allowing threads of multiple processes to be resumed
6761 when an execution command is issued. When @code{on}, all threads of
6762 all processes are allowed to run. When @code{off}, only the threads
6763 of the current process are resumed. The default is @code{off}. The
6764 @code{scheduler-locking} mode takes precedence when set to @code{on},
6765 or while you are stepping and set to @code{step}.
6767 @item show schedule-multiple
6768 Display the current mode for resuming the execution of threads of
6773 @subsection Non-Stop Mode
6775 @cindex non-stop mode
6777 @c This section is really only a place-holder, and needs to be expanded
6778 @c with more details.
6780 For some multi-threaded targets, @value{GDBN} supports an optional
6781 mode of operation in which you can examine stopped program threads in
6782 the debugger while other threads continue to execute freely. This
6783 minimizes intrusion when debugging live systems, such as programs
6784 where some threads have real-time constraints or must continue to
6785 respond to external events. This is referred to as @dfn{non-stop} mode.
6787 In non-stop mode, when a thread stops to report a debugging event,
6788 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6789 threads as well, in contrast to the all-stop mode behavior. Additionally,
6790 execution commands such as @code{continue} and @code{step} apply by default
6791 only to the current thread in non-stop mode, rather than all threads as
6792 in all-stop mode. This allows you to control threads explicitly in
6793 ways that are not possible in all-stop mode --- for example, stepping
6794 one thread while allowing others to run freely, stepping
6795 one thread while holding all others stopped, or stepping several threads
6796 independently and simultaneously.
6798 To enter non-stop mode, use this sequence of commands before you run
6799 or attach to your program:
6802 # If using the CLI, pagination breaks non-stop.
6805 # Finally, turn it on!
6809 You can use these commands to manipulate the non-stop mode setting:
6812 @kindex set non-stop
6813 @item set non-stop on
6814 Enable selection of non-stop mode.
6815 @item set non-stop off
6816 Disable selection of non-stop mode.
6817 @kindex show non-stop
6819 Show the current non-stop enablement setting.
6822 Note these commands only reflect whether non-stop mode is enabled,
6823 not whether the currently-executing program is being run in non-stop mode.
6824 In particular, the @code{set non-stop} preference is only consulted when
6825 @value{GDBN} starts or connects to the target program, and it is generally
6826 not possible to switch modes once debugging has started. Furthermore,
6827 since not all targets support non-stop mode, even when you have enabled
6828 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6831 In non-stop mode, all execution commands apply only to the current thread
6832 by default. That is, @code{continue} only continues one thread.
6833 To continue all threads, issue @code{continue -a} or @code{c -a}.
6835 You can use @value{GDBN}'s background execution commands
6836 (@pxref{Background Execution}) to run some threads in the background
6837 while you continue to examine or step others from @value{GDBN}.
6838 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6839 always executed asynchronously in non-stop mode.
6841 Suspending execution is done with the @code{interrupt} command when
6842 running in the background, or @kbd{Ctrl-c} during foreground execution.
6843 In all-stop mode, this stops the whole process;
6844 but in non-stop mode the interrupt applies only to the current thread.
6845 To stop the whole program, use @code{interrupt -a}.
6847 Other execution commands do not currently support the @code{-a} option.
6849 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6850 that thread current, as it does in all-stop mode. This is because the
6851 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6852 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6853 changed to a different thread just as you entered a command to operate on the
6854 previously current thread.
6856 @node Background Execution
6857 @subsection Background Execution
6859 @cindex foreground execution
6860 @cindex background execution
6861 @cindex asynchronous execution
6862 @cindex execution, foreground, background and asynchronous
6864 @value{GDBN}'s execution commands have two variants: the normal
6865 foreground (synchronous) behavior, and a background
6866 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6867 the program to report that some thread has stopped before prompting for
6868 another command. In background execution, @value{GDBN} immediately gives
6869 a command prompt so that you can issue other commands while your program runs.
6871 If the target doesn't support async mode, @value{GDBN} issues an error
6872 message if you attempt to use the background execution commands.
6874 @cindex @code{&}, background execution of commands
6875 To specify background execution, add a @code{&} to the command. For example,
6876 the background form of the @code{continue} command is @code{continue&}, or
6877 just @code{c&}. The execution commands that accept background execution
6883 @xref{Starting, , Starting your Program}.
6887 @xref{Attach, , Debugging an Already-running Process}.
6891 @xref{Continuing and Stepping, step}.
6895 @xref{Continuing and Stepping, stepi}.
6899 @xref{Continuing and Stepping, next}.
6903 @xref{Continuing and Stepping, nexti}.
6907 @xref{Continuing and Stepping, continue}.
6911 @xref{Continuing and Stepping, finish}.
6915 @xref{Continuing and Stepping, until}.
6919 Background execution is especially useful in conjunction with non-stop
6920 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6921 However, you can also use these commands in the normal all-stop mode with
6922 the restriction that you cannot issue another execution command until the
6923 previous one finishes. Examples of commands that are valid in all-stop
6924 mode while the program is running include @code{help} and @code{info break}.
6926 You can interrupt your program while it is running in the background by
6927 using the @code{interrupt} command.
6934 Suspend execution of the running program. In all-stop mode,
6935 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6936 only the current thread. To stop the whole program in non-stop mode,
6937 use @code{interrupt -a}.
6940 @node Thread-Specific Breakpoints
6941 @subsection Thread-Specific Breakpoints
6943 When your program has multiple threads (@pxref{Threads,, Debugging
6944 Programs with Multiple Threads}), you can choose whether to set
6945 breakpoints on all threads, or on a particular thread.
6948 @cindex breakpoints and threads
6949 @cindex thread breakpoints
6950 @kindex break @dots{} thread @var{thread-id}
6951 @item break @var{location} thread @var{thread-id}
6952 @itemx break @var{location} thread @var{thread-id} if @dots{}
6953 @var{location} specifies source lines; there are several ways of
6954 writing them (@pxref{Specify Location}), but the effect is always to
6955 specify some source line.
6957 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6958 to specify that you only want @value{GDBN} to stop the program when a
6959 particular thread reaches this breakpoint. The @var{thread-id} specifier
6960 is one of the thread identifiers assigned by @value{GDBN}, shown
6961 in the first column of the @samp{info threads} display.
6963 If you do not specify @samp{thread @var{thread-id}} when you set a
6964 breakpoint, the breakpoint applies to @emph{all} threads of your
6967 You can use the @code{thread} qualifier on conditional breakpoints as
6968 well; in this case, place @samp{thread @var{thread-id}} before or
6969 after the breakpoint condition, like this:
6972 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6977 Thread-specific breakpoints are automatically deleted when
6978 @value{GDBN} detects the corresponding thread is no longer in the
6979 thread list. For example:
6983 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6986 There are several ways for a thread to disappear, such as a regular
6987 thread exit, but also when you detach from the process with the
6988 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6989 Process}), or if @value{GDBN} loses the remote connection
6990 (@pxref{Remote Debugging}), etc. Note that with some targets,
6991 @value{GDBN} is only able to detect a thread has exited when the user
6992 explictly asks for the thread list with the @code{info threads}
6995 @node Interrupted System Calls
6996 @subsection Interrupted System Calls
6998 @cindex thread breakpoints and system calls
6999 @cindex system calls and thread breakpoints
7000 @cindex premature return from system calls
7001 There is an unfortunate side effect when using @value{GDBN} to debug
7002 multi-threaded programs. If one thread stops for a
7003 breakpoint, or for some other reason, and another thread is blocked in a
7004 system call, then the system call may return prematurely. This is a
7005 consequence of the interaction between multiple threads and the signals
7006 that @value{GDBN} uses to implement breakpoints and other events that
7009 To handle this problem, your program should check the return value of
7010 each system call and react appropriately. This is good programming
7013 For example, do not write code like this:
7019 The call to @code{sleep} will return early if a different thread stops
7020 at a breakpoint or for some other reason.
7022 Instead, write this:
7027 unslept = sleep (unslept);
7030 A system call is allowed to return early, so the system is still
7031 conforming to its specification. But @value{GDBN} does cause your
7032 multi-threaded program to behave differently than it would without
7035 Also, @value{GDBN} uses internal breakpoints in the thread library to
7036 monitor certain events such as thread creation and thread destruction.
7037 When such an event happens, a system call in another thread may return
7038 prematurely, even though your program does not appear to stop.
7041 @subsection Observer Mode
7043 If you want to build on non-stop mode and observe program behavior
7044 without any chance of disruption by @value{GDBN}, you can set
7045 variables to disable all of the debugger's attempts to modify state,
7046 whether by writing memory, inserting breakpoints, etc. These operate
7047 at a low level, intercepting operations from all commands.
7049 When all of these are set to @code{off}, then @value{GDBN} is said to
7050 be @dfn{observer mode}. As a convenience, the variable
7051 @code{observer} can be set to disable these, plus enable non-stop
7054 Note that @value{GDBN} will not prevent you from making nonsensical
7055 combinations of these settings. For instance, if you have enabled
7056 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7057 then breakpoints that work by writing trap instructions into the code
7058 stream will still not be able to be placed.
7063 @item set observer on
7064 @itemx set observer off
7065 When set to @code{on}, this disables all the permission variables
7066 below (except for @code{insert-fast-tracepoints}), plus enables
7067 non-stop debugging. Setting this to @code{off} switches back to
7068 normal debugging, though remaining in non-stop mode.
7071 Show whether observer mode is on or off.
7073 @kindex may-write-registers
7074 @item set may-write-registers on
7075 @itemx set may-write-registers off
7076 This controls whether @value{GDBN} will attempt to alter the values of
7077 registers, such as with assignment expressions in @code{print}, or the
7078 @code{jump} command. It defaults to @code{on}.
7080 @item show may-write-registers
7081 Show the current permission to write registers.
7083 @kindex may-write-memory
7084 @item set may-write-memory on
7085 @itemx set may-write-memory off
7086 This controls whether @value{GDBN} will attempt to alter the contents
7087 of memory, such as with assignment expressions in @code{print}. It
7088 defaults to @code{on}.
7090 @item show may-write-memory
7091 Show the current permission to write memory.
7093 @kindex may-insert-breakpoints
7094 @item set may-insert-breakpoints on
7095 @itemx set may-insert-breakpoints off
7096 This controls whether @value{GDBN} will attempt to insert breakpoints.
7097 This affects all breakpoints, including internal breakpoints defined
7098 by @value{GDBN}. It defaults to @code{on}.
7100 @item show may-insert-breakpoints
7101 Show the current permission to insert breakpoints.
7103 @kindex may-insert-tracepoints
7104 @item set may-insert-tracepoints on
7105 @itemx set may-insert-tracepoints off
7106 This controls whether @value{GDBN} will attempt to insert (regular)
7107 tracepoints at the beginning of a tracing experiment. It affects only
7108 non-fast tracepoints, fast tracepoints being under the control of
7109 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7111 @item show may-insert-tracepoints
7112 Show the current permission to insert tracepoints.
7114 @kindex may-insert-fast-tracepoints
7115 @item set may-insert-fast-tracepoints on
7116 @itemx set may-insert-fast-tracepoints off
7117 This controls whether @value{GDBN} will attempt to insert fast
7118 tracepoints at the beginning of a tracing experiment. It affects only
7119 fast tracepoints, regular (non-fast) tracepoints being under the
7120 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7122 @item show may-insert-fast-tracepoints
7123 Show the current permission to insert fast tracepoints.
7125 @kindex may-interrupt
7126 @item set may-interrupt on
7127 @itemx set may-interrupt off
7128 This controls whether @value{GDBN} will attempt to interrupt or stop
7129 program execution. When this variable is @code{off}, the
7130 @code{interrupt} command will have no effect, nor will
7131 @kbd{Ctrl-c}. It defaults to @code{on}.
7133 @item show may-interrupt
7134 Show the current permission to interrupt or stop the program.
7138 @node Reverse Execution
7139 @chapter Running programs backward
7140 @cindex reverse execution
7141 @cindex running programs backward
7143 When you are debugging a program, it is not unusual to realize that
7144 you have gone too far, and some event of interest has already happened.
7145 If the target environment supports it, @value{GDBN} can allow you to
7146 ``rewind'' the program by running it backward.
7148 A target environment that supports reverse execution should be able
7149 to ``undo'' the changes in machine state that have taken place as the
7150 program was executing normally. Variables, registers etc.@: should
7151 revert to their previous values. Obviously this requires a great
7152 deal of sophistication on the part of the target environment; not
7153 all target environments can support reverse execution.
7155 When a program is executed in reverse, the instructions that
7156 have most recently been executed are ``un-executed'', in reverse
7157 order. The program counter runs backward, following the previous
7158 thread of execution in reverse. As each instruction is ``un-executed'',
7159 the values of memory and/or registers that were changed by that
7160 instruction are reverted to their previous states. After executing
7161 a piece of source code in reverse, all side effects of that code
7162 should be ``undone'', and all variables should be returned to their
7163 prior values@footnote{
7164 Note that some side effects are easier to undo than others. For instance,
7165 memory and registers are relatively easy, but device I/O is hard. Some
7166 targets may be able undo things like device I/O, and some may not.
7168 The contract between @value{GDBN} and the reverse executing target
7169 requires only that the target do something reasonable when
7170 @value{GDBN} tells it to execute backwards, and then report the
7171 results back to @value{GDBN}. Whatever the target reports back to
7172 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7173 assumes that the memory and registers that the target reports are in a
7174 consistent state, but @value{GDBN} accepts whatever it is given.
7177 On some platforms, @value{GDBN} has built-in support for reverse
7178 execution, activated with the @code{record} or @code{record btrace}
7179 commands. @xref{Process Record and Replay}. Some remote targets,
7180 typically full system emulators, support reverse execution directly
7181 without requiring any special command.
7183 If you are debugging in a target environment that supports
7184 reverse execution, @value{GDBN} provides the following commands.
7187 @kindex reverse-continue
7188 @kindex rc @r{(@code{reverse-continue})}
7189 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7190 @itemx rc @r{[}@var{ignore-count}@r{]}
7191 Beginning at the point where your program last stopped, start executing
7192 in reverse. Reverse execution will stop for breakpoints and synchronous
7193 exceptions (signals), just like normal execution. Behavior of
7194 asynchronous signals depends on the target environment.
7196 @kindex reverse-step
7197 @kindex rs @r{(@code{step})}
7198 @item reverse-step @r{[}@var{count}@r{]}
7199 Run the program backward until control reaches the start of a
7200 different source line; then stop it, and return control to @value{GDBN}.
7202 Like the @code{step} command, @code{reverse-step} will only stop
7203 at the beginning of a source line. It ``un-executes'' the previously
7204 executed source line. If the previous source line included calls to
7205 debuggable functions, @code{reverse-step} will step (backward) into
7206 the called function, stopping at the beginning of the @emph{last}
7207 statement in the called function (typically a return statement).
7209 Also, as with the @code{step} command, if non-debuggable functions are
7210 called, @code{reverse-step} will run thru them backward without stopping.
7212 @kindex reverse-stepi
7213 @kindex rsi @r{(@code{reverse-stepi})}
7214 @item reverse-stepi @r{[}@var{count}@r{]}
7215 Reverse-execute one machine instruction. Note that the instruction
7216 to be reverse-executed is @emph{not} the one pointed to by the program
7217 counter, but the instruction executed prior to that one. For instance,
7218 if the last instruction was a jump, @code{reverse-stepi} will take you
7219 back from the destination of the jump to the jump instruction itself.
7221 @kindex reverse-next
7222 @kindex rn @r{(@code{reverse-next})}
7223 @item reverse-next @r{[}@var{count}@r{]}
7224 Run backward to the beginning of the previous line executed in
7225 the current (innermost) stack frame. If the line contains function
7226 calls, they will be ``un-executed'' without stopping. Starting from
7227 the first line of a function, @code{reverse-next} will take you back
7228 to the caller of that function, @emph{before} the function was called,
7229 just as the normal @code{next} command would take you from the last
7230 line of a function back to its return to its caller
7231 @footnote{Unless the code is too heavily optimized.}.
7233 @kindex reverse-nexti
7234 @kindex rni @r{(@code{reverse-nexti})}
7235 @item reverse-nexti @r{[}@var{count}@r{]}
7236 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7237 in reverse, except that called functions are ``un-executed'' atomically.
7238 That is, if the previously executed instruction was a return from
7239 another function, @code{reverse-nexti} will continue to execute
7240 in reverse until the call to that function (from the current stack
7243 @kindex reverse-finish
7244 @item reverse-finish
7245 Just as the @code{finish} command takes you to the point where the
7246 current function returns, @code{reverse-finish} takes you to the point
7247 where it was called. Instead of ending up at the end of the current
7248 function invocation, you end up at the beginning.
7250 @kindex set exec-direction
7251 @item set exec-direction
7252 Set the direction of target execution.
7253 @item set exec-direction reverse
7254 @cindex execute forward or backward in time
7255 @value{GDBN} will perform all execution commands in reverse, until the
7256 exec-direction mode is changed to ``forward''. Affected commands include
7257 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7258 command cannot be used in reverse mode.
7259 @item set exec-direction forward
7260 @value{GDBN} will perform all execution commands in the normal fashion.
7261 This is the default.
7265 @node Process Record and Replay
7266 @chapter Recording Inferior's Execution and Replaying It
7267 @cindex process record and replay
7268 @cindex recording inferior's execution and replaying it
7270 On some platforms, @value{GDBN} provides a special @dfn{process record
7271 and replay} target that can record a log of the process execution, and
7272 replay it later with both forward and reverse execution commands.
7275 When this target is in use, if the execution log includes the record
7276 for the next instruction, @value{GDBN} will debug in @dfn{replay
7277 mode}. In the replay mode, the inferior does not really execute code
7278 instructions. Instead, all the events that normally happen during
7279 code execution are taken from the execution log. While code is not
7280 really executed in replay mode, the values of registers (including the
7281 program counter register) and the memory of the inferior are still
7282 changed as they normally would. Their contents are taken from the
7286 If the record for the next instruction is not in the execution log,
7287 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7288 inferior executes normally, and @value{GDBN} records the execution log
7291 The process record and replay target supports reverse execution
7292 (@pxref{Reverse Execution}), even if the platform on which the
7293 inferior runs does not. However, the reverse execution is limited in
7294 this case by the range of the instructions recorded in the execution
7295 log. In other words, reverse execution on platforms that don't
7296 support it directly can only be done in the replay mode.
7298 When debugging in the reverse direction, @value{GDBN} will work in
7299 replay mode as long as the execution log includes the record for the
7300 previous instruction; otherwise, it will work in record mode, if the
7301 platform supports reverse execution, or stop if not.
7303 Currently, process record and replay is supported on ARM, Aarch64,
7304 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7305 GNU/Linux. Process record and replay can be used both when native
7306 debugging, and when remote debugging via @code{gdbserver}.
7308 For architecture environments that support process record and replay,
7309 @value{GDBN} provides the following commands:
7312 @kindex target record
7313 @kindex target record-full
7314 @kindex target record-btrace
7317 @kindex record btrace
7318 @kindex record btrace bts
7319 @kindex record btrace pt
7325 @kindex rec btrace bts
7326 @kindex rec btrace pt
7329 @item record @var{method}
7330 This command starts the process record and replay target. The
7331 recording method can be specified as parameter. Without a parameter
7332 the command uses the @code{full} recording method. The following
7333 recording methods are available:
7337 Full record/replay recording using @value{GDBN}'s software record and
7338 replay implementation. This method allows replaying and reverse
7341 @item btrace @var{format}
7342 Hardware-supported instruction recording, supported on Intel
7343 processors. This method does not record data. Further, the data is
7344 collected in a ring buffer so old data will be overwritten when the
7345 buffer is full. It allows limited reverse execution. Variables and
7346 registers are not available during reverse execution. In remote
7347 debugging, recording continues on disconnect. Recorded data can be
7348 inspected after reconnecting. The recording may be stopped using
7351 The recording format can be specified as parameter. Without a parameter
7352 the command chooses the recording format. The following recording
7353 formats are available:
7357 @cindex branch trace store
7358 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7359 this format, the processor stores a from/to record for each executed
7360 branch in the btrace ring buffer.
7363 @cindex Intel Processor Trace
7364 Use the @dfn{Intel Processor Trace} recording format. In this
7365 format, the processor stores the execution trace in a compressed form
7366 that is afterwards decoded by @value{GDBN}.
7368 The trace can be recorded with very low overhead. The compressed
7369 trace format also allows small trace buffers to already contain a big
7370 number of instructions compared to @acronym{BTS}.
7372 Decoding the recorded execution trace, on the other hand, is more
7373 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7374 increased number of instructions to process. You should increase the
7375 buffer-size with care.
7378 Not all recording formats may be available on all processors.
7381 The process record and replay target can only debug a process that is
7382 already running. Therefore, you need first to start the process with
7383 the @kbd{run} or @kbd{start} commands, and then start the recording
7384 with the @kbd{record @var{method}} command.
7386 @cindex displaced stepping, and process record and replay
7387 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7388 will be automatically disabled when process record and replay target
7389 is started. That's because the process record and replay target
7390 doesn't support displaced stepping.
7392 @cindex non-stop mode, and process record and replay
7393 @cindex asynchronous execution, and process record and replay
7394 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7395 the asynchronous execution mode (@pxref{Background Execution}), not
7396 all recording methods are available. The @code{full} recording method
7397 does not support these two modes.
7402 Stop the process record and replay target. When process record and
7403 replay target stops, the entire execution log will be deleted and the
7404 inferior will either be terminated, or will remain in its final state.
7406 When you stop the process record and replay target in record mode (at
7407 the end of the execution log), the inferior will be stopped at the
7408 next instruction that would have been recorded. In other words, if
7409 you record for a while and then stop recording, the inferior process
7410 will be left in the same state as if the recording never happened.
7412 On the other hand, if the process record and replay target is stopped
7413 while in replay mode (that is, not at the end of the execution log,
7414 but at some earlier point), the inferior process will become ``live''
7415 at that earlier state, and it will then be possible to continue the
7416 usual ``live'' debugging of the process from that state.
7418 When the inferior process exits, or @value{GDBN} detaches from it,
7419 process record and replay target will automatically stop itself.
7423 Go to a specific location in the execution log. There are several
7424 ways to specify the location to go to:
7427 @item record goto begin
7428 @itemx record goto start
7429 Go to the beginning of the execution log.
7431 @item record goto end
7432 Go to the end of the execution log.
7434 @item record goto @var{n}
7435 Go to instruction number @var{n} in the execution log.
7439 @item record save @var{filename}
7440 Save the execution log to a file @file{@var{filename}}.
7441 Default filename is @file{gdb_record.@var{process_id}}, where
7442 @var{process_id} is the process ID of the inferior.
7444 This command may not be available for all recording methods.
7446 @kindex record restore
7447 @item record restore @var{filename}
7448 Restore the execution log from a file @file{@var{filename}}.
7449 File must have been created with @code{record save}.
7451 @kindex set record full
7452 @item set record full insn-number-max @var{limit}
7453 @itemx set record full insn-number-max unlimited
7454 Set the limit of instructions to be recorded for the @code{full}
7455 recording method. Default value is 200000.
7457 If @var{limit} is a positive number, then @value{GDBN} will start
7458 deleting instructions from the log once the number of the record
7459 instructions becomes greater than @var{limit}. For every new recorded
7460 instruction, @value{GDBN} will delete the earliest recorded
7461 instruction to keep the number of recorded instructions at the limit.
7462 (Since deleting recorded instructions loses information, @value{GDBN}
7463 lets you control what happens when the limit is reached, by means of
7464 the @code{stop-at-limit} option, described below.)
7466 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7467 delete recorded instructions from the execution log. The number of
7468 recorded instructions is limited only by the available memory.
7470 @kindex show record full
7471 @item show record full insn-number-max
7472 Show the limit of instructions to be recorded with the @code{full}
7475 @item set record full stop-at-limit
7476 Control the behavior of the @code{full} recording method when the
7477 number of recorded instructions reaches the limit. If ON (the
7478 default), @value{GDBN} will stop when the limit is reached for the
7479 first time and ask you whether you want to stop the inferior or
7480 continue running it and recording the execution log. If you decide
7481 to continue recording, each new recorded instruction will cause the
7482 oldest one to be deleted.
7484 If this option is OFF, @value{GDBN} will automatically delete the
7485 oldest record to make room for each new one, without asking.
7487 @item show record full stop-at-limit
7488 Show the current setting of @code{stop-at-limit}.
7490 @item set record full memory-query
7491 Control the behavior when @value{GDBN} is unable to record memory
7492 changes caused by an instruction for the @code{full} recording method.
7493 If ON, @value{GDBN} will query whether to stop the inferior in that
7496 If this option is OFF (the default), @value{GDBN} will automatically
7497 ignore the effect of such instructions on memory. Later, when
7498 @value{GDBN} replays this execution log, it will mark the log of this
7499 instruction as not accessible, and it will not affect the replay
7502 @item show record full memory-query
7503 Show the current setting of @code{memory-query}.
7505 @kindex set record btrace
7506 The @code{btrace} record target does not trace data. As a
7507 convenience, when replaying, @value{GDBN} reads read-only memory off
7508 the live program directly, assuming that the addresses of the
7509 read-only areas don't change. This for example makes it possible to
7510 disassemble code while replaying, but not to print variables.
7511 In some cases, being able to inspect variables might be useful.
7512 You can use the following command for that:
7514 @item set record btrace replay-memory-access
7515 Control the behavior of the @code{btrace} recording method when
7516 accessing memory during replay. If @code{read-only} (the default),
7517 @value{GDBN} will only allow accesses to read-only memory.
7518 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7519 and to read-write memory. Beware that the accessed memory corresponds
7520 to the live target and not necessarily to the current replay
7523 @item set record btrace cpu @var{identifier}
7524 Set the processor to be used for enabling workarounds for processor
7525 errata when decoding the trace.
7527 Processor errata are defects in processor operation, caused by its
7528 design or manufacture. They can cause a trace not to match the
7529 specification. This, in turn, may cause trace decode to fail.
7530 @value{GDBN} can detect erroneous trace packets and correct them, thus
7531 avoiding the decoding failures. These corrections are known as
7532 @dfn{errata workarounds}, and are enabled based on the processor on
7533 which the trace was recorded.
7535 By default, @value{GDBN} attempts to detect the processor
7536 automatically, and apply the necessary workarounds for it. However,
7537 you may need to specify the processor if @value{GDBN} does not yet
7538 support it. This command allows you to do that, and also allows to
7539 disable the workarounds.
7541 The argument @var{identifier} identifies the @sc{cpu} and is of the
7542 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7543 there are two special identifiers, @code{none} and @code{auto}
7546 The following vendor identifiers and corresponding processor
7547 identifiers are currently supported:
7549 @multitable @columnfractions .1 .9
7552 @tab @var{family}/@var{model}[/@var{stepping}]
7556 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7557 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7559 If @var{identifier} is @code{auto}, enable errata workarounds for the
7560 processor on which the trace was recorded. If @var{identifier} is
7561 @code{none}, errata workarounds are disabled.
7563 For example, when using an old @value{GDBN} on a new system, decode
7564 may fail because @value{GDBN} does not support the new processor. It
7565 often suffices to specify an older processor that @value{GDBN}
7570 Active record target: record-btrace
7571 Recording format: Intel Processor Trace.
7573 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7574 (gdb) set record btrace cpu intel:6/158
7576 Active record target: record-btrace
7577 Recording format: Intel Processor Trace.
7579 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7582 @kindex show record btrace
7583 @item show record btrace replay-memory-access
7584 Show the current setting of @code{replay-memory-access}.
7586 @item show record btrace cpu
7587 Show the processor to be used for enabling trace decode errata
7590 @kindex set record btrace bts
7591 @item set record btrace bts buffer-size @var{size}
7592 @itemx set record btrace bts buffer-size unlimited
7593 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7594 format. Default is 64KB.
7596 If @var{size} is a positive number, then @value{GDBN} will try to
7597 allocate a buffer of at least @var{size} bytes for each new thread
7598 that uses the btrace recording method and the @acronym{BTS} format.
7599 The actually obtained buffer size may differ from the requested
7600 @var{size}. Use the @code{info record} command to see the actual
7601 buffer size for each thread that uses the btrace recording method and
7602 the @acronym{BTS} format.
7604 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7605 allocate a buffer of 4MB.
7607 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7608 also need longer to process the branch trace data before it can be used.
7610 @item show record btrace bts buffer-size @var{size}
7611 Show the current setting of the requested ring buffer size for branch
7612 tracing in @acronym{BTS} format.
7614 @kindex set record btrace pt
7615 @item set record btrace pt buffer-size @var{size}
7616 @itemx set record btrace pt buffer-size unlimited
7617 Set the requested ring buffer size for branch tracing in Intel
7618 Processor Trace format. Default is 16KB.
7620 If @var{size} is a positive number, then @value{GDBN} will try to
7621 allocate a buffer of at least @var{size} bytes for each new thread
7622 that uses the btrace recording method and the Intel Processor Trace
7623 format. The actually obtained buffer size may differ from the
7624 requested @var{size}. Use the @code{info record} command to see the
7625 actual buffer size for each thread.
7627 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7628 allocate a buffer of 4MB.
7630 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7631 also need longer to process the branch trace data before it can be used.
7633 @item show record btrace pt buffer-size @var{size}
7634 Show the current setting of the requested ring buffer size for branch
7635 tracing in Intel Processor Trace format.
7639 Show various statistics about the recording depending on the recording
7644 For the @code{full} recording method, it shows the state of process
7645 record and its in-memory execution log buffer, including:
7649 Whether in record mode or replay mode.
7651 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7653 Highest recorded instruction number.
7655 Current instruction about to be replayed (if in replay mode).
7657 Number of instructions contained in the execution log.
7659 Maximum number of instructions that may be contained in the execution log.
7663 For the @code{btrace} recording method, it shows:
7669 Number of instructions that have been recorded.
7671 Number of blocks of sequential control-flow formed by the recorded
7674 Whether in record mode or replay mode.
7677 For the @code{bts} recording format, it also shows:
7680 Size of the perf ring buffer.
7683 For the @code{pt} recording format, it also shows:
7686 Size of the perf ring buffer.
7690 @kindex record delete
7693 When record target runs in replay mode (``in the past''), delete the
7694 subsequent execution log and begin to record a new execution log starting
7695 from the current address. This means you will abandon the previously
7696 recorded ``future'' and begin recording a new ``future''.
7698 @kindex record instruction-history
7699 @kindex rec instruction-history
7700 @item record instruction-history
7701 Disassembles instructions from the recorded execution log. By
7702 default, ten instructions are disassembled. This can be changed using
7703 the @code{set record instruction-history-size} command. Instructions
7704 are printed in execution order.
7706 It can also print mixed source+disassembly if you specify the the
7707 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7708 as well as in symbolic form by specifying the @code{/r} modifier.
7710 The current position marker is printed for the instruction at the
7711 current program counter value. This instruction can appear multiple
7712 times in the trace and the current position marker will be printed
7713 every time. To omit the current position marker, specify the
7716 To better align the printed instructions when the trace contains
7717 instructions from more than one function, the function name may be
7718 omitted by specifying the @code{/f} modifier.
7720 Speculatively executed instructions are prefixed with @samp{?}. This
7721 feature is not available for all recording formats.
7723 There are several ways to specify what part of the execution log to
7727 @item record instruction-history @var{insn}
7728 Disassembles ten instructions starting from instruction number
7731 @item record instruction-history @var{insn}, +/-@var{n}
7732 Disassembles @var{n} instructions around instruction number
7733 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7734 @var{n} instructions after instruction number @var{insn}. If
7735 @var{n} is preceded with @code{-}, disassembles @var{n}
7736 instructions before instruction number @var{insn}.
7738 @item record instruction-history
7739 Disassembles ten more instructions after the last disassembly.
7741 @item record instruction-history -
7742 Disassembles ten more instructions before the last disassembly.
7744 @item record instruction-history @var{begin}, @var{end}
7745 Disassembles instructions beginning with instruction number
7746 @var{begin} until instruction number @var{end}. The instruction
7747 number @var{end} is included.
7750 This command may not be available for all recording methods.
7753 @item set record instruction-history-size @var{size}
7754 @itemx set record instruction-history-size unlimited
7755 Define how many instructions to disassemble in the @code{record
7756 instruction-history} command. The default value is 10.
7757 A @var{size} of @code{unlimited} means unlimited instructions.
7760 @item show record instruction-history-size
7761 Show how many instructions to disassemble in the @code{record
7762 instruction-history} command.
7764 @kindex record function-call-history
7765 @kindex rec function-call-history
7766 @item record function-call-history
7767 Prints the execution history at function granularity. It prints one
7768 line for each sequence of instructions that belong to the same
7769 function giving the name of that function, the source lines
7770 for this instruction sequence (if the @code{/l} modifier is
7771 specified), and the instructions numbers that form the sequence (if
7772 the @code{/i} modifier is specified). The function names are indented
7773 to reflect the call stack depth if the @code{/c} modifier is
7774 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7778 (@value{GDBP}) @b{list 1, 10}
7789 (@value{GDBP}) @b{record function-call-history /ilc}
7790 1 bar inst 1,4 at foo.c:6,8
7791 2 foo inst 5,10 at foo.c:2,3
7792 3 bar inst 11,13 at foo.c:9,10
7795 By default, ten lines are printed. This can be changed using the
7796 @code{set record function-call-history-size} command. Functions are
7797 printed in execution order. There are several ways to specify what
7801 @item record function-call-history @var{func}
7802 Prints ten functions starting from function number @var{func}.
7804 @item record function-call-history @var{func}, +/-@var{n}
7805 Prints @var{n} functions around function number @var{func}. If
7806 @var{n} is preceded with @code{+}, prints @var{n} functions after
7807 function number @var{func}. If @var{n} is preceded with @code{-},
7808 prints @var{n} functions before function number @var{func}.
7810 @item record function-call-history
7811 Prints ten more functions after the last ten-line print.
7813 @item record function-call-history -
7814 Prints ten more functions before the last ten-line print.
7816 @item record function-call-history @var{begin}, @var{end}
7817 Prints functions beginning with function number @var{begin} until
7818 function number @var{end}. The function number @var{end} is included.
7821 This command may not be available for all recording methods.
7823 @item set record function-call-history-size @var{size}
7824 @itemx set record function-call-history-size unlimited
7825 Define how many lines to print in the
7826 @code{record function-call-history} command. The default value is 10.
7827 A size of @code{unlimited} means unlimited lines.
7829 @item show record function-call-history-size
7830 Show how many lines to print in the
7831 @code{record function-call-history} command.
7836 @chapter Examining the Stack
7838 When your program has stopped, the first thing you need to know is where it
7839 stopped and how it got there.
7842 Each time your program performs a function call, information about the call
7844 That information includes the location of the call in your program,
7845 the arguments of the call,
7846 and the local variables of the function being called.
7847 The information is saved in a block of data called a @dfn{stack frame}.
7848 The stack frames are allocated in a region of memory called the @dfn{call
7851 When your program stops, the @value{GDBN} commands for examining the
7852 stack allow you to see all of this information.
7854 @cindex selected frame
7855 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7856 @value{GDBN} commands refer implicitly to the selected frame. In
7857 particular, whenever you ask @value{GDBN} for the value of a variable in
7858 your program, the value is found in the selected frame. There are
7859 special @value{GDBN} commands to select whichever frame you are
7860 interested in. @xref{Selection, ,Selecting a Frame}.
7862 When your program stops, @value{GDBN} automatically selects the
7863 currently executing frame and describes it briefly, similar to the
7864 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7867 * Frames:: Stack frames
7868 * Backtrace:: Backtraces
7869 * Selection:: Selecting a frame
7870 * Frame Info:: Information on a frame
7871 * Frame Apply:: Applying a command to several frames
7872 * Frame Filter Management:: Managing frame filters
7877 @section Stack Frames
7879 @cindex frame, definition
7881 The call stack is divided up into contiguous pieces called @dfn{stack
7882 frames}, or @dfn{frames} for short; each frame is the data associated
7883 with one call to one function. The frame contains the arguments given
7884 to the function, the function's local variables, and the address at
7885 which the function is executing.
7887 @cindex initial frame
7888 @cindex outermost frame
7889 @cindex innermost frame
7890 When your program is started, the stack has only one frame, that of the
7891 function @code{main}. This is called the @dfn{initial} frame or the
7892 @dfn{outermost} frame. Each time a function is called, a new frame is
7893 made. Each time a function returns, the frame for that function invocation
7894 is eliminated. If a function is recursive, there can be many frames for
7895 the same function. The frame for the function in which execution is
7896 actually occurring is called the @dfn{innermost} frame. This is the most
7897 recently created of all the stack frames that still exist.
7899 @cindex frame pointer
7900 Inside your program, stack frames are identified by their addresses. A
7901 stack frame consists of many bytes, each of which has its own address; each
7902 kind of computer has a convention for choosing one byte whose
7903 address serves as the address of the frame. Usually this address is kept
7904 in a register called the @dfn{frame pointer register}
7905 (@pxref{Registers, $fp}) while execution is going on in that frame.
7908 @cindex frame number
7909 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7910 number that is zero for the innermost frame, one for the frame that
7911 called it, and so on upward. These level numbers give you a way of
7912 designating stack frames in @value{GDBN} commands. The terms
7913 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7914 describe this number.
7916 @c The -fomit-frame-pointer below perennially causes hbox overflow
7917 @c underflow problems.
7918 @cindex frameless execution
7919 Some compilers provide a way to compile functions so that they operate
7920 without stack frames. (For example, the @value{NGCC} option
7922 @samp{-fomit-frame-pointer}
7924 generates functions without a frame.)
7925 This is occasionally done with heavily used library functions to save
7926 the frame setup time. @value{GDBN} has limited facilities for dealing
7927 with these function invocations. If the innermost function invocation
7928 has no stack frame, @value{GDBN} nevertheless regards it as though
7929 it had a separate frame, which is numbered zero as usual, allowing
7930 correct tracing of the function call chain. However, @value{GDBN} has
7931 no provision for frameless functions elsewhere in the stack.
7937 @cindex call stack traces
7938 A backtrace is a summary of how your program got where it is. It shows one
7939 line per frame, for many frames, starting with the currently executing
7940 frame (frame zero), followed by its caller (frame one), and on up the
7943 @anchor{backtrace-command}
7945 @kindex bt @r{(@code{backtrace})}
7946 To print a backtrace of the entire stack, use the @code{backtrace}
7947 command, or its alias @code{bt}. This command will print one line per
7948 frame for frames in the stack. By default, all stack frames are
7949 printed. You can stop the backtrace at any time by typing the system
7950 interrupt character, normally @kbd{Ctrl-c}.
7953 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
7954 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
7955 Print the backtrace of the entire stack.
7957 The optional @var{count} can be one of the following:
7962 Print only the innermost @var{n} frames, where @var{n} is a positive
7967 Print only the outermost @var{n} frames, where @var{n} is a positive
7975 Print the values of the local variables also. This can be combined
7976 with the optional @var{count} to limit the number of frames shown.
7979 Do not run Python frame filters on this backtrace. @xref{Frame
7980 Filter API}, for more information. Additionally use @ref{disable
7981 frame-filter all} to turn off all frame filters. This is only
7982 relevant when @value{GDBN} has been configured with @code{Python}
7986 A Python frame filter might decide to ``elide'' some frames. Normally
7987 such elided frames are still printed, but they are indented relative
7988 to the filtered frames that cause them to be elided. The @code{-hide}
7989 option causes elided frames to not be printed at all.
7992 The @code{backtrace} command also supports a number of options that
7993 allow overriding relevant global print settings as set by @code{set
7994 backtrace} and @code{set print} subcommands:
7997 @item -past-main [@code{on}|@code{off}]
7998 Set whether backtraces should continue past @code{main}. Related setting:
7999 @ref{set backtrace past-main}.
8001 @item -past-entry [@code{on}|@code{off}]
8002 Set whether backtraces should continue past the entry point of a program.
8003 Related setting: @ref{set backtrace past-entry}.
8005 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8006 Set printing of function arguments at function entry.
8007 Related setting: @ref{set print entry-values}.
8009 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8010 Set printing of non-scalar frame arguments.
8011 Related setting: @ref{set print frame-arguments}.
8013 @item -raw-frame-arguments [@code{on}|@code{off}]
8014 Set whether to print frame arguments in raw form.
8015 Related setting: @ref{set print raw-frame-arguments}.
8017 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8018 Set printing of frame information.
8019 Related setting: @ref{set print frame-info}.
8022 The optional @var{qualifier} is maintained for backward compatibility.
8023 It can be one of the following:
8027 Equivalent to the @code{-full} option.
8030 Equivalent to the @code{-no-filters} option.
8033 Equivalent to the @code{-hide} option.
8040 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8041 are additional aliases for @code{backtrace}.
8043 @cindex multiple threads, backtrace
8044 In a multi-threaded program, @value{GDBN} by default shows the
8045 backtrace only for the current thread. To display the backtrace for
8046 several or all of the threads, use the command @code{thread apply}
8047 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8048 apply all backtrace}, @value{GDBN} will display the backtrace for all
8049 the threads; this is handy when you debug a core dump of a
8050 multi-threaded program.
8052 Each line in the backtrace shows the frame number and the function name.
8053 The program counter value is also shown---unless you use @code{set
8054 print address off}. The backtrace also shows the source file name and
8055 line number, as well as the arguments to the function. The program
8056 counter value is omitted if it is at the beginning of the code for that
8059 Here is an example of a backtrace. It was made with the command
8060 @samp{bt 3}, so it shows the innermost three frames.
8064 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8066 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8067 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8069 (More stack frames follow...)
8074 The display for frame zero does not begin with a program counter
8075 value, indicating that your program has stopped at the beginning of the
8076 code for line @code{993} of @code{builtin.c}.
8079 The value of parameter @code{data} in frame 1 has been replaced by
8080 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8081 only if it is a scalar (integer, pointer, enumeration, etc). See command
8082 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8083 on how to configure the way function parameter values are printed.
8084 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8085 what frame information is printed.
8087 @cindex optimized out, in backtrace
8088 @cindex function call arguments, optimized out
8089 If your program was compiled with optimizations, some compilers will
8090 optimize away arguments passed to functions if those arguments are
8091 never used after the call. Such optimizations generate code that
8092 passes arguments through registers, but doesn't store those arguments
8093 in the stack frame. @value{GDBN} has no way of displaying such
8094 arguments in stack frames other than the innermost one. Here's what
8095 such a backtrace might look like:
8099 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8101 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8102 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8104 (More stack frames follow...)
8109 The values of arguments that were not saved in their stack frames are
8110 shown as @samp{<optimized out>}.
8112 If you need to display the values of such optimized-out arguments,
8113 either deduce that from other variables whose values depend on the one
8114 you are interested in, or recompile without optimizations.
8116 @cindex backtrace beyond @code{main} function
8117 @cindex program entry point
8118 @cindex startup code, and backtrace
8119 Most programs have a standard user entry point---a place where system
8120 libraries and startup code transition into user code. For C this is
8121 @code{main}@footnote{
8122 Note that embedded programs (the so-called ``free-standing''
8123 environment) are not required to have a @code{main} function as the
8124 entry point. They could even have multiple entry points.}.
8125 When @value{GDBN} finds the entry function in a backtrace
8126 it will terminate the backtrace, to avoid tracing into highly
8127 system-specific (and generally uninteresting) code.
8129 If you need to examine the startup code, or limit the number of levels
8130 in a backtrace, you can change this behavior:
8133 @item set backtrace past-main
8134 @itemx set backtrace past-main on
8135 @anchor{set backtrace past-main}
8136 @kindex set backtrace
8137 Backtraces will continue past the user entry point.
8139 @item set backtrace past-main off
8140 Backtraces will stop when they encounter the user entry point. This is the
8143 @item show backtrace past-main
8144 @kindex show backtrace
8145 Display the current user entry point backtrace policy.
8147 @item set backtrace past-entry
8148 @itemx set backtrace past-entry on
8149 @anchor{set backtrace past-entry}
8150 Backtraces will continue past the internal entry point of an application.
8151 This entry point is encoded by the linker when the application is built,
8152 and is likely before the user entry point @code{main} (or equivalent) is called.
8154 @item set backtrace past-entry off
8155 Backtraces will stop when they encounter the internal entry point of an
8156 application. This is the default.
8158 @item show backtrace past-entry
8159 Display the current internal entry point backtrace policy.
8161 @item set backtrace limit @var{n}
8162 @itemx set backtrace limit 0
8163 @itemx set backtrace limit unlimited
8164 @anchor{set backtrace limit}
8165 @cindex backtrace limit
8166 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8167 or zero means unlimited levels.
8169 @item show backtrace limit
8170 Display the current limit on backtrace levels.
8173 You can control how file names are displayed.
8176 @item set filename-display
8177 @itemx set filename-display relative
8178 @cindex filename-display
8179 Display file names relative to the compilation directory. This is the default.
8181 @item set filename-display basename
8182 Display only basename of a filename.
8184 @item set filename-display absolute
8185 Display an absolute filename.
8187 @item show filename-display
8188 Show the current way to display filenames.
8192 @section Selecting a Frame
8194 Most commands for examining the stack and other data in your program work on
8195 whichever stack frame is selected at the moment. Here are the commands for
8196 selecting a stack frame; all of them finish by printing a brief description
8197 of the stack frame just selected.
8200 @kindex frame@r{, selecting}
8201 @kindex f @r{(@code{frame})}
8202 @item frame @r{[} @var{frame-selection-spec} @r{]}
8203 @item f @r{[} @var{frame-selection-spec} @r{]}
8204 The @command{frame} command allows different stack frames to be
8205 selected. The @var{frame-selection-spec} can be any of the following:
8210 @item level @var{num}
8211 Select frame level @var{num}. Recall that frame zero is the innermost
8212 (currently executing) frame, frame one is the frame that called the
8213 innermost one, and so on. The highest level frame is usually the one
8216 As this is the most common method of navigating the frame stack, the
8217 string @command{level} can be omitted. For example, the following two
8218 commands are equivalent:
8221 (@value{GDBP}) frame 3
8222 (@value{GDBP}) frame level 3
8225 @kindex frame address
8226 @item address @var{stack-address}
8227 Select the frame with stack address @var{stack-address}. The
8228 @var{stack-address} for a frame can be seen in the output of
8229 @command{info frame}, for example:
8233 Stack level 1, frame at 0x7fffffffda30:
8234 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8235 tail call frame, caller of frame at 0x7fffffffda30
8236 source language c++.
8237 Arglist at unknown address.
8238 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8241 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8242 indicated by the line:
8245 Stack level 1, frame at 0x7fffffffda30:
8248 @kindex frame function
8249 @item function @var{function-name}
8250 Select the stack frame for function @var{function-name}. If there are
8251 multiple stack frames for function @var{function-name} then the inner
8252 most stack frame is selected.
8255 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8256 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8257 viewed has stack address @var{stack-addr}, and optionally, a program
8258 counter address of @var{pc-addr}.
8260 This is useful mainly if the chaining of stack frames has been
8261 damaged by a bug, making it impossible for @value{GDBN} to assign
8262 numbers properly to all frames. In addition, this can be useful
8263 when your program has multiple stacks and switches between them.
8265 When viewing a frame outside the current backtrace using
8266 @command{frame view} then you can always return to the original
8267 stack using one of the previous stack frame selection instructions,
8268 for example @command{frame level 0}.
8274 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8275 numbers @var{n}, this advances toward the outermost frame, to higher
8276 frame numbers, to frames that have existed longer.
8279 @kindex do @r{(@code{down})}
8281 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8282 positive numbers @var{n}, this advances toward the innermost frame, to
8283 lower frame numbers, to frames that were created more recently.
8284 You may abbreviate @code{down} as @code{do}.
8287 All of these commands end by printing two lines of output describing the
8288 frame. The first line shows the frame number, the function name, the
8289 arguments, and the source file and line number of execution in that
8290 frame. The second line shows the text of that source line.
8298 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8300 10 read_input_file (argv[i]);
8304 After such a printout, the @code{list} command with no arguments
8305 prints ten lines centered on the point of execution in the frame.
8306 You can also edit the program at the point of execution with your favorite
8307 editing program by typing @code{edit}.
8308 @xref{List, ,Printing Source Lines},
8312 @kindex select-frame
8313 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8314 The @code{select-frame} command is a variant of @code{frame} that does
8315 not display the new frame after selecting it. This command is
8316 intended primarily for use in @value{GDBN} command scripts, where the
8317 output might be unnecessary and distracting. The
8318 @var{frame-selection-spec} is as for the @command{frame} command
8319 described in @ref{Selection, ,Selecting a Frame}.
8321 @kindex down-silently
8323 @item up-silently @var{n}
8324 @itemx down-silently @var{n}
8325 These two commands are variants of @code{up} and @code{down},
8326 respectively; they differ in that they do their work silently, without
8327 causing display of the new frame. They are intended primarily for use
8328 in @value{GDBN} command scripts, where the output might be unnecessary and
8333 @section Information About a Frame
8335 There are several other commands to print information about the selected
8341 When used without any argument, this command does not change which
8342 frame is selected, but prints a brief description of the currently
8343 selected stack frame. It can be abbreviated @code{f}. With an
8344 argument, this command is used to select a stack frame.
8345 @xref{Selection, ,Selecting a Frame}.
8348 @kindex info f @r{(@code{info frame})}
8351 This command prints a verbose description of the selected stack frame,
8356 the address of the frame
8358 the address of the next frame down (called by this frame)
8360 the address of the next frame up (caller of this frame)
8362 the language in which the source code corresponding to this frame is written
8364 the address of the frame's arguments
8366 the address of the frame's local variables
8368 the program counter saved in it (the address of execution in the caller frame)
8370 which registers were saved in the frame
8373 @noindent The verbose description is useful when
8374 something has gone wrong that has made the stack format fail to fit
8375 the usual conventions.
8377 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8378 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8379 Print a verbose description of the frame selected by
8380 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8381 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8382 a Frame}). The selected frame remains unchanged by this command.
8385 @item info args [-q]
8386 Print the arguments of the selected frame, each on a separate line.
8388 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8389 printing header information and messages explaining why no argument
8392 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8393 Like @kbd{info args}, but only print the arguments selected
8394 with the provided regexp(s).
8396 If @var{regexp} is provided, print only the arguments whose names
8397 match the regular expression @var{regexp}.
8399 If @var{type_regexp} is provided, print only the arguments whose
8400 types, as printed by the @code{whatis} command, match
8401 the regular expression @var{type_regexp}.
8402 If @var{type_regexp} contains space(s), it should be enclosed in
8403 quote characters. If needed, use backslash to escape the meaning
8404 of special characters or quotes.
8406 If both @var{regexp} and @var{type_regexp} are provided, an argument
8407 is printed only if its name matches @var{regexp} and its type matches
8410 @item info locals [-q]
8412 Print the local variables of the selected frame, each on a separate
8413 line. These are all variables (declared either static or automatic)
8414 accessible at the point of execution of the selected frame.
8416 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8417 printing header information and messages explaining why no local variables
8420 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8421 Like @kbd{info locals}, but only print the local variables selected
8422 with the provided regexp(s).
8424 If @var{regexp} is provided, print only the local variables whose names
8425 match the regular expression @var{regexp}.
8427 If @var{type_regexp} is provided, print only the local variables whose
8428 types, as printed by the @code{whatis} command, match
8429 the regular expression @var{type_regexp}.
8430 If @var{type_regexp} contains space(s), it should be enclosed in
8431 quote characters. If needed, use backslash to escape the meaning
8432 of special characters or quotes.
8434 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8435 is printed only if its name matches @var{regexp} and its type matches
8438 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8439 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8440 For example, your program might use Resource Acquisition Is
8441 Initialization types (RAII) such as @code{lock_something_t}: each
8442 local variable of type @code{lock_something_t} automatically places a
8443 lock that is destroyed when the variable goes out of scope. You can
8444 then list all acquired locks in your program by doing
8446 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8449 or the equivalent shorter form
8451 tfaas i lo -q -t lock_something_t
8457 @section Applying a Command to Several Frames.
8459 @cindex apply command to several frames
8461 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8462 The @code{frame apply} command allows you to apply the named
8463 @var{command} to one or more frames.
8467 Specify @code{all} to apply @var{command} to all frames.
8470 Use @var{count} to apply @var{command} to the innermost @var{count}
8471 frames, where @var{count} is a positive number.
8474 Use @var{-count} to apply @var{command} to the outermost @var{count}
8475 frames, where @var{count} is a positive number.
8478 Use @code{level} to apply @var{command} to the set of frames identified
8479 by the @var{level} list. @var{level} is a frame level or a range of frame
8480 levels as @var{level1}-@var{level2}. The frame level is the number shown
8481 in the first field of the @samp{backtrace} command output.
8482 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8483 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8487 Note that the frames on which @code{frame apply} applies a command are
8488 also influenced by the @code{set backtrace} settings such as @code{set
8489 backtrace past-main} and @code{set backtrace limit N}.
8490 @xref{Backtrace,,Backtraces}.
8492 The @code{frame apply} command also supports a number of options that
8493 allow overriding relevant @code{set backtrace} settings:
8496 @item -past-main [@code{on}|@code{off}]
8497 Whether backtraces should continue past @code{main}.
8498 Related setting: @ref{set backtrace past-main}.
8500 @item -past-entry [@code{on}|@code{off}]
8501 Whether backtraces should continue past the entry point of a program.
8502 Related setting: @ref{set backtrace past-entry}.
8505 By default, @value{GDBN} displays some frame information before the
8506 output produced by @var{command}, and an error raised during the
8507 execution of a @var{command} will abort @code{frame apply}. The
8508 following options can be used to fine-tune these behaviors:
8512 The flag @code{-c}, which stands for @samp{continue}, causes any
8513 errors in @var{command} to be displayed, and the execution of
8514 @code{frame apply} then continues.
8516 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8517 or empty output produced by a @var{command} to be silently ignored.
8518 That is, the execution continues, but the frame information and errors
8521 The flag @code{-q} (@samp{quiet}) disables printing the frame
8525 The following example shows how the flags @code{-c} and @code{-s} are
8526 working when applying the command @code{p j} to all frames, where
8527 variable @code{j} can only be successfully printed in the outermost
8528 @code{#1 main} frame.
8532 (gdb) frame apply all p j
8533 #0 some_function (i=5) at fun.c:4
8534 No symbol "j" in current context.
8535 (gdb) frame apply all -c p j
8536 #0 some_function (i=5) at fun.c:4
8537 No symbol "j" in current context.
8538 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8540 (gdb) frame apply all -s p j
8541 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8547 By default, @samp{frame apply}, prints the frame location
8548 information before the command output:
8552 (gdb) frame apply all p $sp
8553 #0 some_function (i=5) at fun.c:4
8554 $4 = (void *) 0xffffd1e0
8555 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8556 $5 = (void *) 0xffffd1f0
8561 If the flag @code{-q} is given, no frame information is printed:
8564 (gdb) frame apply all -q p $sp
8565 $12 = (void *) 0xffffd1e0
8566 $13 = (void *) 0xffffd1f0
8576 @cindex apply a command to all frames (ignoring errors and empty output)
8577 @item faas @var{command}
8578 Shortcut for @code{frame apply all -s @var{command}}.
8579 Applies @var{command} on all frames, ignoring errors and empty output.
8581 It can for example be used to print a local variable or a function
8582 argument without knowing the frame where this variable or argument
8585 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8588 The @code{faas} command accepts the same options as the @code{frame
8589 apply} command. @xref{Frame Apply,,frame apply}.
8591 Note that the command @code{tfaas @var{command}} applies @var{command}
8592 on all frames of all threads. See @xref{Threads,,Threads}.
8596 @node Frame Filter Management
8597 @section Management of Frame Filters.
8598 @cindex managing frame filters
8600 Frame filters are Python based utilities to manage and decorate the
8601 output of frames. @xref{Frame Filter API}, for further information.
8603 Managing frame filters is performed by several commands available
8604 within @value{GDBN}, detailed here.
8607 @kindex info frame-filter
8608 @item info frame-filter
8609 Print a list of installed frame filters from all dictionaries, showing
8610 their name, priority and enabled status.
8612 @kindex disable frame-filter
8613 @anchor{disable frame-filter all}
8614 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8615 Disable a frame filter in the dictionary matching
8616 @var{filter-dictionary} and @var{filter-name}. The
8617 @var{filter-dictionary} may be @code{all}, @code{global},
8618 @code{progspace}, or the name of the object file where the frame filter
8619 dictionary resides. When @code{all} is specified, all frame filters
8620 across all dictionaries are disabled. The @var{filter-name} is the name
8621 of the frame filter and is used when @code{all} is not the option for
8622 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8623 may be enabled again later.
8625 @kindex enable frame-filter
8626 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8627 Enable a frame filter in the dictionary matching
8628 @var{filter-dictionary} and @var{filter-name}. The
8629 @var{filter-dictionary} may be @code{all}, @code{global},
8630 @code{progspace} or the name of the object file where the frame filter
8631 dictionary resides. When @code{all} is specified, all frame filters across
8632 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8633 filter and is used when @code{all} is not the option for
8634 @var{filter-dictionary}.
8639 (gdb) info frame-filter
8641 global frame-filters:
8642 Priority Enabled Name
8643 1000 No PrimaryFunctionFilter
8646 progspace /build/test frame-filters:
8647 Priority Enabled Name
8648 100 Yes ProgspaceFilter
8650 objfile /build/test frame-filters:
8651 Priority Enabled Name
8652 999 Yes BuildProgramFilter
8654 (gdb) disable frame-filter /build/test BuildProgramFilter
8655 (gdb) info frame-filter
8657 global frame-filters:
8658 Priority Enabled Name
8659 1000 No PrimaryFunctionFilter
8662 progspace /build/test frame-filters:
8663 Priority Enabled Name
8664 100 Yes ProgspaceFilter
8666 objfile /build/test frame-filters:
8667 Priority Enabled Name
8668 999 No BuildProgramFilter
8670 (gdb) enable frame-filter global PrimaryFunctionFilter
8671 (gdb) info frame-filter
8673 global frame-filters:
8674 Priority Enabled Name
8675 1000 Yes PrimaryFunctionFilter
8678 progspace /build/test frame-filters:
8679 Priority Enabled Name
8680 100 Yes ProgspaceFilter
8682 objfile /build/test frame-filters:
8683 Priority Enabled Name
8684 999 No BuildProgramFilter
8687 @kindex set frame-filter priority
8688 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8689 Set the @var{priority} of a frame filter in the dictionary matching
8690 @var{filter-dictionary}, and the frame filter name matching
8691 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8692 @code{progspace} or the name of the object file where the frame filter
8693 dictionary resides. The @var{priority} is an integer.
8695 @kindex show frame-filter priority
8696 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8697 Show the @var{priority} of a frame filter in the dictionary matching
8698 @var{filter-dictionary}, and the frame filter name matching
8699 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8700 @code{progspace} or the name of the object file where the frame filter
8706 (gdb) info frame-filter
8708 global frame-filters:
8709 Priority Enabled Name
8710 1000 Yes PrimaryFunctionFilter
8713 progspace /build/test frame-filters:
8714 Priority Enabled Name
8715 100 Yes ProgspaceFilter
8717 objfile /build/test frame-filters:
8718 Priority Enabled Name
8719 999 No BuildProgramFilter
8721 (gdb) set frame-filter priority global Reverse 50
8722 (gdb) info frame-filter
8724 global frame-filters:
8725 Priority Enabled Name
8726 1000 Yes PrimaryFunctionFilter
8729 progspace /build/test frame-filters:
8730 Priority Enabled Name
8731 100 Yes ProgspaceFilter
8733 objfile /build/test frame-filters:
8734 Priority Enabled Name
8735 999 No BuildProgramFilter
8740 @chapter Examining Source Files
8742 @value{GDBN} can print parts of your program's source, since the debugging
8743 information recorded in the program tells @value{GDBN} what source files were
8744 used to build it. When your program stops, @value{GDBN} spontaneously prints
8745 the line where it stopped. Likewise, when you select a stack frame
8746 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8747 execution in that frame has stopped. You can print other portions of
8748 source files by explicit command.
8750 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8751 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8752 @value{GDBN} under @sc{gnu} Emacs}.
8755 * List:: Printing source lines
8756 * Specify Location:: How to specify code locations
8757 * Edit:: Editing source files
8758 * Search:: Searching source files
8759 * Source Path:: Specifying source directories
8760 * Machine Code:: Source and machine code
8764 @section Printing Source Lines
8767 @kindex l @r{(@code{list})}
8768 To print lines from a source file, use the @code{list} command
8769 (abbreviated @code{l}). By default, ten lines are printed.
8770 There are several ways to specify what part of the file you want to
8771 print; see @ref{Specify Location}, for the full list.
8773 Here are the forms of the @code{list} command most commonly used:
8776 @item list @var{linenum}
8777 Print lines centered around line number @var{linenum} in the
8778 current source file.
8780 @item list @var{function}
8781 Print lines centered around the beginning of function
8785 Print more lines. If the last lines printed were printed with a
8786 @code{list} command, this prints lines following the last lines
8787 printed; however, if the last line printed was a solitary line printed
8788 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8789 Stack}), this prints lines centered around that line.
8792 Print lines just before the lines last printed.
8795 @cindex @code{list}, how many lines to display
8796 By default, @value{GDBN} prints ten source lines with any of these forms of
8797 the @code{list} command. You can change this using @code{set listsize}:
8800 @kindex set listsize
8801 @item set listsize @var{count}
8802 @itemx set listsize unlimited
8803 Make the @code{list} command display @var{count} source lines (unless
8804 the @code{list} argument explicitly specifies some other number).
8805 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8807 @kindex show listsize
8809 Display the number of lines that @code{list} prints.
8812 Repeating a @code{list} command with @key{RET} discards the argument,
8813 so it is equivalent to typing just @code{list}. This is more useful
8814 than listing the same lines again. An exception is made for an
8815 argument of @samp{-}; that argument is preserved in repetition so that
8816 each repetition moves up in the source file.
8818 In general, the @code{list} command expects you to supply zero, one or two
8819 @dfn{locations}. Locations specify source lines; there are several ways
8820 of writing them (@pxref{Specify Location}), but the effect is always
8821 to specify some source line.
8823 Here is a complete description of the possible arguments for @code{list}:
8826 @item list @var{location}
8827 Print lines centered around the line specified by @var{location}.
8829 @item list @var{first},@var{last}
8830 Print lines from @var{first} to @var{last}. Both arguments are
8831 locations. When a @code{list} command has two locations, and the
8832 source file of the second location is omitted, this refers to
8833 the same source file as the first location.
8835 @item list ,@var{last}
8836 Print lines ending with @var{last}.
8838 @item list @var{first},
8839 Print lines starting with @var{first}.
8842 Print lines just after the lines last printed.
8845 Print lines just before the lines last printed.
8848 As described in the preceding table.
8851 @node Specify Location
8852 @section Specifying a Location
8853 @cindex specifying location
8855 @cindex source location
8858 * Linespec Locations:: Linespec locations
8859 * Explicit Locations:: Explicit locations
8860 * Address Locations:: Address locations
8863 Several @value{GDBN} commands accept arguments that specify a location
8864 of your program's code. Since @value{GDBN} is a source-level
8865 debugger, a location usually specifies some line in the source code.
8866 Locations may be specified using three different formats:
8867 linespec locations, explicit locations, or address locations.
8869 @node Linespec Locations
8870 @subsection Linespec Locations
8871 @cindex linespec locations
8873 A @dfn{linespec} is a colon-separated list of source location parameters such
8874 as file name, function name, etc. Here are all the different ways of
8875 specifying a linespec:
8879 Specifies the line number @var{linenum} of the current source file.
8882 @itemx +@var{offset}
8883 Specifies the line @var{offset} lines before or after the @dfn{current
8884 line}. For the @code{list} command, the current line is the last one
8885 printed; for the breakpoint commands, this is the line at which
8886 execution stopped in the currently selected @dfn{stack frame}
8887 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8888 used as the second of the two linespecs in a @code{list} command,
8889 this specifies the line @var{offset} lines up or down from the first
8892 @item @var{filename}:@var{linenum}
8893 Specifies the line @var{linenum} in the source file @var{filename}.
8894 If @var{filename} is a relative file name, then it will match any
8895 source file name with the same trailing components. For example, if
8896 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8897 name of @file{/build/trunk/gcc/expr.c}, but not
8898 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8900 @item @var{function}
8901 Specifies the line that begins the body of the function @var{function}.
8902 For example, in C, this is the line with the open brace.
8904 By default, in C@t{++} and Ada, @var{function} is interpreted as
8905 specifying all functions named @var{function} in all scopes. For
8906 C@t{++}, this means in all namespaces and classes. For Ada, this
8907 means in all packages.
8909 For example, assuming a program with C@t{++} symbols named
8910 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8911 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8913 Commands that accept a linespec let you override this with the
8914 @code{-qualified} option. For example, @w{@kbd{break -qualified
8915 func}} sets a breakpoint on a free-function named @code{func} ignoring
8916 any C@t{++} class methods and namespace functions called @code{func}.
8918 @xref{Explicit Locations}.
8920 @item @var{function}:@var{label}
8921 Specifies the line where @var{label} appears in @var{function}.
8923 @item @var{filename}:@var{function}
8924 Specifies the line that begins the body of the function @var{function}
8925 in the file @var{filename}. You only need the file name with a
8926 function name to avoid ambiguity when there are identically named
8927 functions in different source files.
8930 Specifies the line at which the label named @var{label} appears
8931 in the function corresponding to the currently selected stack frame.
8932 If there is no current selected stack frame (for instance, if the inferior
8933 is not running), then @value{GDBN} will not search for a label.
8935 @cindex breakpoint at static probe point
8936 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8937 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8938 applications to embed static probes. @xref{Static Probe Points}, for more
8939 information on finding and using static probes. This form of linespec
8940 specifies the location of such a static probe.
8942 If @var{objfile} is given, only probes coming from that shared library
8943 or executable matching @var{objfile} as a regular expression are considered.
8944 If @var{provider} is given, then only probes from that provider are considered.
8945 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8946 each one of those probes.
8949 @node Explicit Locations
8950 @subsection Explicit Locations
8951 @cindex explicit locations
8953 @dfn{Explicit locations} allow the user to directly specify the source
8954 location's parameters using option-value pairs.
8956 Explicit locations are useful when several functions, labels, or
8957 file names have the same name (base name for files) in the program's
8958 sources. In these cases, explicit locations point to the source
8959 line you meant more accurately and unambiguously. Also, using
8960 explicit locations might be faster in large programs.
8962 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8963 defined in the file named @file{foo} or the label @code{bar} in a function
8964 named @code{foo}. @value{GDBN} must search either the file system or
8965 the symbol table to know.
8967 The list of valid explicit location options is summarized in the
8971 @item -source @var{filename}
8972 The value specifies the source file name. To differentiate between
8973 files with the same base name, prepend as many directories as is necessary
8974 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8975 @value{GDBN} will use the first file it finds with the given base
8976 name. This option requires the use of either @code{-function} or @code{-line}.
8978 @item -function @var{function}
8979 The value specifies the name of a function. Operations
8980 on function locations unmodified by other options (such as @code{-label}
8981 or @code{-line}) refer to the line that begins the body of the function.
8982 In C, for example, this is the line with the open brace.
8984 By default, in C@t{++} and Ada, @var{function} is interpreted as
8985 specifying all functions named @var{function} in all scopes. For
8986 C@t{++}, this means in all namespaces and classes. For Ada, this
8987 means in all packages.
8989 For example, assuming a program with C@t{++} symbols named
8990 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8991 -function func}} and @w{@kbd{break -function B::func}} set a
8992 breakpoint on both symbols.
8994 You can use the @kbd{-qualified} flag to override this (see below).
8998 This flag makes @value{GDBN} interpret a function name specified with
8999 @kbd{-function} as a complete fully-qualified name.
9001 For example, assuming a C@t{++} program with symbols named
9002 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9003 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9005 (Note: the @kbd{-qualified} option can precede a linespec as well
9006 (@pxref{Linespec Locations}), so the particular example above could be
9007 simplified as @w{@kbd{break -qualified B::func}}.)
9009 @item -label @var{label}
9010 The value specifies the name of a label. When the function
9011 name is not specified, the label is searched in the function of the currently
9012 selected stack frame.
9014 @item -line @var{number}
9015 The value specifies a line offset for the location. The offset may either
9016 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9017 the command. When specified without any other options, the line offset is
9018 relative to the current line.
9021 Explicit location options may be abbreviated by omitting any non-unique
9022 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9024 @node Address Locations
9025 @subsection Address Locations
9026 @cindex address locations
9028 @dfn{Address locations} indicate a specific program address. They have
9029 the generalized form *@var{address}.
9031 For line-oriented commands, such as @code{list} and @code{edit}, this
9032 specifies a source line that contains @var{address}. For @code{break} and
9033 other breakpoint-oriented commands, this can be used to set breakpoints in
9034 parts of your program which do not have debugging information or
9037 Here @var{address} may be any expression valid in the current working
9038 language (@pxref{Languages, working language}) that specifies a code
9039 address. In addition, as a convenience, @value{GDBN} extends the
9040 semantics of expressions used in locations to cover several situations
9041 that frequently occur during debugging. Here are the various forms
9045 @item @var{expression}
9046 Any expression valid in the current working language.
9048 @item @var{funcaddr}
9049 An address of a function or procedure derived from its name. In C,
9050 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9051 simply the function's name @var{function} (and actually a special case
9052 of a valid expression). In Pascal and Modula-2, this is
9053 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9054 (although the Pascal form also works).
9056 This form specifies the address of the function's first instruction,
9057 before the stack frame and arguments have been set up.
9059 @item '@var{filename}':@var{funcaddr}
9060 Like @var{funcaddr} above, but also specifies the name of the source
9061 file explicitly. This is useful if the name of the function does not
9062 specify the function unambiguously, e.g., if there are several
9063 functions with identical names in different source files.
9067 @section Editing Source Files
9068 @cindex editing source files
9071 @kindex e @r{(@code{edit})}
9072 To edit the lines in a source file, use the @code{edit} command.
9073 The editing program of your choice
9074 is invoked with the current line set to
9075 the active line in the program.
9076 Alternatively, there are several ways to specify what part of the file you
9077 want to print if you want to see other parts of the program:
9080 @item edit @var{location}
9081 Edit the source file specified by @code{location}. Editing starts at
9082 that @var{location}, e.g., at the specified source line of the
9083 specified file. @xref{Specify Location}, for all the possible forms
9084 of the @var{location} argument; here are the forms of the @code{edit}
9085 command most commonly used:
9088 @item edit @var{number}
9089 Edit the current source file with @var{number} as the active line number.
9091 @item edit @var{function}
9092 Edit the file containing @var{function} at the beginning of its definition.
9097 @subsection Choosing your Editor
9098 You can customize @value{GDBN} to use any editor you want
9100 The only restriction is that your editor (say @code{ex}), recognizes the
9101 following command-line syntax:
9103 ex +@var{number} file
9105 The optional numeric value +@var{number} specifies the number of the line in
9106 the file where to start editing.}.
9107 By default, it is @file{@value{EDITOR}}, but you can change this
9108 by setting the environment variable @code{EDITOR} before using
9109 @value{GDBN}. For example, to configure @value{GDBN} to use the
9110 @code{vi} editor, you could use these commands with the @code{sh} shell:
9116 or in the @code{csh} shell,
9118 setenv EDITOR /usr/bin/vi
9123 @section Searching Source Files
9124 @cindex searching source files
9126 There are two commands for searching through the current source file for a
9131 @kindex forward-search
9132 @kindex fo @r{(@code{forward-search})}
9133 @item forward-search @var{regexp}
9134 @itemx search @var{regexp}
9135 The command @samp{forward-search @var{regexp}} checks each line,
9136 starting with the one following the last line listed, for a match for
9137 @var{regexp}. It lists the line that is found. You can use the
9138 synonym @samp{search @var{regexp}} or abbreviate the command name as
9141 @kindex reverse-search
9142 @item reverse-search @var{regexp}
9143 The command @samp{reverse-search @var{regexp}} checks each line, starting
9144 with the one before the last line listed and going backward, for a match
9145 for @var{regexp}. It lists the line that is found. You can abbreviate
9146 this command as @code{rev}.
9150 @section Specifying Source Directories
9153 @cindex directories for source files
9154 Executable programs sometimes do not record the directories of the source
9155 files from which they were compiled, just the names. Even when they do,
9156 the directories could be moved between the compilation and your debugging
9157 session. @value{GDBN} has a list of directories to search for source files;
9158 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9159 it tries all the directories in the list, in the order they are present
9160 in the list, until it finds a file with the desired name.
9162 For example, suppose an executable references the file
9163 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9164 directory, and the @dfn{source path} is @file{/mnt/cross}.
9165 @value{GDBN} would look for the source file in the following
9170 @item @file{/usr/src/foo-1.0/lib/foo.c}
9171 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9172 @item @file{/mnt/cross/foo.c}
9176 If the source file is not present at any of the above locations then
9177 an error is printed. @value{GDBN} does not look up the parts of the
9178 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9179 Likewise, the subdirectories of the source path are not searched: if
9180 the source path is @file{/mnt/cross}, and the binary refers to
9181 @file{foo.c}, @value{GDBN} would not find it under
9182 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9184 Plain file names, relative file names with leading directories, file
9185 names containing dots, etc.@: are all treated as described above,
9186 except that non-absolute file names are not looked up literally. If
9187 the @dfn{source path} is @file{/mnt/cross}, the source file is
9188 recorded as @file{../lib/foo.c}, and no compilation directory is
9189 recorded, then @value{GDBN} will search in the following locations:
9193 @item @file{/mnt/cross/../lib/foo.c}
9194 @item @file{/mnt/cross/foo.c}
9200 @vindex $cdir@r{, convenience variable}
9201 @vindex $cwd@r{, convenience variable}
9202 @cindex compilation directory
9203 @cindex current directory
9204 @cindex working directory
9205 @cindex directory, current
9206 @cindex directory, compilation
9207 The @dfn{source path} will always include two special entries
9208 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9209 (if one is recorded) and the current working directory respectively.
9211 @samp{$cdir} causes @value{GDBN} to search within the compilation
9212 directory, if one is recorded in the debug information. If no
9213 compilation directory is recorded in the debug information then
9214 @samp{$cdir} is ignored.
9216 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9217 current working directory as it changes during your @value{GDBN}
9218 session, while the latter is immediately expanded to the current
9219 directory at the time you add an entry to the source path.
9221 If a compilation directory is recorded in the debug information, and
9222 @value{GDBN} has not found the source file after the first search
9223 using @dfn{source path}, then @value{GDBN} will combine the
9224 compilation directory and the filename, and then search for the source
9225 file again using the @dfn{source path}.
9227 For example, if the executable records the source file as
9228 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9229 recorded as @file{/project/build}, and the @dfn{source path} is
9230 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9231 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9232 search for the source file in the following locations:
9236 @item @file{/usr/src/foo-1.0/lib/foo.c}
9237 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9238 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9239 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9240 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9241 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9242 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9243 @item @file{/mnt/cross/foo.c}
9244 @item @file{/project/build/foo.c}
9245 @item @file{/home/user/foo.c}
9249 If the file name in the previous example had been recorded in the
9250 executable as a relative path rather than an absolute path, then the
9251 first look up would not have occurred, but all of the remaining steps
9254 When searching for source files on MS-DOS and MS-Windows, where
9255 absolute paths start with a drive letter (e.g.
9256 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9257 from the file name before appending it to a search directory from
9258 @dfn{source path}; for instance if the executable references the
9259 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9260 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9261 locations for the source file:
9265 @item @file{C:/project/foo.c}
9266 @item @file{D:/mnt/cross/project/foo.c}
9267 @item @file{D:/mnt/cross/foo.c}
9271 Note that the executable search path is @emph{not} used to locate the
9274 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9275 any information it has cached about where source files are found and where
9276 each line is in the file.
9280 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9281 and @samp{$cwd}, in that order.
9282 To add other directories, use the @code{directory} command.
9284 The search path is used to find both program source files and @value{GDBN}
9285 script files (read using the @samp{-command} option and @samp{source} command).
9287 In addition to the source path, @value{GDBN} provides a set of commands
9288 that manage a list of source path substitution rules. A @dfn{substitution
9289 rule} specifies how to rewrite source directories stored in the program's
9290 debug information in case the sources were moved to a different
9291 directory between compilation and debugging. A rule is made of
9292 two strings, the first specifying what needs to be rewritten in
9293 the path, and the second specifying how it should be rewritten.
9294 In @ref{set substitute-path}, we name these two parts @var{from} and
9295 @var{to} respectively. @value{GDBN} does a simple string replacement
9296 of @var{from} with @var{to} at the start of the directory part of the
9297 source file name, and uses that result instead of the original file
9298 name to look up the sources.
9300 Using the previous example, suppose the @file{foo-1.0} tree has been
9301 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9302 @value{GDBN} to replace @file{/usr/src} in all source path names with
9303 @file{/mnt/cross}. The first lookup will then be
9304 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9305 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9306 substitution rule, use the @code{set substitute-path} command
9307 (@pxref{set substitute-path}).
9309 To avoid unexpected substitution results, a rule is applied only if the
9310 @var{from} part of the directory name ends at a directory separator.
9311 For instance, a rule substituting @file{/usr/source} into
9312 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9313 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9314 is applied only at the beginning of the directory name, this rule will
9315 not be applied to @file{/root/usr/source/baz.c} either.
9317 In many cases, you can achieve the same result using the @code{directory}
9318 command. However, @code{set substitute-path} can be more efficient in
9319 the case where the sources are organized in a complex tree with multiple
9320 subdirectories. With the @code{directory} command, you need to add each
9321 subdirectory of your project. If you moved the entire tree while
9322 preserving its internal organization, then @code{set substitute-path}
9323 allows you to direct the debugger to all the sources with one single
9326 @code{set substitute-path} is also more than just a shortcut command.
9327 The source path is only used if the file at the original location no
9328 longer exists. On the other hand, @code{set substitute-path} modifies
9329 the debugger behavior to look at the rewritten location instead. So, if
9330 for any reason a source file that is not relevant to your executable is
9331 located at the original location, a substitution rule is the only
9332 method available to point @value{GDBN} at the new location.
9334 @cindex @samp{--with-relocated-sources}
9335 @cindex default source path substitution
9336 You can configure a default source path substitution rule by
9337 configuring @value{GDBN} with the
9338 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9339 should be the name of a directory under @value{GDBN}'s configured
9340 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9341 directory names in debug information under @var{dir} will be adjusted
9342 automatically if the installed @value{GDBN} is moved to a new
9343 location. This is useful if @value{GDBN}, libraries or executables
9344 with debug information and corresponding source code are being moved
9348 @item directory @var{dirname} @dots{}
9349 @item dir @var{dirname} @dots{}
9350 Add directory @var{dirname} to the front of the source path. Several
9351 directory names may be given to this command, separated by @samp{:}
9352 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9353 part of absolute file names) or
9354 whitespace. You may specify a directory that is already in the source
9355 path; this moves it forward, so @value{GDBN} searches it sooner.
9357 The special strings @samp{$cdir} (to refer to the compilation
9358 directory, if one is recorded), and @samp{$cwd} (to refer to the
9359 current working directory) can also be included in the list of
9360 directories @var{dirname}. Though these will already be in the source
9361 path they will be moved forward in the list so @value{GDBN} searches
9365 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9367 @c RET-repeat for @code{directory} is explicitly disabled, but since
9368 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9370 @item set directories @var{path-list}
9371 @kindex set directories
9372 Set the source path to @var{path-list}.
9373 @samp{$cdir:$cwd} are added if missing.
9375 @item show directories
9376 @kindex show directories
9377 Print the source path: show which directories it contains.
9379 @anchor{set substitute-path}
9380 @item set substitute-path @var{from} @var{to}
9381 @kindex set substitute-path
9382 Define a source path substitution rule, and add it at the end of the
9383 current list of existing substitution rules. If a rule with the same
9384 @var{from} was already defined, then the old rule is also deleted.
9386 For example, if the file @file{/foo/bar/baz.c} was moved to
9387 @file{/mnt/cross/baz.c}, then the command
9390 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9394 will tell @value{GDBN} to replace @samp{/foo/bar} with
9395 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9396 @file{baz.c} even though it was moved.
9398 In the case when more than one substitution rule have been defined,
9399 the rules are evaluated one by one in the order where they have been
9400 defined. The first one matching, if any, is selected to perform
9403 For instance, if we had entered the following commands:
9406 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9407 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9411 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9412 @file{/mnt/include/defs.h} by using the first rule. However, it would
9413 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9414 @file{/mnt/src/lib/foo.c}.
9417 @item unset substitute-path [path]
9418 @kindex unset substitute-path
9419 If a path is specified, search the current list of substitution rules
9420 for a rule that would rewrite that path. Delete that rule if found.
9421 A warning is emitted by the debugger if no rule could be found.
9423 If no path is specified, then all substitution rules are deleted.
9425 @item show substitute-path [path]
9426 @kindex show substitute-path
9427 If a path is specified, then print the source path substitution rule
9428 which would rewrite that path, if any.
9430 If no path is specified, then print all existing source path substitution
9435 If your source path is cluttered with directories that are no longer of
9436 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9437 versions of source. You can correct the situation as follows:
9441 Use @code{directory} with no argument to reset the source path to its default value.
9444 Use @code{directory} with suitable arguments to reinstall the
9445 directories you want in the source path. You can add all the
9446 directories in one command.
9450 @section Source and Machine Code
9451 @cindex source line and its code address
9453 You can use the command @code{info line} to map source lines to program
9454 addresses (and vice versa), and the command @code{disassemble} to display
9455 a range of addresses as machine instructions. You can use the command
9456 @code{set disassemble-next-line} to set whether to disassemble next
9457 source line when execution stops. When run under @sc{gnu} Emacs
9458 mode, the @code{info line} command causes the arrow to point to the
9459 line specified. Also, @code{info line} prints addresses in symbolic form as
9465 @itemx info line @var{location}
9466 Print the starting and ending addresses of the compiled code for
9467 source line @var{location}. You can specify source lines in any of
9468 the ways documented in @ref{Specify Location}. With no @var{location}
9469 information about the current source line is printed.
9472 For example, we can use @code{info line} to discover the location of
9473 the object code for the first line of function
9474 @code{m4_changequote}:
9477 (@value{GDBP}) info line m4_changequote
9478 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9479 ends at 0x6350 <m4_changequote+4>.
9483 @cindex code address and its source line
9484 We can also inquire (using @code{*@var{addr}} as the form for
9485 @var{location}) what source line covers a particular address:
9487 (@value{GDBP}) info line *0x63ff
9488 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9489 ends at 0x6404 <m4_changequote+184>.
9492 @cindex @code{$_} and @code{info line}
9493 @cindex @code{x} command, default address
9494 @kindex x@r{(examine), and} info line
9495 After @code{info line}, the default address for the @code{x} command
9496 is changed to the starting address of the line, so that @samp{x/i} is
9497 sufficient to begin examining the machine code (@pxref{Memory,
9498 ,Examining Memory}). Also, this address is saved as the value of the
9499 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9502 @cindex info line, repeated calls
9503 After @code{info line}, using @code{info line} again without
9504 specifying a location will display information about the next source
9509 @cindex assembly instructions
9510 @cindex instructions, assembly
9511 @cindex machine instructions
9512 @cindex listing machine instructions
9514 @itemx disassemble /m
9515 @itemx disassemble /s
9516 @itemx disassemble /r
9517 This specialized command dumps a range of memory as machine
9518 instructions. It can also print mixed source+disassembly by specifying
9519 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9520 as well as in symbolic form by specifying the @code{/r} modifier.
9521 The default memory range is the function surrounding the
9522 program counter of the selected frame. A single argument to this
9523 command is a program counter value; @value{GDBN} dumps the function
9524 surrounding this value. When two arguments are given, they should
9525 be separated by a comma, possibly surrounded by whitespace. The
9526 arguments specify a range of addresses to dump, in one of two forms:
9529 @item @var{start},@var{end}
9530 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9531 @item @var{start},+@var{length}
9532 the addresses from @var{start} (inclusive) to
9533 @code{@var{start}+@var{length}} (exclusive).
9537 When 2 arguments are specified, the name of the function is also
9538 printed (since there could be several functions in the given range).
9540 The argument(s) can be any expression yielding a numeric value, such as
9541 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9543 If the range of memory being disassembled contains current program counter,
9544 the instruction at that location is shown with a @code{=>} marker.
9547 The following example shows the disassembly of a range of addresses of
9548 HP PA-RISC 2.0 code:
9551 (@value{GDBP}) disas 0x32c4, 0x32e4
9552 Dump of assembler code from 0x32c4 to 0x32e4:
9553 0x32c4 <main+204>: addil 0,dp
9554 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9555 0x32cc <main+212>: ldil 0x3000,r31
9556 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9557 0x32d4 <main+220>: ldo 0(r31),rp
9558 0x32d8 <main+224>: addil -0x800,dp
9559 0x32dc <main+228>: ldo 0x588(r1),r26
9560 0x32e0 <main+232>: ldil 0x3000,r31
9561 End of assembler dump.
9564 Here is an example showing mixed source+assembly for Intel x86
9565 with @code{/m} or @code{/s}, when the program is stopped just after
9566 function prologue in a non-optimized function with no inline code.
9569 (@value{GDBP}) disas /m main
9570 Dump of assembler code for function main:
9572 0x08048330 <+0>: push %ebp
9573 0x08048331 <+1>: mov %esp,%ebp
9574 0x08048333 <+3>: sub $0x8,%esp
9575 0x08048336 <+6>: and $0xfffffff0,%esp
9576 0x08048339 <+9>: sub $0x10,%esp
9578 6 printf ("Hello.\n");
9579 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9580 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9584 0x08048348 <+24>: mov $0x0,%eax
9585 0x0804834d <+29>: leave
9586 0x0804834e <+30>: ret
9588 End of assembler dump.
9591 The @code{/m} option is deprecated as its output is not useful when
9592 there is either inlined code or re-ordered code.
9593 The @code{/s} option is the preferred choice.
9594 Here is an example for AMD x86-64 showing the difference between
9595 @code{/m} output and @code{/s} output.
9596 This example has one inline function defined in a header file,
9597 and the code is compiled with @samp{-O2} optimization.
9598 Note how the @code{/m} output is missing the disassembly of
9599 several instructions that are present in the @code{/s} output.
9629 (@value{GDBP}) disas /m main
9630 Dump of assembler code for function main:
9634 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9635 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9639 0x000000000040041d <+29>: xor %eax,%eax
9640 0x000000000040041f <+31>: retq
9641 0x0000000000400420 <+32>: add %eax,%eax
9642 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9644 End of assembler dump.
9645 (@value{GDBP}) disas /s main
9646 Dump of assembler code for function main:
9650 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9654 0x0000000000400406 <+6>: test %eax,%eax
9655 0x0000000000400408 <+8>: js 0x400420 <main+32>
9660 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9661 0x000000000040040d <+13>: test %eax,%eax
9662 0x000000000040040f <+15>: mov $0x1,%eax
9663 0x0000000000400414 <+20>: cmovne %edx,%eax
9667 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9671 0x000000000040041d <+29>: xor %eax,%eax
9672 0x000000000040041f <+31>: retq
9676 0x0000000000400420 <+32>: add %eax,%eax
9677 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9678 End of assembler dump.
9681 Here is another example showing raw instructions in hex for AMD x86-64,
9684 (gdb) disas /r 0x400281,+10
9685 Dump of assembler code from 0x400281 to 0x40028b:
9686 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9687 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9688 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9689 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9690 End of assembler dump.
9693 Addresses cannot be specified as a location (@pxref{Specify Location}).
9694 So, for example, if you want to disassemble function @code{bar}
9695 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9696 and not @samp{disassemble foo.c:bar}.
9698 Some architectures have more than one commonly-used set of instruction
9699 mnemonics or other syntax.
9701 For programs that were dynamically linked and use shared libraries,
9702 instructions that call functions or branch to locations in the shared
9703 libraries might show a seemingly bogus location---it's actually a
9704 location of the relocation table. On some architectures, @value{GDBN}
9705 might be able to resolve these to actual function names.
9708 @kindex set disassembler-options
9709 @cindex disassembler options
9710 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9711 This command controls the passing of target specific information to
9712 the disassembler. For a list of valid options, please refer to the
9713 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9714 manual and/or the output of @kbd{objdump --help}
9715 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9716 The default value is the empty string.
9718 If it is necessary to specify more than one disassembler option, then
9719 multiple options can be placed together into a comma separated list.
9720 Currently this command is only supported on targets ARM, MIPS, PowerPC
9723 @kindex show disassembler-options
9724 @item show disassembler-options
9725 Show the current setting of the disassembler options.
9729 @kindex set disassembly-flavor
9730 @cindex Intel disassembly flavor
9731 @cindex AT&T disassembly flavor
9732 @item set disassembly-flavor @var{instruction-set}
9733 Select the instruction set to use when disassembling the
9734 program via the @code{disassemble} or @code{x/i} commands.
9736 Currently this command is only defined for the Intel x86 family. You
9737 can set @var{instruction-set} to either @code{intel} or @code{att}.
9738 The default is @code{att}, the AT&T flavor used by default by Unix
9739 assemblers for x86-based targets.
9741 @kindex show disassembly-flavor
9742 @item show disassembly-flavor
9743 Show the current setting of the disassembly flavor.
9747 @kindex set disassemble-next-line
9748 @kindex show disassemble-next-line
9749 @item set disassemble-next-line
9750 @itemx show disassemble-next-line
9751 Control whether or not @value{GDBN} will disassemble the next source
9752 line or instruction when execution stops. If ON, @value{GDBN} will
9753 display disassembly of the next source line when execution of the
9754 program being debugged stops. This is @emph{in addition} to
9755 displaying the source line itself, which @value{GDBN} always does if
9756 possible. If the next source line cannot be displayed for some reason
9757 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9758 info in the debug info), @value{GDBN} will display disassembly of the
9759 next @emph{instruction} instead of showing the next source line. If
9760 AUTO, @value{GDBN} will display disassembly of next instruction only
9761 if the source line cannot be displayed. This setting causes
9762 @value{GDBN} to display some feedback when you step through a function
9763 with no line info or whose source file is unavailable. The default is
9764 OFF, which means never display the disassembly of the next line or
9770 @chapter Examining Data
9772 @cindex printing data
9773 @cindex examining data
9776 The usual way to examine data in your program is with the @code{print}
9777 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9778 evaluates and prints the value of an expression of the language your
9779 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9780 Different Languages}). It may also print the expression using a
9781 Python-based pretty-printer (@pxref{Pretty Printing}).
9784 @item print [[@var{options}] --] @var{expr}
9785 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9786 @var{expr} is an expression (in the source language). By default the
9787 value of @var{expr} is printed in a format appropriate to its data type;
9788 you can choose a different format by specifying @samp{/@var{f}}, where
9789 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9792 @anchor{print options}
9793 The @code{print} command supports a number of options that allow
9794 overriding relevant global print settings as set by @code{set print}
9798 @item -address [@code{on}|@code{off}]
9799 Set printing of addresses.
9800 Related setting: @ref{set print address}.
9802 @item -array [@code{on}|@code{off}]
9803 Pretty formatting of arrays.
9804 Related setting: @ref{set print array}.
9806 @item -array-indexes [@code{on}|@code{off}]
9807 Set printing of array indexes.
9808 Related setting: @ref{set print array-indexes}.
9810 @item -elements @var{number-of-elements}|@code{unlimited}
9811 Set limit on string chars or array elements to print. The value
9812 @code{unlimited} causes there to be no limit. Related setting:
9813 @ref{set print elements}.
9815 @item -max-depth @var{depth}|@code{unlimited}
9816 Set the threshold after which nested structures are replaced with
9817 ellipsis. Related setting: @ref{set print max-depth}.
9819 @item -null-stop [@code{on}|@code{off}]
9820 Set printing of char arrays to stop at first null char. Related
9821 setting: @ref{set print null-stop}.
9823 @item -object [@code{on}|@code{off}]
9824 Set printing C@t{++} virtual function tables. Related setting:
9825 @ref{set print object}.
9827 @item -pretty [@code{on}|@code{off}]
9828 Set pretty formatting of structures. Related setting: @ref{set print
9831 @item -raw-values [@code{on}|@code{off}]
9832 Set whether to print values in raw form, bypassing any
9833 pretty-printers for that value. Related setting: @ref{set print
9836 @item -repeats @var{number-of-repeats}|@code{unlimited}
9837 Set threshold for repeated print elements. @code{unlimited} causes
9838 all elements to be individually printed. Related setting: @ref{set
9841 @item -static-members [@code{on}|@code{off}]
9842 Set printing C@t{++} static members. Related setting: @ref{set print
9845 @item -symbol [@code{on}|@code{off}]
9846 Set printing of symbol names when printing pointers. Related setting:
9847 @ref{set print symbol}.
9849 @item -union [@code{on}|@code{off}]
9850 Set printing of unions interior to structures. Related setting:
9851 @ref{set print union}.
9853 @item -vtbl [@code{on}|@code{off}]
9854 Set printing of C++ virtual function tables. Related setting:
9855 @ref{set print vtbl}.
9858 Because the @code{print} command accepts arbitrary expressions which
9859 may look like options (including abbreviations), if you specify any
9860 command option, then you must use a double dash (@code{--}) to mark
9861 the end of option processing.
9863 For example, this prints the value of the @code{-p} expression:
9866 (@value{GDBP}) print -p
9869 While this repeats the last value in the value history (see below)
9870 with the @code{-pretty} option in effect:
9873 (@value{GDBP}) print -p --
9876 Here is an example including both on option and an expression:
9880 (@value{GDBP}) print -pretty -- *myptr
9892 @item print [@var{options}]
9893 @itemx print [@var{options}] /@var{f}
9894 @cindex reprint the last value
9895 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9896 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9897 conveniently inspect the same value in an alternative format.
9900 A more low-level way of examining data is with the @code{x} command.
9901 It examines data in memory at a specified address and prints it in a
9902 specified format. @xref{Memory, ,Examining Memory}.
9904 If you are interested in information about types, or about how the
9905 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9906 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9909 @cindex exploring hierarchical data structures
9911 Another way of examining values of expressions and type information is
9912 through the Python extension command @code{explore} (available only if
9913 the @value{GDBN} build is configured with @code{--with-python}). It
9914 offers an interactive way to start at the highest level (or, the most
9915 abstract level) of the data type of an expression (or, the data type
9916 itself) and explore all the way down to leaf scalar values/fields
9917 embedded in the higher level data types.
9920 @item explore @var{arg}
9921 @var{arg} is either an expression (in the source language), or a type
9922 visible in the current context of the program being debugged.
9925 The working of the @code{explore} command can be illustrated with an
9926 example. If a data type @code{struct ComplexStruct} is defined in your
9936 struct ComplexStruct
9938 struct SimpleStruct *ss_p;
9944 followed by variable declarations as
9947 struct SimpleStruct ss = @{ 10, 1.11 @};
9948 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9952 then, the value of the variable @code{cs} can be explored using the
9953 @code{explore} command as follows.
9957 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9958 the following fields:
9960 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9961 arr = <Enter 1 to explore this field of type `int [10]'>
9963 Enter the field number of choice:
9967 Since the fields of @code{cs} are not scalar values, you are being
9968 prompted to chose the field you want to explore. Let's say you choose
9969 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9970 pointer, you will be asked if it is pointing to a single value. From
9971 the declaration of @code{cs} above, it is indeed pointing to a single
9972 value, hence you enter @code{y}. If you enter @code{n}, then you will
9973 be asked if it were pointing to an array of values, in which case this
9974 field will be explored as if it were an array.
9977 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9978 Continue exploring it as a pointer to a single value [y/n]: y
9979 The value of `*(cs.ss_p)' is a struct/class of type `struct
9980 SimpleStruct' with the following fields:
9982 i = 10 .. (Value of type `int')
9983 d = 1.1100000000000001 .. (Value of type `double')
9985 Press enter to return to parent value:
9989 If the field @code{arr} of @code{cs} was chosen for exploration by
9990 entering @code{1} earlier, then since it is as array, you will be
9991 prompted to enter the index of the element in the array that you want
9995 `cs.arr' is an array of `int'.
9996 Enter the index of the element you want to explore in `cs.arr': 5
9998 `(cs.arr)[5]' is a scalar value of type `int'.
10002 Press enter to return to parent value:
10005 In general, at any stage of exploration, you can go deeper towards the
10006 leaf values by responding to the prompts appropriately, or hit the
10007 return key to return to the enclosing data structure (the @i{higher}
10008 level data structure).
10010 Similar to exploring values, you can use the @code{explore} command to
10011 explore types. Instead of specifying a value (which is typically a
10012 variable name or an expression valid in the current context of the
10013 program being debugged), you specify a type name. If you consider the
10014 same example as above, your can explore the type
10015 @code{struct ComplexStruct} by passing the argument
10016 @code{struct ComplexStruct} to the @code{explore} command.
10019 (gdb) explore struct ComplexStruct
10023 By responding to the prompts appropriately in the subsequent interactive
10024 session, you can explore the type @code{struct ComplexStruct} in a
10025 manner similar to how the value @code{cs} was explored in the above
10028 The @code{explore} command also has two sub-commands,
10029 @code{explore value} and @code{explore type}. The former sub-command is
10030 a way to explicitly specify that value exploration of the argument is
10031 being invoked, while the latter is a way to explicitly specify that type
10032 exploration of the argument is being invoked.
10035 @item explore value @var{expr}
10036 @cindex explore value
10037 This sub-command of @code{explore} explores the value of the
10038 expression @var{expr} (if @var{expr} is an expression valid in the
10039 current context of the program being debugged). The behavior of this
10040 command is identical to that of the behavior of the @code{explore}
10041 command being passed the argument @var{expr}.
10043 @item explore type @var{arg}
10044 @cindex explore type
10045 This sub-command of @code{explore} explores the type of @var{arg} (if
10046 @var{arg} is a type visible in the current context of program being
10047 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10048 is an expression valid in the current context of the program being
10049 debugged). If @var{arg} is a type, then the behavior of this command is
10050 identical to that of the @code{explore} command being passed the
10051 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10052 this command will be identical to that of the @code{explore} command
10053 being passed the type of @var{arg} as the argument.
10057 * Expressions:: Expressions
10058 * Ambiguous Expressions:: Ambiguous Expressions
10059 * Variables:: Program variables
10060 * Arrays:: Artificial arrays
10061 * Output Formats:: Output formats
10062 * Memory:: Examining memory
10063 * Auto Display:: Automatic display
10064 * Print Settings:: Print settings
10065 * Pretty Printing:: Python pretty printing
10066 * Value History:: Value history
10067 * Convenience Vars:: Convenience variables
10068 * Convenience Funs:: Convenience functions
10069 * Registers:: Registers
10070 * Floating Point Hardware:: Floating point hardware
10071 * Vector Unit:: Vector Unit
10072 * OS Information:: Auxiliary data provided by operating system
10073 * Memory Region Attributes:: Memory region attributes
10074 * Dump/Restore Files:: Copy between memory and a file
10075 * Core File Generation:: Cause a program dump its core
10076 * Character Sets:: Debugging programs that use a different
10077 character set than GDB does
10078 * Caching Target Data:: Data caching for targets
10079 * Searching Memory:: Searching memory for a sequence of bytes
10080 * Value Sizes:: Managing memory allocated for values
10084 @section Expressions
10086 @cindex expressions
10087 @code{print} and many other @value{GDBN} commands accept an expression and
10088 compute its value. Any kind of constant, variable or operator defined
10089 by the programming language you are using is valid in an expression in
10090 @value{GDBN}. This includes conditional expressions, function calls,
10091 casts, and string constants. It also includes preprocessor macros, if
10092 you compiled your program to include this information; see
10095 @cindex arrays in expressions
10096 @value{GDBN} supports array constants in expressions input by
10097 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10098 you can use the command @code{print @{1, 2, 3@}} to create an array
10099 of three integers. If you pass an array to a function or assign it
10100 to a program variable, @value{GDBN} copies the array to memory that
10101 is @code{malloc}ed in the target program.
10103 Because C is so widespread, most of the expressions shown in examples in
10104 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10105 Languages}, for information on how to use expressions in other
10108 In this section, we discuss operators that you can use in @value{GDBN}
10109 expressions regardless of your programming language.
10111 @cindex casts, in expressions
10112 Casts are supported in all languages, not just in C, because it is so
10113 useful to cast a number into a pointer in order to examine a structure
10114 at that address in memory.
10115 @c FIXME: casts supported---Mod2 true?
10117 @value{GDBN} supports these operators, in addition to those common
10118 to programming languages:
10122 @samp{@@} is a binary operator for treating parts of memory as arrays.
10123 @xref{Arrays, ,Artificial Arrays}, for more information.
10126 @samp{::} allows you to specify a variable in terms of the file or
10127 function where it is defined. @xref{Variables, ,Program Variables}.
10129 @cindex @{@var{type}@}
10130 @cindex type casting memory
10131 @cindex memory, viewing as typed object
10132 @cindex casts, to view memory
10133 @item @{@var{type}@} @var{addr}
10134 Refers to an object of type @var{type} stored at address @var{addr} in
10135 memory. The address @var{addr} may be any expression whose value is
10136 an integer or pointer (but parentheses are required around binary
10137 operators, just as in a cast). This construct is allowed regardless
10138 of what kind of data is normally supposed to reside at @var{addr}.
10141 @node Ambiguous Expressions
10142 @section Ambiguous Expressions
10143 @cindex ambiguous expressions
10145 Expressions can sometimes contain some ambiguous elements. For instance,
10146 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10147 a single function name to be defined several times, for application in
10148 different contexts. This is called @dfn{overloading}. Another example
10149 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10150 templates and is typically instantiated several times, resulting in
10151 the same function name being defined in different contexts.
10153 In some cases and depending on the language, it is possible to adjust
10154 the expression to remove the ambiguity. For instance in C@t{++}, you
10155 can specify the signature of the function you want to break on, as in
10156 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10157 qualified name of your function often makes the expression unambiguous
10160 When an ambiguity that needs to be resolved is detected, the debugger
10161 has the capability to display a menu of numbered choices for each
10162 possibility, and then waits for the selection with the prompt @samp{>}.
10163 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10164 aborts the current command. If the command in which the expression was
10165 used allows more than one choice to be selected, the next option in the
10166 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10169 For example, the following session excerpt shows an attempt to set a
10170 breakpoint at the overloaded symbol @code{String::after}.
10171 We choose three particular definitions of that function name:
10173 @c FIXME! This is likely to change to show arg type lists, at least
10176 (@value{GDBP}) b String::after
10179 [2] file:String.cc; line number:867
10180 [3] file:String.cc; line number:860
10181 [4] file:String.cc; line number:875
10182 [5] file:String.cc; line number:853
10183 [6] file:String.cc; line number:846
10184 [7] file:String.cc; line number:735
10186 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10187 Breakpoint 2 at 0xb344: file String.cc, line 875.
10188 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10189 Multiple breakpoints were set.
10190 Use the "delete" command to delete unwanted
10197 @kindex set multiple-symbols
10198 @item set multiple-symbols @var{mode}
10199 @cindex multiple-symbols menu
10201 This option allows you to adjust the debugger behavior when an expression
10204 By default, @var{mode} is set to @code{all}. If the command with which
10205 the expression is used allows more than one choice, then @value{GDBN}
10206 automatically selects all possible choices. For instance, inserting
10207 a breakpoint on a function using an ambiguous name results in a breakpoint
10208 inserted on each possible match. However, if a unique choice must be made,
10209 then @value{GDBN} uses the menu to help you disambiguate the expression.
10210 For instance, printing the address of an overloaded function will result
10211 in the use of the menu.
10213 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10214 when an ambiguity is detected.
10216 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10217 an error due to the ambiguity and the command is aborted.
10219 @kindex show multiple-symbols
10220 @item show multiple-symbols
10221 Show the current value of the @code{multiple-symbols} setting.
10225 @section Program Variables
10227 The most common kind of expression to use is the name of a variable
10230 Variables in expressions are understood in the selected stack frame
10231 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10235 global (or file-static)
10242 visible according to the scope rules of the
10243 programming language from the point of execution in that frame
10246 @noindent This means that in the function
10261 you can examine and use the variable @code{a} whenever your program is
10262 executing within the function @code{foo}, but you can only use or
10263 examine the variable @code{b} while your program is executing inside
10264 the block where @code{b} is declared.
10266 @cindex variable name conflict
10267 There is an exception: you can refer to a variable or function whose
10268 scope is a single source file even if the current execution point is not
10269 in this file. But it is possible to have more than one such variable or
10270 function with the same name (in different source files). If that
10271 happens, referring to that name has unpredictable effects. If you wish,
10272 you can specify a static variable in a particular function or file by
10273 using the colon-colon (@code{::}) notation:
10275 @cindex colon-colon, context for variables/functions
10277 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10278 @cindex @code{::}, context for variables/functions
10281 @var{file}::@var{variable}
10282 @var{function}::@var{variable}
10286 Here @var{file} or @var{function} is the name of the context for the
10287 static @var{variable}. In the case of file names, you can use quotes to
10288 make sure @value{GDBN} parses the file name as a single word---for example,
10289 to print a global value of @code{x} defined in @file{f2.c}:
10292 (@value{GDBP}) p 'f2.c'::x
10295 The @code{::} notation is normally used for referring to
10296 static variables, since you typically disambiguate uses of local variables
10297 in functions by selecting the appropriate frame and using the
10298 simple name of the variable. However, you may also use this notation
10299 to refer to local variables in frames enclosing the selected frame:
10308 process (a); /* Stop here */
10319 For example, if there is a breakpoint at the commented line,
10320 here is what you might see
10321 when the program stops after executing the call @code{bar(0)}:
10326 (@value{GDBP}) p bar::a
10328 (@value{GDBP}) up 2
10329 #2 0x080483d0 in foo (a=5) at foobar.c:12
10332 (@value{GDBP}) p bar::a
10336 @cindex C@t{++} scope resolution
10337 These uses of @samp{::} are very rarely in conflict with the very
10338 similar use of the same notation in C@t{++}. When they are in
10339 conflict, the C@t{++} meaning takes precedence; however, this can be
10340 overridden by quoting the file or function name with single quotes.
10342 For example, suppose the program is stopped in a method of a class
10343 that has a field named @code{includefile}, and there is also an
10344 include file named @file{includefile} that defines a variable,
10345 @code{some_global}.
10348 (@value{GDBP}) p includefile
10350 (@value{GDBP}) p includefile::some_global
10351 A syntax error in expression, near `'.
10352 (@value{GDBP}) p 'includefile'::some_global
10356 @cindex wrong values
10357 @cindex variable values, wrong
10358 @cindex function entry/exit, wrong values of variables
10359 @cindex optimized code, wrong values of variables
10361 @emph{Warning:} Occasionally, a local variable may appear to have the
10362 wrong value at certain points in a function---just after entry to a new
10363 scope, and just before exit.
10365 You may see this problem when you are stepping by machine instructions.
10366 This is because, on most machines, it takes more than one instruction to
10367 set up a stack frame (including local variable definitions); if you are
10368 stepping by machine instructions, variables may appear to have the wrong
10369 values until the stack frame is completely built. On exit, it usually
10370 also takes more than one machine instruction to destroy a stack frame;
10371 after you begin stepping through that group of instructions, local
10372 variable definitions may be gone.
10374 This may also happen when the compiler does significant optimizations.
10375 To be sure of always seeing accurate values, turn off all optimization
10378 @cindex ``No symbol "foo" in current context''
10379 Another possible effect of compiler optimizations is to optimize
10380 unused variables out of existence, or assign variables to registers (as
10381 opposed to memory addresses). Depending on the support for such cases
10382 offered by the debug info format used by the compiler, @value{GDBN}
10383 might not be able to display values for such local variables. If that
10384 happens, @value{GDBN} will print a message like this:
10387 No symbol "foo" in current context.
10390 To solve such problems, either recompile without optimizations, or use a
10391 different debug info format, if the compiler supports several such
10392 formats. @xref{Compilation}, for more information on choosing compiler
10393 options. @xref{C, ,C and C@t{++}}, for more information about debug
10394 info formats that are best suited to C@t{++} programs.
10396 If you ask to print an object whose contents are unknown to
10397 @value{GDBN}, e.g., because its data type is not completely specified
10398 by the debug information, @value{GDBN} will say @samp{<incomplete
10399 type>}. @xref{Symbols, incomplete type}, for more about this.
10401 @cindex no debug info variables
10402 If you try to examine or use the value of a (global) variable for
10403 which @value{GDBN} has no type information, e.g., because the program
10404 includes no debug information, @value{GDBN} displays an error message.
10405 @xref{Symbols, unknown type}, for more about unknown types. If you
10406 cast the variable to its declared type, @value{GDBN} gets the
10407 variable's value using the cast-to type as the variable's type. For
10408 example, in a C program:
10411 (@value{GDBP}) p var
10412 'var' has unknown type; cast it to its declared type
10413 (@value{GDBP}) p (float) var
10417 If you append @kbd{@@entry} string to a function parameter name you get its
10418 value at the time the function got called. If the value is not available an
10419 error message is printed. Entry values are available only with some compilers.
10420 Entry values are normally also printed at the function parameter list according
10421 to @ref{set print entry-values}.
10424 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10430 (gdb) print i@@entry
10434 Strings are identified as arrays of @code{char} values without specified
10435 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10436 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10437 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10438 defines literal string type @code{"char"} as @code{char} without a sign.
10443 signed char var1[] = "A";
10446 You get during debugging
10451 $2 = @{65 'A', 0 '\0'@}
10455 @section Artificial Arrays
10457 @cindex artificial array
10459 @kindex @@@r{, referencing memory as an array}
10460 It is often useful to print out several successive objects of the
10461 same type in memory; a section of an array, or an array of
10462 dynamically determined size for which only a pointer exists in the
10465 You can do this by referring to a contiguous span of memory as an
10466 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10467 operand of @samp{@@} should be the first element of the desired array
10468 and be an individual object. The right operand should be the desired length
10469 of the array. The result is an array value whose elements are all of
10470 the type of the left argument. The first element is actually the left
10471 argument; the second element comes from bytes of memory immediately
10472 following those that hold the first element, and so on. Here is an
10473 example. If a program says
10476 int *array = (int *) malloc (len * sizeof (int));
10480 you can print the contents of @code{array} with
10486 The left operand of @samp{@@} must reside in memory. Array values made
10487 with @samp{@@} in this way behave just like other arrays in terms of
10488 subscripting, and are coerced to pointers when used in expressions.
10489 Artificial arrays most often appear in expressions via the value history
10490 (@pxref{Value History, ,Value History}), after printing one out.
10492 Another way to create an artificial array is to use a cast.
10493 This re-interprets a value as if it were an array.
10494 The value need not be in memory:
10496 (@value{GDBP}) p/x (short[2])0x12345678
10497 $1 = @{0x1234, 0x5678@}
10500 As a convenience, if you leave the array length out (as in
10501 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10502 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10504 (@value{GDBP}) p/x (short[])0x12345678
10505 $2 = @{0x1234, 0x5678@}
10508 Sometimes the artificial array mechanism is not quite enough; in
10509 moderately complex data structures, the elements of interest may not
10510 actually be adjacent---for example, if you are interested in the values
10511 of pointers in an array. One useful work-around in this situation is
10512 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10513 Variables}) as a counter in an expression that prints the first
10514 interesting value, and then repeat that expression via @key{RET}. For
10515 instance, suppose you have an array @code{dtab} of pointers to
10516 structures, and you are interested in the values of a field @code{fv}
10517 in each structure. Here is an example of what you might type:
10527 @node Output Formats
10528 @section Output Formats
10530 @cindex formatted output
10531 @cindex output formats
10532 By default, @value{GDBN} prints a value according to its data type. Sometimes
10533 this is not what you want. For example, you might want to print a number
10534 in hex, or a pointer in decimal. Or you might want to view data in memory
10535 at a certain address as a character string or as an instruction. To do
10536 these things, specify an @dfn{output format} when you print a value.
10538 The simplest use of output formats is to say how to print a value
10539 already computed. This is done by starting the arguments of the
10540 @code{print} command with a slash and a format letter. The format
10541 letters supported are:
10545 Regard the bits of the value as an integer, and print the integer in
10549 Print as integer in signed decimal.
10552 Print as integer in unsigned decimal.
10555 Print as integer in octal.
10558 Print as integer in binary. The letter @samp{t} stands for ``two''.
10559 @footnote{@samp{b} cannot be used because these format letters are also
10560 used with the @code{x} command, where @samp{b} stands for ``byte'';
10561 see @ref{Memory,,Examining Memory}.}
10564 @cindex unknown address, locating
10565 @cindex locate address
10566 Print as an address, both absolute in hexadecimal and as an offset from
10567 the nearest preceding symbol. You can use this format used to discover
10568 where (in what function) an unknown address is located:
10571 (@value{GDBP}) p/a 0x54320
10572 $3 = 0x54320 <_initialize_vx+396>
10576 The command @code{info symbol 0x54320} yields similar results.
10577 @xref{Symbols, info symbol}.
10580 Regard as an integer and print it as a character constant. This
10581 prints both the numerical value and its character representation. The
10582 character representation is replaced with the octal escape @samp{\nnn}
10583 for characters outside the 7-bit @sc{ascii} range.
10585 Without this format, @value{GDBN} displays @code{char},
10586 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10587 constants. Single-byte members of vectors are displayed as integer
10591 Regard the bits of the value as a floating point number and print
10592 using typical floating point syntax.
10595 @cindex printing strings
10596 @cindex printing byte arrays
10597 Regard as a string, if possible. With this format, pointers to single-byte
10598 data are displayed as null-terminated strings and arrays of single-byte data
10599 are displayed as fixed-length strings. Other values are displayed in their
10602 Without this format, @value{GDBN} displays pointers to and arrays of
10603 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10604 strings. Single-byte members of a vector are displayed as an integer
10608 Like @samp{x} formatting, the value is treated as an integer and
10609 printed as hexadecimal, but leading zeros are printed to pad the value
10610 to the size of the integer type.
10613 @cindex raw printing
10614 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10615 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10616 Printing}). This typically results in a higher-level display of the
10617 value's contents. The @samp{r} format bypasses any Python
10618 pretty-printer which might exist.
10621 For example, to print the program counter in hex (@pxref{Registers}), type
10628 Note that no space is required before the slash; this is because command
10629 names in @value{GDBN} cannot contain a slash.
10631 To reprint the last value in the value history with a different format,
10632 you can use the @code{print} command with just a format and no
10633 expression. For example, @samp{p/x} reprints the last value in hex.
10636 @section Examining Memory
10638 You can use the command @code{x} (for ``examine'') to examine memory in
10639 any of several formats, independently of your program's data types.
10641 @cindex examining memory
10643 @kindex x @r{(examine memory)}
10644 @item x/@var{nfu} @var{addr}
10645 @itemx x @var{addr}
10647 Use the @code{x} command to examine memory.
10650 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10651 much memory to display and how to format it; @var{addr} is an
10652 expression giving the address where you want to start displaying memory.
10653 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10654 Several commands set convenient defaults for @var{addr}.
10657 @item @var{n}, the repeat count
10658 The repeat count is a decimal integer; the default is 1. It specifies
10659 how much memory (counting by units @var{u}) to display. If a negative
10660 number is specified, memory is examined backward from @var{addr}.
10661 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10664 @item @var{f}, the display format
10665 The display format is one of the formats used by @code{print}
10666 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10667 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
10668 The default is @samp{x} (hexadecimal) initially. The default changes
10669 each time you use either @code{x} or @code{print}.
10671 @item @var{u}, the unit size
10672 The unit size is any of
10678 Halfwords (two bytes).
10680 Words (four bytes). This is the initial default.
10682 Giant words (eight bytes).
10685 Each time you specify a unit size with @code{x}, that size becomes the
10686 default unit the next time you use @code{x}. For the @samp{i} format,
10687 the unit size is ignored and is normally not written. For the @samp{s} format,
10688 the unit size defaults to @samp{b}, unless it is explicitly given.
10689 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10690 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10691 Note that the results depend on the programming language of the
10692 current compilation unit. If the language is C, the @samp{s}
10693 modifier will use the UTF-16 encoding while @samp{w} will use
10694 UTF-32. The encoding is set by the programming language and cannot
10697 @item @var{addr}, starting display address
10698 @var{addr} is the address where you want @value{GDBN} to begin displaying
10699 memory. The expression need not have a pointer value (though it may);
10700 it is always interpreted as an integer address of a byte of memory.
10701 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10702 @var{addr} is usually just after the last address examined---but several
10703 other commands also set the default address: @code{info breakpoints} (to
10704 the address of the last breakpoint listed), @code{info line} (to the
10705 starting address of a line), and @code{print} (if you use it to display
10706 a value from memory).
10709 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10710 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10711 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10712 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10713 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10715 You can also specify a negative repeat count to examine memory backward
10716 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10717 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
10719 Since the letters indicating unit sizes are all distinct from the
10720 letters specifying output formats, you do not have to remember whether
10721 unit size or format comes first; either order works. The output
10722 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10723 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10725 Even though the unit size @var{u} is ignored for the formats @samp{s}
10726 and @samp{i}, you might still want to use a count @var{n}; for example,
10727 @samp{3i} specifies that you want to see three machine instructions,
10728 including any operands. For convenience, especially when used with
10729 the @code{display} command, the @samp{i} format also prints branch delay
10730 slot instructions, if any, beyond the count specified, which immediately
10731 follow the last instruction that is within the count. The command
10732 @code{disassemble} gives an alternative way of inspecting machine
10733 instructions; see @ref{Machine Code,,Source and Machine Code}.
10735 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10736 the command displays null-terminated strings or instructions before the given
10737 address as many as the absolute value of the given number. For the @samp{i}
10738 format, we use line number information in the debug info to accurately locate
10739 instruction boundaries while disassembling backward. If line info is not
10740 available, the command stops examining memory with an error message.
10742 All the defaults for the arguments to @code{x} are designed to make it
10743 easy to continue scanning memory with minimal specifications each time
10744 you use @code{x}. For example, after you have inspected three machine
10745 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10746 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10747 the repeat count @var{n} is used again; the other arguments default as
10748 for successive uses of @code{x}.
10750 When examining machine instructions, the instruction at current program
10751 counter is shown with a @code{=>} marker. For example:
10754 (@value{GDBP}) x/5i $pc-6
10755 0x804837f <main+11>: mov %esp,%ebp
10756 0x8048381 <main+13>: push %ecx
10757 0x8048382 <main+14>: sub $0x4,%esp
10758 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10759 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10762 @cindex @code{$_}, @code{$__}, and value history
10763 The addresses and contents printed by the @code{x} command are not saved
10764 in the value history because there is often too much of them and they
10765 would get in the way. Instead, @value{GDBN} makes these values available for
10766 subsequent use in expressions as values of the convenience variables
10767 @code{$_} and @code{$__}. After an @code{x} command, the last address
10768 examined is available for use in expressions in the convenience variable
10769 @code{$_}. The contents of that address, as examined, are available in
10770 the convenience variable @code{$__}.
10772 If the @code{x} command has a repeat count, the address and contents saved
10773 are from the last memory unit printed; this is not the same as the last
10774 address printed if several units were printed on the last line of output.
10776 @anchor{addressable memory unit}
10777 @cindex addressable memory unit
10778 Most targets have an addressable memory unit size of 8 bits. This means
10779 that to each memory address are associated 8 bits of data. Some
10780 targets, however, have other addressable memory unit sizes.
10781 Within @value{GDBN} and this document, the term
10782 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10783 when explicitly referring to a chunk of data of that size. The word
10784 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10785 the addressable memory unit size of the target. For most systems,
10786 addressable memory unit is a synonym of byte.
10788 @cindex remote memory comparison
10789 @cindex target memory comparison
10790 @cindex verify remote memory image
10791 @cindex verify target memory image
10792 When you are debugging a program running on a remote target machine
10793 (@pxref{Remote Debugging}), you may wish to verify the program's image
10794 in the remote machine's memory against the executable file you
10795 downloaded to the target. Or, on any target, you may want to check
10796 whether the program has corrupted its own read-only sections. The
10797 @code{compare-sections} command is provided for such situations.
10800 @kindex compare-sections
10801 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10802 Compare the data of a loadable section @var{section-name} in the
10803 executable file of the program being debugged with the same section in
10804 the target machine's memory, and report any mismatches. With no
10805 arguments, compares all loadable sections. With an argument of
10806 @code{-r}, compares all loadable read-only sections.
10808 Note: for remote targets, this command can be accelerated if the
10809 target supports computing the CRC checksum of a block of memory
10810 (@pxref{qCRC packet}).
10814 @section Automatic Display
10815 @cindex automatic display
10816 @cindex display of expressions
10818 If you find that you want to print the value of an expression frequently
10819 (to see how it changes), you might want to add it to the @dfn{automatic
10820 display list} so that @value{GDBN} prints its value each time your program stops.
10821 Each expression added to the list is given a number to identify it;
10822 to remove an expression from the list, you specify that number.
10823 The automatic display looks like this:
10827 3: bar[5] = (struct hack *) 0x3804
10831 This display shows item numbers, expressions and their current values. As with
10832 displays you request manually using @code{x} or @code{print}, you can
10833 specify the output format you prefer; in fact, @code{display} decides
10834 whether to use @code{print} or @code{x} depending your format
10835 specification---it uses @code{x} if you specify either the @samp{i}
10836 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10840 @item display @var{expr}
10841 Add the expression @var{expr} to the list of expressions to display
10842 each time your program stops. @xref{Expressions, ,Expressions}.
10844 @code{display} does not repeat if you press @key{RET} again after using it.
10846 @item display/@var{fmt} @var{expr}
10847 For @var{fmt} specifying only a display format and not a size or
10848 count, add the expression @var{expr} to the auto-display list but
10849 arrange to display it each time in the specified format @var{fmt}.
10850 @xref{Output Formats,,Output Formats}.
10852 @item display/@var{fmt} @var{addr}
10853 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10854 number of units, add the expression @var{addr} as a memory address to
10855 be examined each time your program stops. Examining means in effect
10856 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10859 For example, @samp{display/i $pc} can be helpful, to see the machine
10860 instruction about to be executed each time execution stops (@samp{$pc}
10861 is a common name for the program counter; @pxref{Registers, ,Registers}).
10864 @kindex delete display
10866 @item undisplay @var{dnums}@dots{}
10867 @itemx delete display @var{dnums}@dots{}
10868 Remove items from the list of expressions to display. Specify the
10869 numbers of the displays that you want affected with the command
10870 argument @var{dnums}. It can be a single display number, one of the
10871 numbers shown in the first field of the @samp{info display} display;
10872 or it could be a range of display numbers, as in @code{2-4}.
10874 @code{undisplay} does not repeat if you press @key{RET} after using it.
10875 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10877 @kindex disable display
10878 @item disable display @var{dnums}@dots{}
10879 Disable the display of item numbers @var{dnums}. A disabled display
10880 item is not printed automatically, but is not forgotten. It may be
10881 enabled again later. Specify the numbers of the displays that you
10882 want affected with the command argument @var{dnums}. It can be a
10883 single display number, one of the numbers shown in the first field of
10884 the @samp{info display} display; or it could be a range of display
10885 numbers, as in @code{2-4}.
10887 @kindex enable display
10888 @item enable display @var{dnums}@dots{}
10889 Enable display of item numbers @var{dnums}. It becomes effective once
10890 again in auto display of its expression, until you specify otherwise.
10891 Specify the numbers of the displays that you want affected with the
10892 command argument @var{dnums}. It can be a single display number, one
10893 of the numbers shown in the first field of the @samp{info display}
10894 display; or it could be a range of display numbers, as in @code{2-4}.
10897 Display the current values of the expressions on the list, just as is
10898 done when your program stops.
10900 @kindex info display
10902 Print the list of expressions previously set up to display
10903 automatically, each one with its item number, but without showing the
10904 values. This includes disabled expressions, which are marked as such.
10905 It also includes expressions which would not be displayed right now
10906 because they refer to automatic variables not currently available.
10909 @cindex display disabled out of scope
10910 If a display expression refers to local variables, then it does not make
10911 sense outside the lexical context for which it was set up. Such an
10912 expression is disabled when execution enters a context where one of its
10913 variables is not defined. For example, if you give the command
10914 @code{display last_char} while inside a function with an argument
10915 @code{last_char}, @value{GDBN} displays this argument while your program
10916 continues to stop inside that function. When it stops elsewhere---where
10917 there is no variable @code{last_char}---the display is disabled
10918 automatically. The next time your program stops where @code{last_char}
10919 is meaningful, you can enable the display expression once again.
10921 @node Print Settings
10922 @section Print Settings
10924 @cindex format options
10925 @cindex print settings
10926 @value{GDBN} provides the following ways to control how arrays, structures,
10927 and symbols are printed.
10930 These settings are useful for debugging programs in any language:
10934 @anchor{set print address}
10935 @item set print address
10936 @itemx set print address on
10937 @cindex print/don't print memory addresses
10938 @value{GDBN} prints memory addresses showing the location of stack
10939 traces, structure values, pointer values, breakpoints, and so forth,
10940 even when it also displays the contents of those addresses. The default
10941 is @code{on}. For example, this is what a stack frame display looks like with
10942 @code{set print address on}:
10947 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10949 530 if (lquote != def_lquote)
10953 @item set print address off
10954 Do not print addresses when displaying their contents. For example,
10955 this is the same stack frame displayed with @code{set print address off}:
10959 (@value{GDBP}) set print addr off
10961 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10962 530 if (lquote != def_lquote)
10966 You can use @samp{set print address off} to eliminate all machine
10967 dependent displays from the @value{GDBN} interface. For example, with
10968 @code{print address off}, you should get the same text for backtraces on
10969 all machines---whether or not they involve pointer arguments.
10972 @item show print address
10973 Show whether or not addresses are to be printed.
10976 When @value{GDBN} prints a symbolic address, it normally prints the
10977 closest earlier symbol plus an offset. If that symbol does not uniquely
10978 identify the address (for example, it is a name whose scope is a single
10979 source file), you may need to clarify. One way to do this is with
10980 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10981 you can set @value{GDBN} to print the source file and line number when
10982 it prints a symbolic address:
10985 @item set print symbol-filename on
10986 @cindex source file and line of a symbol
10987 @cindex symbol, source file and line
10988 Tell @value{GDBN} to print the source file name and line number of a
10989 symbol in the symbolic form of an address.
10991 @item set print symbol-filename off
10992 Do not print source file name and line number of a symbol. This is the
10995 @item show print symbol-filename
10996 Show whether or not @value{GDBN} will print the source file name and
10997 line number of a symbol in the symbolic form of an address.
11000 Another situation where it is helpful to show symbol filenames and line
11001 numbers is when disassembling code; @value{GDBN} shows you the line
11002 number and source file that corresponds to each instruction.
11004 Also, you may wish to see the symbolic form only if the address being
11005 printed is reasonably close to the closest earlier symbol:
11008 @item set print max-symbolic-offset @var{max-offset}
11009 @itemx set print max-symbolic-offset unlimited
11010 @cindex maximum value for offset of closest symbol
11011 Tell @value{GDBN} to only display the symbolic form of an address if the
11012 offset between the closest earlier symbol and the address is less than
11013 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11014 to always print the symbolic form of an address if any symbol precedes
11015 it. Zero is equivalent to @code{unlimited}.
11017 @item show print max-symbolic-offset
11018 Ask how large the maximum offset is that @value{GDBN} prints in a
11022 @cindex wild pointer, interpreting
11023 @cindex pointer, finding referent
11024 If you have a pointer and you are not sure where it points, try
11025 @samp{set print symbol-filename on}. Then you can determine the name
11026 and source file location of the variable where it points, using
11027 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11028 For example, here @value{GDBN} shows that a variable @code{ptt} points
11029 at another variable @code{t}, defined in @file{hi2.c}:
11032 (@value{GDBP}) set print symbol-filename on
11033 (@value{GDBP}) p/a ptt
11034 $4 = 0xe008 <t in hi2.c>
11038 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11039 does not show the symbol name and filename of the referent, even with
11040 the appropriate @code{set print} options turned on.
11043 You can also enable @samp{/a}-like formatting all the time using
11044 @samp{set print symbol on}:
11046 @anchor{set print symbol}
11048 @item set print symbol on
11049 Tell @value{GDBN} to print the symbol corresponding to an address, if
11052 @item set print symbol off
11053 Tell @value{GDBN} not to print the symbol corresponding to an
11054 address. In this mode, @value{GDBN} will still print the symbol
11055 corresponding to pointers to functions. This is the default.
11057 @item show print symbol
11058 Show whether @value{GDBN} will display the symbol corresponding to an
11062 Other settings control how different kinds of objects are printed:
11065 @anchor{set print array}
11066 @item set print array
11067 @itemx set print array on
11068 @cindex pretty print arrays
11069 Pretty print arrays. This format is more convenient to read,
11070 but uses more space. The default is off.
11072 @item set print array off
11073 Return to compressed format for arrays.
11075 @item show print array
11076 Show whether compressed or pretty format is selected for displaying
11079 @cindex print array indexes
11080 @anchor{set print array-indexes}
11081 @item set print array-indexes
11082 @itemx set print array-indexes on
11083 Print the index of each element when displaying arrays. May be more
11084 convenient to locate a given element in the array or quickly find the
11085 index of a given element in that printed array. The default is off.
11087 @item set print array-indexes off
11088 Stop printing element indexes when displaying arrays.
11090 @item show print array-indexes
11091 Show whether the index of each element is printed when displaying
11094 @anchor{set print elements}
11095 @item set print elements @var{number-of-elements}
11096 @itemx set print elements unlimited
11097 @cindex number of array elements to print
11098 @cindex limit on number of printed array elements
11099 Set a limit on how many elements of an array @value{GDBN} will print.
11100 If @value{GDBN} is printing a large array, it stops printing after it has
11101 printed the number of elements set by the @code{set print elements} command.
11102 This limit also applies to the display of strings.
11103 When @value{GDBN} starts, this limit is set to 200.
11104 Setting @var{number-of-elements} to @code{unlimited} or zero means
11105 that the number of elements to print is unlimited.
11107 @item show print elements
11108 Display the number of elements of a large array that @value{GDBN} will print.
11109 If the number is 0, then the printing is unlimited.
11111 @anchor{set print frame-arguments}
11112 @item set print frame-arguments @var{value}
11113 @kindex set print frame-arguments
11114 @cindex printing frame argument values
11115 @cindex print all frame argument values
11116 @cindex print frame argument values for scalars only
11117 @cindex do not print frame arguments
11118 This command allows to control how the values of arguments are printed
11119 when the debugger prints a frame (@pxref{Frames}). The possible
11124 The values of all arguments are printed.
11127 Print the value of an argument only if it is a scalar. The value of more
11128 complex arguments such as arrays, structures, unions, etc, is replaced
11129 by @code{@dots{}}. This is the default. Here is an example where
11130 only scalar arguments are shown:
11133 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11138 None of the argument values are printed. Instead, the value of each argument
11139 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11142 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11147 Only the presence of arguments is indicated by @code{@dots{}}.
11148 The @code{@dots{}} are not printed for function without any arguments.
11149 None of the argument names and values are printed.
11150 In this case, the example above now becomes:
11153 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11158 By default, only scalar arguments are printed. This command can be used
11159 to configure the debugger to print the value of all arguments, regardless
11160 of their type. However, it is often advantageous to not print the value
11161 of more complex parameters. For instance, it reduces the amount of
11162 information printed in each frame, making the backtrace more readable.
11163 Also, it improves performance when displaying Ada frames, because
11164 the computation of large arguments can sometimes be CPU-intensive,
11165 especially in large applications. Setting @code{print frame-arguments}
11166 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11167 this computation, thus speeding up the display of each Ada frame.
11169 @item show print frame-arguments
11170 Show how the value of arguments should be displayed when printing a frame.
11172 @anchor{set print raw-frame-arguments}
11173 @item set print raw-frame-arguments on
11174 Print frame arguments in raw, non pretty-printed, form.
11176 @item set print raw-frame-arguments off
11177 Print frame arguments in pretty-printed form, if there is a pretty-printer
11178 for the value (@pxref{Pretty Printing}),
11179 otherwise print the value in raw form.
11180 This is the default.
11182 @item show print raw-frame-arguments
11183 Show whether to print frame arguments in raw form.
11185 @anchor{set print entry-values}
11186 @item set print entry-values @var{value}
11187 @kindex set print entry-values
11188 Set printing of frame argument values at function entry. In some cases
11189 @value{GDBN} can determine the value of function argument which was passed by
11190 the function caller, even if the value was modified inside the called function
11191 and therefore is different. With optimized code, the current value could be
11192 unavailable, but the entry value may still be known.
11194 The default value is @code{default} (see below for its description). Older
11195 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11196 this feature will behave in the @code{default} setting the same way as with the
11199 This functionality is currently supported only by DWARF 2 debugging format and
11200 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11201 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11204 The @var{value} parameter can be one of the following:
11208 Print only actual parameter values, never print values from function entry
11212 #0 different (val=6)
11213 #0 lost (val=<optimized out>)
11215 #0 invalid (val=<optimized out>)
11219 Print only parameter values from function entry point. The actual parameter
11220 values are never printed.
11222 #0 equal (val@@entry=5)
11223 #0 different (val@@entry=5)
11224 #0 lost (val@@entry=5)
11225 #0 born (val@@entry=<optimized out>)
11226 #0 invalid (val@@entry=<optimized out>)
11230 Print only parameter values from function entry point. If value from function
11231 entry point is not known while the actual value is known, print the actual
11232 value for such parameter.
11234 #0 equal (val@@entry=5)
11235 #0 different (val@@entry=5)
11236 #0 lost (val@@entry=5)
11238 #0 invalid (val@@entry=<optimized out>)
11242 Print actual parameter values. If actual parameter value is not known while
11243 value from function entry point is known, print the entry point value for such
11247 #0 different (val=6)
11248 #0 lost (val@@entry=5)
11250 #0 invalid (val=<optimized out>)
11254 Always print both the actual parameter value and its value from function entry
11255 point, even if values of one or both are not available due to compiler
11258 #0 equal (val=5, val@@entry=5)
11259 #0 different (val=6, val@@entry=5)
11260 #0 lost (val=<optimized out>, val@@entry=5)
11261 #0 born (val=10, val@@entry=<optimized out>)
11262 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11266 Print the actual parameter value if it is known and also its value from
11267 function entry point if it is known. If neither is known, print for the actual
11268 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11269 values are known and identical, print the shortened
11270 @code{param=param@@entry=VALUE} notation.
11272 #0 equal (val=val@@entry=5)
11273 #0 different (val=6, val@@entry=5)
11274 #0 lost (val@@entry=5)
11276 #0 invalid (val=<optimized out>)
11280 Always print the actual parameter value. Print also its value from function
11281 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11282 if both values are known and identical, print the shortened
11283 @code{param=param@@entry=VALUE} notation.
11285 #0 equal (val=val@@entry=5)
11286 #0 different (val=6, val@@entry=5)
11287 #0 lost (val=<optimized out>, val@@entry=5)
11289 #0 invalid (val=<optimized out>)
11293 For analysis messages on possible failures of frame argument values at function
11294 entry resolution see @ref{set debug entry-values}.
11296 @item show print entry-values
11297 Show the method being used for printing of frame argument values at function
11300 @anchor{set print frame-info}
11301 @item set print frame-info @var{value}
11302 @kindex set print frame-info
11303 @cindex printing frame information
11304 @cindex frame information, printing
11305 This command allows to control the information printed when
11306 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11307 for a general explanation about frames and frame information.
11308 Note that some other settings (such as @code{set print frame-arguments}
11309 and @code{set print address}) are also influencing if and how some frame
11310 information is displayed. In particular, the frame program counter is never
11311 printed if @code{set print address} is off.
11313 The possible values for @code{set print frame-info} are:
11315 @item short-location
11316 Print the frame level, the program counter (if not at the
11317 beginning of the location source line), the function, the function
11320 Same as @code{short-location} but also print the source file and source line
11322 @item location-and-address
11323 Same as @code{location} but print the program counter even if located at the
11324 beginning of the location source line.
11326 Print the program counter (if not at the beginning of the location
11327 source line), the line number and the source line.
11328 @item source-and-location
11329 Print what @code{location} and @code{source-line} are printing.
11331 The information printed for a frame is decided automatically
11332 by the @value{GDBN} command that prints a frame.
11333 For example, @code{frame} prints the information printed by
11334 @code{source-and-location} while @code{stepi} will switch between
11335 @code{source-line} and @code{source-and-location} depending on the program
11337 The default value is @code{auto}.
11340 @anchor{set print repeats}
11341 @item set print repeats @var{number-of-repeats}
11342 @itemx set print repeats unlimited
11343 @cindex repeated array elements
11344 Set the threshold for suppressing display of repeated array
11345 elements. When the number of consecutive identical elements of an
11346 array exceeds the threshold, @value{GDBN} prints the string
11347 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11348 identical repetitions, instead of displaying the identical elements
11349 themselves. Setting the threshold to @code{unlimited} or zero will
11350 cause all elements to be individually printed. The default threshold
11353 @item show print repeats
11354 Display the current threshold for printing repeated identical
11357 @anchor{set print max-depth}
11358 @item set print max-depth @var{depth}
11359 @item set print max-depth unlimited
11360 @cindex printing nested structures
11361 Set the threshold after which nested structures are replaced with
11362 ellipsis, this can make visualising deeply nested structures easier.
11364 For example, given this C code
11367 typedef struct s1 @{ int a; @} s1;
11368 typedef struct s2 @{ s1 b; @} s2;
11369 typedef struct s3 @{ s2 c; @} s3;
11370 typedef struct s4 @{ s3 d; @} s4;
11372 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11375 The following table shows how different values of @var{depth} will
11376 effect how @code{var} is printed by @value{GDBN}:
11378 @multitable @columnfractions .3 .7
11379 @headitem @var{depth} setting @tab Result of @samp{p var}
11381 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11383 @tab @code{$1 = @{...@}}
11385 @tab @code{$1 = @{d = @{...@}@}}
11387 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11389 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11391 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11394 To see the contents of structures that have been hidden the user can
11395 either increase the print max-depth, or they can print the elements of
11396 the structure that are visible, for example
11399 (gdb) set print max-depth 2
11401 $1 = @{d = @{c = @{...@}@}@}
11403 $2 = @{c = @{b = @{...@}@}@}
11405 $3 = @{b = @{a = 3@}@}
11408 The pattern used to replace nested structures varies based on
11409 language, for most languages @code{@{...@}} is used, but Fortran uses
11412 @item show print max-depth
11413 Display the current threshold after which nested structures are
11414 replaces with ellipsis.
11416 @anchor{set print null-stop}
11417 @item set print null-stop
11418 @cindex @sc{null} elements in arrays
11419 Cause @value{GDBN} to stop printing the characters of an array when the first
11420 @sc{null} is encountered. This is useful when large arrays actually
11421 contain only short strings.
11422 The default is off.
11424 @item show print null-stop
11425 Show whether @value{GDBN} stops printing an array on the first
11426 @sc{null} character.
11428 @anchor{set print pretty}
11429 @item set print pretty on
11430 @cindex print structures in indented form
11431 @cindex indentation in structure display
11432 Cause @value{GDBN} to print structures in an indented format with one member
11433 per line, like this:
11448 @item set print pretty off
11449 Cause @value{GDBN} to print structures in a compact format, like this:
11453 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11454 meat = 0x54 "Pork"@}
11459 This is the default format.
11461 @item show print pretty
11462 Show which format @value{GDBN} is using to print structures.
11464 @anchor{set print raw-values}
11465 @item set print raw-values on
11466 Print values in raw form, without applying the pretty
11467 printers for the value.
11469 @item set print raw-values off
11470 Print values in pretty-printed form, if there is a pretty-printer
11471 for the value (@pxref{Pretty Printing}),
11472 otherwise print the value in raw form.
11474 The default setting is ``off''.
11476 @item show print raw-values
11477 Show whether to print values in raw form.
11479 @item set print sevenbit-strings on
11480 @cindex eight-bit characters in strings
11481 @cindex octal escapes in strings
11482 Print using only seven-bit characters; if this option is set,
11483 @value{GDBN} displays any eight-bit characters (in strings or
11484 character values) using the notation @code{\}@var{nnn}. This setting is
11485 best if you are working in English (@sc{ascii}) and you use the
11486 high-order bit of characters as a marker or ``meta'' bit.
11488 @item set print sevenbit-strings off
11489 Print full eight-bit characters. This allows the use of more
11490 international character sets, and is the default.
11492 @item show print sevenbit-strings
11493 Show whether or not @value{GDBN} is printing only seven-bit characters.
11495 @anchor{set print union}
11496 @item set print union on
11497 @cindex unions in structures, printing
11498 Tell @value{GDBN} to print unions which are contained in structures
11499 and other unions. This is the default setting.
11501 @item set print union off
11502 Tell @value{GDBN} not to print unions which are contained in
11503 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11506 @item show print union
11507 Ask @value{GDBN} whether or not it will print unions which are contained in
11508 structures and other unions.
11510 For example, given the declarations
11513 typedef enum @{Tree, Bug@} Species;
11514 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11515 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11526 struct thing foo = @{Tree, @{Acorn@}@};
11530 with @code{set print union on} in effect @samp{p foo} would print
11533 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11537 and with @code{set print union off} in effect it would print
11540 $1 = @{it = Tree, form = @{...@}@}
11544 @code{set print union} affects programs written in C-like languages
11550 These settings are of interest when debugging C@t{++} programs:
11553 @cindex demangling C@t{++} names
11554 @item set print demangle
11555 @itemx set print demangle on
11556 Print C@t{++} names in their source form rather than in the encoded
11557 (``mangled'') form passed to the assembler and linker for type-safe
11558 linkage. The default is on.
11560 @item show print demangle
11561 Show whether C@t{++} names are printed in mangled or demangled form.
11563 @item set print asm-demangle
11564 @itemx set print asm-demangle on
11565 Print C@t{++} names in their source form rather than their mangled form, even
11566 in assembler code printouts such as instruction disassemblies.
11567 The default is off.
11569 @item show print asm-demangle
11570 Show whether C@t{++} names in assembly listings are printed in mangled
11573 @cindex C@t{++} symbol decoding style
11574 @cindex symbol decoding style, C@t{++}
11575 @kindex set demangle-style
11576 @item set demangle-style @var{style}
11577 Choose among several encoding schemes used by different compilers to represent
11578 C@t{++} names. If you omit @var{style}, you will see a list of possible
11579 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11580 decoding style by inspecting your program.
11582 @item show demangle-style
11583 Display the encoding style currently in use for decoding C@t{++} symbols.
11585 @anchor{set print object}
11586 @item set print object
11587 @itemx set print object on
11588 @cindex derived type of an object, printing
11589 @cindex display derived types
11590 When displaying a pointer to an object, identify the @emph{actual}
11591 (derived) type of the object rather than the @emph{declared} type, using
11592 the virtual function table. Note that the virtual function table is
11593 required---this feature can only work for objects that have run-time
11594 type identification; a single virtual method in the object's declared
11595 type is sufficient. Note that this setting is also taken into account when
11596 working with variable objects via MI (@pxref{GDB/MI}).
11598 @item set print object off
11599 Display only the declared type of objects, without reference to the
11600 virtual function table. This is the default setting.
11602 @item show print object
11603 Show whether actual, or declared, object types are displayed.
11605 @anchor{set print static-members}
11606 @item set print static-members
11607 @itemx set print static-members on
11608 @cindex static members of C@t{++} objects
11609 Print static members when displaying a C@t{++} object. The default is on.
11611 @item set print static-members off
11612 Do not print static members when displaying a C@t{++} object.
11614 @item show print static-members
11615 Show whether C@t{++} static members are printed or not.
11617 @item set print pascal_static-members
11618 @itemx set print pascal_static-members on
11619 @cindex static members of Pascal objects
11620 @cindex Pascal objects, static members display
11621 Print static members when displaying a Pascal object. The default is on.
11623 @item set print pascal_static-members off
11624 Do not print static members when displaying a Pascal object.
11626 @item show print pascal_static-members
11627 Show whether Pascal static members are printed or not.
11629 @c These don't work with HP ANSI C++ yet.
11630 @anchor{set print vtbl}
11631 @item set print vtbl
11632 @itemx set print vtbl on
11633 @cindex pretty print C@t{++} virtual function tables
11634 @cindex virtual functions (C@t{++}) display
11635 @cindex VTBL display
11636 Pretty print C@t{++} virtual function tables. The default is off.
11637 (The @code{vtbl} commands do not work on programs compiled with the HP
11638 ANSI C@t{++} compiler (@code{aCC}).)
11640 @item set print vtbl off
11641 Do not pretty print C@t{++} virtual function tables.
11643 @item show print vtbl
11644 Show whether C@t{++} virtual function tables are pretty printed, or not.
11647 @node Pretty Printing
11648 @section Pretty Printing
11650 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11651 Python code. It greatly simplifies the display of complex objects. This
11652 mechanism works for both MI and the CLI.
11655 * Pretty-Printer Introduction:: Introduction to pretty-printers
11656 * Pretty-Printer Example:: An example pretty-printer
11657 * Pretty-Printer Commands:: Pretty-printer commands
11660 @node Pretty-Printer Introduction
11661 @subsection Pretty-Printer Introduction
11663 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11664 registered for the value. If there is then @value{GDBN} invokes the
11665 pretty-printer to print the value. Otherwise the value is printed normally.
11667 Pretty-printers are normally named. This makes them easy to manage.
11668 The @samp{info pretty-printer} command will list all the installed
11669 pretty-printers with their names.
11670 If a pretty-printer can handle multiple data types, then its
11671 @dfn{subprinters} are the printers for the individual data types.
11672 Each such subprinter has its own name.
11673 The format of the name is @var{printer-name};@var{subprinter-name}.
11675 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11676 Typically they are automatically loaded and registered when the corresponding
11677 debug information is loaded, thus making them available without having to
11678 do anything special.
11680 There are three places where a pretty-printer can be registered.
11684 Pretty-printers registered globally are available when debugging
11688 Pretty-printers registered with a program space are available only
11689 when debugging that program.
11690 @xref{Progspaces In Python}, for more details on program spaces in Python.
11693 Pretty-printers registered with an objfile are loaded and unloaded
11694 with the corresponding objfile (e.g., shared library).
11695 @xref{Objfiles In Python}, for more details on objfiles in Python.
11698 @xref{Selecting Pretty-Printers}, for further information on how
11699 pretty-printers are selected,
11701 @xref{Writing a Pretty-Printer}, for implementing pretty printers
11704 @node Pretty-Printer Example
11705 @subsection Pretty-Printer Example
11707 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
11710 (@value{GDBP}) print s
11712 static npos = 4294967295,
11714 <std::allocator<char>> = @{
11715 <__gnu_cxx::new_allocator<char>> = @{
11716 <No data fields>@}, <No data fields>
11718 members of std::basic_string<char, std::char_traits<char>,
11719 std::allocator<char> >::_Alloc_hider:
11720 _M_p = 0x804a014 "abcd"
11725 With a pretty-printer for @code{std::string} only the contents are printed:
11728 (@value{GDBP}) print s
11732 @node Pretty-Printer Commands
11733 @subsection Pretty-Printer Commands
11734 @cindex pretty-printer commands
11737 @kindex info pretty-printer
11738 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11739 Print the list of installed pretty-printers.
11740 This includes disabled pretty-printers, which are marked as such.
11742 @var{object-regexp} is a regular expression matching the objects
11743 whose pretty-printers to list.
11744 Objects can be @code{global}, the program space's file
11745 (@pxref{Progspaces In Python}),
11746 and the object files within that program space (@pxref{Objfiles In Python}).
11747 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
11748 looks up a printer from these three objects.
11750 @var{name-regexp} is a regular expression matching the name of the printers
11753 @kindex disable pretty-printer
11754 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11755 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11756 A disabled pretty-printer is not forgotten, it may be enabled again later.
11758 @kindex enable pretty-printer
11759 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
11760 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
11765 Suppose we have three pretty-printers installed: one from library1.so
11766 named @code{foo} that prints objects of type @code{foo}, and
11767 another from library2.so named @code{bar} that prints two types of objects,
11768 @code{bar1} and @code{bar2}.
11771 (gdb) info pretty-printer
11778 (gdb) info pretty-printer library2
11783 (gdb) disable pretty-printer library1
11785 2 of 3 printers enabled
11786 (gdb) info pretty-printer
11793 (gdb) disable pretty-printer library2 bar;bar1
11795 1 of 3 printers enabled
11796 (gdb) info pretty-printer library2
11803 (gdb) disable pretty-printer library2 bar
11805 0 of 3 printers enabled
11806 (gdb) info pretty-printer library2
11815 Note that for @code{bar} the entire printer can be disabled,
11816 as can each individual subprinter.
11818 Printing values and frame arguments is done by default using
11819 the enabled pretty printers.
11821 The print option @code{-raw-values} and @value{GDBN} setting
11822 @code{set print raw-values} (@pxref{set print raw-values}) can be
11823 used to print values without applying the enabled pretty printers.
11825 Similarly, the backtrace option @code{-raw-frame-arguments} and
11826 @value{GDBN} setting @code{set print raw-frame-arguments}
11827 (@pxref{set print raw-frame-arguments}) can be used to ignore the
11828 enabled pretty printers when printing frame argument values.
11830 @node Value History
11831 @section Value History
11833 @cindex value history
11834 @cindex history of values printed by @value{GDBN}
11835 Values printed by the @code{print} command are saved in the @value{GDBN}
11836 @dfn{value history}. This allows you to refer to them in other expressions.
11837 Values are kept until the symbol table is re-read or discarded
11838 (for example with the @code{file} or @code{symbol-file} commands).
11839 When the symbol table changes, the value history is discarded,
11840 since the values may contain pointers back to the types defined in the
11845 @cindex history number
11846 The values printed are given @dfn{history numbers} by which you can
11847 refer to them. These are successive integers starting with one.
11848 @code{print} shows you the history number assigned to a value by
11849 printing @samp{$@var{num} = } before the value; here @var{num} is the
11852 To refer to any previous value, use @samp{$} followed by the value's
11853 history number. The way @code{print} labels its output is designed to
11854 remind you of this. Just @code{$} refers to the most recent value in
11855 the history, and @code{$$} refers to the value before that.
11856 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
11857 is the value just prior to @code{$$}, @code{$$1} is equivalent to
11858 @code{$$}, and @code{$$0} is equivalent to @code{$}.
11860 For example, suppose you have just printed a pointer to a structure and
11861 want to see the contents of the structure. It suffices to type
11867 If you have a chain of structures where the component @code{next} points
11868 to the next one, you can print the contents of the next one with this:
11875 You can print successive links in the chain by repeating this
11876 command---which you can do by just typing @key{RET}.
11878 Note that the history records values, not expressions. If the value of
11879 @code{x} is 4 and you type these commands:
11887 then the value recorded in the value history by the @code{print} command
11888 remains 4 even though the value of @code{x} has changed.
11891 @kindex show values
11893 Print the last ten values in the value history, with their item numbers.
11894 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11895 values} does not change the history.
11897 @item show values @var{n}
11898 Print ten history values centered on history item number @var{n}.
11900 @item show values +
11901 Print ten history values just after the values last printed. If no more
11902 values are available, @code{show values +} produces no display.
11905 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11906 same effect as @samp{show values +}.
11908 @node Convenience Vars
11909 @section Convenience Variables
11911 @cindex convenience variables
11912 @cindex user-defined variables
11913 @value{GDBN} provides @dfn{convenience variables} that you can use within
11914 @value{GDBN} to hold on to a value and refer to it later. These variables
11915 exist entirely within @value{GDBN}; they are not part of your program, and
11916 setting a convenience variable has no direct effect on further execution
11917 of your program. That is why you can use them freely.
11919 Convenience variables are prefixed with @samp{$}. Any name preceded by
11920 @samp{$} can be used for a convenience variable, unless it is one of
11921 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11922 (Value history references, in contrast, are @emph{numbers} preceded
11923 by @samp{$}. @xref{Value History, ,Value History}.)
11925 You can save a value in a convenience variable with an assignment
11926 expression, just as you would set a variable in your program.
11930 set $foo = *object_ptr
11934 would save in @code{$foo} the value contained in the object pointed to by
11937 Using a convenience variable for the first time creates it, but its
11938 value is @code{void} until you assign a new value. You can alter the
11939 value with another assignment at any time.
11941 Convenience variables have no fixed types. You can assign a convenience
11942 variable any type of value, including structures and arrays, even if
11943 that variable already has a value of a different type. The convenience
11944 variable, when used as an expression, has the type of its current value.
11947 @kindex show convenience
11948 @cindex show all user variables and functions
11949 @item show convenience
11950 Print a list of convenience variables used so far, and their values,
11951 as well as a list of the convenience functions.
11952 Abbreviated @code{show conv}.
11954 @kindex init-if-undefined
11955 @cindex convenience variables, initializing
11956 @item init-if-undefined $@var{variable} = @var{expression}
11957 Set a convenience variable if it has not already been set. This is useful
11958 for user-defined commands that keep some state. It is similar, in concept,
11959 to using local static variables with initializers in C (except that
11960 convenience variables are global). It can also be used to allow users to
11961 override default values used in a command script.
11963 If the variable is already defined then the expression is not evaluated so
11964 any side-effects do not occur.
11967 One of the ways to use a convenience variable is as a counter to be
11968 incremented or a pointer to be advanced. For example, to print
11969 a field from successive elements of an array of structures:
11973 print bar[$i++]->contents
11977 Repeat that command by typing @key{RET}.
11979 Some convenience variables are created automatically by @value{GDBN} and given
11980 values likely to be useful.
11983 @vindex $_@r{, convenience variable}
11985 The variable @code{$_} is automatically set by the @code{x} command to
11986 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11987 commands which provide a default address for @code{x} to examine also
11988 set @code{$_} to that address; these commands include @code{info line}
11989 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11990 except when set by the @code{x} command, in which case it is a pointer
11991 to the type of @code{$__}.
11993 @vindex $__@r{, convenience variable}
11995 The variable @code{$__} is automatically set by the @code{x} command
11996 to the value found in the last address examined. Its type is chosen
11997 to match the format in which the data was printed.
12000 @vindex $_exitcode@r{, convenience variable}
12001 When the program being debugged terminates normally, @value{GDBN}
12002 automatically sets this variable to the exit code of the program, and
12003 resets @code{$_exitsignal} to @code{void}.
12006 @vindex $_exitsignal@r{, convenience variable}
12007 When the program being debugged dies due to an uncaught signal,
12008 @value{GDBN} automatically sets this variable to that signal's number,
12009 and resets @code{$_exitcode} to @code{void}.
12011 To distinguish between whether the program being debugged has exited
12012 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12013 @code{$_exitsignal} is not @code{void}), the convenience function
12014 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12015 Functions}). For example, considering the following source code:
12018 #include <signal.h>
12021 main (int argc, char *argv[])
12028 A valid way of telling whether the program being debugged has exited
12029 or signalled would be:
12032 (@value{GDBP}) define has_exited_or_signalled
12033 Type commands for definition of ``has_exited_or_signalled''.
12034 End with a line saying just ``end''.
12035 >if $_isvoid ($_exitsignal)
12036 >echo The program has exited\n
12038 >echo The program has signalled\n
12044 Program terminated with signal SIGALRM, Alarm clock.
12045 The program no longer exists.
12046 (@value{GDBP}) has_exited_or_signalled
12047 The program has signalled
12050 As can be seen, @value{GDBN} correctly informs that the program being
12051 debugged has signalled, since it calls @code{raise} and raises a
12052 @code{SIGALRM} signal. If the program being debugged had not called
12053 @code{raise}, then @value{GDBN} would report a normal exit:
12056 (@value{GDBP}) has_exited_or_signalled
12057 The program has exited
12061 The variable @code{$_exception} is set to the exception object being
12062 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12064 @item $_ada_exception
12065 The variable @code{$_ada_exception} is set to the address of the
12066 exception being caught or thrown at an Ada exception-related
12067 catchpoint. @xref{Set Catchpoints}.
12070 @itemx $_probe_arg0@dots{}$_probe_arg11
12071 Arguments to a static probe. @xref{Static Probe Points}.
12074 @vindex $_sdata@r{, inspect, convenience variable}
12075 The variable @code{$_sdata} contains extra collected static tracepoint
12076 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12077 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12078 if extra static tracepoint data has not been collected.
12081 @vindex $_siginfo@r{, convenience variable}
12082 The variable @code{$_siginfo} contains extra signal information
12083 (@pxref{extra signal information}). Note that @code{$_siginfo}
12084 could be empty, if the application has not yet received any signals.
12085 For example, it will be empty before you execute the @code{run} command.
12088 @vindex $_tlb@r{, convenience variable}
12089 The variable @code{$_tlb} is automatically set when debugging
12090 applications running on MS-Windows in native mode or connected to
12091 gdbserver that supports the @code{qGetTIBAddr} request.
12092 @xref{General Query Packets}.
12093 This variable contains the address of the thread information block.
12096 The number of the current inferior. @xref{Inferiors Connections and
12097 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12100 The thread number of the current thread. @xref{thread numbers}.
12103 The global number of the current thread. @xref{global thread numbers}.
12107 @vindex $_gdb_major@r{, convenience variable}
12108 @vindex $_gdb_minor@r{, convenience variable}
12109 The major and minor version numbers of the running @value{GDBN}.
12110 Development snapshots and pretest versions have their minor version
12111 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12112 the value 12 for @code{$_gdb_minor}. These variables allow you to
12113 write scripts that work with different versions of @value{GDBN}
12114 without errors caused by features unavailable in some of those
12117 @item $_shell_exitcode
12118 @itemx $_shell_exitsignal
12119 @vindex $_shell_exitcode@r{, convenience variable}
12120 @vindex $_shell_exitsignal@r{, convenience variable}
12121 @cindex shell command, exit code
12122 @cindex shell command, exit signal
12123 @cindex exit status of shell commands
12124 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12125 shell commands. When a launched command terminates, @value{GDBN}
12126 automatically maintains the variables @code{$_shell_exitcode}
12127 and @code{$_shell_exitsignal} according to the exit status of the last
12128 launched command. These variables are set and used similarly to
12129 the variables @code{$_exitcode} and @code{$_exitsignal}.
12133 @node Convenience Funs
12134 @section Convenience Functions
12136 @cindex convenience functions
12137 @value{GDBN} also supplies some @dfn{convenience functions}. These
12138 have a syntax similar to convenience variables. A convenience
12139 function can be used in an expression just like an ordinary function;
12140 however, a convenience function is implemented internally to
12143 These functions do not require @value{GDBN} to be configured with
12144 @code{Python} support, which means that they are always available.
12148 @item $_isvoid (@var{expr})
12149 @findex $_isvoid@r{, convenience function}
12150 Return one if the expression @var{expr} is @code{void}. Otherwise it
12153 A @code{void} expression is an expression where the type of the result
12154 is @code{void}. For example, you can examine a convenience variable
12155 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12159 (@value{GDBP}) print $_exitcode
12161 (@value{GDBP}) print $_isvoid ($_exitcode)
12164 Starting program: ./a.out
12165 [Inferior 1 (process 29572) exited normally]
12166 (@value{GDBP}) print $_exitcode
12168 (@value{GDBP}) print $_isvoid ($_exitcode)
12172 In the example above, we used @code{$_isvoid} to check whether
12173 @code{$_exitcode} is @code{void} before and after the execution of the
12174 program being debugged. Before the execution there is no exit code to
12175 be examined, therefore @code{$_exitcode} is @code{void}. After the
12176 execution the program being debugged returned zero, therefore
12177 @code{$_exitcode} is zero, which means that it is not @code{void}
12180 The @code{void} expression can also be a call of a function from the
12181 program being debugged. For example, given the following function:
12190 The result of calling it inside @value{GDBN} is @code{void}:
12193 (@value{GDBP}) print foo ()
12195 (@value{GDBP}) print $_isvoid (foo ())
12197 (@value{GDBP}) set $v = foo ()
12198 (@value{GDBP}) print $v
12200 (@value{GDBP}) print $_isvoid ($v)
12204 @item $_gdb_setting_str (@var{setting})
12205 @findex $_gdb_setting_str@r{, convenience function}
12206 Return the value of the @value{GDBN} @var{setting} as a string.
12207 @var{setting} is any setting that can be used in a @code{set} or
12208 @code{show} command (@pxref{Controlling GDB}).
12211 (@value{GDBP}) show print frame-arguments
12212 Printing of non-scalar frame arguments is "scalars".
12213 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12215 (@value{GDBP}) p $_gdb_setting_str("height")
12220 @item $_gdb_setting (@var{setting})
12221 @findex $_gdb_setting@r{, convenience function}
12222 Return the value of the @value{GDBN} @var{setting}.
12223 The type of the returned value depends on the setting.
12225 The value type for boolean and auto boolean settings is @code{int}.
12226 The boolean values @code{off} and @code{on} are converted to
12227 the integer values @code{0} and @code{1}. The value @code{auto} is
12228 converted to the value @code{-1}.
12230 The value type for integer settings is either @code{unsigned int}
12231 or @code{int}, depending on the setting.
12233 Some integer settings accept an @code{unlimited} value.
12234 Depending on the setting, the @code{set} command also accepts
12235 the value @code{0} or the value @code{@minus{}1} as a synonym for
12237 For example, @code{set height unlimited} is equivalent to
12238 @code{set height 0}.
12240 Some other settings that accept the @code{unlimited} value
12241 use the value @code{0} to literally mean zero.
12242 For example, @code{set history size 0} indicates to not
12243 record any @value{GDBN} commands in the command history.
12244 For such settings, @code{@minus{}1} is the synonym
12245 for @code{unlimited}.
12247 See the documentation of the corresponding @code{set} command for
12248 the numerical value equivalent to @code{unlimited}.
12250 The @code{$_gdb_setting} function converts the unlimited value
12251 to a @code{0} or a @code{@minus{}1} value according to what the
12252 @code{set} command uses.
12256 (@value{GDBP}) p $_gdb_setting_str("height")
12258 (@value{GDBP}) p $_gdb_setting("height")
12260 (@value{GDBP}) set height unlimited
12261 (@value{GDBP}) p $_gdb_setting_str("height")
12263 (@value{GDBP}) p $_gdb_setting("height")
12267 (@value{GDBP}) p $_gdb_setting_str("history size")
12269 (@value{GDBP}) p $_gdb_setting("history size")
12271 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12273 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12279 Other setting types (enum, filename, optional filename, string, string noescape)
12280 are returned as string values.
12283 @item $_gdb_maint_setting_str (@var{setting})
12284 @findex $_gdb_maint_setting_str@r{, convenience function}
12285 Like the @code{$_gdb_setting_str} function, but works with
12286 @code{maintenance set} variables.
12288 @item $_gdb_maint_setting (@var{setting})
12289 @findex $_gdb_maint_setting@r{, convenience function}
12290 Like the @code{$_gdb_setting} function, but works with
12291 @code{maintenance set} variables.
12295 The following functions require @value{GDBN} to be configured with
12296 @code{Python} support.
12300 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12301 @findex $_memeq@r{, convenience function}
12302 Returns one if the @var{length} bytes at the addresses given by
12303 @var{buf1} and @var{buf2} are equal.
12304 Otherwise it returns zero.
12306 @item $_regex(@var{str}, @var{regex})
12307 @findex $_regex@r{, convenience function}
12308 Returns one if the string @var{str} matches the regular expression
12309 @var{regex}. Otherwise it returns zero.
12310 The syntax of the regular expression is that specified by @code{Python}'s
12311 regular expression support.
12313 @item $_streq(@var{str1}, @var{str2})
12314 @findex $_streq@r{, convenience function}
12315 Returns one if the strings @var{str1} and @var{str2} are equal.
12316 Otherwise it returns zero.
12318 @item $_strlen(@var{str})
12319 @findex $_strlen@r{, convenience function}
12320 Returns the length of string @var{str}.
12322 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12323 @findex $_caller_is@r{, convenience function}
12324 Returns one if the calling function's name is equal to @var{name}.
12325 Otherwise it returns zero.
12327 If the optional argument @var{number_of_frames} is provided,
12328 it is the number of frames up in the stack to look.
12336 at testsuite/gdb.python/py-caller-is.c:21
12337 #1 0x00000000004005a0 in middle_func ()
12338 at testsuite/gdb.python/py-caller-is.c:27
12339 #2 0x00000000004005ab in top_func ()
12340 at testsuite/gdb.python/py-caller-is.c:33
12341 #3 0x00000000004005b6 in main ()
12342 at testsuite/gdb.python/py-caller-is.c:39
12343 (gdb) print $_caller_is ("middle_func")
12345 (gdb) print $_caller_is ("top_func", 2)
12349 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12350 @findex $_caller_matches@r{, convenience function}
12351 Returns one if the calling function's name matches the regular expression
12352 @var{regexp}. Otherwise it returns zero.
12354 If the optional argument @var{number_of_frames} is provided,
12355 it is the number of frames up in the stack to look.
12358 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12359 @findex $_any_caller_is@r{, convenience function}
12360 Returns one if any calling function's name is equal to @var{name}.
12361 Otherwise it returns zero.
12363 If the optional argument @var{number_of_frames} is provided,
12364 it is the number of frames up in the stack to look.
12367 This function differs from @code{$_caller_is} in that this function
12368 checks all stack frames from the immediate caller to the frame specified
12369 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12370 frame specified by @var{number_of_frames}.
12372 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12373 @findex $_any_caller_matches@r{, convenience function}
12374 Returns one if any calling function's name matches the regular expression
12375 @var{regexp}. Otherwise it returns zero.
12377 If the optional argument @var{number_of_frames} is provided,
12378 it is the number of frames up in the stack to look.
12381 This function differs from @code{$_caller_matches} in that this function
12382 checks all stack frames from the immediate caller to the frame specified
12383 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12384 frame specified by @var{number_of_frames}.
12386 @item $_as_string(@var{value})
12387 @findex $_as_string@r{, convenience function}
12388 Return the string representation of @var{value}.
12390 This function is useful to obtain the textual label (enumerator) of an
12391 enumeration value. For example, assuming the variable @var{node} is of
12392 an enumerated type:
12395 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12396 Visiting node of type NODE_INTEGER
12399 @item $_cimag(@var{value})
12400 @itemx $_creal(@var{value})
12401 @findex $_cimag@r{, convenience function}
12402 @findex $_creal@r{, convenience function}
12403 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12404 the complex number @var{value}.
12406 The type of the imaginary or real part depends on the type of the
12407 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12408 will return an imaginary part of type @code{float}.
12412 @value{GDBN} provides the ability to list and get help on
12413 convenience functions.
12416 @item help function
12417 @kindex help function
12418 @cindex show all convenience functions
12419 Print a list of all convenience functions.
12426 You can refer to machine register contents, in expressions, as variables
12427 with names starting with @samp{$}. The names of registers are different
12428 for each machine; use @code{info registers} to see the names used on
12432 @kindex info registers
12433 @item info registers
12434 Print the names and values of all registers except floating-point
12435 and vector registers (in the selected stack frame).
12437 @kindex info all-registers
12438 @cindex floating point registers
12439 @item info all-registers
12440 Print the names and values of all registers, including floating-point
12441 and vector registers (in the selected stack frame).
12443 @anchor{info_registers_reggroup}
12444 @item info registers @var{reggroup} @dots{}
12445 Print the name and value of the registers in each of the specified
12446 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12447 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12449 @item info registers @var{regname} @dots{}
12450 Print the @dfn{relativized} value of each specified register @var{regname}.
12451 As discussed in detail below, register values are normally relative to
12452 the selected stack frame. The @var{regname} may be any register name valid on
12453 the machine you are using, with or without the initial @samp{$}.
12456 @anchor{standard registers}
12457 @cindex stack pointer register
12458 @cindex program counter register
12459 @cindex process status register
12460 @cindex frame pointer register
12461 @cindex standard registers
12462 @value{GDBN} has four ``standard'' register names that are available (in
12463 expressions) on most machines---whenever they do not conflict with an
12464 architecture's canonical mnemonics for registers. The register names
12465 @code{$pc} and @code{$sp} are used for the program counter register and
12466 the stack pointer. @code{$fp} is used for a register that contains a
12467 pointer to the current stack frame, and @code{$ps} is used for a
12468 register that contains the processor status. For example,
12469 you could print the program counter in hex with
12476 or print the instruction to be executed next with
12483 or add four to the stack pointer@footnote{This is a way of removing
12484 one word from the stack, on machines where stacks grow downward in
12485 memory (most machines, nowadays). This assumes that the innermost
12486 stack frame is selected; setting @code{$sp} is not allowed when other
12487 stack frames are selected. To pop entire frames off the stack,
12488 regardless of machine architecture, use @code{return};
12489 see @ref{Returning, ,Returning from a Function}.} with
12495 Whenever possible, these four standard register names are available on
12496 your machine even though the machine has different canonical mnemonics,
12497 so long as there is no conflict. The @code{info registers} command
12498 shows the canonical names. For example, on the SPARC, @code{info
12499 registers} displays the processor status register as @code{$psr} but you
12500 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12501 is an alias for the @sc{eflags} register.
12503 @value{GDBN} always considers the contents of an ordinary register as an
12504 integer when the register is examined in this way. Some machines have
12505 special registers which can hold nothing but floating point; these
12506 registers are considered to have floating point values. There is no way
12507 to refer to the contents of an ordinary register as floating point value
12508 (although you can @emph{print} it as a floating point value with
12509 @samp{print/f $@var{regname}}).
12511 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12512 means that the data format in which the register contents are saved by
12513 the operating system is not the same one that your program normally
12514 sees. For example, the registers of the 68881 floating point
12515 coprocessor are always saved in ``extended'' (raw) format, but all C
12516 programs expect to work with ``double'' (virtual) format. In such
12517 cases, @value{GDBN} normally works with the virtual format only (the format
12518 that makes sense for your program), but the @code{info registers} command
12519 prints the data in both formats.
12521 @cindex SSE registers (x86)
12522 @cindex MMX registers (x86)
12523 Some machines have special registers whose contents can be interpreted
12524 in several different ways. For example, modern x86-based machines
12525 have SSE and MMX registers that can hold several values packed
12526 together in several different formats. @value{GDBN} refers to such
12527 registers in @code{struct} notation:
12530 (@value{GDBP}) print $xmm1
12532 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12533 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12534 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12535 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12536 v4_int32 = @{0, 20657912, 11, 13@},
12537 v2_int64 = @{88725056443645952, 55834574859@},
12538 uint128 = 0x0000000d0000000b013b36f800000000
12543 To set values of such registers, you need to tell @value{GDBN} which
12544 view of the register you wish to change, as if you were assigning
12545 value to a @code{struct} member:
12548 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12551 Normally, register values are relative to the selected stack frame
12552 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12553 value that the register would contain if all stack frames farther in
12554 were exited and their saved registers restored. In order to see the
12555 true contents of hardware registers, you must select the innermost
12556 frame (with @samp{frame 0}).
12558 @cindex caller-saved registers
12559 @cindex call-clobbered registers
12560 @cindex volatile registers
12561 @cindex <not saved> values
12562 Usually ABIs reserve some registers as not needed to be saved by the
12563 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12564 registers). It may therefore not be possible for @value{GDBN} to know
12565 the value a register had before the call (in other words, in the outer
12566 frame), if the register value has since been changed by the callee.
12567 @value{GDBN} tries to deduce where the inner frame saved
12568 (``callee-saved'') registers, from the debug info, unwind info, or the
12569 machine code generated by your compiler. If some register is not
12570 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12571 its own knowledge of the ABI, or because the debug/unwind info
12572 explicitly says the register's value is undefined), @value{GDBN}
12573 displays @w{@samp{<not saved>}} as the register's value. With targets
12574 that @value{GDBN} has no knowledge of the register saving convention,
12575 if a register was not saved by the callee, then its value and location
12576 in the outer frame are assumed to be the same of the inner frame.
12577 This is usually harmless, because if the register is call-clobbered,
12578 the caller either does not care what is in the register after the
12579 call, or has code to restore the value that it does care about. Note,
12580 however, that if you change such a register in the outer frame, you
12581 may also be affecting the inner frame. Also, the more ``outer'' the
12582 frame is you're looking at, the more likely a call-clobbered
12583 register's value is to be wrong, in the sense that it doesn't actually
12584 represent the value the register had just before the call.
12586 @node Floating Point Hardware
12587 @section Floating Point Hardware
12588 @cindex floating point
12590 Depending on the configuration, @value{GDBN} may be able to give
12591 you more information about the status of the floating point hardware.
12596 Display hardware-dependent information about the floating
12597 point unit. The exact contents and layout vary depending on the
12598 floating point chip. Currently, @samp{info float} is supported on
12599 the ARM and x86 machines.
12603 @section Vector Unit
12604 @cindex vector unit
12606 Depending on the configuration, @value{GDBN} may be able to give you
12607 more information about the status of the vector unit.
12610 @kindex info vector
12612 Display information about the vector unit. The exact contents and
12613 layout vary depending on the hardware.
12616 @node OS Information
12617 @section Operating System Auxiliary Information
12618 @cindex OS information
12620 @value{GDBN} provides interfaces to useful OS facilities that can help
12621 you debug your program.
12623 @cindex auxiliary vector
12624 @cindex vector, auxiliary
12625 Some operating systems supply an @dfn{auxiliary vector} to programs at
12626 startup. This is akin to the arguments and environment that you
12627 specify for a program, but contains a system-dependent variety of
12628 binary values that tell system libraries important details about the
12629 hardware, operating system, and process. Each value's purpose is
12630 identified by an integer tag; the meanings are well-known but system-specific.
12631 Depending on the configuration and operating system facilities,
12632 @value{GDBN} may be able to show you this information. For remote
12633 targets, this functionality may further depend on the remote stub's
12634 support of the @samp{qXfer:auxv:read} packet, see
12635 @ref{qXfer auxiliary vector read}.
12640 Display the auxiliary vector of the inferior, which can be either a
12641 live process or a core dump file. @value{GDBN} prints each tag value
12642 numerically, and also shows names and text descriptions for recognized
12643 tags. Some values in the vector are numbers, some bit masks, and some
12644 pointers to strings or other data. @value{GDBN} displays each value in the
12645 most appropriate form for a recognized tag, and in hexadecimal for
12646 an unrecognized tag.
12649 On some targets, @value{GDBN} can access operating system-specific
12650 information and show it to you. The types of information available
12651 will differ depending on the type of operating system running on the
12652 target. The mechanism used to fetch the data is described in
12653 @ref{Operating System Information}. For remote targets, this
12654 functionality depends on the remote stub's support of the
12655 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12659 @item info os @var{infotype}
12661 Display OS information of the requested type.
12663 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12665 @anchor{linux info os infotypes}
12667 @kindex info os cpus
12669 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12670 the available fields from /proc/cpuinfo. For each supported architecture
12671 different fields are available. Two common entries are processor which gives
12672 CPU number and bogomips; a system constant that is calculated during
12673 kernel initialization.
12675 @kindex info os files
12677 Display the list of open file descriptors on the target. For each
12678 file descriptor, @value{GDBN} prints the identifier of the process
12679 owning the descriptor, the command of the owning process, the value
12680 of the descriptor, and the target of the descriptor.
12682 @kindex info os modules
12684 Display the list of all loaded kernel modules on the target. For each
12685 module, @value{GDBN} prints the module name, the size of the module in
12686 bytes, the number of times the module is used, the dependencies of the
12687 module, the status of the module, and the address of the loaded module
12690 @kindex info os msg
12692 Display the list of all System V message queues on the target. For each
12693 message queue, @value{GDBN} prints the message queue key, the message
12694 queue identifier, the access permissions, the current number of bytes
12695 on the queue, the current number of messages on the queue, the processes
12696 that last sent and received a message on the queue, the user and group
12697 of the owner and creator of the message queue, the times at which a
12698 message was last sent and received on the queue, and the time at which
12699 the message queue was last changed.
12701 @kindex info os processes
12703 Display the list of processes on the target. For each process,
12704 @value{GDBN} prints the process identifier, the name of the user, the
12705 command corresponding to the process, and the list of processor cores
12706 that the process is currently running on. (To understand what these
12707 properties mean, for this and the following info types, please consult
12708 the general @sc{gnu}/Linux documentation.)
12710 @kindex info os procgroups
12712 Display the list of process groups on the target. For each process,
12713 @value{GDBN} prints the identifier of the process group that it belongs
12714 to, the command corresponding to the process group leader, the process
12715 identifier, and the command line of the process. The list is sorted
12716 first by the process group identifier, then by the process identifier,
12717 so that processes belonging to the same process group are grouped together
12718 and the process group leader is listed first.
12720 @kindex info os semaphores
12722 Display the list of all System V semaphore sets on the target. For each
12723 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
12724 set identifier, the access permissions, the number of semaphores in the
12725 set, the user and group of the owner and creator of the semaphore set,
12726 and the times at which the semaphore set was operated upon and changed.
12728 @kindex info os shm
12730 Display the list of all System V shared-memory regions on the target.
12731 For each shared-memory region, @value{GDBN} prints the region key,
12732 the shared-memory identifier, the access permissions, the size of the
12733 region, the process that created the region, the process that last
12734 attached to or detached from the region, the current number of live
12735 attaches to the region, and the times at which the region was last
12736 attached to, detach from, and changed.
12738 @kindex info os sockets
12740 Display the list of Internet-domain sockets on the target. For each
12741 socket, @value{GDBN} prints the address and port of the local and
12742 remote endpoints, the current state of the connection, the creator of
12743 the socket, the IP address family of the socket, and the type of the
12746 @kindex info os threads
12748 Display the list of threads running on the target. For each thread,
12749 @value{GDBN} prints the identifier of the process that the thread
12750 belongs to, the command of the process, the thread identifier, and the
12751 processor core that it is currently running on. The main thread of a
12752 process is not listed.
12756 If @var{infotype} is omitted, then list the possible values for
12757 @var{infotype} and the kind of OS information available for each
12758 @var{infotype}. If the target does not return a list of possible
12759 types, this command will report an error.
12762 @node Memory Region Attributes
12763 @section Memory Region Attributes
12764 @cindex memory region attributes
12766 @dfn{Memory region attributes} allow you to describe special handling
12767 required by regions of your target's memory. @value{GDBN} uses
12768 attributes to determine whether to allow certain types of memory
12769 accesses; whether to use specific width accesses; and whether to cache
12770 target memory. By default the description of memory regions is
12771 fetched from the target (if the current target supports this), but the
12772 user can override the fetched regions.
12774 Defined memory regions can be individually enabled and disabled. When a
12775 memory region is disabled, @value{GDBN} uses the default attributes when
12776 accessing memory in that region. Similarly, if no memory regions have
12777 been defined, @value{GDBN} uses the default attributes when accessing
12780 When a memory region is defined, it is given a number to identify it;
12781 to enable, disable, or remove a memory region, you specify that number.
12785 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
12786 Define a memory region bounded by @var{lower} and @var{upper} with
12787 attributes @var{attributes}@dots{}, and add it to the list of regions
12788 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
12789 case: it is treated as the target's maximum memory address.
12790 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
12793 Discard any user changes to the memory regions and use target-supplied
12794 regions, if available, or no regions if the target does not support.
12797 @item delete mem @var{nums}@dots{}
12798 Remove memory regions @var{nums}@dots{} from the list of regions
12799 monitored by @value{GDBN}.
12801 @kindex disable mem
12802 @item disable mem @var{nums}@dots{}
12803 Disable monitoring of memory regions @var{nums}@dots{}.
12804 A disabled memory region is not forgotten.
12805 It may be enabled again later.
12808 @item enable mem @var{nums}@dots{}
12809 Enable monitoring of memory regions @var{nums}@dots{}.
12813 Print a table of all defined memory regions, with the following columns
12817 @item Memory Region Number
12818 @item Enabled or Disabled.
12819 Enabled memory regions are marked with @samp{y}.
12820 Disabled memory regions are marked with @samp{n}.
12823 The address defining the inclusive lower bound of the memory region.
12826 The address defining the exclusive upper bound of the memory region.
12829 The list of attributes set for this memory region.
12834 @subsection Attributes
12836 @subsubsection Memory Access Mode
12837 The access mode attributes set whether @value{GDBN} may make read or
12838 write accesses to a memory region.
12840 While these attributes prevent @value{GDBN} from performing invalid
12841 memory accesses, they do nothing to prevent the target system, I/O DMA,
12842 etc.@: from accessing memory.
12846 Memory is read only.
12848 Memory is write only.
12850 Memory is read/write. This is the default.
12853 @subsubsection Memory Access Size
12854 The access size attribute tells @value{GDBN} to use specific sized
12855 accesses in the memory region. Often memory mapped device registers
12856 require specific sized accesses. If no access size attribute is
12857 specified, @value{GDBN} may use accesses of any size.
12861 Use 8 bit memory accesses.
12863 Use 16 bit memory accesses.
12865 Use 32 bit memory accesses.
12867 Use 64 bit memory accesses.
12870 @c @subsubsection Hardware/Software Breakpoints
12871 @c The hardware/software breakpoint attributes set whether @value{GDBN}
12872 @c will use hardware or software breakpoints for the internal breakpoints
12873 @c used by the step, next, finish, until, etc. commands.
12877 @c Always use hardware breakpoints
12878 @c @item swbreak (default)
12881 @subsubsection Data Cache
12882 The data cache attributes set whether @value{GDBN} will cache target
12883 memory. While this generally improves performance by reducing debug
12884 protocol overhead, it can lead to incorrect results because @value{GDBN}
12885 does not know about volatile variables or memory mapped device
12890 Enable @value{GDBN} to cache target memory.
12892 Disable @value{GDBN} from caching target memory. This is the default.
12895 @subsection Memory Access Checking
12896 @value{GDBN} can be instructed to refuse accesses to memory that is
12897 not explicitly described. This can be useful if accessing such
12898 regions has undesired effects for a specific target, or to provide
12899 better error checking. The following commands control this behaviour.
12902 @kindex set mem inaccessible-by-default
12903 @item set mem inaccessible-by-default [on|off]
12904 If @code{on} is specified, make @value{GDBN} treat memory not
12905 explicitly described by the memory ranges as non-existent and refuse accesses
12906 to such memory. The checks are only performed if there's at least one
12907 memory range defined. If @code{off} is specified, make @value{GDBN}
12908 treat the memory not explicitly described by the memory ranges as RAM.
12909 The default value is @code{on}.
12910 @kindex show mem inaccessible-by-default
12911 @item show mem inaccessible-by-default
12912 Show the current handling of accesses to unknown memory.
12916 @c @subsubsection Memory Write Verification
12917 @c The memory write verification attributes set whether @value{GDBN}
12918 @c will re-reads data after each write to verify the write was successful.
12922 @c @item noverify (default)
12925 @node Dump/Restore Files
12926 @section Copy Between Memory and a File
12927 @cindex dump/restore files
12928 @cindex append data to a file
12929 @cindex dump data to a file
12930 @cindex restore data from a file
12932 You can use the commands @code{dump}, @code{append}, and
12933 @code{restore} to copy data between target memory and a file. The
12934 @code{dump} and @code{append} commands write data to a file, and the
12935 @code{restore} command reads data from a file back into the inferior's
12936 memory. Files may be in binary, Motorola S-record, Intel hex,
12937 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
12938 append to binary files, and cannot read from Verilog Hex files.
12943 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12944 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
12945 Dump the contents of memory from @var{start_addr} to @var{end_addr},
12946 or the value of @var{expr}, to @var{filename} in the given format.
12948 The @var{format} parameter may be any one of:
12955 Motorola S-record format.
12957 Tektronix Hex format.
12959 Verilog Hex format.
12962 @value{GDBN} uses the same definitions of these formats as the
12963 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
12964 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
12968 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12969 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
12970 Append the contents of memory from @var{start_addr} to @var{end_addr},
12971 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
12972 (@value{GDBN} can only append data to files in raw binary form.)
12975 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
12976 Restore the contents of file @var{filename} into memory. The
12977 @code{restore} command can automatically recognize any known @sc{bfd}
12978 file format, except for raw binary. To restore a raw binary file you
12979 must specify the optional keyword @code{binary} after the filename.
12981 If @var{bias} is non-zero, its value will be added to the addresses
12982 contained in the file. Binary files always start at address zero, so
12983 they will be restored at address @var{bias}. Other bfd files have
12984 a built-in location; they will be restored at offset @var{bias}
12985 from that location.
12987 If @var{start} and/or @var{end} are non-zero, then only data between
12988 file offset @var{start} and file offset @var{end} will be restored.
12989 These offsets are relative to the addresses in the file, before
12990 the @var{bias} argument is applied.
12994 @node Core File Generation
12995 @section How to Produce a Core File from Your Program
12996 @cindex dump core from inferior
12998 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12999 image of a running process and its process status (register values
13000 etc.). Its primary use is post-mortem debugging of a program that
13001 crashed while it ran outside a debugger. A program that crashes
13002 automatically produces a core file, unless this feature is disabled by
13003 the user. @xref{Files}, for information on invoking @value{GDBN} in
13004 the post-mortem debugging mode.
13006 Occasionally, you may wish to produce a core file of the program you
13007 are debugging in order to preserve a snapshot of its state.
13008 @value{GDBN} has a special command for that.
13012 @kindex generate-core-file
13013 @item generate-core-file [@var{file}]
13014 @itemx gcore [@var{file}]
13015 Produce a core dump of the inferior process. The optional argument
13016 @var{file} specifies the file name where to put the core dump. If not
13017 specified, the file name defaults to @file{core.@var{pid}}, where
13018 @var{pid} is the inferior process ID.
13020 Note that this command is implemented only for some systems (as of
13021 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13023 On @sc{gnu}/Linux, this command can take into account the value of the
13024 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13025 dump (@pxref{set use-coredump-filter}), and by default honors the
13026 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13027 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13029 @kindex set use-coredump-filter
13030 @anchor{set use-coredump-filter}
13031 @item set use-coredump-filter on
13032 @itemx set use-coredump-filter off
13033 Enable or disable the use of the file
13034 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13035 files. This file is used by the Linux kernel to decide what types of
13036 memory mappings will be dumped or ignored when generating a core dump
13037 file. @var{pid} is the process ID of a currently running process.
13039 To make use of this feature, you have to write in the
13040 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13041 which is a bit mask representing the memory mapping types. If a bit
13042 is set in the bit mask, then the memory mappings of the corresponding
13043 types will be dumped; otherwise, they will be ignored. This
13044 configuration is inherited by child processes. For more information
13045 about the bits that can be set in the
13046 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13047 manpage of @code{core(5)}.
13049 By default, this option is @code{on}. If this option is turned
13050 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13051 and instead uses the same default value as the Linux kernel in order
13052 to decide which pages will be dumped in the core dump file. This
13053 value is currently @code{0x33}, which means that bits @code{0}
13054 (anonymous private mappings), @code{1} (anonymous shared mappings),
13055 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13056 This will cause these memory mappings to be dumped automatically.
13058 @kindex set dump-excluded-mappings
13059 @anchor{set dump-excluded-mappings}
13060 @item set dump-excluded-mappings on
13061 @itemx set dump-excluded-mappings off
13062 If @code{on} is specified, @value{GDBN} will dump memory mappings
13063 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13064 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13066 The default value is @code{off}.
13069 @node Character Sets
13070 @section Character Sets
13071 @cindex character sets
13073 @cindex translating between character sets
13074 @cindex host character set
13075 @cindex target character set
13077 If the program you are debugging uses a different character set to
13078 represent characters and strings than the one @value{GDBN} uses itself,
13079 @value{GDBN} can automatically translate between the character sets for
13080 you. The character set @value{GDBN} uses we call the @dfn{host
13081 character set}; the one the inferior program uses we call the
13082 @dfn{target character set}.
13084 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13085 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13086 remote protocol (@pxref{Remote Debugging}) to debug a program
13087 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13088 then the host character set is Latin-1, and the target character set is
13089 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13090 target-charset EBCDIC-US}, then @value{GDBN} translates between
13091 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13092 character and string literals in expressions.
13094 @value{GDBN} has no way to automatically recognize which character set
13095 the inferior program uses; you must tell it, using the @code{set
13096 target-charset} command, described below.
13098 Here are the commands for controlling @value{GDBN}'s character set
13102 @item set target-charset @var{charset}
13103 @kindex set target-charset
13104 Set the current target character set to @var{charset}. To display the
13105 list of supported target character sets, type
13106 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13108 @item set host-charset @var{charset}
13109 @kindex set host-charset
13110 Set the current host character set to @var{charset}.
13112 By default, @value{GDBN} uses a host character set appropriate to the
13113 system it is running on; you can override that default using the
13114 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13115 automatically determine the appropriate host character set. In this
13116 case, @value{GDBN} uses @samp{UTF-8}.
13118 @value{GDBN} can only use certain character sets as its host character
13119 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13120 @value{GDBN} will list the host character sets it supports.
13122 @item set charset @var{charset}
13123 @kindex set charset
13124 Set the current host and target character sets to @var{charset}. As
13125 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13126 @value{GDBN} will list the names of the character sets that can be used
13127 for both host and target.
13130 @kindex show charset
13131 Show the names of the current host and target character sets.
13133 @item show host-charset
13134 @kindex show host-charset
13135 Show the name of the current host character set.
13137 @item show target-charset
13138 @kindex show target-charset
13139 Show the name of the current target character set.
13141 @item set target-wide-charset @var{charset}
13142 @kindex set target-wide-charset
13143 Set the current target's wide character set to @var{charset}. This is
13144 the character set used by the target's @code{wchar_t} type. To
13145 display the list of supported wide character sets, type
13146 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13148 @item show target-wide-charset
13149 @kindex show target-wide-charset
13150 Show the name of the current target's wide character set.
13153 Here is an example of @value{GDBN}'s character set support in action.
13154 Assume that the following source code has been placed in the file
13155 @file{charset-test.c}:
13161 = @{72, 101, 108, 108, 111, 44, 32, 119,
13162 111, 114, 108, 100, 33, 10, 0@};
13163 char ibm1047_hello[]
13164 = @{200, 133, 147, 147, 150, 107, 64, 166,
13165 150, 153, 147, 132, 90, 37, 0@};
13169 printf ("Hello, world!\n");
13173 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13174 containing the string @samp{Hello, world!} followed by a newline,
13175 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13177 We compile the program, and invoke the debugger on it:
13180 $ gcc -g charset-test.c -o charset-test
13181 $ gdb -nw charset-test
13182 GNU gdb 2001-12-19-cvs
13183 Copyright 2001 Free Software Foundation, Inc.
13188 We can use the @code{show charset} command to see what character sets
13189 @value{GDBN} is currently using to interpret and display characters and
13193 (@value{GDBP}) show charset
13194 The current host and target character set is `ISO-8859-1'.
13198 For the sake of printing this manual, let's use @sc{ascii} as our
13199 initial character set:
13201 (@value{GDBP}) set charset ASCII
13202 (@value{GDBP}) show charset
13203 The current host and target character set is `ASCII'.
13207 Let's assume that @sc{ascii} is indeed the correct character set for our
13208 host system --- in other words, let's assume that if @value{GDBN} prints
13209 characters using the @sc{ascii} character set, our terminal will display
13210 them properly. Since our current target character set is also
13211 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13214 (@value{GDBP}) print ascii_hello
13215 $1 = 0x401698 "Hello, world!\n"
13216 (@value{GDBP}) print ascii_hello[0]
13221 @value{GDBN} uses the target character set for character and string
13222 literals you use in expressions:
13225 (@value{GDBP}) print '+'
13230 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13233 @value{GDBN} relies on the user to tell it which character set the
13234 target program uses. If we print @code{ibm1047_hello} while our target
13235 character set is still @sc{ascii}, we get jibberish:
13238 (@value{GDBP}) print ibm1047_hello
13239 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13240 (@value{GDBP}) print ibm1047_hello[0]
13245 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13246 @value{GDBN} tells us the character sets it supports:
13249 (@value{GDBP}) set target-charset
13250 ASCII EBCDIC-US IBM1047 ISO-8859-1
13251 (@value{GDBP}) set target-charset
13254 We can select @sc{ibm1047} as our target character set, and examine the
13255 program's strings again. Now the @sc{ascii} string is wrong, but
13256 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13257 target character set, @sc{ibm1047}, to the host character set,
13258 @sc{ascii}, and they display correctly:
13261 (@value{GDBP}) set target-charset IBM1047
13262 (@value{GDBP}) show charset
13263 The current host character set is `ASCII'.
13264 The current target character set is `IBM1047'.
13265 (@value{GDBP}) print ascii_hello
13266 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13267 (@value{GDBP}) print ascii_hello[0]
13269 (@value{GDBP}) print ibm1047_hello
13270 $8 = 0x4016a8 "Hello, world!\n"
13271 (@value{GDBP}) print ibm1047_hello[0]
13276 As above, @value{GDBN} uses the target character set for character and
13277 string literals you use in expressions:
13280 (@value{GDBP}) print '+'
13285 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13288 @node Caching Target Data
13289 @section Caching Data of Targets
13290 @cindex caching data of targets
13292 @value{GDBN} caches data exchanged between the debugger and a target.
13293 Each cache is associated with the address space of the inferior.
13294 @xref{Inferiors Connections and Programs}, about inferior and address space.
13295 Such caching generally improves performance in remote debugging
13296 (@pxref{Remote Debugging}), because it reduces the overhead of the
13297 remote protocol by bundling memory reads and writes into large chunks.
13298 Unfortunately, simply caching everything would lead to incorrect results,
13299 since @value{GDBN} does not necessarily know anything about volatile
13300 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13301 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13303 Therefore, by default, @value{GDBN} only caches data
13304 known to be on the stack@footnote{In non-stop mode, it is moderately
13305 rare for a running thread to modify the stack of a stopped thread
13306 in a way that would interfere with a backtrace, and caching of
13307 stack reads provides a significant speed up of remote backtraces.} or
13308 in the code segment.
13309 Other regions of memory can be explicitly marked as
13310 cacheable; @pxref{Memory Region Attributes}.
13313 @kindex set remotecache
13314 @item set remotecache on
13315 @itemx set remotecache off
13316 This option no longer does anything; it exists for compatibility
13319 @kindex show remotecache
13320 @item show remotecache
13321 Show the current state of the obsolete remotecache flag.
13323 @kindex set stack-cache
13324 @item set stack-cache on
13325 @itemx set stack-cache off
13326 Enable or disable caching of stack accesses. When @code{on}, use
13327 caching. By default, this option is @code{on}.
13329 @kindex show stack-cache
13330 @item show stack-cache
13331 Show the current state of data caching for memory accesses.
13333 @kindex set code-cache
13334 @item set code-cache on
13335 @itemx set code-cache off
13336 Enable or disable caching of code segment accesses. When @code{on},
13337 use caching. By default, this option is @code{on}. This improves
13338 performance of disassembly in remote debugging.
13340 @kindex show code-cache
13341 @item show code-cache
13342 Show the current state of target memory cache for code segment
13345 @kindex info dcache
13346 @item info dcache @r{[}line@r{]}
13347 Print the information about the performance of data cache of the
13348 current inferior's address space. The information displayed
13349 includes the dcache width and depth, and for each cache line, its
13350 number, address, and how many times it was referenced. This
13351 command is useful for debugging the data cache operation.
13353 If a line number is specified, the contents of that line will be
13356 @item set dcache size @var{size}
13357 @cindex dcache size
13358 @kindex set dcache size
13359 Set maximum number of entries in dcache (dcache depth above).
13361 @item set dcache line-size @var{line-size}
13362 @cindex dcache line-size
13363 @kindex set dcache line-size
13364 Set number of bytes each dcache entry caches (dcache width above).
13365 Must be a power of 2.
13367 @item show dcache size
13368 @kindex show dcache size
13369 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13371 @item show dcache line-size
13372 @kindex show dcache line-size
13373 Show default size of dcache lines.
13377 @node Searching Memory
13378 @section Search Memory
13379 @cindex searching memory
13381 Memory can be searched for a particular sequence of bytes with the
13382 @code{find} command.
13386 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13387 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13388 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13389 etc. The search begins at address @var{start_addr} and continues for either
13390 @var{len} bytes or through to @var{end_addr} inclusive.
13393 @var{s} and @var{n} are optional parameters.
13394 They may be specified in either order, apart or together.
13397 @item @var{s}, search query size
13398 The size of each search query value.
13404 halfwords (two bytes)
13408 giant words (eight bytes)
13411 All values are interpreted in the current language.
13412 This means, for example, that if the current source language is C/C@t{++}
13413 then searching for the string ``hello'' includes the trailing '\0'.
13414 The null terminator can be removed from searching by using casts,
13415 e.g.: @samp{@{char[5]@}"hello"}.
13417 If the value size is not specified, it is taken from the
13418 value's type in the current language.
13419 This is useful when one wants to specify the search
13420 pattern as a mixture of types.
13421 Note that this means, for example, that in the case of C-like languages
13422 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13423 which is typically four bytes.
13425 @item @var{n}, maximum number of finds
13426 The maximum number of matches to print. The default is to print all finds.
13429 You can use strings as search values. Quote them with double-quotes
13431 The string value is copied into the search pattern byte by byte,
13432 regardless of the endianness of the target and the size specification.
13434 The address of each match found is printed as well as a count of the
13435 number of matches found.
13437 The address of the last value found is stored in convenience variable
13439 A count of the number of matches is stored in @samp{$numfound}.
13441 For example, if stopped at the @code{printf} in this function:
13447 static char hello[] = "hello-hello";
13448 static struct @{ char c; short s; int i; @}
13449 __attribute__ ((packed)) mixed
13450 = @{ 'c', 0x1234, 0x87654321 @};
13451 printf ("%s\n", hello);
13456 you get during debugging:
13459 (gdb) find &hello[0], +sizeof(hello), "hello"
13460 0x804956d <hello.1620+6>
13462 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13463 0x8049567 <hello.1620>
13464 0x804956d <hello.1620+6>
13466 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13467 0x8049567 <hello.1620>
13468 0x804956d <hello.1620+6>
13470 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13471 0x8049567 <hello.1620>
13473 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13474 0x8049560 <mixed.1625>
13476 (gdb) print $numfound
13479 $2 = (void *) 0x8049560
13483 @section Value Sizes
13485 Whenever @value{GDBN} prints a value memory will be allocated within
13486 @value{GDBN} to hold the contents of the value. It is possible in
13487 some languages with dynamic typing systems, that an invalid program
13488 may indicate a value that is incorrectly large, this in turn may cause
13489 @value{GDBN} to try and allocate an overly large amount of memory.
13492 @kindex set max-value-size
13493 @item set max-value-size @var{bytes}
13494 @itemx set max-value-size unlimited
13495 Set the maximum size of memory that @value{GDBN} will allocate for the
13496 contents of a value to @var{bytes}, trying to display a value that
13497 requires more memory than that will result in an error.
13499 Setting this variable does not effect values that have already been
13500 allocated within @value{GDBN}, only future allocations.
13502 There's a minimum size that @code{max-value-size} can be set to in
13503 order that @value{GDBN} can still operate correctly, this minimum is
13504 currently 16 bytes.
13506 The limit applies to the results of some subexpressions as well as to
13507 complete expressions. For example, an expression denoting a simple
13508 integer component, such as @code{x.y.z}, may fail if the size of
13509 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13510 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13511 @var{A} is an array variable with non-constant size, will generally
13512 succeed regardless of the bounds on @var{A}, as long as the component
13513 size is less than @var{bytes}.
13515 The default value of @code{max-value-size} is currently 64k.
13517 @kindex show max-value-size
13518 @item show max-value-size
13519 Show the maximum size of memory, in bytes, that @value{GDBN} will
13520 allocate for the contents of a value.
13523 @node Optimized Code
13524 @chapter Debugging Optimized Code
13525 @cindex optimized code, debugging
13526 @cindex debugging optimized code
13528 Almost all compilers support optimization. With optimization
13529 disabled, the compiler generates assembly code that corresponds
13530 directly to your source code, in a simplistic way. As the compiler
13531 applies more powerful optimizations, the generated assembly code
13532 diverges from your original source code. With help from debugging
13533 information generated by the compiler, @value{GDBN} can map from
13534 the running program back to constructs from your original source.
13536 @value{GDBN} is more accurate with optimization disabled. If you
13537 can recompile without optimization, it is easier to follow the
13538 progress of your program during debugging. But, there are many cases
13539 where you may need to debug an optimized version.
13541 When you debug a program compiled with @samp{-g -O}, remember that the
13542 optimizer has rearranged your code; the debugger shows you what is
13543 really there. Do not be too surprised when the execution path does not
13544 exactly match your source file! An extreme example: if you define a
13545 variable, but never use it, @value{GDBN} never sees that
13546 variable---because the compiler optimizes it out of existence.
13548 Some things do not work as well with @samp{-g -O} as with just
13549 @samp{-g}, particularly on machines with instruction scheduling. If in
13550 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13551 please report it to us as a bug (including a test case!).
13552 @xref{Variables}, for more information about debugging optimized code.
13555 * Inline Functions:: How @value{GDBN} presents inlining
13556 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13559 @node Inline Functions
13560 @section Inline Functions
13561 @cindex inline functions, debugging
13563 @dfn{Inlining} is an optimization that inserts a copy of the function
13564 body directly at each call site, instead of jumping to a shared
13565 routine. @value{GDBN} displays inlined functions just like
13566 non-inlined functions. They appear in backtraces. You can view their
13567 arguments and local variables, step into them with @code{step}, skip
13568 them with @code{next}, and escape from them with @code{finish}.
13569 You can check whether a function was inlined by using the
13570 @code{info frame} command.
13572 For @value{GDBN} to support inlined functions, the compiler must
13573 record information about inlining in the debug information ---
13574 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13575 other compilers do also. @value{GDBN} only supports inlined functions
13576 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13577 do not emit two required attributes (@samp{DW_AT_call_file} and
13578 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13579 function calls with earlier versions of @value{NGCC}. It instead
13580 displays the arguments and local variables of inlined functions as
13581 local variables in the caller.
13583 The body of an inlined function is directly included at its call site;
13584 unlike a non-inlined function, there are no instructions devoted to
13585 the call. @value{GDBN} still pretends that the call site and the
13586 start of the inlined function are different instructions. Stepping to
13587 the call site shows the call site, and then stepping again shows
13588 the first line of the inlined function, even though no additional
13589 instructions are executed.
13591 This makes source-level debugging much clearer; you can see both the
13592 context of the call and then the effect of the call. Only stepping by
13593 a single instruction using @code{stepi} or @code{nexti} does not do
13594 this; single instruction steps always show the inlined body.
13596 There are some ways that @value{GDBN} does not pretend that inlined
13597 function calls are the same as normal calls:
13601 Setting breakpoints at the call site of an inlined function may not
13602 work, because the call site does not contain any code. @value{GDBN}
13603 may incorrectly move the breakpoint to the next line of the enclosing
13604 function, after the call. This limitation will be removed in a future
13605 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13606 or inside the inlined function instead.
13609 @value{GDBN} cannot locate the return value of inlined calls after
13610 using the @code{finish} command. This is a limitation of compiler-generated
13611 debugging information; after @code{finish}, you can step to the next line
13612 and print a variable where your program stored the return value.
13616 @node Tail Call Frames
13617 @section Tail Call Frames
13618 @cindex tail call frames, debugging
13620 Function @code{B} can call function @code{C} in its very last statement. In
13621 unoptimized compilation the call of @code{C} is immediately followed by return
13622 instruction at the end of @code{B} code. Optimizing compiler may replace the
13623 call and return in function @code{B} into one jump to function @code{C}
13624 instead. Such use of a jump instruction is called @dfn{tail call}.
13626 During execution of function @code{C}, there will be no indication in the
13627 function call stack frames that it was tail-called from @code{B}. If function
13628 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13629 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13630 some cases @value{GDBN} can determine that @code{C} was tail-called from
13631 @code{B}, and it will then create fictitious call frame for that, with the
13632 return address set up as if @code{B} called @code{C} normally.
13634 This functionality is currently supported only by DWARF 2 debugging format and
13635 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13636 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13639 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13640 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13644 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13646 Stack level 1, frame at 0x7fffffffda30:
13647 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13648 tail call frame, caller of frame at 0x7fffffffda30
13649 source language c++.
13650 Arglist at unknown address.
13651 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13654 The detection of all the possible code path executions can find them ambiguous.
13655 There is no execution history stored (possible @ref{Reverse Execution} is never
13656 used for this purpose) and the last known caller could have reached the known
13657 callee by multiple different jump sequences. In such case @value{GDBN} still
13658 tries to show at least all the unambiguous top tail callers and all the
13659 unambiguous bottom tail calees, if any.
13662 @anchor{set debug entry-values}
13663 @item set debug entry-values
13664 @kindex set debug entry-values
13665 When set to on, enables printing of analysis messages for both frame argument
13666 values at function entry and tail calls. It will show all the possible valid
13667 tail calls code paths it has considered. It will also print the intersection
13668 of them with the final unambiguous (possibly partial or even empty) code path
13671 @item show debug entry-values
13672 @kindex show debug entry-values
13673 Show the current state of analysis messages printing for both frame argument
13674 values at function entry and tail calls.
13677 The analysis messages for tail calls can for example show why the virtual tail
13678 call frame for function @code{c} has not been recognized (due to the indirect
13679 reference by variable @code{x}):
13682 static void __attribute__((noinline, noclone)) c (void);
13683 void (*x) (void) = c;
13684 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13685 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13686 int main (void) @{ x (); return 0; @}
13688 Breakpoint 1, DW_OP_entry_value resolving cannot find
13689 DW_TAG_call_site 0x40039a in main
13691 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13694 #1 0x000000000040039a in main () at t.c:5
13697 Another possibility is an ambiguous virtual tail call frames resolution:
13701 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
13702 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
13703 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
13704 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
13705 static void __attribute__((noinline, noclone)) b (void)
13706 @{ if (i) c (); else e (); @}
13707 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
13708 int main (void) @{ a (); return 0; @}
13710 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
13711 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
13712 tailcall: reduced: 0x4004d2(a) |
13715 #1 0x00000000004004d2 in a () at t.c:8
13716 #2 0x0000000000400395 in main () at t.c:9
13719 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
13720 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
13722 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
13723 @ifset HAVE_MAKEINFO_CLICK
13724 @set ARROW @click{}
13725 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
13726 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
13728 @ifclear HAVE_MAKEINFO_CLICK
13730 @set CALLSEQ1B @value{CALLSEQ1A}
13731 @set CALLSEQ2B @value{CALLSEQ2A}
13734 Frames #0 and #2 are real, #1 is a virtual tail call frame.
13735 The code can have possible execution paths @value{CALLSEQ1B} or
13736 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
13738 @code{initial:} state shows some random possible calling sequence @value{GDBN}
13739 has found. It then finds another possible calling sequence - that one is
13740 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
13741 printed as the @code{reduced:} calling sequence. That one could have many
13742 further @code{compare:} and @code{reduced:} statements as long as there remain
13743 any non-ambiguous sequence entries.
13745 For the frame of function @code{b} in both cases there are different possible
13746 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
13747 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
13748 therefore this one is displayed to the user while the ambiguous frames are
13751 There can be also reasons why printing of frame argument values at function
13756 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
13757 static void __attribute__((noinline, noclone)) a (int i);
13758 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
13759 static void __attribute__((noinline, noclone)) a (int i)
13760 @{ if (i) b (i - 1); else c (0); @}
13761 int main (void) @{ a (5); return 0; @}
13764 #0 c (i=i@@entry=0) at t.c:2
13765 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
13766 function "a" at 0x400420 can call itself via tail calls
13767 i=<optimized out>) at t.c:6
13768 #2 0x000000000040036e in main () at t.c:7
13771 @value{GDBN} cannot find out from the inferior state if and how many times did
13772 function @code{a} call itself (via function @code{b}) as these calls would be
13773 tail calls. Such tail calls would modify the @code{i} variable, therefore
13774 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
13775 prints @code{<optimized out>} instead.
13778 @chapter C Preprocessor Macros
13780 Some languages, such as C and C@t{++}, provide a way to define and invoke
13781 ``preprocessor macros'' which expand into strings of tokens.
13782 @value{GDBN} can evaluate expressions containing macro invocations, show
13783 the result of macro expansion, and show a macro's definition, including
13784 where it was defined.
13786 You may need to compile your program specially to provide @value{GDBN}
13787 with information about preprocessor macros. Most compilers do not
13788 include macros in their debugging information, even when you compile
13789 with the @option{-g} flag. @xref{Compilation}.
13791 A program may define a macro at one point, remove that definition later,
13792 and then provide a different definition after that. Thus, at different
13793 points in the program, a macro may have different definitions, or have
13794 no definition at all. If there is a current stack frame, @value{GDBN}
13795 uses the macros in scope at that frame's source code line. Otherwise,
13796 @value{GDBN} uses the macros in scope at the current listing location;
13799 Whenever @value{GDBN} evaluates an expression, it always expands any
13800 macro invocations present in the expression. @value{GDBN} also provides
13801 the following commands for working with macros explicitly.
13805 @kindex macro expand
13806 @cindex macro expansion, showing the results of preprocessor
13807 @cindex preprocessor macro expansion, showing the results of
13808 @cindex expanding preprocessor macros
13809 @item macro expand @var{expression}
13810 @itemx macro exp @var{expression}
13811 Show the results of expanding all preprocessor macro invocations in
13812 @var{expression}. Since @value{GDBN} simply expands macros, but does
13813 not parse the result, @var{expression} need not be a valid expression;
13814 it can be any string of tokens.
13817 @item macro expand-once @var{expression}
13818 @itemx macro exp1 @var{expression}
13819 @cindex expand macro once
13820 @i{(This command is not yet implemented.)} Show the results of
13821 expanding those preprocessor macro invocations that appear explicitly in
13822 @var{expression}. Macro invocations appearing in that expansion are
13823 left unchanged. This command allows you to see the effect of a
13824 particular macro more clearly, without being confused by further
13825 expansions. Since @value{GDBN} simply expands macros, but does not
13826 parse the result, @var{expression} need not be a valid expression; it
13827 can be any string of tokens.
13830 @cindex macro definition, showing
13831 @cindex definition of a macro, showing
13832 @cindex macros, from debug info
13833 @item info macro [-a|-all] [--] @var{macro}
13834 Show the current definition or all definitions of the named @var{macro},
13835 and describe the source location or compiler command-line where that
13836 definition was established. The optional double dash is to signify the end of
13837 argument processing and the beginning of @var{macro} for non C-like macros where
13838 the macro may begin with a hyphen.
13840 @kindex info macros
13841 @item info macros @var{location}
13842 Show all macro definitions that are in effect at the location specified
13843 by @var{location}, and describe the source location or compiler
13844 command-line where those definitions were established.
13846 @kindex macro define
13847 @cindex user-defined macros
13848 @cindex defining macros interactively
13849 @cindex macros, user-defined
13850 @item macro define @var{macro} @var{replacement-list}
13851 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
13852 Introduce a definition for a preprocessor macro named @var{macro},
13853 invocations of which are replaced by the tokens given in
13854 @var{replacement-list}. The first form of this command defines an
13855 ``object-like'' macro, which takes no arguments; the second form
13856 defines a ``function-like'' macro, which takes the arguments given in
13859 A definition introduced by this command is in scope in every
13860 expression evaluated in @value{GDBN}, until it is removed with the
13861 @code{macro undef} command, described below. The definition overrides
13862 all definitions for @var{macro} present in the program being debugged,
13863 as well as any previous user-supplied definition.
13865 @kindex macro undef
13866 @item macro undef @var{macro}
13867 Remove any user-supplied definition for the macro named @var{macro}.
13868 This command only affects definitions provided with the @code{macro
13869 define} command, described above; it cannot remove definitions present
13870 in the program being debugged.
13874 List all the macros defined using the @code{macro define} command.
13877 @cindex macros, example of debugging with
13878 Here is a transcript showing the above commands in action. First, we
13879 show our source files:
13884 #include "sample.h"
13887 #define ADD(x) (M + x)
13892 printf ("Hello, world!\n");
13894 printf ("We're so creative.\n");
13896 printf ("Goodbye, world!\n");
13903 Now, we compile the program using the @sc{gnu} C compiler,
13904 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
13905 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
13906 and @option{-gdwarf-4}; we recommend always choosing the most recent
13907 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
13908 includes information about preprocessor macros in the debugging
13912 $ gcc -gdwarf-2 -g3 sample.c -o sample
13916 Now, we start @value{GDBN} on our sample program:
13920 GNU gdb 2002-05-06-cvs
13921 Copyright 2002 Free Software Foundation, Inc.
13922 GDB is free software, @dots{}
13926 We can expand macros and examine their definitions, even when the
13927 program is not running. @value{GDBN} uses the current listing position
13928 to decide which macro definitions are in scope:
13931 (@value{GDBP}) list main
13934 5 #define ADD(x) (M + x)
13939 10 printf ("Hello, world!\n");
13941 12 printf ("We're so creative.\n");
13942 (@value{GDBP}) info macro ADD
13943 Defined at /home/jimb/gdb/macros/play/sample.c:5
13944 #define ADD(x) (M + x)
13945 (@value{GDBP}) info macro Q
13946 Defined at /home/jimb/gdb/macros/play/sample.h:1
13947 included at /home/jimb/gdb/macros/play/sample.c:2
13949 (@value{GDBP}) macro expand ADD(1)
13950 expands to: (42 + 1)
13951 (@value{GDBP}) macro expand-once ADD(1)
13952 expands to: once (M + 1)
13956 In the example above, note that @code{macro expand-once} expands only
13957 the macro invocation explicit in the original text --- the invocation of
13958 @code{ADD} --- but does not expand the invocation of the macro @code{M},
13959 which was introduced by @code{ADD}.
13961 Once the program is running, @value{GDBN} uses the macro definitions in
13962 force at the source line of the current stack frame:
13965 (@value{GDBP}) break main
13966 Breakpoint 1 at 0x8048370: file sample.c, line 10.
13968 Starting program: /home/jimb/gdb/macros/play/sample
13970 Breakpoint 1, main () at sample.c:10
13971 10 printf ("Hello, world!\n");
13975 At line 10, the definition of the macro @code{N} at line 9 is in force:
13978 (@value{GDBP}) info macro N
13979 Defined at /home/jimb/gdb/macros/play/sample.c:9
13981 (@value{GDBP}) macro expand N Q M
13982 expands to: 28 < 42
13983 (@value{GDBP}) print N Q M
13988 As we step over directives that remove @code{N}'s definition, and then
13989 give it a new definition, @value{GDBN} finds the definition (or lack
13990 thereof) in force at each point:
13993 (@value{GDBP}) next
13995 12 printf ("We're so creative.\n");
13996 (@value{GDBP}) info macro N
13997 The symbol `N' has no definition as a C/C++ preprocessor macro
13998 at /home/jimb/gdb/macros/play/sample.c:12
13999 (@value{GDBP}) next
14001 14 printf ("Goodbye, world!\n");
14002 (@value{GDBP}) info macro N
14003 Defined at /home/jimb/gdb/macros/play/sample.c:13
14005 (@value{GDBP}) macro expand N Q M
14006 expands to: 1729 < 42
14007 (@value{GDBP}) print N Q M
14012 In addition to source files, macros can be defined on the compilation command
14013 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14014 such a way, @value{GDBN} displays the location of their definition as line zero
14015 of the source file submitted to the compiler.
14018 (@value{GDBP}) info macro __STDC__
14019 Defined at /home/jimb/gdb/macros/play/sample.c:0
14026 @chapter Tracepoints
14027 @c This chapter is based on the documentation written by Michael
14028 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14030 @cindex tracepoints
14031 In some applications, it is not feasible for the debugger to interrupt
14032 the program's execution long enough for the developer to learn
14033 anything helpful about its behavior. If the program's correctness
14034 depends on its real-time behavior, delays introduced by a debugger
14035 might cause the program to change its behavior drastically, or perhaps
14036 fail, even when the code itself is correct. It is useful to be able
14037 to observe the program's behavior without interrupting it.
14039 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14040 specify locations in the program, called @dfn{tracepoints}, and
14041 arbitrary expressions to evaluate when those tracepoints are reached.
14042 Later, using the @code{tfind} command, you can examine the values
14043 those expressions had when the program hit the tracepoints. The
14044 expressions may also denote objects in memory---structures or arrays,
14045 for example---whose values @value{GDBN} should record; while visiting
14046 a particular tracepoint, you may inspect those objects as if they were
14047 in memory at that moment. However, because @value{GDBN} records these
14048 values without interacting with you, it can do so quickly and
14049 unobtrusively, hopefully not disturbing the program's behavior.
14051 The tracepoint facility is currently available only for remote
14052 targets. @xref{Targets}. In addition, your remote target must know
14053 how to collect trace data. This functionality is implemented in the
14054 remote stub; however, none of the stubs distributed with @value{GDBN}
14055 support tracepoints as of this writing. The format of the remote
14056 packets used to implement tracepoints are described in @ref{Tracepoint
14059 It is also possible to get trace data from a file, in a manner reminiscent
14060 of corefiles; you specify the filename, and use @code{tfind} to search
14061 through the file. @xref{Trace Files}, for more details.
14063 This chapter describes the tracepoint commands and features.
14066 * Set Tracepoints::
14067 * Analyze Collected Data::
14068 * Tracepoint Variables::
14072 @node Set Tracepoints
14073 @section Commands to Set Tracepoints
14075 Before running such a @dfn{trace experiment}, an arbitrary number of
14076 tracepoints can be set. A tracepoint is actually a special type of
14077 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14078 standard breakpoint commands. For instance, as with breakpoints,
14079 tracepoint numbers are successive integers starting from one, and many
14080 of the commands associated with tracepoints take the tracepoint number
14081 as their argument, to identify which tracepoint to work on.
14083 For each tracepoint, you can specify, in advance, some arbitrary set
14084 of data that you want the target to collect in the trace buffer when
14085 it hits that tracepoint. The collected data can include registers,
14086 local variables, or global data. Later, you can use @value{GDBN}
14087 commands to examine the values these data had at the time the
14088 tracepoint was hit.
14090 Tracepoints do not support every breakpoint feature. Ignore counts on
14091 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14092 commands when they are hit. Tracepoints may not be thread-specific
14095 @cindex fast tracepoints
14096 Some targets may support @dfn{fast tracepoints}, which are inserted in
14097 a different way (such as with a jump instead of a trap), that is
14098 faster but possibly restricted in where they may be installed.
14100 @cindex static tracepoints
14101 @cindex markers, static tracepoints
14102 @cindex probing markers, static tracepoints
14103 Regular and fast tracepoints are dynamic tracing facilities, meaning
14104 that they can be used to insert tracepoints at (almost) any location
14105 in the target. Some targets may also support controlling @dfn{static
14106 tracepoints} from @value{GDBN}. With static tracing, a set of
14107 instrumentation points, also known as @dfn{markers}, are embedded in
14108 the target program, and can be activated or deactivated by name or
14109 address. These are usually placed at locations which facilitate
14110 investigating what the target is actually doing. @value{GDBN}'s
14111 support for static tracing includes being able to list instrumentation
14112 points, and attach them with @value{GDBN} defined high level
14113 tracepoints that expose the whole range of convenience of
14114 @value{GDBN}'s tracepoints support. Namely, support for collecting
14115 registers values and values of global or local (to the instrumentation
14116 point) variables; tracepoint conditions and trace state variables.
14117 The act of installing a @value{GDBN} static tracepoint on an
14118 instrumentation point, or marker, is referred to as @dfn{probing} a
14119 static tracepoint marker.
14121 @code{gdbserver} supports tracepoints on some target systems.
14122 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14124 This section describes commands to set tracepoints and associated
14125 conditions and actions.
14128 * Create and Delete Tracepoints::
14129 * Enable and Disable Tracepoints::
14130 * Tracepoint Passcounts::
14131 * Tracepoint Conditions::
14132 * Trace State Variables::
14133 * Tracepoint Actions::
14134 * Listing Tracepoints::
14135 * Listing Static Tracepoint Markers::
14136 * Starting and Stopping Trace Experiments::
14137 * Tracepoint Restrictions::
14140 @node Create and Delete Tracepoints
14141 @subsection Create and Delete Tracepoints
14144 @cindex set tracepoint
14146 @item trace @var{location}
14147 The @code{trace} command is very similar to the @code{break} command.
14148 Its argument @var{location} can be any valid location.
14149 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
14150 which is a point in the target program where the debugger will briefly stop,
14151 collect some data, and then allow the program to continue. Setting a tracepoint
14152 or changing its actions takes effect immediately if the remote stub
14153 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14155 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14156 these changes don't take effect until the next @code{tstart}
14157 command, and once a trace experiment is running, further changes will
14158 not have any effect until the next trace experiment starts. In addition,
14159 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14160 address is not yet resolved. (This is similar to pending breakpoints.)
14161 Pending tracepoints are not downloaded to the target and not installed
14162 until they are resolved. The resolution of pending tracepoints requires
14163 @value{GDBN} support---when debugging with the remote target, and
14164 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14165 tracing}), pending tracepoints can not be resolved (and downloaded to
14166 the remote stub) while @value{GDBN} is disconnected.
14168 Here are some examples of using the @code{trace} command:
14171 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14173 (@value{GDBP}) @b{trace +2} // 2 lines forward
14175 (@value{GDBP}) @b{trace my_function} // first source line of function
14177 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14179 (@value{GDBP}) @b{trace *0x2117c4} // an address
14183 You can abbreviate @code{trace} as @code{tr}.
14185 @item trace @var{location} if @var{cond}
14186 Set a tracepoint with condition @var{cond}; evaluate the expression
14187 @var{cond} each time the tracepoint is reached, and collect data only
14188 if the value is nonzero---that is, if @var{cond} evaluates as true.
14189 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14190 information on tracepoint conditions.
14192 @item ftrace @var{location} [ if @var{cond} ]
14193 @cindex set fast tracepoint
14194 @cindex fast tracepoints, setting
14196 The @code{ftrace} command sets a fast tracepoint. For targets that
14197 support them, fast tracepoints will use a more efficient but possibly
14198 less general technique to trigger data collection, such as a jump
14199 instruction instead of a trap, or some sort of hardware support. It
14200 may not be possible to create a fast tracepoint at the desired
14201 location, in which case the command will exit with an explanatory
14204 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14207 On 32-bit x86-architecture systems, fast tracepoints normally need to
14208 be placed at an instruction that is 5 bytes or longer, but can be
14209 placed at 4-byte instructions if the low 64K of memory of the target
14210 program is available to install trampolines. Some Unix-type systems,
14211 such as @sc{gnu}/Linux, exclude low addresses from the program's
14212 address space; but for instance with the Linux kernel it is possible
14213 to let @value{GDBN} use this area by doing a @command{sysctl} command
14214 to set the @code{mmap_min_addr} kernel parameter, as in
14217 sudo sysctl -w vm.mmap_min_addr=32768
14221 which sets the low address to 32K, which leaves plenty of room for
14222 trampolines. The minimum address should be set to a page boundary.
14224 @item strace @var{location} [ if @var{cond} ]
14225 @cindex set static tracepoint
14226 @cindex static tracepoints, setting
14227 @cindex probe static tracepoint marker
14229 The @code{strace} command sets a static tracepoint. For targets that
14230 support it, setting a static tracepoint probes a static
14231 instrumentation point, or marker, found at @var{location}. It may not
14232 be possible to set a static tracepoint at the desired location, in
14233 which case the command will exit with an explanatory message.
14235 @value{GDBN} handles arguments to @code{strace} exactly as for
14236 @code{trace}, with the addition that the user can also specify
14237 @code{-m @var{marker}} as @var{location}. This probes the marker
14238 identified by the @var{marker} string identifier. This identifier
14239 depends on the static tracepoint backend library your program is
14240 using. You can find all the marker identifiers in the @samp{ID} field
14241 of the @code{info static-tracepoint-markers} command output.
14242 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14243 Markers}. For example, in the following small program using the UST
14249 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14254 the marker id is composed of joining the first two arguments to the
14255 @code{trace_mark} call with a slash, which translates to:
14258 (@value{GDBP}) info static-tracepoint-markers
14259 Cnt Enb ID Address What
14260 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14266 so you may probe the marker above with:
14269 (@value{GDBP}) strace -m ust/bar33
14272 Static tracepoints accept an extra collect action --- @code{collect
14273 $_sdata}. This collects arbitrary user data passed in the probe point
14274 call to the tracing library. In the UST example above, you'll see
14275 that the third argument to @code{trace_mark} is a printf-like format
14276 string. The user data is then the result of running that formatting
14277 string against the following arguments. Note that @code{info
14278 static-tracepoint-markers} command output lists that format string in
14279 the @samp{Data:} field.
14281 You can inspect this data when analyzing the trace buffer, by printing
14282 the $_sdata variable like any other variable available to
14283 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14286 @cindex last tracepoint number
14287 @cindex recent tracepoint number
14288 @cindex tracepoint number
14289 The convenience variable @code{$tpnum} records the tracepoint number
14290 of the most recently set tracepoint.
14292 @kindex delete tracepoint
14293 @cindex tracepoint deletion
14294 @item delete tracepoint @r{[}@var{num}@r{]}
14295 Permanently delete one or more tracepoints. With no argument, the
14296 default is to delete all tracepoints. Note that the regular
14297 @code{delete} command can remove tracepoints also.
14302 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14304 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14308 You can abbreviate this command as @code{del tr}.
14311 @node Enable and Disable Tracepoints
14312 @subsection Enable and Disable Tracepoints
14314 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14317 @kindex disable tracepoint
14318 @item disable tracepoint @r{[}@var{num}@r{]}
14319 Disable tracepoint @var{num}, or all tracepoints if no argument
14320 @var{num} is given. A disabled tracepoint will have no effect during
14321 a trace experiment, but it is not forgotten. You can re-enable
14322 a disabled tracepoint using the @code{enable tracepoint} command.
14323 If the command is issued during a trace experiment and the debug target
14324 has support for disabling tracepoints during a trace experiment, then the
14325 change will be effective immediately. Otherwise, it will be applied to the
14326 next trace experiment.
14328 @kindex enable tracepoint
14329 @item enable tracepoint @r{[}@var{num}@r{]}
14330 Enable tracepoint @var{num}, or all tracepoints. If this command is
14331 issued during a trace experiment and the debug target supports enabling
14332 tracepoints during a trace experiment, then the enabled tracepoints will
14333 become effective immediately. Otherwise, they will become effective the
14334 next time a trace experiment is run.
14337 @node Tracepoint Passcounts
14338 @subsection Tracepoint Passcounts
14342 @cindex tracepoint pass count
14343 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14344 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14345 automatically stop a trace experiment. If a tracepoint's passcount is
14346 @var{n}, then the trace experiment will be automatically stopped on
14347 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14348 @var{num} is not specified, the @code{passcount} command sets the
14349 passcount of the most recently defined tracepoint. If no passcount is
14350 given, the trace experiment will run until stopped explicitly by the
14356 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14357 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14359 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14360 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14361 (@value{GDBP}) @b{trace foo}
14362 (@value{GDBP}) @b{pass 3}
14363 (@value{GDBP}) @b{trace bar}
14364 (@value{GDBP}) @b{pass 2}
14365 (@value{GDBP}) @b{trace baz}
14366 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14367 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14368 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14369 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14373 @node Tracepoint Conditions
14374 @subsection Tracepoint Conditions
14375 @cindex conditional tracepoints
14376 @cindex tracepoint conditions
14378 The simplest sort of tracepoint collects data every time your program
14379 reaches a specified place. You can also specify a @dfn{condition} for
14380 a tracepoint. A condition is just a Boolean expression in your
14381 programming language (@pxref{Expressions, ,Expressions}). A
14382 tracepoint with a condition evaluates the expression each time your
14383 program reaches it, and data collection happens only if the condition
14386 Tracepoint conditions can be specified when a tracepoint is set, by
14387 using @samp{if} in the arguments to the @code{trace} command.
14388 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14389 also be set or changed at any time with the @code{condition} command,
14390 just as with breakpoints.
14392 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14393 the conditional expression itself. Instead, @value{GDBN} encodes the
14394 expression into an agent expression (@pxref{Agent Expressions})
14395 suitable for execution on the target, independently of @value{GDBN}.
14396 Global variables become raw memory locations, locals become stack
14397 accesses, and so forth.
14399 For instance, suppose you have a function that is usually called
14400 frequently, but should not be called after an error has occurred. You
14401 could use the following tracepoint command to collect data about calls
14402 of that function that happen while the error code is propagating
14403 through the program; an unconditional tracepoint could end up
14404 collecting thousands of useless trace frames that you would have to
14408 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14411 @node Trace State Variables
14412 @subsection Trace State Variables
14413 @cindex trace state variables
14415 A @dfn{trace state variable} is a special type of variable that is
14416 created and managed by target-side code. The syntax is the same as
14417 that for GDB's convenience variables (a string prefixed with ``$''),
14418 but they are stored on the target. They must be created explicitly,
14419 using a @code{tvariable} command. They are always 64-bit signed
14422 Trace state variables are remembered by @value{GDBN}, and downloaded
14423 to the target along with tracepoint information when the trace
14424 experiment starts. There are no intrinsic limits on the number of
14425 trace state variables, beyond memory limitations of the target.
14427 @cindex convenience variables, and trace state variables
14428 Although trace state variables are managed by the target, you can use
14429 them in print commands and expressions as if they were convenience
14430 variables; @value{GDBN} will get the current value from the target
14431 while the trace experiment is running. Trace state variables share
14432 the same namespace as other ``$'' variables, which means that you
14433 cannot have trace state variables with names like @code{$23} or
14434 @code{$pc}, nor can you have a trace state variable and a convenience
14435 variable with the same name.
14439 @item tvariable $@var{name} [ = @var{expression} ]
14441 The @code{tvariable} command creates a new trace state variable named
14442 @code{$@var{name}}, and optionally gives it an initial value of
14443 @var{expression}. The @var{expression} is evaluated when this command is
14444 entered; the result will be converted to an integer if possible,
14445 otherwise @value{GDBN} will report an error. A subsequent
14446 @code{tvariable} command specifying the same name does not create a
14447 variable, but instead assigns the supplied initial value to the
14448 existing variable of that name, overwriting any previous initial
14449 value. The default initial value is 0.
14451 @item info tvariables
14452 @kindex info tvariables
14453 List all the trace state variables along with their initial values.
14454 Their current values may also be displayed, if the trace experiment is
14457 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14458 @kindex delete tvariable
14459 Delete the given trace state variables, or all of them if no arguments
14464 @node Tracepoint Actions
14465 @subsection Tracepoint Action Lists
14469 @cindex tracepoint actions
14470 @item actions @r{[}@var{num}@r{]}
14471 This command will prompt for a list of actions to be taken when the
14472 tracepoint is hit. If the tracepoint number @var{num} is not
14473 specified, this command sets the actions for the one that was most
14474 recently defined (so that you can define a tracepoint and then say
14475 @code{actions} without bothering about its number). You specify the
14476 actions themselves on the following lines, one action at a time, and
14477 terminate the actions list with a line containing just @code{end}. So
14478 far, the only defined actions are @code{collect}, @code{teval}, and
14479 @code{while-stepping}.
14481 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14482 Commands, ,Breakpoint Command Lists}), except that only the defined
14483 actions are allowed; any other @value{GDBN} command is rejected.
14485 @cindex remove actions from a tracepoint
14486 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14487 and follow it immediately with @samp{end}.
14490 (@value{GDBP}) @b{collect @var{data}} // collect some data
14492 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14494 (@value{GDBP}) @b{end} // signals the end of actions.
14497 In the following example, the action list begins with @code{collect}
14498 commands indicating the things to be collected when the tracepoint is
14499 hit. Then, in order to single-step and collect additional data
14500 following the tracepoint, a @code{while-stepping} command is used,
14501 followed by the list of things to be collected after each step in a
14502 sequence of single steps. The @code{while-stepping} command is
14503 terminated by its own separate @code{end} command. Lastly, the action
14504 list is terminated by an @code{end} command.
14507 (@value{GDBP}) @b{trace foo}
14508 (@value{GDBP}) @b{actions}
14509 Enter actions for tracepoint 1, one per line:
14512 > while-stepping 12
14513 > collect $pc, arr[i]
14518 @kindex collect @r{(tracepoints)}
14519 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14520 Collect values of the given expressions when the tracepoint is hit.
14521 This command accepts a comma-separated list of any valid expressions.
14522 In addition to global, static, or local variables, the following
14523 special arguments are supported:
14527 Collect all registers.
14530 Collect all function arguments.
14533 Collect all local variables.
14536 Collect the return address. This is helpful if you want to see more
14539 @emph{Note:} The return address location can not always be reliably
14540 determined up front, and the wrong address / registers may end up
14541 collected instead. On some architectures the reliability is higher
14542 for tracepoints at function entry, while on others it's the opposite.
14543 When this happens, backtracing will stop because the return address is
14544 found unavailable (unless another collect rule happened to match it).
14547 Collects the number of arguments from the static probe at which the
14548 tracepoint is located.
14549 @xref{Static Probe Points}.
14551 @item $_probe_arg@var{n}
14552 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14553 from the static probe at which the tracepoint is located.
14554 @xref{Static Probe Points}.
14557 @vindex $_sdata@r{, collect}
14558 Collect static tracepoint marker specific data. Only available for
14559 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14560 Lists}. On the UST static tracepoints library backend, an
14561 instrumentation point resembles a @code{printf} function call. The
14562 tracing library is able to collect user specified data formatted to a
14563 character string using the format provided by the programmer that
14564 instrumented the program. Other backends have similar mechanisms.
14565 Here's an example of a UST marker call:
14568 const char master_name[] = "$your_name";
14569 trace_mark(channel1, marker1, "hello %s", master_name)
14572 In this case, collecting @code{$_sdata} collects the string
14573 @samp{hello $yourname}. When analyzing the trace buffer, you can
14574 inspect @samp{$_sdata} like any other variable available to
14578 You can give several consecutive @code{collect} commands, each one
14579 with a single argument, or one @code{collect} command with several
14580 arguments separated by commas; the effect is the same.
14582 The optional @var{mods} changes the usual handling of the arguments.
14583 @code{s} requests that pointers to chars be handled as strings, in
14584 particular collecting the contents of the memory being pointed at, up
14585 to the first zero. The upper bound is by default the value of the
14586 @code{print elements} variable; if @code{s} is followed by a decimal
14587 number, that is the upper bound instead. So for instance
14588 @samp{collect/s25 mystr} collects as many as 25 characters at
14591 The command @code{info scope} (@pxref{Symbols, info scope}) is
14592 particularly useful for figuring out what data to collect.
14594 @kindex teval @r{(tracepoints)}
14595 @item teval @var{expr1}, @var{expr2}, @dots{}
14596 Evaluate the given expressions when the tracepoint is hit. This
14597 command accepts a comma-separated list of expressions. The results
14598 are discarded, so this is mainly useful for assigning values to trace
14599 state variables (@pxref{Trace State Variables}) without adding those
14600 values to the trace buffer, as would be the case if the @code{collect}
14603 @kindex while-stepping @r{(tracepoints)}
14604 @item while-stepping @var{n}
14605 Perform @var{n} single-step instruction traces after the tracepoint,
14606 collecting new data after each step. The @code{while-stepping}
14607 command is followed by the list of what to collect while stepping
14608 (followed by its own @code{end} command):
14611 > while-stepping 12
14612 > collect $regs, myglobal
14618 Note that @code{$pc} is not automatically collected by
14619 @code{while-stepping}; you need to explicitly collect that register if
14620 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14623 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14624 @kindex set default-collect
14625 @cindex default collection action
14626 This variable is a list of expressions to collect at each tracepoint
14627 hit. It is effectively an additional @code{collect} action prepended
14628 to every tracepoint action list. The expressions are parsed
14629 individually for each tracepoint, so for instance a variable named
14630 @code{xyz} may be interpreted as a global for one tracepoint, and a
14631 local for another, as appropriate to the tracepoint's location.
14633 @item show default-collect
14634 @kindex show default-collect
14635 Show the list of expressions that are collected by default at each
14640 @node Listing Tracepoints
14641 @subsection Listing Tracepoints
14644 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14645 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14646 @cindex information about tracepoints
14647 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14648 Display information about the tracepoint @var{num}. If you don't
14649 specify a tracepoint number, displays information about all the
14650 tracepoints defined so far. The format is similar to that used for
14651 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14652 command, simply restricting itself to tracepoints.
14654 A tracepoint's listing may include additional information specific to
14659 its passcount as given by the @code{passcount @var{n}} command
14662 the state about installed on target of each location
14666 (@value{GDBP}) @b{info trace}
14667 Num Type Disp Enb Address What
14668 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14670 collect globfoo, $regs
14675 2 tracepoint keep y <MULTIPLE>
14677 2.1 y 0x0804859c in func4 at change-loc.h:35
14678 installed on target
14679 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14680 installed on target
14681 2.3 y <PENDING> set_tracepoint
14682 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14683 not installed on target
14688 This command can be abbreviated @code{info tp}.
14691 @node Listing Static Tracepoint Markers
14692 @subsection Listing Static Tracepoint Markers
14695 @kindex info static-tracepoint-markers
14696 @cindex information about static tracepoint markers
14697 @item info static-tracepoint-markers
14698 Display information about all static tracepoint markers defined in the
14701 For each marker, the following columns are printed:
14705 An incrementing counter, output to help readability. This is not a
14708 The marker ID, as reported by the target.
14709 @item Enabled or Disabled
14710 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
14711 that are not enabled.
14713 Where the marker is in your program, as a memory address.
14715 Where the marker is in the source for your program, as a file and line
14716 number. If the debug information included in the program does not
14717 allow @value{GDBN} to locate the source of the marker, this column
14718 will be left blank.
14722 In addition, the following information may be printed for each marker:
14726 User data passed to the tracing library by the marker call. In the
14727 UST backend, this is the format string passed as argument to the
14729 @item Static tracepoints probing the marker
14730 The list of static tracepoints attached to the marker.
14734 (@value{GDBP}) info static-tracepoint-markers
14735 Cnt ID Enb Address What
14736 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
14737 Data: number1 %d number2 %d
14738 Probed by static tracepoints: #2
14739 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
14745 @node Starting and Stopping Trace Experiments
14746 @subsection Starting and Stopping Trace Experiments
14749 @kindex tstart [ @var{notes} ]
14750 @cindex start a new trace experiment
14751 @cindex collected data discarded
14753 This command starts the trace experiment, and begins collecting data.
14754 It has the side effect of discarding all the data collected in the
14755 trace buffer during the previous trace experiment. If any arguments
14756 are supplied, they are taken as a note and stored with the trace
14757 experiment's state. The notes may be arbitrary text, and are
14758 especially useful with disconnected tracing in a multi-user context;
14759 the notes can explain what the trace is doing, supply user contact
14760 information, and so forth.
14762 @kindex tstop [ @var{notes} ]
14763 @cindex stop a running trace experiment
14765 This command stops the trace experiment. If any arguments are
14766 supplied, they are recorded with the experiment as a note. This is
14767 useful if you are stopping a trace started by someone else, for
14768 instance if the trace is interfering with the system's behavior and
14769 needs to be stopped quickly.
14771 @strong{Note}: a trace experiment and data collection may stop
14772 automatically if any tracepoint's passcount is reached
14773 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
14776 @cindex status of trace data collection
14777 @cindex trace experiment, status of
14779 This command displays the status of the current trace data
14783 Here is an example of the commands we described so far:
14786 (@value{GDBP}) @b{trace gdb_c_test}
14787 (@value{GDBP}) @b{actions}
14788 Enter actions for tracepoint #1, one per line.
14789 > collect $regs,$locals,$args
14790 > while-stepping 11
14794 (@value{GDBP}) @b{tstart}
14795 [time passes @dots{}]
14796 (@value{GDBP}) @b{tstop}
14799 @anchor{disconnected tracing}
14800 @cindex disconnected tracing
14801 You can choose to continue running the trace experiment even if
14802 @value{GDBN} disconnects from the target, voluntarily or
14803 involuntarily. For commands such as @code{detach}, the debugger will
14804 ask what you want to do with the trace. But for unexpected
14805 terminations (@value{GDBN} crash, network outage), it would be
14806 unfortunate to lose hard-won trace data, so the variable
14807 @code{disconnected-tracing} lets you decide whether the trace should
14808 continue running without @value{GDBN}.
14811 @item set disconnected-tracing on
14812 @itemx set disconnected-tracing off
14813 @kindex set disconnected-tracing
14814 Choose whether a tracing run should continue to run if @value{GDBN}
14815 has disconnected from the target. Note that @code{detach} or
14816 @code{quit} will ask you directly what to do about a running trace no
14817 matter what this variable's setting, so the variable is mainly useful
14818 for handling unexpected situations, such as loss of the network.
14820 @item show disconnected-tracing
14821 @kindex show disconnected-tracing
14822 Show the current choice for disconnected tracing.
14826 When you reconnect to the target, the trace experiment may or may not
14827 still be running; it might have filled the trace buffer in the
14828 meantime, or stopped for one of the other reasons. If it is running,
14829 it will continue after reconnection.
14831 Upon reconnection, the target will upload information about the
14832 tracepoints in effect. @value{GDBN} will then compare that
14833 information to the set of tracepoints currently defined, and attempt
14834 to match them up, allowing for the possibility that the numbers may
14835 have changed due to creation and deletion in the meantime. If one of
14836 the target's tracepoints does not match any in @value{GDBN}, the
14837 debugger will create a new tracepoint, so that you have a number with
14838 which to specify that tracepoint. This matching-up process is
14839 necessarily heuristic, and it may result in useless tracepoints being
14840 created; you may simply delete them if they are of no use.
14842 @cindex circular trace buffer
14843 If your target agent supports a @dfn{circular trace buffer}, then you
14844 can run a trace experiment indefinitely without filling the trace
14845 buffer; when space runs out, the agent deletes already-collected trace
14846 frames, oldest first, until there is enough room to continue
14847 collecting. This is especially useful if your tracepoints are being
14848 hit too often, and your trace gets terminated prematurely because the
14849 buffer is full. To ask for a circular trace buffer, simply set
14850 @samp{circular-trace-buffer} to on. You can set this at any time,
14851 including during tracing; if the agent can do it, it will change
14852 buffer handling on the fly, otherwise it will not take effect until
14856 @item set circular-trace-buffer on
14857 @itemx set circular-trace-buffer off
14858 @kindex set circular-trace-buffer
14859 Choose whether a tracing run should use a linear or circular buffer
14860 for trace data. A linear buffer will not lose any trace data, but may
14861 fill up prematurely, while a circular buffer will discard old trace
14862 data, but it will have always room for the latest tracepoint hits.
14864 @item show circular-trace-buffer
14865 @kindex show circular-trace-buffer
14866 Show the current choice for the trace buffer. Note that this may not
14867 match the agent's current buffer handling, nor is it guaranteed to
14868 match the setting that might have been in effect during a past run,
14869 for instance if you are looking at frames from a trace file.
14874 @item set trace-buffer-size @var{n}
14875 @itemx set trace-buffer-size unlimited
14876 @kindex set trace-buffer-size
14877 Request that the target use a trace buffer of @var{n} bytes. Not all
14878 targets will honor the request; they may have a compiled-in size for
14879 the trace buffer, or some other limitation. Set to a value of
14880 @code{unlimited} or @code{-1} to let the target use whatever size it
14881 likes. This is also the default.
14883 @item show trace-buffer-size
14884 @kindex show trace-buffer-size
14885 Show the current requested size for the trace buffer. Note that this
14886 will only match the actual size if the target supports size-setting,
14887 and was able to handle the requested size. For instance, if the
14888 target can only change buffer size between runs, this variable will
14889 not reflect the change until the next run starts. Use @code{tstatus}
14890 to get a report of the actual buffer size.
14894 @item set trace-user @var{text}
14895 @kindex set trace-user
14897 @item show trace-user
14898 @kindex show trace-user
14900 @item set trace-notes @var{text}
14901 @kindex set trace-notes
14902 Set the trace run's notes.
14904 @item show trace-notes
14905 @kindex show trace-notes
14906 Show the trace run's notes.
14908 @item set trace-stop-notes @var{text}
14909 @kindex set trace-stop-notes
14910 Set the trace run's stop notes. The handling of the note is as for
14911 @code{tstop} arguments; the set command is convenient way to fix a
14912 stop note that is mistaken or incomplete.
14914 @item show trace-stop-notes
14915 @kindex show trace-stop-notes
14916 Show the trace run's stop notes.
14920 @node Tracepoint Restrictions
14921 @subsection Tracepoint Restrictions
14923 @cindex tracepoint restrictions
14924 There are a number of restrictions on the use of tracepoints. As
14925 described above, tracepoint data gathering occurs on the target
14926 without interaction from @value{GDBN}. Thus the full capabilities of
14927 the debugger are not available during data gathering, and then at data
14928 examination time, you will be limited by only having what was
14929 collected. The following items describe some common problems, but it
14930 is not exhaustive, and you may run into additional difficulties not
14936 Tracepoint expressions are intended to gather objects (lvalues). Thus
14937 the full flexibility of GDB's expression evaluator is not available.
14938 You cannot call functions, cast objects to aggregate types, access
14939 convenience variables or modify values (except by assignment to trace
14940 state variables). Some language features may implicitly call
14941 functions (for instance Objective-C fields with accessors), and therefore
14942 cannot be collected either.
14945 Collection of local variables, either individually or in bulk with
14946 @code{$locals} or @code{$args}, during @code{while-stepping} may
14947 behave erratically. The stepping action may enter a new scope (for
14948 instance by stepping into a function), or the location of the variable
14949 may change (for instance it is loaded into a register). The
14950 tracepoint data recorded uses the location information for the
14951 variables that is correct for the tracepoint location. When the
14952 tracepoint is created, it is not possible, in general, to determine
14953 where the steps of a @code{while-stepping} sequence will advance the
14954 program---particularly if a conditional branch is stepped.
14957 Collection of an incompletely-initialized or partially-destroyed object
14958 may result in something that @value{GDBN} cannot display, or displays
14959 in a misleading way.
14962 When @value{GDBN} displays a pointer to character it automatically
14963 dereferences the pointer to also display characters of the string
14964 being pointed to. However, collecting the pointer during tracing does
14965 not automatically collect the string. You need to explicitly
14966 dereference the pointer and provide size information if you want to
14967 collect not only the pointer, but the memory pointed to. For example,
14968 @code{*ptr@@50} can be used to collect the 50 element array pointed to
14972 It is not possible to collect a complete stack backtrace at a
14973 tracepoint. Instead, you may collect the registers and a few hundred
14974 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
14975 (adjust to use the name of the actual stack pointer register on your
14976 target architecture, and the amount of stack you wish to capture).
14977 Then the @code{backtrace} command will show a partial backtrace when
14978 using a trace frame. The number of stack frames that can be examined
14979 depends on the sizes of the frames in the collected stack. Note that
14980 if you ask for a block so large that it goes past the bottom of the
14981 stack, the target agent may report an error trying to read from an
14985 If you do not collect registers at a tracepoint, @value{GDBN} can
14986 infer that the value of @code{$pc} must be the same as the address of
14987 the tracepoint and use that when you are looking at a trace frame
14988 for that tracepoint. However, this cannot work if the tracepoint has
14989 multiple locations (for instance if it was set in a function that was
14990 inlined), or if it has a @code{while-stepping} loop. In those cases
14991 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
14996 @node Analyze Collected Data
14997 @section Using the Collected Data
14999 After the tracepoint experiment ends, you use @value{GDBN} commands
15000 for examining the trace data. The basic idea is that each tracepoint
15001 collects a trace @dfn{snapshot} every time it is hit and another
15002 snapshot every time it single-steps. All these snapshots are
15003 consecutively numbered from zero and go into a buffer, and you can
15004 examine them later. The way you examine them is to @dfn{focus} on a
15005 specific trace snapshot. When the remote stub is focused on a trace
15006 snapshot, it will respond to all @value{GDBN} requests for memory and
15007 registers by reading from the buffer which belongs to that snapshot,
15008 rather than from @emph{real} memory or registers of the program being
15009 debugged. This means that @strong{all} @value{GDBN} commands
15010 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15011 behave as if we were currently debugging the program state as it was
15012 when the tracepoint occurred. Any requests for data that are not in
15013 the buffer will fail.
15016 * tfind:: How to select a trace snapshot
15017 * tdump:: How to display all data for a snapshot
15018 * save tracepoints:: How to save tracepoints for a future run
15022 @subsection @code{tfind @var{n}}
15025 @cindex select trace snapshot
15026 @cindex find trace snapshot
15027 The basic command for selecting a trace snapshot from the buffer is
15028 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15029 counting from zero. If no argument @var{n} is given, the next
15030 snapshot is selected.
15032 Here are the various forms of using the @code{tfind} command.
15036 Find the first snapshot in the buffer. This is a synonym for
15037 @code{tfind 0} (since 0 is the number of the first snapshot).
15040 Stop debugging trace snapshots, resume @emph{live} debugging.
15043 Same as @samp{tfind none}.
15046 No argument means find the next trace snapshot or find the first
15047 one if no trace snapshot is selected.
15050 Find the previous trace snapshot before the current one. This permits
15051 retracing earlier steps.
15053 @item tfind tracepoint @var{num}
15054 Find the next snapshot associated with tracepoint @var{num}. Search
15055 proceeds forward from the last examined trace snapshot. If no
15056 argument @var{num} is given, it means find the next snapshot collected
15057 for the same tracepoint as the current snapshot.
15059 @item tfind pc @var{addr}
15060 Find the next snapshot associated with the value @var{addr} of the
15061 program counter. Search proceeds forward from the last examined trace
15062 snapshot. If no argument @var{addr} is given, it means find the next
15063 snapshot with the same value of PC as the current snapshot.
15065 @item tfind outside @var{addr1}, @var{addr2}
15066 Find the next snapshot whose PC is outside the given range of
15067 addresses (exclusive).
15069 @item tfind range @var{addr1}, @var{addr2}
15070 Find the next snapshot whose PC is between @var{addr1} and
15071 @var{addr2} (inclusive).
15073 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15074 Find the next snapshot associated with the source line @var{n}. If
15075 the optional argument @var{file} is given, refer to line @var{n} in
15076 that source file. Search proceeds forward from the last examined
15077 trace snapshot. If no argument @var{n} is given, it means find the
15078 next line other than the one currently being examined; thus saying
15079 @code{tfind line} repeatedly can appear to have the same effect as
15080 stepping from line to line in a @emph{live} debugging session.
15083 The default arguments for the @code{tfind} commands are specifically
15084 designed to make it easy to scan through the trace buffer. For
15085 instance, @code{tfind} with no argument selects the next trace
15086 snapshot, and @code{tfind -} with no argument selects the previous
15087 trace snapshot. So, by giving one @code{tfind} command, and then
15088 simply hitting @key{RET} repeatedly you can examine all the trace
15089 snapshots in order. Or, by saying @code{tfind -} and then hitting
15090 @key{RET} repeatedly you can examine the snapshots in reverse order.
15091 The @code{tfind line} command with no argument selects the snapshot
15092 for the next source line executed. The @code{tfind pc} command with
15093 no argument selects the next snapshot with the same program counter
15094 (PC) as the current frame. The @code{tfind tracepoint} command with
15095 no argument selects the next trace snapshot collected by the same
15096 tracepoint as the current one.
15098 In addition to letting you scan through the trace buffer manually,
15099 these commands make it easy to construct @value{GDBN} scripts that
15100 scan through the trace buffer and print out whatever collected data
15101 you are interested in. Thus, if we want to examine the PC, FP, and SP
15102 registers from each trace frame in the buffer, we can say this:
15105 (@value{GDBP}) @b{tfind start}
15106 (@value{GDBP}) @b{while ($trace_frame != -1)}
15107 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15108 $trace_frame, $pc, $sp, $fp
15112 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15113 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15114 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15115 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15116 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15117 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15118 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15119 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15120 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15121 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15122 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15125 Or, if we want to examine the variable @code{X} at each source line in
15129 (@value{GDBP}) @b{tfind start}
15130 (@value{GDBP}) @b{while ($trace_frame != -1)}
15131 > printf "Frame %d, X == %d\n", $trace_frame, X
15141 @subsection @code{tdump}
15143 @cindex dump all data collected at tracepoint
15144 @cindex tracepoint data, display
15146 This command takes no arguments. It prints all the data collected at
15147 the current trace snapshot.
15150 (@value{GDBP}) @b{trace 444}
15151 (@value{GDBP}) @b{actions}
15152 Enter actions for tracepoint #2, one per line:
15153 > collect $regs, $locals, $args, gdb_long_test
15156 (@value{GDBP}) @b{tstart}
15158 (@value{GDBP}) @b{tfind line 444}
15159 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15161 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15163 (@value{GDBP}) @b{tdump}
15164 Data collected at tracepoint 2, trace frame 1:
15165 d0 0xc4aa0085 -995491707
15169 d4 0x71aea3d 119204413
15172 d7 0x380035 3670069
15173 a0 0x19e24a 1696330
15174 a1 0x3000668 50333288
15176 a3 0x322000 3284992
15177 a4 0x3000698 50333336
15178 a5 0x1ad3cc 1758156
15179 fp 0x30bf3c 0x30bf3c
15180 sp 0x30bf34 0x30bf34
15182 pc 0x20b2c8 0x20b2c8
15186 p = 0x20e5b4 "gdb-test"
15193 gdb_long_test = 17 '\021'
15198 @code{tdump} works by scanning the tracepoint's current collection
15199 actions and printing the value of each expression listed. So
15200 @code{tdump} can fail, if after a run, you change the tracepoint's
15201 actions to mention variables that were not collected during the run.
15203 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15204 uses the collected value of @code{$pc} to distinguish between trace
15205 frames that were collected at the tracepoint hit, and frames that were
15206 collected while stepping. This allows it to correctly choose whether
15207 to display the basic list of collections, or the collections from the
15208 body of the while-stepping loop. However, if @code{$pc} was not collected,
15209 then @code{tdump} will always attempt to dump using the basic collection
15210 list, and may fail if a while-stepping frame does not include all the
15211 same data that is collected at the tracepoint hit.
15212 @c This is getting pretty arcane, example would be good.
15214 @node save tracepoints
15215 @subsection @code{save tracepoints @var{filename}}
15216 @kindex save tracepoints
15217 @kindex save-tracepoints
15218 @cindex save tracepoints for future sessions
15220 This command saves all current tracepoint definitions together with
15221 their actions and passcounts, into a file @file{@var{filename}}
15222 suitable for use in a later debugging session. To read the saved
15223 tracepoint definitions, use the @code{source} command (@pxref{Command
15224 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15225 alias for @w{@code{save tracepoints}}
15227 @node Tracepoint Variables
15228 @section Convenience Variables for Tracepoints
15229 @cindex tracepoint variables
15230 @cindex convenience variables for tracepoints
15233 @vindex $trace_frame
15234 @item (int) $trace_frame
15235 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15236 snapshot is selected.
15238 @vindex $tracepoint
15239 @item (int) $tracepoint
15240 The tracepoint for the current trace snapshot.
15242 @vindex $trace_line
15243 @item (int) $trace_line
15244 The line number for the current trace snapshot.
15246 @vindex $trace_file
15247 @item (char []) $trace_file
15248 The source file for the current trace snapshot.
15250 @vindex $trace_func
15251 @item (char []) $trace_func
15252 The name of the function containing @code{$tracepoint}.
15255 Note: @code{$trace_file} is not suitable for use in @code{printf},
15256 use @code{output} instead.
15258 Here's a simple example of using these convenience variables for
15259 stepping through all the trace snapshots and printing some of their
15260 data. Note that these are not the same as trace state variables,
15261 which are managed by the target.
15264 (@value{GDBP}) @b{tfind start}
15266 (@value{GDBP}) @b{while $trace_frame != -1}
15267 > output $trace_file
15268 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15274 @section Using Trace Files
15275 @cindex trace files
15277 In some situations, the target running a trace experiment may no
15278 longer be available; perhaps it crashed, or the hardware was needed
15279 for a different activity. To handle these cases, you can arrange to
15280 dump the trace data into a file, and later use that file as a source
15281 of trace data, via the @code{target tfile} command.
15286 @item tsave [ -r ] @var{filename}
15287 @itemx tsave [-ctf] @var{dirname}
15288 Save the trace data to @var{filename}. By default, this command
15289 assumes that @var{filename} refers to the host filesystem, so if
15290 necessary @value{GDBN} will copy raw trace data up from the target and
15291 then save it. If the target supports it, you can also supply the
15292 optional argument @code{-r} (``remote'') to direct the target to save
15293 the data directly into @var{filename} in its own filesystem, which may be
15294 more efficient if the trace buffer is very large. (Note, however, that
15295 @code{target tfile} can only read from files accessible to the host.)
15296 By default, this command will save trace frame in tfile format.
15297 You can supply the optional argument @code{-ctf} to save data in CTF
15298 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15299 that can be shared by multiple debugging and tracing tools. Please go to
15300 @indicateurl{http://www.efficios.com/ctf} to get more information.
15302 @kindex target tfile
15306 @item target tfile @var{filename}
15307 @itemx target ctf @var{dirname}
15308 Use the file named @var{filename} or directory named @var{dirname} as
15309 a source of trace data. Commands that examine data work as they do with
15310 a live target, but it is not possible to run any new trace experiments.
15311 @code{tstatus} will report the state of the trace run at the moment
15312 the data was saved, as well as the current trace frame you are examining.
15313 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15317 (@value{GDBP}) target ctf ctf.ctf
15318 (@value{GDBP}) tfind
15319 Found trace frame 0, tracepoint 2
15320 39 ++a; /* set tracepoint 1 here */
15321 (@value{GDBP}) tdump
15322 Data collected at tracepoint 2, trace frame 0:
15326 c = @{"123", "456", "789", "123", "456", "789"@}
15327 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15335 @chapter Debugging Programs That Use Overlays
15338 If your program is too large to fit completely in your target system's
15339 memory, you can sometimes use @dfn{overlays} to work around this
15340 problem. @value{GDBN} provides some support for debugging programs that
15344 * How Overlays Work:: A general explanation of overlays.
15345 * Overlay Commands:: Managing overlays in @value{GDBN}.
15346 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15347 mapped by asking the inferior.
15348 * Overlay Sample Program:: A sample program using overlays.
15351 @node How Overlays Work
15352 @section How Overlays Work
15353 @cindex mapped overlays
15354 @cindex unmapped overlays
15355 @cindex load address, overlay's
15356 @cindex mapped address
15357 @cindex overlay area
15359 Suppose you have a computer whose instruction address space is only 64
15360 kilobytes long, but which has much more memory which can be accessed by
15361 other means: special instructions, segment registers, or memory
15362 management hardware, for example. Suppose further that you want to
15363 adapt a program which is larger than 64 kilobytes to run on this system.
15365 One solution is to identify modules of your program which are relatively
15366 independent, and need not call each other directly; call these modules
15367 @dfn{overlays}. Separate the overlays from the main program, and place
15368 their machine code in the larger memory. Place your main program in
15369 instruction memory, but leave at least enough space there to hold the
15370 largest overlay as well.
15372 Now, to call a function located in an overlay, you must first copy that
15373 overlay's machine code from the large memory into the space set aside
15374 for it in the instruction memory, and then jump to its entry point
15377 @c NB: In the below the mapped area's size is greater or equal to the
15378 @c size of all overlays. This is intentional to remind the developer
15379 @c that overlays don't necessarily need to be the same size.
15383 Data Instruction Larger
15384 Address Space Address Space Address Space
15385 +-----------+ +-----------+ +-----------+
15387 +-----------+ +-----------+ +-----------+<-- overlay 1
15388 | program | | main | .----| overlay 1 | load address
15389 | variables | | program | | +-----------+
15390 | and heap | | | | | |
15391 +-----------+ | | | +-----------+<-- overlay 2
15392 | | +-----------+ | | | load address
15393 +-----------+ | | | .-| overlay 2 |
15395 mapped --->+-----------+ | | +-----------+
15396 address | | | | | |
15397 | overlay | <-' | | |
15398 | area | <---' +-----------+<-- overlay 3
15399 | | <---. | | load address
15400 +-----------+ `--| overlay 3 |
15407 @anchor{A code overlay}A code overlay
15411 The diagram (@pxref{A code overlay}) shows a system with separate data
15412 and instruction address spaces. To map an overlay, the program copies
15413 its code from the larger address space to the instruction address space.
15414 Since the overlays shown here all use the same mapped address, only one
15415 may be mapped at a time. For a system with a single address space for
15416 data and instructions, the diagram would be similar, except that the
15417 program variables and heap would share an address space with the main
15418 program and the overlay area.
15420 An overlay loaded into instruction memory and ready for use is called a
15421 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15422 instruction memory. An overlay not present (or only partially present)
15423 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15424 is its address in the larger memory. The mapped address is also called
15425 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15426 called the @dfn{load memory address}, or @dfn{LMA}.
15428 Unfortunately, overlays are not a completely transparent way to adapt a
15429 program to limited instruction memory. They introduce a new set of
15430 global constraints you must keep in mind as you design your program:
15435 Before calling or returning to a function in an overlay, your program
15436 must make sure that overlay is actually mapped. Otherwise, the call or
15437 return will transfer control to the right address, but in the wrong
15438 overlay, and your program will probably crash.
15441 If the process of mapping an overlay is expensive on your system, you
15442 will need to choose your overlays carefully to minimize their effect on
15443 your program's performance.
15446 The executable file you load onto your system must contain each
15447 overlay's instructions, appearing at the overlay's load address, not its
15448 mapped address. However, each overlay's instructions must be relocated
15449 and its symbols defined as if the overlay were at its mapped address.
15450 You can use GNU linker scripts to specify different load and relocation
15451 addresses for pieces of your program; see @ref{Overlay Description,,,
15452 ld.info, Using ld: the GNU linker}.
15455 The procedure for loading executable files onto your system must be able
15456 to load their contents into the larger address space as well as the
15457 instruction and data spaces.
15461 The overlay system described above is rather simple, and could be
15462 improved in many ways:
15467 If your system has suitable bank switch registers or memory management
15468 hardware, you could use those facilities to make an overlay's load area
15469 contents simply appear at their mapped address in instruction space.
15470 This would probably be faster than copying the overlay to its mapped
15471 area in the usual way.
15474 If your overlays are small enough, you could set aside more than one
15475 overlay area, and have more than one overlay mapped at a time.
15478 You can use overlays to manage data, as well as instructions. In
15479 general, data overlays are even less transparent to your design than
15480 code overlays: whereas code overlays only require care when you call or
15481 return to functions, data overlays require care every time you access
15482 the data. Also, if you change the contents of a data overlay, you
15483 must copy its contents back out to its load address before you can copy a
15484 different data overlay into the same mapped area.
15489 @node Overlay Commands
15490 @section Overlay Commands
15492 To use @value{GDBN}'s overlay support, each overlay in your program must
15493 correspond to a separate section of the executable file. The section's
15494 virtual memory address and load memory address must be the overlay's
15495 mapped and load addresses. Identifying overlays with sections allows
15496 @value{GDBN} to determine the appropriate address of a function or
15497 variable, depending on whether the overlay is mapped or not.
15499 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15500 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15505 Disable @value{GDBN}'s overlay support. When overlay support is
15506 disabled, @value{GDBN} assumes that all functions and variables are
15507 always present at their mapped addresses. By default, @value{GDBN}'s
15508 overlay support is disabled.
15510 @item overlay manual
15511 @cindex manual overlay debugging
15512 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15513 relies on you to tell it which overlays are mapped, and which are not,
15514 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15515 commands described below.
15517 @item overlay map-overlay @var{overlay}
15518 @itemx overlay map @var{overlay}
15519 @cindex map an overlay
15520 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15521 be the name of the object file section containing the overlay. When an
15522 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15523 functions and variables at their mapped addresses. @value{GDBN} assumes
15524 that any other overlays whose mapped ranges overlap that of
15525 @var{overlay} are now unmapped.
15527 @item overlay unmap-overlay @var{overlay}
15528 @itemx overlay unmap @var{overlay}
15529 @cindex unmap an overlay
15530 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15531 must be the name of the object file section containing the overlay.
15532 When an overlay is unmapped, @value{GDBN} assumes it can find the
15533 overlay's functions and variables at their load addresses.
15536 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15537 consults a data structure the overlay manager maintains in the inferior
15538 to see which overlays are mapped. For details, see @ref{Automatic
15539 Overlay Debugging}.
15541 @item overlay load-target
15542 @itemx overlay load
15543 @cindex reloading the overlay table
15544 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15545 re-reads the table @value{GDBN} automatically each time the inferior
15546 stops, so this command should only be necessary if you have changed the
15547 overlay mapping yourself using @value{GDBN}. This command is only
15548 useful when using automatic overlay debugging.
15550 @item overlay list-overlays
15551 @itemx overlay list
15552 @cindex listing mapped overlays
15553 Display a list of the overlays currently mapped, along with their mapped
15554 addresses, load addresses, and sizes.
15558 Normally, when @value{GDBN} prints a code address, it includes the name
15559 of the function the address falls in:
15562 (@value{GDBP}) print main
15563 $3 = @{int ()@} 0x11a0 <main>
15566 When overlay debugging is enabled, @value{GDBN} recognizes code in
15567 unmapped overlays, and prints the names of unmapped functions with
15568 asterisks around them. For example, if @code{foo} is a function in an
15569 unmapped overlay, @value{GDBN} prints it this way:
15572 (@value{GDBP}) overlay list
15573 No sections are mapped.
15574 (@value{GDBP}) print foo
15575 $5 = @{int (int)@} 0x100000 <*foo*>
15578 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15582 (@value{GDBP}) overlay list
15583 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15584 mapped at 0x1016 - 0x104a
15585 (@value{GDBP}) print foo
15586 $6 = @{int (int)@} 0x1016 <foo>
15589 When overlay debugging is enabled, @value{GDBN} can find the correct
15590 address for functions and variables in an overlay, whether or not the
15591 overlay is mapped. This allows most @value{GDBN} commands, like
15592 @code{break} and @code{disassemble}, to work normally, even on unmapped
15593 code. However, @value{GDBN}'s breakpoint support has some limitations:
15597 @cindex breakpoints in overlays
15598 @cindex overlays, setting breakpoints in
15599 You can set breakpoints in functions in unmapped overlays, as long as
15600 @value{GDBN} can write to the overlay at its load address.
15602 @value{GDBN} can not set hardware or simulator-based breakpoints in
15603 unmapped overlays. However, if you set a breakpoint at the end of your
15604 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15605 you are using manual overlay management), @value{GDBN} will re-set its
15606 breakpoints properly.
15610 @node Automatic Overlay Debugging
15611 @section Automatic Overlay Debugging
15612 @cindex automatic overlay debugging
15614 @value{GDBN} can automatically track which overlays are mapped and which
15615 are not, given some simple co-operation from the overlay manager in the
15616 inferior. If you enable automatic overlay debugging with the
15617 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15618 looks in the inferior's memory for certain variables describing the
15619 current state of the overlays.
15621 Here are the variables your overlay manager must define to support
15622 @value{GDBN}'s automatic overlay debugging:
15626 @item @code{_ovly_table}:
15627 This variable must be an array of the following structures:
15632 /* The overlay's mapped address. */
15635 /* The size of the overlay, in bytes. */
15636 unsigned long size;
15638 /* The overlay's load address. */
15641 /* Non-zero if the overlay is currently mapped;
15643 unsigned long mapped;
15647 @item @code{_novlys}:
15648 This variable must be a four-byte signed integer, holding the total
15649 number of elements in @code{_ovly_table}.
15653 To decide whether a particular overlay is mapped or not, @value{GDBN}
15654 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15655 @code{lma} members equal the VMA and LMA of the overlay's section in the
15656 executable file. When @value{GDBN} finds a matching entry, it consults
15657 the entry's @code{mapped} member to determine whether the overlay is
15660 In addition, your overlay manager may define a function called
15661 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15662 will silently set a breakpoint there. If the overlay manager then
15663 calls this function whenever it has changed the overlay table, this
15664 will enable @value{GDBN} to accurately keep track of which overlays
15665 are in program memory, and update any breakpoints that may be set
15666 in overlays. This will allow breakpoints to work even if the
15667 overlays are kept in ROM or other non-writable memory while they
15668 are not being executed.
15670 @node Overlay Sample Program
15671 @section Overlay Sample Program
15672 @cindex overlay example program
15674 When linking a program which uses overlays, you must place the overlays
15675 at their load addresses, while relocating them to run at their mapped
15676 addresses. To do this, you must write a linker script (@pxref{Overlay
15677 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15678 since linker scripts are specific to a particular host system, target
15679 architecture, and target memory layout, this manual cannot provide
15680 portable sample code demonstrating @value{GDBN}'s overlay support.
15682 However, the @value{GDBN} source distribution does contain an overlaid
15683 program, with linker scripts for a few systems, as part of its test
15684 suite. The program consists of the following files from
15685 @file{gdb/testsuite/gdb.base}:
15689 The main program file.
15691 A simple overlay manager, used by @file{overlays.c}.
15696 Overlay modules, loaded and used by @file{overlays.c}.
15699 Linker scripts for linking the test program on the @code{d10v-elf}
15700 and @code{m32r-elf} targets.
15703 You can build the test program using the @code{d10v-elf} GCC
15704 cross-compiler like this:
15707 $ d10v-elf-gcc -g -c overlays.c
15708 $ d10v-elf-gcc -g -c ovlymgr.c
15709 $ d10v-elf-gcc -g -c foo.c
15710 $ d10v-elf-gcc -g -c bar.c
15711 $ d10v-elf-gcc -g -c baz.c
15712 $ d10v-elf-gcc -g -c grbx.c
15713 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
15714 baz.o grbx.o -Wl,-Td10v.ld -o overlays
15717 The build process is identical for any other architecture, except that
15718 you must substitute the appropriate compiler and linker script for the
15719 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
15723 @chapter Using @value{GDBN} with Different Languages
15726 Although programming languages generally have common aspects, they are
15727 rarely expressed in the same manner. For instance, in ANSI C,
15728 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
15729 Modula-2, it is accomplished by @code{p^}. Values can also be
15730 represented (and displayed) differently. Hex numbers in C appear as
15731 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
15733 @cindex working language
15734 Language-specific information is built into @value{GDBN} for some languages,
15735 allowing you to express operations like the above in your program's
15736 native language, and allowing @value{GDBN} to output values in a manner
15737 consistent with the syntax of your program's native language. The
15738 language you use to build expressions is called the @dfn{working
15742 * Setting:: Switching between source languages
15743 * Show:: Displaying the language
15744 * Checks:: Type and range checks
15745 * Supported Languages:: Supported languages
15746 * Unsupported Languages:: Unsupported languages
15750 @section Switching Between Source Languages
15752 There are two ways to control the working language---either have @value{GDBN}
15753 set it automatically, or select it manually yourself. You can use the
15754 @code{set language} command for either purpose. On startup, @value{GDBN}
15755 defaults to setting the language automatically. The working language is
15756 used to determine how expressions you type are interpreted, how values
15759 In addition to the working language, every source file that
15760 @value{GDBN} knows about has its own working language. For some object
15761 file formats, the compiler might indicate which language a particular
15762 source file is in. However, most of the time @value{GDBN} infers the
15763 language from the name of the file. The language of a source file
15764 controls whether C@t{++} names are demangled---this way @code{backtrace} can
15765 show each frame appropriately for its own language. There is no way to
15766 set the language of a source file from within @value{GDBN}, but you can
15767 set the language associated with a filename extension. @xref{Show, ,
15768 Displaying the Language}.
15770 This is most commonly a problem when you use a program, such
15771 as @code{cfront} or @code{f2c}, that generates C but is written in
15772 another language. In that case, make the
15773 program use @code{#line} directives in its C output; that way
15774 @value{GDBN} will know the correct language of the source code of the original
15775 program, and will display that source code, not the generated C code.
15778 * Filenames:: Filename extensions and languages.
15779 * Manually:: Setting the working language manually
15780 * Automatically:: Having @value{GDBN} infer the source language
15784 @subsection List of Filename Extensions and Languages
15786 If a source file name ends in one of the following extensions, then
15787 @value{GDBN} infers that its language is the one indicated.
15805 C@t{++} source file
15811 Objective-C source file
15815 Fortran source file
15818 Modula-2 source file
15822 Assembler source file. This actually behaves almost like C, but
15823 @value{GDBN} does not skip over function prologues when stepping.
15826 In addition, you may set the language associated with a filename
15827 extension. @xref{Show, , Displaying the Language}.
15830 @subsection Setting the Working Language
15832 If you allow @value{GDBN} to set the language automatically,
15833 expressions are interpreted the same way in your debugging session and
15836 @kindex set language
15837 If you wish, you may set the language manually. To do this, issue the
15838 command @samp{set language @var{lang}}, where @var{lang} is the name of
15839 a language, such as
15840 @code{c} or @code{modula-2}.
15841 For a list of the supported languages, type @samp{set language}.
15843 Setting the language manually prevents @value{GDBN} from updating the working
15844 language automatically. This can lead to confusion if you try
15845 to debug a program when the working language is not the same as the
15846 source language, when an expression is acceptable to both
15847 languages---but means different things. For instance, if the current
15848 source file were written in C, and @value{GDBN} was parsing Modula-2, a
15856 might not have the effect you intended. In C, this means to add
15857 @code{b} and @code{c} and place the result in @code{a}. The result
15858 printed would be the value of @code{a}. In Modula-2, this means to compare
15859 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
15861 @node Automatically
15862 @subsection Having @value{GDBN} Infer the Source Language
15864 To have @value{GDBN} set the working language automatically, use
15865 @samp{set language local} or @samp{set language auto}. @value{GDBN}
15866 then infers the working language. That is, when your program stops in a
15867 frame (usually by encountering a breakpoint), @value{GDBN} sets the
15868 working language to the language recorded for the function in that
15869 frame. If the language for a frame is unknown (that is, if the function
15870 or block corresponding to the frame was defined in a source file that
15871 does not have a recognized extension), the current working language is
15872 not changed, and @value{GDBN} issues a warning.
15874 This may not seem necessary for most programs, which are written
15875 entirely in one source language. However, program modules and libraries
15876 written in one source language can be used by a main program written in
15877 a different source language. Using @samp{set language auto} in this
15878 case frees you from having to set the working language manually.
15881 @section Displaying the Language
15883 The following commands help you find out which language is the
15884 working language, and also what language source files were written in.
15887 @item show language
15888 @anchor{show language}
15889 @kindex show language
15890 Display the current working language. This is the
15891 language you can use with commands such as @code{print} to
15892 build and compute expressions that may involve variables in your program.
15895 @kindex info frame@r{, show the source language}
15896 Display the source language for this frame. This language becomes the
15897 working language if you use an identifier from this frame.
15898 @xref{Frame Info, ,Information about a Frame}, to identify the other
15899 information listed here.
15902 @kindex info source@r{, show the source language}
15903 Display the source language of this source file.
15904 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
15905 information listed here.
15908 In unusual circumstances, you may have source files with extensions
15909 not in the standard list. You can then set the extension associated
15910 with a language explicitly:
15913 @item set extension-language @var{ext} @var{language}
15914 @kindex set extension-language
15915 Tell @value{GDBN} that source files with extension @var{ext} are to be
15916 assumed as written in the source language @var{language}.
15918 @item info extensions
15919 @kindex info extensions
15920 List all the filename extensions and the associated languages.
15924 @section Type and Range Checking
15926 Some languages are designed to guard you against making seemingly common
15927 errors through a series of compile- and run-time checks. These include
15928 checking the type of arguments to functions and operators and making
15929 sure mathematical overflows are caught at run time. Checks such as
15930 these help to ensure a program's correctness once it has been compiled
15931 by eliminating type mismatches and providing active checks for range
15932 errors when your program is running.
15934 By default @value{GDBN} checks for these errors according to the
15935 rules of the current source language. Although @value{GDBN} does not check
15936 the statements in your program, it can check expressions entered directly
15937 into @value{GDBN} for evaluation via the @code{print} command, for example.
15940 * Type Checking:: An overview of type checking
15941 * Range Checking:: An overview of range checking
15944 @cindex type checking
15945 @cindex checks, type
15946 @node Type Checking
15947 @subsection An Overview of Type Checking
15949 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
15950 arguments to operators and functions have to be of the correct type,
15951 otherwise an error occurs. These checks prevent type mismatch
15952 errors from ever causing any run-time problems. For example,
15955 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
15957 (@value{GDBP}) print obj.my_method (0)
15960 (@value{GDBP}) print obj.my_method (0x1234)
15961 Cannot resolve method klass::my_method to any overloaded instance
15964 The second example fails because in C@t{++} the integer constant
15965 @samp{0x1234} is not type-compatible with the pointer parameter type.
15967 For the expressions you use in @value{GDBN} commands, you can tell
15968 @value{GDBN} to not enforce strict type checking or
15969 to treat any mismatches as errors and abandon the expression;
15970 When type checking is disabled, @value{GDBN} successfully evaluates
15971 expressions like the second example above.
15973 Even if type checking is off, there may be other reasons
15974 related to type that prevent @value{GDBN} from evaluating an expression.
15975 For instance, @value{GDBN} does not know how to add an @code{int} and
15976 a @code{struct foo}. These particular type errors have nothing to do
15977 with the language in use and usually arise from expressions which make
15978 little sense to evaluate anyway.
15980 @value{GDBN} provides some additional commands for controlling type checking:
15982 @kindex set check type
15983 @kindex show check type
15985 @item set check type on
15986 @itemx set check type off
15987 Set strict type checking on or off. If any type mismatches occur in
15988 evaluating an expression while type checking is on, @value{GDBN} prints a
15989 message and aborts evaluation of the expression.
15991 @item show check type
15992 Show the current setting of type checking and whether @value{GDBN}
15993 is enforcing strict type checking rules.
15996 @cindex range checking
15997 @cindex checks, range
15998 @node Range Checking
15999 @subsection An Overview of Range Checking
16001 In some languages (such as Modula-2), it is an error to exceed the
16002 bounds of a type; this is enforced with run-time checks. Such range
16003 checking is meant to ensure program correctness by making sure
16004 computations do not overflow, or indices on an array element access do
16005 not exceed the bounds of the array.
16007 For expressions you use in @value{GDBN} commands, you can tell
16008 @value{GDBN} to treat range errors in one of three ways: ignore them,
16009 always treat them as errors and abandon the expression, or issue
16010 warnings but evaluate the expression anyway.
16012 A range error can result from numerical overflow, from exceeding an
16013 array index bound, or when you type a constant that is not a member
16014 of any type. Some languages, however, do not treat overflows as an
16015 error. In many implementations of C, mathematical overflow causes the
16016 result to ``wrap around'' to lower values---for example, if @var{m} is
16017 the largest integer value, and @var{s} is the smallest, then
16020 @var{m} + 1 @result{} @var{s}
16023 This, too, is specific to individual languages, and in some cases
16024 specific to individual compilers or machines. @xref{Supported Languages, ,
16025 Supported Languages}, for further details on specific languages.
16027 @value{GDBN} provides some additional commands for controlling the range checker:
16029 @kindex set check range
16030 @kindex show check range
16032 @item set check range auto
16033 Set range checking on or off based on the current working language.
16034 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16037 @item set check range on
16038 @itemx set check range off
16039 Set range checking on or off, overriding the default setting for the
16040 current working language. A warning is issued if the setting does not
16041 match the language default. If a range error occurs and range checking is on,
16042 then a message is printed and evaluation of the expression is aborted.
16044 @item set check range warn
16045 Output messages when the @value{GDBN} range checker detects a range error,
16046 but attempt to evaluate the expression anyway. Evaluating the
16047 expression may still be impossible for other reasons, such as accessing
16048 memory that the process does not own (a typical example from many Unix
16052 Show the current setting of the range checker, and whether or not it is
16053 being set automatically by @value{GDBN}.
16056 @node Supported Languages
16057 @section Supported Languages
16059 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16060 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16061 @c This is false ...
16062 Some @value{GDBN} features may be used in expressions regardless of the
16063 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16064 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16065 ,Expressions}) can be used with the constructs of any supported
16068 The following sections detail to what degree each source language is
16069 supported by @value{GDBN}. These sections are not meant to be language
16070 tutorials or references, but serve only as a reference guide to what the
16071 @value{GDBN} expression parser accepts, and what input and output
16072 formats should look like for different languages. There are many good
16073 books written on each of these languages; please look to these for a
16074 language reference or tutorial.
16077 * C:: C and C@t{++}
16080 * Objective-C:: Objective-C
16081 * OpenCL C:: OpenCL C
16082 * Fortran:: Fortran
16085 * Modula-2:: Modula-2
16090 @subsection C and C@t{++}
16092 @cindex C and C@t{++}
16093 @cindex expressions in C or C@t{++}
16095 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16096 to both languages. Whenever this is the case, we discuss those languages
16100 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16101 @cindex @sc{gnu} C@t{++}
16102 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16103 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16104 effectively, you must compile your C@t{++} programs with a supported
16105 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16106 compiler (@code{aCC}).
16109 * C Operators:: C and C@t{++} operators
16110 * C Constants:: C and C@t{++} constants
16111 * C Plus Plus Expressions:: C@t{++} expressions
16112 * C Defaults:: Default settings for C and C@t{++}
16113 * C Checks:: C and C@t{++} type and range checks
16114 * Debugging C:: @value{GDBN} and C
16115 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16116 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16120 @subsubsection C and C@t{++} Operators
16122 @cindex C and C@t{++} operators
16124 Operators must be defined on values of specific types. For instance,
16125 @code{+} is defined on numbers, but not on structures. Operators are
16126 often defined on groups of types.
16128 For the purposes of C and C@t{++}, the following definitions hold:
16133 @emph{Integral types} include @code{int} with any of its storage-class
16134 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16137 @emph{Floating-point types} include @code{float}, @code{double}, and
16138 @code{long double} (if supported by the target platform).
16141 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16144 @emph{Scalar types} include all of the above.
16149 The following operators are supported. They are listed here
16150 in order of increasing precedence:
16154 The comma or sequencing operator. Expressions in a comma-separated list
16155 are evaluated from left to right, with the result of the entire
16156 expression being the last expression evaluated.
16159 Assignment. The value of an assignment expression is the value
16160 assigned. Defined on scalar types.
16163 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16164 and translated to @w{@code{@var{a} = @var{a op b}}}.
16165 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16166 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16167 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16170 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16171 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16172 should be of an integral type.
16175 Logical @sc{or}. Defined on integral types.
16178 Logical @sc{and}. Defined on integral types.
16181 Bitwise @sc{or}. Defined on integral types.
16184 Bitwise exclusive-@sc{or}. Defined on integral types.
16187 Bitwise @sc{and}. Defined on integral types.
16190 Equality and inequality. Defined on scalar types. The value of these
16191 expressions is 0 for false and non-zero for true.
16193 @item <@r{, }>@r{, }<=@r{, }>=
16194 Less than, greater than, less than or equal, greater than or equal.
16195 Defined on scalar types. The value of these expressions is 0 for false
16196 and non-zero for true.
16199 left shift, and right shift. Defined on integral types.
16202 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16205 Addition and subtraction. Defined on integral types, floating-point types and
16208 @item *@r{, }/@r{, }%
16209 Multiplication, division, and modulus. Multiplication and division are
16210 defined on integral and floating-point types. Modulus is defined on
16214 Increment and decrement. When appearing before a variable, the
16215 operation is performed before the variable is used in an expression;
16216 when appearing after it, the variable's value is used before the
16217 operation takes place.
16220 Pointer dereferencing. Defined on pointer types. Same precedence as
16224 Address operator. Defined on variables. Same precedence as @code{++}.
16226 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16227 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16228 to examine the address
16229 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16233 Negative. Defined on integral and floating-point types. Same
16234 precedence as @code{++}.
16237 Logical negation. Defined on integral types. Same precedence as
16241 Bitwise complement operator. Defined on integral types. Same precedence as
16246 Structure member, and pointer-to-structure member. For convenience,
16247 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16248 pointer based on the stored type information.
16249 Defined on @code{struct} and @code{union} data.
16252 Dereferences of pointers to members.
16255 Array indexing. @code{@var{a}[@var{i}]} is defined as
16256 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16259 Function parameter list. Same precedence as @code{->}.
16262 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16263 and @code{class} types.
16266 Doubled colons also represent the @value{GDBN} scope operator
16267 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16271 If an operator is redefined in the user code, @value{GDBN} usually
16272 attempts to invoke the redefined version instead of using the operator's
16273 predefined meaning.
16276 @subsubsection C and C@t{++} Constants
16278 @cindex C and C@t{++} constants
16280 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16285 Integer constants are a sequence of digits. Octal constants are
16286 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16287 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16288 @samp{l}, specifying that the constant should be treated as a
16292 Floating point constants are a sequence of digits, followed by a decimal
16293 point, followed by a sequence of digits, and optionally followed by an
16294 exponent. An exponent is of the form:
16295 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16296 sequence of digits. The @samp{+} is optional for positive exponents.
16297 A floating-point constant may also end with a letter @samp{f} or
16298 @samp{F}, specifying that the constant should be treated as being of
16299 the @code{float} (as opposed to the default @code{double}) type; or with
16300 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16304 Enumerated constants consist of enumerated identifiers, or their
16305 integral equivalents.
16308 Character constants are a single character surrounded by single quotes
16309 (@code{'}), or a number---the ordinal value of the corresponding character
16310 (usually its @sc{ascii} value). Within quotes, the single character may
16311 be represented by a letter or by @dfn{escape sequences}, which are of
16312 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16313 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16314 @samp{@var{x}} is a predefined special character---for example,
16315 @samp{\n} for newline.
16317 Wide character constants can be written by prefixing a character
16318 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16319 form of @samp{x}. The target wide character set is used when
16320 computing the value of this constant (@pxref{Character Sets}).
16323 String constants are a sequence of character constants surrounded by
16324 double quotes (@code{"}). Any valid character constant (as described
16325 above) may appear. Double quotes within the string must be preceded by
16326 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16329 Wide string constants can be written by prefixing a string constant
16330 with @samp{L}, as in C. The target wide character set is used when
16331 computing the value of this constant (@pxref{Character Sets}).
16334 Pointer constants are an integral value. You can also write pointers
16335 to constants using the C operator @samp{&}.
16338 Array constants are comma-separated lists surrounded by braces @samp{@{}
16339 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16340 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16341 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16344 @node C Plus Plus Expressions
16345 @subsubsection C@t{++} Expressions
16347 @cindex expressions in C@t{++}
16348 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16350 @cindex debugging C@t{++} programs
16351 @cindex C@t{++} compilers
16352 @cindex debug formats and C@t{++}
16353 @cindex @value{NGCC} and C@t{++}
16355 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16356 the proper compiler and the proper debug format. Currently,
16357 @value{GDBN} works best when debugging C@t{++} code that is compiled
16358 with the most recent version of @value{NGCC} possible. The DWARF
16359 debugging format is preferred; @value{NGCC} defaults to this on most
16360 popular platforms. Other compilers and/or debug formats are likely to
16361 work badly or not at all when using @value{GDBN} to debug C@t{++}
16362 code. @xref{Compilation}.
16367 @cindex member functions
16369 Member function calls are allowed; you can use expressions like
16372 count = aml->GetOriginal(x, y)
16375 @vindex this@r{, inside C@t{++} member functions}
16376 @cindex namespace in C@t{++}
16378 While a member function is active (in the selected stack frame), your
16379 expressions have the same namespace available as the member function;
16380 that is, @value{GDBN} allows implicit references to the class instance
16381 pointer @code{this} following the same rules as C@t{++}. @code{using}
16382 declarations in the current scope are also respected by @value{GDBN}.
16384 @cindex call overloaded functions
16385 @cindex overloaded functions, calling
16386 @cindex type conversions in C@t{++}
16388 You can call overloaded functions; @value{GDBN} resolves the function
16389 call to the right definition, with some restrictions. @value{GDBN} does not
16390 perform overload resolution involving user-defined type conversions,
16391 calls to constructors, or instantiations of templates that do not exist
16392 in the program. It also cannot handle ellipsis argument lists or
16395 It does perform integral conversions and promotions, floating-point
16396 promotions, arithmetic conversions, pointer conversions, conversions of
16397 class objects to base classes, and standard conversions such as those of
16398 functions or arrays to pointers; it requires an exact match on the
16399 number of function arguments.
16401 Overload resolution is always performed, unless you have specified
16402 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16403 ,@value{GDBN} Features for C@t{++}}.
16405 You must specify @code{set overload-resolution off} in order to use an
16406 explicit function signature to call an overloaded function, as in
16408 p 'foo(char,int)'('x', 13)
16411 The @value{GDBN} command-completion facility can simplify this;
16412 see @ref{Completion, ,Command Completion}.
16414 @cindex reference declarations
16416 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16417 references; you can use them in expressions just as you do in C@t{++}
16418 source---they are automatically dereferenced.
16420 In the parameter list shown when @value{GDBN} displays a frame, the values of
16421 reference variables are not displayed (unlike other variables); this
16422 avoids clutter, since references are often used for large structures.
16423 The @emph{address} of a reference variable is always shown, unless
16424 you have specified @samp{set print address off}.
16427 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16428 expressions can use it just as expressions in your program do. Since
16429 one scope may be defined in another, you can use @code{::} repeatedly if
16430 necessary, for example in an expression like
16431 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16432 resolving name scope by reference to source files, in both C and C@t{++}
16433 debugging (@pxref{Variables, ,Program Variables}).
16436 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16441 @subsubsection C and C@t{++} Defaults
16443 @cindex C and C@t{++} defaults
16445 If you allow @value{GDBN} to set range checking automatically, it
16446 defaults to @code{off} whenever the working language changes to
16447 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16448 selects the working language.
16450 If you allow @value{GDBN} to set the language automatically, it
16451 recognizes source files whose names end with @file{.c}, @file{.C}, or
16452 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16453 these files, it sets the working language to C or C@t{++}.
16454 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16455 for further details.
16458 @subsubsection C and C@t{++} Type and Range Checks
16460 @cindex C and C@t{++} checks
16462 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16463 checking is used. However, if you turn type checking off, @value{GDBN}
16464 will allow certain non-standard conversions, such as promoting integer
16465 constants to pointers.
16467 Range checking, if turned on, is done on mathematical operations. Array
16468 indices are not checked, since they are often used to index a pointer
16469 that is not itself an array.
16472 @subsubsection @value{GDBN} and C
16474 The @code{set print union} and @code{show print union} commands apply to
16475 the @code{union} type. When set to @samp{on}, any @code{union} that is
16476 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16477 appears as @samp{@{...@}}.
16479 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16480 with pointers and a memory allocation function. @xref{Expressions,
16483 @node Debugging C Plus Plus
16484 @subsubsection @value{GDBN} Features for C@t{++}
16486 @cindex commands for C@t{++}
16488 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16489 designed specifically for use with C@t{++}. Here is a summary:
16492 @cindex break in overloaded functions
16493 @item @r{breakpoint menus}
16494 When you want a breakpoint in a function whose name is overloaded,
16495 @value{GDBN} has the capability to display a menu of possible breakpoint
16496 locations to help you specify which function definition you want.
16497 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16499 @cindex overloading in C@t{++}
16500 @item rbreak @var{regex}
16501 Setting breakpoints using regular expressions is helpful for setting
16502 breakpoints on overloaded functions that are not members of any special
16504 @xref{Set Breaks, ,Setting Breakpoints}.
16506 @cindex C@t{++} exception handling
16508 @itemx catch rethrow
16510 Debug C@t{++} exception handling using these commands. @xref{Set
16511 Catchpoints, , Setting Catchpoints}.
16513 @cindex inheritance
16514 @item ptype @var{typename}
16515 Print inheritance relationships as well as other information for type
16517 @xref{Symbols, ,Examining the Symbol Table}.
16519 @item info vtbl @var{expression}.
16520 The @code{info vtbl} command can be used to display the virtual
16521 method tables of the object computed by @var{expression}. This shows
16522 one entry per virtual table; there may be multiple virtual tables when
16523 multiple inheritance is in use.
16525 @cindex C@t{++} demangling
16526 @item demangle @var{name}
16527 Demangle @var{name}.
16528 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16530 @cindex C@t{++} symbol display
16531 @item set print demangle
16532 @itemx show print demangle
16533 @itemx set print asm-demangle
16534 @itemx show print asm-demangle
16535 Control whether C@t{++} symbols display in their source form, both when
16536 displaying code as C@t{++} source and when displaying disassemblies.
16537 @xref{Print Settings, ,Print Settings}.
16539 @item set print object
16540 @itemx show print object
16541 Choose whether to print derived (actual) or declared types of objects.
16542 @xref{Print Settings, ,Print Settings}.
16544 @item set print vtbl
16545 @itemx show print vtbl
16546 Control the format for printing virtual function tables.
16547 @xref{Print Settings, ,Print Settings}.
16548 (The @code{vtbl} commands do not work on programs compiled with the HP
16549 ANSI C@t{++} compiler (@code{aCC}).)
16551 @kindex set overload-resolution
16552 @cindex overloaded functions, overload resolution
16553 @item set overload-resolution on
16554 Enable overload resolution for C@t{++} expression evaluation. The default
16555 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16556 and searches for a function whose signature matches the argument types,
16557 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16558 Expressions, ,C@t{++} Expressions}, for details).
16559 If it cannot find a match, it emits a message.
16561 @item set overload-resolution off
16562 Disable overload resolution for C@t{++} expression evaluation. For
16563 overloaded functions that are not class member functions, @value{GDBN}
16564 chooses the first function of the specified name that it finds in the
16565 symbol table, whether or not its arguments are of the correct type. For
16566 overloaded functions that are class member functions, @value{GDBN}
16567 searches for a function whose signature @emph{exactly} matches the
16570 @kindex show overload-resolution
16571 @item show overload-resolution
16572 Show the current setting of overload resolution.
16574 @item @r{Overloaded symbol names}
16575 You can specify a particular definition of an overloaded symbol, using
16576 the same notation that is used to declare such symbols in C@t{++}: type
16577 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16578 also use the @value{GDBN} command-line word completion facilities to list the
16579 available choices, or to finish the type list for you.
16580 @xref{Completion,, Command Completion}, for details on how to do this.
16582 @item @r{Breakpoints in functions with ABI tags}
16584 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16585 correspond to changes in the ABI of a type, function, or variable that
16586 would not otherwise be reflected in a mangled name. See
16587 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16590 The ABI tags are visible in C@t{++} demangled names. For example, a
16591 function that returns a std::string:
16594 std::string function(int);
16598 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16599 tag, and @value{GDBN} displays the symbol like this:
16602 function[abi:cxx11](int)
16605 You can set a breakpoint on such functions simply as if they had no
16609 (gdb) b function(int)
16610 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16611 (gdb) info breakpoints
16612 Num Type Disp Enb Address What
16613 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16617 On the rare occasion you need to disambiguate between different ABI
16618 tags, you can do so by simply including the ABI tag in the function
16622 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16626 @node Decimal Floating Point
16627 @subsubsection Decimal Floating Point format
16628 @cindex decimal floating point format
16630 @value{GDBN} can examine, set and perform computations with numbers in
16631 decimal floating point format, which in the C language correspond to the
16632 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16633 specified by the extension to support decimal floating-point arithmetic.
16635 There are two encodings in use, depending on the architecture: BID (Binary
16636 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16637 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16640 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16641 to manipulate decimal floating point numbers, it is not possible to convert
16642 (using a cast, for example) integers wider than 32-bit to decimal float.
16644 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16645 point computations, error checking in decimal float operations ignores
16646 underflow, overflow and divide by zero exceptions.
16648 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16649 to inspect @code{_Decimal128} values stored in floating point registers.
16650 See @ref{PowerPC,,PowerPC} for more details.
16656 @value{GDBN} can be used to debug programs written in D and compiled with
16657 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16658 specific feature --- dynamic arrays.
16663 @cindex Go (programming language)
16664 @value{GDBN} can be used to debug programs written in Go and compiled with
16665 @file{gccgo} or @file{6g} compilers.
16667 Here is a summary of the Go-specific features and restrictions:
16670 @cindex current Go package
16671 @item The current Go package
16672 The name of the current package does not need to be specified when
16673 specifying global variables and functions.
16675 For example, given the program:
16679 var myglob = "Shall we?"
16685 When stopped inside @code{main} either of these work:
16689 (gdb) p main.myglob
16692 @cindex builtin Go types
16693 @item Builtin Go types
16694 The @code{string} type is recognized by @value{GDBN} and is printed
16697 @cindex builtin Go functions
16698 @item Builtin Go functions
16699 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
16700 function and handles it internally.
16702 @cindex restrictions on Go expressions
16703 @item Restrictions on Go expressions
16704 All Go operators are supported except @code{&^}.
16705 The Go @code{_} ``blank identifier'' is not supported.
16706 Automatic dereferencing of pointers is not supported.
16710 @subsection Objective-C
16712 @cindex Objective-C
16713 This section provides information about some commands and command
16714 options that are useful for debugging Objective-C code. See also
16715 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
16716 few more commands specific to Objective-C support.
16719 * Method Names in Commands::
16720 * The Print Command with Objective-C::
16723 @node Method Names in Commands
16724 @subsubsection Method Names in Commands
16726 The following commands have been extended to accept Objective-C method
16727 names as line specifications:
16729 @kindex clear@r{, and Objective-C}
16730 @kindex break@r{, and Objective-C}
16731 @kindex info line@r{, and Objective-C}
16732 @kindex jump@r{, and Objective-C}
16733 @kindex list@r{, and Objective-C}
16737 @item @code{info line}
16742 A fully qualified Objective-C method name is specified as
16745 -[@var{Class} @var{methodName}]
16748 where the minus sign is used to indicate an instance method and a
16749 plus sign (not shown) is used to indicate a class method. The class
16750 name @var{Class} and method name @var{methodName} are enclosed in
16751 brackets, similar to the way messages are specified in Objective-C
16752 source code. For example, to set a breakpoint at the @code{create}
16753 instance method of class @code{Fruit} in the program currently being
16757 break -[Fruit create]
16760 To list ten program lines around the @code{initialize} class method,
16764 list +[NSText initialize]
16767 In the current version of @value{GDBN}, the plus or minus sign is
16768 required. In future versions of @value{GDBN}, the plus or minus
16769 sign will be optional, but you can use it to narrow the search. It
16770 is also possible to specify just a method name:
16776 You must specify the complete method name, including any colons. If
16777 your program's source files contain more than one @code{create} method,
16778 you'll be presented with a numbered list of classes that implement that
16779 method. Indicate your choice by number, or type @samp{0} to exit if
16782 As another example, to clear a breakpoint established at the
16783 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
16786 clear -[NSWindow makeKeyAndOrderFront:]
16789 @node The Print Command with Objective-C
16790 @subsubsection The Print Command With Objective-C
16791 @cindex Objective-C, print objects
16792 @kindex print-object
16793 @kindex po @r{(@code{print-object})}
16795 The print command has also been extended to accept methods. For example:
16798 print -[@var{object} hash]
16801 @cindex print an Objective-C object description
16802 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
16804 will tell @value{GDBN} to send the @code{hash} message to @var{object}
16805 and print the result. Also, an additional command has been added,
16806 @code{print-object} or @code{po} for short, which is meant to print
16807 the description of an object. However, this command may only work
16808 with certain Objective-C libraries that have a particular hook
16809 function, @code{_NSPrintForDebugger}, defined.
16812 @subsection OpenCL C
16815 This section provides information about @value{GDBN}s OpenCL C support.
16818 * OpenCL C Datatypes::
16819 * OpenCL C Expressions::
16820 * OpenCL C Operators::
16823 @node OpenCL C Datatypes
16824 @subsubsection OpenCL C Datatypes
16826 @cindex OpenCL C Datatypes
16827 @value{GDBN} supports the builtin scalar and vector datatypes specified
16828 by OpenCL 1.1. In addition the half- and double-precision floating point
16829 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
16830 extensions are also known to @value{GDBN}.
16832 @node OpenCL C Expressions
16833 @subsubsection OpenCL C Expressions
16835 @cindex OpenCL C Expressions
16836 @value{GDBN} supports accesses to vector components including the access as
16837 lvalue where possible. Since OpenCL C is based on C99 most C expressions
16838 supported by @value{GDBN} can be used as well.
16840 @node OpenCL C Operators
16841 @subsubsection OpenCL C Operators
16843 @cindex OpenCL C Operators
16844 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
16848 @subsection Fortran
16849 @cindex Fortran-specific support in @value{GDBN}
16851 @value{GDBN} can be used to debug programs written in Fortran, but it
16852 currently supports only the features of Fortran 77 language.
16854 @cindex trailing underscore, in Fortran symbols
16855 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
16856 among them) append an underscore to the names of variables and
16857 functions. When you debug programs compiled by those compilers, you
16858 will need to refer to variables and functions with a trailing
16862 * Fortran Operators:: Fortran operators and expressions
16863 * Fortran Defaults:: Default settings for Fortran
16864 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
16867 @node Fortran Operators
16868 @subsubsection Fortran Operators and Expressions
16870 @cindex Fortran operators and expressions
16872 Operators must be defined on values of specific types. For instance,
16873 @code{+} is defined on numbers, but not on characters or other non-
16874 arithmetic types. Operators are often defined on groups of types.
16878 The exponentiation operator. It raises the first operand to the power
16882 The range operator. Normally used in the form of array(low:high) to
16883 represent a section of array.
16886 The access component operator. Normally used to access elements in derived
16887 types. Also suitable for unions. As unions aren't part of regular Fortran,
16888 this can only happen when accessing a register that uses a gdbarch-defined
16891 The scope operator. Normally used to access variables in modules or
16892 to set breakpoints on subroutines nested in modules or in other
16893 subroutines (internal subroutines).
16896 @node Fortran Defaults
16897 @subsubsection Fortran Defaults
16899 @cindex Fortran Defaults
16901 Fortran symbols are usually case-insensitive, so @value{GDBN} by
16902 default uses case-insensitive matches for Fortran symbols. You can
16903 change that with the @samp{set case-insensitive} command, see
16904 @ref{Symbols}, for the details.
16906 @node Special Fortran Commands
16907 @subsubsection Special Fortran Commands
16909 @cindex Special Fortran commands
16911 @value{GDBN} has some commands to support Fortran-specific features,
16912 such as displaying common blocks.
16915 @cindex @code{COMMON} blocks, Fortran
16916 @kindex info common
16917 @item info common @r{[}@var{common-name}@r{]}
16918 This command prints the values contained in the Fortran @code{COMMON}
16919 block whose name is @var{common-name}. With no argument, the names of
16920 all @code{COMMON} blocks visible at the current program location are
16927 @cindex Pascal support in @value{GDBN}, limitations
16928 Debugging Pascal programs which use sets, subranges, file variables, or
16929 nested functions does not currently work. @value{GDBN} does not support
16930 entering expressions, printing values, or similar features using Pascal
16933 The Pascal-specific command @code{set print pascal_static-members}
16934 controls whether static members of Pascal objects are displayed.
16935 @xref{Print Settings, pascal_static-members}.
16940 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
16941 Programming Language}. Type- and value-printing, and expression
16942 parsing, are reasonably complete. However, there are a few
16943 peculiarities and holes to be aware of.
16947 Linespecs (@pxref{Specify Location}) are never relative to the current
16948 crate. Instead, they act as if there were a global namespace of
16949 crates, somewhat similar to the way @code{extern crate} behaves.
16951 That is, if @value{GDBN} is stopped at a breakpoint in a function in
16952 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
16953 to set a breakpoint in a function named @samp{f} in a crate named
16956 As a consequence of this approach, linespecs also cannot refer to
16957 items using @samp{self::} or @samp{super::}.
16960 Because @value{GDBN} implements Rust name-lookup semantics in
16961 expressions, it will sometimes prepend the current crate to a name.
16962 For example, if @value{GDBN} is stopped at a breakpoint in the crate
16963 @samp{K}, then @code{print ::x::y} will try to find the symbol
16966 However, since it is useful to be able to refer to other crates when
16967 debugging, @value{GDBN} provides the @code{extern} extension to
16968 circumvent this. To use the extension, just put @code{extern} before
16969 a path expression to refer to the otherwise unavailable ``global''
16972 In the above example, if you wanted to refer to the symbol @samp{y} in
16973 the crate @samp{x}, you would use @code{print extern x::y}.
16976 The Rust expression evaluator does not support ``statement-like''
16977 expressions such as @code{if} or @code{match}, or lambda expressions.
16980 Tuple expressions are not implemented.
16983 The Rust expression evaluator does not currently implement the
16984 @code{Drop} trait. Objects that may be created by the evaluator will
16985 never be destroyed.
16988 @value{GDBN} does not implement type inference for generics. In order
16989 to call generic functions or otherwise refer to generic items, you
16990 will have to specify the type parameters manually.
16993 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
16994 cases this does not cause any problems. However, in an expression
16995 context, completing a generic function name will give syntactically
16996 invalid results. This happens because Rust requires the @samp{::}
16997 operator between the function name and its generic arguments. For
16998 example, @value{GDBN} might provide a completion like
16999 @code{crate::f<u32>}, where the parser would require
17000 @code{crate::f::<u32>}.
17003 As of this writing, the Rust compiler (version 1.8) has a few holes in
17004 the debugging information it generates. These holes prevent certain
17005 features from being implemented by @value{GDBN}:
17009 Method calls cannot be made via traits.
17012 Operator overloading is not implemented.
17015 When debugging in a monomorphized function, you cannot use the generic
17019 The type @code{Self} is not available.
17022 @code{use} statements are not available, so some names may not be
17023 available in the crate.
17028 @subsection Modula-2
17030 @cindex Modula-2, @value{GDBN} support
17032 The extensions made to @value{GDBN} to support Modula-2 only support
17033 output from the @sc{gnu} Modula-2 compiler (which is currently being
17034 developed). Other Modula-2 compilers are not currently supported, and
17035 attempting to debug executables produced by them is most likely
17036 to give an error as @value{GDBN} reads in the executable's symbol
17039 @cindex expressions in Modula-2
17041 * M2 Operators:: Built-in operators
17042 * Built-In Func/Proc:: Built-in functions and procedures
17043 * M2 Constants:: Modula-2 constants
17044 * M2 Types:: Modula-2 types
17045 * M2 Defaults:: Default settings for Modula-2
17046 * Deviations:: Deviations from standard Modula-2
17047 * M2 Checks:: Modula-2 type and range checks
17048 * M2 Scope:: The scope operators @code{::} and @code{.}
17049 * GDB/M2:: @value{GDBN} and Modula-2
17053 @subsubsection Operators
17054 @cindex Modula-2 operators
17056 Operators must be defined on values of specific types. For instance,
17057 @code{+} is defined on numbers, but not on structures. Operators are
17058 often defined on groups of types. For the purposes of Modula-2, the
17059 following definitions hold:
17064 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17068 @emph{Character types} consist of @code{CHAR} and its subranges.
17071 @emph{Floating-point types} consist of @code{REAL}.
17074 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17078 @emph{Scalar types} consist of all of the above.
17081 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17084 @emph{Boolean types} consist of @code{BOOLEAN}.
17088 The following operators are supported, and appear in order of
17089 increasing precedence:
17093 Function argument or array index separator.
17096 Assignment. The value of @var{var} @code{:=} @var{value} is
17100 Less than, greater than on integral, floating-point, or enumerated
17104 Less than or equal to, greater than or equal to
17105 on integral, floating-point and enumerated types, or set inclusion on
17106 set types. Same precedence as @code{<}.
17108 @item =@r{, }<>@r{, }#
17109 Equality and two ways of expressing inequality, valid on scalar types.
17110 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17111 available for inequality, since @code{#} conflicts with the script
17115 Set membership. Defined on set types and the types of their members.
17116 Same precedence as @code{<}.
17119 Boolean disjunction. Defined on boolean types.
17122 Boolean conjunction. Defined on boolean types.
17125 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17128 Addition and subtraction on integral and floating-point types, or union
17129 and difference on set types.
17132 Multiplication on integral and floating-point types, or set intersection
17136 Division on floating-point types, or symmetric set difference on set
17137 types. Same precedence as @code{*}.
17140 Integer division and remainder. Defined on integral types. Same
17141 precedence as @code{*}.
17144 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17147 Pointer dereferencing. Defined on pointer types.
17150 Boolean negation. Defined on boolean types. Same precedence as
17154 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17155 precedence as @code{^}.
17158 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17161 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17165 @value{GDBN} and Modula-2 scope operators.
17169 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17170 treats the use of the operator @code{IN}, or the use of operators
17171 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17172 @code{<=}, and @code{>=} on sets as an error.
17176 @node Built-In Func/Proc
17177 @subsubsection Built-in Functions and Procedures
17178 @cindex Modula-2 built-ins
17180 Modula-2 also makes available several built-in procedures and functions.
17181 In describing these, the following metavariables are used:
17186 represents an @code{ARRAY} variable.
17189 represents a @code{CHAR} constant or variable.
17192 represents a variable or constant of integral type.
17195 represents an identifier that belongs to a set. Generally used in the
17196 same function with the metavariable @var{s}. The type of @var{s} should
17197 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17200 represents a variable or constant of integral or floating-point type.
17203 represents a variable or constant of floating-point type.
17209 represents a variable.
17212 represents a variable or constant of one of many types. See the
17213 explanation of the function for details.
17216 All Modula-2 built-in procedures also return a result, described below.
17220 Returns the absolute value of @var{n}.
17223 If @var{c} is a lower case letter, it returns its upper case
17224 equivalent, otherwise it returns its argument.
17227 Returns the character whose ordinal value is @var{i}.
17230 Decrements the value in the variable @var{v} by one. Returns the new value.
17232 @item DEC(@var{v},@var{i})
17233 Decrements the value in the variable @var{v} by @var{i}. Returns the
17236 @item EXCL(@var{m},@var{s})
17237 Removes the element @var{m} from the set @var{s}. Returns the new
17240 @item FLOAT(@var{i})
17241 Returns the floating point equivalent of the integer @var{i}.
17243 @item HIGH(@var{a})
17244 Returns the index of the last member of @var{a}.
17247 Increments the value in the variable @var{v} by one. Returns the new value.
17249 @item INC(@var{v},@var{i})
17250 Increments the value in the variable @var{v} by @var{i}. Returns the
17253 @item INCL(@var{m},@var{s})
17254 Adds the element @var{m} to the set @var{s} if it is not already
17255 there. Returns the new set.
17258 Returns the maximum value of the type @var{t}.
17261 Returns the minimum value of the type @var{t}.
17264 Returns boolean TRUE if @var{i} is an odd number.
17267 Returns the ordinal value of its argument. For example, the ordinal
17268 value of a character is its @sc{ascii} value (on machines supporting
17269 the @sc{ascii} character set). The argument @var{x} must be of an
17270 ordered type, which include integral, character and enumerated types.
17272 @item SIZE(@var{x})
17273 Returns the size of its argument. The argument @var{x} can be a
17274 variable or a type.
17276 @item TRUNC(@var{r})
17277 Returns the integral part of @var{r}.
17279 @item TSIZE(@var{x})
17280 Returns the size of its argument. The argument @var{x} can be a
17281 variable or a type.
17283 @item VAL(@var{t},@var{i})
17284 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17288 @emph{Warning:} Sets and their operations are not yet supported, so
17289 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17293 @cindex Modula-2 constants
17295 @subsubsection Constants
17297 @value{GDBN} allows you to express the constants of Modula-2 in the following
17303 Integer constants are simply a sequence of digits. When used in an
17304 expression, a constant is interpreted to be type-compatible with the
17305 rest of the expression. Hexadecimal integers are specified by a
17306 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17309 Floating point constants appear as a sequence of digits, followed by a
17310 decimal point and another sequence of digits. An optional exponent can
17311 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17312 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17313 digits of the floating point constant must be valid decimal (base 10)
17317 Character constants consist of a single character enclosed by a pair of
17318 like quotes, either single (@code{'}) or double (@code{"}). They may
17319 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17320 followed by a @samp{C}.
17323 String constants consist of a sequence of characters enclosed by a
17324 pair of like quotes, either single (@code{'}) or double (@code{"}).
17325 Escape sequences in the style of C are also allowed. @xref{C
17326 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17330 Enumerated constants consist of an enumerated identifier.
17333 Boolean constants consist of the identifiers @code{TRUE} and
17337 Pointer constants consist of integral values only.
17340 Set constants are not yet supported.
17344 @subsubsection Modula-2 Types
17345 @cindex Modula-2 types
17347 Currently @value{GDBN} can print the following data types in Modula-2
17348 syntax: array types, record types, set types, pointer types, procedure
17349 types, enumerated types, subrange types and base types. You can also
17350 print the contents of variables declared using these type.
17351 This section gives a number of simple source code examples together with
17352 sample @value{GDBN} sessions.
17354 The first example contains the following section of code:
17363 and you can request @value{GDBN} to interrogate the type and value of
17364 @code{r} and @code{s}.
17367 (@value{GDBP}) print s
17369 (@value{GDBP}) ptype s
17371 (@value{GDBP}) print r
17373 (@value{GDBP}) ptype r
17378 Likewise if your source code declares @code{s} as:
17382 s: SET ['A'..'Z'] ;
17386 then you may query the type of @code{s} by:
17389 (@value{GDBP}) ptype s
17390 type = SET ['A'..'Z']
17394 Note that at present you cannot interactively manipulate set
17395 expressions using the debugger.
17397 The following example shows how you might declare an array in Modula-2
17398 and how you can interact with @value{GDBN} to print its type and contents:
17402 s: ARRAY [-10..10] OF CHAR ;
17406 (@value{GDBP}) ptype s
17407 ARRAY [-10..10] OF CHAR
17410 Note that the array handling is not yet complete and although the type
17411 is printed correctly, expression handling still assumes that all
17412 arrays have a lower bound of zero and not @code{-10} as in the example
17415 Here are some more type related Modula-2 examples:
17419 colour = (blue, red, yellow, green) ;
17420 t = [blue..yellow] ;
17428 The @value{GDBN} interaction shows how you can query the data type
17429 and value of a variable.
17432 (@value{GDBP}) print s
17434 (@value{GDBP}) ptype t
17435 type = [blue..yellow]
17439 In this example a Modula-2 array is declared and its contents
17440 displayed. Observe that the contents are written in the same way as
17441 their @code{C} counterparts.
17445 s: ARRAY [1..5] OF CARDINAL ;
17451 (@value{GDBP}) print s
17452 $1 = @{1, 0, 0, 0, 0@}
17453 (@value{GDBP}) ptype s
17454 type = ARRAY [1..5] OF CARDINAL
17457 The Modula-2 language interface to @value{GDBN} also understands
17458 pointer types as shown in this example:
17462 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
17469 and you can request that @value{GDBN} describes the type of @code{s}.
17472 (@value{GDBP}) ptype s
17473 type = POINTER TO ARRAY [1..5] OF CARDINAL
17476 @value{GDBN} handles compound types as we can see in this example.
17477 Here we combine array types, record types, pointer types and subrange
17488 myarray = ARRAY myrange OF CARDINAL ;
17489 myrange = [-2..2] ;
17491 s: POINTER TO ARRAY myrange OF foo ;
17495 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17499 (@value{GDBP}) ptype s
17500 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17503 f3 : ARRAY [-2..2] OF CARDINAL;
17508 @subsubsection Modula-2 Defaults
17509 @cindex Modula-2 defaults
17511 If type and range checking are set automatically by @value{GDBN}, they
17512 both default to @code{on} whenever the working language changes to
17513 Modula-2. This happens regardless of whether you or @value{GDBN}
17514 selected the working language.
17516 If you allow @value{GDBN} to set the language automatically, then entering
17517 code compiled from a file whose name ends with @file{.mod} sets the
17518 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17519 Infer the Source Language}, for further details.
17522 @subsubsection Deviations from Standard Modula-2
17523 @cindex Modula-2, deviations from
17525 A few changes have been made to make Modula-2 programs easier to debug.
17526 This is done primarily via loosening its type strictness:
17530 Unlike in standard Modula-2, pointer constants can be formed by
17531 integers. This allows you to modify pointer variables during
17532 debugging. (In standard Modula-2, the actual address contained in a
17533 pointer variable is hidden from you; it can only be modified
17534 through direct assignment to another pointer variable or expression that
17535 returned a pointer.)
17538 C escape sequences can be used in strings and characters to represent
17539 non-printable characters. @value{GDBN} prints out strings with these
17540 escape sequences embedded. Single non-printable characters are
17541 printed using the @samp{CHR(@var{nnn})} format.
17544 The assignment operator (@code{:=}) returns the value of its right-hand
17548 All built-in procedures both modify @emph{and} return their argument.
17552 @subsubsection Modula-2 Type and Range Checks
17553 @cindex Modula-2 checks
17556 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
17559 @c FIXME remove warning when type/range checks added
17561 @value{GDBN} considers two Modula-2 variables type equivalent if:
17565 They are of types that have been declared equivalent via a @code{TYPE
17566 @var{t1} = @var{t2}} statement
17569 They have been declared on the same line. (Note: This is true of the
17570 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
17573 As long as type checking is enabled, any attempt to combine variables
17574 whose types are not equivalent is an error.
17576 Range checking is done on all mathematical operations, assignment, array
17577 index bounds, and all built-in functions and procedures.
17580 @subsubsection The Scope Operators @code{::} and @code{.}
17582 @cindex @code{.}, Modula-2 scope operator
17583 @cindex colon, doubled as scope operator
17585 @vindex colon-colon@r{, in Modula-2}
17586 @c Info cannot handle :: but TeX can.
17589 @vindex ::@r{, in Modula-2}
17592 There are a few subtle differences between the Modula-2 scope operator
17593 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
17598 @var{module} . @var{id}
17599 @var{scope} :: @var{id}
17603 where @var{scope} is the name of a module or a procedure,
17604 @var{module} the name of a module, and @var{id} is any declared
17605 identifier within your program, except another module.
17607 Using the @code{::} operator makes @value{GDBN} search the scope
17608 specified by @var{scope} for the identifier @var{id}. If it is not
17609 found in the specified scope, then @value{GDBN} searches all scopes
17610 enclosing the one specified by @var{scope}.
17612 Using the @code{.} operator makes @value{GDBN} search the current scope for
17613 the identifier specified by @var{id} that was imported from the
17614 definition module specified by @var{module}. With this operator, it is
17615 an error if the identifier @var{id} was not imported from definition
17616 module @var{module}, or if @var{id} is not an identifier in
17620 @subsubsection @value{GDBN} and Modula-2
17622 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
17623 Five subcommands of @code{set print} and @code{show print} apply
17624 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
17625 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
17626 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
17627 analogue in Modula-2.
17629 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
17630 with any language, is not useful with Modula-2. Its
17631 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
17632 created in Modula-2 as they can in C or C@t{++}. However, because an
17633 address can be specified by an integral constant, the construct
17634 @samp{@{@var{type}@}@var{adrexp}} is still useful.
17636 @cindex @code{#} in Modula-2
17637 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
17638 interpreted as the beginning of a comment. Use @code{<>} instead.
17644 The extensions made to @value{GDBN} for Ada only support
17645 output from the @sc{gnu} Ada (GNAT) compiler.
17646 Other Ada compilers are not currently supported, and
17647 attempting to debug executables produced by them is most likely
17651 @cindex expressions in Ada
17653 * Ada Mode Intro:: General remarks on the Ada syntax
17654 and semantics supported by Ada mode
17656 * Omissions from Ada:: Restrictions on the Ada expression syntax.
17657 * Additions to Ada:: Extensions of the Ada expression syntax.
17658 * Overloading support for Ada:: Support for expressions involving overloaded
17660 * Stopping Before Main Program:: Debugging the program during elaboration.
17661 * Ada Exceptions:: Ada Exceptions
17662 * Ada Tasks:: Listing and setting breakpoints in tasks.
17663 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
17664 * Ravenscar Profile:: Tasking Support when using the Ravenscar
17666 * Ada Settings:: New settable GDB parameters for Ada.
17667 * Ada Glitches:: Known peculiarities of Ada mode.
17670 @node Ada Mode Intro
17671 @subsubsection Introduction
17672 @cindex Ada mode, general
17674 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
17675 syntax, with some extensions.
17676 The philosophy behind the design of this subset is
17680 That @value{GDBN} should provide basic literals and access to operations for
17681 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
17682 leaving more sophisticated computations to subprograms written into the
17683 program (which therefore may be called from @value{GDBN}).
17686 That type safety and strict adherence to Ada language restrictions
17687 are not particularly important to the @value{GDBN} user.
17690 That brevity is important to the @value{GDBN} user.
17693 Thus, for brevity, the debugger acts as if all names declared in
17694 user-written packages are directly visible, even if they are not visible
17695 according to Ada rules, thus making it unnecessary to fully qualify most
17696 names with their packages, regardless of context. Where this causes
17697 ambiguity, @value{GDBN} asks the user's intent.
17699 The debugger will start in Ada mode if it detects an Ada main program.
17700 As for other languages, it will enter Ada mode when stopped in a program that
17701 was translated from an Ada source file.
17703 While in Ada mode, you may use `@t{--}' for comments. This is useful
17704 mostly for documenting command files. The standard @value{GDBN} comment
17705 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
17706 middle (to allow based literals).
17708 @node Omissions from Ada
17709 @subsubsection Omissions from Ada
17710 @cindex Ada, omissions from
17712 Here are the notable omissions from the subset:
17716 Only a subset of the attributes are supported:
17720 @t{'First}, @t{'Last}, and @t{'Length}
17721 on array objects (not on types and subtypes).
17724 @t{'Min} and @t{'Max}.
17727 @t{'Pos} and @t{'Val}.
17733 @t{'Range} on array objects (not subtypes), but only as the right
17734 operand of the membership (@code{in}) operator.
17737 @t{'Access}, @t{'Unchecked_Access}, and
17738 @t{'Unrestricted_Access} (a GNAT extension).
17746 @code{Characters.Latin_1} are not available and
17747 concatenation is not implemented. Thus, escape characters in strings are
17748 not currently available.
17751 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
17752 equality of representations. They will generally work correctly
17753 for strings and arrays whose elements have integer or enumeration types.
17754 They may not work correctly for arrays whose element
17755 types have user-defined equality, for arrays of real values
17756 (in particular, IEEE-conformant floating point, because of negative
17757 zeroes and NaNs), and for arrays whose elements contain unused bits with
17758 indeterminate values.
17761 The other component-by-component array operations (@code{and}, @code{or},
17762 @code{xor}, @code{not}, and relational tests other than equality)
17763 are not implemented.
17766 @cindex array aggregates (Ada)
17767 @cindex record aggregates (Ada)
17768 @cindex aggregates (Ada)
17769 There is limited support for array and record aggregates. They are
17770 permitted only on the right sides of assignments, as in these examples:
17773 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
17774 (@value{GDBP}) set An_Array := (1, others => 0)
17775 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
17776 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
17777 (@value{GDBP}) set A_Record := (1, "Peter", True);
17778 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
17782 discriminant's value by assigning an aggregate has an
17783 undefined effect if that discriminant is used within the record.
17784 However, you can first modify discriminants by directly assigning to
17785 them (which normally would not be allowed in Ada), and then performing an
17786 aggregate assignment. For example, given a variable @code{A_Rec}
17787 declared to have a type such as:
17790 type Rec (Len : Small_Integer := 0) is record
17792 Vals : IntArray (1 .. Len);
17796 you can assign a value with a different size of @code{Vals} with two
17800 (@value{GDBP}) set A_Rec.Len := 4
17801 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
17804 As this example also illustrates, @value{GDBN} is very loose about the usual
17805 rules concerning aggregates. You may leave out some of the
17806 components of an array or record aggregate (such as the @code{Len}
17807 component in the assignment to @code{A_Rec} above); they will retain their
17808 original values upon assignment. You may freely use dynamic values as
17809 indices in component associations. You may even use overlapping or
17810 redundant component associations, although which component values are
17811 assigned in such cases is not defined.
17814 Calls to dispatching subprograms are not implemented.
17817 The overloading algorithm is much more limited (i.e., less selective)
17818 than that of real Ada. It makes only limited use of the context in
17819 which a subexpression appears to resolve its meaning, and it is much
17820 looser in its rules for allowing type matches. As a result, some
17821 function calls will be ambiguous, and the user will be asked to choose
17822 the proper resolution.
17825 The @code{new} operator is not implemented.
17828 Entry calls are not implemented.
17831 Aside from printing, arithmetic operations on the native VAX floating-point
17832 formats are not supported.
17835 It is not possible to slice a packed array.
17838 The names @code{True} and @code{False}, when not part of a qualified name,
17839 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
17841 Should your program
17842 redefine these names in a package or procedure (at best a dubious practice),
17843 you will have to use fully qualified names to access their new definitions.
17846 @node Additions to Ada
17847 @subsubsection Additions to Ada
17848 @cindex Ada, deviations from
17850 As it does for other languages, @value{GDBN} makes certain generic
17851 extensions to Ada (@pxref{Expressions}):
17855 If the expression @var{E} is a variable residing in memory (typically
17856 a local variable or array element) and @var{N} is a positive integer,
17857 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
17858 @var{N}-1 adjacent variables following it in memory as an array. In
17859 Ada, this operator is generally not necessary, since its prime use is
17860 in displaying parts of an array, and slicing will usually do this in
17861 Ada. However, there are occasional uses when debugging programs in
17862 which certain debugging information has been optimized away.
17865 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
17866 appears in function or file @var{B}.'' When @var{B} is a file name,
17867 you must typically surround it in single quotes.
17870 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
17871 @var{type} that appears at address @var{addr}.''
17874 A name starting with @samp{$} is a convenience variable
17875 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
17878 In addition, @value{GDBN} provides a few other shortcuts and outright
17879 additions specific to Ada:
17883 The assignment statement is allowed as an expression, returning
17884 its right-hand operand as its value. Thus, you may enter
17887 (@value{GDBP}) set x := y + 3
17888 (@value{GDBP}) print A(tmp := y + 1)
17892 The semicolon is allowed as an ``operator,'' returning as its value
17893 the value of its right-hand operand.
17894 This allows, for example,
17895 complex conditional breaks:
17898 (@value{GDBP}) break f
17899 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
17903 Rather than use catenation and symbolic character names to introduce special
17904 characters into strings, one may instead use a special bracket notation,
17905 which is also used to print strings. A sequence of characters of the form
17906 @samp{["@var{XX}"]} within a string or character literal denotes the
17907 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
17908 sequence of characters @samp{["""]} also denotes a single quotation mark
17909 in strings. For example,
17911 "One line.["0a"]Next line.["0a"]"
17914 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
17918 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
17919 @t{'Max} is optional (and is ignored in any case). For example, it is valid
17923 (@value{GDBP}) print 'max(x, y)
17927 When printing arrays, @value{GDBN} uses positional notation when the
17928 array has a lower bound of 1, and uses a modified named notation otherwise.
17929 For example, a one-dimensional array of three integers with a lower bound
17930 of 3 might print as
17937 That is, in contrast to valid Ada, only the first component has a @code{=>}
17941 You may abbreviate attributes in expressions with any unique,
17942 multi-character subsequence of
17943 their names (an exact match gets preference).
17944 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
17945 in place of @t{a'length}.
17948 @cindex quoting Ada internal identifiers
17949 Since Ada is case-insensitive, the debugger normally maps identifiers you type
17950 to lower case. The GNAT compiler uses upper-case characters for
17951 some of its internal identifiers, which are normally of no interest to users.
17952 For the rare occasions when you actually have to look at them,
17953 enclose them in angle brackets to avoid the lower-case mapping.
17956 (@value{GDBP}) print <JMPBUF_SAVE>[0]
17960 Printing an object of class-wide type or dereferencing an
17961 access-to-class-wide value will display all the components of the object's
17962 specific type (as indicated by its run-time tag). Likewise, component
17963 selection on such a value will operate on the specific type of the
17968 @node Overloading support for Ada
17969 @subsubsection Overloading support for Ada
17970 @cindex overloading, Ada
17972 The debugger supports limited overloading. Given a subprogram call in which
17973 the function symbol has multiple definitions, it will use the number of
17974 actual parameters and some information about their types to attempt to narrow
17975 the set of definitions. It also makes very limited use of context, preferring
17976 procedures to functions in the context of the @code{call} command, and
17977 functions to procedures elsewhere.
17979 If, after narrowing, the set of matching definitions still contains more than
17980 one definition, @value{GDBN} will display a menu to query which one it should
17984 (@value{GDBP}) print f(1)
17985 Multiple matches for f
17987 [1] foo.f (integer) return boolean at foo.adb:23
17988 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
17992 In this case, just select one menu entry either to cancel expression evaluation
17993 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
17994 instance (type the corresponding number and press @key{RET}).
17996 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18001 @kindex set ada print-signatures
18002 @item set ada print-signatures
18003 Control whether parameter types and return types are displayed in overloads
18004 selection menus. It is @code{on} by default.
18005 @xref{Overloading support for Ada}.
18007 @kindex show ada print-signatures
18008 @item show ada print-signatures
18009 Show the current setting for displaying parameter types and return types in
18010 overloads selection menu.
18011 @xref{Overloading support for Ada}.
18015 @node Stopping Before Main Program
18016 @subsubsection Stopping at the Very Beginning
18018 @cindex breakpointing Ada elaboration code
18019 It is sometimes necessary to debug the program during elaboration, and
18020 before reaching the main procedure.
18021 As defined in the Ada Reference
18022 Manual, the elaboration code is invoked from a procedure called
18023 @code{adainit}. To run your program up to the beginning of
18024 elaboration, simply use the following two commands:
18025 @code{tbreak adainit} and @code{run}.
18027 @node Ada Exceptions
18028 @subsubsection Ada Exceptions
18030 A command is provided to list all Ada exceptions:
18033 @kindex info exceptions
18034 @item info exceptions
18035 @itemx info exceptions @var{regexp}
18036 The @code{info exceptions} command allows you to list all Ada exceptions
18037 defined within the program being debugged, as well as their addresses.
18038 With a regular expression, @var{regexp}, as argument, only those exceptions
18039 whose names match @var{regexp} are listed.
18042 Below is a small example, showing how the command can be used, first
18043 without argument, and next with a regular expression passed as an
18047 (@value{GDBP}) info exceptions
18048 All defined Ada exceptions:
18049 constraint_error: 0x613da0
18050 program_error: 0x613d20
18051 storage_error: 0x613ce0
18052 tasking_error: 0x613ca0
18053 const.aint_global_e: 0x613b00
18054 (@value{GDBP}) info exceptions const.aint
18055 All Ada exceptions matching regular expression "const.aint":
18056 constraint_error: 0x613da0
18057 const.aint_global_e: 0x613b00
18060 It is also possible to ask @value{GDBN} to stop your program's execution
18061 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18064 @subsubsection Extensions for Ada Tasks
18065 @cindex Ada, tasking
18067 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18068 @value{GDBN} provides the following task-related commands:
18073 This command shows a list of current Ada tasks, as in the following example:
18080 (@value{GDBP}) info tasks
18081 ID TID P-ID Pri State Name
18082 1 8088000 0 15 Child Activation Wait main_task
18083 2 80a4000 1 15 Accept Statement b
18084 3 809a800 1 15 Child Activation Wait a
18085 * 4 80ae800 3 15 Runnable c
18090 In this listing, the asterisk before the last task indicates it to be the
18091 task currently being inspected.
18095 Represents @value{GDBN}'s internal task number.
18101 The parent's task ID (@value{GDBN}'s internal task number).
18104 The base priority of the task.
18107 Current state of the task.
18111 The task has been created but has not been activated. It cannot be
18115 The task is not blocked for any reason known to Ada. (It may be waiting
18116 for a mutex, though.) It is conceptually "executing" in normal mode.
18119 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18120 that were waiting on terminate alternatives have been awakened and have
18121 terminated themselves.
18123 @item Child Activation Wait
18124 The task is waiting for created tasks to complete activation.
18126 @item Accept Statement
18127 The task is waiting on an accept or selective wait statement.
18129 @item Waiting on entry call
18130 The task is waiting on an entry call.
18132 @item Async Select Wait
18133 The task is waiting to start the abortable part of an asynchronous
18137 The task is waiting on a select statement with only a delay
18140 @item Child Termination Wait
18141 The task is sleeping having completed a master within itself, and is
18142 waiting for the tasks dependent on that master to become terminated or
18143 waiting on a terminate Phase.
18145 @item Wait Child in Term Alt
18146 The task is sleeping waiting for tasks on terminate alternatives to
18147 finish terminating.
18149 @item Accepting RV with @var{taskno}
18150 The task is accepting a rendez-vous with the task @var{taskno}.
18154 Name of the task in the program.
18158 @kindex info task @var{taskno}
18159 @item info task @var{taskno}
18160 This command shows detailed informations on the specified task, as in
18161 the following example:
18166 (@value{GDBP}) info tasks
18167 ID TID P-ID Pri State Name
18168 1 8077880 0 15 Child Activation Wait main_task
18169 * 2 807c468 1 15 Runnable task_1
18170 (@value{GDBP}) info task 2
18171 Ada Task: 0x807c468
18175 Parent: 1 ("main_task")
18181 @kindex task@r{ (Ada)}
18182 @cindex current Ada task ID
18183 This command prints the ID and name of the current task.
18189 (@value{GDBP}) info tasks
18190 ID TID P-ID Pri State Name
18191 1 8077870 0 15 Child Activation Wait main_task
18192 * 2 807c458 1 15 Runnable some_task
18193 (@value{GDBP}) task
18194 [Current task is 2 "some_task"]
18197 @item task @var{taskno}
18198 @cindex Ada task switching
18199 This command is like the @code{thread @var{thread-id}}
18200 command (@pxref{Threads}). It switches the context of debugging
18201 from the current task to the given task.
18207 (@value{GDBP}) info tasks
18208 ID TID P-ID Pri State Name
18209 1 8077870 0 15 Child Activation Wait main_task
18210 * 2 807c458 1 15 Runnable some_task
18211 (@value{GDBP}) task 1
18212 [Switching to task 1 "main_task"]
18213 #0 0x8067726 in pthread_cond_wait ()
18215 #0 0x8067726 in pthread_cond_wait ()
18216 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18217 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18218 #3 0x806153e in system.tasking.stages.activate_tasks ()
18219 #4 0x804aacc in un () at un.adb:5
18222 @item break @var{location} task @var{taskno}
18223 @itemx break @var{location} task @var{taskno} if @dots{}
18224 @cindex breakpoints and tasks, in Ada
18225 @cindex task breakpoints, in Ada
18226 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18227 These commands are like the @code{break @dots{} thread @dots{}}
18228 command (@pxref{Thread Stops}). The
18229 @var{location} argument specifies source lines, as described
18230 in @ref{Specify Location}.
18232 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18233 to specify that you only want @value{GDBN} to stop the program when a
18234 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18235 numeric task identifiers assigned by @value{GDBN}, shown in the first
18236 column of the @samp{info tasks} display.
18238 If you do not specify @samp{task @var{taskno}} when you set a
18239 breakpoint, the breakpoint applies to @emph{all} tasks of your
18242 You can use the @code{task} qualifier on conditional breakpoints as
18243 well; in this case, place @samp{task @var{taskno}} before the
18244 breakpoint condition (before the @code{if}).
18252 (@value{GDBP}) info tasks
18253 ID TID P-ID Pri State Name
18254 1 140022020 0 15 Child Activation Wait main_task
18255 2 140045060 1 15 Accept/Select Wait t2
18256 3 140044840 1 15 Runnable t1
18257 * 4 140056040 1 15 Runnable t3
18258 (@value{GDBP}) b 15 task 2
18259 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18260 (@value{GDBP}) cont
18265 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18267 (@value{GDBP}) info tasks
18268 ID TID P-ID Pri State Name
18269 1 140022020 0 15 Child Activation Wait main_task
18270 * 2 140045060 1 15 Runnable t2
18271 3 140044840 1 15 Runnable t1
18272 4 140056040 1 15 Delay Sleep t3
18276 @node Ada Tasks and Core Files
18277 @subsubsection Tasking Support when Debugging Core Files
18278 @cindex Ada tasking and core file debugging
18280 When inspecting a core file, as opposed to debugging a live program,
18281 tasking support may be limited or even unavailable, depending on
18282 the platform being used.
18283 For instance, on x86-linux, the list of tasks is available, but task
18284 switching is not supported.
18286 On certain platforms, the debugger needs to perform some
18287 memory writes in order to provide Ada tasking support. When inspecting
18288 a core file, this means that the core file must be opened with read-write
18289 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
18290 Under these circumstances, you should make a backup copy of the core
18291 file before inspecting it with @value{GDBN}.
18293 @node Ravenscar Profile
18294 @subsubsection Tasking Support when using the Ravenscar Profile
18295 @cindex Ravenscar Profile
18297 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
18298 specifically designed for systems with safety-critical real-time
18302 @kindex set ravenscar task-switching on
18303 @cindex task switching with program using Ravenscar Profile
18304 @item set ravenscar task-switching on
18305 Allows task switching when debugging a program that uses the Ravenscar
18306 Profile. This is the default.
18308 @kindex set ravenscar task-switching off
18309 @item set ravenscar task-switching off
18310 Turn off task switching when debugging a program that uses the Ravenscar
18311 Profile. This is mostly intended to disable the code that adds support
18312 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
18313 the Ravenscar runtime is preventing @value{GDBN} from working properly.
18314 To be effective, this command should be run before the program is started.
18316 @kindex show ravenscar task-switching
18317 @item show ravenscar task-switching
18318 Show whether it is possible to switch from task to task in a program
18319 using the Ravenscar Profile.
18323 @cindex Ravenscar thread
18324 When Ravenscar task-switching is enabled, Ravenscar tasks are
18325 announced by @value{GDBN} as if they were threads:
18329 [New Ravenscar Thread 0x2b8f0]
18332 Both Ravenscar tasks and the underlying CPU threads will show up in
18333 the output of @code{info threads}:
18338 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
18339 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
18340 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
18341 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
18342 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
18343 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
18346 One known limitation of the Ravenscar support in @value{GDBN} is that
18347 it isn't currently possible to single-step through the runtime
18348 initialization sequence. If you need to debug this code, you should
18349 use @code{set ravenscar task-switching off}.
18352 @subsubsection Ada Settings
18353 @cindex Ada settings
18356 @kindex set varsize-limit
18357 @item set varsize-limit @var{size}
18358 Prevent @value{GDBN} from attempting to evaluate objects whose size
18359 is above the given limit (@var{size}) when those sizes are computed
18360 from run-time quantities. This is typically the case when the object
18361 has a variable size, such as an array whose bounds are not known at
18362 compile time for example. Setting @var{size} to @code{unlimited}
18363 removes the size limitation. By default, the limit is about 65KB.
18365 The purpose of having such a limit is to prevent @value{GDBN} from
18366 trying to grab enormous chunks of virtual memory when asked to evaluate
18367 a quantity whose bounds have been corrupted or have not yet been fully
18368 initialized. The limit applies to the results of some subexpressions
18369 as well as to complete expressions. For example, an expression denoting
18370 a simple integer component, such as @code{x.y.z}, may fail if the size of
18371 @code{x.y} is variable and exceeds @code{size}. On the other hand,
18372 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
18373 @code{A} is an array variable with non-constant size, will generally
18374 succeed regardless of the bounds on @code{A}, as long as the component
18375 size is less than @var{size}.
18377 @kindex show varsize-limit
18378 @item show varsize-limit
18379 Show the limit on types whose size is determined by run-time quantities.
18383 @subsubsection Known Peculiarities of Ada Mode
18384 @cindex Ada, problems
18386 Besides the omissions listed previously (@pxref{Omissions from Ada}),
18387 we know of several problems with and limitations of Ada mode in
18389 some of which will be fixed with planned future releases of the debugger
18390 and the GNU Ada compiler.
18394 Static constants that the compiler chooses not to materialize as objects in
18395 storage are invisible to the debugger.
18398 Named parameter associations in function argument lists are ignored (the
18399 argument lists are treated as positional).
18402 Many useful library packages are currently invisible to the debugger.
18405 Fixed-point arithmetic, conversions, input, and output is carried out using
18406 floating-point arithmetic, and may give results that only approximate those on
18410 The GNAT compiler never generates the prefix @code{Standard} for any of
18411 the standard symbols defined by the Ada language. @value{GDBN} knows about
18412 this: it will strip the prefix from names when you use it, and will never
18413 look for a name you have so qualified among local symbols, nor match against
18414 symbols in other packages or subprograms. If you have
18415 defined entities anywhere in your program other than parameters and
18416 local variables whose simple names match names in @code{Standard},
18417 GNAT's lack of qualification here can cause confusion. When this happens,
18418 you can usually resolve the confusion
18419 by qualifying the problematic names with package
18420 @code{Standard} explicitly.
18423 Older versions of the compiler sometimes generate erroneous debugging
18424 information, resulting in the debugger incorrectly printing the value
18425 of affected entities. In some cases, the debugger is able to work
18426 around an issue automatically. In other cases, the debugger is able
18427 to work around the issue, but the work-around has to be specifically
18430 @kindex set ada trust-PAD-over-XVS
18431 @kindex show ada trust-PAD-over-XVS
18434 @item set ada trust-PAD-over-XVS on
18435 Configure GDB to strictly follow the GNAT encoding when computing the
18436 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
18437 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
18438 a complete description of the encoding used by the GNAT compiler).
18439 This is the default.
18441 @item set ada trust-PAD-over-XVS off
18442 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
18443 sometimes prints the wrong value for certain entities, changing @code{ada
18444 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
18445 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
18446 @code{off}, but this incurs a slight performance penalty, so it is
18447 recommended to leave this setting to @code{on} unless necessary.
18451 @cindex GNAT descriptive types
18452 @cindex GNAT encoding
18453 Internally, the debugger also relies on the compiler following a number
18454 of conventions known as the @samp{GNAT Encoding}, all documented in
18455 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
18456 how the debugging information should be generated for certain types.
18457 In particular, this convention makes use of @dfn{descriptive types},
18458 which are artificial types generated purely to help the debugger.
18460 These encodings were defined at a time when the debugging information
18461 format used was not powerful enough to describe some of the more complex
18462 types available in Ada. Since DWARF allows us to express nearly all
18463 Ada features, the long-term goal is to slowly replace these descriptive
18464 types by their pure DWARF equivalent. To facilitate that transition,
18465 a new maintenance option is available to force the debugger to ignore
18466 those descriptive types. It allows the user to quickly evaluate how
18467 well @value{GDBN} works without them.
18471 @kindex maint ada set ignore-descriptive-types
18472 @item maintenance ada set ignore-descriptive-types [on|off]
18473 Control whether the debugger should ignore descriptive types.
18474 The default is not to ignore descriptives types (@code{off}).
18476 @kindex maint ada show ignore-descriptive-types
18477 @item maintenance ada show ignore-descriptive-types
18478 Show if descriptive types are ignored by @value{GDBN}.
18482 @node Unsupported Languages
18483 @section Unsupported Languages
18485 @cindex unsupported languages
18486 @cindex minimal language
18487 In addition to the other fully-supported programming languages,
18488 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
18489 It does not represent a real programming language, but provides a set
18490 of capabilities close to what the C or assembly languages provide.
18491 This should allow most simple operations to be performed while debugging
18492 an application that uses a language currently not supported by @value{GDBN}.
18494 If the language is set to @code{auto}, @value{GDBN} will automatically
18495 select this language if the current frame corresponds to an unsupported
18499 @chapter Examining the Symbol Table
18501 The commands described in this chapter allow you to inquire about the
18502 symbols (names of variables, functions and types) defined in your
18503 program. This information is inherent in the text of your program and
18504 does not change as your program executes. @value{GDBN} finds it in your
18505 program's symbol table, in the file indicated when you started @value{GDBN}
18506 (@pxref{File Options, ,Choosing Files}), or by one of the
18507 file-management commands (@pxref{Files, ,Commands to Specify Files}).
18509 @cindex symbol names
18510 @cindex names of symbols
18511 @cindex quoting names
18512 @anchor{quoting names}
18513 Occasionally, you may need to refer to symbols that contain unusual
18514 characters, which @value{GDBN} ordinarily treats as word delimiters. The
18515 most frequent case is in referring to static variables in other
18516 source files (@pxref{Variables,,Program Variables}). File names
18517 are recorded in object files as debugging symbols, but @value{GDBN} would
18518 ordinarily parse a typical file name, like @file{foo.c}, as the three words
18519 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
18520 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
18527 looks up the value of @code{x} in the scope of the file @file{foo.c}.
18530 @cindex case-insensitive symbol names
18531 @cindex case sensitivity in symbol names
18532 @kindex set case-sensitive
18533 @item set case-sensitive on
18534 @itemx set case-sensitive off
18535 @itemx set case-sensitive auto
18536 Normally, when @value{GDBN} looks up symbols, it matches their names
18537 with case sensitivity determined by the current source language.
18538 Occasionally, you may wish to control that. The command @code{set
18539 case-sensitive} lets you do that by specifying @code{on} for
18540 case-sensitive matches or @code{off} for case-insensitive ones. If
18541 you specify @code{auto}, case sensitivity is reset to the default
18542 suitable for the source language. The default is case-sensitive
18543 matches for all languages except for Fortran, for which the default is
18544 case-insensitive matches.
18546 @kindex show case-sensitive
18547 @item show case-sensitive
18548 This command shows the current setting of case sensitivity for symbols
18551 @kindex set print type methods
18552 @item set print type methods
18553 @itemx set print type methods on
18554 @itemx set print type methods off
18555 Normally, when @value{GDBN} prints a class, it displays any methods
18556 declared in that class. You can control this behavior either by
18557 passing the appropriate flag to @code{ptype}, or using @command{set
18558 print type methods}. Specifying @code{on} will cause @value{GDBN} to
18559 display the methods; this is the default. Specifying @code{off} will
18560 cause @value{GDBN} to omit the methods.
18562 @kindex show print type methods
18563 @item show print type methods
18564 This command shows the current setting of method display when printing
18567 @kindex set print type nested-type-limit
18568 @item set print type nested-type-limit @var{limit}
18569 @itemx set print type nested-type-limit unlimited
18570 Set the limit of displayed nested types that the type printer will
18571 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
18572 nested definitions. By default, the type printer will not show any nested
18573 types defined in classes.
18575 @kindex show print type nested-type-limit
18576 @item show print type nested-type-limit
18577 This command shows the current display limit of nested types when
18580 @kindex set print type typedefs
18581 @item set print type typedefs
18582 @itemx set print type typedefs on
18583 @itemx set print type typedefs off
18585 Normally, when @value{GDBN} prints a class, it displays any typedefs
18586 defined in that class. You can control this behavior either by
18587 passing the appropriate flag to @code{ptype}, or using @command{set
18588 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
18589 display the typedef definitions; this is the default. Specifying
18590 @code{off} will cause @value{GDBN} to omit the typedef definitions.
18591 Note that this controls whether the typedef definition itself is
18592 printed, not whether typedef names are substituted when printing other
18595 @kindex show print type typedefs
18596 @item show print type typedefs
18597 This command shows the current setting of typedef display when
18600 @kindex info address
18601 @cindex address of a symbol
18602 @item info address @var{symbol}
18603 Describe where the data for @var{symbol} is stored. For a register
18604 variable, this says which register it is kept in. For a non-register
18605 local variable, this prints the stack-frame offset at which the variable
18608 Note the contrast with @samp{print &@var{symbol}}, which does not work
18609 at all for a register variable, and for a stack local variable prints
18610 the exact address of the current instantiation of the variable.
18612 @kindex info symbol
18613 @cindex symbol from address
18614 @cindex closest symbol and offset for an address
18615 @item info symbol @var{addr}
18616 Print the name of a symbol which is stored at the address @var{addr}.
18617 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
18618 nearest symbol and an offset from it:
18621 (@value{GDBP}) info symbol 0x54320
18622 _initialize_vx + 396 in section .text
18626 This is the opposite of the @code{info address} command. You can use
18627 it to find out the name of a variable or a function given its address.
18629 For dynamically linked executables, the name of executable or shared
18630 library containing the symbol is also printed:
18633 (@value{GDBP}) info symbol 0x400225
18634 _start + 5 in section .text of /tmp/a.out
18635 (@value{GDBP}) info symbol 0x2aaaac2811cf
18636 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
18641 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
18642 Demangle @var{name}.
18643 If @var{language} is provided it is the name of the language to demangle
18644 @var{name} in. Otherwise @var{name} is demangled in the current language.
18646 The @samp{--} option specifies the end of options,
18647 and is useful when @var{name} begins with a dash.
18649 The parameter @code{demangle-style} specifies how to interpret the kind
18650 of mangling used. @xref{Print Settings}.
18653 @item whatis[/@var{flags}] [@var{arg}]
18654 Print the data type of @var{arg}, which can be either an expression
18655 or a name of a data type. With no argument, print the data type of
18656 @code{$}, the last value in the value history.
18658 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
18659 is not actually evaluated, and any side-effecting operations (such as
18660 assignments or function calls) inside it do not take place.
18662 If @var{arg} is a variable or an expression, @code{whatis} prints its
18663 literal type as it is used in the source code. If the type was
18664 defined using a @code{typedef}, @code{whatis} will @emph{not} print
18665 the data type underlying the @code{typedef}. If the type of the
18666 variable or the expression is a compound data type, such as
18667 @code{struct} or @code{class}, @code{whatis} never prints their
18668 fields or methods. It just prints the @code{struct}/@code{class}
18669 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
18670 such a compound data type, use @code{ptype}.
18672 If @var{arg} is a type name that was defined using @code{typedef},
18673 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
18674 Unrolling means that @code{whatis} will show the underlying type used
18675 in the @code{typedef} declaration of @var{arg}. However, if that
18676 underlying type is also a @code{typedef}, @code{whatis} will not
18679 For C code, the type names may also have the form @samp{class
18680 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
18681 @var{union-tag}} or @samp{enum @var{enum-tag}}.
18683 @var{flags} can be used to modify how the type is displayed.
18684 Available flags are:
18688 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
18689 parameters and typedefs defined in a class when printing the class'
18690 members. The @code{/r} flag disables this.
18693 Do not print methods defined in the class.
18696 Print methods defined in the class. This is the default, but the flag
18697 exists in case you change the default with @command{set print type methods}.
18700 Do not print typedefs defined in the class. Note that this controls
18701 whether the typedef definition itself is printed, not whether typedef
18702 names are substituted when printing other types.
18705 Print typedefs defined in the class. This is the default, but the flag
18706 exists in case you change the default with @command{set print type typedefs}.
18709 Print the offsets and sizes of fields in a struct, similar to what the
18710 @command{pahole} tool does. This option implies the @code{/tm} flags.
18712 For example, given the following declarations:
18748 Issuing a @kbd{ptype /o struct tuv} command would print:
18751 (@value{GDBP}) ptype /o struct tuv
18752 /* offset | size */ type = struct tuv @{
18753 /* 0 | 4 */ int a1;
18754 /* XXX 4-byte hole */
18755 /* 8 | 8 */ char *a2;
18756 /* 16 | 4 */ int a3;
18758 /* total size (bytes): 24 */
18762 Notice the format of the first column of comments. There, you can
18763 find two parts separated by the @samp{|} character: the @emph{offset},
18764 which indicates where the field is located inside the struct, in
18765 bytes, and the @emph{size} of the field. Another interesting line is
18766 the marker of a @emph{hole} in the struct, indicating that it may be
18767 possible to pack the struct and make it use less space by reorganizing
18770 It is also possible to print offsets inside an union:
18773 (@value{GDBP}) ptype /o union qwe
18774 /* offset | size */ type = union qwe @{
18775 /* 24 */ struct tuv @{
18776 /* 0 | 4 */ int a1;
18777 /* XXX 4-byte hole */
18778 /* 8 | 8 */ char *a2;
18779 /* 16 | 4 */ int a3;
18781 /* total size (bytes): 24 */
18783 /* 40 */ struct xyz @{
18784 /* 0 | 4 */ int f1;
18785 /* 4 | 1 */ char f2;
18786 /* XXX 3-byte hole */
18787 /* 8 | 8 */ void *f3;
18788 /* 16 | 24 */ struct tuv @{
18789 /* 16 | 4 */ int a1;
18790 /* XXX 4-byte hole */
18791 /* 24 | 8 */ char *a2;
18792 /* 32 | 4 */ int a3;
18794 /* total size (bytes): 24 */
18797 /* total size (bytes): 40 */
18800 /* total size (bytes): 40 */
18804 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
18805 same space (because we are dealing with an union), the offset is not
18806 printed for them. However, you can still examine the offset of each
18807 of these structures' fields.
18809 Another useful scenario is printing the offsets of a struct containing
18813 (@value{GDBP}) ptype /o struct tyu
18814 /* offset | size */ type = struct tyu @{
18815 /* 0:31 | 4 */ int a1 : 1;
18816 /* 0:28 | 4 */ int a2 : 3;
18817 /* 0: 5 | 4 */ int a3 : 23;
18818 /* 3: 3 | 1 */ signed char a4 : 2;
18819 /* XXX 3-bit hole */
18820 /* XXX 4-byte hole */
18821 /* 8 | 8 */ int64_t a5;
18822 /* 16: 0 | 4 */ int a6 : 5;
18823 /* 16: 5 | 8 */ int64_t a7 : 3;
18824 "/* XXX 7-byte padding */
18826 /* total size (bytes): 24 */
18830 Note how the offset information is now extended to also include the
18831 first bit of the bitfield.
18835 @item ptype[/@var{flags}] [@var{arg}]
18836 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
18837 detailed description of the type, instead of just the name of the type.
18838 @xref{Expressions, ,Expressions}.
18840 Contrary to @code{whatis}, @code{ptype} always unrolls any
18841 @code{typedef}s in its argument declaration, whether the argument is
18842 a variable, expression, or a data type. This means that @code{ptype}
18843 of a variable or an expression will not print literally its type as
18844 present in the source code---use @code{whatis} for that. @code{typedef}s at
18845 the pointer or reference targets are also unrolled. Only @code{typedef}s of
18846 fields, methods and inner @code{class typedef}s of @code{struct}s,
18847 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
18849 For example, for this variable declaration:
18852 typedef double real_t;
18853 struct complex @{ real_t real; double imag; @};
18854 typedef struct complex complex_t;
18856 real_t *real_pointer_var;
18860 the two commands give this output:
18864 (@value{GDBP}) whatis var
18866 (@value{GDBP}) ptype var
18867 type = struct complex @{
18871 (@value{GDBP}) whatis complex_t
18872 type = struct complex
18873 (@value{GDBP}) whatis struct complex
18874 type = struct complex
18875 (@value{GDBP}) ptype struct complex
18876 type = struct complex @{
18880 (@value{GDBP}) whatis real_pointer_var
18882 (@value{GDBP}) ptype real_pointer_var
18888 As with @code{whatis}, using @code{ptype} without an argument refers to
18889 the type of @code{$}, the last value in the value history.
18891 @cindex incomplete type
18892 Sometimes, programs use opaque data types or incomplete specifications
18893 of complex data structure. If the debug information included in the
18894 program does not allow @value{GDBN} to display a full declaration of
18895 the data type, it will say @samp{<incomplete type>}. For example,
18896 given these declarations:
18900 struct foo *fooptr;
18904 but no definition for @code{struct foo} itself, @value{GDBN} will say:
18907 (@value{GDBP}) ptype foo
18908 $1 = <incomplete type>
18912 ``Incomplete type'' is C terminology for data types that are not
18913 completely specified.
18915 @cindex unknown type
18916 Othertimes, information about a variable's type is completely absent
18917 from the debug information included in the program. This most often
18918 happens when the program or library where the variable is defined
18919 includes no debug information at all. @value{GDBN} knows the variable
18920 exists from inspecting the linker/loader symbol table (e.g., the ELF
18921 dynamic symbol table), but such symbols do not contain type
18922 information. Inspecting the type of a (global) variable for which
18923 @value{GDBN} has no type information shows:
18926 (@value{GDBP}) ptype var
18927 type = <data variable, no debug info>
18930 @xref{Variables, no debug info variables}, for how to print the values
18934 @item info types [-q] [@var{regexp}]
18935 Print a brief description of all types whose names match the regular
18936 expression @var{regexp} (or all types in your program, if you supply
18937 no argument). Each complete typename is matched as though it were a
18938 complete line; thus, @samp{i type value} gives information on all
18939 types in your program whose names include the string @code{value}, but
18940 @samp{i type ^value$} gives information only on types whose complete
18941 name is @code{value}.
18943 In programs using different languages, @value{GDBN} chooses the syntax
18944 to print the type description according to the
18945 @samp{set language} value: using @samp{set language auto}
18946 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18947 language of the type, other values mean to use
18948 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18950 This command differs from @code{ptype} in two ways: first, like
18951 @code{whatis}, it does not print a detailed description; second, it
18952 lists all source files and line numbers where a type is defined.
18954 The output from @samp{into types} is proceeded with a header line
18955 describing what types are being listed. The optional flag @samp{-q},
18956 which stands for @samp{quiet}, disables printing this header
18959 @kindex info type-printers
18960 @item info type-printers
18961 Versions of @value{GDBN} that ship with Python scripting enabled may
18962 have ``type printers'' available. When using @command{ptype} or
18963 @command{whatis}, these printers are consulted when the name of a type
18964 is needed. @xref{Type Printing API}, for more information on writing
18967 @code{info type-printers} displays all the available type printers.
18969 @kindex enable type-printer
18970 @kindex disable type-printer
18971 @item enable type-printer @var{name}@dots{}
18972 @item disable type-printer @var{name}@dots{}
18973 These commands can be used to enable or disable type printers.
18976 @cindex local variables
18977 @item info scope @var{location}
18978 List all the variables local to a particular scope. This command
18979 accepts a @var{location} argument---a function name, a source line, or
18980 an address preceded by a @samp{*}, and prints all the variables local
18981 to the scope defined by that location. (@xref{Specify Location}, for
18982 details about supported forms of @var{location}.) For example:
18985 (@value{GDBP}) @b{info scope command_line_handler}
18986 Scope for command_line_handler:
18987 Symbol rl is an argument at stack/frame offset 8, length 4.
18988 Symbol linebuffer is in static storage at address 0x150a18, length 4.
18989 Symbol linelength is in static storage at address 0x150a1c, length 4.
18990 Symbol p is a local variable in register $esi, length 4.
18991 Symbol p1 is a local variable in register $ebx, length 4.
18992 Symbol nline is a local variable in register $edx, length 4.
18993 Symbol repeat is a local variable at frame offset -8, length 4.
18997 This command is especially useful for determining what data to collect
18998 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19001 @kindex info source
19003 Show information about the current source file---that is, the source file for
19004 the function containing the current point of execution:
19007 the name of the source file, and the directory containing it,
19009 the directory it was compiled in,
19011 its length, in lines,
19013 which programming language it is written in,
19015 if the debug information provides it, the program that compiled the file
19016 (which may include, e.g., the compiler version and command line arguments),
19018 whether the executable includes debugging information for that file, and
19019 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19021 whether the debugging information includes information about
19022 preprocessor macros.
19026 @kindex info sources
19028 Print the names of all source files in your program for which there is
19029 debugging information, organized into two lists: files whose symbols
19030 have already been read, and files whose symbols will be read when needed.
19032 @item info sources [-dirname | -basename] [--] [@var{regexp}]
19033 Like @samp{info sources}, but only print the names of the files
19034 matching the provided @var{regexp}.
19035 By default, the @var{regexp} is used to match anywhere in the filename.
19036 If @code{-dirname}, only files having a dirname matching @var{regexp} are shown.
19037 If @code{-basename}, only files having a basename matching @var{regexp}
19039 The matching is case-sensitive, except on operating systems that
19040 have case-insensitive filesystem (e.g., MS-Windows).
19042 @kindex info functions
19043 @item info functions [-q] [-n]
19044 Print the names and data types of all defined functions.
19045 Similarly to @samp{info types}, this command groups its output by source
19046 files and annotates each function definition with its source line
19049 In programs using different languages, @value{GDBN} chooses the syntax
19050 to print the function name and type according to the
19051 @samp{set language} value: using @samp{set language auto}
19052 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19053 language of the function, other values mean to use
19054 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19056 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19057 results. A non-debugging symbol is a symbol that comes from the
19058 executable's symbol table, not from the debug information (for
19059 example, DWARF) associated with the executable.
19061 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19062 printing header information and messages explaining why no functions
19065 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19066 Like @samp{info functions}, but only print the names and data types
19067 of the functions selected with the provided regexp(s).
19069 If @var{regexp} is provided, print only the functions whose names
19070 match the regular expression @var{regexp}.
19071 Thus, @samp{info fun step} finds all functions whose
19072 names include @code{step}; @samp{info fun ^step} finds those whose names
19073 start with @code{step}. If a function name contains characters that
19074 conflict with the regular expression language (e.g.@:
19075 @samp{operator*()}), they may be quoted with a backslash.
19077 If @var{type_regexp} is provided, print only the functions whose
19078 types, as printed by the @code{whatis} command, match
19079 the regular expression @var{type_regexp}.
19080 If @var{type_regexp} contains space(s), it should be enclosed in
19081 quote characters. If needed, use backslash to escape the meaning
19082 of special characters or quotes.
19083 Thus, @samp{info fun -t '^int ('} finds the functions that return
19084 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19085 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19086 finds the functions whose names start with @code{step} and that return
19089 If both @var{regexp} and @var{type_regexp} are provided, a function
19090 is printed only if its name matches @var{regexp} and its type matches
19094 @kindex info variables
19095 @item info variables [-q] [-n]
19096 Print the names and data types of all variables that are defined
19097 outside of functions (i.e.@: excluding local variables).
19098 The printed variables are grouped by source files and annotated with
19099 their respective source line numbers.
19101 In programs using different languages, @value{GDBN} chooses the syntax
19102 to print the variable name and type according to the
19103 @samp{set language} value: using @samp{set language auto}
19104 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19105 language of the variable, other values mean to use
19106 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19108 The @samp{-n} flag excludes non-debugging symbols from the results.
19110 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19111 printing header information and messages explaining why no variables
19114 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19115 Like @kbd{info variables}, but only print the variables selected
19116 with the provided regexp(s).
19118 If @var{regexp} is provided, print only the variables whose names
19119 match the regular expression @var{regexp}.
19121 If @var{type_regexp} is provided, print only the variables whose
19122 types, as printed by the @code{whatis} command, match
19123 the regular expression @var{type_regexp}.
19124 If @var{type_regexp} contains space(s), it should be enclosed in
19125 quote characters. If needed, use backslash to escape the meaning
19126 of special characters or quotes.
19128 If both @var{regexp} and @var{type_regexp} are provided, an argument
19129 is printed only if its name matches @var{regexp} and its type matches
19132 @kindex info modules
19134 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19135 List all Fortran modules in the program, or all modules matching the
19136 optional regular expression @var{regexp}.
19138 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19139 printing header information and messages explaining why no modules
19142 @kindex info module
19143 @cindex Fortran modules, information about
19144 @cindex functions and variables by Fortran module
19145 @cindex module functions and variables
19146 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19147 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19148 List all functions or variables within all Fortran modules. The set
19149 of functions or variables listed can be limited by providing some or
19150 all of the optional regular expressions. If @var{module-regexp} is
19151 provided, then only Fortran modules matching @var{module-regexp} will
19152 be searched. Only functions or variables whose type matches the
19153 optional regular expression @var{type-regexp} will be listed. And
19154 only functions or variables whose name matches the optional regular
19155 expression @var{regexp} will be listed.
19157 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19158 printing header information and messages explaining why no functions
19159 or variables have been printed.
19161 @kindex info classes
19162 @cindex Objective-C, classes and selectors
19164 @itemx info classes @var{regexp}
19165 Display all Objective-C classes in your program, or
19166 (with the @var{regexp} argument) all those matching a particular regular
19169 @kindex info selectors
19170 @item info selectors
19171 @itemx info selectors @var{regexp}
19172 Display all Objective-C selectors in your program, or
19173 (with the @var{regexp} argument) all those matching a particular regular
19177 This was never implemented.
19178 @kindex info methods
19180 @itemx info methods @var{regexp}
19181 The @code{info methods} command permits the user to examine all defined
19182 methods within C@t{++} program, or (with the @var{regexp} argument) a
19183 specific set of methods found in the various C@t{++} classes. Many
19184 C@t{++} classes provide a large number of methods. Thus, the output
19185 from the @code{ptype} command can be overwhelming and hard to use. The
19186 @code{info-methods} command filters the methods, printing only those
19187 which match the regular-expression @var{regexp}.
19190 @cindex opaque data types
19191 @kindex set opaque-type-resolution
19192 @item set opaque-type-resolution on
19193 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19194 declared as a pointer to a @code{struct}, @code{class}, or
19195 @code{union}---for example, @code{struct MyType *}---that is used in one
19196 source file although the full declaration of @code{struct MyType} is in
19197 another source file. The default is on.
19199 A change in the setting of this subcommand will not take effect until
19200 the next time symbols for a file are loaded.
19202 @item set opaque-type-resolution off
19203 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19204 is printed as follows:
19206 @{<no data fields>@}
19209 @kindex show opaque-type-resolution
19210 @item show opaque-type-resolution
19211 Show whether opaque types are resolved or not.
19213 @kindex set print symbol-loading
19214 @cindex print messages when symbols are loaded
19215 @item set print symbol-loading
19216 @itemx set print symbol-loading full
19217 @itemx set print symbol-loading brief
19218 @itemx set print symbol-loading off
19219 The @code{set print symbol-loading} command allows you to control the
19220 printing of messages when @value{GDBN} loads symbol information.
19221 By default a message is printed for the executable and one for each
19222 shared library, and normally this is what you want. However, when
19223 debugging apps with large numbers of shared libraries these messages
19225 When set to @code{brief} a message is printed for each executable,
19226 and when @value{GDBN} loads a collection of shared libraries at once
19227 it will only print one message regardless of the number of shared
19228 libraries. When set to @code{off} no messages are printed.
19230 @kindex show print symbol-loading
19231 @item show print symbol-loading
19232 Show whether messages will be printed when a @value{GDBN} command
19233 entered from the keyboard causes symbol information to be loaded.
19235 @kindex maint print symbols
19236 @cindex symbol dump
19237 @kindex maint print psymbols
19238 @cindex partial symbol dump
19239 @kindex maint print msymbols
19240 @cindex minimal symbol dump
19241 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19242 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19243 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19244 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19245 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19246 Write a dump of debugging symbol data into the file @var{filename} or
19247 the terminal if @var{filename} is unspecified.
19248 If @code{-objfile @var{objfile}} is specified, only dump symbols for
19250 If @code{-pc @var{address}} is specified, only dump symbols for the file
19251 with code at that address. Note that @var{address} may be a symbol like
19253 If @code{-source @var{source}} is specified, only dump symbols for that
19256 These commands are used to debug the @value{GDBN} symbol-reading code.
19257 These commands do not modify internal @value{GDBN} state, therefore
19258 @samp{maint print symbols} will only print symbols for already expanded symbol
19260 You can use the command @code{info sources} to find out which files these are.
19261 If you use @samp{maint print psymbols} instead, the dump shows information
19262 about symbols that @value{GDBN} only knows partially---that is, symbols
19263 defined in files that @value{GDBN} has skimmed, but not yet read completely.
19264 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
19267 @xref{Files, ,Commands to Specify Files}, for a discussion of how
19268 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
19270 @kindex maint info symtabs
19271 @kindex maint info psymtabs
19272 @cindex listing @value{GDBN}'s internal symbol tables
19273 @cindex symbol tables, listing @value{GDBN}'s internal
19274 @cindex full symbol tables, listing @value{GDBN}'s internal
19275 @cindex partial symbol tables, listing @value{GDBN}'s internal
19276 @item maint info symtabs @r{[} @var{regexp} @r{]}
19277 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
19279 List the @code{struct symtab} or @code{struct partial_symtab}
19280 structures whose names match @var{regexp}. If @var{regexp} is not
19281 given, list them all. The output includes expressions which you can
19282 copy into a @value{GDBN} debugging this one to examine a particular
19283 structure in more detail. For example:
19286 (@value{GDBP}) maint info psymtabs dwarf2read
19287 @{ objfile /home/gnu/build/gdb/gdb
19288 ((struct objfile *) 0x82e69d0)
19289 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
19290 ((struct partial_symtab *) 0x8474b10)
19293 text addresses 0x814d3c8 -- 0x8158074
19294 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
19295 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
19296 dependencies (none)
19299 (@value{GDBP}) maint info symtabs
19303 We see that there is one partial symbol table whose filename contains
19304 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
19305 and we see that @value{GDBN} has not read in any symtabs yet at all.
19306 If we set a breakpoint on a function, that will cause @value{GDBN} to
19307 read the symtab for the compilation unit containing that function:
19310 (@value{GDBP}) break dwarf2_psymtab_to_symtab
19311 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
19313 (@value{GDBP}) maint info symtabs
19314 @{ objfile /home/gnu/build/gdb/gdb
19315 ((struct objfile *) 0x82e69d0)
19316 @{ symtab /home/gnu/src/gdb/dwarf2read.c
19317 ((struct symtab *) 0x86c1f38)
19320 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
19321 linetable ((struct linetable *) 0x8370fa0)
19322 debugformat DWARF 2
19328 @kindex maint info line-table
19329 @cindex listing @value{GDBN}'s internal line tables
19330 @cindex line tables, listing @value{GDBN}'s internal
19331 @item maint info line-table @r{[} @var{regexp} @r{]}
19333 List the @code{struct linetable} from all @code{struct symtab}
19334 instances whose name matches @var{regexp}. If @var{regexp} is not
19335 given, list the @code{struct linetable} from all @code{struct symtab}.
19337 @kindex maint set symbol-cache-size
19338 @cindex symbol cache size
19339 @item maint set symbol-cache-size @var{size}
19340 Set the size of the symbol cache to @var{size}.
19341 The default size is intended to be good enough for debugging
19342 most applications. This option exists to allow for experimenting
19343 with different sizes.
19345 @kindex maint show symbol-cache-size
19346 @item maint show symbol-cache-size
19347 Show the size of the symbol cache.
19349 @kindex maint print symbol-cache
19350 @cindex symbol cache, printing its contents
19351 @item maint print symbol-cache
19352 Print the contents of the symbol cache.
19353 This is useful when debugging symbol cache issues.
19355 @kindex maint print symbol-cache-statistics
19356 @cindex symbol cache, printing usage statistics
19357 @item maint print symbol-cache-statistics
19358 Print symbol cache usage statistics.
19359 This helps determine how well the cache is being utilized.
19361 @kindex maint flush-symbol-cache
19362 @cindex symbol cache, flushing
19363 @item maint flush-symbol-cache
19364 Flush the contents of the symbol cache, all entries are removed.
19365 This command is useful when debugging the symbol cache.
19366 It is also useful when collecting performance data.
19371 @chapter Altering Execution
19373 Once you think you have found an error in your program, you might want to
19374 find out for certain whether correcting the apparent error would lead to
19375 correct results in the rest of the run. You can find the answer by
19376 experiment, using the @value{GDBN} features for altering execution of the
19379 For example, you can store new values into variables or memory
19380 locations, give your program a signal, restart it at a different
19381 address, or even return prematurely from a function.
19384 * Assignment:: Assignment to variables
19385 * Jumping:: Continuing at a different address
19386 * Signaling:: Giving your program a signal
19387 * Returning:: Returning from a function
19388 * Calling:: Calling your program's functions
19389 * Patching:: Patching your program
19390 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
19394 @section Assignment to Variables
19397 @cindex setting variables
19398 To alter the value of a variable, evaluate an assignment expression.
19399 @xref{Expressions, ,Expressions}. For example,
19406 stores the value 4 into the variable @code{x}, and then prints the
19407 value of the assignment expression (which is 4).
19408 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
19409 information on operators in supported languages.
19411 @kindex set variable
19412 @cindex variables, setting
19413 If you are not interested in seeing the value of the assignment, use the
19414 @code{set} command instead of the @code{print} command. @code{set} is
19415 really the same as @code{print} except that the expression's value is
19416 not printed and is not put in the value history (@pxref{Value History,
19417 ,Value History}). The expression is evaluated only for its effects.
19419 If the beginning of the argument string of the @code{set} command
19420 appears identical to a @code{set} subcommand, use the @code{set
19421 variable} command instead of just @code{set}. This command is identical
19422 to @code{set} except for its lack of subcommands. For example, if your
19423 program has a variable @code{width}, you get an error if you try to set
19424 a new value with just @samp{set width=13}, because @value{GDBN} has the
19425 command @code{set width}:
19428 (@value{GDBP}) whatis width
19430 (@value{GDBP}) p width
19432 (@value{GDBP}) set width=47
19433 Invalid syntax in expression.
19437 The invalid expression, of course, is @samp{=47}. In
19438 order to actually set the program's variable @code{width}, use
19441 (@value{GDBP}) set var width=47
19444 Because the @code{set} command has many subcommands that can conflict
19445 with the names of program variables, it is a good idea to use the
19446 @code{set variable} command instead of just @code{set}. For example, if
19447 your program has a variable @code{g}, you run into problems if you try
19448 to set a new value with just @samp{set g=4}, because @value{GDBN} has
19449 the command @code{set gnutarget}, abbreviated @code{set g}:
19453 (@value{GDBP}) whatis g
19457 (@value{GDBP}) set g=4
19461 The program being debugged has been started already.
19462 Start it from the beginning? (y or n) y
19463 Starting program: /home/smith/cc_progs/a.out
19464 "/home/smith/cc_progs/a.out": can't open to read symbols:
19465 Invalid bfd target.
19466 (@value{GDBP}) show g
19467 The current BFD target is "=4".
19472 The program variable @code{g} did not change, and you silently set the
19473 @code{gnutarget} to an invalid value. In order to set the variable
19477 (@value{GDBP}) set var g=4
19480 @value{GDBN} allows more implicit conversions in assignments than C; you can
19481 freely store an integer value into a pointer variable or vice versa,
19482 and you can convert any structure to any other structure that is the
19483 same length or shorter.
19484 @comment FIXME: how do structs align/pad in these conversions?
19485 @comment /doc@cygnus.com 18dec1990
19487 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
19488 construct to generate a value of specified type at a specified address
19489 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
19490 to memory location @code{0x83040} as an integer (which implies a certain size
19491 and representation in memory), and
19494 set @{int@}0x83040 = 4
19498 stores the value 4 into that memory location.
19501 @section Continuing at a Different Address
19503 Ordinarily, when you continue your program, you do so at the place where
19504 it stopped, with the @code{continue} command. You can instead continue at
19505 an address of your own choosing, with the following commands:
19509 @kindex j @r{(@code{jump})}
19510 @item jump @var{location}
19511 @itemx j @var{location}
19512 Resume execution at @var{location}. Execution stops again immediately
19513 if there is a breakpoint there. @xref{Specify Location}, for a description
19514 of the different forms of @var{location}. It is common
19515 practice to use the @code{tbreak} command in conjunction with
19516 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
19518 The @code{jump} command does not change the current stack frame, or
19519 the stack pointer, or the contents of any memory location or any
19520 register other than the program counter. If @var{location} is in
19521 a different function from the one currently executing, the results may
19522 be bizarre if the two functions expect different patterns of arguments or
19523 of local variables. For this reason, the @code{jump} command requests
19524 confirmation if the specified line is not in the function currently
19525 executing. However, even bizarre results are predictable if you are
19526 well acquainted with the machine-language code of your program.
19529 On many systems, you can get much the same effect as the @code{jump}
19530 command by storing a new value into the register @code{$pc}. The
19531 difference is that this does not start your program running; it only
19532 changes the address of where it @emph{will} run when you continue. For
19540 makes the next @code{continue} command or stepping command execute at
19541 address @code{0x485}, rather than at the address where your program stopped.
19542 @xref{Continuing and Stepping, ,Continuing and Stepping}.
19544 The most common occasion to use the @code{jump} command is to back
19545 up---perhaps with more breakpoints set---over a portion of a program
19546 that has already executed, in order to examine its execution in more
19551 @section Giving your Program a Signal
19552 @cindex deliver a signal to a program
19556 @item signal @var{signal}
19557 Resume execution where your program is stopped, but immediately give it the
19558 signal @var{signal}. The @var{signal} can be the name or the number of a
19559 signal. For example, on many systems @code{signal 2} and @code{signal
19560 SIGINT} are both ways of sending an interrupt signal.
19562 Alternatively, if @var{signal} is zero, continue execution without
19563 giving a signal. This is useful when your program stopped on account of
19564 a signal and would ordinarily see the signal when resumed with the
19565 @code{continue} command; @samp{signal 0} causes it to resume without a
19568 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
19569 delivered to the currently selected thread, not the thread that last
19570 reported a stop. This includes the situation where a thread was
19571 stopped due to a signal. So if you want to continue execution
19572 suppressing the signal that stopped a thread, you should select that
19573 same thread before issuing the @samp{signal 0} command. If you issue
19574 the @samp{signal 0} command with another thread as the selected one,
19575 @value{GDBN} detects that and asks for confirmation.
19577 Invoking the @code{signal} command is not the same as invoking the
19578 @code{kill} utility from the shell. Sending a signal with @code{kill}
19579 causes @value{GDBN} to decide what to do with the signal depending on
19580 the signal handling tables (@pxref{Signals}). The @code{signal} command
19581 passes the signal directly to your program.
19583 @code{signal} does not repeat when you press @key{RET} a second time
19584 after executing the command.
19586 @kindex queue-signal
19587 @item queue-signal @var{signal}
19588 Queue @var{signal} to be delivered immediately to the current thread
19589 when execution of the thread resumes. The @var{signal} can be the name or
19590 the number of a signal. For example, on many systems @code{signal 2} and
19591 @code{signal SIGINT} are both ways of sending an interrupt signal.
19592 The handling of the signal must be set to pass the signal to the program,
19593 otherwise @value{GDBN} will report an error.
19594 You can control the handling of signals from @value{GDBN} with the
19595 @code{handle} command (@pxref{Signals}).
19597 Alternatively, if @var{signal} is zero, any currently queued signal
19598 for the current thread is discarded and when execution resumes no signal
19599 will be delivered. This is useful when your program stopped on account
19600 of a signal and would ordinarily see the signal when resumed with the
19601 @code{continue} command.
19603 This command differs from the @code{signal} command in that the signal
19604 is just queued, execution is not resumed. And @code{queue-signal} cannot
19605 be used to pass a signal whose handling state has been set to @code{nopass}
19610 @xref{stepping into signal handlers}, for information on how stepping
19611 commands behave when the thread has a signal queued.
19614 @section Returning from a Function
19617 @cindex returning from a function
19620 @itemx return @var{expression}
19621 You can cancel execution of a function call with the @code{return}
19622 command. If you give an
19623 @var{expression} argument, its value is used as the function's return
19627 When you use @code{return}, @value{GDBN} discards the selected stack frame
19628 (and all frames within it). You can think of this as making the
19629 discarded frame return prematurely. If you wish to specify a value to
19630 be returned, give that value as the argument to @code{return}.
19632 This pops the selected stack frame (@pxref{Selection, ,Selecting a
19633 Frame}), and any other frames inside of it, leaving its caller as the
19634 innermost remaining frame. That frame becomes selected. The
19635 specified value is stored in the registers used for returning values
19638 The @code{return} command does not resume execution; it leaves the
19639 program stopped in the state that would exist if the function had just
19640 returned. In contrast, the @code{finish} command (@pxref{Continuing
19641 and Stepping, ,Continuing and Stepping}) resumes execution until the
19642 selected stack frame returns naturally.
19644 @value{GDBN} needs to know how the @var{expression} argument should be set for
19645 the inferior. The concrete registers assignment depends on the OS ABI and the
19646 type being returned by the selected stack frame. For example it is common for
19647 OS ABI to return floating point values in FPU registers while integer values in
19648 CPU registers. Still some ABIs return even floating point values in CPU
19649 registers. Larger integer widths (such as @code{long long int}) also have
19650 specific placement rules. @value{GDBN} already knows the OS ABI from its
19651 current target so it needs to find out also the type being returned to make the
19652 assignment into the right register(s).
19654 Normally, the selected stack frame has debug info. @value{GDBN} will always
19655 use the debug info instead of the implicit type of @var{expression} when the
19656 debug info is available. For example, if you type @kbd{return -1}, and the
19657 function in the current stack frame is declared to return a @code{long long
19658 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
19659 into a @code{long long int}:
19662 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
19664 (@value{GDBP}) return -1
19665 Make func return now? (y or n) y
19666 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
19667 43 printf ("result=%lld\n", func ());
19671 However, if the selected stack frame does not have a debug info, e.g., if the
19672 function was compiled without debug info, @value{GDBN} has to find out the type
19673 to return from user. Specifying a different type by mistake may set the value
19674 in different inferior registers than the caller code expects. For example,
19675 typing @kbd{return -1} with its implicit type @code{int} would set only a part
19676 of a @code{long long int} result for a debug info less function (on 32-bit
19677 architectures). Therefore the user is required to specify the return type by
19678 an appropriate cast explicitly:
19681 Breakpoint 2, 0x0040050b in func ()
19682 (@value{GDBP}) return -1
19683 Return value type not available for selected stack frame.
19684 Please use an explicit cast of the value to return.
19685 (@value{GDBP}) return (long long int) -1
19686 Make selected stack frame return now? (y or n) y
19687 #0 0x00400526 in main ()
19692 @section Calling Program Functions
19695 @cindex calling functions
19696 @cindex inferior functions, calling
19697 @item print @var{expr}
19698 Evaluate the expression @var{expr} and display the resulting value.
19699 The expression may include calls to functions in the program being
19703 @item call @var{expr}
19704 Evaluate the expression @var{expr} without displaying @code{void}
19707 You can use this variant of the @code{print} command if you want to
19708 execute a function from your program that does not return anything
19709 (a.k.a.@: @dfn{a void function}), but without cluttering the output
19710 with @code{void} returned values that @value{GDBN} will otherwise
19711 print. If the result is not void, it is printed and saved in the
19715 It is possible for the function you call via the @code{print} or
19716 @code{call} command to generate a signal (e.g., if there's a bug in
19717 the function, or if you passed it incorrect arguments). What happens
19718 in that case is controlled by the @code{set unwindonsignal} command.
19720 Similarly, with a C@t{++} program it is possible for the function you
19721 call via the @code{print} or @code{call} command to generate an
19722 exception that is not handled due to the constraints of the dummy
19723 frame. In this case, any exception that is raised in the frame, but has
19724 an out-of-frame exception handler will not be found. GDB builds a
19725 dummy-frame for the inferior function call, and the unwinder cannot
19726 seek for exception handlers outside of this dummy-frame. What happens
19727 in that case is controlled by the
19728 @code{set unwind-on-terminating-exception} command.
19731 @item set unwindonsignal
19732 @kindex set unwindonsignal
19733 @cindex unwind stack in called functions
19734 @cindex call dummy stack unwinding
19735 Set unwinding of the stack if a signal is received while in a function
19736 that @value{GDBN} called in the program being debugged. If set to on,
19737 @value{GDBN} unwinds the stack it created for the call and restores
19738 the context to what it was before the call. If set to off (the
19739 default), @value{GDBN} stops in the frame where the signal was
19742 @item show unwindonsignal
19743 @kindex show unwindonsignal
19744 Show the current setting of stack unwinding in the functions called by
19747 @item set unwind-on-terminating-exception
19748 @kindex set unwind-on-terminating-exception
19749 @cindex unwind stack in called functions with unhandled exceptions
19750 @cindex call dummy stack unwinding on unhandled exception.
19751 Set unwinding of the stack if a C@t{++} exception is raised, but left
19752 unhandled while in a function that @value{GDBN} called in the program being
19753 debugged. If set to on (the default), @value{GDBN} unwinds the stack
19754 it created for the call and restores the context to what it was before
19755 the call. If set to off, @value{GDBN} the exception is delivered to
19756 the default C@t{++} exception handler and the inferior terminated.
19758 @item show unwind-on-terminating-exception
19759 @kindex show unwind-on-terminating-exception
19760 Show the current setting of stack unwinding in the functions called by
19763 @item set may-call-functions
19764 @kindex set may-call-functions
19765 @cindex disabling calling functions in the program
19766 @cindex calling functions in the program, disabling
19767 Set permission to call functions in the program.
19768 This controls whether @value{GDBN} will attempt to call functions in
19769 the program, such as with expressions in the @code{print} command. It
19770 defaults to @code{on}.
19772 To call a function in the program, @value{GDBN} has to temporarily
19773 modify the state of the inferior. This has potentially undesired side
19774 effects. Also, having @value{GDBN} call nested functions is likely to
19775 be erroneous and may even crash the program being debugged. You can
19776 avoid such hazards by forbidding @value{GDBN} from calling functions
19777 in the program being debugged. If calling functions in the program
19778 is forbidden, GDB will throw an error when a command (such as printing
19779 an expression) starts a function call in the program.
19781 @item show may-call-functions
19782 @kindex show may-call-functions
19783 Show permission to call functions in the program.
19787 @subsection Calling functions with no debug info
19789 @cindex no debug info functions
19790 Sometimes, a function you wish to call is missing debug information.
19791 In such case, @value{GDBN} does not know the type of the function,
19792 including the types of the function's parameters. To avoid calling
19793 the inferior function incorrectly, which could result in the called
19794 function functioning erroneously and even crash, @value{GDBN} refuses
19795 to call the function unless you tell it the type of the function.
19797 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
19798 to do that. The simplest is to cast the call to the function's
19799 declared return type. For example:
19802 (@value{GDBP}) p getenv ("PATH")
19803 'getenv' has unknown return type; cast the call to its declared return type
19804 (@value{GDBP}) p (char *) getenv ("PATH")
19805 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
19808 Casting the return type of a no-debug function is equivalent to
19809 casting the function to a pointer to a prototyped function that has a
19810 prototype that matches the types of the passed-in arguments, and
19811 calling that. I.e., the call above is equivalent to:
19814 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
19818 and given this prototyped C or C++ function with float parameters:
19821 float multiply (float v1, float v2) @{ return v1 * v2; @}
19825 these calls are equivalent:
19828 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
19829 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
19832 If the function you wish to call is declared as unprototyped (i.e.@:
19833 old K&R style), you must use the cast-to-function-pointer syntax, so
19834 that @value{GDBN} knows that it needs to apply default argument
19835 promotions (promote float arguments to double). @xref{ABI, float
19836 promotion}. For example, given this unprototyped C function with
19837 float parameters, and no debug info:
19841 multiply_noproto (v1, v2)
19849 you call it like this:
19852 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
19856 @section Patching Programs
19858 @cindex patching binaries
19859 @cindex writing into executables
19860 @cindex writing into corefiles
19862 By default, @value{GDBN} opens the file containing your program's
19863 executable code (or the corefile) read-only. This prevents accidental
19864 alterations to machine code; but it also prevents you from intentionally
19865 patching your program's binary.
19867 If you'd like to be able to patch the binary, you can specify that
19868 explicitly with the @code{set write} command. For example, you might
19869 want to turn on internal debugging flags, or even to make emergency
19875 @itemx set write off
19876 If you specify @samp{set write on}, @value{GDBN} opens executable and
19877 core files for both reading and writing; if you specify @kbd{set write
19878 off} (the default), @value{GDBN} opens them read-only.
19880 If you have already loaded a file, you must load it again (using the
19881 @code{exec-file} or @code{core-file} command) after changing @code{set
19882 write}, for your new setting to take effect.
19886 Display whether executable files and core files are opened for writing
19887 as well as reading.
19890 @node Compiling and Injecting Code
19891 @section Compiling and injecting code in @value{GDBN}
19892 @cindex injecting code
19893 @cindex writing into executables
19894 @cindex compiling code
19896 @value{GDBN} supports on-demand compilation and code injection into
19897 programs running under @value{GDBN}. GCC 5.0 or higher built with
19898 @file{libcc1.so} must be installed for this functionality to be enabled.
19899 This functionality is implemented with the following commands.
19902 @kindex compile code
19903 @item compile code @var{source-code}
19904 @itemx compile code -raw @var{--} @var{source-code}
19905 Compile @var{source-code} with the compiler language found as the current
19906 language in @value{GDBN} (@pxref{Languages}). If compilation and
19907 injection is not supported with the current language specified in
19908 @value{GDBN}, or the compiler does not support this feature, an error
19909 message will be printed. If @var{source-code} compiles and links
19910 successfully, @value{GDBN} will load the object-code emitted,
19911 and execute it within the context of the currently selected inferior.
19912 It is important to note that the compiled code is executed immediately.
19913 After execution, the compiled code is removed from @value{GDBN} and any
19914 new types or variables you have defined will be deleted.
19916 The command allows you to specify @var{source-code} in two ways.
19917 The simplest method is to provide a single line of code to the command.
19921 compile code printf ("hello world\n");
19924 If you specify options on the command line as well as source code, they
19925 may conflict. The @samp{--} delimiter can be used to separate options
19926 from actual source code. E.g.:
19929 compile code -r -- printf ("hello world\n");
19932 Alternatively you can enter source code as multiple lines of text. To
19933 enter this mode, invoke the @samp{compile code} command without any text
19934 following the command. This will start the multiple-line editor and
19935 allow you to type as many lines of source code as required. When you
19936 have completed typing, enter @samp{end} on its own line to exit the
19941 >printf ("hello\n");
19942 >printf ("world\n");
19946 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
19947 provided @var{source-code} in a callable scope. In this case, you must
19948 specify the entry point of the code by defining a function named
19949 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
19950 inferior. Using @samp{-raw} option may be needed for example when
19951 @var{source-code} requires @samp{#include} lines which may conflict with
19952 inferior symbols otherwise.
19954 @kindex compile file
19955 @item compile file @var{filename}
19956 @itemx compile file -raw @var{filename}
19957 Like @code{compile code}, but take the source code from @var{filename}.
19960 compile file /home/user/example.c
19965 @item compile print [[@var{options}] --] @var{expr}
19966 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
19967 Compile and execute @var{expr} with the compiler language found as the
19968 current language in @value{GDBN} (@pxref{Languages}). By default the
19969 value of @var{expr} is printed in a format appropriate to its data type;
19970 you can choose a different format by specifying @samp{/@var{f}}, where
19971 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
19972 Formats}. The @code{compile print} command accepts the same options
19973 as the @code{print} command; see @ref{print options}.
19975 @item compile print [[@var{options}] --]
19976 @itemx compile print [[@var{options}] --] /@var{f}
19977 @cindex reprint the last value
19978 Alternatively you can enter the expression (source code producing it) as
19979 multiple lines of text. To enter this mode, invoke the @samp{compile print}
19980 command without any text following the command. This will start the
19981 multiple-line editor.
19985 The process of compiling and injecting the code can be inspected using:
19988 @anchor{set debug compile}
19989 @item set debug compile
19990 @cindex compile command debugging info
19991 Turns on or off display of @value{GDBN} process of compiling and
19992 injecting the code. The default is off.
19994 @item show debug compile
19995 Displays the current state of displaying @value{GDBN} process of
19996 compiling and injecting the code.
19998 @anchor{set debug compile-cplus-types}
19999 @item set debug compile-cplus-types
20000 @cindex compile C@t{++} type conversion
20001 Turns on or off the display of C@t{++} type conversion debugging information.
20002 The default is off.
20004 @item show debug compile-cplus-types
20005 Displays the current state of displaying debugging information for
20006 C@t{++} type conversion.
20009 @subsection Compilation options for the @code{compile} command
20011 @value{GDBN} needs to specify the right compilation options for the code
20012 to be injected, in part to make its ABI compatible with the inferior
20013 and in part to make the injected code compatible with @value{GDBN}'s
20017 The options used, in increasing precedence:
20020 @item target architecture and OS options (@code{gdbarch})
20021 These options depend on target processor type and target operating
20022 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20023 (@code{-m64}) compilation option.
20025 @item compilation options recorded in the target
20026 @value{NGCC} (since version 4.7) stores the options used for compilation
20027 into @code{DW_AT_producer} part of DWARF debugging information according
20028 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20029 explicitly specify @code{-g} during inferior compilation otherwise
20030 @value{NGCC} produces no DWARF. This feature is only relevant for
20031 platforms where @code{-g} produces DWARF by default, otherwise one may
20032 try to enforce DWARF by using @code{-gdwarf-4}.
20034 @item compilation options set by @code{set compile-args}
20038 You can override compilation options using the following command:
20041 @item set compile-args
20042 @cindex compile command options override
20043 Set compilation options used for compiling and injecting code with the
20044 @code{compile} commands. These options override any conflicting ones
20045 from the target architecture and/or options stored during inferior
20048 @item show compile-args
20049 Displays the current state of compilation options override.
20050 This does not show all the options actually used during compilation,
20051 use @ref{set debug compile} for that.
20054 @subsection Caveats when using the @code{compile} command
20056 There are a few caveats to keep in mind when using the @code{compile}
20057 command. As the caveats are different per language, the table below
20058 highlights specific issues on a per language basis.
20061 @item C code examples and caveats
20062 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20063 attempt to compile the source code with a @samp{C} compiler. The source
20064 code provided to the @code{compile} command will have much the same
20065 access to variables and types as it normally would if it were part of
20066 the program currently being debugged in @value{GDBN}.
20068 Below is a sample program that forms the basis of the examples that
20069 follow. This program has been compiled and loaded into @value{GDBN},
20070 much like any other normal debugging session.
20073 void function1 (void)
20076 printf ("function 1\n");
20079 void function2 (void)
20094 For the purposes of the examples in this section, the program above has
20095 been compiled, loaded into @value{GDBN}, stopped at the function
20096 @code{main}, and @value{GDBN} is awaiting input from the user.
20098 To access variables and types for any program in @value{GDBN}, the
20099 program must be compiled and packaged with debug information. The
20100 @code{compile} command is not an exception to this rule. Without debug
20101 information, you can still use the @code{compile} command, but you will
20102 be very limited in what variables and types you can access.
20104 So with that in mind, the example above has been compiled with debug
20105 information enabled. The @code{compile} command will have access to
20106 all variables and types (except those that may have been optimized
20107 out). Currently, as @value{GDBN} has stopped the program in the
20108 @code{main} function, the @code{compile} command would have access to
20109 the variable @code{k}. You could invoke the @code{compile} command
20110 and type some source code to set the value of @code{k}. You can also
20111 read it, or do anything with that variable you would normally do in
20112 @code{C}. Be aware that changes to inferior variables in the
20113 @code{compile} command are persistent. In the following example:
20116 compile code k = 3;
20120 the variable @code{k} is now 3. It will retain that value until
20121 something else in the example program changes it, or another
20122 @code{compile} command changes it.
20124 Normal scope and access rules apply to source code compiled and
20125 injected by the @code{compile} command. In the example, the variables
20126 @code{j} and @code{k} are not accessible yet, because the program is
20127 currently stopped in the @code{main} function, where these variables
20128 are not in scope. Therefore, the following command
20131 compile code j = 3;
20135 will result in a compilation error message.
20137 Once the program is continued, execution will bring these variables in
20138 scope, and they will become accessible; then the code you specify via
20139 the @code{compile} command will be able to access them.
20141 You can create variables and types with the @code{compile} command as
20142 part of your source code. Variables and types that are created as part
20143 of the @code{compile} command are not visible to the rest of the program for
20144 the duration of its run. This example is valid:
20147 compile code int ff = 5; printf ("ff is %d\n", ff);
20150 However, if you were to type the following into @value{GDBN} after that
20151 command has completed:
20154 compile code printf ("ff is %d\n'', ff);
20158 a compiler error would be raised as the variable @code{ff} no longer
20159 exists. Object code generated and injected by the @code{compile}
20160 command is removed when its execution ends. Caution is advised
20161 when assigning to program variables values of variables created by the
20162 code submitted to the @code{compile} command. This example is valid:
20165 compile code int ff = 5; k = ff;
20168 The value of the variable @code{ff} is assigned to @code{k}. The variable
20169 @code{k} does not require the existence of @code{ff} to maintain the value
20170 it has been assigned. However, pointers require particular care in
20171 assignment. If the source code compiled with the @code{compile} command
20172 changed the address of a pointer in the example program, perhaps to a
20173 variable created in the @code{compile} command, that pointer would point
20174 to an invalid location when the command exits. The following example
20175 would likely cause issues with your debugged program:
20178 compile code int ff = 5; p = &ff;
20181 In this example, @code{p} would point to @code{ff} when the
20182 @code{compile} command is executing the source code provided to it.
20183 However, as variables in the (example) program persist with their
20184 assigned values, the variable @code{p} would point to an invalid
20185 location when the command exists. A general rule should be followed
20186 in that you should either assign @code{NULL} to any assigned pointers,
20187 or restore a valid location to the pointer before the command exits.
20189 Similar caution must be exercised with any structs, unions, and typedefs
20190 defined in @code{compile} command. Types defined in the @code{compile}
20191 command will no longer be available in the next @code{compile} command.
20192 Therefore, if you cast a variable to a type defined in the
20193 @code{compile} command, care must be taken to ensure that any future
20194 need to resolve the type can be achieved.
20197 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
20198 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
20199 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
20200 Compilation failed.
20201 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
20205 Variables that have been optimized away by the compiler are not
20206 accessible to the code submitted to the @code{compile} command.
20207 Access to those variables will generate a compiler error which @value{GDBN}
20208 will print to the console.
20211 @subsection Compiler search for the @code{compile} command
20213 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
20214 which may not be obvious for remote targets of different architecture
20215 than where @value{GDBN} is running. Environment variable @code{PATH} on
20216 @value{GDBN} host is searched for @value{NGCC} binary matching the
20217 target architecture and operating system. This search can be overriden
20218 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
20219 taken from shell that executed @value{GDBN}, it is not the value set by
20220 @value{GDBN} command @code{set environment}). @xref{Environment}.
20223 Specifically @code{PATH} is searched for binaries matching regular expression
20224 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
20225 debugged. @var{arch} is processor name --- multiarch is supported, so for
20226 example both @code{i386} and @code{x86_64} targets look for pattern
20227 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
20228 for pattern @code{s390x?}. @var{os} is currently supported only for
20229 pattern @code{linux(-gnu)?}.
20231 On Posix hosts the compiler driver @value{GDBN} needs to find also
20232 shared library @file{libcc1.so} from the compiler. It is searched in
20233 default shared library search path (overridable with usual environment
20234 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
20235 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
20236 according to the installation of the found compiler --- as possibly
20237 specified by the @code{set compile-gcc} command.
20240 @item set compile-gcc
20241 @cindex compile command driver filename override
20242 Set compilation command used for compiling and injecting code with the
20243 @code{compile} commands. If this option is not set (it is set to
20244 an empty string), the search described above will occur --- that is the
20247 @item show compile-gcc
20248 Displays the current compile command @value{NGCC} driver filename.
20249 If set, it is the main command @command{gcc}, found usually for example
20250 under name @file{x86_64-linux-gnu-gcc}.
20254 @chapter @value{GDBN} Files
20256 @value{GDBN} needs to know the file name of the program to be debugged,
20257 both in order to read its symbol table and in order to start your
20258 program. To debug a core dump of a previous run, you must also tell
20259 @value{GDBN} the name of the core dump file.
20262 * Files:: Commands to specify files
20263 * File Caching:: Information about @value{GDBN}'s file caching
20264 * Separate Debug Files:: Debugging information in separate files
20265 * MiniDebugInfo:: Debugging information in a special section
20266 * Index Files:: Index files speed up GDB
20267 * Symbol Errors:: Errors reading symbol files
20268 * Data Files:: GDB data files
20272 @section Commands to Specify Files
20274 @cindex symbol table
20275 @cindex core dump file
20277 You may want to specify executable and core dump file names. The usual
20278 way to do this is at start-up time, using the arguments to
20279 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
20280 Out of @value{GDBN}}).
20282 Occasionally it is necessary to change to a different file during a
20283 @value{GDBN} session. Or you may run @value{GDBN} and forget to
20284 specify a file you want to use. Or you are debugging a remote target
20285 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
20286 Program}). In these situations the @value{GDBN} commands to specify
20287 new files are useful.
20290 @cindex executable file
20292 @item file @var{filename}
20293 Use @var{filename} as the program to be debugged. It is read for its
20294 symbols and for the contents of pure memory. It is also the program
20295 executed when you use the @code{run} command. If you do not specify a
20296 directory and the file is not found in the @value{GDBN} working directory,
20297 @value{GDBN} uses the environment variable @code{PATH} as a list of
20298 directories to search, just as the shell does when looking for a program
20299 to run. You can change the value of this variable, for both @value{GDBN}
20300 and your program, using the @code{path} command.
20302 @cindex unlinked object files
20303 @cindex patching object files
20304 You can load unlinked object @file{.o} files into @value{GDBN} using
20305 the @code{file} command. You will not be able to ``run'' an object
20306 file, but you can disassemble functions and inspect variables. Also,
20307 if the underlying BFD functionality supports it, you could use
20308 @kbd{gdb -write} to patch object files using this technique. Note
20309 that @value{GDBN} can neither interpret nor modify relocations in this
20310 case, so branches and some initialized variables will appear to go to
20311 the wrong place. But this feature is still handy from time to time.
20314 @code{file} with no argument makes @value{GDBN} discard any information it
20315 has on both executable file and the symbol table.
20318 @item exec-file @r{[} @var{filename} @r{]}
20319 Specify that the program to be run (but not the symbol table) is found
20320 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
20321 if necessary to locate your program. Omitting @var{filename} means to
20322 discard information on the executable file.
20324 @kindex symbol-file
20325 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
20326 Read symbol table information from file @var{filename}. @code{PATH} is
20327 searched when necessary. Use the @code{file} command to get both symbol
20328 table and program to run from the same file.
20330 If an optional @var{offset} is specified, it is added to the start
20331 address of each section in the symbol file. This is useful if the
20332 program is relocated at runtime, such as the Linux kernel with kASLR
20335 @code{symbol-file} with no argument clears out @value{GDBN} information on your
20336 program's symbol table.
20338 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
20339 some breakpoints and auto-display expressions. This is because they may
20340 contain pointers to the internal data recording symbols and data types,
20341 which are part of the old symbol table data being discarded inside
20344 @code{symbol-file} does not repeat if you press @key{RET} again after
20347 When @value{GDBN} is configured for a particular environment, it
20348 understands debugging information in whatever format is the standard
20349 generated for that environment; you may use either a @sc{gnu} compiler, or
20350 other compilers that adhere to the local conventions.
20351 Best results are usually obtained from @sc{gnu} compilers; for example,
20352 using @code{@value{NGCC}} you can generate debugging information for
20355 For most kinds of object files, with the exception of old SVR3 systems
20356 using COFF, the @code{symbol-file} command does not normally read the
20357 symbol table in full right away. Instead, it scans the symbol table
20358 quickly to find which source files and which symbols are present. The
20359 details are read later, one source file at a time, as they are needed.
20361 The purpose of this two-stage reading strategy is to make @value{GDBN}
20362 start up faster. For the most part, it is invisible except for
20363 occasional pauses while the symbol table details for a particular source
20364 file are being read. (The @code{set verbose} command can turn these
20365 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
20366 Warnings and Messages}.)
20368 We have not implemented the two-stage strategy for COFF yet. When the
20369 symbol table is stored in COFF format, @code{symbol-file} reads the
20370 symbol table data in full right away. Note that ``stabs-in-COFF''
20371 still does the two-stage strategy, since the debug info is actually
20375 @cindex reading symbols immediately
20376 @cindex symbols, reading immediately
20377 @item symbol-file @r{[} -readnow @r{]} @var{filename}
20378 @itemx file @r{[} -readnow @r{]} @var{filename}
20379 You can override the @value{GDBN} two-stage strategy for reading symbol
20380 tables by using the @samp{-readnow} option with any of the commands that
20381 load symbol table information, if you want to be sure @value{GDBN} has the
20382 entire symbol table available.
20384 @cindex @code{-readnever}, option for symbol-file command
20385 @cindex never read symbols
20386 @cindex symbols, never read
20387 @item symbol-file @r{[} -readnever @r{]} @var{filename}
20388 @itemx file @r{[} -readnever @r{]} @var{filename}
20389 You can instruct @value{GDBN} to never read the symbolic information
20390 contained in @var{filename} by using the @samp{-readnever} option.
20391 @xref{--readnever}.
20393 @c FIXME: for now no mention of directories, since this seems to be in
20394 @c flux. 13mar1992 status is that in theory GDB would look either in
20395 @c current dir or in same dir as myprog; but issues like competing
20396 @c GDB's, or clutter in system dirs, mean that in practice right now
20397 @c only current dir is used. FFish says maybe a special GDB hierarchy
20398 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
20402 @item core-file @r{[}@var{filename}@r{]}
20404 Specify the whereabouts of a core dump file to be used as the ``contents
20405 of memory''. Traditionally, core files contain only some parts of the
20406 address space of the process that generated them; @value{GDBN} can access the
20407 executable file itself for other parts.
20409 @code{core-file} with no argument specifies that no core file is
20412 Note that the core file is ignored when your program is actually running
20413 under @value{GDBN}. So, if you have been running your program and you
20414 wish to debug a core file instead, you must kill the subprocess in which
20415 the program is running. To do this, use the @code{kill} command
20416 (@pxref{Kill Process, ,Killing the Child Process}).
20418 @kindex add-symbol-file
20419 @cindex dynamic linking
20420 @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{]}
20421 The @code{add-symbol-file} command reads additional symbol table
20422 information from the file @var{filename}. You would use this command
20423 when @var{filename} has been dynamically loaded (by some other means)
20424 into the program that is running. The @var{textaddress} parameter gives
20425 the memory address at which the file's text section has been loaded.
20426 You can additionally specify the base address of other sections using
20427 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
20428 If a section is omitted, @value{GDBN} will use its default addresses
20429 as found in @var{filename}. Any @var{address} or @var{textaddress}
20430 can be given as an expression.
20432 If an optional @var{offset} is specified, it is added to the start
20433 address of each section, except those for which the address was
20434 specified explicitly.
20436 The symbol table of the file @var{filename} is added to the symbol table
20437 originally read with the @code{symbol-file} command. You can use the
20438 @code{add-symbol-file} command any number of times; the new symbol data
20439 thus read is kept in addition to the old.
20441 Changes can be reverted using the command @code{remove-symbol-file}.
20443 @cindex relocatable object files, reading symbols from
20444 @cindex object files, relocatable, reading symbols from
20445 @cindex reading symbols from relocatable object files
20446 @cindex symbols, reading from relocatable object files
20447 @cindex @file{.o} files, reading symbols from
20448 Although @var{filename} is typically a shared library file, an
20449 executable file, or some other object file which has been fully
20450 relocated for loading into a process, you can also load symbolic
20451 information from relocatable @file{.o} files, as long as:
20455 the file's symbolic information refers only to linker symbols defined in
20456 that file, not to symbols defined by other object files,
20458 every section the file's symbolic information refers to has actually
20459 been loaded into the inferior, as it appears in the file, and
20461 you can determine the address at which every section was loaded, and
20462 provide these to the @code{add-symbol-file} command.
20466 Some embedded operating systems, like Sun Chorus and VxWorks, can load
20467 relocatable files into an already running program; such systems
20468 typically make the requirements above easy to meet. However, it's
20469 important to recognize that many native systems use complex link
20470 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
20471 assembly, for example) that make the requirements difficult to meet. In
20472 general, one cannot assume that using @code{add-symbol-file} to read a
20473 relocatable object file's symbolic information will have the same effect
20474 as linking the relocatable object file into the program in the normal
20477 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
20479 @kindex remove-symbol-file
20480 @item remove-symbol-file @var{filename}
20481 @item remove-symbol-file -a @var{address}
20482 Remove a symbol file added via the @code{add-symbol-file} command. The
20483 file to remove can be identified by its @var{filename} or by an @var{address}
20484 that lies within the boundaries of this symbol file in memory. Example:
20487 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
20488 add symbol table from file "/home/user/gdb/mylib.so" at
20489 .text_addr = 0x7ffff7ff9480
20491 Reading symbols from /home/user/gdb/mylib.so...
20492 (gdb) remove-symbol-file -a 0x7ffff7ff9480
20493 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
20498 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
20500 @kindex add-symbol-file-from-memory
20501 @cindex @code{syscall DSO}
20502 @cindex load symbols from memory
20503 @item add-symbol-file-from-memory @var{address}
20504 Load symbols from the given @var{address} in a dynamically loaded
20505 object file whose image is mapped directly into the inferior's memory.
20506 For example, the Linux kernel maps a @code{syscall DSO} into each
20507 process's address space; this DSO provides kernel-specific code for
20508 some system calls. The argument can be any expression whose
20509 evaluation yields the address of the file's shared object file header.
20510 For this command to work, you must have used @code{symbol-file} or
20511 @code{exec-file} commands in advance.
20514 @item section @var{section} @var{addr}
20515 The @code{section} command changes the base address of the named
20516 @var{section} of the exec file to @var{addr}. This can be used if the
20517 exec file does not contain section addresses, (such as in the
20518 @code{a.out} format), or when the addresses specified in the file
20519 itself are wrong. Each section must be changed separately. The
20520 @code{info files} command, described below, lists all the sections and
20524 @kindex info target
20527 @code{info files} and @code{info target} are synonymous; both print the
20528 current target (@pxref{Targets, ,Specifying a Debugging Target}),
20529 including the names of the executable and core dump files currently in
20530 use by @value{GDBN}, and the files from which symbols were loaded. The
20531 command @code{help target} lists all possible targets rather than
20534 @kindex maint info sections
20535 @item maint info sections
20536 Another command that can give you extra information about program sections
20537 is @code{maint info sections}. In addition to the section information
20538 displayed by @code{info files}, this command displays the flags and file
20539 offset of each section in the executable and core dump files. In addition,
20540 @code{maint info sections} provides the following command options (which
20541 may be arbitrarily combined):
20545 Display sections for all loaded object files, including shared libraries.
20546 @item @var{sections}
20547 Display info only for named @var{sections}.
20548 @item @var{section-flags}
20549 Display info only for sections for which @var{section-flags} are true.
20550 The section flags that @value{GDBN} currently knows about are:
20553 Section will have space allocated in the process when loaded.
20554 Set for all sections except those containing debug information.
20556 Section will be loaded from the file into the child process memory.
20557 Set for pre-initialized code and data, clear for @code{.bss} sections.
20559 Section needs to be relocated before loading.
20561 Section cannot be modified by the child process.
20563 Section contains executable code only.
20565 Section contains data only (no executable code).
20567 Section will reside in ROM.
20569 Section contains data for constructor/destructor lists.
20571 Section is not empty.
20573 An instruction to the linker to not output the section.
20574 @item COFF_SHARED_LIBRARY
20575 A notification to the linker that the section contains
20576 COFF shared library information.
20578 Section contains common symbols.
20581 @kindex set trust-readonly-sections
20582 @cindex read-only sections
20583 @item set trust-readonly-sections on
20584 Tell @value{GDBN} that readonly sections in your object file
20585 really are read-only (i.e.@: that their contents will not change).
20586 In that case, @value{GDBN} can fetch values from these sections
20587 out of the object file, rather than from the target program.
20588 For some targets (notably embedded ones), this can be a significant
20589 enhancement to debugging performance.
20591 The default is off.
20593 @item set trust-readonly-sections off
20594 Tell @value{GDBN} not to trust readonly sections. This means that
20595 the contents of the section might change while the program is running,
20596 and must therefore be fetched from the target when needed.
20598 @item show trust-readonly-sections
20599 Show the current setting of trusting readonly sections.
20602 All file-specifying commands allow both absolute and relative file names
20603 as arguments. @value{GDBN} always converts the file name to an absolute file
20604 name and remembers it that way.
20606 @cindex shared libraries
20607 @anchor{Shared Libraries}
20608 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
20609 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
20610 DSBT (TIC6X) shared libraries.
20612 On MS-Windows @value{GDBN} must be linked with the Expat library to support
20613 shared libraries. @xref{Expat}.
20615 @value{GDBN} automatically loads symbol definitions from shared libraries
20616 when you use the @code{run} command, or when you examine a core file.
20617 (Before you issue the @code{run} command, @value{GDBN} does not understand
20618 references to a function in a shared library, however---unless you are
20619 debugging a core file).
20621 @c FIXME: some @value{GDBN} release may permit some refs to undef
20622 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
20623 @c FIXME...lib; check this from time to time when updating manual
20625 There are times, however, when you may wish to not automatically load
20626 symbol definitions from shared libraries, such as when they are
20627 particularly large or there are many of them.
20629 To control the automatic loading of shared library symbols, use the
20633 @kindex set auto-solib-add
20634 @item set auto-solib-add @var{mode}
20635 If @var{mode} is @code{on}, symbols from all shared object libraries
20636 will be loaded automatically when the inferior begins execution, you
20637 attach to an independently started inferior, or when the dynamic linker
20638 informs @value{GDBN} that a new library has been loaded. If @var{mode}
20639 is @code{off}, symbols must be loaded manually, using the
20640 @code{sharedlibrary} command. The default value is @code{on}.
20642 @cindex memory used for symbol tables
20643 If your program uses lots of shared libraries with debug info that
20644 takes large amounts of memory, you can decrease the @value{GDBN}
20645 memory footprint by preventing it from automatically loading the
20646 symbols from shared libraries. To that end, type @kbd{set
20647 auto-solib-add off} before running the inferior, then load each
20648 library whose debug symbols you do need with @kbd{sharedlibrary
20649 @var{regexp}}, where @var{regexp} is a regular expression that matches
20650 the libraries whose symbols you want to be loaded.
20652 @kindex show auto-solib-add
20653 @item show auto-solib-add
20654 Display the current autoloading mode.
20657 @cindex load shared library
20658 To explicitly load shared library symbols, use the @code{sharedlibrary}
20662 @kindex info sharedlibrary
20664 @item info share @var{regex}
20665 @itemx info sharedlibrary @var{regex}
20666 Print the names of the shared libraries which are currently loaded
20667 that match @var{regex}. If @var{regex} is omitted then print
20668 all shared libraries that are loaded.
20671 @item info dll @var{regex}
20672 This is an alias of @code{info sharedlibrary}.
20674 @kindex sharedlibrary
20676 @item sharedlibrary @var{regex}
20677 @itemx share @var{regex}
20678 Load shared object library symbols for files matching a
20679 Unix regular expression.
20680 As with files loaded automatically, it only loads shared libraries
20681 required by your program for a core file or after typing @code{run}. If
20682 @var{regex} is omitted all shared libraries required by your program are
20685 @item nosharedlibrary
20686 @kindex nosharedlibrary
20687 @cindex unload symbols from shared libraries
20688 Unload all shared object library symbols. This discards all symbols
20689 that have been loaded from all shared libraries. Symbols from shared
20690 libraries that were loaded by explicit user requests are not
20694 Sometimes you may wish that @value{GDBN} stops and gives you control
20695 when any of shared library events happen. The best way to do this is
20696 to use @code{catch load} and @code{catch unload} (@pxref{Set
20699 @value{GDBN} also supports the @code{set stop-on-solib-events}
20700 command for this. This command exists for historical reasons. It is
20701 less useful than setting a catchpoint, because it does not allow for
20702 conditions or commands as a catchpoint does.
20705 @item set stop-on-solib-events
20706 @kindex set stop-on-solib-events
20707 This command controls whether @value{GDBN} should give you control
20708 when the dynamic linker notifies it about some shared library event.
20709 The most common event of interest is loading or unloading of a new
20712 @item show stop-on-solib-events
20713 @kindex show stop-on-solib-events
20714 Show whether @value{GDBN} stops and gives you control when shared
20715 library events happen.
20718 Shared libraries are also supported in many cross or remote debugging
20719 configurations. @value{GDBN} needs to have access to the target's libraries;
20720 this can be accomplished either by providing copies of the libraries
20721 on the host system, or by asking @value{GDBN} to automatically retrieve the
20722 libraries from the target. If copies of the target libraries are
20723 provided, they need to be the same as the target libraries, although the
20724 copies on the target can be stripped as long as the copies on the host are
20727 @cindex where to look for shared libraries
20728 For remote debugging, you need to tell @value{GDBN} where the target
20729 libraries are, so that it can load the correct copies---otherwise, it
20730 may try to load the host's libraries. @value{GDBN} has two variables
20731 to specify the search directories for target libraries.
20734 @cindex prefix for executable and shared library file names
20735 @cindex system root, alternate
20736 @kindex set solib-absolute-prefix
20737 @kindex set sysroot
20738 @item set sysroot @var{path}
20739 Use @var{path} as the system root for the program being debugged. Any
20740 absolute shared library paths will be prefixed with @var{path}; many
20741 runtime loaders store the absolute paths to the shared library in the
20742 target program's memory. When starting processes remotely, and when
20743 attaching to already-running processes (local or remote), their
20744 executable filenames will be prefixed with @var{path} if reported to
20745 @value{GDBN} as absolute by the operating system. If you use
20746 @code{set sysroot} to find executables and shared libraries, they need
20747 to be laid out in the same way that they are on the target, with
20748 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
20751 If @var{path} starts with the sequence @file{target:} and the target
20752 system is remote then @value{GDBN} will retrieve the target binaries
20753 from the remote system. This is only supported when using a remote
20754 target that supports the @code{remote get} command (@pxref{File
20755 Transfer,,Sending files to a remote system}). The part of @var{path}
20756 following the initial @file{target:} (if present) is used as system
20757 root prefix on the remote file system. If @var{path} starts with the
20758 sequence @file{remote:} this is converted to the sequence
20759 @file{target:} by @code{set sysroot}@footnote{Historically the
20760 functionality to retrieve binaries from the remote system was
20761 provided by prefixing @var{path} with @file{remote:}}. If you want
20762 to specify a local system root using a directory that happens to be
20763 named @file{target:} or @file{remote:}, you need to use some
20764 equivalent variant of the name like @file{./target:}.
20766 For targets with an MS-DOS based filesystem, such as MS-Windows and
20767 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
20768 absolute file name with @var{path}. But first, on Unix hosts,
20769 @value{GDBN} converts all backslash directory separators into forward
20770 slashes, because the backslash is not a directory separator on Unix:
20773 c:\foo\bar.dll @result{} c:/foo/bar.dll
20776 Then, @value{GDBN} attempts prefixing the target file name with
20777 @var{path}, and looks for the resulting file name in the host file
20781 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
20784 If that does not find the binary, @value{GDBN} tries removing
20785 the @samp{:} character from the drive spec, both for convenience, and,
20786 for the case of the host file system not supporting file names with
20790 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
20793 This makes it possible to have a system root that mirrors a target
20794 with more than one drive. E.g., you may want to setup your local
20795 copies of the target system shared libraries like so (note @samp{c} vs
20799 @file{/path/to/sysroot/c/sys/bin/foo.dll}
20800 @file{/path/to/sysroot/c/sys/bin/bar.dll}
20801 @file{/path/to/sysroot/z/sys/bin/bar.dll}
20805 and point the system root at @file{/path/to/sysroot}, so that
20806 @value{GDBN} can find the correct copies of both
20807 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
20809 If that still does not find the binary, @value{GDBN} tries
20810 removing the whole drive spec from the target file name:
20813 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
20816 This last lookup makes it possible to not care about the drive name,
20817 if you don't want or need to.
20819 The @code{set solib-absolute-prefix} command is an alias for @code{set
20822 @cindex default system root
20823 @cindex @samp{--with-sysroot}
20824 You can set the default system root by using the configure-time
20825 @samp{--with-sysroot} option. If the system root is inside
20826 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20827 @samp{--exec-prefix}), then the default system root will be updated
20828 automatically if the installed @value{GDBN} is moved to a new
20831 @kindex show sysroot
20833 Display the current executable and shared library prefix.
20835 @kindex set solib-search-path
20836 @item set solib-search-path @var{path}
20837 If this variable is set, @var{path} is a colon-separated list of
20838 directories to search for shared libraries. @samp{solib-search-path}
20839 is used after @samp{sysroot} fails to locate the library, or if the
20840 path to the library is relative instead of absolute. If you want to
20841 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
20842 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
20843 finding your host's libraries. @samp{sysroot} is preferred; setting
20844 it to a nonexistent directory may interfere with automatic loading
20845 of shared library symbols.
20847 @kindex show solib-search-path
20848 @item show solib-search-path
20849 Display the current shared library search path.
20851 @cindex DOS file-name semantics of file names.
20852 @kindex set target-file-system-kind (unix|dos-based|auto)
20853 @kindex show target-file-system-kind
20854 @item set target-file-system-kind @var{kind}
20855 Set assumed file system kind for target reported file names.
20857 Shared library file names as reported by the target system may not
20858 make sense as is on the system @value{GDBN} is running on. For
20859 example, when remote debugging a target that has MS-DOS based file
20860 system semantics, from a Unix host, the target may be reporting to
20861 @value{GDBN} a list of loaded shared libraries with file names such as
20862 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
20863 drive letters, so the @samp{c:\} prefix is not normally understood as
20864 indicating an absolute file name, and neither is the backslash
20865 normally considered a directory separator character. In that case,
20866 the native file system would interpret this whole absolute file name
20867 as a relative file name with no directory components. This would make
20868 it impossible to point @value{GDBN} at a copy of the remote target's
20869 shared libraries on the host using @code{set sysroot}, and impractical
20870 with @code{set solib-search-path}. Setting
20871 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
20872 to interpret such file names similarly to how the target would, and to
20873 map them to file names valid on @value{GDBN}'s native file system
20874 semantics. The value of @var{kind} can be @code{"auto"}, in addition
20875 to one of the supported file system kinds. In that case, @value{GDBN}
20876 tries to determine the appropriate file system variant based on the
20877 current target's operating system (@pxref{ABI, ,Configuring the
20878 Current ABI}). The supported file system settings are:
20882 Instruct @value{GDBN} to assume the target file system is of Unix
20883 kind. Only file names starting the forward slash (@samp{/}) character
20884 are considered absolute, and the directory separator character is also
20888 Instruct @value{GDBN} to assume the target file system is DOS based.
20889 File names starting with either a forward slash, or a drive letter
20890 followed by a colon (e.g., @samp{c:}), are considered absolute, and
20891 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
20892 considered directory separators.
20895 Instruct @value{GDBN} to use the file system kind associated with the
20896 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
20897 This is the default.
20901 @cindex file name canonicalization
20902 @cindex base name differences
20903 When processing file names provided by the user, @value{GDBN}
20904 frequently needs to compare them to the file names recorded in the
20905 program's debug info. Normally, @value{GDBN} compares just the
20906 @dfn{base names} of the files as strings, which is reasonably fast
20907 even for very large programs. (The base name of a file is the last
20908 portion of its name, after stripping all the leading directories.)
20909 This shortcut in comparison is based upon the assumption that files
20910 cannot have more than one base name. This is usually true, but
20911 references to files that use symlinks or similar filesystem
20912 facilities violate that assumption. If your program records files
20913 using such facilities, or if you provide file names to @value{GDBN}
20914 using symlinks etc., you can set @code{basenames-may-differ} to
20915 @code{true} to instruct @value{GDBN} to completely canonicalize each
20916 pair of file names it needs to compare. This will make file-name
20917 comparisons accurate, but at a price of a significant slowdown.
20920 @item set basenames-may-differ
20921 @kindex set basenames-may-differ
20922 Set whether a source file may have multiple base names.
20924 @item show basenames-may-differ
20925 @kindex show basenames-may-differ
20926 Show whether a source file may have multiple base names.
20930 @section File Caching
20931 @cindex caching of opened files
20932 @cindex caching of bfd objects
20934 To speed up file loading, and reduce memory usage, @value{GDBN} will
20935 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
20936 BFD, bfd, The Binary File Descriptor Library}. The following commands
20937 allow visibility and control of the caching behavior.
20940 @kindex maint info bfds
20941 @item maint info bfds
20942 This prints information about each @code{bfd} object that is known to
20945 @kindex maint set bfd-sharing
20946 @kindex maint show bfd-sharing
20947 @kindex bfd caching
20948 @item maint set bfd-sharing
20949 @item maint show bfd-sharing
20950 Control whether @code{bfd} objects can be shared. When sharing is
20951 enabled @value{GDBN} reuses already open @code{bfd} objects rather
20952 than reopening the same file. Turning sharing off does not cause
20953 already shared @code{bfd} objects to be unshared, but all future files
20954 that are opened will create a new @code{bfd} object. Similarly,
20955 re-enabling sharing does not cause multiple existing @code{bfd}
20956 objects to be collapsed into a single shared @code{bfd} object.
20958 @kindex set debug bfd-cache @var{level}
20959 @kindex bfd caching
20960 @item set debug bfd-cache @var{level}
20961 Turns on debugging of the bfd cache, setting the level to @var{level}.
20963 @kindex show debug bfd-cache
20964 @kindex bfd caching
20965 @item show debug bfd-cache
20966 Show the current debugging level of the bfd cache.
20969 @node Separate Debug Files
20970 @section Debugging Information in Separate Files
20971 @cindex separate debugging information files
20972 @cindex debugging information in separate files
20973 @cindex @file{.debug} subdirectories
20974 @cindex debugging information directory, global
20975 @cindex global debugging information directories
20976 @cindex build ID, and separate debugging files
20977 @cindex @file{.build-id} directory
20979 @value{GDBN} allows you to put a program's debugging information in a
20980 file separate from the executable itself, in a way that allows
20981 @value{GDBN} to find and load the debugging information automatically.
20982 Since debugging information can be very large---sometimes larger
20983 than the executable code itself---some systems distribute debugging
20984 information for their executables in separate files, which users can
20985 install only when they need to debug a problem.
20987 @value{GDBN} supports two ways of specifying the separate debug info
20992 The executable contains a @dfn{debug link} that specifies the name of
20993 the separate debug info file. The separate debug file's name is
20994 usually @file{@var{executable}.debug}, where @var{executable} is the
20995 name of the corresponding executable file without leading directories
20996 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
20997 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
20998 checksum for the debug file, which @value{GDBN} uses to validate that
20999 the executable and the debug file came from the same build.
21003 The executable contains a @dfn{build ID}, a unique bit string that is
21004 also present in the corresponding debug info file. (This is supported
21005 only on some operating systems, when using the ELF or PE file formats
21006 for binary files and the @sc{gnu} Binutils.) For more details about
21007 this feature, see the description of the @option{--build-id}
21008 command-line option in @ref{Options, , Command Line Options, ld,
21009 The GNU Linker}. The debug info file's name is not specified
21010 explicitly by the build ID, but can be computed from the build ID, see
21014 Depending on the way the debug info file is specified, @value{GDBN}
21015 uses two different methods of looking for the debug file:
21019 For the ``debug link'' method, @value{GDBN} looks up the named file in
21020 the directory of the executable file, then in a subdirectory of that
21021 directory named @file{.debug}, and finally under each one of the
21022 global debug directories, in a subdirectory whose name is identical to
21023 the leading directories of the executable's absolute file name. (On
21024 MS-Windows/MS-DOS, the drive letter of the executable's leading
21025 directories is converted to a one-letter subdirectory, i.e.@:
21026 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21027 filesystems disallow colons in file names.)
21030 For the ``build ID'' method, @value{GDBN} looks in the
21031 @file{.build-id} subdirectory of each one of the global debug directories for
21032 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21033 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21034 are the rest of the bit string. (Real build ID strings are 32 or more
21035 hex characters, not 10.)
21038 So, for example, suppose you ask @value{GDBN} to debug
21039 @file{/usr/bin/ls}, which has a debug link that specifies the
21040 file @file{ls.debug}, and a build ID whose value in hex is
21041 @code{abcdef1234}. If the list of the global debug directories includes
21042 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21043 debug information files, in the indicated order:
21047 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21049 @file{/usr/bin/ls.debug}
21051 @file{/usr/bin/.debug/ls.debug}
21053 @file{/usr/lib/debug/usr/bin/ls.debug}.
21056 @anchor{debug-file-directory}
21057 Global debugging info directories default to what is set by @value{GDBN}
21058 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21059 you can also set the global debugging info directories, and view the list
21060 @value{GDBN} is currently using.
21064 @kindex set debug-file-directory
21065 @item set debug-file-directory @var{directories}
21066 Set the directories which @value{GDBN} searches for separate debugging
21067 information files to @var{directory}. Multiple path components can be set
21068 concatenating them by a path separator.
21070 @kindex show debug-file-directory
21071 @item show debug-file-directory
21072 Show the directories @value{GDBN} searches for separate debugging
21077 @cindex @code{.gnu_debuglink} sections
21078 @cindex debug link sections
21079 A debug link is a special section of the executable file named
21080 @code{.gnu_debuglink}. The section must contain:
21084 A filename, with any leading directory components removed, followed by
21087 zero to three bytes of padding, as needed to reach the next four-byte
21088 boundary within the section, and
21090 a four-byte CRC checksum, stored in the same endianness used for the
21091 executable file itself. The checksum is computed on the debugging
21092 information file's full contents by the function given below, passing
21093 zero as the @var{crc} argument.
21096 Any executable file format can carry a debug link, as long as it can
21097 contain a section named @code{.gnu_debuglink} with the contents
21100 @cindex @code{.note.gnu.build-id} sections
21101 @cindex build ID sections
21102 The build ID is a special section in the executable file (and in other
21103 ELF binary files that @value{GDBN} may consider). This section is
21104 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21105 It contains unique identification for the built files---the ID remains
21106 the same across multiple builds of the same build tree. The default
21107 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21108 content for the build ID string. The same section with an identical
21109 value is present in the original built binary with symbols, in its
21110 stripped variant, and in the separate debugging information file.
21112 The debugging information file itself should be an ordinary
21113 executable, containing a full set of linker symbols, sections, and
21114 debugging information. The sections of the debugging information file
21115 should have the same names, addresses, and sizes as the original file,
21116 but they need not contain any data---much like a @code{.bss} section
21117 in an ordinary executable.
21119 The @sc{gnu} binary utilities (Binutils) package includes the
21120 @samp{objcopy} utility that can produce
21121 the separated executable / debugging information file pairs using the
21122 following commands:
21125 @kbd{objcopy --only-keep-debug foo foo.debug}
21130 These commands remove the debugging
21131 information from the executable file @file{foo} and place it in the file
21132 @file{foo.debug}. You can use the first, second or both methods to link the
21137 The debug link method needs the following additional command to also leave
21138 behind a debug link in @file{foo}:
21141 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21144 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21145 a version of the @code{strip} command such that the command @kbd{strip foo -f
21146 foo.debug} has the same functionality as the two @code{objcopy} commands and
21147 the @code{ln -s} command above, together.
21150 Build ID gets embedded into the main executable using @code{ld --build-id} or
21151 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21152 compatibility fixes for debug files separation are present in @sc{gnu} binary
21153 utilities (Binutils) package since version 2.18.
21158 @cindex CRC algorithm definition
21159 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21160 IEEE 802.3 using the polynomial:
21162 @c TexInfo requires naked braces for multi-digit exponents for Tex
21163 @c output, but this causes HTML output to barf. HTML has to be set using
21164 @c raw commands. So we end up having to specify this equation in 2
21169 <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>
21170 + <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
21176 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21177 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
21181 The function is computed byte at a time, taking the least
21182 significant bit of each byte first. The initial pattern
21183 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
21184 the final result is inverted to ensure trailing zeros also affect the
21187 @emph{Note:} This is the same CRC polynomial as used in handling the
21188 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
21189 However in the case of the Remote Serial Protocol, the CRC is computed
21190 @emph{most} significant bit first, and the result is not inverted, so
21191 trailing zeros have no effect on the CRC value.
21193 To complete the description, we show below the code of the function
21194 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
21195 initially supplied @code{crc} argument means that an initial call to
21196 this function passing in zero will start computing the CRC using
21199 @kindex gnu_debuglink_crc32
21202 gnu_debuglink_crc32 (unsigned long crc,
21203 unsigned char *buf, size_t len)
21205 static const unsigned long crc32_table[256] =
21207 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
21208 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
21209 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
21210 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
21211 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
21212 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
21213 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
21214 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
21215 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
21216 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
21217 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
21218 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
21219 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
21220 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
21221 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
21222 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
21223 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
21224 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
21225 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
21226 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
21227 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
21228 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
21229 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
21230 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
21231 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
21232 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
21233 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
21234 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
21235 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
21236 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
21237 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
21238 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
21239 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
21240 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
21241 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
21242 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
21243 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
21244 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
21245 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
21246 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
21247 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
21248 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
21249 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
21250 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
21251 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
21252 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
21253 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
21254 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
21255 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
21256 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
21257 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
21260 unsigned char *end;
21262 crc = ~crc & 0xffffffff;
21263 for (end = buf + len; buf < end; ++buf)
21264 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
21265 return ~crc & 0xffffffff;
21270 This computation does not apply to the ``build ID'' method.
21272 @node MiniDebugInfo
21273 @section Debugging information in a special section
21274 @cindex separate debug sections
21275 @cindex @samp{.gnu_debugdata} section
21277 Some systems ship pre-built executables and libraries that have a
21278 special @samp{.gnu_debugdata} section. This feature is called
21279 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
21280 is used to supply extra symbols for backtraces.
21282 The intent of this section is to provide extra minimal debugging
21283 information for use in simple backtraces. It is not intended to be a
21284 replacement for full separate debugging information (@pxref{Separate
21285 Debug Files}). The example below shows the intended use; however,
21286 @value{GDBN} does not currently put restrictions on what sort of
21287 debugging information might be included in the section.
21289 @value{GDBN} has support for this extension. If the section exists,
21290 then it is used provided that no other source of debugging information
21291 can be found, and that @value{GDBN} was configured with LZMA support.
21293 This section can be easily created using @command{objcopy} and other
21294 standard utilities:
21297 # Extract the dynamic symbols from the main binary, there is no need
21298 # to also have these in the normal symbol table.
21299 nm -D @var{binary} --format=posix --defined-only \
21300 | awk '@{ print $1 @}' | sort > dynsyms
21302 # Extract all the text (i.e. function) symbols from the debuginfo.
21303 # (Note that we actually also accept "D" symbols, for the benefit
21304 # of platforms like PowerPC64 that use function descriptors.)
21305 nm @var{binary} --format=posix --defined-only \
21306 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
21309 # Keep all the function symbols not already in the dynamic symbol
21311 comm -13 dynsyms funcsyms > keep_symbols
21313 # Separate full debug info into debug binary.
21314 objcopy --only-keep-debug @var{binary} debug
21316 # Copy the full debuginfo, keeping only a minimal set of symbols and
21317 # removing some unnecessary sections.
21318 objcopy -S --remove-section .gdb_index --remove-section .comment \
21319 --keep-symbols=keep_symbols debug mini_debuginfo
21321 # Drop the full debug info from the original binary.
21322 strip --strip-all -R .comment @var{binary}
21324 # Inject the compressed data into the .gnu_debugdata section of the
21327 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
21331 @section Index Files Speed Up @value{GDBN}
21332 @cindex index files
21333 @cindex @samp{.gdb_index} section
21335 When @value{GDBN} finds a symbol file, it scans the symbols in the
21336 file in order to construct an internal symbol table. This lets most
21337 @value{GDBN} operations work quickly---at the cost of a delay early
21338 on. For large programs, this delay can be quite lengthy, so
21339 @value{GDBN} provides a way to build an index, which speeds up
21342 For convenience, @value{GDBN} comes with a program,
21343 @command{gdb-add-index}, which can be used to add the index to a
21344 symbol file. It takes the symbol file as its only argument:
21347 $ gdb-add-index symfile
21350 @xref{gdb-add-index}.
21352 It is also possible to do the work manually. Here is what
21353 @command{gdb-add-index} does behind the curtains.
21355 The index is stored as a section in the symbol file. @value{GDBN} can
21356 write the index to a file, then you can put it into the symbol file
21357 using @command{objcopy}.
21359 To create an index file, use the @code{save gdb-index} command:
21362 @item save gdb-index [-dwarf-5] @var{directory}
21363 @kindex save gdb-index
21364 Create index files for all symbol files currently known by
21365 @value{GDBN}. For each known @var{symbol-file}, this command by
21366 default creates it produces a single file
21367 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
21368 the @option{-dwarf-5} option, it produces 2 files:
21369 @file{@var{symbol-file}.debug_names} and
21370 @file{@var{symbol-file}.debug_str}. The files are created in the
21371 given @var{directory}.
21374 Once you have created an index file you can merge it into your symbol
21375 file, here named @file{symfile}, using @command{objcopy}:
21378 $ objcopy --add-section .gdb_index=symfile.gdb-index \
21379 --set-section-flags .gdb_index=readonly symfile symfile
21382 Or for @code{-dwarf-5}:
21385 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
21386 $ cat symfile.debug_str >>symfile.debug_str.new
21387 $ objcopy --add-section .debug_names=symfile.gdb-index \
21388 --set-section-flags .debug_names=readonly \
21389 --update-section .debug_str=symfile.debug_str.new symfile symfile
21392 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
21393 sections that have been deprecated. Usually they are deprecated because
21394 they are missing a new feature or have performance issues.
21395 To tell @value{GDBN} to use a deprecated index section anyway
21396 specify @code{set use-deprecated-index-sections on}.
21397 The default is @code{off}.
21398 This can speed up startup, but may result in some functionality being lost.
21399 @xref{Index Section Format}.
21401 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
21402 must be done before gdb reads the file. The following will not work:
21405 $ gdb -ex "set use-deprecated-index-sections on" <program>
21408 Instead you must do, for example,
21411 $ gdb -iex "set use-deprecated-index-sections on" <program>
21414 Indices only work when using DWARF debugging information, not stabs.
21416 @subsection Automatic symbol index cache
21418 @cindex automatic symbol index cache
21419 It is possible for @value{GDBN} to automatically save a copy of this index in a
21420 cache on disk and retrieve it from there when loading the same binary in the
21421 future. This feature can be turned on with @kbd{set index-cache on}. The
21422 following commands can be used to tweak the behavior of the index cache.
21426 @kindex set index-cache
21427 @item set index-cache on
21428 @itemx set index-cache off
21429 Enable or disable the use of the symbol index cache.
21431 @item set index-cache directory @var{directory}
21432 @kindex show index-cache
21433 @itemx show index-cache directory
21434 Set/show the directory where index files will be saved.
21436 The default value for this directory depends on the host platform. On
21437 most systems, the index is cached in the @file{gdb} subdirectory of
21438 the directory pointed to by the @env{XDG_CACHE_HOME} environment
21439 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
21440 of your home directory. However, on some systems, the default may
21441 differ according to local convention.
21443 There is no limit on the disk space used by index cache. It is perfectly safe
21444 to delete the content of that directory to free up disk space.
21446 @item show index-cache stats
21447 Print the number of cache hits and misses since the launch of @value{GDBN}.
21451 @node Symbol Errors
21452 @section Errors Reading Symbol Files
21454 While reading a symbol file, @value{GDBN} occasionally encounters problems,
21455 such as symbol types it does not recognize, or known bugs in compiler
21456 output. By default, @value{GDBN} does not notify you of such problems, since
21457 they are relatively common and primarily of interest to people
21458 debugging compilers. If you are interested in seeing information
21459 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
21460 only one message about each such type of problem, no matter how many
21461 times the problem occurs; or you can ask @value{GDBN} to print more messages,
21462 to see how many times the problems occur, with the @code{set
21463 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
21466 The messages currently printed, and their meanings, include:
21469 @item inner block not inside outer block in @var{symbol}
21471 The symbol information shows where symbol scopes begin and end
21472 (such as at the start of a function or a block of statements). This
21473 error indicates that an inner scope block is not fully contained
21474 in its outer scope blocks.
21476 @value{GDBN} circumvents the problem by treating the inner block as if it had
21477 the same scope as the outer block. In the error message, @var{symbol}
21478 may be shown as ``@code{(don't know)}'' if the outer block is not a
21481 @item block at @var{address} out of order
21483 The symbol information for symbol scope blocks should occur in
21484 order of increasing addresses. This error indicates that it does not
21487 @value{GDBN} does not circumvent this problem, and has trouble
21488 locating symbols in the source file whose symbols it is reading. (You
21489 can often determine what source file is affected by specifying
21490 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
21493 @item bad block start address patched
21495 The symbol information for a symbol scope block has a start address
21496 smaller than the address of the preceding source line. This is known
21497 to occur in the SunOS 4.1.1 (and earlier) C compiler.
21499 @value{GDBN} circumvents the problem by treating the symbol scope block as
21500 starting on the previous source line.
21502 @item bad string table offset in symbol @var{n}
21505 Symbol number @var{n} contains a pointer into the string table which is
21506 larger than the size of the string table.
21508 @value{GDBN} circumvents the problem by considering the symbol to have the
21509 name @code{foo}, which may cause other problems if many symbols end up
21512 @item unknown symbol type @code{0x@var{nn}}
21514 The symbol information contains new data types that @value{GDBN} does
21515 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
21516 uncomprehended information, in hexadecimal.
21518 @value{GDBN} circumvents the error by ignoring this symbol information.
21519 This usually allows you to debug your program, though certain symbols
21520 are not accessible. If you encounter such a problem and feel like
21521 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
21522 on @code{complain}, then go up to the function @code{read_dbx_symtab}
21523 and examine @code{*bufp} to see the symbol.
21525 @item stub type has NULL name
21527 @value{GDBN} could not find the full definition for a struct or class.
21529 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
21530 The symbol information for a C@t{++} member function is missing some
21531 information that recent versions of the compiler should have output for
21534 @item info mismatch between compiler and debugger
21536 @value{GDBN} could not parse a type specification output by the compiler.
21541 @section GDB Data Files
21543 @cindex prefix for data files
21544 @value{GDBN} will sometimes read an auxiliary data file. These files
21545 are kept in a directory known as the @dfn{data directory}.
21547 You can set the data directory's name, and view the name @value{GDBN}
21548 is currently using.
21551 @kindex set data-directory
21552 @item set data-directory @var{directory}
21553 Set the directory which @value{GDBN} searches for auxiliary data files
21554 to @var{directory}.
21556 @kindex show data-directory
21557 @item show data-directory
21558 Show the directory @value{GDBN} searches for auxiliary data files.
21561 @cindex default data directory
21562 @cindex @samp{--with-gdb-datadir}
21563 You can set the default data directory by using the configure-time
21564 @samp{--with-gdb-datadir} option. If the data directory is inside
21565 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21566 @samp{--exec-prefix}), then the default data directory will be updated
21567 automatically if the installed @value{GDBN} is moved to a new
21570 The data directory may also be specified with the
21571 @code{--data-directory} command line option.
21572 @xref{Mode Options}.
21575 @chapter Specifying a Debugging Target
21577 @cindex debugging target
21578 A @dfn{target} is the execution environment occupied by your program.
21580 Often, @value{GDBN} runs in the same host environment as your program;
21581 in that case, the debugging target is specified as a side effect when
21582 you use the @code{file} or @code{core} commands. When you need more
21583 flexibility---for example, running @value{GDBN} on a physically separate
21584 host, or controlling a standalone system over a serial port or a
21585 realtime system over a TCP/IP connection---you can use the @code{target}
21586 command to specify one of the target types configured for @value{GDBN}
21587 (@pxref{Target Commands, ,Commands for Managing Targets}).
21589 @cindex target architecture
21590 It is possible to build @value{GDBN} for several different @dfn{target
21591 architectures}. When @value{GDBN} is built like that, you can choose
21592 one of the available architectures with the @kbd{set architecture}
21596 @kindex set architecture
21597 @kindex show architecture
21598 @item set architecture @var{arch}
21599 This command sets the current target architecture to @var{arch}. The
21600 value of @var{arch} can be @code{"auto"}, in addition to one of the
21601 supported architectures.
21603 @item show architecture
21604 Show the current target architecture.
21606 @item set processor
21608 @kindex set processor
21609 @kindex show processor
21610 These are alias commands for, respectively, @code{set architecture}
21611 and @code{show architecture}.
21615 * Active Targets:: Active targets
21616 * Target Commands:: Commands for managing targets
21617 * Byte Order:: Choosing target byte order
21620 @node Active Targets
21621 @section Active Targets
21623 @cindex stacking targets
21624 @cindex active targets
21625 @cindex multiple targets
21627 There are multiple classes of targets such as: processes, executable files or
21628 recording sessions. Core files belong to the process class, making core file
21629 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
21630 on multiple active targets, one in each class. This allows you to (for
21631 example) start a process and inspect its activity, while still having access to
21632 the executable file after the process finishes. Or if you start process
21633 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
21634 presented a virtual layer of the recording target, while the process target
21635 remains stopped at the chronologically last point of the process execution.
21637 Use the @code{core-file} and @code{exec-file} commands to select a new core
21638 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
21639 specify as a target a process that is already running, use the @code{attach}
21640 command (@pxref{Attach, ,Debugging an Already-running Process}).
21642 @node Target Commands
21643 @section Commands for Managing Targets
21646 @item target @var{type} @var{parameters}
21647 Connects the @value{GDBN} host environment to a target machine or
21648 process. A target is typically a protocol for talking to debugging
21649 facilities. You use the argument @var{type} to specify the type or
21650 protocol of the target machine.
21652 Further @var{parameters} are interpreted by the target protocol, but
21653 typically include things like device names or host names to connect
21654 with, process numbers, and baud rates.
21656 The @code{target} command does not repeat if you press @key{RET} again
21657 after executing the command.
21659 @kindex help target
21661 Displays the names of all targets available. To display targets
21662 currently selected, use either @code{info target} or @code{info files}
21663 (@pxref{Files, ,Commands to Specify Files}).
21665 @item help target @var{name}
21666 Describe a particular target, including any parameters necessary to
21669 @kindex set gnutarget
21670 @item set gnutarget @var{args}
21671 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
21672 knows whether it is reading an @dfn{executable},
21673 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
21674 with the @code{set gnutarget} command. Unlike most @code{target} commands,
21675 with @code{gnutarget} the @code{target} refers to a program, not a machine.
21678 @emph{Warning:} To specify a file format with @code{set gnutarget},
21679 you must know the actual BFD name.
21683 @xref{Files, , Commands to Specify Files}.
21685 @kindex show gnutarget
21686 @item show gnutarget
21687 Use the @code{show gnutarget} command to display what file format
21688 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
21689 @value{GDBN} will determine the file format for each file automatically,
21690 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
21693 @cindex common targets
21694 Here are some common targets (available, or not, depending on the GDB
21699 @item target exec @var{program}
21700 @cindex executable file target
21701 An executable file. @samp{target exec @var{program}} is the same as
21702 @samp{exec-file @var{program}}.
21704 @item target core @var{filename}
21705 @cindex core dump file target
21706 A core dump file. @samp{target core @var{filename}} is the same as
21707 @samp{core-file @var{filename}}.
21709 @item target remote @var{medium}
21710 @cindex remote target
21711 A remote system connected to @value{GDBN} via a serial line or network
21712 connection. This command tells @value{GDBN} to use its own remote
21713 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
21715 For example, if you have a board connected to @file{/dev/ttya} on the
21716 machine running @value{GDBN}, you could say:
21719 target remote /dev/ttya
21722 @code{target remote} supports the @code{load} command. This is only
21723 useful if you have some other way of getting the stub to the target
21724 system, and you can put it somewhere in memory where it won't get
21725 clobbered by the download.
21727 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21728 @cindex built-in simulator target
21729 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
21737 works; however, you cannot assume that a specific memory map, device
21738 drivers, or even basic I/O is available, although some simulators do
21739 provide these. For info about any processor-specific simulator details,
21740 see the appropriate section in @ref{Embedded Processors, ,Embedded
21743 @item target native
21744 @cindex native target
21745 Setup for local/native process debugging. Useful to make the
21746 @code{run} command spawn native processes (likewise @code{attach},
21747 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
21748 (@pxref{set auto-connect-native-target}).
21752 Different targets are available on different configurations of @value{GDBN};
21753 your configuration may have more or fewer targets.
21755 Many remote targets require you to download the executable's code once
21756 you've successfully established a connection. You may wish to control
21757 various aspects of this process.
21762 @kindex set hash@r{, for remote monitors}
21763 @cindex hash mark while downloading
21764 This command controls whether a hash mark @samp{#} is displayed while
21765 downloading a file to the remote monitor. If on, a hash mark is
21766 displayed after each S-record is successfully downloaded to the
21770 @kindex show hash@r{, for remote monitors}
21771 Show the current status of displaying the hash mark.
21773 @item set debug monitor
21774 @kindex set debug monitor
21775 @cindex display remote monitor communications
21776 Enable or disable display of communications messages between
21777 @value{GDBN} and the remote monitor.
21779 @item show debug monitor
21780 @kindex show debug monitor
21781 Show the current status of displaying communications between
21782 @value{GDBN} and the remote monitor.
21787 @kindex load @var{filename} @var{offset}
21788 @item load @var{filename} @var{offset}
21790 Depending on what remote debugging facilities are configured into
21791 @value{GDBN}, the @code{load} command may be available. Where it exists, it
21792 is meant to make @var{filename} (an executable) available for debugging
21793 on the remote system---by downloading, or dynamic linking, for example.
21794 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
21795 the @code{add-symbol-file} command.
21797 If your @value{GDBN} does not have a @code{load} command, attempting to
21798 execute it gets the error message ``@code{You can't do that when your
21799 target is @dots{}}''
21801 The file is loaded at whatever address is specified in the executable.
21802 For some object file formats, you can specify the load address when you
21803 link the program; for other formats, like a.out, the object file format
21804 specifies a fixed address.
21805 @c FIXME! This would be a good place for an xref to the GNU linker doc.
21807 It is also possible to tell @value{GDBN} to load the executable file at a
21808 specific offset described by the optional argument @var{offset}. When
21809 @var{offset} is provided, @var{filename} must also be provided.
21811 Depending on the remote side capabilities, @value{GDBN} may be able to
21812 load programs into flash memory.
21814 @code{load} does not repeat if you press @key{RET} again after using it.
21819 @kindex flash-erase
21821 @anchor{flash-erase}
21823 Erases all known flash memory regions on the target.
21828 @section Choosing Target Byte Order
21830 @cindex choosing target byte order
21831 @cindex target byte order
21833 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
21834 offer the ability to run either big-endian or little-endian byte
21835 orders. Usually the executable or symbol will include a bit to
21836 designate the endian-ness, and you will not need to worry about
21837 which to use. However, you may still find it useful to adjust
21838 @value{GDBN}'s idea of processor endian-ness manually.
21842 @item set endian big
21843 Instruct @value{GDBN} to assume the target is big-endian.
21845 @item set endian little
21846 Instruct @value{GDBN} to assume the target is little-endian.
21848 @item set endian auto
21849 Instruct @value{GDBN} to use the byte order associated with the
21853 Display @value{GDBN}'s current idea of the target byte order.
21857 If the @code{set endian auto} mode is in effect and no executable has
21858 been selected, then the endianness used is the last one chosen either
21859 by one of the @code{set endian big} and @code{set endian little}
21860 commands or by inferring from the last executable used. If no
21861 endianness has been previously chosen, then the default for this mode
21862 is inferred from the target @value{GDBN} has been built for, and is
21863 @code{little} if the name of the target CPU has an @code{el} suffix
21864 and @code{big} otherwise.
21866 Note that these commands merely adjust interpretation of symbolic
21867 data on the host, and that they have absolutely no effect on the
21871 @node Remote Debugging
21872 @chapter Debugging Remote Programs
21873 @cindex remote debugging
21875 If you are trying to debug a program running on a machine that cannot run
21876 @value{GDBN} in the usual way, it is often useful to use remote debugging.
21877 For example, you might use remote debugging on an operating system kernel,
21878 or on a small system which does not have a general purpose operating system
21879 powerful enough to run a full-featured debugger.
21881 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
21882 to make this work with particular debugging targets. In addition,
21883 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
21884 but not specific to any particular target system) which you can use if you
21885 write the remote stubs---the code that runs on the remote system to
21886 communicate with @value{GDBN}.
21888 Other remote targets may be available in your
21889 configuration of @value{GDBN}; use @code{help target} to list them.
21892 * Connecting:: Connecting to a remote target
21893 * File Transfer:: Sending files to a remote system
21894 * Server:: Using the gdbserver program
21895 * Remote Configuration:: Remote configuration
21896 * Remote Stub:: Implementing a remote stub
21900 @section Connecting to a Remote Target
21901 @cindex remote debugging, connecting
21902 @cindex @code{gdbserver}, connecting
21903 @cindex remote debugging, types of connections
21904 @cindex @code{gdbserver}, types of connections
21905 @cindex @code{gdbserver}, @code{target remote} mode
21906 @cindex @code{gdbserver}, @code{target extended-remote} mode
21908 This section describes how to connect to a remote target, including the
21909 types of connections and their differences, how to set up executable and
21910 symbol files on the host and target, and the commands used for
21911 connecting to and disconnecting from the remote target.
21913 @subsection Types of Remote Connections
21915 @value{GDBN} supports two types of remote connections, @code{target remote}
21916 mode and @code{target extended-remote} mode. Note that many remote targets
21917 support only @code{target remote} mode. There are several major
21918 differences between the two types of connections, enumerated here:
21922 @cindex remote debugging, detach and program exit
21923 @item Result of detach or program exit
21924 @strong{With target remote mode:} When the debugged program exits or you
21925 detach from it, @value{GDBN} disconnects from the target. When using
21926 @code{gdbserver}, @code{gdbserver} will exit.
21928 @strong{With target extended-remote mode:} When the debugged program exits or
21929 you detach from it, @value{GDBN} remains connected to the target, even
21930 though no program is running. You can rerun the program, attach to a
21931 running program, or use @code{monitor} commands specific to the target.
21933 When using @code{gdbserver} in this case, it does not exit unless it was
21934 invoked using the @option{--once} option. If the @option{--once} option
21935 was not used, you can ask @code{gdbserver} to exit using the
21936 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
21938 @item Specifying the program to debug
21939 For both connection types you use the @code{file} command to specify the
21940 program on the host system. If you are using @code{gdbserver} there are
21941 some differences in how to specify the location of the program on the
21944 @strong{With target remote mode:} You must either specify the program to debug
21945 on the @code{gdbserver} command line or use the @option{--attach} option
21946 (@pxref{Attaching to a program,,Attaching to a Running Program}).
21948 @cindex @option{--multi}, @code{gdbserver} option
21949 @strong{With target extended-remote mode:} You may specify the program to debug
21950 on the @code{gdbserver} command line, or you can load the program or attach
21951 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
21953 @anchor{--multi Option in Types of Remote Connnections}
21954 You can start @code{gdbserver} without supplying an initial command to run
21955 or process ID to attach. To do this, use the @option{--multi} command line
21956 option. Then you can connect using @code{target extended-remote} and start
21957 the program you want to debug (see below for details on using the
21958 @code{run} command in this scenario). Note that the conditions under which
21959 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
21960 (@code{target remote} or @code{target extended-remote}). The
21961 @option{--multi} option to @code{gdbserver} has no influence on that.
21963 @item The @code{run} command
21964 @strong{With target remote mode:} The @code{run} command is not
21965 supported. Once a connection has been established, you can use all
21966 the usual @value{GDBN} commands to examine and change data. The
21967 remote program is already running, so you can use commands like
21968 @kbd{step} and @kbd{continue}.
21970 @strong{With target extended-remote mode:} The @code{run} command is
21971 supported. The @code{run} command uses the value set by
21972 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
21973 the program to run. Command line arguments are supported, except for
21974 wildcard expansion and I/O redirection (@pxref{Arguments}).
21976 If you specify the program to debug on the command line, then the
21977 @code{run} command is not required to start execution, and you can
21978 resume using commands like @kbd{step} and @kbd{continue} as with
21979 @code{target remote} mode.
21981 @anchor{Attaching in Types of Remote Connections}
21983 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
21984 not supported. To attach to a running program using @code{gdbserver}, you
21985 must use the @option{--attach} option (@pxref{Running gdbserver}).
21987 @strong{With target extended-remote mode:} To attach to a running program,
21988 you may use the @code{attach} command after the connection has been
21989 established. If you are using @code{gdbserver}, you may also invoke
21990 @code{gdbserver} using the @option{--attach} option
21991 (@pxref{Running gdbserver}).
21993 Some remote targets allow @value{GDBN} to determine the executable file running
21994 in the process the debugger is attaching to. In such a case, @value{GDBN}
21995 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
21996 between the executable file name running in the process and the name of the
21997 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22001 @anchor{Host and target files}
22002 @subsection Host and Target Files
22003 @cindex remote debugging, symbol files
22004 @cindex symbol files, remote debugging
22006 @value{GDBN}, running on the host, needs access to symbol and debugging
22007 information for your program running on the target. This requires
22008 access to an unstripped copy of your program, and possibly any associated
22009 symbol files. Note that this section applies equally to both @code{target
22010 remote} mode and @code{target extended-remote} mode.
22012 Some remote targets (@pxref{qXfer executable filename read}, and
22013 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22014 the same connection used to communicate with @value{GDBN}. With such a
22015 target, if the remote program is unstripped, the only command you need is
22016 @code{target remote} (or @code{target extended-remote}).
22018 If the remote program is stripped, or the target does not support remote
22019 program file access, start up @value{GDBN} using the name of the local
22020 unstripped copy of your program as the first argument, or use the
22021 @code{file} command. Use @code{set sysroot} to specify the location (on
22022 the host) of target libraries (unless your @value{GDBN} was compiled with
22023 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22024 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22027 The symbol file and target libraries must exactly match the executable
22028 and libraries on the target, with one exception: the files on the host
22029 system should not be stripped, even if the files on the target system
22030 are. Mismatched or missing files will lead to confusing results
22031 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22032 files may also prevent @code{gdbserver} from debugging multi-threaded
22035 @subsection Remote Connection Commands
22036 @cindex remote connection commands
22037 @value{GDBN} can communicate with the target over a serial line, a
22038 local Unix domain socket, or
22039 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22040 each case, @value{GDBN} uses the same protocol for debugging your
22041 program; only the medium carrying the debugging packets varies. The
22042 @code{target remote} and @code{target extended-remote} commands
22043 establish a connection to the target. Both commands accept the same
22044 arguments, which indicate the medium to use:
22048 @item target remote @var{serial-device}
22049 @itemx target extended-remote @var{serial-device}
22050 @cindex serial line, @code{target remote}
22051 Use @var{serial-device} to communicate with the target. For example,
22052 to use a serial line connected to the device named @file{/dev/ttyb}:
22055 target remote /dev/ttyb
22058 If you're using a serial line, you may want to give @value{GDBN} the
22059 @samp{--baud} option, or use the @code{set serial baud} command
22060 (@pxref{Remote Configuration, set serial baud}) before the
22061 @code{target} command.
22063 @item target remote @var{local-socket}
22064 @itemx target extended-remote @var{local-socket}
22065 @cindex local socket, @code{target remote}
22066 @cindex Unix domain socket
22067 Use @var{local-socket} to communicate with the target. For example,
22068 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22071 target remote /tmp/gdb-socket0
22074 Note that this command has the same form as the command to connect
22075 to a serial line. @value{GDBN} will automatically determine which
22076 kind of file you have specified and will make the appropriate kind
22078 This feature is not available if the host system does not support
22079 Unix domain sockets.
22081 @item target remote @code{@var{host}:@var{port}}
22082 @itemx target remote @code{[@var{host}]:@var{port}}
22083 @itemx target remote @code{tcp:@var{host}:@var{port}}
22084 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22085 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22086 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22087 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22088 @itemx target extended-remote @code{@var{host}:@var{port}}
22089 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22090 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22091 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22092 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22093 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22094 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22095 @cindex @acronym{TCP} port, @code{target remote}
22096 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22097 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22098 address, or a numeric @acronym{IPv6} address (with or without the
22099 square brackets to separate the address from the port); @var{port}
22100 must be a decimal number. The @var{host} could be the target machine
22101 itself, if it is directly connected to the net, or it might be a
22102 terminal server which in turn has a serial line to the target.
22104 For example, to connect to port 2828 on a terminal server named
22108 target remote manyfarms:2828
22111 To connect to port 2828 on a terminal server whose address is
22112 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22113 square bracket syntax:
22116 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22120 or explicitly specify the @acronym{IPv6} protocol:
22123 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22126 This last example may be confusing to the reader, because there is no
22127 visible separation between the hostname and the port number.
22128 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22129 using square brackets for clarity. However, it is important to
22130 mention that for @value{GDBN} there is no ambiguity: the number after
22131 the last colon is considered to be the port number.
22133 If your remote target is actually running on the same machine as your
22134 debugger session (e.g.@: a simulator for your target running on the
22135 same host), you can omit the hostname. For example, to connect to
22136 port 1234 on your local machine:
22139 target remote :1234
22143 Note that the colon is still required here.
22145 @item target remote @code{udp:@var{host}:@var{port}}
22146 @itemx target remote @code{udp:[@var{host}]:@var{port}}
22147 @itemx target remote @code{udp4:@var{host}:@var{port}}
22148 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
22149 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22150 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22151 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
22152 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22153 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22154 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
22155 @cindex @acronym{UDP} port, @code{target remote}
22156 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22157 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22160 target remote udp:manyfarms:2828
22163 When using a @acronym{UDP} connection for remote debugging, you should
22164 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22165 can silently drop packets on busy or unreliable networks, which will
22166 cause havoc with your debugging session.
22168 @item target remote | @var{command}
22169 @itemx target extended-remote | @var{command}
22170 @cindex pipe, @code{target remote} to
22171 Run @var{command} in the background and communicate with it using a
22172 pipe. The @var{command} is a shell command, to be parsed and expanded
22173 by the system's command shell, @code{/bin/sh}; it should expect remote
22174 protocol packets on its standard input, and send replies on its
22175 standard output. You could use this to run a stand-alone simulator
22176 that speaks the remote debugging protocol, to make net connections
22177 using programs like @code{ssh}, or for other similar tricks.
22179 If @var{command} closes its standard output (perhaps by exiting),
22180 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
22181 program has already exited, this will have no effect.)
22185 @cindex interrupting remote programs
22186 @cindex remote programs, interrupting
22187 Whenever @value{GDBN} is waiting for the remote program, if you type the
22188 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
22189 program. This may or may not succeed, depending in part on the hardware
22190 and the serial drivers the remote system uses. If you type the
22191 interrupt character once again, @value{GDBN} displays this prompt:
22194 Interrupted while waiting for the program.
22195 Give up (and stop debugging it)? (y or n)
22198 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
22199 the remote debugging session. (If you decide you want to try again later,
22200 you can use @kbd{target remote} again to connect once more.) If you type
22201 @kbd{n}, @value{GDBN} goes back to waiting.
22203 In @code{target extended-remote} mode, typing @kbd{n} will leave
22204 @value{GDBN} connected to the target.
22207 @kindex detach (remote)
22209 When you have finished debugging the remote program, you can use the
22210 @code{detach} command to release it from @value{GDBN} control.
22211 Detaching from the target normally resumes its execution, but the results
22212 will depend on your particular remote stub. After the @code{detach}
22213 command in @code{target remote} mode, @value{GDBN} is free to connect to
22214 another target. In @code{target extended-remote} mode, @value{GDBN} is
22215 still connected to the target.
22219 The @code{disconnect} command closes the connection to the target, and
22220 the target is generally not resumed. It will wait for @value{GDBN}
22221 (this instance or another one) to connect and continue debugging. After
22222 the @code{disconnect} command, @value{GDBN} is again free to connect to
22225 @cindex send command to remote monitor
22226 @cindex extend @value{GDBN} for remote targets
22227 @cindex add new commands for external monitor
22229 @item monitor @var{cmd}
22230 This command allows you to send arbitrary commands directly to the
22231 remote monitor. Since @value{GDBN} doesn't care about the commands it
22232 sends like this, this command is the way to extend @value{GDBN}---you
22233 can add new commands that only the external monitor will understand
22237 @node File Transfer
22238 @section Sending files to a remote system
22239 @cindex remote target, file transfer
22240 @cindex file transfer
22241 @cindex sending files to remote systems
22243 Some remote targets offer the ability to transfer files over the same
22244 connection used to communicate with @value{GDBN}. This is convenient
22245 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
22246 running @code{gdbserver} over a network interface. For other targets,
22247 e.g.@: embedded devices with only a single serial port, this may be
22248 the only way to upload or download files.
22250 Not all remote targets support these commands.
22254 @item remote put @var{hostfile} @var{targetfile}
22255 Copy file @var{hostfile} from the host system (the machine running
22256 @value{GDBN}) to @var{targetfile} on the target system.
22259 @item remote get @var{targetfile} @var{hostfile}
22260 Copy file @var{targetfile} from the target system to @var{hostfile}
22261 on the host system.
22263 @kindex remote delete
22264 @item remote delete @var{targetfile}
22265 Delete @var{targetfile} from the target system.
22270 @section Using the @code{gdbserver} Program
22273 @cindex remote connection without stubs
22274 @code{gdbserver} is a control program for Unix-like systems, which
22275 allows you to connect your program with a remote @value{GDBN} via
22276 @code{target remote} or @code{target extended-remote}---but without
22277 linking in the usual debugging stub.
22279 @code{gdbserver} is not a complete replacement for the debugging stubs,
22280 because it requires essentially the same operating-system facilities
22281 that @value{GDBN} itself does. In fact, a system that can run
22282 @code{gdbserver} to connect to a remote @value{GDBN} could also run
22283 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
22284 because it is a much smaller program than @value{GDBN} itself. It is
22285 also easier to port than all of @value{GDBN}, so you may be able to get
22286 started more quickly on a new system by using @code{gdbserver}.
22287 Finally, if you develop code for real-time systems, you may find that
22288 the tradeoffs involved in real-time operation make it more convenient to
22289 do as much development work as possible on another system, for example
22290 by cross-compiling. You can use @code{gdbserver} to make a similar
22291 choice for debugging.
22293 @value{GDBN} and @code{gdbserver} communicate via either a serial line
22294 or a TCP connection, using the standard @value{GDBN} remote serial
22298 @emph{Warning:} @code{gdbserver} does not have any built-in security.
22299 Do not run @code{gdbserver} connected to any public network; a
22300 @value{GDBN} connection to @code{gdbserver} provides access to the
22301 target system with the same privileges as the user running
22305 @anchor{Running gdbserver}
22306 @subsection Running @code{gdbserver}
22307 @cindex arguments, to @code{gdbserver}
22308 @cindex @code{gdbserver}, command-line arguments
22310 Run @code{gdbserver} on the target system. You need a copy of the
22311 program you want to debug, including any libraries it requires.
22312 @code{gdbserver} does not need your program's symbol table, so you can
22313 strip the program if necessary to save space. @value{GDBN} on the host
22314 system does all the symbol handling.
22316 To use the server, you must tell it how to communicate with @value{GDBN};
22317 the name of your program; and the arguments for your program. The usual
22321 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
22324 @var{comm} is either a device name (to use a serial line), or a TCP
22325 hostname and portnumber, or @code{-} or @code{stdio} to use
22326 stdin/stdout of @code{gdbserver}.
22327 For example, to debug Emacs with the argument
22328 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
22332 target> gdbserver /dev/com1 emacs foo.txt
22335 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
22338 To use a TCP connection instead of a serial line:
22341 target> gdbserver host:2345 emacs foo.txt
22344 The only difference from the previous example is the first argument,
22345 specifying that you are communicating with the host @value{GDBN} via
22346 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
22347 expect a TCP connection from machine @samp{host} to local TCP port 2345.
22348 (Currently, the @samp{host} part is ignored.) You can choose any number
22349 you want for the port number as long as it does not conflict with any
22350 TCP ports already in use on the target system (for example, @code{23} is
22351 reserved for @code{telnet}).@footnote{If you choose a port number that
22352 conflicts with another service, @code{gdbserver} prints an error message
22353 and exits.} You must use the same port number with the host @value{GDBN}
22354 @code{target remote} command.
22356 The @code{stdio} connection is useful when starting @code{gdbserver}
22360 (gdb) target remote | ssh -T hostname gdbserver - hello
22363 The @samp{-T} option to ssh is provided because we don't need a remote pty,
22364 and we don't want escape-character handling. Ssh does this by default when
22365 a command is provided, the flag is provided to make it explicit.
22366 You could elide it if you want to.
22368 Programs started with stdio-connected gdbserver have @file{/dev/null} for
22369 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
22370 display through a pipe connected to gdbserver.
22371 Both @code{stdout} and @code{stderr} use the same pipe.
22373 @anchor{Attaching to a program}
22374 @subsubsection Attaching to a Running Program
22375 @cindex attach to a program, @code{gdbserver}
22376 @cindex @option{--attach}, @code{gdbserver} option
22378 On some targets, @code{gdbserver} can also attach to running programs.
22379 This is accomplished via the @code{--attach} argument. The syntax is:
22382 target> gdbserver --attach @var{comm} @var{pid}
22385 @var{pid} is the process ID of a currently running process. It isn't
22386 necessary to point @code{gdbserver} at a binary for the running process.
22388 In @code{target extended-remote} mode, you can also attach using the
22389 @value{GDBN} attach command
22390 (@pxref{Attaching in Types of Remote Connections}).
22393 You can debug processes by name instead of process ID if your target has the
22394 @code{pidof} utility:
22397 target> gdbserver --attach @var{comm} `pidof @var{program}`
22400 In case more than one copy of @var{program} is running, or @var{program}
22401 has multiple threads, most versions of @code{pidof} support the
22402 @code{-s} option to only return the first process ID.
22404 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
22406 This section applies only when @code{gdbserver} is run to listen on a TCP
22409 @code{gdbserver} normally terminates after all of its debugged processes have
22410 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
22411 extended-remote}, @code{gdbserver} stays running even with no processes left.
22412 @value{GDBN} normally terminates the spawned debugged process on its exit,
22413 which normally also terminates @code{gdbserver} in the @kbd{target remote}
22414 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
22415 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
22416 stays running even in the @kbd{target remote} mode.
22418 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
22419 Such reconnecting is useful for features like @ref{disconnected tracing}. For
22420 completeness, at most one @value{GDBN} can be connected at a time.
22422 @cindex @option{--once}, @code{gdbserver} option
22423 By default, @code{gdbserver} keeps the listening TCP port open, so that
22424 subsequent connections are possible. However, if you start @code{gdbserver}
22425 with the @option{--once} option, it will stop listening for any further
22426 connection attempts after connecting to the first @value{GDBN} session. This
22427 means no further connections to @code{gdbserver} will be possible after the
22428 first one. It also means @code{gdbserver} will terminate after the first
22429 connection with remote @value{GDBN} has closed, even for unexpectedly closed
22430 connections and even in the @kbd{target extended-remote} mode. The
22431 @option{--once} option allows reusing the same port number for connecting to
22432 multiple instances of @code{gdbserver} running on the same host, since each
22433 instance closes its port after the first connection.
22435 @anchor{Other Command-Line Arguments for gdbserver}
22436 @subsubsection Other Command-Line Arguments for @code{gdbserver}
22438 You can use the @option{--multi} option to start @code{gdbserver} without
22439 specifying a program to debug or a process to attach to. Then you can
22440 attach in @code{target extended-remote} mode and run or attach to a
22441 program. For more information,
22442 @pxref{--multi Option in Types of Remote Connnections}.
22444 @cindex @option{--debug}, @code{gdbserver} option
22445 The @option{--debug} option tells @code{gdbserver} to display extra
22446 status information about the debugging process.
22447 @cindex @option{--remote-debug}, @code{gdbserver} option
22448 The @option{--remote-debug} option tells @code{gdbserver} to display
22449 remote protocol debug output.
22450 @cindex @option{--debug-file}, @code{gdbserver} option
22451 @cindex @code{gdbserver}, send all debug output to a single file
22452 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
22453 write any debug output to the given @var{filename}. These options are intended
22454 for @code{gdbserver} development and for bug reports to the developers.
22456 @cindex @option{--debug-format}, @code{gdbserver} option
22457 The @option{--debug-format=option1[,option2,...]} option tells
22458 @code{gdbserver} to include additional information in each output.
22459 Possible options are:
22463 Turn off all extra information in debugging output.
22465 Turn on all extra information in debugging output.
22467 Include a timestamp in each line of debugging output.
22470 Options are processed in order. Thus, for example, if @option{none}
22471 appears last then no additional information is added to debugging output.
22473 @cindex @option{--wrapper}, @code{gdbserver} option
22474 The @option{--wrapper} option specifies a wrapper to launch programs
22475 for debugging. The option should be followed by the name of the
22476 wrapper, then any command-line arguments to pass to the wrapper, then
22477 @kbd{--} indicating the end of the wrapper arguments.
22479 @code{gdbserver} runs the specified wrapper program with a combined
22480 command line including the wrapper arguments, then the name of the
22481 program to debug, then any arguments to the program. The wrapper
22482 runs until it executes your program, and then @value{GDBN} gains control.
22484 You can use any program that eventually calls @code{execve} with
22485 its arguments as a wrapper. Several standard Unix utilities do
22486 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
22487 with @code{exec "$@@"} will also work.
22489 For example, you can use @code{env} to pass an environment variable to
22490 the debugged program, without setting the variable in @code{gdbserver}'s
22494 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
22497 @cindex @option{--selftest}
22498 The @option{--selftest} option runs the self tests in @code{gdbserver}:
22501 $ gdbserver --selftest
22502 Ran 2 unit tests, 0 failed
22505 These tests are disabled in release.
22506 @subsection Connecting to @code{gdbserver}
22508 The basic procedure for connecting to the remote target is:
22512 Run @value{GDBN} on the host system.
22515 Make sure you have the necessary symbol files
22516 (@pxref{Host and target files}).
22517 Load symbols for your application using the @code{file} command before you
22518 connect. Use @code{set sysroot} to locate target libraries (unless your
22519 @value{GDBN} was compiled with the correct sysroot using
22520 @code{--with-sysroot}).
22523 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
22524 For TCP connections, you must start up @code{gdbserver} prior to using
22525 the @code{target} command. Otherwise you may get an error whose
22526 text depends on the host system, but which usually looks something like
22527 @samp{Connection refused}. Don't use the @code{load}
22528 command in @value{GDBN} when using @code{target remote} mode, since the
22529 program is already on the target.
22533 @anchor{Monitor Commands for gdbserver}
22534 @subsection Monitor Commands for @code{gdbserver}
22535 @cindex monitor commands, for @code{gdbserver}
22537 During a @value{GDBN} session using @code{gdbserver}, you can use the
22538 @code{monitor} command to send special requests to @code{gdbserver}.
22539 Here are the available commands.
22543 List the available monitor commands.
22545 @item monitor set debug 0
22546 @itemx monitor set debug 1
22547 Disable or enable general debugging messages.
22549 @item monitor set remote-debug 0
22550 @itemx monitor set remote-debug 1
22551 Disable or enable specific debugging messages associated with the remote
22552 protocol (@pxref{Remote Protocol}).
22554 @item monitor set debug-file filename
22555 @itemx monitor set debug-file
22556 Send any debug output to the given file, or to stderr.
22558 @item monitor set debug-format option1@r{[},option2,...@r{]}
22559 Specify additional text to add to debugging messages.
22560 Possible options are:
22564 Turn off all extra information in debugging output.
22566 Turn on all extra information in debugging output.
22568 Include a timestamp in each line of debugging output.
22571 Options are processed in order. Thus, for example, if @option{none}
22572 appears last then no additional information is added to debugging output.
22574 @item monitor set libthread-db-search-path [PATH]
22575 @cindex gdbserver, search path for @code{libthread_db}
22576 When this command is issued, @var{path} is a colon-separated list of
22577 directories to search for @code{libthread_db} (@pxref{Threads,,set
22578 libthread-db-search-path}). If you omit @var{path},
22579 @samp{libthread-db-search-path} will be reset to its default value.
22581 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
22582 not supported in @code{gdbserver}.
22585 Tell gdbserver to exit immediately. This command should be followed by
22586 @code{disconnect} to close the debugging session. @code{gdbserver} will
22587 detach from any attached processes and kill any processes it created.
22588 Use @code{monitor exit} to terminate @code{gdbserver} at the end
22589 of a multi-process mode debug session.
22593 @subsection Tracepoints support in @code{gdbserver}
22594 @cindex tracepoints support in @code{gdbserver}
22596 On some targets, @code{gdbserver} supports tracepoints, fast
22597 tracepoints and static tracepoints.
22599 For fast or static tracepoints to work, a special library called the
22600 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
22601 This library is built and distributed as an integral part of
22602 @code{gdbserver}. In addition, support for static tracepoints
22603 requires building the in-process agent library with static tracepoints
22604 support. At present, the UST (LTTng Userspace Tracer,
22605 @url{http://lttng.org/ust}) tracing engine is supported. This support
22606 is automatically available if UST development headers are found in the
22607 standard include path when @code{gdbserver} is built, or if
22608 @code{gdbserver} was explicitly configured using @option{--with-ust}
22609 to point at such headers. You can explicitly disable the support
22610 using @option{--with-ust=no}.
22612 There are several ways to load the in-process agent in your program:
22615 @item Specifying it as dependency at link time
22617 You can link your program dynamically with the in-process agent
22618 library. On most systems, this is accomplished by adding
22619 @code{-linproctrace} to the link command.
22621 @item Using the system's preloading mechanisms
22623 You can force loading the in-process agent at startup time by using
22624 your system's support for preloading shared libraries. Many Unixes
22625 support the concept of preloading user defined libraries. In most
22626 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
22627 in the environment. See also the description of @code{gdbserver}'s
22628 @option{--wrapper} command line option.
22630 @item Using @value{GDBN} to force loading the agent at run time
22632 On some systems, you can force the inferior to load a shared library,
22633 by calling a dynamic loader function in the inferior that takes care
22634 of dynamically looking up and loading a shared library. On most Unix
22635 systems, the function is @code{dlopen}. You'll use the @code{call}
22636 command for that. For example:
22639 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
22642 Note that on most Unix systems, for the @code{dlopen} function to be
22643 available, the program needs to be linked with @code{-ldl}.
22646 On systems that have a userspace dynamic loader, like most Unix
22647 systems, when you connect to @code{gdbserver} using @code{target
22648 remote}, you'll find that the program is stopped at the dynamic
22649 loader's entry point, and no shared library has been loaded in the
22650 program's address space yet, including the in-process agent. In that
22651 case, before being able to use any of the fast or static tracepoints
22652 features, you need to let the loader run and load the shared
22653 libraries. The simplest way to do that is to run the program to the
22654 main procedure. E.g., if debugging a C or C@t{++} program, start
22655 @code{gdbserver} like so:
22658 $ gdbserver :9999 myprogram
22661 Start GDB and connect to @code{gdbserver} like so, and run to main:
22665 (@value{GDBP}) target remote myhost:9999
22666 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
22667 (@value{GDBP}) b main
22668 (@value{GDBP}) continue
22671 The in-process tracing agent library should now be loaded into the
22672 process; you can confirm it with the @code{info sharedlibrary}
22673 command, which will list @file{libinproctrace.so} as loaded in the
22674 process. You are now ready to install fast tracepoints, list static
22675 tracepoint markers, probe static tracepoints markers, and start
22678 @node Remote Configuration
22679 @section Remote Configuration
22682 @kindex show remote
22683 This section documents the configuration options available when
22684 debugging remote programs. For the options related to the File I/O
22685 extensions of the remote protocol, see @ref{system,
22686 system-call-allowed}.
22689 @item set remoteaddresssize @var{bits}
22690 @cindex address size for remote targets
22691 @cindex bits in remote address
22692 Set the maximum size of address in a memory packet to the specified
22693 number of bits. @value{GDBN} will mask off the address bits above
22694 that number, when it passes addresses to the remote target. The
22695 default value is the number of bits in the target's address.
22697 @item show remoteaddresssize
22698 Show the current value of remote address size in bits.
22700 @item set serial baud @var{n}
22701 @cindex baud rate for remote targets
22702 Set the baud rate for the remote serial I/O to @var{n} baud. The
22703 value is used to set the speed of the serial port used for debugging
22706 @item show serial baud
22707 Show the current speed of the remote connection.
22709 @item set serial parity @var{parity}
22710 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
22711 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
22713 @item show serial parity
22714 Show the current parity of the serial port.
22716 @item set remotebreak
22717 @cindex interrupt remote programs
22718 @cindex BREAK signal instead of Ctrl-C
22719 @anchor{set remotebreak}
22720 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
22721 when you type @kbd{Ctrl-c} to interrupt the program running
22722 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
22723 character instead. The default is off, since most remote systems
22724 expect to see @samp{Ctrl-C} as the interrupt signal.
22726 @item show remotebreak
22727 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
22728 interrupt the remote program.
22730 @item set remoteflow on
22731 @itemx set remoteflow off
22732 @kindex set remoteflow
22733 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
22734 on the serial port used to communicate to the remote target.
22736 @item show remoteflow
22737 @kindex show remoteflow
22738 Show the current setting of hardware flow control.
22740 @item set remotelogbase @var{base}
22741 Set the base (a.k.a.@: radix) of logging serial protocol
22742 communications to @var{base}. Supported values of @var{base} are:
22743 @code{ascii}, @code{octal}, and @code{hex}. The default is
22746 @item show remotelogbase
22747 Show the current setting of the radix for logging remote serial
22750 @item set remotelogfile @var{file}
22751 @cindex record serial communications on file
22752 Record remote serial communications on the named @var{file}. The
22753 default is not to record at all.
22755 @item show remotelogfile
22756 Show the current setting of the file name on which to record the
22757 serial communications.
22759 @item set remotetimeout @var{num}
22760 @cindex timeout for serial communications
22761 @cindex remote timeout
22762 Set the timeout limit to wait for the remote target to respond to
22763 @var{num} seconds. The default is 2 seconds.
22765 @item show remotetimeout
22766 Show the current number of seconds to wait for the remote target
22769 @cindex limit hardware breakpoints and watchpoints
22770 @cindex remote target, limit break- and watchpoints
22771 @anchor{set remote hardware-watchpoint-limit}
22772 @anchor{set remote hardware-breakpoint-limit}
22773 @item set remote hardware-watchpoint-limit @var{limit}
22774 @itemx set remote hardware-breakpoint-limit @var{limit}
22775 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
22776 or breakpoints. The @var{limit} can be set to 0 to disable hardware
22777 watchpoints or breakpoints, and @code{unlimited} for unlimited
22778 watchpoints or breakpoints.
22780 @item show remote hardware-watchpoint-limit
22781 @itemx show remote hardware-breakpoint-limit
22782 Show the current limit for the number of hardware watchpoints or
22783 breakpoints that @value{GDBN} can use.
22785 @cindex limit hardware watchpoints length
22786 @cindex remote target, limit watchpoints length
22787 @anchor{set remote hardware-watchpoint-length-limit}
22788 @item set remote hardware-watchpoint-length-limit @var{limit}
22789 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
22790 length of a remote hardware watchpoint. A @var{limit} of 0 disables
22791 hardware watchpoints and @code{unlimited} allows watchpoints of any
22794 @item show remote hardware-watchpoint-length-limit
22795 Show the current limit (in bytes) of the maximum length of
22796 a remote hardware watchpoint.
22798 @item set remote exec-file @var{filename}
22799 @itemx show remote exec-file
22800 @anchor{set remote exec-file}
22801 @cindex executable file, for remote target
22802 Select the file used for @code{run} with @code{target
22803 extended-remote}. This should be set to a filename valid on the
22804 target system. If it is not set, the target will use a default
22805 filename (e.g.@: the last program run).
22807 @item set remote interrupt-sequence
22808 @cindex interrupt remote programs
22809 @cindex select Ctrl-C, BREAK or BREAK-g
22810 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
22811 @samp{BREAK-g} as the
22812 sequence to the remote target in order to interrupt the execution.
22813 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
22814 is high level of serial line for some certain time.
22815 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
22816 It is @code{BREAK} signal followed by character @code{g}.
22818 @item show interrupt-sequence
22819 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
22820 is sent by @value{GDBN} to interrupt the remote program.
22821 @code{BREAK-g} is BREAK signal followed by @code{g} and
22822 also known as Magic SysRq g.
22824 @item set remote interrupt-on-connect
22825 @cindex send interrupt-sequence on start
22826 Specify whether interrupt-sequence is sent to remote target when
22827 @value{GDBN} connects to it. This is mostly needed when you debug
22828 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
22829 which is known as Magic SysRq g in order to connect @value{GDBN}.
22831 @item show interrupt-on-connect
22832 Show whether interrupt-sequence is sent
22833 to remote target when @value{GDBN} connects to it.
22837 @item set tcp auto-retry on
22838 @cindex auto-retry, for remote TCP target
22839 Enable auto-retry for remote TCP connections. This is useful if the remote
22840 debugging agent is launched in parallel with @value{GDBN}; there is a race
22841 condition because the agent may not become ready to accept the connection
22842 before @value{GDBN} attempts to connect. When auto-retry is
22843 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
22844 to establish the connection using the timeout specified by
22845 @code{set tcp connect-timeout}.
22847 @item set tcp auto-retry off
22848 Do not auto-retry failed TCP connections.
22850 @item show tcp auto-retry
22851 Show the current auto-retry setting.
22853 @item set tcp connect-timeout @var{seconds}
22854 @itemx set tcp connect-timeout unlimited
22855 @cindex connection timeout, for remote TCP target
22856 @cindex timeout, for remote target connection
22857 Set the timeout for establishing a TCP connection to the remote target to
22858 @var{seconds}. The timeout affects both polling to retry failed connections
22859 (enabled by @code{set tcp auto-retry on}) and waiting for connections
22860 that are merely slow to complete, and represents an approximate cumulative
22861 value. If @var{seconds} is @code{unlimited}, there is no timeout and
22862 @value{GDBN} will keep attempting to establish a connection forever,
22863 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
22865 @item show tcp connect-timeout
22866 Show the current connection timeout setting.
22869 @cindex remote packets, enabling and disabling
22870 The @value{GDBN} remote protocol autodetects the packets supported by
22871 your debugging stub. If you need to override the autodetection, you
22872 can use these commands to enable or disable individual packets. Each
22873 packet can be set to @samp{on} (the remote target supports this
22874 packet), @samp{off} (the remote target does not support this packet),
22875 or @samp{auto} (detect remote target support for this packet). They
22876 all default to @samp{auto}. For more information about each packet,
22877 see @ref{Remote Protocol}.
22879 During normal use, you should not have to use any of these commands.
22880 If you do, that may be a bug in your remote debugging stub, or a bug
22881 in @value{GDBN}. You may want to report the problem to the
22882 @value{GDBN} developers.
22884 For each packet @var{name}, the command to enable or disable the
22885 packet is @code{set remote @var{name}-packet}. The available settings
22888 @multitable @columnfractions 0.28 0.32 0.25
22891 @tab Related Features
22893 @item @code{fetch-register}
22895 @tab @code{info registers}
22897 @item @code{set-register}
22901 @item @code{binary-download}
22903 @tab @code{load}, @code{set}
22905 @item @code{read-aux-vector}
22906 @tab @code{qXfer:auxv:read}
22907 @tab @code{info auxv}
22909 @item @code{symbol-lookup}
22910 @tab @code{qSymbol}
22911 @tab Detecting multiple threads
22913 @item @code{attach}
22914 @tab @code{vAttach}
22917 @item @code{verbose-resume}
22919 @tab Stepping or resuming multiple threads
22925 @item @code{software-breakpoint}
22929 @item @code{hardware-breakpoint}
22933 @item @code{write-watchpoint}
22937 @item @code{read-watchpoint}
22941 @item @code{access-watchpoint}
22945 @item @code{pid-to-exec-file}
22946 @tab @code{qXfer:exec-file:read}
22947 @tab @code{attach}, @code{run}
22949 @item @code{target-features}
22950 @tab @code{qXfer:features:read}
22951 @tab @code{set architecture}
22953 @item @code{library-info}
22954 @tab @code{qXfer:libraries:read}
22955 @tab @code{info sharedlibrary}
22957 @item @code{memory-map}
22958 @tab @code{qXfer:memory-map:read}
22959 @tab @code{info mem}
22961 @item @code{read-sdata-object}
22962 @tab @code{qXfer:sdata:read}
22963 @tab @code{print $_sdata}
22965 @item @code{read-siginfo-object}
22966 @tab @code{qXfer:siginfo:read}
22967 @tab @code{print $_siginfo}
22969 @item @code{write-siginfo-object}
22970 @tab @code{qXfer:siginfo:write}
22971 @tab @code{set $_siginfo}
22973 @item @code{threads}
22974 @tab @code{qXfer:threads:read}
22975 @tab @code{info threads}
22977 @item @code{get-thread-local-@*storage-address}
22978 @tab @code{qGetTLSAddr}
22979 @tab Displaying @code{__thread} variables
22981 @item @code{get-thread-information-block-address}
22982 @tab @code{qGetTIBAddr}
22983 @tab Display MS-Windows Thread Information Block.
22985 @item @code{search-memory}
22986 @tab @code{qSearch:memory}
22989 @item @code{supported-packets}
22990 @tab @code{qSupported}
22991 @tab Remote communications parameters
22993 @item @code{catch-syscalls}
22994 @tab @code{QCatchSyscalls}
22995 @tab @code{catch syscall}
22997 @item @code{pass-signals}
22998 @tab @code{QPassSignals}
22999 @tab @code{handle @var{signal}}
23001 @item @code{program-signals}
23002 @tab @code{QProgramSignals}
23003 @tab @code{handle @var{signal}}
23005 @item @code{hostio-close-packet}
23006 @tab @code{vFile:close}
23007 @tab @code{remote get}, @code{remote put}
23009 @item @code{hostio-open-packet}
23010 @tab @code{vFile:open}
23011 @tab @code{remote get}, @code{remote put}
23013 @item @code{hostio-pread-packet}
23014 @tab @code{vFile:pread}
23015 @tab @code{remote get}, @code{remote put}
23017 @item @code{hostio-pwrite-packet}
23018 @tab @code{vFile:pwrite}
23019 @tab @code{remote get}, @code{remote put}
23021 @item @code{hostio-unlink-packet}
23022 @tab @code{vFile:unlink}
23023 @tab @code{remote delete}
23025 @item @code{hostio-readlink-packet}
23026 @tab @code{vFile:readlink}
23029 @item @code{hostio-fstat-packet}
23030 @tab @code{vFile:fstat}
23033 @item @code{hostio-setfs-packet}
23034 @tab @code{vFile:setfs}
23037 @item @code{noack-packet}
23038 @tab @code{QStartNoAckMode}
23039 @tab Packet acknowledgment
23041 @item @code{osdata}
23042 @tab @code{qXfer:osdata:read}
23043 @tab @code{info os}
23045 @item @code{query-attached}
23046 @tab @code{qAttached}
23047 @tab Querying remote process attach state.
23049 @item @code{trace-buffer-size}
23050 @tab @code{QTBuffer:size}
23051 @tab @code{set trace-buffer-size}
23053 @item @code{trace-status}
23054 @tab @code{qTStatus}
23055 @tab @code{tstatus}
23057 @item @code{traceframe-info}
23058 @tab @code{qXfer:traceframe-info:read}
23059 @tab Traceframe info
23061 @item @code{install-in-trace}
23062 @tab @code{InstallInTrace}
23063 @tab Install tracepoint in tracing
23065 @item @code{disable-randomization}
23066 @tab @code{QDisableRandomization}
23067 @tab @code{set disable-randomization}
23069 @item @code{startup-with-shell}
23070 @tab @code{QStartupWithShell}
23071 @tab @code{set startup-with-shell}
23073 @item @code{environment-hex-encoded}
23074 @tab @code{QEnvironmentHexEncoded}
23075 @tab @code{set environment}
23077 @item @code{environment-unset}
23078 @tab @code{QEnvironmentUnset}
23079 @tab @code{unset environment}
23081 @item @code{environment-reset}
23082 @tab @code{QEnvironmentReset}
23083 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23085 @item @code{set-working-dir}
23086 @tab @code{QSetWorkingDir}
23087 @tab @code{set cwd}
23089 @item @code{conditional-breakpoints-packet}
23090 @tab @code{Z0 and Z1}
23091 @tab @code{Support for target-side breakpoint condition evaluation}
23093 @item @code{multiprocess-extensions}
23094 @tab @code{multiprocess extensions}
23095 @tab Debug multiple processes and remote process PID awareness
23097 @item @code{swbreak-feature}
23098 @tab @code{swbreak stop reason}
23101 @item @code{hwbreak-feature}
23102 @tab @code{hwbreak stop reason}
23105 @item @code{fork-event-feature}
23106 @tab @code{fork stop reason}
23109 @item @code{vfork-event-feature}
23110 @tab @code{vfork stop reason}
23113 @item @code{exec-event-feature}
23114 @tab @code{exec stop reason}
23117 @item @code{thread-events}
23118 @tab @code{QThreadEvents}
23119 @tab Tracking thread lifetime.
23121 @item @code{no-resumed-stop-reply}
23122 @tab @code{no resumed thread left stop reply}
23123 @tab Tracking thread lifetime.
23128 @section Implementing a Remote Stub
23130 @cindex debugging stub, example
23131 @cindex remote stub, example
23132 @cindex stub example, remote debugging
23133 The stub files provided with @value{GDBN} implement the target side of the
23134 communication protocol, and the @value{GDBN} side is implemented in the
23135 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23136 these subroutines to communicate, and ignore the details. (If you're
23137 implementing your own stub file, you can still ignore the details: start
23138 with one of the existing stub files. @file{sparc-stub.c} is the best
23139 organized, and therefore the easiest to read.)
23141 @cindex remote serial debugging, overview
23142 To debug a program running on another machine (the debugging
23143 @dfn{target} machine), you must first arrange for all the usual
23144 prerequisites for the program to run by itself. For example, for a C
23149 A startup routine to set up the C runtime environment; these usually
23150 have a name like @file{crt0}. The startup routine may be supplied by
23151 your hardware supplier, or you may have to write your own.
23154 A C subroutine library to support your program's
23155 subroutine calls, notably managing input and output.
23158 A way of getting your program to the other machine---for example, a
23159 download program. These are often supplied by the hardware
23160 manufacturer, but you may have to write your own from hardware
23164 The next step is to arrange for your program to use a serial port to
23165 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23166 machine). In general terms, the scheme looks like this:
23170 @value{GDBN} already understands how to use this protocol; when everything
23171 else is set up, you can simply use the @samp{target remote} command
23172 (@pxref{Targets,,Specifying a Debugging Target}).
23174 @item On the target,
23175 you must link with your program a few special-purpose subroutines that
23176 implement the @value{GDBN} remote serial protocol. The file containing these
23177 subroutines is called a @dfn{debugging stub}.
23179 On certain remote targets, you can use an auxiliary program
23180 @code{gdbserver} instead of linking a stub into your program.
23181 @xref{Server,,Using the @code{gdbserver} Program}, for details.
23184 The debugging stub is specific to the architecture of the remote
23185 machine; for example, use @file{sparc-stub.c} to debug programs on
23188 @cindex remote serial stub list
23189 These working remote stubs are distributed with @value{GDBN}:
23194 @cindex @file{i386-stub.c}
23197 For Intel 386 and compatible architectures.
23200 @cindex @file{m68k-stub.c}
23201 @cindex Motorola 680x0
23203 For Motorola 680x0 architectures.
23206 @cindex @file{sh-stub.c}
23209 For Renesas SH architectures.
23212 @cindex @file{sparc-stub.c}
23214 For @sc{sparc} architectures.
23216 @item sparcl-stub.c
23217 @cindex @file{sparcl-stub.c}
23220 For Fujitsu @sc{sparclite} architectures.
23224 The @file{README} file in the @value{GDBN} distribution may list other
23225 recently added stubs.
23228 * Stub Contents:: What the stub can do for you
23229 * Bootstrapping:: What you must do for the stub
23230 * Debug Session:: Putting it all together
23233 @node Stub Contents
23234 @subsection What the Stub Can Do for You
23236 @cindex remote serial stub
23237 The debugging stub for your architecture supplies these three
23241 @item set_debug_traps
23242 @findex set_debug_traps
23243 @cindex remote serial stub, initialization
23244 This routine arranges for @code{handle_exception} to run when your
23245 program stops. You must call this subroutine explicitly in your
23246 program's startup code.
23248 @item handle_exception
23249 @findex handle_exception
23250 @cindex remote serial stub, main routine
23251 This is the central workhorse, but your program never calls it
23252 explicitly---the setup code arranges for @code{handle_exception} to
23253 run when a trap is triggered.
23255 @code{handle_exception} takes control when your program stops during
23256 execution (for example, on a breakpoint), and mediates communications
23257 with @value{GDBN} on the host machine. This is where the communications
23258 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
23259 representative on the target machine. It begins by sending summary
23260 information on the state of your program, then continues to execute,
23261 retrieving and transmitting any information @value{GDBN} needs, until you
23262 execute a @value{GDBN} command that makes your program resume; at that point,
23263 @code{handle_exception} returns control to your own code on the target
23267 @cindex @code{breakpoint} subroutine, remote
23268 Use this auxiliary subroutine to make your program contain a
23269 breakpoint. Depending on the particular situation, this may be the only
23270 way for @value{GDBN} to get control. For instance, if your target
23271 machine has some sort of interrupt button, you won't need to call this;
23272 pressing the interrupt button transfers control to
23273 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
23274 simply receiving characters on the serial port may also trigger a trap;
23275 again, in that situation, you don't need to call @code{breakpoint} from
23276 your own program---simply running @samp{target remote} from the host
23277 @value{GDBN} session gets control.
23279 Call @code{breakpoint} if none of these is true, or if you simply want
23280 to make certain your program stops at a predetermined point for the
23281 start of your debugging session.
23284 @node Bootstrapping
23285 @subsection What You Must Do for the Stub
23287 @cindex remote stub, support routines
23288 The debugging stubs that come with @value{GDBN} are set up for a particular
23289 chip architecture, but they have no information about the rest of your
23290 debugging target machine.
23292 First of all you need to tell the stub how to communicate with the
23296 @item int getDebugChar()
23297 @findex getDebugChar
23298 Write this subroutine to read a single character from the serial port.
23299 It may be identical to @code{getchar} for your target system; a
23300 different name is used to allow you to distinguish the two if you wish.
23302 @item void putDebugChar(int)
23303 @findex putDebugChar
23304 Write this subroutine to write a single character to the serial port.
23305 It may be identical to @code{putchar} for your target system; a
23306 different name is used to allow you to distinguish the two if you wish.
23309 @cindex control C, and remote debugging
23310 @cindex interrupting remote targets
23311 If you want @value{GDBN} to be able to stop your program while it is
23312 running, you need to use an interrupt-driven serial driver, and arrange
23313 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
23314 character). That is the character which @value{GDBN} uses to tell the
23315 remote system to stop.
23317 Getting the debugging target to return the proper status to @value{GDBN}
23318 probably requires changes to the standard stub; one quick and dirty way
23319 is to just execute a breakpoint instruction (the ``dirty'' part is that
23320 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
23322 Other routines you need to supply are:
23325 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
23326 @findex exceptionHandler
23327 Write this function to install @var{exception_address} in the exception
23328 handling tables. You need to do this because the stub does not have any
23329 way of knowing what the exception handling tables on your target system
23330 are like (for example, the processor's table might be in @sc{rom},
23331 containing entries which point to a table in @sc{ram}).
23332 The @var{exception_number} specifies the exception which should be changed;
23333 its meaning is architecture-dependent (for example, different numbers
23334 might represent divide by zero, misaligned access, etc). When this
23335 exception occurs, control should be transferred directly to
23336 @var{exception_address}, and the processor state (stack, registers,
23337 and so on) should be just as it is when a processor exception occurs. So if
23338 you want to use a jump instruction to reach @var{exception_address}, it
23339 should be a simple jump, not a jump to subroutine.
23341 For the 386, @var{exception_address} should be installed as an interrupt
23342 gate so that interrupts are masked while the handler runs. The gate
23343 should be at privilege level 0 (the most privileged level). The
23344 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
23345 help from @code{exceptionHandler}.
23347 @item void flush_i_cache()
23348 @findex flush_i_cache
23349 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
23350 instruction cache, if any, on your target machine. If there is no
23351 instruction cache, this subroutine may be a no-op.
23353 On target machines that have instruction caches, @value{GDBN} requires this
23354 function to make certain that the state of your program is stable.
23358 You must also make sure this library routine is available:
23361 @item void *memset(void *, int, int)
23363 This is the standard library function @code{memset} that sets an area of
23364 memory to a known value. If you have one of the free versions of
23365 @code{libc.a}, @code{memset} can be found there; otherwise, you must
23366 either obtain it from your hardware manufacturer, or write your own.
23369 If you do not use the GNU C compiler, you may need other standard
23370 library subroutines as well; this varies from one stub to another,
23371 but in general the stubs are likely to use any of the common library
23372 subroutines which @code{@value{NGCC}} generates as inline code.
23375 @node Debug Session
23376 @subsection Putting it All Together
23378 @cindex remote serial debugging summary
23379 In summary, when your program is ready to debug, you must follow these
23384 Make sure you have defined the supporting low-level routines
23385 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
23387 @code{getDebugChar}, @code{putDebugChar},
23388 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
23392 Insert these lines in your program's startup code, before the main
23393 procedure is called:
23400 On some machines, when a breakpoint trap is raised, the hardware
23401 automatically makes the PC point to the instruction after the
23402 breakpoint. If your machine doesn't do that, you may need to adjust
23403 @code{handle_exception} to arrange for it to return to the instruction
23404 after the breakpoint on this first invocation, so that your program
23405 doesn't keep hitting the initial breakpoint instead of making
23409 For the 680x0 stub only, you need to provide a variable called
23410 @code{exceptionHook}. Normally you just use:
23413 void (*exceptionHook)() = 0;
23417 but if before calling @code{set_debug_traps}, you set it to point to a
23418 function in your program, that function is called when
23419 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
23420 error). The function indicated by @code{exceptionHook} is called with
23421 one parameter: an @code{int} which is the exception number.
23424 Compile and link together: your program, the @value{GDBN} debugging stub for
23425 your target architecture, and the supporting subroutines.
23428 Make sure you have a serial connection between your target machine and
23429 the @value{GDBN} host, and identify the serial port on the host.
23432 @c The "remote" target now provides a `load' command, so we should
23433 @c document that. FIXME.
23434 Download your program to your target machine (or get it there by
23435 whatever means the manufacturer provides), and start it.
23438 Start @value{GDBN} on the host, and connect to the target
23439 (@pxref{Connecting,,Connecting to a Remote Target}).
23443 @node Configurations
23444 @chapter Configuration-Specific Information
23446 While nearly all @value{GDBN} commands are available for all native and
23447 cross versions of the debugger, there are some exceptions. This chapter
23448 describes things that are only available in certain configurations.
23450 There are three major categories of configurations: native
23451 configurations, where the host and target are the same, embedded
23452 operating system configurations, which are usually the same for several
23453 different processor architectures, and bare embedded processors, which
23454 are quite different from each other.
23459 * Embedded Processors::
23466 This section describes details specific to particular native
23470 * BSD libkvm Interface:: Debugging BSD kernel memory images
23471 * Process Information:: Process information
23472 * DJGPP Native:: Features specific to the DJGPP port
23473 * Cygwin Native:: Features specific to the Cygwin port
23474 * Hurd Native:: Features specific to @sc{gnu} Hurd
23475 * Darwin:: Features specific to Darwin
23476 * FreeBSD:: Features specific to FreeBSD
23479 @node BSD libkvm Interface
23480 @subsection BSD libkvm Interface
23483 @cindex kernel memory image
23484 @cindex kernel crash dump
23486 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
23487 interface that provides a uniform interface for accessing kernel virtual
23488 memory images, including live systems and crash dumps. @value{GDBN}
23489 uses this interface to allow you to debug live kernels and kernel crash
23490 dumps on many native BSD configurations. This is implemented as a
23491 special @code{kvm} debugging target. For debugging a live system, load
23492 the currently running kernel into @value{GDBN} and connect to the
23496 (@value{GDBP}) @b{target kvm}
23499 For debugging crash dumps, provide the file name of the crash dump as an
23503 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
23506 Once connected to the @code{kvm} target, the following commands are
23512 Set current context from the @dfn{Process Control Block} (PCB) address.
23515 Set current context from proc address. This command isn't available on
23516 modern FreeBSD systems.
23519 @node Process Information
23520 @subsection Process Information
23522 @cindex examine process image
23523 @cindex process info via @file{/proc}
23525 Some operating systems provide interfaces to fetch additional
23526 information about running processes beyond memory and per-thread
23527 register state. If @value{GDBN} is configured for an operating system
23528 with a supported interface, the command @code{info proc} is available
23529 to report information about the process running your program, or about
23530 any process running on your system.
23532 One supported interface is a facility called @samp{/proc} that can be
23533 used to examine the image of a running process using file-system
23534 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
23537 On FreeBSD and NetBSD systems, system control nodes are used to query
23538 process information.
23540 In addition, some systems may provide additional process information
23541 in core files. Note that a core file may include a subset of the
23542 information available from a live process. Process information is
23543 currently available from cores created on @sc{gnu}/Linux and FreeBSD
23550 @itemx info proc @var{process-id}
23551 Summarize available information about a process. If a
23552 process ID is specified by @var{process-id}, display information about
23553 that process; otherwise display information about the program being
23554 debugged. The summary includes the debugged process ID, the command
23555 line used to invoke it, its current working directory, and its
23556 executable file's absolute file name.
23558 On some systems, @var{process-id} can be of the form
23559 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
23560 within a process. If the optional @var{pid} part is missing, it means
23561 a thread from the process being debugged (the leading @samp{/} still
23562 needs to be present, or else @value{GDBN} will interpret the number as
23563 a process ID rather than a thread ID).
23565 @item info proc cmdline
23566 @cindex info proc cmdline
23567 Show the original command line of the process. This command is
23568 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
23570 @item info proc cwd
23571 @cindex info proc cwd
23572 Show the current working directory of the process. This command is
23573 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
23575 @item info proc exe
23576 @cindex info proc exe
23577 Show the name of executable of the process. This command is supported
23578 on @sc{gnu}/Linux, FreeBSD and NetBSD.
23580 @item info proc files
23581 @cindex info proc files
23582 Show the file descriptors open by the process. For each open file
23583 descriptor, @value{GDBN} shows its number, type (file, directory,
23584 character device, socket), file pointer offset, and the name of the
23585 resource open on the descriptor. The resource name can be a file name
23586 (for files, directories, and devices) or a protocol followed by socket
23587 address (for network connections). This command is supported on
23590 This example shows the open file descriptors for a process using a
23591 tty for standard input and output as well as two network sockets:
23594 (gdb) info proc files 22136
23598 FD Type Offset Flags Name
23599 text file - r-------- /usr/bin/ssh
23600 ctty chr - rw------- /dev/pts/20
23601 cwd dir - r-------- /usr/home/john
23602 root dir - r-------- /
23603 0 chr 0x32933a4 rw------- /dev/pts/20
23604 1 chr 0x32933a4 rw------- /dev/pts/20
23605 2 chr 0x32933a4 rw------- /dev/pts/20
23606 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
23607 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
23610 @item info proc mappings
23611 @cindex memory address space mappings
23612 Report the memory address space ranges accessible in a process. On
23613 Solaris, FreeBSD and NetBSD systems, each memory range includes information
23614 on whether the process has read, write, or execute access rights to each
23615 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
23616 includes the object file which is mapped to that range.
23618 @item info proc stat
23619 @itemx info proc status
23620 @cindex process detailed status information
23621 Show additional process-related information, including the user ID and
23622 group ID; virtual memory usage; the signals that are pending, blocked,
23623 and ignored; its TTY; its consumption of system and user time; its
23624 stack size; its @samp{nice} value; etc. These commands are supported
23625 on @sc{gnu}/Linux, FreeBSD and NetBSD.
23627 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
23628 information (type @kbd{man 5 proc} from your shell prompt).
23630 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
23631 @code{info proc status}.
23633 @item info proc all
23634 Show all the information about the process described under all of the
23635 above @code{info proc} subcommands.
23638 @comment These sub-options of 'info proc' were not included when
23639 @comment procfs.c was re-written. Keep their descriptions around
23640 @comment against the day when someone finds the time to put them back in.
23641 @kindex info proc times
23642 @item info proc times
23643 Starting time, user CPU time, and system CPU time for your program and
23646 @kindex info proc id
23648 Report on the process IDs related to your program: its own process ID,
23649 the ID of its parent, the process group ID, and the session ID.
23652 @item set procfs-trace
23653 @kindex set procfs-trace
23654 @cindex @code{procfs} API calls
23655 This command enables and disables tracing of @code{procfs} API calls.
23657 @item show procfs-trace
23658 @kindex show procfs-trace
23659 Show the current state of @code{procfs} API call tracing.
23661 @item set procfs-file @var{file}
23662 @kindex set procfs-file
23663 Tell @value{GDBN} to write @code{procfs} API trace to the named
23664 @var{file}. @value{GDBN} appends the trace info to the previous
23665 contents of the file. The default is to display the trace on the
23668 @item show procfs-file
23669 @kindex show procfs-file
23670 Show the file to which @code{procfs} API trace is written.
23672 @item proc-trace-entry
23673 @itemx proc-trace-exit
23674 @itemx proc-untrace-entry
23675 @itemx proc-untrace-exit
23676 @kindex proc-trace-entry
23677 @kindex proc-trace-exit
23678 @kindex proc-untrace-entry
23679 @kindex proc-untrace-exit
23680 These commands enable and disable tracing of entries into and exits
23681 from the @code{syscall} interface.
23684 @kindex info pidlist
23685 @cindex process list, QNX Neutrino
23686 For QNX Neutrino only, this command displays the list of all the
23687 processes and all the threads within each process.
23690 @kindex info meminfo
23691 @cindex mapinfo list, QNX Neutrino
23692 For QNX Neutrino only, this command displays the list of all mapinfos.
23696 @subsection Features for Debugging @sc{djgpp} Programs
23697 @cindex @sc{djgpp} debugging
23698 @cindex native @sc{djgpp} debugging
23699 @cindex MS-DOS-specific commands
23702 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
23703 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
23704 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
23705 top of real-mode DOS systems and their emulations.
23707 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
23708 defines a few commands specific to the @sc{djgpp} port. This
23709 subsection describes those commands.
23714 This is a prefix of @sc{djgpp}-specific commands which print
23715 information about the target system and important OS structures.
23718 @cindex MS-DOS system info
23719 @cindex free memory information (MS-DOS)
23720 @item info dos sysinfo
23721 This command displays assorted information about the underlying
23722 platform: the CPU type and features, the OS version and flavor, the
23723 DPMI version, and the available conventional and DPMI memory.
23728 @cindex segment descriptor tables
23729 @cindex descriptor tables display
23731 @itemx info dos ldt
23732 @itemx info dos idt
23733 These 3 commands display entries from, respectively, Global, Local,
23734 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
23735 tables are data structures which store a descriptor for each segment
23736 that is currently in use. The segment's selector is an index into a
23737 descriptor table; the table entry for that index holds the
23738 descriptor's base address and limit, and its attributes and access
23741 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
23742 segment (used for both data and the stack), and a DOS segment (which
23743 allows access to DOS/BIOS data structures and absolute addresses in
23744 conventional memory). However, the DPMI host will usually define
23745 additional segments in order to support the DPMI environment.
23747 @cindex garbled pointers
23748 These commands allow to display entries from the descriptor tables.
23749 Without an argument, all entries from the specified table are
23750 displayed. An argument, which should be an integer expression, means
23751 display a single entry whose index is given by the argument. For
23752 example, here's a convenient way to display information about the
23753 debugged program's data segment:
23756 @exdent @code{(@value{GDBP}) info dos ldt $ds}
23757 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
23761 This comes in handy when you want to see whether a pointer is outside
23762 the data segment's limit (i.e.@: @dfn{garbled}).
23764 @cindex page tables display (MS-DOS)
23766 @itemx info dos pte
23767 These two commands display entries from, respectively, the Page
23768 Directory and the Page Tables. Page Directories and Page Tables are
23769 data structures which control how virtual memory addresses are mapped
23770 into physical addresses. A Page Table includes an entry for every
23771 page of memory that is mapped into the program's address space; there
23772 may be several Page Tables, each one holding up to 4096 entries. A
23773 Page Directory has up to 4096 entries, one each for every Page Table
23774 that is currently in use.
23776 Without an argument, @kbd{info dos pde} displays the entire Page
23777 Directory, and @kbd{info dos pte} displays all the entries in all of
23778 the Page Tables. An argument, an integer expression, given to the
23779 @kbd{info dos pde} command means display only that entry from the Page
23780 Directory table. An argument given to the @kbd{info dos pte} command
23781 means display entries from a single Page Table, the one pointed to by
23782 the specified entry in the Page Directory.
23784 @cindex direct memory access (DMA) on MS-DOS
23785 These commands are useful when your program uses @dfn{DMA} (Direct
23786 Memory Access), which needs physical addresses to program the DMA
23789 These commands are supported only with some DPMI servers.
23791 @cindex physical address from linear address
23792 @item info dos address-pte @var{addr}
23793 This command displays the Page Table entry for a specified linear
23794 address. The argument @var{addr} is a linear address which should
23795 already have the appropriate segment's base address added to it,
23796 because this command accepts addresses which may belong to @emph{any}
23797 segment. For example, here's how to display the Page Table entry for
23798 the page where a variable @code{i} is stored:
23801 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
23802 @exdent @code{Page Table entry for address 0x11a00d30:}
23803 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
23807 This says that @code{i} is stored at offset @code{0xd30} from the page
23808 whose physical base address is @code{0x02698000}, and shows all the
23809 attributes of that page.
23811 Note that you must cast the addresses of variables to a @code{char *},
23812 since otherwise the value of @code{__djgpp_base_address}, the base
23813 address of all variables and functions in a @sc{djgpp} program, will
23814 be added using the rules of C pointer arithmetics: if @code{i} is
23815 declared an @code{int}, @value{GDBN} will add 4 times the value of
23816 @code{__djgpp_base_address} to the address of @code{i}.
23818 Here's another example, it displays the Page Table entry for the
23822 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
23823 @exdent @code{Page Table entry for address 0x29110:}
23824 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
23828 (The @code{+ 3} offset is because the transfer buffer's address is the
23829 3rd member of the @code{_go32_info_block} structure.) The output
23830 clearly shows that this DPMI server maps the addresses in conventional
23831 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
23832 linear (@code{0x29110}) addresses are identical.
23834 This command is supported only with some DPMI servers.
23837 @cindex DOS serial data link, remote debugging
23838 In addition to native debugging, the DJGPP port supports remote
23839 debugging via a serial data link. The following commands are specific
23840 to remote serial debugging in the DJGPP port of @value{GDBN}.
23843 @kindex set com1base
23844 @kindex set com1irq
23845 @kindex set com2base
23846 @kindex set com2irq
23847 @kindex set com3base
23848 @kindex set com3irq
23849 @kindex set com4base
23850 @kindex set com4irq
23851 @item set com1base @var{addr}
23852 This command sets the base I/O port address of the @file{COM1} serial
23855 @item set com1irq @var{irq}
23856 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
23857 for the @file{COM1} serial port.
23859 There are similar commands @samp{set com2base}, @samp{set com3irq},
23860 etc.@: for setting the port address and the @code{IRQ} lines for the
23863 @kindex show com1base
23864 @kindex show com1irq
23865 @kindex show com2base
23866 @kindex show com2irq
23867 @kindex show com3base
23868 @kindex show com3irq
23869 @kindex show com4base
23870 @kindex show com4irq
23871 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
23872 display the current settings of the base address and the @code{IRQ}
23873 lines used by the COM ports.
23876 @kindex info serial
23877 @cindex DOS serial port status
23878 This command prints the status of the 4 DOS serial ports. For each
23879 port, it prints whether it's active or not, its I/O base address and
23880 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
23881 counts of various errors encountered so far.
23885 @node Cygwin Native
23886 @subsection Features for Debugging MS Windows PE Executables
23887 @cindex MS Windows debugging
23888 @cindex native Cygwin debugging
23889 @cindex Cygwin-specific commands
23891 @value{GDBN} supports native debugging of MS Windows programs, including
23892 DLLs with and without symbolic debugging information.
23894 @cindex Ctrl-BREAK, MS-Windows
23895 @cindex interrupt debuggee on MS-Windows
23896 MS-Windows programs that call @code{SetConsoleMode} to switch off the
23897 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
23898 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
23899 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
23900 sequence, which can be used to interrupt the debuggee even if it
23903 There are various additional Cygwin-specific commands, described in
23904 this section. Working with DLLs that have no debugging symbols is
23905 described in @ref{Non-debug DLL Symbols}.
23910 This is a prefix of MS Windows-specific commands which print
23911 information about the target system and important OS structures.
23913 @item info w32 selector
23914 This command displays information returned by
23915 the Win32 API @code{GetThreadSelectorEntry} function.
23916 It takes an optional argument that is evaluated to
23917 a long value to give the information about this given selector.
23918 Without argument, this command displays information
23919 about the six segment registers.
23921 @item info w32 thread-information-block
23922 This command displays thread specific information stored in the
23923 Thread Information Block (readable on the X86 CPU family using @code{$fs}
23924 selector for 32-bit programs and @code{$gs} for 64-bit programs).
23926 @kindex signal-event
23927 @item signal-event @var{id}
23928 This command signals an event with user-provided @var{id}. Used to resume
23929 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
23931 To use it, create or edit the following keys in
23932 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
23933 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
23934 (for x86_64 versions):
23938 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
23939 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
23940 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
23942 The first @code{%ld} will be replaced by the process ID of the
23943 crashing process, the second @code{%ld} will be replaced by the ID of
23944 the event that blocks the crashing process, waiting for @value{GDBN}
23948 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
23949 make the system run debugger specified by the Debugger key
23950 automatically, @code{0} will cause a dialog box with ``OK'' and
23951 ``Cancel'' buttons to appear, which allows the user to either
23952 terminate the crashing process (OK) or debug it (Cancel).
23955 @kindex set cygwin-exceptions
23956 @cindex debugging the Cygwin DLL
23957 @cindex Cygwin DLL, debugging
23958 @item set cygwin-exceptions @var{mode}
23959 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
23960 happen inside the Cygwin DLL. If @var{mode} is @code{off},
23961 @value{GDBN} will delay recognition of exceptions, and may ignore some
23962 exceptions which seem to be caused by internal Cygwin DLL
23963 ``bookkeeping''. This option is meant primarily for debugging the
23964 Cygwin DLL itself; the default value is @code{off} to avoid annoying
23965 @value{GDBN} users with false @code{SIGSEGV} signals.
23967 @kindex show cygwin-exceptions
23968 @item show cygwin-exceptions
23969 Displays whether @value{GDBN} will break on exceptions that happen
23970 inside the Cygwin DLL itself.
23972 @kindex set new-console
23973 @item set new-console @var{mode}
23974 If @var{mode} is @code{on} the debuggee will
23975 be started in a new console on next start.
23976 If @var{mode} is @code{off}, the debuggee will
23977 be started in the same console as the debugger.
23979 @kindex show new-console
23980 @item show new-console
23981 Displays whether a new console is used
23982 when the debuggee is started.
23984 @kindex set new-group
23985 @item set new-group @var{mode}
23986 This boolean value controls whether the debuggee should
23987 start a new group or stay in the same group as the debugger.
23988 This affects the way the Windows OS handles
23991 @kindex show new-group
23992 @item show new-group
23993 Displays current value of new-group boolean.
23995 @kindex set debugevents
23996 @item set debugevents
23997 This boolean value adds debug output concerning kernel events related
23998 to the debuggee seen by the debugger. This includes events that
23999 signal thread and process creation and exit, DLL loading and
24000 unloading, console interrupts, and debugging messages produced by the
24001 Windows @code{OutputDebugString} API call.
24003 @kindex set debugexec
24004 @item set debugexec
24005 This boolean value adds debug output concerning execute events
24006 (such as resume thread) seen by the debugger.
24008 @kindex set debugexceptions
24009 @item set debugexceptions
24010 This boolean value adds debug output concerning exceptions in the
24011 debuggee seen by the debugger.
24013 @kindex set debugmemory
24014 @item set debugmemory
24015 This boolean value adds debug output concerning debuggee memory reads
24016 and writes by the debugger.
24020 This boolean values specifies whether the debuggee is called
24021 via a shell or directly (default value is on).
24025 Displays if the debuggee will be started with a shell.
24030 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24033 @node Non-debug DLL Symbols
24034 @subsubsection Support for DLLs without Debugging Symbols
24035 @cindex DLLs with no debugging symbols
24036 @cindex Minimal symbols and DLLs
24038 Very often on windows, some of the DLLs that your program relies on do
24039 not include symbolic debugging information (for example,
24040 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24041 symbols in a DLL, it relies on the minimal amount of symbolic
24042 information contained in the DLL's export table. This section
24043 describes working with such symbols, known internally to @value{GDBN} as
24044 ``minimal symbols''.
24046 Note that before the debugged program has started execution, no DLLs
24047 will have been loaded. The easiest way around this problem is simply to
24048 start the program --- either by setting a breakpoint or letting the
24049 program run once to completion.
24051 @subsubsection DLL Name Prefixes
24053 In keeping with the naming conventions used by the Microsoft debugging
24054 tools, DLL export symbols are made available with a prefix based on the
24055 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24056 also entered into the symbol table, so @code{CreateFileA} is often
24057 sufficient. In some cases there will be name clashes within a program
24058 (particularly if the executable itself includes full debugging symbols)
24059 necessitating the use of the fully qualified name when referring to the
24060 contents of the DLL. Use single-quotes around the name to avoid the
24061 exclamation mark (``!'') being interpreted as a language operator.
24063 Note that the internal name of the DLL may be all upper-case, even
24064 though the file name of the DLL is lower-case, or vice-versa. Since
24065 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24066 some confusion. If in doubt, try the @code{info functions} and
24067 @code{info variables} commands or even @code{maint print msymbols}
24068 (@pxref{Symbols}). Here's an example:
24071 (@value{GDBP}) info function CreateFileA
24072 All functions matching regular expression "CreateFileA":
24074 Non-debugging symbols:
24075 0x77e885f4 CreateFileA
24076 0x77e885f4 KERNEL32!CreateFileA
24080 (@value{GDBP}) info function !
24081 All functions matching regular expression "!":
24083 Non-debugging symbols:
24084 0x6100114c cygwin1!__assert
24085 0x61004034 cygwin1!_dll_crt0@@0
24086 0x61004240 cygwin1!dll_crt0(per_process *)
24090 @subsubsection Working with Minimal Symbols
24092 Symbols extracted from a DLL's export table do not contain very much
24093 type information. All that @value{GDBN} can do is guess whether a symbol
24094 refers to a function or variable depending on the linker section that
24095 contains the symbol. Also note that the actual contents of the memory
24096 contained in a DLL are not available unless the program is running. This
24097 means that you cannot examine the contents of a variable or disassemble
24098 a function within a DLL without a running program.
24100 Variables are generally treated as pointers and dereferenced
24101 automatically. For this reason, it is often necessary to prefix a
24102 variable name with the address-of operator (``&'') and provide explicit
24103 type information in the command. Here's an example of the type of
24107 (@value{GDBP}) print 'cygwin1!__argv'
24108 'cygwin1!__argv' has unknown type; cast it to its declared type
24112 (@value{GDBP}) x 'cygwin1!__argv'
24113 'cygwin1!__argv' has unknown type; cast it to its declared type
24116 And two possible solutions:
24119 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24120 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24124 (@value{GDBP}) x/2x &'cygwin1!__argv'
24125 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24126 (@value{GDBP}) x/x 0x10021608
24127 0x10021608: 0x0022fd98
24128 (@value{GDBP}) x/s 0x0022fd98
24129 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24132 Setting a break point within a DLL is possible even before the program
24133 starts execution. However, under these circumstances, @value{GDBN} can't
24134 examine the initial instructions of the function in order to skip the
24135 function's frame set-up code. You can work around this by using ``*&''
24136 to set the breakpoint at a raw memory address:
24139 (@value{GDBP}) break *&'python22!PyOS_Readline'
24140 Breakpoint 1 at 0x1e04eff0
24143 The author of these extensions is not entirely convinced that setting a
24144 break point within a shared DLL like @file{kernel32.dll} is completely
24148 @subsection Commands Specific to @sc{gnu} Hurd Systems
24149 @cindex @sc{gnu} Hurd debugging
24151 This subsection describes @value{GDBN} commands specific to the
24152 @sc{gnu} Hurd native debugging.
24157 @kindex set signals@r{, Hurd command}
24158 @kindex set sigs@r{, Hurd command}
24159 This command toggles the state of inferior signal interception by
24160 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24161 affected by this command. @code{sigs} is a shorthand alias for
24166 @kindex show signals@r{, Hurd command}
24167 @kindex show sigs@r{, Hurd command}
24168 Show the current state of intercepting inferior's signals.
24170 @item set signal-thread
24171 @itemx set sigthread
24172 @kindex set signal-thread
24173 @kindex set sigthread
24174 This command tells @value{GDBN} which thread is the @code{libc} signal
24175 thread. That thread is run when a signal is delivered to a running
24176 process. @code{set sigthread} is the shorthand alias of @code{set
24179 @item show signal-thread
24180 @itemx show sigthread
24181 @kindex show signal-thread
24182 @kindex show sigthread
24183 These two commands show which thread will run when the inferior is
24184 delivered a signal.
24187 @kindex set stopped@r{, Hurd command}
24188 This commands tells @value{GDBN} that the inferior process is stopped,
24189 as with the @code{SIGSTOP} signal. The stopped process can be
24190 continued by delivering a signal to it.
24193 @kindex show stopped@r{, Hurd command}
24194 This command shows whether @value{GDBN} thinks the debuggee is
24197 @item set exceptions
24198 @kindex set exceptions@r{, Hurd command}
24199 Use this command to turn off trapping of exceptions in the inferior.
24200 When exception trapping is off, neither breakpoints nor
24201 single-stepping will work. To restore the default, set exception
24204 @item show exceptions
24205 @kindex show exceptions@r{, Hurd command}
24206 Show the current state of trapping exceptions in the inferior.
24208 @item set task pause
24209 @kindex set task@r{, Hurd commands}
24210 @cindex task attributes (@sc{gnu} Hurd)
24211 @cindex pause current task (@sc{gnu} Hurd)
24212 This command toggles task suspension when @value{GDBN} has control.
24213 Setting it to on takes effect immediately, and the task is suspended
24214 whenever @value{GDBN} gets control. Setting it to off will take
24215 effect the next time the inferior is continued. If this option is set
24216 to off, you can use @code{set thread default pause on} or @code{set
24217 thread pause on} (see below) to pause individual threads.
24219 @item show task pause
24220 @kindex show task@r{, Hurd commands}
24221 Show the current state of task suspension.
24223 @item set task detach-suspend-count
24224 @cindex task suspend count
24225 @cindex detach from task, @sc{gnu} Hurd
24226 This command sets the suspend count the task will be left with when
24227 @value{GDBN} detaches from it.
24229 @item show task detach-suspend-count
24230 Show the suspend count the task will be left with when detaching.
24232 @item set task exception-port
24233 @itemx set task excp
24234 @cindex task exception port, @sc{gnu} Hurd
24235 This command sets the task exception port to which @value{GDBN} will
24236 forward exceptions. The argument should be the value of the @dfn{send
24237 rights} of the task. @code{set task excp} is a shorthand alias.
24239 @item set noninvasive
24240 @cindex noninvasive task options
24241 This command switches @value{GDBN} to a mode that is the least
24242 invasive as far as interfering with the inferior is concerned. This
24243 is the same as using @code{set task pause}, @code{set exceptions}, and
24244 @code{set signals} to values opposite to the defaults.
24246 @item info send-rights
24247 @itemx info receive-rights
24248 @itemx info port-rights
24249 @itemx info port-sets
24250 @itemx info dead-names
24253 @cindex send rights, @sc{gnu} Hurd
24254 @cindex receive rights, @sc{gnu} Hurd
24255 @cindex port rights, @sc{gnu} Hurd
24256 @cindex port sets, @sc{gnu} Hurd
24257 @cindex dead names, @sc{gnu} Hurd
24258 These commands display information about, respectively, send rights,
24259 receive rights, port rights, port sets, and dead names of a task.
24260 There are also shorthand aliases: @code{info ports} for @code{info
24261 port-rights} and @code{info psets} for @code{info port-sets}.
24263 @item set thread pause
24264 @kindex set thread@r{, Hurd command}
24265 @cindex thread properties, @sc{gnu} Hurd
24266 @cindex pause current thread (@sc{gnu} Hurd)
24267 This command toggles current thread suspension when @value{GDBN} has
24268 control. Setting it to on takes effect immediately, and the current
24269 thread is suspended whenever @value{GDBN} gets control. Setting it to
24270 off will take effect the next time the inferior is continued.
24271 Normally, this command has no effect, since when @value{GDBN} has
24272 control, the whole task is suspended. However, if you used @code{set
24273 task pause off} (see above), this command comes in handy to suspend
24274 only the current thread.
24276 @item show thread pause
24277 @kindex show thread@r{, Hurd command}
24278 This command shows the state of current thread suspension.
24280 @item set thread run
24281 This command sets whether the current thread is allowed to run.
24283 @item show thread run
24284 Show whether the current thread is allowed to run.
24286 @item set thread detach-suspend-count
24287 @cindex thread suspend count, @sc{gnu} Hurd
24288 @cindex detach from thread, @sc{gnu} Hurd
24289 This command sets the suspend count @value{GDBN} will leave on a
24290 thread when detaching. This number is relative to the suspend count
24291 found by @value{GDBN} when it notices the thread; use @code{set thread
24292 takeover-suspend-count} to force it to an absolute value.
24294 @item show thread detach-suspend-count
24295 Show the suspend count @value{GDBN} will leave on the thread when
24298 @item set thread exception-port
24299 @itemx set thread excp
24300 Set the thread exception port to which to forward exceptions. This
24301 overrides the port set by @code{set task exception-port} (see above).
24302 @code{set thread excp} is the shorthand alias.
24304 @item set thread takeover-suspend-count
24305 Normally, @value{GDBN}'s thread suspend counts are relative to the
24306 value @value{GDBN} finds when it notices each thread. This command
24307 changes the suspend counts to be absolute instead.
24309 @item set thread default
24310 @itemx show thread default
24311 @cindex thread default settings, @sc{gnu} Hurd
24312 Each of the above @code{set thread} commands has a @code{set thread
24313 default} counterpart (e.g., @code{set thread default pause}, @code{set
24314 thread default exception-port}, etc.). The @code{thread default}
24315 variety of commands sets the default thread properties for all
24316 threads; you can then change the properties of individual threads with
24317 the non-default commands.
24324 @value{GDBN} provides the following commands specific to the Darwin target:
24327 @item set debug darwin @var{num}
24328 @kindex set debug darwin
24329 When set to a non zero value, enables debugging messages specific to
24330 the Darwin support. Higher values produce more verbose output.
24332 @item show debug darwin
24333 @kindex show debug darwin
24334 Show the current state of Darwin messages.
24336 @item set debug mach-o @var{num}
24337 @kindex set debug mach-o
24338 When set to a non zero value, enables debugging messages while
24339 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
24340 file format used on Darwin for object and executable files.) Higher
24341 values produce more verbose output. This is a command to diagnose
24342 problems internal to @value{GDBN} and should not be needed in normal
24345 @item show debug mach-o
24346 @kindex show debug mach-o
24347 Show the current state of Mach-O file messages.
24349 @item set mach-exceptions on
24350 @itemx set mach-exceptions off
24351 @kindex set mach-exceptions
24352 On Darwin, faults are first reported as a Mach exception and are then
24353 mapped to a Posix signal. Use this command to turn on trapping of
24354 Mach exceptions in the inferior. This might be sometimes useful to
24355 better understand the cause of a fault. The default is off.
24357 @item show mach-exceptions
24358 @kindex show mach-exceptions
24359 Show the current state of exceptions trapping.
24363 @subsection FreeBSD
24366 When the ABI of a system call is changed in the FreeBSD kernel, this
24367 is implemented by leaving a compatibility system call using the old
24368 ABI at the existing number and allocating a new system call number for
24369 the version using the new ABI. As a convenience, when a system call
24370 is caught by name (@pxref{catch syscall}), compatibility system calls
24373 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
24374 system call and catching the @code{kevent} system call by name catches
24378 (@value{GDBP}) catch syscall kevent
24379 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
24385 @section Embedded Operating Systems
24387 This section describes configurations involving the debugging of
24388 embedded operating systems that are available for several different
24391 @value{GDBN} includes the ability to debug programs running on
24392 various real-time operating systems.
24394 @node Embedded Processors
24395 @section Embedded Processors
24397 This section goes into details specific to particular embedded
24400 @cindex send command to simulator
24401 Whenever a specific embedded processor has a simulator, @value{GDBN}
24402 allows to send an arbitrary command to the simulator.
24405 @item sim @var{command}
24406 @kindex sim@r{, a command}
24407 Send an arbitrary @var{command} string to the simulator. Consult the
24408 documentation for the specific simulator in use for information about
24409 acceptable commands.
24414 * ARC:: Synopsys ARC
24417 * M68K:: Motorola M68K
24418 * MicroBlaze:: Xilinx MicroBlaze
24419 * MIPS Embedded:: MIPS Embedded
24420 * OpenRISC 1000:: OpenRISC 1000 (or1k)
24421 * PowerPC Embedded:: PowerPC Embedded
24424 * Super-H:: Renesas Super-H
24428 @subsection Synopsys ARC
24429 @cindex Synopsys ARC
24430 @cindex ARC specific commands
24436 @value{GDBN} provides the following ARC-specific commands:
24439 @item set debug arc
24440 @kindex set debug arc
24441 Control the level of ARC specific debug messages. Use 0 for no messages (the
24442 default), 1 for debug messages, and 2 for even more debug messages.
24444 @item show debug arc
24445 @kindex show debug arc
24446 Show the level of ARC specific debugging in operation.
24448 @item maint print arc arc-instruction @var{address}
24449 @kindex maint print arc arc-instruction
24450 Print internal disassembler information about instruction at a given address.
24457 @value{GDBN} provides the following ARM-specific commands:
24460 @item set arm disassembler
24462 This commands selects from a list of disassembly styles. The
24463 @code{"std"} style is the standard style.
24465 @item show arm disassembler
24467 Show the current disassembly style.
24469 @item set arm apcs32
24470 @cindex ARM 32-bit mode
24471 This command toggles ARM operation mode between 32-bit and 26-bit.
24473 @item show arm apcs32
24474 Display the current usage of the ARM 32-bit mode.
24476 @item set arm fpu @var{fputype}
24477 This command sets the ARM floating-point unit (FPU) type. The
24478 argument @var{fputype} can be one of these:
24482 Determine the FPU type by querying the OS ABI.
24484 Software FPU, with mixed-endian doubles on little-endian ARM
24487 GCC-compiled FPA co-processor.
24489 Software FPU with pure-endian doubles.
24495 Show the current type of the FPU.
24498 This command forces @value{GDBN} to use the specified ABI.
24501 Show the currently used ABI.
24503 @item set arm fallback-mode (arm|thumb|auto)
24504 @value{GDBN} uses the symbol table, when available, to determine
24505 whether instructions are ARM or Thumb. This command controls
24506 @value{GDBN}'s default behavior when the symbol table is not
24507 available. The default is @samp{auto}, which causes @value{GDBN} to
24508 use the current execution mode (from the @code{T} bit in the @code{CPSR}
24511 @item show arm fallback-mode
24512 Show the current fallback instruction mode.
24514 @item set arm force-mode (arm|thumb|auto)
24515 This command overrides use of the symbol table to determine whether
24516 instructions are ARM or Thumb. The default is @samp{auto}, which
24517 causes @value{GDBN} to use the symbol table and then the setting
24518 of @samp{set arm fallback-mode}.
24520 @item show arm force-mode
24521 Show the current forced instruction mode.
24523 @item set debug arm
24524 Toggle whether to display ARM-specific debugging messages from the ARM
24525 target support subsystem.
24527 @item show debug arm
24528 Show whether ARM-specific debugging messages are enabled.
24532 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24533 The @value{GDBN} ARM simulator accepts the following optional arguments.
24536 @item --swi-support=@var{type}
24537 Tell the simulator which SWI interfaces to support. The argument
24538 @var{type} may be a comma separated list of the following values.
24539 The default value is @code{all}.
24555 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24556 The @value{GDBN} BPF simulator accepts the following optional arguments.
24559 @item --skb-data-offset=@var{offset}
24560 Tell the simulator the offset, measured in bytes, of the
24561 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
24562 This offset is used by some BPF specific-purpose load/store
24563 instructions. Defaults to 0.
24570 The Motorola m68k configuration includes ColdFire support.
24573 @subsection MicroBlaze
24574 @cindex Xilinx MicroBlaze
24575 @cindex XMD, Xilinx Microprocessor Debugger
24577 The MicroBlaze is a soft-core processor supported on various Xilinx
24578 FPGAs, such as Spartan or Virtex series. Boards with these processors
24579 usually have JTAG ports which connect to a host system running the Xilinx
24580 Embedded Development Kit (EDK) or Software Development Kit (SDK).
24581 This host system is used to download the configuration bitstream to
24582 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
24583 communicates with the target board using the JTAG interface and
24584 presents a @code{gdbserver} interface to the board. By default
24585 @code{xmd} uses port @code{1234}. (While it is possible to change
24586 this default port, it requires the use of undocumented @code{xmd}
24587 commands. Contact Xilinx support if you need to do this.)
24589 Use these GDB commands to connect to the MicroBlaze target processor.
24592 @item target remote :1234
24593 Use this command to connect to the target if you are running @value{GDBN}
24594 on the same system as @code{xmd}.
24596 @item target remote @var{xmd-host}:1234
24597 Use this command to connect to the target if it is connected to @code{xmd}
24598 running on a different system named @var{xmd-host}.
24601 Use this command to download a program to the MicroBlaze target.
24603 @item set debug microblaze @var{n}
24604 Enable MicroBlaze-specific debugging messages if non-zero.
24606 @item show debug microblaze @var{n}
24607 Show MicroBlaze-specific debugging level.
24610 @node MIPS Embedded
24611 @subsection @acronym{MIPS} Embedded
24614 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
24617 @item set mipsfpu double
24618 @itemx set mipsfpu single
24619 @itemx set mipsfpu none
24620 @itemx set mipsfpu auto
24621 @itemx show mipsfpu
24622 @kindex set mipsfpu
24623 @kindex show mipsfpu
24624 @cindex @acronym{MIPS} remote floating point
24625 @cindex floating point, @acronym{MIPS} remote
24626 If your target board does not support the @acronym{MIPS} floating point
24627 coprocessor, you should use the command @samp{set mipsfpu none} (if you
24628 need this, you may wish to put the command in your @value{GDBN} init
24629 file). This tells @value{GDBN} how to find the return value of
24630 functions which return floating point values. It also allows
24631 @value{GDBN} to avoid saving the floating point registers when calling
24632 functions on the board. If you are using a floating point coprocessor
24633 with only single precision floating point support, as on the @sc{r4650}
24634 processor, use the command @samp{set mipsfpu single}. The default
24635 double precision floating point coprocessor may be selected using
24636 @samp{set mipsfpu double}.
24638 In previous versions the only choices were double precision or no
24639 floating point, so @samp{set mipsfpu on} will select double precision
24640 and @samp{set mipsfpu off} will select no floating point.
24642 As usual, you can inquire about the @code{mipsfpu} variable with
24643 @samp{show mipsfpu}.
24646 @node OpenRISC 1000
24647 @subsection OpenRISC 1000
24648 @cindex OpenRISC 1000
24651 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
24652 mainly provided as a soft-core which can run on Xilinx, Altera and other
24655 @value{GDBN} for OpenRISC supports the below commands when connecting to
24663 Runs the builtin CPU simulator which can run very basic
24664 programs but does not support most hardware functions like MMU.
24665 For more complex use cases the user is advised to run an external
24666 target, and connect using @samp{target remote}.
24668 Example: @code{target sim}
24670 @item set debug or1k
24671 Toggle whether to display OpenRISC-specific debugging messages from the
24672 OpenRISC target support subsystem.
24674 @item show debug or1k
24675 Show whether OpenRISC-specific debugging messages are enabled.
24678 @node PowerPC Embedded
24679 @subsection PowerPC Embedded
24681 @cindex DVC register
24682 @value{GDBN} supports using the DVC (Data Value Compare) register to
24683 implement in hardware simple hardware watchpoint conditions of the form:
24686 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
24687 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
24690 The DVC register will be automatically used when @value{GDBN} detects
24691 such pattern in a condition expression, and the created watchpoint uses one
24692 debug register (either the @code{exact-watchpoints} option is on and the
24693 variable is scalar, or the variable has a length of one byte). This feature
24694 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
24697 When running on PowerPC embedded processors, @value{GDBN} automatically uses
24698 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
24699 in which case watchpoints using only one debug register are created when
24700 watching variables of scalar types.
24702 You can create an artificial array to watch an arbitrary memory
24703 region using one of the following commands (@pxref{Expressions}):
24706 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
24707 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
24710 PowerPC embedded processors support masked watchpoints. See the discussion
24711 about the @code{mask} argument in @ref{Set Watchpoints}.
24713 @cindex ranged breakpoint
24714 PowerPC embedded processors support hardware accelerated
24715 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
24716 the inferior whenever it executes an instruction at any address within
24717 the range it specifies. To set a ranged breakpoint in @value{GDBN},
24718 use the @code{break-range} command.
24720 @value{GDBN} provides the following PowerPC-specific commands:
24723 @kindex break-range
24724 @item break-range @var{start-location}, @var{end-location}
24725 Set a breakpoint for an address range given by
24726 @var{start-location} and @var{end-location}, which can specify a function name,
24727 a line number, an offset of lines from the current line or from the start
24728 location, or an address of an instruction (see @ref{Specify Location},
24729 for a list of all the possible ways to specify a @var{location}.)
24730 The breakpoint will stop execution of the inferior whenever it
24731 executes an instruction at any address within the specified range,
24732 (including @var{start-location} and @var{end-location}.)
24734 @kindex set powerpc
24735 @item set powerpc soft-float
24736 @itemx show powerpc soft-float
24737 Force @value{GDBN} to use (or not use) a software floating point calling
24738 convention. By default, @value{GDBN} selects the calling convention based
24739 on the selected architecture and the provided executable file.
24741 @item set powerpc vector-abi
24742 @itemx show powerpc vector-abi
24743 Force @value{GDBN} to use the specified calling convention for vector
24744 arguments and return values. The valid options are @samp{auto};
24745 @samp{generic}, to avoid vector registers even if they are present;
24746 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
24747 registers. By default, @value{GDBN} selects the calling convention
24748 based on the selected architecture and the provided executable file.
24750 @item set powerpc exact-watchpoints
24751 @itemx show powerpc exact-watchpoints
24752 Allow @value{GDBN} to use only one debug register when watching a variable
24753 of scalar type, thus assuming that the variable is accessed through the
24754 address of its first byte.
24759 @subsection Atmel AVR
24762 When configured for debugging the Atmel AVR, @value{GDBN} supports the
24763 following AVR-specific commands:
24766 @item info io_registers
24767 @kindex info io_registers@r{, AVR}
24768 @cindex I/O registers (Atmel AVR)
24769 This command displays information about the AVR I/O registers. For
24770 each register, @value{GDBN} prints its number and value.
24777 When configured for debugging CRIS, @value{GDBN} provides the
24778 following CRIS-specific commands:
24781 @item set cris-version @var{ver}
24782 @cindex CRIS version
24783 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
24784 The CRIS version affects register names and sizes. This command is useful in
24785 case autodetection of the CRIS version fails.
24787 @item show cris-version
24788 Show the current CRIS version.
24790 @item set cris-dwarf2-cfi
24791 @cindex DWARF-2 CFI and CRIS
24792 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
24793 Change to @samp{off} when using @code{gcc-cris} whose version is below
24796 @item show cris-dwarf2-cfi
24797 Show the current state of using DWARF-2 CFI.
24799 @item set cris-mode @var{mode}
24801 Set the current CRIS mode to @var{mode}. It should only be changed when
24802 debugging in guru mode, in which case it should be set to
24803 @samp{guru} (the default is @samp{normal}).
24805 @item show cris-mode
24806 Show the current CRIS mode.
24810 @subsection Renesas Super-H
24813 For the Renesas Super-H processor, @value{GDBN} provides these
24817 @item set sh calling-convention @var{convention}
24818 @kindex set sh calling-convention
24819 Set the calling-convention used when calling functions from @value{GDBN}.
24820 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
24821 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
24822 convention. If the DWARF-2 information of the called function specifies
24823 that the function follows the Renesas calling convention, the function
24824 is called using the Renesas calling convention. If the calling convention
24825 is set to @samp{renesas}, the Renesas calling convention is always used,
24826 regardless of the DWARF-2 information. This can be used to override the
24827 default of @samp{gcc} if debug information is missing, or the compiler
24828 does not emit the DWARF-2 calling convention entry for a function.
24830 @item show sh calling-convention
24831 @kindex show sh calling-convention
24832 Show the current calling convention setting.
24837 @node Architectures
24838 @section Architectures
24840 This section describes characteristics of architectures that affect
24841 all uses of @value{GDBN} with the architecture, both native and cross.
24848 * HPPA:: HP PA architecture
24856 @subsection AArch64
24857 @cindex AArch64 support
24859 When @value{GDBN} is debugging the AArch64 architecture, it provides the
24860 following special commands:
24863 @item set debug aarch64
24864 @kindex set debug aarch64
24865 This command determines whether AArch64 architecture-specific debugging
24866 messages are to be displayed.
24868 @item show debug aarch64
24869 Show whether AArch64 debugging messages are displayed.
24873 @subsubsection AArch64 SVE.
24874 @cindex AArch64 SVE.
24876 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
24877 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
24878 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
24879 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
24880 @code{$vg} will be provided. This is the vector granule for the current thread
24881 and represents the number of 64-bit chunks in an SVE @code{z} register.
24883 If the vector length changes, then the @code{$vg} register will be updated,
24884 but the lengths of the @code{z} and @code{p} registers will not change. This
24885 is a known limitation of @value{GDBN} and does not affect the execution of the
24888 @subsubsection AArch64 Pointer Authentication.
24889 @cindex AArch64 Pointer Authentication.
24891 When @value{GDBN} is debugging the AArch64 architecture, and the program is
24892 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
24893 register @code{$lr} is pointing to an PAC function its value will be masked.
24894 When GDB prints a backtrace, any addresses that required unmasking will be
24895 postfixed with the marker [PAC]. When using the MI, this is printed as part
24896 of the @code{addr_flags} field.
24899 @subsection x86 Architecture-specific Issues
24902 @item set struct-convention @var{mode}
24903 @kindex set struct-convention
24904 @cindex struct return convention
24905 @cindex struct/union returned in registers
24906 Set the convention used by the inferior to return @code{struct}s and
24907 @code{union}s from functions to @var{mode}. Possible values of
24908 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
24909 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
24910 are returned on the stack, while @code{"reg"} means that a
24911 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
24912 be returned in a register.
24914 @item show struct-convention
24915 @kindex show struct-convention
24916 Show the current setting of the convention to return @code{struct}s
24921 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
24922 @cindex Intel Memory Protection Extensions (MPX).
24924 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
24925 @footnote{The register named with capital letters represent the architecture
24926 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
24927 which are the lower bound and upper bound. Bounds are effective addresses or
24928 memory locations. The upper bounds are architecturally represented in 1's
24929 complement form. A bound having lower bound = 0, and upper bound = 0
24930 (1's complement of all bits set) will allow access to the entire address space.
24932 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
24933 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
24934 display the upper bound performing the complement of one operation on the
24935 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
24936 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
24937 can also be noted that the upper bounds are inclusive.
24939 As an example, assume that the register BND0 holds bounds for a pointer having
24940 access allowed for the range between 0x32 and 0x71. The values present on
24941 bnd0raw and bnd registers are presented as follows:
24944 bnd0raw = @{0x32, 0xffffffff8e@}
24945 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
24948 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
24949 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
24950 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
24951 Python, the display includes the memory size, in bits, accessible to
24954 Bounds can also be stored in bounds tables, which are stored in
24955 application memory. These tables store bounds for pointers by specifying
24956 the bounds pointer's value along with its bounds. Evaluating and changing
24957 bounds located in bound tables is therefore interesting while investigating
24958 bugs on MPX context. @value{GDBN} provides commands for this purpose:
24961 @item show mpx bound @var{pointer}
24962 @kindex show mpx bound
24963 Display bounds of the given @var{pointer}.
24965 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
24966 @kindex set mpx bound
24967 Set the bounds of a pointer in the bound table.
24968 This command takes three parameters: @var{pointer} is the pointers
24969 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
24970 for lower and upper bounds respectively.
24973 When you call an inferior function on an Intel MPX enabled program,
24974 GDB sets the inferior's bound registers to the init (disabled) state
24975 before calling the function. As a consequence, bounds checks for the
24976 pointer arguments passed to the function will always pass.
24978 This is necessary because when you call an inferior function, the
24979 program is usually in the middle of the execution of other function.
24980 Since at that point bound registers are in an arbitrary state, not
24981 clearing them would lead to random bound violations in the called
24984 You can still examine the influence of the bound registers on the
24985 execution of the called function by stopping the execution of the
24986 called function at its prologue, setting bound registers, and
24987 continuing the execution. For example:
24991 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
24992 $ print upper (a, b, c, d, 1)
24993 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
24995 @{lbound = 0x0, ubound = ffffffff@} : size -1
24998 At this last step the value of bnd0 can be changed for investigation of bound
24999 violations caused along the execution of the call. In order to know how to
25000 set the bound registers or bound table for the call consult the ABI.
25005 See the following section.
25008 @subsection @acronym{MIPS}
25010 @cindex stack on Alpha
25011 @cindex stack on @acronym{MIPS}
25012 @cindex Alpha stack
25013 @cindex @acronym{MIPS} stack
25014 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
25015 sometimes requires @value{GDBN} to search backward in the object code to
25016 find the beginning of a function.
25018 @cindex response time, @acronym{MIPS} debugging
25019 To improve response time (especially for embedded applications, where
25020 @value{GDBN} may be restricted to a slow serial line for this search)
25021 you may want to limit the size of this search, using one of these
25025 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
25026 @item set heuristic-fence-post @var{limit}
25027 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
25028 search for the beginning of a function. A value of @var{0} (the
25029 default) means there is no limit. However, except for @var{0}, the
25030 larger the limit the more bytes @code{heuristic-fence-post} must search
25031 and therefore the longer it takes to run. You should only need to use
25032 this command when debugging a stripped executable.
25034 @item show heuristic-fence-post
25035 Display the current limit.
25039 These commands are available @emph{only} when @value{GDBN} is configured
25040 for debugging programs on Alpha or @acronym{MIPS} processors.
25042 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
25046 @item set mips abi @var{arg}
25047 @kindex set mips abi
25048 @cindex set ABI for @acronym{MIPS}
25049 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
25050 values of @var{arg} are:
25054 The default ABI associated with the current binary (this is the
25064 @item show mips abi
25065 @kindex show mips abi
25066 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
25068 @item set mips compression @var{arg}
25069 @kindex set mips compression
25070 @cindex code compression, @acronym{MIPS}
25071 Tell @value{GDBN} which @acronym{MIPS} compressed
25072 @acronym{ISA, Instruction Set Architecture} encoding is used by the
25073 inferior. @value{GDBN} uses this for code disassembly and other
25074 internal interpretation purposes. This setting is only referred to
25075 when no executable has been associated with the debugging session or
25076 the executable does not provide information about the encoding it uses.
25077 Otherwise this setting is automatically updated from information
25078 provided by the executable.
25080 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
25081 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
25082 executables containing @acronym{MIPS16} code frequently are not
25083 identified as such.
25085 This setting is ``sticky''; that is, it retains its value across
25086 debugging sessions until reset either explicitly with this command or
25087 implicitly from an executable.
25089 The compiler and/or assembler typically add symbol table annotations to
25090 identify functions compiled for the @acronym{MIPS16} or
25091 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
25092 are present, @value{GDBN} uses them in preference to the global
25093 compressed @acronym{ISA} encoding setting.
25095 @item show mips compression
25096 @kindex show mips compression
25097 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
25098 @value{GDBN} to debug the inferior.
25101 @itemx show mipsfpu
25102 @xref{MIPS Embedded, set mipsfpu}.
25104 @item set mips mask-address @var{arg}
25105 @kindex set mips mask-address
25106 @cindex @acronym{MIPS} addresses, masking
25107 This command determines whether the most-significant 32 bits of 64-bit
25108 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
25109 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
25110 setting, which lets @value{GDBN} determine the correct value.
25112 @item show mips mask-address
25113 @kindex show mips mask-address
25114 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
25117 @item set remote-mips64-transfers-32bit-regs
25118 @kindex set remote-mips64-transfers-32bit-regs
25119 This command controls compatibility with 64-bit @acronym{MIPS} targets that
25120 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
25121 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
25122 and 64 bits for other registers, set this option to @samp{on}.
25124 @item show remote-mips64-transfers-32bit-regs
25125 @kindex show remote-mips64-transfers-32bit-regs
25126 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
25128 @item set debug mips
25129 @kindex set debug mips
25130 This command turns on and off debugging messages for the @acronym{MIPS}-specific
25131 target code in @value{GDBN}.
25133 @item show debug mips
25134 @kindex show debug mips
25135 Show the current setting of @acronym{MIPS} debugging messages.
25141 @cindex HPPA support
25143 When @value{GDBN} is debugging the HP PA architecture, it provides the
25144 following special commands:
25147 @item set debug hppa
25148 @kindex set debug hppa
25149 This command determines whether HPPA architecture-specific debugging
25150 messages are to be displayed.
25152 @item show debug hppa
25153 Show whether HPPA debugging messages are displayed.
25155 @item maint print unwind @var{address}
25156 @kindex maint print unwind@r{, HPPA}
25157 This command displays the contents of the unwind table entry at the
25158 given @var{address}.
25164 @subsection PowerPC
25165 @cindex PowerPC architecture
25167 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
25168 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
25169 numbers stored in the floating point registers. These values must be stored
25170 in two consecutive registers, always starting at an even register like
25171 @code{f0} or @code{f2}.
25173 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
25174 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
25175 @code{f2} and @code{f3} for @code{$dl1} and so on.
25177 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
25178 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
25181 @subsection Nios II
25182 @cindex Nios II architecture
25184 When @value{GDBN} is debugging the Nios II architecture,
25185 it provides the following special commands:
25189 @item set debug nios2
25190 @kindex set debug nios2
25191 This command turns on and off debugging messages for the Nios II
25192 target code in @value{GDBN}.
25194 @item show debug nios2
25195 @kindex show debug nios2
25196 Show the current setting of Nios II debugging messages.
25200 @subsection Sparc64
25201 @cindex Sparc64 support
25202 @cindex Application Data Integrity
25203 @subsubsection ADI Support
25205 The M7 processor supports an Application Data Integrity (ADI) feature that
25206 detects invalid data accesses. When software allocates memory and enables
25207 ADI on the allocated memory, it chooses a 4-bit version number, sets the
25208 version in the upper 4 bits of the 64-bit pointer to that data, and stores
25209 the 4-bit version in every cacheline of that data. Hardware saves the latter
25210 in spare bits in the cache and memory hierarchy. On each load and store,
25211 the processor compares the upper 4 VA (virtual address) bits to the
25212 cacheline's version. If there is a mismatch, the processor generates a
25213 version mismatch trap which can be either precise or disrupting. The trap
25214 is an error condition which the kernel delivers to the process as a SIGSEGV
25217 Note that only 64-bit applications can use ADI and need to be built with
25220 Values of the ADI version tags, which are in granularity of a
25221 cacheline (64 bytes), can be viewed or modified.
25225 @kindex adi examine
25226 @item adi (examine | x) [ / @var{n} ] @var{addr}
25228 The @code{adi examine} command displays the value of one ADI version tag per
25231 @var{n} is a decimal integer specifying the number in bytes; the default
25232 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
25233 block size, to display.
25235 @var{addr} is the address in user address space where you want @value{GDBN}
25236 to begin displaying the ADI version tags.
25238 Below is an example of displaying ADI versions of variable "shmaddr".
25241 (@value{GDBP}) adi x/100 shmaddr
25242 0xfff800010002c000: 0 0
25246 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
25248 The @code{adi assign} command is used to assign new ADI version tag
25251 @var{n} is a decimal integer specifying the number in bytes;
25252 the default is 1. It specifies how much ADI version information, at the
25253 ratio of 1:ADI block size, to modify.
25255 @var{addr} is the address in user address space where you want @value{GDBN}
25256 to begin modifying the ADI version tags.
25258 @var{tag} is the new ADI version tag.
25260 For example, do the following to modify then verify ADI versions of
25261 variable "shmaddr":
25264 (@value{GDBP}) adi a/100 shmaddr = 7
25265 (@value{GDBP}) adi x/100 shmaddr
25266 0xfff800010002c000: 7 7
25273 @cindex S12Z support
25275 When @value{GDBN} is debugging the S12Z architecture,
25276 it provides the following special command:
25279 @item maint info bdccsr
25280 @kindex maint info bdccsr@r{, S12Z}
25281 This command displays the current value of the microprocessor's
25286 @node Controlling GDB
25287 @chapter Controlling @value{GDBN}
25289 You can alter the way @value{GDBN} interacts with you by using the
25290 @code{set} command. For commands controlling how @value{GDBN} displays
25291 data, see @ref{Print Settings, ,Print Settings}. Other settings are
25296 * Editing:: Command editing
25297 * Command History:: Command history
25298 * Screen Size:: Screen size
25299 * Output Styling:: Output styling
25300 * Numbers:: Numbers
25301 * ABI:: Configuring the current ABI
25302 * Auto-loading:: Automatically loading associated files
25303 * Messages/Warnings:: Optional warnings and messages
25304 * Debugging Output:: Optional messages about internal happenings
25305 * Other Misc Settings:: Other Miscellaneous Settings
25313 @value{GDBN} indicates its readiness to read a command by printing a string
25314 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
25315 can change the prompt string with the @code{set prompt} command. For
25316 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
25317 the prompt in one of the @value{GDBN} sessions so that you can always tell
25318 which one you are talking to.
25320 @emph{Note:} @code{set prompt} does not add a space for you after the
25321 prompt you set. This allows you to set a prompt which ends in a space
25322 or a prompt that does not.
25326 @item set prompt @var{newprompt}
25327 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
25329 @kindex show prompt
25331 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
25334 Versions of @value{GDBN} that ship with Python scripting enabled have
25335 prompt extensions. The commands for interacting with these extensions
25339 @kindex set extended-prompt
25340 @item set extended-prompt @var{prompt}
25341 Set an extended prompt that allows for substitutions.
25342 @xref{gdb.prompt}, for a list of escape sequences that can be used for
25343 substitution. Any escape sequences specified as part of the prompt
25344 string are replaced with the corresponding strings each time the prompt
25350 set extended-prompt Current working directory: \w (gdb)
25353 Note that when an extended-prompt is set, it takes control of the
25354 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
25356 @kindex show extended-prompt
25357 @item show extended-prompt
25358 Prints the extended prompt. Any escape sequences specified as part of
25359 the prompt string with @code{set extended-prompt}, are replaced with the
25360 corresponding strings each time the prompt is displayed.
25364 @section Command Editing
25366 @cindex command line editing
25368 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
25369 @sc{gnu} library provides consistent behavior for programs which provide a
25370 command line interface to the user. Advantages are @sc{gnu} Emacs-style
25371 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
25372 substitution, and a storage and recall of command history across
25373 debugging sessions.
25375 You may control the behavior of command line editing in @value{GDBN} with the
25376 command @code{set}.
25379 @kindex set editing
25382 @itemx set editing on
25383 Enable command line editing (enabled by default).
25385 @item set editing off
25386 Disable command line editing.
25388 @kindex show editing
25390 Show whether command line editing is enabled.
25393 @ifset SYSTEM_READLINE
25394 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
25396 @ifclear SYSTEM_READLINE
25397 @xref{Command Line Editing},
25399 for more details about the Readline
25400 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
25401 encouraged to read that chapter.
25403 @cindex Readline application name
25404 @value{GDBN} sets the Readline application name to @samp{gdb}. This
25405 is useful for conditions in @file{.inputrc}.
25407 @cindex operate-and-get-next
25408 @value{GDBN} defines a bindable Readline command,
25409 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
25410 This command accepts the current line for execution and fetches the
25411 next line relative to the current line from the history for editing.
25412 Any argument is ignored.
25414 @node Command History
25415 @section Command History
25416 @cindex command history
25418 @value{GDBN} can keep track of the commands you type during your
25419 debugging sessions, so that you can be certain of precisely what
25420 happened. Use these commands to manage the @value{GDBN} command
25423 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
25424 package, to provide the history facility.
25425 @ifset SYSTEM_READLINE
25426 @xref{Using History Interactively, , , history, GNU History Library},
25428 @ifclear SYSTEM_READLINE
25429 @xref{Using History Interactively},
25431 for the detailed description of the History library.
25433 To issue a command to @value{GDBN} without affecting certain aspects of
25434 the state which is seen by users, prefix it with @samp{server }
25435 (@pxref{Server Prefix}). This
25436 means that this command will not affect the command history, nor will it
25437 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
25438 pressed on a line by itself.
25440 @cindex @code{server}, command prefix
25441 The server prefix does not affect the recording of values into the value
25442 history; to print a value without recording it into the value history,
25443 use the @code{output} command instead of the @code{print} command.
25445 Here is the description of @value{GDBN} commands related to command
25449 @cindex history substitution
25450 @cindex history file
25451 @kindex set history filename
25452 @cindex @env{GDBHISTFILE}, environment variable
25453 @item set history filename @r{[}@var{fname}@r{]}
25454 Set the name of the @value{GDBN} command history file to @var{fname}.
25455 This is the file where @value{GDBN} reads an initial command history
25456 list, and where it writes the command history from this session when it
25457 exits. You can access this list through history expansion or through
25458 the history command editing characters listed below. This file defaults
25459 to the value of the environment variable @code{GDBHISTFILE}, or to
25460 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
25463 The @code{GDBHISTFILE} environment variable is read after processing
25464 any @value{GDBN} initialization files (@pxref{Startup}) and after
25465 processing any commands passed using command line options (for
25466 example, @code{-ex}).
25468 If the @var{fname} argument is not given, or if the @code{GDBHISTFILE}
25469 is the empty string then @value{GDBN} will neither try to load an
25470 existing history file, nor will it try to save the history on exit.
25472 @cindex save command history
25473 @kindex set history save
25474 @item set history save
25475 @itemx set history save on
25476 Record command history in a file, whose name may be specified with the
25477 @code{set history filename} command. By default, this option is
25478 disabled. The command history will be recorded when @value{GDBN}
25479 exits. If @code{set history filename} is set to the empty string then
25480 history saving is disabled, even when @code{set history save} is
25483 @item set history save off
25484 Don't record the command history into the file specified by @code{set
25485 history filename} when @value{GDBN} exits.
25487 @cindex history size
25488 @kindex set history size
25489 @cindex @env{GDBHISTSIZE}, environment variable
25490 @item set history size @var{size}
25491 @itemx set history size unlimited
25492 Set the number of commands which @value{GDBN} keeps in its history list.
25493 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
25494 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
25495 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
25496 either a negative number or the empty string, then the number of commands
25497 @value{GDBN} keeps in the history list is unlimited.
25499 The @code{GDBHISTSIZE} environment variable is read after processing
25500 any @value{GDBN} initialization files (@pxref{Startup}) and after
25501 processing any commands passed using command line options (for
25502 example, @code{-ex}).
25504 @cindex remove duplicate history
25505 @kindex set history remove-duplicates
25506 @item set history remove-duplicates @var{count}
25507 @itemx set history remove-duplicates unlimited
25508 Control the removal of duplicate history entries in the command history list.
25509 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
25510 history entries and remove the first entry that is a duplicate of the current
25511 entry being added to the command history list. If @var{count} is
25512 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
25513 removal of duplicate history entries is disabled.
25515 Only history entries added during the current session are considered for
25516 removal. This option is set to 0 by default.
25520 History expansion assigns special meaning to the character @kbd{!}.
25521 @ifset SYSTEM_READLINE
25522 @xref{Event Designators, , , history, GNU History Library},
25524 @ifclear SYSTEM_READLINE
25525 @xref{Event Designators},
25529 @cindex history expansion, turn on/off
25530 Since @kbd{!} is also the logical not operator in C, history expansion
25531 is off by default. If you decide to enable history expansion with the
25532 @code{set history expansion on} command, you may sometimes need to
25533 follow @kbd{!} (when it is used as logical not, in an expression) with
25534 a space or a tab to prevent it from being expanded. The readline
25535 history facilities do not attempt substitution on the strings
25536 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
25538 The commands to control history expansion are:
25541 @item set history expansion on
25542 @itemx set history expansion
25543 @kindex set history expansion
25544 Enable history expansion. History expansion is off by default.
25546 @item set history expansion off
25547 Disable history expansion.
25550 @kindex show history
25552 @itemx show history filename
25553 @itemx show history save
25554 @itemx show history size
25555 @itemx show history expansion
25556 These commands display the state of the @value{GDBN} history parameters.
25557 @code{show history} by itself displays all four states.
25562 @kindex show commands
25563 @cindex show last commands
25564 @cindex display command history
25565 @item show commands
25566 Display the last ten commands in the command history.
25568 @item show commands @var{n}
25569 Print ten commands centered on command number @var{n}.
25571 @item show commands +
25572 Print ten commands just after the commands last printed.
25576 @section Screen Size
25577 @cindex size of screen
25578 @cindex screen size
25581 @cindex pauses in output
25583 Certain commands to @value{GDBN} may produce large amounts of
25584 information output to the screen. To help you read all of it,
25585 @value{GDBN} pauses and asks you for input at the end of each page of
25586 output. Type @key{RET} when you want to see one more page of output,
25587 @kbd{q} to discard the remaining output, or @kbd{c} to continue
25588 without paging for the rest of the current command. Also, the screen
25589 width setting determines when to wrap lines of output. Depending on
25590 what is being printed, @value{GDBN} tries to break the line at a
25591 readable place, rather than simply letting it overflow onto the
25594 Normally @value{GDBN} knows the size of the screen from the terminal
25595 driver software. For example, on Unix @value{GDBN} uses the termcap data base
25596 together with the value of the @code{TERM} environment variable and the
25597 @code{stty rows} and @code{stty cols} settings. If this is not correct,
25598 you can override it with the @code{set height} and @code{set
25605 @kindex show height
25606 @item set height @var{lpp}
25607 @itemx set height unlimited
25609 @itemx set width @var{cpl}
25610 @itemx set width unlimited
25612 These @code{set} commands specify a screen height of @var{lpp} lines and
25613 a screen width of @var{cpl} characters. The associated @code{show}
25614 commands display the current settings.
25616 If you specify a height of either @code{unlimited} or zero lines,
25617 @value{GDBN} does not pause during output no matter how long the
25618 output is. This is useful if output is to a file or to an editor
25621 Likewise, you can specify @samp{set width unlimited} or @samp{set
25622 width 0} to prevent @value{GDBN} from wrapping its output.
25624 @item set pagination on
25625 @itemx set pagination off
25626 @kindex set pagination
25627 Turn the output pagination on or off; the default is on. Turning
25628 pagination off is the alternative to @code{set height unlimited}. Note that
25629 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
25630 Options, -batch}) also automatically disables pagination.
25632 @item show pagination
25633 @kindex show pagination
25634 Show the current pagination mode.
25637 @node Output Styling
25638 @section Output Styling
25644 @value{GDBN} can style its output on a capable terminal. This is
25645 enabled by default on most systems, but disabled by default when in
25646 batch mode (@pxref{Mode Options}). Various style settings are available;
25647 and styles can also be disabled entirely.
25650 @item set style enabled @samp{on|off}
25651 Enable or disable all styling. The default is host-dependent, with
25652 most hosts defaulting to @samp{on}.
25654 @item show style enabled
25655 Show the current state of styling.
25657 @item set style sources @samp{on|off}
25658 Enable or disable source code styling. This affects whether source
25659 code, such as the output of the @code{list} command, is styled. Note
25660 that source styling only works if styling in general is enabled, and
25661 if @value{GDBN} was linked with the GNU Source Highlight library. The
25662 default is @samp{on}.
25664 @item show style sources
25665 Show the current state of source code styling.
25668 Subcommands of @code{set style} control specific forms of styling.
25669 These subcommands all follow the same pattern: each style-able object
25670 can be styled with a foreground color, a background color, and an
25673 For example, the style of file names can be controlled using the
25674 @code{set style filename} group of commands:
25677 @item set style filename background @var{color}
25678 Set the background to @var{color}. Valid colors are @samp{none}
25679 (meaning the terminal's default color), @samp{black}, @samp{red},
25680 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25683 @item set style filename foreground @var{color}
25684 Set the foreground to @var{color}. Valid colors are @samp{none}
25685 (meaning the terminal's default color), @samp{black}, @samp{red},
25686 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
25689 @item set style filename intensity @var{value}
25690 Set the intensity to @var{value}. Valid intensities are @samp{normal}
25691 (the default), @samp{bold}, and @samp{dim}.
25694 The @code{show style} command and its subcommands are styling
25695 a style name in their output using its own style.
25696 So, use @command{show style} to see the complete list of styles,
25697 their characteristics and the visual aspect of each style.
25699 The style-able objects are:
25702 Control the styling of file names. By default, this style's
25703 foreground color is green.
25706 Control the styling of function names. These are managed with the
25707 @code{set style function} family of commands. By default, this
25708 style's foreground color is yellow.
25711 Control the styling of variable names. These are managed with the
25712 @code{set style variable} family of commands. By default, this style's
25713 foreground color is cyan.
25716 Control the styling of addresses. These are managed with the
25717 @code{set style address} family of commands. By default, this style's
25718 foreground color is blue.
25721 Control the styling of titles. These are managed with the
25722 @code{set style title} family of commands. By default, this style's
25723 intensity is bold. Commands are using the title style to improve
25724 the readability of large output. For example, the commands
25725 @command{apropos} and @command{help} are using the title style
25726 for the command names.
25729 Control the styling of highlightings. These are managed with the
25730 @code{set style highlight} family of commands. By default, this style's
25731 foreground color is red. Commands are using the highlight style to draw
25732 the user attention to some specific parts of their output. For example,
25733 the command @command{apropos -v REGEXP} uses the highlight style to
25734 mark the documentation parts matching @var{regexp}.
25737 Control the styling of the TUI border. Note that, unlike other
25738 styling options, only the color of the border can be controlled via
25739 @code{set style}. This was done for compatibility reasons, as TUI
25740 controls to set the border's intensity predated the addition of
25741 general styling to @value{GDBN}. @xref{TUI Configuration}.
25743 @item tui-active-border
25744 Control the styling of the active TUI border; that is, the TUI window
25745 that has the focus.
25751 @cindex number representation
25752 @cindex entering numbers
25754 You can always enter numbers in octal, decimal, or hexadecimal in
25755 @value{GDBN} by the usual conventions: octal numbers begin with
25756 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
25757 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
25758 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
25759 10; likewise, the default display for numbers---when no particular
25760 format is specified---is base 10. You can change the default base for
25761 both input and output with the commands described below.
25764 @kindex set input-radix
25765 @item set input-radix @var{base}
25766 Set the default base for numeric input. Supported choices
25767 for @var{base} are decimal 8, 10, or 16. The base must itself be
25768 specified either unambiguously or using the current input radix; for
25772 set input-radix 012
25773 set input-radix 10.
25774 set input-radix 0xa
25778 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
25779 leaves the input radix unchanged, no matter what it was, since
25780 @samp{10}, being without any leading or trailing signs of its base, is
25781 interpreted in the current radix. Thus, if the current radix is 16,
25782 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
25785 @kindex set output-radix
25786 @item set output-radix @var{base}
25787 Set the default base for numeric display. Supported choices
25788 for @var{base} are decimal 8, 10, or 16. The base must itself be
25789 specified either unambiguously or using the current input radix.
25791 @kindex show input-radix
25792 @item show input-radix
25793 Display the current default base for numeric input.
25795 @kindex show output-radix
25796 @item show output-radix
25797 Display the current default base for numeric display.
25799 @item set radix @r{[}@var{base}@r{]}
25803 These commands set and show the default base for both input and output
25804 of numbers. @code{set radix} sets the radix of input and output to
25805 the same base; without an argument, it resets the radix back to its
25806 default value of 10.
25811 @section Configuring the Current ABI
25813 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
25814 application automatically. However, sometimes you need to override its
25815 conclusions. Use these commands to manage @value{GDBN}'s view of the
25821 @cindex Newlib OS ABI and its influence on the longjmp handling
25823 One @value{GDBN} configuration can debug binaries for multiple operating
25824 system targets, either via remote debugging or native emulation.
25825 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
25826 but you can override its conclusion using the @code{set osabi} command.
25827 One example where this is useful is in debugging of binaries which use
25828 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
25829 not have the same identifying marks that the standard C library for your
25832 When @value{GDBN} is debugging the AArch64 architecture, it provides a
25833 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
25834 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
25835 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
25839 Show the OS ABI currently in use.
25842 With no argument, show the list of registered available OS ABI's.
25844 @item set osabi @var{abi}
25845 Set the current OS ABI to @var{abi}.
25848 @cindex float promotion
25850 Generally, the way that an argument of type @code{float} is passed to a
25851 function depends on whether the function is prototyped. For a prototyped
25852 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
25853 according to the architecture's convention for @code{float}. For unprototyped
25854 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
25855 @code{double} and then passed.
25857 Unfortunately, some forms of debug information do not reliably indicate whether
25858 a function is prototyped. If @value{GDBN} calls a function that is not marked
25859 as prototyped, it consults @kbd{set coerce-float-to-double}.
25862 @kindex set coerce-float-to-double
25863 @item set coerce-float-to-double
25864 @itemx set coerce-float-to-double on
25865 Arguments of type @code{float} will be promoted to @code{double} when passed
25866 to an unprototyped function. This is the default setting.
25868 @item set coerce-float-to-double off
25869 Arguments of type @code{float} will be passed directly to unprototyped
25872 @kindex show coerce-float-to-double
25873 @item show coerce-float-to-double
25874 Show the current setting of promoting @code{float} to @code{double}.
25878 @kindex show cp-abi
25879 @value{GDBN} needs to know the ABI used for your program's C@t{++}
25880 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
25881 used to build your application. @value{GDBN} only fully supports
25882 programs with a single C@t{++} ABI; if your program contains code using
25883 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
25884 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
25885 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
25886 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
25887 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
25888 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
25893 Show the C@t{++} ABI currently in use.
25896 With no argument, show the list of supported C@t{++} ABI's.
25898 @item set cp-abi @var{abi}
25899 @itemx set cp-abi auto
25900 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
25904 @section Automatically loading associated files
25905 @cindex auto-loading
25907 @value{GDBN} sometimes reads files with commands and settings automatically,
25908 without being explicitly told so by the user. We call this feature
25909 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
25910 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
25911 results or introduce security risks (e.g., if the file comes from untrusted
25915 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
25916 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
25918 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
25919 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
25922 There are various kinds of files @value{GDBN} can automatically load.
25923 In addition to these files, @value{GDBN} supports auto-loading code written
25924 in various extension languages. @xref{Auto-loading extensions}.
25926 Note that loading of these associated files (including the local @file{.gdbinit}
25927 file) requires accordingly configured @code{auto-load safe-path}
25928 (@pxref{Auto-loading safe path}).
25930 For these reasons, @value{GDBN} includes commands and options to let you
25931 control when to auto-load files and which files should be auto-loaded.
25934 @anchor{set auto-load off}
25935 @kindex set auto-load off
25936 @item set auto-load off
25937 Globally disable loading of all auto-loaded files.
25938 You may want to use this command with the @samp{-iex} option
25939 (@pxref{Option -init-eval-command}) such as:
25941 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
25944 Be aware that system init file (@pxref{System-wide configuration})
25945 and init files from your home directory (@pxref{Home Directory Init File})
25946 still get read (as they come from generally trusted directories).
25947 To prevent @value{GDBN} from auto-loading even those init files, use the
25948 @option{-nx} option (@pxref{Mode Options}), in addition to
25949 @code{set auto-load no}.
25951 @anchor{show auto-load}
25952 @kindex show auto-load
25953 @item show auto-load
25954 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
25958 (gdb) show auto-load
25959 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
25960 libthread-db: Auto-loading of inferior specific libthread_db is on.
25961 local-gdbinit: Auto-loading of .gdbinit script from current directory
25963 python-scripts: Auto-loading of Python scripts is on.
25964 safe-path: List of directories from which it is safe to auto-load files
25965 is $debugdir:$datadir/auto-load.
25966 scripts-directory: List of directories from which to load auto-loaded scripts
25967 is $debugdir:$datadir/auto-load.
25970 @anchor{info auto-load}
25971 @kindex info auto-load
25972 @item info auto-load
25973 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
25977 (gdb) info auto-load
25980 Yes /home/user/gdb/gdb-gdb.gdb
25981 libthread-db: No auto-loaded libthread-db.
25982 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
25986 Yes /home/user/gdb/gdb-gdb.py
25990 These are @value{GDBN} control commands for the auto-loading:
25992 @multitable @columnfractions .5 .5
25993 @item @xref{set auto-load off}.
25994 @tab Disable auto-loading globally.
25995 @item @xref{show auto-load}.
25996 @tab Show setting of all kinds of files.
25997 @item @xref{info auto-load}.
25998 @tab Show state of all kinds of files.
25999 @item @xref{set auto-load gdb-scripts}.
26000 @tab Control for @value{GDBN} command scripts.
26001 @item @xref{show auto-load gdb-scripts}.
26002 @tab Show setting of @value{GDBN} command scripts.
26003 @item @xref{info auto-load gdb-scripts}.
26004 @tab Show state of @value{GDBN} command scripts.
26005 @item @xref{set auto-load python-scripts}.
26006 @tab Control for @value{GDBN} Python scripts.
26007 @item @xref{show auto-load python-scripts}.
26008 @tab Show setting of @value{GDBN} Python scripts.
26009 @item @xref{info auto-load python-scripts}.
26010 @tab Show state of @value{GDBN} Python scripts.
26011 @item @xref{set auto-load guile-scripts}.
26012 @tab Control for @value{GDBN} Guile scripts.
26013 @item @xref{show auto-load guile-scripts}.
26014 @tab Show setting of @value{GDBN} Guile scripts.
26015 @item @xref{info auto-load guile-scripts}.
26016 @tab Show state of @value{GDBN} Guile scripts.
26017 @item @xref{set auto-load scripts-directory}.
26018 @tab Control for @value{GDBN} auto-loaded scripts location.
26019 @item @xref{show auto-load scripts-directory}.
26020 @tab Show @value{GDBN} auto-loaded scripts location.
26021 @item @xref{add-auto-load-scripts-directory}.
26022 @tab Add directory for auto-loaded scripts location list.
26023 @item @xref{set auto-load local-gdbinit}.
26024 @tab Control for init file in the current directory.
26025 @item @xref{show auto-load local-gdbinit}.
26026 @tab Show setting of init file in the current directory.
26027 @item @xref{info auto-load local-gdbinit}.
26028 @tab Show state of init file in the current directory.
26029 @item @xref{set auto-load libthread-db}.
26030 @tab Control for thread debugging library.
26031 @item @xref{show auto-load libthread-db}.
26032 @tab Show setting of thread debugging library.
26033 @item @xref{info auto-load libthread-db}.
26034 @tab Show state of thread debugging library.
26035 @item @xref{set auto-load safe-path}.
26036 @tab Control directories trusted for automatic loading.
26037 @item @xref{show auto-load safe-path}.
26038 @tab Show directories trusted for automatic loading.
26039 @item @xref{add-auto-load-safe-path}.
26040 @tab Add directory trusted for automatic loading.
26043 @node Init File in the Current Directory
26044 @subsection Automatically loading init file in the current directory
26045 @cindex auto-loading init file in the current directory
26047 By default, @value{GDBN} reads and executes the canned sequences of commands
26048 from init file (if any) in the current working directory,
26049 see @ref{Init File in the Current Directory during Startup}.
26051 Note that loading of this local @file{.gdbinit} file also requires accordingly
26052 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26055 @anchor{set auto-load local-gdbinit}
26056 @kindex set auto-load local-gdbinit
26057 @item set auto-load local-gdbinit [on|off]
26058 Enable or disable the auto-loading of canned sequences of commands
26059 (@pxref{Sequences}) found in init file in the current directory.
26061 @anchor{show auto-load local-gdbinit}
26062 @kindex show auto-load local-gdbinit
26063 @item show auto-load local-gdbinit
26064 Show whether auto-loading of canned sequences of commands from init file in the
26065 current directory is enabled or disabled.
26067 @anchor{info auto-load local-gdbinit}
26068 @kindex info auto-load local-gdbinit
26069 @item info auto-load local-gdbinit
26070 Print whether canned sequences of commands from init file in the
26071 current directory have been auto-loaded.
26074 @node libthread_db.so.1 file
26075 @subsection Automatically loading thread debugging library
26076 @cindex auto-loading libthread_db.so.1
26078 This feature is currently present only on @sc{gnu}/Linux native hosts.
26080 @value{GDBN} reads in some cases thread debugging library from places specific
26081 to the inferior (@pxref{set libthread-db-search-path}).
26083 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
26084 without checking this @samp{set auto-load libthread-db} switch as system
26085 libraries have to be trusted in general. In all other cases of
26086 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
26087 auto-load libthread-db} is enabled before trying to open such thread debugging
26090 Note that loading of this debugging library also requires accordingly configured
26091 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26094 @anchor{set auto-load libthread-db}
26095 @kindex set auto-load libthread-db
26096 @item set auto-load libthread-db [on|off]
26097 Enable or disable the auto-loading of inferior specific thread debugging library.
26099 @anchor{show auto-load libthread-db}
26100 @kindex show auto-load libthread-db
26101 @item show auto-load libthread-db
26102 Show whether auto-loading of inferior specific thread debugging library is
26103 enabled or disabled.
26105 @anchor{info auto-load libthread-db}
26106 @kindex info auto-load libthread-db
26107 @item info auto-load libthread-db
26108 Print the list of all loaded inferior specific thread debugging libraries and
26109 for each such library print list of inferior @var{pid}s using it.
26112 @node Auto-loading safe path
26113 @subsection Security restriction for auto-loading
26114 @cindex auto-loading safe-path
26116 As the files of inferior can come from untrusted source (such as submitted by
26117 an application user) @value{GDBN} does not always load any files automatically.
26118 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
26119 directories trusted for loading files not explicitly requested by user.
26120 Each directory can also be a shell wildcard pattern.
26122 If the path is not set properly you will see a warning and the file will not
26127 Reading symbols from /home/user/gdb/gdb...
26128 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
26129 declined by your `auto-load safe-path' set
26130 to "$debugdir:$datadir/auto-load".
26131 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
26132 declined by your `auto-load safe-path' set
26133 to "$debugdir:$datadir/auto-load".
26137 To instruct @value{GDBN} to go ahead and use the init files anyway,
26138 invoke @value{GDBN} like this:
26141 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
26144 The list of trusted directories is controlled by the following commands:
26147 @anchor{set auto-load safe-path}
26148 @kindex set auto-load safe-path
26149 @item set auto-load safe-path @r{[}@var{directories}@r{]}
26150 Set the list of directories (and their subdirectories) trusted for automatic
26151 loading and execution of scripts. You can also enter a specific trusted file.
26152 Each directory can also be a shell wildcard pattern; wildcards do not match
26153 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
26154 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
26155 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
26156 its default value as specified during @value{GDBN} compilation.
26158 The list of directories uses path separator (@samp{:} on GNU and Unix
26159 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26160 to the @env{PATH} environment variable.
26162 @anchor{show auto-load safe-path}
26163 @kindex show auto-load safe-path
26164 @item show auto-load safe-path
26165 Show the list of directories trusted for automatic loading and execution of
26168 @anchor{add-auto-load-safe-path}
26169 @kindex add-auto-load-safe-path
26170 @item add-auto-load-safe-path
26171 Add an entry (or list of entries) to the list of directories trusted for
26172 automatic loading and execution of scripts. Multiple entries may be delimited
26173 by the host platform path separator in use.
26176 This variable defaults to what @code{--with-auto-load-dir} has been configured
26177 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
26178 substitution applies the same as for @ref{set auto-load scripts-directory}.
26179 The default @code{set auto-load safe-path} value can be also overriden by
26180 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
26182 Setting this variable to @file{/} disables this security protection,
26183 corresponding @value{GDBN} configuration option is
26184 @option{--without-auto-load-safe-path}.
26185 This variable is supposed to be set to the system directories writable by the
26186 system superuser only. Users can add their source directories in init files in
26187 their home directories (@pxref{Home Directory Init File}). See also deprecated
26188 init file in the current directory
26189 (@pxref{Init File in the Current Directory during Startup}).
26191 To force @value{GDBN} to load the files it declined to load in the previous
26192 example, you could use one of the following ways:
26195 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
26196 Specify this trusted directory (or a file) as additional component of the list.
26197 You have to specify also any existing directories displayed by
26198 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
26200 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
26201 Specify this directory as in the previous case but just for a single
26202 @value{GDBN} session.
26204 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
26205 Disable auto-loading safety for a single @value{GDBN} session.
26206 This assumes all the files you debug during this @value{GDBN} session will come
26207 from trusted sources.
26209 @item @kbd{./configure --without-auto-load-safe-path}
26210 During compilation of @value{GDBN} you may disable any auto-loading safety.
26211 This assumes all the files you will ever debug with this @value{GDBN} come from
26215 On the other hand you can also explicitly forbid automatic files loading which
26216 also suppresses any such warning messages:
26219 @item @kbd{gdb -iex "set auto-load no" @dots{}}
26220 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
26222 @item @file{~/.gdbinit}: @samp{set auto-load no}
26223 Disable auto-loading globally for the user
26224 (@pxref{Home Directory Init File}). While it is improbable, you could also
26225 use system init file instead (@pxref{System-wide configuration}).
26228 This setting applies to the file names as entered by user. If no entry matches
26229 @value{GDBN} tries as a last resort to also resolve all the file names into
26230 their canonical form (typically resolving symbolic links) and compare the
26231 entries again. @value{GDBN} already canonicalizes most of the filenames on its
26232 own before starting the comparison so a canonical form of directories is
26233 recommended to be entered.
26235 @node Auto-loading verbose mode
26236 @subsection Displaying files tried for auto-load
26237 @cindex auto-loading verbose mode
26239 For better visibility of all the file locations where you can place scripts to
26240 be auto-loaded with inferior --- or to protect yourself against accidental
26241 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
26242 all the files attempted to be loaded. Both existing and non-existing files may
26245 For example the list of directories from which it is safe to auto-load files
26246 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
26247 may not be too obvious while setting it up.
26250 (gdb) set debug auto-load on
26251 (gdb) file ~/src/t/true
26252 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
26253 for objfile "/tmp/true".
26254 auto-load: Updating directories of "/usr:/opt".
26255 auto-load: Using directory "/usr".
26256 auto-load: Using directory "/opt".
26257 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
26258 by your `auto-load safe-path' set to "/usr:/opt".
26262 @anchor{set debug auto-load}
26263 @kindex set debug auto-load
26264 @item set debug auto-load [on|off]
26265 Set whether to print the filenames attempted to be auto-loaded.
26267 @anchor{show debug auto-load}
26268 @kindex show debug auto-load
26269 @item show debug auto-load
26270 Show whether printing of the filenames attempted to be auto-loaded is turned
26274 @node Messages/Warnings
26275 @section Optional Warnings and Messages
26277 @cindex verbose operation
26278 @cindex optional warnings
26279 By default, @value{GDBN} is silent about its inner workings. If you are
26280 running on a slow machine, you may want to use the @code{set verbose}
26281 command. This makes @value{GDBN} tell you when it does a lengthy
26282 internal operation, so you will not think it has crashed.
26284 Currently, the messages controlled by @code{set verbose} are those
26285 which announce that the symbol table for a source file is being read;
26286 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
26289 @kindex set verbose
26290 @item set verbose on
26291 Enables @value{GDBN} output of certain informational messages.
26293 @item set verbose off
26294 Disables @value{GDBN} output of certain informational messages.
26296 @kindex show verbose
26298 Displays whether @code{set verbose} is on or off.
26301 By default, if @value{GDBN} encounters bugs in the symbol table of an
26302 object file, it is silent; but if you are debugging a compiler, you may
26303 find this information useful (@pxref{Symbol Errors, ,Errors Reading
26308 @kindex set complaints
26309 @item set complaints @var{limit}
26310 Permits @value{GDBN} to output @var{limit} complaints about each type of
26311 unusual symbols before becoming silent about the problem. Set
26312 @var{limit} to zero to suppress all complaints; set it to a large number
26313 to prevent complaints from being suppressed.
26315 @kindex show complaints
26316 @item show complaints
26317 Displays how many symbol complaints @value{GDBN} is permitted to produce.
26321 @anchor{confirmation requests}
26322 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
26323 lot of stupid questions to confirm certain commands. For example, if
26324 you try to run a program which is already running:
26328 The program being debugged has been started already.
26329 Start it from the beginning? (y or n)
26332 If you are willing to unflinchingly face the consequences of your own
26333 commands, you can disable this ``feature'':
26337 @kindex set confirm
26339 @cindex confirmation
26340 @cindex stupid questions
26341 @item set confirm off
26342 Disables confirmation requests. Note that running @value{GDBN} with
26343 the @option{--batch} option (@pxref{Mode Options, -batch}) also
26344 automatically disables confirmation requests.
26346 @item set confirm on
26347 Enables confirmation requests (the default).
26349 @kindex show confirm
26351 Displays state of confirmation requests.
26355 @cindex command tracing
26356 If you need to debug user-defined commands or sourced files you may find it
26357 useful to enable @dfn{command tracing}. In this mode each command will be
26358 printed as it is executed, prefixed with one or more @samp{+} symbols, the
26359 quantity denoting the call depth of each command.
26362 @kindex set trace-commands
26363 @cindex command scripts, debugging
26364 @item set trace-commands on
26365 Enable command tracing.
26366 @item set trace-commands off
26367 Disable command tracing.
26368 @item show trace-commands
26369 Display the current state of command tracing.
26372 @node Debugging Output
26373 @section Optional Messages about Internal Happenings
26374 @cindex optional debugging messages
26376 @value{GDBN} has commands that enable optional debugging messages from
26377 various @value{GDBN} subsystems; normally these commands are of
26378 interest to @value{GDBN} maintainers, or when reporting a bug. This
26379 section documents those commands.
26382 @kindex set exec-done-display
26383 @item set exec-done-display
26384 Turns on or off the notification of asynchronous commands'
26385 completion. When on, @value{GDBN} will print a message when an
26386 asynchronous command finishes its execution. The default is off.
26387 @kindex show exec-done-display
26388 @item show exec-done-display
26389 Displays the current setting of asynchronous command completion
26393 @cindex ARM AArch64
26394 @item set debug aarch64
26395 Turns on or off display of debugging messages related to ARM AArch64.
26396 The default is off.
26398 @item show debug aarch64
26399 Displays the current state of displaying debugging messages related to
26402 @cindex gdbarch debugging info
26403 @cindex architecture debugging info
26404 @item set debug arch
26405 Turns on or off display of gdbarch debugging info. The default is off
26406 @item show debug arch
26407 Displays the current state of displaying gdbarch debugging info.
26409 @item set debug aix-solib
26410 @cindex AIX shared library debugging
26411 Control display of debugging messages from the AIX shared library
26412 support module. The default is off.
26413 @item show debug aix-solib
26414 Show the current state of displaying AIX shared library debugging messages.
26416 @item set debug aix-thread
26417 @cindex AIX threads
26418 Display debugging messages about inner workings of the AIX thread
26420 @item show debug aix-thread
26421 Show the current state of AIX thread debugging info display.
26423 @item set debug check-physname
26425 Check the results of the ``physname'' computation. When reading DWARF
26426 debugging information for C@t{++}, @value{GDBN} attempts to compute
26427 each entity's name. @value{GDBN} can do this computation in two
26428 different ways, depending on exactly what information is present.
26429 When enabled, this setting causes @value{GDBN} to compute the names
26430 both ways and display any discrepancies.
26431 @item show debug check-physname
26432 Show the current state of ``physname'' checking.
26434 @item set debug coff-pe-read
26435 @cindex COFF/PE exported symbols
26436 Control display of debugging messages related to reading of COFF/PE
26437 exported symbols. The default is off.
26438 @item show debug coff-pe-read
26439 Displays the current state of displaying debugging messages related to
26440 reading of COFF/PE exported symbols.
26442 @item set debug dwarf-die
26444 Dump DWARF DIEs after they are read in.
26445 The value is the number of nesting levels to print.
26446 A value of zero turns off the display.
26447 @item show debug dwarf-die
26448 Show the current state of DWARF DIE debugging.
26450 @item set debug dwarf-line
26451 @cindex DWARF Line Tables
26452 Turns on or off display of debugging messages related to reading
26453 DWARF line tables. The default is 0 (off).
26454 A value of 1 provides basic information.
26455 A value greater than 1 provides more verbose information.
26456 @item show debug dwarf-line
26457 Show the current state of DWARF line table debugging.
26459 @item set debug dwarf-read
26460 @cindex DWARF Reading
26461 Turns on or off display of debugging messages related to reading
26462 DWARF debug info. The default is 0 (off).
26463 A value of 1 provides basic information.
26464 A value greater than 1 provides more verbose information.
26465 @item show debug dwarf-read
26466 Show the current state of DWARF reader debugging.
26468 @item set debug displaced
26469 @cindex displaced stepping debugging info
26470 Turns on or off display of @value{GDBN} debugging info for the
26471 displaced stepping support. The default is off.
26472 @item show debug displaced
26473 Displays the current state of displaying @value{GDBN} debugging info
26474 related to displaced stepping.
26476 @item set debug event
26477 @cindex event debugging info
26478 Turns on or off display of @value{GDBN} event debugging info. The
26480 @item show debug event
26481 Displays the current state of displaying @value{GDBN} event debugging
26484 @item set debug expression
26485 @cindex expression debugging info
26486 Turns on or off display of debugging info about @value{GDBN}
26487 expression parsing. The default is off.
26488 @item show debug expression
26489 Displays the current state of displaying debugging info about
26490 @value{GDBN} expression parsing.
26492 @item set debug fbsd-lwp
26493 @cindex FreeBSD LWP debug messages
26494 Turns on or off debugging messages from the FreeBSD LWP debug support.
26495 @item show debug fbsd-lwp
26496 Show the current state of FreeBSD LWP debugging messages.
26498 @item set debug fbsd-nat
26499 @cindex FreeBSD native target debug messages
26500 Turns on or off debugging messages from the FreeBSD native target.
26501 @item show debug fbsd-nat
26502 Show the current state of FreeBSD native target debugging messages.
26504 @item set debug frame
26505 @cindex frame debugging info
26506 Turns on or off display of @value{GDBN} frame debugging info. The
26508 @item show debug frame
26509 Displays the current state of displaying @value{GDBN} frame debugging
26512 @item set debug gnu-nat
26513 @cindex @sc{gnu}/Hurd debug messages
26514 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
26515 @item show debug gnu-nat
26516 Show the current state of @sc{gnu}/Hurd debugging messages.
26518 @item set debug infrun
26519 @cindex inferior debugging info
26520 Turns on or off display of @value{GDBN} debugging info for running the inferior.
26521 The default is off. @file{infrun.c} contains GDB's runtime state machine used
26522 for implementing operations such as single-stepping the inferior.
26523 @item show debug infrun
26524 Displays the current state of @value{GDBN} inferior debugging.
26526 @item set debug jit
26527 @cindex just-in-time compilation, debugging messages
26528 Turn on or off debugging messages from JIT debug support.
26529 @item show debug jit
26530 Displays the current state of @value{GDBN} JIT debugging.
26532 @item set debug lin-lwp
26533 @cindex @sc{gnu}/Linux LWP debug messages
26534 @cindex Linux lightweight processes
26535 Turn on or off debugging messages from the Linux LWP debug support.
26536 @item show debug lin-lwp
26537 Show the current state of Linux LWP debugging messages.
26539 @item set debug linux-namespaces
26540 @cindex @sc{gnu}/Linux namespaces debug messages
26541 Turn on or off debugging messages from the Linux namespaces debug support.
26542 @item show debug linux-namespaces
26543 Show the current state of Linux namespaces debugging messages.
26545 @item set debug mach-o
26546 @cindex Mach-O symbols processing
26547 Control display of debugging messages related to Mach-O symbols
26548 processing. The default is off.
26549 @item show debug mach-o
26550 Displays the current state of displaying debugging messages related to
26551 reading of COFF/PE exported symbols.
26553 @item set debug notification
26554 @cindex remote async notification debugging info
26555 Turn on or off debugging messages about remote async notification.
26556 The default is off.
26557 @item show debug notification
26558 Displays the current state of remote async notification debugging messages.
26560 @item set debug observer
26561 @cindex observer debugging info
26562 Turns on or off display of @value{GDBN} observer debugging. This
26563 includes info such as the notification of observable events.
26564 @item show debug observer
26565 Displays the current state of observer debugging.
26567 @item set debug overload
26568 @cindex C@t{++} overload debugging info
26569 Turns on or off display of @value{GDBN} C@t{++} overload debugging
26570 info. This includes info such as ranking of functions, etc. The default
26572 @item show debug overload
26573 Displays the current state of displaying @value{GDBN} C@t{++} overload
26576 @cindex expression parser, debugging info
26577 @cindex debug expression parser
26578 @item set debug parser
26579 Turns on or off the display of expression parser debugging output.
26580 Internally, this sets the @code{yydebug} variable in the expression
26581 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
26582 details. The default is off.
26583 @item show debug parser
26584 Show the current state of expression parser debugging.
26586 @cindex packets, reporting on stdout
26587 @cindex serial connections, debugging
26588 @cindex debug remote protocol
26589 @cindex remote protocol debugging
26590 @cindex display remote packets
26591 @item set debug remote
26592 Turns on or off display of reports on all packets sent back and forth across
26593 the serial line to the remote machine. The info is printed on the
26594 @value{GDBN} standard output stream. The default is off.
26595 @item show debug remote
26596 Displays the state of display of remote packets.
26598 @item set debug remote-packet-max-chars
26599 Sets the maximum number of characters to display for each remote packet when
26600 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
26601 displaying lengthy remote packets and polluting the console.
26603 The default value is @code{512}, which means @value{GDBN} will truncate each
26604 remote packet after 512 bytes.
26606 Setting this option to @code{unlimited} will disable truncation and will output
26607 the full length of the remote packets.
26608 @item show debug remote-packet-max-chars
26609 Displays the number of bytes to output for remote packet debugging.
26611 @item set debug separate-debug-file
26612 Turns on or off display of debug output about separate debug file search.
26613 @item show debug separate-debug-file
26614 Displays the state of separate debug file search debug output.
26616 @item set debug serial
26617 Turns on or off display of @value{GDBN} serial debugging info. The
26619 @item show debug serial
26620 Displays the current state of displaying @value{GDBN} serial debugging
26623 @item set debug solib-frv
26624 @cindex FR-V shared-library debugging
26625 Turn on or off debugging messages for FR-V shared-library code.
26626 @item show debug solib-frv
26627 Display the current state of FR-V shared-library code debugging
26630 @item set debug symbol-lookup
26631 @cindex symbol lookup
26632 Turns on or off display of debugging messages related to symbol lookup.
26633 The default is 0 (off).
26634 A value of 1 provides basic information.
26635 A value greater than 1 provides more verbose information.
26636 @item show debug symbol-lookup
26637 Show the current state of symbol lookup debugging messages.
26639 @item set debug symfile
26640 @cindex symbol file functions
26641 Turns on or off display of debugging messages related to symbol file functions.
26642 The default is off. @xref{Files}.
26643 @item show debug symfile
26644 Show the current state of symbol file debugging messages.
26646 @item set debug symtab-create
26647 @cindex symbol table creation
26648 Turns on or off display of debugging messages related to symbol table creation.
26649 The default is 0 (off).
26650 A value of 1 provides basic information.
26651 A value greater than 1 provides more verbose information.
26652 @item show debug symtab-create
26653 Show the current state of symbol table creation debugging.
26655 @item set debug target
26656 @cindex target debugging info
26657 Turns on or off display of @value{GDBN} target debugging info. This info
26658 includes what is going on at the target level of GDB, as it happens. The
26659 default is 0. Set it to 1 to track events, and to 2 to also track the
26660 value of large memory transfers.
26661 @item show debug target
26662 Displays the current state of displaying @value{GDBN} target debugging
26665 @item set debug timestamp
26666 @cindex timestamping debugging info
26667 Turns on or off display of timestamps with @value{GDBN} debugging info.
26668 When enabled, seconds and microseconds are displayed before each debugging
26670 @item show debug timestamp
26671 Displays the current state of displaying timestamps with @value{GDBN}
26674 @item set debug varobj
26675 @cindex variable object debugging info
26676 Turns on or off display of @value{GDBN} variable object debugging
26677 info. The default is off.
26678 @item show debug varobj
26679 Displays the current state of displaying @value{GDBN} variable object
26682 @item set debug xml
26683 @cindex XML parser debugging
26684 Turn on or off debugging messages for built-in XML parsers.
26685 @item show debug xml
26686 Displays the current state of XML debugging messages.
26689 @node Other Misc Settings
26690 @section Other Miscellaneous Settings
26691 @cindex miscellaneous settings
26694 @kindex set interactive-mode
26695 @item set interactive-mode
26696 If @code{on}, forces @value{GDBN} to assume that GDB was started
26697 in a terminal. In practice, this means that @value{GDBN} should wait
26698 for the user to answer queries generated by commands entered at
26699 the command prompt. If @code{off}, forces @value{GDBN} to operate
26700 in the opposite mode, and it uses the default answers to all queries.
26701 If @code{auto} (the default), @value{GDBN} tries to determine whether
26702 its standard input is a terminal, and works in interactive-mode if it
26703 is, non-interactively otherwise.
26705 In the vast majority of cases, the debugger should be able to guess
26706 correctly which mode should be used. But this setting can be useful
26707 in certain specific cases, such as running a MinGW @value{GDBN}
26708 inside a cygwin window.
26710 @kindex show interactive-mode
26711 @item show interactive-mode
26712 Displays whether the debugger is operating in interactive mode or not.
26715 @node Extending GDB
26716 @chapter Extending @value{GDBN}
26717 @cindex extending GDB
26719 @value{GDBN} provides several mechanisms for extension.
26720 @value{GDBN} also provides the ability to automatically load
26721 extensions when it reads a file for debugging. This allows the
26722 user to automatically customize @value{GDBN} for the program
26726 * Sequences:: Canned Sequences of @value{GDBN} Commands
26727 * Python:: Extending @value{GDBN} using Python
26728 * Guile:: Extending @value{GDBN} using Guile
26729 * Auto-loading extensions:: Automatically loading extensions
26730 * Multiple Extension Languages:: Working with multiple extension languages
26731 * Aliases:: Creating new spellings of existing commands
26734 To facilitate the use of extension languages, @value{GDBN} is capable
26735 of evaluating the contents of a file. When doing so, @value{GDBN}
26736 can recognize which extension language is being used by looking at
26737 the filename extension. Files with an unrecognized filename extension
26738 are always treated as a @value{GDBN} Command Files.
26739 @xref{Command Files,, Command files}.
26741 You can control how @value{GDBN} evaluates these files with the following
26745 @kindex set script-extension
26746 @kindex show script-extension
26747 @item set script-extension off
26748 All scripts are always evaluated as @value{GDBN} Command Files.
26750 @item set script-extension soft
26751 The debugger determines the scripting language based on filename
26752 extension. If this scripting language is supported, @value{GDBN}
26753 evaluates the script using that language. Otherwise, it evaluates
26754 the file as a @value{GDBN} Command File.
26756 @item set script-extension strict
26757 The debugger determines the scripting language based on filename
26758 extension, and evaluates the script using that language. If the
26759 language is not supported, then the evaluation fails.
26761 @item show script-extension
26762 Display the current value of the @code{script-extension} option.
26766 @ifset SYSTEM_GDBINIT_DIR
26767 This setting is not used for files in the system-wide gdbinit directory.
26768 Files in that directory must have an extension matching their language,
26769 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
26770 commands. @xref{Startup}.
26774 @section Canned Sequences of Commands
26776 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
26777 Command Lists}), @value{GDBN} provides two ways to store sequences of
26778 commands for execution as a unit: user-defined commands and command
26782 * Define:: How to define your own commands
26783 * Hooks:: Hooks for user-defined commands
26784 * Command Files:: How to write scripts of commands to be stored in a file
26785 * Output:: Commands for controlled output
26786 * Auto-loading sequences:: Controlling auto-loaded command files
26790 @subsection User-defined Commands
26792 @cindex user-defined command
26793 @cindex arguments, to user-defined commands
26794 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
26795 which you assign a new name as a command. This is done with the
26796 @code{define} command. User commands may accept an unlimited number of arguments
26797 separated by whitespace. Arguments are accessed within the user command
26798 via @code{$arg0@dots{}$argN}. A trivial example:
26802 print $arg0 + $arg1 + $arg2
26807 To execute the command use:
26814 This defines the command @code{adder}, which prints the sum of
26815 its three arguments. Note the arguments are text substitutions, so they may
26816 reference variables, use complex expressions, or even perform inferior
26819 @cindex argument count in user-defined commands
26820 @cindex how many arguments (user-defined commands)
26821 In addition, @code{$argc} may be used to find out how many arguments have
26827 print $arg0 + $arg1
26830 print $arg0 + $arg1 + $arg2
26835 Combining with the @code{eval} command (@pxref{eval}) makes it easier
26836 to process a variable number of arguments:
26843 eval "set $sum = $sum + $arg%d", $i
26853 @item define @var{commandname}
26854 Define a command named @var{commandname}. If there is already a command
26855 by that name, you are asked to confirm that you want to redefine it.
26856 The argument @var{commandname} may be a bare command name consisting of letters,
26857 numbers, dashes, dots, and underscores. It may also start with any
26858 predefined or user-defined prefix command.
26859 For example, @samp{define target my-target} creates
26860 a user-defined @samp{target my-target} command.
26862 The definition of the command is made up of other @value{GDBN} command lines,
26863 which are given following the @code{define} command. The end of these
26864 commands is marked by a line containing @code{end}.
26867 @kindex end@r{ (user-defined commands)}
26868 @item document @var{commandname}
26869 Document the user-defined command @var{commandname}, so that it can be
26870 accessed by @code{help}. The command @var{commandname} must already be
26871 defined. This command reads lines of documentation just as @code{define}
26872 reads the lines of the command definition, ending with @code{end}.
26873 After the @code{document} command is finished, @code{help} on command
26874 @var{commandname} displays the documentation you have written.
26876 You may use the @code{document} command again to change the
26877 documentation of a command. Redefining the command with @code{define}
26878 does not change the documentation.
26880 @kindex define-prefix
26881 @item define-prefix @var{commandname}
26882 Define or mark the command @var{commandname} as a user-defined prefix
26883 command. Once marked, @var{commandname} can be used as prefix command
26884 by the @code{define} command.
26885 Note that @code{define-prefix} can be used with a not yet defined
26886 @var{commandname}. In such a case, @var{commandname} is defined as
26887 an empty user-defined command.
26888 In case you redefine a command that was marked as a user-defined
26889 prefix command, the subcommands of the redefined command are kept
26890 (and @value{GDBN} indicates so to the user).
26894 (gdb) define-prefix abc
26895 (gdb) define-prefix abc def
26896 (gdb) define abc def
26897 Type commands for definition of "abc def".
26898 End with a line saying just "end".
26899 >echo command initial def\n
26901 (gdb) define abc def ghi
26902 Type commands for definition of "abc def ghi".
26903 End with a line saying just "end".
26904 >echo command ghi\n
26906 (gdb) define abc def
26907 Keeping subcommands of prefix command "def".
26908 Redefine command "def"? (y or n) y
26909 Type commands for definition of "abc def".
26910 End with a line saying just "end".
26911 >echo command def\n
26920 @kindex dont-repeat
26921 @cindex don't repeat command
26923 Used inside a user-defined command, this tells @value{GDBN} that this
26924 command should not be repeated when the user hits @key{RET}
26925 (@pxref{Command Syntax, repeat last command}).
26927 @kindex help user-defined
26928 @item help user-defined
26929 List all user-defined commands and all python commands defined in class
26930 COMMAND_USER. The first line of the documentation or docstring is
26935 @itemx show user @var{commandname}
26936 Display the @value{GDBN} commands used to define @var{commandname} (but
26937 not its documentation). If no @var{commandname} is given, display the
26938 definitions for all user-defined commands.
26939 This does not work for user-defined python commands.
26941 @cindex infinite recursion in user-defined commands
26942 @kindex show max-user-call-depth
26943 @kindex set max-user-call-depth
26944 @item show max-user-call-depth
26945 @itemx set max-user-call-depth
26946 The value of @code{max-user-call-depth} controls how many recursion
26947 levels are allowed in user-defined commands before @value{GDBN} suspects an
26948 infinite recursion and aborts the command.
26949 This does not apply to user-defined python commands.
26952 In addition to the above commands, user-defined commands frequently
26953 use control flow commands, described in @ref{Command Files}.
26955 When user-defined commands are executed, the
26956 commands of the definition are not printed. An error in any command
26957 stops execution of the user-defined command.
26959 If used interactively, commands that would ask for confirmation proceed
26960 without asking when used inside a user-defined command. Many @value{GDBN}
26961 commands that normally print messages to say what they are doing omit the
26962 messages when used in a user-defined command.
26965 @subsection User-defined Command Hooks
26966 @cindex command hooks
26967 @cindex hooks, for commands
26968 @cindex hooks, pre-command
26971 You may define @dfn{hooks}, which are a special kind of user-defined
26972 command. Whenever you run the command @samp{foo}, if the user-defined
26973 command @samp{hook-foo} exists, it is executed (with no arguments)
26974 before that command.
26976 @cindex hooks, post-command
26978 A hook may also be defined which is run after the command you executed.
26979 Whenever you run the command @samp{foo}, if the user-defined command
26980 @samp{hookpost-foo} exists, it is executed (with no arguments) after
26981 that command. Post-execution hooks may exist simultaneously with
26982 pre-execution hooks, for the same command.
26984 It is valid for a hook to call the command which it hooks. If this
26985 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
26987 @c It would be nice if hookpost could be passed a parameter indicating
26988 @c if the command it hooks executed properly or not. FIXME!
26990 @kindex stop@r{, a pseudo-command}
26991 In addition, a pseudo-command, @samp{stop} exists. Defining
26992 (@samp{hook-stop}) makes the associated commands execute every time
26993 execution stops in your program: before breakpoint commands are run,
26994 displays are printed, or the stack frame is printed.
26996 For example, to ignore @code{SIGALRM} signals while
26997 single-stepping, but treat them normally during normal execution,
27002 handle SIGALRM nopass
27006 handle SIGALRM pass
27009 define hook-continue
27010 handle SIGALRM pass
27014 As a further example, to hook at the beginning and end of the @code{echo}
27015 command, and to add extra text to the beginning and end of the message,
27023 define hookpost-echo
27027 (@value{GDBP}) echo Hello World
27028 <<<---Hello World--->>>
27033 You can define a hook for any single-word command in @value{GDBN}, but
27034 not for command aliases; you should define a hook for the basic command
27035 name, e.g.@: @code{backtrace} rather than @code{bt}.
27036 @c FIXME! So how does Joe User discover whether a command is an alias
27038 You can hook a multi-word command by adding @code{hook-} or
27039 @code{hookpost-} to the last word of the command, e.g.@:
27040 @samp{define target hook-remote} to add a hook to @samp{target remote}.
27042 If an error occurs during the execution of your hook, execution of
27043 @value{GDBN} commands stops and @value{GDBN} issues a prompt
27044 (before the command that you actually typed had a chance to run).
27046 If you try to define a hook which does not match any known command, you
27047 get a warning from the @code{define} command.
27049 @node Command Files
27050 @subsection Command Files
27052 @cindex command files
27053 @cindex scripting commands
27054 A command file for @value{GDBN} is a text file made of lines that are
27055 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
27056 also be included. An empty line in a command file does nothing; it
27057 does not mean to repeat the last command, as it would from the
27060 You can request the execution of a command file with the @code{source}
27061 command. Note that the @code{source} command is also used to evaluate
27062 scripts that are not Command Files. The exact behavior can be configured
27063 using the @code{script-extension} setting.
27064 @xref{Extending GDB,, Extending GDB}.
27068 @cindex execute commands from a file
27069 @item source [-s] [-v] @var{filename}
27070 Execute the command file @var{filename}.
27073 The lines in a command file are generally executed sequentially,
27074 unless the order of execution is changed by one of the
27075 @emph{flow-control commands} described below. The commands are not
27076 printed as they are executed. An error in any command terminates
27077 execution of the command file and control is returned to the console.
27079 @value{GDBN} first searches for @var{filename} in the current directory.
27080 If the file is not found there, and @var{filename} does not specify a
27081 directory, then @value{GDBN} also looks for the file on the source search path
27082 (specified with the @samp{directory} command);
27083 except that @file{$cdir} is not searched because the compilation directory
27084 is not relevant to scripts.
27086 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
27087 on the search path even if @var{filename} specifies a directory.
27088 The search is done by appending @var{filename} to each element of the
27089 search path. So, for example, if @var{filename} is @file{mylib/myscript}
27090 and the search path contains @file{/home/user} then @value{GDBN} will
27091 look for the script @file{/home/user/mylib/myscript}.
27092 The search is also done if @var{filename} is an absolute path.
27093 For example, if @var{filename} is @file{/tmp/myscript} and
27094 the search path contains @file{/home/user} then @value{GDBN} will
27095 look for the script @file{/home/user/tmp/myscript}.
27096 For DOS-like systems, if @var{filename} contains a drive specification,
27097 it is stripped before concatenation. For example, if @var{filename} is
27098 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
27099 will look for the script @file{c:/tmp/myscript}.
27101 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
27102 each command as it is executed. The option must be given before
27103 @var{filename}, and is interpreted as part of the filename anywhere else.
27105 Commands that would ask for confirmation if used interactively proceed
27106 without asking when used in a command file. Many @value{GDBN} commands that
27107 normally print messages to say what they are doing omit the messages
27108 when called from command files.
27110 @value{GDBN} also accepts command input from standard input. In this
27111 mode, normal output goes to standard output and error output goes to
27112 standard error. Errors in a command file supplied on standard input do
27113 not terminate execution of the command file---execution continues with
27117 gdb < cmds > log 2>&1
27120 (The syntax above will vary depending on the shell used.) This example
27121 will execute commands from the file @file{cmds}. All output and errors
27122 would be directed to @file{log}.
27124 Since commands stored on command files tend to be more general than
27125 commands typed interactively, they frequently need to deal with
27126 complicated situations, such as different or unexpected values of
27127 variables and symbols, changes in how the program being debugged is
27128 built, etc. @value{GDBN} provides a set of flow-control commands to
27129 deal with these complexities. Using these commands, you can write
27130 complex scripts that loop over data structures, execute commands
27131 conditionally, etc.
27138 This command allows to include in your script conditionally executed
27139 commands. The @code{if} command takes a single argument, which is an
27140 expression to evaluate. It is followed by a series of commands that
27141 are executed only if the expression is true (its value is nonzero).
27142 There can then optionally be an @code{else} line, followed by a series
27143 of commands that are only executed if the expression was false. The
27144 end of the list is marked by a line containing @code{end}.
27148 This command allows to write loops. Its syntax is similar to
27149 @code{if}: the command takes a single argument, which is an expression
27150 to evaluate, and must be followed by the commands to execute, one per
27151 line, terminated by an @code{end}. These commands are called the
27152 @dfn{body} of the loop. The commands in the body of @code{while} are
27153 executed repeatedly as long as the expression evaluates to true.
27157 This command exits the @code{while} loop in whose body it is included.
27158 Execution of the script continues after that @code{while}s @code{end}
27161 @kindex loop_continue
27162 @item loop_continue
27163 This command skips the execution of the rest of the body of commands
27164 in the @code{while} loop in whose body it is included. Execution
27165 branches to the beginning of the @code{while} loop, where it evaluates
27166 the controlling expression.
27168 @kindex end@r{ (if/else/while commands)}
27170 Terminate the block of commands that are the body of @code{if},
27171 @code{else}, or @code{while} flow-control commands.
27176 @subsection Commands for Controlled Output
27178 During the execution of a command file or a user-defined command, normal
27179 @value{GDBN} output is suppressed; the only output that appears is what is
27180 explicitly printed by the commands in the definition. This section
27181 describes three commands useful for generating exactly the output you
27186 @item echo @var{text}
27187 @c I do not consider backslash-space a standard C escape sequence
27188 @c because it is not in ANSI.
27189 Print @var{text}. Nonprinting characters can be included in
27190 @var{text} using C escape sequences, such as @samp{\n} to print a
27191 newline. @strong{No newline is printed unless you specify one.}
27192 In addition to the standard C escape sequences, a backslash followed
27193 by a space stands for a space. This is useful for displaying a
27194 string with spaces at the beginning or the end, since leading and
27195 trailing spaces are otherwise trimmed from all arguments.
27196 To print @samp{@w{ }and foo =@w{ }}, use the command
27197 @samp{echo \@w{ }and foo = \@w{ }}.
27199 A backslash at the end of @var{text} can be used, as in C, to continue
27200 the command onto subsequent lines. For example,
27203 echo This is some text\n\
27204 which is continued\n\
27205 onto several lines.\n
27208 produces the same output as
27211 echo This is some text\n
27212 echo which is continued\n
27213 echo onto several lines.\n
27217 @item output @var{expression}
27218 Print the value of @var{expression} and nothing but that value: no
27219 newlines, no @samp{$@var{nn} = }. The value is not entered in the
27220 value history either. @xref{Expressions, ,Expressions}, for more information
27223 @item output/@var{fmt} @var{expression}
27224 Print the value of @var{expression} in format @var{fmt}. You can use
27225 the same formats as for @code{print}. @xref{Output Formats,,Output
27226 Formats}, for more information.
27229 @item printf @var{template}, @var{expressions}@dots{}
27230 Print the values of one or more @var{expressions} under the control of
27231 the string @var{template}. To print several values, make
27232 @var{expressions} be a comma-separated list of individual expressions,
27233 which may be either numbers or pointers. Their values are printed as
27234 specified by @var{template}, exactly as a C program would do by
27235 executing the code below:
27238 printf (@var{template}, @var{expressions}@dots{});
27241 As in @code{C} @code{printf}, ordinary characters in @var{template}
27242 are printed verbatim, while @dfn{conversion specification} introduced
27243 by the @samp{%} character cause subsequent @var{expressions} to be
27244 evaluated, their values converted and formatted according to type and
27245 style information encoded in the conversion specifications, and then
27248 For example, you can print two values in hex like this:
27251 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
27254 @code{printf} supports all the standard @code{C} conversion
27255 specifications, including the flags and modifiers between the @samp{%}
27256 character and the conversion letter, with the following exceptions:
27260 The argument-ordering modifiers, such as @samp{2$}, are not supported.
27263 The modifier @samp{*} is not supported for specifying precision or
27267 The @samp{'} flag (for separation of digits into groups according to
27268 @code{LC_NUMERIC'}) is not supported.
27271 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
27275 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
27278 The conversion letters @samp{a} and @samp{A} are not supported.
27282 Note that the @samp{ll} type modifier is supported only if the
27283 underlying @code{C} implementation used to build @value{GDBN} supports
27284 the @code{long long int} type, and the @samp{L} type modifier is
27285 supported only if @code{long double} type is available.
27287 As in @code{C}, @code{printf} supports simple backslash-escape
27288 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
27289 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
27290 single character. Octal and hexadecimal escape sequences are not
27293 Additionally, @code{printf} supports conversion specifications for DFP
27294 (@dfn{Decimal Floating Point}) types using the following length modifiers
27295 together with a floating point specifier.
27300 @samp{H} for printing @code{Decimal32} types.
27303 @samp{D} for printing @code{Decimal64} types.
27306 @samp{DD} for printing @code{Decimal128} types.
27309 If the underlying @code{C} implementation used to build @value{GDBN} has
27310 support for the three length modifiers for DFP types, other modifiers
27311 such as width and precision will also be available for @value{GDBN} to use.
27313 In case there is no such @code{C} support, no additional modifiers will be
27314 available and the value will be printed in the standard way.
27316 Here's an example of printing DFP types using the above conversion letters:
27318 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
27323 @item eval @var{template}, @var{expressions}@dots{}
27324 Convert the values of one or more @var{expressions} under the control of
27325 the string @var{template} to a command line, and call it.
27329 @node Auto-loading sequences
27330 @subsection Controlling auto-loading native @value{GDBN} scripts
27331 @cindex native script auto-loading
27333 When a new object file is read (for example, due to the @code{file}
27334 command, or because the inferior has loaded a shared library),
27335 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
27336 @xref{Auto-loading extensions}.
27338 Auto-loading can be enabled or disabled,
27339 and the list of auto-loaded scripts can be printed.
27342 @anchor{set auto-load gdb-scripts}
27343 @kindex set auto-load gdb-scripts
27344 @item set auto-load gdb-scripts [on|off]
27345 Enable or disable the auto-loading of canned sequences of commands scripts.
27347 @anchor{show auto-load gdb-scripts}
27348 @kindex show auto-load gdb-scripts
27349 @item show auto-load gdb-scripts
27350 Show whether auto-loading of canned sequences of commands scripts is enabled or
27353 @anchor{info auto-load gdb-scripts}
27354 @kindex info auto-load gdb-scripts
27355 @cindex print list of auto-loaded canned sequences of commands scripts
27356 @item info auto-load gdb-scripts [@var{regexp}]
27357 Print the list of all canned sequences of commands scripts that @value{GDBN}
27361 If @var{regexp} is supplied only canned sequences of commands scripts with
27362 matching names are printed.
27364 @c Python docs live in a separate file.
27365 @include python.texi
27367 @c Guile docs live in a separate file.
27368 @include guile.texi
27370 @node Auto-loading extensions
27371 @section Auto-loading extensions
27372 @cindex auto-loading extensions
27374 @value{GDBN} provides two mechanisms for automatically loading extensions
27375 when a new object file is read (for example, due to the @code{file}
27376 command, or because the inferior has loaded a shared library):
27377 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
27378 section of modern file formats like ELF.
27381 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
27382 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
27383 * Which flavor to choose?::
27386 The auto-loading feature is useful for supplying application-specific
27387 debugging commands and features.
27389 Auto-loading can be enabled or disabled,
27390 and the list of auto-loaded scripts can be printed.
27391 See the @samp{auto-loading} section of each extension language
27392 for more information.
27393 For @value{GDBN} command files see @ref{Auto-loading sequences}.
27394 For Python files see @ref{Python Auto-loading}.
27396 Note that loading of this script file also requires accordingly configured
27397 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27399 @node objfile-gdbdotext file
27400 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
27401 @cindex @file{@var{objfile}-gdb.gdb}
27402 @cindex @file{@var{objfile}-gdb.py}
27403 @cindex @file{@var{objfile}-gdb.scm}
27405 When a new object file is read, @value{GDBN} looks for a file named
27406 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
27407 where @var{objfile} is the object file's name and
27408 where @var{ext} is the file extension for the extension language:
27411 @item @file{@var{objfile}-gdb.gdb}
27412 GDB's own command language
27413 @item @file{@var{objfile}-gdb.py}
27415 @item @file{@var{objfile}-gdb.scm}
27419 @var{script-name} is formed by ensuring that the file name of @var{objfile}
27420 is absolute, following all symlinks, and resolving @code{.} and @code{..}
27421 components, and appending the @file{-gdb.@var{ext}} suffix.
27422 If this file exists and is readable, @value{GDBN} will evaluate it as a
27423 script in the specified extension language.
27425 If this file does not exist, then @value{GDBN} will look for
27426 @var{script-name} file in all of the directories as specified below.
27427 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
27428 directories is converted to a one-letter subdirectory, i.e.@:
27429 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
27430 filesystems disallow colons in file names.)
27432 Note that loading of these files requires an accordingly configured
27433 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27435 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27436 scripts normally according to its @file{.exe} filename. But if no scripts are
27437 found @value{GDBN} also tries script filenames matching the object file without
27438 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27439 is attempted on any platform. This makes the script filenames compatible
27440 between Unix and MS-Windows hosts.
27443 @anchor{set auto-load scripts-directory}
27444 @kindex set auto-load scripts-directory
27445 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27446 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27447 may be delimited by the host platform path separator in use
27448 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27450 Each entry here needs to be covered also by the security setting
27451 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27453 @anchor{with-auto-load-dir}
27454 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27455 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27456 configuration option @option{--with-auto-load-dir}.
27458 Any reference to @file{$debugdir} will get replaced by
27459 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27460 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27461 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27462 @file{$datadir} must be placed as a directory component --- either alone or
27463 delimited by @file{/} or @file{\} directory separators, depending on the host
27466 The list of directories uses path separator (@samp{:} on GNU and Unix
27467 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27468 to the @env{PATH} environment variable.
27470 @anchor{show auto-load scripts-directory}
27471 @kindex show auto-load scripts-directory
27472 @item show auto-load scripts-directory
27473 Show @value{GDBN} auto-loaded scripts location.
27475 @anchor{add-auto-load-scripts-directory}
27476 @kindex add-auto-load-scripts-directory
27477 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
27478 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
27479 Multiple entries may be delimited by the host platform path separator in use.
27482 @value{GDBN} does not track which files it has already auto-loaded this way.
27483 @value{GDBN} will load the associated script every time the corresponding
27484 @var{objfile} is opened.
27485 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
27486 is evaluated more than once.
27488 @node dotdebug_gdb_scripts section
27489 @subsection The @code{.debug_gdb_scripts} section
27490 @cindex @code{.debug_gdb_scripts} section
27492 For systems using file formats like ELF and COFF,
27493 when @value{GDBN} loads a new object file
27494 it will look for a special section named @code{.debug_gdb_scripts}.
27495 If this section exists, its contents is a list of null-terminated entries
27496 specifying scripts to load. Each entry begins with a non-null prefix byte that
27497 specifies the kind of entry, typically the extension language and whether the
27498 script is in a file or inlined in @code{.debug_gdb_scripts}.
27500 The following entries are supported:
27503 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
27504 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
27505 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
27506 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
27509 @subsubsection Script File Entries
27511 If the entry specifies a file, @value{GDBN} will look for the file first
27512 in the current directory and then along the source search path
27513 (@pxref{Source Path, ,Specifying Source Directories}),
27514 except that @file{$cdir} is not searched, since the compilation
27515 directory is not relevant to scripts.
27517 File entries can be placed in section @code{.debug_gdb_scripts} with,
27518 for example, this GCC macro for Python scripts.
27521 /* Note: The "MS" section flags are to remove duplicates. */
27522 #define DEFINE_GDB_PY_SCRIPT(script_name) \
27524 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27525 .byte 1 /* Python */\n\
27526 .asciz \"" script_name "\"\n\
27532 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
27533 Then one can reference the macro in a header or source file like this:
27536 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
27539 The script name may include directories if desired.
27541 Note that loading of this script file also requires accordingly configured
27542 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27544 If the macro invocation is put in a header, any application or library
27545 using this header will get a reference to the specified script,
27546 and with the use of @code{"MS"} attributes on the section, the linker
27547 will remove duplicates.
27549 @subsubsection Script Text Entries
27551 Script text entries allow to put the executable script in the entry
27552 itself instead of loading it from a file.
27553 The first line of the entry, everything after the prefix byte and up to
27554 the first newline (@code{0xa}) character, is the script name, and must not
27555 contain any kind of space character, e.g., spaces or tabs.
27556 The rest of the entry, up to the trailing null byte, is the script to
27557 execute in the specified language. The name needs to be unique among
27558 all script names, as @value{GDBN} executes each script only once based
27561 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
27565 #include "symcat.h"
27566 #include "gdb/section-scripts.h"
27568 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
27569 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
27570 ".ascii \"gdb.inlined-script\\n\"\n"
27571 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
27572 ".ascii \" def __init__ (self):\\n\"\n"
27573 ".ascii \" super (test_cmd, self).__init__ ("
27574 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
27575 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
27576 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
27577 ".ascii \"test_cmd ()\\n\"\n"
27583 Loading of inlined scripts requires a properly configured
27584 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27585 The path to specify in @code{auto-load safe-path} is the path of the file
27586 containing the @code{.debug_gdb_scripts} section.
27588 @node Which flavor to choose?
27589 @subsection Which flavor to choose?
27591 Given the multiple ways of auto-loading extensions, it might not always
27592 be clear which one to choose. This section provides some guidance.
27595 Benefits of the @file{-gdb.@var{ext}} way:
27599 Can be used with file formats that don't support multiple sections.
27602 Ease of finding scripts for public libraries.
27604 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27605 in the source search path.
27606 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27607 isn't a source directory in which to find the script.
27610 Doesn't require source code additions.
27614 Benefits of the @code{.debug_gdb_scripts} way:
27618 Works with static linking.
27620 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
27621 trigger their loading. When an application is statically linked the only
27622 objfile available is the executable, and it is cumbersome to attach all the
27623 scripts from all the input libraries to the executable's
27624 @file{-gdb.@var{ext}} script.
27627 Works with classes that are entirely inlined.
27629 Some classes can be entirely inlined, and thus there may not be an associated
27630 shared library to attach a @file{-gdb.@var{ext}} script to.
27633 Scripts needn't be copied out of the source tree.
27635 In some circumstances, apps can be built out of large collections of internal
27636 libraries, and the build infrastructure necessary to install the
27637 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
27638 cumbersome. It may be easier to specify the scripts in the
27639 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27640 top of the source tree to the source search path.
27643 @node Multiple Extension Languages
27644 @section Multiple Extension Languages
27646 The Guile and Python extension languages do not share any state,
27647 and generally do not interfere with each other.
27648 There are some things to be aware of, however.
27650 @subsection Python comes first
27652 Python was @value{GDBN}'s first extension language, and to avoid breaking
27653 existing behaviour Python comes first. This is generally solved by the
27654 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
27655 extension languages, and when it makes a call to an extension language,
27656 (say to pretty-print a value), it tries each in turn until an extension
27657 language indicates it has performed the request (e.g., has returned the
27658 pretty-printed form of a value).
27659 This extends to errors while performing such requests: If an error happens
27660 while, for example, trying to pretty-print an object then the error is
27661 reported and any following extension languages are not tried.
27664 @section Creating new spellings of existing commands
27665 @cindex aliases for commands
27667 It is often useful to define alternate spellings of existing commands.
27668 For example, if a new @value{GDBN} command defined in Python has
27669 a long name to type, it is handy to have an abbreviated version of it
27670 that involves less typing.
27672 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27673 of the @samp{step} command even though it is otherwise an ambiguous
27674 abbreviation of other commands like @samp{set} and @samp{show}.
27676 Aliases are also used to provide shortened or more common versions
27677 of multi-word commands. For example, @value{GDBN} provides the
27678 @samp{tty} alias of the @samp{set inferior-tty} command.
27680 You can define a new alias with the @samp{alias} command.
27685 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND} [DEFAULT-ARGS...]
27689 @var{ALIAS} specifies the name of the new alias.
27690 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
27693 @var{COMMAND} specifies the name of an existing command
27694 that is being aliased.
27696 @var{COMMAND} can also be the name of an existing alias. In this case,
27697 @var{COMMAND} cannot be an alias that has default arguments.
27699 The @samp{-a} option specifies that the new alias is an abbreviation
27700 of the command. Abbreviations are not used in command completion.
27702 The @samp{--} option specifies the end of options,
27703 and is useful when @var{ALIAS} begins with a dash.
27705 You can specify @var{default-args} for your alias.
27706 These @var{default-args} will be automatically added before the alias
27707 arguments typed explicitly on the command line.
27709 For example, the below defines an alias @code{btfullall} that shows all local
27710 variables and all frame arguments:
27712 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
27715 For more information about @var{default-args}, see @ref{Command aliases default args,
27716 ,Automatically prepend default arguments to user-defined aliases}.
27718 Here is a simple example showing how to make an abbreviation
27719 of a command so that there is less to type.
27720 Suppose you were tired of typing @samp{disas}, the current
27721 shortest unambiguous abbreviation of the @samp{disassemble} command
27722 and you wanted an even shorter version named @samp{di}.
27723 The following will accomplish this.
27726 (gdb) alias -a di = disas
27729 Note that aliases are different from user-defined commands.
27730 With a user-defined command, you also need to write documentation
27731 for it with the @samp{document} command.
27732 An alias automatically picks up the documentation of the existing command.
27734 Here is an example where we make @samp{elms} an abbreviation of
27735 @samp{elements} in the @samp{set print elements} command.
27736 This is to show that you can make an abbreviation of any part
27740 (gdb) alias -a set print elms = set print elements
27741 (gdb) alias -a show print elms = show print elements
27742 (gdb) set p elms 20
27744 Limit on string chars or array elements to print is 200.
27747 Note that if you are defining an alias of a @samp{set} command,
27748 and you want to have an alias for the corresponding @samp{show}
27749 command, then you need to define the latter separately.
27751 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
27752 @var{ALIAS}, just as they are normally.
27755 (gdb) alias -a set pr elms = set p ele
27758 Finally, here is an example showing the creation of a one word
27759 alias for a more complex command.
27760 This creates alias @samp{spe} of the command @samp{set print elements}.
27763 (gdb) alias spe = set print elements
27768 @chapter Command Interpreters
27769 @cindex command interpreters
27771 @value{GDBN} supports multiple command interpreters, and some command
27772 infrastructure to allow users or user interface writers to switch
27773 between interpreters or run commands in other interpreters.
27775 @value{GDBN} currently supports two command interpreters, the console
27776 interpreter (sometimes called the command-line interpreter or @sc{cli})
27777 and the machine interface interpreter (or @sc{gdb/mi}). This manual
27778 describes both of these interfaces in great detail.
27780 By default, @value{GDBN} will start with the console interpreter.
27781 However, the user may choose to start @value{GDBN} with another
27782 interpreter by specifying the @option{-i} or @option{--interpreter}
27783 startup options. Defined interpreters include:
27787 @cindex console interpreter
27788 The traditional console or command-line interpreter. This is the most often
27789 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
27790 @value{GDBN} will use this interpreter.
27793 @cindex mi interpreter
27794 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
27795 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
27796 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
27800 @cindex mi3 interpreter
27801 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
27804 @cindex mi2 interpreter
27805 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
27808 @cindex mi1 interpreter
27809 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
27813 @cindex invoke another interpreter
27815 @kindex interpreter-exec
27816 You may execute commands in any interpreter from the current
27817 interpreter using the appropriate command. If you are running the
27818 console interpreter, simply use the @code{interpreter-exec} command:
27821 interpreter-exec mi "-data-list-register-names"
27824 @sc{gdb/mi} has a similar command, although it is only available in versions of
27825 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
27827 Note that @code{interpreter-exec} only changes the interpreter for the
27828 duration of the specified command. It does not change the interpreter
27831 @cindex start a new independent interpreter
27833 Although you may only choose a single interpreter at startup, it is
27834 possible to run an independent interpreter on a specified input/output
27835 device (usually a tty).
27837 For example, consider a debugger GUI or IDE that wants to provide a
27838 @value{GDBN} console view. It may do so by embedding a terminal
27839 emulator widget in its GUI, starting @value{GDBN} in the traditional
27840 command-line mode with stdin/stdout/stderr redirected to that
27841 terminal, and then creating an MI interpreter running on a specified
27842 input/output device. The console interpreter created by @value{GDBN}
27843 at startup handles commands the user types in the terminal widget,
27844 while the GUI controls and synchronizes state with @value{GDBN} using
27845 the separate MI interpreter.
27847 To start a new secondary @dfn{user interface} running MI, use the
27848 @code{new-ui} command:
27851 @cindex new user interface
27853 new-ui @var{interpreter} @var{tty}
27856 The @var{interpreter} parameter specifies the interpreter to run.
27857 This accepts the same values as the @code{interpreter-exec} command.
27858 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
27859 @var{tty} parameter specifies the name of the bidirectional file the
27860 interpreter uses for input/output, usually the name of a
27861 pseudoterminal slave on Unix systems. For example:
27864 (@value{GDBP}) new-ui mi /dev/pts/9
27868 runs an MI interpreter on @file{/dev/pts/9}.
27871 @chapter @value{GDBN} Text User Interface
27873 @cindex Text User Interface
27876 * TUI Overview:: TUI overview
27877 * TUI Keys:: TUI key bindings
27878 * TUI Single Key Mode:: TUI single key mode
27879 * TUI Commands:: TUI-specific commands
27880 * TUI Configuration:: TUI configuration variables
27883 The @value{GDBN} Text User Interface (TUI) is a terminal
27884 interface which uses the @code{curses} library to show the source
27885 file, the assembly output, the program registers and @value{GDBN}
27886 commands in separate text windows. The TUI mode is supported only
27887 on platforms where a suitable version of the @code{curses} library
27890 The TUI mode is enabled by default when you invoke @value{GDBN} as
27891 @samp{@value{GDBP} -tui}.
27892 You can also switch in and out of TUI mode while @value{GDBN} runs by
27893 using various TUI commands and key bindings, such as @command{tui
27894 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
27895 @ref{TUI Keys, ,TUI Key Bindings}.
27898 @section TUI Overview
27900 In TUI mode, @value{GDBN} can display several text windows:
27904 This window is the @value{GDBN} command window with the @value{GDBN}
27905 prompt and the @value{GDBN} output. The @value{GDBN} input is still
27906 managed using readline.
27909 The source window shows the source file of the program. The current
27910 line and active breakpoints are displayed in this window.
27913 The assembly window shows the disassembly output of the program.
27916 This window shows the processor registers. Registers are highlighted
27917 when their values change.
27920 The source and assembly windows show the current program position
27921 by highlighting the current line and marking it with a @samp{>} marker.
27922 Breakpoints are indicated with two markers. The first marker
27923 indicates the breakpoint type:
27927 Breakpoint which was hit at least once.
27930 Breakpoint which was never hit.
27933 Hardware breakpoint which was hit at least once.
27936 Hardware breakpoint which was never hit.
27939 The second marker indicates whether the breakpoint is enabled or not:
27943 Breakpoint is enabled.
27946 Breakpoint is disabled.
27949 The source, assembly and register windows are updated when the current
27950 thread changes, when the frame changes, or when the program counter
27953 These windows are not all visible at the same time. The command
27954 window is always visible. The others can be arranged in several
27965 source and assembly,
27968 source and registers, or
27971 assembly and registers.
27974 These are the standard layouts, but other layouts can be defined.
27976 A status line above the command window shows the following information:
27980 Indicates the current @value{GDBN} target.
27981 (@pxref{Targets, ,Specifying a Debugging Target}).
27984 Gives the current process or thread number.
27985 When no process is being debugged, this field is set to @code{No process}.
27988 Gives the current function name for the selected frame.
27989 The name is demangled if demangling is turned on (@pxref{Print Settings}).
27990 When there is no symbol corresponding to the current program counter,
27991 the string @code{??} is displayed.
27994 Indicates the current line number for the selected frame.
27995 When the current line number is not known, the string @code{??} is displayed.
27998 Indicates the current program counter address.
28002 @section TUI Key Bindings
28003 @cindex TUI key bindings
28005 The TUI installs several key bindings in the readline keymaps
28006 @ifset SYSTEM_READLINE
28007 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28009 @ifclear SYSTEM_READLINE
28010 (@pxref{Command Line Editing}).
28012 The following key bindings are installed for both TUI mode and the
28013 @value{GDBN} standard mode.
28022 Enter or leave the TUI mode. When leaving the TUI mode,
28023 the curses window management stops and @value{GDBN} operates using
28024 its standard mode, writing on the terminal directly. When reentering
28025 the TUI mode, control is given back to the curses windows.
28026 The screen is then refreshed.
28028 This key binding uses the bindable Readline function
28029 @code{tui-switch-mode}.
28033 Use a TUI layout with only one window. The layout will
28034 either be @samp{source} or @samp{assembly}. When the TUI mode
28035 is not active, it will switch to the TUI mode.
28037 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28039 This key binding uses the bindable Readline function
28040 @code{tui-delete-other-windows}.
28044 Use a TUI layout with at least two windows. When the current
28045 layout already has two windows, the next layout with two windows is used.
28046 When a new layout is chosen, one window will always be common to the
28047 previous layout and the new one.
28049 Think of it as the Emacs @kbd{C-x 2} binding.
28051 This key binding uses the bindable Readline function
28052 @code{tui-change-windows}.
28056 Change the active window. The TUI associates several key bindings
28057 (like scrolling and arrow keys) with the active window. This command
28058 gives the focus to the next TUI window.
28060 Think of it as the Emacs @kbd{C-x o} binding.
28062 This key binding uses the bindable Readline function
28063 @code{tui-other-window}.
28067 Switch in and out of the TUI SingleKey mode that binds single
28068 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28070 This key binding uses the bindable Readline function
28071 @code{next-keymap}.
28074 The following key bindings only work in the TUI mode:
28079 Scroll the active window one page up.
28083 Scroll the active window one page down.
28087 Scroll the active window one line up.
28091 Scroll the active window one line down.
28095 Scroll the active window one column left.
28099 Scroll the active window one column right.
28103 Refresh the screen.
28106 Because the arrow keys scroll the active window in the TUI mode, they
28107 are not available for their normal use by readline unless the command
28108 window has the focus. When another window is active, you must use
28109 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28110 and @kbd{C-f} to control the command window.
28112 @node TUI Single Key Mode
28113 @section TUI Single Key Mode
28114 @cindex TUI single key mode
28116 The TUI also provides a @dfn{SingleKey} mode, which binds several
28117 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28118 switch into this mode, where the following key bindings are used:
28121 @kindex c @r{(SingleKey TUI key)}
28125 @kindex d @r{(SingleKey TUI key)}
28129 @kindex f @r{(SingleKey TUI key)}
28133 @kindex n @r{(SingleKey TUI key)}
28137 @kindex o @r{(SingleKey TUI key)}
28139 nexti. The shortcut letter @samp{o} stands for ``step Over''.
28141 @kindex q @r{(SingleKey TUI key)}
28143 exit the SingleKey mode.
28145 @kindex r @r{(SingleKey TUI key)}
28149 @kindex s @r{(SingleKey TUI key)}
28153 @kindex i @r{(SingleKey TUI key)}
28155 stepi. The shortcut letter @samp{i} stands for ``step Into''.
28157 @kindex u @r{(SingleKey TUI key)}
28161 @kindex v @r{(SingleKey TUI key)}
28165 @kindex w @r{(SingleKey TUI key)}
28170 Other keys temporarily switch to the @value{GDBN} command prompt.
28171 The key that was pressed is inserted in the editing buffer so that
28172 it is possible to type most @value{GDBN} commands without interaction
28173 with the TUI SingleKey mode. Once the command is entered the TUI
28174 SingleKey mode is restored. The only way to permanently leave
28175 this mode is by typing @kbd{q} or @kbd{C-x s}.
28177 @cindex SingleKey keymap name
28178 If @value{GDBN} was built with Readline 8.0 or later, the TUI
28179 SingleKey keymap will be named @samp{SingleKey}. This can be used in
28180 @file{.inputrc} to add additional bindings to this keymap.
28183 @section TUI-specific Commands
28184 @cindex TUI commands
28186 The TUI has specific commands to control the text windows.
28187 These commands are always available, even when @value{GDBN} is not in
28188 the TUI mode. When @value{GDBN} is in the standard mode, most
28189 of these commands will automatically switch to the TUI mode.
28191 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28192 terminal, or @value{GDBN} has been started with the machine interface
28193 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28194 these commands will fail with an error, because it would not be
28195 possible or desirable to enable curses window management.
28200 Activate TUI mode. The last active TUI window layout will be used if
28201 TUI mode has previously been used in the current debugging session,
28202 otherwise a default layout is used.
28205 @kindex tui disable
28206 Disable TUI mode, returning to the console interpreter.
28210 List and give the size of all displayed windows.
28212 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
28213 @kindex tui new-layout
28214 Create a new TUI layout. The new layout will be named @var{name}, and
28215 can be accessed using the @code{layout} command (see below).
28217 Each @var{window} parameter is either the name of a window to display,
28218 or a window description. The windows will be displayed from top to
28219 bottom in the order listed.
28221 The names of the windows are the same as the ones given to the
28222 @code{focus} command (see below); additional, the @code{status}
28223 window can be specified. Note that, because it is of fixed height,
28224 the weight assigned to the status window is of no importance. It is
28225 conventional to use @samp{0} here.
28227 A window description looks a bit like an invocation of @code{tui
28228 new-layout}, and is of the form
28229 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
28231 This specifies a sub-layout. If @code{-horizontal} is given, the
28232 windows in this description will be arranged side-by-side, rather than
28235 Each @var{weight} is an integer. It is the weight of this window
28236 relative to all the other windows in the layout. These numbers are
28237 used to calculate how much of the screen is given to each window.
28242 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
28245 Here, the new layout is called @samp{example}. It shows the source
28246 and register windows, followed by the status window, and then finally
28247 the command window. The non-status windows all have the same weight,
28248 so the terminal will be split into three roughly equal sections.
28250 Here is a more complex example, showing a horizontal layout:
28253 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
28256 This will result in side-by-side source and assembly windows; with the
28257 status and command window being beneath these, filling the entire
28258 width of the terminal. Because they have weight 2, the source and
28259 assembly windows will be twice the height of the command window.
28261 @item layout @var{name}
28263 Changes which TUI windows are displayed. The @var{name} parameter
28264 controls which layout is shown. It can be either one of the built-in
28265 layout names, or the name of a layout defined by the user using
28266 @code{tui new-layout}.
28268 The built-in layouts are as follows:
28272 Display the next layout.
28275 Display the previous layout.
28278 Display the source and command windows.
28281 Display the assembly and command windows.
28284 Display the source, assembly, and command windows.
28287 When in @code{src} layout display the register, source, and command
28288 windows. When in @code{asm} or @code{split} layout display the
28289 register, assembler, and command windows.
28292 @item focus @var{name}
28294 Changes which TUI window is currently active for scrolling. The
28295 @var{name} parameter can be any of the following:
28299 Make the next window active for scrolling.
28302 Make the previous window active for scrolling.
28305 Make the source window active for scrolling.
28308 Make the assembly window active for scrolling.
28311 Make the register window active for scrolling.
28314 Make the command window active for scrolling.
28319 Refresh the screen. This is similar to typing @kbd{C-L}.
28321 @item tui reg @var{group}
28323 Changes the register group displayed in the tui register window to
28324 @var{group}. If the register window is not currently displayed this
28325 command will cause the register window to be displayed. The list of
28326 register groups, as well as their order is target specific. The
28327 following groups are available on most targets:
28330 Repeatedly selecting this group will cause the display to cycle
28331 through all of the available register groups.
28334 Repeatedly selecting this group will cause the display to cycle
28335 through all of the available register groups in the reverse order to
28339 Display the general registers.
28341 Display the floating point registers.
28343 Display the system registers.
28345 Display the vector registers.
28347 Display all registers.
28352 Update the source window and the current execution point.
28354 @item winheight @var{name} +@var{count}
28355 @itemx winheight @var{name} -@var{count}
28357 Change the height of the window @var{name} by @var{count}
28358 lines. Positive counts increase the height, while negative counts
28359 decrease it. The @var{name} parameter can be one of @code{src} (the
28360 source window), @code{cmd} (the command window), @code{asm} (the
28361 disassembly window), or @code{regs} (the register display window).
28364 @node TUI Configuration
28365 @section TUI Configuration Variables
28366 @cindex TUI configuration variables
28368 Several configuration variables control the appearance of TUI windows.
28371 @item set tui border-kind @var{kind}
28372 @kindex set tui border-kind
28373 Select the border appearance for the source, assembly and register windows.
28374 The possible values are the following:
28377 Use a space character to draw the border.
28380 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28383 Use the Alternate Character Set to draw the border. The border is
28384 drawn using character line graphics if the terminal supports them.
28387 @item set tui border-mode @var{mode}
28388 @kindex set tui border-mode
28389 @itemx set tui active-border-mode @var{mode}
28390 @kindex set tui active-border-mode
28391 Select the display attributes for the borders of the inactive windows
28392 or the active window. The @var{mode} can be one of the following:
28395 Use normal attributes to display the border.
28401 Use reverse video mode.
28404 Use half bright mode.
28406 @item half-standout
28407 Use half bright and standout mode.
28410 Use extra bright or bold mode.
28412 @item bold-standout
28413 Use extra bright or bold and standout mode.
28416 @item set tui tab-width @var{nchars}
28417 @kindex set tui tab-width
28419 Set the width of tab stops to be @var{nchars} characters. This
28420 setting affects the display of TAB characters in the source and
28423 @item set tui compact-source @r{[}on@r{|}off@r{]}
28424 @kindex set tui compact-source
28425 Set whether the TUI source window is displayed in ``compact'' form.
28426 The default display uses more space for line numbers and starts the
28427 source text at the next tab stop; the compact display uses only as
28428 much space as is needed for the line numbers in the current file, and
28429 only a single space to separate the line numbers from the source.
28432 Note that the colors of the TUI borders can be controlled using the
28433 appropriate @code{set style} commands. @xref{Output Styling}.
28436 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28439 @cindex @sc{gnu} Emacs
28440 A special interface allows you to use @sc{gnu} Emacs to view (and
28441 edit) the source files for the program you are debugging with
28444 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28445 executable file you want to debug as an argument. This command starts
28446 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28447 created Emacs buffer.
28448 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28450 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28455 All ``terminal'' input and output goes through an Emacs buffer, called
28458 This applies both to @value{GDBN} commands and their output, and to the input
28459 and output done by the program you are debugging.
28461 This is useful because it means that you can copy the text of previous
28462 commands and input them again; you can even use parts of the output
28465 All the facilities of Emacs' Shell mode are available for interacting
28466 with your program. In particular, you can send signals the usual
28467 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28471 @value{GDBN} displays source code through Emacs.
28473 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28474 source file for that frame and puts an arrow (@samp{=>}) at the
28475 left margin of the current line. Emacs uses a separate buffer for
28476 source display, and splits the screen to show both your @value{GDBN} session
28479 Explicit @value{GDBN} @code{list} or search commands still produce output as
28480 usual, but you probably have no reason to use them from Emacs.
28483 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28484 a graphical mode, enabled by default, which provides further buffers
28485 that can control the execution and describe the state of your program.
28486 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28488 If you specify an absolute file name when prompted for the @kbd{M-x
28489 gdb} argument, then Emacs sets your current working directory to where
28490 your program resides. If you only specify the file name, then Emacs
28491 sets your current working directory to the directory associated
28492 with the previous buffer. In this case, @value{GDBN} may find your
28493 program by searching your environment's @code{PATH} variable, but on
28494 some operating systems it might not find the source. So, although the
28495 @value{GDBN} input and output session proceeds normally, the auxiliary
28496 buffer does not display the current source and line of execution.
28498 The initial working directory of @value{GDBN} is printed on the top
28499 line of the GUD buffer and this serves as a default for the commands
28500 that specify files for @value{GDBN} to operate on. @xref{Files,
28501 ,Commands to Specify Files}.
28503 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28504 need to call @value{GDBN} by a different name (for example, if you
28505 keep several configurations around, with different names) you can
28506 customize the Emacs variable @code{gud-gdb-command-name} to run the
28509 In the GUD buffer, you can use these special Emacs commands in
28510 addition to the standard Shell mode commands:
28514 Describe the features of Emacs' GUD Mode.
28517 Execute to another source line, like the @value{GDBN} @code{step} command; also
28518 update the display window to show the current file and location.
28521 Execute to next source line in this function, skipping all function
28522 calls, like the @value{GDBN} @code{next} command. Then update the display window
28523 to show the current file and location.
28526 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28527 display window accordingly.
28530 Execute until exit from the selected stack frame, like the @value{GDBN}
28531 @code{finish} command.
28534 Continue execution of your program, like the @value{GDBN} @code{continue}
28538 Go up the number of frames indicated by the numeric argument
28539 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28540 like the @value{GDBN} @code{up} command.
28543 Go down the number of frames indicated by the numeric argument, like the
28544 @value{GDBN} @code{down} command.
28547 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28548 tells @value{GDBN} to set a breakpoint on the source line point is on.
28550 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28551 separate frame which shows a backtrace when the GUD buffer is current.
28552 Move point to any frame in the stack and type @key{RET} to make it
28553 become the current frame and display the associated source in the
28554 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28555 selected frame become the current one. In graphical mode, the
28556 speedbar displays watch expressions.
28558 If you accidentally delete the source-display buffer, an easy way to get
28559 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28560 request a frame display; when you run under Emacs, this recreates
28561 the source buffer if necessary to show you the context of the current
28564 The source files displayed in Emacs are in ordinary Emacs buffers
28565 which are visiting the source files in the usual way. You can edit
28566 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28567 communicates with Emacs in terms of line numbers. If you add or
28568 delete lines from the text, the line numbers that @value{GDBN} knows cease
28569 to correspond properly with the code.
28571 A more detailed description of Emacs' interaction with @value{GDBN} is
28572 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28576 @chapter The @sc{gdb/mi} Interface
28578 @unnumberedsec Function and Purpose
28580 @cindex @sc{gdb/mi}, its purpose
28581 @sc{gdb/mi} is a line based machine oriented text interface to
28582 @value{GDBN} and is activated by specifying using the
28583 @option{--interpreter} command line option (@pxref{Mode Options}). It
28584 is specifically intended to support the development of systems which
28585 use the debugger as just one small component of a larger system.
28587 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28588 in the form of a reference manual.
28590 Note that @sc{gdb/mi} is still under construction, so some of the
28591 features described below are incomplete and subject to change
28592 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28594 @unnumberedsec Notation and Terminology
28596 @cindex notational conventions, for @sc{gdb/mi}
28597 This chapter uses the following notation:
28601 @code{|} separates two alternatives.
28604 @code{[ @var{something} ]} indicates that @var{something} is optional:
28605 it may or may not be given.
28608 @code{( @var{group} )*} means that @var{group} inside the parentheses
28609 may repeat zero or more times.
28612 @code{( @var{group} )+} means that @var{group} inside the parentheses
28613 may repeat one or more times.
28616 @code{"@var{string}"} means a literal @var{string}.
28620 @heading Dependencies
28624 * GDB/MI General Design::
28625 * GDB/MI Command Syntax::
28626 * GDB/MI Compatibility with CLI::
28627 * GDB/MI Development and Front Ends::
28628 * GDB/MI Output Records::
28629 * GDB/MI Simple Examples::
28630 * GDB/MI Command Description Format::
28631 * GDB/MI Breakpoint Commands::
28632 * GDB/MI Catchpoint Commands::
28633 * GDB/MI Program Context::
28634 * GDB/MI Thread Commands::
28635 * GDB/MI Ada Tasking Commands::
28636 * GDB/MI Program Execution::
28637 * GDB/MI Stack Manipulation::
28638 * GDB/MI Variable Objects::
28639 * GDB/MI Data Manipulation::
28640 * GDB/MI Tracepoint Commands::
28641 * GDB/MI Symbol Query::
28642 * GDB/MI File Commands::
28644 * GDB/MI Kod Commands::
28645 * GDB/MI Memory Overlay Commands::
28646 * GDB/MI Signal Handling Commands::
28648 * GDB/MI Target Manipulation::
28649 * GDB/MI File Transfer Commands::
28650 * GDB/MI Ada Exceptions Commands::
28651 * GDB/MI Support Commands::
28652 * GDB/MI Miscellaneous Commands::
28655 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28656 @node GDB/MI General Design
28657 @section @sc{gdb/mi} General Design
28658 @cindex GDB/MI General Design
28660 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28661 parts---commands sent to @value{GDBN}, responses to those commands
28662 and notifications. Each command results in exactly one response,
28663 indicating either successful completion of the command, or an error.
28664 For the commands that do not resume the target, the response contains the
28665 requested information. For the commands that resume the target, the
28666 response only indicates whether the target was successfully resumed.
28667 Notifications is the mechanism for reporting changes in the state of the
28668 target, or in @value{GDBN} state, that cannot conveniently be associated with
28669 a command and reported as part of that command response.
28671 The important examples of notifications are:
28675 Exec notifications. These are used to report changes in
28676 target state---when a target is resumed, or stopped. It would not
28677 be feasible to include this information in response of resuming
28678 commands, because one resume commands can result in multiple events in
28679 different threads. Also, quite some time may pass before any event
28680 happens in the target, while a frontend needs to know whether the resuming
28681 command itself was successfully executed.
28684 Console output, and status notifications. Console output
28685 notifications are used to report output of CLI commands, as well as
28686 diagnostics for other commands. Status notifications are used to
28687 report the progress of a long-running operation. Naturally, including
28688 this information in command response would mean no output is produced
28689 until the command is finished, which is undesirable.
28692 General notifications. Commands may have various side effects on
28693 the @value{GDBN} or target state beyond their official purpose. For example,
28694 a command may change the selected thread. Although such changes can
28695 be included in command response, using notification allows for more
28696 orthogonal frontend design.
28700 There's no guarantee that whenever an MI command reports an error,
28701 @value{GDBN} or the target are in any specific state, and especially,
28702 the state is not reverted to the state before the MI command was
28703 processed. Therefore, whenever an MI command results in an error,
28704 we recommend that the frontend refreshes all the information shown in
28705 the user interface.
28709 * Context management::
28710 * Asynchronous and non-stop modes::
28714 @node Context management
28715 @subsection Context management
28717 @subsubsection Threads and Frames
28719 In most cases when @value{GDBN} accesses the target, this access is
28720 done in context of a specific thread and frame (@pxref{Frames}).
28721 Often, even when accessing global data, the target requires that a thread
28722 be specified. The CLI interface maintains the selected thread and frame,
28723 and supplies them to target on each command. This is convenient,
28724 because a command line user would not want to specify that information
28725 explicitly on each command, and because user interacts with
28726 @value{GDBN} via a single terminal, so no confusion is possible as
28727 to what thread and frame are the current ones.
28729 In the case of MI, the concept of selected thread and frame is less
28730 useful. First, a frontend can easily remember this information
28731 itself. Second, a graphical frontend can have more than one window,
28732 each one used for debugging a different thread, and the frontend might
28733 want to access additional threads for internal purposes. This
28734 increases the risk that by relying on implicitly selected thread, the
28735 frontend may be operating on a wrong one. Therefore, each MI command
28736 should explicitly specify which thread and frame to operate on. To
28737 make it possible, each MI command accepts the @samp{--thread} and
28738 @samp{--frame} options, the value to each is @value{GDBN} global
28739 identifier for thread and frame to operate on.
28741 Usually, each top-level window in a frontend allows the user to select
28742 a thread and a frame, and remembers the user selection for further
28743 operations. However, in some cases @value{GDBN} may suggest that the
28744 current thread or frame be changed. For example, when stopping on a
28745 breakpoint it is reasonable to switch to the thread where breakpoint is
28746 hit. For another example, if the user issues the CLI @samp{thread} or
28747 @samp{frame} commands via the frontend, it is desirable to change the
28748 frontend's selection to the one specified by user. @value{GDBN}
28749 communicates the suggestion to change current thread and frame using the
28750 @samp{=thread-selected} notification.
28752 Note that historically, MI shares the selected thread with CLI, so
28753 frontends used the @code{-thread-select} to execute commands in the
28754 right context. However, getting this to work right is cumbersome. The
28755 simplest way is for frontend to emit @code{-thread-select} command
28756 before every command. This doubles the number of commands that need
28757 to be sent. The alternative approach is to suppress @code{-thread-select}
28758 if the selected thread in @value{GDBN} is supposed to be identical to the
28759 thread the frontend wants to operate on. However, getting this
28760 optimization right can be tricky. In particular, if the frontend
28761 sends several commands to @value{GDBN}, and one of the commands changes the
28762 selected thread, then the behaviour of subsequent commands will
28763 change. So, a frontend should either wait for response from such
28764 problematic commands, or explicitly add @code{-thread-select} for
28765 all subsequent commands. No frontend is known to do this exactly
28766 right, so it is suggested to just always pass the @samp{--thread} and
28767 @samp{--frame} options.
28769 @subsubsection Language
28771 The execution of several commands depends on which language is selected.
28772 By default, the current language (@pxref{show language}) is used.
28773 But for commands known to be language-sensitive, it is recommended
28774 to use the @samp{--language} option. This option takes one argument,
28775 which is the name of the language to use while executing the command.
28779 -data-evaluate-expression --language c "sizeof (void*)"
28784 The valid language names are the same names accepted by the
28785 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
28786 @samp{local} or @samp{unknown}.
28788 @node Asynchronous and non-stop modes
28789 @subsection Asynchronous command execution and non-stop mode
28791 On some targets, @value{GDBN} is capable of processing MI commands
28792 even while the target is running. This is called @dfn{asynchronous
28793 command execution} (@pxref{Background Execution}). The frontend may
28794 specify a preference for asynchronous execution using the
28795 @code{-gdb-set mi-async 1} command, which should be emitted before
28796 either running the executable or attaching to the target. After the
28797 frontend has started the executable or attached to the target, it can
28798 find if asynchronous execution is enabled using the
28799 @code{-list-target-features} command.
28802 @item -gdb-set mi-async on
28803 @item -gdb-set mi-async off
28804 Set whether MI is in asynchronous mode.
28806 When @code{off}, which is the default, MI execution commands (e.g.,
28807 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
28808 for the program to stop before processing further commands.
28810 When @code{on}, MI execution commands are background execution
28811 commands (e.g., @code{-exec-continue} becomes the equivalent of the
28812 @code{c&} CLI command), and so @value{GDBN} is capable of processing
28813 MI commands even while the target is running.
28815 @item -gdb-show mi-async
28816 Show whether MI asynchronous mode is enabled.
28819 Note: In @value{GDBN} version 7.7 and earlier, this option was called
28820 @code{target-async} instead of @code{mi-async}, and it had the effect
28821 of both putting MI in asynchronous mode and making CLI background
28822 commands possible. CLI background commands are now always possible
28823 ``out of the box'' if the target supports them. The old spelling is
28824 kept as a deprecated alias for backwards compatibility.
28826 Even if @value{GDBN} can accept a command while target is running,
28827 many commands that access the target do not work when the target is
28828 running. Therefore, asynchronous command execution is most useful
28829 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28830 it is possible to examine the state of one thread, while other threads
28833 When a given thread is running, MI commands that try to access the
28834 target in the context of that thread may not work, or may work only on
28835 some targets. In particular, commands that try to operate on thread's
28836 stack will not work, on any target. Commands that read memory, or
28837 modify breakpoints, may work or not work, depending on the target. Note
28838 that even commands that operate on global state, such as @code{print},
28839 @code{set}, and breakpoint commands, still access the target in the
28840 context of a specific thread, so frontend should try to find a
28841 stopped thread and perform the operation on that thread (using the
28842 @samp{--thread} option).
28844 Which commands will work in the context of a running thread is
28845 highly target dependent. However, the two commands
28846 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28847 to find the state of a thread, will always work.
28849 @node Thread groups
28850 @subsection Thread groups
28851 @value{GDBN} may be used to debug several processes at the same time.
28852 On some platforms, @value{GDBN} may support debugging of several
28853 hardware systems, each one having several cores with several different
28854 processes running on each core. This section describes the MI
28855 mechanism to support such debugging scenarios.
28857 The key observation is that regardless of the structure of the
28858 target, MI can have a global list of threads, because most commands that
28859 accept the @samp{--thread} option do not need to know what process that
28860 thread belongs to. Therefore, it is not necessary to introduce
28861 neither additional @samp{--process} option, nor an notion of the
28862 current process in the MI interface. The only strictly new feature
28863 that is required is the ability to find how the threads are grouped
28866 To allow the user to discover such grouping, and to support arbitrary
28867 hierarchy of machines/cores/processes, MI introduces the concept of a
28868 @dfn{thread group}. Thread group is a collection of threads and other
28869 thread groups. A thread group always has a string identifier, a type,
28870 and may have additional attributes specific to the type. A new
28871 command, @code{-list-thread-groups}, returns the list of top-level
28872 thread groups, which correspond to processes that @value{GDBN} is
28873 debugging at the moment. By passing an identifier of a thread group
28874 to the @code{-list-thread-groups} command, it is possible to obtain
28875 the members of specific thread group.
28877 To allow the user to easily discover processes, and other objects, he
28878 wishes to debug, a concept of @dfn{available thread group} is
28879 introduced. Available thread group is an thread group that
28880 @value{GDBN} is not debugging, but that can be attached to, using the
28881 @code{-target-attach} command. The list of available top-level thread
28882 groups can be obtained using @samp{-list-thread-groups --available}.
28883 In general, the content of a thread group may be only retrieved only
28884 after attaching to that thread group.
28886 Thread groups are related to inferiors (@pxref{Inferiors Connections and
28887 Programs}). Each inferior corresponds to a thread group of a special
28888 type @samp{process}, and some additional operations are permitted on
28889 such thread groups.
28891 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28892 @node GDB/MI Command Syntax
28893 @section @sc{gdb/mi} Command Syntax
28896 * GDB/MI Input Syntax::
28897 * GDB/MI Output Syntax::
28900 @node GDB/MI Input Syntax
28901 @subsection @sc{gdb/mi} Input Syntax
28903 @cindex input syntax for @sc{gdb/mi}
28904 @cindex @sc{gdb/mi}, input syntax
28906 @item @var{command} @expansion{}
28907 @code{@var{cli-command} | @var{mi-command}}
28909 @item @var{cli-command} @expansion{}
28910 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
28911 @var{cli-command} is any existing @value{GDBN} CLI command.
28913 @item @var{mi-command} @expansion{}
28914 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
28915 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
28917 @item @var{token} @expansion{}
28918 "any sequence of digits"
28920 @item @var{option} @expansion{}
28921 @code{"-" @var{parameter} [ " " @var{parameter} ]}
28923 @item @var{parameter} @expansion{}
28924 @code{@var{non-blank-sequence} | @var{c-string}}
28926 @item @var{operation} @expansion{}
28927 @emph{any of the operations described in this chapter}
28929 @item @var{non-blank-sequence} @expansion{}
28930 @emph{anything, provided it doesn't contain special characters such as
28931 "-", @var{nl}, """ and of course " "}
28933 @item @var{c-string} @expansion{}
28934 @code{""" @var{seven-bit-iso-c-string-content} """}
28936 @item @var{nl} @expansion{}
28945 The CLI commands are still handled by the @sc{mi} interpreter; their
28946 output is described below.
28949 The @code{@var{token}}, when present, is passed back when the command
28953 Some @sc{mi} commands accept optional arguments as part of the parameter
28954 list. Each option is identified by a leading @samp{-} (dash) and may be
28955 followed by an optional argument parameter. Options occur first in the
28956 parameter list and can be delimited from normal parameters using
28957 @samp{--} (this is useful when some parameters begin with a dash).
28964 We want easy access to the existing CLI syntax (for debugging).
28967 We want it to be easy to spot a @sc{mi} operation.
28970 @node GDB/MI Output Syntax
28971 @subsection @sc{gdb/mi} Output Syntax
28973 @cindex output syntax of @sc{gdb/mi}
28974 @cindex @sc{gdb/mi}, output syntax
28975 The output from @sc{gdb/mi} consists of zero or more out-of-band records
28976 followed, optionally, by a single result record. This result record
28977 is for the most recent command. The sequence of output records is
28978 terminated by @samp{(gdb)}.
28980 If an input command was prefixed with a @code{@var{token}} then the
28981 corresponding output for that command will also be prefixed by that same
28985 @item @var{output} @expansion{}
28986 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
28988 @item @var{result-record} @expansion{}
28989 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
28991 @item @var{out-of-band-record} @expansion{}
28992 @code{@var{async-record} | @var{stream-record}}
28994 @item @var{async-record} @expansion{}
28995 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
28997 @item @var{exec-async-output} @expansion{}
28998 @code{[ @var{token} ] "*" @var{async-output nl}}
29000 @item @var{status-async-output} @expansion{}
29001 @code{[ @var{token} ] "+" @var{async-output nl}}
29003 @item @var{notify-async-output} @expansion{}
29004 @code{[ @var{token} ] "=" @var{async-output nl}}
29006 @item @var{async-output} @expansion{}
29007 @code{@var{async-class} ( "," @var{result} )*}
29009 @item @var{result-class} @expansion{}
29010 @code{"done" | "running" | "connected" | "error" | "exit"}
29012 @item @var{async-class} @expansion{}
29013 @code{"stopped" | @var{others}} (where @var{others} will be added
29014 depending on the needs---this is still in development).
29016 @item @var{result} @expansion{}
29017 @code{ @var{variable} "=" @var{value}}
29019 @item @var{variable} @expansion{}
29020 @code{ @var{string} }
29022 @item @var{value} @expansion{}
29023 @code{ @var{const} | @var{tuple} | @var{list} }
29025 @item @var{const} @expansion{}
29026 @code{@var{c-string}}
29028 @item @var{tuple} @expansion{}
29029 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29031 @item @var{list} @expansion{}
29032 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29033 @var{result} ( "," @var{result} )* "]" }
29035 @item @var{stream-record} @expansion{}
29036 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29038 @item @var{console-stream-output} @expansion{}
29039 @code{"~" @var{c-string nl}}
29041 @item @var{target-stream-output} @expansion{}
29042 @code{"@@" @var{c-string nl}}
29044 @item @var{log-stream-output} @expansion{}
29045 @code{"&" @var{c-string nl}}
29047 @item @var{nl} @expansion{}
29050 @item @var{token} @expansion{}
29051 @emph{any sequence of digits}.
29059 All output sequences end in a single line containing a period.
29062 The @code{@var{token}} is from the corresponding request. Note that
29063 for all async output, while the token is allowed by the grammar and
29064 may be output by future versions of @value{GDBN} for select async
29065 output messages, it is generally omitted. Frontends should treat
29066 all async output as reporting general changes in the state of the
29067 target and there should be no need to associate async output to any
29071 @cindex status output in @sc{gdb/mi}
29072 @var{status-async-output} contains on-going status information about the
29073 progress of a slow operation. It can be discarded. All status output is
29074 prefixed by @samp{+}.
29077 @cindex async output in @sc{gdb/mi}
29078 @var{exec-async-output} contains asynchronous state change on the target
29079 (stopped, started, disappeared). All async output is prefixed by
29083 @cindex notify output in @sc{gdb/mi}
29084 @var{notify-async-output} contains supplementary information that the
29085 client should handle (e.g., a new breakpoint information). All notify
29086 output is prefixed by @samp{=}.
29089 @cindex console output in @sc{gdb/mi}
29090 @var{console-stream-output} is output that should be displayed as is in the
29091 console. It is the textual response to a CLI command. All the console
29092 output is prefixed by @samp{~}.
29095 @cindex target output in @sc{gdb/mi}
29096 @var{target-stream-output} is the output produced by the target program.
29097 All the target output is prefixed by @samp{@@}.
29100 @cindex log output in @sc{gdb/mi}
29101 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29102 instance messages that should be displayed as part of an error log. All
29103 the log output is prefixed by @samp{&}.
29106 @cindex list output in @sc{gdb/mi}
29107 New @sc{gdb/mi} commands should only output @var{lists} containing
29113 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29114 details about the various output records.
29116 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29117 @node GDB/MI Compatibility with CLI
29118 @section @sc{gdb/mi} Compatibility with CLI
29120 @cindex compatibility, @sc{gdb/mi} and CLI
29121 @cindex @sc{gdb/mi}, compatibility with CLI
29123 For the developers convenience CLI commands can be entered directly,
29124 but there may be some unexpected behaviour. For example, commands
29125 that query the user will behave as if the user replied yes, breakpoint
29126 command lists are not executed and some CLI commands, such as
29127 @code{if}, @code{when} and @code{define}, prompt for further input with
29128 @samp{>}, which is not valid MI output.
29130 This feature may be removed at some stage in the future and it is
29131 recommended that front ends use the @code{-interpreter-exec} command
29132 (@pxref{-interpreter-exec}).
29134 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29135 @node GDB/MI Development and Front Ends
29136 @section @sc{gdb/mi} Development and Front Ends
29137 @cindex @sc{gdb/mi} development
29139 The application which takes the MI output and presents the state of the
29140 program being debugged to the user is called a @dfn{front end}.
29142 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
29143 to the MI interface may break existing usage. This section describes how the
29144 protocol changes and how to request previous version of the protocol when it
29147 Some changes in MI need not break a carefully designed front end, and
29148 for these the MI version will remain unchanged. The following is a
29149 list of changes that may occur within one level, so front ends should
29150 parse MI output in a way that can handle them:
29154 New MI commands may be added.
29157 New fields may be added to the output of any MI command.
29160 The range of values for fields with specified values, e.g.,
29161 @code{in_scope} (@pxref{-var-update}) may be extended.
29163 @c The format of field's content e.g type prefix, may change so parse it
29164 @c at your own risk. Yes, in general?
29166 @c The order of fields may change? Shouldn't really matter but it might
29167 @c resolve inconsistencies.
29170 If the changes are likely to break front ends, the MI version level
29171 will be increased by one. The new versions of the MI protocol are not compatible
29172 with the old versions. Old versions of MI remain available, allowing front ends
29173 to keep using them until they are modified to use the latest MI version.
29175 Since @code{--interpreter=mi} always points to the latest MI version, it is
29176 recommended that front ends request a specific version of MI when launching
29177 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
29178 interpreter with the MI version they expect.
29180 The following table gives a summary of the released versions of the MI
29181 interface: the version number, the version of GDB in which it first appeared
29182 and the breaking changes compared to the previous version.
29184 @multitable @columnfractions .05 .05 .9
29185 @headitem MI version @tab GDB version @tab Breaking changes
29202 The @code{-environment-pwd}, @code{-environment-directory} and
29203 @code{-environment-path} commands now returns values using the MI output
29204 syntax, rather than CLI output syntax.
29207 @code{-var-list-children}'s @code{children} result field is now a list, rather
29211 @code{-var-update}'s @code{changelist} result field is now a list, rather than
29223 The output of information about multi-location breakpoints has changed in the
29224 responses to the @code{-break-insert} and @code{-break-info} commands, as well
29225 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
29226 The multiple locations are now placed in a @code{locations} field, whose value
29232 If your front end cannot yet migrate to a more recent version of the
29233 MI protocol, you can nevertheless selectively enable specific features
29234 available in those recent MI versions, using the following commands:
29238 @item -fix-multi-location-breakpoint-output
29239 Use the output for multi-location breakpoints which was introduced by
29240 MI 3, even when using MI versions 2 or 1. This command has no
29241 effect when using MI version 3 or later.
29245 The best way to avoid unexpected changes in MI that might break your front
29246 end is to make your project known to @value{GDBN} developers and
29247 follow development on @email{gdb@@sourceware.org} and
29248 @email{gdb-patches@@sourceware.org}.
29249 @cindex mailing lists
29251 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29252 @node GDB/MI Output Records
29253 @section @sc{gdb/mi} Output Records
29256 * GDB/MI Result Records::
29257 * GDB/MI Stream Records::
29258 * GDB/MI Async Records::
29259 * GDB/MI Breakpoint Information::
29260 * GDB/MI Frame Information::
29261 * GDB/MI Thread Information::
29262 * GDB/MI Ada Exception Information::
29265 @node GDB/MI Result Records
29266 @subsection @sc{gdb/mi} Result Records
29268 @cindex result records in @sc{gdb/mi}
29269 @cindex @sc{gdb/mi}, result records
29270 In addition to a number of out-of-band notifications, the response to a
29271 @sc{gdb/mi} command includes one of the following result indications:
29275 @item "^done" [ "," @var{results} ]
29276 The synchronous operation was successful, @code{@var{results}} are the return
29281 This result record is equivalent to @samp{^done}. Historically, it
29282 was output instead of @samp{^done} if the command has resumed the
29283 target. This behaviour is maintained for backward compatibility, but
29284 all frontends should treat @samp{^done} and @samp{^running}
29285 identically and rely on the @samp{*running} output record to determine
29286 which threads are resumed.
29290 @value{GDBN} has connected to a remote target.
29292 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29294 The operation failed. The @code{msg=@var{c-string}} variable contains
29295 the corresponding error message.
29297 If present, the @code{code=@var{c-string}} variable provides an error
29298 code on which consumers can rely on to detect the corresponding
29299 error condition. At present, only one error code is defined:
29302 @item "undefined-command"
29303 Indicates that the command causing the error does not exist.
29308 @value{GDBN} has terminated.
29312 @node GDB/MI Stream Records
29313 @subsection @sc{gdb/mi} Stream Records
29315 @cindex @sc{gdb/mi}, stream records
29316 @cindex stream records in @sc{gdb/mi}
29317 @value{GDBN} internally maintains a number of output streams: the console, the
29318 target, and the log. The output intended for each of these streams is
29319 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29321 Each stream record begins with a unique @dfn{prefix character} which
29322 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29323 Syntax}). In addition to the prefix, each stream record contains a
29324 @code{@var{string-output}}. This is either raw text (with an implicit new
29325 line) or a quoted C string (which does not contain an implicit newline).
29328 @item "~" @var{string-output}
29329 The console output stream contains text that should be displayed in the
29330 CLI console window. It contains the textual responses to CLI commands.
29332 @item "@@" @var{string-output}
29333 The target output stream contains any textual output from the running
29334 target. This is only present when GDB's event loop is truly
29335 asynchronous, which is currently only the case for remote targets.
29337 @item "&" @var{string-output}
29338 The log stream contains debugging messages being produced by @value{GDBN}'s
29342 @node GDB/MI Async Records
29343 @subsection @sc{gdb/mi} Async Records
29345 @cindex async records in @sc{gdb/mi}
29346 @cindex @sc{gdb/mi}, async records
29347 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29348 additional changes that have occurred. Those changes can either be a
29349 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29350 target activity (e.g., target stopped).
29352 The following is the list of possible async records:
29356 @item *running,thread-id="@var{thread}"
29357 The target is now running. The @var{thread} field can be the global
29358 thread ID of the thread that is now running, and it can be
29359 @samp{all} if all threads are running. The frontend should assume
29360 that no interaction with a running thread is possible after this
29361 notification is produced. The frontend should not assume that this
29362 notification is output only once for any command. @value{GDBN} may
29363 emit this notification several times, either for different threads,
29364 because it cannot resume all threads together, or even for a single
29365 thread, if the thread must be stepped though some code before letting
29368 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29369 The target has stopped. The @var{reason} field can have one of the
29373 @item breakpoint-hit
29374 A breakpoint was reached.
29375 @item watchpoint-trigger
29376 A watchpoint was triggered.
29377 @item read-watchpoint-trigger
29378 A read watchpoint was triggered.
29379 @item access-watchpoint-trigger
29380 An access watchpoint was triggered.
29381 @item function-finished
29382 An -exec-finish or similar CLI command was accomplished.
29383 @item location-reached
29384 An -exec-until or similar CLI command was accomplished.
29385 @item watchpoint-scope
29386 A watchpoint has gone out of scope.
29387 @item end-stepping-range
29388 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29389 similar CLI command was accomplished.
29390 @item exited-signalled
29391 The inferior exited because of a signal.
29393 The inferior exited.
29394 @item exited-normally
29395 The inferior exited normally.
29396 @item signal-received
29397 A signal was received by the inferior.
29399 The inferior has stopped due to a library being loaded or unloaded.
29400 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29401 set or when a @code{catch load} or @code{catch unload} catchpoint is
29402 in use (@pxref{Set Catchpoints}).
29404 The inferior has forked. This is reported when @code{catch fork}
29405 (@pxref{Set Catchpoints}) has been used.
29407 The inferior has vforked. This is reported in when @code{catch vfork}
29408 (@pxref{Set Catchpoints}) has been used.
29409 @item syscall-entry
29410 The inferior entered a system call. This is reported when @code{catch
29411 syscall} (@pxref{Set Catchpoints}) has been used.
29412 @item syscall-return
29413 The inferior returned from a system call. This is reported when
29414 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29416 The inferior called @code{exec}. This is reported when @code{catch exec}
29417 (@pxref{Set Catchpoints}) has been used.
29420 The @var{id} field identifies the global thread ID of the thread
29421 that directly caused the stop -- for example by hitting a breakpoint.
29422 Depending on whether all-stop
29423 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29424 stop all threads, or only the thread that directly triggered the stop.
29425 If all threads are stopped, the @var{stopped} field will have the
29426 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29427 field will be a list of thread identifiers. Presently, this list will
29428 always include a single thread, but frontend should be prepared to see
29429 several threads in the list. The @var{core} field reports the
29430 processor core on which the stop event has happened. This field may be absent
29431 if such information is not available.
29433 @item =thread-group-added,id="@var{id}"
29434 @itemx =thread-group-removed,id="@var{id}"
29435 A thread group was either added or removed. The @var{id} field
29436 contains the @value{GDBN} identifier of the thread group. When a thread
29437 group is added, it generally might not be associated with a running
29438 process. When a thread group is removed, its id becomes invalid and
29439 cannot be used in any way.
29441 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29442 A thread group became associated with a running program,
29443 either because the program was just started or the thread group
29444 was attached to a program. The @var{id} field contains the
29445 @value{GDBN} identifier of the thread group. The @var{pid} field
29446 contains process identifier, specific to the operating system.
29448 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29449 A thread group is no longer associated with a running program,
29450 either because the program has exited, or because it was detached
29451 from. The @var{id} field contains the @value{GDBN} identifier of the
29452 thread group. The @var{code} field is the exit code of the inferior; it exists
29453 only when the inferior exited with some code.
29455 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29456 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29457 A thread either was created, or has exited. The @var{id} field
29458 contains the global @value{GDBN} identifier of the thread. The @var{gid}
29459 field identifies the thread group this thread belongs to.
29461 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
29462 Informs that the selected thread or frame were changed. This notification
29463 is not emitted as result of the @code{-thread-select} or
29464 @code{-stack-select-frame} commands, but is emitted whenever an MI command
29465 that is not documented to change the selected thread and frame actually
29466 changes them. In particular, invoking, directly or indirectly
29467 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
29468 will generate this notification. Changing the thread or frame from another
29469 user interface (see @ref{Interpreters}) will also generate this notification.
29471 The @var{frame} field is only present if the newly selected thread is
29472 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
29474 We suggest that in response to this notification, front ends
29475 highlight the selected thread and cause subsequent commands to apply to
29478 @item =library-loaded,...
29479 Reports that a new library file was loaded by the program. This
29480 notification has 5 fields---@var{id}, @var{target-name},
29481 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
29482 opaque identifier of the library. For remote debugging case,
29483 @var{target-name} and @var{host-name} fields give the name of the
29484 library file on the target, and on the host respectively. For native
29485 debugging, both those fields have the same value. The
29486 @var{symbols-loaded} field is emitted only for backward compatibility
29487 and should not be relied on to convey any useful information. The
29488 @var{thread-group} field, if present, specifies the id of the thread
29489 group in whose context the library was loaded. If the field is
29490 absent, it means the library was loaded in the context of all present
29491 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
29494 @item =library-unloaded,...
29495 Reports that a library was unloaded by the program. This notification
29496 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29497 the same meaning as for the @code{=library-loaded} notification.
29498 The @var{thread-group} field, if present, specifies the id of the
29499 thread group in whose context the library was unloaded. If the field is
29500 absent, it means the library was unloaded in the context of all present
29503 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29504 @itemx =traceframe-changed,end
29505 Reports that the trace frame was changed and its new number is
29506 @var{tfnum}. The number of the tracepoint associated with this trace
29507 frame is @var{tpnum}.
29509 @item =tsv-created,name=@var{name},initial=@var{initial}
29510 Reports that the new trace state variable @var{name} is created with
29511 initial value @var{initial}.
29513 @item =tsv-deleted,name=@var{name}
29514 @itemx =tsv-deleted
29515 Reports that the trace state variable @var{name} is deleted or all
29516 trace state variables are deleted.
29518 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29519 Reports that the trace state variable @var{name} is modified with
29520 the initial value @var{initial}. The current value @var{current} of
29521 trace state variable is optional and is reported if the current
29522 value of trace state variable is known.
29524 @item =breakpoint-created,bkpt=@{...@}
29525 @itemx =breakpoint-modified,bkpt=@{...@}
29526 @itemx =breakpoint-deleted,id=@var{number}
29527 Reports that a breakpoint was created, modified, or deleted,
29528 respectively. Only user-visible breakpoints are reported to the MI
29531 The @var{bkpt} argument is of the same form as returned by the various
29532 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29533 @var{number} is the ordinal number of the breakpoint.
29535 Note that if a breakpoint is emitted in the result record of a
29536 command, then it will not also be emitted in an async record.
29538 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
29539 @itemx =record-stopped,thread-group="@var{id}"
29540 Execution log recording was either started or stopped on an
29541 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29542 group corresponding to the affected inferior.
29544 The @var{method} field indicates the method used to record execution. If the
29545 method in use supports multiple recording formats, @var{format} will be present
29546 and contain the currently used format. @xref{Process Record and Replay},
29547 for existing method and format values.
29549 @item =cmd-param-changed,param=@var{param},value=@var{value}
29550 Reports that a parameter of the command @code{set @var{param}} is
29551 changed to @var{value}. In the multi-word @code{set} command,
29552 the @var{param} is the whole parameter list to @code{set} command.
29553 For example, In command @code{set check type on}, @var{param}
29554 is @code{check type} and @var{value} is @code{on}.
29556 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29557 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29558 written in an inferior. The @var{id} is the identifier of the
29559 thread group corresponding to the affected inferior. The optional
29560 @code{type="code"} part is reported if the memory written to holds
29564 @node GDB/MI Breakpoint Information
29565 @subsection @sc{gdb/mi} Breakpoint Information
29567 When @value{GDBN} reports information about a breakpoint, a
29568 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29573 The breakpoint number.
29576 The type of the breakpoint. For ordinary breakpoints this will be
29577 @samp{breakpoint}, but many values are possible.
29580 If the type of the breakpoint is @samp{catchpoint}, then this
29581 indicates the exact type of catchpoint.
29584 This is the breakpoint disposition---either @samp{del}, meaning that
29585 the breakpoint will be deleted at the next stop, or @samp{keep},
29586 meaning that the breakpoint will not be deleted.
29589 This indicates whether the breakpoint is enabled, in which case the
29590 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29591 Note that this is not the same as the field @code{enable}.
29594 The address of the breakpoint. This may be a hexidecimal number,
29595 giving the address; or the string @samp{<PENDING>}, for a pending
29596 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29597 multiple locations. This field will not be present if no address can
29598 be determined. For example, a watchpoint does not have an address.
29601 Optional field containing any flags related to the address. These flags are
29602 architecture-dependent; see @ref{Architectures} for their meaning for a
29606 If known, the function in which the breakpoint appears.
29607 If not known, this field is not present.
29610 The name of the source file which contains this function, if known.
29611 If not known, this field is not present.
29614 The full file name of the source file which contains this function, if
29615 known. If not known, this field is not present.
29618 The line number at which this breakpoint appears, if known.
29619 If not known, this field is not present.
29622 If the source file is not known, this field may be provided. If
29623 provided, this holds the address of the breakpoint, possibly followed
29627 If this breakpoint is pending, this field is present and holds the
29628 text used to set the breakpoint, as entered by the user.
29631 Where this breakpoint's condition is evaluated, either @samp{host} or
29635 If this is a thread-specific breakpoint, then this identifies the
29636 thread in which the breakpoint can trigger.
29639 If this breakpoint is restricted to a particular Ada task, then this
29640 field will hold the task identifier.
29643 If the breakpoint is conditional, this is the condition expression.
29646 The ignore count of the breakpoint.
29649 The enable count of the breakpoint.
29651 @item traceframe-usage
29654 @item static-tracepoint-marker-string-id
29655 For a static tracepoint, the name of the static tracepoint marker.
29658 For a masked watchpoint, this is the mask.
29661 A tracepoint's pass count.
29663 @item original-location
29664 The location of the breakpoint as originally specified by the user.
29665 This field is optional.
29668 The number of times the breakpoint has been hit.
29671 This field is only given for tracepoints. This is either @samp{y},
29672 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29676 Some extra data, the exact contents of which are type-dependent.
29679 This field is present if the breakpoint has multiple locations. It is also
29680 exceptionally present if the breakpoint is enabled and has a single, disabled
29683 The value is a list of locations. The format of a location is described below.
29687 A location in a multi-location breakpoint is represented as a tuple with the
29693 The location number as a dotted pair, like @samp{1.2}. The first digit is the
29694 number of the parent breakpoint. The second digit is the number of the
29695 location within that breakpoint.
29698 This indicates whether the location is enabled, in which case the
29699 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29700 Note that this is not the same as the field @code{enable}.
29703 The address of this location as an hexidecimal number.
29706 Optional field containing any flags related to the address. These flags are
29707 architecture-dependent; see @ref{Architectures} for their meaning for a
29711 If known, the function in which the location appears.
29712 If not known, this field is not present.
29715 The name of the source file which contains this location, if known.
29716 If not known, this field is not present.
29719 The full file name of the source file which contains this location, if
29720 known. If not known, this field is not present.
29723 The line number at which this location appears, if known.
29724 If not known, this field is not present.
29726 @item thread-groups
29727 The thread groups this location is in.
29731 For example, here is what the output of @code{-break-insert}
29732 (@pxref{GDB/MI Breakpoint Commands}) might be:
29735 -> -break-insert main
29736 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29737 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29738 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29743 @node GDB/MI Frame Information
29744 @subsection @sc{gdb/mi} Frame Information
29746 Response from many MI commands includes an information about stack
29747 frame. This information is a tuple that may have the following
29752 The level of the stack frame. The innermost frame has the level of
29753 zero. This field is always present.
29756 The name of the function corresponding to the frame. This field may
29757 be absent if @value{GDBN} is unable to determine the function name.
29760 The code address for the frame. This field is always present.
29763 Optional field containing any flags related to the address. These flags are
29764 architecture-dependent; see @ref{Architectures} for their meaning for a
29768 The name of the source files that correspond to the frame's code
29769 address. This field may be absent.
29772 The source line corresponding to the frames' code address. This field
29776 The name of the binary file (either executable or shared library) the
29777 corresponds to the frame's code address. This field may be absent.
29781 @node GDB/MI Thread Information
29782 @subsection @sc{gdb/mi} Thread Information
29784 Whenever @value{GDBN} has to report an information about a thread, it
29785 uses a tuple with the following fields. The fields are always present unless
29790 The global numeric id assigned to the thread by @value{GDBN}.
29793 The target-specific string identifying the thread.
29796 Additional information about the thread provided by the target.
29797 It is supposed to be human-readable and not interpreted by the
29798 frontend. This field is optional.
29801 The name of the thread. If the user specified a name using the
29802 @code{thread name} command, then this name is given. Otherwise, if
29803 @value{GDBN} can extract the thread name from the target, then that
29804 name is given. If @value{GDBN} cannot find the thread name, then this
29808 The execution state of the thread, either @samp{stopped} or @samp{running},
29809 depending on whether the thread is presently running.
29812 The stack frame currently executing in the thread. This field is only present
29813 if the thread is stopped. Its format is documented in
29814 @ref{GDB/MI Frame Information}.
29817 The value of this field is an integer number of the processor core the
29818 thread was last seen on. This field is optional.
29821 @node GDB/MI Ada Exception Information
29822 @subsection @sc{gdb/mi} Ada Exception Information
29824 Whenever a @code{*stopped} record is emitted because the program
29825 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29826 @value{GDBN} provides the name of the exception that was raised via
29827 the @code{exception-name} field. Also, for exceptions that were raised
29828 with an exception message, @value{GDBN} provides that message via
29829 the @code{exception-message} field.
29831 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29832 @node GDB/MI Simple Examples
29833 @section Simple Examples of @sc{gdb/mi} Interaction
29834 @cindex @sc{gdb/mi}, simple examples
29836 This subsection presents several simple examples of interaction using
29837 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29838 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29839 the output received from @sc{gdb/mi}.
29841 Note the line breaks shown in the examples are here only for
29842 readability, they don't appear in the real output.
29844 @subheading Setting a Breakpoint
29846 Setting a breakpoint generates synchronous output which contains detailed
29847 information of the breakpoint.
29850 -> -break-insert main
29851 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29852 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29853 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29858 @subheading Program Execution
29860 Program execution generates asynchronous records and MI gives the
29861 reason that execution stopped.
29867 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29868 frame=@{addr="0x08048564",func="main",
29869 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29870 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
29871 arch="i386:x86_64"@}
29876 <- *stopped,reason="exited-normally"
29880 @subheading Quitting @value{GDBN}
29882 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29890 Please note that @samp{^exit} is printed immediately, but it might
29891 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29892 performs necessary cleanups, including killing programs being debugged
29893 or disconnecting from debug hardware, so the frontend should wait till
29894 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29895 fails to exit in reasonable time.
29897 @subheading A Bad Command
29899 Here's what happens if you pass a non-existent command:
29903 <- ^error,msg="Undefined MI command: rubbish"
29908 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29909 @node GDB/MI Command Description Format
29910 @section @sc{gdb/mi} Command Description Format
29912 The remaining sections describe blocks of commands. Each block of
29913 commands is laid out in a fashion similar to this section.
29915 @subheading Motivation
29917 The motivation for this collection of commands.
29919 @subheading Introduction
29921 A brief introduction to this collection of commands as a whole.
29923 @subheading Commands
29925 For each command in the block, the following is described:
29927 @subsubheading Synopsis
29930 -command @var{args}@dots{}
29933 @subsubheading Result
29935 @subsubheading @value{GDBN} Command
29937 The corresponding @value{GDBN} CLI command(s), if any.
29939 @subsubheading Example
29941 Example(s) formatted for readability. Some of the described commands have
29942 not been implemented yet and these are labeled N.A.@: (not available).
29945 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29946 @node GDB/MI Breakpoint Commands
29947 @section @sc{gdb/mi} Breakpoint Commands
29949 @cindex breakpoint commands for @sc{gdb/mi}
29950 @cindex @sc{gdb/mi}, breakpoint commands
29951 This section documents @sc{gdb/mi} commands for manipulating
29954 @subheading The @code{-break-after} Command
29955 @findex -break-after
29957 @subsubheading Synopsis
29960 -break-after @var{number} @var{count}
29963 The breakpoint number @var{number} is not in effect until it has been
29964 hit @var{count} times. To see how this is reflected in the output of
29965 the @samp{-break-list} command, see the description of the
29966 @samp{-break-list} command below.
29968 @subsubheading @value{GDBN} Command
29970 The corresponding @value{GDBN} command is @samp{ignore}.
29972 @subsubheading Example
29977 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29978 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29979 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29987 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29988 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29989 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29990 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29991 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29992 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29993 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29994 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29995 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29996 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30001 @subheading The @code{-break-catch} Command
30002 @findex -break-catch
30005 @subheading The @code{-break-commands} Command
30006 @findex -break-commands
30008 @subsubheading Synopsis
30011 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30014 Specifies the CLI commands that should be executed when breakpoint
30015 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30016 are the commands. If no command is specified, any previously-set
30017 commands are cleared. @xref{Break Commands}. Typical use of this
30018 functionality is tracing a program, that is, printing of values of
30019 some variables whenever breakpoint is hit and then continuing.
30021 @subsubheading @value{GDBN} Command
30023 The corresponding @value{GDBN} command is @samp{commands}.
30025 @subsubheading Example
30030 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30031 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30032 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30035 -break-commands 1 "print v" "continue"
30040 @subheading The @code{-break-condition} Command
30041 @findex -break-condition
30043 @subsubheading Synopsis
30046 -break-condition @var{number} @var{expr}
30049 Breakpoint @var{number} will stop the program only if the condition in
30050 @var{expr} is true. The condition becomes part of the
30051 @samp{-break-list} output (see the description of the @samp{-break-list}
30054 @subsubheading @value{GDBN} Command
30056 The corresponding @value{GDBN} command is @samp{condition}.
30058 @subsubheading Example
30062 -break-condition 1 1
30066 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30067 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30068 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30069 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30070 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30071 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30072 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30073 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30074 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30075 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30079 @subheading The @code{-break-delete} Command
30080 @findex -break-delete
30082 @subsubheading Synopsis
30085 -break-delete ( @var{breakpoint} )+
30088 Delete the breakpoint(s) whose number(s) are specified in the argument
30089 list. This is obviously reflected in the breakpoint list.
30091 @subsubheading @value{GDBN} Command
30093 The corresponding @value{GDBN} command is @samp{delete}.
30095 @subsubheading Example
30103 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30104 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30105 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30106 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30107 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30108 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30109 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30114 @subheading The @code{-break-disable} Command
30115 @findex -break-disable
30117 @subsubheading Synopsis
30120 -break-disable ( @var{breakpoint} )+
30123 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30124 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30126 @subsubheading @value{GDBN} Command
30128 The corresponding @value{GDBN} command is @samp{disable}.
30130 @subsubheading Example
30138 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30139 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30140 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30141 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30142 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30143 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30144 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30145 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30146 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30147 line="5",thread-groups=["i1"],times="0"@}]@}
30151 @subheading The @code{-break-enable} Command
30152 @findex -break-enable
30154 @subsubheading Synopsis
30157 -break-enable ( @var{breakpoint} )+
30160 Enable (previously disabled) @var{breakpoint}(s).
30162 @subsubheading @value{GDBN} Command
30164 The corresponding @value{GDBN} command is @samp{enable}.
30166 @subsubheading Example
30174 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30175 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30176 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30177 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30178 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30179 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30180 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30181 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30182 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30183 line="5",thread-groups=["i1"],times="0"@}]@}
30187 @subheading The @code{-break-info} Command
30188 @findex -break-info
30190 @subsubheading Synopsis
30193 -break-info @var{breakpoint}
30197 Get information about a single breakpoint.
30199 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30200 Information}, for details on the format of each breakpoint in the
30203 @subsubheading @value{GDBN} Command
30205 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30207 @subsubheading Example
30210 @subheading The @code{-break-insert} Command
30211 @findex -break-insert
30212 @anchor{-break-insert}
30214 @subsubheading Synopsis
30217 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
30218 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30219 [ -p @var{thread-id} ] [ @var{location} ]
30223 If specified, @var{location}, can be one of:
30226 @item linespec location
30227 A linespec location. @xref{Linespec Locations}.
30229 @item explicit location
30230 An explicit location. @sc{gdb/mi} explicit locations are
30231 analogous to the CLI's explicit locations using the option names
30232 listed below. @xref{Explicit Locations}.
30235 @item --source @var{filename}
30236 The source file name of the location. This option requires the use
30237 of either @samp{--function} or @samp{--line}.
30239 @item --function @var{function}
30240 The name of a function or method.
30242 @item --label @var{label}
30243 The name of a label.
30245 @item --line @var{lineoffset}
30246 An absolute or relative line offset from the start of the location.
30249 @item address location
30250 An address location, *@var{address}. @xref{Address Locations}.
30254 The possible optional parameters of this command are:
30258 Insert a temporary breakpoint.
30260 Insert a hardware breakpoint.
30262 If @var{location} cannot be parsed (for example if it
30263 refers to unknown files or functions), create a pending
30264 breakpoint. Without this flag, @value{GDBN} will report
30265 an error, and won't create a breakpoint, if @var{location}
30268 Create a disabled breakpoint.
30270 Create a tracepoint. @xref{Tracepoints}. When this parameter
30271 is used together with @samp{-h}, a fast tracepoint is created.
30272 @item -c @var{condition}
30273 Make the breakpoint conditional on @var{condition}.
30274 @item -i @var{ignore-count}
30275 Initialize the @var{ignore-count}.
30276 @item -p @var{thread-id}
30277 Restrict the breakpoint to the thread with the specified global
30280 This option makes @value{GDBN} interpret a function name specified as
30281 a complete fully-qualified name.
30284 @subsubheading Result
30286 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30287 resulting breakpoint.
30289 Note: this format is open to change.
30290 @c An out-of-band breakpoint instead of part of the result?
30292 @subsubheading @value{GDBN} Command
30294 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30295 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30297 @subsubheading Example
30302 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30303 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30306 -break-insert -t foo
30307 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30308 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30312 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30313 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30314 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30315 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30316 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30317 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30318 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30319 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30320 addr="0x0001072c", func="main",file="recursive2.c",
30321 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30323 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30324 addr="0x00010774",func="foo",file="recursive2.c",
30325 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30328 @c -break-insert -r foo.*
30329 @c ~int foo(int, int);
30330 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30331 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30336 @subheading The @code{-dprintf-insert} Command
30337 @findex -dprintf-insert
30339 @subsubheading Synopsis
30342 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
30343 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30344 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30349 If supplied, @var{location} and @code{--qualified} may be specified
30350 the same way as for the @code{-break-insert} command.
30351 @xref{-break-insert}.
30353 The possible optional parameters of this command are:
30357 Insert a temporary breakpoint.
30359 If @var{location} cannot be parsed (for example, if it
30360 refers to unknown files or functions), create a pending
30361 breakpoint. Without this flag, @value{GDBN} will report
30362 an error, and won't create a breakpoint, if @var{location}
30365 Create a disabled breakpoint.
30366 @item -c @var{condition}
30367 Make the breakpoint conditional on @var{condition}.
30368 @item -i @var{ignore-count}
30369 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30370 to @var{ignore-count}.
30371 @item -p @var{thread-id}
30372 Restrict the breakpoint to the thread with the specified global
30376 @subsubheading Result
30378 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30379 resulting breakpoint.
30381 @c An out-of-band breakpoint instead of part of the result?
30383 @subsubheading @value{GDBN} Command
30385 The corresponding @value{GDBN} command is @samp{dprintf}.
30387 @subsubheading Example
30391 4-dprintf-insert foo "At foo entry\n"
30392 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30393 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30394 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30395 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30396 original-location="foo"@}
30398 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30399 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30400 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30401 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30402 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30403 original-location="mi-dprintf.c:26"@}
30407 @subheading The @code{-break-list} Command
30408 @findex -break-list
30410 @subsubheading Synopsis
30416 Displays the list of inserted breakpoints, showing the following fields:
30420 number of the breakpoint
30422 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30424 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30427 is the breakpoint enabled or no: @samp{y} or @samp{n}
30429 memory location at which the breakpoint is set
30431 logical location of the breakpoint, expressed by function name, file
30433 @item Thread-groups
30434 list of thread groups to which this breakpoint applies
30436 number of times the breakpoint has been hit
30439 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30440 @code{body} field is an empty list.
30442 @subsubheading @value{GDBN} Command
30444 The corresponding @value{GDBN} command is @samp{info break}.
30446 @subsubheading Example
30451 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30452 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30453 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30454 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30455 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30456 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30457 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30458 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30459 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30461 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30462 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30463 line="13",thread-groups=["i1"],times="0"@}]@}
30467 Here's an example of the result when there are no breakpoints:
30472 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30473 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30474 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30475 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30476 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30477 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30478 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30483 @subheading The @code{-break-passcount} Command
30484 @findex -break-passcount
30486 @subsubheading Synopsis
30489 -break-passcount @var{tracepoint-number} @var{passcount}
30492 Set the passcount for tracepoint @var{tracepoint-number} to
30493 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30494 is not a tracepoint, error is emitted. This corresponds to CLI
30495 command @samp{passcount}.
30497 @subheading The @code{-break-watch} Command
30498 @findex -break-watch
30500 @subsubheading Synopsis
30503 -break-watch [ -a | -r ]
30506 Create a watchpoint. With the @samp{-a} option it will create an
30507 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30508 read from or on a write to the memory location. With the @samp{-r}
30509 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30510 trigger only when the memory location is accessed for reading. Without
30511 either of the options, the watchpoint created is a regular watchpoint,
30512 i.e., it will trigger when the memory location is accessed for writing.
30513 @xref{Set Watchpoints, , Setting Watchpoints}.
30515 Note that @samp{-break-list} will report a single list of watchpoints and
30516 breakpoints inserted.
30518 @subsubheading @value{GDBN} Command
30520 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30523 @subsubheading Example
30525 Setting a watchpoint on a variable in the @code{main} function:
30530 ^done,wpt=@{number="2",exp="x"@}
30535 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30536 value=@{old="-268439212",new="55"@},
30537 frame=@{func="main",args=[],file="recursive2.c",
30538 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
30542 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30543 the program execution twice: first for the variable changing value, then
30544 for the watchpoint going out of scope.
30549 ^done,wpt=@{number="5",exp="C"@}
30554 *stopped,reason="watchpoint-trigger",
30555 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30556 frame=@{func="callee4",args=[],
30557 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30558 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
30559 arch="i386:x86_64"@}
30564 *stopped,reason="watchpoint-scope",wpnum="5",
30565 frame=@{func="callee3",args=[@{name="strarg",
30566 value="0x11940 \"A string argument.\""@}],
30567 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30568 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30569 arch="i386:x86_64"@}
30573 Listing breakpoints and watchpoints, at different points in the program
30574 execution. Note that once the watchpoint goes out of scope, it is
30580 ^done,wpt=@{number="2",exp="C"@}
30583 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30584 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30585 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30586 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30587 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30588 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30589 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30590 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30591 addr="0x00010734",func="callee4",
30592 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30593 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30595 bkpt=@{number="2",type="watchpoint",disp="keep",
30596 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30601 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30602 value=@{old="-276895068",new="3"@},
30603 frame=@{func="callee4",args=[],
30604 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30605 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
30606 arch="i386:x86_64"@}
30609 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30610 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30611 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30612 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30613 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30614 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30615 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30616 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30617 addr="0x00010734",func="callee4",
30618 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30619 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30621 bkpt=@{number="2",type="watchpoint",disp="keep",
30622 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30626 ^done,reason="watchpoint-scope",wpnum="2",
30627 frame=@{func="callee3",args=[@{name="strarg",
30628 value="0x11940 \"A string argument.\""@}],
30629 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30630 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30631 arch="i386:x86_64"@}
30634 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30635 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30636 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30637 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30638 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30639 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30640 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30641 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30642 addr="0x00010734",func="callee4",
30643 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30644 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30645 thread-groups=["i1"],times="1"@}]@}
30650 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30651 @node GDB/MI Catchpoint Commands
30652 @section @sc{gdb/mi} Catchpoint Commands
30654 This section documents @sc{gdb/mi} commands for manipulating
30658 * Shared Library GDB/MI Catchpoint Commands::
30659 * Ada Exception GDB/MI Catchpoint Commands::
30660 * C++ Exception GDB/MI Catchpoint Commands::
30663 @node Shared Library GDB/MI Catchpoint Commands
30664 @subsection Shared Library @sc{gdb/mi} Catchpoints
30666 @subheading The @code{-catch-load} Command
30667 @findex -catch-load
30669 @subsubheading Synopsis
30672 -catch-load [ -t ] [ -d ] @var{regexp}
30675 Add a catchpoint for library load events. If the @samp{-t} option is used,
30676 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30677 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30678 in a disabled state. The @samp{regexp} argument is a regular
30679 expression used to match the name of the loaded library.
30682 @subsubheading @value{GDBN} Command
30684 The corresponding @value{GDBN} command is @samp{catch load}.
30686 @subsubheading Example
30689 -catch-load -t foo.so
30690 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30691 what="load of library matching foo.so",catch-type="load",times="0"@}
30696 @subheading The @code{-catch-unload} Command
30697 @findex -catch-unload
30699 @subsubheading Synopsis
30702 -catch-unload [ -t ] [ -d ] @var{regexp}
30705 Add a catchpoint for library unload events. If the @samp{-t} option is
30706 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30707 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30708 created in a disabled state. The @samp{regexp} argument is a regular
30709 expression used to match the name of the unloaded library.
30711 @subsubheading @value{GDBN} Command
30713 The corresponding @value{GDBN} command is @samp{catch unload}.
30715 @subsubheading Example
30718 -catch-unload -d bar.so
30719 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30720 what="load of library matching bar.so",catch-type="unload",times="0"@}
30724 @node Ada Exception GDB/MI Catchpoint Commands
30725 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30727 The following @sc{gdb/mi} commands can be used to create catchpoints
30728 that stop the execution when Ada exceptions are being raised.
30730 @subheading The @code{-catch-assert} Command
30731 @findex -catch-assert
30733 @subsubheading Synopsis
30736 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30739 Add a catchpoint for failed Ada assertions.
30741 The possible optional parameters for this command are:
30744 @item -c @var{condition}
30745 Make the catchpoint conditional on @var{condition}.
30747 Create a disabled catchpoint.
30749 Create a temporary catchpoint.
30752 @subsubheading @value{GDBN} Command
30754 The corresponding @value{GDBN} command is @samp{catch assert}.
30756 @subsubheading Example
30760 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30761 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30762 thread-groups=["i1"],times="0",
30763 original-location="__gnat_debug_raise_assert_failure"@}
30767 @subheading The @code{-catch-exception} Command
30768 @findex -catch-exception
30770 @subsubheading Synopsis
30773 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30777 Add a catchpoint stopping when Ada exceptions are raised.
30778 By default, the command stops the program when any Ada exception
30779 gets raised. But it is also possible, by using some of the
30780 optional parameters described below, to create more selective
30783 The possible optional parameters for this command are:
30786 @item -c @var{condition}
30787 Make the catchpoint conditional on @var{condition}.
30789 Create a disabled catchpoint.
30790 @item -e @var{exception-name}
30791 Only stop when @var{exception-name} is raised. This option cannot
30792 be used combined with @samp{-u}.
30794 Create a temporary catchpoint.
30796 Stop only when an unhandled exception gets raised. This option
30797 cannot be used combined with @samp{-e}.
30800 @subsubheading @value{GDBN} Command
30802 The corresponding @value{GDBN} commands are @samp{catch exception}
30803 and @samp{catch exception unhandled}.
30805 @subsubheading Example
30808 -catch-exception -e Program_Error
30809 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30810 enabled="y",addr="0x0000000000404874",
30811 what="`Program_Error' Ada exception", thread-groups=["i1"],
30812 times="0",original-location="__gnat_debug_raise_exception"@}
30816 @subheading The @code{-catch-handlers} Command
30817 @findex -catch-handlers
30819 @subsubheading Synopsis
30822 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30826 Add a catchpoint stopping when Ada exceptions are handled.
30827 By default, the command stops the program when any Ada exception
30828 gets handled. But it is also possible, by using some of the
30829 optional parameters described below, to create more selective
30832 The possible optional parameters for this command are:
30835 @item -c @var{condition}
30836 Make the catchpoint conditional on @var{condition}.
30838 Create a disabled catchpoint.
30839 @item -e @var{exception-name}
30840 Only stop when @var{exception-name} is handled.
30842 Create a temporary catchpoint.
30845 @subsubheading @value{GDBN} Command
30847 The corresponding @value{GDBN} command is @samp{catch handlers}.
30849 @subsubheading Example
30852 -catch-handlers -e Constraint_Error
30853 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30854 enabled="y",addr="0x0000000000402f68",
30855 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
30856 times="0",original-location="__gnat_begin_handler"@}
30860 @node C++ Exception GDB/MI Catchpoint Commands
30861 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
30863 The following @sc{gdb/mi} commands can be used to create catchpoints
30864 that stop the execution when C@t{++} exceptions are being throw, rethrown,
30867 @subheading The @code{-catch-throw} Command
30868 @findex -catch-throw
30870 @subsubheading Synopsis
30873 -catch-throw [ -t ] [ -r @var{regexp}]
30876 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
30877 given, then only exceptions whose type matches the regular expression
30880 If @samp{-t} is given, then the catchpoint is enabled only for one
30881 stop, the catchpoint is automatically deleted after stopping once for
30884 @subsubheading @value{GDBN} Command
30886 The corresponding @value{GDBN} commands are @samp{catch throw}
30887 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
30889 @subsubheading Example
30892 -catch-throw -r exception_type
30893 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30894 what="exception throw",catch-type="throw",
30895 thread-groups=["i1"],
30896 regexp="exception_type",times="0"@}
30902 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
30903 in __cxa_throw () from /lib64/libstdc++.so.6\n"
30904 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30905 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
30906 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30907 thread-id="1",stopped-threads="all",core="6"
30911 @subheading The @code{-catch-rethrow} Command
30912 @findex -catch-rethrow
30914 @subsubheading Synopsis
30917 -catch-rethrow [ -t ] [ -r @var{regexp}]
30920 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
30921 then only exceptions whose type matches the regular expression will be
30924 If @samp{-t} is given, then the catchpoint is enabled only for one
30925 stop, the catchpoint is automatically deleted after the first event is
30928 @subsubheading @value{GDBN} Command
30930 The corresponding @value{GDBN} commands are @samp{catch rethrow}
30931 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
30933 @subsubheading Example
30936 -catch-rethrow -r exception_type
30937 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30938 what="exception rethrow",catch-type="rethrow",
30939 thread-groups=["i1"],
30940 regexp="exception_type",times="0"@}
30946 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
30947 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
30948 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30949 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
30950 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30951 thread-id="1",stopped-threads="all",core="6"
30955 @subheading The @code{-catch-catch} Command
30956 @findex -catch-catch
30958 @subsubheading Synopsis
30961 -catch-catch [ -t ] [ -r @var{regexp}]
30964 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
30965 is given, then only exceptions whose type matches the regular
30966 expression will be caught.
30968 If @samp{-t} is given, then the catchpoint is enabled only for one
30969 stop, the catchpoint is automatically deleted after the first event is
30972 @subsubheading @value{GDBN} Command
30974 The corresponding @value{GDBN} commands are @samp{catch catch}
30975 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
30977 @subsubheading Example
30980 -catch-catch -r exception_type
30981 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
30982 what="exception catch",catch-type="catch",
30983 thread-groups=["i1"],
30984 regexp="exception_type",times="0"@}
30990 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
30991 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
30992 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
30993 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
30994 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
30995 thread-id="1",stopped-threads="all",core="6"
30999 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31000 @node GDB/MI Program Context
31001 @section @sc{gdb/mi} Program Context
31003 @subheading The @code{-exec-arguments} Command
31004 @findex -exec-arguments
31007 @subsubheading Synopsis
31010 -exec-arguments @var{args}
31013 Set the inferior program arguments, to be used in the next
31016 @subsubheading @value{GDBN} Command
31018 The corresponding @value{GDBN} command is @samp{set args}.
31020 @subsubheading Example
31024 -exec-arguments -v word
31031 @subheading The @code{-exec-show-arguments} Command
31032 @findex -exec-show-arguments
31034 @subsubheading Synopsis
31037 -exec-show-arguments
31040 Print the arguments of the program.
31042 @subsubheading @value{GDBN} Command
31044 The corresponding @value{GDBN} command is @samp{show args}.
31046 @subsubheading Example
31051 @subheading The @code{-environment-cd} Command
31052 @findex -environment-cd
31054 @subsubheading Synopsis
31057 -environment-cd @var{pathdir}
31060 Set @value{GDBN}'s working directory.
31062 @subsubheading @value{GDBN} Command
31064 The corresponding @value{GDBN} command is @samp{cd}.
31066 @subsubheading Example
31070 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31076 @subheading The @code{-environment-directory} Command
31077 @findex -environment-directory
31079 @subsubheading Synopsis
31082 -environment-directory [ -r ] [ @var{pathdir} ]+
31085 Add directories @var{pathdir} to beginning of search path for source files.
31086 If the @samp{-r} option is used, the search path is reset to the default
31087 search path. If directories @var{pathdir} are supplied in addition to the
31088 @samp{-r} option, the search path is first reset and then addition
31090 Multiple directories may be specified, separated by blanks. Specifying
31091 multiple directories in a single command
31092 results in the directories added to the beginning of the
31093 search path in the same order they were presented in the command.
31094 If blanks are needed as
31095 part of a directory name, double-quotes should be used around
31096 the name. In the command output, the path will show up separated
31097 by the system directory-separator character. The directory-separator
31098 character must not be used
31099 in any directory name.
31100 If no directories are specified, the current search path is displayed.
31102 @subsubheading @value{GDBN} Command
31104 The corresponding @value{GDBN} command is @samp{dir}.
31106 @subsubheading Example
31110 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31111 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31113 -environment-directory ""
31114 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31116 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
31117 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
31119 -environment-directory -r
31120 ^done,source-path="$cdir:$cwd"
31125 @subheading The @code{-environment-path} Command
31126 @findex -environment-path
31128 @subsubheading Synopsis
31131 -environment-path [ -r ] [ @var{pathdir} ]+
31134 Add directories @var{pathdir} to beginning of search path for object files.
31135 If the @samp{-r} option is used, the search path is reset to the original
31136 search path that existed at gdb start-up. If directories @var{pathdir} are
31137 supplied in addition to the
31138 @samp{-r} option, the search path is first reset and then addition
31140 Multiple directories may be specified, separated by blanks. Specifying
31141 multiple directories in a single command
31142 results in the directories added to the beginning of the
31143 search path in the same order they were presented in the command.
31144 If blanks are needed as
31145 part of a directory name, double-quotes should be used around
31146 the name. In the command output, the path will show up separated
31147 by the system directory-separator character. The directory-separator
31148 character must not be used
31149 in any directory name.
31150 If no directories are specified, the current path is displayed.
31153 @subsubheading @value{GDBN} Command
31155 The corresponding @value{GDBN} command is @samp{path}.
31157 @subsubheading Example
31162 ^done,path="/usr/bin"
31164 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31165 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31167 -environment-path -r /usr/local/bin
31168 ^done,path="/usr/local/bin:/usr/bin"
31173 @subheading The @code{-environment-pwd} Command
31174 @findex -environment-pwd
31176 @subsubheading Synopsis
31182 Show the current working directory.
31184 @subsubheading @value{GDBN} Command
31186 The corresponding @value{GDBN} command is @samp{pwd}.
31188 @subsubheading Example
31193 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
31197 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31198 @node GDB/MI Thread Commands
31199 @section @sc{gdb/mi} Thread Commands
31202 @subheading The @code{-thread-info} Command
31203 @findex -thread-info
31205 @subsubheading Synopsis
31208 -thread-info [ @var{thread-id} ]
31211 Reports information about either a specific thread, if the
31212 @var{thread-id} parameter is present, or about all threads.
31213 @var{thread-id} is the thread's global thread ID. When printing
31214 information about all threads, also reports the global ID of the
31217 @subsubheading @value{GDBN} Command
31219 The @samp{info thread} command prints the same information
31222 @subsubheading Result
31224 The result contains the following attributes:
31228 A list of threads. The format of the elements of the list is described in
31229 @ref{GDB/MI Thread Information}.
31231 @item current-thread-id
31232 The global id of the currently selected thread. This field is omitted if there
31233 is no selected thread (for example, when the selected inferior is not running,
31234 and therefore has no threads) or if a @var{thread-id} argument was passed to
31239 @subsubheading Example
31244 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31245 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31246 args=[]@},state="running"@},
31247 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31248 frame=@{level="0",addr="0x0804891f",func="foo",
31249 args=[@{name="i",value="10"@}],
31250 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
31251 state="running"@}],
31252 current-thread-id="1"
31256 @subheading The @code{-thread-list-ids} Command
31257 @findex -thread-list-ids
31259 @subsubheading Synopsis
31265 Produces a list of the currently known global @value{GDBN} thread ids.
31266 At the end of the list it also prints the total number of such
31269 This command is retained for historical reasons, the
31270 @code{-thread-info} command should be used instead.
31272 @subsubheading @value{GDBN} Command
31274 Part of @samp{info threads} supplies the same information.
31276 @subsubheading Example
31281 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31282 current-thread-id="1",number-of-threads="3"
31287 @subheading The @code{-thread-select} Command
31288 @findex -thread-select
31290 @subsubheading Synopsis
31293 -thread-select @var{thread-id}
31296 Make thread with global thread number @var{thread-id} the current
31297 thread. It prints the number of the new current thread, and the
31298 topmost frame for that thread.
31300 This command is deprecated in favor of explicitly using the
31301 @samp{--thread} option to each command.
31303 @subsubheading @value{GDBN} Command
31305 The corresponding @value{GDBN} command is @samp{thread}.
31307 @subsubheading Example
31314 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31315 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31319 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31320 number-of-threads="3"
31323 ^done,new-thread-id="3",
31324 frame=@{level="0",func="vprintf",
31325 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31326 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
31330 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31331 @node GDB/MI Ada Tasking Commands
31332 @section @sc{gdb/mi} Ada Tasking Commands
31334 @subheading The @code{-ada-task-info} Command
31335 @findex -ada-task-info
31337 @subsubheading Synopsis
31340 -ada-task-info [ @var{task-id} ]
31343 Reports information about either a specific Ada task, if the
31344 @var{task-id} parameter is present, or about all Ada tasks.
31346 @subsubheading @value{GDBN} Command
31348 The @samp{info tasks} command prints the same information
31349 about all Ada tasks (@pxref{Ada Tasks}).
31351 @subsubheading Result
31353 The result is a table of Ada tasks. The following columns are
31354 defined for each Ada task:
31358 This field exists only for the current thread. It has the value @samp{*}.
31361 The identifier that @value{GDBN} uses to refer to the Ada task.
31364 The identifier that the target uses to refer to the Ada task.
31367 The global thread identifier of the thread corresponding to the Ada
31370 This field should always exist, as Ada tasks are always implemented
31371 on top of a thread. But if @value{GDBN} cannot find this corresponding
31372 thread for any reason, the field is omitted.
31375 This field exists only when the task was created by another task.
31376 In this case, it provides the ID of the parent task.
31379 The base priority of the task.
31382 The current state of the task. For a detailed description of the
31383 possible states, see @ref{Ada Tasks}.
31386 The name of the task.
31390 @subsubheading Example
31394 ^done,tasks=@{nr_rows="3",nr_cols="8",
31395 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31396 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31397 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31398 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31399 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31400 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31401 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31402 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31403 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31404 state="Child Termination Wait",name="main_task"@}]@}
31408 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31409 @node GDB/MI Program Execution
31410 @section @sc{gdb/mi} Program Execution
31412 These are the asynchronous commands which generate the out-of-band
31413 record @samp{*stopped}. Currently @value{GDBN} only really executes
31414 asynchronously with remote targets and this interaction is mimicked in
31417 @subheading The @code{-exec-continue} Command
31418 @findex -exec-continue
31420 @subsubheading Synopsis
31423 -exec-continue [--reverse] [--all|--thread-group N]
31426 Resumes the execution of the inferior program, which will continue
31427 to execute until it reaches a debugger stop event. If the
31428 @samp{--reverse} option is specified, execution resumes in reverse until
31429 it reaches a stop event. Stop events may include
31432 breakpoints or watchpoints
31434 signals or exceptions
31436 the end of the process (or its beginning under @samp{--reverse})
31438 the end or beginning of a replay log if one is being used.
31440 In all-stop mode (@pxref{All-Stop
31441 Mode}), may resume only one thread, or all threads, depending on the
31442 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31443 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31444 ignored in all-stop mode. If the @samp{--thread-group} options is
31445 specified, then all threads in that thread group are resumed.
31447 @subsubheading @value{GDBN} Command
31449 The corresponding @value{GDBN} corresponding is @samp{continue}.
31451 @subsubheading Example
31458 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31459 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31460 line="13",arch="i386:x86_64"@}
31465 @subheading The @code{-exec-finish} Command
31466 @findex -exec-finish
31468 @subsubheading Synopsis
31471 -exec-finish [--reverse]
31474 Resumes the execution of the inferior program until the current
31475 function is exited. Displays the results returned by the function.
31476 If the @samp{--reverse} option is specified, resumes the reverse
31477 execution of the inferior program until the point where current
31478 function was called.
31480 @subsubheading @value{GDBN} Command
31482 The corresponding @value{GDBN} command is @samp{finish}.
31484 @subsubheading Example
31486 Function returning @code{void}.
31493 *stopped,reason="function-finished",frame=@{func="main",args=[],
31494 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
31498 Function returning other than @code{void}. The name of the internal
31499 @value{GDBN} variable storing the result is printed, together with the
31506 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31507 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31508 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
31509 arch="i386:x86_64"@},
31510 gdb-result-var="$1",return-value="0"
31515 @subheading The @code{-exec-interrupt} Command
31516 @findex -exec-interrupt
31518 @subsubheading Synopsis
31521 -exec-interrupt [--all|--thread-group N]
31524 Interrupts the background execution of the target. Note how the token
31525 associated with the stop message is the one for the execution command
31526 that has been interrupted. The token for the interrupt itself only
31527 appears in the @samp{^done} output. If the user is trying to
31528 interrupt a non-running program, an error message will be printed.
31530 Note that when asynchronous execution is enabled, this command is
31531 asynchronous just like other execution commands. That is, first the
31532 @samp{^done} response will be printed, and the target stop will be
31533 reported after that using the @samp{*stopped} notification.
31535 In non-stop mode, only the context thread is interrupted by default.
31536 All threads (in all inferiors) will be interrupted if the
31537 @samp{--all} option is specified. If the @samp{--thread-group}
31538 option is specified, all threads in that group will be interrupted.
31540 @subsubheading @value{GDBN} Command
31542 The corresponding @value{GDBN} command is @samp{interrupt}.
31544 @subsubheading Example
31555 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31556 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31557 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
31562 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31566 @subheading The @code{-exec-jump} Command
31569 @subsubheading Synopsis
31572 -exec-jump @var{location}
31575 Resumes execution of the inferior program at the location specified by
31576 parameter. @xref{Specify Location}, for a description of the
31577 different forms of @var{location}.
31579 @subsubheading @value{GDBN} Command
31581 The corresponding @value{GDBN} command is @samp{jump}.
31583 @subsubheading Example
31586 -exec-jump foo.c:10
31587 *running,thread-id="all"
31592 @subheading The @code{-exec-next} Command
31595 @subsubheading Synopsis
31598 -exec-next [--reverse]
31601 Resumes execution of the inferior program, stopping when the beginning
31602 of the next source line is reached.
31604 If the @samp{--reverse} option is specified, resumes reverse execution
31605 of the inferior program, stopping at the beginning of the previous
31606 source line. If you issue this command on the first line of a
31607 function, it will take you back to the caller of that function, to the
31608 source line where the function was called.
31611 @subsubheading @value{GDBN} Command
31613 The corresponding @value{GDBN} command is @samp{next}.
31615 @subsubheading Example
31621 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31626 @subheading The @code{-exec-next-instruction} Command
31627 @findex -exec-next-instruction
31629 @subsubheading Synopsis
31632 -exec-next-instruction [--reverse]
31635 Executes one machine instruction. If the instruction is a function
31636 call, continues until the function returns. If the program stops at an
31637 instruction in the middle of a source line, the address will be
31640 If the @samp{--reverse} option is specified, resumes reverse execution
31641 of the inferior program, stopping at the previous instruction. If the
31642 previously executed instruction was a return from another function,
31643 it will continue to execute in reverse until the call to that function
31644 (from the current stack frame) is reached.
31646 @subsubheading @value{GDBN} Command
31648 The corresponding @value{GDBN} command is @samp{nexti}.
31650 @subsubheading Example
31654 -exec-next-instruction
31658 *stopped,reason="end-stepping-range",
31659 addr="0x000100d4",line="5",file="hello.c"
31664 @subheading The @code{-exec-return} Command
31665 @findex -exec-return
31667 @subsubheading Synopsis
31673 Makes current function return immediately. Doesn't execute the inferior.
31674 Displays the new current frame.
31676 @subsubheading @value{GDBN} Command
31678 The corresponding @value{GDBN} command is @samp{return}.
31680 @subsubheading Example
31684 200-break-insert callee4
31685 200^done,bkpt=@{number="1",addr="0x00010734",
31686 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31691 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31692 frame=@{func="callee4",args=[],
31693 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31694 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31695 arch="i386:x86_64"@}
31701 111^done,frame=@{level="0",func="callee3",
31702 args=[@{name="strarg",
31703 value="0x11940 \"A string argument.\""@}],
31704 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31705 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31706 arch="i386:x86_64"@}
31711 @subheading The @code{-exec-run} Command
31714 @subsubheading Synopsis
31717 -exec-run [ --all | --thread-group N ] [ --start ]
31720 Starts execution of the inferior from the beginning. The inferior
31721 executes until either a breakpoint is encountered or the program
31722 exits. In the latter case the output will include an exit code, if
31723 the program has exited exceptionally.
31725 When neither the @samp{--all} nor the @samp{--thread-group} option
31726 is specified, the current inferior is started. If the
31727 @samp{--thread-group} option is specified, it should refer to a thread
31728 group of type @samp{process}, and that thread group will be started.
31729 If the @samp{--all} option is specified, then all inferiors will be started.
31731 Using the @samp{--start} option instructs the debugger to stop
31732 the execution at the start of the inferior's main subprogram,
31733 following the same behavior as the @code{start} command
31734 (@pxref{Starting}).
31736 @subsubheading @value{GDBN} Command
31738 The corresponding @value{GDBN} command is @samp{run}.
31740 @subsubheading Examples
31745 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31750 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31751 frame=@{func="main",args=[],file="recursive2.c",
31752 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
31757 Program exited normally:
31765 *stopped,reason="exited-normally"
31770 Program exited exceptionally:
31778 *stopped,reason="exited",exit-code="01"
31782 Another way the program can terminate is if it receives a signal such as
31783 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31787 *stopped,reason="exited-signalled",signal-name="SIGINT",
31788 signal-meaning="Interrupt"
31792 @c @subheading -exec-signal
31795 @subheading The @code{-exec-step} Command
31798 @subsubheading Synopsis
31801 -exec-step [--reverse]
31804 Resumes execution of the inferior program, stopping when the beginning
31805 of the next source line is reached, if the next source line is not a
31806 function call. If it is, stop at the first instruction of the called
31807 function. If the @samp{--reverse} option is specified, resumes reverse
31808 execution of the inferior program, stopping at the beginning of the
31809 previously executed source line.
31811 @subsubheading @value{GDBN} Command
31813 The corresponding @value{GDBN} command is @samp{step}.
31815 @subsubheading Example
31817 Stepping into a function:
31823 *stopped,reason="end-stepping-range",
31824 frame=@{func="foo",args=[@{name="a",value="10"@},
31825 @{name="b",value="0"@}],file="recursive2.c",
31826 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
31836 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31841 @subheading The @code{-exec-step-instruction} Command
31842 @findex -exec-step-instruction
31844 @subsubheading Synopsis
31847 -exec-step-instruction [--reverse]
31850 Resumes the inferior which executes one machine instruction. If the
31851 @samp{--reverse} option is specified, resumes reverse execution of the
31852 inferior program, stopping at the previously executed instruction.
31853 The output, once @value{GDBN} has stopped, will vary depending on
31854 whether we have stopped in the middle of a source line or not. In the
31855 former case, the address at which the program stopped will be printed
31858 @subsubheading @value{GDBN} Command
31860 The corresponding @value{GDBN} command is @samp{stepi}.
31862 @subsubheading Example
31866 -exec-step-instruction
31870 *stopped,reason="end-stepping-range",
31871 frame=@{func="foo",args=[],file="try.c",
31872 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
31874 -exec-step-instruction
31878 *stopped,reason="end-stepping-range",
31879 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31880 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
31885 @subheading The @code{-exec-until} Command
31886 @findex -exec-until
31888 @subsubheading Synopsis
31891 -exec-until [ @var{location} ]
31894 Executes the inferior until the @var{location} specified in the
31895 argument is reached. If there is no argument, the inferior executes
31896 until a source line greater than the current one is reached. The
31897 reason for stopping in this case will be @samp{location-reached}.
31899 @subsubheading @value{GDBN} Command
31901 The corresponding @value{GDBN} command is @samp{until}.
31903 @subsubheading Example
31907 -exec-until recursive2.c:6
31911 *stopped,reason="location-reached",frame=@{func="main",args=[],
31912 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
31913 arch="i386:x86_64"@}
31918 @subheading -file-clear
31919 Is this going away????
31922 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31923 @node GDB/MI Stack Manipulation
31924 @section @sc{gdb/mi} Stack Manipulation Commands
31926 @subheading The @code{-enable-frame-filters} Command
31927 @findex -enable-frame-filters
31930 -enable-frame-filters
31933 @value{GDBN} allows Python-based frame filters to affect the output of
31934 the MI commands relating to stack traces. As there is no way to
31935 implement this in a fully backward-compatible way, a front end must
31936 request that this functionality be enabled.
31938 Once enabled, this feature cannot be disabled.
31940 Note that if Python support has not been compiled into @value{GDBN},
31941 this command will still succeed (and do nothing).
31943 @subheading The @code{-stack-info-frame} Command
31944 @findex -stack-info-frame
31946 @subsubheading Synopsis
31952 Get info on the selected frame.
31954 @subsubheading @value{GDBN} Command
31956 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31957 (without arguments).
31959 @subsubheading Example
31964 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31965 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31966 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
31967 arch="i386:x86_64"@}
31971 @subheading The @code{-stack-info-depth} Command
31972 @findex -stack-info-depth
31974 @subsubheading Synopsis
31977 -stack-info-depth [ @var{max-depth} ]
31980 Return the depth of the stack. If the integer argument @var{max-depth}
31981 is specified, do not count beyond @var{max-depth} frames.
31983 @subsubheading @value{GDBN} Command
31985 There's no equivalent @value{GDBN} command.
31987 @subsubheading Example
31989 For a stack with frame levels 0 through 11:
31996 -stack-info-depth 4
31999 -stack-info-depth 12
32002 -stack-info-depth 11
32005 -stack-info-depth 13
32010 @anchor{-stack-list-arguments}
32011 @subheading The @code{-stack-list-arguments} Command
32012 @findex -stack-list-arguments
32014 @subsubheading Synopsis
32017 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32018 [ @var{low-frame} @var{high-frame} ]
32021 Display a list of the arguments for the frames between @var{low-frame}
32022 and @var{high-frame} (inclusive). If @var{low-frame} and
32023 @var{high-frame} are not provided, list the arguments for the whole
32024 call stack. If the two arguments are equal, show the single frame
32025 at the corresponding level. It is an error if @var{low-frame} is
32026 larger than the actual number of frames. On the other hand,
32027 @var{high-frame} may be larger than the actual number of frames, in
32028 which case only existing frames will be returned.
32030 If @var{print-values} is 0 or @code{--no-values}, print only the names of
32031 the variables; if it is 1 or @code{--all-values}, print also their
32032 values; and if it is 2 or @code{--simple-values}, print the name,
32033 type and value for simple data types, and the name and type for arrays,
32034 structures and unions. If the option @code{--no-frame-filters} is
32035 supplied, then Python frame filters will not be executed.
32037 If the @code{--skip-unavailable} option is specified, arguments that
32038 are not available are not listed. Partially available arguments
32039 are still displayed, however.
32041 Use of this command to obtain arguments in a single frame is
32042 deprecated in favor of the @samp{-stack-list-variables} command.
32044 @subsubheading @value{GDBN} Command
32046 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
32047 @samp{gdb_get_args} command which partially overlaps with the
32048 functionality of @samp{-stack-list-arguments}.
32050 @subsubheading Example
32057 frame=@{level="0",addr="0x00010734",func="callee4",
32058 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32059 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32060 arch="i386:x86_64"@},
32061 frame=@{level="1",addr="0x0001076c",func="callee3",
32062 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32063 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32064 arch="i386:x86_64"@},
32065 frame=@{level="2",addr="0x0001078c",func="callee2",
32066 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32067 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
32068 arch="i386:x86_64"@},
32069 frame=@{level="3",addr="0x000107b4",func="callee1",
32070 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32071 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
32072 arch="i386:x86_64"@},
32073 frame=@{level="4",addr="0x000107e0",func="main",
32074 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32075 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
32076 arch="i386:x86_64"@}]
32078 -stack-list-arguments 0
32081 frame=@{level="0",args=[]@},
32082 frame=@{level="1",args=[name="strarg"]@},
32083 frame=@{level="2",args=[name="intarg",name="strarg"]@},
32084 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
32085 frame=@{level="4",args=[]@}]
32087 -stack-list-arguments 1
32090 frame=@{level="0",args=[]@},
32092 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32093 frame=@{level="2",args=[
32094 @{name="intarg",value="2"@},
32095 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32096 @{frame=@{level="3",args=[
32097 @{name="intarg",value="2"@},
32098 @{name="strarg",value="0x11940 \"A string argument.\""@},
32099 @{name="fltarg",value="3.5"@}]@},
32100 frame=@{level="4",args=[]@}]
32102 -stack-list-arguments 0 2 2
32103 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
32105 -stack-list-arguments 1 2 2
32106 ^done,stack-args=[frame=@{level="2",
32107 args=[@{name="intarg",value="2"@},
32108 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
32112 @c @subheading -stack-list-exception-handlers
32115 @anchor{-stack-list-frames}
32116 @subheading The @code{-stack-list-frames} Command
32117 @findex -stack-list-frames
32119 @subsubheading Synopsis
32122 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
32125 List the frames currently on the stack. For each frame it displays the
32130 The frame number, 0 being the topmost frame, i.e., the innermost function.
32132 The @code{$pc} value for that frame.
32136 File name of the source file where the function lives.
32137 @item @var{fullname}
32138 The full file name of the source file where the function lives.
32140 Line number corresponding to the @code{$pc}.
32142 The shared library where this function is defined. This is only given
32143 if the frame's function is not known.
32145 Frame's architecture.
32148 If invoked without arguments, this command prints a backtrace for the
32149 whole stack. If given two integer arguments, it shows the frames whose
32150 levels are between the two arguments (inclusive). If the two arguments
32151 are equal, it shows the single frame at the corresponding level. It is
32152 an error if @var{low-frame} is larger than the actual number of
32153 frames. On the other hand, @var{high-frame} may be larger than the
32154 actual number of frames, in which case only existing frames will be
32155 returned. If the option @code{--no-frame-filters} is supplied, then
32156 Python frame filters will not be executed.
32158 @subsubheading @value{GDBN} Command
32160 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32162 @subsubheading Example
32164 Full stack backtrace:
32170 [frame=@{level="0",addr="0x0001076c",func="foo",
32171 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
32172 arch="i386:x86_64"@},
32173 frame=@{level="1",addr="0x000107a4",func="foo",
32174 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32175 arch="i386:x86_64"@},
32176 frame=@{level="2",addr="0x000107a4",func="foo",
32177 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32178 arch="i386:x86_64"@},
32179 frame=@{level="3",addr="0x000107a4",func="foo",
32180 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32181 arch="i386:x86_64"@},
32182 frame=@{level="4",addr="0x000107a4",func="foo",
32183 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32184 arch="i386:x86_64"@},
32185 frame=@{level="5",addr="0x000107a4",func="foo",
32186 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32187 arch="i386:x86_64"@},
32188 frame=@{level="6",addr="0x000107a4",func="foo",
32189 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32190 arch="i386:x86_64"@},
32191 frame=@{level="7",addr="0x000107a4",func="foo",
32192 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32193 arch="i386:x86_64"@},
32194 frame=@{level="8",addr="0x000107a4",func="foo",
32195 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32196 arch="i386:x86_64"@},
32197 frame=@{level="9",addr="0x000107a4",func="foo",
32198 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32199 arch="i386:x86_64"@},
32200 frame=@{level="10",addr="0x000107a4",func="foo",
32201 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32202 arch="i386:x86_64"@},
32203 frame=@{level="11",addr="0x00010738",func="main",
32204 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
32205 arch="i386:x86_64"@}]
32209 Show frames between @var{low_frame} and @var{high_frame}:
32213 -stack-list-frames 3 5
32215 [frame=@{level="3",addr="0x000107a4",func="foo",
32216 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32217 arch="i386:x86_64"@},
32218 frame=@{level="4",addr="0x000107a4",func="foo",
32219 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32220 arch="i386:x86_64"@},
32221 frame=@{level="5",addr="0x000107a4",func="foo",
32222 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32223 arch="i386:x86_64"@}]
32227 Show a single frame:
32231 -stack-list-frames 3 3
32233 [frame=@{level="3",addr="0x000107a4",func="foo",
32234 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32235 arch="i386:x86_64"@}]
32240 @subheading The @code{-stack-list-locals} Command
32241 @findex -stack-list-locals
32242 @anchor{-stack-list-locals}
32244 @subsubheading Synopsis
32247 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32250 Display the local variable names for the selected frame. If
32251 @var{print-values} is 0 or @code{--no-values}, print only the names of
32252 the variables; if it is 1 or @code{--all-values}, print also their
32253 values; and if it is 2 or @code{--simple-values}, print the name,
32254 type and value for simple data types, and the name and type for arrays,
32255 structures and unions. In this last case, a frontend can immediately
32256 display the value of simple data types and create variable objects for
32257 other data types when the user wishes to explore their values in
32258 more detail. If the option @code{--no-frame-filters} is supplied, then
32259 Python frame filters will not be executed.
32261 If the @code{--skip-unavailable} option is specified, local variables
32262 that are not available are not listed. Partially available local
32263 variables are still displayed, however.
32265 This command is deprecated in favor of the
32266 @samp{-stack-list-variables} command.
32268 @subsubheading @value{GDBN} Command
32270 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32272 @subsubheading Example
32276 -stack-list-locals 0
32277 ^done,locals=[name="A",name="B",name="C"]
32279 -stack-list-locals --all-values
32280 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32281 @{name="C",value="@{1, 2, 3@}"@}]
32282 -stack-list-locals --simple-values
32283 ^done,locals=[@{name="A",type="int",value="1"@},
32284 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32288 @anchor{-stack-list-variables}
32289 @subheading The @code{-stack-list-variables} Command
32290 @findex -stack-list-variables
32292 @subsubheading Synopsis
32295 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32298 Display the names of local variables and function arguments for the selected frame. If
32299 @var{print-values} is 0 or @code{--no-values}, print only the names of
32300 the variables; if it is 1 or @code{--all-values}, print also their
32301 values; and if it is 2 or @code{--simple-values}, print the name,
32302 type and value for simple data types, and the name and type for arrays,
32303 structures and unions. If the option @code{--no-frame-filters} is
32304 supplied, then Python frame filters will not be executed.
32306 If the @code{--skip-unavailable} option is specified, local variables
32307 and arguments that are not available are not listed. Partially
32308 available arguments and local variables are still displayed, however.
32310 @subsubheading Example
32314 -stack-list-variables --thread 1 --frame 0 --all-values
32315 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32320 @subheading The @code{-stack-select-frame} Command
32321 @findex -stack-select-frame
32323 @subsubheading Synopsis
32326 -stack-select-frame @var{framenum}
32329 Change the selected frame. Select a different frame @var{framenum} on
32332 This command in deprecated in favor of passing the @samp{--frame}
32333 option to every command.
32335 @subsubheading @value{GDBN} Command
32337 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32338 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32340 @subsubheading Example
32344 -stack-select-frame 2
32349 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32350 @node GDB/MI Variable Objects
32351 @section @sc{gdb/mi} Variable Objects
32355 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32357 For the implementation of a variable debugger window (locals, watched
32358 expressions, etc.), we are proposing the adaptation of the existing code
32359 used by @code{Insight}.
32361 The two main reasons for that are:
32365 It has been proven in practice (it is already on its second generation).
32368 It will shorten development time (needless to say how important it is
32372 The original interface was designed to be used by Tcl code, so it was
32373 slightly changed so it could be used through @sc{gdb/mi}. This section
32374 describes the @sc{gdb/mi} operations that will be available and gives some
32375 hints about their use.
32377 @emph{Note}: In addition to the set of operations described here, we
32378 expect the @sc{gui} implementation of a variable window to require, at
32379 least, the following operations:
32382 @item @code{-gdb-show} @code{output-radix}
32383 @item @code{-stack-list-arguments}
32384 @item @code{-stack-list-locals}
32385 @item @code{-stack-select-frame}
32390 @subheading Introduction to Variable Objects
32392 @cindex variable objects in @sc{gdb/mi}
32394 Variable objects are "object-oriented" MI interface for examining and
32395 changing values of expressions. Unlike some other MI interfaces that
32396 work with expressions, variable objects are specifically designed for
32397 simple and efficient presentation in the frontend. A variable object
32398 is identified by string name. When a variable object is created, the
32399 frontend specifies the expression for that variable object. The
32400 expression can be a simple variable, or it can be an arbitrary complex
32401 expression, and can even involve CPU registers. After creating a
32402 variable object, the frontend can invoke other variable object
32403 operations---for example to obtain or change the value of a variable
32404 object, or to change display format.
32406 Variable objects have hierarchical tree structure. Any variable object
32407 that corresponds to a composite type, such as structure in C, has
32408 a number of child variable objects, for example corresponding to each
32409 element of a structure. A child variable object can itself have
32410 children, recursively. Recursion ends when we reach
32411 leaf variable objects, which always have built-in types. Child variable
32412 objects are created only by explicit request, so if a frontend
32413 is not interested in the children of a particular variable object, no
32414 child will be created.
32416 For a leaf variable object it is possible to obtain its value as a
32417 string, or set the value from a string. String value can be also
32418 obtained for a non-leaf variable object, but it's generally a string
32419 that only indicates the type of the object, and does not list its
32420 contents. Assignment to a non-leaf variable object is not allowed.
32422 A frontend does not need to read the values of all variable objects each time
32423 the program stops. Instead, MI provides an update command that lists all
32424 variable objects whose values has changed since the last update
32425 operation. This considerably reduces the amount of data that must
32426 be transferred to the frontend. As noted above, children variable
32427 objects are created on demand, and only leaf variable objects have a
32428 real value. As result, gdb will read target memory only for leaf
32429 variables that frontend has created.
32431 The automatic update is not always desirable. For example, a frontend
32432 might want to keep a value of some expression for future reference,
32433 and never update it. For another example, fetching memory is
32434 relatively slow for embedded targets, so a frontend might want
32435 to disable automatic update for the variables that are either not
32436 visible on the screen, or ``closed''. This is possible using so
32437 called ``frozen variable objects''. Such variable objects are never
32438 implicitly updated.
32440 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32441 fixed variable object, the expression is parsed when the variable
32442 object is created, including associating identifiers to specific
32443 variables. The meaning of expression never changes. For a floating
32444 variable object the values of variables whose names appear in the
32445 expressions are re-evaluated every time in the context of the current
32446 frame. Consider this example:
32451 struct work_state state;
32458 If a fixed variable object for the @code{state} variable is created in
32459 this function, and we enter the recursive call, the variable
32460 object will report the value of @code{state} in the top-level
32461 @code{do_work} invocation. On the other hand, a floating variable
32462 object will report the value of @code{state} in the current frame.
32464 If an expression specified when creating a fixed variable object
32465 refers to a local variable, the variable object becomes bound to the
32466 thread and frame in which the variable object is created. When such
32467 variable object is updated, @value{GDBN} makes sure that the
32468 thread/frame combination the variable object is bound to still exists,
32469 and re-evaluates the variable object in context of that thread/frame.
32471 The following is the complete set of @sc{gdb/mi} operations defined to
32472 access this functionality:
32474 @multitable @columnfractions .4 .6
32475 @item @strong{Operation}
32476 @tab @strong{Description}
32478 @item @code{-enable-pretty-printing}
32479 @tab enable Python-based pretty-printing
32480 @item @code{-var-create}
32481 @tab create a variable object
32482 @item @code{-var-delete}
32483 @tab delete the variable object and/or its children
32484 @item @code{-var-set-format}
32485 @tab set the display format of this variable
32486 @item @code{-var-show-format}
32487 @tab show the display format of this variable
32488 @item @code{-var-info-num-children}
32489 @tab tells how many children this object has
32490 @item @code{-var-list-children}
32491 @tab return a list of the object's children
32492 @item @code{-var-info-type}
32493 @tab show the type of this variable object
32494 @item @code{-var-info-expression}
32495 @tab print parent-relative expression that this variable object represents
32496 @item @code{-var-info-path-expression}
32497 @tab print full expression that this variable object represents
32498 @item @code{-var-show-attributes}
32499 @tab is this variable editable? does it exist here?
32500 @item @code{-var-evaluate-expression}
32501 @tab get the value of this variable
32502 @item @code{-var-assign}
32503 @tab set the value of this variable
32504 @item @code{-var-update}
32505 @tab update the variable and its children
32506 @item @code{-var-set-frozen}
32507 @tab set frozenness attribute
32508 @item @code{-var-set-update-range}
32509 @tab set range of children to display on update
32512 In the next subsection we describe each operation in detail and suggest
32513 how it can be used.
32515 @subheading Description And Use of Operations on Variable Objects
32517 @subheading The @code{-enable-pretty-printing} Command
32518 @findex -enable-pretty-printing
32521 -enable-pretty-printing
32524 @value{GDBN} allows Python-based visualizers to affect the output of the
32525 MI variable object commands. However, because there was no way to
32526 implement this in a fully backward-compatible way, a front end must
32527 request that this functionality be enabled.
32529 Once enabled, this feature cannot be disabled.
32531 Note that if Python support has not been compiled into @value{GDBN},
32532 this command will still succeed (and do nothing).
32534 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32535 may work differently in future versions of @value{GDBN}.
32537 @subheading The @code{-var-create} Command
32538 @findex -var-create
32540 @subsubheading Synopsis
32543 -var-create @{@var{name} | "-"@}
32544 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32547 This operation creates a variable object, which allows the monitoring of
32548 a variable, the result of an expression, a memory cell or a CPU
32551 The @var{name} parameter is the string by which the object can be
32552 referenced. It must be unique. If @samp{-} is specified, the varobj
32553 system will generate a string ``varNNNNNN'' automatically. It will be
32554 unique provided that one does not specify @var{name} of that format.
32555 The command fails if a duplicate name is found.
32557 The frame under which the expression should be evaluated can be
32558 specified by @var{frame-addr}. A @samp{*} indicates that the current
32559 frame should be used. A @samp{@@} indicates that a floating variable
32560 object must be created.
32562 @var{expression} is any expression valid on the current language set (must not
32563 begin with a @samp{*}), or one of the following:
32567 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32570 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32573 @samp{$@var{regname}} --- a CPU register name
32576 @cindex dynamic varobj
32577 A varobj's contents may be provided by a Python-based pretty-printer. In this
32578 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32579 have slightly different semantics in some cases. If the
32580 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32581 will never create a dynamic varobj. This ensures backward
32582 compatibility for existing clients.
32584 @subsubheading Result
32586 This operation returns attributes of the newly-created varobj. These
32591 The name of the varobj.
32594 The number of children of the varobj. This number is not necessarily
32595 reliable for a dynamic varobj. Instead, you must examine the
32596 @samp{has_more} attribute.
32599 The varobj's scalar value. For a varobj whose type is some sort of
32600 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32601 will not be interesting.
32604 The varobj's type. This is a string representation of the type, as
32605 would be printed by the @value{GDBN} CLI. If @samp{print object}
32606 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32607 @emph{actual} (derived) type of the object is shown rather than the
32608 @emph{declared} one.
32611 If a variable object is bound to a specific thread, then this is the
32612 thread's global identifier.
32615 For a dynamic varobj, this indicates whether there appear to be any
32616 children available. For a non-dynamic varobj, this will be 0.
32619 This attribute will be present and have the value @samp{1} if the
32620 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32621 then this attribute will not be present.
32624 A dynamic varobj can supply a display hint to the front end. The
32625 value comes directly from the Python pretty-printer object's
32626 @code{display_hint} method. @xref{Pretty Printing API}.
32629 Typical output will look like this:
32632 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32633 has_more="@var{has_more}"
32637 @subheading The @code{-var-delete} Command
32638 @findex -var-delete
32640 @subsubheading Synopsis
32643 -var-delete [ -c ] @var{name}
32646 Deletes a previously created variable object and all of its children.
32647 With the @samp{-c} option, just deletes the children.
32649 Returns an error if the object @var{name} is not found.
32652 @subheading The @code{-var-set-format} Command
32653 @findex -var-set-format
32655 @subsubheading Synopsis
32658 -var-set-format @var{name} @var{format-spec}
32661 Sets the output format for the value of the object @var{name} to be
32664 @anchor{-var-set-format}
32665 The syntax for the @var{format-spec} is as follows:
32668 @var{format-spec} @expansion{}
32669 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
32672 The natural format is the default format choosen automatically
32673 based on the variable type (like decimal for an @code{int}, hex
32674 for pointers, etc.).
32676 The zero-hexadecimal format has a representation similar to hexadecimal
32677 but with padding zeroes to the left of the value. For example, a 32-bit
32678 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
32679 zero-hexadecimal format.
32681 For a variable with children, the format is set only on the
32682 variable itself, and the children are not affected.
32684 @subheading The @code{-var-show-format} Command
32685 @findex -var-show-format
32687 @subsubheading Synopsis
32690 -var-show-format @var{name}
32693 Returns the format used to display the value of the object @var{name}.
32696 @var{format} @expansion{}
32701 @subheading The @code{-var-info-num-children} Command
32702 @findex -var-info-num-children
32704 @subsubheading Synopsis
32707 -var-info-num-children @var{name}
32710 Returns the number of children of a variable object @var{name}:
32716 Note that this number is not completely reliable for a dynamic varobj.
32717 It will return the current number of children, but more children may
32721 @subheading The @code{-var-list-children} Command
32722 @findex -var-list-children
32724 @subsubheading Synopsis
32727 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32729 @anchor{-var-list-children}
32731 Return a list of the children of the specified variable object and
32732 create variable objects for them, if they do not already exist. With
32733 a single argument or if @var{print-values} has a value of 0 or
32734 @code{--no-values}, print only the names of the variables; if
32735 @var{print-values} is 1 or @code{--all-values}, also print their
32736 values; and if it is 2 or @code{--simple-values} print the name and
32737 value for simple data types and just the name for arrays, structures
32740 @var{from} and @var{to}, if specified, indicate the range of children
32741 to report. If @var{from} or @var{to} is less than zero, the range is
32742 reset and all children will be reported. Otherwise, children starting
32743 at @var{from} (zero-based) and up to and excluding @var{to} will be
32746 If a child range is requested, it will only affect the current call to
32747 @code{-var-list-children}, but not future calls to @code{-var-update}.
32748 For this, you must instead use @code{-var-set-update-range}. The
32749 intent of this approach is to enable a front end to implement any
32750 update approach it likes; for example, scrolling a view may cause the
32751 front end to request more children with @code{-var-list-children}, and
32752 then the front end could call @code{-var-set-update-range} with a
32753 different range to ensure that future updates are restricted to just
32756 For each child the following results are returned:
32761 Name of the variable object created for this child.
32764 The expression to be shown to the user by the front end to designate this child.
32765 For example this may be the name of a structure member.
32767 For a dynamic varobj, this value cannot be used to form an
32768 expression. There is no way to do this at all with a dynamic varobj.
32770 For C/C@t{++} structures there are several pseudo children returned to
32771 designate access qualifiers. For these pseudo children @var{exp} is
32772 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32773 type and value are not present.
32775 A dynamic varobj will not report the access qualifying
32776 pseudo-children, regardless of the language. This information is not
32777 available at all with a dynamic varobj.
32780 Number of children this child has. For a dynamic varobj, this will be
32784 The type of the child. If @samp{print object}
32785 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32786 @emph{actual} (derived) type of the object is shown rather than the
32787 @emph{declared} one.
32790 If values were requested, this is the value.
32793 If this variable object is associated with a thread, this is the
32794 thread's global thread id. Otherwise this result is not present.
32797 If the variable object is frozen, this variable will be present with a value of 1.
32800 A dynamic varobj can supply a display hint to the front end. The
32801 value comes directly from the Python pretty-printer object's
32802 @code{display_hint} method. @xref{Pretty Printing API}.
32805 This attribute will be present and have the value @samp{1} if the
32806 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32807 then this attribute will not be present.
32811 The result may have its own attributes:
32815 A dynamic varobj can supply a display hint to the front end. The
32816 value comes directly from the Python pretty-printer object's
32817 @code{display_hint} method. @xref{Pretty Printing API}.
32820 This is an integer attribute which is nonzero if there are children
32821 remaining after the end of the selected range.
32824 @subsubheading Example
32828 -var-list-children n
32829 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32830 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32832 -var-list-children --all-values n
32833 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32834 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32838 @subheading The @code{-var-info-type} Command
32839 @findex -var-info-type
32841 @subsubheading Synopsis
32844 -var-info-type @var{name}
32847 Returns the type of the specified variable @var{name}. The type is
32848 returned as a string in the same format as it is output by the
32852 type=@var{typename}
32856 @subheading The @code{-var-info-expression} Command
32857 @findex -var-info-expression
32859 @subsubheading Synopsis
32862 -var-info-expression @var{name}
32865 Returns a string that is suitable for presenting this
32866 variable object in user interface. The string is generally
32867 not valid expression in the current language, and cannot be evaluated.
32869 For example, if @code{a} is an array, and variable object
32870 @code{A} was created for @code{a}, then we'll get this output:
32873 (gdb) -var-info-expression A.1
32874 ^done,lang="C",exp="1"
32878 Here, the value of @code{lang} is the language name, which can be
32879 found in @ref{Supported Languages}.
32881 Note that the output of the @code{-var-list-children} command also
32882 includes those expressions, so the @code{-var-info-expression} command
32885 @subheading The @code{-var-info-path-expression} Command
32886 @findex -var-info-path-expression
32888 @subsubheading Synopsis
32891 -var-info-path-expression @var{name}
32894 Returns an expression that can be evaluated in the current
32895 context and will yield the same value that a variable object has.
32896 Compare this with the @code{-var-info-expression} command, which
32897 result can be used only for UI presentation. Typical use of
32898 the @code{-var-info-path-expression} command is creating a
32899 watchpoint from a variable object.
32901 This command is currently not valid for children of a dynamic varobj,
32902 and will give an error when invoked on one.
32904 For example, suppose @code{C} is a C@t{++} class, derived from class
32905 @code{Base}, and that the @code{Base} class has a member called
32906 @code{m_size}. Assume a variable @code{c} is has the type of
32907 @code{C} and a variable object @code{C} was created for variable
32908 @code{c}. Then, we'll get this output:
32910 (gdb) -var-info-path-expression C.Base.public.m_size
32911 ^done,path_expr=((Base)c).m_size)
32914 @subheading The @code{-var-show-attributes} Command
32915 @findex -var-show-attributes
32917 @subsubheading Synopsis
32920 -var-show-attributes @var{name}
32923 List attributes of the specified variable object @var{name}:
32926 status=@var{attr} [ ( ,@var{attr} )* ]
32930 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32932 @subheading The @code{-var-evaluate-expression} Command
32933 @findex -var-evaluate-expression
32935 @subsubheading Synopsis
32938 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32941 Evaluates the expression that is represented by the specified variable
32942 object and returns its value as a string. The format of the string
32943 can be specified with the @samp{-f} option. The possible values of
32944 this option are the same as for @code{-var-set-format}
32945 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32946 the current display format will be used. The current display format
32947 can be changed using the @code{-var-set-format} command.
32953 Note that one must invoke @code{-var-list-children} for a variable
32954 before the value of a child variable can be evaluated.
32956 @subheading The @code{-var-assign} Command
32957 @findex -var-assign
32959 @subsubheading Synopsis
32962 -var-assign @var{name} @var{expression}
32965 Assigns the value of @var{expression} to the variable object specified
32966 by @var{name}. The object must be @samp{editable}. If the variable's
32967 value is altered by the assign, the variable will show up in any
32968 subsequent @code{-var-update} list.
32970 @subsubheading Example
32978 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32982 @subheading The @code{-var-update} Command
32983 @findex -var-update
32985 @subsubheading Synopsis
32988 -var-update [@var{print-values}] @{@var{name} | "*"@}
32991 Reevaluate the expressions corresponding to the variable object
32992 @var{name} and all its direct and indirect children, and return the
32993 list of variable objects whose values have changed; @var{name} must
32994 be a root variable object. Here, ``changed'' means that the result of
32995 @code{-var-evaluate-expression} before and after the
32996 @code{-var-update} is different. If @samp{*} is used as the variable
32997 object names, all existing variable objects are updated, except
32998 for frozen ones (@pxref{-var-set-frozen}). The option
32999 @var{print-values} determines whether both names and values, or just
33000 names are printed. The possible values of this option are the same
33001 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
33002 recommended to use the @samp{--all-values} option, to reduce the
33003 number of MI commands needed on each program stop.
33005 With the @samp{*} parameter, if a variable object is bound to a
33006 currently running thread, it will not be updated, without any
33009 If @code{-var-set-update-range} was previously used on a varobj, then
33010 only the selected range of children will be reported.
33012 @code{-var-update} reports all the changed varobjs in a tuple named
33015 Each item in the change list is itself a tuple holding:
33019 The name of the varobj.
33022 If values were requested for this update, then this field will be
33023 present and will hold the value of the varobj.
33026 @anchor{-var-update}
33027 This field is a string which may take one of three values:
33031 The variable object's current value is valid.
33034 The variable object does not currently hold a valid value but it may
33035 hold one in the future if its associated expression comes back into
33039 The variable object no longer holds a valid value.
33040 This can occur when the executable file being debugged has changed,
33041 either through recompilation or by using the @value{GDBN} @code{file}
33042 command. The front end should normally choose to delete these variable
33046 In the future new values may be added to this list so the front should
33047 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
33050 This is only present if the varobj is still valid. If the type
33051 changed, then this will be the string @samp{true}; otherwise it will
33054 When a varobj's type changes, its children are also likely to have
33055 become incorrect. Therefore, the varobj's children are automatically
33056 deleted when this attribute is @samp{true}. Also, the varobj's update
33057 range, when set using the @code{-var-set-update-range} command, is
33061 If the varobj's type changed, then this field will be present and will
33064 @item new_num_children
33065 For a dynamic varobj, if the number of children changed, or if the
33066 type changed, this will be the new number of children.
33068 The @samp{numchild} field in other varobj responses is generally not
33069 valid for a dynamic varobj -- it will show the number of children that
33070 @value{GDBN} knows about, but because dynamic varobjs lazily
33071 instantiate their children, this will not reflect the number of
33072 children which may be available.
33074 The @samp{new_num_children} attribute only reports changes to the
33075 number of children known by @value{GDBN}. This is the only way to
33076 detect whether an update has removed children (which necessarily can
33077 only happen at the end of the update range).
33080 The display hint, if any.
33083 This is an integer value, which will be 1 if there are more children
33084 available outside the varobj's update range.
33087 This attribute will be present and have the value @samp{1} if the
33088 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33089 then this attribute will not be present.
33092 If new children were added to a dynamic varobj within the selected
33093 update range (as set by @code{-var-set-update-range}), then they will
33094 be listed in this attribute.
33097 @subsubheading Example
33104 -var-update --all-values var1
33105 ^done,changelist=[@{name="var1",value="3",in_scope="true",
33106 type_changed="false"@}]
33110 @subheading The @code{-var-set-frozen} Command
33111 @findex -var-set-frozen
33112 @anchor{-var-set-frozen}
33114 @subsubheading Synopsis
33117 -var-set-frozen @var{name} @var{flag}
33120 Set the frozenness flag on the variable object @var{name}. The
33121 @var{flag} parameter should be either @samp{1} to make the variable
33122 frozen or @samp{0} to make it unfrozen. If a variable object is
33123 frozen, then neither itself, nor any of its children, are
33124 implicitly updated by @code{-var-update} of
33125 a parent variable or by @code{-var-update *}. Only
33126 @code{-var-update} of the variable itself will update its value and
33127 values of its children. After a variable object is unfrozen, it is
33128 implicitly updated by all subsequent @code{-var-update} operations.
33129 Unfreezing a variable does not update it, only subsequent
33130 @code{-var-update} does.
33132 @subsubheading Example
33136 -var-set-frozen V 1
33141 @subheading The @code{-var-set-update-range} command
33142 @findex -var-set-update-range
33143 @anchor{-var-set-update-range}
33145 @subsubheading Synopsis
33148 -var-set-update-range @var{name} @var{from} @var{to}
33151 Set the range of children to be returned by future invocations of
33152 @code{-var-update}.
33154 @var{from} and @var{to} indicate the range of children to report. If
33155 @var{from} or @var{to} is less than zero, the range is reset and all
33156 children will be reported. Otherwise, children starting at @var{from}
33157 (zero-based) and up to and excluding @var{to} will be reported.
33159 @subsubheading Example
33163 -var-set-update-range V 1 2
33167 @subheading The @code{-var-set-visualizer} command
33168 @findex -var-set-visualizer
33169 @anchor{-var-set-visualizer}
33171 @subsubheading Synopsis
33174 -var-set-visualizer @var{name} @var{visualizer}
33177 Set a visualizer for the variable object @var{name}.
33179 @var{visualizer} is the visualizer to use. The special value
33180 @samp{None} means to disable any visualizer in use.
33182 If not @samp{None}, @var{visualizer} must be a Python expression.
33183 This expression must evaluate to a callable object which accepts a
33184 single argument. @value{GDBN} will call this object with the value of
33185 the varobj @var{name} as an argument (this is done so that the same
33186 Python pretty-printing code can be used for both the CLI and MI).
33187 When called, this object must return an object which conforms to the
33188 pretty-printing interface (@pxref{Pretty Printing API}).
33190 The pre-defined function @code{gdb.default_visualizer} may be used to
33191 select a visualizer by following the built-in process
33192 (@pxref{Selecting Pretty-Printers}). This is done automatically when
33193 a varobj is created, and so ordinarily is not needed.
33195 This feature is only available if Python support is enabled. The MI
33196 command @code{-list-features} (@pxref{GDB/MI Support Commands})
33197 can be used to check this.
33199 @subsubheading Example
33201 Resetting the visualizer:
33205 -var-set-visualizer V None
33209 Reselecting the default (type-based) visualizer:
33213 -var-set-visualizer V gdb.default_visualizer
33217 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33218 can be used to instantiate this class for a varobj:
33222 -var-set-visualizer V "lambda val: SomeClass()"
33226 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33227 @node GDB/MI Data Manipulation
33228 @section @sc{gdb/mi} Data Manipulation
33230 @cindex data manipulation, in @sc{gdb/mi}
33231 @cindex @sc{gdb/mi}, data manipulation
33232 This section describes the @sc{gdb/mi} commands that manipulate data:
33233 examine memory and registers, evaluate expressions, etc.
33235 For details about what an addressable memory unit is,
33236 @pxref{addressable memory unit}.
33238 @c REMOVED FROM THE INTERFACE.
33239 @c @subheading -data-assign
33240 @c Change the value of a program variable. Plenty of side effects.
33241 @c @subsubheading GDB Command
33243 @c @subsubheading Example
33246 @subheading The @code{-data-disassemble} Command
33247 @findex -data-disassemble
33249 @subsubheading Synopsis
33253 [ -s @var{start-addr} -e @var{end-addr} ]
33254 | [ -a @var{addr} ]
33255 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33263 @item @var{start-addr}
33264 is the beginning address (or @code{$pc})
33265 @item @var{end-addr}
33268 is an address anywhere within (or the name of) the function to
33269 disassemble. If an address is specified, the whole function
33270 surrounding that address will be disassembled. If a name is
33271 specified, the whole function with that name will be disassembled.
33272 @item @var{filename}
33273 is the name of the file to disassemble
33274 @item @var{linenum}
33275 is the line number to disassemble around
33277 is the number of disassembly lines to be produced. If it is -1,
33278 the whole function will be disassembled, in case no @var{end-addr} is
33279 specified. If @var{end-addr} is specified as a non-zero value, and
33280 @var{lines} is lower than the number of disassembly lines between
33281 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33282 displayed; if @var{lines} is higher than the number of lines between
33283 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33288 @item 0 disassembly only
33289 @item 1 mixed source and disassembly (deprecated)
33290 @item 2 disassembly with raw opcodes
33291 @item 3 mixed source and disassembly with raw opcodes (deprecated)
33292 @item 4 mixed source and disassembly
33293 @item 5 mixed source and disassembly with raw opcodes
33296 Modes 1 and 3 are deprecated. The output is ``source centric''
33297 which hasn't proved useful in practice.
33298 @xref{Machine Code}, for a discussion of the difference between
33299 @code{/m} and @code{/s} output of the @code{disassemble} command.
33302 @subsubheading Result
33304 The result of the @code{-data-disassemble} command will be a list named
33305 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33306 used with the @code{-data-disassemble} command.
33308 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33313 The address at which this instruction was disassembled.
33316 The name of the function this instruction is within.
33319 The decimal offset in bytes from the start of @samp{func-name}.
33322 The text disassembly for this @samp{address}.
33325 This field is only present for modes 2, 3 and 5. This contains the raw opcode
33326 bytes for the @samp{inst} field.
33330 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
33331 @samp{src_and_asm_line}, each of which has the following fields:
33335 The line number within @samp{file}.
33338 The file name from the compilation unit. This might be an absolute
33339 file name or a relative file name depending on the compile command
33343 Absolute file name of @samp{file}. It is converted to a canonical form
33344 using the source file search path
33345 (@pxref{Source Path, ,Specifying Source Directories})
33346 and after resolving all the symbolic links.
33348 If the source file is not found this field will contain the path as
33349 present in the debug information.
33351 @item line_asm_insn
33352 This is a list of tuples containing the disassembly for @samp{line} in
33353 @samp{file}. The fields of each tuple are the same as for
33354 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33355 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33360 Note that whatever included in the @samp{inst} field, is not
33361 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33364 @subsubheading @value{GDBN} Command
33366 The corresponding @value{GDBN} command is @samp{disassemble}.
33368 @subsubheading Example
33370 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33374 -data-disassemble -s $pc -e "$pc + 20" -- 0
33377 @{address="0x000107c0",func-name="main",offset="4",
33378 inst="mov 2, %o0"@},
33379 @{address="0x000107c4",func-name="main",offset="8",
33380 inst="sethi %hi(0x11800), %o2"@},
33381 @{address="0x000107c8",func-name="main",offset="12",
33382 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33383 @{address="0x000107cc",func-name="main",offset="16",
33384 inst="sethi %hi(0x11800), %o2"@},
33385 @{address="0x000107d0",func-name="main",offset="20",
33386 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33390 Disassemble the whole @code{main} function. Line 32 is part of
33394 -data-disassemble -f basics.c -l 32 -- 0
33396 @{address="0x000107bc",func-name="main",offset="0",
33397 inst="save %sp, -112, %sp"@},
33398 @{address="0x000107c0",func-name="main",offset="4",
33399 inst="mov 2, %o0"@},
33400 @{address="0x000107c4",func-name="main",offset="8",
33401 inst="sethi %hi(0x11800), %o2"@},
33403 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33404 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33408 Disassemble 3 instructions from the start of @code{main}:
33412 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33414 @{address="0x000107bc",func-name="main",offset="0",
33415 inst="save %sp, -112, %sp"@},
33416 @{address="0x000107c0",func-name="main",offset="4",
33417 inst="mov 2, %o0"@},
33418 @{address="0x000107c4",func-name="main",offset="8",
33419 inst="sethi %hi(0x11800), %o2"@}]
33423 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33427 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33429 src_and_asm_line=@{line="31",
33430 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33431 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33432 line_asm_insn=[@{address="0x000107bc",
33433 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33434 src_and_asm_line=@{line="32",
33435 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33436 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33437 line_asm_insn=[@{address="0x000107c0",
33438 func-name="main",offset="4",inst="mov 2, %o0"@},
33439 @{address="0x000107c4",func-name="main",offset="8",
33440 inst="sethi %hi(0x11800), %o2"@}]@}]
33445 @subheading The @code{-data-evaluate-expression} Command
33446 @findex -data-evaluate-expression
33448 @subsubheading Synopsis
33451 -data-evaluate-expression @var{expr}
33454 Evaluate @var{expr} as an expression. The expression could contain an
33455 inferior function call. The function call will execute synchronously.
33456 If the expression contains spaces, it must be enclosed in double quotes.
33458 @subsubheading @value{GDBN} Command
33460 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33461 @samp{call}. In @code{gdbtk} only, there's a corresponding
33462 @samp{gdb_eval} command.
33464 @subsubheading Example
33466 In the following example, the numbers that precede the commands are the
33467 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33468 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33472 211-data-evaluate-expression A
33475 311-data-evaluate-expression &A
33476 311^done,value="0xefffeb7c"
33478 411-data-evaluate-expression A+3
33481 511-data-evaluate-expression "A + 3"
33487 @subheading The @code{-data-list-changed-registers} Command
33488 @findex -data-list-changed-registers
33490 @subsubheading Synopsis
33493 -data-list-changed-registers
33496 Display a list of the registers that have changed.
33498 @subsubheading @value{GDBN} Command
33500 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33501 has the corresponding command @samp{gdb_changed_register_list}.
33503 @subsubheading Example
33505 On a PPC MBX board:
33513 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33514 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33515 line="5",arch="powerpc"@}
33517 -data-list-changed-registers
33518 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33519 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33520 "24","25","26","27","28","30","31","64","65","66","67","69"]
33525 @subheading The @code{-data-list-register-names} Command
33526 @findex -data-list-register-names
33528 @subsubheading Synopsis
33531 -data-list-register-names [ ( @var{regno} )+ ]
33534 Show a list of register names for the current target. If no arguments
33535 are given, it shows a list of the names of all the registers. If
33536 integer numbers are given as arguments, it will print a list of the
33537 names of the registers corresponding to the arguments. To ensure
33538 consistency between a register name and its number, the output list may
33539 include empty register names.
33541 @subsubheading @value{GDBN} Command
33543 @value{GDBN} does not have a command which corresponds to
33544 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33545 corresponding command @samp{gdb_regnames}.
33547 @subsubheading Example
33549 For the PPC MBX board:
33552 -data-list-register-names
33553 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33554 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33555 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33556 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33557 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33558 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33559 "", "pc","ps","cr","lr","ctr","xer"]
33561 -data-list-register-names 1 2 3
33562 ^done,register-names=["r1","r2","r3"]
33566 @subheading The @code{-data-list-register-values} Command
33567 @findex -data-list-register-values
33569 @subsubheading Synopsis
33572 -data-list-register-values
33573 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33576 Display the registers' contents. The format according to which the
33577 registers' contents are to be returned is given by @var{fmt}, followed
33578 by an optional list of numbers specifying the registers to display. A
33579 missing list of numbers indicates that the contents of all the
33580 registers must be returned. The @code{--skip-unavailable} option
33581 indicates that only the available registers are to be returned.
33583 Allowed formats for @var{fmt} are:
33600 @subsubheading @value{GDBN} Command
33602 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33603 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33605 @subsubheading Example
33607 For a PPC MBX board (note: line breaks are for readability only, they
33608 don't appear in the actual output):
33612 -data-list-register-values r 64 65
33613 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33614 @{number="65",value="0x00029002"@}]
33616 -data-list-register-values x
33617 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33618 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33619 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33620 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33621 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33622 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33623 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33624 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33625 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33626 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33627 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33628 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33629 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33630 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33631 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33632 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33633 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33634 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33635 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33636 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33637 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33638 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33639 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33640 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33641 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33642 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33643 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33644 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33645 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33646 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33647 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33648 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33649 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33650 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33651 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33652 @{number="69",value="0x20002b03"@}]
33657 @subheading The @code{-data-read-memory} Command
33658 @findex -data-read-memory
33660 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33662 @subsubheading Synopsis
33665 -data-read-memory [ -o @var{byte-offset} ]
33666 @var{address} @var{word-format} @var{word-size}
33667 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33674 @item @var{address}
33675 An expression specifying the address of the first memory word to be
33676 read. Complex expressions containing embedded white space should be
33677 quoted using the C convention.
33679 @item @var{word-format}
33680 The format to be used to print the memory words. The notation is the
33681 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33684 @item @var{word-size}
33685 The size of each memory word in bytes.
33687 @item @var{nr-rows}
33688 The number of rows in the output table.
33690 @item @var{nr-cols}
33691 The number of columns in the output table.
33694 If present, indicates that each row should include an @sc{ascii} dump. The
33695 value of @var{aschar} is used as a padding character when a byte is not a
33696 member of the printable @sc{ascii} character set (printable @sc{ascii}
33697 characters are those whose code is between 32 and 126, inclusively).
33699 @item @var{byte-offset}
33700 An offset to add to the @var{address} before fetching memory.
33703 This command displays memory contents as a table of @var{nr-rows} by
33704 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33705 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33706 (returned as @samp{total-bytes}). Should less than the requested number
33707 of bytes be returned by the target, the missing words are identified
33708 using @samp{N/A}. The number of bytes read from the target is returned
33709 in @samp{nr-bytes} and the starting address used to read memory in
33712 The address of the next/previous row or page is available in
33713 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33716 @subsubheading @value{GDBN} Command
33718 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33719 @samp{gdb_get_mem} memory read command.
33721 @subsubheading Example
33723 Read six bytes of memory starting at @code{bytes+6} but then offset by
33724 @code{-6} bytes. Format as three rows of two columns. One byte per
33725 word. Display each word in hex.
33729 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33730 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33731 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33732 prev-page="0x0000138a",memory=[
33733 @{addr="0x00001390",data=["0x00","0x01"]@},
33734 @{addr="0x00001392",data=["0x02","0x03"]@},
33735 @{addr="0x00001394",data=["0x04","0x05"]@}]
33739 Read two bytes of memory starting at address @code{shorts + 64} and
33740 display as a single word formatted in decimal.
33744 5-data-read-memory shorts+64 d 2 1 1
33745 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33746 next-row="0x00001512",prev-row="0x0000150e",
33747 next-page="0x00001512",prev-page="0x0000150e",memory=[
33748 @{addr="0x00001510",data=["128"]@}]
33752 Read thirty two bytes of memory starting at @code{bytes+16} and format
33753 as eight rows of four columns. Include a string encoding with @samp{x}
33754 used as the non-printable character.
33758 4-data-read-memory bytes+16 x 1 8 4 x
33759 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33760 next-row="0x000013c0",prev-row="0x0000139c",
33761 next-page="0x000013c0",prev-page="0x00001380",memory=[
33762 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33763 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33764 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33765 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33766 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33767 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33768 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33769 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33773 @subheading The @code{-data-read-memory-bytes} Command
33774 @findex -data-read-memory-bytes
33776 @subsubheading Synopsis
33779 -data-read-memory-bytes [ -o @var{offset} ]
33780 @var{address} @var{count}
33787 @item @var{address}
33788 An expression specifying the address of the first addressable memory unit
33789 to be read. Complex expressions containing embedded white space should be
33790 quoted using the C convention.
33793 The number of addressable memory units to read. This should be an integer
33797 The offset relative to @var{address} at which to start reading. This
33798 should be an integer literal. This option is provided so that a frontend
33799 is not required to first evaluate address and then perform address
33800 arithmetics itself.
33804 This command attempts to read all accessible memory regions in the
33805 specified range. First, all regions marked as unreadable in the memory
33806 map (if one is defined) will be skipped. @xref{Memory Region
33807 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33808 regions. For each one, if reading full region results in an errors,
33809 @value{GDBN} will try to read a subset of the region.
33811 In general, every single memory unit in the region may be readable or not,
33812 and the only way to read every readable unit is to try a read at
33813 every address, which is not practical. Therefore, @value{GDBN} will
33814 attempt to read all accessible memory units at either beginning or the end
33815 of the region, using a binary division scheme. This heuristic works
33816 well for reading across a memory map boundary. Note that if a region
33817 has a readable range that is neither at the beginning or the end,
33818 @value{GDBN} will not read it.
33820 The result record (@pxref{GDB/MI Result Records}) that is output of
33821 the command includes a field named @samp{memory} whose content is a
33822 list of tuples. Each tuple represent a successfully read memory block
33823 and has the following fields:
33827 The start address of the memory block, as hexadecimal literal.
33830 The end address of the memory block, as hexadecimal literal.
33833 The offset of the memory block, as hexadecimal literal, relative to
33834 the start address passed to @code{-data-read-memory-bytes}.
33837 The contents of the memory block, in hex.
33843 @subsubheading @value{GDBN} Command
33845 The corresponding @value{GDBN} command is @samp{x}.
33847 @subsubheading Example
33851 -data-read-memory-bytes &a 10
33852 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33854 contents="01000000020000000300"@}]
33859 @subheading The @code{-data-write-memory-bytes} Command
33860 @findex -data-write-memory-bytes
33862 @subsubheading Synopsis
33865 -data-write-memory-bytes @var{address} @var{contents}
33866 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33873 @item @var{address}
33874 An expression specifying the address of the first addressable memory unit
33875 to be written. Complex expressions containing embedded white space should
33876 be quoted using the C convention.
33878 @item @var{contents}
33879 The hex-encoded data to write. It is an error if @var{contents} does
33880 not represent an integral number of addressable memory units.
33883 Optional argument indicating the number of addressable memory units to be
33884 written. If @var{count} is greater than @var{contents}' length,
33885 @value{GDBN} will repeatedly write @var{contents} until it fills
33886 @var{count} memory units.
33890 @subsubheading @value{GDBN} Command
33892 There's no corresponding @value{GDBN} command.
33894 @subsubheading Example
33898 -data-write-memory-bytes &a "aabbccdd"
33905 -data-write-memory-bytes &a "aabbccdd" 16e
33910 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33911 @node GDB/MI Tracepoint Commands
33912 @section @sc{gdb/mi} Tracepoint Commands
33914 The commands defined in this section implement MI support for
33915 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33917 @subheading The @code{-trace-find} Command
33918 @findex -trace-find
33920 @subsubheading Synopsis
33923 -trace-find @var{mode} [@var{parameters}@dots{}]
33926 Find a trace frame using criteria defined by @var{mode} and
33927 @var{parameters}. The following table lists permissible
33928 modes and their parameters. For details of operation, see @ref{tfind}.
33933 No parameters are required. Stops examining trace frames.
33936 An integer is required as parameter. Selects tracepoint frame with
33939 @item tracepoint-number
33940 An integer is required as parameter. Finds next
33941 trace frame that corresponds to tracepoint with the specified number.
33944 An address is required as parameter. Finds
33945 next trace frame that corresponds to any tracepoint at the specified
33948 @item pc-inside-range
33949 Two addresses are required as parameters. Finds next trace
33950 frame that corresponds to a tracepoint at an address inside the
33951 specified range. Both bounds are considered to be inside the range.
33953 @item pc-outside-range
33954 Two addresses are required as parameters. Finds
33955 next trace frame that corresponds to a tracepoint at an address outside
33956 the specified range. Both bounds are considered to be inside the range.
33959 Line specification is required as parameter. @xref{Specify Location}.
33960 Finds next trace frame that corresponds to a tracepoint at
33961 the specified location.
33965 If @samp{none} was passed as @var{mode}, the response does not
33966 have fields. Otherwise, the response may have the following fields:
33970 This field has either @samp{0} or @samp{1} as the value, depending
33971 on whether a matching tracepoint was found.
33974 The index of the found traceframe. This field is present iff
33975 the @samp{found} field has value of @samp{1}.
33978 The index of the found tracepoint. This field is present iff
33979 the @samp{found} field has value of @samp{1}.
33982 The information about the frame corresponding to the found trace
33983 frame. This field is present only if a trace frame was found.
33984 @xref{GDB/MI Frame Information}, for description of this field.
33988 @subsubheading @value{GDBN} Command
33990 The corresponding @value{GDBN} command is @samp{tfind}.
33992 @subheading -trace-define-variable
33993 @findex -trace-define-variable
33995 @subsubheading Synopsis
33998 -trace-define-variable @var{name} [ @var{value} ]
34001 Create trace variable @var{name} if it does not exist. If
34002 @var{value} is specified, sets the initial value of the specified
34003 trace variable to that value. Note that the @var{name} should start
34004 with the @samp{$} character.
34006 @subsubheading @value{GDBN} Command
34008 The corresponding @value{GDBN} command is @samp{tvariable}.
34010 @subheading The @code{-trace-frame-collected} Command
34011 @findex -trace-frame-collected
34013 @subsubheading Synopsis
34016 -trace-frame-collected
34017 [--var-print-values @var{var_pval}]
34018 [--comp-print-values @var{comp_pval}]
34019 [--registers-format @var{regformat}]
34020 [--memory-contents]
34023 This command returns the set of collected objects, register names,
34024 trace state variable names, memory ranges and computed expressions
34025 that have been collected at a particular trace frame. The optional
34026 parameters to the command affect the output format in different ways.
34027 See the output description table below for more details.
34029 The reported names can be used in the normal manner to create
34030 varobjs and inspect the objects themselves. The items returned by
34031 this command are categorized so that it is clear which is a variable,
34032 which is a register, which is a trace state variable, which is a
34033 memory range and which is a computed expression.
34035 For instance, if the actions were
34037 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
34038 collect *(int*)0xaf02bef0@@40
34042 the object collected in its entirety would be @code{myVar}. The
34043 object @code{myArray} would be partially collected, because only the
34044 element at index @code{myIndex} would be collected. The remaining
34045 objects would be computed expressions.
34047 An example output would be:
34051 -trace-frame-collected
34053 explicit-variables=[@{name="myVar",value="1"@}],
34054 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
34055 @{name="myObj.field",value="0"@},
34056 @{name="myPtr->field",value="1"@},
34057 @{name="myCount + 2",value="3"@},
34058 @{name="$tvar1 + 1",value="43970027"@}],
34059 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
34060 @{number="1",value="0x0"@},
34061 @{number="2",value="0x4"@},
34063 @{number="125",value="0x0"@}],
34064 tvars=[@{name="$tvar1",current="43970026"@}],
34065 memory=[@{address="0x0000000000602264",length="4"@},
34066 @{address="0x0000000000615bc0",length="4"@}]
34073 @item explicit-variables
34074 The set of objects that have been collected in their entirety (as
34075 opposed to collecting just a few elements of an array or a few struct
34076 members). For each object, its name and value are printed.
34077 The @code{--var-print-values} option affects how or whether the value
34078 field is output. If @var{var_pval} is 0, then print only the names;
34079 if it is 1, print also their values; and if it is 2, print the name,
34080 type and value for simple data types, and the name and type for
34081 arrays, structures and unions.
34083 @item computed-expressions
34084 The set of computed expressions that have been collected at the
34085 current trace frame. The @code{--comp-print-values} option affects
34086 this set like the @code{--var-print-values} option affects the
34087 @code{explicit-variables} set. See above.
34090 The registers that have been collected at the current trace frame.
34091 For each register collected, the name and current value are returned.
34092 The value is formatted according to the @code{--registers-format}
34093 option. See the @command{-data-list-register-values} command for a
34094 list of the allowed formats. The default is @samp{x}.
34097 The trace state variables that have been collected at the current
34098 trace frame. For each trace state variable collected, the name and
34099 current value are returned.
34102 The set of memory ranges that have been collected at the current trace
34103 frame. Its content is a list of tuples. Each tuple represents a
34104 collected memory range and has the following fields:
34108 The start address of the memory range, as hexadecimal literal.
34111 The length of the memory range, as decimal literal.
34114 The contents of the memory block, in hex. This field is only present
34115 if the @code{--memory-contents} option is specified.
34121 @subsubheading @value{GDBN} Command
34123 There is no corresponding @value{GDBN} command.
34125 @subsubheading Example
34127 @subheading -trace-list-variables
34128 @findex -trace-list-variables
34130 @subsubheading Synopsis
34133 -trace-list-variables
34136 Return a table of all defined trace variables. Each element of the
34137 table has the following fields:
34141 The name of the trace variable. This field is always present.
34144 The initial value. This is a 64-bit signed integer. This
34145 field is always present.
34148 The value the trace variable has at the moment. This is a 64-bit
34149 signed integer. This field is absent iff current value is
34150 not defined, for example if the trace was never run, or is
34155 @subsubheading @value{GDBN} Command
34157 The corresponding @value{GDBN} command is @samp{tvariables}.
34159 @subsubheading Example
34163 -trace-list-variables
34164 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
34165 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
34166 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
34167 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
34168 body=[variable=@{name="$trace_timestamp",initial="0"@}
34169 variable=@{name="$foo",initial="10",current="15"@}]@}
34173 @subheading -trace-save
34174 @findex -trace-save
34176 @subsubheading Synopsis
34179 -trace-save [ -r ] [ -ctf ] @var{filename}
34182 Saves the collected trace data to @var{filename}. Without the
34183 @samp{-r} option, the data is downloaded from the target and saved
34184 in a local file. With the @samp{-r} option the target is asked
34185 to perform the save.
34187 By default, this command will save the trace in the tfile format. You can
34188 supply the optional @samp{-ctf} argument to save it the CTF format. See
34189 @ref{Trace Files} for more information about CTF.
34191 @subsubheading @value{GDBN} Command
34193 The corresponding @value{GDBN} command is @samp{tsave}.
34196 @subheading -trace-start
34197 @findex -trace-start
34199 @subsubheading Synopsis
34205 Starts a tracing experiment. The result of this command does not
34208 @subsubheading @value{GDBN} Command
34210 The corresponding @value{GDBN} command is @samp{tstart}.
34212 @subheading -trace-status
34213 @findex -trace-status
34215 @subsubheading Synopsis
34221 Obtains the status of a tracing experiment. The result may include
34222 the following fields:
34227 May have a value of either @samp{0}, when no tracing operations are
34228 supported, @samp{1}, when all tracing operations are supported, or
34229 @samp{file} when examining trace file. In the latter case, examining
34230 of trace frame is possible but new tracing experiement cannot be
34231 started. This field is always present.
34234 May have a value of either @samp{0} or @samp{1} depending on whether
34235 tracing experiement is in progress on target. This field is present
34236 if @samp{supported} field is not @samp{0}.
34239 Report the reason why the tracing was stopped last time. This field
34240 may be absent iff tracing was never stopped on target yet. The
34241 value of @samp{request} means the tracing was stopped as result of
34242 the @code{-trace-stop} command. The value of @samp{overflow} means
34243 the tracing buffer is full. The value of @samp{disconnection} means
34244 tracing was automatically stopped when @value{GDBN} has disconnected.
34245 The value of @samp{passcount} means tracing was stopped when a
34246 tracepoint was passed a maximal number of times for that tracepoint.
34247 This field is present if @samp{supported} field is not @samp{0}.
34249 @item stopping-tracepoint
34250 The number of tracepoint whose passcount as exceeded. This field is
34251 present iff the @samp{stop-reason} field has the value of
34255 @itemx frames-created
34256 The @samp{frames} field is a count of the total number of trace frames
34257 in the trace buffer, while @samp{frames-created} is the total created
34258 during the run, including ones that were discarded, such as when a
34259 circular trace buffer filled up. Both fields are optional.
34263 These fields tell the current size of the tracing buffer and the
34264 remaining space. These fields are optional.
34267 The value of the circular trace buffer flag. @code{1} means that the
34268 trace buffer is circular and old trace frames will be discarded if
34269 necessary to make room, @code{0} means that the trace buffer is linear
34273 The value of the disconnected tracing flag. @code{1} means that
34274 tracing will continue after @value{GDBN} disconnects, @code{0} means
34275 that the trace run will stop.
34278 The filename of the trace file being examined. This field is
34279 optional, and only present when examining a trace file.
34283 @subsubheading @value{GDBN} Command
34285 The corresponding @value{GDBN} command is @samp{tstatus}.
34287 @subheading -trace-stop
34288 @findex -trace-stop
34290 @subsubheading Synopsis
34296 Stops a tracing experiment. The result of this command has the same
34297 fields as @code{-trace-status}, except that the @samp{supported} and
34298 @samp{running} fields are not output.
34300 @subsubheading @value{GDBN} Command
34302 The corresponding @value{GDBN} command is @samp{tstop}.
34305 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34306 @node GDB/MI Symbol Query
34307 @section @sc{gdb/mi} Symbol Query Commands
34311 @subheading The @code{-symbol-info-address} Command
34312 @findex -symbol-info-address
34314 @subsubheading Synopsis
34317 -symbol-info-address @var{symbol}
34320 Describe where @var{symbol} is stored.
34322 @subsubheading @value{GDBN} Command
34324 The corresponding @value{GDBN} command is @samp{info address}.
34326 @subsubheading Example
34330 @subheading The @code{-symbol-info-file} Command
34331 @findex -symbol-info-file
34333 @subsubheading Synopsis
34339 Show the file for the symbol.
34341 @subsubheading @value{GDBN} Command
34343 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34344 @samp{gdb_find_file}.
34346 @subsubheading Example
34350 @subheading The @code{-symbol-info-functions} Command
34351 @findex -symbol-info-functions
34352 @anchor{-symbol-info-functions}
34354 @subsubheading Synopsis
34357 -symbol-info-functions [--include-nondebug]
34358 [--type @var{type_regexp}]
34359 [--name @var{name_regexp}]
34360 [--max-results @var{limit}]
34364 Return a list containing the names and types for all global functions
34365 taken from the debug information. The functions are grouped by source
34366 file, and shown with the line number on which each function is
34369 The @code{--include-nondebug} option causes the output to include
34370 code symbols from the symbol table.
34372 The options @code{--type} and @code{--name} allow the symbols returned
34373 to be filtered based on either the name of the function, or the type
34374 signature of the function.
34376 The option @code{--max-results} restricts the command to return no
34377 more than @var{limit} results. If exactly @var{limit} results are
34378 returned then there might be additional results available if a higher
34381 @subsubheading @value{GDBN} Command
34383 The corresponding @value{GDBN} command is @samp{info functions}.
34385 @subsubheading Example
34389 -symbol-info-functions
34392 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34393 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34394 symbols=[@{line="36", name="f4", type="void (int *)",
34395 description="void f4(int *);"@},
34396 @{line="42", name="main", type="int ()",
34397 description="int main();"@},
34398 @{line="30", name="f1", type="my_int_t (int, int)",
34399 description="static my_int_t f1(int, int);"@}]@},
34400 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34401 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34402 symbols=[@{line="33", name="f2", type="float (another_float_t)",
34403 description="float f2(another_float_t);"@},
34404 @{line="39", name="f3", type="int (another_int_t)",
34405 description="int f3(another_int_t);"@},
34406 @{line="27", name="f1", type="another_float_t (int)",
34407 description="static another_float_t f1(int);"@}]@}]@}
34411 -symbol-info-functions --name f1
34414 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34415 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34416 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
34417 description="static my_int_t f1(int, int);"@}]@},
34418 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34419 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34420 symbols=[@{line="27", name="f1", type="another_float_t (int)",
34421 description="static another_float_t f1(int);"@}]@}]@}
34425 -symbol-info-functions --type void
34428 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34429 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34430 symbols=[@{line="36", name="f4", type="void (int *)",
34431 description="void f4(int *);"@}]@}]@}
34435 -symbol-info-functions --include-nondebug
34438 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34439 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34440 symbols=[@{line="36", name="f4", type="void (int *)",
34441 description="void f4(int *);"@},
34442 @{line="42", name="main", type="int ()",
34443 description="int main();"@},
34444 @{line="30", name="f1", type="my_int_t (int, int)",
34445 description="static my_int_t f1(int, int);"@}]@},
34446 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34447 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34448 symbols=[@{line="33", name="f2", type="float (another_float_t)",
34449 description="float f2(another_float_t);"@},
34450 @{line="39", name="f3", type="int (another_int_t)",
34451 description="int f3(another_int_t);"@},
34452 @{line="27", name="f1", type="another_float_t (int)",
34453 description="static another_float_t f1(int);"@}]@}],
34455 [@{address="0x0000000000400398",name="_init"@},
34456 @{address="0x00000000004003b0",name="_start"@},
34462 @subheading The @code{-symbol-info-module-functions} Command
34463 @findex -symbol-info-module-functions
34464 @anchor{-symbol-info-module-functions}
34466 @subsubheading Synopsis
34469 -symbol-info-module-functions [--module @var{module_regexp}]
34470 [--name @var{name_regexp}]
34471 [--type @var{type_regexp}]
34475 Return a list containing the names of all known functions within all
34476 know Fortran modules. The functions are grouped by source file and
34477 containing module, and shown with the line number on which each
34478 function is defined.
34480 The option @code{--module} only returns results for modules matching
34481 @var{module_regexp}. The option @code{--name} only returns functions
34482 whose name matches @var{name_regexp}, and @code{--type} only returns
34483 functions whose type matches @var{type_regexp}.
34485 @subsubheading @value{GDBN} Command
34487 The corresponding @value{GDBN} command is @samp{info module functions}.
34489 @subsubheading Example
34494 -symbol-info-module-functions
34497 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34498 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34499 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
34500 description="void mod1::check_all(void);"@}]@}]@},
34502 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34503 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34504 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
34505 description="void mod2::check_var_i(void);"@}]@}]@},
34507 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34508 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34509 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
34510 description="void mod3::check_all(void);"@},
34511 @{line="27",name="mod3::check_mod2",type="void (void)",
34512 description="void mod3::check_mod2(void);"@}]@}]@},
34513 @{module="modmany",
34514 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34515 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34516 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
34517 description="void modmany::check_some(void);"@}]@}]@},
34519 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34520 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34521 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
34522 description="void moduse::check_all(void);"@},
34523 @{line="49",name="moduse::check_var_x",type="void (void)",
34524 description="void moduse::check_var_x(void);"@}]@}]@}]
34528 @subheading The @code{-symbol-info-module-variables} Command
34529 @findex -symbol-info-module-variables
34530 @anchor{-symbol-info-module-variables}
34532 @subsubheading Synopsis
34535 -symbol-info-module-variables [--module @var{module_regexp}]
34536 [--name @var{name_regexp}]
34537 [--type @var{type_regexp}]
34541 Return a list containing the names of all known variables within all
34542 know Fortran modules. The variables are grouped by source file and
34543 containing module, and shown with the line number on which each
34544 variable is defined.
34546 The option @code{--module} only returns results for modules matching
34547 @var{module_regexp}. The option @code{--name} only returns variables
34548 whose name matches @var{name_regexp}, and @code{--type} only returns
34549 variables whose type matches @var{type_regexp}.
34551 @subsubheading @value{GDBN} Command
34553 The corresponding @value{GDBN} command is @samp{info module variables}.
34555 @subsubheading Example
34560 -symbol-info-module-variables
34563 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34564 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34565 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
34566 description="integer(kind=4) mod1::var_const;"@},
34567 @{line="17",name="mod1::var_i",type="integer(kind=4)",
34568 description="integer(kind=4) mod1::var_i;"@}]@}]@},
34570 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34571 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34572 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
34573 description="integer(kind=4) mod2::var_i;"@}]@}]@},
34575 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34576 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34577 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
34578 description="integer(kind=4) mod3::mod1;"@},
34579 @{line="17",name="mod3::mod2",type="integer(kind=4)",
34580 description="integer(kind=4) mod3::mod2;"@},
34581 @{line="19",name="mod3::var_i",type="integer(kind=4)",
34582 description="integer(kind=4) mod3::var_i;"@}]@}]@},
34583 @{module="modmany",
34584 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34585 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34586 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
34587 description="integer(kind=4) modmany::var_a;"@},
34588 @{line="33",name="modmany::var_b",type="integer(kind=4)",
34589 description="integer(kind=4) modmany::var_b;"@},
34590 @{line="33",name="modmany::var_c",type="integer(kind=4)",
34591 description="integer(kind=4) modmany::var_c;"@},
34592 @{line="33",name="modmany::var_i",type="integer(kind=4)",
34593 description="integer(kind=4) modmany::var_i;"@}]@}]@},
34595 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34596 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34597 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
34598 description="integer(kind=4) moduse::var_x;"@},
34599 @{line="42",name="moduse::var_y",type="integer(kind=4)",
34600 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
34604 @subheading The @code{-symbol-info-modules} Command
34605 @findex -symbol-info-modules
34606 @anchor{-symbol-info-modules}
34608 @subsubheading Synopsis
34611 -symbol-info-modules [--name @var{name_regexp}]
34612 [--max-results @var{limit}]
34617 Return a list containing the names of all known Fortran modules. The
34618 modules are grouped by source file, and shown with the line number on
34619 which each modules is defined.
34621 The option @code{--name} allows the modules returned to be filtered
34622 based the name of the module.
34624 The option @code{--max-results} restricts the command to return no
34625 more than @var{limit} results. If exactly @var{limit} results are
34626 returned then there might be additional results available if a higher
34629 @subsubheading @value{GDBN} Command
34631 The corresponding @value{GDBN} command is @samp{info modules}.
34633 @subsubheading Example
34637 -symbol-info-modules
34640 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34641 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34642 symbols=[@{line="16",name="mod1"@},
34643 @{line="22",name="mod2"@}]@},
34644 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34645 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34646 symbols=[@{line="16",name="mod3"@},
34647 @{line="22",name="modmany"@},
34648 @{line="26",name="moduse"@}]@}]@}
34652 -symbol-info-modules --name mod[123]
34655 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34656 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
34657 symbols=[@{line="16",name="mod1"@},
34658 @{line="22",name="mod2"@}]@},
34659 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34660 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
34661 symbols=[@{line="16",name="mod3"@}]@}]@}
34665 @subheading The @code{-symbol-info-types} Command
34666 @findex -symbol-info-types
34667 @anchor{-symbol-info-types}
34669 @subsubheading Synopsis
34672 -symbol-info-types [--name @var{name_regexp}]
34673 [--max-results @var{limit}]
34678 Return a list of all defined types. The types are grouped by source
34679 file, and shown with the line number on which each user defined type
34680 is defined. Some base types are not defined in the source code but
34681 are added to the debug information by the compiler, for example
34682 @code{int}, @code{float}, etc.; these types do not have an associated
34685 The option @code{--name} allows the list of types returned to be
34688 The option @code{--max-results} restricts the command to return no
34689 more than @var{limit} results. If exactly @var{limit} results are
34690 returned then there might be additional results available if a higher
34693 @subsubheading @value{GDBN} Command
34695 The corresponding @value{GDBN} command is @samp{info types}.
34697 @subsubheading Example
34704 [@{filename="gdb.mi/mi-sym-info-1.c",
34705 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34706 symbols=[@{name="float"@},
34708 @{line="27",name="typedef int my_int_t;"@}]@},
34709 @{filename="gdb.mi/mi-sym-info-2.c",
34710 fullname="/project/gdb.mi/mi-sym-info-2.c",
34711 symbols=[@{line="24",name="typedef float another_float_t;"@},
34712 @{line="23",name="typedef int another_int_t;"@},
34714 @{name="int"@}]@}]@}
34718 -symbol-info-types --name _int_
34721 [@{filename="gdb.mi/mi-sym-info-1.c",
34722 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34723 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
34724 @{filename="gdb.mi/mi-sym-info-2.c",
34725 fullname="/project/gdb.mi/mi-sym-info-2.c",
34726 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
34730 @subheading The @code{-symbol-info-variables} Command
34731 @findex -symbol-info-variables
34732 @anchor{-symbol-info-variables}
34734 @subsubheading Synopsis
34737 -symbol-info-variables [--include-nondebug]
34738 [--type @var{type_regexp}]
34739 [--name @var{name_regexp}]
34740 [--max-results @var{limit}]
34745 Return a list containing the names and types for all global variables
34746 taken from the debug information. The variables are grouped by source
34747 file, and shown with the line number on which each variable is
34750 The @code{--include-nondebug} option causes the output to include
34751 data symbols from the symbol table.
34753 The options @code{--type} and @code{--name} allow the symbols returned
34754 to be filtered based on either the name of the variable, or the type
34757 The option @code{--max-results} restricts the command to return no
34758 more than @var{limit} results. If exactly @var{limit} results are
34759 returned then there might be additional results available if a higher
34762 @subsubheading @value{GDBN} Command
34764 The corresponding @value{GDBN} command is @samp{info variables}.
34766 @subsubheading Example
34770 -symbol-info-variables
34773 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34774 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34775 symbols=[@{line="25",name="global_f1",type="float",
34776 description="static float global_f1;"@},
34777 @{line="24",name="global_i1",type="int",
34778 description="static int global_i1;"@}]@},
34779 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34780 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34781 symbols=[@{line="21",name="global_f2",type="int",
34782 description="int global_f2;"@},
34783 @{line="20",name="global_i2",type="int",
34784 description="int global_i2;"@},
34785 @{line="19",name="global_f1",type="float",
34786 description="static float global_f1;"@},
34787 @{line="18",name="global_i1",type="int",
34788 description="static int global_i1;"@}]@}]@}
34792 -symbol-info-variables --name f1
34795 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34796 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34797 symbols=[@{line="25",name="global_f1",type="float",
34798 description="static float global_f1;"@}]@},
34799 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34800 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34801 symbols=[@{line="19",name="global_f1",type="float",
34802 description="static float global_f1;"@}]@}]@}
34806 -symbol-info-variables --type float
34809 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34810 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34811 symbols=[@{line="25",name="global_f1",type="float",
34812 description="static float global_f1;"@}]@},
34813 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34814 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34815 symbols=[@{line="19",name="global_f1",type="float",
34816 description="static float global_f1;"@}]@}]@}
34820 -symbol-info-variables --include-nondebug
34823 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34824 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
34825 symbols=[@{line="25",name="global_f1",type="float",
34826 description="static float global_f1;"@},
34827 @{line="24",name="global_i1",type="int",
34828 description="static int global_i1;"@}]@},
34829 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34830 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
34831 symbols=[@{line="21",name="global_f2",type="int",
34832 description="int global_f2;"@},
34833 @{line="20",name="global_i2",type="int",
34834 description="int global_i2;"@},
34835 @{line="19",name="global_f1",type="float",
34836 description="static float global_f1;"@},
34837 @{line="18",name="global_i1",type="int",
34838 description="static int global_i1;"@}]@}],
34840 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
34841 @{address="0x00000000004005d8",name="__dso_handle"@}
34848 @subheading The @code{-symbol-info-line} Command
34849 @findex -symbol-info-line
34851 @subsubheading Synopsis
34857 Show the core addresses of the code for a source line.
34859 @subsubheading @value{GDBN} Command
34861 The corresponding @value{GDBN} command is @samp{info line}.
34862 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34864 @subsubheading Example
34868 @subheading The @code{-symbol-info-symbol} Command
34869 @findex -symbol-info-symbol
34871 @subsubheading Synopsis
34874 -symbol-info-symbol @var{addr}
34877 Describe what symbol is at location @var{addr}.
34879 @subsubheading @value{GDBN} Command
34881 The corresponding @value{GDBN} command is @samp{info symbol}.
34883 @subsubheading Example
34887 @subheading The @code{-symbol-list-functions} Command
34888 @findex -symbol-list-functions
34890 @subsubheading Synopsis
34893 -symbol-list-functions
34896 List the functions in the executable.
34898 @subsubheading @value{GDBN} Command
34900 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34901 @samp{gdb_search} in @code{gdbtk}.
34903 @subsubheading Example
34908 @subheading The @code{-symbol-list-lines} Command
34909 @findex -symbol-list-lines
34911 @subsubheading Synopsis
34914 -symbol-list-lines @var{filename}
34917 Print the list of lines that contain code and their associated program
34918 addresses for the given source filename. The entries are sorted in
34919 ascending PC order.
34921 @subsubheading @value{GDBN} Command
34923 There is no corresponding @value{GDBN} command.
34925 @subsubheading Example
34928 -symbol-list-lines basics.c
34929 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34935 @subheading The @code{-symbol-list-types} Command
34936 @findex -symbol-list-types
34938 @subsubheading Synopsis
34944 List all the type names.
34946 @subsubheading @value{GDBN} Command
34948 The corresponding commands are @samp{info types} in @value{GDBN},
34949 @samp{gdb_search} in @code{gdbtk}.
34951 @subsubheading Example
34955 @subheading The @code{-symbol-list-variables} Command
34956 @findex -symbol-list-variables
34958 @subsubheading Synopsis
34961 -symbol-list-variables
34964 List all the global and static variable names.
34966 @subsubheading @value{GDBN} Command
34968 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34970 @subsubheading Example
34974 @subheading The @code{-symbol-locate} Command
34975 @findex -symbol-locate
34977 @subsubheading Synopsis
34983 @subsubheading @value{GDBN} Command
34985 @samp{gdb_loc} in @code{gdbtk}.
34987 @subsubheading Example
34991 @subheading The @code{-symbol-type} Command
34992 @findex -symbol-type
34994 @subsubheading Synopsis
34997 -symbol-type @var{variable}
35000 Show type of @var{variable}.
35002 @subsubheading @value{GDBN} Command
35004 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
35005 @samp{gdb_obj_variable}.
35007 @subsubheading Example
35012 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35013 @node GDB/MI File Commands
35014 @section @sc{gdb/mi} File Commands
35016 This section describes the GDB/MI commands to specify executable file names
35017 and to read in and obtain symbol table information.
35019 @subheading The @code{-file-exec-and-symbols} Command
35020 @findex -file-exec-and-symbols
35022 @subsubheading Synopsis
35025 -file-exec-and-symbols @var{file}
35028 Specify the executable file to be debugged. This file is the one from
35029 which the symbol table is also read. If no file is specified, the
35030 command clears the executable and symbol information. If breakpoints
35031 are set when using this command with no arguments, @value{GDBN} will produce
35032 error messages. Otherwise, no output is produced, except a completion
35035 @subsubheading @value{GDBN} Command
35037 The corresponding @value{GDBN} command is @samp{file}.
35039 @subsubheading Example
35043 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35049 @subheading The @code{-file-exec-file} Command
35050 @findex -file-exec-file
35052 @subsubheading Synopsis
35055 -file-exec-file @var{file}
35058 Specify the executable file to be debugged. Unlike
35059 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
35060 from this file. If used without argument, @value{GDBN} clears the information
35061 about the executable file. No output is produced, except a completion
35064 @subsubheading @value{GDBN} Command
35066 The corresponding @value{GDBN} command is @samp{exec-file}.
35068 @subsubheading Example
35072 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35079 @subheading The @code{-file-list-exec-sections} Command
35080 @findex -file-list-exec-sections
35082 @subsubheading Synopsis
35085 -file-list-exec-sections
35088 List the sections of the current executable file.
35090 @subsubheading @value{GDBN} Command
35092 The @value{GDBN} command @samp{info file} shows, among the rest, the same
35093 information as this command. @code{gdbtk} has a corresponding command
35094 @samp{gdb_load_info}.
35096 @subsubheading Example
35101 @subheading The @code{-file-list-exec-source-file} Command
35102 @findex -file-list-exec-source-file
35104 @subsubheading Synopsis
35107 -file-list-exec-source-file
35110 List the line number, the current source file, and the absolute path
35111 to the current source file for the current executable. The macro
35112 information field has a value of @samp{1} or @samp{0} depending on
35113 whether or not the file includes preprocessor macro information.
35115 @subsubheading @value{GDBN} Command
35117 The @value{GDBN} equivalent is @samp{info source}
35119 @subsubheading Example
35123 123-file-list-exec-source-file
35124 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
35129 @subheading The @code{-file-list-exec-source-files} Command
35130 @findex -file-list-exec-source-files
35132 @subsubheading Synopsis
35135 -file-list-exec-source-files
35138 List the source files for the current executable.
35140 It will always output both the filename and fullname (absolute file
35141 name) of a source file.
35143 @subsubheading @value{GDBN} Command
35145 The @value{GDBN} equivalent is @samp{info sources}.
35146 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
35148 @subsubheading Example
35151 -file-list-exec-source-files
35153 @{file=foo.c,fullname=/home/foo.c@},
35154 @{file=/home/bar.c,fullname=/home/bar.c@},
35155 @{file=gdb_could_not_find_fullpath.c@}]
35159 @subheading The @code{-file-list-shared-libraries} Command
35160 @findex -file-list-shared-libraries
35162 @subsubheading Synopsis
35165 -file-list-shared-libraries [ @var{regexp} ]
35168 List the shared libraries in the program.
35169 With a regular expression @var{regexp}, only those libraries whose
35170 names match @var{regexp} are listed.
35172 @subsubheading @value{GDBN} Command
35174 The corresponding @value{GDBN} command is @samp{info shared}. The fields
35175 have a similar meaning to the @code{=library-loaded} notification.
35176 The @code{ranges} field specifies the multiple segments belonging to this
35177 library. Each range has the following fields:
35181 The address defining the inclusive lower bound of the segment.
35183 The address defining the exclusive upper bound of the segment.
35186 @subsubheading Example
35189 -file-list-exec-source-files
35190 ^done,shared-libraries=[
35191 @{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"@}]@},
35192 @{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"@}]@}]
35198 @subheading The @code{-file-list-symbol-files} Command
35199 @findex -file-list-symbol-files
35201 @subsubheading Synopsis
35204 -file-list-symbol-files
35209 @subsubheading @value{GDBN} Command
35211 The corresponding @value{GDBN} command is @samp{info file} (part of it).
35213 @subsubheading Example
35218 @subheading The @code{-file-symbol-file} Command
35219 @findex -file-symbol-file
35221 @subsubheading Synopsis
35224 -file-symbol-file @var{file}
35227 Read symbol table info from the specified @var{file} argument. When
35228 used without arguments, clears @value{GDBN}'s symbol table info. No output is
35229 produced, except for a completion notification.
35231 @subsubheading @value{GDBN} Command
35233 The corresponding @value{GDBN} command is @samp{symbol-file}.
35235 @subsubheading Example
35239 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35245 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35246 @node GDB/MI Memory Overlay Commands
35247 @section @sc{gdb/mi} Memory Overlay Commands
35249 The memory overlay commands are not implemented.
35251 @c @subheading -overlay-auto
35253 @c @subheading -overlay-list-mapping-state
35255 @c @subheading -overlay-list-overlays
35257 @c @subheading -overlay-map
35259 @c @subheading -overlay-off
35261 @c @subheading -overlay-on
35263 @c @subheading -overlay-unmap
35265 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35266 @node GDB/MI Signal Handling Commands
35267 @section @sc{gdb/mi} Signal Handling Commands
35269 Signal handling commands are not implemented.
35271 @c @subheading -signal-handle
35273 @c @subheading -signal-list-handle-actions
35275 @c @subheading -signal-list-signal-types
35279 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35280 @node GDB/MI Target Manipulation
35281 @section @sc{gdb/mi} Target Manipulation Commands
35284 @subheading The @code{-target-attach} Command
35285 @findex -target-attach
35287 @subsubheading Synopsis
35290 -target-attach @var{pid} | @var{gid} | @var{file}
35293 Attach to a process @var{pid} or a file @var{file} outside of
35294 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
35295 group, the id previously returned by
35296 @samp{-list-thread-groups --available} must be used.
35298 @subsubheading @value{GDBN} Command
35300 The corresponding @value{GDBN} command is @samp{attach}.
35302 @subsubheading Example
35306 =thread-created,id="1"
35307 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
35313 @subheading The @code{-target-compare-sections} Command
35314 @findex -target-compare-sections
35316 @subsubheading Synopsis
35319 -target-compare-sections [ @var{section} ]
35322 Compare data of section @var{section} on target to the exec file.
35323 Without the argument, all sections are compared.
35325 @subsubheading @value{GDBN} Command
35327 The @value{GDBN} equivalent is @samp{compare-sections}.
35329 @subsubheading Example
35334 @subheading The @code{-target-detach} Command
35335 @findex -target-detach
35337 @subsubheading Synopsis
35340 -target-detach [ @var{pid} | @var{gid} ]
35343 Detach from the remote target which normally resumes its execution.
35344 If either @var{pid} or @var{gid} is specified, detaches from either
35345 the specified process, or specified thread group. There's no output.
35347 @subsubheading @value{GDBN} Command
35349 The corresponding @value{GDBN} command is @samp{detach}.
35351 @subsubheading Example
35361 @subheading The @code{-target-disconnect} Command
35362 @findex -target-disconnect
35364 @subsubheading Synopsis
35370 Disconnect from the remote target. There's no output and the target is
35371 generally not resumed.
35373 @subsubheading @value{GDBN} Command
35375 The corresponding @value{GDBN} command is @samp{disconnect}.
35377 @subsubheading Example
35387 @subheading The @code{-target-download} Command
35388 @findex -target-download
35390 @subsubheading Synopsis
35396 Loads the executable onto the remote target.
35397 It prints out an update message every half second, which includes the fields:
35401 The name of the section.
35403 The size of what has been sent so far for that section.
35405 The size of the section.
35407 The total size of what was sent so far (the current and the previous sections).
35409 The size of the overall executable to download.
35413 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
35414 @sc{gdb/mi} Output Syntax}).
35416 In addition, it prints the name and size of the sections, as they are
35417 downloaded. These messages include the following fields:
35421 The name of the section.
35423 The size of the section.
35425 The size of the overall executable to download.
35429 At the end, a summary is printed.
35431 @subsubheading @value{GDBN} Command
35433 The corresponding @value{GDBN} command is @samp{load}.
35435 @subsubheading Example
35437 Note: each status message appears on a single line. Here the messages
35438 have been broken down so that they can fit onto a page.
35443 +download,@{section=".text",section-size="6668",total-size="9880"@}
35444 +download,@{section=".text",section-sent="512",section-size="6668",
35445 total-sent="512",total-size="9880"@}
35446 +download,@{section=".text",section-sent="1024",section-size="6668",
35447 total-sent="1024",total-size="9880"@}
35448 +download,@{section=".text",section-sent="1536",section-size="6668",
35449 total-sent="1536",total-size="9880"@}
35450 +download,@{section=".text",section-sent="2048",section-size="6668",
35451 total-sent="2048",total-size="9880"@}
35452 +download,@{section=".text",section-sent="2560",section-size="6668",
35453 total-sent="2560",total-size="9880"@}
35454 +download,@{section=".text",section-sent="3072",section-size="6668",
35455 total-sent="3072",total-size="9880"@}
35456 +download,@{section=".text",section-sent="3584",section-size="6668",
35457 total-sent="3584",total-size="9880"@}
35458 +download,@{section=".text",section-sent="4096",section-size="6668",
35459 total-sent="4096",total-size="9880"@}
35460 +download,@{section=".text",section-sent="4608",section-size="6668",
35461 total-sent="4608",total-size="9880"@}
35462 +download,@{section=".text",section-sent="5120",section-size="6668",
35463 total-sent="5120",total-size="9880"@}
35464 +download,@{section=".text",section-sent="5632",section-size="6668",
35465 total-sent="5632",total-size="9880"@}
35466 +download,@{section=".text",section-sent="6144",section-size="6668",
35467 total-sent="6144",total-size="9880"@}
35468 +download,@{section=".text",section-sent="6656",section-size="6668",
35469 total-sent="6656",total-size="9880"@}
35470 +download,@{section=".init",section-size="28",total-size="9880"@}
35471 +download,@{section=".fini",section-size="28",total-size="9880"@}
35472 +download,@{section=".data",section-size="3156",total-size="9880"@}
35473 +download,@{section=".data",section-sent="512",section-size="3156",
35474 total-sent="7236",total-size="9880"@}
35475 +download,@{section=".data",section-sent="1024",section-size="3156",
35476 total-sent="7748",total-size="9880"@}
35477 +download,@{section=".data",section-sent="1536",section-size="3156",
35478 total-sent="8260",total-size="9880"@}
35479 +download,@{section=".data",section-sent="2048",section-size="3156",
35480 total-sent="8772",total-size="9880"@}
35481 +download,@{section=".data",section-sent="2560",section-size="3156",
35482 total-sent="9284",total-size="9880"@}
35483 +download,@{section=".data",section-sent="3072",section-size="3156",
35484 total-sent="9796",total-size="9880"@}
35485 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
35492 @subheading The @code{-target-exec-status} Command
35493 @findex -target-exec-status
35495 @subsubheading Synopsis
35498 -target-exec-status
35501 Provide information on the state of the target (whether it is running or
35502 not, for instance).
35504 @subsubheading @value{GDBN} Command
35506 There's no equivalent @value{GDBN} command.
35508 @subsubheading Example
35512 @subheading The @code{-target-list-available-targets} Command
35513 @findex -target-list-available-targets
35515 @subsubheading Synopsis
35518 -target-list-available-targets
35521 List the possible targets to connect to.
35523 @subsubheading @value{GDBN} Command
35525 The corresponding @value{GDBN} command is @samp{help target}.
35527 @subsubheading Example
35531 @subheading The @code{-target-list-current-targets} Command
35532 @findex -target-list-current-targets
35534 @subsubheading Synopsis
35537 -target-list-current-targets
35540 Describe the current target.
35542 @subsubheading @value{GDBN} Command
35544 The corresponding information is printed by @samp{info file} (among
35547 @subsubheading Example
35551 @subheading The @code{-target-list-parameters} Command
35552 @findex -target-list-parameters
35554 @subsubheading Synopsis
35557 -target-list-parameters
35563 @subsubheading @value{GDBN} Command
35567 @subsubheading Example
35570 @subheading The @code{-target-flash-erase} Command
35571 @findex -target-flash-erase
35573 @subsubheading Synopsis
35576 -target-flash-erase
35579 Erases all known flash memory regions on the target.
35581 The corresponding @value{GDBN} command is @samp{flash-erase}.
35583 The output is a list of flash regions that have been erased, with starting
35584 addresses and memory region sizes.
35588 -target-flash-erase
35589 ^done,erased-regions=@{address="0x0",size="0x40000"@}
35593 @subheading The @code{-target-select} Command
35594 @findex -target-select
35596 @subsubheading Synopsis
35599 -target-select @var{type} @var{parameters @dots{}}
35602 Connect @value{GDBN} to the remote target. This command takes two args:
35606 The type of target, for instance @samp{remote}, etc.
35607 @item @var{parameters}
35608 Device names, host names and the like. @xref{Target Commands, ,
35609 Commands for Managing Targets}, for more details.
35612 The output is a connection notification, followed by the address at
35613 which the target program is, in the following form:
35616 ^connected,addr="@var{address}",func="@var{function name}",
35617 args=[@var{arg list}]
35620 @subsubheading @value{GDBN} Command
35622 The corresponding @value{GDBN} command is @samp{target}.
35624 @subsubheading Example
35628 -target-select remote /dev/ttya
35629 ^connected,addr="0xfe00a300",func="??",args=[]
35633 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35634 @node GDB/MI File Transfer Commands
35635 @section @sc{gdb/mi} File Transfer Commands
35638 @subheading The @code{-target-file-put} Command
35639 @findex -target-file-put
35641 @subsubheading Synopsis
35644 -target-file-put @var{hostfile} @var{targetfile}
35647 Copy file @var{hostfile} from the host system (the machine running
35648 @value{GDBN}) to @var{targetfile} on the target system.
35650 @subsubheading @value{GDBN} Command
35652 The corresponding @value{GDBN} command is @samp{remote put}.
35654 @subsubheading Example
35658 -target-file-put localfile remotefile
35664 @subheading The @code{-target-file-get} Command
35665 @findex -target-file-get
35667 @subsubheading Synopsis
35670 -target-file-get @var{targetfile} @var{hostfile}
35673 Copy file @var{targetfile} from the target system to @var{hostfile}
35674 on the host system.
35676 @subsubheading @value{GDBN} Command
35678 The corresponding @value{GDBN} command is @samp{remote get}.
35680 @subsubheading Example
35684 -target-file-get remotefile localfile
35690 @subheading The @code{-target-file-delete} Command
35691 @findex -target-file-delete
35693 @subsubheading Synopsis
35696 -target-file-delete @var{targetfile}
35699 Delete @var{targetfile} from the target system.
35701 @subsubheading @value{GDBN} Command
35703 The corresponding @value{GDBN} command is @samp{remote delete}.
35705 @subsubheading Example
35709 -target-file-delete remotefile
35715 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35716 @node GDB/MI Ada Exceptions Commands
35717 @section Ada Exceptions @sc{gdb/mi} Commands
35719 @subheading The @code{-info-ada-exceptions} Command
35720 @findex -info-ada-exceptions
35722 @subsubheading Synopsis
35725 -info-ada-exceptions [ @var{regexp}]
35728 List all Ada exceptions defined within the program being debugged.
35729 With a regular expression @var{regexp}, only those exceptions whose
35730 names match @var{regexp} are listed.
35732 @subsubheading @value{GDBN} Command
35734 The corresponding @value{GDBN} command is @samp{info exceptions}.
35736 @subsubheading Result
35738 The result is a table of Ada exceptions. The following columns are
35739 defined for each exception:
35743 The name of the exception.
35746 The address of the exception.
35750 @subsubheading Example
35753 -info-ada-exceptions aint
35754 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
35755 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
35756 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
35757 body=[@{name="constraint_error",address="0x0000000000613da0"@},
35758 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
35761 @subheading Catching Ada Exceptions
35763 The commands describing how to ask @value{GDBN} to stop when a program
35764 raises an exception are described at @ref{Ada Exception GDB/MI
35765 Catchpoint Commands}.
35768 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35769 @node GDB/MI Support Commands
35770 @section @sc{gdb/mi} Support Commands
35772 Since new commands and features get regularly added to @sc{gdb/mi},
35773 some commands are available to help front-ends query the debugger
35774 about support for these capabilities. Similarly, it is also possible
35775 to query @value{GDBN} about target support of certain features.
35777 @subheading The @code{-info-gdb-mi-command} Command
35778 @cindex @code{-info-gdb-mi-command}
35779 @findex -info-gdb-mi-command
35781 @subsubheading Synopsis
35784 -info-gdb-mi-command @var{cmd_name}
35787 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
35789 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
35790 is technically not part of the command name (@pxref{GDB/MI Input
35791 Syntax}), and thus should be omitted in @var{cmd_name}. However,
35792 for ease of use, this command also accepts the form with the leading
35795 @subsubheading @value{GDBN} Command
35797 There is no corresponding @value{GDBN} command.
35799 @subsubheading Result
35801 The result is a tuple. There is currently only one field:
35805 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
35806 @code{"false"} otherwise.
35810 @subsubheading Example
35812 Here is an example where the @sc{gdb/mi} command does not exist:
35815 -info-gdb-mi-command unsupported-command
35816 ^done,command=@{exists="false"@}
35820 And here is an example where the @sc{gdb/mi} command is known
35824 -info-gdb-mi-command symbol-list-lines
35825 ^done,command=@{exists="true"@}
35828 @subheading The @code{-list-features} Command
35829 @findex -list-features
35830 @cindex supported @sc{gdb/mi} features, list
35832 Returns a list of particular features of the MI protocol that
35833 this version of gdb implements. A feature can be a command,
35834 or a new field in an output of some command, or even an
35835 important bugfix. While a frontend can sometimes detect presence
35836 of a feature at runtime, it is easier to perform detection at debugger
35839 The command returns a list of strings, with each string naming an
35840 available feature. Each returned string is just a name, it does not
35841 have any internal structure. The list of possible feature names
35847 (gdb) -list-features
35848 ^done,result=["feature1","feature2"]
35851 The current list of features is:
35854 @item frozen-varobjs
35855 Indicates support for the @code{-var-set-frozen} command, as well
35856 as possible presence of the @code{frozen} field in the output
35857 of @code{-varobj-create}.
35858 @item pending-breakpoints
35859 Indicates support for the @option{-f} option to the @code{-break-insert}
35862 Indicates Python scripting support, Python-based
35863 pretty-printing commands, and possible presence of the
35864 @samp{display_hint} field in the output of @code{-var-list-children}
35866 Indicates support for the @code{-thread-info} command.
35867 @item data-read-memory-bytes
35868 Indicates support for the @code{-data-read-memory-bytes} and the
35869 @code{-data-write-memory-bytes} commands.
35870 @item breakpoint-notifications
35871 Indicates that changes to breakpoints and breakpoints created via the
35872 CLI will be announced via async records.
35873 @item ada-task-info
35874 Indicates support for the @code{-ada-task-info} command.
35875 @item language-option
35876 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
35877 option (@pxref{Context management}).
35878 @item info-gdb-mi-command
35879 Indicates support for the @code{-info-gdb-mi-command} command.
35880 @item undefined-command-error-code
35881 Indicates support for the "undefined-command" error code in error result
35882 records, produced when trying to execute an undefined @sc{gdb/mi} command
35883 (@pxref{GDB/MI Result Records}).
35884 @item exec-run-start-option
35885 Indicates that the @code{-exec-run} command supports the @option{--start}
35886 option (@pxref{GDB/MI Program Execution}).
35887 @item data-disassemble-a-option
35888 Indicates that the @code{-data-disassemble} command supports the @option{-a}
35889 option (@pxref{GDB/MI Data Manipulation}).
35892 @subheading The @code{-list-target-features} Command
35893 @findex -list-target-features
35895 Returns a list of particular features that are supported by the
35896 target. Those features affect the permitted MI commands, but
35897 unlike the features reported by the @code{-list-features} command, the
35898 features depend on which target GDB is using at the moment. Whenever
35899 a target can change, due to commands such as @code{-target-select},
35900 @code{-target-attach} or @code{-exec-run}, the list of target features
35901 may change, and the frontend should obtain it again.
35905 (gdb) -list-target-features
35906 ^done,result=["async"]
35909 The current list of features is:
35913 Indicates that the target is capable of asynchronous command
35914 execution, which means that @value{GDBN} will accept further commands
35915 while the target is running.
35918 Indicates that the target is capable of reverse execution.
35919 @xref{Reverse Execution}, for more information.
35923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35924 @node GDB/MI Miscellaneous Commands
35925 @section Miscellaneous @sc{gdb/mi} Commands
35927 @c @subheading -gdb-complete
35929 @subheading The @code{-gdb-exit} Command
35932 @subsubheading Synopsis
35938 Exit @value{GDBN} immediately.
35940 @subsubheading @value{GDBN} Command
35942 Approximately corresponds to @samp{quit}.
35944 @subsubheading Example
35954 @subheading The @code{-exec-abort} Command
35955 @findex -exec-abort
35957 @subsubheading Synopsis
35963 Kill the inferior running program.
35965 @subsubheading @value{GDBN} Command
35967 The corresponding @value{GDBN} command is @samp{kill}.
35969 @subsubheading Example
35974 @subheading The @code{-gdb-set} Command
35977 @subsubheading Synopsis
35983 Set an internal @value{GDBN} variable.
35984 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
35986 @subsubheading @value{GDBN} Command
35988 The corresponding @value{GDBN} command is @samp{set}.
35990 @subsubheading Example
36000 @subheading The @code{-gdb-show} Command
36003 @subsubheading Synopsis
36009 Show the current value of a @value{GDBN} variable.
36011 @subsubheading @value{GDBN} Command
36013 The corresponding @value{GDBN} command is @samp{show}.
36015 @subsubheading Example
36024 @c @subheading -gdb-source
36027 @subheading The @code{-gdb-version} Command
36028 @findex -gdb-version
36030 @subsubheading Synopsis
36036 Show version information for @value{GDBN}. Used mostly in testing.
36038 @subsubheading @value{GDBN} Command
36040 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
36041 default shows this information when you start an interactive session.
36043 @subsubheading Example
36045 @c This example modifies the actual output from GDB to avoid overfull
36051 ~Copyright 2000 Free Software Foundation, Inc.
36052 ~GDB is free software, covered by the GNU General Public License, and
36053 ~you are welcome to change it and/or distribute copies of it under
36054 ~ certain conditions.
36055 ~Type "show copying" to see the conditions.
36056 ~There is absolutely no warranty for GDB. Type "show warranty" for
36058 ~This GDB was configured as
36059 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
36064 @subheading The @code{-list-thread-groups} Command
36065 @findex -list-thread-groups
36067 @subheading Synopsis
36070 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
36073 Lists thread groups (@pxref{Thread groups}). When a single thread
36074 group is passed as the argument, lists the children of that group.
36075 When several thread group are passed, lists information about those
36076 thread groups. Without any parameters, lists information about all
36077 top-level thread groups.
36079 Normally, thread groups that are being debugged are reported.
36080 With the @samp{--available} option, @value{GDBN} reports thread groups
36081 available on the target.
36083 The output of this command may have either a @samp{threads} result or
36084 a @samp{groups} result. The @samp{thread} result has a list of tuples
36085 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
36086 Information}). The @samp{groups} result has a list of tuples as value,
36087 each tuple describing a thread group. If top-level groups are
36088 requested (that is, no parameter is passed), or when several groups
36089 are passed, the output always has a @samp{groups} result. The format
36090 of the @samp{group} result is described below.
36092 To reduce the number of roundtrips it's possible to list thread groups
36093 together with their children, by passing the @samp{--recurse} option
36094 and the recursion depth. Presently, only recursion depth of 1 is
36095 permitted. If this option is present, then every reported thread group
36096 will also include its children, either as @samp{group} or
36097 @samp{threads} field.
36099 In general, any combination of option and parameters is permitted, with
36100 the following caveats:
36104 When a single thread group is passed, the output will typically
36105 be the @samp{threads} result. Because threads may not contain
36106 anything, the @samp{recurse} option will be ignored.
36109 When the @samp{--available} option is passed, limited information may
36110 be available. In particular, the list of threads of a process might
36111 be inaccessible. Further, specifying specific thread groups might
36112 not give any performance advantage over listing all thread groups.
36113 The frontend should assume that @samp{-list-thread-groups --available}
36114 is always an expensive operation and cache the results.
36118 The @samp{groups} result is a list of tuples, where each tuple may
36119 have the following fields:
36123 Identifier of the thread group. This field is always present.
36124 The identifier is an opaque string; frontends should not try to
36125 convert it to an integer, even though it might look like one.
36128 The type of the thread group. At present, only @samp{process} is a
36132 The target-specific process identifier. This field is only present
36133 for thread groups of type @samp{process} and only if the process exists.
36136 The exit code of this group's last exited thread, formatted in octal.
36137 This field is only present for thread groups of type @samp{process} and
36138 only if the process is not running.
36141 The number of children this thread group has. This field may be
36142 absent for an available thread group.
36145 This field has a list of tuples as value, each tuple describing a
36146 thread. It may be present if the @samp{--recurse} option is
36147 specified, and it's actually possible to obtain the threads.
36150 This field is a list of integers, each identifying a core that one
36151 thread of the group is running on. This field may be absent if
36152 such information is not available.
36155 The name of the executable file that corresponds to this thread group.
36156 The field is only present for thread groups of type @samp{process},
36157 and only if there is a corresponding executable file.
36161 @subheading Example
36165 -list-thread-groups
36166 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
36167 -list-thread-groups 17
36168 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
36169 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
36170 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
36171 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
36172 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
36173 -list-thread-groups --available
36174 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
36175 -list-thread-groups --available --recurse 1
36176 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
36177 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
36178 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
36179 -list-thread-groups --available --recurse 1 17 18
36180 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
36181 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
36182 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
36185 @subheading The @code{-info-os} Command
36188 @subsubheading Synopsis
36191 -info-os [ @var{type} ]
36194 If no argument is supplied, the command returns a table of available
36195 operating-system-specific information types. If one of these types is
36196 supplied as an argument @var{type}, then the command returns a table
36197 of data of that type.
36199 The types of information available depend on the target operating
36202 @subsubheading @value{GDBN} Command
36204 The corresponding @value{GDBN} command is @samp{info os}.
36206 @subsubheading Example
36208 When run on a @sc{gnu}/Linux system, the output will look something
36214 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
36215 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
36216 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
36217 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
36218 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
36220 item=@{col0="files",col1="Listing of all file descriptors",
36221 col2="File descriptors"@},
36222 item=@{col0="modules",col1="Listing of all loaded kernel modules",
36223 col2="Kernel modules"@},
36224 item=@{col0="msg",col1="Listing of all message queues",
36225 col2="Message queues"@},
36226 item=@{col0="processes",col1="Listing of all processes",
36227 col2="Processes"@},
36228 item=@{col0="procgroups",col1="Listing of all process groups",
36229 col2="Process groups"@},
36230 item=@{col0="semaphores",col1="Listing of all semaphores",
36231 col2="Semaphores"@},
36232 item=@{col0="shm",col1="Listing of all shared-memory regions",
36233 col2="Shared-memory regions"@},
36234 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
36236 item=@{col0="threads",col1="Listing of all threads",
36240 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
36241 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
36242 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
36243 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
36244 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
36245 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
36246 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
36247 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
36249 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
36250 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
36254 (Note that the MI output here includes a @code{"Title"} column that
36255 does not appear in command-line @code{info os}; this column is useful
36256 for MI clients that want to enumerate the types of data, such as in a
36257 popup menu, but is needless clutter on the command line, and
36258 @code{info os} omits it.)
36260 @subheading The @code{-add-inferior} Command
36261 @findex -add-inferior
36263 @subheading Synopsis
36269 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
36270 inferior is not associated with any executable. Such association may
36271 be established with the @samp{-file-exec-and-symbols} command
36272 (@pxref{GDB/MI File Commands}). The command response has a single
36273 field, @samp{inferior}, whose value is the identifier of the
36274 thread group corresponding to the new inferior.
36276 @subheading Example
36281 ^done,inferior="i3"
36284 @subheading The @code{-interpreter-exec} Command
36285 @findex -interpreter-exec
36287 @subheading Synopsis
36290 -interpreter-exec @var{interpreter} @var{command}
36292 @anchor{-interpreter-exec}
36294 Execute the specified @var{command} in the given @var{interpreter}.
36296 @subheading @value{GDBN} Command
36298 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
36300 @subheading Example
36304 -interpreter-exec console "break main"
36305 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
36306 &"During symbol reading, bad structure-type format.\n"
36307 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
36312 @subheading The @code{-inferior-tty-set} Command
36313 @findex -inferior-tty-set
36315 @subheading Synopsis
36318 -inferior-tty-set /dev/pts/1
36321 Set terminal for future runs of the program being debugged.
36323 @subheading @value{GDBN} Command
36325 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
36327 @subheading Example
36331 -inferior-tty-set /dev/pts/1
36336 @subheading The @code{-inferior-tty-show} Command
36337 @findex -inferior-tty-show
36339 @subheading Synopsis
36345 Show terminal for future runs of program being debugged.
36347 @subheading @value{GDBN} Command
36349 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
36351 @subheading Example
36355 -inferior-tty-set /dev/pts/1
36359 ^done,inferior_tty_terminal="/dev/pts/1"
36363 @subheading The @code{-enable-timings} Command
36364 @findex -enable-timings
36366 @subheading Synopsis
36369 -enable-timings [yes | no]
36372 Toggle the printing of the wallclock, user and system times for an MI
36373 command as a field in its output. This command is to help frontend
36374 developers optimize the performance of their code. No argument is
36375 equivalent to @samp{yes}.
36377 @subheading @value{GDBN} Command
36381 @subheading Example
36389 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
36390 addr="0x080484ed",func="main",file="myprog.c",
36391 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
36393 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
36401 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
36402 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
36403 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
36404 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
36408 @subheading The @code{-complete} Command
36411 @subheading Synopsis
36414 -complete @var{command}
36417 Show a list of completions for partially typed CLI @var{command}.
36419 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
36420 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
36421 because @value{GDBN} is used remotely via a SSH connection.
36425 The result consists of two or three fields:
36429 This field contains the completed @var{command}. If @var{command}
36430 has no known completions, this field is omitted.
36433 This field contains a (possibly empty) array of matches. It is always present.
36435 @item max_completions_reached
36436 This field contains @code{1} if number of known completions is above
36437 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
36438 @code{0}. It is always present.
36442 @subheading @value{GDBN} Command
36444 The corresponding @value{GDBN} command is @samp{complete}.
36446 @subheading Example
36451 ^done,completion="break",
36452 matches=["break","break-range"],
36453 max_completions_reached="0"
36456 ^done,completion="b ma",
36457 matches=["b madvise","b main"],max_completions_reached="0"
36459 -complete "b push_b"
36460 ^done,completion="b push_back(",
36462 "b A::push_back(void*)",
36463 "b std::string::push_back(char)",
36464 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
36465 max_completions_reached="0"
36467 -complete "nonexist"
36468 ^done,matches=[],max_completions_reached="0"
36474 @chapter @value{GDBN} Annotations
36476 This chapter describes annotations in @value{GDBN}. Annotations were
36477 designed to interface @value{GDBN} to graphical user interfaces or other
36478 similar programs which want to interact with @value{GDBN} at a
36479 relatively high level.
36481 The annotation mechanism has largely been superseded by @sc{gdb/mi}
36485 This is Edition @value{EDITION}, @value{DATE}.
36489 * Annotations Overview:: What annotations are; the general syntax.
36490 * Server Prefix:: Issuing a command without affecting user state.
36491 * Prompting:: Annotations marking @value{GDBN}'s need for input.
36492 * Errors:: Annotations for error messages.
36493 * Invalidation:: Some annotations describe things now invalid.
36494 * Annotations for Running::
36495 Whether the program is running, how it stopped, etc.
36496 * Source Annotations:: Annotations describing source code.
36499 @node Annotations Overview
36500 @section What is an Annotation?
36501 @cindex annotations
36503 Annotations start with a newline character, two @samp{control-z}
36504 characters, and the name of the annotation. If there is no additional
36505 information associated with this annotation, the name of the annotation
36506 is followed immediately by a newline. If there is additional
36507 information, the name of the annotation is followed by a space, the
36508 additional information, and a newline. The additional information
36509 cannot contain newline characters.
36511 Any output not beginning with a newline and two @samp{control-z}
36512 characters denotes literal output from @value{GDBN}. Currently there is
36513 no need for @value{GDBN} to output a newline followed by two
36514 @samp{control-z} characters, but if there was such a need, the
36515 annotations could be extended with an @samp{escape} annotation which
36516 means those three characters as output.
36518 The annotation @var{level}, which is specified using the
36519 @option{--annotate} command line option (@pxref{Mode Options}), controls
36520 how much information @value{GDBN} prints together with its prompt,
36521 values of expressions, source lines, and other types of output. Level 0
36522 is for no annotations, level 1 is for use when @value{GDBN} is run as a
36523 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
36524 for programs that control @value{GDBN}, and level 2 annotations have
36525 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
36526 Interface, annotate, GDB's Obsolete Annotations}).
36529 @kindex set annotate
36530 @item set annotate @var{level}
36531 The @value{GDBN} command @code{set annotate} sets the level of
36532 annotations to the specified @var{level}.
36534 @item show annotate
36535 @kindex show annotate
36536 Show the current annotation level.
36539 This chapter describes level 3 annotations.
36541 A simple example of starting up @value{GDBN} with annotations is:
36544 $ @kbd{gdb --annotate=3}
36546 Copyright 2003 Free Software Foundation, Inc.
36547 GDB is free software, covered by the GNU General Public License,
36548 and you are welcome to change it and/or distribute copies of it
36549 under certain conditions.
36550 Type "show copying" to see the conditions.
36551 There is absolutely no warranty for GDB. Type "show warranty"
36553 This GDB was configured as "i386-pc-linux-gnu"
36564 Here @samp{quit} is input to @value{GDBN}; the rest is output from
36565 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
36566 denotes a @samp{control-z} character) are annotations; the rest is
36567 output from @value{GDBN}.
36569 @node Server Prefix
36570 @section The Server Prefix
36571 @cindex server prefix
36573 If you prefix a command with @samp{server } then it will not affect
36574 the command history, nor will it affect @value{GDBN}'s notion of which
36575 command to repeat if @key{RET} is pressed on a line by itself. This
36576 means that commands can be run behind a user's back by a front-end in
36577 a transparent manner.
36579 The @code{server } prefix does not affect the recording of values into
36580 the value history; to print a value without recording it into the
36581 value history, use the @code{output} command instead of the
36582 @code{print} command.
36584 Using this prefix also disables confirmation requests
36585 (@pxref{confirmation requests}).
36588 @section Annotation for @value{GDBN} Input
36590 @cindex annotations for prompts
36591 When @value{GDBN} prompts for input, it annotates this fact so it is possible
36592 to know when to send output, when the output from a given command is
36595 Different kinds of input each have a different @dfn{input type}. Each
36596 input type has three annotations: a @code{pre-} annotation, which
36597 denotes the beginning of any prompt which is being output, a plain
36598 annotation, which denotes the end of the prompt, and then a @code{post-}
36599 annotation which denotes the end of any echo which may (or may not) be
36600 associated with the input. For example, the @code{prompt} input type
36601 features the following annotations:
36609 The input types are
36612 @findex pre-prompt annotation
36613 @findex prompt annotation
36614 @findex post-prompt annotation
36616 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
36618 @findex pre-commands annotation
36619 @findex commands annotation
36620 @findex post-commands annotation
36622 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
36623 command. The annotations are repeated for each command which is input.
36625 @findex pre-overload-choice annotation
36626 @findex overload-choice annotation
36627 @findex post-overload-choice annotation
36628 @item overload-choice
36629 When @value{GDBN} wants the user to select between various overloaded functions.
36631 @findex pre-query annotation
36632 @findex query annotation
36633 @findex post-query annotation
36635 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
36637 @findex pre-prompt-for-continue annotation
36638 @findex prompt-for-continue annotation
36639 @findex post-prompt-for-continue annotation
36640 @item prompt-for-continue
36641 When @value{GDBN} is asking the user to press return to continue. Note: Don't
36642 expect this to work well; instead use @code{set height 0} to disable
36643 prompting. This is because the counting of lines is buggy in the
36644 presence of annotations.
36649 @cindex annotations for errors, warnings and interrupts
36651 @findex quit annotation
36656 This annotation occurs right before @value{GDBN} responds to an interrupt.
36658 @findex error annotation
36663 This annotation occurs right before @value{GDBN} responds to an error.
36665 Quit and error annotations indicate that any annotations which @value{GDBN} was
36666 in the middle of may end abruptly. For example, if a
36667 @code{value-history-begin} annotation is followed by a @code{error}, one
36668 cannot expect to receive the matching @code{value-history-end}. One
36669 cannot expect not to receive it either, however; an error annotation
36670 does not necessarily mean that @value{GDBN} is immediately returning all the way
36673 @findex error-begin annotation
36674 A quit or error annotation may be preceded by
36680 Any output between that and the quit or error annotation is the error
36683 Warning messages are not yet annotated.
36684 @c If we want to change that, need to fix warning(), type_error(),
36685 @c range_error(), and possibly other places.
36688 @section Invalidation Notices
36690 @cindex annotations for invalidation messages
36691 The following annotations say that certain pieces of state may have
36695 @findex frames-invalid annotation
36696 @item ^Z^Zframes-invalid
36698 The frames (for example, output from the @code{backtrace} command) may
36701 @findex breakpoints-invalid annotation
36702 @item ^Z^Zbreakpoints-invalid
36704 The breakpoints may have changed. For example, the user just added or
36705 deleted a breakpoint.
36708 @node Annotations for Running
36709 @section Running the Program
36710 @cindex annotations for running programs
36712 @findex starting annotation
36713 @findex stopping annotation
36714 When the program starts executing due to a @value{GDBN} command such as
36715 @code{step} or @code{continue},
36721 is output. When the program stops,
36727 is output. Before the @code{stopped} annotation, a variety of
36728 annotations describe how the program stopped.
36731 @findex exited annotation
36732 @item ^Z^Zexited @var{exit-status}
36733 The program exited, and @var{exit-status} is the exit status (zero for
36734 successful exit, otherwise nonzero).
36736 @findex signalled annotation
36737 @findex signal-name annotation
36738 @findex signal-name-end annotation
36739 @findex signal-string annotation
36740 @findex signal-string-end annotation
36741 @item ^Z^Zsignalled
36742 The program exited with a signal. After the @code{^Z^Zsignalled}, the
36743 annotation continues:
36749 ^Z^Zsignal-name-end
36753 ^Z^Zsignal-string-end
36758 where @var{name} is the name of the signal, such as @code{SIGILL} or
36759 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
36760 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
36761 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
36762 user's benefit and have no particular format.
36764 @findex signal annotation
36766 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
36767 just saying that the program received the signal, not that it was
36768 terminated with it.
36770 @findex breakpoint annotation
36771 @item ^Z^Zbreakpoint @var{number}
36772 The program hit breakpoint number @var{number}.
36774 @findex watchpoint annotation
36775 @item ^Z^Zwatchpoint @var{number}
36776 The program hit watchpoint number @var{number}.
36779 @node Source Annotations
36780 @section Displaying Source
36781 @cindex annotations for source display
36783 @findex source annotation
36784 The following annotation is used instead of displaying source code:
36787 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
36790 where @var{filename} is an absolute file name indicating which source
36791 file, @var{line} is the line number within that file (where 1 is the
36792 first line in the file), @var{character} is the character position
36793 within the file (where 0 is the first character in the file) (for most
36794 debug formats this will necessarily point to the beginning of a line),
36795 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
36796 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
36797 @var{addr} is the address in the target program associated with the
36798 source which is being displayed. The @var{addr} is in the form @samp{0x}
36799 followed by one or more lowercase hex digits (note that this does not
36800 depend on the language).
36802 @node JIT Interface
36803 @chapter JIT Compilation Interface
36804 @cindex just-in-time compilation
36805 @cindex JIT compilation interface
36807 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
36808 interface. A JIT compiler is a program or library that generates native
36809 executable code at runtime and executes it, usually in order to achieve good
36810 performance while maintaining platform independence.
36812 Programs that use JIT compilation are normally difficult to debug because
36813 portions of their code are generated at runtime, instead of being loaded from
36814 object files, which is where @value{GDBN} normally finds the program's symbols
36815 and debug information. In order to debug programs that use JIT compilation,
36816 @value{GDBN} has an interface that allows the program to register in-memory
36817 symbol files with @value{GDBN} at runtime.
36819 If you are using @value{GDBN} to debug a program that uses this interface, then
36820 it should work transparently so long as you have not stripped the binary. If
36821 you are developing a JIT compiler, then the interface is documented in the rest
36822 of this chapter. At this time, the only known client of this interface is the
36825 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
36826 JIT compiler communicates with @value{GDBN} by writing data into a global
36827 variable and calling a function at a well-known symbol. When @value{GDBN}
36828 attaches, it reads a linked list of symbol files from the global variable to
36829 find existing code, and puts a breakpoint in the function so that it can find
36830 out about additional code.
36833 * Declarations:: Relevant C struct declarations
36834 * Registering Code:: Steps to register code
36835 * Unregistering Code:: Steps to unregister code
36836 * Custom Debug Info:: Emit debug information in a custom format
36840 @section JIT Declarations
36842 These are the relevant struct declarations that a C program should include to
36843 implement the interface:
36853 struct jit_code_entry
36855 struct jit_code_entry *next_entry;
36856 struct jit_code_entry *prev_entry;
36857 const char *symfile_addr;
36858 uint64_t symfile_size;
36861 struct jit_descriptor
36864 /* This type should be jit_actions_t, but we use uint32_t
36865 to be explicit about the bitwidth. */
36866 uint32_t action_flag;
36867 struct jit_code_entry *relevant_entry;
36868 struct jit_code_entry *first_entry;
36871 /* GDB puts a breakpoint in this function. */
36872 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
36874 /* Make sure to specify the version statically, because the
36875 debugger may check the version before we can set it. */
36876 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
36879 If the JIT is multi-threaded, then it is important that the JIT synchronize any
36880 modifications to this global data properly, which can easily be done by putting
36881 a global mutex around modifications to these structures.
36883 @node Registering Code
36884 @section Registering Code
36886 To register code with @value{GDBN}, the JIT should follow this protocol:
36890 Generate an object file in memory with symbols and other desired debug
36891 information. The file must include the virtual addresses of the sections.
36894 Create a code entry for the file, which gives the start and size of the symbol
36898 Add it to the linked list in the JIT descriptor.
36901 Point the relevant_entry field of the descriptor at the entry.
36904 Set @code{action_flag} to @code{JIT_REGISTER} and call
36905 @code{__jit_debug_register_code}.
36908 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
36909 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
36910 new code. However, the linked list must still be maintained in order to allow
36911 @value{GDBN} to attach to a running process and still find the symbol files.
36913 @node Unregistering Code
36914 @section Unregistering Code
36916 If code is freed, then the JIT should use the following protocol:
36920 Remove the code entry corresponding to the code from the linked list.
36923 Point the @code{relevant_entry} field of the descriptor at the code entry.
36926 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
36927 @code{__jit_debug_register_code}.
36930 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
36931 and the JIT will leak the memory used for the associated symbol files.
36933 @node Custom Debug Info
36934 @section Custom Debug Info
36935 @cindex custom JIT debug info
36936 @cindex JIT debug info reader
36938 Generating debug information in platform-native file formats (like ELF
36939 or COFF) may be an overkill for JIT compilers; especially if all the
36940 debug info is used for is displaying a meaningful backtrace. The
36941 issue can be resolved by having the JIT writers decide on a debug info
36942 format and also provide a reader that parses the debug info generated
36943 by the JIT compiler. This section gives a brief overview on writing
36944 such a parser. More specific details can be found in the source file
36945 @file{gdb/jit-reader.in}, which is also installed as a header at
36946 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
36948 The reader is implemented as a shared object (so this functionality is
36949 not available on platforms which don't allow loading shared objects at
36950 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
36951 @code{jit-reader-unload} are provided, to be used to load and unload
36952 the readers from a preconfigured directory. Once loaded, the shared
36953 object is used the parse the debug information emitted by the JIT
36957 * Using JIT Debug Info Readers:: How to use supplied readers correctly
36958 * Writing JIT Debug Info Readers:: Creating a debug-info reader
36961 @node Using JIT Debug Info Readers
36962 @subsection Using JIT Debug Info Readers
36963 @kindex jit-reader-load
36964 @kindex jit-reader-unload
36966 Readers can be loaded and unloaded using the @code{jit-reader-load}
36967 and @code{jit-reader-unload} commands.
36970 @item jit-reader-load @var{reader}
36971 Load the JIT reader named @var{reader}, which is a shared
36972 object specified as either an absolute or a relative file name. In
36973 the latter case, @value{GDBN} will try to load the reader from a
36974 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
36975 system (here @var{libdir} is the system library directory, often
36976 @file{/usr/local/lib}).
36978 Only one reader can be active at a time; trying to load a second
36979 reader when one is already loaded will result in @value{GDBN}
36980 reporting an error. A new JIT reader can be loaded by first unloading
36981 the current one using @code{jit-reader-unload} and then invoking
36982 @code{jit-reader-load}.
36984 @item jit-reader-unload
36985 Unload the currently loaded JIT reader.
36989 @node Writing JIT Debug Info Readers
36990 @subsection Writing JIT Debug Info Readers
36991 @cindex writing JIT debug info readers
36993 As mentioned, a reader is essentially a shared object conforming to a
36994 certain ABI. This ABI is described in @file{jit-reader.h}.
36996 @file{jit-reader.h} defines the structures, macros and functions
36997 required to write a reader. It is installed (along with
36998 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36999 the system include directory.
37001 Readers need to be released under a GPL compatible license. A reader
37002 can be declared as released under such a license by placing the macro
37003 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
37005 The entry point for readers is the symbol @code{gdb_init_reader},
37006 which is expected to be a function with the prototype
37008 @findex gdb_init_reader
37010 extern struct gdb_reader_funcs *gdb_init_reader (void);
37013 @cindex @code{struct gdb_reader_funcs}
37015 @code{struct gdb_reader_funcs} contains a set of pointers to callback
37016 functions. These functions are executed to read the debug info
37017 generated by the JIT compiler (@code{read}), to unwind stack frames
37018 (@code{unwind}) and to create canonical frame IDs
37019 (@code{get_frame_id}). It also has a callback that is called when the
37020 reader is being unloaded (@code{destroy}). The struct looks like this
37023 struct gdb_reader_funcs
37025 /* Must be set to GDB_READER_INTERFACE_VERSION. */
37026 int reader_version;
37028 /* For use by the reader. */
37031 gdb_read_debug_info *read;
37032 gdb_unwind_frame *unwind;
37033 gdb_get_frame_id *get_frame_id;
37034 gdb_destroy_reader *destroy;
37038 @cindex @code{struct gdb_symbol_callbacks}
37039 @cindex @code{struct gdb_unwind_callbacks}
37041 The callbacks are provided with another set of callbacks by
37042 @value{GDBN} to do their job. For @code{read}, these callbacks are
37043 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
37044 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
37045 @code{struct gdb_symbol_callbacks} has callbacks to create new object
37046 files and new symbol tables inside those object files. @code{struct
37047 gdb_unwind_callbacks} has callbacks to read registers off the current
37048 frame and to write out the values of the registers in the previous
37049 frame. Both have a callback (@code{target_read}) to read bytes off the
37050 target's address space.
37052 @node In-Process Agent
37053 @chapter In-Process Agent
37054 @cindex debugging agent
37055 The traditional debugging model is conceptually low-speed, but works fine,
37056 because most bugs can be reproduced in debugging-mode execution. However,
37057 as multi-core or many-core processors are becoming mainstream, and
37058 multi-threaded programs become more and more popular, there should be more
37059 and more bugs that only manifest themselves at normal-mode execution, for
37060 example, thread races, because debugger's interference with the program's
37061 timing may conceal the bugs. On the other hand, in some applications,
37062 it is not feasible for the debugger to interrupt the program's execution
37063 long enough for the developer to learn anything helpful about its behavior.
37064 If the program's correctness depends on its real-time behavior, delays
37065 introduced by a debugger might cause the program to fail, even when the
37066 code itself is correct. It is useful to be able to observe the program's
37067 behavior without interrupting it.
37069 Therefore, traditional debugging model is too intrusive to reproduce
37070 some bugs. In order to reduce the interference with the program, we can
37071 reduce the number of operations performed by debugger. The
37072 @dfn{In-Process Agent}, a shared library, is running within the same
37073 process with inferior, and is able to perform some debugging operations
37074 itself. As a result, debugger is only involved when necessary, and
37075 performance of debugging can be improved accordingly. Note that
37076 interference with program can be reduced but can't be removed completely,
37077 because the in-process agent will still stop or slow down the program.
37079 The in-process agent can interpret and execute Agent Expressions
37080 (@pxref{Agent Expressions}) during performing debugging operations. The
37081 agent expressions can be used for different purposes, such as collecting
37082 data in tracepoints, and condition evaluation in breakpoints.
37084 @anchor{Control Agent}
37085 You can control whether the in-process agent is used as an aid for
37086 debugging with the following commands:
37089 @kindex set agent on
37091 Causes the in-process agent to perform some operations on behalf of the
37092 debugger. Just which operations requested by the user will be done
37093 by the in-process agent depends on the its capabilities. For example,
37094 if you request to evaluate breakpoint conditions in the in-process agent,
37095 and the in-process agent has such capability as well, then breakpoint
37096 conditions will be evaluated in the in-process agent.
37098 @kindex set agent off
37099 @item set agent off
37100 Disables execution of debugging operations by the in-process agent. All
37101 of the operations will be performed by @value{GDBN}.
37105 Display the current setting of execution of debugging operations by
37106 the in-process agent.
37110 * In-Process Agent Protocol::
37113 @node In-Process Agent Protocol
37114 @section In-Process Agent Protocol
37115 @cindex in-process agent protocol
37117 The in-process agent is able to communicate with both @value{GDBN} and
37118 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
37119 used for communications between @value{GDBN} or GDBserver and the IPA.
37120 In general, @value{GDBN} or GDBserver sends commands
37121 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
37122 in-process agent replies back with the return result of the command, or
37123 some other information. The data sent to in-process agent is composed
37124 of primitive data types, such as 4-byte or 8-byte type, and composite
37125 types, which are called objects (@pxref{IPA Protocol Objects}).
37128 * IPA Protocol Objects::
37129 * IPA Protocol Commands::
37132 @node IPA Protocol Objects
37133 @subsection IPA Protocol Objects
37134 @cindex ipa protocol objects
37136 The commands sent to and results received from agent may contain some
37137 complex data types called @dfn{objects}.
37139 The in-process agent is running on the same machine with @value{GDBN}
37140 or GDBserver, so it doesn't have to handle as much differences between
37141 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
37142 However, there are still some differences of two ends in two processes:
37146 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
37147 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
37149 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
37150 GDBserver is compiled with one, and in-process agent is compiled with
37154 Here are the IPA Protocol Objects:
37158 agent expression object. It represents an agent expression
37159 (@pxref{Agent Expressions}).
37160 @anchor{agent expression object}
37162 tracepoint action object. It represents a tracepoint action
37163 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
37164 memory, static trace data and to evaluate expression.
37165 @anchor{tracepoint action object}
37167 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
37168 @anchor{tracepoint object}
37172 The following table describes important attributes of each IPA protocol
37175 @multitable @columnfractions .30 .20 .50
37176 @headitem Name @tab Size @tab Description
37177 @item @emph{agent expression object} @tab @tab
37178 @item length @tab 4 @tab length of bytes code
37179 @item byte code @tab @var{length} @tab contents of byte code
37180 @item @emph{tracepoint action for collecting memory} @tab @tab
37181 @item 'M' @tab 1 @tab type of tracepoint action
37182 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
37183 address of the lowest byte to collect, otherwise @var{addr} is the offset
37184 of @var{basereg} for memory collecting.
37185 @item len @tab 8 @tab length of memory for collecting
37186 @item basereg @tab 4 @tab the register number containing the starting
37187 memory address for collecting.
37188 @item @emph{tracepoint action for collecting registers} @tab @tab
37189 @item 'R' @tab 1 @tab type of tracepoint action
37190 @item @emph{tracepoint action for collecting static trace data} @tab @tab
37191 @item 'L' @tab 1 @tab type of tracepoint action
37192 @item @emph{tracepoint action for expression evaluation} @tab @tab
37193 @item 'X' @tab 1 @tab type of tracepoint action
37194 @item agent expression @tab length of @tab @ref{agent expression object}
37195 @item @emph{tracepoint object} @tab @tab
37196 @item number @tab 4 @tab number of tracepoint
37197 @item address @tab 8 @tab address of tracepoint inserted on
37198 @item type @tab 4 @tab type of tracepoint
37199 @item enabled @tab 1 @tab enable or disable of tracepoint
37200 @item step_count @tab 8 @tab step
37201 @item pass_count @tab 8 @tab pass
37202 @item numactions @tab 4 @tab number of tracepoint actions
37203 @item hit count @tab 8 @tab hit count
37204 @item trace frame usage @tab 8 @tab trace frame usage
37205 @item compiled_cond @tab 8 @tab compiled condition
37206 @item orig_size @tab 8 @tab orig size
37207 @item condition @tab 4 if condition is NULL otherwise length of
37208 @ref{agent expression object}
37209 @tab zero if condition is NULL, otherwise is
37210 @ref{agent expression object}
37211 @item actions @tab variable
37212 @tab numactions number of @ref{tracepoint action object}
37215 @node IPA Protocol Commands
37216 @subsection IPA Protocol Commands
37217 @cindex ipa protocol commands
37219 The spaces in each command are delimiters to ease reading this commands
37220 specification. They don't exist in real commands.
37224 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
37225 Installs a new fast tracepoint described by @var{tracepoint_object}
37226 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
37227 head of @dfn{jumppad}, which is used to jump to data collection routine
37232 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
37233 @var{target_address} is address of tracepoint in the inferior.
37234 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
37235 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
37236 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
37237 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
37244 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
37245 is about to kill inferiors.
37253 @item probe_marker_at:@var{address}
37254 Asks in-process agent to probe the marker at @var{address}.
37261 @item unprobe_marker_at:@var{address}
37262 Asks in-process agent to unprobe the marker at @var{address}.
37266 @chapter Reporting Bugs in @value{GDBN}
37267 @cindex bugs in @value{GDBN}
37268 @cindex reporting bugs in @value{GDBN}
37270 Your bug reports play an essential role in making @value{GDBN} reliable.
37272 Reporting a bug may help you by bringing a solution to your problem, or it
37273 may not. But in any case the principal function of a bug report is to help
37274 the entire community by making the next version of @value{GDBN} work better. Bug
37275 reports are your contribution to the maintenance of @value{GDBN}.
37277 In order for a bug report to serve its purpose, you must include the
37278 information that enables us to fix the bug.
37281 * Bug Criteria:: Have you found a bug?
37282 * Bug Reporting:: How to report bugs
37286 @section Have You Found a Bug?
37287 @cindex bug criteria
37289 If you are not sure whether you have found a bug, here are some guidelines:
37292 @cindex fatal signal
37293 @cindex debugger crash
37294 @cindex crash of debugger
37296 If the debugger gets a fatal signal, for any input whatever, that is a
37297 @value{GDBN} bug. Reliable debuggers never crash.
37299 @cindex error on valid input
37301 If @value{GDBN} produces an error message for valid input, that is a
37302 bug. (Note that if you're cross debugging, the problem may also be
37303 somewhere in the connection to the target.)
37305 @cindex invalid input
37307 If @value{GDBN} does not produce an error message for invalid input,
37308 that is a bug. However, you should note that your idea of
37309 ``invalid input'' might be our idea of ``an extension'' or ``support
37310 for traditional practice''.
37313 If you are an experienced user of debugging tools, your suggestions
37314 for improvement of @value{GDBN} are welcome in any case.
37317 @node Bug Reporting
37318 @section How to Report Bugs
37319 @cindex bug reports
37320 @cindex @value{GDBN} bugs, reporting
37322 A number of companies and individuals offer support for @sc{gnu} products.
37323 If you obtained @value{GDBN} from a support organization, we recommend you
37324 contact that organization first.
37326 You can find contact information for many support companies and
37327 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
37329 @c should add a web page ref...
37332 @ifset BUGURL_DEFAULT
37333 In any event, we also recommend that you submit bug reports for
37334 @value{GDBN}. The preferred method is to submit them directly using
37335 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
37336 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
37339 @strong{Do not send bug reports to @samp{info-gdb}, or to
37340 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
37341 not want to receive bug reports. Those that do have arranged to receive
37344 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
37345 serves as a repeater. The mailing list and the newsgroup carry exactly
37346 the same messages. Often people think of posting bug reports to the
37347 newsgroup instead of mailing them. This appears to work, but it has one
37348 problem which can be crucial: a newsgroup posting often lacks a mail
37349 path back to the sender. Thus, if we need to ask for more information,
37350 we may be unable to reach you. For this reason, it is better to send
37351 bug reports to the mailing list.
37353 @ifclear BUGURL_DEFAULT
37354 In any event, we also recommend that you submit bug reports for
37355 @value{GDBN} to @value{BUGURL}.
37359 The fundamental principle of reporting bugs usefully is this:
37360 @strong{report all the facts}. If you are not sure whether to state a
37361 fact or leave it out, state it!
37363 Often people omit facts because they think they know what causes the
37364 problem and assume that some details do not matter. Thus, you might
37365 assume that the name of the variable you use in an example does not matter.
37366 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
37367 stray memory reference which happens to fetch from the location where that
37368 name is stored in memory; perhaps, if the name were different, the contents
37369 of that location would fool the debugger into doing the right thing despite
37370 the bug. Play it safe and give a specific, complete example. That is the
37371 easiest thing for you to do, and the most helpful.
37373 Keep in mind that the purpose of a bug report is to enable us to fix the
37374 bug. It may be that the bug has been reported previously, but neither
37375 you nor we can know that unless your bug report is complete and
37378 Sometimes people give a few sketchy facts and ask, ``Does this ring a
37379 bell?'' Those bug reports are useless, and we urge everyone to
37380 @emph{refuse to respond to them} except to chide the sender to report
37383 To enable us to fix the bug, you should include all these things:
37387 The version of @value{GDBN}. @value{GDBN} announces it if you start
37388 with no arguments; you can also print it at any time using @code{show
37391 Without this, we will not know whether there is any point in looking for
37392 the bug in the current version of @value{GDBN}.
37395 The type of machine you are using, and the operating system name and
37399 The details of the @value{GDBN} build-time configuration.
37400 @value{GDBN} shows these details if you invoke it with the
37401 @option{--configuration} command-line option, or if you type
37402 @code{show configuration} at @value{GDBN}'s prompt.
37405 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
37406 ``@value{GCC}--2.8.1''.
37409 What compiler (and its version) was used to compile the program you are
37410 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
37411 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
37412 to get this information; for other compilers, see the documentation for
37416 The command arguments you gave the compiler to compile your example and
37417 observe the bug. For example, did you use @samp{-O}? To guarantee
37418 you will not omit something important, list them all. A copy of the
37419 Makefile (or the output from make) is sufficient.
37421 If we were to try to guess the arguments, we would probably guess wrong
37422 and then we might not encounter the bug.
37425 A complete input script, and all necessary source files, that will
37429 A description of what behavior you observe that you believe is
37430 incorrect. For example, ``It gets a fatal signal.''
37432 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
37433 will certainly notice it. But if the bug is incorrect output, we might
37434 not notice unless it is glaringly wrong. You might as well not give us
37435 a chance to make a mistake.
37437 Even if the problem you experience is a fatal signal, you should still
37438 say so explicitly. Suppose something strange is going on, such as, your
37439 copy of @value{GDBN} is out of synch, or you have encountered a bug in
37440 the C library on your system. (This has happened!) Your copy might
37441 crash and ours would not. If you told us to expect a crash, then when
37442 ours fails to crash, we would know that the bug was not happening for
37443 us. If you had not told us to expect a crash, then we would not be able
37444 to draw any conclusion from our observations.
37447 @cindex recording a session script
37448 To collect all this information, you can use a session recording program
37449 such as @command{script}, which is available on many Unix systems.
37450 Just run your @value{GDBN} session inside @command{script} and then
37451 include the @file{typescript} file with your bug report.
37453 Another way to record a @value{GDBN} session is to run @value{GDBN}
37454 inside Emacs and then save the entire buffer to a file.
37457 If you wish to suggest changes to the @value{GDBN} source, send us context
37458 diffs. If you even discuss something in the @value{GDBN} source, refer to
37459 it by context, not by line number.
37461 The line numbers in our development sources will not match those in your
37462 sources. Your line numbers would convey no useful information to us.
37466 Here are some things that are not necessary:
37470 A description of the envelope of the bug.
37472 Often people who encounter a bug spend a lot of time investigating
37473 which changes to the input file will make the bug go away and which
37474 changes will not affect it.
37476 This is often time consuming and not very useful, because the way we
37477 will find the bug is by running a single example under the debugger
37478 with breakpoints, not by pure deduction from a series of examples.
37479 We recommend that you save your time for something else.
37481 Of course, if you can find a simpler example to report @emph{instead}
37482 of the original one, that is a convenience for us. Errors in the
37483 output will be easier to spot, running under the debugger will take
37484 less time, and so on.
37486 However, simplification is not vital; if you do not want to do this,
37487 report the bug anyway and send us the entire test case you used.
37490 A patch for the bug.
37492 A patch for the bug does help us if it is a good one. But do not omit
37493 the necessary information, such as the test case, on the assumption that
37494 a patch is all we need. We might see problems with your patch and decide
37495 to fix the problem another way, or we might not understand it at all.
37497 Sometimes with a program as complicated as @value{GDBN} it is very hard to
37498 construct an example that will make the program follow a certain path
37499 through the code. If you do not send us the example, we will not be able
37500 to construct one, so we will not be able to verify that the bug is fixed.
37502 And if we cannot understand what bug you are trying to fix, or why your
37503 patch should be an improvement, we will not install it. A test case will
37504 help us to understand.
37507 A guess about what the bug is or what it depends on.
37509 Such guesses are usually wrong. Even we cannot guess right about such
37510 things without first using the debugger to find the facts.
37513 @c The readline documentation is distributed with the readline code
37514 @c and consists of the two following files:
37517 @c Use -I with makeinfo to point to the appropriate directory,
37518 @c environment var TEXINPUTS with TeX.
37519 @ifclear SYSTEM_READLINE
37520 @include rluser.texi
37521 @include hsuser.texi
37525 @appendix In Memoriam
37527 The @value{GDBN} project mourns the loss of the following long-time
37532 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
37533 to Free Software in general. Outside of @value{GDBN}, he was known in
37534 the Amiga world for his series of Fish Disks, and the GeekGadget project.
37536 @item Michael Snyder
37537 Michael was one of the Global Maintainers of the @value{GDBN} project,
37538 with contributions recorded as early as 1996, until 2011. In addition
37539 to his day to day participation, he was a large driving force behind
37540 adding Reverse Debugging to @value{GDBN}.
37543 Beyond their technical contributions to the project, they were also
37544 enjoyable members of the Free Software Community. We will miss them.
37546 @node Formatting Documentation
37547 @appendix Formatting Documentation
37549 @cindex @value{GDBN} reference card
37550 @cindex reference card
37551 The @value{GDBN} 4 release includes an already-formatted reference card, ready
37552 for printing with PostScript or Ghostscript, in the @file{gdb}
37553 subdirectory of the main source directory@footnote{In
37554 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
37555 release.}. If you can use PostScript or Ghostscript with your printer,
37556 you can print the reference card immediately with @file{refcard.ps}.
37558 The release also includes the source for the reference card. You
37559 can format it, using @TeX{}, by typing:
37565 The @value{GDBN} reference card is designed to print in @dfn{landscape}
37566 mode on US ``letter'' size paper;
37567 that is, on a sheet 11 inches wide by 8.5 inches
37568 high. You will need to specify this form of printing as an option to
37569 your @sc{dvi} output program.
37571 @cindex documentation
37573 All the documentation for @value{GDBN} comes as part of the machine-readable
37574 distribution. The documentation is written in Texinfo format, which is
37575 a documentation system that uses a single source file to produce both
37576 on-line information and a printed manual. You can use one of the Info
37577 formatting commands to create the on-line version of the documentation
37578 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
37580 @value{GDBN} includes an already formatted copy of the on-line Info
37581 version of this manual in the @file{gdb} subdirectory. The main Info
37582 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
37583 subordinate files matching @samp{gdb.info*} in the same directory. If
37584 necessary, you can print out these files, or read them with any editor;
37585 but they are easier to read using the @code{info} subsystem in @sc{gnu}
37586 Emacs or the standalone @code{info} program, available as part of the
37587 @sc{gnu} Texinfo distribution.
37589 If you want to format these Info files yourself, you need one of the
37590 Info formatting programs, such as @code{texinfo-format-buffer} or
37593 If you have @code{makeinfo} installed, and are in the top level
37594 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
37595 version @value{GDBVN}), you can make the Info file by typing:
37602 If you want to typeset and print copies of this manual, you need @TeX{},
37603 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
37604 Texinfo definitions file.
37606 @TeX{} is a typesetting program; it does not print files directly, but
37607 produces output files called @sc{dvi} files. To print a typeset
37608 document, you need a program to print @sc{dvi} files. If your system
37609 has @TeX{} installed, chances are it has such a program. The precise
37610 command to use depends on your system; @kbd{lpr -d} is common; another
37611 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
37612 require a file name without any extension or a @samp{.dvi} extension.
37614 @TeX{} also requires a macro definitions file called
37615 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
37616 written in Texinfo format. On its own, @TeX{} cannot either read or
37617 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
37618 and is located in the @file{gdb-@var{version-number}/texinfo}
37621 If you have @TeX{} and a @sc{dvi} printer program installed, you can
37622 typeset and print this manual. First switch to the @file{gdb}
37623 subdirectory of the main source directory (for example, to
37624 @file{gdb-@value{GDBVN}/gdb}) and type:
37630 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
37632 @node Installing GDB
37633 @appendix Installing @value{GDBN}
37634 @cindex installation
37637 * Requirements:: Requirements for building @value{GDBN}
37638 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
37639 * Separate Objdir:: Compiling @value{GDBN} in another directory
37640 * Config Names:: Specifying names for hosts and targets
37641 * Configure Options:: Summary of options for configure
37642 * System-wide configuration:: Having a system-wide init file
37646 @section Requirements for Building @value{GDBN}
37647 @cindex building @value{GDBN}, requirements for
37649 Building @value{GDBN} requires various tools and packages to be available.
37650 Other packages will be used only if they are found.
37652 @heading Tools/Packages Necessary for Building @value{GDBN}
37654 @item C@t{++}11 compiler
37655 @value{GDBN} is written in C@t{++}11. It should be buildable with any
37656 recent C@t{++}11 compiler, e.g.@: GCC.
37659 @value{GDBN}'s build system relies on features only found in the GNU
37660 make program. Other variants of @code{make} will not work.
37663 @heading Tools/Packages Optional for Building @value{GDBN}
37667 @value{GDBN} can use the Expat XML parsing library. This library may be
37668 included with your operating system distribution; if it is not, you
37669 can get the latest version from @url{http://expat.sourceforge.net}.
37670 The @file{configure} script will search for this library in several
37671 standard locations; if it is installed in an unusual path, you can
37672 use the @option{--with-libexpat-prefix} option to specify its location.
37678 Remote protocol memory maps (@pxref{Memory Map Format})
37680 Target descriptions (@pxref{Target Descriptions})
37682 Remote shared library lists (@xref{Library List Format},
37683 or alternatively @pxref{Library List Format for SVR4 Targets})
37685 MS-Windows shared libraries (@pxref{Shared Libraries})
37687 Traceframe info (@pxref{Traceframe Info Format})
37689 Branch trace (@pxref{Branch Trace Format},
37690 @pxref{Branch Trace Configuration Format})
37694 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
37695 default, @value{GDBN} will be compiled if the Guile libraries are
37696 installed and are found by @file{configure}. You can use the
37697 @code{--with-guile} option to request Guile, and pass either the Guile
37698 version number or the file name of the relevant @code{pkg-config}
37699 program to choose a particular version of Guile.
37702 @value{GDBN}'s features related to character sets (@pxref{Character
37703 Sets}) require a functioning @code{iconv} implementation. If you are
37704 on a GNU system, then this is provided by the GNU C Library. Some
37705 other systems also provide a working @code{iconv}.
37707 If @value{GDBN} is using the @code{iconv} program which is installed
37708 in a non-standard place, you will need to tell @value{GDBN} where to
37709 find it. This is done with @option{--with-iconv-bin} which specifies
37710 the directory that contains the @code{iconv} program. This program is
37711 run in order to make a list of the available character sets.
37713 On systems without @code{iconv}, you can install GNU Libiconv. If
37714 Libiconv is installed in a standard place, @value{GDBN} will
37715 automatically use it if it is needed. If you have previously
37716 installed Libiconv in a non-standard place, you can use the
37717 @option{--with-libiconv-prefix} option to @file{configure}.
37719 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
37720 arrange to build Libiconv if a directory named @file{libiconv} appears
37721 in the top-most source directory. If Libiconv is built this way, and
37722 if the operating system does not provide a suitable @code{iconv}
37723 implementation, then the just-built library will automatically be used
37724 by @value{GDBN}. One easy way to set this up is to download GNU
37725 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
37726 source tree, and then rename the directory holding the Libiconv source
37727 code to @samp{libiconv}.
37730 @value{GDBN} can support debugging sections that are compressed with
37731 the LZMA library. @xref{MiniDebugInfo}. If this library is not
37732 included with your operating system, you can find it in the xz package
37733 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
37734 the usual place, then the @file{configure} script will use it
37735 automatically. If it is installed in an unusual path, you can use the
37736 @option{--with-lzma-prefix} option to specify its location.
37740 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
37741 library. This library may be included with your operating system
37742 distribution; if it is not, you can get the latest version from
37743 @url{http://www.mpfr.org}. The @file{configure} script will search
37744 for this library in several standard locations; if it is installed
37745 in an unusual path, you can use the @option{--with-libmpfr-prefix}
37746 option to specify its location.
37748 GNU MPFR is used to emulate target floating-point arithmetic during
37749 expression evaluation when the target uses different floating-point
37750 formats than the host. If GNU MPFR it is not available, @value{GDBN}
37751 will fall back to using host floating-point arithmetic.
37754 @value{GDBN} can be scripted using Python language. @xref{Python}.
37755 By default, @value{GDBN} will be compiled if the Python libraries are
37756 installed and are found by @file{configure}. You can use the
37757 @code{--with-python} option to request Python, and pass either the
37758 file name of the relevant @code{python} executable, or the name of the
37759 directory in which Python is installed, to choose a particular
37760 installation of Python.
37763 @cindex compressed debug sections
37764 @value{GDBN} will use the @samp{zlib} library, if available, to read
37765 compressed debug sections. Some linkers, such as GNU gold, are capable
37766 of producing binaries with compressed debug sections. If @value{GDBN}
37767 is compiled with @samp{zlib}, it will be able to read the debug
37768 information in such binaries.
37770 The @samp{zlib} library is likely included with your operating system
37771 distribution; if it is not, you can get the latest version from
37772 @url{http://zlib.net}.
37775 @node Running Configure
37776 @section Invoking the @value{GDBN} @file{configure} Script
37777 @cindex configuring @value{GDBN}
37778 @value{GDBN} comes with a @file{configure} script that automates the process
37779 of preparing @value{GDBN} for installation; you can then use @code{make} to
37780 build the @code{gdb} program.
37782 @c irrelevant in info file; it's as current as the code it lives with.
37783 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
37784 look at the @file{README} file in the sources; we may have improved the
37785 installation procedures since publishing this manual.}
37788 The @value{GDBN} distribution includes all the source code you need for
37789 @value{GDBN} in a single directory, whose name is usually composed by
37790 appending the version number to @samp{gdb}.
37792 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
37793 @file{gdb-@value{GDBVN}} directory. That directory contains:
37796 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
37797 script for configuring @value{GDBN} and all its supporting libraries
37799 @item gdb-@value{GDBVN}/gdb
37800 the source specific to @value{GDBN} itself
37802 @item gdb-@value{GDBVN}/bfd
37803 source for the Binary File Descriptor library
37805 @item gdb-@value{GDBVN}/include
37806 @sc{gnu} include files
37808 @item gdb-@value{GDBVN}/libiberty
37809 source for the @samp{-liberty} free software library
37811 @item gdb-@value{GDBVN}/opcodes
37812 source for the library of opcode tables and disassemblers
37814 @item gdb-@value{GDBVN}/readline
37815 source for the @sc{gnu} command-line interface
37818 There may be other subdirectories as well.
37820 The simplest way to configure and build @value{GDBN} is to run @file{configure}
37821 from the @file{gdb-@var{version-number}} source directory, which in
37822 this example is the @file{gdb-@value{GDBVN}} directory.
37824 First switch to the @file{gdb-@var{version-number}} source directory
37825 if you are not already in it; then run @file{configure}. Pass the
37826 identifier for the platform on which @value{GDBN} will run as an
37832 cd gdb-@value{GDBVN}
37837 Running @samp{configure} and then running @code{make} builds the
37838 included supporting libraries, then @code{gdb} itself. The configured
37839 source files, and the binaries, are left in the corresponding source
37843 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
37844 system does not recognize this automatically when you run a different
37845 shell, you may need to run @code{sh} on it explicitly:
37851 You should run the @file{configure} script from the top directory in the
37852 source tree, the @file{gdb-@var{version-number}} directory. If you run
37853 @file{configure} from one of the subdirectories, you will configure only
37854 that subdirectory. That is usually not what you want. In particular,
37855 if you run the first @file{configure} from the @file{gdb} subdirectory
37856 of the @file{gdb-@var{version-number}} directory, you will omit the
37857 configuration of @file{bfd}, @file{readline}, and other sibling
37858 directories of the @file{gdb} subdirectory. This leads to build errors
37859 about missing include files such as @file{bfd/bfd.h}.
37861 You can install @code{@value{GDBN}} anywhere. The best way to do this
37862 is to pass the @code{--prefix} option to @code{configure}, and then
37863 install it with @code{make install}.
37865 @node Separate Objdir
37866 @section Compiling @value{GDBN} in Another Directory
37868 If you want to run @value{GDBN} versions for several host or target machines,
37869 you need a different @code{gdb} compiled for each combination of
37870 host and target. @file{configure} is designed to make this easy by
37871 allowing you to generate each configuration in a separate subdirectory,
37872 rather than in the source directory. If your @code{make} program
37873 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
37874 @code{make} in each of these directories builds the @code{gdb}
37875 program specified there.
37877 To build @code{gdb} in a separate directory, run @file{configure}
37878 with the @samp{--srcdir} option to specify where to find the source.
37879 (You also need to specify a path to find @file{configure}
37880 itself from your working directory. If the path to @file{configure}
37881 would be the same as the argument to @samp{--srcdir}, you can leave out
37882 the @samp{--srcdir} option; it is assumed.)
37884 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
37885 separate directory for a Sun 4 like this:
37889 cd gdb-@value{GDBVN}
37892 ../gdb-@value{GDBVN}/configure
37897 When @file{configure} builds a configuration using a remote source
37898 directory, it creates a tree for the binaries with the same structure
37899 (and using the same names) as the tree under the source directory. In
37900 the example, you'd find the Sun 4 library @file{libiberty.a} in the
37901 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
37902 @file{gdb-sun4/gdb}.
37904 Make sure that your path to the @file{configure} script has just one
37905 instance of @file{gdb} in it. If your path to @file{configure} looks
37906 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
37907 one subdirectory of @value{GDBN}, not the whole package. This leads to
37908 build errors about missing include files such as @file{bfd/bfd.h}.
37910 One popular reason to build several @value{GDBN} configurations in separate
37911 directories is to configure @value{GDBN} for cross-compiling (where
37912 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
37913 programs that run on another machine---the @dfn{target}).
37914 You specify a cross-debugging target by
37915 giving the @samp{--target=@var{target}} option to @file{configure}.
37917 When you run @code{make} to build a program or library, you must run
37918 it in a configured directory---whatever directory you were in when you
37919 called @file{configure} (or one of its subdirectories).
37921 The @code{Makefile} that @file{configure} generates in each source
37922 directory also runs recursively. If you type @code{make} in a source
37923 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
37924 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
37925 will build all the required libraries, and then build GDB.
37927 When you have multiple hosts or targets configured in separate
37928 directories, you can run @code{make} on them in parallel (for example,
37929 if they are NFS-mounted on each of the hosts); they will not interfere
37933 @section Specifying Names for Hosts and Targets
37935 The specifications used for hosts and targets in the @file{configure}
37936 script are based on a three-part naming scheme, but some short predefined
37937 aliases are also supported. The full naming scheme encodes three pieces
37938 of information in the following pattern:
37941 @var{architecture}-@var{vendor}-@var{os}
37944 For example, you can use the alias @code{sun4} as a @var{host} argument,
37945 or as the value for @var{target} in a @code{--target=@var{target}}
37946 option. The equivalent full name is @samp{sparc-sun-sunos4}.
37948 The @file{configure} script accompanying @value{GDBN} does not provide
37949 any query facility to list all supported host and target names or
37950 aliases. @file{configure} calls the Bourne shell script
37951 @code{config.sub} to map abbreviations to full names; you can read the
37952 script, if you wish, or you can use it to test your guesses on
37953 abbreviations---for example:
37956 % sh config.sub i386-linux
37958 % sh config.sub alpha-linux
37959 alpha-unknown-linux-gnu
37960 % sh config.sub hp9k700
37962 % sh config.sub sun4
37963 sparc-sun-sunos4.1.1
37964 % sh config.sub sun3
37965 m68k-sun-sunos4.1.1
37966 % sh config.sub i986v
37967 Invalid configuration `i986v': machine `i986v' not recognized
37971 @code{config.sub} is also distributed in the @value{GDBN} source
37972 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
37974 @node Configure Options
37975 @section @file{configure} Options
37977 Here is a summary of the @file{configure} options and arguments that
37978 are most often useful for building @value{GDBN}. @file{configure}
37979 also has several other options not listed here. @inforef{Running
37980 configure scripts,,autoconf.info}, for a full
37981 explanation of @file{configure}.
37984 configure @r{[}--help@r{]}
37985 @r{[}--prefix=@var{dir}@r{]}
37986 @r{[}--exec-prefix=@var{dir}@r{]}
37987 @r{[}--srcdir=@var{dirname}@r{]}
37988 @r{[}--target=@var{target}@r{]}
37992 You may introduce options with a single @samp{-} rather than
37993 @samp{--} if you prefer; but you may abbreviate option names if you use
37998 Display a quick summary of how to invoke @file{configure}.
38000 @item --prefix=@var{dir}
38001 Configure the source to install programs and files under directory
38004 @item --exec-prefix=@var{dir}
38005 Configure the source to install programs under directory
38008 @c avoid splitting the warning from the explanation:
38010 @item --srcdir=@var{dirname}
38011 Use this option to make configurations in directories separate from the
38012 @value{GDBN} source directories. Among other things, you can use this to
38013 build (or maintain) several configurations simultaneously, in separate
38014 directories. @file{configure} writes configuration-specific files in
38015 the current directory, but arranges for them to use the source in the
38016 directory @var{dirname}. @file{configure} creates directories under
38017 the working directory in parallel to the source directories below
38020 @item --target=@var{target}
38021 Configure @value{GDBN} for cross-debugging programs running on the specified
38022 @var{target}. Without this option, @value{GDBN} is configured to debug
38023 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
38025 There is no convenient way to generate a list of all available
38026 targets. Also see the @code{--enable-targets} option, below.
38029 There are many other options that are specific to @value{GDBN}. This
38030 lists just the most common ones; there are some very specialized
38031 options not described here.
38034 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
38035 @itemx --enable-targets=all
38036 Configure @value{GDBN} for cross-debugging programs running on the
38037 specified list of targets. The special value @samp{all} configures
38038 @value{GDBN} for debugging programs running on any target it supports.
38040 @item --with-gdb-datadir=@var{path}
38041 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
38042 here for certain supporting files or scripts. This defaults to the
38043 @file{gdb} subdirectory of @samp{datadir} (which can be set using
38046 @item --with-relocated-sources=@var{dir}
38047 Sets up the default source path substitution rule so that directory
38048 names recorded in debug information will be automatically adjusted for
38049 any directory under @var{dir}. @var{dir} should be a subdirectory of
38050 @value{GDBN}'s configured prefix, the one mentioned in the
38051 @code{--prefix} or @code{--exec-prefix} options to configure. This
38052 option is useful if GDB is supposed to be moved to a different place
38055 @item --enable-64-bit-bfd
38056 Enable 64-bit support in BFD on 32-bit hosts.
38058 @item --disable-gdbmi
38059 Build @value{GDBN} without the GDB/MI machine interface
38063 Build @value{GDBN} with the text-mode full-screen user interface
38064 (TUI). Requires a curses library (ncurses and cursesX are also
38067 @item --with-curses
38068 Use the curses library instead of the termcap library, for text-mode
38069 terminal operations.
38071 @item --with-debuginfod
38072 Build @value{GDBN} with libdebuginfod, the debuginfod client library.
38073 Used to automatically fetch source files and separate debug files from
38074 debuginfod servers using the associated executable's build ID. Enabled
38075 by default if libdebuginfod is installed and found at configure time.
38076 debuginfod is packaged with elfutils, starting with version 0.178. You
38077 can get the latest version from `https://sourceware.org/elfutils/'.
38079 @item --with-libunwind-ia64
38080 Use the libunwind library for unwinding function call stack on ia64
38081 target platforms. See http://www.nongnu.org/libunwind/index.html for
38084 @item --with-system-readline
38085 Use the readline library installed on the host, rather than the
38086 library supplied as part of @value{GDBN}. Readline 7 or newer is
38087 required; this is enforced by the build system.
38089 @item --with-system-zlib
38090 Use the zlib library installed on the host, rather than the library
38091 supplied as part of @value{GDBN}.
38094 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
38095 default if libexpat is installed and found at configure time.) This
38096 library is used to read XML files supplied with @value{GDBN}. If it
38097 is unavailable, some features, such as remote protocol memory maps,
38098 target descriptions, and shared library lists, that are based on XML
38099 files, will not be available in @value{GDBN}. If your host does not
38100 have libexpat installed, you can get the latest version from
38101 `http://expat.sourceforge.net'.
38103 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
38105 Build @value{GDBN} with GNU libiconv, a character set encoding
38106 conversion library. This is not done by default, as on GNU systems
38107 the @code{iconv} that is built in to the C library is sufficient. If
38108 your host does not have a working @code{iconv}, you can get the latest
38109 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
38111 @value{GDBN}'s build system also supports building GNU libiconv as
38112 part of the overall build. @xref{Requirements}.
38115 Build @value{GDBN} with LZMA, a compression library. (Done by default
38116 if liblzma is installed and found at configure time.) LZMA is used by
38117 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
38118 platforms using the ELF object file format. If your host does not
38119 have liblzma installed, you can get the latest version from
38120 `https://tukaani.org/xz/'.
38123 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
38124 floating-point computation with correct rounding. (Done by default if
38125 GNU MPFR is installed and found at configure time.) This library is
38126 used to emulate target floating-point arithmetic during expression
38127 evaluation when the target uses different floating-point formats than
38128 the host. If GNU MPFR is not available, @value{GDBN} will fall back
38129 to using host floating-point arithmetic. If your host does not have
38130 GNU MPFR installed, you can get the latest version from
38131 `http://www.mpfr.org'.
38133 @item --with-python@r{[}=@var{python}@r{]}
38134 Build @value{GDBN} with Python scripting support. (Done by default if
38135 libpython is present and found at configure time.) Python makes
38136 @value{GDBN} scripting much more powerful than the restricted CLI
38137 scripting language. If your host does not have Python installed, you
38138 can find it on `http://www.python.org/download/'. The oldest version
38139 of Python supported by GDB is 2.6. The optional argument @var{python}
38140 is used to find the Python headers and libraries. It can be either
38141 the name of a Python executable, or the name of the directory in which
38142 Python is installed.
38144 @item --with-guile[=GUILE]'
38145 Build @value{GDBN} with GNU Guile scripting support. (Done by default
38146 if libguile is present and found at configure time.) If your host
38147 does not have Guile installed, you can find it at
38148 `https://www.gnu.org/software/guile/'. The optional argument GUILE
38149 can be a version number, which will cause @code{configure} to try to
38150 use that version of Guile; or the file name of a @code{pkg-config}
38151 executable, which will be queried to find the information needed to
38152 compile and link against Guile.
38154 @item --without-included-regex
38155 Don't use the regex library included with @value{GDBN} (as part of the
38156 libiberty library). This is the default on hosts with version 2 of
38159 @item --with-sysroot=@var{dir}
38160 Use @var{dir} as the default system root directory for libraries whose
38161 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
38162 @var{dir} can be modified at run time by using the @command{set
38163 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
38164 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
38165 default system root will be automatically adjusted if and when
38166 @value{GDBN} is moved to a different location.
38168 @item --with-system-gdbinit=@var{file}
38169 Configure @value{GDBN} to automatically load a system-wide init file.
38170 @var{file} should be an absolute file name. If @var{file} is in a
38171 directory under the configured prefix, and @value{GDBN} is moved to
38172 another location after being built, the location of the system-wide
38173 init file will be adjusted accordingly.
38175 @item --with-system-gdbinit-dir=@var{directory}
38176 Configure @value{GDBN} to automatically load init files from a
38177 system-wide directory. @var{directory} should be an absolute directory
38178 name. If @var{directory} is in a directory under the configured
38179 prefix, and @value{GDBN} is moved to another location after being
38180 built, the location of the system-wide init directory will be
38181 adjusted accordingly.
38183 @item --enable-build-warnings
38184 When building the @value{GDBN} sources, ask the compiler to warn about
38185 any code which looks even vaguely suspicious. It passes many
38186 different warning flags, depending on the exact version of the
38187 compiler you are using.
38189 @item --enable-werror
38190 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
38191 to the compiler, which will fail the compilation if the compiler
38192 outputs any warning messages.
38194 @item --enable-ubsan
38195 Enable the GCC undefined behavior sanitizer. This is disabled by
38196 default, but passing @code{--enable-ubsan=yes} or
38197 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
38198 undefined behavior sanitizer checks for C@t{++} undefined behavior.
38199 It has a performance cost, so if you are looking at @value{GDBN}'s
38200 performance, you should disable it. The undefined behavior sanitizer
38201 was first introduced in GCC 4.9.
38204 @node System-wide configuration
38205 @section System-wide configuration and settings
38206 @cindex system-wide init file
38208 @value{GDBN} can be configured to have a system-wide init file and a
38209 system-wide init file directory; this file and files in that directory
38210 (if they have a recognized file extension) will be read and executed at
38211 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
38213 Here are the corresponding configure options:
38216 @item --with-system-gdbinit=@var{file}
38217 Specify that the default location of the system-wide init file is
38219 @item --with-system-gdbinit-dir=@var{directory}
38220 Specify that the default location of the system-wide init file directory
38221 is @var{directory}.
38224 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
38225 they may be subject to relocation. Two possible cases:
38229 If the default location of this init file/directory contains @file{$prefix},
38230 it will be subject to relocation. Suppose that the configure options
38231 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
38232 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
38233 init file is looked for as @file{$install/etc/gdbinit} instead of
38234 @file{$prefix/etc/gdbinit}.
38237 By contrast, if the default location does not contain the prefix,
38238 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
38239 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
38240 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
38241 wherever @value{GDBN} is installed.
38244 If the configured location of the system-wide init file (as given by the
38245 @option{--with-system-gdbinit} option at configure time) is in the
38246 data-directory (as specified by @option{--with-gdb-datadir} at configure
38247 time) or in one of its subdirectories, then @value{GDBN} will look for the
38248 system-wide init file in the directory specified by the
38249 @option{--data-directory} command-line option.
38250 Note that the system-wide init file is only read once, during @value{GDBN}
38251 initialization. If the data-directory is changed after @value{GDBN} has
38252 started with the @code{set data-directory} command, the file will not be
38255 This applies similarly to the system-wide directory specified in
38256 @option{--with-system-gdbinit-dir}.
38258 Any supported scripting language can be used for these init files, as long
38259 as the file extension matches the scripting language. To be interpreted
38260 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
38264 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
38267 @node System-wide Configuration Scripts
38268 @subsection Installed System-wide Configuration Scripts
38269 @cindex system-wide configuration scripts
38271 The @file{system-gdbinit} directory, located inside the data-directory
38272 (as specified by @option{--with-gdb-datadir} at configure time) contains
38273 a number of scripts which can be used as system-wide init files. To
38274 automatically source those scripts at startup, @value{GDBN} should be
38275 configured with @option{--with-system-gdbinit}. Otherwise, any user
38276 should be able to source them by hand as needed.
38278 The following scripts are currently available:
38281 @item @file{elinos.py}
38283 @cindex ELinOS system-wide configuration script
38284 This script is useful when debugging a program on an ELinOS target.
38285 It takes advantage of the environment variables defined in a standard
38286 ELinOS environment in order to determine the location of the system
38287 shared libraries, and then sets the @samp{solib-absolute-prefix}
38288 and @samp{solib-search-path} variables appropriately.
38290 @item @file{wrs-linux.py}
38291 @pindex wrs-linux.py
38292 @cindex Wind River Linux system-wide configuration script
38293 This script is useful when debugging a program on a target running
38294 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
38295 the host-side sysroot used by the target system.
38299 @node Maintenance Commands
38300 @appendix Maintenance Commands
38301 @cindex maintenance commands
38302 @cindex internal commands
38304 In addition to commands intended for @value{GDBN} users, @value{GDBN}
38305 includes a number of commands intended for @value{GDBN} developers,
38306 that are not documented elsewhere in this manual. These commands are
38307 provided here for reference. (For commands that turn on debugging
38308 messages, see @ref{Debugging Output}.)
38311 @kindex maint agent
38312 @kindex maint agent-eval
38313 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
38314 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
38315 Translate the given @var{expression} into remote agent bytecodes.
38316 This command is useful for debugging the Agent Expression mechanism
38317 (@pxref{Agent Expressions}). The @samp{agent} version produces an
38318 expression useful for data collection, such as by tracepoints, while
38319 @samp{maint agent-eval} produces an expression that evaluates directly
38320 to a result. For instance, a collection expression for @code{globa +
38321 globb} will include bytecodes to record four bytes of memory at each
38322 of the addresses of @code{globa} and @code{globb}, while discarding
38323 the result of the addition, while an evaluation expression will do the
38324 addition and return the sum.
38325 If @code{-at} is given, generate remote agent bytecode for @var{location}.
38326 If not, generate remote agent bytecode for current frame PC address.
38328 @kindex maint agent-printf
38329 @item maint agent-printf @var{format},@var{expr},...
38330 Translate the given format string and list of argument expressions
38331 into remote agent bytecodes and display them as a disassembled list.
38332 This command is useful for debugging the agent version of dynamic
38333 printf (@pxref{Dynamic Printf}).
38335 @kindex maint info breakpoints
38336 @item @anchor{maint info breakpoints}maint info breakpoints
38337 Using the same format as @samp{info breakpoints}, display both the
38338 breakpoints you've set explicitly, and those @value{GDBN} is using for
38339 internal purposes. Internal breakpoints are shown with negative
38340 breakpoint numbers. The type column identifies what kind of breakpoint
38345 Normal, explicitly set breakpoint.
38348 Normal, explicitly set watchpoint.
38351 Internal breakpoint, used to handle correctly stepping through
38352 @code{longjmp} calls.
38354 @item longjmp resume
38355 Internal breakpoint at the target of a @code{longjmp}.
38358 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
38361 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
38364 Shared library events.
38368 @kindex maint info btrace
38369 @item maint info btrace
38370 Pint information about raw branch tracing data.
38372 @kindex maint btrace packet-history
38373 @item maint btrace packet-history
38374 Print the raw branch trace packets that are used to compute the
38375 execution history for the @samp{record btrace} command. Both the
38376 information and the format in which it is printed depend on the btrace
38381 For the BTS recording format, print a list of blocks of sequential
38382 code. For each block, the following information is printed:
38386 Newer blocks have higher numbers. The oldest block has number zero.
38387 @item Lowest @samp{PC}
38388 @item Highest @samp{PC}
38392 For the Intel Processor Trace recording format, print a list of
38393 Intel Processor Trace packets. For each packet, the following
38394 information is printed:
38397 @item Packet number
38398 Newer packets have higher numbers. The oldest packet has number zero.
38400 The packet's offset in the trace stream.
38401 @item Packet opcode and payload
38405 @kindex maint btrace clear-packet-history
38406 @item maint btrace clear-packet-history
38407 Discards the cached packet history printed by the @samp{maint btrace
38408 packet-history} command. The history will be computed again when
38411 @kindex maint btrace clear
38412 @item maint btrace clear
38413 Discard the branch trace data. The data will be fetched anew and the
38414 branch trace will be recomputed when needed.
38416 This implicitly truncates the branch trace to a single branch trace
38417 buffer. When updating branch trace incrementally, the branch trace
38418 available to @value{GDBN} may be bigger than a single branch trace
38421 @kindex maint set btrace pt skip-pad
38422 @item maint set btrace pt skip-pad
38423 @kindex maint show btrace pt skip-pad
38424 @item maint show btrace pt skip-pad
38425 Control whether @value{GDBN} will skip PAD packets when computing the
38428 @kindex set displaced-stepping
38429 @kindex show displaced-stepping
38430 @cindex displaced stepping support
38431 @cindex out-of-line single-stepping
38432 @item set displaced-stepping
38433 @itemx show displaced-stepping
38434 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
38435 if the target supports it. Displaced stepping is a way to single-step
38436 over breakpoints without removing them from the inferior, by executing
38437 an out-of-line copy of the instruction that was originally at the
38438 breakpoint location. It is also known as out-of-line single-stepping.
38441 @item set displaced-stepping on
38442 If the target architecture supports it, @value{GDBN} will use
38443 displaced stepping to step over breakpoints.
38445 @item set displaced-stepping off
38446 @value{GDBN} will not use displaced stepping to step over breakpoints,
38447 even if such is supported by the target architecture.
38449 @cindex non-stop mode, and @samp{set displaced-stepping}
38450 @item set displaced-stepping auto
38451 This is the default mode. @value{GDBN} will use displaced stepping
38452 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
38453 architecture supports displaced stepping.
38456 @kindex maint check-psymtabs
38457 @item maint check-psymtabs
38458 Check the consistency of currently expanded psymtabs versus symtabs.
38459 Use this to check, for example, whether a symbol is in one but not the other.
38461 @kindex maint check-symtabs
38462 @item maint check-symtabs
38463 Check the consistency of currently expanded symtabs.
38465 @kindex maint expand-symtabs
38466 @item maint expand-symtabs [@var{regexp}]
38467 Expand symbol tables.
38468 If @var{regexp} is specified, only expand symbol tables for file
38469 names matching @var{regexp}.
38471 @kindex maint set catch-demangler-crashes
38472 @kindex maint show catch-demangler-crashes
38473 @cindex demangler crashes
38474 @item maint set catch-demangler-crashes [on|off]
38475 @itemx maint show catch-demangler-crashes
38476 Control whether @value{GDBN} should attempt to catch crashes in the
38477 symbol name demangler. The default is to attempt to catch crashes.
38478 If enabled, the first time a crash is caught, a core file is created,
38479 the offending symbol is displayed and the user is presented with the
38480 option to terminate the current session.
38482 @kindex maint cplus first_component
38483 @item maint cplus first_component @var{name}
38484 Print the first C@t{++} class/namespace component of @var{name}.
38486 @kindex maint cplus namespace
38487 @item maint cplus namespace
38488 Print the list of possible C@t{++} namespaces.
38490 @kindex maint deprecate
38491 @kindex maint undeprecate
38492 @cindex deprecated commands
38493 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
38494 @itemx maint undeprecate @var{command}
38495 Deprecate or undeprecate the named @var{command}. Deprecated commands
38496 cause @value{GDBN} to issue a warning when you use them. The optional
38497 argument @var{replacement} says which newer command should be used in
38498 favor of the deprecated one; if it is given, @value{GDBN} will mention
38499 the replacement as part of the warning.
38501 @kindex maint dump-me
38502 @item maint dump-me
38503 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
38504 Cause a fatal signal in the debugger and force it to dump its core.
38505 This is supported only on systems which support aborting a program
38506 with the @code{SIGQUIT} signal.
38508 @kindex maint internal-error
38509 @kindex maint internal-warning
38510 @kindex maint demangler-warning
38511 @cindex demangler crashes
38512 @item maint internal-error @r{[}@var{message-text}@r{]}
38513 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
38514 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
38516 Cause @value{GDBN} to call the internal function @code{internal_error},
38517 @code{internal_warning} or @code{demangler_warning} and hence behave
38518 as though an internal problem has been detected. In addition to
38519 reporting the internal problem, these functions give the user the
38520 opportunity to either quit @value{GDBN} or (for @code{internal_error}
38521 and @code{internal_warning}) create a core file of the current
38522 @value{GDBN} session.
38524 These commands take an optional parameter @var{message-text} that is
38525 used as the text of the error or warning message.
38527 Here's an example of using @code{internal-error}:
38530 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
38531 @dots{}/maint.c:121: internal-error: testing, 1, 2
38532 A problem internal to GDB has been detected. Further
38533 debugging may prove unreliable.
38534 Quit this debugging session? (y or n) @kbd{n}
38535 Create a core file? (y or n) @kbd{n}
38539 @cindex @value{GDBN} internal error
38540 @cindex internal errors, control of @value{GDBN} behavior
38541 @cindex demangler crashes
38543 @kindex maint set internal-error
38544 @kindex maint show internal-error
38545 @kindex maint set internal-warning
38546 @kindex maint show internal-warning
38547 @kindex maint set demangler-warning
38548 @kindex maint show demangler-warning
38549 @item maint set internal-error @var{action} [ask|yes|no]
38550 @itemx maint show internal-error @var{action}
38551 @itemx maint set internal-warning @var{action} [ask|yes|no]
38552 @itemx maint show internal-warning @var{action}
38553 @itemx maint set demangler-warning @var{action} [ask|yes|no]
38554 @itemx maint show demangler-warning @var{action}
38555 When @value{GDBN} reports an internal problem (error or warning) it
38556 gives the user the opportunity to both quit @value{GDBN} and create a
38557 core file of the current @value{GDBN} session. These commands let you
38558 override the default behaviour for each particular @var{action},
38559 described in the table below.
38563 You can specify that @value{GDBN} should always (yes) or never (no)
38564 quit. The default is to ask the user what to do.
38567 You can specify that @value{GDBN} should always (yes) or never (no)
38568 create a core file. The default is to ask the user what to do. Note
38569 that there is no @code{corefile} option for @code{demangler-warning}:
38570 demangler warnings always create a core file and this cannot be
38574 @kindex maint packet
38575 @item maint packet @var{text}
38576 If @value{GDBN} is talking to an inferior via the serial protocol,
38577 then this command sends the string @var{text} to the inferior, and
38578 displays the response packet. @value{GDBN} supplies the initial
38579 @samp{$} character, the terminating @samp{#} character, and the
38582 @kindex maint print architecture
38583 @item maint print architecture @r{[}@var{file}@r{]}
38584 Print the entire architecture configuration. The optional argument
38585 @var{file} names the file where the output goes.
38587 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
38588 @item maint print c-tdesc
38589 Print the target description (@pxref{Target Descriptions}) as
38590 a C source file. By default, the target description is for the current
38591 target, but if the optional argument @var{file} is provided, that file
38592 is used to produce the description. The @var{file} should be an XML
38593 document, of the form described in @ref{Target Description Format}.
38594 The created source file is built into @value{GDBN} when @value{GDBN} is
38595 built again. This command is used by developers after they add or
38596 modify XML target descriptions.
38598 @kindex maint print xml-tdesc
38599 @item maint print xml-tdesc @r{[}@var{file}@r{]}
38600 Print the target description (@pxref{Target Descriptions}) as an XML
38601 file. By default print the target description for the current target,
38602 but if the optional argument @var{file} is provided, then that file is
38603 read in by GDB and then used to produce the description. The
38604 @var{file} should be an XML document, of the form described in
38605 @ref{Target Description Format}.
38607 @kindex maint check xml-descriptions
38608 @item maint check xml-descriptions @var{dir}
38609 Check that the target descriptions dynamically created by @value{GDBN}
38610 equal the descriptions created from XML files found in @var{dir}.
38612 @anchor{maint check libthread-db}
38613 @kindex maint check libthread-db
38614 @item maint check libthread-db
38615 Run integrity checks on the current inferior's thread debugging
38616 library. This exercises all @code{libthread_db} functionality used by
38617 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
38618 @code{proc_service} functions provided by @value{GDBN} that
38619 @code{libthread_db} uses. Note that parts of the test may be skipped
38620 on some platforms when debugging core files.
38622 @kindex maint print core-file-backed-mappings
38623 @cindex memory address space mappings
38624 @item maint print core-file-backed-mappings
38625 Print the file-backed mappings which were loaded from a core file note.
38626 This output represents state internal to @value{GDBN} and should be
38627 similar to the mappings displayed by the @code{info proc mappings}
38630 @kindex maint print dummy-frames
38631 @item maint print dummy-frames
38632 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
38635 (@value{GDBP}) @kbd{b add}
38637 (@value{GDBP}) @kbd{print add(2,3)}
38638 Breakpoint 2, add (a=2, b=3) at @dots{}
38640 The program being debugged stopped while in a function called from GDB.
38642 (@value{GDBP}) @kbd{maint print dummy-frames}
38643 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
38647 Takes an optional file parameter.
38649 @kindex maint print registers
38650 @kindex maint print raw-registers
38651 @kindex maint print cooked-registers
38652 @kindex maint print register-groups
38653 @kindex maint print remote-registers
38654 @item maint print registers @r{[}@var{file}@r{]}
38655 @itemx maint print raw-registers @r{[}@var{file}@r{]}
38656 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
38657 @itemx maint print register-groups @r{[}@var{file}@r{]}
38658 @itemx maint print remote-registers @r{[}@var{file}@r{]}
38659 Print @value{GDBN}'s internal register data structures.
38661 The command @code{maint print raw-registers} includes the contents of
38662 the raw register cache; the command @code{maint print
38663 cooked-registers} includes the (cooked) value of all registers,
38664 including registers which aren't available on the target nor visible
38665 to user; the command @code{maint print register-groups} includes the
38666 groups that each register is a member of; and the command @code{maint
38667 print remote-registers} includes the remote target's register numbers
38668 and offsets in the `G' packets.
38670 These commands take an optional parameter, a file name to which to
38671 write the information.
38673 @kindex maint print reggroups
38674 @item maint print reggroups @r{[}@var{file}@r{]}
38675 Print @value{GDBN}'s internal register group data structures. The
38676 optional argument @var{file} tells to what file to write the
38679 The register groups info looks like this:
38682 (@value{GDBP}) @kbd{maint print reggroups}
38695 This command forces @value{GDBN} to flush its internal register cache.
38697 @kindex maint print objfiles
38698 @cindex info for known object files
38699 @item maint print objfiles @r{[}@var{regexp}@r{]}
38700 Print a dump of all known object files.
38701 If @var{regexp} is specified, only print object files whose names
38702 match @var{regexp}. For each object file, this command prints its name,
38703 address in memory, and all of its psymtabs and symtabs.
38705 @kindex maint print user-registers
38706 @cindex user registers
38707 @item maint print user-registers
38708 List all currently available @dfn{user registers}. User registers
38709 typically provide alternate names for actual hardware registers. They
38710 include the four ``standard'' registers @code{$fp}, @code{$pc},
38711 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
38712 registers can be used in expressions in the same way as the canonical
38713 register names, but only the latter are listed by the @code{info
38714 registers} and @code{maint print registers} commands.
38716 @kindex maint print section-scripts
38717 @cindex info for known .debug_gdb_scripts-loaded scripts
38718 @item maint print section-scripts [@var{regexp}]
38719 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
38720 If @var{regexp} is specified, only print scripts loaded by object files
38721 matching @var{regexp}.
38722 For each script, this command prints its name as specified in the objfile,
38723 and the full path if known.
38724 @xref{dotdebug_gdb_scripts section}.
38726 @kindex maint print statistics
38727 @cindex bcache statistics
38728 @item maint print statistics
38729 This command prints, for each object file in the program, various data
38730 about that object file followed by the byte cache (@dfn{bcache})
38731 statistics for the object file. The objfile data includes the number
38732 of minimal, partial, full, and stabs symbols, the number of types
38733 defined by the objfile, the number of as yet unexpanded psym tables,
38734 the number of line tables and string tables, and the amount of memory
38735 used by the various tables. The bcache statistics include the counts,
38736 sizes, and counts of duplicates of all and unique objects, max,
38737 average, and median entry size, total memory used and its overhead and
38738 savings, and various measures of the hash table size and chain
38741 @kindex maint print target-stack
38742 @cindex target stack description
38743 @item maint print target-stack
38744 A @dfn{target} is an interface between the debugger and a particular
38745 kind of file or process. Targets can be stacked in @dfn{strata},
38746 so that more than one target can potentially respond to a request.
38747 In particular, memory accesses will walk down the stack of targets
38748 until they find a target that is interested in handling that particular
38751 This command prints a short description of each layer that was pushed on
38752 the @dfn{target stack}, starting from the top layer down to the bottom one.
38754 @kindex maint print type
38755 @cindex type chain of a data type
38756 @item maint print type @var{expr}
38757 Print the type chain for a type specified by @var{expr}. The argument
38758 can be either a type name or a symbol. If it is a symbol, the type of
38759 that symbol is described. The type chain produced by this command is
38760 a recursive definition of the data type as stored in @value{GDBN}'s
38761 data structures, including its flags and contained types.
38763 @kindex maint selftest
38765 @item maint selftest @r{[}@var{filter}@r{]}
38766 Run any self tests that were compiled in to @value{GDBN}. This will
38767 print a message showing how many tests were run, and how many failed.
38768 If a @var{filter} is passed, only the tests with @var{filter} in their
38771 @kindex maint info selftests
38773 @item maint info selftests
38774 List the selftests compiled in to @value{GDBN}.
38776 @kindex maint set dwarf always-disassemble
38777 @kindex maint show dwarf always-disassemble
38778 @item maint set dwarf always-disassemble
38779 @item maint show dwarf always-disassemble
38780 Control the behavior of @code{info address} when using DWARF debugging
38783 The default is @code{off}, which means that @value{GDBN} should try to
38784 describe a variable's location in an easily readable format. When
38785 @code{on}, @value{GDBN} will instead display the DWARF location
38786 expression in an assembly-like format. Note that some locations are
38787 too complex for @value{GDBN} to describe simply; in this case you will
38788 always see the disassembly form.
38790 Here is an example of the resulting disassembly:
38793 (gdb) info addr argc
38794 Symbol "argc" is a complex DWARF expression:
38798 For more information on these expressions, see
38799 @uref{http://www.dwarfstd.org/, the DWARF standard}.
38801 @kindex maint set dwarf max-cache-age
38802 @kindex maint show dwarf max-cache-age
38803 @item maint set dwarf max-cache-age
38804 @itemx maint show dwarf max-cache-age
38805 Control the DWARF compilation unit cache.
38807 @cindex DWARF compilation units cache
38808 In object files with inter-compilation-unit references, such as those
38809 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
38810 reader needs to frequently refer to previously read compilation units.
38811 This setting controls how long a compilation unit will remain in the
38812 cache if it is not referenced. A higher limit means that cached
38813 compilation units will be stored in memory longer, and more total
38814 memory will be used. Setting it to zero disables caching, which will
38815 slow down @value{GDBN} startup, but reduce memory consumption.
38817 @kindex maint set dwarf unwinders
38818 @kindex maint show dwarf unwinders
38819 @item maint set dwarf unwinders
38820 @itemx maint show dwarf unwinders
38821 Control use of the DWARF frame unwinders.
38823 @cindex DWARF frame unwinders
38824 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
38825 frame unwinders to build the backtrace. Many of these targets will
38826 also have a second mechanism for building the backtrace for use in
38827 cases where DWARF information is not available, this second mechanism
38828 is often an analysis of a function's prologue.
38830 In order to extend testing coverage of the second level stack
38831 unwinding mechanisms it is helpful to be able to disable the DWARF
38832 stack unwinders, this can be done with this switch.
38834 In normal use of @value{GDBN} disabling the DWARF unwinders is not
38835 advisable, there are cases that are better handled through DWARF than
38836 prologue analysis, and the debug experience is likely to be better
38837 with the DWARF frame unwinders enabled.
38839 If DWARF frame unwinders are not supported for a particular target
38840 architecture, then enabling this flag does not cause them to be used.
38842 @kindex maint set worker-threads
38843 @kindex maint show worker-threads
38844 @item maint set worker-threads
38845 @item maint show worker-threads
38846 Control the number of worker threads that may be used by @value{GDBN}.
38847 On capable hosts, @value{GDBN} may use multiple threads to speed up
38848 certain CPU-intensive operations, such as demangling symbol names.
38849 While the number of threads used by @value{GDBN} may vary, this
38850 command can be used to set an upper bound on this number. The default
38851 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
38852 number. Note that this only controls worker threads started by
38853 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
38856 @kindex maint set profile
38857 @kindex maint show profile
38858 @cindex profiling GDB
38859 @item maint set profile
38860 @itemx maint show profile
38861 Control profiling of @value{GDBN}.
38863 Profiling will be disabled until you use the @samp{maint set profile}
38864 command to enable it. When you enable profiling, the system will begin
38865 collecting timing and execution count data; when you disable profiling or
38866 exit @value{GDBN}, the results will be written to a log file. Remember that
38867 if you use profiling, @value{GDBN} will overwrite the profiling log file
38868 (often called @file{gmon.out}). If you have a record of important profiling
38869 data in a @file{gmon.out} file, be sure to move it to a safe location.
38871 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
38872 compiled with the @samp{-pg} compiler option.
38874 @kindex maint set show-debug-regs
38875 @kindex maint show show-debug-regs
38876 @cindex hardware debug registers
38877 @item maint set show-debug-regs
38878 @itemx maint show show-debug-regs
38879 Control whether to show variables that mirror the hardware debug
38880 registers. Use @code{on} to enable, @code{off} to disable. If
38881 enabled, the debug registers values are shown when @value{GDBN} inserts or
38882 removes a hardware breakpoint or watchpoint, and when the inferior
38883 triggers a hardware-assisted breakpoint or watchpoint.
38885 @kindex maint set show-all-tib
38886 @kindex maint show show-all-tib
38887 @item maint set show-all-tib
38888 @itemx maint show show-all-tib
38889 Control whether to show all non zero areas within a 1k block starting
38890 at thread local base, when using the @samp{info w32 thread-information-block}
38893 @kindex maint set target-async
38894 @kindex maint show target-async
38895 @item maint set target-async
38896 @itemx maint show target-async
38897 This controls whether @value{GDBN} targets operate in synchronous or
38898 asynchronous mode (@pxref{Background Execution}). Normally the
38899 default is asynchronous, if it is available; but this can be changed
38900 to more easily debug problems occurring only in synchronous mode.
38902 @kindex maint set target-non-stop @var{mode} [on|off|auto]
38903 @kindex maint show target-non-stop
38904 @item maint set target-non-stop
38905 @itemx maint show target-non-stop
38907 This controls whether @value{GDBN} targets always operate in non-stop
38908 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
38909 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
38910 if supported by the target.
38913 @item maint set target-non-stop auto
38914 This is the default mode. @value{GDBN} controls the target in
38915 non-stop mode if the target supports it.
38917 @item maint set target-non-stop on
38918 @value{GDBN} controls the target in non-stop mode even if the target
38919 does not indicate support.
38921 @item maint set target-non-stop off
38922 @value{GDBN} does not control the target in non-stop mode even if the
38923 target supports it.
38926 @kindex maint set tui-resize-message
38927 @kindex maint show tui-resize-message
38928 @item maint set tui-resize-message
38929 @item maint show tui-resize-message
38930 Control whether @value{GDBN} displays a message each time the terminal
38931 is resized when in TUI mode. The default is @code{off}, which means
38932 that @value{GDBN} is silent during resizes. When @code{on},
38933 @value{GDBN} will display a message after a resize is completed; the
38934 message will include a number indicating how many times the terminal
38935 has been resized. This setting is intended for use by the test suite,
38936 where it would otherwise be difficult to determine when a resize and
38937 refresh has been completed.
38939 @kindex maint set per-command
38940 @kindex maint show per-command
38941 @item maint set per-command
38942 @itemx maint show per-command
38943 @cindex resources used by commands
38945 @value{GDBN} can display the resources used by each command.
38946 This is useful in debugging performance problems.
38949 @item maint set per-command space [on|off]
38950 @itemx maint show per-command space
38951 Enable or disable the printing of the memory used by GDB for each command.
38952 If enabled, @value{GDBN} will display how much memory each command
38953 took, following the command's own output.
38954 This can also be requested by invoking @value{GDBN} with the
38955 @option{--statistics} command-line switch (@pxref{Mode Options}).
38957 @item maint set per-command time [on|off]
38958 @itemx maint show per-command time
38959 Enable or disable the printing of the execution time of @value{GDBN}
38961 If enabled, @value{GDBN} will display how much time it
38962 took to execute each command, following the command's own output.
38963 Both CPU time and wallclock time are printed.
38964 Printing both is useful when trying to determine whether the cost is
38965 CPU or, e.g., disk/network latency.
38966 Note that the CPU time printed is for @value{GDBN} only, it does not include
38967 the execution time of the inferior because there's no mechanism currently
38968 to compute how much time was spent by @value{GDBN} and how much time was
38969 spent by the program been debugged.
38970 This can also be requested by invoking @value{GDBN} with the
38971 @option{--statistics} command-line switch (@pxref{Mode Options}).
38973 @item maint set per-command symtab [on|off]
38974 @itemx maint show per-command symtab
38975 Enable or disable the printing of basic symbol table statistics
38977 If enabled, @value{GDBN} will display the following information:
38981 number of symbol tables
38983 number of primary symbol tables
38985 number of blocks in the blockvector
38989 @kindex maint set check-libthread-db
38990 @kindex maint show check-libthread-db
38991 @item maint set check-libthread-db [on|off]
38992 @itemx maint show check-libthread-db
38993 Control whether @value{GDBN} should run integrity checks on inferior
38994 specific thread debugging libraries as they are loaded. The default
38995 is not to perform such checks. If any check fails @value{GDBN} will
38996 unload the library and continue searching for a suitable candidate as
38997 described in @ref{set libthread-db-search-path}. For more information
38998 about the tests, see @ref{maint check libthread-db}.
39000 @kindex maint space
39001 @cindex memory used by commands
39002 @item maint space @var{value}
39003 An alias for @code{maint set per-command space}.
39004 A non-zero value enables it, zero disables it.
39007 @cindex time of command execution
39008 @item maint time @var{value}
39009 An alias for @code{maint set per-command time}.
39010 A non-zero value enables it, zero disables it.
39012 @kindex maint translate-address
39013 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
39014 Find the symbol stored at the location specified by the address
39015 @var{addr} and an optional section name @var{section}. If found,
39016 @value{GDBN} prints the name of the closest symbol and an offset from
39017 the symbol's location to the specified address. This is similar to
39018 the @code{info address} command (@pxref{Symbols}), except that this
39019 command also allows to find symbols in other sections.
39021 If section was not specified, the section in which the symbol was found
39022 is also printed. For dynamically linked executables, the name of
39023 executable or shared library containing the symbol is printed as well.
39025 @kindex maint test-options
39026 @item maint test-options require-delimiter
39027 @itemx maint test-options unknown-is-error
39028 @itemx maint test-options unknown-is-operand
39029 These commands are used by the testsuite to validate the command
39030 options framework. The @code{require-delimiter} variant requires a
39031 double-dash delimiter to indicate end of options. The
39032 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
39033 @code{unknown-is-error} variant throws an error on unknown option,
39034 while @code{unknown-is-operand} treats unknown options as the start of
39035 the command's operands. When run, the commands output the result of
39036 the processed options. When completed, the commands store the
39037 internal result of completion in a variable exposed by the @code{maint
39038 show test-options-completion-result} command.
39040 @kindex maint show test-options-completion-result
39041 @item maint show test-options-completion-result
39042 Shows the result of completing the @code{maint test-options}
39043 subcommands. This is used by the testsuite to validate completion
39044 support in the command options framework.
39046 @kindex maint set test-settings
39047 @kindex maint show test-settings
39048 @item maint set test-settings @var{kind}
39049 @itemx maint show test-settings @var{kind}
39050 These are representative commands for each @var{kind} of setting type
39051 @value{GDBN} supports. They are used by the testsuite for exercising
39052 the settings infrastructure.
39055 @item maint with @var{setting} [@var{value}] [-- @var{command}]
39056 Like the @code{with} command, but works with @code{maintenance set}
39057 variables. This is used by the testsuite to exercise the @code{with}
39058 command's infrastructure.
39062 The following command is useful for non-interactive invocations of
39063 @value{GDBN}, such as in the test suite.
39066 @item set watchdog @var{nsec}
39067 @kindex set watchdog
39068 @cindex watchdog timer
39069 @cindex timeout for commands
39070 Set the maximum number of seconds @value{GDBN} will wait for the
39071 target operation to finish. If this time expires, @value{GDBN}
39072 reports and error and the command is aborted.
39074 @item show watchdog
39075 Show the current setting of the target wait timeout.
39078 @node Remote Protocol
39079 @appendix @value{GDBN} Remote Serial Protocol
39084 * Stop Reply Packets::
39085 * General Query Packets::
39086 * Architecture-Specific Protocol Details::
39087 * Tracepoint Packets::
39088 * Host I/O Packets::
39090 * Notification Packets::
39091 * Remote Non-Stop::
39092 * Packet Acknowledgment::
39094 * File-I/O Remote Protocol Extension::
39095 * Library List Format::
39096 * Library List Format for SVR4 Targets::
39097 * Memory Map Format::
39098 * Thread List Format::
39099 * Traceframe Info Format::
39100 * Branch Trace Format::
39101 * Branch Trace Configuration Format::
39107 There may be occasions when you need to know something about the
39108 protocol---for example, if there is only one serial port to your target
39109 machine, you might want your program to do something special if it
39110 recognizes a packet meant for @value{GDBN}.
39112 In the examples below, @samp{->} and @samp{<-} are used to indicate
39113 transmitted and received data, respectively.
39115 @cindex protocol, @value{GDBN} remote serial
39116 @cindex serial protocol, @value{GDBN} remote
39117 @cindex remote serial protocol
39118 All @value{GDBN} commands and responses (other than acknowledgments
39119 and notifications, see @ref{Notification Packets}) are sent as a
39120 @var{packet}. A @var{packet} is introduced with the character
39121 @samp{$}, the actual @var{packet-data}, and the terminating character
39122 @samp{#} followed by a two-digit @var{checksum}:
39125 @code{$}@var{packet-data}@code{#}@var{checksum}
39129 @cindex checksum, for @value{GDBN} remote
39131 The two-digit @var{checksum} is computed as the modulo 256 sum of all
39132 characters between the leading @samp{$} and the trailing @samp{#} (an
39133 eight bit unsigned checksum).
39135 Implementors should note that prior to @value{GDBN} 5.0 the protocol
39136 specification also included an optional two-digit @var{sequence-id}:
39139 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
39142 @cindex sequence-id, for @value{GDBN} remote
39144 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
39145 has never output @var{sequence-id}s. Stubs that handle packets added
39146 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
39148 When either the host or the target machine receives a packet, the first
39149 response expected is an acknowledgment: either @samp{+} (to indicate
39150 the package was received correctly) or @samp{-} (to request
39154 -> @code{$}@var{packet-data}@code{#}@var{checksum}
39159 The @samp{+}/@samp{-} acknowledgments can be disabled
39160 once a connection is established.
39161 @xref{Packet Acknowledgment}, for details.
39163 The host (@value{GDBN}) sends @var{command}s, and the target (the
39164 debugging stub incorporated in your program) sends a @var{response}. In
39165 the case of step and continue @var{command}s, the response is only sent
39166 when the operation has completed, and the target has again stopped all
39167 threads in all attached processes. This is the default all-stop mode
39168 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
39169 execution mode; see @ref{Remote Non-Stop}, for details.
39171 @var{packet-data} consists of a sequence of characters with the
39172 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
39175 @cindex remote protocol, field separator
39176 Fields within the packet should be separated using @samp{,} @samp{;} or
39177 @samp{:}. Except where otherwise noted all numbers are represented in
39178 @sc{hex} with leading zeros suppressed.
39180 Implementors should note that prior to @value{GDBN} 5.0, the character
39181 @samp{:} could not appear as the third character in a packet (as it
39182 would potentially conflict with the @var{sequence-id}).
39184 @cindex remote protocol, binary data
39185 @anchor{Binary Data}
39186 Binary data in most packets is encoded either as two hexadecimal
39187 digits per byte of binary data. This allowed the traditional remote
39188 protocol to work over connections which were only seven-bit clean.
39189 Some packets designed more recently assume an eight-bit clean
39190 connection, and use a more efficient encoding to send and receive
39193 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
39194 as an escape character. Any escaped byte is transmitted as the escape
39195 character followed by the original character XORed with @code{0x20}.
39196 For example, the byte @code{0x7d} would be transmitted as the two
39197 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
39198 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
39199 @samp{@}}) must always be escaped. Responses sent by the stub
39200 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
39201 is not interpreted as the start of a run-length encoded sequence
39204 Response @var{data} can be run-length encoded to save space.
39205 Run-length encoding replaces runs of identical characters with one
39206 instance of the repeated character, followed by a @samp{*} and a
39207 repeat count. The repeat count is itself sent encoded, to avoid
39208 binary characters in @var{data}: a value of @var{n} is sent as
39209 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
39210 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
39211 code 32) for a repeat count of 3. (This is because run-length
39212 encoding starts to win for counts 3 or more.) Thus, for example,
39213 @samp{0* } is a run-length encoding of ``0000'': the space character
39214 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
39217 The printable characters @samp{#} and @samp{$} or with a numeric value
39218 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
39219 seven repeats (@samp{$}) can be expanded using a repeat count of only
39220 five (@samp{"}). For example, @samp{00000000} can be encoded as
39223 The error response returned for some packets includes a two character
39224 error number. That number is not well defined.
39226 @cindex empty response, for unsupported packets
39227 For any @var{command} not supported by the stub, an empty response
39228 (@samp{$#00}) should be returned. That way it is possible to extend the
39229 protocol. A newer @value{GDBN} can tell if a packet is supported based
39232 At a minimum, a stub is required to support the @samp{?} command to
39233 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
39234 commands for register access, and the @samp{m} and @samp{M} commands
39235 for memory access. Stubs that only control single-threaded targets
39236 can implement run control with the @samp{c} (continue) command, and if
39237 the target architecture supports hardware-assisted single-stepping,
39238 the @samp{s} (step) command. Stubs that support multi-threading
39239 targets should support the @samp{vCont} command. All other commands
39245 The following table provides a complete list of all currently defined
39246 @var{command}s and their corresponding response @var{data}.
39247 @xref{File-I/O Remote Protocol Extension}, for details about the File
39248 I/O extension of the remote protocol.
39250 Each packet's description has a template showing the packet's overall
39251 syntax, followed by an explanation of the packet's meaning. We
39252 include spaces in some of the templates for clarity; these are not
39253 part of the packet's syntax. No @value{GDBN} packet uses spaces to
39254 separate its components. For example, a template like @samp{foo
39255 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
39256 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
39257 @var{baz}. @value{GDBN} does not transmit a space character between the
39258 @samp{foo} and the @var{bar}, or between the @var{bar} and the
39261 @cindex @var{thread-id}, in remote protocol
39262 @anchor{thread-id syntax}
39263 Several packets and replies include a @var{thread-id} field to identify
39264 a thread. Normally these are positive numbers with a target-specific
39265 interpretation, formatted as big-endian hex strings. A @var{thread-id}
39266 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
39269 In addition, the remote protocol supports a multiprocess feature in
39270 which the @var{thread-id} syntax is extended to optionally include both
39271 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
39272 The @var{pid} (process) and @var{tid} (thread) components each have the
39273 format described above: a positive number with target-specific
39274 interpretation formatted as a big-endian hex string, literal @samp{-1}
39275 to indicate all processes or threads (respectively), or @samp{0} to
39276 indicate an arbitrary process or thread. Specifying just a process, as
39277 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
39278 error to specify all processes but a specific thread, such as
39279 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
39280 for those packets and replies explicitly documented to include a process
39281 ID, rather than a @var{thread-id}.
39283 The multiprocess @var{thread-id} syntax extensions are only used if both
39284 @value{GDBN} and the stub report support for the @samp{multiprocess}
39285 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
39288 Note that all packet forms beginning with an upper- or lower-case
39289 letter, other than those described here, are reserved for future use.
39291 Here are the packet descriptions.
39296 @cindex @samp{!} packet
39297 @anchor{extended mode}
39298 Enable extended mode. In extended mode, the remote server is made
39299 persistent. The @samp{R} packet is used to restart the program being
39305 The remote target both supports and has enabled extended mode.
39309 @cindex @samp{?} packet
39311 Indicate the reason the target halted. The reply is the same as for
39312 step and continue. This packet has a special interpretation when the
39313 target is in non-stop mode; see @ref{Remote Non-Stop}.
39316 @xref{Stop Reply Packets}, for the reply specifications.
39318 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
39319 @cindex @samp{A} packet
39320 Initialized @code{argv[]} array passed into program. @var{arglen}
39321 specifies the number of bytes in the hex encoded byte stream
39322 @var{arg}. See @code{gdbserver} for more details.
39327 The arguments were set.
39333 @cindex @samp{b} packet
39334 (Don't use this packet; its behavior is not well-defined.)
39335 Change the serial line speed to @var{baud}.
39337 JTC: @emph{When does the transport layer state change? When it's
39338 received, or after the ACK is transmitted. In either case, there are
39339 problems if the command or the acknowledgment packet is dropped.}
39341 Stan: @emph{If people really wanted to add something like this, and get
39342 it working for the first time, they ought to modify ser-unix.c to send
39343 some kind of out-of-band message to a specially-setup stub and have the
39344 switch happen "in between" packets, so that from remote protocol's point
39345 of view, nothing actually happened.}
39347 @item B @var{addr},@var{mode}
39348 @cindex @samp{B} packet
39349 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
39350 breakpoint at @var{addr}.
39352 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
39353 (@pxref{insert breakpoint or watchpoint packet}).
39355 @cindex @samp{bc} packet
39358 Backward continue. Execute the target system in reverse. No parameter.
39359 @xref{Reverse Execution}, for more information.
39362 @xref{Stop Reply Packets}, for the reply specifications.
39364 @cindex @samp{bs} packet
39367 Backward single step. Execute one instruction in reverse. No parameter.
39368 @xref{Reverse Execution}, for more information.
39371 @xref{Stop Reply Packets}, for the reply specifications.
39373 @item c @r{[}@var{addr}@r{]}
39374 @cindex @samp{c} packet
39375 Continue at @var{addr}, which is the address to resume. If @var{addr}
39376 is omitted, resume at current address.
39378 This packet is deprecated for multi-threading support. @xref{vCont
39382 @xref{Stop Reply Packets}, for the reply specifications.
39384 @item C @var{sig}@r{[};@var{addr}@r{]}
39385 @cindex @samp{C} packet
39386 Continue with signal @var{sig} (hex signal number). If
39387 @samp{;@var{addr}} is omitted, resume at same address.
39389 This packet is deprecated for multi-threading support. @xref{vCont
39393 @xref{Stop Reply Packets}, for the reply specifications.
39396 @cindex @samp{d} packet
39399 Don't use this packet; instead, define a general set packet
39400 (@pxref{General Query Packets}).
39404 @cindex @samp{D} packet
39405 The first form of the packet is used to detach @value{GDBN} from the
39406 remote system. It is sent to the remote target
39407 before @value{GDBN} disconnects via the @code{detach} command.
39409 The second form, including a process ID, is used when multiprocess
39410 protocol extensions are enabled (@pxref{multiprocess extensions}), to
39411 detach only a specific process. The @var{pid} is specified as a
39412 big-endian hex string.
39422 @item F @var{RC},@var{EE},@var{CF};@var{XX}
39423 @cindex @samp{F} packet
39424 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
39425 This is part of the File-I/O protocol extension. @xref{File-I/O
39426 Remote Protocol Extension}, for the specification.
39429 @anchor{read registers packet}
39430 @cindex @samp{g} packet
39431 Read general registers.
39435 @item @var{XX@dots{}}
39436 Each byte of register data is described by two hex digits. The bytes
39437 with the register are transmitted in target byte order. The size of
39438 each register and their position within the @samp{g} packet are
39439 determined by the @value{GDBN} internal gdbarch functions
39440 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
39442 When reading registers from a trace frame (@pxref{Analyze Collected
39443 Data,,Using the Collected Data}), the stub may also return a string of
39444 literal @samp{x}'s in place of the register data digits, to indicate
39445 that the corresponding register has not been collected, thus its value
39446 is unavailable. For example, for an architecture with 4 registers of
39447 4 bytes each, the following reply indicates to @value{GDBN} that
39448 registers 0 and 2 have not been collected, while registers 1 and 3
39449 have been collected, and both have zero value:
39453 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
39460 @item G @var{XX@dots{}}
39461 @cindex @samp{G} packet
39462 Write general registers. @xref{read registers packet}, for a
39463 description of the @var{XX@dots{}} data.
39473 @item H @var{op} @var{thread-id}
39474 @cindex @samp{H} packet
39475 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
39476 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
39477 should be @samp{c} for step and continue operations (note that this
39478 is deprecated, supporting the @samp{vCont} command is a better
39479 option), and @samp{g} for other operations. The thread designator
39480 @var{thread-id} has the format and interpretation described in
39481 @ref{thread-id syntax}.
39492 @c 'H': How restrictive (or permissive) is the thread model. If a
39493 @c thread is selected and stopped, are other threads allowed
39494 @c to continue to execute? As I mentioned above, I think the
39495 @c semantics of each command when a thread is selected must be
39496 @c described. For example:
39498 @c 'g': If the stub supports threads and a specific thread is
39499 @c selected, returns the register block from that thread;
39500 @c otherwise returns current registers.
39502 @c 'G' If the stub supports threads and a specific thread is
39503 @c selected, sets the registers of the register block of
39504 @c that thread; otherwise sets current registers.
39506 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
39507 @anchor{cycle step packet}
39508 @cindex @samp{i} packet
39509 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
39510 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
39511 step starting at that address.
39514 @cindex @samp{I} packet
39515 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
39519 @cindex @samp{k} packet
39522 The exact effect of this packet is not specified.
39524 For a bare-metal target, it may power cycle or reset the target
39525 system. For that reason, the @samp{k} packet has no reply.
39527 For a single-process target, it may kill that process if possible.
39529 A multiple-process target may choose to kill just one process, or all
39530 that are under @value{GDBN}'s control. For more precise control, use
39531 the vKill packet (@pxref{vKill packet}).
39533 If the target system immediately closes the connection in response to
39534 @samp{k}, @value{GDBN} does not consider the lack of packet
39535 acknowledgment to be an error, and assumes the kill was successful.
39537 If connected using @kbd{target extended-remote}, and the target does
39538 not close the connection in response to a kill request, @value{GDBN}
39539 probes the target state as if a new connection was opened
39540 (@pxref{? packet}).
39542 @item m @var{addr},@var{length}
39543 @cindex @samp{m} packet
39544 Read @var{length} addressable memory units starting at address @var{addr}
39545 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
39546 any particular boundary.
39548 The stub need not use any particular size or alignment when gathering
39549 data from memory for the response; even if @var{addr} is word-aligned
39550 and @var{length} is a multiple of the word size, the stub is free to
39551 use byte accesses, or not. For this reason, this packet may not be
39552 suitable for accessing memory-mapped I/O devices.
39553 @cindex alignment of remote memory accesses
39554 @cindex size of remote memory accesses
39555 @cindex memory, alignment and size of remote accesses
39559 @item @var{XX@dots{}}
39560 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
39561 The reply may contain fewer addressable memory units than requested if the
39562 server was able to read only part of the region of memory.
39567 @item M @var{addr},@var{length}:@var{XX@dots{}}
39568 @cindex @samp{M} packet
39569 Write @var{length} addressable memory units starting at address @var{addr}
39570 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
39571 byte is transmitted as a two-digit hexadecimal number.
39578 for an error (this includes the case where only part of the data was
39583 @cindex @samp{p} packet
39584 Read the value of register @var{n}; @var{n} is in hex.
39585 @xref{read registers packet}, for a description of how the returned
39586 register value is encoded.
39590 @item @var{XX@dots{}}
39591 the register's value
39595 Indicating an unrecognized @var{query}.
39598 @item P @var{n@dots{}}=@var{r@dots{}}
39599 @anchor{write register packet}
39600 @cindex @samp{P} packet
39601 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
39602 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
39603 digits for each byte in the register (target byte order).
39613 @item q @var{name} @var{params}@dots{}
39614 @itemx Q @var{name} @var{params}@dots{}
39615 @cindex @samp{q} packet
39616 @cindex @samp{Q} packet
39617 General query (@samp{q}) and set (@samp{Q}). These packets are
39618 described fully in @ref{General Query Packets}.
39621 @cindex @samp{r} packet
39622 Reset the entire system.
39624 Don't use this packet; use the @samp{R} packet instead.
39627 @cindex @samp{R} packet
39628 Restart the program being debugged. The @var{XX}, while needed, is ignored.
39629 This packet is only available in extended mode (@pxref{extended mode}).
39631 The @samp{R} packet has no reply.
39633 @item s @r{[}@var{addr}@r{]}
39634 @cindex @samp{s} packet
39635 Single step, resuming at @var{addr}. If
39636 @var{addr} is omitted, resume at same address.
39638 This packet is deprecated for multi-threading support. @xref{vCont
39642 @xref{Stop Reply Packets}, for the reply specifications.
39644 @item S @var{sig}@r{[};@var{addr}@r{]}
39645 @anchor{step with signal packet}
39646 @cindex @samp{S} packet
39647 Step with signal. This is analogous to the @samp{C} packet, but
39648 requests a single-step, rather than a normal resumption of execution.
39650 This packet is deprecated for multi-threading support. @xref{vCont
39654 @xref{Stop Reply Packets}, for the reply specifications.
39656 @item t @var{addr}:@var{PP},@var{MM}
39657 @cindex @samp{t} packet
39658 Search backwards starting at address @var{addr} for a match with pattern
39659 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
39660 There must be at least 3 digits in @var{addr}.
39662 @item T @var{thread-id}
39663 @cindex @samp{T} packet
39664 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
39669 thread is still alive
39675 Packets starting with @samp{v} are identified by a multi-letter name,
39676 up to the first @samp{;} or @samp{?} (or the end of the packet).
39678 @item vAttach;@var{pid}
39679 @cindex @samp{vAttach} packet
39680 Attach to a new process with the specified process ID @var{pid}.
39681 The process ID is a
39682 hexadecimal integer identifying the process. In all-stop mode, all
39683 threads in the attached process are stopped; in non-stop mode, it may be
39684 attached without being stopped if that is supported by the target.
39686 @c In non-stop mode, on a successful vAttach, the stub should set the
39687 @c current thread to a thread of the newly-attached process. After
39688 @c attaching, GDB queries for the attached process's thread ID with qC.
39689 @c Also note that, from a user perspective, whether or not the
39690 @c target is stopped on attach in non-stop mode depends on whether you
39691 @c use the foreground or background version of the attach command, not
39692 @c on what vAttach does; GDB does the right thing with respect to either
39693 @c stopping or restarting threads.
39695 This packet is only available in extended mode (@pxref{extended mode}).
39701 @item @r{Any stop packet}
39702 for success in all-stop mode (@pxref{Stop Reply Packets})
39704 for success in non-stop mode (@pxref{Remote Non-Stop})
39707 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
39708 @cindex @samp{vCont} packet
39709 @anchor{vCont packet}
39710 Resume the inferior, specifying different actions for each thread.
39712 For each inferior thread, the leftmost action with a matching
39713 @var{thread-id} is applied. Threads that don't match any action
39714 remain in their current state. Thread IDs are specified using the
39715 syntax described in @ref{thread-id syntax}. If multiprocess
39716 extensions (@pxref{multiprocess extensions}) are supported, actions
39717 can be specified to match all threads in a process by using the
39718 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
39719 @var{thread-id} matches all threads. Specifying no actions is an
39722 Currently supported actions are:
39728 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
39732 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
39735 @item r @var{start},@var{end}
39736 Step once, and then keep stepping as long as the thread stops at
39737 addresses between @var{start} (inclusive) and @var{end} (exclusive).
39738 The remote stub reports a stop reply when either the thread goes out
39739 of the range or is stopped due to an unrelated reason, such as hitting
39740 a breakpoint. @xref{range stepping}.
39742 If the range is empty (@var{start} == @var{end}), then the action
39743 becomes equivalent to the @samp{s} action. In other words,
39744 single-step once, and report the stop (even if the stepped instruction
39745 jumps to @var{start}).
39747 (A stop reply may be sent at any point even if the PC is still within
39748 the stepping range; for example, it is valid to implement this packet
39749 in a degenerate way as a single instruction step operation.)
39753 The optional argument @var{addr} normally associated with the
39754 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
39755 not supported in @samp{vCont}.
39757 The @samp{t} action is only relevant in non-stop mode
39758 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
39759 A stop reply should be generated for any affected thread not already stopped.
39760 When a thread is stopped by means of a @samp{t} action,
39761 the corresponding stop reply should indicate that the thread has stopped with
39762 signal @samp{0}, regardless of whether the target uses some other signal
39763 as an implementation detail.
39765 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
39766 @samp{r} actions for threads that are already running. Conversely,
39767 the server must ignore @samp{t} actions for threads that are already
39770 @emph{Note:} In non-stop mode, a thread is considered running until
39771 @value{GDBN} acknowledges an asynchronous stop notification for it with
39772 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
39774 The stub must support @samp{vCont} if it reports support for
39775 multiprocess extensions (@pxref{multiprocess extensions}).
39778 @xref{Stop Reply Packets}, for the reply specifications.
39781 @cindex @samp{vCont?} packet
39782 Request a list of actions supported by the @samp{vCont} packet.
39786 @item vCont@r{[};@var{action}@dots{}@r{]}
39787 The @samp{vCont} packet is supported. Each @var{action} is a supported
39788 command in the @samp{vCont} packet.
39790 The @samp{vCont} packet is not supported.
39793 @anchor{vCtrlC packet}
39795 @cindex @samp{vCtrlC} packet
39796 Interrupt remote target as if a control-C was pressed on the remote
39797 terminal. This is the equivalent to reacting to the @code{^C}
39798 (@samp{\003}, the control-C character) character in all-stop mode
39799 while the target is running, except this works in non-stop mode.
39800 @xref{interrupting remote targets}, for more info on the all-stop
39811 @item vFile:@var{operation}:@var{parameter}@dots{}
39812 @cindex @samp{vFile} packet
39813 Perform a file operation on the target system. For details,
39814 see @ref{Host I/O Packets}.
39816 @item vFlashErase:@var{addr},@var{length}
39817 @cindex @samp{vFlashErase} packet
39818 Direct the stub to erase @var{length} bytes of flash starting at
39819 @var{addr}. The region may enclose any number of flash blocks, but
39820 its start and end must fall on block boundaries, as indicated by the
39821 flash block size appearing in the memory map (@pxref{Memory Map
39822 Format}). @value{GDBN} groups flash memory programming operations
39823 together, and sends a @samp{vFlashDone} request after each group; the
39824 stub is allowed to delay erase operation until the @samp{vFlashDone}
39825 packet is received.
39835 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
39836 @cindex @samp{vFlashWrite} packet
39837 Direct the stub to write data to flash address @var{addr}. The data
39838 is passed in binary form using the same encoding as for the @samp{X}
39839 packet (@pxref{Binary Data}). The memory ranges specified by
39840 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
39841 not overlap, and must appear in order of increasing addresses
39842 (although @samp{vFlashErase} packets for higher addresses may already
39843 have been received; the ordering is guaranteed only between
39844 @samp{vFlashWrite} packets). If a packet writes to an address that was
39845 neither erased by a preceding @samp{vFlashErase} packet nor by some other
39846 target-specific method, the results are unpredictable.
39854 for vFlashWrite addressing non-flash memory
39860 @cindex @samp{vFlashDone} packet
39861 Indicate to the stub that flash programming operation is finished.
39862 The stub is permitted to delay or batch the effects of a group of
39863 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
39864 @samp{vFlashDone} packet is received. The contents of the affected
39865 regions of flash memory are unpredictable until the @samp{vFlashDone}
39866 request is completed.
39868 @item vKill;@var{pid}
39869 @cindex @samp{vKill} packet
39870 @anchor{vKill packet}
39871 Kill the process with the specified process ID @var{pid}, which is a
39872 hexadecimal integer identifying the process. This packet is used in
39873 preference to @samp{k} when multiprocess protocol extensions are
39874 supported; see @ref{multiprocess extensions}.
39884 @item vMustReplyEmpty
39885 @cindex @samp{vMustReplyEmpty} packet
39886 The correct reply to an unknown @samp{v} packet is to return the empty
39887 string, however, some older versions of @command{gdbserver} would
39888 incorrectly return @samp{OK} for unknown @samp{v} packets.
39890 The @samp{vMustReplyEmpty} is used as a feature test to check how
39891 @command{gdbserver} handles unknown packets, it is important that this
39892 packet be handled in the same way as other unknown @samp{v} packets.
39893 If this packet is handled differently to other unknown @samp{v}
39894 packets then it is possible that @value{GDBN} may run into problems in
39895 other areas, specifically around use of @samp{vFile:setfs:}.
39897 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
39898 @cindex @samp{vRun} packet
39899 Run the program @var{filename}, passing it each @var{argument} on its
39900 command line. The file and arguments are hex-encoded strings. If
39901 @var{filename} is an empty string, the stub may use a default program
39902 (e.g.@: the last program run). The program is created in the stopped
39905 @c FIXME: What about non-stop mode?
39907 This packet is only available in extended mode (@pxref{extended mode}).
39913 @item @r{Any stop packet}
39914 for success (@pxref{Stop Reply Packets})
39918 @cindex @samp{vStopped} packet
39919 @xref{Notification Packets}.
39921 @item X @var{addr},@var{length}:@var{XX@dots{}}
39923 @cindex @samp{X} packet
39924 Write data to memory, where the data is transmitted in binary.
39925 Memory is specified by its address @var{addr} and number of addressable memory
39926 units @var{length} (@pxref{addressable memory unit});
39927 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
39937 @item z @var{type},@var{addr},@var{kind}
39938 @itemx Z @var{type},@var{addr},@var{kind}
39939 @anchor{insert breakpoint or watchpoint packet}
39940 @cindex @samp{z} packet
39941 @cindex @samp{Z} packets
39942 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
39943 watchpoint starting at address @var{address} of kind @var{kind}.
39945 Each breakpoint and watchpoint packet @var{type} is documented
39948 @emph{Implementation notes: A remote target shall return an empty string
39949 for an unrecognized breakpoint or watchpoint packet @var{type}. A
39950 remote target shall support either both or neither of a given
39951 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
39952 avoid potential problems with duplicate packets, the operations should
39953 be implemented in an idempotent way.}
39955 @item z0,@var{addr},@var{kind}
39956 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
39957 @cindex @samp{z0} packet
39958 @cindex @samp{Z0} packet
39959 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
39960 @var{addr} of type @var{kind}.
39962 A software breakpoint is implemented by replacing the instruction at
39963 @var{addr} with a software breakpoint or trap instruction. The
39964 @var{kind} is target-specific and typically indicates the size of the
39965 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
39966 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
39967 architectures have additional meanings for @var{kind}
39968 (@pxref{Architecture-Specific Protocol Details}); if no
39969 architecture-specific value is being used, it should be @samp{0}.
39970 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
39971 conditional expressions in bytecode form that should be evaluated on
39972 the target's side. These are the conditions that should be taken into
39973 consideration when deciding if the breakpoint trigger should be
39974 reported back to @value{GDBN}.
39976 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
39977 for how to best report a software breakpoint event to @value{GDBN}.
39979 The @var{cond_list} parameter is comprised of a series of expressions,
39980 concatenated without separators. Each expression has the following form:
39984 @item X @var{len},@var{expr}
39985 @var{len} is the length of the bytecode expression and @var{expr} is the
39986 actual conditional expression in bytecode form.
39990 The optional @var{cmd_list} parameter introduces commands that may be
39991 run on the target, rather than being reported back to @value{GDBN}.
39992 The parameter starts with a numeric flag @var{persist}; if the flag is
39993 nonzero, then the breakpoint may remain active and the commands
39994 continue to be run even when @value{GDBN} disconnects from the target.
39995 Following this flag is a series of expressions concatenated with no
39996 separators. Each expression has the following form:
40000 @item X @var{len},@var{expr}
40001 @var{len} is the length of the bytecode expression and @var{expr} is the
40002 actual commands expression in bytecode form.
40006 @emph{Implementation note: It is possible for a target to copy or move
40007 code that contains software breakpoints (e.g., when implementing
40008 overlays). The behavior of this packet, in the presence of such a
40009 target, is not defined.}
40021 @item z1,@var{addr},@var{kind}
40022 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
40023 @cindex @samp{z1} packet
40024 @cindex @samp{Z1} packet
40025 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
40026 address @var{addr}.
40028 A hardware breakpoint is implemented using a mechanism that is not
40029 dependent on being able to modify the target's memory. The
40030 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
40031 same meaning as in @samp{Z0} packets.
40033 @emph{Implementation note: A hardware breakpoint is not affected by code
40046 @item z2,@var{addr},@var{kind}
40047 @itemx Z2,@var{addr},@var{kind}
40048 @cindex @samp{z2} packet
40049 @cindex @samp{Z2} packet
40050 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
40051 The number of bytes to watch is specified by @var{kind}.
40063 @item z3,@var{addr},@var{kind}
40064 @itemx Z3,@var{addr},@var{kind}
40065 @cindex @samp{z3} packet
40066 @cindex @samp{Z3} packet
40067 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
40068 The number of bytes to watch is specified by @var{kind}.
40080 @item z4,@var{addr},@var{kind}
40081 @itemx Z4,@var{addr},@var{kind}
40082 @cindex @samp{z4} packet
40083 @cindex @samp{Z4} packet
40084 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
40085 The number of bytes to watch is specified by @var{kind}.
40099 @node Stop Reply Packets
40100 @section Stop Reply Packets
40101 @cindex stop reply packets
40103 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
40104 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
40105 receive any of the below as a reply. Except for @samp{?}
40106 and @samp{vStopped}, that reply is only returned
40107 when the target halts. In the below the exact meaning of @dfn{signal
40108 number} is defined by the header @file{include/gdb/signals.h} in the
40109 @value{GDBN} source code.
40111 In non-stop mode, the server will simply reply @samp{OK} to commands
40112 such as @samp{vCont}; any stop will be the subject of a future
40113 notification. @xref{Remote Non-Stop}.
40115 As in the description of request packets, we include spaces in the
40116 reply templates for clarity; these are not part of the reply packet's
40117 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
40123 The program received signal number @var{AA} (a two-digit hexadecimal
40124 number). This is equivalent to a @samp{T} response with no
40125 @var{n}:@var{r} pairs.
40127 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
40128 @cindex @samp{T} packet reply
40129 The program received signal number @var{AA} (a two-digit hexadecimal
40130 number). This is equivalent to an @samp{S} response, except that the
40131 @samp{@var{n}:@var{r}} pairs can carry values of important registers
40132 and other information directly in the stop reply packet, reducing
40133 round-trip latency. Single-step and breakpoint traps are reported
40134 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
40138 If @var{n} is a hexadecimal number, it is a register number, and the
40139 corresponding @var{r} gives that register's value. The data @var{r} is a
40140 series of bytes in target byte order, with each byte given by a
40141 two-digit hex number.
40144 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
40145 the stopped thread, as specified in @ref{thread-id syntax}.
40148 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
40149 the core on which the stop event was detected.
40152 If @var{n} is a recognized @dfn{stop reason}, it describes a more
40153 specific event that stopped the target. The currently defined stop
40154 reasons are listed below. The @var{aa} should be @samp{05}, the trap
40155 signal. At most one stop reason should be present.
40158 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
40159 and go on to the next; this allows us to extend the protocol in the
40163 The currently defined stop reasons are:
40169 The packet indicates a watchpoint hit, and @var{r} is the data address, in
40172 @item syscall_entry
40173 @itemx syscall_return
40174 The packet indicates a syscall entry or return, and @var{r} is the
40175 syscall number, in hex.
40177 @cindex shared library events, remote reply
40179 The packet indicates that the loaded libraries have changed.
40180 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
40181 list of loaded libraries. The @var{r} part is ignored.
40183 @cindex replay log events, remote reply
40185 The packet indicates that the target cannot continue replaying
40186 logged execution events, because it has reached the end (or the
40187 beginning when executing backward) of the log. The value of @var{r}
40188 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
40189 for more information.
40192 @anchor{swbreak stop reason}
40193 The packet indicates a software breakpoint instruction was executed,
40194 irrespective of whether it was @value{GDBN} that planted the
40195 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
40196 part must be left empty.
40198 On some architectures, such as x86, at the architecture level, when a
40199 breakpoint instruction executes the program counter points at the
40200 breakpoint address plus an offset. On such targets, the stub is
40201 responsible for adjusting the PC to point back at the breakpoint
40204 This packet should not be sent by default; older @value{GDBN} versions
40205 did not support it. @value{GDBN} requests it, by supplying an
40206 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40207 remote stub must also supply the appropriate @samp{qSupported} feature
40208 indicating support.
40210 This packet is required for correct non-stop mode operation.
40213 The packet indicates the target stopped for a hardware breakpoint.
40214 The @var{r} part must be left empty.
40216 The same remarks about @samp{qSupported} and non-stop mode above
40219 @cindex fork events, remote reply
40221 The packet indicates that @code{fork} was called, and @var{r}
40222 is the thread ID of the new child process. Refer to
40223 @ref{thread-id syntax} for the format of the @var{thread-id}
40224 field. This packet is only applicable to targets that support
40227 This packet should not be sent by default; older @value{GDBN} versions
40228 did not support it. @value{GDBN} requests it, by supplying an
40229 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40230 remote stub must also supply the appropriate @samp{qSupported} feature
40231 indicating support.
40233 @cindex vfork events, remote reply
40235 The packet indicates that @code{vfork} was called, and @var{r}
40236 is the thread ID of the new child process. Refer to
40237 @ref{thread-id syntax} for the format of the @var{thread-id}
40238 field. This packet is only applicable to targets that support
40241 This packet should not be sent by default; older @value{GDBN} versions
40242 did not support it. @value{GDBN} requests it, by supplying an
40243 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40244 remote stub must also supply the appropriate @samp{qSupported} feature
40245 indicating support.
40247 @cindex vforkdone events, remote reply
40249 The packet indicates that a child process created by a vfork
40250 has either called @code{exec} or terminated, so that the
40251 address spaces of the parent and child process are no longer
40252 shared. The @var{r} part is ignored. This packet is only
40253 applicable to targets that support vforkdone events.
40255 This packet should not be sent by default; older @value{GDBN} versions
40256 did not support it. @value{GDBN} requests it, by supplying an
40257 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40258 remote stub must also supply the appropriate @samp{qSupported} feature
40259 indicating support.
40261 @cindex exec events, remote reply
40263 The packet indicates that @code{execve} was called, and @var{r}
40264 is the absolute pathname of the file that was executed, in hex.
40265 This packet is only applicable to targets that support exec events.
40267 This packet should not be sent by default; older @value{GDBN} versions
40268 did not support it. @value{GDBN} requests it, by supplying an
40269 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
40270 remote stub must also supply the appropriate @samp{qSupported} feature
40271 indicating support.
40273 @cindex thread create event, remote reply
40274 @anchor{thread create event}
40276 The packet indicates that the thread was just created. The new thread
40277 is stopped until @value{GDBN} sets it running with a resumption packet
40278 (@pxref{vCont packet}). This packet should not be sent by default;
40279 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
40280 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
40281 @var{r} part is ignored.
40286 @itemx W @var{AA} ; process:@var{pid}
40287 The process exited, and @var{AA} is the exit status. This is only
40288 applicable to certain targets.
40290 The second form of the response, including the process ID of the
40291 exited process, can be used only when @value{GDBN} has reported
40292 support for multiprocess protocol extensions; see @ref{multiprocess
40293 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
40297 @itemx X @var{AA} ; process:@var{pid}
40298 The process terminated with signal @var{AA}.
40300 The second form of the response, including the process ID of the
40301 terminated process, can be used only when @value{GDBN} has reported
40302 support for multiprocess protocol extensions; see @ref{multiprocess
40303 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
40306 @anchor{thread exit event}
40307 @cindex thread exit event, remote reply
40308 @item w @var{AA} ; @var{tid}
40310 The thread exited, and @var{AA} is the exit status. This response
40311 should not be sent by default; @value{GDBN} requests it with the
40312 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
40313 @var{AA} is formatted as a big-endian hex string.
40316 There are no resumed threads left in the target. In other words, even
40317 though the process is alive, the last resumed thread has exited. For
40318 example, say the target process has two threads: thread 1 and thread
40319 2. The client leaves thread 1 stopped, and resumes thread 2, which
40320 subsequently exits. At this point, even though the process is still
40321 alive, and thus no @samp{W} stop reply is sent, no thread is actually
40322 executing either. The @samp{N} stop reply thus informs the client
40323 that it can stop waiting for stop replies. This packet should not be
40324 sent by default; older @value{GDBN} versions did not support it.
40325 @value{GDBN} requests it, by supplying an appropriate
40326 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
40327 also supply the appropriate @samp{qSupported} feature indicating
40330 @item O @var{XX}@dots{}
40331 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
40332 written as the program's console output. This can happen at any time
40333 while the program is running and the debugger should continue to wait
40334 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
40336 @item F @var{call-id},@var{parameter}@dots{}
40337 @var{call-id} is the identifier which says which host system call should
40338 be called. This is just the name of the function. Translation into the
40339 correct system call is only applicable as it's defined in @value{GDBN}.
40340 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
40343 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
40344 this very system call.
40346 The target replies with this packet when it expects @value{GDBN} to
40347 call a host system call on behalf of the target. @value{GDBN} replies
40348 with an appropriate @samp{F} packet and keeps up waiting for the next
40349 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
40350 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
40351 Protocol Extension}, for more details.
40355 @node General Query Packets
40356 @section General Query Packets
40357 @cindex remote query requests
40359 Packets starting with @samp{q} are @dfn{general query packets};
40360 packets starting with @samp{Q} are @dfn{general set packets}. General
40361 query and set packets are a semi-unified form for retrieving and
40362 sending information to and from the stub.
40364 The initial letter of a query or set packet is followed by a name
40365 indicating what sort of thing the packet applies to. For example,
40366 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
40367 definitions with the stub. These packet names follow some
40372 The name must not contain commas, colons or semicolons.
40374 Most @value{GDBN} query and set packets have a leading upper case
40377 The names of custom vendor packets should use a company prefix, in
40378 lower case, followed by a period. For example, packets designed at
40379 the Acme Corporation might begin with @samp{qacme.foo} (for querying
40380 foos) or @samp{Qacme.bar} (for setting bars).
40383 The name of a query or set packet should be separated from any
40384 parameters by a @samp{:}; the parameters themselves should be
40385 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
40386 full packet name, and check for a separator or the end of the packet,
40387 in case two packet names share a common prefix. New packets should not begin
40388 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
40389 packets predate these conventions, and have arguments without any terminator
40390 for the packet name; we suspect they are in widespread use in places that
40391 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
40392 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
40395 Like the descriptions of the other packets, each description here
40396 has a template showing the packet's overall syntax, followed by an
40397 explanation of the packet's meaning. We include spaces in some of the
40398 templates for clarity; these are not part of the packet's syntax. No
40399 @value{GDBN} packet uses spaces to separate its components.
40401 Here are the currently defined query and set packets:
40407 Turn on or off the agent as a helper to perform some debugging operations
40408 delegated from @value{GDBN} (@pxref{Control Agent}).
40410 @item QAllow:@var{op}:@var{val}@dots{}
40411 @cindex @samp{QAllow} packet
40412 Specify which operations @value{GDBN} expects to request of the
40413 target, as a semicolon-separated list of operation name and value
40414 pairs. Possible values for @var{op} include @samp{WriteReg},
40415 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
40416 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
40417 indicating that @value{GDBN} will not request the operation, or 1,
40418 indicating that it may. (The target can then use this to set up its
40419 own internals optimally, for instance if the debugger never expects to
40420 insert breakpoints, it may not need to install its own trap handler.)
40423 @cindex current thread, remote request
40424 @cindex @samp{qC} packet
40425 Return the current thread ID.
40429 @item QC @var{thread-id}
40430 Where @var{thread-id} is a thread ID as documented in
40431 @ref{thread-id syntax}.
40432 @item @r{(anything else)}
40433 Any other reply implies the old thread ID.
40436 @item qCRC:@var{addr},@var{length}
40437 @cindex CRC of memory block, remote request
40438 @cindex @samp{qCRC} packet
40439 @anchor{qCRC packet}
40440 Compute the CRC checksum of a block of memory using CRC-32 defined in
40441 IEEE 802.3. The CRC is computed byte at a time, taking the most
40442 significant bit of each byte first. The initial pattern code
40443 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
40445 @emph{Note:} This is the same CRC used in validating separate debug
40446 files (@pxref{Separate Debug Files, , Debugging Information in Separate
40447 Files}). However the algorithm is slightly different. When validating
40448 separate debug files, the CRC is computed taking the @emph{least}
40449 significant bit of each byte first, and the final result is inverted to
40450 detect trailing zeros.
40455 An error (such as memory fault)
40456 @item C @var{crc32}
40457 The specified memory region's checksum is @var{crc32}.
40460 @item QDisableRandomization:@var{value}
40461 @cindex disable address space randomization, remote request
40462 @cindex @samp{QDisableRandomization} packet
40463 Some target operating systems will randomize the virtual address space
40464 of the inferior process as a security feature, but provide a feature
40465 to disable such randomization, e.g.@: to allow for a more deterministic
40466 debugging experience. On such systems, this packet with a @var{value}
40467 of 1 directs the target to disable address space randomization for
40468 processes subsequently started via @samp{vRun} packets, while a packet
40469 with a @var{value} of 0 tells the target to enable address space
40472 This packet is only available in extended mode (@pxref{extended mode}).
40477 The request succeeded.
40480 An error occurred. The error number @var{nn} is given as hex digits.
40483 An empty reply indicates that @samp{QDisableRandomization} is not supported
40487 This packet is not probed by default; the remote stub must request it,
40488 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40489 This should only be done on targets that actually support disabling
40490 address space randomization.
40492 @item QStartupWithShell:@var{value}
40493 @cindex startup with shell, remote request
40494 @cindex @samp{QStartupWithShell} packet
40495 On UNIX-like targets, it is possible to start the inferior using a
40496 shell program. This is the default behavior on both @value{GDBN} and
40497 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
40498 used to inform @command{gdbserver} whether it should start the
40499 inferior using a shell or not.
40501 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
40502 to start the inferior. If @var{value} is @samp{1},
40503 @command{gdbserver} will use a shell to start the inferior. All other
40504 values are considered an error.
40506 This packet is only available in extended mode (@pxref{extended
40512 The request succeeded.
40515 An error occurred. The error number @var{nn} is given as hex digits.
40518 This packet is not probed by default; the remote stub must request it,
40519 by supplying an appropriate @samp{qSupported} response
40520 (@pxref{qSupported}). This should only be done on targets that
40521 actually support starting the inferior using a shell.
40523 Use of this packet is controlled by the @code{set startup-with-shell}
40524 command; @pxref{set startup-with-shell}.
40526 @item QEnvironmentHexEncoded:@var{hex-value}
40527 @anchor{QEnvironmentHexEncoded}
40528 @cindex set environment variable, remote request
40529 @cindex @samp{QEnvironmentHexEncoded} packet
40530 On UNIX-like targets, it is possible to set environment variables that
40531 will be passed to the inferior during the startup process. This
40532 packet is used to inform @command{gdbserver} of an environment
40533 variable that has been defined by the user on @value{GDBN} (@pxref{set
40536 The packet is composed by @var{hex-value}, an hex encoded
40537 representation of the @var{name=value} format representing an
40538 environment variable. The name of the environment variable is
40539 represented by @var{name}, and the value to be assigned to the
40540 environment variable is represented by @var{value}. If the variable
40541 has no value (i.e., the value is @code{null}), then @var{value} will
40544 This packet is only available in extended mode (@pxref{extended
40550 The request succeeded.
40553 This packet is not probed by default; the remote stub must request it,
40554 by supplying an appropriate @samp{qSupported} response
40555 (@pxref{qSupported}). This should only be done on targets that
40556 actually support passing environment variables to the starting
40559 This packet is related to the @code{set environment} command;
40560 @pxref{set environment}.
40562 @item QEnvironmentUnset:@var{hex-value}
40563 @anchor{QEnvironmentUnset}
40564 @cindex unset environment variable, remote request
40565 @cindex @samp{QEnvironmentUnset} packet
40566 On UNIX-like targets, it is possible to unset environment variables
40567 before starting the inferior in the remote target. This packet is
40568 used to inform @command{gdbserver} of an environment variable that has
40569 been unset by the user on @value{GDBN} (@pxref{unset environment}).
40571 The packet is composed by @var{hex-value}, an hex encoded
40572 representation of the name of the environment variable to be unset.
40574 This packet is only available in extended mode (@pxref{extended
40580 The request succeeded.
40583 This packet is not probed by default; the remote stub must request it,
40584 by supplying an appropriate @samp{qSupported} response
40585 (@pxref{qSupported}). This should only be done on targets that
40586 actually support passing environment variables to the starting
40589 This packet is related to the @code{unset environment} command;
40590 @pxref{unset environment}.
40592 @item QEnvironmentReset
40593 @anchor{QEnvironmentReset}
40594 @cindex reset environment, remote request
40595 @cindex @samp{QEnvironmentReset} packet
40596 On UNIX-like targets, this packet is used to reset the state of
40597 environment variables in the remote target before starting the
40598 inferior. In this context, reset means unsetting all environment
40599 variables that were previously set by the user (i.e., were not
40600 initially present in the environment). It is sent to
40601 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
40602 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
40603 (@pxref{QEnvironmentUnset}) packets.
40605 This packet is only available in extended mode (@pxref{extended
40611 The request succeeded.
40614 This packet is not probed by default; the remote stub must request it,
40615 by supplying an appropriate @samp{qSupported} response
40616 (@pxref{qSupported}). This should only be done on targets that
40617 actually support passing environment variables to the starting
40620 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
40621 @anchor{QSetWorkingDir packet}
40622 @cindex set working directory, remote request
40623 @cindex @samp{QSetWorkingDir} packet
40624 This packet is used to inform the remote server of the intended
40625 current working directory for programs that are going to be executed.
40627 The packet is composed by @var{directory}, an hex encoded
40628 representation of the directory that the remote inferior will use as
40629 its current working directory. If @var{directory} is an empty string,
40630 the remote server should reset the inferior's current working
40631 directory to its original, empty value.
40633 This packet is only available in extended mode (@pxref{extended
40639 The request succeeded.
40643 @itemx qsThreadInfo
40644 @cindex list active threads, remote request
40645 @cindex @samp{qfThreadInfo} packet
40646 @cindex @samp{qsThreadInfo} packet
40647 Obtain a list of all active thread IDs from the target (OS). Since there
40648 may be too many active threads to fit into one reply packet, this query
40649 works iteratively: it may require more than one query/reply sequence to
40650 obtain the entire list of threads. The first query of the sequence will
40651 be the @samp{qfThreadInfo} query; subsequent queries in the
40652 sequence will be the @samp{qsThreadInfo} query.
40654 NOTE: This packet replaces the @samp{qL} query (see below).
40658 @item m @var{thread-id}
40660 @item m @var{thread-id},@var{thread-id}@dots{}
40661 a comma-separated list of thread IDs
40663 (lower case letter @samp{L}) denotes end of list.
40666 In response to each query, the target will reply with a list of one or
40667 more thread IDs, separated by commas.
40668 @value{GDBN} will respond to each reply with a request for more thread
40669 ids (using the @samp{qs} form of the query), until the target responds
40670 with @samp{l} (lower-case ell, for @dfn{last}).
40671 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
40674 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
40675 initial connection with the remote target, and the very first thread ID
40676 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
40677 message. Therefore, the stub should ensure that the first thread ID in
40678 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
40680 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
40681 @cindex get thread-local storage address, remote request
40682 @cindex @samp{qGetTLSAddr} packet
40683 Fetch the address associated with thread local storage specified
40684 by @var{thread-id}, @var{offset}, and @var{lm}.
40686 @var{thread-id} is the thread ID associated with the
40687 thread for which to fetch the TLS address. @xref{thread-id syntax}.
40689 @var{offset} is the (big endian, hex encoded) offset associated with the
40690 thread local variable. (This offset is obtained from the debug
40691 information associated with the variable.)
40693 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
40694 load module associated with the thread local storage. For example,
40695 a @sc{gnu}/Linux system will pass the link map address of the shared
40696 object associated with the thread local storage under consideration.
40697 Other operating environments may choose to represent the load module
40698 differently, so the precise meaning of this parameter will vary.
40702 @item @var{XX}@dots{}
40703 Hex encoded (big endian) bytes representing the address of the thread
40704 local storage requested.
40707 An error occurred. The error number @var{nn} is given as hex digits.
40710 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
40713 @item qGetTIBAddr:@var{thread-id}
40714 @cindex get thread information block address
40715 @cindex @samp{qGetTIBAddr} packet
40716 Fetch address of the Windows OS specific Thread Information Block.
40718 @var{thread-id} is the thread ID associated with the thread.
40722 @item @var{XX}@dots{}
40723 Hex encoded (big endian) bytes representing the linear address of the
40724 thread information block.
40727 An error occured. This means that either the thread was not found, or the
40728 address could not be retrieved.
40731 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
40734 @item qL @var{startflag} @var{threadcount} @var{nextthread}
40735 Obtain thread information from RTOS. Where: @var{startflag} (one hex
40736 digit) is one to indicate the first query and zero to indicate a
40737 subsequent query; @var{threadcount} (two hex digits) is the maximum
40738 number of threads the response packet can contain; and @var{nextthread}
40739 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
40740 returned in the response as @var{argthread}.
40742 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
40746 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
40747 Where: @var{count} (two hex digits) is the number of threads being
40748 returned; @var{done} (one hex digit) is zero to indicate more threads
40749 and one indicates no further threads; @var{argthreadid} (eight hex
40750 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
40751 is a sequence of thread IDs, @var{threadid} (eight hex
40752 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
40756 @cindex section offsets, remote request
40757 @cindex @samp{qOffsets} packet
40758 Get section offsets that the target used when relocating the downloaded
40763 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
40764 Relocate the @code{Text} section by @var{xxx} from its original address.
40765 Relocate the @code{Data} section by @var{yyy} from its original address.
40766 If the object file format provides segment information (e.g.@: @sc{elf}
40767 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
40768 segments by the supplied offsets.
40770 @emph{Note: while a @code{Bss} offset may be included in the response,
40771 @value{GDBN} ignores this and instead applies the @code{Data} offset
40772 to the @code{Bss} section.}
40774 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
40775 Relocate the first segment of the object file, which conventionally
40776 contains program code, to a starting address of @var{xxx}. If
40777 @samp{DataSeg} is specified, relocate the second segment, which
40778 conventionally contains modifiable data, to a starting address of
40779 @var{yyy}. @value{GDBN} will report an error if the object file
40780 does not contain segment information, or does not contain at least
40781 as many segments as mentioned in the reply. Extra segments are
40782 kept at fixed offsets relative to the last relocated segment.
40785 @item qP @var{mode} @var{thread-id}
40786 @cindex thread information, remote request
40787 @cindex @samp{qP} packet
40788 Returns information on @var{thread-id}. Where: @var{mode} is a hex
40789 encoded 32 bit mode; @var{thread-id} is a thread ID
40790 (@pxref{thread-id syntax}).
40792 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
40795 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
40799 @cindex non-stop mode, remote request
40800 @cindex @samp{QNonStop} packet
40802 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
40803 @xref{Remote Non-Stop}, for more information.
40808 The request succeeded.
40811 An error occurred. The error number @var{nn} is given as hex digits.
40814 An empty reply indicates that @samp{QNonStop} is not supported by
40818 This packet is not probed by default; the remote stub must request it,
40819 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40820 Use of this packet is controlled by the @code{set non-stop} command;
40821 @pxref{Non-Stop Mode}.
40823 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
40824 @itemx QCatchSyscalls:0
40825 @cindex catch syscalls from inferior, remote request
40826 @cindex @samp{QCatchSyscalls} packet
40827 @anchor{QCatchSyscalls}
40828 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
40829 catching syscalls from the inferior process.
40831 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
40832 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
40833 is listed, every system call should be reported.
40835 Note that if a syscall not in the list is reported, @value{GDBN} will
40836 still filter the event according to its own list from all corresponding
40837 @code{catch syscall} commands. However, it is more efficient to only
40838 report the requested syscalls.
40840 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
40841 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
40843 If the inferior process execs, the state of @samp{QCatchSyscalls} is
40844 kept for the new process too. On targets where exec may affect syscall
40845 numbers, for example with exec between 32 and 64-bit processes, the
40846 client should send a new packet with the new syscall list.
40851 The request succeeded.
40854 An error occurred. @var{nn} are hex digits.
40857 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
40861 Use of this packet is controlled by the @code{set remote catch-syscalls}
40862 command (@pxref{Remote Configuration, set remote catch-syscalls}).
40863 This packet is not probed by default; the remote stub must request it,
40864 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40866 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
40867 @cindex pass signals to inferior, remote request
40868 @cindex @samp{QPassSignals} packet
40869 @anchor{QPassSignals}
40870 Each listed @var{signal} should be passed directly to the inferior process.
40871 Signals are numbered identically to continue packets and stop replies
40872 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
40873 strictly greater than the previous item. These signals do not need to stop
40874 the inferior, or be reported to @value{GDBN}. All other signals should be
40875 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
40876 combine; any earlier @samp{QPassSignals} list is completely replaced by the
40877 new list. This packet improves performance when using @samp{handle
40878 @var{signal} nostop noprint pass}.
40883 The request succeeded.
40886 An error occurred. The error number @var{nn} is given as hex digits.
40889 An empty reply indicates that @samp{QPassSignals} is not supported by
40893 Use of this packet is controlled by the @code{set remote pass-signals}
40894 command (@pxref{Remote Configuration, set remote pass-signals}).
40895 This packet is not probed by default; the remote stub must request it,
40896 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40898 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
40899 @cindex signals the inferior may see, remote request
40900 @cindex @samp{QProgramSignals} packet
40901 @anchor{QProgramSignals}
40902 Each listed @var{signal} may be delivered to the inferior process.
40903 Others should be silently discarded.
40905 In some cases, the remote stub may need to decide whether to deliver a
40906 signal to the program or not without @value{GDBN} involvement. One
40907 example of that is while detaching --- the program's threads may have
40908 stopped for signals that haven't yet had a chance of being reported to
40909 @value{GDBN}, and so the remote stub can use the signal list specified
40910 by this packet to know whether to deliver or ignore those pending
40913 This does not influence whether to deliver a signal as requested by a
40914 resumption packet (@pxref{vCont packet}).
40916 Signals are numbered identically to continue packets and stop replies
40917 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
40918 strictly greater than the previous item. Multiple
40919 @samp{QProgramSignals} packets do not combine; any earlier
40920 @samp{QProgramSignals} list is completely replaced by the new list.
40925 The request succeeded.
40928 An error occurred. The error number @var{nn} is given as hex digits.
40931 An empty reply indicates that @samp{QProgramSignals} is not supported
40935 Use of this packet is controlled by the @code{set remote program-signals}
40936 command (@pxref{Remote Configuration, set remote program-signals}).
40937 This packet is not probed by default; the remote stub must request it,
40938 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40940 @anchor{QThreadEvents}
40941 @item QThreadEvents:1
40942 @itemx QThreadEvents:0
40943 @cindex thread create/exit events, remote request
40944 @cindex @samp{QThreadEvents} packet
40946 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
40947 reporting of thread create and exit events. @xref{thread create
40948 event}, for the reply specifications. For example, this is used in
40949 non-stop mode when @value{GDBN} stops a set of threads and
40950 synchronously waits for the their corresponding stop replies. Without
40951 exit events, if one of the threads exits, @value{GDBN} would hang
40952 forever not knowing that it should no longer expect a stop for that
40953 same thread. @value{GDBN} does not enable this feature unless the
40954 stub reports that it supports it by including @samp{QThreadEvents+} in
40955 its @samp{qSupported} reply.
40960 The request succeeded.
40963 An error occurred. The error number @var{nn} is given as hex digits.
40966 An empty reply indicates that @samp{QThreadEvents} is not supported by
40970 Use of this packet is controlled by the @code{set remote thread-events}
40971 command (@pxref{Remote Configuration, set remote thread-events}).
40973 @item qRcmd,@var{command}
40974 @cindex execute remote command, remote request
40975 @cindex @samp{qRcmd} packet
40976 @var{command} (hex encoded) is passed to the local interpreter for
40977 execution. Invalid commands should be reported using the output
40978 string. Before the final result packet, the target may also respond
40979 with a number of intermediate @samp{O@var{output}} console output
40980 packets. @emph{Implementors should note that providing access to a
40981 stubs's interpreter may have security implications}.
40986 A command response with no output.
40988 A command response with the hex encoded output string @var{OUTPUT}.
40990 Indicate a badly formed request.
40992 An empty reply indicates that @samp{qRcmd} is not recognized.
40995 (Note that the @code{qRcmd} packet's name is separated from the
40996 command by a @samp{,}, not a @samp{:}, contrary to the naming
40997 conventions above. Please don't use this packet as a model for new
41000 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
41001 @cindex searching memory, in remote debugging
41003 @cindex @samp{qSearch:memory} packet
41005 @cindex @samp{qSearch memory} packet
41006 @anchor{qSearch memory}
41007 Search @var{length} bytes at @var{address} for @var{search-pattern}.
41008 Both @var{address} and @var{length} are encoded in hex;
41009 @var{search-pattern} is a sequence of bytes, also hex encoded.
41014 The pattern was not found.
41016 The pattern was found at @var{address}.
41018 A badly formed request or an error was encountered while searching memory.
41020 An empty reply indicates that @samp{qSearch:memory} is not recognized.
41023 @item QStartNoAckMode
41024 @cindex @samp{QStartNoAckMode} packet
41025 @anchor{QStartNoAckMode}
41026 Request that the remote stub disable the normal @samp{+}/@samp{-}
41027 protocol acknowledgments (@pxref{Packet Acknowledgment}).
41032 The stub has switched to no-acknowledgment mode.
41033 @value{GDBN} acknowledges this response,
41034 but neither the stub nor @value{GDBN} shall send or expect further
41035 @samp{+}/@samp{-} acknowledgments in the current connection.
41037 An empty reply indicates that the stub does not support no-acknowledgment mode.
41040 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
41041 @cindex supported packets, remote query
41042 @cindex features of the remote protocol
41043 @cindex @samp{qSupported} packet
41044 @anchor{qSupported}
41045 Tell the remote stub about features supported by @value{GDBN}, and
41046 query the stub for features it supports. This packet allows
41047 @value{GDBN} and the remote stub to take advantage of each others'
41048 features. @samp{qSupported} also consolidates multiple feature probes
41049 at startup, to improve @value{GDBN} performance---a single larger
41050 packet performs better than multiple smaller probe packets on
41051 high-latency links. Some features may enable behavior which must not
41052 be on by default, e.g.@: because it would confuse older clients or
41053 stubs. Other features may describe packets which could be
41054 automatically probed for, but are not. These features must be
41055 reported before @value{GDBN} will use them. This ``default
41056 unsupported'' behavior is not appropriate for all packets, but it
41057 helps to keep the initial connection time under control with new
41058 versions of @value{GDBN} which support increasing numbers of packets.
41062 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
41063 The stub supports or does not support each returned @var{stubfeature},
41064 depending on the form of each @var{stubfeature} (see below for the
41067 An empty reply indicates that @samp{qSupported} is not recognized,
41068 or that no features needed to be reported to @value{GDBN}.
41071 The allowed forms for each feature (either a @var{gdbfeature} in the
41072 @samp{qSupported} packet, or a @var{stubfeature} in the response)
41076 @item @var{name}=@var{value}
41077 The remote protocol feature @var{name} is supported, and associated
41078 with the specified @var{value}. The format of @var{value} depends
41079 on the feature, but it must not include a semicolon.
41081 The remote protocol feature @var{name} is supported, and does not
41082 need an associated value.
41084 The remote protocol feature @var{name} is not supported.
41086 The remote protocol feature @var{name} may be supported, and
41087 @value{GDBN} should auto-detect support in some other way when it is
41088 needed. This form will not be used for @var{gdbfeature} notifications,
41089 but may be used for @var{stubfeature} responses.
41092 Whenever the stub receives a @samp{qSupported} request, the
41093 supplied set of @value{GDBN} features should override any previous
41094 request. This allows @value{GDBN} to put the stub in a known
41095 state, even if the stub had previously been communicating with
41096 a different version of @value{GDBN}.
41098 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
41103 This feature indicates whether @value{GDBN} supports multiprocess
41104 extensions to the remote protocol. @value{GDBN} does not use such
41105 extensions unless the stub also reports that it supports them by
41106 including @samp{multiprocess+} in its @samp{qSupported} reply.
41107 @xref{multiprocess extensions}, for details.
41110 This feature indicates that @value{GDBN} supports the XML target
41111 description. If the stub sees @samp{xmlRegisters=} with target
41112 specific strings separated by a comma, it will report register
41116 This feature indicates whether @value{GDBN} supports the
41117 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
41118 instruction reply packet}).
41121 This feature indicates whether @value{GDBN} supports the swbreak stop
41122 reason in stop replies. @xref{swbreak stop reason}, for details.
41125 This feature indicates whether @value{GDBN} supports the hwbreak stop
41126 reason in stop replies. @xref{swbreak stop reason}, for details.
41129 This feature indicates whether @value{GDBN} supports fork event
41130 extensions to the remote protocol. @value{GDBN} does not use such
41131 extensions unless the stub also reports that it supports them by
41132 including @samp{fork-events+} in its @samp{qSupported} reply.
41135 This feature indicates whether @value{GDBN} supports vfork event
41136 extensions to the remote protocol. @value{GDBN} does not use such
41137 extensions unless the stub also reports that it supports them by
41138 including @samp{vfork-events+} in its @samp{qSupported} reply.
41141 This feature indicates whether @value{GDBN} supports exec event
41142 extensions to the remote protocol. @value{GDBN} does not use such
41143 extensions unless the stub also reports that it supports them by
41144 including @samp{exec-events+} in its @samp{qSupported} reply.
41146 @item vContSupported
41147 This feature indicates whether @value{GDBN} wants to know the
41148 supported actions in the reply to @samp{vCont?} packet.
41151 Stubs should ignore any unknown values for
41152 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
41153 packet supports receiving packets of unlimited length (earlier
41154 versions of @value{GDBN} may reject overly long responses). Additional values
41155 for @var{gdbfeature} may be defined in the future to let the stub take
41156 advantage of new features in @value{GDBN}, e.g.@: incompatible
41157 improvements in the remote protocol---the @samp{multiprocess} feature is
41158 an example of such a feature. The stub's reply should be independent
41159 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
41160 describes all the features it supports, and then the stub replies with
41161 all the features it supports.
41163 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
41164 responses, as long as each response uses one of the standard forms.
41166 Some features are flags. A stub which supports a flag feature
41167 should respond with a @samp{+} form response. Other features
41168 require values, and the stub should respond with an @samp{=}
41171 Each feature has a default value, which @value{GDBN} will use if
41172 @samp{qSupported} is not available or if the feature is not mentioned
41173 in the @samp{qSupported} response. The default values are fixed; a
41174 stub is free to omit any feature responses that match the defaults.
41176 Not all features can be probed, but for those which can, the probing
41177 mechanism is useful: in some cases, a stub's internal
41178 architecture may not allow the protocol layer to know some information
41179 about the underlying target in advance. This is especially common in
41180 stubs which may be configured for multiple targets.
41182 These are the currently defined stub features and their properties:
41184 @multitable @columnfractions 0.35 0.2 0.12 0.2
41185 @c NOTE: The first row should be @headitem, but we do not yet require
41186 @c a new enough version of Texinfo (4.7) to use @headitem.
41188 @tab Value Required
41192 @item @samp{PacketSize}
41197 @item @samp{qXfer:auxv:read}
41202 @item @samp{qXfer:btrace:read}
41207 @item @samp{qXfer:btrace-conf:read}
41212 @item @samp{qXfer:exec-file:read}
41217 @item @samp{qXfer:features:read}
41222 @item @samp{qXfer:libraries:read}
41227 @item @samp{qXfer:libraries-svr4:read}
41232 @item @samp{augmented-libraries-svr4-read}
41237 @item @samp{qXfer:memory-map:read}
41242 @item @samp{qXfer:sdata:read}
41247 @item @samp{qXfer:siginfo:read}
41252 @item @samp{qXfer:siginfo:write}
41257 @item @samp{qXfer:threads:read}
41262 @item @samp{qXfer:traceframe-info:read}
41267 @item @samp{qXfer:uib:read}
41272 @item @samp{qXfer:fdpic:read}
41277 @item @samp{Qbtrace:off}
41282 @item @samp{Qbtrace:bts}
41287 @item @samp{Qbtrace:pt}
41292 @item @samp{Qbtrace-conf:bts:size}
41297 @item @samp{Qbtrace-conf:pt:size}
41302 @item @samp{QNonStop}
41307 @item @samp{QCatchSyscalls}
41312 @item @samp{QPassSignals}
41317 @item @samp{QStartNoAckMode}
41322 @item @samp{multiprocess}
41327 @item @samp{ConditionalBreakpoints}
41332 @item @samp{ConditionalTracepoints}
41337 @item @samp{ReverseContinue}
41342 @item @samp{ReverseStep}
41347 @item @samp{TracepointSource}
41352 @item @samp{QAgent}
41357 @item @samp{QAllow}
41362 @item @samp{QDisableRandomization}
41367 @item @samp{EnableDisableTracepoints}
41372 @item @samp{QTBuffer:size}
41377 @item @samp{tracenz}
41382 @item @samp{BreakpointCommands}
41387 @item @samp{swbreak}
41392 @item @samp{hwbreak}
41397 @item @samp{fork-events}
41402 @item @samp{vfork-events}
41407 @item @samp{exec-events}
41412 @item @samp{QThreadEvents}
41417 @item @samp{no-resumed}
41424 These are the currently defined stub features, in more detail:
41427 @cindex packet size, remote protocol
41428 @item PacketSize=@var{bytes}
41429 The remote stub can accept packets up to at least @var{bytes} in
41430 length. @value{GDBN} will send packets up to this size for bulk
41431 transfers, and will never send larger packets. This is a limit on the
41432 data characters in the packet, including the frame and checksum.
41433 There is no trailing NUL byte in a remote protocol packet; if the stub
41434 stores packets in a NUL-terminated format, it should allow an extra
41435 byte in its buffer for the NUL. If this stub feature is not supported,
41436 @value{GDBN} guesses based on the size of the @samp{g} packet response.
41438 @item qXfer:auxv:read
41439 The remote stub understands the @samp{qXfer:auxv:read} packet
41440 (@pxref{qXfer auxiliary vector read}).
41442 @item qXfer:btrace:read
41443 The remote stub understands the @samp{qXfer:btrace:read}
41444 packet (@pxref{qXfer btrace read}).
41446 @item qXfer:btrace-conf:read
41447 The remote stub understands the @samp{qXfer:btrace-conf:read}
41448 packet (@pxref{qXfer btrace-conf read}).
41450 @item qXfer:exec-file:read
41451 The remote stub understands the @samp{qXfer:exec-file:read} packet
41452 (@pxref{qXfer executable filename read}).
41454 @item qXfer:features:read
41455 The remote stub understands the @samp{qXfer:features:read} packet
41456 (@pxref{qXfer target description read}).
41458 @item qXfer:libraries:read
41459 The remote stub understands the @samp{qXfer:libraries:read} packet
41460 (@pxref{qXfer library list read}).
41462 @item qXfer:libraries-svr4:read
41463 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
41464 (@pxref{qXfer svr4 library list read}).
41466 @item augmented-libraries-svr4-read
41467 The remote stub understands the augmented form of the
41468 @samp{qXfer:libraries-svr4:read} packet
41469 (@pxref{qXfer svr4 library list read}).
41471 @item qXfer:memory-map:read
41472 The remote stub understands the @samp{qXfer:memory-map:read} packet
41473 (@pxref{qXfer memory map read}).
41475 @item qXfer:sdata:read
41476 The remote stub understands the @samp{qXfer:sdata:read} packet
41477 (@pxref{qXfer sdata read}).
41479 @item qXfer:siginfo:read
41480 The remote stub understands the @samp{qXfer:siginfo:read} packet
41481 (@pxref{qXfer siginfo read}).
41483 @item qXfer:siginfo:write
41484 The remote stub understands the @samp{qXfer:siginfo:write} packet
41485 (@pxref{qXfer siginfo write}).
41487 @item qXfer:threads:read
41488 The remote stub understands the @samp{qXfer:threads:read} packet
41489 (@pxref{qXfer threads read}).
41491 @item qXfer:traceframe-info:read
41492 The remote stub understands the @samp{qXfer:traceframe-info:read}
41493 packet (@pxref{qXfer traceframe info read}).
41495 @item qXfer:uib:read
41496 The remote stub understands the @samp{qXfer:uib:read}
41497 packet (@pxref{qXfer unwind info block}).
41499 @item qXfer:fdpic:read
41500 The remote stub understands the @samp{qXfer:fdpic:read}
41501 packet (@pxref{qXfer fdpic loadmap read}).
41504 The remote stub understands the @samp{QNonStop} packet
41505 (@pxref{QNonStop}).
41507 @item QCatchSyscalls
41508 The remote stub understands the @samp{QCatchSyscalls} packet
41509 (@pxref{QCatchSyscalls}).
41512 The remote stub understands the @samp{QPassSignals} packet
41513 (@pxref{QPassSignals}).
41515 @item QStartNoAckMode
41516 The remote stub understands the @samp{QStartNoAckMode} packet and
41517 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
41520 @anchor{multiprocess extensions}
41521 @cindex multiprocess extensions, in remote protocol
41522 The remote stub understands the multiprocess extensions to the remote
41523 protocol syntax. The multiprocess extensions affect the syntax of
41524 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
41525 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
41526 replies. Note that reporting this feature indicates support for the
41527 syntactic extensions only, not that the stub necessarily supports
41528 debugging of more than one process at a time. The stub must not use
41529 multiprocess extensions in packet replies unless @value{GDBN} has also
41530 indicated it supports them in its @samp{qSupported} request.
41532 @item qXfer:osdata:read
41533 The remote stub understands the @samp{qXfer:osdata:read} packet
41534 ((@pxref{qXfer osdata read}).
41536 @item ConditionalBreakpoints
41537 The target accepts and implements evaluation of conditional expressions
41538 defined for breakpoints. The target will only report breakpoint triggers
41539 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
41541 @item ConditionalTracepoints
41542 The remote stub accepts and implements conditional expressions defined
41543 for tracepoints (@pxref{Tracepoint Conditions}).
41545 @item ReverseContinue
41546 The remote stub accepts and implements the reverse continue packet
41550 The remote stub accepts and implements the reverse step packet
41553 @item TracepointSource
41554 The remote stub understands the @samp{QTDPsrc} packet that supplies
41555 the source form of tracepoint definitions.
41558 The remote stub understands the @samp{QAgent} packet.
41561 The remote stub understands the @samp{QAllow} packet.
41563 @item QDisableRandomization
41564 The remote stub understands the @samp{QDisableRandomization} packet.
41566 @item StaticTracepoint
41567 @cindex static tracepoints, in remote protocol
41568 The remote stub supports static tracepoints.
41570 @item InstallInTrace
41571 @anchor{install tracepoint in tracing}
41572 The remote stub supports installing tracepoint in tracing.
41574 @item EnableDisableTracepoints
41575 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
41576 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
41577 to be enabled and disabled while a trace experiment is running.
41579 @item QTBuffer:size
41580 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
41581 packet that allows to change the size of the trace buffer.
41584 @cindex string tracing, in remote protocol
41585 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
41586 See @ref{Bytecode Descriptions} for details about the bytecode.
41588 @item BreakpointCommands
41589 @cindex breakpoint commands, in remote protocol
41590 The remote stub supports running a breakpoint's command list itself,
41591 rather than reporting the hit to @value{GDBN}.
41594 The remote stub understands the @samp{Qbtrace:off} packet.
41597 The remote stub understands the @samp{Qbtrace:bts} packet.
41600 The remote stub understands the @samp{Qbtrace:pt} packet.
41602 @item Qbtrace-conf:bts:size
41603 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
41605 @item Qbtrace-conf:pt:size
41606 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
41609 The remote stub reports the @samp{swbreak} stop reason for memory
41613 The remote stub reports the @samp{hwbreak} stop reason for hardware
41617 The remote stub reports the @samp{fork} stop reason for fork events.
41620 The remote stub reports the @samp{vfork} stop reason for vfork events
41621 and vforkdone events.
41624 The remote stub reports the @samp{exec} stop reason for exec events.
41626 @item vContSupported
41627 The remote stub reports the supported actions in the reply to
41628 @samp{vCont?} packet.
41630 @item QThreadEvents
41631 The remote stub understands the @samp{QThreadEvents} packet.
41634 The remote stub reports the @samp{N} stop reply.
41639 @cindex symbol lookup, remote request
41640 @cindex @samp{qSymbol} packet
41641 Notify the target that @value{GDBN} is prepared to serve symbol lookup
41642 requests. Accept requests from the target for the values of symbols.
41647 The target does not need to look up any (more) symbols.
41648 @item qSymbol:@var{sym_name}
41649 The target requests the value of symbol @var{sym_name} (hex encoded).
41650 @value{GDBN} may provide the value by using the
41651 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
41655 @item qSymbol:@var{sym_value}:@var{sym_name}
41656 Set the value of @var{sym_name} to @var{sym_value}.
41658 @var{sym_name} (hex encoded) is the name of a symbol whose value the
41659 target has previously requested.
41661 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
41662 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
41668 The target does not need to look up any (more) symbols.
41669 @item qSymbol:@var{sym_name}
41670 The target requests the value of a new symbol @var{sym_name} (hex
41671 encoded). @value{GDBN} will continue to supply the values of symbols
41672 (if available), until the target ceases to request them.
41677 @itemx QTDisconnected
41684 @itemx qTMinFTPILen
41686 @xref{Tracepoint Packets}.
41688 @item qThreadExtraInfo,@var{thread-id}
41689 @cindex thread attributes info, remote request
41690 @cindex @samp{qThreadExtraInfo} packet
41691 Obtain from the target OS a printable string description of thread
41692 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
41693 for the forms of @var{thread-id}. This
41694 string may contain anything that the target OS thinks is interesting
41695 for @value{GDBN} to tell the user about the thread. The string is
41696 displayed in @value{GDBN}'s @code{info threads} display. Some
41697 examples of possible thread extra info strings are @samp{Runnable}, or
41698 @samp{Blocked on Mutex}.
41702 @item @var{XX}@dots{}
41703 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
41704 comprising the printable string containing the extra information about
41705 the thread's attributes.
41708 (Note that the @code{qThreadExtraInfo} packet's name is separated from
41709 the command by a @samp{,}, not a @samp{:}, contrary to the naming
41710 conventions above. Please don't use this packet as a model for new
41729 @xref{Tracepoint Packets}.
41731 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
41732 @cindex read special object, remote request
41733 @cindex @samp{qXfer} packet
41734 @anchor{qXfer read}
41735 Read uninterpreted bytes from the target's special data area
41736 identified by the keyword @var{object}. Request @var{length} bytes
41737 starting at @var{offset} bytes into the data. The content and
41738 encoding of @var{annex} is specific to @var{object}; it can supply
41739 additional details about what data to access.
41744 Data @var{data} (@pxref{Binary Data}) has been read from the
41745 target. There may be more data at a higher address (although
41746 it is permitted to return @samp{m} even for the last valid
41747 block of data, as long as at least one byte of data was read).
41748 It is possible for @var{data} to have fewer bytes than the @var{length} in the
41752 Data @var{data} (@pxref{Binary Data}) has been read from the target.
41753 There is no more data to be read. It is possible for @var{data} to
41754 have fewer bytes than the @var{length} in the request.
41757 The @var{offset} in the request is at the end of the data.
41758 There is no more data to be read.
41761 The request was malformed, or @var{annex} was invalid.
41764 The offset was invalid, or there was an error encountered reading the data.
41765 The @var{nn} part is a hex-encoded @code{errno} value.
41768 An empty reply indicates the @var{object} string was not recognized by
41769 the stub, or that the object does not support reading.
41772 Here are the specific requests of this form defined so far. All the
41773 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
41774 formats, listed above.
41777 @item qXfer:auxv:read::@var{offset},@var{length}
41778 @anchor{qXfer auxiliary vector read}
41779 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
41780 auxiliary vector}. Note @var{annex} must be empty.
41782 This packet is not probed by default; the remote stub must request it,
41783 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41785 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
41786 @anchor{qXfer btrace read}
41788 Return a description of the current branch trace.
41789 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
41790 packet may have one of the following values:
41794 Returns all available branch trace.
41797 Returns all available branch trace if the branch trace changed since
41798 the last read request.
41801 Returns the new branch trace since the last read request. Adds a new
41802 block to the end of the trace that begins at zero and ends at the source
41803 location of the first branch in the trace buffer. This extra block is
41804 used to stitch traces together.
41806 If the trace buffer overflowed, returns an error indicating the overflow.
41809 This packet is not probed by default; the remote stub must request it
41810 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41812 @item qXfer:btrace-conf:read::@var{offset},@var{length}
41813 @anchor{qXfer btrace-conf read}
41815 Return a description of the current branch trace configuration.
41816 @xref{Branch Trace Configuration Format}.
41818 This packet is not probed by default; the remote stub must request it
41819 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41821 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
41822 @anchor{qXfer executable filename read}
41823 Return the full absolute name of the file that was executed to create
41824 a process running on the remote system. The annex specifies the
41825 numeric process ID of the process to query, encoded as a hexadecimal
41826 number. If the annex part is empty the remote stub should return the
41827 filename corresponding to the currently executing process.
41829 This packet is not probed by default; the remote stub must request it,
41830 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41832 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
41833 @anchor{qXfer target description read}
41834 Access the @dfn{target description}. @xref{Target Descriptions}. The
41835 annex specifies which XML document to access. The main description is
41836 always loaded from the @samp{target.xml} annex.
41838 This packet is not probed by default; the remote stub must request it,
41839 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41841 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
41842 @anchor{qXfer library list read}
41843 Access the target's list of loaded libraries. @xref{Library List Format}.
41844 The annex part of the generic @samp{qXfer} packet must be empty
41845 (@pxref{qXfer read}).
41847 Targets which maintain a list of libraries in the program's memory do
41848 not need to implement this packet; it is designed for platforms where
41849 the operating system manages the list of loaded libraries.
41851 This packet is not probed by default; the remote stub must request it,
41852 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41854 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
41855 @anchor{qXfer svr4 library list read}
41856 Access the target's list of loaded libraries when the target is an SVR4
41857 platform. @xref{Library List Format for SVR4 Targets}. The annex part
41858 of the generic @samp{qXfer} packet must be empty unless the remote
41859 stub indicated it supports the augmented form of this packet
41860 by supplying an appropriate @samp{qSupported} response
41861 (@pxref{qXfer read}, @ref{qSupported}).
41863 This packet is optional for better performance on SVR4 targets.
41864 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
41866 This packet is not probed by default; the remote stub must request it,
41867 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41869 If the remote stub indicates it supports the augmented form of this
41870 packet then the annex part of the generic @samp{qXfer} packet may
41871 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
41872 arguments. The currently supported arguments are:
41875 @item start=@var{address}
41876 A hexadecimal number specifying the address of the @samp{struct
41877 link_map} to start reading the library list from. If unset or zero
41878 then the first @samp{struct link_map} in the library list will be
41879 chosen as the starting point.
41881 @item prev=@var{address}
41882 A hexadecimal number specifying the address of the @samp{struct
41883 link_map} immediately preceding the @samp{struct link_map}
41884 specified by the @samp{start} argument. If unset or zero then
41885 the remote stub will expect that no @samp{struct link_map}
41886 exists prior to the starting point.
41890 Arguments that are not understood by the remote stub will be silently
41893 @item qXfer:memory-map:read::@var{offset},@var{length}
41894 @anchor{qXfer memory map read}
41895 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
41896 annex part of the generic @samp{qXfer} packet must be empty
41897 (@pxref{qXfer read}).
41899 This packet is not probed by default; the remote stub must request it,
41900 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41902 @item qXfer:sdata:read::@var{offset},@var{length}
41903 @anchor{qXfer sdata read}
41905 Read contents of the extra collected static tracepoint marker
41906 information. The annex part of the generic @samp{qXfer} packet must
41907 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
41910 This packet is not probed by default; the remote stub must request it,
41911 by supplying an appropriate @samp{qSupported} response
41912 (@pxref{qSupported}).
41914 @item qXfer:siginfo:read::@var{offset},@var{length}
41915 @anchor{qXfer siginfo read}
41916 Read contents of the extra signal information on the target
41917 system. The annex part of the generic @samp{qXfer} packet must be
41918 empty (@pxref{qXfer read}).
41920 This packet is not probed by default; the remote stub must request it,
41921 by supplying an appropriate @samp{qSupported} response
41922 (@pxref{qSupported}).
41924 @item qXfer:threads:read::@var{offset},@var{length}
41925 @anchor{qXfer threads read}
41926 Access the list of threads on target. @xref{Thread List Format}. The
41927 annex part of the generic @samp{qXfer} packet must be empty
41928 (@pxref{qXfer read}).
41930 This packet is not probed by default; the remote stub must request it,
41931 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41933 @item qXfer:traceframe-info:read::@var{offset},@var{length}
41934 @anchor{qXfer traceframe info read}
41936 Return a description of the current traceframe's contents.
41937 @xref{Traceframe Info Format}. The annex part of the generic
41938 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
41940 This packet is not probed by default; the remote stub must request it,
41941 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41943 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
41944 @anchor{qXfer unwind info block}
41946 Return the unwind information block for @var{pc}. This packet is used
41947 on OpenVMS/ia64 to ask the kernel unwind information.
41949 This packet is not probed by default.
41951 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
41952 @anchor{qXfer fdpic loadmap read}
41953 Read contents of @code{loadmap}s on the target system. The
41954 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
41955 executable @code{loadmap} or interpreter @code{loadmap} to read.
41957 This packet is not probed by default; the remote stub must request it,
41958 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41960 @item qXfer:osdata:read::@var{offset},@var{length}
41961 @anchor{qXfer osdata read}
41962 Access the target's @dfn{operating system information}.
41963 @xref{Operating System Information}.
41967 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
41968 @cindex write data into object, remote request
41969 @anchor{qXfer write}
41970 Write uninterpreted bytes into the target's special data area
41971 identified by the keyword @var{object}, starting at @var{offset} bytes
41972 into the data. The binary-encoded data (@pxref{Binary Data}) to be
41973 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
41974 is specific to @var{object}; it can supply additional details about what data
41980 @var{nn} (hex encoded) is the number of bytes written.
41981 This may be fewer bytes than supplied in the request.
41984 The request was malformed, or @var{annex} was invalid.
41987 The offset was invalid, or there was an error encountered writing the data.
41988 The @var{nn} part is a hex-encoded @code{errno} value.
41991 An empty reply indicates the @var{object} string was not
41992 recognized by the stub, or that the object does not support writing.
41995 Here are the specific requests of this form defined so far. All the
41996 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
41997 formats, listed above.
42000 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
42001 @anchor{qXfer siginfo write}
42002 Write @var{data} to the extra signal information on the target system.
42003 The annex part of the generic @samp{qXfer} packet must be
42004 empty (@pxref{qXfer write}).
42006 This packet is not probed by default; the remote stub must request it,
42007 by supplying an appropriate @samp{qSupported} response
42008 (@pxref{qSupported}).
42011 @item qXfer:@var{object}:@var{operation}:@dots{}
42012 Requests of this form may be added in the future. When a stub does
42013 not recognize the @var{object} keyword, or its support for
42014 @var{object} does not recognize the @var{operation} keyword, the stub
42015 must respond with an empty packet.
42017 @item qAttached:@var{pid}
42018 @cindex query attached, remote request
42019 @cindex @samp{qAttached} packet
42020 Return an indication of whether the remote server attached to an
42021 existing process or created a new process. When the multiprocess
42022 protocol extensions are supported (@pxref{multiprocess extensions}),
42023 @var{pid} is an integer in hexadecimal format identifying the target
42024 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
42025 the query packet will be simplified as @samp{qAttached}.
42027 This query is used, for example, to know whether the remote process
42028 should be detached or killed when a @value{GDBN} session is ended with
42029 the @code{quit} command.
42034 The remote server attached to an existing process.
42036 The remote server created a new process.
42038 A badly formed request or an error was encountered.
42042 Enable branch tracing for the current thread using Branch Trace Store.
42047 Branch tracing has been enabled.
42049 A badly formed request or an error was encountered.
42053 Enable branch tracing for the current thread using Intel Processor Trace.
42058 Branch tracing has been enabled.
42060 A badly formed request or an error was encountered.
42064 Disable branch tracing for the current thread.
42069 Branch tracing has been disabled.
42071 A badly formed request or an error was encountered.
42074 @item Qbtrace-conf:bts:size=@var{value}
42075 Set the requested ring buffer size for new threads that use the
42076 btrace recording method in bts format.
42081 The ring buffer size has been set.
42083 A badly formed request or an error was encountered.
42086 @item Qbtrace-conf:pt:size=@var{value}
42087 Set the requested ring buffer size for new threads that use the
42088 btrace recording method in pt format.
42093 The ring buffer size has been set.
42095 A badly formed request or an error was encountered.
42100 @node Architecture-Specific Protocol Details
42101 @section Architecture-Specific Protocol Details
42103 This section describes how the remote protocol is applied to specific
42104 target architectures. Also see @ref{Standard Target Features}, for
42105 details of XML target descriptions for each architecture.
42108 * ARM-Specific Protocol Details::
42109 * MIPS-Specific Protocol Details::
42112 @node ARM-Specific Protocol Details
42113 @subsection @acronym{ARM}-specific Protocol Details
42116 * ARM Breakpoint Kinds::
42119 @node ARM Breakpoint Kinds
42120 @subsubsection @acronym{ARM} Breakpoint Kinds
42121 @cindex breakpoint kinds, @acronym{ARM}
42123 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
42128 16-bit Thumb mode breakpoint.
42131 32-bit Thumb mode (Thumb-2) breakpoint.
42134 32-bit @acronym{ARM} mode breakpoint.
42138 @node MIPS-Specific Protocol Details
42139 @subsection @acronym{MIPS}-specific Protocol Details
42142 * MIPS Register packet Format::
42143 * MIPS Breakpoint Kinds::
42146 @node MIPS Register packet Format
42147 @subsubsection @acronym{MIPS} Register Packet Format
42148 @cindex register packet format, @acronym{MIPS}
42150 The following @code{g}/@code{G} packets have previously been defined.
42151 In the below, some thirty-two bit registers are transferred as
42152 sixty-four bits. Those registers should be zero/sign extended (which?)
42153 to fill the space allocated. Register bytes are transferred in target
42154 byte order. The two nibbles within a register byte are transferred
42155 most-significant -- least-significant.
42160 All registers are transferred as thirty-two bit quantities in the order:
42161 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
42162 registers; fsr; fir; fp.
42165 All registers are transferred as sixty-four bit quantities (including
42166 thirty-two bit registers such as @code{sr}). The ordering is the same
42171 @node MIPS Breakpoint Kinds
42172 @subsubsection @acronym{MIPS} Breakpoint Kinds
42173 @cindex breakpoint kinds, @acronym{MIPS}
42175 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
42180 16-bit @acronym{MIPS16} mode breakpoint.
42183 16-bit @acronym{microMIPS} mode breakpoint.
42186 32-bit standard @acronym{MIPS} mode breakpoint.
42189 32-bit @acronym{microMIPS} mode breakpoint.
42193 @node Tracepoint Packets
42194 @section Tracepoint Packets
42195 @cindex tracepoint packets
42196 @cindex packets, tracepoint
42198 Here we describe the packets @value{GDBN} uses to implement
42199 tracepoints (@pxref{Tracepoints}).
42203 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
42204 @cindex @samp{QTDP} packet
42205 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
42206 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
42207 the tracepoint is disabled. The @var{step} gives the tracepoint's step
42208 count, and @var{pass} gives its pass count. If an @samp{F} is present,
42209 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
42210 the number of bytes that the target should copy elsewhere to make room
42211 for the tracepoint. If an @samp{X} is present, it introduces a
42212 tracepoint condition, which consists of a hexadecimal length, followed
42213 by a comma and hex-encoded bytes, in a manner similar to action
42214 encodings as described below. If the trailing @samp{-} is present,
42215 further @samp{QTDP} packets will follow to specify this tracepoint's
42221 The packet was understood and carried out.
42223 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
42225 The packet was not recognized.
42228 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
42229 Define actions to be taken when a tracepoint is hit. The @var{n} and
42230 @var{addr} must be the same as in the initial @samp{QTDP} packet for
42231 this tracepoint. This packet may only be sent immediately after
42232 another @samp{QTDP} packet that ended with a @samp{-}. If the
42233 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
42234 specifying more actions for this tracepoint.
42236 In the series of action packets for a given tracepoint, at most one
42237 can have an @samp{S} before its first @var{action}. If such a packet
42238 is sent, it and the following packets define ``while-stepping''
42239 actions. Any prior packets define ordinary actions --- that is, those
42240 taken when the tracepoint is first hit. If no action packet has an
42241 @samp{S}, then all the packets in the series specify ordinary
42242 tracepoint actions.
42244 The @samp{@var{action}@dots{}} portion of the packet is a series of
42245 actions, concatenated without separators. Each action has one of the
42251 Collect the registers whose bits are set in @var{mask},
42252 a hexadecimal number whose @var{i}'th bit is set if register number
42253 @var{i} should be collected. (The least significant bit is numbered
42254 zero.) Note that @var{mask} may be any number of digits long; it may
42255 not fit in a 32-bit word.
42257 @item M @var{basereg},@var{offset},@var{len}
42258 Collect @var{len} bytes of memory starting at the address in register
42259 number @var{basereg}, plus @var{offset}. If @var{basereg} is
42260 @samp{-1}, then the range has a fixed address: @var{offset} is the
42261 address of the lowest byte to collect. The @var{basereg},
42262 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
42263 values (the @samp{-1} value for @var{basereg} is a special case).
42265 @item X @var{len},@var{expr}
42266 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
42267 it directs. The agent expression @var{expr} is as described in
42268 @ref{Agent Expressions}. Each byte of the expression is encoded as a
42269 two-digit hex number in the packet; @var{len} is the number of bytes
42270 in the expression (and thus one-half the number of hex digits in the
42275 Any number of actions may be packed together in a single @samp{QTDP}
42276 packet, as long as the packet does not exceed the maximum packet
42277 length (400 bytes, for many stubs). There may be only one @samp{R}
42278 action per tracepoint, and it must precede any @samp{M} or @samp{X}
42279 actions. Any registers referred to by @samp{M} and @samp{X} actions
42280 must be collected by a preceding @samp{R} action. (The
42281 ``while-stepping'' actions are treated as if they were attached to a
42282 separate tracepoint, as far as these restrictions are concerned.)
42287 The packet was understood and carried out.
42289 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
42291 The packet was not recognized.
42294 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
42295 @cindex @samp{QTDPsrc} packet
42296 Specify a source string of tracepoint @var{n} at address @var{addr}.
42297 This is useful to get accurate reproduction of the tracepoints
42298 originally downloaded at the beginning of the trace run. The @var{type}
42299 is the name of the tracepoint part, such as @samp{cond} for the
42300 tracepoint's conditional expression (see below for a list of types), while
42301 @var{bytes} is the string, encoded in hexadecimal.
42303 @var{start} is the offset of the @var{bytes} within the overall source
42304 string, while @var{slen} is the total length of the source string.
42305 This is intended for handling source strings that are longer than will
42306 fit in a single packet.
42307 @c Add detailed example when this info is moved into a dedicated
42308 @c tracepoint descriptions section.
42310 The available string types are @samp{at} for the location,
42311 @samp{cond} for the conditional, and @samp{cmd} for an action command.
42312 @value{GDBN} sends a separate packet for each command in the action
42313 list, in the same order in which the commands are stored in the list.
42315 The target does not need to do anything with source strings except
42316 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
42319 Although this packet is optional, and @value{GDBN} will only send it
42320 if the target replies with @samp{TracepointSource} @xref{General
42321 Query Packets}, it makes both disconnected tracing and trace files
42322 much easier to use. Otherwise the user must be careful that the
42323 tracepoints in effect while looking at trace frames are identical to
42324 the ones in effect during the trace run; even a small discrepancy
42325 could cause @samp{tdump} not to work, or a particular trace frame not
42328 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
42329 @cindex define trace state variable, remote request
42330 @cindex @samp{QTDV} packet
42331 Create a new trace state variable, number @var{n}, with an initial
42332 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
42333 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
42334 the option of not using this packet for initial values of zero; the
42335 target should simply create the trace state variables as they are
42336 mentioned in expressions. The value @var{builtin} should be 1 (one)
42337 if the trace state variable is builtin and 0 (zero) if it is not builtin.
42338 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
42339 @samp{qTsV} packet had it set. The contents of @var{name} is the
42340 hex-encoded name (without the leading @samp{$}) of the trace state
42343 @item QTFrame:@var{n}
42344 @cindex @samp{QTFrame} packet
42345 Select the @var{n}'th tracepoint frame from the buffer, and use the
42346 register and memory contents recorded there to answer subsequent
42347 request packets from @value{GDBN}.
42349 A successful reply from the stub indicates that the stub has found the
42350 requested frame. The response is a series of parts, concatenated
42351 without separators, describing the frame we selected. Each part has
42352 one of the following forms:
42356 The selected frame is number @var{n} in the trace frame buffer;
42357 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
42358 was no frame matching the criteria in the request packet.
42361 The selected trace frame records a hit of tracepoint number @var{t};
42362 @var{t} is a hexadecimal number.
42366 @item QTFrame:pc:@var{addr}
42367 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42368 currently selected frame whose PC is @var{addr};
42369 @var{addr} is a hexadecimal number.
42371 @item QTFrame:tdp:@var{t}
42372 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42373 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
42374 is a hexadecimal number.
42376 @item QTFrame:range:@var{start}:@var{end}
42377 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
42378 currently selected frame whose PC is between @var{start} (inclusive)
42379 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
42382 @item QTFrame:outside:@var{start}:@var{end}
42383 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
42384 frame @emph{outside} the given range of addresses (exclusive).
42387 @cindex @samp{qTMinFTPILen} packet
42388 This packet requests the minimum length of instruction at which a fast
42389 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
42390 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
42391 it depends on the target system being able to create trampolines in
42392 the first 64K of memory, which might or might not be possible for that
42393 system. So the reply to this packet will be 4 if it is able to
42400 The minimum instruction length is currently unknown.
42402 The minimum instruction length is @var{length}, where @var{length}
42403 is a hexadecimal number greater or equal to 1. A reply
42404 of 1 means that a fast tracepoint may be placed on any instruction
42405 regardless of size.
42407 An error has occurred.
42409 An empty reply indicates that the request is not supported by the stub.
42413 @cindex @samp{QTStart} packet
42414 Begin the tracepoint experiment. Begin collecting data from
42415 tracepoint hits in the trace frame buffer. This packet supports the
42416 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
42417 instruction reply packet}).
42420 @cindex @samp{QTStop} packet
42421 End the tracepoint experiment. Stop collecting trace frames.
42423 @item QTEnable:@var{n}:@var{addr}
42425 @cindex @samp{QTEnable} packet
42426 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
42427 experiment. If the tracepoint was previously disabled, then collection
42428 of data from it will resume.
42430 @item QTDisable:@var{n}:@var{addr}
42432 @cindex @samp{QTDisable} packet
42433 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
42434 experiment. No more data will be collected from the tracepoint unless
42435 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
42438 @cindex @samp{QTinit} packet
42439 Clear the table of tracepoints, and empty the trace frame buffer.
42441 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
42442 @cindex @samp{QTro} packet
42443 Establish the given ranges of memory as ``transparent''. The stub
42444 will answer requests for these ranges from memory's current contents,
42445 if they were not collected as part of the tracepoint hit.
42447 @value{GDBN} uses this to mark read-only regions of memory, like those
42448 containing program code. Since these areas never change, they should
42449 still have the same contents they did when the tracepoint was hit, so
42450 there's no reason for the stub to refuse to provide their contents.
42452 @item QTDisconnected:@var{value}
42453 @cindex @samp{QTDisconnected} packet
42454 Set the choice to what to do with the tracing run when @value{GDBN}
42455 disconnects from the target. A @var{value} of 1 directs the target to
42456 continue the tracing run, while 0 tells the target to stop tracing if
42457 @value{GDBN} is no longer in the picture.
42460 @cindex @samp{qTStatus} packet
42461 Ask the stub if there is a trace experiment running right now.
42463 The reply has the form:
42467 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
42468 @var{running} is a single digit @code{1} if the trace is presently
42469 running, or @code{0} if not. It is followed by semicolon-separated
42470 optional fields that an agent may use to report additional status.
42474 If the trace is not running, the agent may report any of several
42475 explanations as one of the optional fields:
42480 No trace has been run yet.
42482 @item tstop[:@var{text}]:0
42483 The trace was stopped by a user-originated stop command. The optional
42484 @var{text} field is a user-supplied string supplied as part of the
42485 stop command (for instance, an explanation of why the trace was
42486 stopped manually). It is hex-encoded.
42489 The trace stopped because the trace buffer filled up.
42491 @item tdisconnected:0
42492 The trace stopped because @value{GDBN} disconnected from the target.
42494 @item tpasscount:@var{tpnum}
42495 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
42497 @item terror:@var{text}:@var{tpnum}
42498 The trace stopped because tracepoint @var{tpnum} had an error. The
42499 string @var{text} is available to describe the nature of the error
42500 (for instance, a divide by zero in the condition expression); it
42504 The trace stopped for some other reason.
42508 Additional optional fields supply statistical and other information.
42509 Although not required, they are extremely useful for users monitoring
42510 the progress of a trace run. If a trace has stopped, and these
42511 numbers are reported, they must reflect the state of the just-stopped
42516 @item tframes:@var{n}
42517 The number of trace frames in the buffer.
42519 @item tcreated:@var{n}
42520 The total number of trace frames created during the run. This may
42521 be larger than the trace frame count, if the buffer is circular.
42523 @item tsize:@var{n}
42524 The total size of the trace buffer, in bytes.
42526 @item tfree:@var{n}
42527 The number of bytes still unused in the buffer.
42529 @item circular:@var{n}
42530 The value of the circular trace buffer flag. @code{1} means that the
42531 trace buffer is circular and old trace frames will be discarded if
42532 necessary to make room, @code{0} means that the trace buffer is linear
42535 @item disconn:@var{n}
42536 The value of the disconnected tracing flag. @code{1} means that
42537 tracing will continue after @value{GDBN} disconnects, @code{0} means
42538 that the trace run will stop.
42542 @item qTP:@var{tp}:@var{addr}
42543 @cindex tracepoint status, remote request
42544 @cindex @samp{qTP} packet
42545 Ask the stub for the current state of tracepoint number @var{tp} at
42546 address @var{addr}.
42550 @item V@var{hits}:@var{usage}
42551 The tracepoint has been hit @var{hits} times so far during the trace
42552 run, and accounts for @var{usage} in the trace buffer. Note that
42553 @code{while-stepping} steps are not counted as separate hits, but the
42554 steps' space consumption is added into the usage number.
42558 @item qTV:@var{var}
42559 @cindex trace state variable value, remote request
42560 @cindex @samp{qTV} packet
42561 Ask the stub for the value of the trace state variable number @var{var}.
42566 The value of the variable is @var{value}. This will be the current
42567 value of the variable if the user is examining a running target, or a
42568 saved value if the variable was collected in the trace frame that the
42569 user is looking at. Note that multiple requests may result in
42570 different reply values, such as when requesting values while the
42571 program is running.
42574 The value of the variable is unknown. This would occur, for example,
42575 if the user is examining a trace frame in which the requested variable
42580 @cindex @samp{qTfP} packet
42582 @cindex @samp{qTsP} packet
42583 These packets request data about tracepoints that are being used by
42584 the target. @value{GDBN} sends @code{qTfP} to get the first piece
42585 of data, and multiple @code{qTsP} to get additional pieces. Replies
42586 to these packets generally take the form of the @code{QTDP} packets
42587 that define tracepoints. (FIXME add detailed syntax)
42590 @cindex @samp{qTfV} packet
42592 @cindex @samp{qTsV} packet
42593 These packets request data about trace state variables that are on the
42594 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
42595 and multiple @code{qTsV} to get additional variables. Replies to
42596 these packets follow the syntax of the @code{QTDV} packets that define
42597 trace state variables.
42603 @cindex @samp{qTfSTM} packet
42604 @cindex @samp{qTsSTM} packet
42605 These packets request data about static tracepoint markers that exist
42606 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
42607 first piece of data, and multiple @code{qTsSTM} to get additional
42608 pieces. Replies to these packets take the following form:
42612 @item m @var{address}:@var{id}:@var{extra}
42614 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
42615 a comma-separated list of markers
42617 (lower case letter @samp{L}) denotes end of list.
42619 An error occurred. The error number @var{nn} is given as hex digits.
42621 An empty reply indicates that the request is not supported by the
42625 The @var{address} is encoded in hex;
42626 @var{id} and @var{extra} are strings encoded in hex.
42628 In response to each query, the target will reply with a list of one or
42629 more markers, separated by commas. @value{GDBN} will respond to each
42630 reply with a request for more markers (using the @samp{qs} form of the
42631 query), until the target responds with @samp{l} (lower-case ell, for
42634 @item qTSTMat:@var{address}
42636 @cindex @samp{qTSTMat} packet
42637 This packets requests data about static tracepoint markers in the
42638 target program at @var{address}. Replies to this packet follow the
42639 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
42640 tracepoint markers.
42642 @item QTSave:@var{filename}
42643 @cindex @samp{QTSave} packet
42644 This packet directs the target to save trace data to the file name
42645 @var{filename} in the target's filesystem. The @var{filename} is encoded
42646 as a hex string; the interpretation of the file name (relative vs
42647 absolute, wild cards, etc) is up to the target.
42649 @item qTBuffer:@var{offset},@var{len}
42650 @cindex @samp{qTBuffer} packet
42651 Return up to @var{len} bytes of the current contents of trace buffer,
42652 starting at @var{offset}. The trace buffer is treated as if it were
42653 a contiguous collection of traceframes, as per the trace file format.
42654 The reply consists as many hex-encoded bytes as the target can deliver
42655 in a packet; it is not an error to return fewer than were asked for.
42656 A reply consisting of just @code{l} indicates that no bytes are
42659 @item QTBuffer:circular:@var{value}
42660 This packet directs the target to use a circular trace buffer if
42661 @var{value} is 1, or a linear buffer if the value is 0.
42663 @item QTBuffer:size:@var{size}
42664 @anchor{QTBuffer-size}
42665 @cindex @samp{QTBuffer size} packet
42666 This packet directs the target to make the trace buffer be of size
42667 @var{size} if possible. A value of @code{-1} tells the target to
42668 use whatever size it prefers.
42670 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
42671 @cindex @samp{QTNotes} packet
42672 This packet adds optional textual notes to the trace run. Allowable
42673 types include @code{user}, @code{notes}, and @code{tstop}, the
42674 @var{text} fields are arbitrary strings, hex-encoded.
42678 @subsection Relocate instruction reply packet
42679 When installing fast tracepoints in memory, the target may need to
42680 relocate the instruction currently at the tracepoint address to a
42681 different address in memory. For most instructions, a simple copy is
42682 enough, but, for example, call instructions that implicitly push the
42683 return address on the stack, and relative branches or other
42684 PC-relative instructions require offset adjustment, so that the effect
42685 of executing the instruction at a different address is the same as if
42686 it had executed in the original location.
42688 In response to several of the tracepoint packets, the target may also
42689 respond with a number of intermediate @samp{qRelocInsn} request
42690 packets before the final result packet, to have @value{GDBN} handle
42691 this relocation operation. If a packet supports this mechanism, its
42692 documentation will explicitly say so. See for example the above
42693 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
42694 format of the request is:
42697 @item qRelocInsn:@var{from};@var{to}
42699 This requests @value{GDBN} to copy instruction at address @var{from}
42700 to address @var{to}, possibly adjusted so that executing the
42701 instruction at @var{to} has the same effect as executing it at
42702 @var{from}. @value{GDBN} writes the adjusted instruction to target
42703 memory starting at @var{to}.
42708 @item qRelocInsn:@var{adjusted_size}
42709 Informs the stub the relocation is complete. The @var{adjusted_size} is
42710 the length in bytes of resulting relocated instruction sequence.
42712 A badly formed request was detected, or an error was encountered while
42713 relocating the instruction.
42716 @node Host I/O Packets
42717 @section Host I/O Packets
42718 @cindex Host I/O, remote protocol
42719 @cindex file transfer, remote protocol
42721 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
42722 operations on the far side of a remote link. For example, Host I/O is
42723 used to upload and download files to a remote target with its own
42724 filesystem. Host I/O uses the same constant values and data structure
42725 layout as the target-initiated File-I/O protocol. However, the
42726 Host I/O packets are structured differently. The target-initiated
42727 protocol relies on target memory to store parameters and buffers.
42728 Host I/O requests are initiated by @value{GDBN}, and the
42729 target's memory is not involved. @xref{File-I/O Remote Protocol
42730 Extension}, for more details on the target-initiated protocol.
42732 The Host I/O request packets all encode a single operation along with
42733 its arguments. They have this format:
42737 @item vFile:@var{operation}: @var{parameter}@dots{}
42738 @var{operation} is the name of the particular request; the target
42739 should compare the entire packet name up to the second colon when checking
42740 for a supported operation. The format of @var{parameter} depends on
42741 the operation. Numbers are always passed in hexadecimal. Negative
42742 numbers have an explicit minus sign (i.e.@: two's complement is not
42743 used). Strings (e.g.@: filenames) are encoded as a series of
42744 hexadecimal bytes. The last argument to a system call may be a
42745 buffer of escaped binary data (@pxref{Binary Data}).
42749 The valid responses to Host I/O packets are:
42753 @item F @var{result} [, @var{errno}] [; @var{attachment}]
42754 @var{result} is the integer value returned by this operation, usually
42755 non-negative for success and -1 for errors. If an error has occured,
42756 @var{errno} will be included in the result specifying a
42757 value defined by the File-I/O protocol (@pxref{Errno Values}). For
42758 operations which return data, @var{attachment} supplies the data as a
42759 binary buffer. Binary buffers in response packets are escaped in the
42760 normal way (@pxref{Binary Data}). See the individual packet
42761 documentation for the interpretation of @var{result} and
42765 An empty response indicates that this operation is not recognized.
42769 These are the supported Host I/O operations:
42772 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
42773 Open a file at @var{filename} and return a file descriptor for it, or
42774 return -1 if an error occurs. The @var{filename} is a string,
42775 @var{flags} is an integer indicating a mask of open flags
42776 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
42777 of mode bits to use if the file is created (@pxref{mode_t Values}).
42778 @xref{open}, for details of the open flags and mode values.
42780 @item vFile:close: @var{fd}
42781 Close the open file corresponding to @var{fd} and return 0, or
42782 -1 if an error occurs.
42784 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
42785 Read data from the open file corresponding to @var{fd}. Up to
42786 @var{count} bytes will be read from the file, starting at @var{offset}
42787 relative to the start of the file. The target may read fewer bytes;
42788 common reasons include packet size limits and an end-of-file
42789 condition. The number of bytes read is returned. Zero should only be
42790 returned for a successful read at the end of the file, or if
42791 @var{count} was zero.
42793 The data read should be returned as a binary attachment on success.
42794 If zero bytes were read, the response should include an empty binary
42795 attachment (i.e.@: a trailing semicolon). The return value is the
42796 number of target bytes read; the binary attachment may be longer if
42797 some characters were escaped.
42799 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
42800 Write @var{data} (a binary buffer) to the open file corresponding
42801 to @var{fd}. Start the write at @var{offset} from the start of the
42802 file. Unlike many @code{write} system calls, there is no
42803 separate @var{count} argument; the length of @var{data} in the
42804 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
42805 which may be shorter than the length of @var{data}, or -1 if an
42808 @item vFile:fstat: @var{fd}
42809 Get information about the open file corresponding to @var{fd}.
42810 On success the information is returned as a binary attachment
42811 and the return value is the size of this attachment in bytes.
42812 If an error occurs the return value is -1. The format of the
42813 returned binary attachment is as described in @ref{struct stat}.
42815 @item vFile:unlink: @var{filename}
42816 Delete the file at @var{filename} on the target. Return 0,
42817 or -1 if an error occurs. The @var{filename} is a string.
42819 @item vFile:readlink: @var{filename}
42820 Read value of symbolic link @var{filename} on the target. Return
42821 the number of bytes read, or -1 if an error occurs.
42823 The data read should be returned as a binary attachment on success.
42824 If zero bytes were read, the response should include an empty binary
42825 attachment (i.e.@: a trailing semicolon). The return value is the
42826 number of target bytes read; the binary attachment may be longer if
42827 some characters were escaped.
42829 @item vFile:setfs: @var{pid}
42830 Select the filesystem on which @code{vFile} operations with
42831 @var{filename} arguments will operate. This is required for
42832 @value{GDBN} to be able to access files on remote targets where
42833 the remote stub does not share a common filesystem with the
42836 If @var{pid} is nonzero, select the filesystem as seen by process
42837 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
42838 the remote stub. Return 0 on success, or -1 if an error occurs.
42839 If @code{vFile:setfs:} indicates success, the selected filesystem
42840 remains selected until the next successful @code{vFile:setfs:}
42846 @section Interrupts
42847 @cindex interrupts (remote protocol)
42848 @anchor{interrupting remote targets}
42850 In all-stop mode, when a program on the remote target is running,
42851 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
42852 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
42853 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
42855 The precise meaning of @code{BREAK} is defined by the transport
42856 mechanism and may, in fact, be undefined. @value{GDBN} does not
42857 currently define a @code{BREAK} mechanism for any of the network
42858 interfaces except for TCP, in which case @value{GDBN} sends the
42859 @code{telnet} BREAK sequence.
42861 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
42862 transport mechanisms. It is represented by sending the single byte
42863 @code{0x03} without any of the usual packet overhead described in
42864 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
42865 transmitted as part of a packet, it is considered to be packet data
42866 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
42867 (@pxref{X packet}), used for binary downloads, may include an unescaped
42868 @code{0x03} as part of its packet.
42870 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
42871 When Linux kernel receives this sequence from serial port,
42872 it stops execution and connects to gdb.
42874 In non-stop mode, because packet resumptions are asynchronous
42875 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
42876 command to the remote stub, even when the target is running. For that
42877 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
42878 packet}) with the usual packet framing instead of the single byte
42881 Stubs are not required to recognize these interrupt mechanisms and the
42882 precise meaning associated with receipt of the interrupt is
42883 implementation defined. If the target supports debugging of multiple
42884 threads and/or processes, it should attempt to interrupt all
42885 currently-executing threads and processes.
42886 If the stub is successful at interrupting the
42887 running program, it should send one of the stop
42888 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
42889 of successfully stopping the program in all-stop mode, and a stop reply
42890 for each stopped thread in non-stop mode.
42891 Interrupts received while the
42892 program is stopped are queued and the program will be interrupted when
42893 it is resumed next time.
42895 @node Notification Packets
42896 @section Notification Packets
42897 @cindex notification packets
42898 @cindex packets, notification
42900 The @value{GDBN} remote serial protocol includes @dfn{notifications},
42901 packets that require no acknowledgment. Both the GDB and the stub
42902 may send notifications (although the only notifications defined at
42903 present are sent by the stub). Notifications carry information
42904 without incurring the round-trip latency of an acknowledgment, and so
42905 are useful for low-impact communications where occasional packet loss
42908 A notification packet has the form @samp{% @var{data} #
42909 @var{checksum}}, where @var{data} is the content of the notification,
42910 and @var{checksum} is a checksum of @var{data}, computed and formatted
42911 as for ordinary @value{GDBN} packets. A notification's @var{data}
42912 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
42913 receiving a notification, the recipient sends no @samp{+} or @samp{-}
42914 to acknowledge the notification's receipt or to report its corruption.
42916 Every notification's @var{data} begins with a name, which contains no
42917 colon characters, followed by a colon character.
42919 Recipients should silently ignore corrupted notifications and
42920 notifications they do not understand. Recipients should restart
42921 timeout periods on receipt of a well-formed notification, whether or
42922 not they understand it.
42924 Senders should only send the notifications described here when this
42925 protocol description specifies that they are permitted. In the
42926 future, we may extend the protocol to permit existing notifications in
42927 new contexts; this rule helps older senders avoid confusing newer
42930 (Older versions of @value{GDBN} ignore bytes received until they see
42931 the @samp{$} byte that begins an ordinary packet, so new stubs may
42932 transmit notifications without fear of confusing older clients. There
42933 are no notifications defined for @value{GDBN} to send at the moment, but we
42934 assume that most older stubs would ignore them, as well.)
42936 Each notification is comprised of three parts:
42938 @item @var{name}:@var{event}
42939 The notification packet is sent by the side that initiates the
42940 exchange (currently, only the stub does that), with @var{event}
42941 carrying the specific information about the notification, and
42942 @var{name} specifying the name of the notification.
42944 The acknowledge sent by the other side, usually @value{GDBN}, to
42945 acknowledge the exchange and request the event.
42948 The purpose of an asynchronous notification mechanism is to report to
42949 @value{GDBN} that something interesting happened in the remote stub.
42951 The remote stub may send notification @var{name}:@var{event}
42952 at any time, but @value{GDBN} acknowledges the notification when
42953 appropriate. The notification event is pending before @value{GDBN}
42954 acknowledges. Only one notification at a time may be pending; if
42955 additional events occur before @value{GDBN} has acknowledged the
42956 previous notification, they must be queued by the stub for later
42957 synchronous transmission in response to @var{ack} packets from
42958 @value{GDBN}. Because the notification mechanism is unreliable,
42959 the stub is permitted to resend a notification if it believes
42960 @value{GDBN} may not have received it.
42962 Specifically, notifications may appear when @value{GDBN} is not
42963 otherwise reading input from the stub, or when @value{GDBN} is
42964 expecting to read a normal synchronous response or a
42965 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
42966 Notification packets are distinct from any other communication from
42967 the stub so there is no ambiguity.
42969 After receiving a notification, @value{GDBN} shall acknowledge it by
42970 sending a @var{ack} packet as a regular, synchronous request to the
42971 stub. Such acknowledgment is not required to happen immediately, as
42972 @value{GDBN} is permitted to send other, unrelated packets to the
42973 stub first, which the stub should process normally.
42975 Upon receiving a @var{ack} packet, if the stub has other queued
42976 events to report to @value{GDBN}, it shall respond by sending a
42977 normal @var{event}. @value{GDBN} shall then send another @var{ack}
42978 packet to solicit further responses; again, it is permitted to send
42979 other, unrelated packets as well which the stub should process
42982 If the stub receives a @var{ack} packet and there are no additional
42983 @var{event} to report, the stub shall return an @samp{OK} response.
42984 At this point, @value{GDBN} has finished processing a notification
42985 and the stub has completed sending any queued events. @value{GDBN}
42986 won't accept any new notifications until the final @samp{OK} is
42987 received . If further notification events occur, the stub shall send
42988 a new notification, @value{GDBN} shall accept the notification, and
42989 the process shall be repeated.
42991 The process of asynchronous notification can be illustrated by the
42994 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
42997 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
42999 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
43004 The following notifications are defined:
43005 @multitable @columnfractions 0.12 0.12 0.38 0.38
43014 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
43015 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
43016 for information on how these notifications are acknowledged by
43018 @tab Report an asynchronous stop event in non-stop mode.
43022 @node Remote Non-Stop
43023 @section Remote Protocol Support for Non-Stop Mode
43025 @value{GDBN}'s remote protocol supports non-stop debugging of
43026 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
43027 supports non-stop mode, it should report that to @value{GDBN} by including
43028 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
43030 @value{GDBN} typically sends a @samp{QNonStop} packet only when
43031 establishing a new connection with the stub. Entering non-stop mode
43032 does not alter the state of any currently-running threads, but targets
43033 must stop all threads in any already-attached processes when entering
43034 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
43035 probe the target state after a mode change.
43037 In non-stop mode, when an attached process encounters an event that
43038 would otherwise be reported with a stop reply, it uses the
43039 asynchronous notification mechanism (@pxref{Notification Packets}) to
43040 inform @value{GDBN}. In contrast to all-stop mode, where all threads
43041 in all processes are stopped when a stop reply is sent, in non-stop
43042 mode only the thread reporting the stop event is stopped. That is,
43043 when reporting a @samp{S} or @samp{T} response to indicate completion
43044 of a step operation, hitting a breakpoint, or a fault, only the
43045 affected thread is stopped; any other still-running threads continue
43046 to run. When reporting a @samp{W} or @samp{X} response, all running
43047 threads belonging to other attached processes continue to run.
43049 In non-stop mode, the target shall respond to the @samp{?} packet as
43050 follows. First, any incomplete stop reply notification/@samp{vStopped}
43051 sequence in progress is abandoned. The target must begin a new
43052 sequence reporting stop events for all stopped threads, whether or not
43053 it has previously reported those events to @value{GDBN}. The first
43054 stop reply is sent as a synchronous reply to the @samp{?} packet, and
43055 subsequent stop replies are sent as responses to @samp{vStopped} packets
43056 using the mechanism described above. The target must not send
43057 asynchronous stop reply notifications until the sequence is complete.
43058 If all threads are running when the target receives the @samp{?} packet,
43059 or if the target is not attached to any process, it shall respond
43062 If the stub supports non-stop mode, it should also support the
43063 @samp{swbreak} stop reason if software breakpoints are supported, and
43064 the @samp{hwbreak} stop reason if hardware breakpoints are supported
43065 (@pxref{swbreak stop reason}). This is because given the asynchronous
43066 nature of non-stop mode, between the time a thread hits a breakpoint
43067 and the time the event is finally processed by @value{GDBN}, the
43068 breakpoint may have already been removed from the target. Due to
43069 this, @value{GDBN} needs to be able to tell whether a trap stop was
43070 caused by a delayed breakpoint event, which should be ignored, as
43071 opposed to a random trap signal, which should be reported to the user.
43072 Note the @samp{swbreak} feature implies that the target is responsible
43073 for adjusting the PC when a software breakpoint triggers, if
43074 necessary, such as on the x86 architecture.
43076 @node Packet Acknowledgment
43077 @section Packet Acknowledgment
43079 @cindex acknowledgment, for @value{GDBN} remote
43080 @cindex packet acknowledgment, for @value{GDBN} remote
43081 By default, when either the host or the target machine receives a packet,
43082 the first response expected is an acknowledgment: either @samp{+} (to indicate
43083 the package was received correctly) or @samp{-} (to request retransmission).
43084 This mechanism allows the @value{GDBN} remote protocol to operate over
43085 unreliable transport mechanisms, such as a serial line.
43087 In cases where the transport mechanism is itself reliable (such as a pipe or
43088 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
43089 It may be desirable to disable them in that case to reduce communication
43090 overhead, or for other reasons. This can be accomplished by means of the
43091 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
43093 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
43094 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
43095 and response format still includes the normal checksum, as described in
43096 @ref{Overview}, but the checksum may be ignored by the receiver.
43098 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
43099 no-acknowledgment mode, it should report that to @value{GDBN}
43100 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
43101 @pxref{qSupported}.
43102 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
43103 disabled via the @code{set remote noack-packet off} command
43104 (@pxref{Remote Configuration}),
43105 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
43106 Only then may the stub actually turn off packet acknowledgments.
43107 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
43108 response, which can be safely ignored by the stub.
43110 Note that @code{set remote noack-packet} command only affects negotiation
43111 between @value{GDBN} and the stub when subsequent connections are made;
43112 it does not affect the protocol acknowledgment state for any current
43114 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
43115 new connection is established,
43116 there is also no protocol request to re-enable the acknowledgments
43117 for the current connection, once disabled.
43122 Example sequence of a target being re-started. Notice how the restart
43123 does not get any direct output:
43128 @emph{target restarts}
43131 <- @code{T001:1234123412341234}
43135 Example sequence of a target being stepped by a single instruction:
43138 -> @code{G1445@dots{}}
43143 <- @code{T001:1234123412341234}
43147 <- @code{1455@dots{}}
43151 @node File-I/O Remote Protocol Extension
43152 @section File-I/O Remote Protocol Extension
43153 @cindex File-I/O remote protocol extension
43156 * File-I/O Overview::
43157 * Protocol Basics::
43158 * The F Request Packet::
43159 * The F Reply Packet::
43160 * The Ctrl-C Message::
43162 * List of Supported Calls::
43163 * Protocol-specific Representation of Datatypes::
43165 * File-I/O Examples::
43168 @node File-I/O Overview
43169 @subsection File-I/O Overview
43170 @cindex file-i/o overview
43172 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
43173 target to use the host's file system and console I/O to perform various
43174 system calls. System calls on the target system are translated into a
43175 remote protocol packet to the host system, which then performs the needed
43176 actions and returns a response packet to the target system.
43177 This simulates file system operations even on targets that lack file systems.
43179 The protocol is defined to be independent of both the host and target systems.
43180 It uses its own internal representation of datatypes and values. Both
43181 @value{GDBN} and the target's @value{GDBN} stub are responsible for
43182 translating the system-dependent value representations into the internal
43183 protocol representations when data is transmitted.
43185 The communication is synchronous. A system call is possible only when
43186 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
43187 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
43188 the target is stopped to allow deterministic access to the target's
43189 memory. Therefore File-I/O is not interruptible by target signals. On
43190 the other hand, it is possible to interrupt File-I/O by a user interrupt
43191 (@samp{Ctrl-C}) within @value{GDBN}.
43193 The target's request to perform a host system call does not finish
43194 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
43195 after finishing the system call, the target returns to continuing the
43196 previous activity (continue, step). No additional continue or step
43197 request from @value{GDBN} is required.
43200 (@value{GDBP}) continue
43201 <- target requests 'system call X'
43202 target is stopped, @value{GDBN} executes system call
43203 -> @value{GDBN} returns result
43204 ... target continues, @value{GDBN} returns to wait for the target
43205 <- target hits breakpoint and sends a Txx packet
43208 The protocol only supports I/O on the console and to regular files on
43209 the host file system. Character or block special devices, pipes,
43210 named pipes, sockets or any other communication method on the host
43211 system are not supported by this protocol.
43213 File I/O is not supported in non-stop mode.
43215 @node Protocol Basics
43216 @subsection Protocol Basics
43217 @cindex protocol basics, file-i/o
43219 The File-I/O protocol uses the @code{F} packet as the request as well
43220 as reply packet. Since a File-I/O system call can only occur when
43221 @value{GDBN} is waiting for a response from the continuing or stepping target,
43222 the File-I/O request is a reply that @value{GDBN} has to expect as a result
43223 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
43224 This @code{F} packet contains all information needed to allow @value{GDBN}
43225 to call the appropriate host system call:
43229 A unique identifier for the requested system call.
43232 All parameters to the system call. Pointers are given as addresses
43233 in the target memory address space. Pointers to strings are given as
43234 pointer/length pair. Numerical values are given as they are.
43235 Numerical control flags are given in a protocol-specific representation.
43239 At this point, @value{GDBN} has to perform the following actions.
43243 If the parameters include pointer values to data needed as input to a
43244 system call, @value{GDBN} requests this data from the target with a
43245 standard @code{m} packet request. This additional communication has to be
43246 expected by the target implementation and is handled as any other @code{m}
43250 @value{GDBN} translates all value from protocol representation to host
43251 representation as needed. Datatypes are coerced into the host types.
43254 @value{GDBN} calls the system call.
43257 It then coerces datatypes back to protocol representation.
43260 If the system call is expected to return data in buffer space specified
43261 by pointer parameters to the call, the data is transmitted to the
43262 target using a @code{M} or @code{X} packet. This packet has to be expected
43263 by the target implementation and is handled as any other @code{M} or @code{X}
43268 Eventually @value{GDBN} replies with another @code{F} packet which contains all
43269 necessary information for the target to continue. This at least contains
43276 @code{errno}, if has been changed by the system call.
43283 After having done the needed type and value coercion, the target continues
43284 the latest continue or step action.
43286 @node The F Request Packet
43287 @subsection The @code{F} Request Packet
43288 @cindex file-i/o request packet
43289 @cindex @code{F} request packet
43291 The @code{F} request packet has the following format:
43294 @item F@var{call-id},@var{parameter@dots{}}
43296 @var{call-id} is the identifier to indicate the host system call to be called.
43297 This is just the name of the function.
43299 @var{parameter@dots{}} are the parameters to the system call.
43300 Parameters are hexadecimal integer values, either the actual values in case
43301 of scalar datatypes, pointers to target buffer space in case of compound
43302 datatypes and unspecified memory areas, or pointer/length pairs in case
43303 of string parameters. These are appended to the @var{call-id} as a
43304 comma-delimited list. All values are transmitted in ASCII
43305 string representation, pointer/length pairs separated by a slash.
43311 @node The F Reply Packet
43312 @subsection The @code{F} Reply Packet
43313 @cindex file-i/o reply packet
43314 @cindex @code{F} reply packet
43316 The @code{F} reply packet has the following format:
43320 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
43322 @var{retcode} is the return code of the system call as hexadecimal value.
43324 @var{errno} is the @code{errno} set by the call, in protocol-specific
43326 This parameter can be omitted if the call was successful.
43328 @var{Ctrl-C flag} is only sent if the user requested a break. In this
43329 case, @var{errno} must be sent as well, even if the call was successful.
43330 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
43337 or, if the call was interrupted before the host call has been performed:
43344 assuming 4 is the protocol-specific representation of @code{EINTR}.
43349 @node The Ctrl-C Message
43350 @subsection The @samp{Ctrl-C} Message
43351 @cindex ctrl-c message, in file-i/o protocol
43353 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
43354 reply packet (@pxref{The F Reply Packet}),
43355 the target should behave as if it had
43356 gotten a break message. The meaning for the target is ``system call
43357 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
43358 (as with a break message) and return to @value{GDBN} with a @code{T02}
43361 It's important for the target to know in which
43362 state the system call was interrupted. There are two possible cases:
43366 The system call hasn't been performed on the host yet.
43369 The system call on the host has been finished.
43373 These two states can be distinguished by the target by the value of the
43374 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
43375 call hasn't been performed. This is equivalent to the @code{EINTR} handling
43376 on POSIX systems. In any other case, the target may presume that the
43377 system call has been finished --- successfully or not --- and should behave
43378 as if the break message arrived right after the system call.
43380 @value{GDBN} must behave reliably. If the system call has not been called
43381 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
43382 @code{errno} in the packet. If the system call on the host has been finished
43383 before the user requests a break, the full action must be finished by
43384 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
43385 The @code{F} packet may only be sent when either nothing has happened
43386 or the full action has been completed.
43389 @subsection Console I/O
43390 @cindex console i/o as part of file-i/o
43392 By default and if not explicitly closed by the target system, the file
43393 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
43394 on the @value{GDBN} console is handled as any other file output operation
43395 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
43396 by @value{GDBN} so that after the target read request from file descriptor
43397 0 all following typing is buffered until either one of the following
43402 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
43404 system call is treated as finished.
43407 The user presses @key{RET}. This is treated as end of input with a trailing
43411 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
43412 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
43416 If the user has typed more characters than fit in the buffer given to
43417 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
43418 either another @code{read(0, @dots{})} is requested by the target, or debugging
43419 is stopped at the user's request.
43422 @node List of Supported Calls
43423 @subsection List of Supported Calls
43424 @cindex list of supported file-i/o calls
43441 @unnumberedsubsubsec open
43442 @cindex open, file-i/o system call
43447 int open(const char *pathname, int flags);
43448 int open(const char *pathname, int flags, mode_t mode);
43452 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
43455 @var{flags} is the bitwise @code{OR} of the following values:
43459 If the file does not exist it will be created. The host
43460 rules apply as far as file ownership and time stamps
43464 When used with @code{O_CREAT}, if the file already exists it is
43465 an error and open() fails.
43468 If the file already exists and the open mode allows
43469 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
43470 truncated to zero length.
43473 The file is opened in append mode.
43476 The file is opened for reading only.
43479 The file is opened for writing only.
43482 The file is opened for reading and writing.
43486 Other bits are silently ignored.
43490 @var{mode} is the bitwise @code{OR} of the following values:
43494 User has read permission.
43497 User has write permission.
43500 Group has read permission.
43503 Group has write permission.
43506 Others have read permission.
43509 Others have write permission.
43513 Other bits are silently ignored.
43516 @item Return value:
43517 @code{open} returns the new file descriptor or -1 if an error
43524 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
43527 @var{pathname} refers to a directory.
43530 The requested access is not allowed.
43533 @var{pathname} was too long.
43536 A directory component in @var{pathname} does not exist.
43539 @var{pathname} refers to a device, pipe, named pipe or socket.
43542 @var{pathname} refers to a file on a read-only filesystem and
43543 write access was requested.
43546 @var{pathname} is an invalid pointer value.
43549 No space on device to create the file.
43552 The process already has the maximum number of files open.
43555 The limit on the total number of files open on the system
43559 The call was interrupted by the user.
43565 @unnumberedsubsubsec close
43566 @cindex close, file-i/o system call
43575 @samp{Fclose,@var{fd}}
43577 @item Return value:
43578 @code{close} returns zero on success, or -1 if an error occurred.
43584 @var{fd} isn't a valid open file descriptor.
43587 The call was interrupted by the user.
43593 @unnumberedsubsubsec read
43594 @cindex read, file-i/o system call
43599 int read(int fd, void *buf, unsigned int count);
43603 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
43605 @item Return value:
43606 On success, the number of bytes read is returned.
43607 Zero indicates end of file. If count is zero, read
43608 returns zero as well. On error, -1 is returned.
43614 @var{fd} is not a valid file descriptor or is not open for
43618 @var{bufptr} is an invalid pointer value.
43621 The call was interrupted by the user.
43627 @unnumberedsubsubsec write
43628 @cindex write, file-i/o system call
43633 int write(int fd, const void *buf, unsigned int count);
43637 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
43639 @item Return value:
43640 On success, the number of bytes written are returned.
43641 Zero indicates nothing was written. On error, -1
43648 @var{fd} is not a valid file descriptor or is not open for
43652 @var{bufptr} is an invalid pointer value.
43655 An attempt was made to write a file that exceeds the
43656 host-specific maximum file size allowed.
43659 No space on device to write the data.
43662 The call was interrupted by the user.
43668 @unnumberedsubsubsec lseek
43669 @cindex lseek, file-i/o system call
43674 long lseek (int fd, long offset, int flag);
43678 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
43680 @var{flag} is one of:
43684 The offset is set to @var{offset} bytes.
43687 The offset is set to its current location plus @var{offset}
43691 The offset is set to the size of the file plus @var{offset}
43695 @item Return value:
43696 On success, the resulting unsigned offset in bytes from
43697 the beginning of the file is returned. Otherwise, a
43698 value of -1 is returned.
43704 @var{fd} is not a valid open file descriptor.
43707 @var{fd} is associated with the @value{GDBN} console.
43710 @var{flag} is not a proper value.
43713 The call was interrupted by the user.
43719 @unnumberedsubsubsec rename
43720 @cindex rename, file-i/o system call
43725 int rename(const char *oldpath, const char *newpath);
43729 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
43731 @item Return value:
43732 On success, zero is returned. On error, -1 is returned.
43738 @var{newpath} is an existing directory, but @var{oldpath} is not a
43742 @var{newpath} is a non-empty directory.
43745 @var{oldpath} or @var{newpath} is a directory that is in use by some
43749 An attempt was made to make a directory a subdirectory
43753 A component used as a directory in @var{oldpath} or new
43754 path is not a directory. Or @var{oldpath} is a directory
43755 and @var{newpath} exists but is not a directory.
43758 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
43761 No access to the file or the path of the file.
43765 @var{oldpath} or @var{newpath} was too long.
43768 A directory component in @var{oldpath} or @var{newpath} does not exist.
43771 The file is on a read-only filesystem.
43774 The device containing the file has no room for the new
43778 The call was interrupted by the user.
43784 @unnumberedsubsubsec unlink
43785 @cindex unlink, file-i/o system call
43790 int unlink(const char *pathname);
43794 @samp{Funlink,@var{pathnameptr}/@var{len}}
43796 @item Return value:
43797 On success, zero is returned. On error, -1 is returned.
43803 No access to the file or the path of the file.
43806 The system does not allow unlinking of directories.
43809 The file @var{pathname} cannot be unlinked because it's
43810 being used by another process.
43813 @var{pathnameptr} is an invalid pointer value.
43816 @var{pathname} was too long.
43819 A directory component in @var{pathname} does not exist.
43822 A component of the path is not a directory.
43825 The file is on a read-only filesystem.
43828 The call was interrupted by the user.
43834 @unnumberedsubsubsec stat/fstat
43835 @cindex fstat, file-i/o system call
43836 @cindex stat, file-i/o system call
43841 int stat(const char *pathname, struct stat *buf);
43842 int fstat(int fd, struct stat *buf);
43846 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
43847 @samp{Ffstat,@var{fd},@var{bufptr}}
43849 @item Return value:
43850 On success, zero is returned. On error, -1 is returned.
43856 @var{fd} is not a valid open file.
43859 A directory component in @var{pathname} does not exist or the
43860 path is an empty string.
43863 A component of the path is not a directory.
43866 @var{pathnameptr} is an invalid pointer value.
43869 No access to the file or the path of the file.
43872 @var{pathname} was too long.
43875 The call was interrupted by the user.
43881 @unnumberedsubsubsec gettimeofday
43882 @cindex gettimeofday, file-i/o system call
43887 int gettimeofday(struct timeval *tv, void *tz);
43891 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
43893 @item Return value:
43894 On success, 0 is returned, -1 otherwise.
43900 @var{tz} is a non-NULL pointer.
43903 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
43909 @unnumberedsubsubsec isatty
43910 @cindex isatty, file-i/o system call
43915 int isatty(int fd);
43919 @samp{Fisatty,@var{fd}}
43921 @item Return value:
43922 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
43928 The call was interrupted by the user.
43933 Note that the @code{isatty} call is treated as a special case: it returns
43934 1 to the target if the file descriptor is attached
43935 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
43936 would require implementing @code{ioctl} and would be more complex than
43941 @unnumberedsubsubsec system
43942 @cindex system, file-i/o system call
43947 int system(const char *command);
43951 @samp{Fsystem,@var{commandptr}/@var{len}}
43953 @item Return value:
43954 If @var{len} is zero, the return value indicates whether a shell is
43955 available. A zero return value indicates a shell is not available.
43956 For non-zero @var{len}, the value returned is -1 on error and the
43957 return status of the command otherwise. Only the exit status of the
43958 command is returned, which is extracted from the host's @code{system}
43959 return value by calling @code{WEXITSTATUS(retval)}. In case
43960 @file{/bin/sh} could not be executed, 127 is returned.
43966 The call was interrupted by the user.
43971 @value{GDBN} takes over the full task of calling the necessary host calls
43972 to perform the @code{system} call. The return value of @code{system} on
43973 the host is simplified before it's returned
43974 to the target. Any termination signal information from the child process
43975 is discarded, and the return value consists
43976 entirely of the exit status of the called command.
43978 Due to security concerns, the @code{system} call is by default refused
43979 by @value{GDBN}. The user has to allow this call explicitly with the
43980 @code{set remote system-call-allowed 1} command.
43983 @item set remote system-call-allowed
43984 @kindex set remote system-call-allowed
43985 Control whether to allow the @code{system} calls in the File I/O
43986 protocol for the remote target. The default is zero (disabled).
43988 @item show remote system-call-allowed
43989 @kindex show remote system-call-allowed
43990 Show whether the @code{system} calls are allowed in the File I/O
43994 @node Protocol-specific Representation of Datatypes
43995 @subsection Protocol-specific Representation of Datatypes
43996 @cindex protocol-specific representation of datatypes, in file-i/o protocol
43999 * Integral Datatypes::
44001 * Memory Transfer::
44006 @node Integral Datatypes
44007 @unnumberedsubsubsec Integral Datatypes
44008 @cindex integral datatypes, in file-i/o protocol
44010 The integral datatypes used in the system calls are @code{int},
44011 @code{unsigned int}, @code{long}, @code{unsigned long},
44012 @code{mode_t}, and @code{time_t}.
44014 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
44015 implemented as 32 bit values in this protocol.
44017 @code{long} and @code{unsigned long} are implemented as 64 bit types.
44019 @xref{Limits}, for corresponding MIN and MAX values (similar to those
44020 in @file{limits.h}) to allow range checking on host and target.
44022 @code{time_t} datatypes are defined as seconds since the Epoch.
44024 All integral datatypes transferred as part of a memory read or write of a
44025 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
44028 @node Pointer Values
44029 @unnumberedsubsubsec Pointer Values
44030 @cindex pointer values, in file-i/o protocol
44032 Pointers to target data are transmitted as they are. An exception
44033 is made for pointers to buffers for which the length isn't
44034 transmitted as part of the function call, namely strings. Strings
44035 are transmitted as a pointer/length pair, both as hex values, e.g.@:
44042 which is a pointer to data of length 18 bytes at position 0x1aaf.
44043 The length is defined as the full string length in bytes, including
44044 the trailing null byte. For example, the string @code{"hello world"}
44045 at address 0x123456 is transmitted as
44051 @node Memory Transfer
44052 @unnumberedsubsubsec Memory Transfer
44053 @cindex memory transfer, in file-i/o protocol
44055 Structured data which is transferred using a memory read or write (for
44056 example, a @code{struct stat}) is expected to be in a protocol-specific format
44057 with all scalar multibyte datatypes being big endian. Translation to
44058 this representation needs to be done both by the target before the @code{F}
44059 packet is sent, and by @value{GDBN} before
44060 it transfers memory to the target. Transferred pointers to structured
44061 data should point to the already-coerced data at any time.
44065 @unnumberedsubsubsec struct stat
44066 @cindex struct stat, in file-i/o protocol
44068 The buffer of type @code{struct stat} used by the target and @value{GDBN}
44069 is defined as follows:
44073 unsigned int st_dev; /* device */
44074 unsigned int st_ino; /* inode */
44075 mode_t st_mode; /* protection */
44076 unsigned int st_nlink; /* number of hard links */
44077 unsigned int st_uid; /* user ID of owner */
44078 unsigned int st_gid; /* group ID of owner */
44079 unsigned int st_rdev; /* device type (if inode device) */
44080 unsigned long st_size; /* total size, in bytes */
44081 unsigned long st_blksize; /* blocksize for filesystem I/O */
44082 unsigned long st_blocks; /* number of blocks allocated */
44083 time_t st_atime; /* time of last access */
44084 time_t st_mtime; /* time of last modification */
44085 time_t st_ctime; /* time of last change */
44089 The integral datatypes conform to the definitions given in the
44090 appropriate section (see @ref{Integral Datatypes}, for details) so this
44091 structure is of size 64 bytes.
44093 The values of several fields have a restricted meaning and/or
44099 A value of 0 represents a file, 1 the console.
44102 No valid meaning for the target. Transmitted unchanged.
44105 Valid mode bits are described in @ref{Constants}. Any other
44106 bits have currently no meaning for the target.
44111 No valid meaning for the target. Transmitted unchanged.
44116 These values have a host and file system dependent
44117 accuracy. Especially on Windows hosts, the file system may not
44118 support exact timing values.
44121 The target gets a @code{struct stat} of the above representation and is
44122 responsible for coercing it to the target representation before
44125 Note that due to size differences between the host, target, and protocol
44126 representations of @code{struct stat} members, these members could eventually
44127 get truncated on the target.
44129 @node struct timeval
44130 @unnumberedsubsubsec struct timeval
44131 @cindex struct timeval, in file-i/o protocol
44133 The buffer of type @code{struct timeval} used by the File-I/O protocol
44134 is defined as follows:
44138 time_t tv_sec; /* second */
44139 long tv_usec; /* microsecond */
44143 The integral datatypes conform to the definitions given in the
44144 appropriate section (see @ref{Integral Datatypes}, for details) so this
44145 structure is of size 8 bytes.
44148 @subsection Constants
44149 @cindex constants, in file-i/o protocol
44151 The following values are used for the constants inside of the
44152 protocol. @value{GDBN} and target are responsible for translating these
44153 values before and after the call as needed.
44164 @unnumberedsubsubsec Open Flags
44165 @cindex open flags, in file-i/o protocol
44167 All values are given in hexadecimal representation.
44179 @node mode_t Values
44180 @unnumberedsubsubsec mode_t Values
44181 @cindex mode_t values, in file-i/o protocol
44183 All values are given in octal representation.
44200 @unnumberedsubsubsec Errno Values
44201 @cindex errno values, in file-i/o protocol
44203 All values are given in decimal representation.
44228 @code{EUNKNOWN} is used as a fallback error value if a host system returns
44229 any error value not in the list of supported error numbers.
44232 @unnumberedsubsubsec Lseek Flags
44233 @cindex lseek flags, in file-i/o protocol
44242 @unnumberedsubsubsec Limits
44243 @cindex limits, in file-i/o protocol
44245 All values are given in decimal representation.
44248 INT_MIN -2147483648
44250 UINT_MAX 4294967295
44251 LONG_MIN -9223372036854775808
44252 LONG_MAX 9223372036854775807
44253 ULONG_MAX 18446744073709551615
44256 @node File-I/O Examples
44257 @subsection File-I/O Examples
44258 @cindex file-i/o examples
44260 Example sequence of a write call, file descriptor 3, buffer is at target
44261 address 0x1234, 6 bytes should be written:
44264 <- @code{Fwrite,3,1234,6}
44265 @emph{request memory read from target}
44268 @emph{return "6 bytes written"}
44272 Example sequence of a read call, file descriptor 3, buffer is at target
44273 address 0x1234, 6 bytes should be read:
44276 <- @code{Fread,3,1234,6}
44277 @emph{request memory write to target}
44278 -> @code{X1234,6:XXXXXX}
44279 @emph{return "6 bytes read"}
44283 Example sequence of a read call, call fails on the host due to invalid
44284 file descriptor (@code{EBADF}):
44287 <- @code{Fread,3,1234,6}
44291 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
44295 <- @code{Fread,3,1234,6}
44300 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
44304 <- @code{Fread,3,1234,6}
44305 -> @code{X1234,6:XXXXXX}
44309 @node Library List Format
44310 @section Library List Format
44311 @cindex library list format, remote protocol
44313 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
44314 same process as your application to manage libraries. In this case,
44315 @value{GDBN} can use the loader's symbol table and normal memory
44316 operations to maintain a list of shared libraries. On other
44317 platforms, the operating system manages loaded libraries.
44318 @value{GDBN} can not retrieve the list of currently loaded libraries
44319 through memory operations, so it uses the @samp{qXfer:libraries:read}
44320 packet (@pxref{qXfer library list read}) instead. The remote stub
44321 queries the target's operating system and reports which libraries
44324 The @samp{qXfer:libraries:read} packet returns an XML document which
44325 lists loaded libraries and their offsets. Each library has an
44326 associated name and one or more segment or section base addresses,
44327 which report where the library was loaded in memory.
44329 For the common case of libraries that are fully linked binaries, the
44330 library should have a list of segments. If the target supports
44331 dynamic linking of a relocatable object file, its library XML element
44332 should instead include a list of allocated sections. The segment or
44333 section bases are start addresses, not relocation offsets; they do not
44334 depend on the library's link-time base addresses.
44336 @value{GDBN} must be linked with the Expat library to support XML
44337 library lists. @xref{Expat}.
44339 A simple memory map, with one loaded library relocated by a single
44340 offset, looks like this:
44344 <library name="/lib/libc.so.6">
44345 <segment address="0x10000000"/>
44350 Another simple memory map, with one loaded library with three
44351 allocated sections (.text, .data, .bss), looks like this:
44355 <library name="sharedlib.o">
44356 <section address="0x10000000"/>
44357 <section address="0x20000000"/>
44358 <section address="0x30000000"/>
44363 The format of a library list is described by this DTD:
44366 <!-- library-list: Root element with versioning -->
44367 <!ELEMENT library-list (library)*>
44368 <!ATTLIST library-list version CDATA #FIXED "1.0">
44369 <!ELEMENT library (segment*, section*)>
44370 <!ATTLIST library name CDATA #REQUIRED>
44371 <!ELEMENT segment EMPTY>
44372 <!ATTLIST segment address CDATA #REQUIRED>
44373 <!ELEMENT section EMPTY>
44374 <!ATTLIST section address CDATA #REQUIRED>
44377 In addition, segments and section descriptors cannot be mixed within a
44378 single library element, and you must supply at least one segment or
44379 section for each library.
44381 @node Library List Format for SVR4 Targets
44382 @section Library List Format for SVR4 Targets
44383 @cindex library list format, remote protocol
44385 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
44386 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
44387 shared libraries. Still a special library list provided by this packet is
44388 more efficient for the @value{GDBN} remote protocol.
44390 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
44391 loaded libraries and their SVR4 linker parameters. For each library on SVR4
44392 target, the following parameters are reported:
44396 @code{name}, the absolute file name from the @code{l_name} field of
44397 @code{struct link_map}.
44399 @code{lm} with address of @code{struct link_map} used for TLS
44400 (Thread Local Storage) access.
44402 @code{l_addr}, the displacement as read from the field @code{l_addr} of
44403 @code{struct link_map}. For prelinked libraries this is not an absolute
44404 memory address. It is a displacement of absolute memory address against
44405 address the file was prelinked to during the library load.
44407 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
44410 Additionally the single @code{main-lm} attribute specifies address of
44411 @code{struct link_map} used for the main executable. This parameter is used
44412 for TLS access and its presence is optional.
44414 @value{GDBN} must be linked with the Expat library to support XML
44415 SVR4 library lists. @xref{Expat}.
44417 A simple memory map, with two loaded libraries (which do not use prelink),
44421 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
44422 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
44424 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
44426 </library-list-svr>
44429 The format of an SVR4 library list is described by this DTD:
44432 <!-- library-list-svr4: Root element with versioning -->
44433 <!ELEMENT library-list-svr4 (library)*>
44434 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
44435 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
44436 <!ELEMENT library EMPTY>
44437 <!ATTLIST library name CDATA #REQUIRED>
44438 <!ATTLIST library lm CDATA #REQUIRED>
44439 <!ATTLIST library l_addr CDATA #REQUIRED>
44440 <!ATTLIST library l_ld CDATA #REQUIRED>
44443 @node Memory Map Format
44444 @section Memory Map Format
44445 @cindex memory map format
44447 To be able to write into flash memory, @value{GDBN} needs to obtain a
44448 memory map from the target. This section describes the format of the
44451 The memory map is obtained using the @samp{qXfer:memory-map:read}
44452 (@pxref{qXfer memory map read}) packet and is an XML document that
44453 lists memory regions.
44455 @value{GDBN} must be linked with the Expat library to support XML
44456 memory maps. @xref{Expat}.
44458 The top-level structure of the document is shown below:
44461 <?xml version="1.0"?>
44462 <!DOCTYPE memory-map
44463 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
44464 "http://sourceware.org/gdb/gdb-memory-map.dtd">
44470 Each region can be either:
44475 A region of RAM starting at @var{addr} and extending for @var{length}
44479 <memory type="ram" start="@var{addr}" length="@var{length}"/>
44484 A region of read-only memory:
44487 <memory type="rom" start="@var{addr}" length="@var{length}"/>
44492 A region of flash memory, with erasure blocks @var{blocksize}
44496 <memory type="flash" start="@var{addr}" length="@var{length}">
44497 <property name="blocksize">@var{blocksize}</property>
44503 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
44504 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
44505 packets to write to addresses in such ranges.
44507 The formal DTD for memory map format is given below:
44510 <!-- ................................................... -->
44511 <!-- Memory Map XML DTD ................................ -->
44512 <!-- File: memory-map.dtd .............................. -->
44513 <!-- .................................... .............. -->
44514 <!-- memory-map.dtd -->
44515 <!-- memory-map: Root element with versioning -->
44516 <!ELEMENT memory-map (memory)*>
44517 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
44518 <!ELEMENT memory (property)*>
44519 <!-- memory: Specifies a memory region,
44520 and its type, or device. -->
44521 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
44522 start CDATA #REQUIRED
44523 length CDATA #REQUIRED>
44524 <!-- property: Generic attribute tag -->
44525 <!ELEMENT property (#PCDATA | property)*>
44526 <!ATTLIST property name (blocksize) #REQUIRED>
44529 @node Thread List Format
44530 @section Thread List Format
44531 @cindex thread list format
44533 To efficiently update the list of threads and their attributes,
44534 @value{GDBN} issues the @samp{qXfer:threads:read} packet
44535 (@pxref{qXfer threads read}) and obtains the XML document with
44536 the following structure:
44539 <?xml version="1.0"?>
44541 <thread id="id" core="0" name="name">
44542 ... description ...
44547 Each @samp{thread} element must have the @samp{id} attribute that
44548 identifies the thread (@pxref{thread-id syntax}). The
44549 @samp{core} attribute, if present, specifies which processor core
44550 the thread was last executing on. The @samp{name} attribute, if
44551 present, specifies the human-readable name of the thread. The content
44552 of the of @samp{thread} element is interpreted as human-readable
44553 auxiliary information. The @samp{handle} attribute, if present,
44554 is a hex encoded representation of the thread handle.
44557 @node Traceframe Info Format
44558 @section Traceframe Info Format
44559 @cindex traceframe info format
44561 To be able to know which objects in the inferior can be examined when
44562 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
44563 memory ranges, registers and trace state variables that have been
44564 collected in a traceframe.
44566 This list is obtained using the @samp{qXfer:traceframe-info:read}
44567 (@pxref{qXfer traceframe info read}) packet and is an XML document.
44569 @value{GDBN} must be linked with the Expat library to support XML
44570 traceframe info discovery. @xref{Expat}.
44572 The top-level structure of the document is shown below:
44575 <?xml version="1.0"?>
44576 <!DOCTYPE traceframe-info
44577 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
44578 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
44584 Each traceframe block can be either:
44589 A region of collected memory starting at @var{addr} and extending for
44590 @var{length} bytes from there:
44593 <memory start="@var{addr}" length="@var{length}"/>
44597 A block indicating trace state variable numbered @var{number} has been
44601 <tvar id="@var{number}"/>
44606 The formal DTD for the traceframe info format is given below:
44609 <!ELEMENT traceframe-info (memory | tvar)* >
44610 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
44612 <!ELEMENT memory EMPTY>
44613 <!ATTLIST memory start CDATA #REQUIRED
44614 length CDATA #REQUIRED>
44616 <!ATTLIST tvar id CDATA #REQUIRED>
44619 @node Branch Trace Format
44620 @section Branch Trace Format
44621 @cindex branch trace format
44623 In order to display the branch trace of an inferior thread,
44624 @value{GDBN} needs to obtain the list of branches. This list is
44625 represented as list of sequential code blocks that are connected via
44626 branches. The code in each block has been executed sequentially.
44628 This list is obtained using the @samp{qXfer:btrace:read}
44629 (@pxref{qXfer btrace read}) packet and is an XML document.
44631 @value{GDBN} must be linked with the Expat library to support XML
44632 traceframe info discovery. @xref{Expat}.
44634 The top-level structure of the document is shown below:
44637 <?xml version="1.0"?>
44639 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
44640 "http://sourceware.org/gdb/gdb-btrace.dtd">
44649 A block of sequentially executed instructions starting at @var{begin}
44650 and ending at @var{end}:
44653 <block begin="@var{begin}" end="@var{end}"/>
44658 The formal DTD for the branch trace format is given below:
44661 <!ELEMENT btrace (block* | pt) >
44662 <!ATTLIST btrace version CDATA #FIXED "1.0">
44664 <!ELEMENT block EMPTY>
44665 <!ATTLIST block begin CDATA #REQUIRED
44666 end CDATA #REQUIRED>
44668 <!ELEMENT pt (pt-config?, raw?)>
44670 <!ELEMENT pt-config (cpu?)>
44672 <!ELEMENT cpu EMPTY>
44673 <!ATTLIST cpu vendor CDATA #REQUIRED
44674 family CDATA #REQUIRED
44675 model CDATA #REQUIRED
44676 stepping CDATA #REQUIRED>
44678 <!ELEMENT raw (#PCDATA)>
44681 @node Branch Trace Configuration Format
44682 @section Branch Trace Configuration Format
44683 @cindex branch trace configuration format
44685 For each inferior thread, @value{GDBN} can obtain the branch trace
44686 configuration using the @samp{qXfer:btrace-conf:read}
44687 (@pxref{qXfer btrace-conf read}) packet.
44689 The configuration describes the branch trace format and configuration
44690 settings for that format. The following information is described:
44694 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
44697 The size of the @acronym{BTS} ring buffer in bytes.
44700 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
44704 The size of the @acronym{Intel PT} ring buffer in bytes.
44708 @value{GDBN} must be linked with the Expat library to support XML
44709 branch trace configuration discovery. @xref{Expat}.
44711 The formal DTD for the branch trace configuration format is given below:
44714 <!ELEMENT btrace-conf (bts?, pt?)>
44715 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
44717 <!ELEMENT bts EMPTY>
44718 <!ATTLIST bts size CDATA #IMPLIED>
44720 <!ELEMENT pt EMPTY>
44721 <!ATTLIST pt size CDATA #IMPLIED>
44724 @include agentexpr.texi
44726 @node Target Descriptions
44727 @appendix Target Descriptions
44728 @cindex target descriptions
44730 One of the challenges of using @value{GDBN} to debug embedded systems
44731 is that there are so many minor variants of each processor
44732 architecture in use. It is common practice for vendors to start with
44733 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
44734 and then make changes to adapt it to a particular market niche. Some
44735 architectures have hundreds of variants, available from dozens of
44736 vendors. This leads to a number of problems:
44740 With so many different customized processors, it is difficult for
44741 the @value{GDBN} maintainers to keep up with the changes.
44743 Since individual variants may have short lifetimes or limited
44744 audiences, it may not be worthwhile to carry information about every
44745 variant in the @value{GDBN} source tree.
44747 When @value{GDBN} does support the architecture of the embedded system
44748 at hand, the task of finding the correct architecture name to give the
44749 @command{set architecture} command can be error-prone.
44752 To address these problems, the @value{GDBN} remote protocol allows a
44753 target system to not only identify itself to @value{GDBN}, but to
44754 actually describe its own features. This lets @value{GDBN} support
44755 processor variants it has never seen before --- to the extent that the
44756 descriptions are accurate, and that @value{GDBN} understands them.
44758 @value{GDBN} must be linked with the Expat library to support XML
44759 target descriptions. @xref{Expat}.
44762 * Retrieving Descriptions:: How descriptions are fetched from a target.
44763 * Target Description Format:: The contents of a target description.
44764 * Predefined Target Types:: Standard types available for target
44766 * Enum Target Types:: How to define enum target types.
44767 * Standard Target Features:: Features @value{GDBN} knows about.
44770 @node Retrieving Descriptions
44771 @section Retrieving Descriptions
44773 Target descriptions can be read from the target automatically, or
44774 specified by the user manually. The default behavior is to read the
44775 description from the target. @value{GDBN} retrieves it via the remote
44776 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
44777 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
44778 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
44779 XML document, of the form described in @ref{Target Description
44782 Alternatively, you can specify a file to read for the target description.
44783 If a file is set, the target will not be queried. The commands to
44784 specify a file are:
44787 @cindex set tdesc filename
44788 @item set tdesc filename @var{path}
44789 Read the target description from @var{path}.
44791 @cindex unset tdesc filename
44792 @item unset tdesc filename
44793 Do not read the XML target description from a file. @value{GDBN}
44794 will use the description supplied by the current target.
44796 @cindex show tdesc filename
44797 @item show tdesc filename
44798 Show the filename to read for a target description, if any.
44802 @node Target Description Format
44803 @section Target Description Format
44804 @cindex target descriptions, XML format
44806 A target description annex is an @uref{http://www.w3.org/XML/, XML}
44807 document which complies with the Document Type Definition provided in
44808 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
44809 means you can use generally available tools like @command{xmllint} to
44810 check that your feature descriptions are well-formed and valid.
44811 However, to help people unfamiliar with XML write descriptions for
44812 their targets, we also describe the grammar here.
44814 Target descriptions can identify the architecture of the remote target
44815 and (for some architectures) provide information about custom register
44816 sets. They can also identify the OS ABI of the remote target.
44817 @value{GDBN} can use this information to autoconfigure for your
44818 target, or to warn you if you connect to an unsupported target.
44820 Here is a simple target description:
44823 <target version="1.0">
44824 <architecture>i386:x86-64</architecture>
44829 This minimal description only says that the target uses
44830 the x86-64 architecture.
44832 A target description has the following overall form, with [ ] marking
44833 optional elements and @dots{} marking repeatable elements. The elements
44834 are explained further below.
44837 <?xml version="1.0"?>
44838 <!DOCTYPE target SYSTEM "gdb-target.dtd">
44839 <target version="1.0">
44840 @r{[}@var{architecture}@r{]}
44841 @r{[}@var{osabi}@r{]}
44842 @r{[}@var{compatible}@r{]}
44843 @r{[}@var{feature}@dots{}@r{]}
44848 The description is generally insensitive to whitespace and line
44849 breaks, under the usual common-sense rules. The XML version
44850 declaration and document type declaration can generally be omitted
44851 (@value{GDBN} does not require them), but specifying them may be
44852 useful for XML validation tools. The @samp{version} attribute for
44853 @samp{<target>} may also be omitted, but we recommend
44854 including it; if future versions of @value{GDBN} use an incompatible
44855 revision of @file{gdb-target.dtd}, they will detect and report
44856 the version mismatch.
44858 @subsection Inclusion
44859 @cindex target descriptions, inclusion
44862 @cindex <xi:include>
44865 It can sometimes be valuable to split a target description up into
44866 several different annexes, either for organizational purposes, or to
44867 share files between different possible target descriptions. You can
44868 divide a description into multiple files by replacing any element of
44869 the target description with an inclusion directive of the form:
44872 <xi:include href="@var{document}"/>
44876 When @value{GDBN} encounters an element of this form, it will retrieve
44877 the named XML @var{document}, and replace the inclusion directive with
44878 the contents of that document. If the current description was read
44879 using @samp{qXfer}, then so will be the included document;
44880 @var{document} will be interpreted as the name of an annex. If the
44881 current description was read from a file, @value{GDBN} will look for
44882 @var{document} as a file in the same directory where it found the
44883 original description.
44885 @subsection Architecture
44886 @cindex <architecture>
44888 An @samp{<architecture>} element has this form:
44891 <architecture>@var{arch}</architecture>
44894 @var{arch} is one of the architectures from the set accepted by
44895 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
44898 @cindex @code{<osabi>}
44900 This optional field was introduced in @value{GDBN} version 7.0.
44901 Previous versions of @value{GDBN} ignore it.
44903 An @samp{<osabi>} element has this form:
44906 <osabi>@var{abi-name}</osabi>
44909 @var{abi-name} is an OS ABI name from the same selection accepted by
44910 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
44912 @subsection Compatible Architecture
44913 @cindex @code{<compatible>}
44915 This optional field was introduced in @value{GDBN} version 7.0.
44916 Previous versions of @value{GDBN} ignore it.
44918 A @samp{<compatible>} element has this form:
44921 <compatible>@var{arch}</compatible>
44924 @var{arch} is one of the architectures from the set accepted by
44925 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
44927 A @samp{<compatible>} element is used to specify that the target
44928 is able to run binaries in some other than the main target architecture
44929 given by the @samp{<architecture>} element. For example, on the
44930 Cell Broadband Engine, the main architecture is @code{powerpc:common}
44931 or @code{powerpc:common64}, but the system is able to run binaries
44932 in the @code{spu} architecture as well. The way to describe this
44933 capability with @samp{<compatible>} is as follows:
44936 <architecture>powerpc:common</architecture>
44937 <compatible>spu</compatible>
44940 @subsection Features
44943 Each @samp{<feature>} describes some logical portion of the target
44944 system. Features are currently used to describe available CPU
44945 registers and the types of their contents. A @samp{<feature>} element
44949 <feature name="@var{name}">
44950 @r{[}@var{type}@dots{}@r{]}
44956 Each feature's name should be unique within the description. The name
44957 of a feature does not matter unless @value{GDBN} has some special
44958 knowledge of the contents of that feature; if it does, the feature
44959 should have its standard name. @xref{Standard Target Features}.
44963 Any register's value is a collection of bits which @value{GDBN} must
44964 interpret. The default interpretation is a two's complement integer,
44965 but other types can be requested by name in the register description.
44966 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
44967 Target Types}), and the description can define additional composite
44970 Each type element must have an @samp{id} attribute, which gives
44971 a unique (within the containing @samp{<feature>}) name to the type.
44972 Types must be defined before they are used.
44975 Some targets offer vector registers, which can be treated as arrays
44976 of scalar elements. These types are written as @samp{<vector>} elements,
44977 specifying the array element type, @var{type}, and the number of elements,
44981 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
44985 If a register's value is usefully viewed in multiple ways, define it
44986 with a union type containing the useful representations. The
44987 @samp{<union>} element contains one or more @samp{<field>} elements,
44988 each of which has a @var{name} and a @var{type}:
44991 <union id="@var{id}">
44992 <field name="@var{name}" type="@var{type}"/>
44999 If a register's value is composed from several separate values, define
45000 it with either a structure type or a flags type.
45001 A flags type may only contain bitfields.
45002 A structure type may either contain only bitfields or contain no bitfields.
45003 If the value contains only bitfields, its total size in bytes must be
45006 Non-bitfield values have a @var{name} and @var{type}.
45009 <struct id="@var{id}">
45010 <field name="@var{name}" type="@var{type}"/>
45015 Both @var{name} and @var{type} values are required.
45016 No implicit padding is added.
45018 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
45021 <struct id="@var{id}" size="@var{size}">
45022 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
45028 <flags id="@var{id}" size="@var{size}">
45029 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
45034 The @var{name} value is required.
45035 Bitfield values may be named with the empty string, @samp{""},
45036 in which case the field is ``filler'' and its value is not printed.
45037 Not all bits need to be specified, so ``filler'' fields are optional.
45039 The @var{start} and @var{end} values are required, and @var{type}
45041 The field's @var{start} must be less than or equal to its @var{end},
45042 and zero represents the least significant bit.
45044 The default value of @var{type} is @code{bool} for single bit fields,
45045 and an unsigned integer otherwise.
45047 Which to choose? Structures or flags?
45049 Registers defined with @samp{flags} have these advantages over
45050 defining them with @samp{struct}:
45054 Arithmetic may be performed on them as if they were integers.
45056 They are printed in a more readable fashion.
45059 Registers defined with @samp{struct} have one advantage over
45060 defining them with @samp{flags}:
45064 One can fetch individual fields like in @samp{C}.
45067 (gdb) print $my_struct_reg.field3
45073 @subsection Registers
45076 Each register is represented as an element with this form:
45079 <reg name="@var{name}"
45080 bitsize="@var{size}"
45081 @r{[}regnum="@var{num}"@r{]}
45082 @r{[}save-restore="@var{save-restore}"@r{]}
45083 @r{[}type="@var{type}"@r{]}
45084 @r{[}group="@var{group}"@r{]}/>
45088 The components are as follows:
45093 The register's name; it must be unique within the target description.
45096 The register's size, in bits.
45099 The register's number. If omitted, a register's number is one greater
45100 than that of the previous register (either in the current feature or in
45101 a preceding feature); the first register in the target description
45102 defaults to zero. This register number is used to read or write
45103 the register; e.g.@: it is used in the remote @code{p} and @code{P}
45104 packets, and registers appear in the @code{g} and @code{G} packets
45105 in order of increasing register number.
45108 Whether the register should be preserved across inferior function
45109 calls; this must be either @code{yes} or @code{no}. The default is
45110 @code{yes}, which is appropriate for most registers except for
45111 some system control registers; this is not related to the target's
45115 The type of the register. It may be a predefined type, a type
45116 defined in the current feature, or one of the special types @code{int}
45117 and @code{float}. @code{int} is an integer type of the correct size
45118 for @var{bitsize}, and @code{float} is a floating point type (in the
45119 architecture's normal floating point format) of the correct size for
45120 @var{bitsize}. The default is @code{int}.
45123 The register group to which this register belongs. It can be one of the
45124 standard register groups @code{general}, @code{float}, @code{vector} or an
45125 arbitrary string. Group names should be limited to alphanumeric characters.
45126 If a group name is made up of multiple words the words may be separated by
45127 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
45128 @var{group} is specified, @value{GDBN} will not display the register in
45129 @code{info registers}.
45133 @node Predefined Target Types
45134 @section Predefined Target Types
45135 @cindex target descriptions, predefined types
45137 Type definitions in the self-description can build up composite types
45138 from basic building blocks, but can not define fundamental types. Instead,
45139 standard identifiers are provided by @value{GDBN} for the fundamental
45140 types. The currently supported types are:
45145 Boolean type, occupying a single bit.
45153 Signed integer types holding the specified number of bits.
45161 Unsigned integer types holding the specified number of bits.
45165 Pointers to unspecified code and data. The program counter and
45166 any dedicated return address register may be marked as code
45167 pointers; printing a code pointer converts it into a symbolic
45168 address. The stack pointer and any dedicated address registers
45169 may be marked as data pointers.
45172 Single precision IEEE floating point.
45175 Double precision IEEE floating point.
45178 The 12-byte extended precision format used by ARM FPA registers.
45181 The 10-byte extended precision format used by x87 registers.
45184 32bit @sc{eflags} register used by x86.
45187 32bit @sc{mxcsr} register used by x86.
45191 @node Enum Target Types
45192 @section Enum Target Types
45193 @cindex target descriptions, enum types
45195 Enum target types are useful in @samp{struct} and @samp{flags}
45196 register descriptions. @xref{Target Description Format}.
45198 Enum types have a name, size and a list of name/value pairs.
45201 <enum id="@var{id}" size="@var{size}">
45202 <evalue name="@var{name}" value="@var{value}"/>
45207 Enums must be defined before they are used.
45210 <enum id="levels_type" size="4">
45211 <evalue name="low" value="0"/>
45212 <evalue name="high" value="1"/>
45214 <flags id="flags_type" size="4">
45215 <field name="X" start="0"/>
45216 <field name="LEVEL" start="1" end="1" type="levels_type"/>
45218 <reg name="flags" bitsize="32" type="flags_type"/>
45221 Given that description, a value of 3 for the @samp{flags} register
45222 would be printed as:
45225 (gdb) info register flags
45226 flags 0x3 [ X LEVEL=high ]
45229 @node Standard Target Features
45230 @section Standard Target Features
45231 @cindex target descriptions, standard features
45233 A target description must contain either no registers or all the
45234 target's registers. If the description contains no registers, then
45235 @value{GDBN} will assume a default register layout, selected based on
45236 the architecture. If the description contains any registers, the
45237 default layout will not be used; the standard registers must be
45238 described in the target description, in such a way that @value{GDBN}
45239 can recognize them.
45241 This is accomplished by giving specific names to feature elements
45242 which contain standard registers. @value{GDBN} will look for features
45243 with those names and verify that they contain the expected registers;
45244 if any known feature is missing required registers, or if any required
45245 feature is missing, @value{GDBN} will reject the target
45246 description. You can add additional registers to any of the
45247 standard features --- @value{GDBN} will display them just as if
45248 they were added to an unrecognized feature.
45250 This section lists the known features and their expected contents.
45251 Sample XML documents for these features are included in the
45252 @value{GDBN} source tree, in the directory @file{gdb/features}.
45254 Names recognized by @value{GDBN} should include the name of the
45255 company or organization which selected the name, and the overall
45256 architecture to which the feature applies; so e.g.@: the feature
45257 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
45259 The names of registers are not case sensitive for the purpose
45260 of recognizing standard features, but @value{GDBN} will only display
45261 registers using the capitalization used in the description.
45264 * AArch64 Features::
45268 * MicroBlaze Features::
45272 * Nios II Features::
45273 * OpenRISC 1000 Features::
45274 * PowerPC Features::
45275 * RISC-V Features::
45277 * S/390 and System z Features::
45283 @node AArch64 Features
45284 @subsection AArch64 Features
45285 @cindex target descriptions, AArch64 features
45287 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
45288 targets. It should contain registers @samp{x0} through @samp{x30},
45289 @samp{sp}, @samp{pc}, and @samp{cpsr}.
45291 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
45292 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
45295 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
45296 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
45297 through @samp{p15}, @samp{ffr} and @samp{vg}.
45299 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
45300 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
45303 @subsection ARC Features
45304 @cindex target descriptions, ARC Features
45306 ARC processors are so configurable that even core registers and their numbers
45307 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
45308 registers, which are important to @value{GDBN}, are not ``core'' registers in
45309 ARC. Therefore, there are two features that their presence is mandatory:
45310 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
45312 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
45317 @samp{r0} through @samp{r25} for normal register file targets.
45319 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
45320 register file targets.
45322 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
45323 @samp{blink}, @samp{lp_count}, @samp{pcl}.
45326 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
45327 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
45328 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
45329 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
45330 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
45331 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
45332 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
45333 because of their inaccessibility during user space debugging sessions.
45335 Extension core registers @samp{r32} through @samp{r59} are optional and their
45336 existence depends on the configuration. When debugging GNU/Linux applications,
45337 i.e.@: user space debugging, these core registers are not available.
45339 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
45340 is the list of registers pertinent to this feature:
45344 mandatory: @samp{pc} and @samp{status32}.
45346 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
45350 @subsection ARM Features
45351 @cindex target descriptions, ARM features
45353 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
45355 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
45356 @samp{lr}, @samp{pc}, and @samp{cpsr}.
45358 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
45359 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
45360 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
45363 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
45364 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
45366 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
45367 it should contain at least registers @samp{wR0} through @samp{wR15} and
45368 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
45369 @samp{wCSSF}, and @samp{wCASF} registers are optional.
45371 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
45372 should contain at least registers @samp{d0} through @samp{d15}. If
45373 they are present, @samp{d16} through @samp{d31} should also be included.
45374 @value{GDBN} will synthesize the single-precision registers from
45375 halves of the double-precision registers.
45377 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
45378 need to contain registers; it instructs @value{GDBN} to display the
45379 VFP double-precision registers as vectors and to synthesize the
45380 quad-precision registers from pairs of double-precision registers.
45381 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
45382 be present and include 32 double-precision registers.
45384 @node i386 Features
45385 @subsection i386 Features
45386 @cindex target descriptions, i386 features
45388 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
45389 targets. It should describe the following registers:
45393 @samp{eax} through @samp{edi} plus @samp{eip} for i386
45395 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
45397 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
45398 @samp{fs}, @samp{gs}
45400 @samp{st0} through @samp{st7}
45402 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
45403 @samp{foseg}, @samp{fooff} and @samp{fop}
45406 The register sets may be different, depending on the target.
45408 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
45409 describe registers:
45413 @samp{xmm0} through @samp{xmm7} for i386
45415 @samp{xmm0} through @samp{xmm15} for amd64
45420 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
45421 @samp{org.gnu.gdb.i386.sse} feature. It should
45422 describe the upper 128 bits of @sc{ymm} registers:
45426 @samp{ymm0h} through @samp{ymm7h} for i386
45428 @samp{ymm0h} through @samp{ymm15h} for amd64
45431 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
45432 Memory Protection Extension (MPX). It should describe the following registers:
45436 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
45438 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
45441 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
45442 describe a single register, @samp{orig_eax}.
45444 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
45445 describe two system registers: @samp{fs_base} and @samp{gs_base}.
45447 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
45448 @samp{org.gnu.gdb.i386.avx} feature. It should
45449 describe additional @sc{xmm} registers:
45453 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
45456 It should describe the upper 128 bits of additional @sc{ymm} registers:
45460 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
45464 describe the upper 256 bits of @sc{zmm} registers:
45468 @samp{zmm0h} through @samp{zmm7h} for i386.
45470 @samp{zmm0h} through @samp{zmm15h} for amd64.
45474 describe the additional @sc{zmm} registers:
45478 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
45481 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
45482 describe a single register, @samp{pkru}. It is a 32-bit register
45483 valid for i386 and amd64.
45485 @node MicroBlaze Features
45486 @subsection MicroBlaze Features
45487 @cindex target descriptions, MicroBlaze features
45489 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
45490 targets. It should contain registers @samp{r0} through @samp{r31},
45491 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
45492 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
45493 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
45495 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
45496 If present, it should contain registers @samp{rshr} and @samp{rslr}
45498 @node MIPS Features
45499 @subsection @acronym{MIPS} Features
45500 @cindex target descriptions, @acronym{MIPS} features
45502 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
45503 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
45504 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
45507 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
45508 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
45509 registers. They may be 32-bit or 64-bit depending on the target.
45511 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
45512 it may be optional in a future version of @value{GDBN}. It should
45513 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
45514 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
45516 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
45517 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
45518 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
45519 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
45521 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
45522 contain a single register, @samp{restart}, which is used by the
45523 Linux kernel to control restartable syscalls.
45525 @node M68K Features
45526 @subsection M68K Features
45527 @cindex target descriptions, M68K features
45530 @item @samp{org.gnu.gdb.m68k.core}
45531 @itemx @samp{org.gnu.gdb.coldfire.core}
45532 @itemx @samp{org.gnu.gdb.fido.core}
45533 One of those features must be always present.
45534 The feature that is present determines which flavor of m68k is
45535 used. The feature that is present should contain registers
45536 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
45537 @samp{sp}, @samp{ps} and @samp{pc}.
45539 @item @samp{org.gnu.gdb.coldfire.fp}
45540 This feature is optional. If present, it should contain registers
45541 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
45544 Note that, despite the fact that this feature's name says
45545 @samp{coldfire}, it is used to describe any floating point registers.
45546 The size of the registers must match the main m68k flavor; so, for
45547 example, if the primary feature is reported as @samp{coldfire}, then
45548 64-bit floating point registers are required.
45551 @node NDS32 Features
45552 @subsection NDS32 Features
45553 @cindex target descriptions, NDS32 features
45555 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
45556 targets. It should contain at least registers @samp{r0} through
45557 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
45560 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
45561 it should contain 64-bit double-precision floating-point registers
45562 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
45563 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
45565 @emph{Note:} The first sixteen 64-bit double-precision floating-point
45566 registers are overlapped with the thirty-two 32-bit single-precision
45567 floating-point registers. The 32-bit single-precision registers, if
45568 not being listed explicitly, will be synthesized from halves of the
45569 overlapping 64-bit double-precision registers. Listing 32-bit
45570 single-precision registers explicitly is deprecated, and the
45571 support to it could be totally removed some day.
45573 @node Nios II Features
45574 @subsection Nios II Features
45575 @cindex target descriptions, Nios II features
45577 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
45578 targets. It should contain the 32 core registers (@samp{zero},
45579 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
45580 @samp{pc}, and the 16 control registers (@samp{status} through
45583 @node OpenRISC 1000 Features
45584 @subsection Openrisc 1000 Features
45585 @cindex target descriptions, OpenRISC 1000 features
45587 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
45588 targets. It should contain the 32 general purpose registers (@samp{r0}
45589 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
45591 @node PowerPC Features
45592 @subsection PowerPC Features
45593 @cindex target descriptions, PowerPC features
45595 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
45596 targets. It should contain registers @samp{r0} through @samp{r31},
45597 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
45598 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
45600 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
45601 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
45603 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
45604 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
45605 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
45606 through @samp{v31} as aliases for the corresponding @samp{vrX}
45609 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
45610 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
45611 combine these registers with the floating point registers (@samp{f0}
45612 through @samp{f31}) and the altivec registers (@samp{vr0} through
45613 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
45614 @samp{vs63}, the set of vector-scalar registers for POWER7.
45615 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
45616 @samp{org.gnu.gdb.power.altivec}.
45618 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
45619 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
45620 @samp{spefscr}. SPE targets should provide 32-bit registers in
45621 @samp{org.gnu.gdb.power.core} and provide the upper halves in
45622 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
45623 these to present registers @samp{ev0} through @samp{ev31} to the
45626 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
45627 contain the 64-bit register @samp{ppr}.
45629 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
45630 contain the 64-bit register @samp{dscr}.
45632 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
45633 contain the 64-bit register @samp{tar}.
45635 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
45636 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
45639 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
45640 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
45641 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
45642 server PMU registers provided by @sc{gnu}/Linux.
45644 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
45645 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
45648 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
45649 contain the checkpointed general-purpose registers @samp{cr0} through
45650 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
45651 @samp{cctr}. These registers may all be either 32-bit or 64-bit
45652 depending on the target. It should also contain the checkpointed
45653 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
45656 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
45657 contain the checkpointed 64-bit floating-point registers @samp{cf0}
45658 through @samp{cf31}, as well as the checkpointed 64-bit register
45661 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
45662 should contain the checkpointed altivec registers @samp{cvr0} through
45663 @samp{cvr31}, all 128-bit wide. It should also contain the
45664 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
45667 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
45668 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
45669 will combine these registers with the checkpointed floating point
45670 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
45671 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
45672 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
45673 @samp{cvs63}. Therefore, this feature requires both
45674 @samp{org.gnu.gdb.power.htm.altivec} and
45675 @samp{org.gnu.gdb.power.htm.fpu}.
45677 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
45678 contain the 64-bit checkpointed register @samp{cppr}.
45680 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
45681 contain the 64-bit checkpointed register @samp{cdscr}.
45683 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
45684 contain the 64-bit checkpointed register @samp{ctar}.
45687 @node RISC-V Features
45688 @subsection RISC-V Features
45689 @cindex target descriptions, RISC-V Features
45691 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
45692 targets. It should contain the registers @samp{x0} through
45693 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
45694 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
45697 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
45698 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
45699 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
45700 architectural register names, or the ABI names can be used.
45702 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
45703 it should contain registers that are not backed by real registers on
45704 the target, but are instead virtual, where the register value is
45705 derived from other target state. In many ways these are like
45706 @value{GDBN}s pseudo-registers, except implemented by the target.
45707 Currently the only register expected in this set is the one byte
45708 @samp{priv} register that contains the target's privilege level in the
45709 least significant two bits.
45711 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
45712 should contain all of the target's standard CSRs. Standard CSRs are
45713 those defined in the RISC-V specification documents. There is some
45714 overlap between this feature and the fpu feature; the @samp{fflags},
45715 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
45716 expectation is that these registers will be in the fpu feature if the
45717 target has floating point hardware, but can be moved into the csr
45718 feature if the target has the floating point control registers, but no
45719 other floating point hardware.
45722 @subsection RX Features
45723 @cindex target descriptions, RX Features
45725 The @samp{org.gnu.gdb.rx.core} feature is required for RX
45726 targets. It should contain the registers @samp{r0} through
45727 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
45728 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
45730 @node S/390 and System z Features
45731 @subsection S/390 and System z Features
45732 @cindex target descriptions, S/390 features
45733 @cindex target descriptions, System z features
45735 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
45736 System z targets. It should contain the PSW and the 16 general
45737 registers. In particular, System z targets should provide the 64-bit
45738 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
45739 S/390 targets should provide the 32-bit versions of these registers.
45740 A System z target that runs in 31-bit addressing mode should provide
45741 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
45742 register's upper halves @samp{r0h} through @samp{r15h}, and their
45743 lower halves @samp{r0l} through @samp{r15l}.
45745 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
45746 contain the 64-bit registers @samp{f0} through @samp{f15}, and
45749 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
45750 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
45752 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
45753 contain the register @samp{orig_r2}, which is 64-bit wide on System z
45754 targets and 32-bit otherwise. In addition, the feature may contain
45755 the @samp{last_break} register, whose width depends on the addressing
45756 mode, as well as the @samp{system_call} register, which is always
45759 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
45760 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
45761 @samp{atia}, and @samp{tr0} through @samp{tr15}.
45763 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
45764 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
45765 combined by @value{GDBN} with the floating point registers @samp{f0}
45766 through @samp{f15} to present the 128-bit wide vector registers
45767 @samp{v0} through @samp{v15}. In addition, this feature should
45768 contain the 128-bit wide vector registers @samp{v16} through
45771 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
45772 the 64-bit wide guarded-storage-control registers @samp{gsd},
45773 @samp{gssm}, and @samp{gsepla}.
45775 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
45776 the 64-bit wide guarded-storage broadcast control registers
45777 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
45779 @node Sparc Features
45780 @subsection Sparc Features
45781 @cindex target descriptions, sparc32 features
45782 @cindex target descriptions, sparc64 features
45783 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
45784 targets. It should describe the following registers:
45788 @samp{g0} through @samp{g7}
45790 @samp{o0} through @samp{o7}
45792 @samp{l0} through @samp{l7}
45794 @samp{i0} through @samp{i7}
45797 They may be 32-bit or 64-bit depending on the target.
45799 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
45800 targets. It should describe the following registers:
45804 @samp{f0} through @samp{f31}
45806 @samp{f32} through @samp{f62} for sparc64
45809 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
45810 targets. It should describe the following registers:
45814 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
45815 @samp{fsr}, and @samp{csr} for sparc32
45817 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
45821 @node TIC6x Features
45822 @subsection TMS320C6x Features
45823 @cindex target descriptions, TIC6x features
45824 @cindex target descriptions, TMS320C6x features
45825 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
45826 targets. It should contain registers @samp{A0} through @samp{A15},
45827 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
45829 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
45830 contain registers @samp{A16} through @samp{A31} and @samp{B16}
45831 through @samp{B31}.
45833 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
45834 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
45836 @node Operating System Information
45837 @appendix Operating System Information
45838 @cindex operating system information
45844 Users of @value{GDBN} often wish to obtain information about the state of
45845 the operating system running on the target---for example the list of
45846 processes, or the list of open files. This section describes the
45847 mechanism that makes it possible. This mechanism is similar to the
45848 target features mechanism (@pxref{Target Descriptions}), but focuses
45849 on a different aspect of target.
45851 Operating system information is retrieved from the target via the
45852 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
45853 read}). The object name in the request should be @samp{osdata}, and
45854 the @var{annex} identifies the data to be fetched.
45857 @appendixsection Process list
45858 @cindex operating system information, process list
45860 When requesting the process list, the @var{annex} field in the
45861 @samp{qXfer} request should be @samp{processes}. The returned data is
45862 an XML document. The formal syntax of this document is defined in
45863 @file{gdb/features/osdata.dtd}.
45865 An example document is:
45868 <?xml version="1.0"?>
45869 <!DOCTYPE target SYSTEM "osdata.dtd">
45870 <osdata type="processes">
45872 <column name="pid">1</column>
45873 <column name="user">root</column>
45874 <column name="command">/sbin/init</column>
45875 <column name="cores">1,2,3</column>
45880 Each item should include a column whose name is @samp{pid}. The value
45881 of that column should identify the process on the target. The
45882 @samp{user} and @samp{command} columns are optional, and will be
45883 displayed by @value{GDBN}. The @samp{cores} column, if present,
45884 should contain a comma-separated list of cores that this process
45885 is running on. Target may provide additional columns,
45886 which @value{GDBN} currently ignores.
45888 @node Trace File Format
45889 @appendix Trace File Format
45890 @cindex trace file format
45892 The trace file comes in three parts: a header, a textual description
45893 section, and a trace frame section with binary data.
45895 The header has the form @code{\x7fTRACE0\n}. The first byte is
45896 @code{0x7f} so as to indicate that the file contains binary data,
45897 while the @code{0} is a version number that may have different values
45900 The description section consists of multiple lines of @sc{ascii} text
45901 separated by newline characters (@code{0xa}). The lines may include a
45902 variety of optional descriptive or context-setting information, such
45903 as tracepoint definitions or register set size. @value{GDBN} will
45904 ignore any line that it does not recognize. An empty line marks the end
45909 Specifies the size of a register block in bytes. This is equal to the
45910 size of a @code{g} packet payload in the remote protocol. @var{size}
45911 is an ascii decimal number. There should be only one such line in
45912 a single trace file.
45914 @item status @var{status}
45915 Trace status. @var{status} has the same format as a @code{qTStatus}
45916 remote packet reply. There should be only one such line in a single trace
45919 @item tp @var{payload}
45920 Tracepoint definition. The @var{payload} has the same format as
45921 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
45922 may take multiple lines of definition, corresponding to the multiple
45925 @item tsv @var{payload}
45926 Trace state variable definition. The @var{payload} has the same format as
45927 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
45928 may take multiple lines of definition, corresponding to the multiple
45931 @item tdesc @var{payload}
45932 Target description in XML format. The @var{payload} is a single line of
45933 the XML file. All such lines should be concatenated together to get
45934 the original XML file. This file is in the same format as @code{qXfer}
45935 @code{features} payload, and corresponds to the main @code{target.xml}
45936 file. Includes are not allowed.
45940 The trace frame section consists of a number of consecutive frames.
45941 Each frame begins with a two-byte tracepoint number, followed by a
45942 four-byte size giving the amount of data in the frame. The data in
45943 the frame consists of a number of blocks, each introduced by a
45944 character indicating its type (at least register, memory, and trace
45945 state variable). The data in this section is raw binary, not a
45946 hexadecimal or other encoding; its endianness matches the target's
45949 @c FIXME bi-arch may require endianness/arch info in description section
45952 @item R @var{bytes}
45953 Register block. The number and ordering of bytes matches that of a
45954 @code{g} packet in the remote protocol. Note that these are the
45955 actual bytes, in target order, not a hexadecimal encoding.
45957 @item M @var{address} @var{length} @var{bytes}...
45958 Memory block. This is a contiguous block of memory, at the 8-byte
45959 address @var{address}, with a 2-byte length @var{length}, followed by
45960 @var{length} bytes.
45962 @item V @var{number} @var{value}
45963 Trace state variable block. This records the 8-byte signed value
45964 @var{value} of trace state variable numbered @var{number}.
45968 Future enhancements of the trace file format may include additional types
45971 @node Index Section Format
45972 @appendix @code{.gdb_index} section format
45973 @cindex .gdb_index section format
45974 @cindex index section format
45976 This section documents the index section that is created by @code{save
45977 gdb-index} (@pxref{Index Files}). The index section is
45978 DWARF-specific; some knowledge of DWARF is assumed in this
45981 The mapped index file format is designed to be directly
45982 @code{mmap}able on any architecture. In most cases, a datum is
45983 represented using a little-endian 32-bit integer value, called an
45984 @code{offset_type}. Big endian machines must byte-swap the values
45985 before using them. Exceptions to this rule are noted. The data is
45986 laid out such that alignment is always respected.
45988 A mapped index consists of several areas, laid out in order.
45992 The file header. This is a sequence of values, of @code{offset_type}
45993 unless otherwise noted:
45997 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
45998 Version 4 uses a different hashing function from versions 5 and 6.
45999 Version 6 includes symbols for inlined functions, whereas versions 4
46000 and 5 do not. Version 7 adds attributes to the CU indices in the
46001 symbol table. Version 8 specifies that symbols from DWARF type units
46002 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
46003 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
46005 @value{GDBN} will only read version 4, 5, or 6 indices
46006 by specifying @code{set use-deprecated-index-sections on}.
46007 GDB has a workaround for potentially broken version 7 indices so it is
46008 currently not flagged as deprecated.
46011 The offset, from the start of the file, of the CU list.
46014 The offset, from the start of the file, of the types CU list. Note
46015 that this area can be empty, in which case this offset will be equal
46016 to the next offset.
46019 The offset, from the start of the file, of the address area.
46022 The offset, from the start of the file, of the symbol table.
46025 The offset, from the start of the file, of the constant pool.
46029 The CU list. This is a sequence of pairs of 64-bit little-endian
46030 values, sorted by the CU offset. The first element in each pair is
46031 the offset of a CU in the @code{.debug_info} section. The second
46032 element in each pair is the length of that CU. References to a CU
46033 elsewhere in the map are done using a CU index, which is just the
46034 0-based index into this table. Note that if there are type CUs, then
46035 conceptually CUs and type CUs form a single list for the purposes of
46039 The types CU list. This is a sequence of triplets of 64-bit
46040 little-endian values. In a triplet, the first value is the CU offset,
46041 the second value is the type offset in the CU, and the third value is
46042 the type signature. The types CU list is not sorted.
46045 The address area. The address area consists of a sequence of address
46046 entries. Each address entry has three elements:
46050 The low address. This is a 64-bit little-endian value.
46053 The high address. This is a 64-bit little-endian value. Like
46054 @code{DW_AT_high_pc}, the value is one byte beyond the end.
46057 The CU index. This is an @code{offset_type} value.
46061 The symbol table. This is an open-addressed hash table. The size of
46062 the hash table is always a power of 2.
46064 Each slot in the hash table consists of a pair of @code{offset_type}
46065 values. The first value is the offset of the symbol's name in the
46066 constant pool. The second value is the offset of the CU vector in the
46069 If both values are 0, then this slot in the hash table is empty. This
46070 is ok because while 0 is a valid constant pool index, it cannot be a
46071 valid index for both a string and a CU vector.
46073 The hash value for a table entry is computed by applying an
46074 iterative hash function to the symbol's name. Starting with an
46075 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
46076 the string is incorporated into the hash using the formula depending on the
46081 The formula is @code{r = r * 67 + c - 113}.
46083 @item Versions 5 to 7
46084 The formula is @code{r = r * 67 + tolower (c) - 113}.
46087 The terminating @samp{\0} is not incorporated into the hash.
46089 The step size used in the hash table is computed via
46090 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
46091 value, and @samp{size} is the size of the hash table. The step size
46092 is used to find the next candidate slot when handling a hash
46095 The names of C@t{++} symbols in the hash table are canonicalized. We
46096 don't currently have a simple description of the canonicalization
46097 algorithm; if you intend to create new index sections, you must read
46101 The constant pool. This is simply a bunch of bytes. It is organized
46102 so that alignment is correct: CU vectors are stored first, followed by
46105 A CU vector in the constant pool is a sequence of @code{offset_type}
46106 values. The first value is the number of CU indices in the vector.
46107 Each subsequent value is the index and symbol attributes of a CU in
46108 the CU list. This element in the hash table is used to indicate which
46109 CUs define the symbol and how the symbol is used.
46110 See below for the format of each CU index+attributes entry.
46112 A string in the constant pool is zero-terminated.
46115 Attributes were added to CU index values in @code{.gdb_index} version 7.
46116 If a symbol has multiple uses within a CU then there is one
46117 CU index+attributes value for each use.
46119 The format of each CU index+attributes entry is as follows
46125 This is the index of the CU in the CU list.
46127 These bits are reserved for future purposes and must be zero.
46129 The kind of the symbol in the CU.
46133 This value is reserved and should not be used.
46134 By reserving zero the full @code{offset_type} value is backwards compatible
46135 with previous versions of the index.
46137 The symbol is a type.
46139 The symbol is a variable or an enum value.
46141 The symbol is a function.
46143 Any other kind of symbol.
46145 These values are reserved.
46149 This bit is zero if the value is global and one if it is static.
46151 The determination of whether a symbol is global or static is complicated.
46152 The authorative reference is the file @file{dwarf2read.c} in
46153 @value{GDBN} sources.
46157 This pseudo-code describes the computation of a symbol's kind and
46158 global/static attributes in the index.
46161 is_external = get_attribute (die, DW_AT_external);
46162 language = get_attribute (cu_die, DW_AT_language);
46165 case DW_TAG_typedef:
46166 case DW_TAG_base_type:
46167 case DW_TAG_subrange_type:
46171 case DW_TAG_enumerator:
46173 is_static = language != CPLUS;
46175 case DW_TAG_subprogram:
46177 is_static = ! (is_external || language == ADA);
46179 case DW_TAG_constant:
46181 is_static = ! is_external;
46183 case DW_TAG_variable:
46185 is_static = ! is_external;
46187 case DW_TAG_namespace:
46191 case DW_TAG_class_type:
46192 case DW_TAG_interface_type:
46193 case DW_TAG_structure_type:
46194 case DW_TAG_union_type:
46195 case DW_TAG_enumeration_type:
46197 is_static = language != CPLUS;
46205 @appendix Manual pages
46209 * gdb man:: The GNU Debugger man page
46210 * gdbserver man:: Remote Server for the GNU Debugger man page
46211 * gcore man:: Generate a core file of a running program
46212 * gdbinit man:: gdbinit scripts
46213 * gdb-add-index man:: Add index files to speed up GDB
46219 @c man title gdb The GNU Debugger
46221 @c man begin SYNOPSIS gdb
46222 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
46223 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
46224 [@option{-b}@w{ }@var{bps}]
46225 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
46226 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
46227 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
46228 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
46229 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
46232 @c man begin DESCRIPTION gdb
46233 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
46234 going on ``inside'' another program while it executes -- or what another
46235 program was doing at the moment it crashed.
46237 @value{GDBN} can do four main kinds of things (plus other things in support of
46238 these) to help you catch bugs in the act:
46242 Start your program, specifying anything that might affect its behavior.
46245 Make your program stop on specified conditions.
46248 Examine what has happened, when your program has stopped.
46251 Change things in your program, so you can experiment with correcting the
46252 effects of one bug and go on to learn about another.
46255 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
46258 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
46259 commands from the terminal until you tell it to exit with the @value{GDBN}
46260 command @code{quit}. You can get online help from @value{GDBN} itself
46261 by using the command @code{help}.
46263 You can run @code{gdb} with no arguments or options; but the most
46264 usual way to start @value{GDBN} is with one argument or two, specifying an
46265 executable program as the argument:
46271 You can also start with both an executable program and a core file specified:
46277 You can, instead, specify a process ID as a second argument or use option
46278 @code{-p}, if you want to debug a running process:
46286 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
46287 can omit the @var{program} filename.
46289 Here are some of the most frequently needed @value{GDBN} commands:
46291 @c pod2man highlights the right hand side of the @item lines.
46293 @item break [@var{file}:]@var{function}
46294 Set a breakpoint at @var{function} (in @var{file}).
46296 @item run [@var{arglist}]
46297 Start your program (with @var{arglist}, if specified).
46300 Backtrace: display the program stack.
46302 @item print @var{expr}
46303 Display the value of an expression.
46306 Continue running your program (after stopping, e.g. at a breakpoint).
46309 Execute next program line (after stopping); step @emph{over} any
46310 function calls in the line.
46312 @item edit [@var{file}:]@var{function}
46313 look at the program line where it is presently stopped.
46315 @item list [@var{file}:]@var{function}
46316 type the text of the program in the vicinity of where it is presently stopped.
46319 Execute next program line (after stopping); step @emph{into} any
46320 function calls in the line.
46322 @item help [@var{name}]
46323 Show information about @value{GDBN} command @var{name}, or general information
46324 about using @value{GDBN}.
46327 Exit from @value{GDBN}.
46331 For full details on @value{GDBN},
46332 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46333 by Richard M. Stallman and Roland H. Pesch. The same text is available online
46334 as the @code{gdb} entry in the @code{info} program.
46338 @c man begin OPTIONS gdb
46339 Any arguments other than options specify an executable
46340 file and core file (or process ID); that is, the first argument
46341 encountered with no
46342 associated option flag is equivalent to a @option{-se} option, and the second,
46343 if any, is equivalent to a @option{-c} option if it's the name of a file.
46345 both long and short forms; both are shown here. The long forms are also
46346 recognized if you truncate them, so long as enough of the option is
46347 present to be unambiguous. (If you prefer, you can flag option
46348 arguments with @option{+} rather than @option{-}, though we illustrate the
46349 more usual convention.)
46351 All the options and command line arguments you give are processed
46352 in sequential order. The order makes a difference when the @option{-x}
46358 List all options, with brief explanations.
46360 @item -symbols=@var{file}
46361 @itemx -s @var{file}
46362 Read symbol table from file @var{file}.
46365 Enable writing into executable and core files.
46367 @item -exec=@var{file}
46368 @itemx -e @var{file}
46369 Use file @var{file} as the executable file to execute when
46370 appropriate, and for examining pure data in conjunction with a core
46373 @item -se=@var{file}
46374 Read symbol table from file @var{file} and use it as the executable
46377 @item -core=@var{file}
46378 @itemx -c @var{file}
46379 Use file @var{file} as a core dump to examine.
46381 @item -command=@var{file}
46382 @itemx -x @var{file}
46383 Execute @value{GDBN} commands from file @var{file}.
46385 @item -ex @var{command}
46386 Execute given @value{GDBN} @var{command}.
46388 @item -directory=@var{directory}
46389 @itemx -d @var{directory}
46390 Add @var{directory} to the path to search for source files.
46393 Do not execute commands from @file{~/.gdbinit}.
46397 Do not execute commands from any @file{.gdbinit} initialization files.
46401 ``Quiet''. Do not print the introductory and copyright messages. These
46402 messages are also suppressed in batch mode.
46405 Run in batch mode. Exit with status @code{0} after processing all the command
46406 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
46407 Exit with nonzero status if an error occurs in executing the @value{GDBN}
46408 commands in the command files.
46410 Batch mode may be useful for running @value{GDBN} as a filter, for example to
46411 download and run a program on another computer; in order to make this
46412 more useful, the message
46415 Program exited normally.
46419 (which is ordinarily issued whenever a program running under @value{GDBN} control
46420 terminates) is not issued when running in batch mode.
46422 @item -cd=@var{directory}
46423 Run @value{GDBN} using @var{directory} as its working directory,
46424 instead of the current directory.
46428 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
46429 @value{GDBN} to output the full file name and line number in a standard,
46430 recognizable fashion each time a stack frame is displayed (which
46431 includes each time the program stops). This recognizable format looks
46432 like two @samp{\032} characters, followed by the file name, line number
46433 and character position separated by colons, and a newline. The
46434 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
46435 characters as a signal to display the source code for the frame.
46438 Set the line speed (baud rate or bits per second) of any serial
46439 interface used by @value{GDBN} for remote debugging.
46441 @item -tty=@var{device}
46442 Run using @var{device} for your program's standard input and output.
46446 @c man begin SEEALSO gdb
46448 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46449 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46450 documentation are properly installed at your site, the command
46457 should give you access to the complete manual.
46459 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46460 Richard M. Stallman and Roland H. Pesch, July 1991.
46464 @node gdbserver man
46465 @heading gdbserver man
46467 @c man title gdbserver Remote Server for the GNU Debugger
46469 @c man begin SYNOPSIS gdbserver
46470 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
46472 gdbserver --attach @var{comm} @var{pid}
46474 gdbserver --multi @var{comm}
46478 @c man begin DESCRIPTION gdbserver
46479 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
46480 than the one which is running the program being debugged.
46483 @subheading Usage (server (target) side)
46486 Usage (server (target) side):
46489 First, you need to have a copy of the program you want to debug put onto
46490 the target system. The program can be stripped to save space if needed, as
46491 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
46492 the @value{GDBN} running on the host system.
46494 To use the server, you log on to the target system, and run the @command{gdbserver}
46495 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
46496 your program, and (c) its arguments. The general syntax is:
46499 target> gdbserver @var{comm} @var{program} [@var{args} ...]
46502 For example, using a serial port, you might say:
46506 @c @file would wrap it as F</dev/com1>.
46507 target> gdbserver /dev/com1 emacs foo.txt
46510 target> gdbserver @file{/dev/com1} emacs foo.txt
46514 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
46515 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
46516 waits patiently for the host @value{GDBN} to communicate with it.
46518 To use a TCP connection, you could say:
46521 target> gdbserver host:2345 emacs foo.txt
46524 This says pretty much the same thing as the last example, except that we are
46525 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
46526 that we are expecting to see a TCP connection from @code{host} to local TCP port
46527 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
46528 want for the port number as long as it does not conflict with any existing TCP
46529 ports on the target system. This same port number must be used in the host
46530 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
46531 you chose a port number that conflicts with another service, @command{gdbserver} will
46532 print an error message and exit.
46534 @command{gdbserver} can also attach to running programs.
46535 This is accomplished via the @option{--attach} argument. The syntax is:
46538 target> gdbserver --attach @var{comm} @var{pid}
46541 @var{pid} is the process ID of a currently running process. It isn't
46542 necessary to point @command{gdbserver} at a binary for the running process.
46544 To start @code{gdbserver} without supplying an initial command to run
46545 or process ID to attach, use the @option{--multi} command line option.
46546 In such case you should connect using @kbd{target extended-remote} to start
46547 the program you want to debug.
46550 target> gdbserver --multi @var{comm}
46554 @subheading Usage (host side)
46560 You need an unstripped copy of the target program on your host system, since
46561 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
46562 would, with the target program as the first argument. (You may need to use the
46563 @option{--baud} option if the serial line is running at anything except 9600 baud.)
46564 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
46565 new command you need to know about is @code{target remote}
46566 (or @code{target extended-remote}). Its argument is either
46567 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
46568 descriptor. For example:
46572 @c @file would wrap it as F</dev/ttyb>.
46573 (gdb) target remote /dev/ttyb
46576 (gdb) target remote @file{/dev/ttyb}
46581 communicates with the server via serial line @file{/dev/ttyb}, and:
46584 (gdb) target remote the-target:2345
46588 communicates via a TCP connection to port 2345 on host `the-target', where
46589 you previously started up @command{gdbserver} with the same port number. Note that for
46590 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
46591 command, otherwise you may get an error that looks something like
46592 `Connection refused'.
46594 @command{gdbserver} can also debug multiple inferiors at once,
46597 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
46598 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
46601 @ref{Inferiors Connections and Programs}.
46603 In such case use the @code{extended-remote} @value{GDBN} command variant:
46606 (gdb) target extended-remote the-target:2345
46609 The @command{gdbserver} option @option{--multi} may or may not be used in such
46613 @c man begin OPTIONS gdbserver
46614 There are three different modes for invoking @command{gdbserver}:
46619 Debug a specific program specified by its program name:
46622 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
46625 The @var{comm} parameter specifies how should the server communicate
46626 with @value{GDBN}; it is either a device name (to use a serial line),
46627 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
46628 stdin/stdout of @code{gdbserver}. Specify the name of the program to
46629 debug in @var{prog}. Any remaining arguments will be passed to the
46630 program verbatim. When the program exits, @value{GDBN} will close the
46631 connection, and @code{gdbserver} will exit.
46634 Debug a specific program by specifying the process ID of a running
46638 gdbserver --attach @var{comm} @var{pid}
46641 The @var{comm} parameter is as described above. Supply the process ID
46642 of a running program in @var{pid}; @value{GDBN} will do everything
46643 else. Like with the previous mode, when the process @var{pid} exits,
46644 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
46647 Multi-process mode -- debug more than one program/process:
46650 gdbserver --multi @var{comm}
46653 In this mode, @value{GDBN} can instruct @command{gdbserver} which
46654 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
46655 close the connection when a process being debugged exits, so you can
46656 debug several processes in the same session.
46659 In each of the modes you may specify these options:
46664 List all options, with brief explanations.
46667 This option causes @command{gdbserver} to print its version number and exit.
46670 @command{gdbserver} will attach to a running program. The syntax is:
46673 target> gdbserver --attach @var{comm} @var{pid}
46676 @var{pid} is the process ID of a currently running process. It isn't
46677 necessary to point @command{gdbserver} at a binary for the running process.
46680 To start @code{gdbserver} without supplying an initial command to run
46681 or process ID to attach, use this command line option.
46682 Then you can connect using @kbd{target extended-remote} and start
46683 the program you want to debug. The syntax is:
46686 target> gdbserver --multi @var{comm}
46690 Instruct @code{gdbserver} to display extra status information about the debugging
46692 This option is intended for @code{gdbserver} development and for bug reports to
46695 @item --remote-debug
46696 Instruct @code{gdbserver} to display remote protocol debug output.
46697 This option is intended for @code{gdbserver} development and for bug reports to
46700 @item --debug-file=@var{filename}
46701 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
46702 This option is intended for @code{gdbserver} development and for bug reports to
46705 @item --debug-format=option1@r{[},option2,...@r{]}
46706 Instruct @code{gdbserver} to include extra information in each line
46707 of debugging output.
46708 @xref{Other Command-Line Arguments for gdbserver}.
46711 Specify a wrapper to launch programs
46712 for debugging. The option should be followed by the name of the
46713 wrapper, then any command-line arguments to pass to the wrapper, then
46714 @kbd{--} indicating the end of the wrapper arguments.
46717 By default, @command{gdbserver} keeps the listening TCP port open, so that
46718 additional connections are possible. However, if you start @code{gdbserver}
46719 with the @option{--once} option, it will stop listening for any further
46720 connection attempts after connecting to the first @value{GDBN} session.
46722 @c --disable-packet is not documented for users.
46724 @c --disable-randomization and --no-disable-randomization are superseded by
46725 @c QDisableRandomization.
46730 @c man begin SEEALSO gdbserver
46732 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46733 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46734 documentation are properly installed at your site, the command
46740 should give you access to the complete manual.
46742 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46743 Richard M. Stallman and Roland H. Pesch, July 1991.
46750 @c man title gcore Generate a core file of a running program
46753 @c man begin SYNOPSIS gcore
46754 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
46758 @c man begin DESCRIPTION gcore
46759 Generate core dumps of one or more running programs with process IDs
46760 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
46761 is equivalent to one produced by the kernel when the process crashes
46762 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
46763 limit). However, unlike after a crash, after @command{gcore} finishes
46764 its job the program remains running without any change.
46767 @c man begin OPTIONS gcore
46770 Dump all memory mappings. The actual effect of this option depends on
46771 the Operating System. On @sc{gnu}/Linux, it will disable
46772 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
46773 enable @code{dump-excluded-mappings} (@pxref{set
46774 dump-excluded-mappings}).
46776 @item -o @var{prefix}
46777 The optional argument @var{prefix} specifies the prefix to be used
46778 when composing the file names of the core dumps. The file name is
46779 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
46780 process ID of the running program being analyzed by @command{gcore}.
46781 If not specified, @var{prefix} defaults to @var{gcore}.
46785 @c man begin SEEALSO gcore
46787 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46788 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46789 documentation are properly installed at your site, the command
46796 should give you access to the complete manual.
46798 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46799 Richard M. Stallman and Roland H. Pesch, July 1991.
46806 @c man title gdbinit GDB initialization scripts
46809 @c man begin SYNOPSIS gdbinit
46810 @ifset SYSTEM_GDBINIT
46811 @value{SYSTEM_GDBINIT}
46814 @ifset SYSTEM_GDBINIT_DIR
46815 @value{SYSTEM_GDBINIT_DIR}/*
46824 @c man begin DESCRIPTION gdbinit
46825 These files contain @value{GDBN} commands to automatically execute during
46826 @value{GDBN} startup. The lines of contents are canned sequences of commands,
46829 the @value{GDBN} manual in node @code{Sequences}
46830 -- shell command @code{info -f gdb -n Sequences}.
46836 Please read more in
46838 the @value{GDBN} manual in node @code{Startup}
46839 -- shell command @code{info -f gdb -n Startup}.
46846 @ifset SYSTEM_GDBINIT
46847 @item @value{SYSTEM_GDBINIT}
46849 @ifclear SYSTEM_GDBINIT
46850 @item (not enabled with @code{--with-system-gdbinit} during compilation)
46852 System-wide initialization file. It is executed unless user specified
46853 @value{GDBN} option @code{-nx} or @code{-n}.
46856 the @value{GDBN} manual in node @code{System-wide configuration}
46857 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
46859 @ifset SYSTEM_GDBINIT_DIR
46860 @item @value{SYSTEM_GDBINIT_DIR}
46862 @ifclear SYSTEM_GDBINIT_DIR
46863 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
46865 System-wide initialization directory. All files in this directory are
46866 executed on startup unless user specified @value{GDBN} option @code{-nx} or
46867 @code{-n}, as long as they have a recognized file extension.
46870 the @value{GDBN} manual in node @code{System-wide configuration}
46871 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
46874 @ref{System-wide configuration}.
46878 User initialization file. It is executed unless user specified
46879 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
46882 Initialization file for current directory. It may need to be enabled with
46883 @value{GDBN} security command @code{set auto-load local-gdbinit}.
46886 the @value{GDBN} manual in node @code{Init File in the Current Directory}
46887 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
46890 @ref{Init File in the Current Directory}.
46895 @c man begin SEEALSO gdbinit
46897 gdb(1), @code{info -f gdb -n Startup}
46899 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46900 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46901 documentation are properly installed at your site, the command
46907 should give you access to the complete manual.
46909 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46910 Richard M. Stallman and Roland H. Pesch, July 1991.
46914 @node gdb-add-index man
46915 @heading gdb-add-index
46916 @pindex gdb-add-index
46917 @anchor{gdb-add-index}
46919 @c man title gdb-add-index Add index files to speed up GDB
46921 @c man begin SYNOPSIS gdb-add-index
46922 gdb-add-index @var{filename}
46925 @c man begin DESCRIPTION gdb-add-index
46926 When @value{GDBN} finds a symbol file, it scans the symbols in the
46927 file in order to construct an internal symbol table. This lets most
46928 @value{GDBN} operations work quickly--at the cost of a delay early on.
46929 For large programs, this delay can be quite lengthy, so @value{GDBN}
46930 provides a way to build an index, which speeds up startup.
46932 To determine whether a file contains such an index, use the command
46933 @kbd{readelf -S filename}: the index is stored in a section named
46934 @code{.gdb_index}. The index file can only be produced on systems
46935 which use ELF binaries and DWARF debug information (i.e., sections
46936 named @code{.debug_*}).
46938 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
46939 in the @env{PATH} environment variable. If you want to use different
46940 versions of these programs, you can specify them through the
46941 @env{GDB} and @env{OBJDUMP} environment variables.
46945 the @value{GDBN} manual in node @code{Index Files}
46946 -- shell command @kbd{info -f gdb -n "Index Files"}.
46953 @c man begin SEEALSO gdb-add-index
46955 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
46956 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
46957 documentation are properly installed at your site, the command
46963 should give you access to the complete manual.
46965 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
46966 Richard M. Stallman and Roland H. Pesch, July 1991.
46972 @node GNU Free Documentation License
46973 @appendix GNU Free Documentation License
46976 @node Concept Index
46977 @unnumbered Concept Index
46981 @node Command and Variable Index
46982 @unnumbered Command, Variable, and Function Index
46987 % I think something like @@colophon should be in texinfo. In the
46989 \long\def\colophon{\hbox to0pt{}\vfill
46990 \centerline{The body of this manual is set in}
46991 \centerline{\fontname\tenrm,}
46992 \centerline{with headings in {\bf\fontname\tenbf}}
46993 \centerline{and examples in {\tt\fontname\tentt}.}
46994 \centerline{{\it\fontname\tenit\/},}
46995 \centerline{{\bf\fontname\tenbf}, and}
46996 \centerline{{\sl\fontname\tensl\/}}
46997 \centerline{are used for emphasis.}\vfill}
46999 % Blame: doc@@cygnus.com, 1991.