1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2017 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{} 1988-2017 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2017 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.
550 @chapter A Sample @value{GDBN} Session
552 You can use this manual at your leisure to read all about @value{GDBN}.
553 However, a handful of commands are enough to get started using the
554 debugger. This chapter illustrates those commands.
557 In this sample session, we emphasize user input like this: @b{input},
558 to make it easier to pick out from the surrounding output.
561 @c FIXME: this example may not be appropriate for some configs, where
562 @c FIXME...primary interest is in remote use.
564 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
565 processor) exhibits the following bug: sometimes, when we change its
566 quote strings from the default, the commands used to capture one macro
567 definition within another stop working. In the following short @code{m4}
568 session, we define a macro @code{foo} which expands to @code{0000}; we
569 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
570 same thing. However, when we change the open quote string to
571 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
572 procedure fails to define a new synonym @code{baz}:
581 @b{define(bar,defn(`foo'))}
585 @b{changequote(<QUOTE>,<UNQUOTE>)}
587 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
590 m4: End of input: 0: fatal error: EOF in string
594 Let us use @value{GDBN} to try to see what is going on.
597 $ @b{@value{GDBP} m4}
598 @c FIXME: this falsifies the exact text played out, to permit smallbook
599 @c FIXME... format to come out better.
600 @value{GDBN} is free software and you are welcome to distribute copies
601 of it under certain conditions; type "show copying" to see
603 There is absolutely no warranty for @value{GDBN}; type "show warranty"
606 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
611 @value{GDBN} reads only enough symbol data to know where to find the
612 rest when needed; as a result, the first prompt comes up very quickly.
613 We now tell @value{GDBN} to use a narrower display width than usual, so
614 that examples fit in this manual.
617 (@value{GDBP}) @b{set width 70}
621 We need to see how the @code{m4} built-in @code{changequote} works.
622 Having looked at the source, we know the relevant subroutine is
623 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
624 @code{break} command.
627 (@value{GDBP}) @b{break m4_changequote}
628 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
632 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
633 control; as long as control does not reach the @code{m4_changequote}
634 subroutine, the program runs as usual:
637 (@value{GDBP}) @b{run}
638 Starting program: /work/Editorial/gdb/gnu/m4/m4
646 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
647 suspends execution of @code{m4}, displaying information about the
648 context where it stops.
651 @b{changequote(<QUOTE>,<UNQUOTE>)}
653 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
655 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
659 Now we use the command @code{n} (@code{next}) to advance execution to
660 the next line of the current function.
664 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
669 @code{set_quotes} looks like a promising subroutine. We can go into it
670 by using the command @code{s} (@code{step}) instead of @code{next}.
671 @code{step} goes to the next line to be executed in @emph{any}
672 subroutine, so it steps into @code{set_quotes}.
676 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 530 if (lquote != def_lquote)
682 The display that shows the subroutine where @code{m4} is now
683 suspended (and its arguments) is called a stack frame display. It
684 shows a summary of the stack. We can use the @code{backtrace}
685 command (which can also be spelled @code{bt}), to see where we are
686 in the stack as a whole: the @code{backtrace} command displays a
687 stack frame for each active subroutine.
690 (@value{GDBP}) @b{bt}
691 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
693 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
695 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
696 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
698 #4 0x79dc in expand_input () at macro.c:40
699 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
703 We step through a few more lines to see what happens. The first two
704 times, we can use @samp{s}; the next two times we use @code{n} to avoid
705 falling into the @code{xstrdup} subroutine.
709 0x3b5c 532 if (rquote != def_rquote)
711 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
712 def_lquote : xstrdup(lq);
714 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
717 538 len_lquote = strlen(rquote);
721 The last line displayed looks a little odd; we can examine the variables
722 @code{lquote} and @code{rquote} to see if they are in fact the new left
723 and right quotes we specified. We use the command @code{p}
724 (@code{print}) to see their values.
727 (@value{GDBP}) @b{p lquote}
728 $1 = 0x35d40 "<QUOTE>"
729 (@value{GDBP}) @b{p rquote}
730 $2 = 0x35d50 "<UNQUOTE>"
734 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
735 To look at some context, we can display ten lines of source
736 surrounding the current line with the @code{l} (@code{list}) command.
742 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
744 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
747 538 len_lquote = strlen(rquote);
748 539 len_rquote = strlen(lquote);
755 Let us step past the two lines that set @code{len_lquote} and
756 @code{len_rquote}, and then examine the values of those variables.
760 539 len_rquote = strlen(lquote);
763 (@value{GDBP}) @b{p len_lquote}
765 (@value{GDBP}) @b{p len_rquote}
770 That certainly looks wrong, assuming @code{len_lquote} and
771 @code{len_rquote} are meant to be the lengths of @code{lquote} and
772 @code{rquote} respectively. We can set them to better values using
773 the @code{p} command, since it can print the value of
774 any expression---and that expression can include subroutine calls and
778 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
780 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
785 Is that enough to fix the problem of using the new quotes with the
786 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
787 executing with the @code{c} (@code{continue}) command, and then try the
788 example that caused trouble initially:
794 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
801 Success! The new quotes now work just as well as the default ones. The
802 problem seems to have been just the two typos defining the wrong
803 lengths. We allow @code{m4} exit by giving it an EOF as input:
807 Program exited normally.
811 The message @samp{Program exited normally.} is from @value{GDBN}; it
812 indicates @code{m4} has finished executing. We can end our @value{GDBN}
813 session with the @value{GDBN} @code{quit} command.
816 (@value{GDBP}) @b{quit}
820 @chapter Getting In and Out of @value{GDBN}
822 This chapter discusses how to start @value{GDBN}, and how to get out of it.
826 type @samp{@value{GDBP}} to start @value{GDBN}.
828 type @kbd{quit} or @kbd{Ctrl-d} to exit.
832 * Invoking GDB:: How to start @value{GDBN}
833 * Quitting GDB:: How to quit @value{GDBN}
834 * Shell Commands:: How to use shell commands inside @value{GDBN}
835 * Logging Output:: How to log @value{GDBN}'s output to a file
839 @section Invoking @value{GDBN}
841 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
842 @value{GDBN} reads commands from the terminal until you tell it to exit.
844 You can also run @code{@value{GDBP}} with a variety of arguments and options,
845 to specify more of your debugging environment at the outset.
847 The command-line options described here are designed
848 to cover a variety of situations; in some environments, some of these
849 options may effectively be unavailable.
851 The most usual way to start @value{GDBN} is with one argument,
852 specifying an executable program:
855 @value{GDBP} @var{program}
859 You can also start with both an executable program and a core file
863 @value{GDBP} @var{program} @var{core}
866 You can, instead, specify a process ID as a second argument, if you want
867 to debug a running process:
870 @value{GDBP} @var{program} 1234
874 would attach @value{GDBN} to process @code{1234} (unless you also have a file
875 named @file{1234}; @value{GDBN} does check for a core file first).
877 Taking advantage of the second command-line argument requires a fairly
878 complete operating system; when you use @value{GDBN} as a remote
879 debugger attached to a bare board, there may not be any notion of
880 ``process'', and there is often no way to get a core dump. @value{GDBN}
881 will warn you if it is unable to attach or to read core dumps.
883 You can optionally have @code{@value{GDBP}} pass any arguments after the
884 executable file to the inferior using @code{--args}. This option stops
887 @value{GDBP} --args gcc -O2 -c foo.c
889 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
890 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
892 You can run @code{@value{GDBP}} without printing the front material, which describes
893 @value{GDBN}'s non-warranty, by specifying @code{--silent}
894 (or @code{-q}/@code{--quiet}):
897 @value{GDBP} --silent
901 You can further control how @value{GDBN} starts up by using command-line
902 options. @value{GDBN} itself can remind you of the options available.
912 to display all available options and briefly describe their use
913 (@samp{@value{GDBP} -h} is a shorter equivalent).
915 All options and command line arguments you give are processed
916 in sequential order. The order makes a difference when the
917 @samp{-x} option is used.
921 * File Options:: Choosing files
922 * Mode Options:: Choosing modes
923 * Startup:: What @value{GDBN} does during startup
927 @subsection Choosing Files
929 When @value{GDBN} starts, it reads any arguments other than options as
930 specifying an executable file and core file (or process ID). This is
931 the same as if the arguments were specified by the @samp{-se} and
932 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
933 first argument that does not have an associated option flag as
934 equivalent to the @samp{-se} option followed by that argument; and the
935 second argument that does not have an associated option flag, if any, as
936 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
937 If the second argument begins with a decimal digit, @value{GDBN} will
938 first attempt to attach to it as a process, and if that fails, attempt
939 to open it as a corefile. If you have a corefile whose name begins with
940 a digit, you can prevent @value{GDBN} from treating it as a pid by
941 prefixing it with @file{./}, e.g.@: @file{./12345}.
943 If @value{GDBN} has not been configured to included core file support,
944 such as for most embedded targets, then it will complain about a second
945 argument and ignore it.
947 Many options have both long and short forms; both are shown in the
948 following list. @value{GDBN} also recognizes the long forms if you truncate
949 them, so long as enough of the option is present to be unambiguous.
950 (If you prefer, you can flag option arguments with @samp{--} rather
951 than @samp{-}, though we illustrate the more usual convention.)
953 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
954 @c way, both those who look for -foo and --foo in the index, will find
958 @item -symbols @var{file}
960 @cindex @code{--symbols}
962 Read symbol table from file @var{file}.
964 @item -exec @var{file}
966 @cindex @code{--exec}
968 Use file @var{file} as the executable file to execute when appropriate,
969 and for examining pure data in conjunction with a core dump.
973 Read symbol table from file @var{file} and use it as the executable
976 @item -core @var{file}
978 @cindex @code{--core}
980 Use file @var{file} as a core dump to examine.
982 @item -pid @var{number}
983 @itemx -p @var{number}
986 Connect to process ID @var{number}, as with the @code{attach} command.
988 @item -command @var{file}
990 @cindex @code{--command}
992 Execute commands from file @var{file}. The contents of this file is
993 evaluated exactly as the @code{source} command would.
994 @xref{Command Files,, Command files}.
996 @item -eval-command @var{command}
997 @itemx -ex @var{command}
998 @cindex @code{--eval-command}
1000 Execute a single @value{GDBN} command.
1002 This option may be used multiple times to call multiple commands. It may
1003 also be interleaved with @samp{-command} as required.
1006 @value{GDBP} -ex 'target sim' -ex 'load' \
1007 -x setbreakpoints -ex 'run' a.out
1010 @item -init-command @var{file}
1011 @itemx -ix @var{file}
1012 @cindex @code{--init-command}
1014 Execute commands from file @var{file} before loading the inferior (but
1015 after loading gdbinit files).
1018 @item -init-eval-command @var{command}
1019 @itemx -iex @var{command}
1020 @cindex @code{--init-eval-command}
1022 Execute a single @value{GDBN} command before loading the inferior (but
1023 after loading gdbinit files).
1026 @item -directory @var{directory}
1027 @itemx -d @var{directory}
1028 @cindex @code{--directory}
1030 Add @var{directory} to the path to search for source and script files.
1034 @cindex @code{--readnow}
1036 Read each symbol file's entire symbol table immediately, rather than
1037 the default, which is to read it incrementally as it is needed.
1038 This makes startup slower, but makes future operations faster.
1043 @subsection Choosing Modes
1045 You can run @value{GDBN} in various alternative modes---for example, in
1046 batch mode or quiet mode.
1054 Do not execute commands found in any initialization file.
1055 There are three init files, loaded in the following order:
1058 @item @file{system.gdbinit}
1059 This is the system-wide init file.
1060 Its location is specified with the @code{--with-system-gdbinit}
1061 configure option (@pxref{System-wide configuration}).
1062 It is loaded first when @value{GDBN} starts, before command line options
1063 have been processed.
1064 @item @file{~/.gdbinit}
1065 This is the init file in your home directory.
1066 It is loaded next, after @file{system.gdbinit}, and before
1067 command options have been processed.
1068 @item @file{./.gdbinit}
1069 This is the init file in the current directory.
1070 It is loaded last, after command line options other than @code{-x} and
1071 @code{-ex} have been processed. Command line options @code{-x} and
1072 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1075 For further documentation on startup processing, @xref{Startup}.
1076 For documentation on how to write command files,
1077 @xref{Command Files,,Command Files}.
1082 Do not execute commands found in @file{~/.gdbinit}, the init file
1083 in your home directory.
1089 @cindex @code{--quiet}
1090 @cindex @code{--silent}
1092 ``Quiet''. Do not print the introductory and copyright messages. These
1093 messages are also suppressed in batch mode.
1096 @cindex @code{--batch}
1097 Run in batch mode. Exit with status @code{0} after processing all the
1098 command files specified with @samp{-x} (and all commands from
1099 initialization files, if not inhibited with @samp{-n}). Exit with
1100 nonzero status if an error occurs in executing the @value{GDBN} commands
1101 in the command files. Batch mode also disables pagination, sets unlimited
1102 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1103 off} were in effect (@pxref{Messages/Warnings}).
1105 Batch mode may be useful for running @value{GDBN} as a filter, for
1106 example to download and run a program on another computer; in order to
1107 make this more useful, the message
1110 Program exited normally.
1114 (which is ordinarily issued whenever a program running under
1115 @value{GDBN} control terminates) is not issued when running in batch
1119 @cindex @code{--batch-silent}
1120 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1121 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1122 unaffected). This is much quieter than @samp{-silent} and would be useless
1123 for an interactive session.
1125 This is particularly useful when using targets that give @samp{Loading section}
1126 messages, for example.
1128 Note that targets that give their output via @value{GDBN}, as opposed to
1129 writing directly to @code{stdout}, will also be made silent.
1131 @item -return-child-result
1132 @cindex @code{--return-child-result}
1133 The return code from @value{GDBN} will be the return code from the child
1134 process (the process being debugged), with the following exceptions:
1138 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1139 internal error. In this case the exit code is the same as it would have been
1140 without @samp{-return-child-result}.
1142 The user quits with an explicit value. E.g., @samp{quit 1}.
1144 The child process never runs, or is not allowed to terminate, in which case
1145 the exit code will be -1.
1148 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1149 when @value{GDBN} is being used as a remote program loader or simulator
1154 @cindex @code{--nowindows}
1156 ``No windows''. If @value{GDBN} comes with a graphical user interface
1157 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1158 interface. If no GUI is available, this option has no effect.
1162 @cindex @code{--windows}
1164 If @value{GDBN} includes a GUI, then this option requires it to be
1167 @item -cd @var{directory}
1169 Run @value{GDBN} using @var{directory} as its working directory,
1170 instead of the current directory.
1172 @item -data-directory @var{directory}
1173 @itemx -D @var{directory}
1174 @cindex @code{--data-directory}
1176 Run @value{GDBN} using @var{directory} as its data directory.
1177 The data directory is where @value{GDBN} searches for its
1178 auxiliary files. @xref{Data Files}.
1182 @cindex @code{--fullname}
1184 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1185 subprocess. It tells @value{GDBN} to output the full file name and line
1186 number in a standard, recognizable fashion each time a stack frame is
1187 displayed (which includes each time your program stops). This
1188 recognizable format looks like two @samp{\032} characters, followed by
1189 the file name, line number and character position separated by colons,
1190 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1191 @samp{\032} characters as a signal to display the source code for the
1194 @item -annotate @var{level}
1195 @cindex @code{--annotate}
1196 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1197 effect is identical to using @samp{set annotate @var{level}}
1198 (@pxref{Annotations}). The annotation @var{level} controls how much
1199 information @value{GDBN} prints together with its prompt, values of
1200 expressions, source lines, and other types of output. Level 0 is the
1201 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1202 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1203 that control @value{GDBN}, and level 2 has been deprecated.
1205 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1209 @cindex @code{--args}
1210 Change interpretation of command line so that arguments following the
1211 executable file are passed as command line arguments to the inferior.
1212 This option stops option processing.
1214 @item -baud @var{bps}
1216 @cindex @code{--baud}
1218 Set the line speed (baud rate or bits per second) of any serial
1219 interface used by @value{GDBN} for remote debugging.
1221 @item -l @var{timeout}
1223 Set the timeout (in seconds) of any communication used by @value{GDBN}
1224 for remote debugging.
1226 @item -tty @var{device}
1227 @itemx -t @var{device}
1228 @cindex @code{--tty}
1230 Run using @var{device} for your program's standard input and output.
1231 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1233 @c resolve the situation of these eventually
1235 @cindex @code{--tui}
1236 Activate the @dfn{Text User Interface} when starting. The Text User
1237 Interface manages several text windows on the terminal, showing
1238 source, assembly, registers and @value{GDBN} command outputs
1239 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1240 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1241 Using @value{GDBN} under @sc{gnu} Emacs}).
1243 @item -interpreter @var{interp}
1244 @cindex @code{--interpreter}
1245 Use the interpreter @var{interp} for interface with the controlling
1246 program or device. This option is meant to be set by programs which
1247 communicate with @value{GDBN} using it as a back end.
1248 @xref{Interpreters, , Command Interpreters}.
1250 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1251 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1252 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1253 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1254 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1255 @sc{gdb/mi} interfaces are no longer supported.
1258 @cindex @code{--write}
1259 Open the executable and core files for both reading and writing. This
1260 is equivalent to the @samp{set write on} command inside @value{GDBN}
1264 @cindex @code{--statistics}
1265 This option causes @value{GDBN} to print statistics about time and
1266 memory usage after it completes each command and returns to the prompt.
1269 @cindex @code{--version}
1270 This option causes @value{GDBN} to print its version number and
1271 no-warranty blurb, and exit.
1273 @item -configuration
1274 @cindex @code{--configuration}
1275 This option causes @value{GDBN} to print details about its build-time
1276 configuration parameters, and then exit. These details can be
1277 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1282 @subsection What @value{GDBN} Does During Startup
1283 @cindex @value{GDBN} startup
1285 Here's the description of what @value{GDBN} does during session startup:
1289 Sets up the command interpreter as specified by the command line
1290 (@pxref{Mode Options, interpreter}).
1294 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1295 used when building @value{GDBN}; @pxref{System-wide configuration,
1296 ,System-wide configuration and settings}) and executes all the commands in
1299 @anchor{Home Directory Init File}
1301 Reads the init file (if any) in your home directory@footnote{On
1302 DOS/Windows systems, the home directory is the one pointed to by the
1303 @code{HOME} environment variable.} and executes all the commands in
1306 @anchor{Option -init-eval-command}
1308 Executes commands and command files specified by the @samp{-iex} and
1309 @samp{-ix} options in their specified order. Usually you should use the
1310 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1311 settings before @value{GDBN} init files get executed and before inferior
1315 Processes command line options and operands.
1317 @anchor{Init File in the Current Directory during Startup}
1319 Reads and executes the commands from init file (if any) in the current
1320 working directory as long as @samp{set auto-load local-gdbinit} is set to
1321 @samp{on} (@pxref{Init File in the Current Directory}).
1322 This is only done if the current directory is
1323 different from your home directory. Thus, you can have more than one
1324 init file, one generic in your home directory, and another, specific
1325 to the program you are debugging, in the directory where you invoke
1329 If the command line specified a program to debug, or a process to
1330 attach to, or a core file, @value{GDBN} loads any auto-loaded
1331 scripts provided for the program or for its loaded shared libraries.
1332 @xref{Auto-loading}.
1334 If you wish to disable the auto-loading during startup,
1335 you must do something like the following:
1338 $ gdb -iex "set auto-load python-scripts off" myprogram
1341 Option @samp{-ex} does not work because the auto-loading is then turned
1345 Executes commands and command files specified by the @samp{-ex} and
1346 @samp{-x} options in their specified order. @xref{Command Files}, for
1347 more details about @value{GDBN} command files.
1350 Reads the command history recorded in the @dfn{history file}.
1351 @xref{Command History}, for more details about the command history and the
1352 files where @value{GDBN} records it.
1355 Init files use the same syntax as @dfn{command files} (@pxref{Command
1356 Files}) and are processed by @value{GDBN} in the same way. The init
1357 file in your home directory can set options (such as @samp{set
1358 complaints}) that affect subsequent processing of command line options
1359 and operands. Init files are not executed if you use the @samp{-nx}
1360 option (@pxref{Mode Options, ,Choosing Modes}).
1362 To display the list of init files loaded by gdb at startup, you
1363 can use @kbd{gdb --help}.
1365 @cindex init file name
1366 @cindex @file{.gdbinit}
1367 @cindex @file{gdb.ini}
1368 The @value{GDBN} init files are normally called @file{.gdbinit}.
1369 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1370 the limitations of file names imposed by DOS filesystems. The Windows
1371 port of @value{GDBN} uses the standard name, but if it finds a
1372 @file{gdb.ini} file in your home directory, it warns you about that
1373 and suggests to rename the file to the standard name.
1377 @section Quitting @value{GDBN}
1378 @cindex exiting @value{GDBN}
1379 @cindex leaving @value{GDBN}
1382 @kindex quit @r{[}@var{expression}@r{]}
1383 @kindex q @r{(@code{quit})}
1384 @item quit @r{[}@var{expression}@r{]}
1386 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1387 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1388 do not supply @var{expression}, @value{GDBN} will terminate normally;
1389 otherwise it will terminate using the result of @var{expression} as the
1394 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1395 terminates the action of any @value{GDBN} command that is in progress and
1396 returns to @value{GDBN} command level. It is safe to type the interrupt
1397 character at any time because @value{GDBN} does not allow it to take effect
1398 until a time when it is safe.
1400 If you have been using @value{GDBN} to control an attached process or
1401 device, you can release it with the @code{detach} command
1402 (@pxref{Attach, ,Debugging an Already-running Process}).
1404 @node Shell Commands
1405 @section Shell Commands
1407 If you need to execute occasional shell commands during your
1408 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1409 just use the @code{shell} command.
1414 @cindex shell escape
1415 @item shell @var{command-string}
1416 @itemx !@var{command-string}
1417 Invoke a standard shell to execute @var{command-string}.
1418 Note that no space is needed between @code{!} and @var{command-string}.
1419 If it exists, the environment variable @code{SHELL} determines which
1420 shell to run. Otherwise @value{GDBN} uses the default shell
1421 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1424 The utility @code{make} is often needed in development environments.
1425 You do not have to use the @code{shell} command for this purpose in
1430 @cindex calling make
1431 @item make @var{make-args}
1432 Execute the @code{make} program with the specified
1433 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1436 @node Logging Output
1437 @section Logging Output
1438 @cindex logging @value{GDBN} output
1439 @cindex save @value{GDBN} output to a file
1441 You may want to save the output of @value{GDBN} commands to a file.
1442 There are several commands to control @value{GDBN}'s logging.
1446 @item set logging on
1448 @item set logging off
1450 @cindex logging file name
1451 @item set logging file @var{file}
1452 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1453 @item set logging overwrite [on|off]
1454 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1455 you want @code{set logging on} to overwrite the logfile instead.
1456 @item set logging redirect [on|off]
1457 By default, @value{GDBN} output will go to both the terminal and the logfile.
1458 Set @code{redirect} if you want output to go only to the log file.
1459 @kindex show logging
1461 Show the current values of the logging settings.
1465 @chapter @value{GDBN} Commands
1467 You can abbreviate a @value{GDBN} command to the first few letters of the command
1468 name, if that abbreviation is unambiguous; and you can repeat certain
1469 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1470 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1471 show you the alternatives available, if there is more than one possibility).
1474 * Command Syntax:: How to give commands to @value{GDBN}
1475 * Completion:: Command completion
1476 * Help:: How to ask @value{GDBN} for help
1479 @node Command Syntax
1480 @section Command Syntax
1482 A @value{GDBN} command is a single line of input. There is no limit on
1483 how long it can be. It starts with a command name, which is followed by
1484 arguments whose meaning depends on the command name. For example, the
1485 command @code{step} accepts an argument which is the number of times to
1486 step, as in @samp{step 5}. You can also use the @code{step} command
1487 with no arguments. Some commands do not allow any arguments.
1489 @cindex abbreviation
1490 @value{GDBN} command names may always be truncated if that abbreviation is
1491 unambiguous. Other possible command abbreviations are listed in the
1492 documentation for individual commands. In some cases, even ambiguous
1493 abbreviations are allowed; for example, @code{s} is specially defined as
1494 equivalent to @code{step} even though there are other commands whose
1495 names start with @code{s}. You can test abbreviations by using them as
1496 arguments to the @code{help} command.
1498 @cindex repeating commands
1499 @kindex RET @r{(repeat last command)}
1500 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1501 repeat the previous command. Certain commands (for example, @code{run})
1502 will not repeat this way; these are commands whose unintentional
1503 repetition might cause trouble and which you are unlikely to want to
1504 repeat. User-defined commands can disable this feature; see
1505 @ref{Define, dont-repeat}.
1507 The @code{list} and @code{x} commands, when you repeat them with
1508 @key{RET}, construct new arguments rather than repeating
1509 exactly as typed. This permits easy scanning of source or memory.
1511 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1512 output, in a way similar to the common utility @code{more}
1513 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1514 @key{RET} too many in this situation, @value{GDBN} disables command
1515 repetition after any command that generates this sort of display.
1517 @kindex # @r{(a comment)}
1519 Any text from a @kbd{#} to the end of the line is a comment; it does
1520 nothing. This is useful mainly in command files (@pxref{Command
1521 Files,,Command Files}).
1523 @cindex repeating command sequences
1524 @kindex Ctrl-o @r{(operate-and-get-next)}
1525 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1526 commands. This command accepts the current line, like @key{RET}, and
1527 then fetches the next line relative to the current line from the history
1531 @section Command Completion
1534 @cindex word completion
1535 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1536 only one possibility; it can also show you what the valid possibilities
1537 are for the next word in a command, at any time. This works for @value{GDBN}
1538 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1540 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1541 of a word. If there is only one possibility, @value{GDBN} fills in the
1542 word, and waits for you to finish the command (or press @key{RET} to
1543 enter it). For example, if you type
1545 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1546 @c complete accuracy in these examples; space introduced for clarity.
1547 @c If texinfo enhancements make it unnecessary, it would be nice to
1548 @c replace " @key" by "@key" in the following...
1550 (@value{GDBP}) info bre @key{TAB}
1554 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1555 the only @code{info} subcommand beginning with @samp{bre}:
1558 (@value{GDBP}) info breakpoints
1562 You can either press @key{RET} at this point, to run the @code{info
1563 breakpoints} command, or backspace and enter something else, if
1564 @samp{breakpoints} does not look like the command you expected. (If you
1565 were sure you wanted @code{info breakpoints} in the first place, you
1566 might as well just type @key{RET} immediately after @samp{info bre},
1567 to exploit command abbreviations rather than command completion).
1569 If there is more than one possibility for the next word when you press
1570 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1571 characters and try again, or just press @key{TAB} a second time;
1572 @value{GDBN} displays all the possible completions for that word. For
1573 example, you might want to set a breakpoint on a subroutine whose name
1574 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1575 just sounds the bell. Typing @key{TAB} again displays all the
1576 function names in your program that begin with those characters, for
1580 (@value{GDBP}) b make_ @key{TAB}
1581 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1582 make_a_section_from_file make_environ
1583 make_abs_section make_function_type
1584 make_blockvector make_pointer_type
1585 make_cleanup make_reference_type
1586 make_command make_symbol_completion_list
1587 (@value{GDBP}) b make_
1591 After displaying the available possibilities, @value{GDBN} copies your
1592 partial input (@samp{b make_} in the example) so you can finish the
1595 If you just want to see the list of alternatives in the first place, you
1596 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1597 means @kbd{@key{META} ?}. You can type this either by holding down a
1598 key designated as the @key{META} shift on your keyboard (if there is
1599 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1601 If the number of possible completions is large, @value{GDBN} will
1602 print as much of the list as it has collected, as well as a message
1603 indicating that the list may be truncated.
1606 (@value{GDBP}) b m@key{TAB}@key{TAB}
1608 <... the rest of the possible completions ...>
1609 *** List may be truncated, max-completions reached. ***
1614 This behavior can be controlled with the following commands:
1617 @kindex set max-completions
1618 @item set max-completions @var{limit}
1619 @itemx set max-completions unlimited
1620 Set the maximum number of completion candidates. @value{GDBN} will
1621 stop looking for more completions once it collects this many candidates.
1622 This is useful when completing on things like function names as collecting
1623 all the possible candidates can be time consuming.
1624 The default value is 200. A value of zero disables tab-completion.
1625 Note that setting either no limit or a very large limit can make
1627 @kindex show max-completions
1628 @item show max-completions
1629 Show the maximum number of candidates that @value{GDBN} will collect and show
1633 @cindex quotes in commands
1634 @cindex completion of quoted strings
1635 Sometimes the string you need, while logically a ``word'', may contain
1636 parentheses or other characters that @value{GDBN} normally excludes from
1637 its notion of a word. To permit word completion to work in this
1638 situation, you may enclose words in @code{'} (single quote marks) in
1639 @value{GDBN} commands.
1641 A likely situation where you might need this is in typing an
1642 expression that involves a C@t{++} symbol name with template
1643 parameters. This is because when completing expressions, GDB treats
1644 the @samp{<} character as word delimiter, assuming that it's the
1645 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1648 For example, when you want to call a C@t{++} template function
1649 interactively using the @code{print} or @code{call} commands, you may
1650 need to distinguish whether you mean the version of @code{name} that
1651 was specialized for @code{int}, @code{name<int>()}, or the version
1652 that was specialized for @code{float}, @code{name<float>()}. To use
1653 the word-completion facilities in this situation, type a single quote
1654 @code{'} at the beginning of the function name. This alerts
1655 @value{GDBN} that it may need to consider more information than usual
1656 when you press @key{TAB} or @kbd{M-?} to request word completion:
1659 (@value{GDBP}) p 'func< @kbd{M-?}
1660 func<int>() func<float>()
1661 (@value{GDBP}) p 'func<
1664 When setting breakpoints however (@pxref{Specify Location}), you don't
1665 usually need to type a quote before the function name, because
1666 @value{GDBN} understands that you want to set a breakpoint on a
1670 (@value{GDBP}) b func< @kbd{M-?}
1671 func<int>() func<float>()
1672 (@value{GDBP}) b func<
1675 This is true even in the case of typing the name of C@t{++} overloaded
1676 functions (multiple definitions of the same function, distinguished by
1677 argument type). For example, when you want to set a breakpoint you
1678 don't need to distinguish whether you mean the version of @code{name}
1679 that takes an @code{int} parameter, @code{name(int)}, or the version
1680 that takes a @code{float} parameter, @code{name(float)}.
1683 (@value{GDBP}) b bubble( @kbd{M-?}
1684 bubble(int) bubble(double)
1685 (@value{GDBP}) b bubble(dou @kbd{M-?}
1689 See @ref{quoting names} for a description of other scenarios that
1692 For more information about overloaded functions, see @ref{C Plus Plus
1693 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1694 overload-resolution off} to disable overload resolution;
1695 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1697 @cindex completion of structure field names
1698 @cindex structure field name completion
1699 @cindex completion of union field names
1700 @cindex union field name completion
1701 When completing in an expression which looks up a field in a
1702 structure, @value{GDBN} also tries@footnote{The completer can be
1703 confused by certain kinds of invalid expressions. Also, it only
1704 examines the static type of the expression, not the dynamic type.} to
1705 limit completions to the field names available in the type of the
1709 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1710 magic to_fputs to_rewind
1711 to_data to_isatty to_write
1712 to_delete to_put to_write_async_safe
1717 This is because the @code{gdb_stdout} is a variable of the type
1718 @code{struct ui_file} that is defined in @value{GDBN} sources as
1725 ui_file_flush_ftype *to_flush;
1726 ui_file_write_ftype *to_write;
1727 ui_file_write_async_safe_ftype *to_write_async_safe;
1728 ui_file_fputs_ftype *to_fputs;
1729 ui_file_read_ftype *to_read;
1730 ui_file_delete_ftype *to_delete;
1731 ui_file_isatty_ftype *to_isatty;
1732 ui_file_rewind_ftype *to_rewind;
1733 ui_file_put_ftype *to_put;
1740 @section Getting Help
1741 @cindex online documentation
1744 You can always ask @value{GDBN} itself for information on its commands,
1745 using the command @code{help}.
1748 @kindex h @r{(@code{help})}
1751 You can use @code{help} (abbreviated @code{h}) with no arguments to
1752 display a short list of named classes of commands:
1756 List of classes of commands:
1758 aliases -- Aliases of other commands
1759 breakpoints -- Making program stop at certain points
1760 data -- Examining data
1761 files -- Specifying and examining files
1762 internals -- Maintenance commands
1763 obscure -- Obscure features
1764 running -- Running the program
1765 stack -- Examining the stack
1766 status -- Status inquiries
1767 support -- Support facilities
1768 tracepoints -- Tracing of program execution without
1769 stopping the program
1770 user-defined -- User-defined commands
1772 Type "help" followed by a class name for a list of
1773 commands in that class.
1774 Type "help" followed by command name for full
1776 Command name abbreviations are allowed if unambiguous.
1779 @c the above line break eliminates huge line overfull...
1781 @item help @var{class}
1782 Using one of the general help classes as an argument, you can get a
1783 list of the individual commands in that class. For example, here is the
1784 help display for the class @code{status}:
1787 (@value{GDBP}) help status
1792 @c Line break in "show" line falsifies real output, but needed
1793 @c to fit in smallbook page size.
1794 info -- Generic command for showing things
1795 about the program being debugged
1796 show -- Generic command for showing things
1799 Type "help" followed by command name for full
1801 Command name abbreviations are allowed if unambiguous.
1805 @item help @var{command}
1806 With a command name as @code{help} argument, @value{GDBN} displays a
1807 short paragraph on how to use that command.
1810 @item apropos @var{args}
1811 The @code{apropos} command searches through all of the @value{GDBN}
1812 commands, and their documentation, for the regular expression specified in
1813 @var{args}. It prints out all matches found. For example:
1824 alias -- Define a new command that is an alias of an existing command
1825 aliases -- Aliases of other commands
1826 d -- Delete some breakpoints or auto-display expressions
1827 del -- Delete some breakpoints or auto-display expressions
1828 delete -- Delete some breakpoints or auto-display expressions
1833 @item complete @var{args}
1834 The @code{complete @var{args}} command lists all the possible completions
1835 for the beginning of a command. Use @var{args} to specify the beginning of the
1836 command you want completed. For example:
1842 @noindent results in:
1853 @noindent This is intended for use by @sc{gnu} Emacs.
1856 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1857 and @code{show} to inquire about the state of your program, or the state
1858 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1859 manual introduces each of them in the appropriate context. The listings
1860 under @code{info} and under @code{show} in the Command, Variable, and
1861 Function Index point to all the sub-commands. @xref{Command and Variable
1867 @kindex i @r{(@code{info})}
1869 This command (abbreviated @code{i}) is for describing the state of your
1870 program. For example, you can show the arguments passed to a function
1871 with @code{info args}, list the registers currently in use with @code{info
1872 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1873 You can get a complete list of the @code{info} sub-commands with
1874 @w{@code{help info}}.
1878 You can assign the result of an expression to an environment variable with
1879 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1880 @code{set prompt $}.
1884 In contrast to @code{info}, @code{show} is for describing the state of
1885 @value{GDBN} itself.
1886 You can change most of the things you can @code{show}, by using the
1887 related command @code{set}; for example, you can control what number
1888 system is used for displays with @code{set radix}, or simply inquire
1889 which is currently in use with @code{show radix}.
1892 To display all the settable parameters and their current
1893 values, you can use @code{show} with no arguments; you may also use
1894 @code{info set}. Both commands produce the same display.
1895 @c FIXME: "info set" violates the rule that "info" is for state of
1896 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1897 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1901 Here are several miscellaneous @code{show} subcommands, all of which are
1902 exceptional in lacking corresponding @code{set} commands:
1905 @kindex show version
1906 @cindex @value{GDBN} version number
1908 Show what version of @value{GDBN} is running. You should include this
1909 information in @value{GDBN} bug-reports. If multiple versions of
1910 @value{GDBN} are in use at your site, you may need to determine which
1911 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1912 commands are introduced, and old ones may wither away. Also, many
1913 system vendors ship variant versions of @value{GDBN}, and there are
1914 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1915 The version number is the same as the one announced when you start
1918 @kindex show copying
1919 @kindex info copying
1920 @cindex display @value{GDBN} copyright
1923 Display information about permission for copying @value{GDBN}.
1925 @kindex show warranty
1926 @kindex info warranty
1928 @itemx info warranty
1929 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1930 if your version of @value{GDBN} comes with one.
1932 @kindex show configuration
1933 @item show configuration
1934 Display detailed information about the way @value{GDBN} was configured
1935 when it was built. This displays the optional arguments passed to the
1936 @file{configure} script and also configuration parameters detected
1937 automatically by @command{configure}. When reporting a @value{GDBN}
1938 bug (@pxref{GDB Bugs}), it is important to include this information in
1944 @chapter Running Programs Under @value{GDBN}
1946 When you run a program under @value{GDBN}, you must first generate
1947 debugging information when you compile it.
1949 You may start @value{GDBN} with its arguments, if any, in an environment
1950 of your choice. If you are doing native debugging, you may redirect
1951 your program's input and output, debug an already running process, or
1952 kill a child process.
1955 * Compilation:: Compiling for debugging
1956 * Starting:: Starting your program
1957 * Arguments:: Your program's arguments
1958 * Environment:: Your program's environment
1960 * Working Directory:: Your program's working directory
1961 * Input/Output:: Your program's input and output
1962 * Attach:: Debugging an already-running process
1963 * Kill Process:: Killing the child process
1965 * Inferiors and Programs:: Debugging multiple inferiors and programs
1966 * Threads:: Debugging programs with multiple threads
1967 * Forks:: Debugging forks
1968 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1972 @section Compiling for Debugging
1974 In order to debug a program effectively, you need to generate
1975 debugging information when you compile it. This debugging information
1976 is stored in the object file; it describes the data type of each
1977 variable or function and the correspondence between source line numbers
1978 and addresses in the executable code.
1980 To request debugging information, specify the @samp{-g} option when you run
1983 Programs that are to be shipped to your customers are compiled with
1984 optimizations, using the @samp{-O} compiler option. However, some
1985 compilers are unable to handle the @samp{-g} and @samp{-O} options
1986 together. Using those compilers, you cannot generate optimized
1987 executables containing debugging information.
1989 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1990 without @samp{-O}, making it possible to debug optimized code. We
1991 recommend that you @emph{always} use @samp{-g} whenever you compile a
1992 program. You may think your program is correct, but there is no sense
1993 in pushing your luck. For more information, see @ref{Optimized Code}.
1995 Older versions of the @sc{gnu} C compiler permitted a variant option
1996 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1997 format; if your @sc{gnu} C compiler has this option, do not use it.
1999 @value{GDBN} knows about preprocessor macros and can show you their
2000 expansion (@pxref{Macros}). Most compilers do not include information
2001 about preprocessor macros in the debugging information if you specify
2002 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2003 the @sc{gnu} C compiler, provides macro information if you are using
2004 the DWARF debugging format, and specify the option @option{-g3}.
2006 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2007 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2008 information on @value{NGCC} options affecting debug information.
2010 You will have the best debugging experience if you use the latest
2011 version of the DWARF debugging format that your compiler supports.
2012 DWARF is currently the most expressive and best supported debugging
2013 format in @value{GDBN}.
2017 @section Starting your Program
2023 @kindex r @r{(@code{run})}
2026 Use the @code{run} command to start your program under @value{GDBN}.
2027 You must first specify the program name with an argument to
2028 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2029 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2030 command (@pxref{Files, ,Commands to Specify Files}).
2034 If you are running your program in an execution environment that
2035 supports processes, @code{run} creates an inferior process and makes
2036 that process run your program. In some environments without processes,
2037 @code{run} jumps to the start of your program. Other targets,
2038 like @samp{remote}, are always running. If you get an error
2039 message like this one:
2042 The "remote" target does not support "run".
2043 Try "help target" or "continue".
2047 then use @code{continue} to run your program. You may need @code{load}
2048 first (@pxref{load}).
2050 The execution of a program is affected by certain information it
2051 receives from its superior. @value{GDBN} provides ways to specify this
2052 information, which you must do @emph{before} starting your program. (You
2053 can change it after starting your program, but such changes only affect
2054 your program the next time you start it.) This information may be
2055 divided into four categories:
2058 @item The @emph{arguments.}
2059 Specify the arguments to give your program as the arguments of the
2060 @code{run} command. If a shell is available on your target, the shell
2061 is used to pass the arguments, so that you may use normal conventions
2062 (such as wildcard expansion or variable substitution) in describing
2064 In Unix systems, you can control which shell is used with the
2065 @code{SHELL} environment variable. If you do not define @code{SHELL},
2066 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2067 use of any shell with the @code{set startup-with-shell} command (see
2070 @item The @emph{environment.}
2071 Your program normally inherits its environment from @value{GDBN}, but you can
2072 use the @value{GDBN} commands @code{set environment} and @code{unset
2073 environment} to change parts of the environment that affect
2074 your program. @xref{Environment, ,Your Program's Environment}.
2076 @item The @emph{working directory.}
2077 You can set your program's working directory with the command
2078 @kbd{set cwd}. If you do not set any working directory with this
2079 command, your program will inherit @value{GDBN}'s working directory if
2080 native debugging, or the remote server's working directory if remote
2081 debugging. @xref{Working Directory, ,Your Program's Working
2084 @item The @emph{standard input and output.}
2085 Your program normally uses the same device for standard input and
2086 standard output as @value{GDBN} is using. You can redirect input and output
2087 in the @code{run} command line, or you can use the @code{tty} command to
2088 set a different device for your program.
2089 @xref{Input/Output, ,Your Program's Input and Output}.
2092 @emph{Warning:} While input and output redirection work, you cannot use
2093 pipes to pass the output of the program you are debugging to another
2094 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2098 When you issue the @code{run} command, your program begins to execute
2099 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2100 of how to arrange for your program to stop. Once your program has
2101 stopped, you may call functions in your program, using the @code{print}
2102 or @code{call} commands. @xref{Data, ,Examining Data}.
2104 If the modification time of your symbol file has changed since the last
2105 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2106 table, and reads it again. When it does this, @value{GDBN} tries to retain
2107 your current breakpoints.
2112 @cindex run to main procedure
2113 The name of the main procedure can vary from language to language.
2114 With C or C@t{++}, the main procedure name is always @code{main}, but
2115 other languages such as Ada do not require a specific name for their
2116 main procedure. The debugger provides a convenient way to start the
2117 execution of the program and to stop at the beginning of the main
2118 procedure, depending on the language used.
2120 The @samp{start} command does the equivalent of setting a temporary
2121 breakpoint at the beginning of the main procedure and then invoking
2122 the @samp{run} command.
2124 @cindex elaboration phase
2125 Some programs contain an @dfn{elaboration} phase where some startup code is
2126 executed before the main procedure is called. This depends on the
2127 languages used to write your program. In C@t{++}, for instance,
2128 constructors for static and global objects are executed before
2129 @code{main} is called. It is therefore possible that the debugger stops
2130 before reaching the main procedure. However, the temporary breakpoint
2131 will remain to halt execution.
2133 Specify the arguments to give to your program as arguments to the
2134 @samp{start} command. These arguments will be given verbatim to the
2135 underlying @samp{run} command. Note that the same arguments will be
2136 reused if no argument is provided during subsequent calls to
2137 @samp{start} or @samp{run}.
2139 It is sometimes necessary to debug the program during elaboration. In
2140 these cases, using the @code{start} command would stop the execution
2141 of your program too late, as the program would have already completed
2142 the elaboration phase. Under these circumstances, either insert
2143 breakpoints in your elaboration code before running your program or
2144 use the @code{starti} command.
2148 @cindex run to first instruction
2149 The @samp{starti} command does the equivalent of setting a temporary
2150 breakpoint at the first instruction of a program's execution and then
2151 invoking the @samp{run} command. For programs containing an
2152 elaboration phase, the @code{starti} command will stop execution at
2153 the start of the elaboration phase.
2155 @anchor{set exec-wrapper}
2156 @kindex set exec-wrapper
2157 @item set exec-wrapper @var{wrapper}
2158 @itemx show exec-wrapper
2159 @itemx unset exec-wrapper
2160 When @samp{exec-wrapper} is set, the specified wrapper is used to
2161 launch programs for debugging. @value{GDBN} starts your program
2162 with a shell command of the form @kbd{exec @var{wrapper}
2163 @var{program}}. Quoting is added to @var{program} and its
2164 arguments, but not to @var{wrapper}, so you should add quotes if
2165 appropriate for your shell. The wrapper runs until it executes
2166 your program, and then @value{GDBN} takes control.
2168 You can use any program that eventually calls @code{execve} with
2169 its arguments as a wrapper. Several standard Unix utilities do
2170 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2171 with @code{exec "$@@"} will also work.
2173 For example, you can use @code{env} to pass an environment variable to
2174 the debugged program, without setting the variable in your shell's
2178 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2182 This command is available when debugging locally on most targets, excluding
2183 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2185 @kindex set startup-with-shell
2186 @anchor{set startup-with-shell}
2187 @item set startup-with-shell
2188 @itemx set startup-with-shell on
2189 @itemx set startup-with-shell off
2190 @itemx show startup-with-shell
2191 On Unix systems, by default, if a shell is available on your target,
2192 @value{GDBN}) uses it to start your program. Arguments of the
2193 @code{run} command are passed to the shell, which does variable
2194 substitution, expands wildcard characters and performs redirection of
2195 I/O. In some circumstances, it may be useful to disable such use of a
2196 shell, for example, when debugging the shell itself or diagnosing
2197 startup failures such as:
2201 Starting program: ./a.out
2202 During startup program terminated with signal SIGSEGV, Segmentation fault.
2206 which indicates the shell or the wrapper specified with
2207 @samp{exec-wrapper} crashed, not your program. Most often, this is
2208 caused by something odd in your shell's non-interactive mode
2209 initialization file---such as @file{.cshrc} for C-shell,
2210 $@file{.zshenv} for the Z shell, or the file specified in the
2211 @samp{BASH_ENV} environment variable for BASH.
2213 @anchor{set auto-connect-native-target}
2214 @kindex set auto-connect-native-target
2215 @item set auto-connect-native-target
2216 @itemx set auto-connect-native-target on
2217 @itemx set auto-connect-native-target off
2218 @itemx show auto-connect-native-target
2220 By default, if not connected to any target yet (e.g., with
2221 @code{target remote}), the @code{run} command starts your program as a
2222 native process under @value{GDBN}, on your local machine. If you're
2223 sure you don't want to debug programs on your local machine, you can
2224 tell @value{GDBN} to not connect to the native target automatically
2225 with the @code{set auto-connect-native-target off} command.
2227 If @code{on}, which is the default, and if @value{GDBN} is not
2228 connected to a target already, the @code{run} command automaticaly
2229 connects to the native target, if one is available.
2231 If @code{off}, and if @value{GDBN} is not connected to a target
2232 already, the @code{run} command fails with an error:
2236 Don't know how to run. Try "help target".
2239 If @value{GDBN} is already connected to a target, @value{GDBN} always
2240 uses it with the @code{run} command.
2242 In any case, you can explicitly connect to the native target with the
2243 @code{target native} command. For example,
2246 (@value{GDBP}) set auto-connect-native-target off
2248 Don't know how to run. Try "help target".
2249 (@value{GDBP}) target native
2251 Starting program: ./a.out
2252 [Inferior 1 (process 10421) exited normally]
2255 In case you connected explicitly to the @code{native} target,
2256 @value{GDBN} remains connected even if all inferiors exit, ready for
2257 the next @code{run} command. Use the @code{disconnect} command to
2260 Examples of other commands that likewise respect the
2261 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2262 proc}, @code{info os}.
2264 @kindex set disable-randomization
2265 @item set disable-randomization
2266 @itemx set disable-randomization on
2267 This option (enabled by default in @value{GDBN}) will turn off the native
2268 randomization of the virtual address space of the started program. This option
2269 is useful for multiple debugging sessions to make the execution better
2270 reproducible and memory addresses reusable across debugging sessions.
2272 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2273 On @sc{gnu}/Linux you can get the same behavior using
2276 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2279 @item set disable-randomization off
2280 Leave the behavior of the started executable unchanged. Some bugs rear their
2281 ugly heads only when the program is loaded at certain addresses. If your bug
2282 disappears when you run the program under @value{GDBN}, that might be because
2283 @value{GDBN} by default disables the address randomization on platforms, such
2284 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2285 disable-randomization off} to try to reproduce such elusive bugs.
2287 On targets where it is available, virtual address space randomization
2288 protects the programs against certain kinds of security attacks. In these
2289 cases the attacker needs to know the exact location of a concrete executable
2290 code. Randomizing its location makes it impossible to inject jumps misusing
2291 a code at its expected addresses.
2293 Prelinking shared libraries provides a startup performance advantage but it
2294 makes addresses in these libraries predictable for privileged processes by
2295 having just unprivileged access at the target system. Reading the shared
2296 library binary gives enough information for assembling the malicious code
2297 misusing it. Still even a prelinked shared library can get loaded at a new
2298 random address just requiring the regular relocation process during the
2299 startup. Shared libraries not already prelinked are always loaded at
2300 a randomly chosen address.
2302 Position independent executables (PIE) contain position independent code
2303 similar to the shared libraries and therefore such executables get loaded at
2304 a randomly chosen address upon startup. PIE executables always load even
2305 already prelinked shared libraries at a random address. You can build such
2306 executable using @command{gcc -fPIE -pie}.
2308 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2309 (as long as the randomization is enabled).
2311 @item show disable-randomization
2312 Show the current setting of the explicit disable of the native randomization of
2313 the virtual address space of the started program.
2318 @section Your Program's Arguments
2320 @cindex arguments (to your program)
2321 The arguments to your program can be specified by the arguments of the
2323 They are passed to a shell, which expands wildcard characters and
2324 performs redirection of I/O, and thence to your program. Your
2325 @code{SHELL} environment variable (if it exists) specifies what shell
2326 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2327 the default shell (@file{/bin/sh} on Unix).
2329 On non-Unix systems, the program is usually invoked directly by
2330 @value{GDBN}, which emulates I/O redirection via the appropriate system
2331 calls, and the wildcard characters are expanded by the startup code of
2332 the program, not by the shell.
2334 @code{run} with no arguments uses the same arguments used by the previous
2335 @code{run}, or those set by the @code{set args} command.
2340 Specify the arguments to be used the next time your program is run. If
2341 @code{set args} has no arguments, @code{run} executes your program
2342 with no arguments. Once you have run your program with arguments,
2343 using @code{set args} before the next @code{run} is the only way to run
2344 it again without arguments.
2348 Show the arguments to give your program when it is started.
2352 @section Your Program's Environment
2354 @cindex environment (of your program)
2355 The @dfn{environment} consists of a set of environment variables and
2356 their values. Environment variables conventionally record such things as
2357 your user name, your home directory, your terminal type, and your search
2358 path for programs to run. Usually you set up environment variables with
2359 the shell and they are inherited by all the other programs you run. When
2360 debugging, it can be useful to try running your program with a modified
2361 environment without having to start @value{GDBN} over again.
2365 @item path @var{directory}
2366 Add @var{directory} to the front of the @code{PATH} environment variable
2367 (the search path for executables) that will be passed to your program.
2368 The value of @code{PATH} used by @value{GDBN} does not change.
2369 You may specify several directory names, separated by whitespace or by a
2370 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2371 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2372 is moved to the front, so it is searched sooner.
2374 You can use the string @samp{$cwd} to refer to whatever is the current
2375 working directory at the time @value{GDBN} searches the path. If you
2376 use @samp{.} instead, it refers to the directory where you executed the
2377 @code{path} command. @value{GDBN} replaces @samp{.} in the
2378 @var{directory} argument (with the current path) before adding
2379 @var{directory} to the search path.
2380 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2381 @c document that, since repeating it would be a no-op.
2385 Display the list of search paths for executables (the @code{PATH}
2386 environment variable).
2388 @kindex show environment
2389 @item show environment @r{[}@var{varname}@r{]}
2390 Print the value of environment variable @var{varname} to be given to
2391 your program when it starts. If you do not supply @var{varname},
2392 print the names and values of all environment variables to be given to
2393 your program. You can abbreviate @code{environment} as @code{env}.
2395 @kindex set environment
2396 @anchor{set environment}
2397 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2398 Set environment variable @var{varname} to @var{value}. The value
2399 changes for your program (and the shell @value{GDBN} uses to launch
2400 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2401 values of environment variables are just strings, and any
2402 interpretation is supplied by your program itself. The @var{value}
2403 parameter is optional; if it is eliminated, the variable is set to a
2405 @c "any string" here does not include leading, trailing
2406 @c blanks. Gnu asks: does anyone care?
2408 For example, this command:
2415 tells the debugged program, when subsequently run, that its user is named
2416 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2417 are not actually required.)
2419 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2420 which also inherits the environment set with @code{set environment}.
2421 If necessary, you can avoid that by using the @samp{env} program as a
2422 wrapper instead of using @code{set environment}. @xref{set
2423 exec-wrapper}, for an example doing just that.
2425 Environment variables that are set by the user are also transmitted to
2426 @command{gdbserver} to be used when starting the remote inferior.
2427 @pxref{QEnvironmentHexEncoded}.
2429 @kindex unset environment
2430 @anchor{unset environment}
2431 @item unset environment @var{varname}
2432 Remove variable @var{varname} from the environment to be passed to your
2433 program. This is different from @samp{set env @var{varname} =};
2434 @code{unset environment} removes the variable from the environment,
2435 rather than assigning it an empty value.
2437 Environment variables that are unset by the user are also unset on
2438 @command{gdbserver} when starting the remote inferior.
2439 @pxref{QEnvironmentUnset}.
2442 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2443 the shell indicated by your @code{SHELL} environment variable if it
2444 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2445 names a shell that runs an initialization file when started
2446 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2447 for the Z shell, or the file specified in the @samp{BASH_ENV}
2448 environment variable for BASH---any variables you set in that file
2449 affect your program. You may wish to move setting of environment
2450 variables to files that are only run when you sign on, such as
2451 @file{.login} or @file{.profile}.
2453 @node Working Directory
2454 @section Your Program's Working Directory
2456 @cindex working directory (of your program)
2457 Each time you start your program with @code{run}, the inferior will be
2458 initialized with the current working directory specified by the
2459 @kbd{set cwd} command. If no directory has been specified by this
2460 command, then the inferior will inherit @value{GDBN}'s current working
2461 directory as its working directory if native debugging, or it will
2462 inherit the remote server's current working directory if remote
2467 @cindex change inferior's working directory
2468 @anchor{set cwd command}
2469 @item set cwd @r{[}@var{directory}@r{]}
2470 Set the inferior's working directory to @var{directory}, which will be
2471 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2472 argument has been specified, the command clears the setting and resets
2473 it to an empty state. This setting has no effect on @value{GDBN}'s
2474 working directory, and it only takes effect the next time you start
2475 the inferior. The @file{~} in @var{directory} is a short for the
2476 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2477 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2478 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2481 You can also change @value{GDBN}'s current working directory by using
2482 the @code{cd} command.
2486 @cindex show inferior's working directory
2488 Show the inferior's working directory. If no directory has been
2489 specified by @kbd{set cwd}, then the default inferior's working
2490 directory is the same as @value{GDBN}'s working directory.
2493 @cindex change @value{GDBN}'s working directory
2495 @item cd @r{[}@var{directory}@r{]}
2496 Set the @value{GDBN} working directory to @var{directory}. If not
2497 given, @var{directory} uses @file{'~'}.
2499 The @value{GDBN} working directory serves as a default for the
2500 commands that specify files for @value{GDBN} to operate on.
2501 @xref{Files, ,Commands to Specify Files}.
2502 @xref{set cwd command}
2506 Print the @value{GDBN} working directory.
2509 It is generally impossible to find the current working directory of
2510 the process being debugged (since a program can change its directory
2511 during its run). If you work on a system where @value{GDBN} is
2512 configured with the @file{/proc} support, you can use the @code{info
2513 proc} command (@pxref{SVR4 Process Information}) to find out the
2514 current working directory of the debuggee.
2517 @section Your Program's Input and Output
2522 By default, the program you run under @value{GDBN} does input and output to
2523 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2524 to its own terminal modes to interact with you, but it records the terminal
2525 modes your program was using and switches back to them when you continue
2526 running your program.
2529 @kindex info terminal
2531 Displays information recorded by @value{GDBN} about the terminal modes your
2535 You can redirect your program's input and/or output using shell
2536 redirection with the @code{run} command. For example,
2543 starts your program, diverting its output to the file @file{outfile}.
2546 @cindex controlling terminal
2547 Another way to specify where your program should do input and output is
2548 with the @code{tty} command. This command accepts a file name as
2549 argument, and causes this file to be the default for future @code{run}
2550 commands. It also resets the controlling terminal for the child
2551 process, for future @code{run} commands. For example,
2558 directs that processes started with subsequent @code{run} commands
2559 default to do input and output on the terminal @file{/dev/ttyb} and have
2560 that as their controlling terminal.
2562 An explicit redirection in @code{run} overrides the @code{tty} command's
2563 effect on the input/output device, but not its effect on the controlling
2566 When you use the @code{tty} command or redirect input in the @code{run}
2567 command, only the input @emph{for your program} is affected. The input
2568 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2569 for @code{set inferior-tty}.
2571 @cindex inferior tty
2572 @cindex set inferior controlling terminal
2573 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2574 display the name of the terminal that will be used for future runs of your
2578 @item set inferior-tty [ @var{tty} ]
2579 @kindex set inferior-tty
2580 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2581 restores the default behavior, which is to use the same terminal as
2584 @item show inferior-tty
2585 @kindex show inferior-tty
2586 Show the current tty for the program being debugged.
2590 @section Debugging an Already-running Process
2595 @item attach @var{process-id}
2596 This command attaches to a running process---one that was started
2597 outside @value{GDBN}. (@code{info files} shows your active
2598 targets.) The command takes as argument a process ID. The usual way to
2599 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2600 or with the @samp{jobs -l} shell command.
2602 @code{attach} does not repeat if you press @key{RET} a second time after
2603 executing the command.
2606 To use @code{attach}, your program must be running in an environment
2607 which supports processes; for example, @code{attach} does not work for
2608 programs on bare-board targets that lack an operating system. You must
2609 also have permission to send the process a signal.
2611 When you use @code{attach}, the debugger finds the program running in
2612 the process first by looking in the current working directory, then (if
2613 the program is not found) by using the source file search path
2614 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2615 the @code{file} command to load the program. @xref{Files, ,Commands to
2618 The first thing @value{GDBN} does after arranging to debug the specified
2619 process is to stop it. You can examine and modify an attached process
2620 with all the @value{GDBN} commands that are ordinarily available when
2621 you start processes with @code{run}. You can insert breakpoints; you
2622 can step and continue; you can modify storage. If you would rather the
2623 process continue running, you may use the @code{continue} command after
2624 attaching @value{GDBN} to the process.
2629 When you have finished debugging the attached process, you can use the
2630 @code{detach} command to release it from @value{GDBN} control. Detaching
2631 the process continues its execution. After the @code{detach} command,
2632 that process and @value{GDBN} become completely independent once more, and you
2633 are ready to @code{attach} another process or start one with @code{run}.
2634 @code{detach} does not repeat if you press @key{RET} again after
2635 executing the command.
2638 If you exit @value{GDBN} while you have an attached process, you detach
2639 that process. If you use the @code{run} command, you kill that process.
2640 By default, @value{GDBN} asks for confirmation if you try to do either of these
2641 things; you can control whether or not you need to confirm by using the
2642 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2646 @section Killing the Child Process
2651 Kill the child process in which your program is running under @value{GDBN}.
2654 This command is useful if you wish to debug a core dump instead of a
2655 running process. @value{GDBN} ignores any core dump file while your program
2658 On some operating systems, a program cannot be executed outside @value{GDBN}
2659 while you have breakpoints set on it inside @value{GDBN}. You can use the
2660 @code{kill} command in this situation to permit running your program
2661 outside the debugger.
2663 The @code{kill} command is also useful if you wish to recompile and
2664 relink your program, since on many systems it is impossible to modify an
2665 executable file while it is running in a process. In this case, when you
2666 next type @code{run}, @value{GDBN} notices that the file has changed, and
2667 reads the symbol table again (while trying to preserve your current
2668 breakpoint settings).
2670 @node Inferiors and Programs
2671 @section Debugging Multiple Inferiors and Programs
2673 @value{GDBN} lets you run and debug multiple programs in a single
2674 session. In addition, @value{GDBN} on some systems may let you run
2675 several programs simultaneously (otherwise you have to exit from one
2676 before starting another). In the most general case, you can have
2677 multiple threads of execution in each of multiple processes, launched
2678 from multiple executables.
2681 @value{GDBN} represents the state of each program execution with an
2682 object called an @dfn{inferior}. An inferior typically corresponds to
2683 a process, but is more general and applies also to targets that do not
2684 have processes. Inferiors may be created before a process runs, and
2685 may be retained after a process exits. Inferiors have unique
2686 identifiers that are different from process ids. Usually each
2687 inferior will also have its own distinct address space, although some
2688 embedded targets may have several inferiors running in different parts
2689 of a single address space. Each inferior may in turn have multiple
2690 threads running in it.
2692 To find out what inferiors exist at any moment, use @w{@code{info
2696 @kindex info inferiors
2697 @item info inferiors
2698 Print a list of all inferiors currently being managed by @value{GDBN}.
2700 @value{GDBN} displays for each inferior (in this order):
2704 the inferior number assigned by @value{GDBN}
2707 the target system's inferior identifier
2710 the name of the executable the inferior is running.
2715 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2716 indicates the current inferior.
2720 @c end table here to get a little more width for example
2723 (@value{GDBP}) info inferiors
2724 Num Description Executable
2725 2 process 2307 hello
2726 * 1 process 3401 goodbye
2729 To switch focus between inferiors, use the @code{inferior} command:
2732 @kindex inferior @var{infno}
2733 @item inferior @var{infno}
2734 Make inferior number @var{infno} the current inferior. The argument
2735 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2736 in the first field of the @samp{info inferiors} display.
2739 @vindex $_inferior@r{, convenience variable}
2740 The debugger convenience variable @samp{$_inferior} contains the
2741 number of the current inferior. You may find this useful in writing
2742 breakpoint conditional expressions, command scripts, and so forth.
2743 @xref{Convenience Vars,, Convenience Variables}, for general
2744 information on convenience variables.
2746 You can get multiple executables into a debugging session via the
2747 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2748 systems @value{GDBN} can add inferiors to the debug session
2749 automatically by following calls to @code{fork} and @code{exec}. To
2750 remove inferiors from the debugging session use the
2751 @w{@code{remove-inferiors}} command.
2754 @kindex add-inferior
2755 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2756 Adds @var{n} inferiors to be run using @var{executable} as the
2757 executable; @var{n} defaults to 1. If no executable is specified,
2758 the inferiors begins empty, with no program. You can still assign or
2759 change the program assigned to the inferior at any time by using the
2760 @code{file} command with the executable name as its argument.
2762 @kindex clone-inferior
2763 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2764 Adds @var{n} inferiors ready to execute the same program as inferior
2765 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2766 number of the current inferior. This is a convenient command when you
2767 want to run another instance of the inferior you are debugging.
2770 (@value{GDBP}) info inferiors
2771 Num Description Executable
2772 * 1 process 29964 helloworld
2773 (@value{GDBP}) clone-inferior
2776 (@value{GDBP}) info inferiors
2777 Num Description Executable
2779 * 1 process 29964 helloworld
2782 You can now simply switch focus to inferior 2 and run it.
2784 @kindex remove-inferiors
2785 @item remove-inferiors @var{infno}@dots{}
2786 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2787 possible to remove an inferior that is running with this command. For
2788 those, use the @code{kill} or @code{detach} command first.
2792 To quit debugging one of the running inferiors that is not the current
2793 inferior, you can either detach from it by using the @w{@code{detach
2794 inferior}} command (allowing it to run independently), or kill it
2795 using the @w{@code{kill inferiors}} command:
2798 @kindex detach inferiors @var{infno}@dots{}
2799 @item detach inferior @var{infno}@dots{}
2800 Detach from the inferior or inferiors identified by @value{GDBN}
2801 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2802 still stays on the list of inferiors shown by @code{info inferiors},
2803 but its Description will show @samp{<null>}.
2805 @kindex kill inferiors @var{infno}@dots{}
2806 @item kill inferiors @var{infno}@dots{}
2807 Kill the inferior or inferiors identified by @value{GDBN} inferior
2808 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2809 stays on the list of inferiors shown by @code{info inferiors}, but its
2810 Description will show @samp{<null>}.
2813 After the successful completion of a command such as @code{detach},
2814 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2815 a normal process exit, the inferior is still valid and listed with
2816 @code{info inferiors}, ready to be restarted.
2819 To be notified when inferiors are started or exit under @value{GDBN}'s
2820 control use @w{@code{set print inferior-events}}:
2823 @kindex set print inferior-events
2824 @cindex print messages on inferior start and exit
2825 @item set print inferior-events
2826 @itemx set print inferior-events on
2827 @itemx set print inferior-events off
2828 The @code{set print inferior-events} command allows you to enable or
2829 disable printing of messages when @value{GDBN} notices that new
2830 inferiors have started or that inferiors have exited or have been
2831 detached. By default, these messages will not be printed.
2833 @kindex show print inferior-events
2834 @item show print inferior-events
2835 Show whether messages will be printed when @value{GDBN} detects that
2836 inferiors have started, exited or have been detached.
2839 Many commands will work the same with multiple programs as with a
2840 single program: e.g., @code{print myglobal} will simply display the
2841 value of @code{myglobal} in the current inferior.
2844 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2845 get more info about the relationship of inferiors, programs, address
2846 spaces in a debug session. You can do that with the @w{@code{maint
2847 info program-spaces}} command.
2850 @kindex maint info program-spaces
2851 @item maint info program-spaces
2852 Print a list of all program spaces currently being managed by
2855 @value{GDBN} displays for each program space (in this order):
2859 the program space number assigned by @value{GDBN}
2862 the name of the executable loaded into the program space, with e.g.,
2863 the @code{file} command.
2868 An asterisk @samp{*} preceding the @value{GDBN} program space number
2869 indicates the current program space.
2871 In addition, below each program space line, @value{GDBN} prints extra
2872 information that isn't suitable to display in tabular form. For
2873 example, the list of inferiors bound to the program space.
2876 (@value{GDBP}) maint info program-spaces
2880 Bound inferiors: ID 1 (process 21561)
2883 Here we can see that no inferior is running the program @code{hello},
2884 while @code{process 21561} is running the program @code{goodbye}. On
2885 some targets, it is possible that multiple inferiors are bound to the
2886 same program space. The most common example is that of debugging both
2887 the parent and child processes of a @code{vfork} call. For example,
2890 (@value{GDBP}) maint info program-spaces
2893 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2896 Here, both inferior 2 and inferior 1 are running in the same program
2897 space as a result of inferior 1 having executed a @code{vfork} call.
2901 @section Debugging Programs with Multiple Threads
2903 @cindex threads of execution
2904 @cindex multiple threads
2905 @cindex switching threads
2906 In some operating systems, such as GNU/Linux and Solaris, a single program
2907 may have more than one @dfn{thread} of execution. The precise semantics
2908 of threads differ from one operating system to another, but in general
2909 the threads of a single program are akin to multiple processes---except
2910 that they share one address space (that is, they can all examine and
2911 modify the same variables). On the other hand, each thread has its own
2912 registers and execution stack, and perhaps private memory.
2914 @value{GDBN} provides these facilities for debugging multi-thread
2918 @item automatic notification of new threads
2919 @item @samp{thread @var{thread-id}}, a command to switch among threads
2920 @item @samp{info threads}, a command to inquire about existing threads
2921 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2922 a command to apply a command to a list of threads
2923 @item thread-specific breakpoints
2924 @item @samp{set print thread-events}, which controls printing of
2925 messages on thread start and exit.
2926 @item @samp{set libthread-db-search-path @var{path}}, which lets
2927 the user specify which @code{libthread_db} to use if the default choice
2928 isn't compatible with the program.
2931 @cindex focus of debugging
2932 @cindex current thread
2933 The @value{GDBN} thread debugging facility allows you to observe all
2934 threads while your program runs---but whenever @value{GDBN} takes
2935 control, one thread in particular is always the focus of debugging.
2936 This thread is called the @dfn{current thread}. Debugging commands show
2937 program information from the perspective of the current thread.
2939 @cindex @code{New} @var{systag} message
2940 @cindex thread identifier (system)
2941 @c FIXME-implementors!! It would be more helpful if the [New...] message
2942 @c included GDB's numeric thread handle, so you could just go to that
2943 @c thread without first checking `info threads'.
2944 Whenever @value{GDBN} detects a new thread in your program, it displays
2945 the target system's identification for the thread with a message in the
2946 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2947 whose form varies depending on the particular system. For example, on
2948 @sc{gnu}/Linux, you might see
2951 [New Thread 0x41e02940 (LWP 25582)]
2955 when @value{GDBN} notices a new thread. In contrast, on other systems,
2956 the @var{systag} is simply something like @samp{process 368}, with no
2959 @c FIXME!! (1) Does the [New...] message appear even for the very first
2960 @c thread of a program, or does it only appear for the
2961 @c second---i.e.@: when it becomes obvious we have a multithread
2963 @c (2) *Is* there necessarily a first thread always? Or do some
2964 @c multithread systems permit starting a program with multiple
2965 @c threads ab initio?
2967 @anchor{thread numbers}
2968 @cindex thread number, per inferior
2969 @cindex thread identifier (GDB)
2970 For debugging purposes, @value{GDBN} associates its own thread number
2971 ---always a single integer---with each thread of an inferior. This
2972 number is unique between all threads of an inferior, but not unique
2973 between threads of different inferiors.
2975 @cindex qualified thread ID
2976 You can refer to a given thread in an inferior using the qualified
2977 @var{inferior-num}.@var{thread-num} syntax, also known as
2978 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2979 number and @var{thread-num} being the thread number of the given
2980 inferior. For example, thread @code{2.3} refers to thread number 3 of
2981 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2982 then @value{GDBN} infers you're referring to a thread of the current
2985 Until you create a second inferior, @value{GDBN} does not show the
2986 @var{inferior-num} part of thread IDs, even though you can always use
2987 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2988 of inferior 1, the initial inferior.
2990 @anchor{thread ID lists}
2991 @cindex thread ID lists
2992 Some commands accept a space-separated @dfn{thread ID list} as
2993 argument. A list element can be:
2997 A thread ID as shown in the first field of the @samp{info threads}
2998 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3002 A range of thread numbers, again with or without an inferior
3003 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3004 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3007 All threads of an inferior, specified with a star wildcard, with or
3008 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3009 @samp{1.*}) or @code{*}. The former refers to all threads of the
3010 given inferior, and the latter form without an inferior qualifier
3011 refers to all threads of the current inferior.
3015 For example, if the current inferior is 1, and inferior 7 has one
3016 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3017 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3018 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3019 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3023 @anchor{global thread numbers}
3024 @cindex global thread number
3025 @cindex global thread identifier (GDB)
3026 In addition to a @emph{per-inferior} number, each thread is also
3027 assigned a unique @emph{global} number, also known as @dfn{global
3028 thread ID}, a single integer. Unlike the thread number component of
3029 the thread ID, no two threads have the same global ID, even when
3030 you're debugging multiple inferiors.
3032 From @value{GDBN}'s perspective, a process always has at least one
3033 thread. In other words, @value{GDBN} assigns a thread number to the
3034 program's ``main thread'' even if the program is not multi-threaded.
3036 @vindex $_thread@r{, convenience variable}
3037 @vindex $_gthread@r{, convenience variable}
3038 The debugger convenience variables @samp{$_thread} and
3039 @samp{$_gthread} contain, respectively, the per-inferior thread number
3040 and the global thread number of the current thread. You may find this
3041 useful in writing breakpoint conditional expressions, command scripts,
3042 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3043 general information on convenience variables.
3045 If @value{GDBN} detects the program is multi-threaded, it augments the
3046 usual message about stopping at a breakpoint with the ID and name of
3047 the thread that hit the breakpoint.
3050 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3053 Likewise when the program receives a signal:
3056 Thread 1 "main" received signal SIGINT, Interrupt.
3060 @kindex info threads
3061 @item info threads @r{[}@var{thread-id-list}@r{]}
3063 Display information about one or more threads. With no arguments
3064 displays information about all threads. You can specify the list of
3065 threads that you want to display using the thread ID list syntax
3066 (@pxref{thread ID lists}).
3068 @value{GDBN} displays for each thread (in this order):
3072 the per-inferior thread number assigned by @value{GDBN}
3075 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3076 option was specified
3079 the target system's thread identifier (@var{systag})
3082 the thread's name, if one is known. A thread can either be named by
3083 the user (see @code{thread name}, below), or, in some cases, by the
3087 the current stack frame summary for that thread
3091 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3092 indicates the current thread.
3096 @c end table here to get a little more width for example
3099 (@value{GDBP}) info threads
3101 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3102 2 process 35 thread 23 0x34e5 in sigpause ()
3103 3 process 35 thread 27 0x34e5 in sigpause ()
3107 If you're debugging multiple inferiors, @value{GDBN} displays thread
3108 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3109 Otherwise, only @var{thread-num} is shown.
3111 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3112 indicating each thread's global thread ID:
3115 (@value{GDBP}) info threads
3116 Id GId Target Id Frame
3117 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3118 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3119 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3120 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3123 On Solaris, you can display more information about user threads with a
3124 Solaris-specific command:
3127 @item maint info sol-threads
3128 @kindex maint info sol-threads
3129 @cindex thread info (Solaris)
3130 Display info on Solaris user threads.
3134 @kindex thread @var{thread-id}
3135 @item thread @var{thread-id}
3136 Make thread ID @var{thread-id} the current thread. The command
3137 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3138 the first field of the @samp{info threads} display, with or without an
3139 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3141 @value{GDBN} responds by displaying the system identifier of the
3142 thread you selected, and its current stack frame summary:
3145 (@value{GDBP}) thread 2
3146 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3147 #0 some_function (ignore=0x0) at example.c:8
3148 8 printf ("hello\n");
3152 As with the @samp{[New @dots{}]} message, the form of the text after
3153 @samp{Switching to} depends on your system's conventions for identifying
3156 @kindex thread apply
3157 @cindex apply command to several threads
3158 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3159 The @code{thread apply} command allows you to apply the named
3160 @var{command} to one or more threads. Specify the threads that you
3161 want affected using the thread ID list syntax (@pxref{thread ID
3162 lists}), or specify @code{all} to apply to all threads. To apply a
3163 command to all threads in descending order, type @kbd{thread apply all
3164 @var{command}}. To apply a command to all threads in ascending order,
3165 type @kbd{thread apply all -ascending @var{command}}.
3169 @cindex name a thread
3170 @item thread name [@var{name}]
3171 This command assigns a name to the current thread. If no argument is
3172 given, any existing user-specified name is removed. The thread name
3173 appears in the @samp{info threads} display.
3175 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3176 determine the name of the thread as given by the OS. On these
3177 systems, a name specified with @samp{thread name} will override the
3178 system-give name, and removing the user-specified name will cause
3179 @value{GDBN} to once again display the system-specified name.
3182 @cindex search for a thread
3183 @item thread find [@var{regexp}]
3184 Search for and display thread ids whose name or @var{systag}
3185 matches the supplied regular expression.
3187 As well as being the complement to the @samp{thread name} command,
3188 this command also allows you to identify a thread by its target
3189 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3193 (@value{GDBN}) thread find 26688
3194 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3195 (@value{GDBN}) info thread 4
3197 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3200 @kindex set print thread-events
3201 @cindex print messages on thread start and exit
3202 @item set print thread-events
3203 @itemx set print thread-events on
3204 @itemx set print thread-events off
3205 The @code{set print thread-events} command allows you to enable or
3206 disable printing of messages when @value{GDBN} notices that new threads have
3207 started or that threads have exited. By default, these messages will
3208 be printed if detection of these events is supported by the target.
3209 Note that these messages cannot be disabled on all targets.
3211 @kindex show print thread-events
3212 @item show print thread-events
3213 Show whether messages will be printed when @value{GDBN} detects that threads
3214 have started and exited.
3217 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3218 more information about how @value{GDBN} behaves when you stop and start
3219 programs with multiple threads.
3221 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3222 watchpoints in programs with multiple threads.
3224 @anchor{set libthread-db-search-path}
3226 @kindex set libthread-db-search-path
3227 @cindex search path for @code{libthread_db}
3228 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3229 If this variable is set, @var{path} is a colon-separated list of
3230 directories @value{GDBN} will use to search for @code{libthread_db}.
3231 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3232 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3233 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3236 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3237 @code{libthread_db} library to obtain information about threads in the
3238 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3239 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3240 specific thread debugging library loading is enabled
3241 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3243 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3244 refers to the default system directories that are
3245 normally searched for loading shared libraries. The @samp{$sdir} entry
3246 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3247 (@pxref{libthread_db.so.1 file}).
3249 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3250 refers to the directory from which @code{libpthread}
3251 was loaded in the inferior process.
3253 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3254 @value{GDBN} attempts to initialize it with the current inferior process.
3255 If this initialization fails (which could happen because of a version
3256 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3257 will unload @code{libthread_db}, and continue with the next directory.
3258 If none of @code{libthread_db} libraries initialize successfully,
3259 @value{GDBN} will issue a warning and thread debugging will be disabled.
3261 Setting @code{libthread-db-search-path} is currently implemented
3262 only on some platforms.
3264 @kindex show libthread-db-search-path
3265 @item show libthread-db-search-path
3266 Display current libthread_db search path.
3268 @kindex set debug libthread-db
3269 @kindex show debug libthread-db
3270 @cindex debugging @code{libthread_db}
3271 @item set debug libthread-db
3272 @itemx show debug libthread-db
3273 Turns on or off display of @code{libthread_db}-related events.
3274 Use @code{1} to enable, @code{0} to disable.
3278 @section Debugging Forks
3280 @cindex fork, debugging programs which call
3281 @cindex multiple processes
3282 @cindex processes, multiple
3283 On most systems, @value{GDBN} has no special support for debugging
3284 programs which create additional processes using the @code{fork}
3285 function. When a program forks, @value{GDBN} will continue to debug the
3286 parent process and the child process will run unimpeded. If you have
3287 set a breakpoint in any code which the child then executes, the child
3288 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3289 will cause it to terminate.
3291 However, if you want to debug the child process there is a workaround
3292 which isn't too painful. Put a call to @code{sleep} in the code which
3293 the child process executes after the fork. It may be useful to sleep
3294 only if a certain environment variable is set, or a certain file exists,
3295 so that the delay need not occur when you don't want to run @value{GDBN}
3296 on the child. While the child is sleeping, use the @code{ps} program to
3297 get its process ID. Then tell @value{GDBN} (a new invocation of
3298 @value{GDBN} if you are also debugging the parent process) to attach to
3299 the child process (@pxref{Attach}). From that point on you can debug
3300 the child process just like any other process which you attached to.
3302 On some systems, @value{GDBN} provides support for debugging programs
3303 that create additional processes using the @code{fork} or @code{vfork}
3304 functions. On @sc{gnu}/Linux platforms, this feature is supported
3305 with kernel version 2.5.46 and later.
3307 The fork debugging commands are supported in native mode and when
3308 connected to @code{gdbserver} in either @code{target remote} mode or
3309 @code{target extended-remote} mode.
3311 By default, when a program forks, @value{GDBN} will continue to debug
3312 the parent process and the child process will run unimpeded.
3314 If you want to follow the child process instead of the parent process,
3315 use the command @w{@code{set follow-fork-mode}}.
3318 @kindex set follow-fork-mode
3319 @item set follow-fork-mode @var{mode}
3320 Set the debugger response to a program call of @code{fork} or
3321 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3322 process. The @var{mode} argument can be:
3326 The original process is debugged after a fork. The child process runs
3327 unimpeded. This is the default.
3330 The new process is debugged after a fork. The parent process runs
3335 @kindex show follow-fork-mode
3336 @item show follow-fork-mode
3337 Display the current debugger response to a @code{fork} or @code{vfork} call.
3340 @cindex debugging multiple processes
3341 On Linux, if you want to debug both the parent and child processes, use the
3342 command @w{@code{set detach-on-fork}}.
3345 @kindex set detach-on-fork
3346 @item set detach-on-fork @var{mode}
3347 Tells gdb whether to detach one of the processes after a fork, or
3348 retain debugger control over them both.
3352 The child process (or parent process, depending on the value of
3353 @code{follow-fork-mode}) will be detached and allowed to run
3354 independently. This is the default.
3357 Both processes will be held under the control of @value{GDBN}.
3358 One process (child or parent, depending on the value of
3359 @code{follow-fork-mode}) is debugged as usual, while the other
3364 @kindex show detach-on-fork
3365 @item show detach-on-fork
3366 Show whether detach-on-fork mode is on/off.
3369 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3370 will retain control of all forked processes (including nested forks).
3371 You can list the forked processes under the control of @value{GDBN} by
3372 using the @w{@code{info inferiors}} command, and switch from one fork
3373 to another by using the @code{inferior} command (@pxref{Inferiors and
3374 Programs, ,Debugging Multiple Inferiors and Programs}).
3376 To quit debugging one of the forked processes, you can either detach
3377 from it by using the @w{@code{detach inferiors}} command (allowing it
3378 to run independently), or kill it using the @w{@code{kill inferiors}}
3379 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3382 If you ask to debug a child process and a @code{vfork} is followed by an
3383 @code{exec}, @value{GDBN} executes the new target up to the first
3384 breakpoint in the new target. If you have a breakpoint set on
3385 @code{main} in your original program, the breakpoint will also be set on
3386 the child process's @code{main}.
3388 On some systems, when a child process is spawned by @code{vfork}, you
3389 cannot debug the child or parent until an @code{exec} call completes.
3391 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3392 call executes, the new target restarts. To restart the parent
3393 process, use the @code{file} command with the parent executable name
3394 as its argument. By default, after an @code{exec} call executes,
3395 @value{GDBN} discards the symbols of the previous executable image.
3396 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3400 @kindex set follow-exec-mode
3401 @item set follow-exec-mode @var{mode}
3403 Set debugger response to a program call of @code{exec}. An
3404 @code{exec} call replaces the program image of a process.
3406 @code{follow-exec-mode} can be:
3410 @value{GDBN} creates a new inferior and rebinds the process to this
3411 new inferior. The program the process was running before the
3412 @code{exec} call can be restarted afterwards by restarting the
3418 (@value{GDBP}) info inferiors
3420 Id Description Executable
3423 process 12020 is executing new program: prog2
3424 Program exited normally.
3425 (@value{GDBP}) info inferiors
3426 Id Description Executable
3432 @value{GDBN} keeps the process bound to the same inferior. The new
3433 executable image replaces the previous executable loaded in the
3434 inferior. Restarting the inferior after the @code{exec} call, with
3435 e.g., the @code{run} command, restarts the executable the process was
3436 running after the @code{exec} call. This is the default mode.
3441 (@value{GDBP}) info inferiors
3442 Id Description Executable
3445 process 12020 is executing new program: prog2
3446 Program exited normally.
3447 (@value{GDBP}) info inferiors
3448 Id Description Executable
3455 @code{follow-exec-mode} is supported in native mode and
3456 @code{target extended-remote} mode.
3458 You can use the @code{catch} command to make @value{GDBN} stop whenever
3459 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3460 Catchpoints, ,Setting Catchpoints}.
3462 @node Checkpoint/Restart
3463 @section Setting a @emph{Bookmark} to Return to Later
3468 @cindex snapshot of a process
3469 @cindex rewind program state
3471 On certain operating systems@footnote{Currently, only
3472 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3473 program's state, called a @dfn{checkpoint}, and come back to it
3476 Returning to a checkpoint effectively undoes everything that has
3477 happened in the program since the @code{checkpoint} was saved. This
3478 includes changes in memory, registers, and even (within some limits)
3479 system state. Effectively, it is like going back in time to the
3480 moment when the checkpoint was saved.
3482 Thus, if you're stepping thru a program and you think you're
3483 getting close to the point where things go wrong, you can save
3484 a checkpoint. Then, if you accidentally go too far and miss
3485 the critical statement, instead of having to restart your program
3486 from the beginning, you can just go back to the checkpoint and
3487 start again from there.
3489 This can be especially useful if it takes a lot of time or
3490 steps to reach the point where you think the bug occurs.
3492 To use the @code{checkpoint}/@code{restart} method of debugging:
3497 Save a snapshot of the debugged program's current execution state.
3498 The @code{checkpoint} command takes no arguments, but each checkpoint
3499 is assigned a small integer id, similar to a breakpoint id.
3501 @kindex info checkpoints
3502 @item info checkpoints
3503 List the checkpoints that have been saved in the current debugging
3504 session. For each checkpoint, the following information will be
3511 @item Source line, or label
3514 @kindex restart @var{checkpoint-id}
3515 @item restart @var{checkpoint-id}
3516 Restore the program state that was saved as checkpoint number
3517 @var{checkpoint-id}. All program variables, registers, stack frames
3518 etc.@: will be returned to the values that they had when the checkpoint
3519 was saved. In essence, gdb will ``wind back the clock'' to the point
3520 in time when the checkpoint was saved.
3522 Note that breakpoints, @value{GDBN} variables, command history etc.
3523 are not affected by restoring a checkpoint. In general, a checkpoint
3524 only restores things that reside in the program being debugged, not in
3527 @kindex delete checkpoint @var{checkpoint-id}
3528 @item delete checkpoint @var{checkpoint-id}
3529 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3533 Returning to a previously saved checkpoint will restore the user state
3534 of the program being debugged, plus a significant subset of the system
3535 (OS) state, including file pointers. It won't ``un-write'' data from
3536 a file, but it will rewind the file pointer to the previous location,
3537 so that the previously written data can be overwritten. For files
3538 opened in read mode, the pointer will also be restored so that the
3539 previously read data can be read again.
3541 Of course, characters that have been sent to a printer (or other
3542 external device) cannot be ``snatched back'', and characters received
3543 from eg.@: a serial device can be removed from internal program buffers,
3544 but they cannot be ``pushed back'' into the serial pipeline, ready to
3545 be received again. Similarly, the actual contents of files that have
3546 been changed cannot be restored (at this time).
3548 However, within those constraints, you actually can ``rewind'' your
3549 program to a previously saved point in time, and begin debugging it
3550 again --- and you can change the course of events so as to debug a
3551 different execution path this time.
3553 @cindex checkpoints and process id
3554 Finally, there is one bit of internal program state that will be
3555 different when you return to a checkpoint --- the program's process
3556 id. Each checkpoint will have a unique process id (or @var{pid}),
3557 and each will be different from the program's original @var{pid}.
3558 If your program has saved a local copy of its process id, this could
3559 potentially pose a problem.
3561 @subsection A Non-obvious Benefit of Using Checkpoints
3563 On some systems such as @sc{gnu}/Linux, address space randomization
3564 is performed on new processes for security reasons. This makes it
3565 difficult or impossible to set a breakpoint, or watchpoint, on an
3566 absolute address if you have to restart the program, since the
3567 absolute location of a symbol will change from one execution to the
3570 A checkpoint, however, is an @emph{identical} copy of a process.
3571 Therefore if you create a checkpoint at (eg.@:) the start of main,
3572 and simply return to that checkpoint instead of restarting the
3573 process, you can avoid the effects of address randomization and
3574 your symbols will all stay in the same place.
3577 @chapter Stopping and Continuing
3579 The principal purposes of using a debugger are so that you can stop your
3580 program before it terminates; or so that, if your program runs into
3581 trouble, you can investigate and find out why.
3583 Inside @value{GDBN}, your program may stop for any of several reasons,
3584 such as a signal, a breakpoint, or reaching a new line after a
3585 @value{GDBN} command such as @code{step}. You may then examine and
3586 change variables, set new breakpoints or remove old ones, and then
3587 continue execution. Usually, the messages shown by @value{GDBN} provide
3588 ample explanation of the status of your program---but you can also
3589 explicitly request this information at any time.
3592 @kindex info program
3594 Display information about the status of your program: whether it is
3595 running or not, what process it is, and why it stopped.
3599 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3600 * Continuing and Stepping:: Resuming execution
3601 * Skipping Over Functions and Files::
3602 Skipping over functions and files
3604 * Thread Stops:: Stopping and starting multi-thread programs
3608 @section Breakpoints, Watchpoints, and Catchpoints
3611 A @dfn{breakpoint} makes your program stop whenever a certain point in
3612 the program is reached. For each breakpoint, you can add conditions to
3613 control in finer detail whether your program stops. You can set
3614 breakpoints with the @code{break} command and its variants (@pxref{Set
3615 Breaks, ,Setting Breakpoints}), to specify the place where your program
3616 should stop by line number, function name or exact address in the
3619 On some systems, you can set breakpoints in shared libraries before
3620 the executable is run.
3623 @cindex data breakpoints
3624 @cindex memory tracing
3625 @cindex breakpoint on memory address
3626 @cindex breakpoint on variable modification
3627 A @dfn{watchpoint} is a special breakpoint that stops your program
3628 when the value of an expression changes. The expression may be a value
3629 of a variable, or it could involve values of one or more variables
3630 combined by operators, such as @samp{a + b}. This is sometimes called
3631 @dfn{data breakpoints}. You must use a different command to set
3632 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3633 from that, you can manage a watchpoint like any other breakpoint: you
3634 enable, disable, and delete both breakpoints and watchpoints using the
3637 You can arrange to have values from your program displayed automatically
3638 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3642 @cindex breakpoint on events
3643 A @dfn{catchpoint} is another special breakpoint that stops your program
3644 when a certain kind of event occurs, such as the throwing of a C@t{++}
3645 exception or the loading of a library. As with watchpoints, you use a
3646 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3647 Catchpoints}), but aside from that, you can manage a catchpoint like any
3648 other breakpoint. (To stop when your program receives a signal, use the
3649 @code{handle} command; see @ref{Signals, ,Signals}.)
3651 @cindex breakpoint numbers
3652 @cindex numbers for breakpoints
3653 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3654 catchpoint when you create it; these numbers are successive integers
3655 starting with one. In many of the commands for controlling various
3656 features of breakpoints you use the breakpoint number to say which
3657 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3658 @dfn{disabled}; if disabled, it has no effect on your program until you
3661 @cindex breakpoint ranges
3662 @cindex breakpoint lists
3663 @cindex ranges of breakpoints
3664 @cindex lists of breakpoints
3665 Some @value{GDBN} commands accept a space-separated list of breakpoints
3666 on which to operate. A list element can be either a single breakpoint number,
3667 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3668 When a breakpoint list is given to a command, all breakpoints in that list
3672 * Set Breaks:: Setting breakpoints
3673 * Set Watchpoints:: Setting watchpoints
3674 * Set Catchpoints:: Setting catchpoints
3675 * Delete Breaks:: Deleting breakpoints
3676 * Disabling:: Disabling breakpoints
3677 * Conditions:: Break conditions
3678 * Break Commands:: Breakpoint command lists
3679 * Dynamic Printf:: Dynamic printf
3680 * Save Breakpoints:: How to save breakpoints in a file
3681 * Static Probe Points:: Listing static probe points
3682 * Error in Breakpoints:: ``Cannot insert breakpoints''
3683 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3687 @subsection Setting Breakpoints
3689 @c FIXME LMB what does GDB do if no code on line of breakpt?
3690 @c consider in particular declaration with/without initialization.
3692 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3695 @kindex b @r{(@code{break})}
3696 @vindex $bpnum@r{, convenience variable}
3697 @cindex latest breakpoint
3698 Breakpoints are set with the @code{break} command (abbreviated
3699 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3700 number of the breakpoint you've set most recently; see @ref{Convenience
3701 Vars,, Convenience Variables}, for a discussion of what you can do with
3702 convenience variables.
3705 @item break @var{location}
3706 Set a breakpoint at the given @var{location}, which can specify a
3707 function name, a line number, or an address of an instruction.
3708 (@xref{Specify Location}, for a list of all the possible ways to
3709 specify a @var{location}.) The breakpoint will stop your program just
3710 before it executes any of the code in the specified @var{location}.
3712 When using source languages that permit overloading of symbols, such as
3713 C@t{++}, a function name may refer to more than one possible place to break.
3714 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3717 It is also possible to insert a breakpoint that will stop the program
3718 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3719 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3722 When called without any arguments, @code{break} sets a breakpoint at
3723 the next instruction to be executed in the selected stack frame
3724 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3725 innermost, this makes your program stop as soon as control
3726 returns to that frame. This is similar to the effect of a
3727 @code{finish} command in the frame inside the selected frame---except
3728 that @code{finish} does not leave an active breakpoint. If you use
3729 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3730 the next time it reaches the current location; this may be useful
3733 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3734 least one instruction has been executed. If it did not do this, you
3735 would be unable to proceed past a breakpoint without first disabling the
3736 breakpoint. This rule applies whether or not the breakpoint already
3737 existed when your program stopped.
3739 @item break @dots{} if @var{cond}
3740 Set a breakpoint with condition @var{cond}; evaluate the expression
3741 @var{cond} each time the breakpoint is reached, and stop only if the
3742 value is nonzero---that is, if @var{cond} evaluates as true.
3743 @samp{@dots{}} stands for one of the possible arguments described
3744 above (or no argument) specifying where to break. @xref{Conditions,
3745 ,Break Conditions}, for more information on breakpoint conditions.
3748 @item tbreak @var{args}
3749 Set a breakpoint enabled only for one stop. The @var{args} are the
3750 same as for the @code{break} command, and the breakpoint is set in the same
3751 way, but the breakpoint is automatically deleted after the first time your
3752 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3755 @cindex hardware breakpoints
3756 @item hbreak @var{args}
3757 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3758 @code{break} command and the breakpoint is set in the same way, but the
3759 breakpoint requires hardware support and some target hardware may not
3760 have this support. The main purpose of this is EPROM/ROM code
3761 debugging, so you can set a breakpoint at an instruction without
3762 changing the instruction. This can be used with the new trap-generation
3763 provided by SPARClite DSU and most x86-based targets. These targets
3764 will generate traps when a program accesses some data or instruction
3765 address that is assigned to the debug registers. However the hardware
3766 breakpoint registers can take a limited number of breakpoints. For
3767 example, on the DSU, only two data breakpoints can be set at a time, and
3768 @value{GDBN} will reject this command if more than two are used. Delete
3769 or disable unused hardware breakpoints before setting new ones
3770 (@pxref{Disabling, ,Disabling Breakpoints}).
3771 @xref{Conditions, ,Break Conditions}.
3772 For remote targets, you can restrict the number of hardware
3773 breakpoints @value{GDBN} will use, see @ref{set remote
3774 hardware-breakpoint-limit}.
3777 @item thbreak @var{args}
3778 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3779 are the same as for the @code{hbreak} command and the breakpoint is set in
3780 the same way. However, like the @code{tbreak} command,
3781 the breakpoint is automatically deleted after the
3782 first time your program stops there. Also, like the @code{hbreak}
3783 command, the breakpoint requires hardware support and some target hardware
3784 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3785 See also @ref{Conditions, ,Break Conditions}.
3788 @cindex regular expression
3789 @cindex breakpoints at functions matching a regexp
3790 @cindex set breakpoints in many functions
3791 @item rbreak @var{regex}
3792 Set breakpoints on all functions matching the regular expression
3793 @var{regex}. This command sets an unconditional breakpoint on all
3794 matches, printing a list of all breakpoints it set. Once these
3795 breakpoints are set, they are treated just like the breakpoints set with
3796 the @code{break} command. You can delete them, disable them, or make
3797 them conditional the same way as any other breakpoint.
3799 The syntax of the regular expression is the standard one used with tools
3800 like @file{grep}. Note that this is different from the syntax used by
3801 shells, so for instance @code{foo*} matches all functions that include
3802 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3803 @code{.*} leading and trailing the regular expression you supply, so to
3804 match only functions that begin with @code{foo}, use @code{^foo}.
3806 @cindex non-member C@t{++} functions, set breakpoint in
3807 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3808 breakpoints on overloaded functions that are not members of any special
3811 @cindex set breakpoints on all functions
3812 The @code{rbreak} command can be used to set breakpoints in
3813 @strong{all} the functions in a program, like this:
3816 (@value{GDBP}) rbreak .
3819 @item rbreak @var{file}:@var{regex}
3820 If @code{rbreak} is called with a filename qualification, it limits
3821 the search for functions matching the given regular expression to the
3822 specified @var{file}. This can be used, for example, to set breakpoints on
3823 every function in a given file:
3826 (@value{GDBP}) rbreak file.c:.
3829 The colon separating the filename qualifier from the regex may
3830 optionally be surrounded by spaces.
3832 @kindex info breakpoints
3833 @cindex @code{$_} and @code{info breakpoints}
3834 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3835 @itemx info break @r{[}@var{list}@dots{}@r{]}
3836 Print a table of all breakpoints, watchpoints, and catchpoints set and
3837 not deleted. Optional argument @var{n} means print information only
3838 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3839 For each breakpoint, following columns are printed:
3842 @item Breakpoint Numbers
3844 Breakpoint, watchpoint, or catchpoint.
3846 Whether the breakpoint is marked to be disabled or deleted when hit.
3847 @item Enabled or Disabled
3848 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3849 that are not enabled.
3851 Where the breakpoint is in your program, as a memory address. For a
3852 pending breakpoint whose address is not yet known, this field will
3853 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3854 library that has the symbol or line referred by breakpoint is loaded.
3855 See below for details. A breakpoint with several locations will
3856 have @samp{<MULTIPLE>} in this field---see below for details.
3858 Where the breakpoint is in the source for your program, as a file and
3859 line number. For a pending breakpoint, the original string passed to
3860 the breakpoint command will be listed as it cannot be resolved until
3861 the appropriate shared library is loaded in the future.
3865 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3866 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3867 @value{GDBN} on the host's side. If it is ``target'', then the condition
3868 is evaluated by the target. The @code{info break} command shows
3869 the condition on the line following the affected breakpoint, together with
3870 its condition evaluation mode in between parentheses.
3872 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3873 allowed to have a condition specified for it. The condition is not parsed for
3874 validity until a shared library is loaded that allows the pending
3875 breakpoint to resolve to a valid location.
3878 @code{info break} with a breakpoint
3879 number @var{n} as argument lists only that breakpoint. The
3880 convenience variable @code{$_} and the default examining-address for
3881 the @code{x} command are set to the address of the last breakpoint
3882 listed (@pxref{Memory, ,Examining Memory}).
3885 @code{info break} displays a count of the number of times the breakpoint
3886 has been hit. This is especially useful in conjunction with the
3887 @code{ignore} command. You can ignore a large number of breakpoint
3888 hits, look at the breakpoint info to see how many times the breakpoint
3889 was hit, and then run again, ignoring one less than that number. This
3890 will get you quickly to the last hit of that breakpoint.
3893 For a breakpoints with an enable count (xref) greater than 1,
3894 @code{info break} also displays that count.
3898 @value{GDBN} allows you to set any number of breakpoints at the same place in
3899 your program. There is nothing silly or meaningless about this. When
3900 the breakpoints are conditional, this is even useful
3901 (@pxref{Conditions, ,Break Conditions}).
3903 @cindex multiple locations, breakpoints
3904 @cindex breakpoints, multiple locations
3905 It is possible that a breakpoint corresponds to several locations
3906 in your program. Examples of this situation are:
3910 Multiple functions in the program may have the same name.
3913 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3914 instances of the function body, used in different cases.
3917 For a C@t{++} template function, a given line in the function can
3918 correspond to any number of instantiations.
3921 For an inlined function, a given source line can correspond to
3922 several places where that function is inlined.
3925 In all those cases, @value{GDBN} will insert a breakpoint at all
3926 the relevant locations.
3928 A breakpoint with multiple locations is displayed in the breakpoint
3929 table using several rows---one header row, followed by one row for
3930 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3931 address column. The rows for individual locations contain the actual
3932 addresses for locations, and show the functions to which those
3933 locations belong. The number column for a location is of the form
3934 @var{breakpoint-number}.@var{location-number}.
3939 Num Type Disp Enb Address What
3940 1 breakpoint keep y <MULTIPLE>
3942 breakpoint already hit 1 time
3943 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3944 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3947 You cannot delete the individual locations from a breakpoint. However,
3948 each location can be individually enabled or disabled by passing
3949 @var{breakpoint-number}.@var{location-number} as argument to the
3950 @code{enable} and @code{disable} commands. It's also possible to
3951 @code{enable} and @code{disable} a range of @var{location-number}
3952 locations using a @var{breakpoint-number} and two @var{location-number}s,
3953 in increasing order, separated by a hyphen, like
3954 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
3955 in which case @value{GDBN} acts on all the locations in the range (inclusive).
3956 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
3957 all of the locations that belong to that breakpoint.
3959 @cindex pending breakpoints
3960 It's quite common to have a breakpoint inside a shared library.
3961 Shared libraries can be loaded and unloaded explicitly,
3962 and possibly repeatedly, as the program is executed. To support
3963 this use case, @value{GDBN} updates breakpoint locations whenever
3964 any shared library is loaded or unloaded. Typically, you would
3965 set a breakpoint in a shared library at the beginning of your
3966 debugging session, when the library is not loaded, and when the
3967 symbols from the library are not available. When you try to set
3968 breakpoint, @value{GDBN} will ask you if you want to set
3969 a so called @dfn{pending breakpoint}---breakpoint whose address
3970 is not yet resolved.
3972 After the program is run, whenever a new shared library is loaded,
3973 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3974 shared library contains the symbol or line referred to by some
3975 pending breakpoint, that breakpoint is resolved and becomes an
3976 ordinary breakpoint. When a library is unloaded, all breakpoints
3977 that refer to its symbols or source lines become pending again.
3979 This logic works for breakpoints with multiple locations, too. For
3980 example, if you have a breakpoint in a C@t{++} template function, and
3981 a newly loaded shared library has an instantiation of that template,
3982 a new location is added to the list of locations for the breakpoint.
3984 Except for having unresolved address, pending breakpoints do not
3985 differ from regular breakpoints. You can set conditions or commands,
3986 enable and disable them and perform other breakpoint operations.
3988 @value{GDBN} provides some additional commands for controlling what
3989 happens when the @samp{break} command cannot resolve breakpoint
3990 address specification to an address:
3992 @kindex set breakpoint pending
3993 @kindex show breakpoint pending
3995 @item set breakpoint pending auto
3996 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3997 location, it queries you whether a pending breakpoint should be created.
3999 @item set breakpoint pending on
4000 This indicates that an unrecognized breakpoint location should automatically
4001 result in a pending breakpoint being created.
4003 @item set breakpoint pending off
4004 This indicates that pending breakpoints are not to be created. Any
4005 unrecognized breakpoint location results in an error. This setting does
4006 not affect any pending breakpoints previously created.
4008 @item show breakpoint pending
4009 Show the current behavior setting for creating pending breakpoints.
4012 The settings above only affect the @code{break} command and its
4013 variants. Once breakpoint is set, it will be automatically updated
4014 as shared libraries are loaded and unloaded.
4016 @cindex automatic hardware breakpoints
4017 For some targets, @value{GDBN} can automatically decide if hardware or
4018 software breakpoints should be used, depending on whether the
4019 breakpoint address is read-only or read-write. This applies to
4020 breakpoints set with the @code{break} command as well as to internal
4021 breakpoints set by commands like @code{next} and @code{finish}. For
4022 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4025 You can control this automatic behaviour with the following commands:
4027 @kindex set breakpoint auto-hw
4028 @kindex show breakpoint auto-hw
4030 @item set breakpoint auto-hw on
4031 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4032 will try to use the target memory map to decide if software or hardware
4033 breakpoint must be used.
4035 @item set breakpoint auto-hw off
4036 This indicates @value{GDBN} should not automatically select breakpoint
4037 type. If the target provides a memory map, @value{GDBN} will warn when
4038 trying to set software breakpoint at a read-only address.
4041 @value{GDBN} normally implements breakpoints by replacing the program code
4042 at the breakpoint address with a special instruction, which, when
4043 executed, given control to the debugger. By default, the program
4044 code is so modified only when the program is resumed. As soon as
4045 the program stops, @value{GDBN} restores the original instructions. This
4046 behaviour guards against leaving breakpoints inserted in the
4047 target should gdb abrubptly disconnect. However, with slow remote
4048 targets, inserting and removing breakpoint can reduce the performance.
4049 This behavior can be controlled with the following commands::
4051 @kindex set breakpoint always-inserted
4052 @kindex show breakpoint always-inserted
4054 @item set breakpoint always-inserted off
4055 All breakpoints, including newly added by the user, are inserted in
4056 the target only when the target is resumed. All breakpoints are
4057 removed from the target when it stops. This is the default mode.
4059 @item set breakpoint always-inserted on
4060 Causes all breakpoints to be inserted in the target at all times. If
4061 the user adds a new breakpoint, or changes an existing breakpoint, the
4062 breakpoints in the target are updated immediately. A breakpoint is
4063 removed from the target only when breakpoint itself is deleted.
4066 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4067 when a breakpoint breaks. If the condition is true, then the process being
4068 debugged stops, otherwise the process is resumed.
4070 If the target supports evaluating conditions on its end, @value{GDBN} may
4071 download the breakpoint, together with its conditions, to it.
4073 This feature can be controlled via the following commands:
4075 @kindex set breakpoint condition-evaluation
4076 @kindex show breakpoint condition-evaluation
4078 @item set breakpoint condition-evaluation host
4079 This option commands @value{GDBN} to evaluate the breakpoint
4080 conditions on the host's side. Unconditional breakpoints are sent to
4081 the target which in turn receives the triggers and reports them back to GDB
4082 for condition evaluation. This is the standard evaluation mode.
4084 @item set breakpoint condition-evaluation target
4085 This option commands @value{GDBN} to download breakpoint conditions
4086 to the target at the moment of their insertion. The target
4087 is responsible for evaluating the conditional expression and reporting
4088 breakpoint stop events back to @value{GDBN} whenever the condition
4089 is true. Due to limitations of target-side evaluation, some conditions
4090 cannot be evaluated there, e.g., conditions that depend on local data
4091 that is only known to the host. Examples include
4092 conditional expressions involving convenience variables, complex types
4093 that cannot be handled by the agent expression parser and expressions
4094 that are too long to be sent over to the target, specially when the
4095 target is a remote system. In these cases, the conditions will be
4096 evaluated by @value{GDBN}.
4098 @item set breakpoint condition-evaluation auto
4099 This is the default mode. If the target supports evaluating breakpoint
4100 conditions on its end, @value{GDBN} will download breakpoint conditions to
4101 the target (limitations mentioned previously apply). If the target does
4102 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4103 to evaluating all these conditions on the host's side.
4107 @cindex negative breakpoint numbers
4108 @cindex internal @value{GDBN} breakpoints
4109 @value{GDBN} itself sometimes sets breakpoints in your program for
4110 special purposes, such as proper handling of @code{longjmp} (in C
4111 programs). These internal breakpoints are assigned negative numbers,
4112 starting with @code{-1}; @samp{info breakpoints} does not display them.
4113 You can see these breakpoints with the @value{GDBN} maintenance command
4114 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4117 @node Set Watchpoints
4118 @subsection Setting Watchpoints
4120 @cindex setting watchpoints
4121 You can use a watchpoint to stop execution whenever the value of an
4122 expression changes, without having to predict a particular place where
4123 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4124 The expression may be as simple as the value of a single variable, or
4125 as complex as many variables combined by operators. Examples include:
4129 A reference to the value of a single variable.
4132 An address cast to an appropriate data type. For example,
4133 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4134 address (assuming an @code{int} occupies 4 bytes).
4137 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4138 expression can use any operators valid in the program's native
4139 language (@pxref{Languages}).
4142 You can set a watchpoint on an expression even if the expression can
4143 not be evaluated yet. For instance, you can set a watchpoint on
4144 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4145 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4146 the expression produces a valid value. If the expression becomes
4147 valid in some other way than changing a variable (e.g.@: if the memory
4148 pointed to by @samp{*global_ptr} becomes readable as the result of a
4149 @code{malloc} call), @value{GDBN} may not stop until the next time
4150 the expression changes.
4152 @cindex software watchpoints
4153 @cindex hardware watchpoints
4154 Depending on your system, watchpoints may be implemented in software or
4155 hardware. @value{GDBN} does software watchpointing by single-stepping your
4156 program and testing the variable's value each time, which is hundreds of
4157 times slower than normal execution. (But this may still be worth it, to
4158 catch errors where you have no clue what part of your program is the
4161 On some systems, such as most PowerPC or x86-based targets,
4162 @value{GDBN} includes support for hardware watchpoints, which do not
4163 slow down the running of your program.
4167 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4168 Set a watchpoint for an expression. @value{GDBN} will break when the
4169 expression @var{expr} is written into by the program and its value
4170 changes. The simplest (and the most popular) use of this command is
4171 to watch the value of a single variable:
4174 (@value{GDBP}) watch foo
4177 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4178 argument, @value{GDBN} breaks only when the thread identified by
4179 @var{thread-id} changes the value of @var{expr}. If any other threads
4180 change the value of @var{expr}, @value{GDBN} will not break. Note
4181 that watchpoints restricted to a single thread in this way only work
4182 with Hardware Watchpoints.
4184 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4185 (see below). The @code{-location} argument tells @value{GDBN} to
4186 instead watch the memory referred to by @var{expr}. In this case,
4187 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4188 and watch the memory at that address. The type of the result is used
4189 to determine the size of the watched memory. If the expression's
4190 result does not have an address, then @value{GDBN} will print an
4193 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4194 of masked watchpoints, if the current architecture supports this
4195 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4196 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4197 to an address to watch. The mask specifies that some bits of an address
4198 (the bits which are reset in the mask) should be ignored when matching
4199 the address accessed by the inferior against the watchpoint address.
4200 Thus, a masked watchpoint watches many addresses simultaneously---those
4201 addresses whose unmasked bits are identical to the unmasked bits in the
4202 watchpoint address. The @code{mask} argument implies @code{-location}.
4206 (@value{GDBP}) watch foo mask 0xffff00ff
4207 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4211 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4212 Set a watchpoint that will break when the value of @var{expr} is read
4216 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4217 Set a watchpoint that will break when @var{expr} is either read from
4218 or written into by the program.
4220 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4221 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4222 This command prints a list of watchpoints, using the same format as
4223 @code{info break} (@pxref{Set Breaks}).
4226 If you watch for a change in a numerically entered address you need to
4227 dereference it, as the address itself is just a constant number which will
4228 never change. @value{GDBN} refuses to create a watchpoint that watches
4229 a never-changing value:
4232 (@value{GDBP}) watch 0x600850
4233 Cannot watch constant value 0x600850.
4234 (@value{GDBP}) watch *(int *) 0x600850
4235 Watchpoint 1: *(int *) 6293584
4238 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4239 watchpoints execute very quickly, and the debugger reports a change in
4240 value at the exact instruction where the change occurs. If @value{GDBN}
4241 cannot set a hardware watchpoint, it sets a software watchpoint, which
4242 executes more slowly and reports the change in value at the next
4243 @emph{statement}, not the instruction, after the change occurs.
4245 @cindex use only software watchpoints
4246 You can force @value{GDBN} to use only software watchpoints with the
4247 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4248 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4249 the underlying system supports them. (Note that hardware-assisted
4250 watchpoints that were set @emph{before} setting
4251 @code{can-use-hw-watchpoints} to zero will still use the hardware
4252 mechanism of watching expression values.)
4255 @item set can-use-hw-watchpoints
4256 @kindex set can-use-hw-watchpoints
4257 Set whether or not to use hardware watchpoints.
4259 @item show can-use-hw-watchpoints
4260 @kindex show can-use-hw-watchpoints
4261 Show the current mode of using hardware watchpoints.
4264 For remote targets, you can restrict the number of hardware
4265 watchpoints @value{GDBN} will use, see @ref{set remote
4266 hardware-breakpoint-limit}.
4268 When you issue the @code{watch} command, @value{GDBN} reports
4271 Hardware watchpoint @var{num}: @var{expr}
4275 if it was able to set a hardware watchpoint.
4277 Currently, the @code{awatch} and @code{rwatch} commands can only set
4278 hardware watchpoints, because accesses to data that don't change the
4279 value of the watched expression cannot be detected without examining
4280 every instruction as it is being executed, and @value{GDBN} does not do
4281 that currently. If @value{GDBN} finds that it is unable to set a
4282 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4283 will print a message like this:
4286 Expression cannot be implemented with read/access watchpoint.
4289 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4290 data type of the watched expression is wider than what a hardware
4291 watchpoint on the target machine can handle. For example, some systems
4292 can only watch regions that are up to 4 bytes wide; on such systems you
4293 cannot set hardware watchpoints for an expression that yields a
4294 double-precision floating-point number (which is typically 8 bytes
4295 wide). As a work-around, it might be possible to break the large region
4296 into a series of smaller ones and watch them with separate watchpoints.
4298 If you set too many hardware watchpoints, @value{GDBN} might be unable
4299 to insert all of them when you resume the execution of your program.
4300 Since the precise number of active watchpoints is unknown until such
4301 time as the program is about to be resumed, @value{GDBN} might not be
4302 able to warn you about this when you set the watchpoints, and the
4303 warning will be printed only when the program is resumed:
4306 Hardware watchpoint @var{num}: Could not insert watchpoint
4310 If this happens, delete or disable some of the watchpoints.
4312 Watching complex expressions that reference many variables can also
4313 exhaust the resources available for hardware-assisted watchpoints.
4314 That's because @value{GDBN} needs to watch every variable in the
4315 expression with separately allocated resources.
4317 If you call a function interactively using @code{print} or @code{call},
4318 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4319 kind of breakpoint or the call completes.
4321 @value{GDBN} automatically deletes watchpoints that watch local
4322 (automatic) variables, or expressions that involve such variables, when
4323 they go out of scope, that is, when the execution leaves the block in
4324 which these variables were defined. In particular, when the program
4325 being debugged terminates, @emph{all} local variables go out of scope,
4326 and so only watchpoints that watch global variables remain set. If you
4327 rerun the program, you will need to set all such watchpoints again. One
4328 way of doing that would be to set a code breakpoint at the entry to the
4329 @code{main} function and when it breaks, set all the watchpoints.
4331 @cindex watchpoints and threads
4332 @cindex threads and watchpoints
4333 In multi-threaded programs, watchpoints will detect changes to the
4334 watched expression from every thread.
4337 @emph{Warning:} In multi-threaded programs, software watchpoints
4338 have only limited usefulness. If @value{GDBN} creates a software
4339 watchpoint, it can only watch the value of an expression @emph{in a
4340 single thread}. If you are confident that the expression can only
4341 change due to the current thread's activity (and if you are also
4342 confident that no other thread can become current), then you can use
4343 software watchpoints as usual. However, @value{GDBN} may not notice
4344 when a non-current thread's activity changes the expression. (Hardware
4345 watchpoints, in contrast, watch an expression in all threads.)
4348 @xref{set remote hardware-watchpoint-limit}.
4350 @node Set Catchpoints
4351 @subsection Setting Catchpoints
4352 @cindex catchpoints, setting
4353 @cindex exception handlers
4354 @cindex event handling
4356 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4357 kinds of program events, such as C@t{++} exceptions or the loading of a
4358 shared library. Use the @code{catch} command to set a catchpoint.
4362 @item catch @var{event}
4363 Stop when @var{event} occurs. The @var{event} can be any of the following:
4366 @item throw @r{[}@var{regexp}@r{]}
4367 @itemx rethrow @r{[}@var{regexp}@r{]}
4368 @itemx catch @r{[}@var{regexp}@r{]}
4370 @kindex catch rethrow
4372 @cindex stop on C@t{++} exceptions
4373 The throwing, re-throwing, or catching of a C@t{++} exception.
4375 If @var{regexp} is given, then only exceptions whose type matches the
4376 regular expression will be caught.
4378 @vindex $_exception@r{, convenience variable}
4379 The convenience variable @code{$_exception} is available at an
4380 exception-related catchpoint, on some systems. This holds the
4381 exception being thrown.
4383 There are currently some limitations to C@t{++} exception handling in
4388 The support for these commands is system-dependent. Currently, only
4389 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4393 The regular expression feature and the @code{$_exception} convenience
4394 variable rely on the presence of some SDT probes in @code{libstdc++}.
4395 If these probes are not present, then these features cannot be used.
4396 These probes were first available in the GCC 4.8 release, but whether
4397 or not they are available in your GCC also depends on how it was
4401 The @code{$_exception} convenience variable is only valid at the
4402 instruction at which an exception-related catchpoint is set.
4405 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4406 location in the system library which implements runtime exception
4407 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4408 (@pxref{Selection}) to get to your code.
4411 If you call a function interactively, @value{GDBN} normally returns
4412 control to you when the function has finished executing. If the call
4413 raises an exception, however, the call may bypass the mechanism that
4414 returns control to you and cause your program either to abort or to
4415 simply continue running until it hits a breakpoint, catches a signal
4416 that @value{GDBN} is listening for, or exits. This is the case even if
4417 you set a catchpoint for the exception; catchpoints on exceptions are
4418 disabled within interactive calls. @xref{Calling}, for information on
4419 controlling this with @code{set unwind-on-terminating-exception}.
4422 You cannot raise an exception interactively.
4425 You cannot install an exception handler interactively.
4429 @kindex catch exception
4430 @cindex Ada exception catching
4431 @cindex catch Ada exceptions
4432 An Ada exception being raised. If an exception name is specified
4433 at the end of the command (eg @code{catch exception Program_Error}),
4434 the debugger will stop only when this specific exception is raised.
4435 Otherwise, the debugger stops execution when any Ada exception is raised.
4437 When inserting an exception catchpoint on a user-defined exception whose
4438 name is identical to one of the exceptions defined by the language, the
4439 fully qualified name must be used as the exception name. Otherwise,
4440 @value{GDBN} will assume that it should stop on the pre-defined exception
4441 rather than the user-defined one. For instance, assuming an exception
4442 called @code{Constraint_Error} is defined in package @code{Pck}, then
4443 the command to use to catch such exceptions is @kbd{catch exception
4444 Pck.Constraint_Error}.
4446 @item exception unhandled
4447 @kindex catch exception unhandled
4448 An exception that was raised but is not handled by the program.
4451 @kindex catch assert
4452 A failed Ada assertion.
4456 @cindex break on fork/exec
4457 A call to @code{exec}.
4460 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4461 @kindex catch syscall
4462 @cindex break on a system call.
4463 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4464 syscall is a mechanism for application programs to request a service
4465 from the operating system (OS) or one of the OS system services.
4466 @value{GDBN} can catch some or all of the syscalls issued by the
4467 debuggee, and show the related information for each syscall. If no
4468 argument is specified, calls to and returns from all system calls
4471 @var{name} can be any system call name that is valid for the
4472 underlying OS. Just what syscalls are valid depends on the OS. On
4473 GNU and Unix systems, you can find the full list of valid syscall
4474 names on @file{/usr/include/asm/unistd.h}.
4476 @c For MS-Windows, the syscall names and the corresponding numbers
4477 @c can be found, e.g., on this URL:
4478 @c http://www.metasploit.com/users/opcode/syscalls.html
4479 @c but we don't support Windows syscalls yet.
4481 Normally, @value{GDBN} knows in advance which syscalls are valid for
4482 each OS, so you can use the @value{GDBN} command-line completion
4483 facilities (@pxref{Completion,, command completion}) to list the
4486 You may also specify the system call numerically. A syscall's
4487 number is the value passed to the OS's syscall dispatcher to
4488 identify the requested service. When you specify the syscall by its
4489 name, @value{GDBN} uses its database of syscalls to convert the name
4490 into the corresponding numeric code, but using the number directly
4491 may be useful if @value{GDBN}'s database does not have the complete
4492 list of syscalls on your system (e.g., because @value{GDBN} lags
4493 behind the OS upgrades).
4495 You may specify a group of related syscalls to be caught at once using
4496 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4497 instance, on some platforms @value{GDBN} allows you to catch all
4498 network related syscalls, by passing the argument @code{group:network}
4499 to @code{catch syscall}. Note that not all syscall groups are
4500 available in every system. You can use the command completion
4501 facilities (@pxref{Completion,, command completion}) to list the
4502 syscall groups available on your environment.
4504 The example below illustrates how this command works if you don't provide
4508 (@value{GDBP}) catch syscall
4509 Catchpoint 1 (syscall)
4511 Starting program: /tmp/catch-syscall
4513 Catchpoint 1 (call to syscall 'close'), \
4514 0xffffe424 in __kernel_vsyscall ()
4518 Catchpoint 1 (returned from syscall 'close'), \
4519 0xffffe424 in __kernel_vsyscall ()
4523 Here is an example of catching a system call by name:
4526 (@value{GDBP}) catch syscall chroot
4527 Catchpoint 1 (syscall 'chroot' [61])
4529 Starting program: /tmp/catch-syscall
4531 Catchpoint 1 (call to syscall 'chroot'), \
4532 0xffffe424 in __kernel_vsyscall ()
4536 Catchpoint 1 (returned from syscall 'chroot'), \
4537 0xffffe424 in __kernel_vsyscall ()
4541 An example of specifying a system call numerically. In the case
4542 below, the syscall number has a corresponding entry in the XML
4543 file, so @value{GDBN} finds its name and prints it:
4546 (@value{GDBP}) catch syscall 252
4547 Catchpoint 1 (syscall(s) 'exit_group')
4549 Starting program: /tmp/catch-syscall
4551 Catchpoint 1 (call to syscall 'exit_group'), \
4552 0xffffe424 in __kernel_vsyscall ()
4556 Program exited normally.
4560 Here is an example of catching a syscall group:
4563 (@value{GDBP}) catch syscall group:process
4564 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4565 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4566 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4568 Starting program: /tmp/catch-syscall
4570 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4571 from /lib64/ld-linux-x86-64.so.2
4577 However, there can be situations when there is no corresponding name
4578 in XML file for that syscall number. In this case, @value{GDBN} prints
4579 a warning message saying that it was not able to find the syscall name,
4580 but the catchpoint will be set anyway. See the example below:
4583 (@value{GDBP}) catch syscall 764
4584 warning: The number '764' does not represent a known syscall.
4585 Catchpoint 2 (syscall 764)
4589 If you configure @value{GDBN} using the @samp{--without-expat} option,
4590 it will not be able to display syscall names. Also, if your
4591 architecture does not have an XML file describing its system calls,
4592 you will not be able to see the syscall names. It is important to
4593 notice that these two features are used for accessing the syscall
4594 name database. In either case, you will see a warning like this:
4597 (@value{GDBP}) catch syscall
4598 warning: Could not open "syscalls/i386-linux.xml"
4599 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4600 GDB will not be able to display syscall names.
4601 Catchpoint 1 (syscall)
4605 Of course, the file name will change depending on your architecture and system.
4607 Still using the example above, you can also try to catch a syscall by its
4608 number. In this case, you would see something like:
4611 (@value{GDBP}) catch syscall 252
4612 Catchpoint 1 (syscall(s) 252)
4615 Again, in this case @value{GDBN} would not be able to display syscall's names.
4619 A call to @code{fork}.
4623 A call to @code{vfork}.
4625 @item load @r{[}regexp@r{]}
4626 @itemx unload @r{[}regexp@r{]}
4628 @kindex catch unload
4629 The loading or unloading of a shared library. If @var{regexp} is
4630 given, then the catchpoint will stop only if the regular expression
4631 matches one of the affected libraries.
4633 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4634 @kindex catch signal
4635 The delivery of a signal.
4637 With no arguments, this catchpoint will catch any signal that is not
4638 used internally by @value{GDBN}, specifically, all signals except
4639 @samp{SIGTRAP} and @samp{SIGINT}.
4641 With the argument @samp{all}, all signals, including those used by
4642 @value{GDBN}, will be caught. This argument cannot be used with other
4645 Otherwise, the arguments are a list of signal names as given to
4646 @code{handle} (@pxref{Signals}). Only signals specified in this list
4649 One reason that @code{catch signal} can be more useful than
4650 @code{handle} is that you can attach commands and conditions to the
4653 When a signal is caught by a catchpoint, the signal's @code{stop} and
4654 @code{print} settings, as specified by @code{handle}, are ignored.
4655 However, whether the signal is still delivered to the inferior depends
4656 on the @code{pass} setting; this can be changed in the catchpoint's
4661 @item tcatch @var{event}
4663 Set a catchpoint that is enabled only for one stop. The catchpoint is
4664 automatically deleted after the first time the event is caught.
4668 Use the @code{info break} command to list the current catchpoints.
4672 @subsection Deleting Breakpoints
4674 @cindex clearing breakpoints, watchpoints, catchpoints
4675 @cindex deleting breakpoints, watchpoints, catchpoints
4676 It is often necessary to eliminate a breakpoint, watchpoint, or
4677 catchpoint once it has done its job and you no longer want your program
4678 to stop there. This is called @dfn{deleting} the breakpoint. A
4679 breakpoint that has been deleted no longer exists; it is forgotten.
4681 With the @code{clear} command you can delete breakpoints according to
4682 where they are in your program. With the @code{delete} command you can
4683 delete individual breakpoints, watchpoints, or catchpoints by specifying
4684 their breakpoint numbers.
4686 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4687 automatically ignores breakpoints on the first instruction to be executed
4688 when you continue execution without changing the execution address.
4693 Delete any breakpoints at the next instruction to be executed in the
4694 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4695 the innermost frame is selected, this is a good way to delete a
4696 breakpoint where your program just stopped.
4698 @item clear @var{location}
4699 Delete any breakpoints set at the specified @var{location}.
4700 @xref{Specify Location}, for the various forms of @var{location}; the
4701 most useful ones are listed below:
4704 @item clear @var{function}
4705 @itemx clear @var{filename}:@var{function}
4706 Delete any breakpoints set at entry to the named @var{function}.
4708 @item clear @var{linenum}
4709 @itemx clear @var{filename}:@var{linenum}
4710 Delete any breakpoints set at or within the code of the specified
4711 @var{linenum} of the specified @var{filename}.
4714 @cindex delete breakpoints
4716 @kindex d @r{(@code{delete})}
4717 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4718 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4719 list specified as argument. If no argument is specified, delete all
4720 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4721 confirm off}). You can abbreviate this command as @code{d}.
4725 @subsection Disabling Breakpoints
4727 @cindex enable/disable a breakpoint
4728 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4729 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4730 it had been deleted, but remembers the information on the breakpoint so
4731 that you can @dfn{enable} it again later.
4733 You disable and enable breakpoints, watchpoints, and catchpoints with
4734 the @code{enable} and @code{disable} commands, optionally specifying
4735 one or more breakpoint numbers as arguments. Use @code{info break} to
4736 print a list of all breakpoints, watchpoints, and catchpoints if you
4737 do not know which numbers to use.
4739 Disabling and enabling a breakpoint that has multiple locations
4740 affects all of its locations.
4742 A breakpoint, watchpoint, or catchpoint can have any of several
4743 different states of enablement:
4747 Enabled. The breakpoint stops your program. A breakpoint set
4748 with the @code{break} command starts out in this state.
4750 Disabled. The breakpoint has no effect on your program.
4752 Enabled once. The breakpoint stops your program, but then becomes
4755 Enabled for a count. The breakpoint stops your program for the next
4756 N times, then becomes disabled.
4758 Enabled for deletion. The breakpoint stops your program, but
4759 immediately after it does so it is deleted permanently. A breakpoint
4760 set with the @code{tbreak} command starts out in this state.
4763 You can use the following commands to enable or disable breakpoints,
4764 watchpoints, and catchpoints:
4768 @kindex dis @r{(@code{disable})}
4769 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4770 Disable the specified breakpoints---or all breakpoints, if none are
4771 listed. A disabled breakpoint has no effect but is not forgotten. All
4772 options such as ignore-counts, conditions and commands are remembered in
4773 case the breakpoint is enabled again later. You may abbreviate
4774 @code{disable} as @code{dis}.
4777 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4778 Enable the specified breakpoints (or all defined breakpoints). They
4779 become effective once again in stopping your program.
4781 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4782 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4783 of these breakpoints immediately after stopping your program.
4785 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4786 Enable the specified breakpoints temporarily. @value{GDBN} records
4787 @var{count} with each of the specified breakpoints, and decrements a
4788 breakpoint's count when it is hit. When any count reaches 0,
4789 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4790 count (@pxref{Conditions, ,Break Conditions}), that will be
4791 decremented to 0 before @var{count} is affected.
4793 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4794 Enable the specified breakpoints to work once, then die. @value{GDBN}
4795 deletes any of these breakpoints as soon as your program stops there.
4796 Breakpoints set by the @code{tbreak} command start out in this state.
4799 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4800 @c confusing: tbreak is also initially enabled.
4801 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4802 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4803 subsequently, they become disabled or enabled only when you use one of
4804 the commands above. (The command @code{until} can set and delete a
4805 breakpoint of its own, but it does not change the state of your other
4806 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4810 @subsection Break Conditions
4811 @cindex conditional breakpoints
4812 @cindex breakpoint conditions
4814 @c FIXME what is scope of break condition expr? Context where wanted?
4815 @c in particular for a watchpoint?
4816 The simplest sort of breakpoint breaks every time your program reaches a
4817 specified place. You can also specify a @dfn{condition} for a
4818 breakpoint. A condition is just a Boolean expression in your
4819 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4820 a condition evaluates the expression each time your program reaches it,
4821 and your program stops only if the condition is @emph{true}.
4823 This is the converse of using assertions for program validation; in that
4824 situation, you want to stop when the assertion is violated---that is,
4825 when the condition is false. In C, if you want to test an assertion expressed
4826 by the condition @var{assert}, you should set the condition
4827 @samp{! @var{assert}} on the appropriate breakpoint.
4829 Conditions are also accepted for watchpoints; you may not need them,
4830 since a watchpoint is inspecting the value of an expression anyhow---but
4831 it might be simpler, say, to just set a watchpoint on a variable name,
4832 and specify a condition that tests whether the new value is an interesting
4835 Break conditions can have side effects, and may even call functions in
4836 your program. This can be useful, for example, to activate functions
4837 that log program progress, or to use your own print functions to
4838 format special data structures. The effects are completely predictable
4839 unless there is another enabled breakpoint at the same address. (In
4840 that case, @value{GDBN} might see the other breakpoint first and stop your
4841 program without checking the condition of this one.) Note that
4842 breakpoint commands are usually more convenient and flexible than break
4844 purpose of performing side effects when a breakpoint is reached
4845 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4847 Breakpoint conditions can also be evaluated on the target's side if
4848 the target supports it. Instead of evaluating the conditions locally,
4849 @value{GDBN} encodes the expression into an agent expression
4850 (@pxref{Agent Expressions}) suitable for execution on the target,
4851 independently of @value{GDBN}. Global variables become raw memory
4852 locations, locals become stack accesses, and so forth.
4854 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4855 when its condition evaluates to true. This mechanism may provide faster
4856 response times depending on the performance characteristics of the target
4857 since it does not need to keep @value{GDBN} informed about
4858 every breakpoint trigger, even those with false conditions.
4860 Break conditions can be specified when a breakpoint is set, by using
4861 @samp{if} in the arguments to the @code{break} command. @xref{Set
4862 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4863 with the @code{condition} command.
4865 You can also use the @code{if} keyword with the @code{watch} command.
4866 The @code{catch} command does not recognize the @code{if} keyword;
4867 @code{condition} is the only way to impose a further condition on a
4872 @item condition @var{bnum} @var{expression}
4873 Specify @var{expression} as the break condition for breakpoint,
4874 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4875 breakpoint @var{bnum} stops your program only if the value of
4876 @var{expression} is true (nonzero, in C). When you use
4877 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4878 syntactic correctness, and to determine whether symbols in it have
4879 referents in the context of your breakpoint. If @var{expression} uses
4880 symbols not referenced in the context of the breakpoint, @value{GDBN}
4881 prints an error message:
4884 No symbol "foo" in current context.
4889 not actually evaluate @var{expression} at the time the @code{condition}
4890 command (or a command that sets a breakpoint with a condition, like
4891 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4893 @item condition @var{bnum}
4894 Remove the condition from breakpoint number @var{bnum}. It becomes
4895 an ordinary unconditional breakpoint.
4898 @cindex ignore count (of breakpoint)
4899 A special case of a breakpoint condition is to stop only when the
4900 breakpoint has been reached a certain number of times. This is so
4901 useful that there is a special way to do it, using the @dfn{ignore
4902 count} of the breakpoint. Every breakpoint has an ignore count, which
4903 is an integer. Most of the time, the ignore count is zero, and
4904 therefore has no effect. But if your program reaches a breakpoint whose
4905 ignore count is positive, then instead of stopping, it just decrements
4906 the ignore count by one and continues. As a result, if the ignore count
4907 value is @var{n}, the breakpoint does not stop the next @var{n} times
4908 your program reaches it.
4912 @item ignore @var{bnum} @var{count}
4913 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4914 The next @var{count} times the breakpoint is reached, your program's
4915 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4918 To make the breakpoint stop the next time it is reached, specify
4921 When you use @code{continue} to resume execution of your program from a
4922 breakpoint, you can specify an ignore count directly as an argument to
4923 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4924 Stepping,,Continuing and Stepping}.
4926 If a breakpoint has a positive ignore count and a condition, the
4927 condition is not checked. Once the ignore count reaches zero,
4928 @value{GDBN} resumes checking the condition.
4930 You could achieve the effect of the ignore count with a condition such
4931 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4932 is decremented each time. @xref{Convenience Vars, ,Convenience
4936 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4939 @node Break Commands
4940 @subsection Breakpoint Command Lists
4942 @cindex breakpoint commands
4943 You can give any breakpoint (or watchpoint or catchpoint) a series of
4944 commands to execute when your program stops due to that breakpoint. For
4945 example, you might want to print the values of certain expressions, or
4946 enable other breakpoints.
4950 @kindex end@r{ (breakpoint commands)}
4951 @item commands @r{[}@var{list}@dots{}@r{]}
4952 @itemx @dots{} @var{command-list} @dots{}
4954 Specify a list of commands for the given breakpoints. The commands
4955 themselves appear on the following lines. Type a line containing just
4956 @code{end} to terminate the commands.
4958 To remove all commands from a breakpoint, type @code{commands} and
4959 follow it immediately with @code{end}; that is, give no commands.
4961 With no argument, @code{commands} refers to the last breakpoint,
4962 watchpoint, or catchpoint set (not to the breakpoint most recently
4963 encountered). If the most recent breakpoints were set with a single
4964 command, then the @code{commands} will apply to all the breakpoints
4965 set by that command. This applies to breakpoints set by
4966 @code{rbreak}, and also applies when a single @code{break} command
4967 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4971 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4972 disabled within a @var{command-list}.
4974 You can use breakpoint commands to start your program up again. Simply
4975 use the @code{continue} command, or @code{step}, or any other command
4976 that resumes execution.
4978 Any other commands in the command list, after a command that resumes
4979 execution, are ignored. This is because any time you resume execution
4980 (even with a simple @code{next} or @code{step}), you may encounter
4981 another breakpoint---which could have its own command list, leading to
4982 ambiguities about which list to execute.
4985 If the first command you specify in a command list is @code{silent}, the
4986 usual message about stopping at a breakpoint is not printed. This may
4987 be desirable for breakpoints that are to print a specific message and
4988 then continue. If none of the remaining commands print anything, you
4989 see no sign that the breakpoint was reached. @code{silent} is
4990 meaningful only at the beginning of a breakpoint command list.
4992 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4993 print precisely controlled output, and are often useful in silent
4994 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4996 For example, here is how you could use breakpoint commands to print the
4997 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5003 printf "x is %d\n",x
5008 One application for breakpoint commands is to compensate for one bug so
5009 you can test for another. Put a breakpoint just after the erroneous line
5010 of code, give it a condition to detect the case in which something
5011 erroneous has been done, and give it commands to assign correct values
5012 to any variables that need them. End with the @code{continue} command
5013 so that your program does not stop, and start with the @code{silent}
5014 command so that no output is produced. Here is an example:
5025 @node Dynamic Printf
5026 @subsection Dynamic Printf
5028 @cindex dynamic printf
5030 The dynamic printf command @code{dprintf} combines a breakpoint with
5031 formatted printing of your program's data to give you the effect of
5032 inserting @code{printf} calls into your program on-the-fly, without
5033 having to recompile it.
5035 In its most basic form, the output goes to the GDB console. However,
5036 you can set the variable @code{dprintf-style} for alternate handling.
5037 For instance, you can ask to format the output by calling your
5038 program's @code{printf} function. This has the advantage that the
5039 characters go to the program's output device, so they can recorded in
5040 redirects to files and so forth.
5042 If you are doing remote debugging with a stub or agent, you can also
5043 ask to have the printf handled by the remote agent. In addition to
5044 ensuring that the output goes to the remote program's device along
5045 with any other output the program might produce, you can also ask that
5046 the dprintf remain active even after disconnecting from the remote
5047 target. Using the stub/agent is also more efficient, as it can do
5048 everything without needing to communicate with @value{GDBN}.
5052 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5053 Whenever execution reaches @var{location}, print the values of one or
5054 more @var{expressions} under the control of the string @var{template}.
5055 To print several values, separate them with commas.
5057 @item set dprintf-style @var{style}
5058 Set the dprintf output to be handled in one of several different
5059 styles enumerated below. A change of style affects all existing
5060 dynamic printfs immediately. (If you need individual control over the
5061 print commands, simply define normal breakpoints with
5062 explicitly-supplied command lists.)
5066 @kindex dprintf-style gdb
5067 Handle the output using the @value{GDBN} @code{printf} command.
5070 @kindex dprintf-style call
5071 Handle the output by calling a function in your program (normally
5075 @kindex dprintf-style agent
5076 Have the remote debugging agent (such as @code{gdbserver}) handle
5077 the output itself. This style is only available for agents that
5078 support running commands on the target.
5081 @item set dprintf-function @var{function}
5082 Set the function to call if the dprintf style is @code{call}. By
5083 default its value is @code{printf}. You may set it to any expression.
5084 that @value{GDBN} can evaluate to a function, as per the @code{call}
5087 @item set dprintf-channel @var{channel}
5088 Set a ``channel'' for dprintf. If set to a non-empty value,
5089 @value{GDBN} will evaluate it as an expression and pass the result as
5090 a first argument to the @code{dprintf-function}, in the manner of
5091 @code{fprintf} and similar functions. Otherwise, the dprintf format
5092 string will be the first argument, in the manner of @code{printf}.
5094 As an example, if you wanted @code{dprintf} output to go to a logfile
5095 that is a standard I/O stream assigned to the variable @code{mylog},
5096 you could do the following:
5099 (gdb) set dprintf-style call
5100 (gdb) set dprintf-function fprintf
5101 (gdb) set dprintf-channel mylog
5102 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5103 Dprintf 1 at 0x123456: file main.c, line 25.
5105 1 dprintf keep y 0x00123456 in main at main.c:25
5106 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5111 Note that the @code{info break} displays the dynamic printf commands
5112 as normal breakpoint commands; you can thus easily see the effect of
5113 the variable settings.
5115 @item set disconnected-dprintf on
5116 @itemx set disconnected-dprintf off
5117 @kindex set disconnected-dprintf
5118 Choose whether @code{dprintf} commands should continue to run if
5119 @value{GDBN} has disconnected from the target. This only applies
5120 if the @code{dprintf-style} is @code{agent}.
5122 @item show disconnected-dprintf off
5123 @kindex show disconnected-dprintf
5124 Show the current choice for disconnected @code{dprintf}.
5128 @value{GDBN} does not check the validity of function and channel,
5129 relying on you to supply values that are meaningful for the contexts
5130 in which they are being used. For instance, the function and channel
5131 may be the values of local variables, but if that is the case, then
5132 all enabled dynamic prints must be at locations within the scope of
5133 those locals. If evaluation fails, @value{GDBN} will report an error.
5135 @node Save Breakpoints
5136 @subsection How to save breakpoints to a file
5138 To save breakpoint definitions to a file use the @w{@code{save
5139 breakpoints}} command.
5142 @kindex save breakpoints
5143 @cindex save breakpoints to a file for future sessions
5144 @item save breakpoints [@var{filename}]
5145 This command saves all current breakpoint definitions together with
5146 their commands and ignore counts, into a file @file{@var{filename}}
5147 suitable for use in a later debugging session. This includes all
5148 types of breakpoints (breakpoints, watchpoints, catchpoints,
5149 tracepoints). To read the saved breakpoint definitions, use the
5150 @code{source} command (@pxref{Command Files}). Note that watchpoints
5151 with expressions involving local variables may fail to be recreated
5152 because it may not be possible to access the context where the
5153 watchpoint is valid anymore. Because the saved breakpoint definitions
5154 are simply a sequence of @value{GDBN} commands that recreate the
5155 breakpoints, you can edit the file in your favorite editing program,
5156 and remove the breakpoint definitions you're not interested in, or
5157 that can no longer be recreated.
5160 @node Static Probe Points
5161 @subsection Static Probe Points
5163 @cindex static probe point, SystemTap
5164 @cindex static probe point, DTrace
5165 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5166 for Statically Defined Tracing, and the probes are designed to have a tiny
5167 runtime code and data footprint, and no dynamic relocations.
5169 Currently, the following types of probes are supported on
5170 ELF-compatible systems:
5174 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5175 @acronym{SDT} probes@footnote{See
5176 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5177 for more information on how to add @code{SystemTap} @acronym{SDT}
5178 probes in your applications.}. @code{SystemTap} probes are usable
5179 from assembly, C and C@t{++} languages@footnote{See
5180 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5181 for a good reference on how the @acronym{SDT} probes are implemented.}.
5183 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5184 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5188 @cindex semaphores on static probe points
5189 Some @code{SystemTap} probes have an associated semaphore variable;
5190 for instance, this happens automatically if you defined your probe
5191 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5192 @value{GDBN} will automatically enable it when you specify a
5193 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5194 breakpoint at a probe's location by some other method (e.g.,
5195 @code{break file:line}), then @value{GDBN} will not automatically set
5196 the semaphore. @code{DTrace} probes do not support semaphores.
5198 You can examine the available static static probes using @code{info
5199 probes}, with optional arguments:
5203 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5204 If given, @var{type} is either @code{stap} for listing
5205 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5206 probes. If omitted all probes are listed regardless of their types.
5208 If given, @var{provider} is a regular expression used to match against provider
5209 names when selecting which probes to list. If omitted, probes by all
5210 probes from all providers are listed.
5212 If given, @var{name} is a regular expression to match against probe names
5213 when selecting which probes to list. If omitted, probe names are not
5214 considered when deciding whether to display them.
5216 If given, @var{objfile} is a regular expression used to select which
5217 object files (executable or shared libraries) to examine. If not
5218 given, all object files are considered.
5220 @item info probes all
5221 List the available static probes, from all types.
5224 @cindex enabling and disabling probes
5225 Some probe points can be enabled and/or disabled. The effect of
5226 enabling or disabling a probe depends on the type of probe being
5227 handled. Some @code{DTrace} probes can be enabled or
5228 disabled, but @code{SystemTap} probes cannot be disabled.
5230 You can enable (or disable) one or more probes using the following
5231 commands, with optional arguments:
5234 @kindex enable probes
5235 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5236 If given, @var{provider} is a regular expression used to match against
5237 provider names when selecting which probes to enable. If omitted,
5238 all probes from all providers are enabled.
5240 If given, @var{name} is a regular expression to match against probe
5241 names when selecting which probes to enable. If omitted, probe names
5242 are not considered when deciding whether to enable them.
5244 If given, @var{objfile} is a regular expression used to select which
5245 object files (executable or shared libraries) to examine. If not
5246 given, all object files are considered.
5248 @kindex disable probes
5249 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5250 See the @code{enable probes} command above for a description of the
5251 optional arguments accepted by this command.
5254 @vindex $_probe_arg@r{, convenience variable}
5255 A probe may specify up to twelve arguments. These are available at the
5256 point at which the probe is defined---that is, when the current PC is
5257 at the probe's location. The arguments are available using the
5258 convenience variables (@pxref{Convenience Vars})
5259 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5260 probes each probe argument is an integer of the appropriate size;
5261 types are not preserved. In @code{DTrace} probes types are preserved
5262 provided that they are recognized as such by @value{GDBN}; otherwise
5263 the value of the probe argument will be a long integer. The
5264 convenience variable @code{$_probe_argc} holds the number of arguments
5265 at the current probe point.
5267 These variables are always available, but attempts to access them at
5268 any location other than a probe point will cause @value{GDBN} to give
5272 @c @ifclear BARETARGET
5273 @node Error in Breakpoints
5274 @subsection ``Cannot insert breakpoints''
5276 If you request too many active hardware-assisted breakpoints and
5277 watchpoints, you will see this error message:
5279 @c FIXME: the precise wording of this message may change; the relevant
5280 @c source change is not committed yet (Sep 3, 1999).
5282 Stopped; cannot insert breakpoints.
5283 You may have requested too many hardware breakpoints and watchpoints.
5287 This message is printed when you attempt to resume the program, since
5288 only then @value{GDBN} knows exactly how many hardware breakpoints and
5289 watchpoints it needs to insert.
5291 When this message is printed, you need to disable or remove some of the
5292 hardware-assisted breakpoints and watchpoints, and then continue.
5294 @node Breakpoint-related Warnings
5295 @subsection ``Breakpoint address adjusted...''
5296 @cindex breakpoint address adjusted
5298 Some processor architectures place constraints on the addresses at
5299 which breakpoints may be placed. For architectures thus constrained,
5300 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5301 with the constraints dictated by the architecture.
5303 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5304 a VLIW architecture in which a number of RISC-like instructions may be
5305 bundled together for parallel execution. The FR-V architecture
5306 constrains the location of a breakpoint instruction within such a
5307 bundle to the instruction with the lowest address. @value{GDBN}
5308 honors this constraint by adjusting a breakpoint's address to the
5309 first in the bundle.
5311 It is not uncommon for optimized code to have bundles which contain
5312 instructions from different source statements, thus it may happen that
5313 a breakpoint's address will be adjusted from one source statement to
5314 another. Since this adjustment may significantly alter @value{GDBN}'s
5315 breakpoint related behavior from what the user expects, a warning is
5316 printed when the breakpoint is first set and also when the breakpoint
5319 A warning like the one below is printed when setting a breakpoint
5320 that's been subject to address adjustment:
5323 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5326 Such warnings are printed both for user settable and @value{GDBN}'s
5327 internal breakpoints. If you see one of these warnings, you should
5328 verify that a breakpoint set at the adjusted address will have the
5329 desired affect. If not, the breakpoint in question may be removed and
5330 other breakpoints may be set which will have the desired behavior.
5331 E.g., it may be sufficient to place the breakpoint at a later
5332 instruction. A conditional breakpoint may also be useful in some
5333 cases to prevent the breakpoint from triggering too often.
5335 @value{GDBN} will also issue a warning when stopping at one of these
5336 adjusted breakpoints:
5339 warning: Breakpoint 1 address previously adjusted from 0x00010414
5343 When this warning is encountered, it may be too late to take remedial
5344 action except in cases where the breakpoint is hit earlier or more
5345 frequently than expected.
5347 @node Continuing and Stepping
5348 @section Continuing and Stepping
5352 @cindex resuming execution
5353 @dfn{Continuing} means resuming program execution until your program
5354 completes normally. In contrast, @dfn{stepping} means executing just
5355 one more ``step'' of your program, where ``step'' may mean either one
5356 line of source code, or one machine instruction (depending on what
5357 particular command you use). Either when continuing or when stepping,
5358 your program may stop even sooner, due to a breakpoint or a signal. (If
5359 it stops due to a signal, you may want to use @code{handle}, or use
5360 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5361 or you may step into the signal's handler (@pxref{stepping and signal
5366 @kindex c @r{(@code{continue})}
5367 @kindex fg @r{(resume foreground execution)}
5368 @item continue @r{[}@var{ignore-count}@r{]}
5369 @itemx c @r{[}@var{ignore-count}@r{]}
5370 @itemx fg @r{[}@var{ignore-count}@r{]}
5371 Resume program execution, at the address where your program last stopped;
5372 any breakpoints set at that address are bypassed. The optional argument
5373 @var{ignore-count} allows you to specify a further number of times to
5374 ignore a breakpoint at this location; its effect is like that of
5375 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5377 The argument @var{ignore-count} is meaningful only when your program
5378 stopped due to a breakpoint. At other times, the argument to
5379 @code{continue} is ignored.
5381 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5382 debugged program is deemed to be the foreground program) are provided
5383 purely for convenience, and have exactly the same behavior as
5387 To resume execution at a different place, you can use @code{return}
5388 (@pxref{Returning, ,Returning from a Function}) to go back to the
5389 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5390 Different Address}) to go to an arbitrary location in your program.
5392 A typical technique for using stepping is to set a breakpoint
5393 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5394 beginning of the function or the section of your program where a problem
5395 is believed to lie, run your program until it stops at that breakpoint,
5396 and then step through the suspect area, examining the variables that are
5397 interesting, until you see the problem happen.
5401 @kindex s @r{(@code{step})}
5403 Continue running your program until control reaches a different source
5404 line, then stop it and return control to @value{GDBN}. This command is
5405 abbreviated @code{s}.
5408 @c "without debugging information" is imprecise; actually "without line
5409 @c numbers in the debugging information". (gcc -g1 has debugging info but
5410 @c not line numbers). But it seems complex to try to make that
5411 @c distinction here.
5412 @emph{Warning:} If you use the @code{step} command while control is
5413 within a function that was compiled without debugging information,
5414 execution proceeds until control reaches a function that does have
5415 debugging information. Likewise, it will not step into a function which
5416 is compiled without debugging information. To step through functions
5417 without debugging information, use the @code{stepi} command, described
5421 The @code{step} command only stops at the first instruction of a source
5422 line. This prevents the multiple stops that could otherwise occur in
5423 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5424 to stop if a function that has debugging information is called within
5425 the line. In other words, @code{step} @emph{steps inside} any functions
5426 called within the line.
5428 Also, the @code{step} command only enters a function if there is line
5429 number information for the function. Otherwise it acts like the
5430 @code{next} command. This avoids problems when using @code{cc -gl}
5431 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5432 was any debugging information about the routine.
5434 @item step @var{count}
5435 Continue running as in @code{step}, but do so @var{count} times. If a
5436 breakpoint is reached, or a signal not related to stepping occurs before
5437 @var{count} steps, stepping stops right away.
5440 @kindex n @r{(@code{next})}
5441 @item next @r{[}@var{count}@r{]}
5442 Continue to the next source line in the current (innermost) stack frame.
5443 This is similar to @code{step}, but function calls that appear within
5444 the line of code are executed without stopping. Execution stops when
5445 control reaches a different line of code at the original stack level
5446 that was executing when you gave the @code{next} command. This command
5447 is abbreviated @code{n}.
5449 An argument @var{count} is a repeat count, as for @code{step}.
5452 @c FIX ME!! Do we delete this, or is there a way it fits in with
5453 @c the following paragraph? --- Vctoria
5455 @c @code{next} within a function that lacks debugging information acts like
5456 @c @code{step}, but any function calls appearing within the code of the
5457 @c function are executed without stopping.
5459 The @code{next} command only stops at the first instruction of a
5460 source line. This prevents multiple stops that could otherwise occur in
5461 @code{switch} statements, @code{for} loops, etc.
5463 @kindex set step-mode
5465 @cindex functions without line info, and stepping
5466 @cindex stepping into functions with no line info
5467 @itemx set step-mode on
5468 The @code{set step-mode on} command causes the @code{step} command to
5469 stop at the first instruction of a function which contains no debug line
5470 information rather than stepping over it.
5472 This is useful in cases where you may be interested in inspecting the
5473 machine instructions of a function which has no symbolic info and do not
5474 want @value{GDBN} to automatically skip over this function.
5476 @item set step-mode off
5477 Causes the @code{step} command to step over any functions which contains no
5478 debug information. This is the default.
5480 @item show step-mode
5481 Show whether @value{GDBN} will stop in or step over functions without
5482 source line debug information.
5485 @kindex fin @r{(@code{finish})}
5487 Continue running until just after function in the selected stack frame
5488 returns. Print the returned value (if any). This command can be
5489 abbreviated as @code{fin}.
5491 Contrast this with the @code{return} command (@pxref{Returning,
5492 ,Returning from a Function}).
5495 @kindex u @r{(@code{until})}
5496 @cindex run until specified location
5499 Continue running until a source line past the current line, in the
5500 current stack frame, is reached. This command is used to avoid single
5501 stepping through a loop more than once. It is like the @code{next}
5502 command, except that when @code{until} encounters a jump, it
5503 automatically continues execution until the program counter is greater
5504 than the address of the jump.
5506 This means that when you reach the end of a loop after single stepping
5507 though it, @code{until} makes your program continue execution until it
5508 exits the loop. In contrast, a @code{next} command at the end of a loop
5509 simply steps back to the beginning of the loop, which forces you to step
5510 through the next iteration.
5512 @code{until} always stops your program if it attempts to exit the current
5515 @code{until} may produce somewhat counterintuitive results if the order
5516 of machine code does not match the order of the source lines. For
5517 example, in the following excerpt from a debugging session, the @code{f}
5518 (@code{frame}) command shows that execution is stopped at line
5519 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5523 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5525 (@value{GDBP}) until
5526 195 for ( ; argc > 0; NEXTARG) @{
5529 This happened because, for execution efficiency, the compiler had
5530 generated code for the loop closure test at the end, rather than the
5531 start, of the loop---even though the test in a C @code{for}-loop is
5532 written before the body of the loop. The @code{until} command appeared
5533 to step back to the beginning of the loop when it advanced to this
5534 expression; however, it has not really gone to an earlier
5535 statement---not in terms of the actual machine code.
5537 @code{until} with no argument works by means of single
5538 instruction stepping, and hence is slower than @code{until} with an
5541 @item until @var{location}
5542 @itemx u @var{location}
5543 Continue running your program until either the specified @var{location} is
5544 reached, or the current stack frame returns. The location is any of
5545 the forms described in @ref{Specify Location}.
5546 This form of the command uses temporary breakpoints, and
5547 hence is quicker than @code{until} without an argument. The specified
5548 location is actually reached only if it is in the current frame. This
5549 implies that @code{until} can be used to skip over recursive function
5550 invocations. For instance in the code below, if the current location is
5551 line @code{96}, issuing @code{until 99} will execute the program up to
5552 line @code{99} in the same invocation of factorial, i.e., after the inner
5553 invocations have returned.
5556 94 int factorial (int value)
5558 96 if (value > 1) @{
5559 97 value *= factorial (value - 1);
5566 @kindex advance @var{location}
5567 @item advance @var{location}
5568 Continue running the program up to the given @var{location}. An argument is
5569 required, which should be of one of the forms described in
5570 @ref{Specify Location}.
5571 Execution will also stop upon exit from the current stack
5572 frame. This command is similar to @code{until}, but @code{advance} will
5573 not skip over recursive function calls, and the target location doesn't
5574 have to be in the same frame as the current one.
5578 @kindex si @r{(@code{stepi})}
5580 @itemx stepi @var{arg}
5582 Execute one machine instruction, then stop and return to the debugger.
5584 It is often useful to do @samp{display/i $pc} when stepping by machine
5585 instructions. This makes @value{GDBN} automatically display the next
5586 instruction to be executed, each time your program stops. @xref{Auto
5587 Display,, Automatic Display}.
5589 An argument is a repeat count, as in @code{step}.
5593 @kindex ni @r{(@code{nexti})}
5595 @itemx nexti @var{arg}
5597 Execute one machine instruction, but if it is a function call,
5598 proceed until the function returns.
5600 An argument is a repeat count, as in @code{next}.
5604 @anchor{range stepping}
5605 @cindex range stepping
5606 @cindex target-assisted range stepping
5607 By default, and if available, @value{GDBN} makes use of
5608 target-assisted @dfn{range stepping}. In other words, whenever you
5609 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5610 tells the target to step the corresponding range of instruction
5611 addresses instead of issuing multiple single-steps. This speeds up
5612 line stepping, particularly for remote targets. Ideally, there should
5613 be no reason you would want to turn range stepping off. However, it's
5614 possible that a bug in the debug info, a bug in the remote stub (for
5615 remote targets), or even a bug in @value{GDBN} could make line
5616 stepping behave incorrectly when target-assisted range stepping is
5617 enabled. You can use the following command to turn off range stepping
5621 @kindex set range-stepping
5622 @kindex show range-stepping
5623 @item set range-stepping
5624 @itemx show range-stepping
5625 Control whether range stepping is enabled.
5627 If @code{on}, and the target supports it, @value{GDBN} tells the
5628 target to step a range of addresses itself, instead of issuing
5629 multiple single-steps. If @code{off}, @value{GDBN} always issues
5630 single-steps, even if range stepping is supported by the target. The
5631 default is @code{on}.
5635 @node Skipping Over Functions and Files
5636 @section Skipping Over Functions and Files
5637 @cindex skipping over functions and files
5639 The program you are debugging may contain some functions which are
5640 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5641 skip a function, all functions in a file or a particular function in
5642 a particular file when stepping.
5644 For example, consider the following C function:
5655 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5656 are not interested in stepping through @code{boring}. If you run @code{step}
5657 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5658 step over both @code{foo} and @code{boring}!
5660 One solution is to @code{step} into @code{boring} and use the @code{finish}
5661 command to immediately exit it. But this can become tedious if @code{boring}
5662 is called from many places.
5664 A more flexible solution is to execute @kbd{skip boring}. This instructs
5665 @value{GDBN} never to step into @code{boring}. Now when you execute
5666 @code{step} at line 103, you'll step over @code{boring} and directly into
5669 Functions may be skipped by providing either a function name, linespec
5670 (@pxref{Specify Location}), regular expression that matches the function's
5671 name, file name or a @code{glob}-style pattern that matches the file name.
5673 On Posix systems the form of the regular expression is
5674 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5675 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5676 expression is whatever is provided by the @code{regcomp} function of
5677 the underlying system.
5678 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5679 description of @code{glob}-style patterns.
5683 @item skip @r{[}@var{options}@r{]}
5684 The basic form of the @code{skip} command takes zero or more options
5685 that specify what to skip.
5686 The @var{options} argument is any useful combination of the following:
5689 @item -file @var{file}
5690 @itemx -fi @var{file}
5691 Functions in @var{file} will be skipped over when stepping.
5693 @item -gfile @var{file-glob-pattern}
5694 @itemx -gfi @var{file-glob-pattern}
5695 @cindex skipping over files via glob-style patterns
5696 Functions in files matching @var{file-glob-pattern} will be skipped
5700 (gdb) skip -gfi utils/*.c
5703 @item -function @var{linespec}
5704 @itemx -fu @var{linespec}
5705 Functions named by @var{linespec} or the function containing the line
5706 named by @var{linespec} will be skipped over when stepping.
5707 @xref{Specify Location}.
5709 @item -rfunction @var{regexp}
5710 @itemx -rfu @var{regexp}
5711 @cindex skipping over functions via regular expressions
5712 Functions whose name matches @var{regexp} will be skipped over when stepping.
5714 This form is useful for complex function names.
5715 For example, there is generally no need to step into C@t{++} @code{std::string}
5716 constructors or destructors. Plus with C@t{++} templates it can be hard to
5717 write out the full name of the function, and often it doesn't matter what
5718 the template arguments are. Specifying the function to be skipped as a
5719 regular expression makes this easier.
5722 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5725 If you want to skip every templated C@t{++} constructor and destructor
5726 in the @code{std} namespace you can do:
5729 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5733 If no options are specified, the function you're currently debugging
5736 @kindex skip function
5737 @item skip function @r{[}@var{linespec}@r{]}
5738 After running this command, the function named by @var{linespec} or the
5739 function containing the line named by @var{linespec} will be skipped over when
5740 stepping. @xref{Specify Location}.
5742 If you do not specify @var{linespec}, the function you're currently debugging
5745 (If you have a function called @code{file} that you want to skip, use
5746 @kbd{skip function file}.)
5749 @item skip file @r{[}@var{filename}@r{]}
5750 After running this command, any function whose source lives in @var{filename}
5751 will be skipped over when stepping.
5754 (gdb) skip file boring.c
5755 File boring.c will be skipped when stepping.
5758 If you do not specify @var{filename}, functions whose source lives in the file
5759 you're currently debugging will be skipped.
5762 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5763 These are the commands for managing your list of skips:
5767 @item info skip @r{[}@var{range}@r{]}
5768 Print details about the specified skip(s). If @var{range} is not specified,
5769 print a table with details about all functions and files marked for skipping.
5770 @code{info skip} prints the following information about each skip:
5774 A number identifying this skip.
5775 @item Enabled or Disabled
5776 Enabled skips are marked with @samp{y}.
5777 Disabled skips are marked with @samp{n}.
5779 If the file name is a @samp{glob} pattern this is @samp{y}.
5780 Otherwise it is @samp{n}.
5782 The name or @samp{glob} pattern of the file to be skipped.
5783 If no file is specified this is @samp{<none>}.
5785 If the function name is a @samp{regular expression} this is @samp{y}.
5786 Otherwise it is @samp{n}.
5788 The name or regular expression of the function to skip.
5789 If no function is specified this is @samp{<none>}.
5793 @item skip delete @r{[}@var{range}@r{]}
5794 Delete the specified skip(s). If @var{range} is not specified, delete all
5798 @item skip enable @r{[}@var{range}@r{]}
5799 Enable the specified skip(s). If @var{range} is not specified, enable all
5802 @kindex skip disable
5803 @item skip disable @r{[}@var{range}@r{]}
5804 Disable the specified skip(s). If @var{range} is not specified, disable all
5813 A signal is an asynchronous event that can happen in a program. The
5814 operating system defines the possible kinds of signals, and gives each
5815 kind a name and a number. For example, in Unix @code{SIGINT} is the
5816 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5817 @code{SIGSEGV} is the signal a program gets from referencing a place in
5818 memory far away from all the areas in use; @code{SIGALRM} occurs when
5819 the alarm clock timer goes off (which happens only if your program has
5820 requested an alarm).
5822 @cindex fatal signals
5823 Some signals, including @code{SIGALRM}, are a normal part of the
5824 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5825 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5826 program has not specified in advance some other way to handle the signal.
5827 @code{SIGINT} does not indicate an error in your program, but it is normally
5828 fatal so it can carry out the purpose of the interrupt: to kill the program.
5830 @value{GDBN} has the ability to detect any occurrence of a signal in your
5831 program. You can tell @value{GDBN} in advance what to do for each kind of
5834 @cindex handling signals
5835 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5836 @code{SIGALRM} be silently passed to your program
5837 (so as not to interfere with their role in the program's functioning)
5838 but to stop your program immediately whenever an error signal happens.
5839 You can change these settings with the @code{handle} command.
5842 @kindex info signals
5846 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5847 handle each one. You can use this to see the signal numbers of all
5848 the defined types of signals.
5850 @item info signals @var{sig}
5851 Similar, but print information only about the specified signal number.
5853 @code{info handle} is an alias for @code{info signals}.
5855 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5856 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5857 for details about this command.
5860 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5861 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5862 can be the number of a signal or its name (with or without the
5863 @samp{SIG} at the beginning); a list of signal numbers of the form
5864 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5865 known signals. Optional arguments @var{keywords}, described below,
5866 say what change to make.
5870 The keywords allowed by the @code{handle} command can be abbreviated.
5871 Their full names are:
5875 @value{GDBN} should not stop your program when this signal happens. It may
5876 still print a message telling you that the signal has come in.
5879 @value{GDBN} should stop your program when this signal happens. This implies
5880 the @code{print} keyword as well.
5883 @value{GDBN} should print a message when this signal happens.
5886 @value{GDBN} should not mention the occurrence of the signal at all. This
5887 implies the @code{nostop} keyword as well.
5891 @value{GDBN} should allow your program to see this signal; your program
5892 can handle the signal, or else it may terminate if the signal is fatal
5893 and not handled. @code{pass} and @code{noignore} are synonyms.
5897 @value{GDBN} should not allow your program to see this signal.
5898 @code{nopass} and @code{ignore} are synonyms.
5902 When a signal stops your program, the signal is not visible to the
5904 continue. Your program sees the signal then, if @code{pass} is in
5905 effect for the signal in question @emph{at that time}. In other words,
5906 after @value{GDBN} reports a signal, you can use the @code{handle}
5907 command with @code{pass} or @code{nopass} to control whether your
5908 program sees that signal when you continue.
5910 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5911 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5912 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5915 You can also use the @code{signal} command to prevent your program from
5916 seeing a signal, or cause it to see a signal it normally would not see,
5917 or to give it any signal at any time. For example, if your program stopped
5918 due to some sort of memory reference error, you might store correct
5919 values into the erroneous variables and continue, hoping to see more
5920 execution; but your program would probably terminate immediately as
5921 a result of the fatal signal once it saw the signal. To prevent this,
5922 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5925 @cindex stepping and signal handlers
5926 @anchor{stepping and signal handlers}
5928 @value{GDBN} optimizes for stepping the mainline code. If a signal
5929 that has @code{handle nostop} and @code{handle pass} set arrives while
5930 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5931 in progress, @value{GDBN} lets the signal handler run and then resumes
5932 stepping the mainline code once the signal handler returns. In other
5933 words, @value{GDBN} steps over the signal handler. This prevents
5934 signals that you've specified as not interesting (with @code{handle
5935 nostop}) from changing the focus of debugging unexpectedly. Note that
5936 the signal handler itself may still hit a breakpoint, stop for another
5937 signal that has @code{handle stop} in effect, or for any other event
5938 that normally results in stopping the stepping command sooner. Also
5939 note that @value{GDBN} still informs you that the program received a
5940 signal if @code{handle print} is set.
5942 @anchor{stepping into signal handlers}
5944 If you set @code{handle pass} for a signal, and your program sets up a
5945 handler for it, then issuing a stepping command, such as @code{step}
5946 or @code{stepi}, when your program is stopped due to the signal will
5947 step @emph{into} the signal handler (if the target supports that).
5949 Likewise, if you use the @code{queue-signal} command to queue a signal
5950 to be delivered to the current thread when execution of the thread
5951 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5952 stepping command will step into the signal handler.
5954 Here's an example, using @code{stepi} to step to the first instruction
5955 of @code{SIGUSR1}'s handler:
5958 (@value{GDBP}) handle SIGUSR1
5959 Signal Stop Print Pass to program Description
5960 SIGUSR1 Yes Yes Yes User defined signal 1
5964 Program received signal SIGUSR1, User defined signal 1.
5965 main () sigusr1.c:28
5968 sigusr1_handler () at sigusr1.c:9
5972 The same, but using @code{queue-signal} instead of waiting for the
5973 program to receive the signal first:
5978 (@value{GDBP}) queue-signal SIGUSR1
5980 sigusr1_handler () at sigusr1.c:9
5985 @cindex extra signal information
5986 @anchor{extra signal information}
5988 On some targets, @value{GDBN} can inspect extra signal information
5989 associated with the intercepted signal, before it is actually
5990 delivered to the program being debugged. This information is exported
5991 by the convenience variable @code{$_siginfo}, and consists of data
5992 that is passed by the kernel to the signal handler at the time of the
5993 receipt of a signal. The data type of the information itself is
5994 target dependent. You can see the data type using the @code{ptype
5995 $_siginfo} command. On Unix systems, it typically corresponds to the
5996 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5999 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6000 referenced address that raised a segmentation fault.
6004 (@value{GDBP}) continue
6005 Program received signal SIGSEGV, Segmentation fault.
6006 0x0000000000400766 in main ()
6008 (@value{GDBP}) ptype $_siginfo
6015 struct @{...@} _kill;
6016 struct @{...@} _timer;
6018 struct @{...@} _sigchld;
6019 struct @{...@} _sigfault;
6020 struct @{...@} _sigpoll;
6023 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6027 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6028 $1 = (void *) 0x7ffff7ff7000
6032 Depending on target support, @code{$_siginfo} may also be writable.
6034 @cindex Intel MPX boundary violations
6035 @cindex boundary violations, Intel MPX
6036 On some targets, a @code{SIGSEGV} can be caused by a boundary
6037 violation, i.e., accessing an address outside of the allowed range.
6038 In those cases @value{GDBN} may displays additional information,
6039 depending on how @value{GDBN} has been told to handle the signal.
6040 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6041 kind: "Upper" or "Lower", the memory address accessed and the
6042 bounds, while with @code{handle nostop SIGSEGV} no additional
6043 information is displayed.
6045 The usual output of a segfault is:
6047 Program received signal SIGSEGV, Segmentation fault
6048 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6049 68 value = *(p + len);
6052 While a bound violation is presented as:
6054 Program received signal SIGSEGV, Segmentation fault
6055 Upper bound violation while accessing address 0x7fffffffc3b3
6056 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6057 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6058 68 value = *(p + len);
6062 @section Stopping and Starting Multi-thread Programs
6064 @cindex stopped threads
6065 @cindex threads, stopped
6067 @cindex continuing threads
6068 @cindex threads, continuing
6070 @value{GDBN} supports debugging programs with multiple threads
6071 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6072 are two modes of controlling execution of your program within the
6073 debugger. In the default mode, referred to as @dfn{all-stop mode},
6074 when any thread in your program stops (for example, at a breakpoint
6075 or while being stepped), all other threads in the program are also stopped by
6076 @value{GDBN}. On some targets, @value{GDBN} also supports
6077 @dfn{non-stop mode}, in which other threads can continue to run freely while
6078 you examine the stopped thread in the debugger.
6081 * All-Stop Mode:: All threads stop when GDB takes control
6082 * Non-Stop Mode:: Other threads continue to execute
6083 * Background Execution:: Running your program asynchronously
6084 * Thread-Specific Breakpoints:: Controlling breakpoints
6085 * Interrupted System Calls:: GDB may interfere with system calls
6086 * Observer Mode:: GDB does not alter program behavior
6090 @subsection All-Stop Mode
6092 @cindex all-stop mode
6094 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6095 @emph{all} threads of execution stop, not just the current thread. This
6096 allows you to examine the overall state of the program, including
6097 switching between threads, without worrying that things may change
6100 Conversely, whenever you restart the program, @emph{all} threads start
6101 executing. @emph{This is true even when single-stepping} with commands
6102 like @code{step} or @code{next}.
6104 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6105 Since thread scheduling is up to your debugging target's operating
6106 system (not controlled by @value{GDBN}), other threads may
6107 execute more than one statement while the current thread completes a
6108 single step. Moreover, in general other threads stop in the middle of a
6109 statement, rather than at a clean statement boundary, when the program
6112 You might even find your program stopped in another thread after
6113 continuing or even single-stepping. This happens whenever some other
6114 thread runs into a breakpoint, a signal, or an exception before the
6115 first thread completes whatever you requested.
6117 @cindex automatic thread selection
6118 @cindex switching threads automatically
6119 @cindex threads, automatic switching
6120 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6121 signal, it automatically selects the thread where that breakpoint or
6122 signal happened. @value{GDBN} alerts you to the context switch with a
6123 message such as @samp{[Switching to Thread @var{n}]} to identify the
6126 On some OSes, you can modify @value{GDBN}'s default behavior by
6127 locking the OS scheduler to allow only a single thread to run.
6130 @item set scheduler-locking @var{mode}
6131 @cindex scheduler locking mode
6132 @cindex lock scheduler
6133 Set the scheduler locking mode. It applies to normal execution,
6134 record mode, and replay mode. If it is @code{off}, then there is no
6135 locking and any thread may run at any time. If @code{on}, then only
6136 the current thread may run when the inferior is resumed. The
6137 @code{step} mode optimizes for single-stepping; it prevents other
6138 threads from preempting the current thread while you are stepping, so
6139 that the focus of debugging does not change unexpectedly. Other
6140 threads never get a chance to run when you step, and they are
6141 completely free to run when you use commands like @samp{continue},
6142 @samp{until}, or @samp{finish}. However, unless another thread hits a
6143 breakpoint during its timeslice, @value{GDBN} does not change the
6144 current thread away from the thread that you are debugging. The
6145 @code{replay} mode behaves like @code{off} in record mode and like
6146 @code{on} in replay mode.
6148 @item show scheduler-locking
6149 Display the current scheduler locking mode.
6152 @cindex resume threads of multiple processes simultaneously
6153 By default, when you issue one of the execution commands such as
6154 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6155 threads of the current inferior to run. For example, if @value{GDBN}
6156 is attached to two inferiors, each with two threads, the
6157 @code{continue} command resumes only the two threads of the current
6158 inferior. This is useful, for example, when you debug a program that
6159 forks and you want to hold the parent stopped (so that, for instance,
6160 it doesn't run to exit), while you debug the child. In other
6161 situations, you may not be interested in inspecting the current state
6162 of any of the processes @value{GDBN} is attached to, and you may want
6163 to resume them all until some breakpoint is hit. In the latter case,
6164 you can instruct @value{GDBN} to allow all threads of all the
6165 inferiors to run with the @w{@code{set schedule-multiple}} command.
6168 @kindex set schedule-multiple
6169 @item set schedule-multiple
6170 Set the mode for allowing threads of multiple processes to be resumed
6171 when an execution command is issued. When @code{on}, all threads of
6172 all processes are allowed to run. When @code{off}, only the threads
6173 of the current process are resumed. The default is @code{off}. The
6174 @code{scheduler-locking} mode takes precedence when set to @code{on},
6175 or while you are stepping and set to @code{step}.
6177 @item show schedule-multiple
6178 Display the current mode for resuming the execution of threads of
6183 @subsection Non-Stop Mode
6185 @cindex non-stop mode
6187 @c This section is really only a place-holder, and needs to be expanded
6188 @c with more details.
6190 For some multi-threaded targets, @value{GDBN} supports an optional
6191 mode of operation in which you can examine stopped program threads in
6192 the debugger while other threads continue to execute freely. This
6193 minimizes intrusion when debugging live systems, such as programs
6194 where some threads have real-time constraints or must continue to
6195 respond to external events. This is referred to as @dfn{non-stop} mode.
6197 In non-stop mode, when a thread stops to report a debugging event,
6198 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6199 threads as well, in contrast to the all-stop mode behavior. Additionally,
6200 execution commands such as @code{continue} and @code{step} apply by default
6201 only to the current thread in non-stop mode, rather than all threads as
6202 in all-stop mode. This allows you to control threads explicitly in
6203 ways that are not possible in all-stop mode --- for example, stepping
6204 one thread while allowing others to run freely, stepping
6205 one thread while holding all others stopped, or stepping several threads
6206 independently and simultaneously.
6208 To enter non-stop mode, use this sequence of commands before you run
6209 or attach to your program:
6212 # If using the CLI, pagination breaks non-stop.
6215 # Finally, turn it on!
6219 You can use these commands to manipulate the non-stop mode setting:
6222 @kindex set non-stop
6223 @item set non-stop on
6224 Enable selection of non-stop mode.
6225 @item set non-stop off
6226 Disable selection of non-stop mode.
6227 @kindex show non-stop
6229 Show the current non-stop enablement setting.
6232 Note these commands only reflect whether non-stop mode is enabled,
6233 not whether the currently-executing program is being run in non-stop mode.
6234 In particular, the @code{set non-stop} preference is only consulted when
6235 @value{GDBN} starts or connects to the target program, and it is generally
6236 not possible to switch modes once debugging has started. Furthermore,
6237 since not all targets support non-stop mode, even when you have enabled
6238 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6241 In non-stop mode, all execution commands apply only to the current thread
6242 by default. That is, @code{continue} only continues one thread.
6243 To continue all threads, issue @code{continue -a} or @code{c -a}.
6245 You can use @value{GDBN}'s background execution commands
6246 (@pxref{Background Execution}) to run some threads in the background
6247 while you continue to examine or step others from @value{GDBN}.
6248 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6249 always executed asynchronously in non-stop mode.
6251 Suspending execution is done with the @code{interrupt} command when
6252 running in the background, or @kbd{Ctrl-c} during foreground execution.
6253 In all-stop mode, this stops the whole process;
6254 but in non-stop mode the interrupt applies only to the current thread.
6255 To stop the whole program, use @code{interrupt -a}.
6257 Other execution commands do not currently support the @code{-a} option.
6259 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6260 that thread current, as it does in all-stop mode. This is because the
6261 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6262 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6263 changed to a different thread just as you entered a command to operate on the
6264 previously current thread.
6266 @node Background Execution
6267 @subsection Background Execution
6269 @cindex foreground execution
6270 @cindex background execution
6271 @cindex asynchronous execution
6272 @cindex execution, foreground, background and asynchronous
6274 @value{GDBN}'s execution commands have two variants: the normal
6275 foreground (synchronous) behavior, and a background
6276 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6277 the program to report that some thread has stopped before prompting for
6278 another command. In background execution, @value{GDBN} immediately gives
6279 a command prompt so that you can issue other commands while your program runs.
6281 If the target doesn't support async mode, @value{GDBN} issues an error
6282 message if you attempt to use the background execution commands.
6284 To specify background execution, add a @code{&} to the command. For example,
6285 the background form of the @code{continue} command is @code{continue&}, or
6286 just @code{c&}. The execution commands that accept background execution
6292 @xref{Starting, , Starting your Program}.
6296 @xref{Attach, , Debugging an Already-running Process}.
6300 @xref{Continuing and Stepping, step}.
6304 @xref{Continuing and Stepping, stepi}.
6308 @xref{Continuing and Stepping, next}.
6312 @xref{Continuing and Stepping, nexti}.
6316 @xref{Continuing and Stepping, continue}.
6320 @xref{Continuing and Stepping, finish}.
6324 @xref{Continuing and Stepping, until}.
6328 Background execution is especially useful in conjunction with non-stop
6329 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6330 However, you can also use these commands in the normal all-stop mode with
6331 the restriction that you cannot issue another execution command until the
6332 previous one finishes. Examples of commands that are valid in all-stop
6333 mode while the program is running include @code{help} and @code{info break}.
6335 You can interrupt your program while it is running in the background by
6336 using the @code{interrupt} command.
6343 Suspend execution of the running program. In all-stop mode,
6344 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6345 only the current thread. To stop the whole program in non-stop mode,
6346 use @code{interrupt -a}.
6349 @node Thread-Specific Breakpoints
6350 @subsection Thread-Specific Breakpoints
6352 When your program has multiple threads (@pxref{Threads,, Debugging
6353 Programs with Multiple Threads}), you can choose whether to set
6354 breakpoints on all threads, or on a particular thread.
6357 @cindex breakpoints and threads
6358 @cindex thread breakpoints
6359 @kindex break @dots{} thread @var{thread-id}
6360 @item break @var{location} thread @var{thread-id}
6361 @itemx break @var{location} thread @var{thread-id} if @dots{}
6362 @var{location} specifies source lines; there are several ways of
6363 writing them (@pxref{Specify Location}), but the effect is always to
6364 specify some source line.
6366 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6367 to specify that you only want @value{GDBN} to stop the program when a
6368 particular thread reaches this breakpoint. The @var{thread-id} specifier
6369 is one of the thread identifiers assigned by @value{GDBN}, shown
6370 in the first column of the @samp{info threads} display.
6372 If you do not specify @samp{thread @var{thread-id}} when you set a
6373 breakpoint, the breakpoint applies to @emph{all} threads of your
6376 You can use the @code{thread} qualifier on conditional breakpoints as
6377 well; in this case, place @samp{thread @var{thread-id}} before or
6378 after the breakpoint condition, like this:
6381 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6386 Thread-specific breakpoints are automatically deleted when
6387 @value{GDBN} detects the corresponding thread is no longer in the
6388 thread list. For example:
6392 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6395 There are several ways for a thread to disappear, such as a regular
6396 thread exit, but also when you detach from the process with the
6397 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6398 Process}), or if @value{GDBN} loses the remote connection
6399 (@pxref{Remote Debugging}), etc. Note that with some targets,
6400 @value{GDBN} is only able to detect a thread has exited when the user
6401 explictly asks for the thread list with the @code{info threads}
6404 @node Interrupted System Calls
6405 @subsection Interrupted System Calls
6407 @cindex thread breakpoints and system calls
6408 @cindex system calls and thread breakpoints
6409 @cindex premature return from system calls
6410 There is an unfortunate side effect when using @value{GDBN} to debug
6411 multi-threaded programs. If one thread stops for a
6412 breakpoint, or for some other reason, and another thread is blocked in a
6413 system call, then the system call may return prematurely. This is a
6414 consequence of the interaction between multiple threads and the signals
6415 that @value{GDBN} uses to implement breakpoints and other events that
6418 To handle this problem, your program should check the return value of
6419 each system call and react appropriately. This is good programming
6422 For example, do not write code like this:
6428 The call to @code{sleep} will return early if a different thread stops
6429 at a breakpoint or for some other reason.
6431 Instead, write this:
6436 unslept = sleep (unslept);
6439 A system call is allowed to return early, so the system is still
6440 conforming to its specification. But @value{GDBN} does cause your
6441 multi-threaded program to behave differently than it would without
6444 Also, @value{GDBN} uses internal breakpoints in the thread library to
6445 monitor certain events such as thread creation and thread destruction.
6446 When such an event happens, a system call in another thread may return
6447 prematurely, even though your program does not appear to stop.
6450 @subsection Observer Mode
6452 If you want to build on non-stop mode and observe program behavior
6453 without any chance of disruption by @value{GDBN}, you can set
6454 variables to disable all of the debugger's attempts to modify state,
6455 whether by writing memory, inserting breakpoints, etc. These operate
6456 at a low level, intercepting operations from all commands.
6458 When all of these are set to @code{off}, then @value{GDBN} is said to
6459 be @dfn{observer mode}. As a convenience, the variable
6460 @code{observer} can be set to disable these, plus enable non-stop
6463 Note that @value{GDBN} will not prevent you from making nonsensical
6464 combinations of these settings. For instance, if you have enabled
6465 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6466 then breakpoints that work by writing trap instructions into the code
6467 stream will still not be able to be placed.
6472 @item set observer on
6473 @itemx set observer off
6474 When set to @code{on}, this disables all the permission variables
6475 below (except for @code{insert-fast-tracepoints}), plus enables
6476 non-stop debugging. Setting this to @code{off} switches back to
6477 normal debugging, though remaining in non-stop mode.
6480 Show whether observer mode is on or off.
6482 @kindex may-write-registers
6483 @item set may-write-registers on
6484 @itemx set may-write-registers off
6485 This controls whether @value{GDBN} will attempt to alter the values of
6486 registers, such as with assignment expressions in @code{print}, or the
6487 @code{jump} command. It defaults to @code{on}.
6489 @item show may-write-registers
6490 Show the current permission to write registers.
6492 @kindex may-write-memory
6493 @item set may-write-memory on
6494 @itemx set may-write-memory off
6495 This controls whether @value{GDBN} will attempt to alter the contents
6496 of memory, such as with assignment expressions in @code{print}. It
6497 defaults to @code{on}.
6499 @item show may-write-memory
6500 Show the current permission to write memory.
6502 @kindex may-insert-breakpoints
6503 @item set may-insert-breakpoints on
6504 @itemx set may-insert-breakpoints off
6505 This controls whether @value{GDBN} will attempt to insert breakpoints.
6506 This affects all breakpoints, including internal breakpoints defined
6507 by @value{GDBN}. It defaults to @code{on}.
6509 @item show may-insert-breakpoints
6510 Show the current permission to insert breakpoints.
6512 @kindex may-insert-tracepoints
6513 @item set may-insert-tracepoints on
6514 @itemx set may-insert-tracepoints off
6515 This controls whether @value{GDBN} will attempt to insert (regular)
6516 tracepoints at the beginning of a tracing experiment. It affects only
6517 non-fast tracepoints, fast tracepoints being under the control of
6518 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6520 @item show may-insert-tracepoints
6521 Show the current permission to insert tracepoints.
6523 @kindex may-insert-fast-tracepoints
6524 @item set may-insert-fast-tracepoints on
6525 @itemx set may-insert-fast-tracepoints off
6526 This controls whether @value{GDBN} will attempt to insert fast
6527 tracepoints at the beginning of a tracing experiment. It affects only
6528 fast tracepoints, regular (non-fast) tracepoints being under the
6529 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6531 @item show may-insert-fast-tracepoints
6532 Show the current permission to insert fast tracepoints.
6534 @kindex may-interrupt
6535 @item set may-interrupt on
6536 @itemx set may-interrupt off
6537 This controls whether @value{GDBN} will attempt to interrupt or stop
6538 program execution. When this variable is @code{off}, the
6539 @code{interrupt} command will have no effect, nor will
6540 @kbd{Ctrl-c}. It defaults to @code{on}.
6542 @item show may-interrupt
6543 Show the current permission to interrupt or stop the program.
6547 @node Reverse Execution
6548 @chapter Running programs backward
6549 @cindex reverse execution
6550 @cindex running programs backward
6552 When you are debugging a program, it is not unusual to realize that
6553 you have gone too far, and some event of interest has already happened.
6554 If the target environment supports it, @value{GDBN} can allow you to
6555 ``rewind'' the program by running it backward.
6557 A target environment that supports reverse execution should be able
6558 to ``undo'' the changes in machine state that have taken place as the
6559 program was executing normally. Variables, registers etc.@: should
6560 revert to their previous values. Obviously this requires a great
6561 deal of sophistication on the part of the target environment; not
6562 all target environments can support reverse execution.
6564 When a program is executed in reverse, the instructions that
6565 have most recently been executed are ``un-executed'', in reverse
6566 order. The program counter runs backward, following the previous
6567 thread of execution in reverse. As each instruction is ``un-executed'',
6568 the values of memory and/or registers that were changed by that
6569 instruction are reverted to their previous states. After executing
6570 a piece of source code in reverse, all side effects of that code
6571 should be ``undone'', and all variables should be returned to their
6572 prior values@footnote{
6573 Note that some side effects are easier to undo than others. For instance,
6574 memory and registers are relatively easy, but device I/O is hard. Some
6575 targets may be able undo things like device I/O, and some may not.
6577 The contract between @value{GDBN} and the reverse executing target
6578 requires only that the target do something reasonable when
6579 @value{GDBN} tells it to execute backwards, and then report the
6580 results back to @value{GDBN}. Whatever the target reports back to
6581 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6582 assumes that the memory and registers that the target reports are in a
6583 consistant state, but @value{GDBN} accepts whatever it is given.
6586 If you are debugging in a target environment that supports
6587 reverse execution, @value{GDBN} provides the following commands.
6590 @kindex reverse-continue
6591 @kindex rc @r{(@code{reverse-continue})}
6592 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6593 @itemx rc @r{[}@var{ignore-count}@r{]}
6594 Beginning at the point where your program last stopped, start executing
6595 in reverse. Reverse execution will stop for breakpoints and synchronous
6596 exceptions (signals), just like normal execution. Behavior of
6597 asynchronous signals depends on the target environment.
6599 @kindex reverse-step
6600 @kindex rs @r{(@code{step})}
6601 @item reverse-step @r{[}@var{count}@r{]}
6602 Run the program backward until control reaches the start of a
6603 different source line; then stop it, and return control to @value{GDBN}.
6605 Like the @code{step} command, @code{reverse-step} will only stop
6606 at the beginning of a source line. It ``un-executes'' the previously
6607 executed source line. If the previous source line included calls to
6608 debuggable functions, @code{reverse-step} will step (backward) into
6609 the called function, stopping at the beginning of the @emph{last}
6610 statement in the called function (typically a return statement).
6612 Also, as with the @code{step} command, if non-debuggable functions are
6613 called, @code{reverse-step} will run thru them backward without stopping.
6615 @kindex reverse-stepi
6616 @kindex rsi @r{(@code{reverse-stepi})}
6617 @item reverse-stepi @r{[}@var{count}@r{]}
6618 Reverse-execute one machine instruction. Note that the instruction
6619 to be reverse-executed is @emph{not} the one pointed to by the program
6620 counter, but the instruction executed prior to that one. For instance,
6621 if the last instruction was a jump, @code{reverse-stepi} will take you
6622 back from the destination of the jump to the jump instruction itself.
6624 @kindex reverse-next
6625 @kindex rn @r{(@code{reverse-next})}
6626 @item reverse-next @r{[}@var{count}@r{]}
6627 Run backward to the beginning of the previous line executed in
6628 the current (innermost) stack frame. If the line contains function
6629 calls, they will be ``un-executed'' without stopping. Starting from
6630 the first line of a function, @code{reverse-next} will take you back
6631 to the caller of that function, @emph{before} the function was called,
6632 just as the normal @code{next} command would take you from the last
6633 line of a function back to its return to its caller
6634 @footnote{Unless the code is too heavily optimized.}.
6636 @kindex reverse-nexti
6637 @kindex rni @r{(@code{reverse-nexti})}
6638 @item reverse-nexti @r{[}@var{count}@r{]}
6639 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6640 in reverse, except that called functions are ``un-executed'' atomically.
6641 That is, if the previously executed instruction was a return from
6642 another function, @code{reverse-nexti} will continue to execute
6643 in reverse until the call to that function (from the current stack
6646 @kindex reverse-finish
6647 @item reverse-finish
6648 Just as the @code{finish} command takes you to the point where the
6649 current function returns, @code{reverse-finish} takes you to the point
6650 where it was called. Instead of ending up at the end of the current
6651 function invocation, you end up at the beginning.
6653 @kindex set exec-direction
6654 @item set exec-direction
6655 Set the direction of target execution.
6656 @item set exec-direction reverse
6657 @cindex execute forward or backward in time
6658 @value{GDBN} will perform all execution commands in reverse, until the
6659 exec-direction mode is changed to ``forward''. Affected commands include
6660 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6661 command cannot be used in reverse mode.
6662 @item set exec-direction forward
6663 @value{GDBN} will perform all execution commands in the normal fashion.
6664 This is the default.
6668 @node Process Record and Replay
6669 @chapter Recording Inferior's Execution and Replaying It
6670 @cindex process record and replay
6671 @cindex recording inferior's execution and replaying it
6673 On some platforms, @value{GDBN} provides a special @dfn{process record
6674 and replay} target that can record a log of the process execution, and
6675 replay it later with both forward and reverse execution commands.
6678 When this target is in use, if the execution log includes the record
6679 for the next instruction, @value{GDBN} will debug in @dfn{replay
6680 mode}. In the replay mode, the inferior does not really execute code
6681 instructions. Instead, all the events that normally happen during
6682 code execution are taken from the execution log. While code is not
6683 really executed in replay mode, the values of registers (including the
6684 program counter register) and the memory of the inferior are still
6685 changed as they normally would. Their contents are taken from the
6689 If the record for the next instruction is not in the execution log,
6690 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6691 inferior executes normally, and @value{GDBN} records the execution log
6694 The process record and replay target supports reverse execution
6695 (@pxref{Reverse Execution}), even if the platform on which the
6696 inferior runs does not. However, the reverse execution is limited in
6697 this case by the range of the instructions recorded in the execution
6698 log. In other words, reverse execution on platforms that don't
6699 support it directly can only be done in the replay mode.
6701 When debugging in the reverse direction, @value{GDBN} will work in
6702 replay mode as long as the execution log includes the record for the
6703 previous instruction; otherwise, it will work in record mode, if the
6704 platform supports reverse execution, or stop if not.
6706 For architecture environments that support process record and replay,
6707 @value{GDBN} provides the following commands:
6710 @kindex target record
6711 @kindex target record-full
6712 @kindex target record-btrace
6715 @kindex record btrace
6716 @kindex record btrace bts
6717 @kindex record btrace pt
6723 @kindex rec btrace bts
6724 @kindex rec btrace pt
6727 @item record @var{method}
6728 This command starts the process record and replay target. The
6729 recording method can be specified as parameter. Without a parameter
6730 the command uses the @code{full} recording method. The following
6731 recording methods are available:
6735 Full record/replay recording using @value{GDBN}'s software record and
6736 replay implementation. This method allows replaying and reverse
6739 @item btrace @var{format}
6740 Hardware-supported instruction recording. This method does not record
6741 data. Further, the data is collected in a ring buffer so old data will
6742 be overwritten when the buffer is full. It allows limited reverse
6743 execution. Variables and registers are not available during reverse
6744 execution. In remote debugging, recording continues on disconnect.
6745 Recorded data can be inspected after reconnecting. The recording may
6746 be stopped using @code{record stop}.
6748 The recording format can be specified as parameter. Without a parameter
6749 the command chooses the recording format. The following recording
6750 formats are available:
6754 @cindex branch trace store
6755 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6756 this format, the processor stores a from/to record for each executed
6757 branch in the btrace ring buffer.
6760 @cindex Intel Processor Trace
6761 Use the @dfn{Intel Processor Trace} recording format. In this
6762 format, the processor stores the execution trace in a compressed form
6763 that is afterwards decoded by @value{GDBN}.
6765 The trace can be recorded with very low overhead. The compressed
6766 trace format also allows small trace buffers to already contain a big
6767 number of instructions compared to @acronym{BTS}.
6769 Decoding the recorded execution trace, on the other hand, is more
6770 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6771 increased number of instructions to process. You should increase the
6772 buffer-size with care.
6775 Not all recording formats may be available on all processors.
6778 The process record and replay target can only debug a process that is
6779 already running. Therefore, you need first to start the process with
6780 the @kbd{run} or @kbd{start} commands, and then start the recording
6781 with the @kbd{record @var{method}} command.
6783 @cindex displaced stepping, and process record and replay
6784 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6785 will be automatically disabled when process record and replay target
6786 is started. That's because the process record and replay target
6787 doesn't support displaced stepping.
6789 @cindex non-stop mode, and process record and replay
6790 @cindex asynchronous execution, and process record and replay
6791 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6792 the asynchronous execution mode (@pxref{Background Execution}), not
6793 all recording methods are available. The @code{full} recording method
6794 does not support these two modes.
6799 Stop the process record and replay target. When process record and
6800 replay target stops, the entire execution log will be deleted and the
6801 inferior will either be terminated, or will remain in its final state.
6803 When you stop the process record and replay target in record mode (at
6804 the end of the execution log), the inferior will be stopped at the
6805 next instruction that would have been recorded. In other words, if
6806 you record for a while and then stop recording, the inferior process
6807 will be left in the same state as if the recording never happened.
6809 On the other hand, if the process record and replay target is stopped
6810 while in replay mode (that is, not at the end of the execution log,
6811 but at some earlier point), the inferior process will become ``live''
6812 at that earlier state, and it will then be possible to continue the
6813 usual ``live'' debugging of the process from that state.
6815 When the inferior process exits, or @value{GDBN} detaches from it,
6816 process record and replay target will automatically stop itself.
6820 Go to a specific location in the execution log. There are several
6821 ways to specify the location to go to:
6824 @item record goto begin
6825 @itemx record goto start
6826 Go to the beginning of the execution log.
6828 @item record goto end
6829 Go to the end of the execution log.
6831 @item record goto @var{n}
6832 Go to instruction number @var{n} in the execution log.
6836 @item record save @var{filename}
6837 Save the execution log to a file @file{@var{filename}}.
6838 Default filename is @file{gdb_record.@var{process_id}}, where
6839 @var{process_id} is the process ID of the inferior.
6841 This command may not be available for all recording methods.
6843 @kindex record restore
6844 @item record restore @var{filename}
6845 Restore the execution log from a file @file{@var{filename}}.
6846 File must have been created with @code{record save}.
6848 @kindex set record full
6849 @item set record full insn-number-max @var{limit}
6850 @itemx set record full insn-number-max unlimited
6851 Set the limit of instructions to be recorded for the @code{full}
6852 recording method. Default value is 200000.
6854 If @var{limit} is a positive number, then @value{GDBN} will start
6855 deleting instructions from the log once the number of the record
6856 instructions becomes greater than @var{limit}. For every new recorded
6857 instruction, @value{GDBN} will delete the earliest recorded
6858 instruction to keep the number of recorded instructions at the limit.
6859 (Since deleting recorded instructions loses information, @value{GDBN}
6860 lets you control what happens when the limit is reached, by means of
6861 the @code{stop-at-limit} option, described below.)
6863 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6864 delete recorded instructions from the execution log. The number of
6865 recorded instructions is limited only by the available memory.
6867 @kindex show record full
6868 @item show record full insn-number-max
6869 Show the limit of instructions to be recorded with the @code{full}
6872 @item set record full stop-at-limit
6873 Control the behavior of the @code{full} recording method when the
6874 number of recorded instructions reaches the limit. If ON (the
6875 default), @value{GDBN} will stop when the limit is reached for the
6876 first time and ask you whether you want to stop the inferior or
6877 continue running it and recording the execution log. If you decide
6878 to continue recording, each new recorded instruction will cause the
6879 oldest one to be deleted.
6881 If this option is OFF, @value{GDBN} will automatically delete the
6882 oldest record to make room for each new one, without asking.
6884 @item show record full stop-at-limit
6885 Show the current setting of @code{stop-at-limit}.
6887 @item set record full memory-query
6888 Control the behavior when @value{GDBN} is unable to record memory
6889 changes caused by an instruction for the @code{full} recording method.
6890 If ON, @value{GDBN} will query whether to stop the inferior in that
6893 If this option is OFF (the default), @value{GDBN} will automatically
6894 ignore the effect of such instructions on memory. Later, when
6895 @value{GDBN} replays this execution log, it will mark the log of this
6896 instruction as not accessible, and it will not affect the replay
6899 @item show record full memory-query
6900 Show the current setting of @code{memory-query}.
6902 @kindex set record btrace
6903 The @code{btrace} record target does not trace data. As a
6904 convenience, when replaying, @value{GDBN} reads read-only memory off
6905 the live program directly, assuming that the addresses of the
6906 read-only areas don't change. This for example makes it possible to
6907 disassemble code while replaying, but not to print variables.
6908 In some cases, being able to inspect variables might be useful.
6909 You can use the following command for that:
6911 @item set record btrace replay-memory-access
6912 Control the behavior of the @code{btrace} recording method when
6913 accessing memory during replay. If @code{read-only} (the default),
6914 @value{GDBN} will only allow accesses to read-only memory.
6915 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6916 and to read-write memory. Beware that the accessed memory corresponds
6917 to the live target and not necessarily to the current replay
6920 @kindex show record btrace
6921 @item show record btrace replay-memory-access
6922 Show the current setting of @code{replay-memory-access}.
6924 @kindex set record btrace bts
6925 @item set record btrace bts buffer-size @var{size}
6926 @itemx set record btrace bts buffer-size unlimited
6927 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6928 format. Default is 64KB.
6930 If @var{size} is a positive number, then @value{GDBN} will try to
6931 allocate a buffer of at least @var{size} bytes for each new thread
6932 that uses the btrace recording method and the @acronym{BTS} format.
6933 The actually obtained buffer size may differ from the requested
6934 @var{size}. Use the @code{info record} command to see the actual
6935 buffer size for each thread that uses the btrace recording method and
6936 the @acronym{BTS} format.
6938 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6939 allocate a buffer of 4MB.
6941 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6942 also need longer to process the branch trace data before it can be used.
6944 @item show record btrace bts buffer-size @var{size}
6945 Show the current setting of the requested ring buffer size for branch
6946 tracing in @acronym{BTS} format.
6948 @kindex set record btrace pt
6949 @item set record btrace pt buffer-size @var{size}
6950 @itemx set record btrace pt buffer-size unlimited
6951 Set the requested ring buffer size for branch tracing in Intel
6952 Processor Trace format. Default is 16KB.
6954 If @var{size} is a positive number, then @value{GDBN} will try to
6955 allocate a buffer of at least @var{size} bytes for each new thread
6956 that uses the btrace recording method and the Intel Processor Trace
6957 format. The actually obtained buffer size may differ from the
6958 requested @var{size}. Use the @code{info record} command to see the
6959 actual buffer size for each thread.
6961 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6962 allocate a buffer of 4MB.
6964 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6965 also need longer to process the branch trace data before it can be used.
6967 @item show record btrace pt buffer-size @var{size}
6968 Show the current setting of the requested ring buffer size for branch
6969 tracing in Intel Processor Trace format.
6973 Show various statistics about the recording depending on the recording
6978 For the @code{full} recording method, it shows the state of process
6979 record and its in-memory execution log buffer, including:
6983 Whether in record mode or replay mode.
6985 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6987 Highest recorded instruction number.
6989 Current instruction about to be replayed (if in replay mode).
6991 Number of instructions contained in the execution log.
6993 Maximum number of instructions that may be contained in the execution log.
6997 For the @code{btrace} recording method, it shows:
7003 Number of instructions that have been recorded.
7005 Number of blocks of sequential control-flow formed by the recorded
7008 Whether in record mode or replay mode.
7011 For the @code{bts} recording format, it also shows:
7014 Size of the perf ring buffer.
7017 For the @code{pt} recording format, it also shows:
7020 Size of the perf ring buffer.
7024 @kindex record delete
7027 When record target runs in replay mode (``in the past''), delete the
7028 subsequent execution log and begin to record a new execution log starting
7029 from the current address. This means you will abandon the previously
7030 recorded ``future'' and begin recording a new ``future''.
7032 @kindex record instruction-history
7033 @kindex rec instruction-history
7034 @item record instruction-history
7035 Disassembles instructions from the recorded execution log. By
7036 default, ten instructions are disassembled. This can be changed using
7037 the @code{set record instruction-history-size} command. Instructions
7038 are printed in execution order.
7040 It can also print mixed source+disassembly if you specify the the
7041 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7042 as well as in symbolic form by specifying the @code{/r} modifier.
7044 The current position marker is printed for the instruction at the
7045 current program counter value. This instruction can appear multiple
7046 times in the trace and the current position marker will be printed
7047 every time. To omit the current position marker, specify the
7050 To better align the printed instructions when the trace contains
7051 instructions from more than one function, the function name may be
7052 omitted by specifying the @code{/f} modifier.
7054 Speculatively executed instructions are prefixed with @samp{?}. This
7055 feature is not available for all recording formats.
7057 There are several ways to specify what part of the execution log to
7061 @item record instruction-history @var{insn}
7062 Disassembles ten instructions starting from instruction number
7065 @item record instruction-history @var{insn}, +/-@var{n}
7066 Disassembles @var{n} instructions around instruction number
7067 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7068 @var{n} instructions after instruction number @var{insn}. If
7069 @var{n} is preceded with @code{-}, disassembles @var{n}
7070 instructions before instruction number @var{insn}.
7072 @item record instruction-history
7073 Disassembles ten more instructions after the last disassembly.
7075 @item record instruction-history -
7076 Disassembles ten more instructions before the last disassembly.
7078 @item record instruction-history @var{begin}, @var{end}
7079 Disassembles instructions beginning with instruction number
7080 @var{begin} until instruction number @var{end}. The instruction
7081 number @var{end} is included.
7084 This command may not be available for all recording methods.
7087 @item set record instruction-history-size @var{size}
7088 @itemx set record instruction-history-size unlimited
7089 Define how many instructions to disassemble in the @code{record
7090 instruction-history} command. The default value is 10.
7091 A @var{size} of @code{unlimited} means unlimited instructions.
7094 @item show record instruction-history-size
7095 Show how many instructions to disassemble in the @code{record
7096 instruction-history} command.
7098 @kindex record function-call-history
7099 @kindex rec function-call-history
7100 @item record function-call-history
7101 Prints the execution history at function granularity. It prints one
7102 line for each sequence of instructions that belong to the same
7103 function giving the name of that function, the source lines
7104 for this instruction sequence (if the @code{/l} modifier is
7105 specified), and the instructions numbers that form the sequence (if
7106 the @code{/i} modifier is specified). The function names are indented
7107 to reflect the call stack depth if the @code{/c} modifier is
7108 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7112 (@value{GDBP}) @b{list 1, 10}
7123 (@value{GDBP}) @b{record function-call-history /ilc}
7124 1 bar inst 1,4 at foo.c:6,8
7125 2 foo inst 5,10 at foo.c:2,3
7126 3 bar inst 11,13 at foo.c:9,10
7129 By default, ten lines are printed. This can be changed using the
7130 @code{set record function-call-history-size} command. Functions are
7131 printed in execution order. There are several ways to specify what
7135 @item record function-call-history @var{func}
7136 Prints ten functions starting from function number @var{func}.
7138 @item record function-call-history @var{func}, +/-@var{n}
7139 Prints @var{n} functions around function number @var{func}. If
7140 @var{n} is preceded with @code{+}, prints @var{n} functions after
7141 function number @var{func}. If @var{n} is preceded with @code{-},
7142 prints @var{n} functions before function number @var{func}.
7144 @item record function-call-history
7145 Prints ten more functions after the last ten-line print.
7147 @item record function-call-history -
7148 Prints ten more functions before the last ten-line print.
7150 @item record function-call-history @var{begin}, @var{end}
7151 Prints functions beginning with function number @var{begin} until
7152 function number @var{end}. The function number @var{end} is included.
7155 This command may not be available for all recording methods.
7157 @item set record function-call-history-size @var{size}
7158 @itemx set record function-call-history-size unlimited
7159 Define how many lines to print in the
7160 @code{record function-call-history} command. The default value is 10.
7161 A size of @code{unlimited} means unlimited lines.
7163 @item show record function-call-history-size
7164 Show how many lines to print in the
7165 @code{record function-call-history} command.
7170 @chapter Examining the Stack
7172 When your program has stopped, the first thing you need to know is where it
7173 stopped and how it got there.
7176 Each time your program performs a function call, information about the call
7178 That information includes the location of the call in your program,
7179 the arguments of the call,
7180 and the local variables of the function being called.
7181 The information is saved in a block of data called a @dfn{stack frame}.
7182 The stack frames are allocated in a region of memory called the @dfn{call
7185 When your program stops, the @value{GDBN} commands for examining the
7186 stack allow you to see all of this information.
7188 @cindex selected frame
7189 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7190 @value{GDBN} commands refer implicitly to the selected frame. In
7191 particular, whenever you ask @value{GDBN} for the value of a variable in
7192 your program, the value is found in the selected frame. There are
7193 special @value{GDBN} commands to select whichever frame you are
7194 interested in. @xref{Selection, ,Selecting a Frame}.
7196 When your program stops, @value{GDBN} automatically selects the
7197 currently executing frame and describes it briefly, similar to the
7198 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7201 * Frames:: Stack frames
7202 * Backtrace:: Backtraces
7203 * Selection:: Selecting a frame
7204 * Frame Info:: Information on a frame
7205 * Frame Filter Management:: Managing frame filters
7210 @section Stack Frames
7212 @cindex frame, definition
7214 The call stack is divided up into contiguous pieces called @dfn{stack
7215 frames}, or @dfn{frames} for short; each frame is the data associated
7216 with one call to one function. The frame contains the arguments given
7217 to the function, the function's local variables, and the address at
7218 which the function is executing.
7220 @cindex initial frame
7221 @cindex outermost frame
7222 @cindex innermost frame
7223 When your program is started, the stack has only one frame, that of the
7224 function @code{main}. This is called the @dfn{initial} frame or the
7225 @dfn{outermost} frame. Each time a function is called, a new frame is
7226 made. Each time a function returns, the frame for that function invocation
7227 is eliminated. If a function is recursive, there can be many frames for
7228 the same function. The frame for the function in which execution is
7229 actually occurring is called the @dfn{innermost} frame. This is the most
7230 recently created of all the stack frames that still exist.
7232 @cindex frame pointer
7233 Inside your program, stack frames are identified by their addresses. A
7234 stack frame consists of many bytes, each of which has its own address; each
7235 kind of computer has a convention for choosing one byte whose
7236 address serves as the address of the frame. Usually this address is kept
7237 in a register called the @dfn{frame pointer register}
7238 (@pxref{Registers, $fp}) while execution is going on in that frame.
7240 @cindex frame number
7241 @value{GDBN} assigns numbers to all existing stack frames, starting with
7242 zero for the innermost frame, one for the frame that called it,
7243 and so on upward. These numbers do not really exist in your program;
7244 they are assigned by @value{GDBN} to give you a way of designating stack
7245 frames in @value{GDBN} commands.
7247 @c The -fomit-frame-pointer below perennially causes hbox overflow
7248 @c underflow problems.
7249 @cindex frameless execution
7250 Some compilers provide a way to compile functions so that they operate
7251 without stack frames. (For example, the @value{NGCC} option
7253 @samp{-fomit-frame-pointer}
7255 generates functions without a frame.)
7256 This is occasionally done with heavily used library functions to save
7257 the frame setup time. @value{GDBN} has limited facilities for dealing
7258 with these function invocations. If the innermost function invocation
7259 has no stack frame, @value{GDBN} nevertheless regards it as though
7260 it had a separate frame, which is numbered zero as usual, allowing
7261 correct tracing of the function call chain. However, @value{GDBN} has
7262 no provision for frameless functions elsewhere in the stack.
7268 @cindex call stack traces
7269 A backtrace is a summary of how your program got where it is. It shows one
7270 line per frame, for many frames, starting with the currently executing
7271 frame (frame zero), followed by its caller (frame one), and on up the
7274 @anchor{backtrace-command}
7277 @kindex bt @r{(@code{backtrace})}
7280 Print a backtrace of the entire stack: one line per frame for all
7281 frames in the stack.
7283 You can stop the backtrace at any time by typing the system interrupt
7284 character, normally @kbd{Ctrl-c}.
7286 @item backtrace @var{n}
7288 Similar, but print only the innermost @var{n} frames.
7290 @item backtrace -@var{n}
7292 Similar, but print only the outermost @var{n} frames.
7294 @item backtrace full
7296 @itemx bt full @var{n}
7297 @itemx bt full -@var{n}
7298 Print the values of the local variables also. As described above,
7299 @var{n} specifies the number of frames to print.
7301 @item backtrace no-filters
7302 @itemx bt no-filters
7303 @itemx bt no-filters @var{n}
7304 @itemx bt no-filters -@var{n}
7305 @itemx bt no-filters full
7306 @itemx bt no-filters full @var{n}
7307 @itemx bt no-filters full -@var{n}
7308 Do not run Python frame filters on this backtrace. @xref{Frame
7309 Filter API}, for more information. Additionally use @ref{disable
7310 frame-filter all} to turn off all frame filters. This is only
7311 relevant when @value{GDBN} has been configured with @code{Python}
7317 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7318 are additional aliases for @code{backtrace}.
7320 @cindex multiple threads, backtrace
7321 In a multi-threaded program, @value{GDBN} by default shows the
7322 backtrace only for the current thread. To display the backtrace for
7323 several or all of the threads, use the command @code{thread apply}
7324 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7325 apply all backtrace}, @value{GDBN} will display the backtrace for all
7326 the threads; this is handy when you debug a core dump of a
7327 multi-threaded program.
7329 Each line in the backtrace shows the frame number and the function name.
7330 The program counter value is also shown---unless you use @code{set
7331 print address off}. The backtrace also shows the source file name and
7332 line number, as well as the arguments to the function. The program
7333 counter value is omitted if it is at the beginning of the code for that
7336 Here is an example of a backtrace. It was made with the command
7337 @samp{bt 3}, so it shows the innermost three frames.
7341 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7343 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7344 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7346 (More stack frames follow...)
7351 The display for frame zero does not begin with a program counter
7352 value, indicating that your program has stopped at the beginning of the
7353 code for line @code{993} of @code{builtin.c}.
7356 The value of parameter @code{data} in frame 1 has been replaced by
7357 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7358 only if it is a scalar (integer, pointer, enumeration, etc). See command
7359 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7360 on how to configure the way function parameter values are printed.
7362 @cindex optimized out, in backtrace
7363 @cindex function call arguments, optimized out
7364 If your program was compiled with optimizations, some compilers will
7365 optimize away arguments passed to functions if those arguments are
7366 never used after the call. Such optimizations generate code that
7367 passes arguments through registers, but doesn't store those arguments
7368 in the stack frame. @value{GDBN} has no way of displaying such
7369 arguments in stack frames other than the innermost one. Here's what
7370 such a backtrace might look like:
7374 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7376 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7377 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7379 (More stack frames follow...)
7384 The values of arguments that were not saved in their stack frames are
7385 shown as @samp{<optimized out>}.
7387 If you need to display the values of such optimized-out arguments,
7388 either deduce that from other variables whose values depend on the one
7389 you are interested in, or recompile without optimizations.
7391 @cindex backtrace beyond @code{main} function
7392 @cindex program entry point
7393 @cindex startup code, and backtrace
7394 Most programs have a standard user entry point---a place where system
7395 libraries and startup code transition into user code. For C this is
7396 @code{main}@footnote{
7397 Note that embedded programs (the so-called ``free-standing''
7398 environment) are not required to have a @code{main} function as the
7399 entry point. They could even have multiple entry points.}.
7400 When @value{GDBN} finds the entry function in a backtrace
7401 it will terminate the backtrace, to avoid tracing into highly
7402 system-specific (and generally uninteresting) code.
7404 If you need to examine the startup code, or limit the number of levels
7405 in a backtrace, you can change this behavior:
7408 @item set backtrace past-main
7409 @itemx set backtrace past-main on
7410 @kindex set backtrace
7411 Backtraces will continue past the user entry point.
7413 @item set backtrace past-main off
7414 Backtraces will stop when they encounter the user entry point. This is the
7417 @item show backtrace past-main
7418 @kindex show backtrace
7419 Display the current user entry point backtrace policy.
7421 @item set backtrace past-entry
7422 @itemx set backtrace past-entry on
7423 Backtraces will continue past the internal entry point of an application.
7424 This entry point is encoded by the linker when the application is built,
7425 and is likely before the user entry point @code{main} (or equivalent) is called.
7427 @item set backtrace past-entry off
7428 Backtraces will stop when they encounter the internal entry point of an
7429 application. This is the default.
7431 @item show backtrace past-entry
7432 Display the current internal entry point backtrace policy.
7434 @item set backtrace limit @var{n}
7435 @itemx set backtrace limit 0
7436 @itemx set backtrace limit unlimited
7437 @cindex backtrace limit
7438 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7439 or zero means unlimited levels.
7441 @item show backtrace limit
7442 Display the current limit on backtrace levels.
7445 You can control how file names are displayed.
7448 @item set filename-display
7449 @itemx set filename-display relative
7450 @cindex filename-display
7451 Display file names relative to the compilation directory. This is the default.
7453 @item set filename-display basename
7454 Display only basename of a filename.
7456 @item set filename-display absolute
7457 Display an absolute filename.
7459 @item show filename-display
7460 Show the current way to display filenames.
7464 @section Selecting a Frame
7466 Most commands for examining the stack and other data in your program work on
7467 whichever stack frame is selected at the moment. Here are the commands for
7468 selecting a stack frame; all of them finish by printing a brief description
7469 of the stack frame just selected.
7472 @kindex frame@r{, selecting}
7473 @kindex f @r{(@code{frame})}
7476 Select frame number @var{n}. Recall that frame zero is the innermost
7477 (currently executing) frame, frame one is the frame that called the
7478 innermost one, and so on. The highest-numbered frame is the one for
7481 @item frame @var{stack-addr} [ @var{pc-addr} ]
7482 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7483 Select the frame at address @var{stack-addr}. This is useful mainly if the
7484 chaining of stack frames has been damaged by a bug, making it
7485 impossible for @value{GDBN} to assign numbers properly to all frames. In
7486 addition, this can be useful when your program has multiple stacks and
7487 switches between them. The optional @var{pc-addr} can also be given to
7488 specify the value of PC for the stack frame.
7492 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7493 numbers @var{n}, this advances toward the outermost frame, to higher
7494 frame numbers, to frames that have existed longer.
7497 @kindex do @r{(@code{down})}
7499 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7500 positive numbers @var{n}, this advances toward the innermost frame, to
7501 lower frame numbers, to frames that were created more recently.
7502 You may abbreviate @code{down} as @code{do}.
7505 All of these commands end by printing two lines of output describing the
7506 frame. The first line shows the frame number, the function name, the
7507 arguments, and the source file and line number of execution in that
7508 frame. The second line shows the text of that source line.
7516 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7518 10 read_input_file (argv[i]);
7522 After such a printout, the @code{list} command with no arguments
7523 prints ten lines centered on the point of execution in the frame.
7524 You can also edit the program at the point of execution with your favorite
7525 editing program by typing @code{edit}.
7526 @xref{List, ,Printing Source Lines},
7530 @kindex select-frame
7532 The @code{select-frame} command is a variant of @code{frame} that does
7533 not display the new frame after selecting it. This command is
7534 intended primarily for use in @value{GDBN} command scripts, where the
7535 output might be unnecessary and distracting.
7537 @kindex down-silently
7539 @item up-silently @var{n}
7540 @itemx down-silently @var{n}
7541 These two commands are variants of @code{up} and @code{down},
7542 respectively; they differ in that they do their work silently, without
7543 causing display of the new frame. They are intended primarily for use
7544 in @value{GDBN} command scripts, where the output might be unnecessary and
7549 @section Information About a Frame
7551 There are several other commands to print information about the selected
7557 When used without any argument, this command does not change which
7558 frame is selected, but prints a brief description of the currently
7559 selected stack frame. It can be abbreviated @code{f}. With an
7560 argument, this command is used to select a stack frame.
7561 @xref{Selection, ,Selecting a Frame}.
7564 @kindex info f @r{(@code{info frame})}
7567 This command prints a verbose description of the selected stack frame,
7572 the address of the frame
7574 the address of the next frame down (called by this frame)
7576 the address of the next frame up (caller of this frame)
7578 the language in which the source code corresponding to this frame is written
7580 the address of the frame's arguments
7582 the address of the frame's local variables
7584 the program counter saved in it (the address of execution in the caller frame)
7586 which registers were saved in the frame
7589 @noindent The verbose description is useful when
7590 something has gone wrong that has made the stack format fail to fit
7591 the usual conventions.
7593 @item info frame @var{addr}
7594 @itemx info f @var{addr}
7595 Print a verbose description of the frame at address @var{addr}, without
7596 selecting that frame. The selected frame remains unchanged by this
7597 command. This requires the same kind of address (more than one for some
7598 architectures) that you specify in the @code{frame} command.
7599 @xref{Selection, ,Selecting a Frame}.
7603 Print the arguments of the selected frame, each on a separate line.
7607 Print the local variables of the selected frame, each on a separate
7608 line. These are all variables (declared either static or automatic)
7609 accessible at the point of execution of the selected frame.
7613 @node Frame Filter Management
7614 @section Management of Frame Filters.
7615 @cindex managing frame filters
7617 Frame filters are Python based utilities to manage and decorate the
7618 output of frames. @xref{Frame Filter API}, for further information.
7620 Managing frame filters is performed by several commands available
7621 within @value{GDBN}, detailed here.
7624 @kindex info frame-filter
7625 @item info frame-filter
7626 Print a list of installed frame filters from all dictionaries, showing
7627 their name, priority and enabled status.
7629 @kindex disable frame-filter
7630 @anchor{disable frame-filter all}
7631 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7632 Disable a frame filter in the dictionary matching
7633 @var{filter-dictionary} and @var{filter-name}. The
7634 @var{filter-dictionary} may be @code{all}, @code{global},
7635 @code{progspace}, or the name of the object file where the frame filter
7636 dictionary resides. When @code{all} is specified, all frame filters
7637 across all dictionaries are disabled. The @var{filter-name} is the name
7638 of the frame filter and is used when @code{all} is not the option for
7639 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7640 may be enabled again later.
7642 @kindex enable frame-filter
7643 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7644 Enable a frame filter in the dictionary matching
7645 @var{filter-dictionary} and @var{filter-name}. The
7646 @var{filter-dictionary} may be @code{all}, @code{global},
7647 @code{progspace} or the name of the object file where the frame filter
7648 dictionary resides. When @code{all} is specified, all frame filters across
7649 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7650 filter and is used when @code{all} is not the option for
7651 @var{filter-dictionary}.
7656 (gdb) info frame-filter
7658 global frame-filters:
7659 Priority Enabled Name
7660 1000 No PrimaryFunctionFilter
7663 progspace /build/test frame-filters:
7664 Priority Enabled Name
7665 100 Yes ProgspaceFilter
7667 objfile /build/test frame-filters:
7668 Priority Enabled Name
7669 999 Yes BuildProgra Filter
7671 (gdb) disable frame-filter /build/test BuildProgramFilter
7672 (gdb) info frame-filter
7674 global frame-filters:
7675 Priority Enabled Name
7676 1000 No PrimaryFunctionFilter
7679 progspace /build/test frame-filters:
7680 Priority Enabled Name
7681 100 Yes ProgspaceFilter
7683 objfile /build/test frame-filters:
7684 Priority Enabled Name
7685 999 No BuildProgramFilter
7687 (gdb) enable frame-filter global PrimaryFunctionFilter
7688 (gdb) info frame-filter
7690 global frame-filters:
7691 Priority Enabled Name
7692 1000 Yes PrimaryFunctionFilter
7695 progspace /build/test frame-filters:
7696 Priority Enabled Name
7697 100 Yes ProgspaceFilter
7699 objfile /build/test frame-filters:
7700 Priority Enabled Name
7701 999 No BuildProgramFilter
7704 @kindex set frame-filter priority
7705 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7706 Set the @var{priority} of a frame filter in the dictionary matching
7707 @var{filter-dictionary}, and the frame filter name matching
7708 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7709 @code{progspace} or the name of the object file where the frame filter
7710 dictionary resides. The @var{priority} is an integer.
7712 @kindex show frame-filter priority
7713 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7714 Show the @var{priority} of a frame filter in the dictionary matching
7715 @var{filter-dictionary}, and the frame filter name matching
7716 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7717 @code{progspace} or the name of the object file where the frame filter
7723 (gdb) info frame-filter
7725 global frame-filters:
7726 Priority Enabled Name
7727 1000 Yes PrimaryFunctionFilter
7730 progspace /build/test frame-filters:
7731 Priority Enabled Name
7732 100 Yes ProgspaceFilter
7734 objfile /build/test frame-filters:
7735 Priority Enabled Name
7736 999 No BuildProgramFilter
7738 (gdb) set frame-filter priority global Reverse 50
7739 (gdb) info frame-filter
7741 global frame-filters:
7742 Priority Enabled Name
7743 1000 Yes PrimaryFunctionFilter
7746 progspace /build/test frame-filters:
7747 Priority Enabled Name
7748 100 Yes ProgspaceFilter
7750 objfile /build/test frame-filters:
7751 Priority Enabled Name
7752 999 No BuildProgramFilter
7757 @chapter Examining Source Files
7759 @value{GDBN} can print parts of your program's source, since the debugging
7760 information recorded in the program tells @value{GDBN} what source files were
7761 used to build it. When your program stops, @value{GDBN} spontaneously prints
7762 the line where it stopped. Likewise, when you select a stack frame
7763 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7764 execution in that frame has stopped. You can print other portions of
7765 source files by explicit command.
7767 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7768 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7769 @value{GDBN} under @sc{gnu} Emacs}.
7772 * List:: Printing source lines
7773 * Specify Location:: How to specify code locations
7774 * Edit:: Editing source files
7775 * Search:: Searching source files
7776 * Source Path:: Specifying source directories
7777 * Machine Code:: Source and machine code
7781 @section Printing Source Lines
7784 @kindex l @r{(@code{list})}
7785 To print lines from a source file, use the @code{list} command
7786 (abbreviated @code{l}). By default, ten lines are printed.
7787 There are several ways to specify what part of the file you want to
7788 print; see @ref{Specify Location}, for the full list.
7790 Here are the forms of the @code{list} command most commonly used:
7793 @item list @var{linenum}
7794 Print lines centered around line number @var{linenum} in the
7795 current source file.
7797 @item list @var{function}
7798 Print lines centered around the beginning of function
7802 Print more lines. If the last lines printed were printed with a
7803 @code{list} command, this prints lines following the last lines
7804 printed; however, if the last line printed was a solitary line printed
7805 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7806 Stack}), this prints lines centered around that line.
7809 Print lines just before the lines last printed.
7812 @cindex @code{list}, how many lines to display
7813 By default, @value{GDBN} prints ten source lines with any of these forms of
7814 the @code{list} command. You can change this using @code{set listsize}:
7817 @kindex set listsize
7818 @item set listsize @var{count}
7819 @itemx set listsize unlimited
7820 Make the @code{list} command display @var{count} source lines (unless
7821 the @code{list} argument explicitly specifies some other number).
7822 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7824 @kindex show listsize
7826 Display the number of lines that @code{list} prints.
7829 Repeating a @code{list} command with @key{RET} discards the argument,
7830 so it is equivalent to typing just @code{list}. This is more useful
7831 than listing the same lines again. An exception is made for an
7832 argument of @samp{-}; that argument is preserved in repetition so that
7833 each repetition moves up in the source file.
7835 In general, the @code{list} command expects you to supply zero, one or two
7836 @dfn{locations}. Locations specify source lines; there are several ways
7837 of writing them (@pxref{Specify Location}), but the effect is always
7838 to specify some source line.
7840 Here is a complete description of the possible arguments for @code{list}:
7843 @item list @var{location}
7844 Print lines centered around the line specified by @var{location}.
7846 @item list @var{first},@var{last}
7847 Print lines from @var{first} to @var{last}. Both arguments are
7848 locations. When a @code{list} command has two locations, and the
7849 source file of the second location is omitted, this refers to
7850 the same source file as the first location.
7852 @item list ,@var{last}
7853 Print lines ending with @var{last}.
7855 @item list @var{first},
7856 Print lines starting with @var{first}.
7859 Print lines just after the lines last printed.
7862 Print lines just before the lines last printed.
7865 As described in the preceding table.
7868 @node Specify Location
7869 @section Specifying a Location
7870 @cindex specifying location
7872 @cindex source location
7875 * Linespec Locations:: Linespec locations
7876 * Explicit Locations:: Explicit locations
7877 * Address Locations:: Address locations
7880 Several @value{GDBN} commands accept arguments that specify a location
7881 of your program's code. Since @value{GDBN} is a source-level
7882 debugger, a location usually specifies some line in the source code.
7883 Locations may be specified using three different formats:
7884 linespec locations, explicit locations, or address locations.
7886 @node Linespec Locations
7887 @subsection Linespec Locations
7888 @cindex linespec locations
7890 A @dfn{linespec} is a colon-separated list of source location parameters such
7891 as file name, function name, etc. Here are all the different ways of
7892 specifying a linespec:
7896 Specifies the line number @var{linenum} of the current source file.
7899 @itemx +@var{offset}
7900 Specifies the line @var{offset} lines before or after the @dfn{current
7901 line}. For the @code{list} command, the current line is the last one
7902 printed; for the breakpoint commands, this is the line at which
7903 execution stopped in the currently selected @dfn{stack frame}
7904 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7905 used as the second of the two linespecs in a @code{list} command,
7906 this specifies the line @var{offset} lines up or down from the first
7909 @item @var{filename}:@var{linenum}
7910 Specifies the line @var{linenum} in the source file @var{filename}.
7911 If @var{filename} is a relative file name, then it will match any
7912 source file name with the same trailing components. For example, if
7913 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7914 name of @file{/build/trunk/gcc/expr.c}, but not
7915 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7917 @item @var{function}
7918 Specifies the line that begins the body of the function @var{function}.
7919 For example, in C, this is the line with the open brace.
7921 By default, in C@t{++} and Ada, @var{function} is interpreted as
7922 specifying all functions named @var{function} in all scopes. For
7923 C@t{++}, this means in all namespaces and classes. For Ada, this
7924 means in all packages.
7926 For example, assuming a program with C@t{++} symbols named
7927 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
7928 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
7930 Commands that accept a linespec let you override this with the
7931 @code{-qualified} option. For example, @w{@kbd{break -qualified
7932 func}} sets a breakpoint on a free-function named @code{func} ignoring
7933 any C@t{++} class methods and namespace functions called @code{func}.
7935 @xref{Explicit Locations}.
7937 @item @var{function}:@var{label}
7938 Specifies the line where @var{label} appears in @var{function}.
7940 @item @var{filename}:@var{function}
7941 Specifies the line that begins the body of the function @var{function}
7942 in the file @var{filename}. You only need the file name with a
7943 function name to avoid ambiguity when there are identically named
7944 functions in different source files.
7947 Specifies the line at which the label named @var{label} appears
7948 in the function corresponding to the currently selected stack frame.
7949 If there is no current selected stack frame (for instance, if the inferior
7950 is not running), then @value{GDBN} will not search for a label.
7952 @cindex breakpoint at static probe point
7953 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7954 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7955 applications to embed static probes. @xref{Static Probe Points}, for more
7956 information on finding and using static probes. This form of linespec
7957 specifies the location of such a static probe.
7959 If @var{objfile} is given, only probes coming from that shared library
7960 or executable matching @var{objfile} as a regular expression are considered.
7961 If @var{provider} is given, then only probes from that provider are considered.
7962 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7963 each one of those probes.
7966 @node Explicit Locations
7967 @subsection Explicit Locations
7968 @cindex explicit locations
7970 @dfn{Explicit locations} allow the user to directly specify the source
7971 location's parameters using option-value pairs.
7973 Explicit locations are useful when several functions, labels, or
7974 file names have the same name (base name for files) in the program's
7975 sources. In these cases, explicit locations point to the source
7976 line you meant more accurately and unambiguously. Also, using
7977 explicit locations might be faster in large programs.
7979 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7980 defined in the file named @file{foo} or the label @code{bar} in a function
7981 named @code{foo}. @value{GDBN} must search either the file system or
7982 the symbol table to know.
7984 The list of valid explicit location options is summarized in the
7988 @item -source @var{filename}
7989 The value specifies the source file name. To differentiate between
7990 files with the same base name, prepend as many directories as is necessary
7991 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7992 @value{GDBN} will use the first file it finds with the given base
7993 name. This option requires the use of either @code{-function} or @code{-line}.
7995 @item -function @var{function}
7996 The value specifies the name of a function. Operations
7997 on function locations unmodified by other options (such as @code{-label}
7998 or @code{-line}) refer to the line that begins the body of the function.
7999 In C, for example, this is the line with the open brace.
8001 By default, in C@t{++} and Ada, @var{function} is interpreted as
8002 specifying all functions named @var{function} in all scopes. For
8003 C@t{++}, this means in all namespaces and classes. For Ada, this
8004 means in all packages.
8006 For example, assuming a program with C@t{++} symbols named
8007 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8008 -function func}} and @w{@kbd{break -function B::func}} set a
8009 breakpoint on both symbols.
8011 You can use the @kbd{-qualified} flag to override this (see below).
8015 This flag makes @value{GDBN} interpret a function name specified with
8016 @kbd{-function} as a complete fully-qualified name.
8018 For example, assuming a C@t{++} program with symbols named
8019 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8020 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8022 (Note: the @kbd{-qualified} option can precede a linespec as well
8023 (@pxref{Linespec Locations}), so the particular example above could be
8024 simplified as @w{@kbd{break -qualified B::func}}.)
8026 @item -label @var{label}
8027 The value specifies the name of a label. When the function
8028 name is not specified, the label is searched in the function of the currently
8029 selected stack frame.
8031 @item -line @var{number}
8032 The value specifies a line offset for the location. The offset may either
8033 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8034 the command. When specified without any other options, the line offset is
8035 relative to the current line.
8038 Explicit location options may be abbreviated by omitting any non-unique
8039 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8041 @node Address Locations
8042 @subsection Address Locations
8043 @cindex address locations
8045 @dfn{Address locations} indicate a specific program address. They have
8046 the generalized form *@var{address}.
8048 For line-oriented commands, such as @code{list} and @code{edit}, this
8049 specifies a source line that contains @var{address}. For @code{break} and
8050 other breakpoint-oriented commands, this can be used to set breakpoints in
8051 parts of your program which do not have debugging information or
8054 Here @var{address} may be any expression valid in the current working
8055 language (@pxref{Languages, working language}) that specifies a code
8056 address. In addition, as a convenience, @value{GDBN} extends the
8057 semantics of expressions used in locations to cover several situations
8058 that frequently occur during debugging. Here are the various forms
8062 @item @var{expression}
8063 Any expression valid in the current working language.
8065 @item @var{funcaddr}
8066 An address of a function or procedure derived from its name. In C,
8067 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8068 simply the function's name @var{function} (and actually a special case
8069 of a valid expression). In Pascal and Modula-2, this is
8070 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8071 (although the Pascal form also works).
8073 This form specifies the address of the function's first instruction,
8074 before the stack frame and arguments have been set up.
8076 @item '@var{filename}':@var{funcaddr}
8077 Like @var{funcaddr} above, but also specifies the name of the source
8078 file explicitly. This is useful if the name of the function does not
8079 specify the function unambiguously, e.g., if there are several
8080 functions with identical names in different source files.
8084 @section Editing Source Files
8085 @cindex editing source files
8088 @kindex e @r{(@code{edit})}
8089 To edit the lines in a source file, use the @code{edit} command.
8090 The editing program of your choice
8091 is invoked with the current line set to
8092 the active line in the program.
8093 Alternatively, there are several ways to specify what part of the file you
8094 want to print if you want to see other parts of the program:
8097 @item edit @var{location}
8098 Edit the source file specified by @code{location}. Editing starts at
8099 that @var{location}, e.g., at the specified source line of the
8100 specified file. @xref{Specify Location}, for all the possible forms
8101 of the @var{location} argument; here are the forms of the @code{edit}
8102 command most commonly used:
8105 @item edit @var{number}
8106 Edit the current source file with @var{number} as the active line number.
8108 @item edit @var{function}
8109 Edit the file containing @var{function} at the beginning of its definition.
8114 @subsection Choosing your Editor
8115 You can customize @value{GDBN} to use any editor you want
8117 The only restriction is that your editor (say @code{ex}), recognizes the
8118 following command-line syntax:
8120 ex +@var{number} file
8122 The optional numeric value +@var{number} specifies the number of the line in
8123 the file where to start editing.}.
8124 By default, it is @file{@value{EDITOR}}, but you can change this
8125 by setting the environment variable @code{EDITOR} before using
8126 @value{GDBN}. For example, to configure @value{GDBN} to use the
8127 @code{vi} editor, you could use these commands with the @code{sh} shell:
8133 or in the @code{csh} shell,
8135 setenv EDITOR /usr/bin/vi
8140 @section Searching Source Files
8141 @cindex searching source files
8143 There are two commands for searching through the current source file for a
8148 @kindex forward-search
8149 @kindex fo @r{(@code{forward-search})}
8150 @item forward-search @var{regexp}
8151 @itemx search @var{regexp}
8152 The command @samp{forward-search @var{regexp}} checks each line,
8153 starting with the one following the last line listed, for a match for
8154 @var{regexp}. It lists the line that is found. You can use the
8155 synonym @samp{search @var{regexp}} or abbreviate the command name as
8158 @kindex reverse-search
8159 @item reverse-search @var{regexp}
8160 The command @samp{reverse-search @var{regexp}} checks each line, starting
8161 with the one before the last line listed and going backward, for a match
8162 for @var{regexp}. It lists the line that is found. You can abbreviate
8163 this command as @code{rev}.
8167 @section Specifying Source Directories
8170 @cindex directories for source files
8171 Executable programs sometimes do not record the directories of the source
8172 files from which they were compiled, just the names. Even when they do,
8173 the directories could be moved between the compilation and your debugging
8174 session. @value{GDBN} has a list of directories to search for source files;
8175 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8176 it tries all the directories in the list, in the order they are present
8177 in the list, until it finds a file with the desired name.
8179 For example, suppose an executable references the file
8180 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8181 @file{/mnt/cross}. The file is first looked up literally; if this
8182 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8183 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8184 message is printed. @value{GDBN} does not look up the parts of the
8185 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8186 Likewise, the subdirectories of the source path are not searched: if
8187 the source path is @file{/mnt/cross}, and the binary refers to
8188 @file{foo.c}, @value{GDBN} would not find it under
8189 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8191 Plain file names, relative file names with leading directories, file
8192 names containing dots, etc.@: are all treated as described above; for
8193 instance, if the source path is @file{/mnt/cross}, and the source file
8194 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8195 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8196 that---@file{/mnt/cross/foo.c}.
8198 Note that the executable search path is @emph{not} used to locate the
8201 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8202 any information it has cached about where source files are found and where
8203 each line is in the file.
8207 When you start @value{GDBN}, its source path includes only @samp{cdir}
8208 and @samp{cwd}, in that order.
8209 To add other directories, use the @code{directory} command.
8211 The search path is used to find both program source files and @value{GDBN}
8212 script files (read using the @samp{-command} option and @samp{source} command).
8214 In addition to the source path, @value{GDBN} provides a set of commands
8215 that manage a list of source path substitution rules. A @dfn{substitution
8216 rule} specifies how to rewrite source directories stored in the program's
8217 debug information in case the sources were moved to a different
8218 directory between compilation and debugging. A rule is made of
8219 two strings, the first specifying what needs to be rewritten in
8220 the path, and the second specifying how it should be rewritten.
8221 In @ref{set substitute-path}, we name these two parts @var{from} and
8222 @var{to} respectively. @value{GDBN} does a simple string replacement
8223 of @var{from} with @var{to} at the start of the directory part of the
8224 source file name, and uses that result instead of the original file
8225 name to look up the sources.
8227 Using the previous example, suppose the @file{foo-1.0} tree has been
8228 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8229 @value{GDBN} to replace @file{/usr/src} in all source path names with
8230 @file{/mnt/cross}. The first lookup will then be
8231 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8232 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8233 substitution rule, use the @code{set substitute-path} command
8234 (@pxref{set substitute-path}).
8236 To avoid unexpected substitution results, a rule is applied only if the
8237 @var{from} part of the directory name ends at a directory separator.
8238 For instance, a rule substituting @file{/usr/source} into
8239 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8240 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8241 is applied only at the beginning of the directory name, this rule will
8242 not be applied to @file{/root/usr/source/baz.c} either.
8244 In many cases, you can achieve the same result using the @code{directory}
8245 command. However, @code{set substitute-path} can be more efficient in
8246 the case where the sources are organized in a complex tree with multiple
8247 subdirectories. With the @code{directory} command, you need to add each
8248 subdirectory of your project. If you moved the entire tree while
8249 preserving its internal organization, then @code{set substitute-path}
8250 allows you to direct the debugger to all the sources with one single
8253 @code{set substitute-path} is also more than just a shortcut command.
8254 The source path is only used if the file at the original location no
8255 longer exists. On the other hand, @code{set substitute-path} modifies
8256 the debugger behavior to look at the rewritten location instead. So, if
8257 for any reason a source file that is not relevant to your executable is
8258 located at the original location, a substitution rule is the only
8259 method available to point @value{GDBN} at the new location.
8261 @cindex @samp{--with-relocated-sources}
8262 @cindex default source path substitution
8263 You can configure a default source path substitution rule by
8264 configuring @value{GDBN} with the
8265 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8266 should be the name of a directory under @value{GDBN}'s configured
8267 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8268 directory names in debug information under @var{dir} will be adjusted
8269 automatically if the installed @value{GDBN} is moved to a new
8270 location. This is useful if @value{GDBN}, libraries or executables
8271 with debug information and corresponding source code are being moved
8275 @item directory @var{dirname} @dots{}
8276 @item dir @var{dirname} @dots{}
8277 Add directory @var{dirname} to the front of the source path. Several
8278 directory names may be given to this command, separated by @samp{:}
8279 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8280 part of absolute file names) or
8281 whitespace. You may specify a directory that is already in the source
8282 path; this moves it forward, so @value{GDBN} searches it sooner.
8286 @vindex $cdir@r{, convenience variable}
8287 @vindex $cwd@r{, convenience variable}
8288 @cindex compilation directory
8289 @cindex current directory
8290 @cindex working directory
8291 @cindex directory, current
8292 @cindex directory, compilation
8293 You can use the string @samp{$cdir} to refer to the compilation
8294 directory (if one is recorded), and @samp{$cwd} to refer to the current
8295 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8296 tracks the current working directory as it changes during your @value{GDBN}
8297 session, while the latter is immediately expanded to the current
8298 directory at the time you add an entry to the source path.
8301 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8303 @c RET-repeat for @code{directory} is explicitly disabled, but since
8304 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8306 @item set directories @var{path-list}
8307 @kindex set directories
8308 Set the source path to @var{path-list}.
8309 @samp{$cdir:$cwd} are added if missing.
8311 @item show directories
8312 @kindex show directories
8313 Print the source path: show which directories it contains.
8315 @anchor{set substitute-path}
8316 @item set substitute-path @var{from} @var{to}
8317 @kindex set substitute-path
8318 Define a source path substitution rule, and add it at the end of the
8319 current list of existing substitution rules. If a rule with the same
8320 @var{from} was already defined, then the old rule is also deleted.
8322 For example, if the file @file{/foo/bar/baz.c} was moved to
8323 @file{/mnt/cross/baz.c}, then the command
8326 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8330 will tell @value{GDBN} to replace @samp{/foo/bar} with
8331 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8332 @file{baz.c} even though it was moved.
8334 In the case when more than one substitution rule have been defined,
8335 the rules are evaluated one by one in the order where they have been
8336 defined. The first one matching, if any, is selected to perform
8339 For instance, if we had entered the following commands:
8342 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8343 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8347 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8348 @file{/mnt/include/defs.h} by using the first rule. However, it would
8349 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8350 @file{/mnt/src/lib/foo.c}.
8353 @item unset substitute-path [path]
8354 @kindex unset substitute-path
8355 If a path is specified, search the current list of substitution rules
8356 for a rule that would rewrite that path. Delete that rule if found.
8357 A warning is emitted by the debugger if no rule could be found.
8359 If no path is specified, then all substitution rules are deleted.
8361 @item show substitute-path [path]
8362 @kindex show substitute-path
8363 If a path is specified, then print the source path substitution rule
8364 which would rewrite that path, if any.
8366 If no path is specified, then print all existing source path substitution
8371 If your source path is cluttered with directories that are no longer of
8372 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8373 versions of source. You can correct the situation as follows:
8377 Use @code{directory} with no argument to reset the source path to its default value.
8380 Use @code{directory} with suitable arguments to reinstall the
8381 directories you want in the source path. You can add all the
8382 directories in one command.
8386 @section Source and Machine Code
8387 @cindex source line and its code address
8389 You can use the command @code{info line} to map source lines to program
8390 addresses (and vice versa), and the command @code{disassemble} to display
8391 a range of addresses as machine instructions. You can use the command
8392 @code{set disassemble-next-line} to set whether to disassemble next
8393 source line when execution stops. When run under @sc{gnu} Emacs
8394 mode, the @code{info line} command causes the arrow to point to the
8395 line specified. Also, @code{info line} prints addresses in symbolic form as
8400 @item info line @var{location}
8401 Print the starting and ending addresses of the compiled code for
8402 source line @var{location}. You can specify source lines in any of
8403 the ways documented in @ref{Specify Location}.
8406 For example, we can use @code{info line} to discover the location of
8407 the object code for the first line of function
8408 @code{m4_changequote}:
8410 @c FIXME: I think this example should also show the addresses in
8411 @c symbolic form, as they usually would be displayed.
8413 (@value{GDBP}) info line m4_changequote
8414 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8418 @cindex code address and its source line
8419 We can also inquire (using @code{*@var{addr}} as the form for
8420 @var{location}) what source line covers a particular address:
8422 (@value{GDBP}) info line *0x63ff
8423 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8426 @cindex @code{$_} and @code{info line}
8427 @cindex @code{x} command, default address
8428 @kindex x@r{(examine), and} info line
8429 After @code{info line}, the default address for the @code{x} command
8430 is changed to the starting address of the line, so that @samp{x/i} is
8431 sufficient to begin examining the machine code (@pxref{Memory,
8432 ,Examining Memory}). Also, this address is saved as the value of the
8433 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8438 @cindex assembly instructions
8439 @cindex instructions, assembly
8440 @cindex machine instructions
8441 @cindex listing machine instructions
8443 @itemx disassemble /m
8444 @itemx disassemble /s
8445 @itemx disassemble /r
8446 This specialized command dumps a range of memory as machine
8447 instructions. It can also print mixed source+disassembly by specifying
8448 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8449 as well as in symbolic form by specifying the @code{/r} modifier.
8450 The default memory range is the function surrounding the
8451 program counter of the selected frame. A single argument to this
8452 command is a program counter value; @value{GDBN} dumps the function
8453 surrounding this value. When two arguments are given, they should
8454 be separated by a comma, possibly surrounded by whitespace. The
8455 arguments specify a range of addresses to dump, in one of two forms:
8458 @item @var{start},@var{end}
8459 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8460 @item @var{start},+@var{length}
8461 the addresses from @var{start} (inclusive) to
8462 @code{@var{start}+@var{length}} (exclusive).
8466 When 2 arguments are specified, the name of the function is also
8467 printed (since there could be several functions in the given range).
8469 The argument(s) can be any expression yielding a numeric value, such as
8470 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8472 If the range of memory being disassembled contains current program counter,
8473 the instruction at that location is shown with a @code{=>} marker.
8476 The following example shows the disassembly of a range of addresses of
8477 HP PA-RISC 2.0 code:
8480 (@value{GDBP}) disas 0x32c4, 0x32e4
8481 Dump of assembler code from 0x32c4 to 0x32e4:
8482 0x32c4 <main+204>: addil 0,dp
8483 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8484 0x32cc <main+212>: ldil 0x3000,r31
8485 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8486 0x32d4 <main+220>: ldo 0(r31),rp
8487 0x32d8 <main+224>: addil -0x800,dp
8488 0x32dc <main+228>: ldo 0x588(r1),r26
8489 0x32e0 <main+232>: ldil 0x3000,r31
8490 End of assembler dump.
8493 Here is an example showing mixed source+assembly for Intel x86
8494 with @code{/m} or @code{/s}, when the program is stopped just after
8495 function prologue in a non-optimized function with no inline code.
8498 (@value{GDBP}) disas /m main
8499 Dump of assembler code for function main:
8501 0x08048330 <+0>: push %ebp
8502 0x08048331 <+1>: mov %esp,%ebp
8503 0x08048333 <+3>: sub $0x8,%esp
8504 0x08048336 <+6>: and $0xfffffff0,%esp
8505 0x08048339 <+9>: sub $0x10,%esp
8507 6 printf ("Hello.\n");
8508 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8509 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8513 0x08048348 <+24>: mov $0x0,%eax
8514 0x0804834d <+29>: leave
8515 0x0804834e <+30>: ret
8517 End of assembler dump.
8520 The @code{/m} option is deprecated as its output is not useful when
8521 there is either inlined code or re-ordered code.
8522 The @code{/s} option is the preferred choice.
8523 Here is an example for AMD x86-64 showing the difference between
8524 @code{/m} output and @code{/s} output.
8525 This example has one inline function defined in a header file,
8526 and the code is compiled with @samp{-O2} optimization.
8527 Note how the @code{/m} output is missing the disassembly of
8528 several instructions that are present in the @code{/s} output.
8558 (@value{GDBP}) disas /m main
8559 Dump of assembler code for function main:
8563 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8564 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8568 0x000000000040041d <+29>: xor %eax,%eax
8569 0x000000000040041f <+31>: retq
8570 0x0000000000400420 <+32>: add %eax,%eax
8571 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8573 End of assembler dump.
8574 (@value{GDBP}) disas /s main
8575 Dump of assembler code for function main:
8579 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8583 0x0000000000400406 <+6>: test %eax,%eax
8584 0x0000000000400408 <+8>: js 0x400420 <main+32>
8589 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8590 0x000000000040040d <+13>: test %eax,%eax
8591 0x000000000040040f <+15>: mov $0x1,%eax
8592 0x0000000000400414 <+20>: cmovne %edx,%eax
8596 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8600 0x000000000040041d <+29>: xor %eax,%eax
8601 0x000000000040041f <+31>: retq
8605 0x0000000000400420 <+32>: add %eax,%eax
8606 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8607 End of assembler dump.
8610 Here is another example showing raw instructions in hex for AMD x86-64,
8613 (gdb) disas /r 0x400281,+10
8614 Dump of assembler code from 0x400281 to 0x40028b:
8615 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8616 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8617 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8618 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8619 End of assembler dump.
8622 Addresses cannot be specified as a location (@pxref{Specify Location}).
8623 So, for example, if you want to disassemble function @code{bar}
8624 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8625 and not @samp{disassemble foo.c:bar}.
8627 Some architectures have more than one commonly-used set of instruction
8628 mnemonics or other syntax.
8630 For programs that were dynamically linked and use shared libraries,
8631 instructions that call functions or branch to locations in the shared
8632 libraries might show a seemingly bogus location---it's actually a
8633 location of the relocation table. On some architectures, @value{GDBN}
8634 might be able to resolve these to actual function names.
8637 @kindex set disassembler-options
8638 @cindex disassembler options
8639 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8640 This command controls the passing of target specific information to
8641 the disassembler. For a list of valid options, please refer to the
8642 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8643 manual and/or the output of @kbd{objdump --help}
8644 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8645 The default value is the empty string.
8647 If it is necessary to specify more than one disassembler option, then
8648 multiple options can be placed together into a comma separated list.
8649 Currently this command is only supported on targets ARM, PowerPC
8652 @kindex show disassembler-options
8653 @item show disassembler-options
8654 Show the current setting of the disassembler options.
8658 @kindex set disassembly-flavor
8659 @cindex Intel disassembly flavor
8660 @cindex AT&T disassembly flavor
8661 @item set disassembly-flavor @var{instruction-set}
8662 Select the instruction set to use when disassembling the
8663 program via the @code{disassemble} or @code{x/i} commands.
8665 Currently this command is only defined for the Intel x86 family. You
8666 can set @var{instruction-set} to either @code{intel} or @code{att}.
8667 The default is @code{att}, the AT&T flavor used by default by Unix
8668 assemblers for x86-based targets.
8670 @kindex show disassembly-flavor
8671 @item show disassembly-flavor
8672 Show the current setting of the disassembly flavor.
8676 @kindex set disassemble-next-line
8677 @kindex show disassemble-next-line
8678 @item set disassemble-next-line
8679 @itemx show disassemble-next-line
8680 Control whether or not @value{GDBN} will disassemble the next source
8681 line or instruction when execution stops. If ON, @value{GDBN} will
8682 display disassembly of the next source line when execution of the
8683 program being debugged stops. This is @emph{in addition} to
8684 displaying the source line itself, which @value{GDBN} always does if
8685 possible. If the next source line cannot be displayed for some reason
8686 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8687 info in the debug info), @value{GDBN} will display disassembly of the
8688 next @emph{instruction} instead of showing the next source line. If
8689 AUTO, @value{GDBN} will display disassembly of next instruction only
8690 if the source line cannot be displayed. This setting causes
8691 @value{GDBN} to display some feedback when you step through a function
8692 with no line info or whose source file is unavailable. The default is
8693 OFF, which means never display the disassembly of the next line or
8699 @chapter Examining Data
8701 @cindex printing data
8702 @cindex examining data
8705 The usual way to examine data in your program is with the @code{print}
8706 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8707 evaluates and prints the value of an expression of the language your
8708 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8709 Different Languages}). It may also print the expression using a
8710 Python-based pretty-printer (@pxref{Pretty Printing}).
8713 @item print @var{expr}
8714 @itemx print /@var{f} @var{expr}
8715 @var{expr} is an expression (in the source language). By default the
8716 value of @var{expr} is printed in a format appropriate to its data type;
8717 you can choose a different format by specifying @samp{/@var{f}}, where
8718 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8722 @itemx print /@var{f}
8723 @cindex reprint the last value
8724 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8725 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8726 conveniently inspect the same value in an alternative format.
8729 A more low-level way of examining data is with the @code{x} command.
8730 It examines data in memory at a specified address and prints it in a
8731 specified format. @xref{Memory, ,Examining Memory}.
8733 If you are interested in information about types, or about how the
8734 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8735 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8738 @cindex exploring hierarchical data structures
8740 Another way of examining values of expressions and type information is
8741 through the Python extension command @code{explore} (available only if
8742 the @value{GDBN} build is configured with @code{--with-python}). It
8743 offers an interactive way to start at the highest level (or, the most
8744 abstract level) of the data type of an expression (or, the data type
8745 itself) and explore all the way down to leaf scalar values/fields
8746 embedded in the higher level data types.
8749 @item explore @var{arg}
8750 @var{arg} is either an expression (in the source language), or a type
8751 visible in the current context of the program being debugged.
8754 The working of the @code{explore} command can be illustrated with an
8755 example. If a data type @code{struct ComplexStruct} is defined in your
8765 struct ComplexStruct
8767 struct SimpleStruct *ss_p;
8773 followed by variable declarations as
8776 struct SimpleStruct ss = @{ 10, 1.11 @};
8777 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8781 then, the value of the variable @code{cs} can be explored using the
8782 @code{explore} command as follows.
8786 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8787 the following fields:
8789 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8790 arr = <Enter 1 to explore this field of type `int [10]'>
8792 Enter the field number of choice:
8796 Since the fields of @code{cs} are not scalar values, you are being
8797 prompted to chose the field you want to explore. Let's say you choose
8798 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8799 pointer, you will be asked if it is pointing to a single value. From
8800 the declaration of @code{cs} above, it is indeed pointing to a single
8801 value, hence you enter @code{y}. If you enter @code{n}, then you will
8802 be asked if it were pointing to an array of values, in which case this
8803 field will be explored as if it were an array.
8806 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8807 Continue exploring it as a pointer to a single value [y/n]: y
8808 The value of `*(cs.ss_p)' is a struct/class of type `struct
8809 SimpleStruct' with the following fields:
8811 i = 10 .. (Value of type `int')
8812 d = 1.1100000000000001 .. (Value of type `double')
8814 Press enter to return to parent value:
8818 If the field @code{arr} of @code{cs} was chosen for exploration by
8819 entering @code{1} earlier, then since it is as array, you will be
8820 prompted to enter the index of the element in the array that you want
8824 `cs.arr' is an array of `int'.
8825 Enter the index of the element you want to explore in `cs.arr': 5
8827 `(cs.arr)[5]' is a scalar value of type `int'.
8831 Press enter to return to parent value:
8834 In general, at any stage of exploration, you can go deeper towards the
8835 leaf values by responding to the prompts appropriately, or hit the
8836 return key to return to the enclosing data structure (the @i{higher}
8837 level data structure).
8839 Similar to exploring values, you can use the @code{explore} command to
8840 explore types. Instead of specifying a value (which is typically a
8841 variable name or an expression valid in the current context of the
8842 program being debugged), you specify a type name. If you consider the
8843 same example as above, your can explore the type
8844 @code{struct ComplexStruct} by passing the argument
8845 @code{struct ComplexStruct} to the @code{explore} command.
8848 (gdb) explore struct ComplexStruct
8852 By responding to the prompts appropriately in the subsequent interactive
8853 session, you can explore the type @code{struct ComplexStruct} in a
8854 manner similar to how the value @code{cs} was explored in the above
8857 The @code{explore} command also has two sub-commands,
8858 @code{explore value} and @code{explore type}. The former sub-command is
8859 a way to explicitly specify that value exploration of the argument is
8860 being invoked, while the latter is a way to explicitly specify that type
8861 exploration of the argument is being invoked.
8864 @item explore value @var{expr}
8865 @cindex explore value
8866 This sub-command of @code{explore} explores the value of the
8867 expression @var{expr} (if @var{expr} is an expression valid in the
8868 current context of the program being debugged). The behavior of this
8869 command is identical to that of the behavior of the @code{explore}
8870 command being passed the argument @var{expr}.
8872 @item explore type @var{arg}
8873 @cindex explore type
8874 This sub-command of @code{explore} explores the type of @var{arg} (if
8875 @var{arg} is a type visible in the current context of program being
8876 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8877 is an expression valid in the current context of the program being
8878 debugged). If @var{arg} is a type, then the behavior of this command is
8879 identical to that of the @code{explore} command being passed the
8880 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8881 this command will be identical to that of the @code{explore} command
8882 being passed the type of @var{arg} as the argument.
8886 * Expressions:: Expressions
8887 * Ambiguous Expressions:: Ambiguous Expressions
8888 * Variables:: Program variables
8889 * Arrays:: Artificial arrays
8890 * Output Formats:: Output formats
8891 * Memory:: Examining memory
8892 * Auto Display:: Automatic display
8893 * Print Settings:: Print settings
8894 * Pretty Printing:: Python pretty printing
8895 * Value History:: Value history
8896 * Convenience Vars:: Convenience variables
8897 * Convenience Funs:: Convenience functions
8898 * Registers:: Registers
8899 * Floating Point Hardware:: Floating point hardware
8900 * Vector Unit:: Vector Unit
8901 * OS Information:: Auxiliary data provided by operating system
8902 * Memory Region Attributes:: Memory region attributes
8903 * Dump/Restore Files:: Copy between memory and a file
8904 * Core File Generation:: Cause a program dump its core
8905 * Character Sets:: Debugging programs that use a different
8906 character set than GDB does
8907 * Caching Target Data:: Data caching for targets
8908 * Searching Memory:: Searching memory for a sequence of bytes
8909 * Value Sizes:: Managing memory allocated for values
8913 @section Expressions
8916 @code{print} and many other @value{GDBN} commands accept an expression and
8917 compute its value. Any kind of constant, variable or operator defined
8918 by the programming language you are using is valid in an expression in
8919 @value{GDBN}. This includes conditional expressions, function calls,
8920 casts, and string constants. It also includes preprocessor macros, if
8921 you compiled your program to include this information; see
8924 @cindex arrays in expressions
8925 @value{GDBN} supports array constants in expressions input by
8926 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8927 you can use the command @code{print @{1, 2, 3@}} to create an array
8928 of three integers. If you pass an array to a function or assign it
8929 to a program variable, @value{GDBN} copies the array to memory that
8930 is @code{malloc}ed in the target program.
8932 Because C is so widespread, most of the expressions shown in examples in
8933 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8934 Languages}, for information on how to use expressions in other
8937 In this section, we discuss operators that you can use in @value{GDBN}
8938 expressions regardless of your programming language.
8940 @cindex casts, in expressions
8941 Casts are supported in all languages, not just in C, because it is so
8942 useful to cast a number into a pointer in order to examine a structure
8943 at that address in memory.
8944 @c FIXME: casts supported---Mod2 true?
8946 @value{GDBN} supports these operators, in addition to those common
8947 to programming languages:
8951 @samp{@@} is a binary operator for treating parts of memory as arrays.
8952 @xref{Arrays, ,Artificial Arrays}, for more information.
8955 @samp{::} allows you to specify a variable in terms of the file or
8956 function where it is defined. @xref{Variables, ,Program Variables}.
8958 @cindex @{@var{type}@}
8959 @cindex type casting memory
8960 @cindex memory, viewing as typed object
8961 @cindex casts, to view memory
8962 @item @{@var{type}@} @var{addr}
8963 Refers to an object of type @var{type} stored at address @var{addr} in
8964 memory. The address @var{addr} may be any expression whose value is
8965 an integer or pointer (but parentheses are required around binary
8966 operators, just as in a cast). This construct is allowed regardless
8967 of what kind of data is normally supposed to reside at @var{addr}.
8970 @node Ambiguous Expressions
8971 @section Ambiguous Expressions
8972 @cindex ambiguous expressions
8974 Expressions can sometimes contain some ambiguous elements. For instance,
8975 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8976 a single function name to be defined several times, for application in
8977 different contexts. This is called @dfn{overloading}. Another example
8978 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8979 templates and is typically instantiated several times, resulting in
8980 the same function name being defined in different contexts.
8982 In some cases and depending on the language, it is possible to adjust
8983 the expression to remove the ambiguity. For instance in C@t{++}, you
8984 can specify the signature of the function you want to break on, as in
8985 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8986 qualified name of your function often makes the expression unambiguous
8989 When an ambiguity that needs to be resolved is detected, the debugger
8990 has the capability to display a menu of numbered choices for each
8991 possibility, and then waits for the selection with the prompt @samp{>}.
8992 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8993 aborts the current command. If the command in which the expression was
8994 used allows more than one choice to be selected, the next option in the
8995 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8998 For example, the following session excerpt shows an attempt to set a
8999 breakpoint at the overloaded symbol @code{String::after}.
9000 We choose three particular definitions of that function name:
9002 @c FIXME! This is likely to change to show arg type lists, at least
9005 (@value{GDBP}) b String::after
9008 [2] file:String.cc; line number:867
9009 [3] file:String.cc; line number:860
9010 [4] file:String.cc; line number:875
9011 [5] file:String.cc; line number:853
9012 [6] file:String.cc; line number:846
9013 [7] file:String.cc; line number:735
9015 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9016 Breakpoint 2 at 0xb344: file String.cc, line 875.
9017 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9018 Multiple breakpoints were set.
9019 Use the "delete" command to delete unwanted
9026 @kindex set multiple-symbols
9027 @item set multiple-symbols @var{mode}
9028 @cindex multiple-symbols menu
9030 This option allows you to adjust the debugger behavior when an expression
9033 By default, @var{mode} is set to @code{all}. If the command with which
9034 the expression is used allows more than one choice, then @value{GDBN}
9035 automatically selects all possible choices. For instance, inserting
9036 a breakpoint on a function using an ambiguous name results in a breakpoint
9037 inserted on each possible match. However, if a unique choice must be made,
9038 then @value{GDBN} uses the menu to help you disambiguate the expression.
9039 For instance, printing the address of an overloaded function will result
9040 in the use of the menu.
9042 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9043 when an ambiguity is detected.
9045 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9046 an error due to the ambiguity and the command is aborted.
9048 @kindex show multiple-symbols
9049 @item show multiple-symbols
9050 Show the current value of the @code{multiple-symbols} setting.
9054 @section Program Variables
9056 The most common kind of expression to use is the name of a variable
9059 Variables in expressions are understood in the selected stack frame
9060 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9064 global (or file-static)
9071 visible according to the scope rules of the
9072 programming language from the point of execution in that frame
9075 @noindent This means that in the function
9090 you can examine and use the variable @code{a} whenever your program is
9091 executing within the function @code{foo}, but you can only use or
9092 examine the variable @code{b} while your program is executing inside
9093 the block where @code{b} is declared.
9095 @cindex variable name conflict
9096 There is an exception: you can refer to a variable or function whose
9097 scope is a single source file even if the current execution point is not
9098 in this file. But it is possible to have more than one such variable or
9099 function with the same name (in different source files). If that
9100 happens, referring to that name has unpredictable effects. If you wish,
9101 you can specify a static variable in a particular function or file by
9102 using the colon-colon (@code{::}) notation:
9104 @cindex colon-colon, context for variables/functions
9106 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9107 @cindex @code{::}, context for variables/functions
9110 @var{file}::@var{variable}
9111 @var{function}::@var{variable}
9115 Here @var{file} or @var{function} is the name of the context for the
9116 static @var{variable}. In the case of file names, you can use quotes to
9117 make sure @value{GDBN} parses the file name as a single word---for example,
9118 to print a global value of @code{x} defined in @file{f2.c}:
9121 (@value{GDBP}) p 'f2.c'::x
9124 The @code{::} notation is normally used for referring to
9125 static variables, since you typically disambiguate uses of local variables
9126 in functions by selecting the appropriate frame and using the
9127 simple name of the variable. However, you may also use this notation
9128 to refer to local variables in frames enclosing the selected frame:
9137 process (a); /* Stop here */
9148 For example, if there is a breakpoint at the commented line,
9149 here is what you might see
9150 when the program stops after executing the call @code{bar(0)}:
9155 (@value{GDBP}) p bar::a
9158 #2 0x080483d0 in foo (a=5) at foobar.c:12
9161 (@value{GDBP}) p bar::a
9165 @cindex C@t{++} scope resolution
9166 These uses of @samp{::} are very rarely in conflict with the very
9167 similar use of the same notation in C@t{++}. When they are in
9168 conflict, the C@t{++} meaning takes precedence; however, this can be
9169 overridden by quoting the file or function name with single quotes.
9171 For example, suppose the program is stopped in a method of a class
9172 that has a field named @code{includefile}, and there is also an
9173 include file named @file{includefile} that defines a variable,
9177 (@value{GDBP}) p includefile
9179 (@value{GDBP}) p includefile::some_global
9180 A syntax error in expression, near `'.
9181 (@value{GDBP}) p 'includefile'::some_global
9185 @cindex wrong values
9186 @cindex variable values, wrong
9187 @cindex function entry/exit, wrong values of variables
9188 @cindex optimized code, wrong values of variables
9190 @emph{Warning:} Occasionally, a local variable may appear to have the
9191 wrong value at certain points in a function---just after entry to a new
9192 scope, and just before exit.
9194 You may see this problem when you are stepping by machine instructions.
9195 This is because, on most machines, it takes more than one instruction to
9196 set up a stack frame (including local variable definitions); if you are
9197 stepping by machine instructions, variables may appear to have the wrong
9198 values until the stack frame is completely built. On exit, it usually
9199 also takes more than one machine instruction to destroy a stack frame;
9200 after you begin stepping through that group of instructions, local
9201 variable definitions may be gone.
9203 This may also happen when the compiler does significant optimizations.
9204 To be sure of always seeing accurate values, turn off all optimization
9207 @cindex ``No symbol "foo" in current context''
9208 Another possible effect of compiler optimizations is to optimize
9209 unused variables out of existence, or assign variables to registers (as
9210 opposed to memory addresses). Depending on the support for such cases
9211 offered by the debug info format used by the compiler, @value{GDBN}
9212 might not be able to display values for such local variables. If that
9213 happens, @value{GDBN} will print a message like this:
9216 No symbol "foo" in current context.
9219 To solve such problems, either recompile without optimizations, or use a
9220 different debug info format, if the compiler supports several such
9221 formats. @xref{Compilation}, for more information on choosing compiler
9222 options. @xref{C, ,C and C@t{++}}, for more information about debug
9223 info formats that are best suited to C@t{++} programs.
9225 If you ask to print an object whose contents are unknown to
9226 @value{GDBN}, e.g., because its data type is not completely specified
9227 by the debug information, @value{GDBN} will say @samp{<incomplete
9228 type>}. @xref{Symbols, incomplete type}, for more about this.
9230 @cindex no debug info variables
9231 If you try to examine or use the value of a (global) variable for
9232 which @value{GDBN} has no type information, e.g., because the program
9233 includes no debug information, @value{GDBN} displays an error message.
9234 @xref{Symbols, unknown type}, for more about unknown types. If you
9235 cast the variable to its declared type, @value{GDBN} gets the
9236 variable's value using the cast-to type as the variable's type. For
9237 example, in a C program:
9240 (@value{GDBP}) p var
9241 'var' has unknown type; cast it to its declared type
9242 (@value{GDBP}) p (float) var
9246 If you append @kbd{@@entry} string to a function parameter name you get its
9247 value at the time the function got called. If the value is not available an
9248 error message is printed. Entry values are available only with some compilers.
9249 Entry values are normally also printed at the function parameter list according
9250 to @ref{set print entry-values}.
9253 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9259 (gdb) print i@@entry
9263 Strings are identified as arrays of @code{char} values without specified
9264 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9265 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9266 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9267 defines literal string type @code{"char"} as @code{char} without a sign.
9272 signed char var1[] = "A";
9275 You get during debugging
9280 $2 = @{65 'A', 0 '\0'@}
9284 @section Artificial Arrays
9286 @cindex artificial array
9288 @kindex @@@r{, referencing memory as an array}
9289 It is often useful to print out several successive objects of the
9290 same type in memory; a section of an array, or an array of
9291 dynamically determined size for which only a pointer exists in the
9294 You can do this by referring to a contiguous span of memory as an
9295 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9296 operand of @samp{@@} should be the first element of the desired array
9297 and be an individual object. The right operand should be the desired length
9298 of the array. The result is an array value whose elements are all of
9299 the type of the left argument. The first element is actually the left
9300 argument; the second element comes from bytes of memory immediately
9301 following those that hold the first element, and so on. Here is an
9302 example. If a program says
9305 int *array = (int *) malloc (len * sizeof (int));
9309 you can print the contents of @code{array} with
9315 The left operand of @samp{@@} must reside in memory. Array values made
9316 with @samp{@@} in this way behave just like other arrays in terms of
9317 subscripting, and are coerced to pointers when used in expressions.
9318 Artificial arrays most often appear in expressions via the value history
9319 (@pxref{Value History, ,Value History}), after printing one out.
9321 Another way to create an artificial array is to use a cast.
9322 This re-interprets a value as if it were an array.
9323 The value need not be in memory:
9325 (@value{GDBP}) p/x (short[2])0x12345678
9326 $1 = @{0x1234, 0x5678@}
9329 As a convenience, if you leave the array length out (as in
9330 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9331 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9333 (@value{GDBP}) p/x (short[])0x12345678
9334 $2 = @{0x1234, 0x5678@}
9337 Sometimes the artificial array mechanism is not quite enough; in
9338 moderately complex data structures, the elements of interest may not
9339 actually be adjacent---for example, if you are interested in the values
9340 of pointers in an array. One useful work-around in this situation is
9341 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9342 Variables}) as a counter in an expression that prints the first
9343 interesting value, and then repeat that expression via @key{RET}. For
9344 instance, suppose you have an array @code{dtab} of pointers to
9345 structures, and you are interested in the values of a field @code{fv}
9346 in each structure. Here is an example of what you might type:
9356 @node Output Formats
9357 @section Output Formats
9359 @cindex formatted output
9360 @cindex output formats
9361 By default, @value{GDBN} prints a value according to its data type. Sometimes
9362 this is not what you want. For example, you might want to print a number
9363 in hex, or a pointer in decimal. Or you might want to view data in memory
9364 at a certain address as a character string or as an instruction. To do
9365 these things, specify an @dfn{output format} when you print a value.
9367 The simplest use of output formats is to say how to print a value
9368 already computed. This is done by starting the arguments of the
9369 @code{print} command with a slash and a format letter. The format
9370 letters supported are:
9374 Regard the bits of the value as an integer, and print the integer in
9378 Print as integer in signed decimal.
9381 Print as integer in unsigned decimal.
9384 Print as integer in octal.
9387 Print as integer in binary. The letter @samp{t} stands for ``two''.
9388 @footnote{@samp{b} cannot be used because these format letters are also
9389 used with the @code{x} command, where @samp{b} stands for ``byte'';
9390 see @ref{Memory,,Examining Memory}.}
9393 @cindex unknown address, locating
9394 @cindex locate address
9395 Print as an address, both absolute in hexadecimal and as an offset from
9396 the nearest preceding symbol. You can use this format used to discover
9397 where (in what function) an unknown address is located:
9400 (@value{GDBP}) p/a 0x54320
9401 $3 = 0x54320 <_initialize_vx+396>
9405 The command @code{info symbol 0x54320} yields similar results.
9406 @xref{Symbols, info symbol}.
9409 Regard as an integer and print it as a character constant. This
9410 prints both the numerical value and its character representation. The
9411 character representation is replaced with the octal escape @samp{\nnn}
9412 for characters outside the 7-bit @sc{ascii} range.
9414 Without this format, @value{GDBN} displays @code{char},
9415 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9416 constants. Single-byte members of vectors are displayed as integer
9420 Regard the bits of the value as a floating point number and print
9421 using typical floating point syntax.
9424 @cindex printing strings
9425 @cindex printing byte arrays
9426 Regard as a string, if possible. With this format, pointers to single-byte
9427 data are displayed as null-terminated strings and arrays of single-byte data
9428 are displayed as fixed-length strings. Other values are displayed in their
9431 Without this format, @value{GDBN} displays pointers to and arrays of
9432 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9433 strings. Single-byte members of a vector are displayed as an integer
9437 Like @samp{x} formatting, the value is treated as an integer and
9438 printed as hexadecimal, but leading zeros are printed to pad the value
9439 to the size of the integer type.
9442 @cindex raw printing
9443 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9444 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9445 Printing}). This typically results in a higher-level display of the
9446 value's contents. The @samp{r} format bypasses any Python
9447 pretty-printer which might exist.
9450 For example, to print the program counter in hex (@pxref{Registers}), type
9457 Note that no space is required before the slash; this is because command
9458 names in @value{GDBN} cannot contain a slash.
9460 To reprint the last value in the value history with a different format,
9461 you can use the @code{print} command with just a format and no
9462 expression. For example, @samp{p/x} reprints the last value in hex.
9465 @section Examining Memory
9467 You can use the command @code{x} (for ``examine'') to examine memory in
9468 any of several formats, independently of your program's data types.
9470 @cindex examining memory
9472 @kindex x @r{(examine memory)}
9473 @item x/@var{nfu} @var{addr}
9476 Use the @code{x} command to examine memory.
9479 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9480 much memory to display and how to format it; @var{addr} is an
9481 expression giving the address where you want to start displaying memory.
9482 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9483 Several commands set convenient defaults for @var{addr}.
9486 @item @var{n}, the repeat count
9487 The repeat count is a decimal integer; the default is 1. It specifies
9488 how much memory (counting by units @var{u}) to display. If a negative
9489 number is specified, memory is examined backward from @var{addr}.
9490 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9493 @item @var{f}, the display format
9494 The display format is one of the formats used by @code{print}
9495 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9496 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9497 The default is @samp{x} (hexadecimal) initially. The default changes
9498 each time you use either @code{x} or @code{print}.
9500 @item @var{u}, the unit size
9501 The unit size is any of
9507 Halfwords (two bytes).
9509 Words (four bytes). This is the initial default.
9511 Giant words (eight bytes).
9514 Each time you specify a unit size with @code{x}, that size becomes the
9515 default unit the next time you use @code{x}. For the @samp{i} format,
9516 the unit size is ignored and is normally not written. For the @samp{s} format,
9517 the unit size defaults to @samp{b}, unless it is explicitly given.
9518 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9519 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9520 Note that the results depend on the programming language of the
9521 current compilation unit. If the language is C, the @samp{s}
9522 modifier will use the UTF-16 encoding while @samp{w} will use
9523 UTF-32. The encoding is set by the programming language and cannot
9526 @item @var{addr}, starting display address
9527 @var{addr} is the address where you want @value{GDBN} to begin displaying
9528 memory. The expression need not have a pointer value (though it may);
9529 it is always interpreted as an integer address of a byte of memory.
9530 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9531 @var{addr} is usually just after the last address examined---but several
9532 other commands also set the default address: @code{info breakpoints} (to
9533 the address of the last breakpoint listed), @code{info line} (to the
9534 starting address of a line), and @code{print} (if you use it to display
9535 a value from memory).
9538 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9539 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9540 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9541 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9542 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9544 You can also specify a negative repeat count to examine memory backward
9545 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9546 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9548 Since the letters indicating unit sizes are all distinct from the
9549 letters specifying output formats, you do not have to remember whether
9550 unit size or format comes first; either order works. The output
9551 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9552 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9554 Even though the unit size @var{u} is ignored for the formats @samp{s}
9555 and @samp{i}, you might still want to use a count @var{n}; for example,
9556 @samp{3i} specifies that you want to see three machine instructions,
9557 including any operands. For convenience, especially when used with
9558 the @code{display} command, the @samp{i} format also prints branch delay
9559 slot instructions, if any, beyond the count specified, which immediately
9560 follow the last instruction that is within the count. The command
9561 @code{disassemble} gives an alternative way of inspecting machine
9562 instructions; see @ref{Machine Code,,Source and Machine Code}.
9564 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9565 the command displays null-terminated strings or instructions before the given
9566 address as many as the absolute value of the given number. For the @samp{i}
9567 format, we use line number information in the debug info to accurately locate
9568 instruction boundaries while disassembling backward. If line info is not
9569 available, the command stops examining memory with an error message.
9571 All the defaults for the arguments to @code{x} are designed to make it
9572 easy to continue scanning memory with minimal specifications each time
9573 you use @code{x}. For example, after you have inspected three machine
9574 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9575 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9576 the repeat count @var{n} is used again; the other arguments default as
9577 for successive uses of @code{x}.
9579 When examining machine instructions, the instruction at current program
9580 counter is shown with a @code{=>} marker. For example:
9583 (@value{GDBP}) x/5i $pc-6
9584 0x804837f <main+11>: mov %esp,%ebp
9585 0x8048381 <main+13>: push %ecx
9586 0x8048382 <main+14>: sub $0x4,%esp
9587 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9588 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9591 @cindex @code{$_}, @code{$__}, and value history
9592 The addresses and contents printed by the @code{x} command are not saved
9593 in the value history because there is often too much of them and they
9594 would get in the way. Instead, @value{GDBN} makes these values available for
9595 subsequent use in expressions as values of the convenience variables
9596 @code{$_} and @code{$__}. After an @code{x} command, the last address
9597 examined is available for use in expressions in the convenience variable
9598 @code{$_}. The contents of that address, as examined, are available in
9599 the convenience variable @code{$__}.
9601 If the @code{x} command has a repeat count, the address and contents saved
9602 are from the last memory unit printed; this is not the same as the last
9603 address printed if several units were printed on the last line of output.
9605 @anchor{addressable memory unit}
9606 @cindex addressable memory unit
9607 Most targets have an addressable memory unit size of 8 bits. This means
9608 that to each memory address are associated 8 bits of data. Some
9609 targets, however, have other addressable memory unit sizes.
9610 Within @value{GDBN} and this document, the term
9611 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9612 when explicitly referring to a chunk of data of that size. The word
9613 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9614 the addressable memory unit size of the target. For most systems,
9615 addressable memory unit is a synonym of byte.
9617 @cindex remote memory comparison
9618 @cindex target memory comparison
9619 @cindex verify remote memory image
9620 @cindex verify target memory image
9621 When you are debugging a program running on a remote target machine
9622 (@pxref{Remote Debugging}), you may wish to verify the program's image
9623 in the remote machine's memory against the executable file you
9624 downloaded to the target. Or, on any target, you may want to check
9625 whether the program has corrupted its own read-only sections. The
9626 @code{compare-sections} command is provided for such situations.
9629 @kindex compare-sections
9630 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9631 Compare the data of a loadable section @var{section-name} in the
9632 executable file of the program being debugged with the same section in
9633 the target machine's memory, and report any mismatches. With no
9634 arguments, compares all loadable sections. With an argument of
9635 @code{-r}, compares all loadable read-only sections.
9637 Note: for remote targets, this command can be accelerated if the
9638 target supports computing the CRC checksum of a block of memory
9639 (@pxref{qCRC packet}).
9643 @section Automatic Display
9644 @cindex automatic display
9645 @cindex display of expressions
9647 If you find that you want to print the value of an expression frequently
9648 (to see how it changes), you might want to add it to the @dfn{automatic
9649 display list} so that @value{GDBN} prints its value each time your program stops.
9650 Each expression added to the list is given a number to identify it;
9651 to remove an expression from the list, you specify that number.
9652 The automatic display looks like this:
9656 3: bar[5] = (struct hack *) 0x3804
9660 This display shows item numbers, expressions and their current values. As with
9661 displays you request manually using @code{x} or @code{print}, you can
9662 specify the output format you prefer; in fact, @code{display} decides
9663 whether to use @code{print} or @code{x} depending your format
9664 specification---it uses @code{x} if you specify either the @samp{i}
9665 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9669 @item display @var{expr}
9670 Add the expression @var{expr} to the list of expressions to display
9671 each time your program stops. @xref{Expressions, ,Expressions}.
9673 @code{display} does not repeat if you press @key{RET} again after using it.
9675 @item display/@var{fmt} @var{expr}
9676 For @var{fmt} specifying only a display format and not a size or
9677 count, add the expression @var{expr} to the auto-display list but
9678 arrange to display it each time in the specified format @var{fmt}.
9679 @xref{Output Formats,,Output Formats}.
9681 @item display/@var{fmt} @var{addr}
9682 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9683 number of units, add the expression @var{addr} as a memory address to
9684 be examined each time your program stops. Examining means in effect
9685 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9688 For example, @samp{display/i $pc} can be helpful, to see the machine
9689 instruction about to be executed each time execution stops (@samp{$pc}
9690 is a common name for the program counter; @pxref{Registers, ,Registers}).
9693 @kindex delete display
9695 @item undisplay @var{dnums}@dots{}
9696 @itemx delete display @var{dnums}@dots{}
9697 Remove items from the list of expressions to display. Specify the
9698 numbers of the displays that you want affected with the command
9699 argument @var{dnums}. It can be a single display number, one of the
9700 numbers shown in the first field of the @samp{info display} display;
9701 or it could be a range of display numbers, as in @code{2-4}.
9703 @code{undisplay} does not repeat if you press @key{RET} after using it.
9704 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9706 @kindex disable display
9707 @item disable display @var{dnums}@dots{}
9708 Disable the display of item numbers @var{dnums}. A disabled display
9709 item is not printed automatically, but is not forgotten. It may be
9710 enabled again later. Specify the numbers of the displays that you
9711 want affected with the command argument @var{dnums}. It can be a
9712 single display number, one of the numbers shown in the first field of
9713 the @samp{info display} display; or it could be a range of display
9714 numbers, as in @code{2-4}.
9716 @kindex enable display
9717 @item enable display @var{dnums}@dots{}
9718 Enable display of item numbers @var{dnums}. It becomes effective once
9719 again in auto display of its expression, until you specify otherwise.
9720 Specify the numbers of the displays that you want affected with the
9721 command argument @var{dnums}. It can be a single display number, one
9722 of the numbers shown in the first field of the @samp{info display}
9723 display; or it could be a range of display numbers, as in @code{2-4}.
9726 Display the current values of the expressions on the list, just as is
9727 done when your program stops.
9729 @kindex info display
9731 Print the list of expressions previously set up to display
9732 automatically, each one with its item number, but without showing the
9733 values. This includes disabled expressions, which are marked as such.
9734 It also includes expressions which would not be displayed right now
9735 because they refer to automatic variables not currently available.
9738 @cindex display disabled out of scope
9739 If a display expression refers to local variables, then it does not make
9740 sense outside the lexical context for which it was set up. Such an
9741 expression is disabled when execution enters a context where one of its
9742 variables is not defined. For example, if you give the command
9743 @code{display last_char} while inside a function with an argument
9744 @code{last_char}, @value{GDBN} displays this argument while your program
9745 continues to stop inside that function. When it stops elsewhere---where
9746 there is no variable @code{last_char}---the display is disabled
9747 automatically. The next time your program stops where @code{last_char}
9748 is meaningful, you can enable the display expression once again.
9750 @node Print Settings
9751 @section Print Settings
9753 @cindex format options
9754 @cindex print settings
9755 @value{GDBN} provides the following ways to control how arrays, structures,
9756 and symbols are printed.
9759 These settings are useful for debugging programs in any language:
9763 @item set print address
9764 @itemx set print address on
9765 @cindex print/don't print memory addresses
9766 @value{GDBN} prints memory addresses showing the location of stack
9767 traces, structure values, pointer values, breakpoints, and so forth,
9768 even when it also displays the contents of those addresses. The default
9769 is @code{on}. For example, this is what a stack frame display looks like with
9770 @code{set print address on}:
9775 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9777 530 if (lquote != def_lquote)
9781 @item set print address off
9782 Do not print addresses when displaying their contents. For example,
9783 this is the same stack frame displayed with @code{set print address off}:
9787 (@value{GDBP}) set print addr off
9789 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9790 530 if (lquote != def_lquote)
9794 You can use @samp{set print address off} to eliminate all machine
9795 dependent displays from the @value{GDBN} interface. For example, with
9796 @code{print address off}, you should get the same text for backtraces on
9797 all machines---whether or not they involve pointer arguments.
9800 @item show print address
9801 Show whether or not addresses are to be printed.
9804 When @value{GDBN} prints a symbolic address, it normally prints the
9805 closest earlier symbol plus an offset. If that symbol does not uniquely
9806 identify the address (for example, it is a name whose scope is a single
9807 source file), you may need to clarify. One way to do this is with
9808 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9809 you can set @value{GDBN} to print the source file and line number when
9810 it prints a symbolic address:
9813 @item set print symbol-filename on
9814 @cindex source file and line of a symbol
9815 @cindex symbol, source file and line
9816 Tell @value{GDBN} to print the source file name and line number of a
9817 symbol in the symbolic form of an address.
9819 @item set print symbol-filename off
9820 Do not print source file name and line number of a symbol. This is the
9823 @item show print symbol-filename
9824 Show whether or not @value{GDBN} will print the source file name and
9825 line number of a symbol in the symbolic form of an address.
9828 Another situation where it is helpful to show symbol filenames and line
9829 numbers is when disassembling code; @value{GDBN} shows you the line
9830 number and source file that corresponds to each instruction.
9832 Also, you may wish to see the symbolic form only if the address being
9833 printed is reasonably close to the closest earlier symbol:
9836 @item set print max-symbolic-offset @var{max-offset}
9837 @itemx set print max-symbolic-offset unlimited
9838 @cindex maximum value for offset of closest symbol
9839 Tell @value{GDBN} to only display the symbolic form of an address if the
9840 offset between the closest earlier symbol and the address is less than
9841 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9842 to always print the symbolic form of an address if any symbol precedes
9843 it. Zero is equivalent to @code{unlimited}.
9845 @item show print max-symbolic-offset
9846 Ask how large the maximum offset is that @value{GDBN} prints in a
9850 @cindex wild pointer, interpreting
9851 @cindex pointer, finding referent
9852 If you have a pointer and you are not sure where it points, try
9853 @samp{set print symbol-filename on}. Then you can determine the name
9854 and source file location of the variable where it points, using
9855 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9856 For example, here @value{GDBN} shows that a variable @code{ptt} points
9857 at another variable @code{t}, defined in @file{hi2.c}:
9860 (@value{GDBP}) set print symbol-filename on
9861 (@value{GDBP}) p/a ptt
9862 $4 = 0xe008 <t in hi2.c>
9866 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9867 does not show the symbol name and filename of the referent, even with
9868 the appropriate @code{set print} options turned on.
9871 You can also enable @samp{/a}-like formatting all the time using
9872 @samp{set print symbol on}:
9875 @item set print symbol on
9876 Tell @value{GDBN} to print the symbol corresponding to an address, if
9879 @item set print symbol off
9880 Tell @value{GDBN} not to print the symbol corresponding to an
9881 address. In this mode, @value{GDBN} will still print the symbol
9882 corresponding to pointers to functions. This is the default.
9884 @item show print symbol
9885 Show whether @value{GDBN} will display the symbol corresponding to an
9889 Other settings control how different kinds of objects are printed:
9892 @item set print array
9893 @itemx set print array on
9894 @cindex pretty print arrays
9895 Pretty print arrays. This format is more convenient to read,
9896 but uses more space. The default is off.
9898 @item set print array off
9899 Return to compressed format for arrays.
9901 @item show print array
9902 Show whether compressed or pretty format is selected for displaying
9905 @cindex print array indexes
9906 @item set print array-indexes
9907 @itemx set print array-indexes on
9908 Print the index of each element when displaying arrays. May be more
9909 convenient to locate a given element in the array or quickly find the
9910 index of a given element in that printed array. The default is off.
9912 @item set print array-indexes off
9913 Stop printing element indexes when displaying arrays.
9915 @item show print array-indexes
9916 Show whether the index of each element is printed when displaying
9919 @item set print elements @var{number-of-elements}
9920 @itemx set print elements unlimited
9921 @cindex number of array elements to print
9922 @cindex limit on number of printed array elements
9923 Set a limit on how many elements of an array @value{GDBN} will print.
9924 If @value{GDBN} is printing a large array, it stops printing after it has
9925 printed the number of elements set by the @code{set print elements} command.
9926 This limit also applies to the display of strings.
9927 When @value{GDBN} starts, this limit is set to 200.
9928 Setting @var{number-of-elements} to @code{unlimited} or zero means
9929 that the number of elements to print is unlimited.
9931 @item show print elements
9932 Display the number of elements of a large array that @value{GDBN} will print.
9933 If the number is 0, then the printing is unlimited.
9935 @item set print frame-arguments @var{value}
9936 @kindex set print frame-arguments
9937 @cindex printing frame argument values
9938 @cindex print all frame argument values
9939 @cindex print frame argument values for scalars only
9940 @cindex do not print frame argument values
9941 This command allows to control how the values of arguments are printed
9942 when the debugger prints a frame (@pxref{Frames}). The possible
9947 The values of all arguments are printed.
9950 Print the value of an argument only if it is a scalar. The value of more
9951 complex arguments such as arrays, structures, unions, etc, is replaced
9952 by @code{@dots{}}. This is the default. Here is an example where
9953 only scalar arguments are shown:
9956 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9961 None of the argument values are printed. Instead, the value of each argument
9962 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9965 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9970 By default, only scalar arguments are printed. This command can be used
9971 to configure the debugger to print the value of all arguments, regardless
9972 of their type. However, it is often advantageous to not print the value
9973 of more complex parameters. For instance, it reduces the amount of
9974 information printed in each frame, making the backtrace more readable.
9975 Also, it improves performance when displaying Ada frames, because
9976 the computation of large arguments can sometimes be CPU-intensive,
9977 especially in large applications. Setting @code{print frame-arguments}
9978 to @code{scalars} (the default) or @code{none} avoids this computation,
9979 thus speeding up the display of each Ada frame.
9981 @item show print frame-arguments
9982 Show how the value of arguments should be displayed when printing a frame.
9984 @item set print raw frame-arguments on
9985 Print frame arguments in raw, non pretty-printed, form.
9987 @item set print raw frame-arguments off
9988 Print frame arguments in pretty-printed form, if there is a pretty-printer
9989 for the value (@pxref{Pretty Printing}),
9990 otherwise print the value in raw form.
9991 This is the default.
9993 @item show print raw frame-arguments
9994 Show whether to print frame arguments in raw form.
9996 @anchor{set print entry-values}
9997 @item set print entry-values @var{value}
9998 @kindex set print entry-values
9999 Set printing of frame argument values at function entry. In some cases
10000 @value{GDBN} can determine the value of function argument which was passed by
10001 the function caller, even if the value was modified inside the called function
10002 and therefore is different. With optimized code, the current value could be
10003 unavailable, but the entry value may still be known.
10005 The default value is @code{default} (see below for its description). Older
10006 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10007 this feature will behave in the @code{default} setting the same way as with the
10010 This functionality is currently supported only by DWARF 2 debugging format and
10011 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10012 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10015 The @var{value} parameter can be one of the following:
10019 Print only actual parameter values, never print values from function entry
10023 #0 different (val=6)
10024 #0 lost (val=<optimized out>)
10026 #0 invalid (val=<optimized out>)
10030 Print only parameter values from function entry point. The actual parameter
10031 values are never printed.
10033 #0 equal (val@@entry=5)
10034 #0 different (val@@entry=5)
10035 #0 lost (val@@entry=5)
10036 #0 born (val@@entry=<optimized out>)
10037 #0 invalid (val@@entry=<optimized out>)
10041 Print only parameter values from function entry point. If value from function
10042 entry point is not known while the actual value is known, print the actual
10043 value for such parameter.
10045 #0 equal (val@@entry=5)
10046 #0 different (val@@entry=5)
10047 #0 lost (val@@entry=5)
10049 #0 invalid (val@@entry=<optimized out>)
10053 Print actual parameter values. If actual parameter value is not known while
10054 value from function entry point is known, print the entry point value for such
10058 #0 different (val=6)
10059 #0 lost (val@@entry=5)
10061 #0 invalid (val=<optimized out>)
10065 Always print both the actual parameter value and its value from function entry
10066 point, even if values of one or both are not available due to compiler
10069 #0 equal (val=5, val@@entry=5)
10070 #0 different (val=6, val@@entry=5)
10071 #0 lost (val=<optimized out>, val@@entry=5)
10072 #0 born (val=10, val@@entry=<optimized out>)
10073 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10077 Print the actual parameter value if it is known and also its value from
10078 function entry point if it is known. If neither is known, print for the actual
10079 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10080 values are known and identical, print the shortened
10081 @code{param=param@@entry=VALUE} notation.
10083 #0 equal (val=val@@entry=5)
10084 #0 different (val=6, val@@entry=5)
10085 #0 lost (val@@entry=5)
10087 #0 invalid (val=<optimized out>)
10091 Always print the actual parameter value. Print also its value from function
10092 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10093 if both values are known and identical, print the shortened
10094 @code{param=param@@entry=VALUE} notation.
10096 #0 equal (val=val@@entry=5)
10097 #0 different (val=6, val@@entry=5)
10098 #0 lost (val=<optimized out>, val@@entry=5)
10100 #0 invalid (val=<optimized out>)
10104 For analysis messages on possible failures of frame argument values at function
10105 entry resolution see @ref{set debug entry-values}.
10107 @item show print entry-values
10108 Show the method being used for printing of frame argument values at function
10111 @item set print repeats @var{number-of-repeats}
10112 @itemx set print repeats unlimited
10113 @cindex repeated array elements
10114 Set the threshold for suppressing display of repeated array
10115 elements. When the number of consecutive identical elements of an
10116 array exceeds the threshold, @value{GDBN} prints the string
10117 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10118 identical repetitions, instead of displaying the identical elements
10119 themselves. Setting the threshold to @code{unlimited} or zero will
10120 cause all elements to be individually printed. The default threshold
10123 @item show print repeats
10124 Display the current threshold for printing repeated identical
10127 @item set print null-stop
10128 @cindex @sc{null} elements in arrays
10129 Cause @value{GDBN} to stop printing the characters of an array when the first
10130 @sc{null} is encountered. This is useful when large arrays actually
10131 contain only short strings.
10132 The default is off.
10134 @item show print null-stop
10135 Show whether @value{GDBN} stops printing an array on the first
10136 @sc{null} character.
10138 @item set print pretty on
10139 @cindex print structures in indented form
10140 @cindex indentation in structure display
10141 Cause @value{GDBN} to print structures in an indented format with one member
10142 per line, like this:
10157 @item set print pretty off
10158 Cause @value{GDBN} to print structures in a compact format, like this:
10162 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10163 meat = 0x54 "Pork"@}
10168 This is the default format.
10170 @item show print pretty
10171 Show which format @value{GDBN} is using to print structures.
10173 @item set print sevenbit-strings on
10174 @cindex eight-bit characters in strings
10175 @cindex octal escapes in strings
10176 Print using only seven-bit characters; if this option is set,
10177 @value{GDBN} displays any eight-bit characters (in strings or
10178 character values) using the notation @code{\}@var{nnn}. This setting is
10179 best if you are working in English (@sc{ascii}) and you use the
10180 high-order bit of characters as a marker or ``meta'' bit.
10182 @item set print sevenbit-strings off
10183 Print full eight-bit characters. This allows the use of more
10184 international character sets, and is the default.
10186 @item show print sevenbit-strings
10187 Show whether or not @value{GDBN} is printing only seven-bit characters.
10189 @item set print union on
10190 @cindex unions in structures, printing
10191 Tell @value{GDBN} to print unions which are contained in structures
10192 and other unions. This is the default setting.
10194 @item set print union off
10195 Tell @value{GDBN} not to print unions which are contained in
10196 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10199 @item show print union
10200 Ask @value{GDBN} whether or not it will print unions which are contained in
10201 structures and other unions.
10203 For example, given the declarations
10206 typedef enum @{Tree, Bug@} Species;
10207 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10208 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10219 struct thing foo = @{Tree, @{Acorn@}@};
10223 with @code{set print union on} in effect @samp{p foo} would print
10226 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10230 and with @code{set print union off} in effect it would print
10233 $1 = @{it = Tree, form = @{...@}@}
10237 @code{set print union} affects programs written in C-like languages
10243 These settings are of interest when debugging C@t{++} programs:
10246 @cindex demangling C@t{++} names
10247 @item set print demangle
10248 @itemx set print demangle on
10249 Print C@t{++} names in their source form rather than in the encoded
10250 (``mangled'') form passed to the assembler and linker for type-safe
10251 linkage. The default is on.
10253 @item show print demangle
10254 Show whether C@t{++} names are printed in mangled or demangled form.
10256 @item set print asm-demangle
10257 @itemx set print asm-demangle on
10258 Print C@t{++} names in their source form rather than their mangled form, even
10259 in assembler code printouts such as instruction disassemblies.
10260 The default is off.
10262 @item show print asm-demangle
10263 Show whether C@t{++} names in assembly listings are printed in mangled
10266 @cindex C@t{++} symbol decoding style
10267 @cindex symbol decoding style, C@t{++}
10268 @kindex set demangle-style
10269 @item set demangle-style @var{style}
10270 Choose among several encoding schemes used by different compilers to
10271 represent C@t{++} names. The choices for @var{style} are currently:
10275 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10276 This is the default.
10279 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10282 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10285 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10288 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10289 @strong{Warning:} this setting alone is not sufficient to allow
10290 debugging @code{cfront}-generated executables. @value{GDBN} would
10291 require further enhancement to permit that.
10294 If you omit @var{style}, you will see a list of possible formats.
10296 @item show demangle-style
10297 Display the encoding style currently in use for decoding C@t{++} symbols.
10299 @item set print object
10300 @itemx set print object on
10301 @cindex derived type of an object, printing
10302 @cindex display derived types
10303 When displaying a pointer to an object, identify the @emph{actual}
10304 (derived) type of the object rather than the @emph{declared} type, using
10305 the virtual function table. Note that the virtual function table is
10306 required---this feature can only work for objects that have run-time
10307 type identification; a single virtual method in the object's declared
10308 type is sufficient. Note that this setting is also taken into account when
10309 working with variable objects via MI (@pxref{GDB/MI}).
10311 @item set print object off
10312 Display only the declared type of objects, without reference to the
10313 virtual function table. This is the default setting.
10315 @item show print object
10316 Show whether actual, or declared, object types are displayed.
10318 @item set print static-members
10319 @itemx set print static-members on
10320 @cindex static members of C@t{++} objects
10321 Print static members when displaying a C@t{++} object. The default is on.
10323 @item set print static-members off
10324 Do not print static members when displaying a C@t{++} object.
10326 @item show print static-members
10327 Show whether C@t{++} static members are printed or not.
10329 @item set print pascal_static-members
10330 @itemx set print pascal_static-members on
10331 @cindex static members of Pascal objects
10332 @cindex Pascal objects, static members display
10333 Print static members when displaying a Pascal object. The default is on.
10335 @item set print pascal_static-members off
10336 Do not print static members when displaying a Pascal object.
10338 @item show print pascal_static-members
10339 Show whether Pascal static members are printed or not.
10341 @c These don't work with HP ANSI C++ yet.
10342 @item set print vtbl
10343 @itemx set print vtbl on
10344 @cindex pretty print C@t{++} virtual function tables
10345 @cindex virtual functions (C@t{++}) display
10346 @cindex VTBL display
10347 Pretty print C@t{++} virtual function tables. The default is off.
10348 (The @code{vtbl} commands do not work on programs compiled with the HP
10349 ANSI C@t{++} compiler (@code{aCC}).)
10351 @item set print vtbl off
10352 Do not pretty print C@t{++} virtual function tables.
10354 @item show print vtbl
10355 Show whether C@t{++} virtual function tables are pretty printed, or not.
10358 @node Pretty Printing
10359 @section Pretty Printing
10361 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10362 Python code. It greatly simplifies the display of complex objects. This
10363 mechanism works for both MI and the CLI.
10366 * Pretty-Printer Introduction:: Introduction to pretty-printers
10367 * Pretty-Printer Example:: An example pretty-printer
10368 * Pretty-Printer Commands:: Pretty-printer commands
10371 @node Pretty-Printer Introduction
10372 @subsection Pretty-Printer Introduction
10374 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10375 registered for the value. If there is then @value{GDBN} invokes the
10376 pretty-printer to print the value. Otherwise the value is printed normally.
10378 Pretty-printers are normally named. This makes them easy to manage.
10379 The @samp{info pretty-printer} command will list all the installed
10380 pretty-printers with their names.
10381 If a pretty-printer can handle multiple data types, then its
10382 @dfn{subprinters} are the printers for the individual data types.
10383 Each such subprinter has its own name.
10384 The format of the name is @var{printer-name};@var{subprinter-name}.
10386 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10387 Typically they are automatically loaded and registered when the corresponding
10388 debug information is loaded, thus making them available without having to
10389 do anything special.
10391 There are three places where a pretty-printer can be registered.
10395 Pretty-printers registered globally are available when debugging
10399 Pretty-printers registered with a program space are available only
10400 when debugging that program.
10401 @xref{Progspaces In Python}, for more details on program spaces in Python.
10404 Pretty-printers registered with an objfile are loaded and unloaded
10405 with the corresponding objfile (e.g., shared library).
10406 @xref{Objfiles In Python}, for more details on objfiles in Python.
10409 @xref{Selecting Pretty-Printers}, for further information on how
10410 pretty-printers are selected,
10412 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10415 @node Pretty-Printer Example
10416 @subsection Pretty-Printer Example
10418 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10421 (@value{GDBP}) print s
10423 static npos = 4294967295,
10425 <std::allocator<char>> = @{
10426 <__gnu_cxx::new_allocator<char>> = @{
10427 <No data fields>@}, <No data fields>
10429 members of std::basic_string<char, std::char_traits<char>,
10430 std::allocator<char> >::_Alloc_hider:
10431 _M_p = 0x804a014 "abcd"
10436 With a pretty-printer for @code{std::string} only the contents are printed:
10439 (@value{GDBP}) print s
10443 @node Pretty-Printer Commands
10444 @subsection Pretty-Printer Commands
10445 @cindex pretty-printer commands
10448 @kindex info pretty-printer
10449 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10450 Print the list of installed pretty-printers.
10451 This includes disabled pretty-printers, which are marked as such.
10453 @var{object-regexp} is a regular expression matching the objects
10454 whose pretty-printers to list.
10455 Objects can be @code{global}, the program space's file
10456 (@pxref{Progspaces In Python}),
10457 and the object files within that program space (@pxref{Objfiles In Python}).
10458 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10459 looks up a printer from these three objects.
10461 @var{name-regexp} is a regular expression matching the name of the printers
10464 @kindex disable pretty-printer
10465 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10466 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10467 A disabled pretty-printer is not forgotten, it may be enabled again later.
10469 @kindex enable pretty-printer
10470 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10471 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10476 Suppose we have three pretty-printers installed: one from library1.so
10477 named @code{foo} that prints objects of type @code{foo}, and
10478 another from library2.so named @code{bar} that prints two types of objects,
10479 @code{bar1} and @code{bar2}.
10482 (gdb) info pretty-printer
10489 (gdb) info pretty-printer library2
10494 (gdb) disable pretty-printer library1
10496 2 of 3 printers enabled
10497 (gdb) info pretty-printer
10504 (gdb) disable pretty-printer library2 bar:bar1
10506 1 of 3 printers enabled
10507 (gdb) info pretty-printer library2
10514 (gdb) disable pretty-printer library2 bar
10516 0 of 3 printers enabled
10517 (gdb) info pretty-printer library2
10526 Note that for @code{bar} the entire printer can be disabled,
10527 as can each individual subprinter.
10529 @node Value History
10530 @section Value History
10532 @cindex value history
10533 @cindex history of values printed by @value{GDBN}
10534 Values printed by the @code{print} command are saved in the @value{GDBN}
10535 @dfn{value history}. This allows you to refer to them in other expressions.
10536 Values are kept until the symbol table is re-read or discarded
10537 (for example with the @code{file} or @code{symbol-file} commands).
10538 When the symbol table changes, the value history is discarded,
10539 since the values may contain pointers back to the types defined in the
10544 @cindex history number
10545 The values printed are given @dfn{history numbers} by which you can
10546 refer to them. These are successive integers starting with one.
10547 @code{print} shows you the history number assigned to a value by
10548 printing @samp{$@var{num} = } before the value; here @var{num} is the
10551 To refer to any previous value, use @samp{$} followed by the value's
10552 history number. The way @code{print} labels its output is designed to
10553 remind you of this. Just @code{$} refers to the most recent value in
10554 the history, and @code{$$} refers to the value before that.
10555 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10556 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10557 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10559 For example, suppose you have just printed a pointer to a structure and
10560 want to see the contents of the structure. It suffices to type
10566 If you have a chain of structures where the component @code{next} points
10567 to the next one, you can print the contents of the next one with this:
10574 You can print successive links in the chain by repeating this
10575 command---which you can do by just typing @key{RET}.
10577 Note that the history records values, not expressions. If the value of
10578 @code{x} is 4 and you type these commands:
10586 then the value recorded in the value history by the @code{print} command
10587 remains 4 even though the value of @code{x} has changed.
10590 @kindex show values
10592 Print the last ten values in the value history, with their item numbers.
10593 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10594 values} does not change the history.
10596 @item show values @var{n}
10597 Print ten history values centered on history item number @var{n}.
10599 @item show values +
10600 Print ten history values just after the values last printed. If no more
10601 values are available, @code{show values +} produces no display.
10604 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10605 same effect as @samp{show values +}.
10607 @node Convenience Vars
10608 @section Convenience Variables
10610 @cindex convenience variables
10611 @cindex user-defined variables
10612 @value{GDBN} provides @dfn{convenience variables} that you can use within
10613 @value{GDBN} to hold on to a value and refer to it later. These variables
10614 exist entirely within @value{GDBN}; they are not part of your program, and
10615 setting a convenience variable has no direct effect on further execution
10616 of your program. That is why you can use them freely.
10618 Convenience variables are prefixed with @samp{$}. Any name preceded by
10619 @samp{$} can be used for a convenience variable, unless it is one of
10620 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10621 (Value history references, in contrast, are @emph{numbers} preceded
10622 by @samp{$}. @xref{Value History, ,Value History}.)
10624 You can save a value in a convenience variable with an assignment
10625 expression, just as you would set a variable in your program.
10629 set $foo = *object_ptr
10633 would save in @code{$foo} the value contained in the object pointed to by
10636 Using a convenience variable for the first time creates it, but its
10637 value is @code{void} until you assign a new value. You can alter the
10638 value with another assignment at any time.
10640 Convenience variables have no fixed types. You can assign a convenience
10641 variable any type of value, including structures and arrays, even if
10642 that variable already has a value of a different type. The convenience
10643 variable, when used as an expression, has the type of its current value.
10646 @kindex show convenience
10647 @cindex show all user variables and functions
10648 @item show convenience
10649 Print a list of convenience variables used so far, and their values,
10650 as well as a list of the convenience functions.
10651 Abbreviated @code{show conv}.
10653 @kindex init-if-undefined
10654 @cindex convenience variables, initializing
10655 @item init-if-undefined $@var{variable} = @var{expression}
10656 Set a convenience variable if it has not already been set. This is useful
10657 for user-defined commands that keep some state. It is similar, in concept,
10658 to using local static variables with initializers in C (except that
10659 convenience variables are global). It can also be used to allow users to
10660 override default values used in a command script.
10662 If the variable is already defined then the expression is not evaluated so
10663 any side-effects do not occur.
10666 One of the ways to use a convenience variable is as a counter to be
10667 incremented or a pointer to be advanced. For example, to print
10668 a field from successive elements of an array of structures:
10672 print bar[$i++]->contents
10676 Repeat that command by typing @key{RET}.
10678 Some convenience variables are created automatically by @value{GDBN} and given
10679 values likely to be useful.
10682 @vindex $_@r{, convenience variable}
10684 The variable @code{$_} is automatically set by the @code{x} command to
10685 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10686 commands which provide a default address for @code{x} to examine also
10687 set @code{$_} to that address; these commands include @code{info line}
10688 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10689 except when set by the @code{x} command, in which case it is a pointer
10690 to the type of @code{$__}.
10692 @vindex $__@r{, convenience variable}
10694 The variable @code{$__} is automatically set by the @code{x} command
10695 to the value found in the last address examined. Its type is chosen
10696 to match the format in which the data was printed.
10699 @vindex $_exitcode@r{, convenience variable}
10700 When the program being debugged terminates normally, @value{GDBN}
10701 automatically sets this variable to the exit code of the program, and
10702 resets @code{$_exitsignal} to @code{void}.
10705 @vindex $_exitsignal@r{, convenience variable}
10706 When the program being debugged dies due to an uncaught signal,
10707 @value{GDBN} automatically sets this variable to that signal's number,
10708 and resets @code{$_exitcode} to @code{void}.
10710 To distinguish between whether the program being debugged has exited
10711 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10712 @code{$_exitsignal} is not @code{void}), the convenience function
10713 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10714 Functions}). For example, considering the following source code:
10717 #include <signal.h>
10720 main (int argc, char *argv[])
10727 A valid way of telling whether the program being debugged has exited
10728 or signalled would be:
10731 (@value{GDBP}) define has_exited_or_signalled
10732 Type commands for definition of ``has_exited_or_signalled''.
10733 End with a line saying just ``end''.
10734 >if $_isvoid ($_exitsignal)
10735 >echo The program has exited\n
10737 >echo The program has signalled\n
10743 Program terminated with signal SIGALRM, Alarm clock.
10744 The program no longer exists.
10745 (@value{GDBP}) has_exited_or_signalled
10746 The program has signalled
10749 As can be seen, @value{GDBN} correctly informs that the program being
10750 debugged has signalled, since it calls @code{raise} and raises a
10751 @code{SIGALRM} signal. If the program being debugged had not called
10752 @code{raise}, then @value{GDBN} would report a normal exit:
10755 (@value{GDBP}) has_exited_or_signalled
10756 The program has exited
10760 The variable @code{$_exception} is set to the exception object being
10761 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10764 @itemx $_probe_arg0@dots{}$_probe_arg11
10765 Arguments to a static probe. @xref{Static Probe Points}.
10768 @vindex $_sdata@r{, inspect, convenience variable}
10769 The variable @code{$_sdata} contains extra collected static tracepoint
10770 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10771 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10772 if extra static tracepoint data has not been collected.
10775 @vindex $_siginfo@r{, convenience variable}
10776 The variable @code{$_siginfo} contains extra signal information
10777 (@pxref{extra signal information}). Note that @code{$_siginfo}
10778 could be empty, if the application has not yet received any signals.
10779 For example, it will be empty before you execute the @code{run} command.
10782 @vindex $_tlb@r{, convenience variable}
10783 The variable @code{$_tlb} is automatically set when debugging
10784 applications running on MS-Windows in native mode or connected to
10785 gdbserver that supports the @code{qGetTIBAddr} request.
10786 @xref{General Query Packets}.
10787 This variable contains the address of the thread information block.
10790 The number of the current inferior. @xref{Inferiors and
10791 Programs, ,Debugging Multiple Inferiors and Programs}.
10794 The thread number of the current thread. @xref{thread numbers}.
10797 The global number of the current thread. @xref{global thread numbers}.
10801 @node Convenience Funs
10802 @section Convenience Functions
10804 @cindex convenience functions
10805 @value{GDBN} also supplies some @dfn{convenience functions}. These
10806 have a syntax similar to convenience variables. A convenience
10807 function can be used in an expression just like an ordinary function;
10808 however, a convenience function is implemented internally to
10811 These functions do not require @value{GDBN} to be configured with
10812 @code{Python} support, which means that they are always available.
10816 @item $_isvoid (@var{expr})
10817 @findex $_isvoid@r{, convenience function}
10818 Return one if the expression @var{expr} is @code{void}. Otherwise it
10821 A @code{void} expression is an expression where the type of the result
10822 is @code{void}. For example, you can examine a convenience variable
10823 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10827 (@value{GDBP}) print $_exitcode
10829 (@value{GDBP}) print $_isvoid ($_exitcode)
10832 Starting program: ./a.out
10833 [Inferior 1 (process 29572) exited normally]
10834 (@value{GDBP}) print $_exitcode
10836 (@value{GDBP}) print $_isvoid ($_exitcode)
10840 In the example above, we used @code{$_isvoid} to check whether
10841 @code{$_exitcode} is @code{void} before and after the execution of the
10842 program being debugged. Before the execution there is no exit code to
10843 be examined, therefore @code{$_exitcode} is @code{void}. After the
10844 execution the program being debugged returned zero, therefore
10845 @code{$_exitcode} is zero, which means that it is not @code{void}
10848 The @code{void} expression can also be a call of a function from the
10849 program being debugged. For example, given the following function:
10858 The result of calling it inside @value{GDBN} is @code{void}:
10861 (@value{GDBP}) print foo ()
10863 (@value{GDBP}) print $_isvoid (foo ())
10865 (@value{GDBP}) set $v = foo ()
10866 (@value{GDBP}) print $v
10868 (@value{GDBP}) print $_isvoid ($v)
10874 These functions require @value{GDBN} to be configured with
10875 @code{Python} support.
10879 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10880 @findex $_memeq@r{, convenience function}
10881 Returns one if the @var{length} bytes at the addresses given by
10882 @var{buf1} and @var{buf2} are equal.
10883 Otherwise it returns zero.
10885 @item $_regex(@var{str}, @var{regex})
10886 @findex $_regex@r{, convenience function}
10887 Returns one if the string @var{str} matches the regular expression
10888 @var{regex}. Otherwise it returns zero.
10889 The syntax of the regular expression is that specified by @code{Python}'s
10890 regular expression support.
10892 @item $_streq(@var{str1}, @var{str2})
10893 @findex $_streq@r{, convenience function}
10894 Returns one if the strings @var{str1} and @var{str2} are equal.
10895 Otherwise it returns zero.
10897 @item $_strlen(@var{str})
10898 @findex $_strlen@r{, convenience function}
10899 Returns the length of string @var{str}.
10901 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10902 @findex $_caller_is@r{, convenience function}
10903 Returns one if the calling function's name is equal to @var{name}.
10904 Otherwise it returns zero.
10906 If the optional argument @var{number_of_frames} is provided,
10907 it is the number of frames up in the stack to look.
10915 at testsuite/gdb.python/py-caller-is.c:21
10916 #1 0x00000000004005a0 in middle_func ()
10917 at testsuite/gdb.python/py-caller-is.c:27
10918 #2 0x00000000004005ab in top_func ()
10919 at testsuite/gdb.python/py-caller-is.c:33
10920 #3 0x00000000004005b6 in main ()
10921 at testsuite/gdb.python/py-caller-is.c:39
10922 (gdb) print $_caller_is ("middle_func")
10924 (gdb) print $_caller_is ("top_func", 2)
10928 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10929 @findex $_caller_matches@r{, convenience function}
10930 Returns one if the calling function's name matches the regular expression
10931 @var{regexp}. Otherwise it returns zero.
10933 If the optional argument @var{number_of_frames} is provided,
10934 it is the number of frames up in the stack to look.
10937 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10938 @findex $_any_caller_is@r{, convenience function}
10939 Returns one if any calling function's name is equal to @var{name}.
10940 Otherwise it returns zero.
10942 If the optional argument @var{number_of_frames} is provided,
10943 it is the number of frames up in the stack to look.
10946 This function differs from @code{$_caller_is} in that this function
10947 checks all stack frames from the immediate caller to the frame specified
10948 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10949 frame specified by @var{number_of_frames}.
10951 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10952 @findex $_any_caller_matches@r{, convenience function}
10953 Returns one if any calling function's name matches the regular expression
10954 @var{regexp}. Otherwise it returns zero.
10956 If the optional argument @var{number_of_frames} is provided,
10957 it is the number of frames up in the stack to look.
10960 This function differs from @code{$_caller_matches} in that this function
10961 checks all stack frames from the immediate caller to the frame specified
10962 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10963 frame specified by @var{number_of_frames}.
10965 @item $_as_string(@var{value})
10966 @findex $_as_string@r{, convenience function}
10967 Return the string representation of @var{value}.
10969 This function is useful to obtain the textual label (enumerator) of an
10970 enumeration value. For example, assuming the variable @var{node} is of
10971 an enumerated type:
10974 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10975 Visiting node of type NODE_INTEGER
10980 @value{GDBN} provides the ability to list and get help on
10981 convenience functions.
10984 @item help function
10985 @kindex help function
10986 @cindex show all convenience functions
10987 Print a list of all convenience functions.
10994 You can refer to machine register contents, in expressions, as variables
10995 with names starting with @samp{$}. The names of registers are different
10996 for each machine; use @code{info registers} to see the names used on
11000 @kindex info registers
11001 @item info registers
11002 Print the names and values of all registers except floating-point
11003 and vector registers (in the selected stack frame).
11005 @kindex info all-registers
11006 @cindex floating point registers
11007 @item info all-registers
11008 Print the names and values of all registers, including floating-point
11009 and vector registers (in the selected stack frame).
11011 @item info registers @var{regname} @dots{}
11012 Print the @dfn{relativized} value of each specified register @var{regname}.
11013 As discussed in detail below, register values are normally relative to
11014 the selected stack frame. The @var{regname} may be any register name valid on
11015 the machine you are using, with or without the initial @samp{$}.
11018 @anchor{standard registers}
11019 @cindex stack pointer register
11020 @cindex program counter register
11021 @cindex process status register
11022 @cindex frame pointer register
11023 @cindex standard registers
11024 @value{GDBN} has four ``standard'' register names that are available (in
11025 expressions) on most machines---whenever they do not conflict with an
11026 architecture's canonical mnemonics for registers. The register names
11027 @code{$pc} and @code{$sp} are used for the program counter register and
11028 the stack pointer. @code{$fp} is used for a register that contains a
11029 pointer to the current stack frame, and @code{$ps} is used for a
11030 register that contains the processor status. For example,
11031 you could print the program counter in hex with
11038 or print the instruction to be executed next with
11045 or add four to the stack pointer@footnote{This is a way of removing
11046 one word from the stack, on machines where stacks grow downward in
11047 memory (most machines, nowadays). This assumes that the innermost
11048 stack frame is selected; setting @code{$sp} is not allowed when other
11049 stack frames are selected. To pop entire frames off the stack,
11050 regardless of machine architecture, use @code{return};
11051 see @ref{Returning, ,Returning from a Function}.} with
11057 Whenever possible, these four standard register names are available on
11058 your machine even though the machine has different canonical mnemonics,
11059 so long as there is no conflict. The @code{info registers} command
11060 shows the canonical names. For example, on the SPARC, @code{info
11061 registers} displays the processor status register as @code{$psr} but you
11062 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11063 is an alias for the @sc{eflags} register.
11065 @value{GDBN} always considers the contents of an ordinary register as an
11066 integer when the register is examined in this way. Some machines have
11067 special registers which can hold nothing but floating point; these
11068 registers are considered to have floating point values. There is no way
11069 to refer to the contents of an ordinary register as floating point value
11070 (although you can @emph{print} it as a floating point value with
11071 @samp{print/f $@var{regname}}).
11073 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11074 means that the data format in which the register contents are saved by
11075 the operating system is not the same one that your program normally
11076 sees. For example, the registers of the 68881 floating point
11077 coprocessor are always saved in ``extended'' (raw) format, but all C
11078 programs expect to work with ``double'' (virtual) format. In such
11079 cases, @value{GDBN} normally works with the virtual format only (the format
11080 that makes sense for your program), but the @code{info registers} command
11081 prints the data in both formats.
11083 @cindex SSE registers (x86)
11084 @cindex MMX registers (x86)
11085 Some machines have special registers whose contents can be interpreted
11086 in several different ways. For example, modern x86-based machines
11087 have SSE and MMX registers that can hold several values packed
11088 together in several different formats. @value{GDBN} refers to such
11089 registers in @code{struct} notation:
11092 (@value{GDBP}) print $xmm1
11094 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11095 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11096 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11097 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11098 v4_int32 = @{0, 20657912, 11, 13@},
11099 v2_int64 = @{88725056443645952, 55834574859@},
11100 uint128 = 0x0000000d0000000b013b36f800000000
11105 To set values of such registers, you need to tell @value{GDBN} which
11106 view of the register you wish to change, as if you were assigning
11107 value to a @code{struct} member:
11110 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11113 Normally, register values are relative to the selected stack frame
11114 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11115 value that the register would contain if all stack frames farther in
11116 were exited and their saved registers restored. In order to see the
11117 true contents of hardware registers, you must select the innermost
11118 frame (with @samp{frame 0}).
11120 @cindex caller-saved registers
11121 @cindex call-clobbered registers
11122 @cindex volatile registers
11123 @cindex <not saved> values
11124 Usually ABIs reserve some registers as not needed to be saved by the
11125 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11126 registers). It may therefore not be possible for @value{GDBN} to know
11127 the value a register had before the call (in other words, in the outer
11128 frame), if the register value has since been changed by the callee.
11129 @value{GDBN} tries to deduce where the inner frame saved
11130 (``callee-saved'') registers, from the debug info, unwind info, or the
11131 machine code generated by your compiler. If some register is not
11132 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11133 its own knowledge of the ABI, or because the debug/unwind info
11134 explicitly says the register's value is undefined), @value{GDBN}
11135 displays @w{@samp{<not saved>}} as the register's value. With targets
11136 that @value{GDBN} has no knowledge of the register saving convention,
11137 if a register was not saved by the callee, then its value and location
11138 in the outer frame are assumed to be the same of the inner frame.
11139 This is usually harmless, because if the register is call-clobbered,
11140 the caller either does not care what is in the register after the
11141 call, or has code to restore the value that it does care about. Note,
11142 however, that if you change such a register in the outer frame, you
11143 may also be affecting the inner frame. Also, the more ``outer'' the
11144 frame is you're looking at, the more likely a call-clobbered
11145 register's value is to be wrong, in the sense that it doesn't actually
11146 represent the value the register had just before the call.
11148 @node Floating Point Hardware
11149 @section Floating Point Hardware
11150 @cindex floating point
11152 Depending on the configuration, @value{GDBN} may be able to give
11153 you more information about the status of the floating point hardware.
11158 Display hardware-dependent information about the floating
11159 point unit. The exact contents and layout vary depending on the
11160 floating point chip. Currently, @samp{info float} is supported on
11161 the ARM and x86 machines.
11165 @section Vector Unit
11166 @cindex vector unit
11168 Depending on the configuration, @value{GDBN} may be able to give you
11169 more information about the status of the vector unit.
11172 @kindex info vector
11174 Display information about the vector unit. The exact contents and
11175 layout vary depending on the hardware.
11178 @node OS Information
11179 @section Operating System Auxiliary Information
11180 @cindex OS information
11182 @value{GDBN} provides interfaces to useful OS facilities that can help
11183 you debug your program.
11185 @cindex auxiliary vector
11186 @cindex vector, auxiliary
11187 Some operating systems supply an @dfn{auxiliary vector} to programs at
11188 startup. This is akin to the arguments and environment that you
11189 specify for a program, but contains a system-dependent variety of
11190 binary values that tell system libraries important details about the
11191 hardware, operating system, and process. Each value's purpose is
11192 identified by an integer tag; the meanings are well-known but system-specific.
11193 Depending on the configuration and operating system facilities,
11194 @value{GDBN} may be able to show you this information. For remote
11195 targets, this functionality may further depend on the remote stub's
11196 support of the @samp{qXfer:auxv:read} packet, see
11197 @ref{qXfer auxiliary vector read}.
11202 Display the auxiliary vector of the inferior, which can be either a
11203 live process or a core dump file. @value{GDBN} prints each tag value
11204 numerically, and also shows names and text descriptions for recognized
11205 tags. Some values in the vector are numbers, some bit masks, and some
11206 pointers to strings or other data. @value{GDBN} displays each value in the
11207 most appropriate form for a recognized tag, and in hexadecimal for
11208 an unrecognized tag.
11211 On some targets, @value{GDBN} can access operating system-specific
11212 information and show it to you. The types of information available
11213 will differ depending on the type of operating system running on the
11214 target. The mechanism used to fetch the data is described in
11215 @ref{Operating System Information}. For remote targets, this
11216 functionality depends on the remote stub's support of the
11217 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11221 @item info os @var{infotype}
11223 Display OS information of the requested type.
11225 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11227 @anchor{linux info os infotypes}
11229 @kindex info os cpus
11231 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11232 the available fields from /proc/cpuinfo. For each supported architecture
11233 different fields are available. Two common entries are processor which gives
11234 CPU number and bogomips; a system constant that is calculated during
11235 kernel initialization.
11237 @kindex info os files
11239 Display the list of open file descriptors on the target. For each
11240 file descriptor, @value{GDBN} prints the identifier of the process
11241 owning the descriptor, the command of the owning process, the value
11242 of the descriptor, and the target of the descriptor.
11244 @kindex info os modules
11246 Display the list of all loaded kernel modules on the target. For each
11247 module, @value{GDBN} prints the module name, the size of the module in
11248 bytes, the number of times the module is used, the dependencies of the
11249 module, the status of the module, and the address of the loaded module
11252 @kindex info os msg
11254 Display the list of all System V message queues on the target. For each
11255 message queue, @value{GDBN} prints the message queue key, the message
11256 queue identifier, the access permissions, the current number of bytes
11257 on the queue, the current number of messages on the queue, the processes
11258 that last sent and received a message on the queue, the user and group
11259 of the owner and creator of the message queue, the times at which a
11260 message was last sent and received on the queue, and the time at which
11261 the message queue was last changed.
11263 @kindex info os processes
11265 Display the list of processes on the target. For each process,
11266 @value{GDBN} prints the process identifier, the name of the user, the
11267 command corresponding to the process, and the list of processor cores
11268 that the process is currently running on. (To understand what these
11269 properties mean, for this and the following info types, please consult
11270 the general @sc{gnu}/Linux documentation.)
11272 @kindex info os procgroups
11274 Display the list of process groups on the target. For each process,
11275 @value{GDBN} prints the identifier of the process group that it belongs
11276 to, the command corresponding to the process group leader, the process
11277 identifier, and the command line of the process. The list is sorted
11278 first by the process group identifier, then by the process identifier,
11279 so that processes belonging to the same process group are grouped together
11280 and the process group leader is listed first.
11282 @kindex info os semaphores
11284 Display the list of all System V semaphore sets on the target. For each
11285 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11286 set identifier, the access permissions, the number of semaphores in the
11287 set, the user and group of the owner and creator of the semaphore set,
11288 and the times at which the semaphore set was operated upon and changed.
11290 @kindex info os shm
11292 Display the list of all System V shared-memory regions on the target.
11293 For each shared-memory region, @value{GDBN} prints the region key,
11294 the shared-memory identifier, the access permissions, the size of the
11295 region, the process that created the region, the process that last
11296 attached to or detached from the region, the current number of live
11297 attaches to the region, and the times at which the region was last
11298 attached to, detach from, and changed.
11300 @kindex info os sockets
11302 Display the list of Internet-domain sockets on the target. For each
11303 socket, @value{GDBN} prints the address and port of the local and
11304 remote endpoints, the current state of the connection, the creator of
11305 the socket, the IP address family of the socket, and the type of the
11308 @kindex info os threads
11310 Display the list of threads running on the target. For each thread,
11311 @value{GDBN} prints the identifier of the process that the thread
11312 belongs to, the command of the process, the thread identifier, and the
11313 processor core that it is currently running on. The main thread of a
11314 process is not listed.
11318 If @var{infotype} is omitted, then list the possible values for
11319 @var{infotype} and the kind of OS information available for each
11320 @var{infotype}. If the target does not return a list of possible
11321 types, this command will report an error.
11324 @node Memory Region Attributes
11325 @section Memory Region Attributes
11326 @cindex memory region attributes
11328 @dfn{Memory region attributes} allow you to describe special handling
11329 required by regions of your target's memory. @value{GDBN} uses
11330 attributes to determine whether to allow certain types of memory
11331 accesses; whether to use specific width accesses; and whether to cache
11332 target memory. By default the description of memory regions is
11333 fetched from the target (if the current target supports this), but the
11334 user can override the fetched regions.
11336 Defined memory regions can be individually enabled and disabled. When a
11337 memory region is disabled, @value{GDBN} uses the default attributes when
11338 accessing memory in that region. Similarly, if no memory regions have
11339 been defined, @value{GDBN} uses the default attributes when accessing
11342 When a memory region is defined, it is given a number to identify it;
11343 to enable, disable, or remove a memory region, you specify that number.
11347 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11348 Define a memory region bounded by @var{lower} and @var{upper} with
11349 attributes @var{attributes}@dots{}, and add it to the list of regions
11350 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11351 case: it is treated as the target's maximum memory address.
11352 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11355 Discard any user changes to the memory regions and use target-supplied
11356 regions, if available, or no regions if the target does not support.
11359 @item delete mem @var{nums}@dots{}
11360 Remove memory regions @var{nums}@dots{} from the list of regions
11361 monitored by @value{GDBN}.
11363 @kindex disable mem
11364 @item disable mem @var{nums}@dots{}
11365 Disable monitoring of memory regions @var{nums}@dots{}.
11366 A disabled memory region is not forgotten.
11367 It may be enabled again later.
11370 @item enable mem @var{nums}@dots{}
11371 Enable monitoring of memory regions @var{nums}@dots{}.
11375 Print a table of all defined memory regions, with the following columns
11379 @item Memory Region Number
11380 @item Enabled or Disabled.
11381 Enabled memory regions are marked with @samp{y}.
11382 Disabled memory regions are marked with @samp{n}.
11385 The address defining the inclusive lower bound of the memory region.
11388 The address defining the exclusive upper bound of the memory region.
11391 The list of attributes set for this memory region.
11396 @subsection Attributes
11398 @subsubsection Memory Access Mode
11399 The access mode attributes set whether @value{GDBN} may make read or
11400 write accesses to a memory region.
11402 While these attributes prevent @value{GDBN} from performing invalid
11403 memory accesses, they do nothing to prevent the target system, I/O DMA,
11404 etc.@: from accessing memory.
11408 Memory is read only.
11410 Memory is write only.
11412 Memory is read/write. This is the default.
11415 @subsubsection Memory Access Size
11416 The access size attribute tells @value{GDBN} to use specific sized
11417 accesses in the memory region. Often memory mapped device registers
11418 require specific sized accesses. If no access size attribute is
11419 specified, @value{GDBN} may use accesses of any size.
11423 Use 8 bit memory accesses.
11425 Use 16 bit memory accesses.
11427 Use 32 bit memory accesses.
11429 Use 64 bit memory accesses.
11432 @c @subsubsection Hardware/Software Breakpoints
11433 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11434 @c will use hardware or software breakpoints for the internal breakpoints
11435 @c used by the step, next, finish, until, etc. commands.
11439 @c Always use hardware breakpoints
11440 @c @item swbreak (default)
11443 @subsubsection Data Cache
11444 The data cache attributes set whether @value{GDBN} will cache target
11445 memory. While this generally improves performance by reducing debug
11446 protocol overhead, it can lead to incorrect results because @value{GDBN}
11447 does not know about volatile variables or memory mapped device
11452 Enable @value{GDBN} to cache target memory.
11454 Disable @value{GDBN} from caching target memory. This is the default.
11457 @subsection Memory Access Checking
11458 @value{GDBN} can be instructed to refuse accesses to memory that is
11459 not explicitly described. This can be useful if accessing such
11460 regions has undesired effects for a specific target, or to provide
11461 better error checking. The following commands control this behaviour.
11464 @kindex set mem inaccessible-by-default
11465 @item set mem inaccessible-by-default [on|off]
11466 If @code{on} is specified, make @value{GDBN} treat memory not
11467 explicitly described by the memory ranges as non-existent and refuse accesses
11468 to such memory. The checks are only performed if there's at least one
11469 memory range defined. If @code{off} is specified, make @value{GDBN}
11470 treat the memory not explicitly described by the memory ranges as RAM.
11471 The default value is @code{on}.
11472 @kindex show mem inaccessible-by-default
11473 @item show mem inaccessible-by-default
11474 Show the current handling of accesses to unknown memory.
11478 @c @subsubsection Memory Write Verification
11479 @c The memory write verification attributes set whether @value{GDBN}
11480 @c will re-reads data after each write to verify the write was successful.
11484 @c @item noverify (default)
11487 @node Dump/Restore Files
11488 @section Copy Between Memory and a File
11489 @cindex dump/restore files
11490 @cindex append data to a file
11491 @cindex dump data to a file
11492 @cindex restore data from a file
11494 You can use the commands @code{dump}, @code{append}, and
11495 @code{restore} to copy data between target memory and a file. The
11496 @code{dump} and @code{append} commands write data to a file, and the
11497 @code{restore} command reads data from a file back into the inferior's
11498 memory. Files may be in binary, Motorola S-record, Intel hex,
11499 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11500 append to binary files, and cannot read from Verilog Hex files.
11505 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11506 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11507 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11508 or the value of @var{expr}, to @var{filename} in the given format.
11510 The @var{format} parameter may be any one of:
11517 Motorola S-record format.
11519 Tektronix Hex format.
11521 Verilog Hex format.
11524 @value{GDBN} uses the same definitions of these formats as the
11525 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11526 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11530 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11531 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11532 Append the contents of memory from @var{start_addr} to @var{end_addr},
11533 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11534 (@value{GDBN} can only append data to files in raw binary form.)
11537 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11538 Restore the contents of file @var{filename} into memory. The
11539 @code{restore} command can automatically recognize any known @sc{bfd}
11540 file format, except for raw binary. To restore a raw binary file you
11541 must specify the optional keyword @code{binary} after the filename.
11543 If @var{bias} is non-zero, its value will be added to the addresses
11544 contained in the file. Binary files always start at address zero, so
11545 they will be restored at address @var{bias}. Other bfd files have
11546 a built-in location; they will be restored at offset @var{bias}
11547 from that location.
11549 If @var{start} and/or @var{end} are non-zero, then only data between
11550 file offset @var{start} and file offset @var{end} will be restored.
11551 These offsets are relative to the addresses in the file, before
11552 the @var{bias} argument is applied.
11556 @node Core File Generation
11557 @section How to Produce a Core File from Your Program
11558 @cindex dump core from inferior
11560 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11561 image of a running process and its process status (register values
11562 etc.). Its primary use is post-mortem debugging of a program that
11563 crashed while it ran outside a debugger. A program that crashes
11564 automatically produces a core file, unless this feature is disabled by
11565 the user. @xref{Files}, for information on invoking @value{GDBN} in
11566 the post-mortem debugging mode.
11568 Occasionally, you may wish to produce a core file of the program you
11569 are debugging in order to preserve a snapshot of its state.
11570 @value{GDBN} has a special command for that.
11574 @kindex generate-core-file
11575 @item generate-core-file [@var{file}]
11576 @itemx gcore [@var{file}]
11577 Produce a core dump of the inferior process. The optional argument
11578 @var{file} specifies the file name where to put the core dump. If not
11579 specified, the file name defaults to @file{core.@var{pid}}, where
11580 @var{pid} is the inferior process ID.
11582 Note that this command is implemented only for some systems (as of
11583 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11585 On @sc{gnu}/Linux, this command can take into account the value of the
11586 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11587 dump (@pxref{set use-coredump-filter}).
11589 @kindex set use-coredump-filter
11590 @anchor{set use-coredump-filter}
11591 @item set use-coredump-filter on
11592 @itemx set use-coredump-filter off
11593 Enable or disable the use of the file
11594 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11595 files. This file is used by the Linux kernel to decide what types of
11596 memory mappings will be dumped or ignored when generating a core dump
11597 file. @var{pid} is the process ID of a currently running process.
11599 To make use of this feature, you have to write in the
11600 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11601 which is a bit mask representing the memory mapping types. If a bit
11602 is set in the bit mask, then the memory mappings of the corresponding
11603 types will be dumped; otherwise, they will be ignored. This
11604 configuration is inherited by child processes. For more information
11605 about the bits that can be set in the
11606 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11607 manpage of @code{core(5)}.
11609 By default, this option is @code{on}. If this option is turned
11610 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11611 and instead uses the same default value as the Linux kernel in order
11612 to decide which pages will be dumped in the core dump file. This
11613 value is currently @code{0x33}, which means that bits @code{0}
11614 (anonymous private mappings), @code{1} (anonymous shared mappings),
11615 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11616 This will cause these memory mappings to be dumped automatically.
11619 @node Character Sets
11620 @section Character Sets
11621 @cindex character sets
11623 @cindex translating between character sets
11624 @cindex host character set
11625 @cindex target character set
11627 If the program you are debugging uses a different character set to
11628 represent characters and strings than the one @value{GDBN} uses itself,
11629 @value{GDBN} can automatically translate between the character sets for
11630 you. The character set @value{GDBN} uses we call the @dfn{host
11631 character set}; the one the inferior program uses we call the
11632 @dfn{target character set}.
11634 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11635 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11636 remote protocol (@pxref{Remote Debugging}) to debug a program
11637 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11638 then the host character set is Latin-1, and the target character set is
11639 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11640 target-charset EBCDIC-US}, then @value{GDBN} translates between
11641 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11642 character and string literals in expressions.
11644 @value{GDBN} has no way to automatically recognize which character set
11645 the inferior program uses; you must tell it, using the @code{set
11646 target-charset} command, described below.
11648 Here are the commands for controlling @value{GDBN}'s character set
11652 @item set target-charset @var{charset}
11653 @kindex set target-charset
11654 Set the current target character set to @var{charset}. To display the
11655 list of supported target character sets, type
11656 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11658 @item set host-charset @var{charset}
11659 @kindex set host-charset
11660 Set the current host character set to @var{charset}.
11662 By default, @value{GDBN} uses a host character set appropriate to the
11663 system it is running on; you can override that default using the
11664 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11665 automatically determine the appropriate host character set. In this
11666 case, @value{GDBN} uses @samp{UTF-8}.
11668 @value{GDBN} can only use certain character sets as its host character
11669 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11670 @value{GDBN} will list the host character sets it supports.
11672 @item set charset @var{charset}
11673 @kindex set charset
11674 Set the current host and target character sets to @var{charset}. As
11675 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11676 @value{GDBN} will list the names of the character sets that can be used
11677 for both host and target.
11680 @kindex show charset
11681 Show the names of the current host and target character sets.
11683 @item show host-charset
11684 @kindex show host-charset
11685 Show the name of the current host character set.
11687 @item show target-charset
11688 @kindex show target-charset
11689 Show the name of the current target character set.
11691 @item set target-wide-charset @var{charset}
11692 @kindex set target-wide-charset
11693 Set the current target's wide character set to @var{charset}. This is
11694 the character set used by the target's @code{wchar_t} type. To
11695 display the list of supported wide character sets, type
11696 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11698 @item show target-wide-charset
11699 @kindex show target-wide-charset
11700 Show the name of the current target's wide character set.
11703 Here is an example of @value{GDBN}'s character set support in action.
11704 Assume that the following source code has been placed in the file
11705 @file{charset-test.c}:
11711 = @{72, 101, 108, 108, 111, 44, 32, 119,
11712 111, 114, 108, 100, 33, 10, 0@};
11713 char ibm1047_hello[]
11714 = @{200, 133, 147, 147, 150, 107, 64, 166,
11715 150, 153, 147, 132, 90, 37, 0@};
11719 printf ("Hello, world!\n");
11723 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11724 containing the string @samp{Hello, world!} followed by a newline,
11725 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11727 We compile the program, and invoke the debugger on it:
11730 $ gcc -g charset-test.c -o charset-test
11731 $ gdb -nw charset-test
11732 GNU gdb 2001-12-19-cvs
11733 Copyright 2001 Free Software Foundation, Inc.
11738 We can use the @code{show charset} command to see what character sets
11739 @value{GDBN} is currently using to interpret and display characters and
11743 (@value{GDBP}) show charset
11744 The current host and target character set is `ISO-8859-1'.
11748 For the sake of printing this manual, let's use @sc{ascii} as our
11749 initial character set:
11751 (@value{GDBP}) set charset ASCII
11752 (@value{GDBP}) show charset
11753 The current host and target character set is `ASCII'.
11757 Let's assume that @sc{ascii} is indeed the correct character set for our
11758 host system --- in other words, let's assume that if @value{GDBN} prints
11759 characters using the @sc{ascii} character set, our terminal will display
11760 them properly. Since our current target character set is also
11761 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11764 (@value{GDBP}) print ascii_hello
11765 $1 = 0x401698 "Hello, world!\n"
11766 (@value{GDBP}) print ascii_hello[0]
11771 @value{GDBN} uses the target character set for character and string
11772 literals you use in expressions:
11775 (@value{GDBP}) print '+'
11780 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11783 @value{GDBN} relies on the user to tell it which character set the
11784 target program uses. If we print @code{ibm1047_hello} while our target
11785 character set is still @sc{ascii}, we get jibberish:
11788 (@value{GDBP}) print ibm1047_hello
11789 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11790 (@value{GDBP}) print ibm1047_hello[0]
11795 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11796 @value{GDBN} tells us the character sets it supports:
11799 (@value{GDBP}) set target-charset
11800 ASCII EBCDIC-US IBM1047 ISO-8859-1
11801 (@value{GDBP}) set target-charset
11804 We can select @sc{ibm1047} as our target character set, and examine the
11805 program's strings again. Now the @sc{ascii} string is wrong, but
11806 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11807 target character set, @sc{ibm1047}, to the host character set,
11808 @sc{ascii}, and they display correctly:
11811 (@value{GDBP}) set target-charset IBM1047
11812 (@value{GDBP}) show charset
11813 The current host character set is `ASCII'.
11814 The current target character set is `IBM1047'.
11815 (@value{GDBP}) print ascii_hello
11816 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11817 (@value{GDBP}) print ascii_hello[0]
11819 (@value{GDBP}) print ibm1047_hello
11820 $8 = 0x4016a8 "Hello, world!\n"
11821 (@value{GDBP}) print ibm1047_hello[0]
11826 As above, @value{GDBN} uses the target character set for character and
11827 string literals you use in expressions:
11830 (@value{GDBP}) print '+'
11835 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11838 @node Caching Target Data
11839 @section Caching Data of Targets
11840 @cindex caching data of targets
11842 @value{GDBN} caches data exchanged between the debugger and a target.
11843 Each cache is associated with the address space of the inferior.
11844 @xref{Inferiors and Programs}, about inferior and address space.
11845 Such caching generally improves performance in remote debugging
11846 (@pxref{Remote Debugging}), because it reduces the overhead of the
11847 remote protocol by bundling memory reads and writes into large chunks.
11848 Unfortunately, simply caching everything would lead to incorrect results,
11849 since @value{GDBN} does not necessarily know anything about volatile
11850 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11851 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11853 Therefore, by default, @value{GDBN} only caches data
11854 known to be on the stack@footnote{In non-stop mode, it is moderately
11855 rare for a running thread to modify the stack of a stopped thread
11856 in a way that would interfere with a backtrace, and caching of
11857 stack reads provides a significant speed up of remote backtraces.} or
11858 in the code segment.
11859 Other regions of memory can be explicitly marked as
11860 cacheable; @pxref{Memory Region Attributes}.
11863 @kindex set remotecache
11864 @item set remotecache on
11865 @itemx set remotecache off
11866 This option no longer does anything; it exists for compatibility
11869 @kindex show remotecache
11870 @item show remotecache
11871 Show the current state of the obsolete remotecache flag.
11873 @kindex set stack-cache
11874 @item set stack-cache on
11875 @itemx set stack-cache off
11876 Enable or disable caching of stack accesses. When @code{on}, use
11877 caching. By default, this option is @code{on}.
11879 @kindex show stack-cache
11880 @item show stack-cache
11881 Show the current state of data caching for memory accesses.
11883 @kindex set code-cache
11884 @item set code-cache on
11885 @itemx set code-cache off
11886 Enable or disable caching of code segment accesses. When @code{on},
11887 use caching. By default, this option is @code{on}. This improves
11888 performance of disassembly in remote debugging.
11890 @kindex show code-cache
11891 @item show code-cache
11892 Show the current state of target memory cache for code segment
11895 @kindex info dcache
11896 @item info dcache @r{[}line@r{]}
11897 Print the information about the performance of data cache of the
11898 current inferior's address space. The information displayed
11899 includes the dcache width and depth, and for each cache line, its
11900 number, address, and how many times it was referenced. This
11901 command is useful for debugging the data cache operation.
11903 If a line number is specified, the contents of that line will be
11906 @item set dcache size @var{size}
11907 @cindex dcache size
11908 @kindex set dcache size
11909 Set maximum number of entries in dcache (dcache depth above).
11911 @item set dcache line-size @var{line-size}
11912 @cindex dcache line-size
11913 @kindex set dcache line-size
11914 Set number of bytes each dcache entry caches (dcache width above).
11915 Must be a power of 2.
11917 @item show dcache size
11918 @kindex show dcache size
11919 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11921 @item show dcache line-size
11922 @kindex show dcache line-size
11923 Show default size of dcache lines.
11927 @node Searching Memory
11928 @section Search Memory
11929 @cindex searching memory
11931 Memory can be searched for a particular sequence of bytes with the
11932 @code{find} command.
11936 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11937 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11938 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11939 etc. The search begins at address @var{start_addr} and continues for either
11940 @var{len} bytes or through to @var{end_addr} inclusive.
11943 @var{s} and @var{n} are optional parameters.
11944 They may be specified in either order, apart or together.
11947 @item @var{s}, search query size
11948 The size of each search query value.
11954 halfwords (two bytes)
11958 giant words (eight bytes)
11961 All values are interpreted in the current language.
11962 This means, for example, that if the current source language is C/C@t{++}
11963 then searching for the string ``hello'' includes the trailing '\0'.
11964 The null terminator can be removed from searching by using casts,
11965 e.g.: @samp{@{char[5]@}"hello"}.
11967 If the value size is not specified, it is taken from the
11968 value's type in the current language.
11969 This is useful when one wants to specify the search
11970 pattern as a mixture of types.
11971 Note that this means, for example, that in the case of C-like languages
11972 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11973 which is typically four bytes.
11975 @item @var{n}, maximum number of finds
11976 The maximum number of matches to print. The default is to print all finds.
11979 You can use strings as search values. Quote them with double-quotes
11981 The string value is copied into the search pattern byte by byte,
11982 regardless of the endianness of the target and the size specification.
11984 The address of each match found is printed as well as a count of the
11985 number of matches found.
11987 The address of the last value found is stored in convenience variable
11989 A count of the number of matches is stored in @samp{$numfound}.
11991 For example, if stopped at the @code{printf} in this function:
11997 static char hello[] = "hello-hello";
11998 static struct @{ char c; short s; int i; @}
11999 __attribute__ ((packed)) mixed
12000 = @{ 'c', 0x1234, 0x87654321 @};
12001 printf ("%s\n", hello);
12006 you get during debugging:
12009 (gdb) find &hello[0], +sizeof(hello), "hello"
12010 0x804956d <hello.1620+6>
12012 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12013 0x8049567 <hello.1620>
12014 0x804956d <hello.1620+6>
12016 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12017 0x8049567 <hello.1620>
12018 0x804956d <hello.1620+6>
12020 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12021 0x8049567 <hello.1620>
12023 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12024 0x8049560 <mixed.1625>
12026 (gdb) print $numfound
12029 $2 = (void *) 0x8049560
12033 @section Value Sizes
12035 Whenever @value{GDBN} prints a value memory will be allocated within
12036 @value{GDBN} to hold the contents of the value. It is possible in
12037 some languages with dynamic typing systems, that an invalid program
12038 may indicate a value that is incorrectly large, this in turn may cause
12039 @value{GDBN} to try and allocate an overly large ammount of memory.
12042 @kindex set max-value-size
12043 @item set max-value-size @var{bytes}
12044 @itemx set max-value-size unlimited
12045 Set the maximum size of memory that @value{GDBN} will allocate for the
12046 contents of a value to @var{bytes}, trying to display a value that
12047 requires more memory than that will result in an error.
12049 Setting this variable does not effect values that have already been
12050 allocated within @value{GDBN}, only future allocations.
12052 There's a minimum size that @code{max-value-size} can be set to in
12053 order that @value{GDBN} can still operate correctly, this minimum is
12054 currently 16 bytes.
12056 The limit applies to the results of some subexpressions as well as to
12057 complete expressions. For example, an expression denoting a simple
12058 integer component, such as @code{x.y.z}, may fail if the size of
12059 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12060 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12061 @var{A} is an array variable with non-constant size, will generally
12062 succeed regardless of the bounds on @var{A}, as long as the component
12063 size is less than @var{bytes}.
12065 The default value of @code{max-value-size} is currently 64k.
12067 @kindex show max-value-size
12068 @item show max-value-size
12069 Show the maximum size of memory, in bytes, that @value{GDBN} will
12070 allocate for the contents of a value.
12073 @node Optimized Code
12074 @chapter Debugging Optimized Code
12075 @cindex optimized code, debugging
12076 @cindex debugging optimized code
12078 Almost all compilers support optimization. With optimization
12079 disabled, the compiler generates assembly code that corresponds
12080 directly to your source code, in a simplistic way. As the compiler
12081 applies more powerful optimizations, the generated assembly code
12082 diverges from your original source code. With help from debugging
12083 information generated by the compiler, @value{GDBN} can map from
12084 the running program back to constructs from your original source.
12086 @value{GDBN} is more accurate with optimization disabled. If you
12087 can recompile without optimization, it is easier to follow the
12088 progress of your program during debugging. But, there are many cases
12089 where you may need to debug an optimized version.
12091 When you debug a program compiled with @samp{-g -O}, remember that the
12092 optimizer has rearranged your code; the debugger shows you what is
12093 really there. Do not be too surprised when the execution path does not
12094 exactly match your source file! An extreme example: if you define a
12095 variable, but never use it, @value{GDBN} never sees that
12096 variable---because the compiler optimizes it out of existence.
12098 Some things do not work as well with @samp{-g -O} as with just
12099 @samp{-g}, particularly on machines with instruction scheduling. If in
12100 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12101 please report it to us as a bug (including a test case!).
12102 @xref{Variables}, for more information about debugging optimized code.
12105 * Inline Functions:: How @value{GDBN} presents inlining
12106 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12109 @node Inline Functions
12110 @section Inline Functions
12111 @cindex inline functions, debugging
12113 @dfn{Inlining} is an optimization that inserts a copy of the function
12114 body directly at each call site, instead of jumping to a shared
12115 routine. @value{GDBN} displays inlined functions just like
12116 non-inlined functions. They appear in backtraces. You can view their
12117 arguments and local variables, step into them with @code{step}, skip
12118 them with @code{next}, and escape from them with @code{finish}.
12119 You can check whether a function was inlined by using the
12120 @code{info frame} command.
12122 For @value{GDBN} to support inlined functions, the compiler must
12123 record information about inlining in the debug information ---
12124 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12125 other compilers do also. @value{GDBN} only supports inlined functions
12126 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12127 do not emit two required attributes (@samp{DW_AT_call_file} and
12128 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12129 function calls with earlier versions of @value{NGCC}. It instead
12130 displays the arguments and local variables of inlined functions as
12131 local variables in the caller.
12133 The body of an inlined function is directly included at its call site;
12134 unlike a non-inlined function, there are no instructions devoted to
12135 the call. @value{GDBN} still pretends that the call site and the
12136 start of the inlined function are different instructions. Stepping to
12137 the call site shows the call site, and then stepping again shows
12138 the first line of the inlined function, even though no additional
12139 instructions are executed.
12141 This makes source-level debugging much clearer; you can see both the
12142 context of the call and then the effect of the call. Only stepping by
12143 a single instruction using @code{stepi} or @code{nexti} does not do
12144 this; single instruction steps always show the inlined body.
12146 There are some ways that @value{GDBN} does not pretend that inlined
12147 function calls are the same as normal calls:
12151 Setting breakpoints at the call site of an inlined function may not
12152 work, because the call site does not contain any code. @value{GDBN}
12153 may incorrectly move the breakpoint to the next line of the enclosing
12154 function, after the call. This limitation will be removed in a future
12155 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12156 or inside the inlined function instead.
12159 @value{GDBN} cannot locate the return value of inlined calls after
12160 using the @code{finish} command. This is a limitation of compiler-generated
12161 debugging information; after @code{finish}, you can step to the next line
12162 and print a variable where your program stored the return value.
12166 @node Tail Call Frames
12167 @section Tail Call Frames
12168 @cindex tail call frames, debugging
12170 Function @code{B} can call function @code{C} in its very last statement. In
12171 unoptimized compilation the call of @code{C} is immediately followed by return
12172 instruction at the end of @code{B} code. Optimizing compiler may replace the
12173 call and return in function @code{B} into one jump to function @code{C}
12174 instead. Such use of a jump instruction is called @dfn{tail call}.
12176 During execution of function @code{C}, there will be no indication in the
12177 function call stack frames that it was tail-called from @code{B}. If function
12178 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12179 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12180 some cases @value{GDBN} can determine that @code{C} was tail-called from
12181 @code{B}, and it will then create fictitious call frame for that, with the
12182 return address set up as if @code{B} called @code{C} normally.
12184 This functionality is currently supported only by DWARF 2 debugging format and
12185 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12186 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12189 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12190 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12194 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12196 Stack level 1, frame at 0x7fffffffda30:
12197 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12198 tail call frame, caller of frame at 0x7fffffffda30
12199 source language c++.
12200 Arglist at unknown address.
12201 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12204 The detection of all the possible code path executions can find them ambiguous.
12205 There is no execution history stored (possible @ref{Reverse Execution} is never
12206 used for this purpose) and the last known caller could have reached the known
12207 callee by multiple different jump sequences. In such case @value{GDBN} still
12208 tries to show at least all the unambiguous top tail callers and all the
12209 unambiguous bottom tail calees, if any.
12212 @anchor{set debug entry-values}
12213 @item set debug entry-values
12214 @kindex set debug entry-values
12215 When set to on, enables printing of analysis messages for both frame argument
12216 values at function entry and tail calls. It will show all the possible valid
12217 tail calls code paths it has considered. It will also print the intersection
12218 of them with the final unambiguous (possibly partial or even empty) code path
12221 @item show debug entry-values
12222 @kindex show debug entry-values
12223 Show the current state of analysis messages printing for both frame argument
12224 values at function entry and tail calls.
12227 The analysis messages for tail calls can for example show why the virtual tail
12228 call frame for function @code{c} has not been recognized (due to the indirect
12229 reference by variable @code{x}):
12232 static void __attribute__((noinline, noclone)) c (void);
12233 void (*x) (void) = c;
12234 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12235 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12236 int main (void) @{ x (); return 0; @}
12238 Breakpoint 1, DW_OP_entry_value resolving cannot find
12239 DW_TAG_call_site 0x40039a in main
12241 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12244 #1 0x000000000040039a in main () at t.c:5
12247 Another possibility is an ambiguous virtual tail call frames resolution:
12251 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12252 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12253 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12254 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12255 static void __attribute__((noinline, noclone)) b (void)
12256 @{ if (i) c (); else e (); @}
12257 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12258 int main (void) @{ a (); return 0; @}
12260 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12261 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12262 tailcall: reduced: 0x4004d2(a) |
12265 #1 0x00000000004004d2 in a () at t.c:8
12266 #2 0x0000000000400395 in main () at t.c:9
12269 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12270 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12272 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12273 @ifset HAVE_MAKEINFO_CLICK
12274 @set ARROW @click{}
12275 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12276 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12278 @ifclear HAVE_MAKEINFO_CLICK
12280 @set CALLSEQ1B @value{CALLSEQ1A}
12281 @set CALLSEQ2B @value{CALLSEQ2A}
12284 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12285 The code can have possible execution paths @value{CALLSEQ1B} or
12286 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12288 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12289 has found. It then finds another possible calling sequcen - that one is
12290 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12291 printed as the @code{reduced:} calling sequence. That one could have many
12292 futher @code{compare:} and @code{reduced:} statements as long as there remain
12293 any non-ambiguous sequence entries.
12295 For the frame of function @code{b} in both cases there are different possible
12296 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12297 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12298 therefore this one is displayed to the user while the ambiguous frames are
12301 There can be also reasons why printing of frame argument values at function
12306 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12307 static void __attribute__((noinline, noclone)) a (int i);
12308 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12309 static void __attribute__((noinline, noclone)) a (int i)
12310 @{ if (i) b (i - 1); else c (0); @}
12311 int main (void) @{ a (5); return 0; @}
12314 #0 c (i=i@@entry=0) at t.c:2
12315 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12316 function "a" at 0x400420 can call itself via tail calls
12317 i=<optimized out>) at t.c:6
12318 #2 0x000000000040036e in main () at t.c:7
12321 @value{GDBN} cannot find out from the inferior state if and how many times did
12322 function @code{a} call itself (via function @code{b}) as these calls would be
12323 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12324 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12325 prints @code{<optimized out>} instead.
12328 @chapter C Preprocessor Macros
12330 Some languages, such as C and C@t{++}, provide a way to define and invoke
12331 ``preprocessor macros'' which expand into strings of tokens.
12332 @value{GDBN} can evaluate expressions containing macro invocations, show
12333 the result of macro expansion, and show a macro's definition, including
12334 where it was defined.
12336 You may need to compile your program specially to provide @value{GDBN}
12337 with information about preprocessor macros. Most compilers do not
12338 include macros in their debugging information, even when you compile
12339 with the @option{-g} flag. @xref{Compilation}.
12341 A program may define a macro at one point, remove that definition later,
12342 and then provide a different definition after that. Thus, at different
12343 points in the program, a macro may have different definitions, or have
12344 no definition at all. If there is a current stack frame, @value{GDBN}
12345 uses the macros in scope at that frame's source code line. Otherwise,
12346 @value{GDBN} uses the macros in scope at the current listing location;
12349 Whenever @value{GDBN} evaluates an expression, it always expands any
12350 macro invocations present in the expression. @value{GDBN} also provides
12351 the following commands for working with macros explicitly.
12355 @kindex macro expand
12356 @cindex macro expansion, showing the results of preprocessor
12357 @cindex preprocessor macro expansion, showing the results of
12358 @cindex expanding preprocessor macros
12359 @item macro expand @var{expression}
12360 @itemx macro exp @var{expression}
12361 Show the results of expanding all preprocessor macro invocations in
12362 @var{expression}. Since @value{GDBN} simply expands macros, but does
12363 not parse the result, @var{expression} need not be a valid expression;
12364 it can be any string of tokens.
12367 @item macro expand-once @var{expression}
12368 @itemx macro exp1 @var{expression}
12369 @cindex expand macro once
12370 @i{(This command is not yet implemented.)} Show the results of
12371 expanding those preprocessor macro invocations that appear explicitly in
12372 @var{expression}. Macro invocations appearing in that expansion are
12373 left unchanged. This command allows you to see the effect of a
12374 particular macro more clearly, without being confused by further
12375 expansions. Since @value{GDBN} simply expands macros, but does not
12376 parse the result, @var{expression} need not be a valid expression; it
12377 can be any string of tokens.
12380 @cindex macro definition, showing
12381 @cindex definition of a macro, showing
12382 @cindex macros, from debug info
12383 @item info macro [-a|-all] [--] @var{macro}
12384 Show the current definition or all definitions of the named @var{macro},
12385 and describe the source location or compiler command-line where that
12386 definition was established. The optional double dash is to signify the end of
12387 argument processing and the beginning of @var{macro} for non C-like macros where
12388 the macro may begin with a hyphen.
12390 @kindex info macros
12391 @item info macros @var{location}
12392 Show all macro definitions that are in effect at the location specified
12393 by @var{location}, and describe the source location or compiler
12394 command-line where those definitions were established.
12396 @kindex macro define
12397 @cindex user-defined macros
12398 @cindex defining macros interactively
12399 @cindex macros, user-defined
12400 @item macro define @var{macro} @var{replacement-list}
12401 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12402 Introduce a definition for a preprocessor macro named @var{macro},
12403 invocations of which are replaced by the tokens given in
12404 @var{replacement-list}. The first form of this command defines an
12405 ``object-like'' macro, which takes no arguments; the second form
12406 defines a ``function-like'' macro, which takes the arguments given in
12409 A definition introduced by this command is in scope in every
12410 expression evaluated in @value{GDBN}, until it is removed with the
12411 @code{macro undef} command, described below. The definition overrides
12412 all definitions for @var{macro} present in the program being debugged,
12413 as well as any previous user-supplied definition.
12415 @kindex macro undef
12416 @item macro undef @var{macro}
12417 Remove any user-supplied definition for the macro named @var{macro}.
12418 This command only affects definitions provided with the @code{macro
12419 define} command, described above; it cannot remove definitions present
12420 in the program being debugged.
12424 List all the macros defined using the @code{macro define} command.
12427 @cindex macros, example of debugging with
12428 Here is a transcript showing the above commands in action. First, we
12429 show our source files:
12434 #include "sample.h"
12437 #define ADD(x) (M + x)
12442 printf ("Hello, world!\n");
12444 printf ("We're so creative.\n");
12446 printf ("Goodbye, world!\n");
12453 Now, we compile the program using the @sc{gnu} C compiler,
12454 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12455 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12456 and @option{-gdwarf-4}; we recommend always choosing the most recent
12457 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12458 includes information about preprocessor macros in the debugging
12462 $ gcc -gdwarf-2 -g3 sample.c -o sample
12466 Now, we start @value{GDBN} on our sample program:
12470 GNU gdb 2002-05-06-cvs
12471 Copyright 2002 Free Software Foundation, Inc.
12472 GDB is free software, @dots{}
12476 We can expand macros and examine their definitions, even when the
12477 program is not running. @value{GDBN} uses the current listing position
12478 to decide which macro definitions are in scope:
12481 (@value{GDBP}) list main
12484 5 #define ADD(x) (M + x)
12489 10 printf ("Hello, world!\n");
12491 12 printf ("We're so creative.\n");
12492 (@value{GDBP}) info macro ADD
12493 Defined at /home/jimb/gdb/macros/play/sample.c:5
12494 #define ADD(x) (M + x)
12495 (@value{GDBP}) info macro Q
12496 Defined at /home/jimb/gdb/macros/play/sample.h:1
12497 included at /home/jimb/gdb/macros/play/sample.c:2
12499 (@value{GDBP}) macro expand ADD(1)
12500 expands to: (42 + 1)
12501 (@value{GDBP}) macro expand-once ADD(1)
12502 expands to: once (M + 1)
12506 In the example above, note that @code{macro expand-once} expands only
12507 the macro invocation explicit in the original text --- the invocation of
12508 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12509 which was introduced by @code{ADD}.
12511 Once the program is running, @value{GDBN} uses the macro definitions in
12512 force at the source line of the current stack frame:
12515 (@value{GDBP}) break main
12516 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12518 Starting program: /home/jimb/gdb/macros/play/sample
12520 Breakpoint 1, main () at sample.c:10
12521 10 printf ("Hello, world!\n");
12525 At line 10, the definition of the macro @code{N} at line 9 is in force:
12528 (@value{GDBP}) info macro N
12529 Defined at /home/jimb/gdb/macros/play/sample.c:9
12531 (@value{GDBP}) macro expand N Q M
12532 expands to: 28 < 42
12533 (@value{GDBP}) print N Q M
12538 As we step over directives that remove @code{N}'s definition, and then
12539 give it a new definition, @value{GDBN} finds the definition (or lack
12540 thereof) in force at each point:
12543 (@value{GDBP}) next
12545 12 printf ("We're so creative.\n");
12546 (@value{GDBP}) info macro N
12547 The symbol `N' has no definition as a C/C++ preprocessor macro
12548 at /home/jimb/gdb/macros/play/sample.c:12
12549 (@value{GDBP}) next
12551 14 printf ("Goodbye, world!\n");
12552 (@value{GDBP}) info macro N
12553 Defined at /home/jimb/gdb/macros/play/sample.c:13
12555 (@value{GDBP}) macro expand N Q M
12556 expands to: 1729 < 42
12557 (@value{GDBP}) print N Q M
12562 In addition to source files, macros can be defined on the compilation command
12563 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12564 such a way, @value{GDBN} displays the location of their definition as line zero
12565 of the source file submitted to the compiler.
12568 (@value{GDBP}) info macro __STDC__
12569 Defined at /home/jimb/gdb/macros/play/sample.c:0
12576 @chapter Tracepoints
12577 @c This chapter is based on the documentation written by Michael
12578 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12580 @cindex tracepoints
12581 In some applications, it is not feasible for the debugger to interrupt
12582 the program's execution long enough for the developer to learn
12583 anything helpful about its behavior. If the program's correctness
12584 depends on its real-time behavior, delays introduced by a debugger
12585 might cause the program to change its behavior drastically, or perhaps
12586 fail, even when the code itself is correct. It is useful to be able
12587 to observe the program's behavior without interrupting it.
12589 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12590 specify locations in the program, called @dfn{tracepoints}, and
12591 arbitrary expressions to evaluate when those tracepoints are reached.
12592 Later, using the @code{tfind} command, you can examine the values
12593 those expressions had when the program hit the tracepoints. The
12594 expressions may also denote objects in memory---structures or arrays,
12595 for example---whose values @value{GDBN} should record; while visiting
12596 a particular tracepoint, you may inspect those objects as if they were
12597 in memory at that moment. However, because @value{GDBN} records these
12598 values without interacting with you, it can do so quickly and
12599 unobtrusively, hopefully not disturbing the program's behavior.
12601 The tracepoint facility is currently available only for remote
12602 targets. @xref{Targets}. In addition, your remote target must know
12603 how to collect trace data. This functionality is implemented in the
12604 remote stub; however, none of the stubs distributed with @value{GDBN}
12605 support tracepoints as of this writing. The format of the remote
12606 packets used to implement tracepoints are described in @ref{Tracepoint
12609 It is also possible to get trace data from a file, in a manner reminiscent
12610 of corefiles; you specify the filename, and use @code{tfind} to search
12611 through the file. @xref{Trace Files}, for more details.
12613 This chapter describes the tracepoint commands and features.
12616 * Set Tracepoints::
12617 * Analyze Collected Data::
12618 * Tracepoint Variables::
12622 @node Set Tracepoints
12623 @section Commands to Set Tracepoints
12625 Before running such a @dfn{trace experiment}, an arbitrary number of
12626 tracepoints can be set. A tracepoint is actually a special type of
12627 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12628 standard breakpoint commands. For instance, as with breakpoints,
12629 tracepoint numbers are successive integers starting from one, and many
12630 of the commands associated with tracepoints take the tracepoint number
12631 as their argument, to identify which tracepoint to work on.
12633 For each tracepoint, you can specify, in advance, some arbitrary set
12634 of data that you want the target to collect in the trace buffer when
12635 it hits that tracepoint. The collected data can include registers,
12636 local variables, or global data. Later, you can use @value{GDBN}
12637 commands to examine the values these data had at the time the
12638 tracepoint was hit.
12640 Tracepoints do not support every breakpoint feature. Ignore counts on
12641 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12642 commands when they are hit. Tracepoints may not be thread-specific
12645 @cindex fast tracepoints
12646 Some targets may support @dfn{fast tracepoints}, which are inserted in
12647 a different way (such as with a jump instead of a trap), that is
12648 faster but possibly restricted in where they may be installed.
12650 @cindex static tracepoints
12651 @cindex markers, static tracepoints
12652 @cindex probing markers, static tracepoints
12653 Regular and fast tracepoints are dynamic tracing facilities, meaning
12654 that they can be used to insert tracepoints at (almost) any location
12655 in the target. Some targets may also support controlling @dfn{static
12656 tracepoints} from @value{GDBN}. With static tracing, a set of
12657 instrumentation points, also known as @dfn{markers}, are embedded in
12658 the target program, and can be activated or deactivated by name or
12659 address. These are usually placed at locations which facilitate
12660 investigating what the target is actually doing. @value{GDBN}'s
12661 support for static tracing includes being able to list instrumentation
12662 points, and attach them with @value{GDBN} defined high level
12663 tracepoints that expose the whole range of convenience of
12664 @value{GDBN}'s tracepoints support. Namely, support for collecting
12665 registers values and values of global or local (to the instrumentation
12666 point) variables; tracepoint conditions and trace state variables.
12667 The act of installing a @value{GDBN} static tracepoint on an
12668 instrumentation point, or marker, is referred to as @dfn{probing} a
12669 static tracepoint marker.
12671 @code{gdbserver} supports tracepoints on some target systems.
12672 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12674 This section describes commands to set tracepoints and associated
12675 conditions and actions.
12678 * Create and Delete Tracepoints::
12679 * Enable and Disable Tracepoints::
12680 * Tracepoint Passcounts::
12681 * Tracepoint Conditions::
12682 * Trace State Variables::
12683 * Tracepoint Actions::
12684 * Listing Tracepoints::
12685 * Listing Static Tracepoint Markers::
12686 * Starting and Stopping Trace Experiments::
12687 * Tracepoint Restrictions::
12690 @node Create and Delete Tracepoints
12691 @subsection Create and Delete Tracepoints
12694 @cindex set tracepoint
12696 @item trace @var{location}
12697 The @code{trace} command is very similar to the @code{break} command.
12698 Its argument @var{location} can be any valid location.
12699 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12700 which is a point in the target program where the debugger will briefly stop,
12701 collect some data, and then allow the program to continue. Setting a tracepoint
12702 or changing its actions takes effect immediately if the remote stub
12703 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12705 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12706 these changes don't take effect until the next @code{tstart}
12707 command, and once a trace experiment is running, further changes will
12708 not have any effect until the next trace experiment starts. In addition,
12709 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12710 address is not yet resolved. (This is similar to pending breakpoints.)
12711 Pending tracepoints are not downloaded to the target and not installed
12712 until they are resolved. The resolution of pending tracepoints requires
12713 @value{GDBN} support---when debugging with the remote target, and
12714 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12715 tracing}), pending tracepoints can not be resolved (and downloaded to
12716 the remote stub) while @value{GDBN} is disconnected.
12718 Here are some examples of using the @code{trace} command:
12721 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12723 (@value{GDBP}) @b{trace +2} // 2 lines forward
12725 (@value{GDBP}) @b{trace my_function} // first source line of function
12727 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12729 (@value{GDBP}) @b{trace *0x2117c4} // an address
12733 You can abbreviate @code{trace} as @code{tr}.
12735 @item trace @var{location} if @var{cond}
12736 Set a tracepoint with condition @var{cond}; evaluate the expression
12737 @var{cond} each time the tracepoint is reached, and collect data only
12738 if the value is nonzero---that is, if @var{cond} evaluates as true.
12739 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12740 information on tracepoint conditions.
12742 @item ftrace @var{location} [ if @var{cond} ]
12743 @cindex set fast tracepoint
12744 @cindex fast tracepoints, setting
12746 The @code{ftrace} command sets a fast tracepoint. For targets that
12747 support them, fast tracepoints will use a more efficient but possibly
12748 less general technique to trigger data collection, such as a jump
12749 instruction instead of a trap, or some sort of hardware support. It
12750 may not be possible to create a fast tracepoint at the desired
12751 location, in which case the command will exit with an explanatory
12754 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12757 On 32-bit x86-architecture systems, fast tracepoints normally need to
12758 be placed at an instruction that is 5 bytes or longer, but can be
12759 placed at 4-byte instructions if the low 64K of memory of the target
12760 program is available to install trampolines. Some Unix-type systems,
12761 such as @sc{gnu}/Linux, exclude low addresses from the program's
12762 address space; but for instance with the Linux kernel it is possible
12763 to let @value{GDBN} use this area by doing a @command{sysctl} command
12764 to set the @code{mmap_min_addr} kernel parameter, as in
12767 sudo sysctl -w vm.mmap_min_addr=32768
12771 which sets the low address to 32K, which leaves plenty of room for
12772 trampolines. The minimum address should be set to a page boundary.
12774 @item strace @var{location} [ if @var{cond} ]
12775 @cindex set static tracepoint
12776 @cindex static tracepoints, setting
12777 @cindex probe static tracepoint marker
12779 The @code{strace} command sets a static tracepoint. For targets that
12780 support it, setting a static tracepoint probes a static
12781 instrumentation point, or marker, found at @var{location}. It may not
12782 be possible to set a static tracepoint at the desired location, in
12783 which case the command will exit with an explanatory message.
12785 @value{GDBN} handles arguments to @code{strace} exactly as for
12786 @code{trace}, with the addition that the user can also specify
12787 @code{-m @var{marker}} as @var{location}. This probes the marker
12788 identified by the @var{marker} string identifier. This identifier
12789 depends on the static tracepoint backend library your program is
12790 using. You can find all the marker identifiers in the @samp{ID} field
12791 of the @code{info static-tracepoint-markers} command output.
12792 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12793 Markers}. For example, in the following small program using the UST
12799 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12804 the marker id is composed of joining the first two arguments to the
12805 @code{trace_mark} call with a slash, which translates to:
12808 (@value{GDBP}) info static-tracepoint-markers
12809 Cnt Enb ID Address What
12810 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12816 so you may probe the marker above with:
12819 (@value{GDBP}) strace -m ust/bar33
12822 Static tracepoints accept an extra collect action --- @code{collect
12823 $_sdata}. This collects arbitrary user data passed in the probe point
12824 call to the tracing library. In the UST example above, you'll see
12825 that the third argument to @code{trace_mark} is a printf-like format
12826 string. The user data is then the result of running that formating
12827 string against the following arguments. Note that @code{info
12828 static-tracepoint-markers} command output lists that format string in
12829 the @samp{Data:} field.
12831 You can inspect this data when analyzing the trace buffer, by printing
12832 the $_sdata variable like any other variable available to
12833 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12836 @cindex last tracepoint number
12837 @cindex recent tracepoint number
12838 @cindex tracepoint number
12839 The convenience variable @code{$tpnum} records the tracepoint number
12840 of the most recently set tracepoint.
12842 @kindex delete tracepoint
12843 @cindex tracepoint deletion
12844 @item delete tracepoint @r{[}@var{num}@r{]}
12845 Permanently delete one or more tracepoints. With no argument, the
12846 default is to delete all tracepoints. Note that the regular
12847 @code{delete} command can remove tracepoints also.
12852 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12854 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12858 You can abbreviate this command as @code{del tr}.
12861 @node Enable and Disable Tracepoints
12862 @subsection Enable and Disable Tracepoints
12864 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12867 @kindex disable tracepoint
12868 @item disable tracepoint @r{[}@var{num}@r{]}
12869 Disable tracepoint @var{num}, or all tracepoints if no argument
12870 @var{num} is given. A disabled tracepoint will have no effect during
12871 a trace experiment, but it is not forgotten. You can re-enable
12872 a disabled tracepoint using the @code{enable tracepoint} command.
12873 If the command is issued during a trace experiment and the debug target
12874 has support for disabling tracepoints during a trace experiment, then the
12875 change will be effective immediately. Otherwise, it will be applied to the
12876 next trace experiment.
12878 @kindex enable tracepoint
12879 @item enable tracepoint @r{[}@var{num}@r{]}
12880 Enable tracepoint @var{num}, or all tracepoints. If this command is
12881 issued during a trace experiment and the debug target supports enabling
12882 tracepoints during a trace experiment, then the enabled tracepoints will
12883 become effective immediately. Otherwise, they will become effective the
12884 next time a trace experiment is run.
12887 @node Tracepoint Passcounts
12888 @subsection Tracepoint Passcounts
12892 @cindex tracepoint pass count
12893 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12894 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12895 automatically stop a trace experiment. If a tracepoint's passcount is
12896 @var{n}, then the trace experiment will be automatically stopped on
12897 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12898 @var{num} is not specified, the @code{passcount} command sets the
12899 passcount of the most recently defined tracepoint. If no passcount is
12900 given, the trace experiment will run until stopped explicitly by the
12906 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12907 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12909 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12910 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12911 (@value{GDBP}) @b{trace foo}
12912 (@value{GDBP}) @b{pass 3}
12913 (@value{GDBP}) @b{trace bar}
12914 (@value{GDBP}) @b{pass 2}
12915 (@value{GDBP}) @b{trace baz}
12916 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12917 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12918 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12919 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12923 @node Tracepoint Conditions
12924 @subsection Tracepoint Conditions
12925 @cindex conditional tracepoints
12926 @cindex tracepoint conditions
12928 The simplest sort of tracepoint collects data every time your program
12929 reaches a specified place. You can also specify a @dfn{condition} for
12930 a tracepoint. A condition is just a Boolean expression in your
12931 programming language (@pxref{Expressions, ,Expressions}). A
12932 tracepoint with a condition evaluates the expression each time your
12933 program reaches it, and data collection happens only if the condition
12936 Tracepoint conditions can be specified when a tracepoint is set, by
12937 using @samp{if} in the arguments to the @code{trace} command.
12938 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12939 also be set or changed at any time with the @code{condition} command,
12940 just as with breakpoints.
12942 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12943 the conditional expression itself. Instead, @value{GDBN} encodes the
12944 expression into an agent expression (@pxref{Agent Expressions})
12945 suitable for execution on the target, independently of @value{GDBN}.
12946 Global variables become raw memory locations, locals become stack
12947 accesses, and so forth.
12949 For instance, suppose you have a function that is usually called
12950 frequently, but should not be called after an error has occurred. You
12951 could use the following tracepoint command to collect data about calls
12952 of that function that happen while the error code is propagating
12953 through the program; an unconditional tracepoint could end up
12954 collecting thousands of useless trace frames that you would have to
12958 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12961 @node Trace State Variables
12962 @subsection Trace State Variables
12963 @cindex trace state variables
12965 A @dfn{trace state variable} is a special type of variable that is
12966 created and managed by target-side code. The syntax is the same as
12967 that for GDB's convenience variables (a string prefixed with ``$''),
12968 but they are stored on the target. They must be created explicitly,
12969 using a @code{tvariable} command. They are always 64-bit signed
12972 Trace state variables are remembered by @value{GDBN}, and downloaded
12973 to the target along with tracepoint information when the trace
12974 experiment starts. There are no intrinsic limits on the number of
12975 trace state variables, beyond memory limitations of the target.
12977 @cindex convenience variables, and trace state variables
12978 Although trace state variables are managed by the target, you can use
12979 them in print commands and expressions as if they were convenience
12980 variables; @value{GDBN} will get the current value from the target
12981 while the trace experiment is running. Trace state variables share
12982 the same namespace as other ``$'' variables, which means that you
12983 cannot have trace state variables with names like @code{$23} or
12984 @code{$pc}, nor can you have a trace state variable and a convenience
12985 variable with the same name.
12989 @item tvariable $@var{name} [ = @var{expression} ]
12991 The @code{tvariable} command creates a new trace state variable named
12992 @code{$@var{name}}, and optionally gives it an initial value of
12993 @var{expression}. The @var{expression} is evaluated when this command is
12994 entered; the result will be converted to an integer if possible,
12995 otherwise @value{GDBN} will report an error. A subsequent
12996 @code{tvariable} command specifying the same name does not create a
12997 variable, but instead assigns the supplied initial value to the
12998 existing variable of that name, overwriting any previous initial
12999 value. The default initial value is 0.
13001 @item info tvariables
13002 @kindex info tvariables
13003 List all the trace state variables along with their initial values.
13004 Their current values may also be displayed, if the trace experiment is
13007 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13008 @kindex delete tvariable
13009 Delete the given trace state variables, or all of them if no arguments
13014 @node Tracepoint Actions
13015 @subsection Tracepoint Action Lists
13019 @cindex tracepoint actions
13020 @item actions @r{[}@var{num}@r{]}
13021 This command will prompt for a list of actions to be taken when the
13022 tracepoint is hit. If the tracepoint number @var{num} is not
13023 specified, this command sets the actions for the one that was most
13024 recently defined (so that you can define a tracepoint and then say
13025 @code{actions} without bothering about its number). You specify the
13026 actions themselves on the following lines, one action at a time, and
13027 terminate the actions list with a line containing just @code{end}. So
13028 far, the only defined actions are @code{collect}, @code{teval}, and
13029 @code{while-stepping}.
13031 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13032 Commands, ,Breakpoint Command Lists}), except that only the defined
13033 actions are allowed; any other @value{GDBN} command is rejected.
13035 @cindex remove actions from a tracepoint
13036 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13037 and follow it immediately with @samp{end}.
13040 (@value{GDBP}) @b{collect @var{data}} // collect some data
13042 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13044 (@value{GDBP}) @b{end} // signals the end of actions.
13047 In the following example, the action list begins with @code{collect}
13048 commands indicating the things to be collected when the tracepoint is
13049 hit. Then, in order to single-step and collect additional data
13050 following the tracepoint, a @code{while-stepping} command is used,
13051 followed by the list of things to be collected after each step in a
13052 sequence of single steps. The @code{while-stepping} command is
13053 terminated by its own separate @code{end} command. Lastly, the action
13054 list is terminated by an @code{end} command.
13057 (@value{GDBP}) @b{trace foo}
13058 (@value{GDBP}) @b{actions}
13059 Enter actions for tracepoint 1, one per line:
13062 > while-stepping 12
13063 > collect $pc, arr[i]
13068 @kindex collect @r{(tracepoints)}
13069 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13070 Collect values of the given expressions when the tracepoint is hit.
13071 This command accepts a comma-separated list of any valid expressions.
13072 In addition to global, static, or local variables, the following
13073 special arguments are supported:
13077 Collect all registers.
13080 Collect all function arguments.
13083 Collect all local variables.
13086 Collect the return address. This is helpful if you want to see more
13089 @emph{Note:} The return address location can not always be reliably
13090 determined up front, and the wrong address / registers may end up
13091 collected instead. On some architectures the reliability is higher
13092 for tracepoints at function entry, while on others it's the opposite.
13093 When this happens, backtracing will stop because the return address is
13094 found unavailable (unless another collect rule happened to match it).
13097 Collects the number of arguments from the static probe at which the
13098 tracepoint is located.
13099 @xref{Static Probe Points}.
13101 @item $_probe_arg@var{n}
13102 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13103 from the static probe at which the tracepoint is located.
13104 @xref{Static Probe Points}.
13107 @vindex $_sdata@r{, collect}
13108 Collect static tracepoint marker specific data. Only available for
13109 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13110 Lists}. On the UST static tracepoints library backend, an
13111 instrumentation point resembles a @code{printf} function call. The
13112 tracing library is able to collect user specified data formatted to a
13113 character string using the format provided by the programmer that
13114 instrumented the program. Other backends have similar mechanisms.
13115 Here's an example of a UST marker call:
13118 const char master_name[] = "$your_name";
13119 trace_mark(channel1, marker1, "hello %s", master_name)
13122 In this case, collecting @code{$_sdata} collects the string
13123 @samp{hello $yourname}. When analyzing the trace buffer, you can
13124 inspect @samp{$_sdata} like any other variable available to
13128 You can give several consecutive @code{collect} commands, each one
13129 with a single argument, or one @code{collect} command with several
13130 arguments separated by commas; the effect is the same.
13132 The optional @var{mods} changes the usual handling of the arguments.
13133 @code{s} requests that pointers to chars be handled as strings, in
13134 particular collecting the contents of the memory being pointed at, up
13135 to the first zero. The upper bound is by default the value of the
13136 @code{print elements} variable; if @code{s} is followed by a decimal
13137 number, that is the upper bound instead. So for instance
13138 @samp{collect/s25 mystr} collects as many as 25 characters at
13141 The command @code{info scope} (@pxref{Symbols, info scope}) is
13142 particularly useful for figuring out what data to collect.
13144 @kindex teval @r{(tracepoints)}
13145 @item teval @var{expr1}, @var{expr2}, @dots{}
13146 Evaluate the given expressions when the tracepoint is hit. This
13147 command accepts a comma-separated list of expressions. The results
13148 are discarded, so this is mainly useful for assigning values to trace
13149 state variables (@pxref{Trace State Variables}) without adding those
13150 values to the trace buffer, as would be the case if the @code{collect}
13153 @kindex while-stepping @r{(tracepoints)}
13154 @item while-stepping @var{n}
13155 Perform @var{n} single-step instruction traces after the tracepoint,
13156 collecting new data after each step. The @code{while-stepping}
13157 command is followed by the list of what to collect while stepping
13158 (followed by its own @code{end} command):
13161 > while-stepping 12
13162 > collect $regs, myglobal
13168 Note that @code{$pc} is not automatically collected by
13169 @code{while-stepping}; you need to explicitly collect that register if
13170 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13173 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13174 @kindex set default-collect
13175 @cindex default collection action
13176 This variable is a list of expressions to collect at each tracepoint
13177 hit. It is effectively an additional @code{collect} action prepended
13178 to every tracepoint action list. The expressions are parsed
13179 individually for each tracepoint, so for instance a variable named
13180 @code{xyz} may be interpreted as a global for one tracepoint, and a
13181 local for another, as appropriate to the tracepoint's location.
13183 @item show default-collect
13184 @kindex show default-collect
13185 Show the list of expressions that are collected by default at each
13190 @node Listing Tracepoints
13191 @subsection Listing Tracepoints
13194 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13195 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13196 @cindex information about tracepoints
13197 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13198 Display information about the tracepoint @var{num}. If you don't
13199 specify a tracepoint number, displays information about all the
13200 tracepoints defined so far. The format is similar to that used for
13201 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13202 command, simply restricting itself to tracepoints.
13204 A tracepoint's listing may include additional information specific to
13209 its passcount as given by the @code{passcount @var{n}} command
13212 the state about installed on target of each location
13216 (@value{GDBP}) @b{info trace}
13217 Num Type Disp Enb Address What
13218 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13220 collect globfoo, $regs
13225 2 tracepoint keep y <MULTIPLE>
13227 2.1 y 0x0804859c in func4 at change-loc.h:35
13228 installed on target
13229 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13230 installed on target
13231 2.3 y <PENDING> set_tracepoint
13232 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13233 not installed on target
13238 This command can be abbreviated @code{info tp}.
13241 @node Listing Static Tracepoint Markers
13242 @subsection Listing Static Tracepoint Markers
13245 @kindex info static-tracepoint-markers
13246 @cindex information about static tracepoint markers
13247 @item info static-tracepoint-markers
13248 Display information about all static tracepoint markers defined in the
13251 For each marker, the following columns are printed:
13255 An incrementing counter, output to help readability. This is not a
13258 The marker ID, as reported by the target.
13259 @item Enabled or Disabled
13260 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13261 that are not enabled.
13263 Where the marker is in your program, as a memory address.
13265 Where the marker is in the source for your program, as a file and line
13266 number. If the debug information included in the program does not
13267 allow @value{GDBN} to locate the source of the marker, this column
13268 will be left blank.
13272 In addition, the following information may be printed for each marker:
13276 User data passed to the tracing library by the marker call. In the
13277 UST backend, this is the format string passed as argument to the
13279 @item Static tracepoints probing the marker
13280 The list of static tracepoints attached to the marker.
13284 (@value{GDBP}) info static-tracepoint-markers
13285 Cnt ID Enb Address What
13286 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13287 Data: number1 %d number2 %d
13288 Probed by static tracepoints: #2
13289 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13295 @node Starting and Stopping Trace Experiments
13296 @subsection Starting and Stopping Trace Experiments
13299 @kindex tstart [ @var{notes} ]
13300 @cindex start a new trace experiment
13301 @cindex collected data discarded
13303 This command starts the trace experiment, and begins collecting data.
13304 It has the side effect of discarding all the data collected in the
13305 trace buffer during the previous trace experiment. If any arguments
13306 are supplied, they are taken as a note and stored with the trace
13307 experiment's state. The notes may be arbitrary text, and are
13308 especially useful with disconnected tracing in a multi-user context;
13309 the notes can explain what the trace is doing, supply user contact
13310 information, and so forth.
13312 @kindex tstop [ @var{notes} ]
13313 @cindex stop a running trace experiment
13315 This command stops the trace experiment. If any arguments are
13316 supplied, they are recorded with the experiment as a note. This is
13317 useful if you are stopping a trace started by someone else, for
13318 instance if the trace is interfering with the system's behavior and
13319 needs to be stopped quickly.
13321 @strong{Note}: a trace experiment and data collection may stop
13322 automatically if any tracepoint's passcount is reached
13323 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13326 @cindex status of trace data collection
13327 @cindex trace experiment, status of
13329 This command displays the status of the current trace data
13333 Here is an example of the commands we described so far:
13336 (@value{GDBP}) @b{trace gdb_c_test}
13337 (@value{GDBP}) @b{actions}
13338 Enter actions for tracepoint #1, one per line.
13339 > collect $regs,$locals,$args
13340 > while-stepping 11
13344 (@value{GDBP}) @b{tstart}
13345 [time passes @dots{}]
13346 (@value{GDBP}) @b{tstop}
13349 @anchor{disconnected tracing}
13350 @cindex disconnected tracing
13351 You can choose to continue running the trace experiment even if
13352 @value{GDBN} disconnects from the target, voluntarily or
13353 involuntarily. For commands such as @code{detach}, the debugger will
13354 ask what you want to do with the trace. But for unexpected
13355 terminations (@value{GDBN} crash, network outage), it would be
13356 unfortunate to lose hard-won trace data, so the variable
13357 @code{disconnected-tracing} lets you decide whether the trace should
13358 continue running without @value{GDBN}.
13361 @item set disconnected-tracing on
13362 @itemx set disconnected-tracing off
13363 @kindex set disconnected-tracing
13364 Choose whether a tracing run should continue to run if @value{GDBN}
13365 has disconnected from the target. Note that @code{detach} or
13366 @code{quit} will ask you directly what to do about a running trace no
13367 matter what this variable's setting, so the variable is mainly useful
13368 for handling unexpected situations, such as loss of the network.
13370 @item show disconnected-tracing
13371 @kindex show disconnected-tracing
13372 Show the current choice for disconnected tracing.
13376 When you reconnect to the target, the trace experiment may or may not
13377 still be running; it might have filled the trace buffer in the
13378 meantime, or stopped for one of the other reasons. If it is running,
13379 it will continue after reconnection.
13381 Upon reconnection, the target will upload information about the
13382 tracepoints in effect. @value{GDBN} will then compare that
13383 information to the set of tracepoints currently defined, and attempt
13384 to match them up, allowing for the possibility that the numbers may
13385 have changed due to creation and deletion in the meantime. If one of
13386 the target's tracepoints does not match any in @value{GDBN}, the
13387 debugger will create a new tracepoint, so that you have a number with
13388 which to specify that tracepoint. This matching-up process is
13389 necessarily heuristic, and it may result in useless tracepoints being
13390 created; you may simply delete them if they are of no use.
13392 @cindex circular trace buffer
13393 If your target agent supports a @dfn{circular trace buffer}, then you
13394 can run a trace experiment indefinitely without filling the trace
13395 buffer; when space runs out, the agent deletes already-collected trace
13396 frames, oldest first, until there is enough room to continue
13397 collecting. This is especially useful if your tracepoints are being
13398 hit too often, and your trace gets terminated prematurely because the
13399 buffer is full. To ask for a circular trace buffer, simply set
13400 @samp{circular-trace-buffer} to on. You can set this at any time,
13401 including during tracing; if the agent can do it, it will change
13402 buffer handling on the fly, otherwise it will not take effect until
13406 @item set circular-trace-buffer on
13407 @itemx set circular-trace-buffer off
13408 @kindex set circular-trace-buffer
13409 Choose whether a tracing run should use a linear or circular buffer
13410 for trace data. A linear buffer will not lose any trace data, but may
13411 fill up prematurely, while a circular buffer will discard old trace
13412 data, but it will have always room for the latest tracepoint hits.
13414 @item show circular-trace-buffer
13415 @kindex show circular-trace-buffer
13416 Show the current choice for the trace buffer. Note that this may not
13417 match the agent's current buffer handling, nor is it guaranteed to
13418 match the setting that might have been in effect during a past run,
13419 for instance if you are looking at frames from a trace file.
13424 @item set trace-buffer-size @var{n}
13425 @itemx set trace-buffer-size unlimited
13426 @kindex set trace-buffer-size
13427 Request that the target use a trace buffer of @var{n} bytes. Not all
13428 targets will honor the request; they may have a compiled-in size for
13429 the trace buffer, or some other limitation. Set to a value of
13430 @code{unlimited} or @code{-1} to let the target use whatever size it
13431 likes. This is also the default.
13433 @item show trace-buffer-size
13434 @kindex show trace-buffer-size
13435 Show the current requested size for the trace buffer. Note that this
13436 will only match the actual size if the target supports size-setting,
13437 and was able to handle the requested size. For instance, if the
13438 target can only change buffer size between runs, this variable will
13439 not reflect the change until the next run starts. Use @code{tstatus}
13440 to get a report of the actual buffer size.
13444 @item set trace-user @var{text}
13445 @kindex set trace-user
13447 @item show trace-user
13448 @kindex show trace-user
13450 @item set trace-notes @var{text}
13451 @kindex set trace-notes
13452 Set the trace run's notes.
13454 @item show trace-notes
13455 @kindex show trace-notes
13456 Show the trace run's notes.
13458 @item set trace-stop-notes @var{text}
13459 @kindex set trace-stop-notes
13460 Set the trace run's stop notes. The handling of the note is as for
13461 @code{tstop} arguments; the set command is convenient way to fix a
13462 stop note that is mistaken or incomplete.
13464 @item show trace-stop-notes
13465 @kindex show trace-stop-notes
13466 Show the trace run's stop notes.
13470 @node Tracepoint Restrictions
13471 @subsection Tracepoint Restrictions
13473 @cindex tracepoint restrictions
13474 There are a number of restrictions on the use of tracepoints. As
13475 described above, tracepoint data gathering occurs on the target
13476 without interaction from @value{GDBN}. Thus the full capabilities of
13477 the debugger are not available during data gathering, and then at data
13478 examination time, you will be limited by only having what was
13479 collected. The following items describe some common problems, but it
13480 is not exhaustive, and you may run into additional difficulties not
13486 Tracepoint expressions are intended to gather objects (lvalues). Thus
13487 the full flexibility of GDB's expression evaluator is not available.
13488 You cannot call functions, cast objects to aggregate types, access
13489 convenience variables or modify values (except by assignment to trace
13490 state variables). Some language features may implicitly call
13491 functions (for instance Objective-C fields with accessors), and therefore
13492 cannot be collected either.
13495 Collection of local variables, either individually or in bulk with
13496 @code{$locals} or @code{$args}, during @code{while-stepping} may
13497 behave erratically. The stepping action may enter a new scope (for
13498 instance by stepping into a function), or the location of the variable
13499 may change (for instance it is loaded into a register). The
13500 tracepoint data recorded uses the location information for the
13501 variables that is correct for the tracepoint location. When the
13502 tracepoint is created, it is not possible, in general, to determine
13503 where the steps of a @code{while-stepping} sequence will advance the
13504 program---particularly if a conditional branch is stepped.
13507 Collection of an incompletely-initialized or partially-destroyed object
13508 may result in something that @value{GDBN} cannot display, or displays
13509 in a misleading way.
13512 When @value{GDBN} displays a pointer to character it automatically
13513 dereferences the pointer to also display characters of the string
13514 being pointed to. However, collecting the pointer during tracing does
13515 not automatically collect the string. You need to explicitly
13516 dereference the pointer and provide size information if you want to
13517 collect not only the pointer, but the memory pointed to. For example,
13518 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13522 It is not possible to collect a complete stack backtrace at a
13523 tracepoint. Instead, you may collect the registers and a few hundred
13524 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13525 (adjust to use the name of the actual stack pointer register on your
13526 target architecture, and the amount of stack you wish to capture).
13527 Then the @code{backtrace} command will show a partial backtrace when
13528 using a trace frame. The number of stack frames that can be examined
13529 depends on the sizes of the frames in the collected stack. Note that
13530 if you ask for a block so large that it goes past the bottom of the
13531 stack, the target agent may report an error trying to read from an
13535 If you do not collect registers at a tracepoint, @value{GDBN} can
13536 infer that the value of @code{$pc} must be the same as the address of
13537 the tracepoint and use that when you are looking at a trace frame
13538 for that tracepoint. However, this cannot work if the tracepoint has
13539 multiple locations (for instance if it was set in a function that was
13540 inlined), or if it has a @code{while-stepping} loop. In those cases
13541 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13546 @node Analyze Collected Data
13547 @section Using the Collected Data
13549 After the tracepoint experiment ends, you use @value{GDBN} commands
13550 for examining the trace data. The basic idea is that each tracepoint
13551 collects a trace @dfn{snapshot} every time it is hit and another
13552 snapshot every time it single-steps. All these snapshots are
13553 consecutively numbered from zero and go into a buffer, and you can
13554 examine them later. The way you examine them is to @dfn{focus} on a
13555 specific trace snapshot. When the remote stub is focused on a trace
13556 snapshot, it will respond to all @value{GDBN} requests for memory and
13557 registers by reading from the buffer which belongs to that snapshot,
13558 rather than from @emph{real} memory or registers of the program being
13559 debugged. This means that @strong{all} @value{GDBN} commands
13560 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13561 behave as if we were currently debugging the program state as it was
13562 when the tracepoint occurred. Any requests for data that are not in
13563 the buffer will fail.
13566 * tfind:: How to select a trace snapshot
13567 * tdump:: How to display all data for a snapshot
13568 * save tracepoints:: How to save tracepoints for a future run
13572 @subsection @code{tfind @var{n}}
13575 @cindex select trace snapshot
13576 @cindex find trace snapshot
13577 The basic command for selecting a trace snapshot from the buffer is
13578 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13579 counting from zero. If no argument @var{n} is given, the next
13580 snapshot is selected.
13582 Here are the various forms of using the @code{tfind} command.
13586 Find the first snapshot in the buffer. This is a synonym for
13587 @code{tfind 0} (since 0 is the number of the first snapshot).
13590 Stop debugging trace snapshots, resume @emph{live} debugging.
13593 Same as @samp{tfind none}.
13596 No argument means find the next trace snapshot or find the first
13597 one if no trace snapshot is selected.
13600 Find the previous trace snapshot before the current one. This permits
13601 retracing earlier steps.
13603 @item tfind tracepoint @var{num}
13604 Find the next snapshot associated with tracepoint @var{num}. Search
13605 proceeds forward from the last examined trace snapshot. If no
13606 argument @var{num} is given, it means find the next snapshot collected
13607 for the same tracepoint as the current snapshot.
13609 @item tfind pc @var{addr}
13610 Find the next snapshot associated with the value @var{addr} of the
13611 program counter. Search proceeds forward from the last examined trace
13612 snapshot. If no argument @var{addr} is given, it means find the next
13613 snapshot with the same value of PC as the current snapshot.
13615 @item tfind outside @var{addr1}, @var{addr2}
13616 Find the next snapshot whose PC is outside the given range of
13617 addresses (exclusive).
13619 @item tfind range @var{addr1}, @var{addr2}
13620 Find the next snapshot whose PC is between @var{addr1} and
13621 @var{addr2} (inclusive).
13623 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13624 Find the next snapshot associated with the source line @var{n}. If
13625 the optional argument @var{file} is given, refer to line @var{n} in
13626 that source file. Search proceeds forward from the last examined
13627 trace snapshot. If no argument @var{n} is given, it means find the
13628 next line other than the one currently being examined; thus saying
13629 @code{tfind line} repeatedly can appear to have the same effect as
13630 stepping from line to line in a @emph{live} debugging session.
13633 The default arguments for the @code{tfind} commands are specifically
13634 designed to make it easy to scan through the trace buffer. For
13635 instance, @code{tfind} with no argument selects the next trace
13636 snapshot, and @code{tfind -} with no argument selects the previous
13637 trace snapshot. So, by giving one @code{tfind} command, and then
13638 simply hitting @key{RET} repeatedly you can examine all the trace
13639 snapshots in order. Or, by saying @code{tfind -} and then hitting
13640 @key{RET} repeatedly you can examine the snapshots in reverse order.
13641 The @code{tfind line} command with no argument selects the snapshot
13642 for the next source line executed. The @code{tfind pc} command with
13643 no argument selects the next snapshot with the same program counter
13644 (PC) as the current frame. The @code{tfind tracepoint} command with
13645 no argument selects the next trace snapshot collected by the same
13646 tracepoint as the current one.
13648 In addition to letting you scan through the trace buffer manually,
13649 these commands make it easy to construct @value{GDBN} scripts that
13650 scan through the trace buffer and print out whatever collected data
13651 you are interested in. Thus, if we want to examine the PC, FP, and SP
13652 registers from each trace frame in the buffer, we can say this:
13655 (@value{GDBP}) @b{tfind start}
13656 (@value{GDBP}) @b{while ($trace_frame != -1)}
13657 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13658 $trace_frame, $pc, $sp, $fp
13662 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13663 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13664 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13665 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13666 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13667 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13668 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13669 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13670 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13671 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13672 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13675 Or, if we want to examine the variable @code{X} at each source line in
13679 (@value{GDBP}) @b{tfind start}
13680 (@value{GDBP}) @b{while ($trace_frame != -1)}
13681 > printf "Frame %d, X == %d\n", $trace_frame, X
13691 @subsection @code{tdump}
13693 @cindex dump all data collected at tracepoint
13694 @cindex tracepoint data, display
13696 This command takes no arguments. It prints all the data collected at
13697 the current trace snapshot.
13700 (@value{GDBP}) @b{trace 444}
13701 (@value{GDBP}) @b{actions}
13702 Enter actions for tracepoint #2, one per line:
13703 > collect $regs, $locals, $args, gdb_long_test
13706 (@value{GDBP}) @b{tstart}
13708 (@value{GDBP}) @b{tfind line 444}
13709 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13711 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13713 (@value{GDBP}) @b{tdump}
13714 Data collected at tracepoint 2, trace frame 1:
13715 d0 0xc4aa0085 -995491707
13719 d4 0x71aea3d 119204413
13722 d7 0x380035 3670069
13723 a0 0x19e24a 1696330
13724 a1 0x3000668 50333288
13726 a3 0x322000 3284992
13727 a4 0x3000698 50333336
13728 a5 0x1ad3cc 1758156
13729 fp 0x30bf3c 0x30bf3c
13730 sp 0x30bf34 0x30bf34
13732 pc 0x20b2c8 0x20b2c8
13736 p = 0x20e5b4 "gdb-test"
13743 gdb_long_test = 17 '\021'
13748 @code{tdump} works by scanning the tracepoint's current collection
13749 actions and printing the value of each expression listed. So
13750 @code{tdump} can fail, if after a run, you change the tracepoint's
13751 actions to mention variables that were not collected during the run.
13753 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13754 uses the collected value of @code{$pc} to distinguish between trace
13755 frames that were collected at the tracepoint hit, and frames that were
13756 collected while stepping. This allows it to correctly choose whether
13757 to display the basic list of collections, or the collections from the
13758 body of the while-stepping loop. However, if @code{$pc} was not collected,
13759 then @code{tdump} will always attempt to dump using the basic collection
13760 list, and may fail if a while-stepping frame does not include all the
13761 same data that is collected at the tracepoint hit.
13762 @c This is getting pretty arcane, example would be good.
13764 @node save tracepoints
13765 @subsection @code{save tracepoints @var{filename}}
13766 @kindex save tracepoints
13767 @kindex save-tracepoints
13768 @cindex save tracepoints for future sessions
13770 This command saves all current tracepoint definitions together with
13771 their actions and passcounts, into a file @file{@var{filename}}
13772 suitable for use in a later debugging session. To read the saved
13773 tracepoint definitions, use the @code{source} command (@pxref{Command
13774 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13775 alias for @w{@code{save tracepoints}}
13777 @node Tracepoint Variables
13778 @section Convenience Variables for Tracepoints
13779 @cindex tracepoint variables
13780 @cindex convenience variables for tracepoints
13783 @vindex $trace_frame
13784 @item (int) $trace_frame
13785 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13786 snapshot is selected.
13788 @vindex $tracepoint
13789 @item (int) $tracepoint
13790 The tracepoint for the current trace snapshot.
13792 @vindex $trace_line
13793 @item (int) $trace_line
13794 The line number for the current trace snapshot.
13796 @vindex $trace_file
13797 @item (char []) $trace_file
13798 The source file for the current trace snapshot.
13800 @vindex $trace_func
13801 @item (char []) $trace_func
13802 The name of the function containing @code{$tracepoint}.
13805 Note: @code{$trace_file} is not suitable for use in @code{printf},
13806 use @code{output} instead.
13808 Here's a simple example of using these convenience variables for
13809 stepping through all the trace snapshots and printing some of their
13810 data. Note that these are not the same as trace state variables,
13811 which are managed by the target.
13814 (@value{GDBP}) @b{tfind start}
13816 (@value{GDBP}) @b{while $trace_frame != -1}
13817 > output $trace_file
13818 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13824 @section Using Trace Files
13825 @cindex trace files
13827 In some situations, the target running a trace experiment may no
13828 longer be available; perhaps it crashed, or the hardware was needed
13829 for a different activity. To handle these cases, you can arrange to
13830 dump the trace data into a file, and later use that file as a source
13831 of trace data, via the @code{target tfile} command.
13836 @item tsave [ -r ] @var{filename}
13837 @itemx tsave [-ctf] @var{dirname}
13838 Save the trace data to @var{filename}. By default, this command
13839 assumes that @var{filename} refers to the host filesystem, so if
13840 necessary @value{GDBN} will copy raw trace data up from the target and
13841 then save it. If the target supports it, you can also supply the
13842 optional argument @code{-r} (``remote'') to direct the target to save
13843 the data directly into @var{filename} in its own filesystem, which may be
13844 more efficient if the trace buffer is very large. (Note, however, that
13845 @code{target tfile} can only read from files accessible to the host.)
13846 By default, this command will save trace frame in tfile format.
13847 You can supply the optional argument @code{-ctf} to save data in CTF
13848 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13849 that can be shared by multiple debugging and tracing tools. Please go to
13850 @indicateurl{http://www.efficios.com/ctf} to get more information.
13852 @kindex target tfile
13856 @item target tfile @var{filename}
13857 @itemx target ctf @var{dirname}
13858 Use the file named @var{filename} or directory named @var{dirname} as
13859 a source of trace data. Commands that examine data work as they do with
13860 a live target, but it is not possible to run any new trace experiments.
13861 @code{tstatus} will report the state of the trace run at the moment
13862 the data was saved, as well as the current trace frame you are examining.
13863 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13867 (@value{GDBP}) target ctf ctf.ctf
13868 (@value{GDBP}) tfind
13869 Found trace frame 0, tracepoint 2
13870 39 ++a; /* set tracepoint 1 here */
13871 (@value{GDBP}) tdump
13872 Data collected at tracepoint 2, trace frame 0:
13876 c = @{"123", "456", "789", "123", "456", "789"@}
13877 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13885 @chapter Debugging Programs That Use Overlays
13888 If your program is too large to fit completely in your target system's
13889 memory, you can sometimes use @dfn{overlays} to work around this
13890 problem. @value{GDBN} provides some support for debugging programs that
13894 * How Overlays Work:: A general explanation of overlays.
13895 * Overlay Commands:: Managing overlays in @value{GDBN}.
13896 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13897 mapped by asking the inferior.
13898 * Overlay Sample Program:: A sample program using overlays.
13901 @node How Overlays Work
13902 @section How Overlays Work
13903 @cindex mapped overlays
13904 @cindex unmapped overlays
13905 @cindex load address, overlay's
13906 @cindex mapped address
13907 @cindex overlay area
13909 Suppose you have a computer whose instruction address space is only 64
13910 kilobytes long, but which has much more memory which can be accessed by
13911 other means: special instructions, segment registers, or memory
13912 management hardware, for example. Suppose further that you want to
13913 adapt a program which is larger than 64 kilobytes to run on this system.
13915 One solution is to identify modules of your program which are relatively
13916 independent, and need not call each other directly; call these modules
13917 @dfn{overlays}. Separate the overlays from the main program, and place
13918 their machine code in the larger memory. Place your main program in
13919 instruction memory, but leave at least enough space there to hold the
13920 largest overlay as well.
13922 Now, to call a function located in an overlay, you must first copy that
13923 overlay's machine code from the large memory into the space set aside
13924 for it in the instruction memory, and then jump to its entry point
13927 @c NB: In the below the mapped area's size is greater or equal to the
13928 @c size of all overlays. This is intentional to remind the developer
13929 @c that overlays don't necessarily need to be the same size.
13933 Data Instruction Larger
13934 Address Space Address Space Address Space
13935 +-----------+ +-----------+ +-----------+
13937 +-----------+ +-----------+ +-----------+<-- overlay 1
13938 | program | | main | .----| overlay 1 | load address
13939 | variables | | program | | +-----------+
13940 | and heap | | | | | |
13941 +-----------+ | | | +-----------+<-- overlay 2
13942 | | +-----------+ | | | load address
13943 +-----------+ | | | .-| overlay 2 |
13945 mapped --->+-----------+ | | +-----------+
13946 address | | | | | |
13947 | overlay | <-' | | |
13948 | area | <---' +-----------+<-- overlay 3
13949 | | <---. | | load address
13950 +-----------+ `--| overlay 3 |
13957 @anchor{A code overlay}A code overlay
13961 The diagram (@pxref{A code overlay}) shows a system with separate data
13962 and instruction address spaces. To map an overlay, the program copies
13963 its code from the larger address space to the instruction address space.
13964 Since the overlays shown here all use the same mapped address, only one
13965 may be mapped at a time. For a system with a single address space for
13966 data and instructions, the diagram would be similar, except that the
13967 program variables and heap would share an address space with the main
13968 program and the overlay area.
13970 An overlay loaded into instruction memory and ready for use is called a
13971 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13972 instruction memory. An overlay not present (or only partially present)
13973 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13974 is its address in the larger memory. The mapped address is also called
13975 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13976 called the @dfn{load memory address}, or @dfn{LMA}.
13978 Unfortunately, overlays are not a completely transparent way to adapt a
13979 program to limited instruction memory. They introduce a new set of
13980 global constraints you must keep in mind as you design your program:
13985 Before calling or returning to a function in an overlay, your program
13986 must make sure that overlay is actually mapped. Otherwise, the call or
13987 return will transfer control to the right address, but in the wrong
13988 overlay, and your program will probably crash.
13991 If the process of mapping an overlay is expensive on your system, you
13992 will need to choose your overlays carefully to minimize their effect on
13993 your program's performance.
13996 The executable file you load onto your system must contain each
13997 overlay's instructions, appearing at the overlay's load address, not its
13998 mapped address. However, each overlay's instructions must be relocated
13999 and its symbols defined as if the overlay were at its mapped address.
14000 You can use GNU linker scripts to specify different load and relocation
14001 addresses for pieces of your program; see @ref{Overlay Description,,,
14002 ld.info, Using ld: the GNU linker}.
14005 The procedure for loading executable files onto your system must be able
14006 to load their contents into the larger address space as well as the
14007 instruction and data spaces.
14011 The overlay system described above is rather simple, and could be
14012 improved in many ways:
14017 If your system has suitable bank switch registers or memory management
14018 hardware, you could use those facilities to make an overlay's load area
14019 contents simply appear at their mapped address in instruction space.
14020 This would probably be faster than copying the overlay to its mapped
14021 area in the usual way.
14024 If your overlays are small enough, you could set aside more than one
14025 overlay area, and have more than one overlay mapped at a time.
14028 You can use overlays to manage data, as well as instructions. In
14029 general, data overlays are even less transparent to your design than
14030 code overlays: whereas code overlays only require care when you call or
14031 return to functions, data overlays require care every time you access
14032 the data. Also, if you change the contents of a data overlay, you
14033 must copy its contents back out to its load address before you can copy a
14034 different data overlay into the same mapped area.
14039 @node Overlay Commands
14040 @section Overlay Commands
14042 To use @value{GDBN}'s overlay support, each overlay in your program must
14043 correspond to a separate section of the executable file. The section's
14044 virtual memory address and load memory address must be the overlay's
14045 mapped and load addresses. Identifying overlays with sections allows
14046 @value{GDBN} to determine the appropriate address of a function or
14047 variable, depending on whether the overlay is mapped or not.
14049 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14050 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14055 Disable @value{GDBN}'s overlay support. When overlay support is
14056 disabled, @value{GDBN} assumes that all functions and variables are
14057 always present at their mapped addresses. By default, @value{GDBN}'s
14058 overlay support is disabled.
14060 @item overlay manual
14061 @cindex manual overlay debugging
14062 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14063 relies on you to tell it which overlays are mapped, and which are not,
14064 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14065 commands described below.
14067 @item overlay map-overlay @var{overlay}
14068 @itemx overlay map @var{overlay}
14069 @cindex map an overlay
14070 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14071 be the name of the object file section containing the overlay. When an
14072 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14073 functions and variables at their mapped addresses. @value{GDBN} assumes
14074 that any other overlays whose mapped ranges overlap that of
14075 @var{overlay} are now unmapped.
14077 @item overlay unmap-overlay @var{overlay}
14078 @itemx overlay unmap @var{overlay}
14079 @cindex unmap an overlay
14080 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14081 must be the name of the object file section containing the overlay.
14082 When an overlay is unmapped, @value{GDBN} assumes it can find the
14083 overlay's functions and variables at their load addresses.
14086 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14087 consults a data structure the overlay manager maintains in the inferior
14088 to see which overlays are mapped. For details, see @ref{Automatic
14089 Overlay Debugging}.
14091 @item overlay load-target
14092 @itemx overlay load
14093 @cindex reloading the overlay table
14094 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14095 re-reads the table @value{GDBN} automatically each time the inferior
14096 stops, so this command should only be necessary if you have changed the
14097 overlay mapping yourself using @value{GDBN}. This command is only
14098 useful when using automatic overlay debugging.
14100 @item overlay list-overlays
14101 @itemx overlay list
14102 @cindex listing mapped overlays
14103 Display a list of the overlays currently mapped, along with their mapped
14104 addresses, load addresses, and sizes.
14108 Normally, when @value{GDBN} prints a code address, it includes the name
14109 of the function the address falls in:
14112 (@value{GDBP}) print main
14113 $3 = @{int ()@} 0x11a0 <main>
14116 When overlay debugging is enabled, @value{GDBN} recognizes code in
14117 unmapped overlays, and prints the names of unmapped functions with
14118 asterisks around them. For example, if @code{foo} is a function in an
14119 unmapped overlay, @value{GDBN} prints it this way:
14122 (@value{GDBP}) overlay list
14123 No sections are mapped.
14124 (@value{GDBP}) print foo
14125 $5 = @{int (int)@} 0x100000 <*foo*>
14128 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14132 (@value{GDBP}) overlay list
14133 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14134 mapped at 0x1016 - 0x104a
14135 (@value{GDBP}) print foo
14136 $6 = @{int (int)@} 0x1016 <foo>
14139 When overlay debugging is enabled, @value{GDBN} can find the correct
14140 address for functions and variables in an overlay, whether or not the
14141 overlay is mapped. This allows most @value{GDBN} commands, like
14142 @code{break} and @code{disassemble}, to work normally, even on unmapped
14143 code. However, @value{GDBN}'s breakpoint support has some limitations:
14147 @cindex breakpoints in overlays
14148 @cindex overlays, setting breakpoints in
14149 You can set breakpoints in functions in unmapped overlays, as long as
14150 @value{GDBN} can write to the overlay at its load address.
14152 @value{GDBN} can not set hardware or simulator-based breakpoints in
14153 unmapped overlays. However, if you set a breakpoint at the end of your
14154 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14155 you are using manual overlay management), @value{GDBN} will re-set its
14156 breakpoints properly.
14160 @node Automatic Overlay Debugging
14161 @section Automatic Overlay Debugging
14162 @cindex automatic overlay debugging
14164 @value{GDBN} can automatically track which overlays are mapped and which
14165 are not, given some simple co-operation from the overlay manager in the
14166 inferior. If you enable automatic overlay debugging with the
14167 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14168 looks in the inferior's memory for certain variables describing the
14169 current state of the overlays.
14171 Here are the variables your overlay manager must define to support
14172 @value{GDBN}'s automatic overlay debugging:
14176 @item @code{_ovly_table}:
14177 This variable must be an array of the following structures:
14182 /* The overlay's mapped address. */
14185 /* The size of the overlay, in bytes. */
14186 unsigned long size;
14188 /* The overlay's load address. */
14191 /* Non-zero if the overlay is currently mapped;
14193 unsigned long mapped;
14197 @item @code{_novlys}:
14198 This variable must be a four-byte signed integer, holding the total
14199 number of elements in @code{_ovly_table}.
14203 To decide whether a particular overlay is mapped or not, @value{GDBN}
14204 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14205 @code{lma} members equal the VMA and LMA of the overlay's section in the
14206 executable file. When @value{GDBN} finds a matching entry, it consults
14207 the entry's @code{mapped} member to determine whether the overlay is
14210 In addition, your overlay manager may define a function called
14211 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14212 will silently set a breakpoint there. If the overlay manager then
14213 calls this function whenever it has changed the overlay table, this
14214 will enable @value{GDBN} to accurately keep track of which overlays
14215 are in program memory, and update any breakpoints that may be set
14216 in overlays. This will allow breakpoints to work even if the
14217 overlays are kept in ROM or other non-writable memory while they
14218 are not being executed.
14220 @node Overlay Sample Program
14221 @section Overlay Sample Program
14222 @cindex overlay example program
14224 When linking a program which uses overlays, you must place the overlays
14225 at their load addresses, while relocating them to run at their mapped
14226 addresses. To do this, you must write a linker script (@pxref{Overlay
14227 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14228 since linker scripts are specific to a particular host system, target
14229 architecture, and target memory layout, this manual cannot provide
14230 portable sample code demonstrating @value{GDBN}'s overlay support.
14232 However, the @value{GDBN} source distribution does contain an overlaid
14233 program, with linker scripts for a few systems, as part of its test
14234 suite. The program consists of the following files from
14235 @file{gdb/testsuite/gdb.base}:
14239 The main program file.
14241 A simple overlay manager, used by @file{overlays.c}.
14246 Overlay modules, loaded and used by @file{overlays.c}.
14249 Linker scripts for linking the test program on the @code{d10v-elf}
14250 and @code{m32r-elf} targets.
14253 You can build the test program using the @code{d10v-elf} GCC
14254 cross-compiler like this:
14257 $ d10v-elf-gcc -g -c overlays.c
14258 $ d10v-elf-gcc -g -c ovlymgr.c
14259 $ d10v-elf-gcc -g -c foo.c
14260 $ d10v-elf-gcc -g -c bar.c
14261 $ d10v-elf-gcc -g -c baz.c
14262 $ d10v-elf-gcc -g -c grbx.c
14263 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14264 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14267 The build process is identical for any other architecture, except that
14268 you must substitute the appropriate compiler and linker script for the
14269 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14273 @chapter Using @value{GDBN} with Different Languages
14276 Although programming languages generally have common aspects, they are
14277 rarely expressed in the same manner. For instance, in ANSI C,
14278 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14279 Modula-2, it is accomplished by @code{p^}. Values can also be
14280 represented (and displayed) differently. Hex numbers in C appear as
14281 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14283 @cindex working language
14284 Language-specific information is built into @value{GDBN} for some languages,
14285 allowing you to express operations like the above in your program's
14286 native language, and allowing @value{GDBN} to output values in a manner
14287 consistent with the syntax of your program's native language. The
14288 language you use to build expressions is called the @dfn{working
14292 * Setting:: Switching between source languages
14293 * Show:: Displaying the language
14294 * Checks:: Type and range checks
14295 * Supported Languages:: Supported languages
14296 * Unsupported Languages:: Unsupported languages
14300 @section Switching Between Source Languages
14302 There are two ways to control the working language---either have @value{GDBN}
14303 set it automatically, or select it manually yourself. You can use the
14304 @code{set language} command for either purpose. On startup, @value{GDBN}
14305 defaults to setting the language automatically. The working language is
14306 used to determine how expressions you type are interpreted, how values
14309 In addition to the working language, every source file that
14310 @value{GDBN} knows about has its own working language. For some object
14311 file formats, the compiler might indicate which language a particular
14312 source file is in. However, most of the time @value{GDBN} infers the
14313 language from the name of the file. The language of a source file
14314 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14315 show each frame appropriately for its own language. There is no way to
14316 set the language of a source file from within @value{GDBN}, but you can
14317 set the language associated with a filename extension. @xref{Show, ,
14318 Displaying the Language}.
14320 This is most commonly a problem when you use a program, such
14321 as @code{cfront} or @code{f2c}, that generates C but is written in
14322 another language. In that case, make the
14323 program use @code{#line} directives in its C output; that way
14324 @value{GDBN} will know the correct language of the source code of the original
14325 program, and will display that source code, not the generated C code.
14328 * Filenames:: Filename extensions and languages.
14329 * Manually:: Setting the working language manually
14330 * Automatically:: Having @value{GDBN} infer the source language
14334 @subsection List of Filename Extensions and Languages
14336 If a source file name ends in one of the following extensions, then
14337 @value{GDBN} infers that its language is the one indicated.
14355 C@t{++} source file
14361 Objective-C source file
14365 Fortran source file
14368 Modula-2 source file
14372 Assembler source file. This actually behaves almost like C, but
14373 @value{GDBN} does not skip over function prologues when stepping.
14376 In addition, you may set the language associated with a filename
14377 extension. @xref{Show, , Displaying the Language}.
14380 @subsection Setting the Working Language
14382 If you allow @value{GDBN} to set the language automatically,
14383 expressions are interpreted the same way in your debugging session and
14386 @kindex set language
14387 If you wish, you may set the language manually. To do this, issue the
14388 command @samp{set language @var{lang}}, where @var{lang} is the name of
14389 a language, such as
14390 @code{c} or @code{modula-2}.
14391 For a list of the supported languages, type @samp{set language}.
14393 Setting the language manually prevents @value{GDBN} from updating the working
14394 language automatically. This can lead to confusion if you try
14395 to debug a program when the working language is not the same as the
14396 source language, when an expression is acceptable to both
14397 languages---but means different things. For instance, if the current
14398 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14406 might not have the effect you intended. In C, this means to add
14407 @code{b} and @code{c} and place the result in @code{a}. The result
14408 printed would be the value of @code{a}. In Modula-2, this means to compare
14409 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14411 @node Automatically
14412 @subsection Having @value{GDBN} Infer the Source Language
14414 To have @value{GDBN} set the working language automatically, use
14415 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14416 then infers the working language. That is, when your program stops in a
14417 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14418 working language to the language recorded for the function in that
14419 frame. If the language for a frame is unknown (that is, if the function
14420 or block corresponding to the frame was defined in a source file that
14421 does not have a recognized extension), the current working language is
14422 not changed, and @value{GDBN} issues a warning.
14424 This may not seem necessary for most programs, which are written
14425 entirely in one source language. However, program modules and libraries
14426 written in one source language can be used by a main program written in
14427 a different source language. Using @samp{set language auto} in this
14428 case frees you from having to set the working language manually.
14431 @section Displaying the Language
14433 The following commands help you find out which language is the
14434 working language, and also what language source files were written in.
14437 @item show language
14438 @anchor{show language}
14439 @kindex show language
14440 Display the current working language. This is the
14441 language you can use with commands such as @code{print} to
14442 build and compute expressions that may involve variables in your program.
14445 @kindex info frame@r{, show the source language}
14446 Display the source language for this frame. This language becomes the
14447 working language if you use an identifier from this frame.
14448 @xref{Frame Info, ,Information about a Frame}, to identify the other
14449 information listed here.
14452 @kindex info source@r{, show the source language}
14453 Display the source language of this source file.
14454 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14455 information listed here.
14458 In unusual circumstances, you may have source files with extensions
14459 not in the standard list. You can then set the extension associated
14460 with a language explicitly:
14463 @item set extension-language @var{ext} @var{language}
14464 @kindex set extension-language
14465 Tell @value{GDBN} that source files with extension @var{ext} are to be
14466 assumed as written in the source language @var{language}.
14468 @item info extensions
14469 @kindex info extensions
14470 List all the filename extensions and the associated languages.
14474 @section Type and Range Checking
14476 Some languages are designed to guard you against making seemingly common
14477 errors through a series of compile- and run-time checks. These include
14478 checking the type of arguments to functions and operators and making
14479 sure mathematical overflows are caught at run time. Checks such as
14480 these help to ensure a program's correctness once it has been compiled
14481 by eliminating type mismatches and providing active checks for range
14482 errors when your program is running.
14484 By default @value{GDBN} checks for these errors according to the
14485 rules of the current source language. Although @value{GDBN} does not check
14486 the statements in your program, it can check expressions entered directly
14487 into @value{GDBN} for evaluation via the @code{print} command, for example.
14490 * Type Checking:: An overview of type checking
14491 * Range Checking:: An overview of range checking
14494 @cindex type checking
14495 @cindex checks, type
14496 @node Type Checking
14497 @subsection An Overview of Type Checking
14499 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14500 arguments to operators and functions have to be of the correct type,
14501 otherwise an error occurs. These checks prevent type mismatch
14502 errors from ever causing any run-time problems. For example,
14505 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14507 (@value{GDBP}) print obj.my_method (0)
14510 (@value{GDBP}) print obj.my_method (0x1234)
14511 Cannot resolve method klass::my_method to any overloaded instance
14514 The second example fails because in C@t{++} the integer constant
14515 @samp{0x1234} is not type-compatible with the pointer parameter type.
14517 For the expressions you use in @value{GDBN} commands, you can tell
14518 @value{GDBN} to not enforce strict type checking or
14519 to treat any mismatches as errors and abandon the expression;
14520 When type checking is disabled, @value{GDBN} successfully evaluates
14521 expressions like the second example above.
14523 Even if type checking is off, there may be other reasons
14524 related to type that prevent @value{GDBN} from evaluating an expression.
14525 For instance, @value{GDBN} does not know how to add an @code{int} and
14526 a @code{struct foo}. These particular type errors have nothing to do
14527 with the language in use and usually arise from expressions which make
14528 little sense to evaluate anyway.
14530 @value{GDBN} provides some additional commands for controlling type checking:
14532 @kindex set check type
14533 @kindex show check type
14535 @item set check type on
14536 @itemx set check type off
14537 Set strict type checking on or off. If any type mismatches occur in
14538 evaluating an expression while type checking is on, @value{GDBN} prints a
14539 message and aborts evaluation of the expression.
14541 @item show check type
14542 Show the current setting of type checking and whether @value{GDBN}
14543 is enforcing strict type checking rules.
14546 @cindex range checking
14547 @cindex checks, range
14548 @node Range Checking
14549 @subsection An Overview of Range Checking
14551 In some languages (such as Modula-2), it is an error to exceed the
14552 bounds of a type; this is enforced with run-time checks. Such range
14553 checking is meant to ensure program correctness by making sure
14554 computations do not overflow, or indices on an array element access do
14555 not exceed the bounds of the array.
14557 For expressions you use in @value{GDBN} commands, you can tell
14558 @value{GDBN} to treat range errors in one of three ways: ignore them,
14559 always treat them as errors and abandon the expression, or issue
14560 warnings but evaluate the expression anyway.
14562 A range error can result from numerical overflow, from exceeding an
14563 array index bound, or when you type a constant that is not a member
14564 of any type. Some languages, however, do not treat overflows as an
14565 error. In many implementations of C, mathematical overflow causes the
14566 result to ``wrap around'' to lower values---for example, if @var{m} is
14567 the largest integer value, and @var{s} is the smallest, then
14570 @var{m} + 1 @result{} @var{s}
14573 This, too, is specific to individual languages, and in some cases
14574 specific to individual compilers or machines. @xref{Supported Languages, ,
14575 Supported Languages}, for further details on specific languages.
14577 @value{GDBN} provides some additional commands for controlling the range checker:
14579 @kindex set check range
14580 @kindex show check range
14582 @item set check range auto
14583 Set range checking on or off based on the current working language.
14584 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14587 @item set check range on
14588 @itemx set check range off
14589 Set range checking on or off, overriding the default setting for the
14590 current working language. A warning is issued if the setting does not
14591 match the language default. If a range error occurs and range checking is on,
14592 then a message is printed and evaluation of the expression is aborted.
14594 @item set check range warn
14595 Output messages when the @value{GDBN} range checker detects a range error,
14596 but attempt to evaluate the expression anyway. Evaluating the
14597 expression may still be impossible for other reasons, such as accessing
14598 memory that the process does not own (a typical example from many Unix
14602 Show the current setting of the range checker, and whether or not it is
14603 being set automatically by @value{GDBN}.
14606 @node Supported Languages
14607 @section Supported Languages
14609 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14610 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14611 @c This is false ...
14612 Some @value{GDBN} features may be used in expressions regardless of the
14613 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14614 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14615 ,Expressions}) can be used with the constructs of any supported
14618 The following sections detail to what degree each source language is
14619 supported by @value{GDBN}. These sections are not meant to be language
14620 tutorials or references, but serve only as a reference guide to what the
14621 @value{GDBN} expression parser accepts, and what input and output
14622 formats should look like for different languages. There are many good
14623 books written on each of these languages; please look to these for a
14624 language reference or tutorial.
14627 * C:: C and C@t{++}
14630 * Objective-C:: Objective-C
14631 * OpenCL C:: OpenCL C
14632 * Fortran:: Fortran
14635 * Modula-2:: Modula-2
14640 @subsection C and C@t{++}
14642 @cindex C and C@t{++}
14643 @cindex expressions in C or C@t{++}
14645 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14646 to both languages. Whenever this is the case, we discuss those languages
14650 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14651 @cindex @sc{gnu} C@t{++}
14652 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14653 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14654 effectively, you must compile your C@t{++} programs with a supported
14655 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14656 compiler (@code{aCC}).
14659 * C Operators:: C and C@t{++} operators
14660 * C Constants:: C and C@t{++} constants
14661 * C Plus Plus Expressions:: C@t{++} expressions
14662 * C Defaults:: Default settings for C and C@t{++}
14663 * C Checks:: C and C@t{++} type and range checks
14664 * Debugging C:: @value{GDBN} and C
14665 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14666 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14670 @subsubsection C and C@t{++} Operators
14672 @cindex C and C@t{++} operators
14674 Operators must be defined on values of specific types. For instance,
14675 @code{+} is defined on numbers, but not on structures. Operators are
14676 often defined on groups of types.
14678 For the purposes of C and C@t{++}, the following definitions hold:
14683 @emph{Integral types} include @code{int} with any of its storage-class
14684 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14687 @emph{Floating-point types} include @code{float}, @code{double}, and
14688 @code{long double} (if supported by the target platform).
14691 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14694 @emph{Scalar types} include all of the above.
14699 The following operators are supported. They are listed here
14700 in order of increasing precedence:
14704 The comma or sequencing operator. Expressions in a comma-separated list
14705 are evaluated from left to right, with the result of the entire
14706 expression being the last expression evaluated.
14709 Assignment. The value of an assignment expression is the value
14710 assigned. Defined on scalar types.
14713 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14714 and translated to @w{@code{@var{a} = @var{a op b}}}.
14715 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14716 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14717 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14720 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14721 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14722 should be of an integral type.
14725 Logical @sc{or}. Defined on integral types.
14728 Logical @sc{and}. Defined on integral types.
14731 Bitwise @sc{or}. Defined on integral types.
14734 Bitwise exclusive-@sc{or}. Defined on integral types.
14737 Bitwise @sc{and}. Defined on integral types.
14740 Equality and inequality. Defined on scalar types. The value of these
14741 expressions is 0 for false and non-zero for true.
14743 @item <@r{, }>@r{, }<=@r{, }>=
14744 Less than, greater than, less than or equal, greater than or equal.
14745 Defined on scalar types. The value of these expressions is 0 for false
14746 and non-zero for true.
14749 left shift, and right shift. Defined on integral types.
14752 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14755 Addition and subtraction. Defined on integral types, floating-point types and
14758 @item *@r{, }/@r{, }%
14759 Multiplication, division, and modulus. Multiplication and division are
14760 defined on integral and floating-point types. Modulus is defined on
14764 Increment and decrement. When appearing before a variable, the
14765 operation is performed before the variable is used in an expression;
14766 when appearing after it, the variable's value is used before the
14767 operation takes place.
14770 Pointer dereferencing. Defined on pointer types. Same precedence as
14774 Address operator. Defined on variables. Same precedence as @code{++}.
14776 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14777 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14778 to examine the address
14779 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14783 Negative. Defined on integral and floating-point types. Same
14784 precedence as @code{++}.
14787 Logical negation. Defined on integral types. Same precedence as
14791 Bitwise complement operator. Defined on integral types. Same precedence as
14796 Structure member, and pointer-to-structure member. For convenience,
14797 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14798 pointer based on the stored type information.
14799 Defined on @code{struct} and @code{union} data.
14802 Dereferences of pointers to members.
14805 Array indexing. @code{@var{a}[@var{i}]} is defined as
14806 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14809 Function parameter list. Same precedence as @code{->}.
14812 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14813 and @code{class} types.
14816 Doubled colons also represent the @value{GDBN} scope operator
14817 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14821 If an operator is redefined in the user code, @value{GDBN} usually
14822 attempts to invoke the redefined version instead of using the operator's
14823 predefined meaning.
14826 @subsubsection C and C@t{++} Constants
14828 @cindex C and C@t{++} constants
14830 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14835 Integer constants are a sequence of digits. Octal constants are
14836 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14837 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14838 @samp{l}, specifying that the constant should be treated as a
14842 Floating point constants are a sequence of digits, followed by a decimal
14843 point, followed by a sequence of digits, and optionally followed by an
14844 exponent. An exponent is of the form:
14845 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14846 sequence of digits. The @samp{+} is optional for positive exponents.
14847 A floating-point constant may also end with a letter @samp{f} or
14848 @samp{F}, specifying that the constant should be treated as being of
14849 the @code{float} (as opposed to the default @code{double}) type; or with
14850 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14854 Enumerated constants consist of enumerated identifiers, or their
14855 integral equivalents.
14858 Character constants are a single character surrounded by single quotes
14859 (@code{'}), or a number---the ordinal value of the corresponding character
14860 (usually its @sc{ascii} value). Within quotes, the single character may
14861 be represented by a letter or by @dfn{escape sequences}, which are of
14862 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14863 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14864 @samp{@var{x}} is a predefined special character---for example,
14865 @samp{\n} for newline.
14867 Wide character constants can be written by prefixing a character
14868 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14869 form of @samp{x}. The target wide character set is used when
14870 computing the value of this constant (@pxref{Character Sets}).
14873 String constants are a sequence of character constants surrounded by
14874 double quotes (@code{"}). Any valid character constant (as described
14875 above) may appear. Double quotes within the string must be preceded by
14876 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14879 Wide string constants can be written by prefixing a string constant
14880 with @samp{L}, as in C. The target wide character set is used when
14881 computing the value of this constant (@pxref{Character Sets}).
14884 Pointer constants are an integral value. You can also write pointers
14885 to constants using the C operator @samp{&}.
14888 Array constants are comma-separated lists surrounded by braces @samp{@{}
14889 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14890 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14891 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14894 @node C Plus Plus Expressions
14895 @subsubsection C@t{++} Expressions
14897 @cindex expressions in C@t{++}
14898 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14900 @cindex debugging C@t{++} programs
14901 @cindex C@t{++} compilers
14902 @cindex debug formats and C@t{++}
14903 @cindex @value{NGCC} and C@t{++}
14905 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14906 the proper compiler and the proper debug format. Currently,
14907 @value{GDBN} works best when debugging C@t{++} code that is compiled
14908 with the most recent version of @value{NGCC} possible. The DWARF
14909 debugging format is preferred; @value{NGCC} defaults to this on most
14910 popular platforms. Other compilers and/or debug formats are likely to
14911 work badly or not at all when using @value{GDBN} to debug C@t{++}
14912 code. @xref{Compilation}.
14917 @cindex member functions
14919 Member function calls are allowed; you can use expressions like
14922 count = aml->GetOriginal(x, y)
14925 @vindex this@r{, inside C@t{++} member functions}
14926 @cindex namespace in C@t{++}
14928 While a member function is active (in the selected stack frame), your
14929 expressions have the same namespace available as the member function;
14930 that is, @value{GDBN} allows implicit references to the class instance
14931 pointer @code{this} following the same rules as C@t{++}. @code{using}
14932 declarations in the current scope are also respected by @value{GDBN}.
14934 @cindex call overloaded functions
14935 @cindex overloaded functions, calling
14936 @cindex type conversions in C@t{++}
14938 You can call overloaded functions; @value{GDBN} resolves the function
14939 call to the right definition, with some restrictions. @value{GDBN} does not
14940 perform overload resolution involving user-defined type conversions,
14941 calls to constructors, or instantiations of templates that do not exist
14942 in the program. It also cannot handle ellipsis argument lists or
14945 It does perform integral conversions and promotions, floating-point
14946 promotions, arithmetic conversions, pointer conversions, conversions of
14947 class objects to base classes, and standard conversions such as those of
14948 functions or arrays to pointers; it requires an exact match on the
14949 number of function arguments.
14951 Overload resolution is always performed, unless you have specified
14952 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14953 ,@value{GDBN} Features for C@t{++}}.
14955 You must specify @code{set overload-resolution off} in order to use an
14956 explicit function signature to call an overloaded function, as in
14958 p 'foo(char,int)'('x', 13)
14961 The @value{GDBN} command-completion facility can simplify this;
14962 see @ref{Completion, ,Command Completion}.
14964 @cindex reference declarations
14966 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
14967 references; you can use them in expressions just as you do in C@t{++}
14968 source---they are automatically dereferenced.
14970 In the parameter list shown when @value{GDBN} displays a frame, the values of
14971 reference variables are not displayed (unlike other variables); this
14972 avoids clutter, since references are often used for large structures.
14973 The @emph{address} of a reference variable is always shown, unless
14974 you have specified @samp{set print address off}.
14977 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14978 expressions can use it just as expressions in your program do. Since
14979 one scope may be defined in another, you can use @code{::} repeatedly if
14980 necessary, for example in an expression like
14981 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14982 resolving name scope by reference to source files, in both C and C@t{++}
14983 debugging (@pxref{Variables, ,Program Variables}).
14986 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14991 @subsubsection C and C@t{++} Defaults
14993 @cindex C and C@t{++} defaults
14995 If you allow @value{GDBN} to set range checking automatically, it
14996 defaults to @code{off} whenever the working language changes to
14997 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14998 selects the working language.
15000 If you allow @value{GDBN} to set the language automatically, it
15001 recognizes source files whose names end with @file{.c}, @file{.C}, or
15002 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15003 these files, it sets the working language to C or C@t{++}.
15004 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15005 for further details.
15008 @subsubsection C and C@t{++} Type and Range Checks
15010 @cindex C and C@t{++} checks
15012 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15013 checking is used. However, if you turn type checking off, @value{GDBN}
15014 will allow certain non-standard conversions, such as promoting integer
15015 constants to pointers.
15017 Range checking, if turned on, is done on mathematical operations. Array
15018 indices are not checked, since they are often used to index a pointer
15019 that is not itself an array.
15022 @subsubsection @value{GDBN} and C
15024 The @code{set print union} and @code{show print union} commands apply to
15025 the @code{union} type. When set to @samp{on}, any @code{union} that is
15026 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15027 appears as @samp{@{...@}}.
15029 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15030 with pointers and a memory allocation function. @xref{Expressions,
15033 @node Debugging C Plus Plus
15034 @subsubsection @value{GDBN} Features for C@t{++}
15036 @cindex commands for C@t{++}
15038 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15039 designed specifically for use with C@t{++}. Here is a summary:
15042 @cindex break in overloaded functions
15043 @item @r{breakpoint menus}
15044 When you want a breakpoint in a function whose name is overloaded,
15045 @value{GDBN} has the capability to display a menu of possible breakpoint
15046 locations to help you specify which function definition you want.
15047 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15049 @cindex overloading in C@t{++}
15050 @item rbreak @var{regex}
15051 Setting breakpoints using regular expressions is helpful for setting
15052 breakpoints on overloaded functions that are not members of any special
15054 @xref{Set Breaks, ,Setting Breakpoints}.
15056 @cindex C@t{++} exception handling
15058 @itemx catch rethrow
15060 Debug C@t{++} exception handling using these commands. @xref{Set
15061 Catchpoints, , Setting Catchpoints}.
15063 @cindex inheritance
15064 @item ptype @var{typename}
15065 Print inheritance relationships as well as other information for type
15067 @xref{Symbols, ,Examining the Symbol Table}.
15069 @item info vtbl @var{expression}.
15070 The @code{info vtbl} command can be used to display the virtual
15071 method tables of the object computed by @var{expression}. This shows
15072 one entry per virtual table; there may be multiple virtual tables when
15073 multiple inheritance is in use.
15075 @cindex C@t{++} demangling
15076 @item demangle @var{name}
15077 Demangle @var{name}.
15078 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15080 @cindex C@t{++} symbol display
15081 @item set print demangle
15082 @itemx show print demangle
15083 @itemx set print asm-demangle
15084 @itemx show print asm-demangle
15085 Control whether C@t{++} symbols display in their source form, both when
15086 displaying code as C@t{++} source and when displaying disassemblies.
15087 @xref{Print Settings, ,Print Settings}.
15089 @item set print object
15090 @itemx show print object
15091 Choose whether to print derived (actual) or declared types of objects.
15092 @xref{Print Settings, ,Print Settings}.
15094 @item set print vtbl
15095 @itemx show print vtbl
15096 Control the format for printing virtual function tables.
15097 @xref{Print Settings, ,Print Settings}.
15098 (The @code{vtbl} commands do not work on programs compiled with the HP
15099 ANSI C@t{++} compiler (@code{aCC}).)
15101 @kindex set overload-resolution
15102 @cindex overloaded functions, overload resolution
15103 @item set overload-resolution on
15104 Enable overload resolution for C@t{++} expression evaluation. The default
15105 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15106 and searches for a function whose signature matches the argument types,
15107 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15108 Expressions, ,C@t{++} Expressions}, for details).
15109 If it cannot find a match, it emits a message.
15111 @item set overload-resolution off
15112 Disable overload resolution for C@t{++} expression evaluation. For
15113 overloaded functions that are not class member functions, @value{GDBN}
15114 chooses the first function of the specified name that it finds in the
15115 symbol table, whether or not its arguments are of the correct type. For
15116 overloaded functions that are class member functions, @value{GDBN}
15117 searches for a function whose signature @emph{exactly} matches the
15120 @kindex show overload-resolution
15121 @item show overload-resolution
15122 Show the current setting of overload resolution.
15124 @item @r{Overloaded symbol names}
15125 You can specify a particular definition of an overloaded symbol, using
15126 the same notation that is used to declare such symbols in C@t{++}: type
15127 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15128 also use the @value{GDBN} command-line word completion facilities to list the
15129 available choices, or to finish the type list for you.
15130 @xref{Completion,, Command Completion}, for details on how to do this.
15132 @item @r{Breakpoints in functions with ABI tags}
15134 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15135 correspond to changes in the ABI of a type, function, or variable that
15136 would not otherwise be reflected in a mangled name. See
15137 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15140 The ABI tags are visible in C@t{++} demangled names. For example, a
15141 function that returns a std::string:
15144 std::string function(int);
15148 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15149 tag, and @value{GDBN} displays the symbol like this:
15152 function[abi:cxx11](int)
15155 You can set a breakpoint on such functions simply as if they had no
15159 (gdb) b function(int)
15160 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15161 (gdb) info breakpoints
15162 Num Type Disp Enb Address What
15163 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15167 On the rare occasion you need to disambiguate between different ABI
15168 tags, you can do so by simply including the ABI tag in the function
15172 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15176 @node Decimal Floating Point
15177 @subsubsection Decimal Floating Point format
15178 @cindex decimal floating point format
15180 @value{GDBN} can examine, set and perform computations with numbers in
15181 decimal floating point format, which in the C language correspond to the
15182 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15183 specified by the extension to support decimal floating-point arithmetic.
15185 There are two encodings in use, depending on the architecture: BID (Binary
15186 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15187 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15190 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15191 to manipulate decimal floating point numbers, it is not possible to convert
15192 (using a cast, for example) integers wider than 32-bit to decimal float.
15194 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15195 point computations, error checking in decimal float operations ignores
15196 underflow, overflow and divide by zero exceptions.
15198 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15199 to inspect @code{_Decimal128} values stored in floating point registers.
15200 See @ref{PowerPC,,PowerPC} for more details.
15206 @value{GDBN} can be used to debug programs written in D and compiled with
15207 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15208 specific feature --- dynamic arrays.
15213 @cindex Go (programming language)
15214 @value{GDBN} can be used to debug programs written in Go and compiled with
15215 @file{gccgo} or @file{6g} compilers.
15217 Here is a summary of the Go-specific features and restrictions:
15220 @cindex current Go package
15221 @item The current Go package
15222 The name of the current package does not need to be specified when
15223 specifying global variables and functions.
15225 For example, given the program:
15229 var myglob = "Shall we?"
15235 When stopped inside @code{main} either of these work:
15239 (gdb) p main.myglob
15242 @cindex builtin Go types
15243 @item Builtin Go types
15244 The @code{string} type is recognized by @value{GDBN} and is printed
15247 @cindex builtin Go functions
15248 @item Builtin Go functions
15249 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15250 function and handles it internally.
15252 @cindex restrictions on Go expressions
15253 @item Restrictions on Go expressions
15254 All Go operators are supported except @code{&^}.
15255 The Go @code{_} ``blank identifier'' is not supported.
15256 Automatic dereferencing of pointers is not supported.
15260 @subsection Objective-C
15262 @cindex Objective-C
15263 This section provides information about some commands and command
15264 options that are useful for debugging Objective-C code. See also
15265 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15266 few more commands specific to Objective-C support.
15269 * Method Names in Commands::
15270 * The Print Command with Objective-C::
15273 @node Method Names in Commands
15274 @subsubsection Method Names in Commands
15276 The following commands have been extended to accept Objective-C method
15277 names as line specifications:
15279 @kindex clear@r{, and Objective-C}
15280 @kindex break@r{, and Objective-C}
15281 @kindex info line@r{, and Objective-C}
15282 @kindex jump@r{, and Objective-C}
15283 @kindex list@r{, and Objective-C}
15287 @item @code{info line}
15292 A fully qualified Objective-C method name is specified as
15295 -[@var{Class} @var{methodName}]
15298 where the minus sign is used to indicate an instance method and a
15299 plus sign (not shown) is used to indicate a class method. The class
15300 name @var{Class} and method name @var{methodName} are enclosed in
15301 brackets, similar to the way messages are specified in Objective-C
15302 source code. For example, to set a breakpoint at the @code{create}
15303 instance method of class @code{Fruit} in the program currently being
15307 break -[Fruit create]
15310 To list ten program lines around the @code{initialize} class method,
15314 list +[NSText initialize]
15317 In the current version of @value{GDBN}, the plus or minus sign is
15318 required. In future versions of @value{GDBN}, the plus or minus
15319 sign will be optional, but you can use it to narrow the search. It
15320 is also possible to specify just a method name:
15326 You must specify the complete method name, including any colons. If
15327 your program's source files contain more than one @code{create} method,
15328 you'll be presented with a numbered list of classes that implement that
15329 method. Indicate your choice by number, or type @samp{0} to exit if
15332 As another example, to clear a breakpoint established at the
15333 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15336 clear -[NSWindow makeKeyAndOrderFront:]
15339 @node The Print Command with Objective-C
15340 @subsubsection The Print Command With Objective-C
15341 @cindex Objective-C, print objects
15342 @kindex print-object
15343 @kindex po @r{(@code{print-object})}
15345 The print command has also been extended to accept methods. For example:
15348 print -[@var{object} hash]
15351 @cindex print an Objective-C object description
15352 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15354 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15355 and print the result. Also, an additional command has been added,
15356 @code{print-object} or @code{po} for short, which is meant to print
15357 the description of an object. However, this command may only work
15358 with certain Objective-C libraries that have a particular hook
15359 function, @code{_NSPrintForDebugger}, defined.
15362 @subsection OpenCL C
15365 This section provides information about @value{GDBN}s OpenCL C support.
15368 * OpenCL C Datatypes::
15369 * OpenCL C Expressions::
15370 * OpenCL C Operators::
15373 @node OpenCL C Datatypes
15374 @subsubsection OpenCL C Datatypes
15376 @cindex OpenCL C Datatypes
15377 @value{GDBN} supports the builtin scalar and vector datatypes specified
15378 by OpenCL 1.1. In addition the half- and double-precision floating point
15379 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15380 extensions are also known to @value{GDBN}.
15382 @node OpenCL C Expressions
15383 @subsubsection OpenCL C Expressions
15385 @cindex OpenCL C Expressions
15386 @value{GDBN} supports accesses to vector components including the access as
15387 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15388 supported by @value{GDBN} can be used as well.
15390 @node OpenCL C Operators
15391 @subsubsection OpenCL C Operators
15393 @cindex OpenCL C Operators
15394 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15398 @subsection Fortran
15399 @cindex Fortran-specific support in @value{GDBN}
15401 @value{GDBN} can be used to debug programs written in Fortran, but it
15402 currently supports only the features of Fortran 77 language.
15404 @cindex trailing underscore, in Fortran symbols
15405 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15406 among them) append an underscore to the names of variables and
15407 functions. When you debug programs compiled by those compilers, you
15408 will need to refer to variables and functions with a trailing
15412 * Fortran Operators:: Fortran operators and expressions
15413 * Fortran Defaults:: Default settings for Fortran
15414 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15417 @node Fortran Operators
15418 @subsubsection Fortran Operators and Expressions
15420 @cindex Fortran operators and expressions
15422 Operators must be defined on values of specific types. For instance,
15423 @code{+} is defined on numbers, but not on characters or other non-
15424 arithmetic types. Operators are often defined on groups of types.
15428 The exponentiation operator. It raises the first operand to the power
15432 The range operator. Normally used in the form of array(low:high) to
15433 represent a section of array.
15436 The access component operator. Normally used to access elements in derived
15437 types. Also suitable for unions. As unions aren't part of regular Fortran,
15438 this can only happen when accessing a register that uses a gdbarch-defined
15442 @node Fortran Defaults
15443 @subsubsection Fortran Defaults
15445 @cindex Fortran Defaults
15447 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15448 default uses case-insensitive matches for Fortran symbols. You can
15449 change that with the @samp{set case-insensitive} command, see
15450 @ref{Symbols}, for the details.
15452 @node Special Fortran Commands
15453 @subsubsection Special Fortran Commands
15455 @cindex Special Fortran commands
15457 @value{GDBN} has some commands to support Fortran-specific features,
15458 such as displaying common blocks.
15461 @cindex @code{COMMON} blocks, Fortran
15462 @kindex info common
15463 @item info common @r{[}@var{common-name}@r{]}
15464 This command prints the values contained in the Fortran @code{COMMON}
15465 block whose name is @var{common-name}. With no argument, the names of
15466 all @code{COMMON} blocks visible at the current program location are
15473 @cindex Pascal support in @value{GDBN}, limitations
15474 Debugging Pascal programs which use sets, subranges, file variables, or
15475 nested functions does not currently work. @value{GDBN} does not support
15476 entering expressions, printing values, or similar features using Pascal
15479 The Pascal-specific command @code{set print pascal_static-members}
15480 controls whether static members of Pascal objects are displayed.
15481 @xref{Print Settings, pascal_static-members}.
15486 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15487 Programming Language}. Type- and value-printing, and expression
15488 parsing, are reasonably complete. However, there are a few
15489 peculiarities and holes to be aware of.
15493 Linespecs (@pxref{Specify Location}) are never relative to the current
15494 crate. Instead, they act as if there were a global namespace of
15495 crates, somewhat similar to the way @code{extern crate} behaves.
15497 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15498 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15499 to set a breakpoint in a function named @samp{f} in a crate named
15502 As a consequence of this approach, linespecs also cannot refer to
15503 items using @samp{self::} or @samp{super::}.
15506 Because @value{GDBN} implements Rust name-lookup semantics in
15507 expressions, it will sometimes prepend the current crate to a name.
15508 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15509 @samp{K}, then @code{print ::x::y} will try to find the symbol
15512 However, since it is useful to be able to refer to other crates when
15513 debugging, @value{GDBN} provides the @code{extern} extension to
15514 circumvent this. To use the extension, just put @code{extern} before
15515 a path expression to refer to the otherwise unavailable ``global''
15518 In the above example, if you wanted to refer to the symbol @samp{y} in
15519 the crate @samp{x}, you would use @code{print extern x::y}.
15522 The Rust expression evaluator does not support ``statement-like''
15523 expressions such as @code{if} or @code{match}, or lambda expressions.
15526 Tuple expressions are not implemented.
15529 The Rust expression evaluator does not currently implement the
15530 @code{Drop} trait. Objects that may be created by the evaluator will
15531 never be destroyed.
15534 @value{GDBN} does not implement type inference for generics. In order
15535 to call generic functions or otherwise refer to generic items, you
15536 will have to specify the type parameters manually.
15539 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15540 cases this does not cause any problems. However, in an expression
15541 context, completing a generic function name will give syntactically
15542 invalid results. This happens because Rust requires the @samp{::}
15543 operator between the function name and its generic arguments. For
15544 example, @value{GDBN} might provide a completion like
15545 @code{crate::f<u32>}, where the parser would require
15546 @code{crate::f::<u32>}.
15549 As of this writing, the Rust compiler (version 1.8) has a few holes in
15550 the debugging information it generates. These holes prevent certain
15551 features from being implemented by @value{GDBN}:
15555 Method calls cannot be made via traits.
15558 Trait objects cannot be created or inspected.
15561 Operator overloading is not implemented.
15564 When debugging in a monomorphized function, you cannot use the generic
15568 The type @code{Self} is not available.
15571 @code{use} statements are not available, so some names may not be
15572 available in the crate.
15577 @subsection Modula-2
15579 @cindex Modula-2, @value{GDBN} support
15581 The extensions made to @value{GDBN} to support Modula-2 only support
15582 output from the @sc{gnu} Modula-2 compiler (which is currently being
15583 developed). Other Modula-2 compilers are not currently supported, and
15584 attempting to debug executables produced by them is most likely
15585 to give an error as @value{GDBN} reads in the executable's symbol
15588 @cindex expressions in Modula-2
15590 * M2 Operators:: Built-in operators
15591 * Built-In Func/Proc:: Built-in functions and procedures
15592 * M2 Constants:: Modula-2 constants
15593 * M2 Types:: Modula-2 types
15594 * M2 Defaults:: Default settings for Modula-2
15595 * Deviations:: Deviations from standard Modula-2
15596 * M2 Checks:: Modula-2 type and range checks
15597 * M2 Scope:: The scope operators @code{::} and @code{.}
15598 * GDB/M2:: @value{GDBN} and Modula-2
15602 @subsubsection Operators
15603 @cindex Modula-2 operators
15605 Operators must be defined on values of specific types. For instance,
15606 @code{+} is defined on numbers, but not on structures. Operators are
15607 often defined on groups of types. For the purposes of Modula-2, the
15608 following definitions hold:
15613 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15617 @emph{Character types} consist of @code{CHAR} and its subranges.
15620 @emph{Floating-point types} consist of @code{REAL}.
15623 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15627 @emph{Scalar types} consist of all of the above.
15630 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15633 @emph{Boolean types} consist of @code{BOOLEAN}.
15637 The following operators are supported, and appear in order of
15638 increasing precedence:
15642 Function argument or array index separator.
15645 Assignment. The value of @var{var} @code{:=} @var{value} is
15649 Less than, greater than on integral, floating-point, or enumerated
15653 Less than or equal to, greater than or equal to
15654 on integral, floating-point and enumerated types, or set inclusion on
15655 set types. Same precedence as @code{<}.
15657 @item =@r{, }<>@r{, }#
15658 Equality and two ways of expressing inequality, valid on scalar types.
15659 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15660 available for inequality, since @code{#} conflicts with the script
15664 Set membership. Defined on set types and the types of their members.
15665 Same precedence as @code{<}.
15668 Boolean disjunction. Defined on boolean types.
15671 Boolean conjunction. Defined on boolean types.
15674 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15677 Addition and subtraction on integral and floating-point types, or union
15678 and difference on set types.
15681 Multiplication on integral and floating-point types, or set intersection
15685 Division on floating-point types, or symmetric set difference on set
15686 types. Same precedence as @code{*}.
15689 Integer division and remainder. Defined on integral types. Same
15690 precedence as @code{*}.
15693 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15696 Pointer dereferencing. Defined on pointer types.
15699 Boolean negation. Defined on boolean types. Same precedence as
15703 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15704 precedence as @code{^}.
15707 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15710 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15714 @value{GDBN} and Modula-2 scope operators.
15718 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15719 treats the use of the operator @code{IN}, or the use of operators
15720 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15721 @code{<=}, and @code{>=} on sets as an error.
15725 @node Built-In Func/Proc
15726 @subsubsection Built-in Functions and Procedures
15727 @cindex Modula-2 built-ins
15729 Modula-2 also makes available several built-in procedures and functions.
15730 In describing these, the following metavariables are used:
15735 represents an @code{ARRAY} variable.
15738 represents a @code{CHAR} constant or variable.
15741 represents a variable or constant of integral type.
15744 represents an identifier that belongs to a set. Generally used in the
15745 same function with the metavariable @var{s}. The type of @var{s} should
15746 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15749 represents a variable or constant of integral or floating-point type.
15752 represents a variable or constant of floating-point type.
15758 represents a variable.
15761 represents a variable or constant of one of many types. See the
15762 explanation of the function for details.
15765 All Modula-2 built-in procedures also return a result, described below.
15769 Returns the absolute value of @var{n}.
15772 If @var{c} is a lower case letter, it returns its upper case
15773 equivalent, otherwise it returns its argument.
15776 Returns the character whose ordinal value is @var{i}.
15779 Decrements the value in the variable @var{v} by one. Returns the new value.
15781 @item DEC(@var{v},@var{i})
15782 Decrements the value in the variable @var{v} by @var{i}. Returns the
15785 @item EXCL(@var{m},@var{s})
15786 Removes the element @var{m} from the set @var{s}. Returns the new
15789 @item FLOAT(@var{i})
15790 Returns the floating point equivalent of the integer @var{i}.
15792 @item HIGH(@var{a})
15793 Returns the index of the last member of @var{a}.
15796 Increments the value in the variable @var{v} by one. Returns the new value.
15798 @item INC(@var{v},@var{i})
15799 Increments the value in the variable @var{v} by @var{i}. Returns the
15802 @item INCL(@var{m},@var{s})
15803 Adds the element @var{m} to the set @var{s} if it is not already
15804 there. Returns the new set.
15807 Returns the maximum value of the type @var{t}.
15810 Returns the minimum value of the type @var{t}.
15813 Returns boolean TRUE if @var{i} is an odd number.
15816 Returns the ordinal value of its argument. For example, the ordinal
15817 value of a character is its @sc{ascii} value (on machines supporting
15818 the @sc{ascii} character set). The argument @var{x} must be of an
15819 ordered type, which include integral, character and enumerated types.
15821 @item SIZE(@var{x})
15822 Returns the size of its argument. The argument @var{x} can be a
15823 variable or a type.
15825 @item TRUNC(@var{r})
15826 Returns the integral part of @var{r}.
15828 @item TSIZE(@var{x})
15829 Returns the size of its argument. The argument @var{x} can be a
15830 variable or a type.
15832 @item VAL(@var{t},@var{i})
15833 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15837 @emph{Warning:} Sets and their operations are not yet supported, so
15838 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15842 @cindex Modula-2 constants
15844 @subsubsection Constants
15846 @value{GDBN} allows you to express the constants of Modula-2 in the following
15852 Integer constants are simply a sequence of digits. When used in an
15853 expression, a constant is interpreted to be type-compatible with the
15854 rest of the expression. Hexadecimal integers are specified by a
15855 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15858 Floating point constants appear as a sequence of digits, followed by a
15859 decimal point and another sequence of digits. An optional exponent can
15860 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15861 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15862 digits of the floating point constant must be valid decimal (base 10)
15866 Character constants consist of a single character enclosed by a pair of
15867 like quotes, either single (@code{'}) or double (@code{"}). They may
15868 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15869 followed by a @samp{C}.
15872 String constants consist of a sequence of characters enclosed by a
15873 pair of like quotes, either single (@code{'}) or double (@code{"}).
15874 Escape sequences in the style of C are also allowed. @xref{C
15875 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15879 Enumerated constants consist of an enumerated identifier.
15882 Boolean constants consist of the identifiers @code{TRUE} and
15886 Pointer constants consist of integral values only.
15889 Set constants are not yet supported.
15893 @subsubsection Modula-2 Types
15894 @cindex Modula-2 types
15896 Currently @value{GDBN} can print the following data types in Modula-2
15897 syntax: array types, record types, set types, pointer types, procedure
15898 types, enumerated types, subrange types and base types. You can also
15899 print the contents of variables declared using these type.
15900 This section gives a number of simple source code examples together with
15901 sample @value{GDBN} sessions.
15903 The first example contains the following section of code:
15912 and you can request @value{GDBN} to interrogate the type and value of
15913 @code{r} and @code{s}.
15916 (@value{GDBP}) print s
15918 (@value{GDBP}) ptype s
15920 (@value{GDBP}) print r
15922 (@value{GDBP}) ptype r
15927 Likewise if your source code declares @code{s} as:
15931 s: SET ['A'..'Z'] ;
15935 then you may query the type of @code{s} by:
15938 (@value{GDBP}) ptype s
15939 type = SET ['A'..'Z']
15943 Note that at present you cannot interactively manipulate set
15944 expressions using the debugger.
15946 The following example shows how you might declare an array in Modula-2
15947 and how you can interact with @value{GDBN} to print its type and contents:
15951 s: ARRAY [-10..10] OF CHAR ;
15955 (@value{GDBP}) ptype s
15956 ARRAY [-10..10] OF CHAR
15959 Note that the array handling is not yet complete and although the type
15960 is printed correctly, expression handling still assumes that all
15961 arrays have a lower bound of zero and not @code{-10} as in the example
15964 Here are some more type related Modula-2 examples:
15968 colour = (blue, red, yellow, green) ;
15969 t = [blue..yellow] ;
15977 The @value{GDBN} interaction shows how you can query the data type
15978 and value of a variable.
15981 (@value{GDBP}) print s
15983 (@value{GDBP}) ptype t
15984 type = [blue..yellow]
15988 In this example a Modula-2 array is declared and its contents
15989 displayed. Observe that the contents are written in the same way as
15990 their @code{C} counterparts.
15994 s: ARRAY [1..5] OF CARDINAL ;
16000 (@value{GDBP}) print s
16001 $1 = @{1, 0, 0, 0, 0@}
16002 (@value{GDBP}) ptype s
16003 type = ARRAY [1..5] OF CARDINAL
16006 The Modula-2 language interface to @value{GDBN} also understands
16007 pointer types as shown in this example:
16011 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16018 and you can request that @value{GDBN} describes the type of @code{s}.
16021 (@value{GDBP}) ptype s
16022 type = POINTER TO ARRAY [1..5] OF CARDINAL
16025 @value{GDBN} handles compound types as we can see in this example.
16026 Here we combine array types, record types, pointer types and subrange
16037 myarray = ARRAY myrange OF CARDINAL ;
16038 myrange = [-2..2] ;
16040 s: POINTER TO ARRAY myrange OF foo ;
16044 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16048 (@value{GDBP}) ptype s
16049 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16052 f3 : ARRAY [-2..2] OF CARDINAL;
16057 @subsubsection Modula-2 Defaults
16058 @cindex Modula-2 defaults
16060 If type and range checking are set automatically by @value{GDBN}, they
16061 both default to @code{on} whenever the working language changes to
16062 Modula-2. This happens regardless of whether you or @value{GDBN}
16063 selected the working language.
16065 If you allow @value{GDBN} to set the language automatically, then entering
16066 code compiled from a file whose name ends with @file{.mod} sets the
16067 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16068 Infer the Source Language}, for further details.
16071 @subsubsection Deviations from Standard Modula-2
16072 @cindex Modula-2, deviations from
16074 A few changes have been made to make Modula-2 programs easier to debug.
16075 This is done primarily via loosening its type strictness:
16079 Unlike in standard Modula-2, pointer constants can be formed by
16080 integers. This allows you to modify pointer variables during
16081 debugging. (In standard Modula-2, the actual address contained in a
16082 pointer variable is hidden from you; it can only be modified
16083 through direct assignment to another pointer variable or expression that
16084 returned a pointer.)
16087 C escape sequences can be used in strings and characters to represent
16088 non-printable characters. @value{GDBN} prints out strings with these
16089 escape sequences embedded. Single non-printable characters are
16090 printed using the @samp{CHR(@var{nnn})} format.
16093 The assignment operator (@code{:=}) returns the value of its right-hand
16097 All built-in procedures both modify @emph{and} return their argument.
16101 @subsubsection Modula-2 Type and Range Checks
16102 @cindex Modula-2 checks
16105 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16108 @c FIXME remove warning when type/range checks added
16110 @value{GDBN} considers two Modula-2 variables type equivalent if:
16114 They are of types that have been declared equivalent via a @code{TYPE
16115 @var{t1} = @var{t2}} statement
16118 They have been declared on the same line. (Note: This is true of the
16119 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16122 As long as type checking is enabled, any attempt to combine variables
16123 whose types are not equivalent is an error.
16125 Range checking is done on all mathematical operations, assignment, array
16126 index bounds, and all built-in functions and procedures.
16129 @subsubsection The Scope Operators @code{::} and @code{.}
16131 @cindex @code{.}, Modula-2 scope operator
16132 @cindex colon, doubled as scope operator
16134 @vindex colon-colon@r{, in Modula-2}
16135 @c Info cannot handle :: but TeX can.
16138 @vindex ::@r{, in Modula-2}
16141 There are a few subtle differences between the Modula-2 scope operator
16142 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16147 @var{module} . @var{id}
16148 @var{scope} :: @var{id}
16152 where @var{scope} is the name of a module or a procedure,
16153 @var{module} the name of a module, and @var{id} is any declared
16154 identifier within your program, except another module.
16156 Using the @code{::} operator makes @value{GDBN} search the scope
16157 specified by @var{scope} for the identifier @var{id}. If it is not
16158 found in the specified scope, then @value{GDBN} searches all scopes
16159 enclosing the one specified by @var{scope}.
16161 Using the @code{.} operator makes @value{GDBN} search the current scope for
16162 the identifier specified by @var{id} that was imported from the
16163 definition module specified by @var{module}. With this operator, it is
16164 an error if the identifier @var{id} was not imported from definition
16165 module @var{module}, or if @var{id} is not an identifier in
16169 @subsubsection @value{GDBN} and Modula-2
16171 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16172 Five subcommands of @code{set print} and @code{show print} apply
16173 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16174 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16175 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16176 analogue in Modula-2.
16178 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16179 with any language, is not useful with Modula-2. Its
16180 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16181 created in Modula-2 as they can in C or C@t{++}. However, because an
16182 address can be specified by an integral constant, the construct
16183 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16185 @cindex @code{#} in Modula-2
16186 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16187 interpreted as the beginning of a comment. Use @code{<>} instead.
16193 The extensions made to @value{GDBN} for Ada only support
16194 output from the @sc{gnu} Ada (GNAT) compiler.
16195 Other Ada compilers are not currently supported, and
16196 attempting to debug executables produced by them is most likely
16200 @cindex expressions in Ada
16202 * Ada Mode Intro:: General remarks on the Ada syntax
16203 and semantics supported by Ada mode
16205 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16206 * Additions to Ada:: Extensions of the Ada expression syntax.
16207 * Overloading support for Ada:: Support for expressions involving overloaded
16209 * Stopping Before Main Program:: Debugging the program during elaboration.
16210 * Ada Exceptions:: Ada Exceptions
16211 * Ada Tasks:: Listing and setting breakpoints in tasks.
16212 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16213 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16215 * Ada Glitches:: Known peculiarities of Ada mode.
16218 @node Ada Mode Intro
16219 @subsubsection Introduction
16220 @cindex Ada mode, general
16222 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16223 syntax, with some extensions.
16224 The philosophy behind the design of this subset is
16228 That @value{GDBN} should provide basic literals and access to operations for
16229 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16230 leaving more sophisticated computations to subprograms written into the
16231 program (which therefore may be called from @value{GDBN}).
16234 That type safety and strict adherence to Ada language restrictions
16235 are not particularly important to the @value{GDBN} user.
16238 That brevity is important to the @value{GDBN} user.
16241 Thus, for brevity, the debugger acts as if all names declared in
16242 user-written packages are directly visible, even if they are not visible
16243 according to Ada rules, thus making it unnecessary to fully qualify most
16244 names with their packages, regardless of context. Where this causes
16245 ambiguity, @value{GDBN} asks the user's intent.
16247 The debugger will start in Ada mode if it detects an Ada main program.
16248 As for other languages, it will enter Ada mode when stopped in a program that
16249 was translated from an Ada source file.
16251 While in Ada mode, you may use `@t{--}' for comments. This is useful
16252 mostly for documenting command files. The standard @value{GDBN} comment
16253 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16254 middle (to allow based literals).
16256 @node Omissions from Ada
16257 @subsubsection Omissions from Ada
16258 @cindex Ada, omissions from
16260 Here are the notable omissions from the subset:
16264 Only a subset of the attributes are supported:
16268 @t{'First}, @t{'Last}, and @t{'Length}
16269 on array objects (not on types and subtypes).
16272 @t{'Min} and @t{'Max}.
16275 @t{'Pos} and @t{'Val}.
16281 @t{'Range} on array objects (not subtypes), but only as the right
16282 operand of the membership (@code{in}) operator.
16285 @t{'Access}, @t{'Unchecked_Access}, and
16286 @t{'Unrestricted_Access} (a GNAT extension).
16294 @code{Characters.Latin_1} are not available and
16295 concatenation is not implemented. Thus, escape characters in strings are
16296 not currently available.
16299 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16300 equality of representations. They will generally work correctly
16301 for strings and arrays whose elements have integer or enumeration types.
16302 They may not work correctly for arrays whose element
16303 types have user-defined equality, for arrays of real values
16304 (in particular, IEEE-conformant floating point, because of negative
16305 zeroes and NaNs), and for arrays whose elements contain unused bits with
16306 indeterminate values.
16309 The other component-by-component array operations (@code{and}, @code{or},
16310 @code{xor}, @code{not}, and relational tests other than equality)
16311 are not implemented.
16314 @cindex array aggregates (Ada)
16315 @cindex record aggregates (Ada)
16316 @cindex aggregates (Ada)
16317 There is limited support for array and record aggregates. They are
16318 permitted only on the right sides of assignments, as in these examples:
16321 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16322 (@value{GDBP}) set An_Array := (1, others => 0)
16323 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16324 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16325 (@value{GDBP}) set A_Record := (1, "Peter", True);
16326 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16330 discriminant's value by assigning an aggregate has an
16331 undefined effect if that discriminant is used within the record.
16332 However, you can first modify discriminants by directly assigning to
16333 them (which normally would not be allowed in Ada), and then performing an
16334 aggregate assignment. For example, given a variable @code{A_Rec}
16335 declared to have a type such as:
16338 type Rec (Len : Small_Integer := 0) is record
16340 Vals : IntArray (1 .. Len);
16344 you can assign a value with a different size of @code{Vals} with two
16348 (@value{GDBP}) set A_Rec.Len := 4
16349 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16352 As this example also illustrates, @value{GDBN} is very loose about the usual
16353 rules concerning aggregates. You may leave out some of the
16354 components of an array or record aggregate (such as the @code{Len}
16355 component in the assignment to @code{A_Rec} above); they will retain their
16356 original values upon assignment. You may freely use dynamic values as
16357 indices in component associations. You may even use overlapping or
16358 redundant component associations, although which component values are
16359 assigned in such cases is not defined.
16362 Calls to dispatching subprograms are not implemented.
16365 The overloading algorithm is much more limited (i.e., less selective)
16366 than that of real Ada. It makes only limited use of the context in
16367 which a subexpression appears to resolve its meaning, and it is much
16368 looser in its rules for allowing type matches. As a result, some
16369 function calls will be ambiguous, and the user will be asked to choose
16370 the proper resolution.
16373 The @code{new} operator is not implemented.
16376 Entry calls are not implemented.
16379 Aside from printing, arithmetic operations on the native VAX floating-point
16380 formats are not supported.
16383 It is not possible to slice a packed array.
16386 The names @code{True} and @code{False}, when not part of a qualified name,
16387 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16389 Should your program
16390 redefine these names in a package or procedure (at best a dubious practice),
16391 you will have to use fully qualified names to access their new definitions.
16394 @node Additions to Ada
16395 @subsubsection Additions to Ada
16396 @cindex Ada, deviations from
16398 As it does for other languages, @value{GDBN} makes certain generic
16399 extensions to Ada (@pxref{Expressions}):
16403 If the expression @var{E} is a variable residing in memory (typically
16404 a local variable or array element) and @var{N} is a positive integer,
16405 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16406 @var{N}-1 adjacent variables following it in memory as an array. In
16407 Ada, this operator is generally not necessary, since its prime use is
16408 in displaying parts of an array, and slicing will usually do this in
16409 Ada. However, there are occasional uses when debugging programs in
16410 which certain debugging information has been optimized away.
16413 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16414 appears in function or file @var{B}.'' When @var{B} is a file name,
16415 you must typically surround it in single quotes.
16418 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16419 @var{type} that appears at address @var{addr}.''
16422 A name starting with @samp{$} is a convenience variable
16423 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16426 In addition, @value{GDBN} provides a few other shortcuts and outright
16427 additions specific to Ada:
16431 The assignment statement is allowed as an expression, returning
16432 its right-hand operand as its value. Thus, you may enter
16435 (@value{GDBP}) set x := y + 3
16436 (@value{GDBP}) print A(tmp := y + 1)
16440 The semicolon is allowed as an ``operator,'' returning as its value
16441 the value of its right-hand operand.
16442 This allows, for example,
16443 complex conditional breaks:
16446 (@value{GDBP}) break f
16447 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16451 Rather than use catenation and symbolic character names to introduce special
16452 characters into strings, one may instead use a special bracket notation,
16453 which is also used to print strings. A sequence of characters of the form
16454 @samp{["@var{XX}"]} within a string or character literal denotes the
16455 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16456 sequence of characters @samp{["""]} also denotes a single quotation mark
16457 in strings. For example,
16459 "One line.["0a"]Next line.["0a"]"
16462 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16466 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16467 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16471 (@value{GDBP}) print 'max(x, y)
16475 When printing arrays, @value{GDBN} uses positional notation when the
16476 array has a lower bound of 1, and uses a modified named notation otherwise.
16477 For example, a one-dimensional array of three integers with a lower bound
16478 of 3 might print as
16485 That is, in contrast to valid Ada, only the first component has a @code{=>}
16489 You may abbreviate attributes in expressions with any unique,
16490 multi-character subsequence of
16491 their names (an exact match gets preference).
16492 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16493 in place of @t{a'length}.
16496 @cindex quoting Ada internal identifiers
16497 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16498 to lower case. The GNAT compiler uses upper-case characters for
16499 some of its internal identifiers, which are normally of no interest to users.
16500 For the rare occasions when you actually have to look at them,
16501 enclose them in angle brackets to avoid the lower-case mapping.
16504 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16508 Printing an object of class-wide type or dereferencing an
16509 access-to-class-wide value will display all the components of the object's
16510 specific type (as indicated by its run-time tag). Likewise, component
16511 selection on such a value will operate on the specific type of the
16516 @node Overloading support for Ada
16517 @subsubsection Overloading support for Ada
16518 @cindex overloading, Ada
16520 The debugger supports limited overloading. Given a subprogram call in which
16521 the function symbol has multiple definitions, it will use the number of
16522 actual parameters and some information about their types to attempt to narrow
16523 the set of definitions. It also makes very limited use of context, preferring
16524 procedures to functions in the context of the @code{call} command, and
16525 functions to procedures elsewhere.
16527 If, after narrowing, the set of matching definitions still contains more than
16528 one definition, @value{GDBN} will display a menu to query which one it should
16532 (@value{GDBP}) print f(1)
16533 Multiple matches for f
16535 [1] foo.f (integer) return boolean at foo.adb:23
16536 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16540 In this case, just select one menu entry either to cancel expression evaluation
16541 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16542 instance (type the corresponding number and press @key{RET}).
16544 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16549 @kindex set ada print-signatures
16550 @item set ada print-signatures
16551 Control whether parameter types and return types are displayed in overloads
16552 selection menus. It is @code{on} by default.
16553 @xref{Overloading support for Ada}.
16555 @kindex show ada print-signatures
16556 @item show ada print-signatures
16557 Show the current setting for displaying parameter types and return types in
16558 overloads selection menu.
16559 @xref{Overloading support for Ada}.
16563 @node Stopping Before Main Program
16564 @subsubsection Stopping at the Very Beginning
16566 @cindex breakpointing Ada elaboration code
16567 It is sometimes necessary to debug the program during elaboration, and
16568 before reaching the main procedure.
16569 As defined in the Ada Reference
16570 Manual, the elaboration code is invoked from a procedure called
16571 @code{adainit}. To run your program up to the beginning of
16572 elaboration, simply use the following two commands:
16573 @code{tbreak adainit} and @code{run}.
16575 @node Ada Exceptions
16576 @subsubsection Ada Exceptions
16578 A command is provided to list all Ada exceptions:
16581 @kindex info exceptions
16582 @item info exceptions
16583 @itemx info exceptions @var{regexp}
16584 The @code{info exceptions} command allows you to list all Ada exceptions
16585 defined within the program being debugged, as well as their addresses.
16586 With a regular expression, @var{regexp}, as argument, only those exceptions
16587 whose names match @var{regexp} are listed.
16590 Below is a small example, showing how the command can be used, first
16591 without argument, and next with a regular expression passed as an
16595 (@value{GDBP}) info exceptions
16596 All defined Ada exceptions:
16597 constraint_error: 0x613da0
16598 program_error: 0x613d20
16599 storage_error: 0x613ce0
16600 tasking_error: 0x613ca0
16601 const.aint_global_e: 0x613b00
16602 (@value{GDBP}) info exceptions const.aint
16603 All Ada exceptions matching regular expression "const.aint":
16604 constraint_error: 0x613da0
16605 const.aint_global_e: 0x613b00
16608 It is also possible to ask @value{GDBN} to stop your program's execution
16609 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16612 @subsubsection Extensions for Ada Tasks
16613 @cindex Ada, tasking
16615 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16616 @value{GDBN} provides the following task-related commands:
16621 This command shows a list of current Ada tasks, as in the following example:
16628 (@value{GDBP}) info tasks
16629 ID TID P-ID Pri State Name
16630 1 8088000 0 15 Child Activation Wait main_task
16631 2 80a4000 1 15 Accept Statement b
16632 3 809a800 1 15 Child Activation Wait a
16633 * 4 80ae800 3 15 Runnable c
16638 In this listing, the asterisk before the last task indicates it to be the
16639 task currently being inspected.
16643 Represents @value{GDBN}'s internal task number.
16649 The parent's task ID (@value{GDBN}'s internal task number).
16652 The base priority of the task.
16655 Current state of the task.
16659 The task has been created but has not been activated. It cannot be
16663 The task is not blocked for any reason known to Ada. (It may be waiting
16664 for a mutex, though.) It is conceptually "executing" in normal mode.
16667 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16668 that were waiting on terminate alternatives have been awakened and have
16669 terminated themselves.
16671 @item Child Activation Wait
16672 The task is waiting for created tasks to complete activation.
16674 @item Accept Statement
16675 The task is waiting on an accept or selective wait statement.
16677 @item Waiting on entry call
16678 The task is waiting on an entry call.
16680 @item Async Select Wait
16681 The task is waiting to start the abortable part of an asynchronous
16685 The task is waiting on a select statement with only a delay
16688 @item Child Termination Wait
16689 The task is sleeping having completed a master within itself, and is
16690 waiting for the tasks dependent on that master to become terminated or
16691 waiting on a terminate Phase.
16693 @item Wait Child in Term Alt
16694 The task is sleeping waiting for tasks on terminate alternatives to
16695 finish terminating.
16697 @item Accepting RV with @var{taskno}
16698 The task is accepting a rendez-vous with the task @var{taskno}.
16702 Name of the task in the program.
16706 @kindex info task @var{taskno}
16707 @item info task @var{taskno}
16708 This command shows detailled informations on the specified task, as in
16709 the following example:
16714 (@value{GDBP}) info tasks
16715 ID TID P-ID Pri State Name
16716 1 8077880 0 15 Child Activation Wait main_task
16717 * 2 807c468 1 15 Runnable task_1
16718 (@value{GDBP}) info task 2
16719 Ada Task: 0x807c468
16722 Parent: 1 (main_task)
16728 @kindex task@r{ (Ada)}
16729 @cindex current Ada task ID
16730 This command prints the ID of the current task.
16736 (@value{GDBP}) info tasks
16737 ID TID P-ID Pri State Name
16738 1 8077870 0 15 Child Activation Wait main_task
16739 * 2 807c458 1 15 Runnable t
16740 (@value{GDBP}) task
16741 [Current task is 2]
16744 @item task @var{taskno}
16745 @cindex Ada task switching
16746 This command is like the @code{thread @var{thread-id}}
16747 command (@pxref{Threads}). It switches the context of debugging
16748 from the current task to the given task.
16754 (@value{GDBP}) info tasks
16755 ID TID P-ID Pri State Name
16756 1 8077870 0 15 Child Activation Wait main_task
16757 * 2 807c458 1 15 Runnable t
16758 (@value{GDBP}) task 1
16759 [Switching to task 1]
16760 #0 0x8067726 in pthread_cond_wait ()
16762 #0 0x8067726 in pthread_cond_wait ()
16763 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16764 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16765 #3 0x806153e in system.tasking.stages.activate_tasks ()
16766 #4 0x804aacc in un () at un.adb:5
16769 @item break @var{location} task @var{taskno}
16770 @itemx break @var{location} task @var{taskno} if @dots{}
16771 @cindex breakpoints and tasks, in Ada
16772 @cindex task breakpoints, in Ada
16773 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16774 These commands are like the @code{break @dots{} thread @dots{}}
16775 command (@pxref{Thread Stops}). The
16776 @var{location} argument specifies source lines, as described
16777 in @ref{Specify Location}.
16779 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16780 to specify that you only want @value{GDBN} to stop the program when a
16781 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16782 numeric task identifiers assigned by @value{GDBN}, shown in the first
16783 column of the @samp{info tasks} display.
16785 If you do not specify @samp{task @var{taskno}} when you set a
16786 breakpoint, the breakpoint applies to @emph{all} tasks of your
16789 You can use the @code{task} qualifier on conditional breakpoints as
16790 well; in this case, place @samp{task @var{taskno}} before the
16791 breakpoint condition (before the @code{if}).
16799 (@value{GDBP}) info tasks
16800 ID TID P-ID Pri State Name
16801 1 140022020 0 15 Child Activation Wait main_task
16802 2 140045060 1 15 Accept/Select Wait t2
16803 3 140044840 1 15 Runnable t1
16804 * 4 140056040 1 15 Runnable t3
16805 (@value{GDBP}) b 15 task 2
16806 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16807 (@value{GDBP}) cont
16812 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16814 (@value{GDBP}) info tasks
16815 ID TID P-ID Pri State Name
16816 1 140022020 0 15 Child Activation Wait main_task
16817 * 2 140045060 1 15 Runnable t2
16818 3 140044840 1 15 Runnable t1
16819 4 140056040 1 15 Delay Sleep t3
16823 @node Ada Tasks and Core Files
16824 @subsubsection Tasking Support when Debugging Core Files
16825 @cindex Ada tasking and core file debugging
16827 When inspecting a core file, as opposed to debugging a live program,
16828 tasking support may be limited or even unavailable, depending on
16829 the platform being used.
16830 For instance, on x86-linux, the list of tasks is available, but task
16831 switching is not supported.
16833 On certain platforms, the debugger needs to perform some
16834 memory writes in order to provide Ada tasking support. When inspecting
16835 a core file, this means that the core file must be opened with read-write
16836 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16837 Under these circumstances, you should make a backup copy of the core
16838 file before inspecting it with @value{GDBN}.
16840 @node Ravenscar Profile
16841 @subsubsection Tasking Support when using the Ravenscar Profile
16842 @cindex Ravenscar Profile
16844 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16845 specifically designed for systems with safety-critical real-time
16849 @kindex set ravenscar task-switching on
16850 @cindex task switching with program using Ravenscar Profile
16851 @item set ravenscar task-switching on
16852 Allows task switching when debugging a program that uses the Ravenscar
16853 Profile. This is the default.
16855 @kindex set ravenscar task-switching off
16856 @item set ravenscar task-switching off
16857 Turn off task switching when debugging a program that uses the Ravenscar
16858 Profile. This is mostly intended to disable the code that adds support
16859 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16860 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16861 To be effective, this command should be run before the program is started.
16863 @kindex show ravenscar task-switching
16864 @item show ravenscar task-switching
16865 Show whether it is possible to switch from task to task in a program
16866 using the Ravenscar Profile.
16871 @subsubsection Known Peculiarities of Ada Mode
16872 @cindex Ada, problems
16874 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16875 we know of several problems with and limitations of Ada mode in
16877 some of which will be fixed with planned future releases of the debugger
16878 and the GNU Ada compiler.
16882 Static constants that the compiler chooses not to materialize as objects in
16883 storage are invisible to the debugger.
16886 Named parameter associations in function argument lists are ignored (the
16887 argument lists are treated as positional).
16890 Many useful library packages are currently invisible to the debugger.
16893 Fixed-point arithmetic, conversions, input, and output is carried out using
16894 floating-point arithmetic, and may give results that only approximate those on
16898 The GNAT compiler never generates the prefix @code{Standard} for any of
16899 the standard symbols defined by the Ada language. @value{GDBN} knows about
16900 this: it will strip the prefix from names when you use it, and will never
16901 look for a name you have so qualified among local symbols, nor match against
16902 symbols in other packages or subprograms. If you have
16903 defined entities anywhere in your program other than parameters and
16904 local variables whose simple names match names in @code{Standard},
16905 GNAT's lack of qualification here can cause confusion. When this happens,
16906 you can usually resolve the confusion
16907 by qualifying the problematic names with package
16908 @code{Standard} explicitly.
16911 Older versions of the compiler sometimes generate erroneous debugging
16912 information, resulting in the debugger incorrectly printing the value
16913 of affected entities. In some cases, the debugger is able to work
16914 around an issue automatically. In other cases, the debugger is able
16915 to work around the issue, but the work-around has to be specifically
16918 @kindex set ada trust-PAD-over-XVS
16919 @kindex show ada trust-PAD-over-XVS
16922 @item set ada trust-PAD-over-XVS on
16923 Configure GDB to strictly follow the GNAT encoding when computing the
16924 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16925 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16926 a complete description of the encoding used by the GNAT compiler).
16927 This is the default.
16929 @item set ada trust-PAD-over-XVS off
16930 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16931 sometimes prints the wrong value for certain entities, changing @code{ada
16932 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16933 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16934 @code{off}, but this incurs a slight performance penalty, so it is
16935 recommended to leave this setting to @code{on} unless necessary.
16939 @cindex GNAT descriptive types
16940 @cindex GNAT encoding
16941 Internally, the debugger also relies on the compiler following a number
16942 of conventions known as the @samp{GNAT Encoding}, all documented in
16943 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16944 how the debugging information should be generated for certain types.
16945 In particular, this convention makes use of @dfn{descriptive types},
16946 which are artificial types generated purely to help the debugger.
16948 These encodings were defined at a time when the debugging information
16949 format used was not powerful enough to describe some of the more complex
16950 types available in Ada. Since DWARF allows us to express nearly all
16951 Ada features, the long-term goal is to slowly replace these descriptive
16952 types by their pure DWARF equivalent. To facilitate that transition,
16953 a new maintenance option is available to force the debugger to ignore
16954 those descriptive types. It allows the user to quickly evaluate how
16955 well @value{GDBN} works without them.
16959 @kindex maint ada set ignore-descriptive-types
16960 @item maintenance ada set ignore-descriptive-types [on|off]
16961 Control whether the debugger should ignore descriptive types.
16962 The default is not to ignore descriptives types (@code{off}).
16964 @kindex maint ada show ignore-descriptive-types
16965 @item maintenance ada show ignore-descriptive-types
16966 Show if descriptive types are ignored by @value{GDBN}.
16970 @node Unsupported Languages
16971 @section Unsupported Languages
16973 @cindex unsupported languages
16974 @cindex minimal language
16975 In addition to the other fully-supported programming languages,
16976 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16977 It does not represent a real programming language, but provides a set
16978 of capabilities close to what the C or assembly languages provide.
16979 This should allow most simple operations to be performed while debugging
16980 an application that uses a language currently not supported by @value{GDBN}.
16982 If the language is set to @code{auto}, @value{GDBN} will automatically
16983 select this language if the current frame corresponds to an unsupported
16987 @chapter Examining the Symbol Table
16989 The commands described in this chapter allow you to inquire about the
16990 symbols (names of variables, functions and types) defined in your
16991 program. This information is inherent in the text of your program and
16992 does not change as your program executes. @value{GDBN} finds it in your
16993 program's symbol table, in the file indicated when you started @value{GDBN}
16994 (@pxref{File Options, ,Choosing Files}), or by one of the
16995 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16997 @cindex symbol names
16998 @cindex names of symbols
16999 @cindex quoting names
17000 @anchor{quoting names}
17001 Occasionally, you may need to refer to symbols that contain unusual
17002 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17003 most frequent case is in referring to static variables in other
17004 source files (@pxref{Variables,,Program Variables}). File names
17005 are recorded in object files as debugging symbols, but @value{GDBN} would
17006 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17007 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17008 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17015 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17018 @cindex case-insensitive symbol names
17019 @cindex case sensitivity in symbol names
17020 @kindex set case-sensitive
17021 @item set case-sensitive on
17022 @itemx set case-sensitive off
17023 @itemx set case-sensitive auto
17024 Normally, when @value{GDBN} looks up symbols, it matches their names
17025 with case sensitivity determined by the current source language.
17026 Occasionally, you may wish to control that. The command @code{set
17027 case-sensitive} lets you do that by specifying @code{on} for
17028 case-sensitive matches or @code{off} for case-insensitive ones. If
17029 you specify @code{auto}, case sensitivity is reset to the default
17030 suitable for the source language. The default is case-sensitive
17031 matches for all languages except for Fortran, for which the default is
17032 case-insensitive matches.
17034 @kindex show case-sensitive
17035 @item show case-sensitive
17036 This command shows the current setting of case sensitivity for symbols
17039 @kindex set print type methods
17040 @item set print type methods
17041 @itemx set print type methods on
17042 @itemx set print type methods off
17043 Normally, when @value{GDBN} prints a class, it displays any methods
17044 declared in that class. You can control this behavior either by
17045 passing the appropriate flag to @code{ptype}, or using @command{set
17046 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17047 display the methods; this is the default. Specifying @code{off} will
17048 cause @value{GDBN} to omit the methods.
17050 @kindex show print type methods
17051 @item show print type methods
17052 This command shows the current setting of method display when printing
17055 @kindex set print type typedefs
17056 @item set print type typedefs
17057 @itemx set print type typedefs on
17058 @itemx set print type typedefs off
17060 Normally, when @value{GDBN} prints a class, it displays any typedefs
17061 defined in that class. You can control this behavior either by
17062 passing the appropriate flag to @code{ptype}, or using @command{set
17063 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17064 display the typedef definitions; this is the default. Specifying
17065 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17066 Note that this controls whether the typedef definition itself is
17067 printed, not whether typedef names are substituted when printing other
17070 @kindex show print type typedefs
17071 @item show print type typedefs
17072 This command shows the current setting of typedef display when
17075 @kindex info address
17076 @cindex address of a symbol
17077 @item info address @var{symbol}
17078 Describe where the data for @var{symbol} is stored. For a register
17079 variable, this says which register it is kept in. For a non-register
17080 local variable, this prints the stack-frame offset at which the variable
17083 Note the contrast with @samp{print &@var{symbol}}, which does not work
17084 at all for a register variable, and for a stack local variable prints
17085 the exact address of the current instantiation of the variable.
17087 @kindex info symbol
17088 @cindex symbol from address
17089 @cindex closest symbol and offset for an address
17090 @item info symbol @var{addr}
17091 Print the name of a symbol which is stored at the address @var{addr}.
17092 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17093 nearest symbol and an offset from it:
17096 (@value{GDBP}) info symbol 0x54320
17097 _initialize_vx + 396 in section .text
17101 This is the opposite of the @code{info address} command. You can use
17102 it to find out the name of a variable or a function given its address.
17104 For dynamically linked executables, the name of executable or shared
17105 library containing the symbol is also printed:
17108 (@value{GDBP}) info symbol 0x400225
17109 _start + 5 in section .text of /tmp/a.out
17110 (@value{GDBP}) info symbol 0x2aaaac2811cf
17111 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17116 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17117 Demangle @var{name}.
17118 If @var{language} is provided it is the name of the language to demangle
17119 @var{name} in. Otherwise @var{name} is demangled in the current language.
17121 The @samp{--} option specifies the end of options,
17122 and is useful when @var{name} begins with a dash.
17124 The parameter @code{demangle-style} specifies how to interpret the kind
17125 of mangling used. @xref{Print Settings}.
17128 @item whatis[/@var{flags}] [@var{arg}]
17129 Print the data type of @var{arg}, which can be either an expression
17130 or a name of a data type. With no argument, print the data type of
17131 @code{$}, the last value in the value history.
17133 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17134 is not actually evaluated, and any side-effecting operations (such as
17135 assignments or function calls) inside it do not take place.
17137 If @var{arg} is a variable or an expression, @code{whatis} prints its
17138 literal type as it is used in the source code. If the type was
17139 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17140 the data type underlying the @code{typedef}. If the type of the
17141 variable or the expression is a compound data type, such as
17142 @code{struct} or @code{class}, @code{whatis} never prints their
17143 fields or methods. It just prints the @code{struct}/@code{class}
17144 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17145 such a compound data type, use @code{ptype}.
17147 If @var{arg} is a type name that was defined using @code{typedef},
17148 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17149 Unrolling means that @code{whatis} will show the underlying type used
17150 in the @code{typedef} declaration of @var{arg}. However, if that
17151 underlying type is also a @code{typedef}, @code{whatis} will not
17154 For C code, the type names may also have the form @samp{class
17155 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17156 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17158 @var{flags} can be used to modify how the type is displayed.
17159 Available flags are:
17163 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17164 parameters and typedefs defined in a class when printing the class'
17165 members. The @code{/r} flag disables this.
17168 Do not print methods defined in the class.
17171 Print methods defined in the class. This is the default, but the flag
17172 exists in case you change the default with @command{set print type methods}.
17175 Do not print typedefs defined in the class. Note that this controls
17176 whether the typedef definition itself is printed, not whether typedef
17177 names are substituted when printing other types.
17180 Print typedefs defined in the class. This is the default, but the flag
17181 exists in case you change the default with @command{set print type typedefs}.
17185 @item ptype[/@var{flags}] [@var{arg}]
17186 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17187 detailed description of the type, instead of just the name of the type.
17188 @xref{Expressions, ,Expressions}.
17190 Contrary to @code{whatis}, @code{ptype} always unrolls any
17191 @code{typedef}s in its argument declaration, whether the argument is
17192 a variable, expression, or a data type. This means that @code{ptype}
17193 of a variable or an expression will not print literally its type as
17194 present in the source code---use @code{whatis} for that. @code{typedef}s at
17195 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17196 fields, methods and inner @code{class typedef}s of @code{struct}s,
17197 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17199 For example, for this variable declaration:
17202 typedef double real_t;
17203 struct complex @{ real_t real; double imag; @};
17204 typedef struct complex complex_t;
17206 real_t *real_pointer_var;
17210 the two commands give this output:
17214 (@value{GDBP}) whatis var
17216 (@value{GDBP}) ptype var
17217 type = struct complex @{
17221 (@value{GDBP}) whatis complex_t
17222 type = struct complex
17223 (@value{GDBP}) whatis struct complex
17224 type = struct complex
17225 (@value{GDBP}) ptype struct complex
17226 type = struct complex @{
17230 (@value{GDBP}) whatis real_pointer_var
17232 (@value{GDBP}) ptype real_pointer_var
17238 As with @code{whatis}, using @code{ptype} without an argument refers to
17239 the type of @code{$}, the last value in the value history.
17241 @cindex incomplete type
17242 Sometimes, programs use opaque data types or incomplete specifications
17243 of complex data structure. If the debug information included in the
17244 program does not allow @value{GDBN} to display a full declaration of
17245 the data type, it will say @samp{<incomplete type>}. For example,
17246 given these declarations:
17250 struct foo *fooptr;
17254 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17257 (@value{GDBP}) ptype foo
17258 $1 = <incomplete type>
17262 ``Incomplete type'' is C terminology for data types that are not
17263 completely specified.
17265 @cindex unknown type
17266 Othertimes, information about a variable's type is completely absent
17267 from the debug information included in the program. This most often
17268 happens when the program or library where the variable is defined
17269 includes no debug information at all. @value{GDBN} knows the variable
17270 exists from inspecting the linker/loader symbol table (e.g., the ELF
17271 dynamic symbol table), but such symbols do not contain type
17272 information. Inspecting the type of a (global) variable for which
17273 @value{GDBN} has no type information shows:
17276 (@value{GDBP}) ptype var
17277 type = <data variable, no debug info>
17280 @xref{Variables, no debug info variables}, for how to print the values
17284 @item info types @var{regexp}
17286 Print a brief description of all types whose names match the regular
17287 expression @var{regexp} (or all types in your program, if you supply
17288 no argument). Each complete typename is matched as though it were a
17289 complete line; thus, @samp{i type value} gives information on all
17290 types in your program whose names include the string @code{value}, but
17291 @samp{i type ^value$} gives information only on types whose complete
17292 name is @code{value}.
17294 This command differs from @code{ptype} in two ways: first, like
17295 @code{whatis}, it does not print a detailed description; second, it
17296 lists all source files where a type is defined.
17298 @kindex info type-printers
17299 @item info type-printers
17300 Versions of @value{GDBN} that ship with Python scripting enabled may
17301 have ``type printers'' available. When using @command{ptype} or
17302 @command{whatis}, these printers are consulted when the name of a type
17303 is needed. @xref{Type Printing API}, for more information on writing
17306 @code{info type-printers} displays all the available type printers.
17308 @kindex enable type-printer
17309 @kindex disable type-printer
17310 @item enable type-printer @var{name}@dots{}
17311 @item disable type-printer @var{name}@dots{}
17312 These commands can be used to enable or disable type printers.
17315 @cindex local variables
17316 @item info scope @var{location}
17317 List all the variables local to a particular scope. This command
17318 accepts a @var{location} argument---a function name, a source line, or
17319 an address preceded by a @samp{*}, and prints all the variables local
17320 to the scope defined by that location. (@xref{Specify Location}, for
17321 details about supported forms of @var{location}.) For example:
17324 (@value{GDBP}) @b{info scope command_line_handler}
17325 Scope for command_line_handler:
17326 Symbol rl is an argument at stack/frame offset 8, length 4.
17327 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17328 Symbol linelength is in static storage at address 0x150a1c, length 4.
17329 Symbol p is a local variable in register $esi, length 4.
17330 Symbol p1 is a local variable in register $ebx, length 4.
17331 Symbol nline is a local variable in register $edx, length 4.
17332 Symbol repeat is a local variable at frame offset -8, length 4.
17336 This command is especially useful for determining what data to collect
17337 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17340 @kindex info source
17342 Show information about the current source file---that is, the source file for
17343 the function containing the current point of execution:
17346 the name of the source file, and the directory containing it,
17348 the directory it was compiled in,
17350 its length, in lines,
17352 which programming language it is written in,
17354 if the debug information provides it, the program that compiled the file
17355 (which may include, e.g., the compiler version and command line arguments),
17357 whether the executable includes debugging information for that file, and
17358 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17360 whether the debugging information includes information about
17361 preprocessor macros.
17365 @kindex info sources
17367 Print the names of all source files in your program for which there is
17368 debugging information, organized into two lists: files whose symbols
17369 have already been read, and files whose symbols will be read when needed.
17371 @kindex info functions
17372 @item info functions
17373 Print the names and data types of all defined functions.
17375 @item info functions @var{regexp}
17376 Print the names and data types of all defined functions
17377 whose names contain a match for regular expression @var{regexp}.
17378 Thus, @samp{info fun step} finds all functions whose names
17379 include @code{step}; @samp{info fun ^step} finds those whose names
17380 start with @code{step}. If a function name contains characters
17381 that conflict with the regular expression language (e.g.@:
17382 @samp{operator*()}), they may be quoted with a backslash.
17384 @kindex info variables
17385 @item info variables
17386 Print the names and data types of all variables that are defined
17387 outside of functions (i.e.@: excluding local variables).
17389 @item info variables @var{regexp}
17390 Print the names and data types of all variables (except for local
17391 variables) whose names contain a match for regular expression
17394 @kindex info classes
17395 @cindex Objective-C, classes and selectors
17397 @itemx info classes @var{regexp}
17398 Display all Objective-C classes in your program, or
17399 (with the @var{regexp} argument) all those matching a particular regular
17402 @kindex info selectors
17403 @item info selectors
17404 @itemx info selectors @var{regexp}
17405 Display all Objective-C selectors in your program, or
17406 (with the @var{regexp} argument) all those matching a particular regular
17410 This was never implemented.
17411 @kindex info methods
17413 @itemx info methods @var{regexp}
17414 The @code{info methods} command permits the user to examine all defined
17415 methods within C@t{++} program, or (with the @var{regexp} argument) a
17416 specific set of methods found in the various C@t{++} classes. Many
17417 C@t{++} classes provide a large number of methods. Thus, the output
17418 from the @code{ptype} command can be overwhelming and hard to use. The
17419 @code{info-methods} command filters the methods, printing only those
17420 which match the regular-expression @var{regexp}.
17423 @cindex opaque data types
17424 @kindex set opaque-type-resolution
17425 @item set opaque-type-resolution on
17426 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17427 declared as a pointer to a @code{struct}, @code{class}, or
17428 @code{union}---for example, @code{struct MyType *}---that is used in one
17429 source file although the full declaration of @code{struct MyType} is in
17430 another source file. The default is on.
17432 A change in the setting of this subcommand will not take effect until
17433 the next time symbols for a file are loaded.
17435 @item set opaque-type-resolution off
17436 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17437 is printed as follows:
17439 @{<no data fields>@}
17442 @kindex show opaque-type-resolution
17443 @item show opaque-type-resolution
17444 Show whether opaque types are resolved or not.
17446 @kindex set print symbol-loading
17447 @cindex print messages when symbols are loaded
17448 @item set print symbol-loading
17449 @itemx set print symbol-loading full
17450 @itemx set print symbol-loading brief
17451 @itemx set print symbol-loading off
17452 The @code{set print symbol-loading} command allows you to control the
17453 printing of messages when @value{GDBN} loads symbol information.
17454 By default a message is printed for the executable and one for each
17455 shared library, and normally this is what you want. However, when
17456 debugging apps with large numbers of shared libraries these messages
17458 When set to @code{brief} a message is printed for each executable,
17459 and when @value{GDBN} loads a collection of shared libraries at once
17460 it will only print one message regardless of the number of shared
17461 libraries. When set to @code{off} no messages are printed.
17463 @kindex show print symbol-loading
17464 @item show print symbol-loading
17465 Show whether messages will be printed when a @value{GDBN} command
17466 entered from the keyboard causes symbol information to be loaded.
17468 @kindex maint print symbols
17469 @cindex symbol dump
17470 @kindex maint print psymbols
17471 @cindex partial symbol dump
17472 @kindex maint print msymbols
17473 @cindex minimal symbol dump
17474 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17475 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17476 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17477 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17478 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17479 Write a dump of debugging symbol data into the file @var{filename} or
17480 the terminal if @var{filename} is unspecified.
17481 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17483 If @code{-pc @var{address}} is specified, only dump symbols for the file
17484 with code at that address. Note that @var{address} may be a symbol like
17486 If @code{-source @var{source}} is specified, only dump symbols for that
17489 These commands are used to debug the @value{GDBN} symbol-reading code.
17490 These commands do not modify internal @value{GDBN} state, therefore
17491 @samp{maint print symbols} will only print symbols for already expanded symbol
17493 You can use the command @code{info sources} to find out which files these are.
17494 If you use @samp{maint print psymbols} instead, the dump shows information
17495 about symbols that @value{GDBN} only knows partially---that is, symbols
17496 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17497 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17500 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17501 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17503 @kindex maint info symtabs
17504 @kindex maint info psymtabs
17505 @cindex listing @value{GDBN}'s internal symbol tables
17506 @cindex symbol tables, listing @value{GDBN}'s internal
17507 @cindex full symbol tables, listing @value{GDBN}'s internal
17508 @cindex partial symbol tables, listing @value{GDBN}'s internal
17509 @item maint info symtabs @r{[} @var{regexp} @r{]}
17510 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17512 List the @code{struct symtab} or @code{struct partial_symtab}
17513 structures whose names match @var{regexp}. If @var{regexp} is not
17514 given, list them all. The output includes expressions which you can
17515 copy into a @value{GDBN} debugging this one to examine a particular
17516 structure in more detail. For example:
17519 (@value{GDBP}) maint info psymtabs dwarf2read
17520 @{ objfile /home/gnu/build/gdb/gdb
17521 ((struct objfile *) 0x82e69d0)
17522 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17523 ((struct partial_symtab *) 0x8474b10)
17526 text addresses 0x814d3c8 -- 0x8158074
17527 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17528 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17529 dependencies (none)
17532 (@value{GDBP}) maint info symtabs
17536 We see that there is one partial symbol table whose filename contains
17537 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17538 and we see that @value{GDBN} has not read in any symtabs yet at all.
17539 If we set a breakpoint on a function, that will cause @value{GDBN} to
17540 read the symtab for the compilation unit containing that function:
17543 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17544 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17546 (@value{GDBP}) maint info symtabs
17547 @{ objfile /home/gnu/build/gdb/gdb
17548 ((struct objfile *) 0x82e69d0)
17549 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17550 ((struct symtab *) 0x86c1f38)
17553 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17554 linetable ((struct linetable *) 0x8370fa0)
17555 debugformat DWARF 2
17561 @kindex maint info line-table
17562 @cindex listing @value{GDBN}'s internal line tables
17563 @cindex line tables, listing @value{GDBN}'s internal
17564 @item maint info line-table @r{[} @var{regexp} @r{]}
17566 List the @code{struct linetable} from all @code{struct symtab}
17567 instances whose name matches @var{regexp}. If @var{regexp} is not
17568 given, list the @code{struct linetable} from all @code{struct symtab}.
17570 @kindex maint set symbol-cache-size
17571 @cindex symbol cache size
17572 @item maint set symbol-cache-size @var{size}
17573 Set the size of the symbol cache to @var{size}.
17574 The default size is intended to be good enough for debugging
17575 most applications. This option exists to allow for experimenting
17576 with different sizes.
17578 @kindex maint show symbol-cache-size
17579 @item maint show symbol-cache-size
17580 Show the size of the symbol cache.
17582 @kindex maint print symbol-cache
17583 @cindex symbol cache, printing its contents
17584 @item maint print symbol-cache
17585 Print the contents of the symbol cache.
17586 This is useful when debugging symbol cache issues.
17588 @kindex maint print symbol-cache-statistics
17589 @cindex symbol cache, printing usage statistics
17590 @item maint print symbol-cache-statistics
17591 Print symbol cache usage statistics.
17592 This helps determine how well the cache is being utilized.
17594 @kindex maint flush-symbol-cache
17595 @cindex symbol cache, flushing
17596 @item maint flush-symbol-cache
17597 Flush the contents of the symbol cache, all entries are removed.
17598 This command is useful when debugging the symbol cache.
17599 It is also useful when collecting performance data.
17604 @chapter Altering Execution
17606 Once you think you have found an error in your program, you might want to
17607 find out for certain whether correcting the apparent error would lead to
17608 correct results in the rest of the run. You can find the answer by
17609 experiment, using the @value{GDBN} features for altering execution of the
17612 For example, you can store new values into variables or memory
17613 locations, give your program a signal, restart it at a different
17614 address, or even return prematurely from a function.
17617 * Assignment:: Assignment to variables
17618 * Jumping:: Continuing at a different address
17619 * Signaling:: Giving your program a signal
17620 * Returning:: Returning from a function
17621 * Calling:: Calling your program's functions
17622 * Patching:: Patching your program
17623 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17627 @section Assignment to Variables
17630 @cindex setting variables
17631 To alter the value of a variable, evaluate an assignment expression.
17632 @xref{Expressions, ,Expressions}. For example,
17639 stores the value 4 into the variable @code{x}, and then prints the
17640 value of the assignment expression (which is 4).
17641 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17642 information on operators in supported languages.
17644 @kindex set variable
17645 @cindex variables, setting
17646 If you are not interested in seeing the value of the assignment, use the
17647 @code{set} command instead of the @code{print} command. @code{set} is
17648 really the same as @code{print} except that the expression's value is
17649 not printed and is not put in the value history (@pxref{Value History,
17650 ,Value History}). The expression is evaluated only for its effects.
17652 If the beginning of the argument string of the @code{set} command
17653 appears identical to a @code{set} subcommand, use the @code{set
17654 variable} command instead of just @code{set}. This command is identical
17655 to @code{set} except for its lack of subcommands. For example, if your
17656 program has a variable @code{width}, you get an error if you try to set
17657 a new value with just @samp{set width=13}, because @value{GDBN} has the
17658 command @code{set width}:
17661 (@value{GDBP}) whatis width
17663 (@value{GDBP}) p width
17665 (@value{GDBP}) set width=47
17666 Invalid syntax in expression.
17670 The invalid expression, of course, is @samp{=47}. In
17671 order to actually set the program's variable @code{width}, use
17674 (@value{GDBP}) set var width=47
17677 Because the @code{set} command has many subcommands that can conflict
17678 with the names of program variables, it is a good idea to use the
17679 @code{set variable} command instead of just @code{set}. For example, if
17680 your program has a variable @code{g}, you run into problems if you try
17681 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17682 the command @code{set gnutarget}, abbreviated @code{set g}:
17686 (@value{GDBP}) whatis g
17690 (@value{GDBP}) set g=4
17694 The program being debugged has been started already.
17695 Start it from the beginning? (y or n) y
17696 Starting program: /home/smith/cc_progs/a.out
17697 "/home/smith/cc_progs/a.out": can't open to read symbols:
17698 Invalid bfd target.
17699 (@value{GDBP}) show g
17700 The current BFD target is "=4".
17705 The program variable @code{g} did not change, and you silently set the
17706 @code{gnutarget} to an invalid value. In order to set the variable
17710 (@value{GDBP}) set var g=4
17713 @value{GDBN} allows more implicit conversions in assignments than C; you can
17714 freely store an integer value into a pointer variable or vice versa,
17715 and you can convert any structure to any other structure that is the
17716 same length or shorter.
17717 @comment FIXME: how do structs align/pad in these conversions?
17718 @comment /doc@cygnus.com 18dec1990
17720 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17721 construct to generate a value of specified type at a specified address
17722 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17723 to memory location @code{0x83040} as an integer (which implies a certain size
17724 and representation in memory), and
17727 set @{int@}0x83040 = 4
17731 stores the value 4 into that memory location.
17734 @section Continuing at a Different Address
17736 Ordinarily, when you continue your program, you do so at the place where
17737 it stopped, with the @code{continue} command. You can instead continue at
17738 an address of your own choosing, with the following commands:
17742 @kindex j @r{(@code{jump})}
17743 @item jump @var{location}
17744 @itemx j @var{location}
17745 Resume execution at @var{location}. Execution stops again immediately
17746 if there is a breakpoint there. @xref{Specify Location}, for a description
17747 of the different forms of @var{location}. It is common
17748 practice to use the @code{tbreak} command in conjunction with
17749 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17751 The @code{jump} command does not change the current stack frame, or
17752 the stack pointer, or the contents of any memory location or any
17753 register other than the program counter. If @var{location} is in
17754 a different function from the one currently executing, the results may
17755 be bizarre if the two functions expect different patterns of arguments or
17756 of local variables. For this reason, the @code{jump} command requests
17757 confirmation if the specified line is not in the function currently
17758 executing. However, even bizarre results are predictable if you are
17759 well acquainted with the machine-language code of your program.
17762 On many systems, you can get much the same effect as the @code{jump}
17763 command by storing a new value into the register @code{$pc}. The
17764 difference is that this does not start your program running; it only
17765 changes the address of where it @emph{will} run when you continue. For
17773 makes the next @code{continue} command or stepping command execute at
17774 address @code{0x485}, rather than at the address where your program stopped.
17775 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17777 The most common occasion to use the @code{jump} command is to back
17778 up---perhaps with more breakpoints set---over a portion of a program
17779 that has already executed, in order to examine its execution in more
17784 @section Giving your Program a Signal
17785 @cindex deliver a signal to a program
17789 @item signal @var{signal}
17790 Resume execution where your program is stopped, but immediately give it the
17791 signal @var{signal}. The @var{signal} can be the name or the number of a
17792 signal. For example, on many systems @code{signal 2} and @code{signal
17793 SIGINT} are both ways of sending an interrupt signal.
17795 Alternatively, if @var{signal} is zero, continue execution without
17796 giving a signal. This is useful when your program stopped on account of
17797 a signal and would ordinarily see the signal when resumed with the
17798 @code{continue} command; @samp{signal 0} causes it to resume without a
17801 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17802 delivered to the currently selected thread, not the thread that last
17803 reported a stop. This includes the situation where a thread was
17804 stopped due to a signal. So if you want to continue execution
17805 suppressing the signal that stopped a thread, you should select that
17806 same thread before issuing the @samp{signal 0} command. If you issue
17807 the @samp{signal 0} command with another thread as the selected one,
17808 @value{GDBN} detects that and asks for confirmation.
17810 Invoking the @code{signal} command is not the same as invoking the
17811 @code{kill} utility from the shell. Sending a signal with @code{kill}
17812 causes @value{GDBN} to decide what to do with the signal depending on
17813 the signal handling tables (@pxref{Signals}). The @code{signal} command
17814 passes the signal directly to your program.
17816 @code{signal} does not repeat when you press @key{RET} a second time
17817 after executing the command.
17819 @kindex queue-signal
17820 @item queue-signal @var{signal}
17821 Queue @var{signal} to be delivered immediately to the current thread
17822 when execution of the thread resumes. The @var{signal} can be the name or
17823 the number of a signal. For example, on many systems @code{signal 2} and
17824 @code{signal SIGINT} are both ways of sending an interrupt signal.
17825 The handling of the signal must be set to pass the signal to the program,
17826 otherwise @value{GDBN} will report an error.
17827 You can control the handling of signals from @value{GDBN} with the
17828 @code{handle} command (@pxref{Signals}).
17830 Alternatively, if @var{signal} is zero, any currently queued signal
17831 for the current thread is discarded and when execution resumes no signal
17832 will be delivered. This is useful when your program stopped on account
17833 of a signal and would ordinarily see the signal when resumed with the
17834 @code{continue} command.
17836 This command differs from the @code{signal} command in that the signal
17837 is just queued, execution is not resumed. And @code{queue-signal} cannot
17838 be used to pass a signal whose handling state has been set to @code{nopass}
17843 @xref{stepping into signal handlers}, for information on how stepping
17844 commands behave when the thread has a signal queued.
17847 @section Returning from a Function
17850 @cindex returning from a function
17853 @itemx return @var{expression}
17854 You can cancel execution of a function call with the @code{return}
17855 command. If you give an
17856 @var{expression} argument, its value is used as the function's return
17860 When you use @code{return}, @value{GDBN} discards the selected stack frame
17861 (and all frames within it). You can think of this as making the
17862 discarded frame return prematurely. If you wish to specify a value to
17863 be returned, give that value as the argument to @code{return}.
17865 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17866 Frame}), and any other frames inside of it, leaving its caller as the
17867 innermost remaining frame. That frame becomes selected. The
17868 specified value is stored in the registers used for returning values
17871 The @code{return} command does not resume execution; it leaves the
17872 program stopped in the state that would exist if the function had just
17873 returned. In contrast, the @code{finish} command (@pxref{Continuing
17874 and Stepping, ,Continuing and Stepping}) resumes execution until the
17875 selected stack frame returns naturally.
17877 @value{GDBN} needs to know how the @var{expression} argument should be set for
17878 the inferior. The concrete registers assignment depends on the OS ABI and the
17879 type being returned by the selected stack frame. For example it is common for
17880 OS ABI to return floating point values in FPU registers while integer values in
17881 CPU registers. Still some ABIs return even floating point values in CPU
17882 registers. Larger integer widths (such as @code{long long int}) also have
17883 specific placement rules. @value{GDBN} already knows the OS ABI from its
17884 current target so it needs to find out also the type being returned to make the
17885 assignment into the right register(s).
17887 Normally, the selected stack frame has debug info. @value{GDBN} will always
17888 use the debug info instead of the implicit type of @var{expression} when the
17889 debug info is available. For example, if you type @kbd{return -1}, and the
17890 function in the current stack frame is declared to return a @code{long long
17891 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17892 into a @code{long long int}:
17895 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17897 (@value{GDBP}) return -1
17898 Make func return now? (y or n) y
17899 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17900 43 printf ("result=%lld\n", func ());
17904 However, if the selected stack frame does not have a debug info, e.g., if the
17905 function was compiled without debug info, @value{GDBN} has to find out the type
17906 to return from user. Specifying a different type by mistake may set the value
17907 in different inferior registers than the caller code expects. For example,
17908 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17909 of a @code{long long int} result for a debug info less function (on 32-bit
17910 architectures). Therefore the user is required to specify the return type by
17911 an appropriate cast explicitly:
17914 Breakpoint 2, 0x0040050b in func ()
17915 (@value{GDBP}) return -1
17916 Return value type not available for selected stack frame.
17917 Please use an explicit cast of the value to return.
17918 (@value{GDBP}) return (long long int) -1
17919 Make selected stack frame return now? (y or n) y
17920 #0 0x00400526 in main ()
17925 @section Calling Program Functions
17928 @cindex calling functions
17929 @cindex inferior functions, calling
17930 @item print @var{expr}
17931 Evaluate the expression @var{expr} and display the resulting value.
17932 The expression may include calls to functions in the program being
17936 @item call @var{expr}
17937 Evaluate the expression @var{expr} without displaying @code{void}
17940 You can use this variant of the @code{print} command if you want to
17941 execute a function from your program that does not return anything
17942 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17943 with @code{void} returned values that @value{GDBN} will otherwise
17944 print. If the result is not void, it is printed and saved in the
17948 It is possible for the function you call via the @code{print} or
17949 @code{call} command to generate a signal (e.g., if there's a bug in
17950 the function, or if you passed it incorrect arguments). What happens
17951 in that case is controlled by the @code{set unwindonsignal} command.
17953 Similarly, with a C@t{++} program it is possible for the function you
17954 call via the @code{print} or @code{call} command to generate an
17955 exception that is not handled due to the constraints of the dummy
17956 frame. In this case, any exception that is raised in the frame, but has
17957 an out-of-frame exception handler will not be found. GDB builds a
17958 dummy-frame for the inferior function call, and the unwinder cannot
17959 seek for exception handlers outside of this dummy-frame. What happens
17960 in that case is controlled by the
17961 @code{set unwind-on-terminating-exception} command.
17964 @item set unwindonsignal
17965 @kindex set unwindonsignal
17966 @cindex unwind stack in called functions
17967 @cindex call dummy stack unwinding
17968 Set unwinding of the stack if a signal is received while in a function
17969 that @value{GDBN} called in the program being debugged. If set to on,
17970 @value{GDBN} unwinds the stack it created for the call and restores
17971 the context to what it was before the call. If set to off (the
17972 default), @value{GDBN} stops in the frame where the signal was
17975 @item show unwindonsignal
17976 @kindex show unwindonsignal
17977 Show the current setting of stack unwinding in the functions called by
17980 @item set unwind-on-terminating-exception
17981 @kindex set unwind-on-terminating-exception
17982 @cindex unwind stack in called functions with unhandled exceptions
17983 @cindex call dummy stack unwinding on unhandled exception.
17984 Set unwinding of the stack if a C@t{++} exception is raised, but left
17985 unhandled while in a function that @value{GDBN} called in the program being
17986 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17987 it created for the call and restores the context to what it was before
17988 the call. If set to off, @value{GDBN} the exception is delivered to
17989 the default C@t{++} exception handler and the inferior terminated.
17991 @item show unwind-on-terminating-exception
17992 @kindex show unwind-on-terminating-exception
17993 Show the current setting of stack unwinding in the functions called by
17998 @subsection Calling functions with no debug info
18000 @cindex no debug info functions
18001 Sometimes, a function you wish to call is missing debug information.
18002 In such case, @value{GDBN} does not know the type of the function,
18003 including the types of the function's parameters. To avoid calling
18004 the inferior function incorrectly, which could result in the called
18005 function functioning erroneously and even crash, @value{GDBN} refuses
18006 to call the function unless you tell it the type of the function.
18008 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18009 to do that. The simplest is to cast the call to the function's
18010 declared return type. For example:
18013 (@value{GDBP}) p getenv ("PATH")
18014 'getenv' has unknown return type; cast the call to its declared return type
18015 (@value{GDBP}) p (char *) getenv ("PATH")
18016 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18019 Casting the return type of a no-debug function is equivalent to
18020 casting the function to a pointer to a prototyped function that has a
18021 prototype that matches the types of the passed-in arguments, and
18022 calling that. I.e., the call above is equivalent to:
18025 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18029 and given this prototyped C or C++ function with float parameters:
18032 float multiply (float v1, float v2) @{ return v1 * v2; @}
18036 these calls are equivalent:
18039 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18040 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18043 If the function you wish to call is declared as unprototyped (i.e.@:
18044 old K&R style), you must use the cast-to-function-pointer syntax, so
18045 that @value{GDBN} knows that it needs to apply default argument
18046 promotions (promote float arguments to double). @xref{ABI, float
18047 promotion}. For example, given this unprototyped C function with
18048 float parameters, and no debug info:
18052 multiply_noproto (v1, v2)
18060 you call it like this:
18063 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18067 @section Patching Programs
18069 @cindex patching binaries
18070 @cindex writing into executables
18071 @cindex writing into corefiles
18073 By default, @value{GDBN} opens the file containing your program's
18074 executable code (or the corefile) read-only. This prevents accidental
18075 alterations to machine code; but it also prevents you from intentionally
18076 patching your program's binary.
18078 If you'd like to be able to patch the binary, you can specify that
18079 explicitly with the @code{set write} command. For example, you might
18080 want to turn on internal debugging flags, or even to make emergency
18086 @itemx set write off
18087 If you specify @samp{set write on}, @value{GDBN} opens executable and
18088 core files for both reading and writing; if you specify @kbd{set write
18089 off} (the default), @value{GDBN} opens them read-only.
18091 If you have already loaded a file, you must load it again (using the
18092 @code{exec-file} or @code{core-file} command) after changing @code{set
18093 write}, for your new setting to take effect.
18097 Display whether executable files and core files are opened for writing
18098 as well as reading.
18101 @node Compiling and Injecting Code
18102 @section Compiling and injecting code in @value{GDBN}
18103 @cindex injecting code
18104 @cindex writing into executables
18105 @cindex compiling code
18107 @value{GDBN} supports on-demand compilation and code injection into
18108 programs running under @value{GDBN}. GCC 5.0 or higher built with
18109 @file{libcc1.so} must be installed for this functionality to be enabled.
18110 This functionality is implemented with the following commands.
18113 @kindex compile code
18114 @item compile code @var{source-code}
18115 @itemx compile code -raw @var{--} @var{source-code}
18116 Compile @var{source-code} with the compiler language found as the current
18117 language in @value{GDBN} (@pxref{Languages}). If compilation and
18118 injection is not supported with the current language specified in
18119 @value{GDBN}, or the compiler does not support this feature, an error
18120 message will be printed. If @var{source-code} compiles and links
18121 successfully, @value{GDBN} will load the object-code emitted,
18122 and execute it within the context of the currently selected inferior.
18123 It is important to note that the compiled code is executed immediately.
18124 After execution, the compiled code is removed from @value{GDBN} and any
18125 new types or variables you have defined will be deleted.
18127 The command allows you to specify @var{source-code} in two ways.
18128 The simplest method is to provide a single line of code to the command.
18132 compile code printf ("hello world\n");
18135 If you specify options on the command line as well as source code, they
18136 may conflict. The @samp{--} delimiter can be used to separate options
18137 from actual source code. E.g.:
18140 compile code -r -- printf ("hello world\n");
18143 Alternatively you can enter source code as multiple lines of text. To
18144 enter this mode, invoke the @samp{compile code} command without any text
18145 following the command. This will start the multiple-line editor and
18146 allow you to type as many lines of source code as required. When you
18147 have completed typing, enter @samp{end} on its own line to exit the
18152 >printf ("hello\n");
18153 >printf ("world\n");
18157 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18158 provided @var{source-code} in a callable scope. In this case, you must
18159 specify the entry point of the code by defining a function named
18160 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18161 inferior. Using @samp{-raw} option may be needed for example when
18162 @var{source-code} requires @samp{#include} lines which may conflict with
18163 inferior symbols otherwise.
18165 @kindex compile file
18166 @item compile file @var{filename}
18167 @itemx compile file -raw @var{filename}
18168 Like @code{compile code}, but take the source code from @var{filename}.
18171 compile file /home/user/example.c
18176 @item compile print @var{expr}
18177 @itemx compile print /@var{f} @var{expr}
18178 Compile and execute @var{expr} with the compiler language found as the
18179 current language in @value{GDBN} (@pxref{Languages}). By default the
18180 value of @var{expr} is printed in a format appropriate to its data type;
18181 you can choose a different format by specifying @samp{/@var{f}}, where
18182 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18185 @item compile print
18186 @itemx compile print /@var{f}
18187 @cindex reprint the last value
18188 Alternatively you can enter the expression (source code producing it) as
18189 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18190 command without any text following the command. This will start the
18191 multiple-line editor.
18195 The process of compiling and injecting the code can be inspected using:
18198 @anchor{set debug compile}
18199 @item set debug compile
18200 @cindex compile command debugging info
18201 Turns on or off display of @value{GDBN} process of compiling and
18202 injecting the code. The default is off.
18204 @item show debug compile
18205 Displays the current state of displaying @value{GDBN} process of
18206 compiling and injecting the code.
18209 @subsection Compilation options for the @code{compile} command
18211 @value{GDBN} needs to specify the right compilation options for the code
18212 to be injected, in part to make its ABI compatible with the inferior
18213 and in part to make the injected code compatible with @value{GDBN}'s
18217 The options used, in increasing precedence:
18220 @item target architecture and OS options (@code{gdbarch})
18221 These options depend on target processor type and target operating
18222 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18223 (@code{-m64}) compilation option.
18225 @item compilation options recorded in the target
18226 @value{NGCC} (since version 4.7) stores the options used for compilation
18227 into @code{DW_AT_producer} part of DWARF debugging information according
18228 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18229 explicitly specify @code{-g} during inferior compilation otherwise
18230 @value{NGCC} produces no DWARF. This feature is only relevant for
18231 platforms where @code{-g} produces DWARF by default, otherwise one may
18232 try to enforce DWARF by using @code{-gdwarf-4}.
18234 @item compilation options set by @code{set compile-args}
18238 You can override compilation options using the following command:
18241 @item set compile-args
18242 @cindex compile command options override
18243 Set compilation options used for compiling and injecting code with the
18244 @code{compile} commands. These options override any conflicting ones
18245 from the target architecture and/or options stored during inferior
18248 @item show compile-args
18249 Displays the current state of compilation options override.
18250 This does not show all the options actually used during compilation,
18251 use @ref{set debug compile} for that.
18254 @subsection Caveats when using the @code{compile} command
18256 There are a few caveats to keep in mind when using the @code{compile}
18257 command. As the caveats are different per language, the table below
18258 highlights specific issues on a per language basis.
18261 @item C code examples and caveats
18262 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18263 attempt to compile the source code with a @samp{C} compiler. The source
18264 code provided to the @code{compile} command will have much the same
18265 access to variables and types as it normally would if it were part of
18266 the program currently being debugged in @value{GDBN}.
18268 Below is a sample program that forms the basis of the examples that
18269 follow. This program has been compiled and loaded into @value{GDBN},
18270 much like any other normal debugging session.
18273 void function1 (void)
18276 printf ("function 1\n");
18279 void function2 (void)
18294 For the purposes of the examples in this section, the program above has
18295 been compiled, loaded into @value{GDBN}, stopped at the function
18296 @code{main}, and @value{GDBN} is awaiting input from the user.
18298 To access variables and types for any program in @value{GDBN}, the
18299 program must be compiled and packaged with debug information. The
18300 @code{compile} command is not an exception to this rule. Without debug
18301 information, you can still use the @code{compile} command, but you will
18302 be very limited in what variables and types you can access.
18304 So with that in mind, the example above has been compiled with debug
18305 information enabled. The @code{compile} command will have access to
18306 all variables and types (except those that may have been optimized
18307 out). Currently, as @value{GDBN} has stopped the program in the
18308 @code{main} function, the @code{compile} command would have access to
18309 the variable @code{k}. You could invoke the @code{compile} command
18310 and type some source code to set the value of @code{k}. You can also
18311 read it, or do anything with that variable you would normally do in
18312 @code{C}. Be aware that changes to inferior variables in the
18313 @code{compile} command are persistent. In the following example:
18316 compile code k = 3;
18320 the variable @code{k} is now 3. It will retain that value until
18321 something else in the example program changes it, or another
18322 @code{compile} command changes it.
18324 Normal scope and access rules apply to source code compiled and
18325 injected by the @code{compile} command. In the example, the variables
18326 @code{j} and @code{k} are not accessible yet, because the program is
18327 currently stopped in the @code{main} function, where these variables
18328 are not in scope. Therefore, the following command
18331 compile code j = 3;
18335 will result in a compilation error message.
18337 Once the program is continued, execution will bring these variables in
18338 scope, and they will become accessible; then the code you specify via
18339 the @code{compile} command will be able to access them.
18341 You can create variables and types with the @code{compile} command as
18342 part of your source code. Variables and types that are created as part
18343 of the @code{compile} command are not visible to the rest of the program for
18344 the duration of its run. This example is valid:
18347 compile code int ff = 5; printf ("ff is %d\n", ff);
18350 However, if you were to type the following into @value{GDBN} after that
18351 command has completed:
18354 compile code printf ("ff is %d\n'', ff);
18358 a compiler error would be raised as the variable @code{ff} no longer
18359 exists. Object code generated and injected by the @code{compile}
18360 command is removed when its execution ends. Caution is advised
18361 when assigning to program variables values of variables created by the
18362 code submitted to the @code{compile} command. This example is valid:
18365 compile code int ff = 5; k = ff;
18368 The value of the variable @code{ff} is assigned to @code{k}. The variable
18369 @code{k} does not require the existence of @code{ff} to maintain the value
18370 it has been assigned. However, pointers require particular care in
18371 assignment. If the source code compiled with the @code{compile} command
18372 changed the address of a pointer in the example program, perhaps to a
18373 variable created in the @code{compile} command, that pointer would point
18374 to an invalid location when the command exits. The following example
18375 would likely cause issues with your debugged program:
18378 compile code int ff = 5; p = &ff;
18381 In this example, @code{p} would point to @code{ff} when the
18382 @code{compile} command is executing the source code provided to it.
18383 However, as variables in the (example) program persist with their
18384 assigned values, the variable @code{p} would point to an invalid
18385 location when the command exists. A general rule should be followed
18386 in that you should either assign @code{NULL} to any assigned pointers,
18387 or restore a valid location to the pointer before the command exits.
18389 Similar caution must be exercised with any structs, unions, and typedefs
18390 defined in @code{compile} command. Types defined in the @code{compile}
18391 command will no longer be available in the next @code{compile} command.
18392 Therefore, if you cast a variable to a type defined in the
18393 @code{compile} command, care must be taken to ensure that any future
18394 need to resolve the type can be achieved.
18397 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18398 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18399 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18400 Compilation failed.
18401 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18405 Variables that have been optimized away by the compiler are not
18406 accessible to the code submitted to the @code{compile} command.
18407 Access to those variables will generate a compiler error which @value{GDBN}
18408 will print to the console.
18411 @subsection Compiler search for the @code{compile} command
18413 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18414 which may not be obvious for remote targets of different architecture
18415 than where @value{GDBN} is running. Environment variable @code{PATH} on
18416 @value{GDBN} host is searched for @value{NGCC} binary matching the
18417 target architecture and operating system. This search can be overriden
18418 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18419 taken from shell that executed @value{GDBN}, it is not the value set by
18420 @value{GDBN} command @code{set environment}). @xref{Environment}.
18423 Specifically @code{PATH} is searched for binaries matching regular expression
18424 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18425 debugged. @var{arch} is processor name --- multiarch is supported, so for
18426 example both @code{i386} and @code{x86_64} targets look for pattern
18427 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18428 for pattern @code{s390x?}. @var{os} is currently supported only for
18429 pattern @code{linux(-gnu)?}.
18431 On Posix hosts the compiler driver @value{GDBN} needs to find also
18432 shared library @file{libcc1.so} from the compiler. It is searched in
18433 default shared library search path (overridable with usual environment
18434 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18435 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18436 according to the installation of the found compiler --- as possibly
18437 specified by the @code{set compile-gcc} command.
18440 @item set compile-gcc
18441 @cindex compile command driver filename override
18442 Set compilation command used for compiling and injecting code with the
18443 @code{compile} commands. If this option is not set (it is set to
18444 an empty string), the search described above will occur --- that is the
18447 @item show compile-gcc
18448 Displays the current compile command @value{NGCC} driver filename.
18449 If set, it is the main command @command{gcc}, found usually for example
18450 under name @file{x86_64-linux-gnu-gcc}.
18454 @chapter @value{GDBN} Files
18456 @value{GDBN} needs to know the file name of the program to be debugged,
18457 both in order to read its symbol table and in order to start your
18458 program. To debug a core dump of a previous run, you must also tell
18459 @value{GDBN} the name of the core dump file.
18462 * Files:: Commands to specify files
18463 * File Caching:: Information about @value{GDBN}'s file caching
18464 * Separate Debug Files:: Debugging information in separate files
18465 * MiniDebugInfo:: Debugging information in a special section
18466 * Index Files:: Index files speed up GDB
18467 * Symbol Errors:: Errors reading symbol files
18468 * Data Files:: GDB data files
18472 @section Commands to Specify Files
18474 @cindex symbol table
18475 @cindex core dump file
18477 You may want to specify executable and core dump file names. The usual
18478 way to do this is at start-up time, using the arguments to
18479 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18480 Out of @value{GDBN}}).
18482 Occasionally it is necessary to change to a different file during a
18483 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18484 specify a file you want to use. Or you are debugging a remote target
18485 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18486 Program}). In these situations the @value{GDBN} commands to specify
18487 new files are useful.
18490 @cindex executable file
18492 @item file @var{filename}
18493 Use @var{filename} as the program to be debugged. It is read for its
18494 symbols and for the contents of pure memory. It is also the program
18495 executed when you use the @code{run} command. If you do not specify a
18496 directory and the file is not found in the @value{GDBN} working directory,
18497 @value{GDBN} uses the environment variable @code{PATH} as a list of
18498 directories to search, just as the shell does when looking for a program
18499 to run. You can change the value of this variable, for both @value{GDBN}
18500 and your program, using the @code{path} command.
18502 @cindex unlinked object files
18503 @cindex patching object files
18504 You can load unlinked object @file{.o} files into @value{GDBN} using
18505 the @code{file} command. You will not be able to ``run'' an object
18506 file, but you can disassemble functions and inspect variables. Also,
18507 if the underlying BFD functionality supports it, you could use
18508 @kbd{gdb -write} to patch object files using this technique. Note
18509 that @value{GDBN} can neither interpret nor modify relocations in this
18510 case, so branches and some initialized variables will appear to go to
18511 the wrong place. But this feature is still handy from time to time.
18514 @code{file} with no argument makes @value{GDBN} discard any information it
18515 has on both executable file and the symbol table.
18518 @item exec-file @r{[} @var{filename} @r{]}
18519 Specify that the program to be run (but not the symbol table) is found
18520 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18521 if necessary to locate your program. Omitting @var{filename} means to
18522 discard information on the executable file.
18524 @kindex symbol-file
18525 @item symbol-file @r{[} @var{filename} @r{]}
18526 Read symbol table information from file @var{filename}. @code{PATH} is
18527 searched when necessary. Use the @code{file} command to get both symbol
18528 table and program to run from the same file.
18530 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18531 program's symbol table.
18533 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18534 some breakpoints and auto-display expressions. This is because they may
18535 contain pointers to the internal data recording symbols and data types,
18536 which are part of the old symbol table data being discarded inside
18539 @code{symbol-file} does not repeat if you press @key{RET} again after
18542 When @value{GDBN} is configured for a particular environment, it
18543 understands debugging information in whatever format is the standard
18544 generated for that environment; you may use either a @sc{gnu} compiler, or
18545 other compilers that adhere to the local conventions.
18546 Best results are usually obtained from @sc{gnu} compilers; for example,
18547 using @code{@value{NGCC}} you can generate debugging information for
18550 For most kinds of object files, with the exception of old SVR3 systems
18551 using COFF, the @code{symbol-file} command does not normally read the
18552 symbol table in full right away. Instead, it scans the symbol table
18553 quickly to find which source files and which symbols are present. The
18554 details are read later, one source file at a time, as they are needed.
18556 The purpose of this two-stage reading strategy is to make @value{GDBN}
18557 start up faster. For the most part, it is invisible except for
18558 occasional pauses while the symbol table details for a particular source
18559 file are being read. (The @code{set verbose} command can turn these
18560 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18561 Warnings and Messages}.)
18563 We have not implemented the two-stage strategy for COFF yet. When the
18564 symbol table is stored in COFF format, @code{symbol-file} reads the
18565 symbol table data in full right away. Note that ``stabs-in-COFF''
18566 still does the two-stage strategy, since the debug info is actually
18570 @cindex reading symbols immediately
18571 @cindex symbols, reading immediately
18572 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18573 @itemx file @r{[} -readnow @r{]} @var{filename}
18574 You can override the @value{GDBN} two-stage strategy for reading symbol
18575 tables by using the @samp{-readnow} option with any of the commands that
18576 load symbol table information, if you want to be sure @value{GDBN} has the
18577 entire symbol table available.
18579 @c FIXME: for now no mention of directories, since this seems to be in
18580 @c flux. 13mar1992 status is that in theory GDB would look either in
18581 @c current dir or in same dir as myprog; but issues like competing
18582 @c GDB's, or clutter in system dirs, mean that in practice right now
18583 @c only current dir is used. FFish says maybe a special GDB hierarchy
18584 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18588 @item core-file @r{[}@var{filename}@r{]}
18590 Specify the whereabouts of a core dump file to be used as the ``contents
18591 of memory''. Traditionally, core files contain only some parts of the
18592 address space of the process that generated them; @value{GDBN} can access the
18593 executable file itself for other parts.
18595 @code{core-file} with no argument specifies that no core file is
18598 Note that the core file is ignored when your program is actually running
18599 under @value{GDBN}. So, if you have been running your program and you
18600 wish to debug a core file instead, you must kill the subprocess in which
18601 the program is running. To do this, use the @code{kill} command
18602 (@pxref{Kill Process, ,Killing the Child Process}).
18604 @kindex add-symbol-file
18605 @cindex dynamic linking
18606 @item add-symbol-file @var{filename} @var{address}
18607 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18608 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18609 The @code{add-symbol-file} command reads additional symbol table
18610 information from the file @var{filename}. You would use this command
18611 when @var{filename} has been dynamically loaded (by some other means)
18612 into the program that is running. The @var{address} should give the memory
18613 address at which the file has been loaded; @value{GDBN} cannot figure
18614 this out for itself. You can additionally specify an arbitrary number
18615 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18616 section name and base address for that section. You can specify any
18617 @var{address} as an expression.
18619 The symbol table of the file @var{filename} is added to the symbol table
18620 originally read with the @code{symbol-file} command. You can use the
18621 @code{add-symbol-file} command any number of times; the new symbol data
18622 thus read is kept in addition to the old.
18624 Changes can be reverted using the command @code{remove-symbol-file}.
18626 @cindex relocatable object files, reading symbols from
18627 @cindex object files, relocatable, reading symbols from
18628 @cindex reading symbols from relocatable object files
18629 @cindex symbols, reading from relocatable object files
18630 @cindex @file{.o} files, reading symbols from
18631 Although @var{filename} is typically a shared library file, an
18632 executable file, or some other object file which has been fully
18633 relocated for loading into a process, you can also load symbolic
18634 information from relocatable @file{.o} files, as long as:
18638 the file's symbolic information refers only to linker symbols defined in
18639 that file, not to symbols defined by other object files,
18641 every section the file's symbolic information refers to has actually
18642 been loaded into the inferior, as it appears in the file, and
18644 you can determine the address at which every section was loaded, and
18645 provide these to the @code{add-symbol-file} command.
18649 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18650 relocatable files into an already running program; such systems
18651 typically make the requirements above easy to meet. However, it's
18652 important to recognize that many native systems use complex link
18653 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18654 assembly, for example) that make the requirements difficult to meet. In
18655 general, one cannot assume that using @code{add-symbol-file} to read a
18656 relocatable object file's symbolic information will have the same effect
18657 as linking the relocatable object file into the program in the normal
18660 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18662 @kindex remove-symbol-file
18663 @item remove-symbol-file @var{filename}
18664 @item remove-symbol-file -a @var{address}
18665 Remove a symbol file added via the @code{add-symbol-file} command. The
18666 file to remove can be identified by its @var{filename} or by an @var{address}
18667 that lies within the boundaries of this symbol file in memory. Example:
18670 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18671 add symbol table from file "/home/user/gdb/mylib.so" at
18672 .text_addr = 0x7ffff7ff9480
18674 Reading symbols from /home/user/gdb/mylib.so...done.
18675 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18676 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18681 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18683 @kindex add-symbol-file-from-memory
18684 @cindex @code{syscall DSO}
18685 @cindex load symbols from memory
18686 @item add-symbol-file-from-memory @var{address}
18687 Load symbols from the given @var{address} in a dynamically loaded
18688 object file whose image is mapped directly into the inferior's memory.
18689 For example, the Linux kernel maps a @code{syscall DSO} into each
18690 process's address space; this DSO provides kernel-specific code for
18691 some system calls. The argument can be any expression whose
18692 evaluation yields the address of the file's shared object file header.
18693 For this command to work, you must have used @code{symbol-file} or
18694 @code{exec-file} commands in advance.
18697 @item section @var{section} @var{addr}
18698 The @code{section} command changes the base address of the named
18699 @var{section} of the exec file to @var{addr}. This can be used if the
18700 exec file does not contain section addresses, (such as in the
18701 @code{a.out} format), or when the addresses specified in the file
18702 itself are wrong. Each section must be changed separately. The
18703 @code{info files} command, described below, lists all the sections and
18707 @kindex info target
18710 @code{info files} and @code{info target} are synonymous; both print the
18711 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18712 including the names of the executable and core dump files currently in
18713 use by @value{GDBN}, and the files from which symbols were loaded. The
18714 command @code{help target} lists all possible targets rather than
18717 @kindex maint info sections
18718 @item maint info sections
18719 Another command that can give you extra information about program sections
18720 is @code{maint info sections}. In addition to the section information
18721 displayed by @code{info files}, this command displays the flags and file
18722 offset of each section in the executable and core dump files. In addition,
18723 @code{maint info sections} provides the following command options (which
18724 may be arbitrarily combined):
18728 Display sections for all loaded object files, including shared libraries.
18729 @item @var{sections}
18730 Display info only for named @var{sections}.
18731 @item @var{section-flags}
18732 Display info only for sections for which @var{section-flags} are true.
18733 The section flags that @value{GDBN} currently knows about are:
18736 Section will have space allocated in the process when loaded.
18737 Set for all sections except those containing debug information.
18739 Section will be loaded from the file into the child process memory.
18740 Set for pre-initialized code and data, clear for @code{.bss} sections.
18742 Section needs to be relocated before loading.
18744 Section cannot be modified by the child process.
18746 Section contains executable code only.
18748 Section contains data only (no executable code).
18750 Section will reside in ROM.
18752 Section contains data for constructor/destructor lists.
18754 Section is not empty.
18756 An instruction to the linker to not output the section.
18757 @item COFF_SHARED_LIBRARY
18758 A notification to the linker that the section contains
18759 COFF shared library information.
18761 Section contains common symbols.
18764 @kindex set trust-readonly-sections
18765 @cindex read-only sections
18766 @item set trust-readonly-sections on
18767 Tell @value{GDBN} that readonly sections in your object file
18768 really are read-only (i.e.@: that their contents will not change).
18769 In that case, @value{GDBN} can fetch values from these sections
18770 out of the object file, rather than from the target program.
18771 For some targets (notably embedded ones), this can be a significant
18772 enhancement to debugging performance.
18774 The default is off.
18776 @item set trust-readonly-sections off
18777 Tell @value{GDBN} not to trust readonly sections. This means that
18778 the contents of the section might change while the program is running,
18779 and must therefore be fetched from the target when needed.
18781 @item show trust-readonly-sections
18782 Show the current setting of trusting readonly sections.
18785 All file-specifying commands allow both absolute and relative file names
18786 as arguments. @value{GDBN} always converts the file name to an absolute file
18787 name and remembers it that way.
18789 @cindex shared libraries
18790 @anchor{Shared Libraries}
18791 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18792 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18793 DSBT (TIC6X) shared libraries.
18795 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18796 shared libraries. @xref{Expat}.
18798 @value{GDBN} automatically loads symbol definitions from shared libraries
18799 when you use the @code{run} command, or when you examine a core file.
18800 (Before you issue the @code{run} command, @value{GDBN} does not understand
18801 references to a function in a shared library, however---unless you are
18802 debugging a core file).
18804 @c FIXME: some @value{GDBN} release may permit some refs to undef
18805 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18806 @c FIXME...lib; check this from time to time when updating manual
18808 There are times, however, when you may wish to not automatically load
18809 symbol definitions from shared libraries, such as when they are
18810 particularly large or there are many of them.
18812 To control the automatic loading of shared library symbols, use the
18816 @kindex set auto-solib-add
18817 @item set auto-solib-add @var{mode}
18818 If @var{mode} is @code{on}, symbols from all shared object libraries
18819 will be loaded automatically when the inferior begins execution, you
18820 attach to an independently started inferior, or when the dynamic linker
18821 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18822 is @code{off}, symbols must be loaded manually, using the
18823 @code{sharedlibrary} command. The default value is @code{on}.
18825 @cindex memory used for symbol tables
18826 If your program uses lots of shared libraries with debug info that
18827 takes large amounts of memory, you can decrease the @value{GDBN}
18828 memory footprint by preventing it from automatically loading the
18829 symbols from shared libraries. To that end, type @kbd{set
18830 auto-solib-add off} before running the inferior, then load each
18831 library whose debug symbols you do need with @kbd{sharedlibrary
18832 @var{regexp}}, where @var{regexp} is a regular expression that matches
18833 the libraries whose symbols you want to be loaded.
18835 @kindex show auto-solib-add
18836 @item show auto-solib-add
18837 Display the current autoloading mode.
18840 @cindex load shared library
18841 To explicitly load shared library symbols, use the @code{sharedlibrary}
18845 @kindex info sharedlibrary
18847 @item info share @var{regex}
18848 @itemx info sharedlibrary @var{regex}
18849 Print the names of the shared libraries which are currently loaded
18850 that match @var{regex}. If @var{regex} is omitted then print
18851 all shared libraries that are loaded.
18854 @item info dll @var{regex}
18855 This is an alias of @code{info sharedlibrary}.
18857 @kindex sharedlibrary
18859 @item sharedlibrary @var{regex}
18860 @itemx share @var{regex}
18861 Load shared object library symbols for files matching a
18862 Unix regular expression.
18863 As with files loaded automatically, it only loads shared libraries
18864 required by your program for a core file or after typing @code{run}. If
18865 @var{regex} is omitted all shared libraries required by your program are
18868 @item nosharedlibrary
18869 @kindex nosharedlibrary
18870 @cindex unload symbols from shared libraries
18871 Unload all shared object library symbols. This discards all symbols
18872 that have been loaded from all shared libraries. Symbols from shared
18873 libraries that were loaded by explicit user requests are not
18877 Sometimes you may wish that @value{GDBN} stops and gives you control
18878 when any of shared library events happen. The best way to do this is
18879 to use @code{catch load} and @code{catch unload} (@pxref{Set
18882 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18883 command for this. This command exists for historical reasons. It is
18884 less useful than setting a catchpoint, because it does not allow for
18885 conditions or commands as a catchpoint does.
18888 @item set stop-on-solib-events
18889 @kindex set stop-on-solib-events
18890 This command controls whether @value{GDBN} should give you control
18891 when the dynamic linker notifies it about some shared library event.
18892 The most common event of interest is loading or unloading of a new
18895 @item show stop-on-solib-events
18896 @kindex show stop-on-solib-events
18897 Show whether @value{GDBN} stops and gives you control when shared
18898 library events happen.
18901 Shared libraries are also supported in many cross or remote debugging
18902 configurations. @value{GDBN} needs to have access to the target's libraries;
18903 this can be accomplished either by providing copies of the libraries
18904 on the host system, or by asking @value{GDBN} to automatically retrieve the
18905 libraries from the target. If copies of the target libraries are
18906 provided, they need to be the same as the target libraries, although the
18907 copies on the target can be stripped as long as the copies on the host are
18910 @cindex where to look for shared libraries
18911 For remote debugging, you need to tell @value{GDBN} where the target
18912 libraries are, so that it can load the correct copies---otherwise, it
18913 may try to load the host's libraries. @value{GDBN} has two variables
18914 to specify the search directories for target libraries.
18917 @cindex prefix for executable and shared library file names
18918 @cindex system root, alternate
18919 @kindex set solib-absolute-prefix
18920 @kindex set sysroot
18921 @item set sysroot @var{path}
18922 Use @var{path} as the system root for the program being debugged. Any
18923 absolute shared library paths will be prefixed with @var{path}; many
18924 runtime loaders store the absolute paths to the shared library in the
18925 target program's memory. When starting processes remotely, and when
18926 attaching to already-running processes (local or remote), their
18927 executable filenames will be prefixed with @var{path} if reported to
18928 @value{GDBN} as absolute by the operating system. If you use
18929 @code{set sysroot} to find executables and shared libraries, they need
18930 to be laid out in the same way that they are on the target, with
18931 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18934 If @var{path} starts with the sequence @file{target:} and the target
18935 system is remote then @value{GDBN} will retrieve the target binaries
18936 from the remote system. This is only supported when using a remote
18937 target that supports the @code{remote get} command (@pxref{File
18938 Transfer,,Sending files to a remote system}). The part of @var{path}
18939 following the initial @file{target:} (if present) is used as system
18940 root prefix on the remote file system. If @var{path} starts with the
18941 sequence @file{remote:} this is converted to the sequence
18942 @file{target:} by @code{set sysroot}@footnote{Historically the
18943 functionality to retrieve binaries from the remote system was
18944 provided by prefixing @var{path} with @file{remote:}}. If you want
18945 to specify a local system root using a directory that happens to be
18946 named @file{target:} or @file{remote:}, you need to use some
18947 equivalent variant of the name like @file{./target:}.
18949 For targets with an MS-DOS based filesystem, such as MS-Windows and
18950 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18951 absolute file name with @var{path}. But first, on Unix hosts,
18952 @value{GDBN} converts all backslash directory separators into forward
18953 slashes, because the backslash is not a directory separator on Unix:
18956 c:\foo\bar.dll @result{} c:/foo/bar.dll
18959 Then, @value{GDBN} attempts prefixing the target file name with
18960 @var{path}, and looks for the resulting file name in the host file
18964 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18967 If that does not find the binary, @value{GDBN} tries removing
18968 the @samp{:} character from the drive spec, both for convenience, and,
18969 for the case of the host file system not supporting file names with
18973 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18976 This makes it possible to have a system root that mirrors a target
18977 with more than one drive. E.g., you may want to setup your local
18978 copies of the target system shared libraries like so (note @samp{c} vs
18982 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18983 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18984 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18988 and point the system root at @file{/path/to/sysroot}, so that
18989 @value{GDBN} can find the correct copies of both
18990 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18992 If that still does not find the binary, @value{GDBN} tries
18993 removing the whole drive spec from the target file name:
18996 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18999 This last lookup makes it possible to not care about the drive name,
19000 if you don't want or need to.
19002 The @code{set solib-absolute-prefix} command is an alias for @code{set
19005 @cindex default system root
19006 @cindex @samp{--with-sysroot}
19007 You can set the default system root by using the configure-time
19008 @samp{--with-sysroot} option. If the system root is inside
19009 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19010 @samp{--exec-prefix}), then the default system root will be updated
19011 automatically if the installed @value{GDBN} is moved to a new
19014 @kindex show sysroot
19016 Display the current executable and shared library prefix.
19018 @kindex set solib-search-path
19019 @item set solib-search-path @var{path}
19020 If this variable is set, @var{path} is a colon-separated list of
19021 directories to search for shared libraries. @samp{solib-search-path}
19022 is used after @samp{sysroot} fails to locate the library, or if the
19023 path to the library is relative instead of absolute. If you want to
19024 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19025 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19026 finding your host's libraries. @samp{sysroot} is preferred; setting
19027 it to a nonexistent directory may interfere with automatic loading
19028 of shared library symbols.
19030 @kindex show solib-search-path
19031 @item show solib-search-path
19032 Display the current shared library search path.
19034 @cindex DOS file-name semantics of file names.
19035 @kindex set target-file-system-kind (unix|dos-based|auto)
19036 @kindex show target-file-system-kind
19037 @item set target-file-system-kind @var{kind}
19038 Set assumed file system kind for target reported file names.
19040 Shared library file names as reported by the target system may not
19041 make sense as is on the system @value{GDBN} is running on. For
19042 example, when remote debugging a target that has MS-DOS based file
19043 system semantics, from a Unix host, the target may be reporting to
19044 @value{GDBN} a list of loaded shared libraries with file names such as
19045 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19046 drive letters, so the @samp{c:\} prefix is not normally understood as
19047 indicating an absolute file name, and neither is the backslash
19048 normally considered a directory separator character. In that case,
19049 the native file system would interpret this whole absolute file name
19050 as a relative file name with no directory components. This would make
19051 it impossible to point @value{GDBN} at a copy of the remote target's
19052 shared libraries on the host using @code{set sysroot}, and impractical
19053 with @code{set solib-search-path}. Setting
19054 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19055 to interpret such file names similarly to how the target would, and to
19056 map them to file names valid on @value{GDBN}'s native file system
19057 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19058 to one of the supported file system kinds. In that case, @value{GDBN}
19059 tries to determine the appropriate file system variant based on the
19060 current target's operating system (@pxref{ABI, ,Configuring the
19061 Current ABI}). The supported file system settings are:
19065 Instruct @value{GDBN} to assume the target file system is of Unix
19066 kind. Only file names starting the forward slash (@samp{/}) character
19067 are considered absolute, and the directory separator character is also
19071 Instruct @value{GDBN} to assume the target file system is DOS based.
19072 File names starting with either a forward slash, or a drive letter
19073 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19074 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19075 considered directory separators.
19078 Instruct @value{GDBN} to use the file system kind associated with the
19079 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19080 This is the default.
19084 @cindex file name canonicalization
19085 @cindex base name differences
19086 When processing file names provided by the user, @value{GDBN}
19087 frequently needs to compare them to the file names recorded in the
19088 program's debug info. Normally, @value{GDBN} compares just the
19089 @dfn{base names} of the files as strings, which is reasonably fast
19090 even for very large programs. (The base name of a file is the last
19091 portion of its name, after stripping all the leading directories.)
19092 This shortcut in comparison is based upon the assumption that files
19093 cannot have more than one base name. This is usually true, but
19094 references to files that use symlinks or similar filesystem
19095 facilities violate that assumption. If your program records files
19096 using such facilities, or if you provide file names to @value{GDBN}
19097 using symlinks etc., you can set @code{basenames-may-differ} to
19098 @code{true} to instruct @value{GDBN} to completely canonicalize each
19099 pair of file names it needs to compare. This will make file-name
19100 comparisons accurate, but at a price of a significant slowdown.
19103 @item set basenames-may-differ
19104 @kindex set basenames-may-differ
19105 Set whether a source file may have multiple base names.
19107 @item show basenames-may-differ
19108 @kindex show basenames-may-differ
19109 Show whether a source file may have multiple base names.
19113 @section File Caching
19114 @cindex caching of opened files
19115 @cindex caching of bfd objects
19117 To speed up file loading, and reduce memory usage, @value{GDBN} will
19118 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19119 BFD, bfd, The Binary File Descriptor Library}. The following commands
19120 allow visibility and control of the caching behavior.
19123 @kindex maint info bfds
19124 @item maint info bfds
19125 This prints information about each @code{bfd} object that is known to
19128 @kindex maint set bfd-sharing
19129 @kindex maint show bfd-sharing
19130 @kindex bfd caching
19131 @item maint set bfd-sharing
19132 @item maint show bfd-sharing
19133 Control whether @code{bfd} objects can be shared. When sharing is
19134 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19135 than reopening the same file. Turning sharing off does not cause
19136 already shared @code{bfd} objects to be unshared, but all future files
19137 that are opened will create a new @code{bfd} object. Similarly,
19138 re-enabling sharing does not cause multiple existing @code{bfd}
19139 objects to be collapsed into a single shared @code{bfd} object.
19141 @kindex set debug bfd-cache @var{level}
19142 @kindex bfd caching
19143 @item set debug bfd-cache @var{level}
19144 Turns on debugging of the bfd cache, setting the level to @var{level}.
19146 @kindex show debug bfd-cache
19147 @kindex bfd caching
19148 @item show debug bfd-cache
19149 Show the current debugging level of the bfd cache.
19152 @node Separate Debug Files
19153 @section Debugging Information in Separate Files
19154 @cindex separate debugging information files
19155 @cindex debugging information in separate files
19156 @cindex @file{.debug} subdirectories
19157 @cindex debugging information directory, global
19158 @cindex global debugging information directories
19159 @cindex build ID, and separate debugging files
19160 @cindex @file{.build-id} directory
19162 @value{GDBN} allows you to put a program's debugging information in a
19163 file separate from the executable itself, in a way that allows
19164 @value{GDBN} to find and load the debugging information automatically.
19165 Since debugging information can be very large---sometimes larger
19166 than the executable code itself---some systems distribute debugging
19167 information for their executables in separate files, which users can
19168 install only when they need to debug a problem.
19170 @value{GDBN} supports two ways of specifying the separate debug info
19175 The executable contains a @dfn{debug link} that specifies the name of
19176 the separate debug info file. The separate debug file's name is
19177 usually @file{@var{executable}.debug}, where @var{executable} is the
19178 name of the corresponding executable file without leading directories
19179 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19180 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19181 checksum for the debug file, which @value{GDBN} uses to validate that
19182 the executable and the debug file came from the same build.
19185 The executable contains a @dfn{build ID}, a unique bit string that is
19186 also present in the corresponding debug info file. (This is supported
19187 only on some operating systems, when using the ELF or PE file formats
19188 for binary files and the @sc{gnu} Binutils.) For more details about
19189 this feature, see the description of the @option{--build-id}
19190 command-line option in @ref{Options, , Command Line Options, ld.info,
19191 The GNU Linker}. The debug info file's name is not specified
19192 explicitly by the build ID, but can be computed from the build ID, see
19196 Depending on the way the debug info file is specified, @value{GDBN}
19197 uses two different methods of looking for the debug file:
19201 For the ``debug link'' method, @value{GDBN} looks up the named file in
19202 the directory of the executable file, then in a subdirectory of that
19203 directory named @file{.debug}, and finally under each one of the global debug
19204 directories, in a subdirectory whose name is identical to the leading
19205 directories of the executable's absolute file name.
19208 For the ``build ID'' method, @value{GDBN} looks in the
19209 @file{.build-id} subdirectory of each one of the global debug directories for
19210 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19211 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19212 are the rest of the bit string. (Real build ID strings are 32 or more
19213 hex characters, not 10.)
19216 So, for example, suppose you ask @value{GDBN} to debug
19217 @file{/usr/bin/ls}, which has a debug link that specifies the
19218 file @file{ls.debug}, and a build ID whose value in hex is
19219 @code{abcdef1234}. If the list of the global debug directories includes
19220 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19221 debug information files, in the indicated order:
19225 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19227 @file{/usr/bin/ls.debug}
19229 @file{/usr/bin/.debug/ls.debug}
19231 @file{/usr/lib/debug/usr/bin/ls.debug}.
19234 @anchor{debug-file-directory}
19235 Global debugging info directories default to what is set by @value{GDBN}
19236 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19237 you can also set the global debugging info directories, and view the list
19238 @value{GDBN} is currently using.
19242 @kindex set debug-file-directory
19243 @item set debug-file-directory @var{directories}
19244 Set the directories which @value{GDBN} searches for separate debugging
19245 information files to @var{directory}. Multiple path components can be set
19246 concatenating them by a path separator.
19248 @kindex show debug-file-directory
19249 @item show debug-file-directory
19250 Show the directories @value{GDBN} searches for separate debugging
19255 @cindex @code{.gnu_debuglink} sections
19256 @cindex debug link sections
19257 A debug link is a special section of the executable file named
19258 @code{.gnu_debuglink}. The section must contain:
19262 A filename, with any leading directory components removed, followed by
19265 zero to three bytes of padding, as needed to reach the next four-byte
19266 boundary within the section, and
19268 a four-byte CRC checksum, stored in the same endianness used for the
19269 executable file itself. The checksum is computed on the debugging
19270 information file's full contents by the function given below, passing
19271 zero as the @var{crc} argument.
19274 Any executable file format can carry a debug link, as long as it can
19275 contain a section named @code{.gnu_debuglink} with the contents
19278 @cindex @code{.note.gnu.build-id} sections
19279 @cindex build ID sections
19280 The build ID is a special section in the executable file (and in other
19281 ELF binary files that @value{GDBN} may consider). This section is
19282 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19283 It contains unique identification for the built files---the ID remains
19284 the same across multiple builds of the same build tree. The default
19285 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19286 content for the build ID string. The same section with an identical
19287 value is present in the original built binary with symbols, in its
19288 stripped variant, and in the separate debugging information file.
19290 The debugging information file itself should be an ordinary
19291 executable, containing a full set of linker symbols, sections, and
19292 debugging information. The sections of the debugging information file
19293 should have the same names, addresses, and sizes as the original file,
19294 but they need not contain any data---much like a @code{.bss} section
19295 in an ordinary executable.
19297 The @sc{gnu} binary utilities (Binutils) package includes the
19298 @samp{objcopy} utility that can produce
19299 the separated executable / debugging information file pairs using the
19300 following commands:
19303 @kbd{objcopy --only-keep-debug foo foo.debug}
19308 These commands remove the debugging
19309 information from the executable file @file{foo} and place it in the file
19310 @file{foo.debug}. You can use the first, second or both methods to link the
19315 The debug link method needs the following additional command to also leave
19316 behind a debug link in @file{foo}:
19319 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19322 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19323 a version of the @code{strip} command such that the command @kbd{strip foo -f
19324 foo.debug} has the same functionality as the two @code{objcopy} commands and
19325 the @code{ln -s} command above, together.
19328 Build ID gets embedded into the main executable using @code{ld --build-id} or
19329 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19330 compatibility fixes for debug files separation are present in @sc{gnu} binary
19331 utilities (Binutils) package since version 2.18.
19336 @cindex CRC algorithm definition
19337 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19338 IEEE 802.3 using the polynomial:
19340 @c TexInfo requires naked braces for multi-digit exponents for Tex
19341 @c output, but this causes HTML output to barf. HTML has to be set using
19342 @c raw commands. So we end up having to specify this equation in 2
19347 <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>
19348 + <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
19354 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19355 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19359 The function is computed byte at a time, taking the least
19360 significant bit of each byte first. The initial pattern
19361 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19362 the final result is inverted to ensure trailing zeros also affect the
19365 @emph{Note:} This is the same CRC polynomial as used in handling the
19366 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19367 However in the case of the Remote Serial Protocol, the CRC is computed
19368 @emph{most} significant bit first, and the result is not inverted, so
19369 trailing zeros have no effect on the CRC value.
19371 To complete the description, we show below the code of the function
19372 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19373 initially supplied @code{crc} argument means that an initial call to
19374 this function passing in zero will start computing the CRC using
19377 @kindex gnu_debuglink_crc32
19380 gnu_debuglink_crc32 (unsigned long crc,
19381 unsigned char *buf, size_t len)
19383 static const unsigned long crc32_table[256] =
19385 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19386 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19387 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19388 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19389 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19390 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19391 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19392 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19393 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19394 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19395 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19396 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19397 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19398 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19399 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19400 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19401 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19402 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19403 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19404 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19405 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19406 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19407 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19408 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19409 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19410 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19411 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19412 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19413 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19414 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19415 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19416 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19417 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19418 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19419 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19420 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19421 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19422 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19423 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19424 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19425 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19426 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19427 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19428 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19429 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19430 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19431 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19432 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19433 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19434 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19435 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19438 unsigned char *end;
19440 crc = ~crc & 0xffffffff;
19441 for (end = buf + len; buf < end; ++buf)
19442 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19443 return ~crc & 0xffffffff;
19448 This computation does not apply to the ``build ID'' method.
19450 @node MiniDebugInfo
19451 @section Debugging information in a special section
19452 @cindex separate debug sections
19453 @cindex @samp{.gnu_debugdata} section
19455 Some systems ship pre-built executables and libraries that have a
19456 special @samp{.gnu_debugdata} section. This feature is called
19457 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19458 is used to supply extra symbols for backtraces.
19460 The intent of this section is to provide extra minimal debugging
19461 information for use in simple backtraces. It is not intended to be a
19462 replacement for full separate debugging information (@pxref{Separate
19463 Debug Files}). The example below shows the intended use; however,
19464 @value{GDBN} does not currently put restrictions on what sort of
19465 debugging information might be included in the section.
19467 @value{GDBN} has support for this extension. If the section exists,
19468 then it is used provided that no other source of debugging information
19469 can be found, and that @value{GDBN} was configured with LZMA support.
19471 This section can be easily created using @command{objcopy} and other
19472 standard utilities:
19475 # Extract the dynamic symbols from the main binary, there is no need
19476 # to also have these in the normal symbol table.
19477 nm -D @var{binary} --format=posix --defined-only \
19478 | awk '@{ print $1 @}' | sort > dynsyms
19480 # Extract all the text (i.e. function) symbols from the debuginfo.
19481 # (Note that we actually also accept "D" symbols, for the benefit
19482 # of platforms like PowerPC64 that use function descriptors.)
19483 nm @var{binary} --format=posix --defined-only \
19484 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19487 # Keep all the function symbols not already in the dynamic symbol
19489 comm -13 dynsyms funcsyms > keep_symbols
19491 # Separate full debug info into debug binary.
19492 objcopy --only-keep-debug @var{binary} debug
19494 # Copy the full debuginfo, keeping only a minimal set of symbols and
19495 # removing some unnecessary sections.
19496 objcopy -S --remove-section .gdb_index --remove-section .comment \
19497 --keep-symbols=keep_symbols debug mini_debuginfo
19499 # Drop the full debug info from the original binary.
19500 strip --strip-all -R .comment @var{binary}
19502 # Inject the compressed data into the .gnu_debugdata section of the
19505 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19509 @section Index Files Speed Up @value{GDBN}
19510 @cindex index files
19511 @cindex @samp{.gdb_index} section
19513 When @value{GDBN} finds a symbol file, it scans the symbols in the
19514 file in order to construct an internal symbol table. This lets most
19515 @value{GDBN} operations work quickly---at the cost of a delay early
19516 on. For large programs, this delay can be quite lengthy, so
19517 @value{GDBN} provides a way to build an index, which speeds up
19520 The index is stored as a section in the symbol file. @value{GDBN} can
19521 write the index to a file, then you can put it into the symbol file
19522 using @command{objcopy}.
19524 To create an index file, use the @code{save gdb-index} command:
19527 @item save gdb-index @var{directory}
19528 @kindex save gdb-index
19529 Create an index file for each symbol file currently known by
19530 @value{GDBN}. Each file is named after its corresponding symbol file,
19531 with @samp{.gdb-index} appended, and is written into the given
19535 Once you have created an index file you can merge it into your symbol
19536 file, here named @file{symfile}, using @command{objcopy}:
19539 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19540 --set-section-flags .gdb_index=readonly symfile symfile
19543 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19544 sections that have been deprecated. Usually they are deprecated because
19545 they are missing a new feature or have performance issues.
19546 To tell @value{GDBN} to use a deprecated index section anyway
19547 specify @code{set use-deprecated-index-sections on}.
19548 The default is @code{off}.
19549 This can speed up startup, but may result in some functionality being lost.
19550 @xref{Index Section Format}.
19552 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19553 must be done before gdb reads the file. The following will not work:
19556 $ gdb -ex "set use-deprecated-index-sections on" <program>
19559 Instead you must do, for example,
19562 $ gdb -iex "set use-deprecated-index-sections on" <program>
19565 There are currently some limitation on indices. They only work when
19566 for DWARF debugging information, not stabs. And, they do not
19567 currently work for programs using Ada.
19569 @node Symbol Errors
19570 @section Errors Reading Symbol Files
19572 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19573 such as symbol types it does not recognize, or known bugs in compiler
19574 output. By default, @value{GDBN} does not notify you of such problems, since
19575 they are relatively common and primarily of interest to people
19576 debugging compilers. If you are interested in seeing information
19577 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19578 only one message about each such type of problem, no matter how many
19579 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19580 to see how many times the problems occur, with the @code{set
19581 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19584 The messages currently printed, and their meanings, include:
19587 @item inner block not inside outer block in @var{symbol}
19589 The symbol information shows where symbol scopes begin and end
19590 (such as at the start of a function or a block of statements). This
19591 error indicates that an inner scope block is not fully contained
19592 in its outer scope blocks.
19594 @value{GDBN} circumvents the problem by treating the inner block as if it had
19595 the same scope as the outer block. In the error message, @var{symbol}
19596 may be shown as ``@code{(don't know)}'' if the outer block is not a
19599 @item block at @var{address} out of order
19601 The symbol information for symbol scope blocks should occur in
19602 order of increasing addresses. This error indicates that it does not
19605 @value{GDBN} does not circumvent this problem, and has trouble
19606 locating symbols in the source file whose symbols it is reading. (You
19607 can often determine what source file is affected by specifying
19608 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19611 @item bad block start address patched
19613 The symbol information for a symbol scope block has a start address
19614 smaller than the address of the preceding source line. This is known
19615 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19617 @value{GDBN} circumvents the problem by treating the symbol scope block as
19618 starting on the previous source line.
19620 @item bad string table offset in symbol @var{n}
19623 Symbol number @var{n} contains a pointer into the string table which is
19624 larger than the size of the string table.
19626 @value{GDBN} circumvents the problem by considering the symbol to have the
19627 name @code{foo}, which may cause other problems if many symbols end up
19630 @item unknown symbol type @code{0x@var{nn}}
19632 The symbol information contains new data types that @value{GDBN} does
19633 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19634 uncomprehended information, in hexadecimal.
19636 @value{GDBN} circumvents the error by ignoring this symbol information.
19637 This usually allows you to debug your program, though certain symbols
19638 are not accessible. If you encounter such a problem and feel like
19639 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19640 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19641 and examine @code{*bufp} to see the symbol.
19643 @item stub type has NULL name
19645 @value{GDBN} could not find the full definition for a struct or class.
19647 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19648 The symbol information for a C@t{++} member function is missing some
19649 information that recent versions of the compiler should have output for
19652 @item info mismatch between compiler and debugger
19654 @value{GDBN} could not parse a type specification output by the compiler.
19659 @section GDB Data Files
19661 @cindex prefix for data files
19662 @value{GDBN} will sometimes read an auxiliary data file. These files
19663 are kept in a directory known as the @dfn{data directory}.
19665 You can set the data directory's name, and view the name @value{GDBN}
19666 is currently using.
19669 @kindex set data-directory
19670 @item set data-directory @var{directory}
19671 Set the directory which @value{GDBN} searches for auxiliary data files
19672 to @var{directory}.
19674 @kindex show data-directory
19675 @item show data-directory
19676 Show the directory @value{GDBN} searches for auxiliary data files.
19679 @cindex default data directory
19680 @cindex @samp{--with-gdb-datadir}
19681 You can set the default data directory by using the configure-time
19682 @samp{--with-gdb-datadir} option. If the data directory is inside
19683 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19684 @samp{--exec-prefix}), then the default data directory will be updated
19685 automatically if the installed @value{GDBN} is moved to a new
19688 The data directory may also be specified with the
19689 @code{--data-directory} command line option.
19690 @xref{Mode Options}.
19693 @chapter Specifying a Debugging Target
19695 @cindex debugging target
19696 A @dfn{target} is the execution environment occupied by your program.
19698 Often, @value{GDBN} runs in the same host environment as your program;
19699 in that case, the debugging target is specified as a side effect when
19700 you use the @code{file} or @code{core} commands. When you need more
19701 flexibility---for example, running @value{GDBN} on a physically separate
19702 host, or controlling a standalone system over a serial port or a
19703 realtime system over a TCP/IP connection---you can use the @code{target}
19704 command to specify one of the target types configured for @value{GDBN}
19705 (@pxref{Target Commands, ,Commands for Managing Targets}).
19707 @cindex target architecture
19708 It is possible to build @value{GDBN} for several different @dfn{target
19709 architectures}. When @value{GDBN} is built like that, you can choose
19710 one of the available architectures with the @kbd{set architecture}
19714 @kindex set architecture
19715 @kindex show architecture
19716 @item set architecture @var{arch}
19717 This command sets the current target architecture to @var{arch}. The
19718 value of @var{arch} can be @code{"auto"}, in addition to one of the
19719 supported architectures.
19721 @item show architecture
19722 Show the current target architecture.
19724 @item set processor
19726 @kindex set processor
19727 @kindex show processor
19728 These are alias commands for, respectively, @code{set architecture}
19729 and @code{show architecture}.
19733 * Active Targets:: Active targets
19734 * Target Commands:: Commands for managing targets
19735 * Byte Order:: Choosing target byte order
19738 @node Active Targets
19739 @section Active Targets
19741 @cindex stacking targets
19742 @cindex active targets
19743 @cindex multiple targets
19745 There are multiple classes of targets such as: processes, executable files or
19746 recording sessions. Core files belong to the process class, making core file
19747 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19748 on multiple active targets, one in each class. This allows you to (for
19749 example) start a process and inspect its activity, while still having access to
19750 the executable file after the process finishes. Or if you start process
19751 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19752 presented a virtual layer of the recording target, while the process target
19753 remains stopped at the chronologically last point of the process execution.
19755 Use the @code{core-file} and @code{exec-file} commands to select a new core
19756 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19757 specify as a target a process that is already running, use the @code{attach}
19758 command (@pxref{Attach, ,Debugging an Already-running Process}).
19760 @node Target Commands
19761 @section Commands for Managing Targets
19764 @item target @var{type} @var{parameters}
19765 Connects the @value{GDBN} host environment to a target machine or
19766 process. A target is typically a protocol for talking to debugging
19767 facilities. You use the argument @var{type} to specify the type or
19768 protocol of the target machine.
19770 Further @var{parameters} are interpreted by the target protocol, but
19771 typically include things like device names or host names to connect
19772 with, process numbers, and baud rates.
19774 The @code{target} command does not repeat if you press @key{RET} again
19775 after executing the command.
19777 @kindex help target
19779 Displays the names of all targets available. To display targets
19780 currently selected, use either @code{info target} or @code{info files}
19781 (@pxref{Files, ,Commands to Specify Files}).
19783 @item help target @var{name}
19784 Describe a particular target, including any parameters necessary to
19787 @kindex set gnutarget
19788 @item set gnutarget @var{args}
19789 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19790 knows whether it is reading an @dfn{executable},
19791 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19792 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19793 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19796 @emph{Warning:} To specify a file format with @code{set gnutarget},
19797 you must know the actual BFD name.
19801 @xref{Files, , Commands to Specify Files}.
19803 @kindex show gnutarget
19804 @item show gnutarget
19805 Use the @code{show gnutarget} command to display what file format
19806 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19807 @value{GDBN} will determine the file format for each file automatically,
19808 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19811 @cindex common targets
19812 Here are some common targets (available, or not, depending on the GDB
19817 @item target exec @var{program}
19818 @cindex executable file target
19819 An executable file. @samp{target exec @var{program}} is the same as
19820 @samp{exec-file @var{program}}.
19822 @item target core @var{filename}
19823 @cindex core dump file target
19824 A core dump file. @samp{target core @var{filename}} is the same as
19825 @samp{core-file @var{filename}}.
19827 @item target remote @var{medium}
19828 @cindex remote target
19829 A remote system connected to @value{GDBN} via a serial line or network
19830 connection. This command tells @value{GDBN} to use its own remote
19831 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19833 For example, if you have a board connected to @file{/dev/ttya} on the
19834 machine running @value{GDBN}, you could say:
19837 target remote /dev/ttya
19840 @code{target remote} supports the @code{load} command. This is only
19841 useful if you have some other way of getting the stub to the target
19842 system, and you can put it somewhere in memory where it won't get
19843 clobbered by the download.
19845 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19846 @cindex built-in simulator target
19847 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19855 works; however, you cannot assume that a specific memory map, device
19856 drivers, or even basic I/O is available, although some simulators do
19857 provide these. For info about any processor-specific simulator details,
19858 see the appropriate section in @ref{Embedded Processors, ,Embedded
19861 @item target native
19862 @cindex native target
19863 Setup for local/native process debugging. Useful to make the
19864 @code{run} command spawn native processes (likewise @code{attach},
19865 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19866 (@pxref{set auto-connect-native-target}).
19870 Different targets are available on different configurations of @value{GDBN};
19871 your configuration may have more or fewer targets.
19873 Many remote targets require you to download the executable's code once
19874 you've successfully established a connection. You may wish to control
19875 various aspects of this process.
19880 @kindex set hash@r{, for remote monitors}
19881 @cindex hash mark while downloading
19882 This command controls whether a hash mark @samp{#} is displayed while
19883 downloading a file to the remote monitor. If on, a hash mark is
19884 displayed after each S-record is successfully downloaded to the
19888 @kindex show hash@r{, for remote monitors}
19889 Show the current status of displaying the hash mark.
19891 @item set debug monitor
19892 @kindex set debug monitor
19893 @cindex display remote monitor communications
19894 Enable or disable display of communications messages between
19895 @value{GDBN} and the remote monitor.
19897 @item show debug monitor
19898 @kindex show debug monitor
19899 Show the current status of displaying communications between
19900 @value{GDBN} and the remote monitor.
19905 @kindex load @var{filename} @var{offset}
19906 @item load @var{filename} @var{offset}
19908 Depending on what remote debugging facilities are configured into
19909 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19910 is meant to make @var{filename} (an executable) available for debugging
19911 on the remote system---by downloading, or dynamic linking, for example.
19912 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19913 the @code{add-symbol-file} command.
19915 If your @value{GDBN} does not have a @code{load} command, attempting to
19916 execute it gets the error message ``@code{You can't do that when your
19917 target is @dots{}}''
19919 The file is loaded at whatever address is specified in the executable.
19920 For some object file formats, you can specify the load address when you
19921 link the program; for other formats, like a.out, the object file format
19922 specifies a fixed address.
19923 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19925 It is also possible to tell @value{GDBN} to load the executable file at a
19926 specific offset described by the optional argument @var{offset}. When
19927 @var{offset} is provided, @var{filename} must also be provided.
19929 Depending on the remote side capabilities, @value{GDBN} may be able to
19930 load programs into flash memory.
19932 @code{load} does not repeat if you press @key{RET} again after using it.
19937 @kindex flash-erase
19939 @anchor{flash-erase}
19941 Erases all known flash memory regions on the target.
19946 @section Choosing Target Byte Order
19948 @cindex choosing target byte order
19949 @cindex target byte order
19951 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19952 offer the ability to run either big-endian or little-endian byte
19953 orders. Usually the executable or symbol will include a bit to
19954 designate the endian-ness, and you will not need to worry about
19955 which to use. However, you may still find it useful to adjust
19956 @value{GDBN}'s idea of processor endian-ness manually.
19960 @item set endian big
19961 Instruct @value{GDBN} to assume the target is big-endian.
19963 @item set endian little
19964 Instruct @value{GDBN} to assume the target is little-endian.
19966 @item set endian auto
19967 Instruct @value{GDBN} to use the byte order associated with the
19971 Display @value{GDBN}'s current idea of the target byte order.
19975 Note that these commands merely adjust interpretation of symbolic
19976 data on the host, and that they have absolutely no effect on the
19980 @node Remote Debugging
19981 @chapter Debugging Remote Programs
19982 @cindex remote debugging
19984 If you are trying to debug a program running on a machine that cannot run
19985 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19986 For example, you might use remote debugging on an operating system kernel,
19987 or on a small system which does not have a general purpose operating system
19988 powerful enough to run a full-featured debugger.
19990 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19991 to make this work with particular debugging targets. In addition,
19992 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19993 but not specific to any particular target system) which you can use if you
19994 write the remote stubs---the code that runs on the remote system to
19995 communicate with @value{GDBN}.
19997 Other remote targets may be available in your
19998 configuration of @value{GDBN}; use @code{help target} to list them.
20001 * Connecting:: Connecting to a remote target
20002 * File Transfer:: Sending files to a remote system
20003 * Server:: Using the gdbserver program
20004 * Remote Configuration:: Remote configuration
20005 * Remote Stub:: Implementing a remote stub
20009 @section Connecting to a Remote Target
20010 @cindex remote debugging, connecting
20011 @cindex @code{gdbserver}, connecting
20012 @cindex remote debugging, types of connections
20013 @cindex @code{gdbserver}, types of connections
20014 @cindex @code{gdbserver}, @code{target remote} mode
20015 @cindex @code{gdbserver}, @code{target extended-remote} mode
20017 This section describes how to connect to a remote target, including the
20018 types of connections and their differences, how to set up executable and
20019 symbol files on the host and target, and the commands used for
20020 connecting to and disconnecting from the remote target.
20022 @subsection Types of Remote Connections
20024 @value{GDBN} supports two types of remote connections, @code{target remote}
20025 mode and @code{target extended-remote} mode. Note that many remote targets
20026 support only @code{target remote} mode. There are several major
20027 differences between the two types of connections, enumerated here:
20031 @cindex remote debugging, detach and program exit
20032 @item Result of detach or program exit
20033 @strong{With target remote mode:} When the debugged program exits or you
20034 detach from it, @value{GDBN} disconnects from the target. When using
20035 @code{gdbserver}, @code{gdbserver} will exit.
20037 @strong{With target extended-remote mode:} When the debugged program exits or
20038 you detach from it, @value{GDBN} remains connected to the target, even
20039 though no program is running. You can rerun the program, attach to a
20040 running program, or use @code{monitor} commands specific to the target.
20042 When using @code{gdbserver} in this case, it does not exit unless it was
20043 invoked using the @option{--once} option. If the @option{--once} option
20044 was not used, you can ask @code{gdbserver} to exit using the
20045 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20047 @item Specifying the program to debug
20048 For both connection types you use the @code{file} command to specify the
20049 program on the host system. If you are using @code{gdbserver} there are
20050 some differences in how to specify the location of the program on the
20053 @strong{With target remote mode:} You must either specify the program to debug
20054 on the @code{gdbserver} command line or use the @option{--attach} option
20055 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20057 @cindex @option{--multi}, @code{gdbserver} option
20058 @strong{With target extended-remote mode:} You may specify the program to debug
20059 on the @code{gdbserver} command line, or you can load the program or attach
20060 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20062 @anchor{--multi Option in Types of Remote Connnections}
20063 You can start @code{gdbserver} without supplying an initial command to run
20064 or process ID to attach. To do this, use the @option{--multi} command line
20065 option. Then you can connect using @code{target extended-remote} and start
20066 the program you want to debug (see below for details on using the
20067 @code{run} command in this scenario). Note that the conditions under which
20068 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20069 (@code{target remote} or @code{target extended-remote}). The
20070 @option{--multi} option to @code{gdbserver} has no influence on that.
20072 @item The @code{run} command
20073 @strong{With target remote mode:} The @code{run} command is not
20074 supported. Once a connection has been established, you can use all
20075 the usual @value{GDBN} commands to examine and change data. The
20076 remote program is already running, so you can use commands like
20077 @kbd{step} and @kbd{continue}.
20079 @strong{With target extended-remote mode:} The @code{run} command is
20080 supported. The @code{run} command uses the value set by
20081 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20082 the program to run. Command line arguments are supported, except for
20083 wildcard expansion and I/O redirection (@pxref{Arguments}).
20085 If you specify the program to debug on the command line, then the
20086 @code{run} command is not required to start execution, and you can
20087 resume using commands like @kbd{step} and @kbd{continue} as with
20088 @code{target remote} mode.
20090 @anchor{Attaching in Types of Remote Connections}
20092 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20093 not supported. To attach to a running program using @code{gdbserver}, you
20094 must use the @option{--attach} option (@pxref{Running gdbserver}).
20096 @strong{With target extended-remote mode:} To attach to a running program,
20097 you may use the @code{attach} command after the connection has been
20098 established. If you are using @code{gdbserver}, you may also invoke
20099 @code{gdbserver} using the @option{--attach} option
20100 (@pxref{Running gdbserver}).
20104 @anchor{Host and target files}
20105 @subsection Host and Target Files
20106 @cindex remote debugging, symbol files
20107 @cindex symbol files, remote debugging
20109 @value{GDBN}, running on the host, needs access to symbol and debugging
20110 information for your program running on the target. This requires
20111 access to an unstripped copy of your program, and possibly any associated
20112 symbol files. Note that this section applies equally to both @code{target
20113 remote} mode and @code{target extended-remote} mode.
20115 Some remote targets (@pxref{qXfer executable filename read}, and
20116 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20117 the same connection used to communicate with @value{GDBN}. With such a
20118 target, if the remote program is unstripped, the only command you need is
20119 @code{target remote} (or @code{target extended-remote}).
20121 If the remote program is stripped, or the target does not support remote
20122 program file access, start up @value{GDBN} using the name of the local
20123 unstripped copy of your program as the first argument, or use the
20124 @code{file} command. Use @code{set sysroot} to specify the location (on
20125 the host) of target libraries (unless your @value{GDBN} was compiled with
20126 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20127 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20130 The symbol file and target libraries must exactly match the executable
20131 and libraries on the target, with one exception: the files on the host
20132 system should not be stripped, even if the files on the target system
20133 are. Mismatched or missing files will lead to confusing results
20134 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20135 files may also prevent @code{gdbserver} from debugging multi-threaded
20138 @subsection Remote Connection Commands
20139 @cindex remote connection commands
20140 @value{GDBN} can communicate with the target over a serial line, or
20141 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20142 each case, @value{GDBN} uses the same protocol for debugging your
20143 program; only the medium carrying the debugging packets varies. The
20144 @code{target remote} and @code{target extended-remote} commands
20145 establish a connection to the target. Both commands accept the same
20146 arguments, which indicate the medium to use:
20150 @item target remote @var{serial-device}
20151 @itemx target extended-remote @var{serial-device}
20152 @cindex serial line, @code{target remote}
20153 Use @var{serial-device} to communicate with the target. For example,
20154 to use a serial line connected to the device named @file{/dev/ttyb}:
20157 target remote /dev/ttyb
20160 If you're using a serial line, you may want to give @value{GDBN} the
20161 @samp{--baud} option, or use the @code{set serial baud} command
20162 (@pxref{Remote Configuration, set serial baud}) before the
20163 @code{target} command.
20165 @item target remote @code{@var{host}:@var{port}}
20166 @itemx target remote @code{tcp:@var{host}:@var{port}}
20167 @itemx target extended-remote @code{@var{host}:@var{port}}
20168 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20169 @cindex @acronym{TCP} port, @code{target remote}
20170 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20171 The @var{host} may be either a host name or a numeric @acronym{IP}
20172 address; @var{port} must be a decimal number. The @var{host} could be
20173 the target machine itself, if it is directly connected to the net, or
20174 it might be a terminal server which in turn has a serial line to the
20177 For example, to connect to port 2828 on a terminal server named
20181 target remote manyfarms:2828
20184 If your remote target is actually running on the same machine as your
20185 debugger session (e.g.@: a simulator for your target running on the
20186 same host), you can omit the hostname. For example, to connect to
20187 port 1234 on your local machine:
20190 target remote :1234
20194 Note that the colon is still required here.
20196 @item target remote @code{udp:@var{host}:@var{port}}
20197 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20198 @cindex @acronym{UDP} port, @code{target remote}
20199 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20200 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20203 target remote udp:manyfarms:2828
20206 When using a @acronym{UDP} connection for remote debugging, you should
20207 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20208 can silently drop packets on busy or unreliable networks, which will
20209 cause havoc with your debugging session.
20211 @item target remote | @var{command}
20212 @itemx target extended-remote | @var{command}
20213 @cindex pipe, @code{target remote} to
20214 Run @var{command} in the background and communicate with it using a
20215 pipe. The @var{command} is a shell command, to be parsed and expanded
20216 by the system's command shell, @code{/bin/sh}; it should expect remote
20217 protocol packets on its standard input, and send replies on its
20218 standard output. You could use this to run a stand-alone simulator
20219 that speaks the remote debugging protocol, to make net connections
20220 using programs like @code{ssh}, or for other similar tricks.
20222 If @var{command} closes its standard output (perhaps by exiting),
20223 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20224 program has already exited, this will have no effect.)
20228 @cindex interrupting remote programs
20229 @cindex remote programs, interrupting
20230 Whenever @value{GDBN} is waiting for the remote program, if you type the
20231 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20232 program. This may or may not succeed, depending in part on the hardware
20233 and the serial drivers the remote system uses. If you type the
20234 interrupt character once again, @value{GDBN} displays this prompt:
20237 Interrupted while waiting for the program.
20238 Give up (and stop debugging it)? (y or n)
20241 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20242 the remote debugging session. (If you decide you want to try again later,
20243 you can use @kbd{target remote} again to connect once more.) If you type
20244 @kbd{n}, @value{GDBN} goes back to waiting.
20246 In @code{target extended-remote} mode, typing @kbd{n} will leave
20247 @value{GDBN} connected to the target.
20250 @kindex detach (remote)
20252 When you have finished debugging the remote program, you can use the
20253 @code{detach} command to release it from @value{GDBN} control.
20254 Detaching from the target normally resumes its execution, but the results
20255 will depend on your particular remote stub. After the @code{detach}
20256 command in @code{target remote} mode, @value{GDBN} is free to connect to
20257 another target. In @code{target extended-remote} mode, @value{GDBN} is
20258 still connected to the target.
20262 The @code{disconnect} command closes the connection to the target, and
20263 the target is generally not resumed. It will wait for @value{GDBN}
20264 (this instance or another one) to connect and continue debugging. After
20265 the @code{disconnect} command, @value{GDBN} is again free to connect to
20268 @cindex send command to remote monitor
20269 @cindex extend @value{GDBN} for remote targets
20270 @cindex add new commands for external monitor
20272 @item monitor @var{cmd}
20273 This command allows you to send arbitrary commands directly to the
20274 remote monitor. Since @value{GDBN} doesn't care about the commands it
20275 sends like this, this command is the way to extend @value{GDBN}---you
20276 can add new commands that only the external monitor will understand
20280 @node File Transfer
20281 @section Sending files to a remote system
20282 @cindex remote target, file transfer
20283 @cindex file transfer
20284 @cindex sending files to remote systems
20286 Some remote targets offer the ability to transfer files over the same
20287 connection used to communicate with @value{GDBN}. This is convenient
20288 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20289 running @code{gdbserver} over a network interface. For other targets,
20290 e.g.@: embedded devices with only a single serial port, this may be
20291 the only way to upload or download files.
20293 Not all remote targets support these commands.
20297 @item remote put @var{hostfile} @var{targetfile}
20298 Copy file @var{hostfile} from the host system (the machine running
20299 @value{GDBN}) to @var{targetfile} on the target system.
20302 @item remote get @var{targetfile} @var{hostfile}
20303 Copy file @var{targetfile} from the target system to @var{hostfile}
20304 on the host system.
20306 @kindex remote delete
20307 @item remote delete @var{targetfile}
20308 Delete @var{targetfile} from the target system.
20313 @section Using the @code{gdbserver} Program
20316 @cindex remote connection without stubs
20317 @code{gdbserver} is a control program for Unix-like systems, which
20318 allows you to connect your program with a remote @value{GDBN} via
20319 @code{target remote} or @code{target extended-remote}---but without
20320 linking in the usual debugging stub.
20322 @code{gdbserver} is not a complete replacement for the debugging stubs,
20323 because it requires essentially the same operating-system facilities
20324 that @value{GDBN} itself does. In fact, a system that can run
20325 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20326 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20327 because it is a much smaller program than @value{GDBN} itself. It is
20328 also easier to port than all of @value{GDBN}, so you may be able to get
20329 started more quickly on a new system by using @code{gdbserver}.
20330 Finally, if you develop code for real-time systems, you may find that
20331 the tradeoffs involved in real-time operation make it more convenient to
20332 do as much development work as possible on another system, for example
20333 by cross-compiling. You can use @code{gdbserver} to make a similar
20334 choice for debugging.
20336 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20337 or a TCP connection, using the standard @value{GDBN} remote serial
20341 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20342 Do not run @code{gdbserver} connected to any public network; a
20343 @value{GDBN} connection to @code{gdbserver} provides access to the
20344 target system with the same privileges as the user running
20348 @anchor{Running gdbserver}
20349 @subsection Running @code{gdbserver}
20350 @cindex arguments, to @code{gdbserver}
20351 @cindex @code{gdbserver}, command-line arguments
20353 Run @code{gdbserver} on the target system. You need a copy of the
20354 program you want to debug, including any libraries it requires.
20355 @code{gdbserver} does not need your program's symbol table, so you can
20356 strip the program if necessary to save space. @value{GDBN} on the host
20357 system does all the symbol handling.
20359 To use the server, you must tell it how to communicate with @value{GDBN};
20360 the name of your program; and the arguments for your program. The usual
20364 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20367 @var{comm} is either a device name (to use a serial line), or a TCP
20368 hostname and portnumber, or @code{-} or @code{stdio} to use
20369 stdin/stdout of @code{gdbserver}.
20370 For example, to debug Emacs with the argument
20371 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20375 target> gdbserver /dev/com1 emacs foo.txt
20378 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20381 To use a TCP connection instead of a serial line:
20384 target> gdbserver host:2345 emacs foo.txt
20387 The only difference from the previous example is the first argument,
20388 specifying that you are communicating with the host @value{GDBN} via
20389 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20390 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20391 (Currently, the @samp{host} part is ignored.) You can choose any number
20392 you want for the port number as long as it does not conflict with any
20393 TCP ports already in use on the target system (for example, @code{23} is
20394 reserved for @code{telnet}).@footnote{If you choose a port number that
20395 conflicts with another service, @code{gdbserver} prints an error message
20396 and exits.} You must use the same port number with the host @value{GDBN}
20397 @code{target remote} command.
20399 The @code{stdio} connection is useful when starting @code{gdbserver}
20403 (gdb) target remote | ssh -T hostname gdbserver - hello
20406 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20407 and we don't want escape-character handling. Ssh does this by default when
20408 a command is provided, the flag is provided to make it explicit.
20409 You could elide it if you want to.
20411 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20412 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20413 display through a pipe connected to gdbserver.
20414 Both @code{stdout} and @code{stderr} use the same pipe.
20416 @anchor{Attaching to a program}
20417 @subsubsection Attaching to a Running Program
20418 @cindex attach to a program, @code{gdbserver}
20419 @cindex @option{--attach}, @code{gdbserver} option
20421 On some targets, @code{gdbserver} can also attach to running programs.
20422 This is accomplished via the @code{--attach} argument. The syntax is:
20425 target> gdbserver --attach @var{comm} @var{pid}
20428 @var{pid} is the process ID of a currently running process. It isn't
20429 necessary to point @code{gdbserver} at a binary for the running process.
20431 In @code{target extended-remote} mode, you can also attach using the
20432 @value{GDBN} attach command
20433 (@pxref{Attaching in Types of Remote Connections}).
20436 You can debug processes by name instead of process ID if your target has the
20437 @code{pidof} utility:
20440 target> gdbserver --attach @var{comm} `pidof @var{program}`
20443 In case more than one copy of @var{program} is running, or @var{program}
20444 has multiple threads, most versions of @code{pidof} support the
20445 @code{-s} option to only return the first process ID.
20447 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20449 This section applies only when @code{gdbserver} is run to listen on a TCP
20452 @code{gdbserver} normally terminates after all of its debugged processes have
20453 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20454 extended-remote}, @code{gdbserver} stays running even with no processes left.
20455 @value{GDBN} normally terminates the spawned debugged process on its exit,
20456 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20457 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20458 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20459 stays running even in the @kbd{target remote} mode.
20461 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20462 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20463 completeness, at most one @value{GDBN} can be connected at a time.
20465 @cindex @option{--once}, @code{gdbserver} option
20466 By default, @code{gdbserver} keeps the listening TCP port open, so that
20467 subsequent connections are possible. However, if you start @code{gdbserver}
20468 with the @option{--once} option, it will stop listening for any further
20469 connection attempts after connecting to the first @value{GDBN} session. This
20470 means no further connections to @code{gdbserver} will be possible after the
20471 first one. It also means @code{gdbserver} will terminate after the first
20472 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20473 connections and even in the @kbd{target extended-remote} mode. The
20474 @option{--once} option allows reusing the same port number for connecting to
20475 multiple instances of @code{gdbserver} running on the same host, since each
20476 instance closes its port after the first connection.
20478 @anchor{Other Command-Line Arguments for gdbserver}
20479 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20481 You can use the @option{--multi} option to start @code{gdbserver} without
20482 specifying a program to debug or a process to attach to. Then you can
20483 attach in @code{target extended-remote} mode and run or attach to a
20484 program. For more information,
20485 @pxref{--multi Option in Types of Remote Connnections}.
20487 @cindex @option{--debug}, @code{gdbserver} option
20488 The @option{--debug} option tells @code{gdbserver} to display extra
20489 status information about the debugging process.
20490 @cindex @option{--remote-debug}, @code{gdbserver} option
20491 The @option{--remote-debug} option tells @code{gdbserver} to display
20492 remote protocol debug output. These options are intended for
20493 @code{gdbserver} development and for bug reports to the developers.
20495 @cindex @option{--debug-format}, @code{gdbserver} option
20496 The @option{--debug-format=option1[,option2,...]} option tells
20497 @code{gdbserver} to include additional information in each output.
20498 Possible options are:
20502 Turn off all extra information in debugging output.
20504 Turn on all extra information in debugging output.
20506 Include a timestamp in each line of debugging output.
20509 Options are processed in order. Thus, for example, if @option{none}
20510 appears last then no additional information is added to debugging output.
20512 @cindex @option{--wrapper}, @code{gdbserver} option
20513 The @option{--wrapper} option specifies a wrapper to launch programs
20514 for debugging. The option should be followed by the name of the
20515 wrapper, then any command-line arguments to pass to the wrapper, then
20516 @kbd{--} indicating the end of the wrapper arguments.
20518 @code{gdbserver} runs the specified wrapper program with a combined
20519 command line including the wrapper arguments, then the name of the
20520 program to debug, then any arguments to the program. The wrapper
20521 runs until it executes your program, and then @value{GDBN} gains control.
20523 You can use any program that eventually calls @code{execve} with
20524 its arguments as a wrapper. Several standard Unix utilities do
20525 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20526 with @code{exec "$@@"} will also work.
20528 For example, you can use @code{env} to pass an environment variable to
20529 the debugged program, without setting the variable in @code{gdbserver}'s
20533 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20536 @cindex @option{--selftest}
20537 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20540 $ gdbserver --selftest
20541 Ran 2 unit tests, 0 failed
20544 These tests are disabled in release.
20545 @subsection Connecting to @code{gdbserver}
20547 The basic procedure for connecting to the remote target is:
20551 Run @value{GDBN} on the host system.
20554 Make sure you have the necessary symbol files
20555 (@pxref{Host and target files}).
20556 Load symbols for your application using the @code{file} command before you
20557 connect. Use @code{set sysroot} to locate target libraries (unless your
20558 @value{GDBN} was compiled with the correct sysroot using
20559 @code{--with-sysroot}).
20562 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20563 For TCP connections, you must start up @code{gdbserver} prior to using
20564 the @code{target} command. Otherwise you may get an error whose
20565 text depends on the host system, but which usually looks something like
20566 @samp{Connection refused}. Don't use the @code{load}
20567 command in @value{GDBN} when using @code{target remote} mode, since the
20568 program is already on the target.
20572 @anchor{Monitor Commands for gdbserver}
20573 @subsection Monitor Commands for @code{gdbserver}
20574 @cindex monitor commands, for @code{gdbserver}
20576 During a @value{GDBN} session using @code{gdbserver}, you can use the
20577 @code{monitor} command to send special requests to @code{gdbserver}.
20578 Here are the available commands.
20582 List the available monitor commands.
20584 @item monitor set debug 0
20585 @itemx monitor set debug 1
20586 Disable or enable general debugging messages.
20588 @item monitor set remote-debug 0
20589 @itemx monitor set remote-debug 1
20590 Disable or enable specific debugging messages associated with the remote
20591 protocol (@pxref{Remote Protocol}).
20593 @item monitor set debug-format option1@r{[},option2,...@r{]}
20594 Specify additional text to add to debugging messages.
20595 Possible options are:
20599 Turn off all extra information in debugging output.
20601 Turn on all extra information in debugging output.
20603 Include a timestamp in each line of debugging output.
20606 Options are processed in order. Thus, for example, if @option{none}
20607 appears last then no additional information is added to debugging output.
20609 @item monitor set libthread-db-search-path [PATH]
20610 @cindex gdbserver, search path for @code{libthread_db}
20611 When this command is issued, @var{path} is a colon-separated list of
20612 directories to search for @code{libthread_db} (@pxref{Threads,,set
20613 libthread-db-search-path}). If you omit @var{path},
20614 @samp{libthread-db-search-path} will be reset to its default value.
20616 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20617 not supported in @code{gdbserver}.
20620 Tell gdbserver to exit immediately. This command should be followed by
20621 @code{disconnect} to close the debugging session. @code{gdbserver} will
20622 detach from any attached processes and kill any processes it created.
20623 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20624 of a multi-process mode debug session.
20628 @subsection Tracepoints support in @code{gdbserver}
20629 @cindex tracepoints support in @code{gdbserver}
20631 On some targets, @code{gdbserver} supports tracepoints, fast
20632 tracepoints and static tracepoints.
20634 For fast or static tracepoints to work, a special library called the
20635 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20636 This library is built and distributed as an integral part of
20637 @code{gdbserver}. In addition, support for static tracepoints
20638 requires building the in-process agent library with static tracepoints
20639 support. At present, the UST (LTTng Userspace Tracer,
20640 @url{http://lttng.org/ust}) tracing engine is supported. This support
20641 is automatically available if UST development headers are found in the
20642 standard include path when @code{gdbserver} is built, or if
20643 @code{gdbserver} was explicitly configured using @option{--with-ust}
20644 to point at such headers. You can explicitly disable the support
20645 using @option{--with-ust=no}.
20647 There are several ways to load the in-process agent in your program:
20650 @item Specifying it as dependency at link time
20652 You can link your program dynamically with the in-process agent
20653 library. On most systems, this is accomplished by adding
20654 @code{-linproctrace} to the link command.
20656 @item Using the system's preloading mechanisms
20658 You can force loading the in-process agent at startup time by using
20659 your system's support for preloading shared libraries. Many Unixes
20660 support the concept of preloading user defined libraries. In most
20661 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20662 in the environment. See also the description of @code{gdbserver}'s
20663 @option{--wrapper} command line option.
20665 @item Using @value{GDBN} to force loading the agent at run time
20667 On some systems, you can force the inferior to load a shared library,
20668 by calling a dynamic loader function in the inferior that takes care
20669 of dynamically looking up and loading a shared library. On most Unix
20670 systems, the function is @code{dlopen}. You'll use the @code{call}
20671 command for that. For example:
20674 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20677 Note that on most Unix systems, for the @code{dlopen} function to be
20678 available, the program needs to be linked with @code{-ldl}.
20681 On systems that have a userspace dynamic loader, like most Unix
20682 systems, when you connect to @code{gdbserver} using @code{target
20683 remote}, you'll find that the program is stopped at the dynamic
20684 loader's entry point, and no shared library has been loaded in the
20685 program's address space yet, including the in-process agent. In that
20686 case, before being able to use any of the fast or static tracepoints
20687 features, you need to let the loader run and load the shared
20688 libraries. The simplest way to do that is to run the program to the
20689 main procedure. E.g., if debugging a C or C@t{++} program, start
20690 @code{gdbserver} like so:
20693 $ gdbserver :9999 myprogram
20696 Start GDB and connect to @code{gdbserver} like so, and run to main:
20700 (@value{GDBP}) target remote myhost:9999
20701 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20702 (@value{GDBP}) b main
20703 (@value{GDBP}) continue
20706 The in-process tracing agent library should now be loaded into the
20707 process; you can confirm it with the @code{info sharedlibrary}
20708 command, which will list @file{libinproctrace.so} as loaded in the
20709 process. You are now ready to install fast tracepoints, list static
20710 tracepoint markers, probe static tracepoints markers, and start
20713 @node Remote Configuration
20714 @section Remote Configuration
20717 @kindex show remote
20718 This section documents the configuration options available when
20719 debugging remote programs. For the options related to the File I/O
20720 extensions of the remote protocol, see @ref{system,
20721 system-call-allowed}.
20724 @item set remoteaddresssize @var{bits}
20725 @cindex address size for remote targets
20726 @cindex bits in remote address
20727 Set the maximum size of address in a memory packet to the specified
20728 number of bits. @value{GDBN} will mask off the address bits above
20729 that number, when it passes addresses to the remote target. The
20730 default value is the number of bits in the target's address.
20732 @item show remoteaddresssize
20733 Show the current value of remote address size in bits.
20735 @item set serial baud @var{n}
20736 @cindex baud rate for remote targets
20737 Set the baud rate for the remote serial I/O to @var{n} baud. The
20738 value is used to set the speed of the serial port used for debugging
20741 @item show serial baud
20742 Show the current speed of the remote connection.
20744 @item set serial parity @var{parity}
20745 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20746 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20748 @item show serial parity
20749 Show the current parity of the serial port.
20751 @item set remotebreak
20752 @cindex interrupt remote programs
20753 @cindex BREAK signal instead of Ctrl-C
20754 @anchor{set remotebreak}
20755 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20756 when you type @kbd{Ctrl-c} to interrupt the program running
20757 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20758 character instead. The default is off, since most remote systems
20759 expect to see @samp{Ctrl-C} as the interrupt signal.
20761 @item show remotebreak
20762 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20763 interrupt the remote program.
20765 @item set remoteflow on
20766 @itemx set remoteflow off
20767 @kindex set remoteflow
20768 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20769 on the serial port used to communicate to the remote target.
20771 @item show remoteflow
20772 @kindex show remoteflow
20773 Show the current setting of hardware flow control.
20775 @item set remotelogbase @var{base}
20776 Set the base (a.k.a.@: radix) of logging serial protocol
20777 communications to @var{base}. Supported values of @var{base} are:
20778 @code{ascii}, @code{octal}, and @code{hex}. The default is
20781 @item show remotelogbase
20782 Show the current setting of the radix for logging remote serial
20785 @item set remotelogfile @var{file}
20786 @cindex record serial communications on file
20787 Record remote serial communications on the named @var{file}. The
20788 default is not to record at all.
20790 @item show remotelogfile.
20791 Show the current setting of the file name on which to record the
20792 serial communications.
20794 @item set remotetimeout @var{num}
20795 @cindex timeout for serial communications
20796 @cindex remote timeout
20797 Set the timeout limit to wait for the remote target to respond to
20798 @var{num} seconds. The default is 2 seconds.
20800 @item show remotetimeout
20801 Show the current number of seconds to wait for the remote target
20804 @cindex limit hardware breakpoints and watchpoints
20805 @cindex remote target, limit break- and watchpoints
20806 @anchor{set remote hardware-watchpoint-limit}
20807 @anchor{set remote hardware-breakpoint-limit}
20808 @item set remote hardware-watchpoint-limit @var{limit}
20809 @itemx set remote hardware-breakpoint-limit @var{limit}
20810 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20811 watchpoints. A limit of -1, the default, is treated as unlimited.
20813 @cindex limit hardware watchpoints length
20814 @cindex remote target, limit watchpoints length
20815 @anchor{set remote hardware-watchpoint-length-limit}
20816 @item set remote hardware-watchpoint-length-limit @var{limit}
20817 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20818 a remote hardware watchpoint. A limit of -1, the default, is treated
20821 @item show remote hardware-watchpoint-length-limit
20822 Show the current limit (in bytes) of the maximum length of
20823 a remote hardware watchpoint.
20825 @item set remote exec-file @var{filename}
20826 @itemx show remote exec-file
20827 @anchor{set remote exec-file}
20828 @cindex executable file, for remote target
20829 Select the file used for @code{run} with @code{target
20830 extended-remote}. This should be set to a filename valid on the
20831 target system. If it is not set, the target will use a default
20832 filename (e.g.@: the last program run).
20834 @item set remote interrupt-sequence
20835 @cindex interrupt remote programs
20836 @cindex select Ctrl-C, BREAK or BREAK-g
20837 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20838 @samp{BREAK-g} as the
20839 sequence to the remote target in order to interrupt the execution.
20840 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20841 is high level of serial line for some certain time.
20842 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20843 It is @code{BREAK} signal followed by character @code{g}.
20845 @item show interrupt-sequence
20846 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20847 is sent by @value{GDBN} to interrupt the remote program.
20848 @code{BREAK-g} is BREAK signal followed by @code{g} and
20849 also known as Magic SysRq g.
20851 @item set remote interrupt-on-connect
20852 @cindex send interrupt-sequence on start
20853 Specify whether interrupt-sequence is sent to remote target when
20854 @value{GDBN} connects to it. This is mostly needed when you debug
20855 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20856 which is known as Magic SysRq g in order to connect @value{GDBN}.
20858 @item show interrupt-on-connect
20859 Show whether interrupt-sequence is sent
20860 to remote target when @value{GDBN} connects to it.
20864 @item set tcp auto-retry on
20865 @cindex auto-retry, for remote TCP target
20866 Enable auto-retry for remote TCP connections. This is useful if the remote
20867 debugging agent is launched in parallel with @value{GDBN}; there is a race
20868 condition because the agent may not become ready to accept the connection
20869 before @value{GDBN} attempts to connect. When auto-retry is
20870 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20871 to establish the connection using the timeout specified by
20872 @code{set tcp connect-timeout}.
20874 @item set tcp auto-retry off
20875 Do not auto-retry failed TCP connections.
20877 @item show tcp auto-retry
20878 Show the current auto-retry setting.
20880 @item set tcp connect-timeout @var{seconds}
20881 @itemx set tcp connect-timeout unlimited
20882 @cindex connection timeout, for remote TCP target
20883 @cindex timeout, for remote target connection
20884 Set the timeout for establishing a TCP connection to the remote target to
20885 @var{seconds}. The timeout affects both polling to retry failed connections
20886 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20887 that are merely slow to complete, and represents an approximate cumulative
20888 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20889 @value{GDBN} will keep attempting to establish a connection forever,
20890 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20892 @item show tcp connect-timeout
20893 Show the current connection timeout setting.
20896 @cindex remote packets, enabling and disabling
20897 The @value{GDBN} remote protocol autodetects the packets supported by
20898 your debugging stub. If you need to override the autodetection, you
20899 can use these commands to enable or disable individual packets. Each
20900 packet can be set to @samp{on} (the remote target supports this
20901 packet), @samp{off} (the remote target does not support this packet),
20902 or @samp{auto} (detect remote target support for this packet). They
20903 all default to @samp{auto}. For more information about each packet,
20904 see @ref{Remote Protocol}.
20906 During normal use, you should not have to use any of these commands.
20907 If you do, that may be a bug in your remote debugging stub, or a bug
20908 in @value{GDBN}. You may want to report the problem to the
20909 @value{GDBN} developers.
20911 For each packet @var{name}, the command to enable or disable the
20912 packet is @code{set remote @var{name}-packet}. The available settings
20915 @multitable @columnfractions 0.28 0.32 0.25
20918 @tab Related Features
20920 @item @code{fetch-register}
20922 @tab @code{info registers}
20924 @item @code{set-register}
20928 @item @code{binary-download}
20930 @tab @code{load}, @code{set}
20932 @item @code{read-aux-vector}
20933 @tab @code{qXfer:auxv:read}
20934 @tab @code{info auxv}
20936 @item @code{symbol-lookup}
20937 @tab @code{qSymbol}
20938 @tab Detecting multiple threads
20940 @item @code{attach}
20941 @tab @code{vAttach}
20944 @item @code{verbose-resume}
20946 @tab Stepping or resuming multiple threads
20952 @item @code{software-breakpoint}
20956 @item @code{hardware-breakpoint}
20960 @item @code{write-watchpoint}
20964 @item @code{read-watchpoint}
20968 @item @code{access-watchpoint}
20972 @item @code{pid-to-exec-file}
20973 @tab @code{qXfer:exec-file:read}
20974 @tab @code{attach}, @code{run}
20976 @item @code{target-features}
20977 @tab @code{qXfer:features:read}
20978 @tab @code{set architecture}
20980 @item @code{library-info}
20981 @tab @code{qXfer:libraries:read}
20982 @tab @code{info sharedlibrary}
20984 @item @code{memory-map}
20985 @tab @code{qXfer:memory-map:read}
20986 @tab @code{info mem}
20988 @item @code{read-sdata-object}
20989 @tab @code{qXfer:sdata:read}
20990 @tab @code{print $_sdata}
20992 @item @code{read-spu-object}
20993 @tab @code{qXfer:spu:read}
20994 @tab @code{info spu}
20996 @item @code{write-spu-object}
20997 @tab @code{qXfer:spu:write}
20998 @tab @code{info spu}
21000 @item @code{read-siginfo-object}
21001 @tab @code{qXfer:siginfo:read}
21002 @tab @code{print $_siginfo}
21004 @item @code{write-siginfo-object}
21005 @tab @code{qXfer:siginfo:write}
21006 @tab @code{set $_siginfo}
21008 @item @code{threads}
21009 @tab @code{qXfer:threads:read}
21010 @tab @code{info threads}
21012 @item @code{get-thread-local-@*storage-address}
21013 @tab @code{qGetTLSAddr}
21014 @tab Displaying @code{__thread} variables
21016 @item @code{get-thread-information-block-address}
21017 @tab @code{qGetTIBAddr}
21018 @tab Display MS-Windows Thread Information Block.
21020 @item @code{search-memory}
21021 @tab @code{qSearch:memory}
21024 @item @code{supported-packets}
21025 @tab @code{qSupported}
21026 @tab Remote communications parameters
21028 @item @code{catch-syscalls}
21029 @tab @code{QCatchSyscalls}
21030 @tab @code{catch syscall}
21032 @item @code{pass-signals}
21033 @tab @code{QPassSignals}
21034 @tab @code{handle @var{signal}}
21036 @item @code{program-signals}
21037 @tab @code{QProgramSignals}
21038 @tab @code{handle @var{signal}}
21040 @item @code{hostio-close-packet}
21041 @tab @code{vFile:close}
21042 @tab @code{remote get}, @code{remote put}
21044 @item @code{hostio-open-packet}
21045 @tab @code{vFile:open}
21046 @tab @code{remote get}, @code{remote put}
21048 @item @code{hostio-pread-packet}
21049 @tab @code{vFile:pread}
21050 @tab @code{remote get}, @code{remote put}
21052 @item @code{hostio-pwrite-packet}
21053 @tab @code{vFile:pwrite}
21054 @tab @code{remote get}, @code{remote put}
21056 @item @code{hostio-unlink-packet}
21057 @tab @code{vFile:unlink}
21058 @tab @code{remote delete}
21060 @item @code{hostio-readlink-packet}
21061 @tab @code{vFile:readlink}
21064 @item @code{hostio-fstat-packet}
21065 @tab @code{vFile:fstat}
21068 @item @code{hostio-setfs-packet}
21069 @tab @code{vFile:setfs}
21072 @item @code{noack-packet}
21073 @tab @code{QStartNoAckMode}
21074 @tab Packet acknowledgment
21076 @item @code{osdata}
21077 @tab @code{qXfer:osdata:read}
21078 @tab @code{info os}
21080 @item @code{query-attached}
21081 @tab @code{qAttached}
21082 @tab Querying remote process attach state.
21084 @item @code{trace-buffer-size}
21085 @tab @code{QTBuffer:size}
21086 @tab @code{set trace-buffer-size}
21088 @item @code{trace-status}
21089 @tab @code{qTStatus}
21090 @tab @code{tstatus}
21092 @item @code{traceframe-info}
21093 @tab @code{qXfer:traceframe-info:read}
21094 @tab Traceframe info
21096 @item @code{install-in-trace}
21097 @tab @code{InstallInTrace}
21098 @tab Install tracepoint in tracing
21100 @item @code{disable-randomization}
21101 @tab @code{QDisableRandomization}
21102 @tab @code{set disable-randomization}
21104 @item @code{startup-with-shell}
21105 @tab @code{QStartupWithShell}
21106 @tab @code{set startup-with-shell}
21108 @item @code{environment-hex-encoded}
21109 @tab @code{QEnvironmentHexEncoded}
21110 @tab @code{set environment}
21112 @item @code{environment-unset}
21113 @tab @code{QEnvironmentUnset}
21114 @tab @code{unset environment}
21116 @item @code{environment-reset}
21117 @tab @code{QEnvironmentReset}
21118 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21120 @item @code{set-working-dir}
21121 @tab @code{QSetWorkingDir}
21122 @tab @code{set cwd}
21124 @item @code{conditional-breakpoints-packet}
21125 @tab @code{Z0 and Z1}
21126 @tab @code{Support for target-side breakpoint condition evaluation}
21128 @item @code{multiprocess-extensions}
21129 @tab @code{multiprocess extensions}
21130 @tab Debug multiple processes and remote process PID awareness
21132 @item @code{swbreak-feature}
21133 @tab @code{swbreak stop reason}
21136 @item @code{hwbreak-feature}
21137 @tab @code{hwbreak stop reason}
21140 @item @code{fork-event-feature}
21141 @tab @code{fork stop reason}
21144 @item @code{vfork-event-feature}
21145 @tab @code{vfork stop reason}
21148 @item @code{exec-event-feature}
21149 @tab @code{exec stop reason}
21152 @item @code{thread-events}
21153 @tab @code{QThreadEvents}
21154 @tab Tracking thread lifetime.
21156 @item @code{no-resumed-stop-reply}
21157 @tab @code{no resumed thread left stop reply}
21158 @tab Tracking thread lifetime.
21163 @section Implementing a Remote Stub
21165 @cindex debugging stub, example
21166 @cindex remote stub, example
21167 @cindex stub example, remote debugging
21168 The stub files provided with @value{GDBN} implement the target side of the
21169 communication protocol, and the @value{GDBN} side is implemented in the
21170 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21171 these subroutines to communicate, and ignore the details. (If you're
21172 implementing your own stub file, you can still ignore the details: start
21173 with one of the existing stub files. @file{sparc-stub.c} is the best
21174 organized, and therefore the easiest to read.)
21176 @cindex remote serial debugging, overview
21177 To debug a program running on another machine (the debugging
21178 @dfn{target} machine), you must first arrange for all the usual
21179 prerequisites for the program to run by itself. For example, for a C
21184 A startup routine to set up the C runtime environment; these usually
21185 have a name like @file{crt0}. The startup routine may be supplied by
21186 your hardware supplier, or you may have to write your own.
21189 A C subroutine library to support your program's
21190 subroutine calls, notably managing input and output.
21193 A way of getting your program to the other machine---for example, a
21194 download program. These are often supplied by the hardware
21195 manufacturer, but you may have to write your own from hardware
21199 The next step is to arrange for your program to use a serial port to
21200 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21201 machine). In general terms, the scheme looks like this:
21205 @value{GDBN} already understands how to use this protocol; when everything
21206 else is set up, you can simply use the @samp{target remote} command
21207 (@pxref{Targets,,Specifying a Debugging Target}).
21209 @item On the target,
21210 you must link with your program a few special-purpose subroutines that
21211 implement the @value{GDBN} remote serial protocol. The file containing these
21212 subroutines is called a @dfn{debugging stub}.
21214 On certain remote targets, you can use an auxiliary program
21215 @code{gdbserver} instead of linking a stub into your program.
21216 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21219 The debugging stub is specific to the architecture of the remote
21220 machine; for example, use @file{sparc-stub.c} to debug programs on
21223 @cindex remote serial stub list
21224 These working remote stubs are distributed with @value{GDBN}:
21229 @cindex @file{i386-stub.c}
21232 For Intel 386 and compatible architectures.
21235 @cindex @file{m68k-stub.c}
21236 @cindex Motorola 680x0
21238 For Motorola 680x0 architectures.
21241 @cindex @file{sh-stub.c}
21244 For Renesas SH architectures.
21247 @cindex @file{sparc-stub.c}
21249 For @sc{sparc} architectures.
21251 @item sparcl-stub.c
21252 @cindex @file{sparcl-stub.c}
21255 For Fujitsu @sc{sparclite} architectures.
21259 The @file{README} file in the @value{GDBN} distribution may list other
21260 recently added stubs.
21263 * Stub Contents:: What the stub can do for you
21264 * Bootstrapping:: What you must do for the stub
21265 * Debug Session:: Putting it all together
21268 @node Stub Contents
21269 @subsection What the Stub Can Do for You
21271 @cindex remote serial stub
21272 The debugging stub for your architecture supplies these three
21276 @item set_debug_traps
21277 @findex set_debug_traps
21278 @cindex remote serial stub, initialization
21279 This routine arranges for @code{handle_exception} to run when your
21280 program stops. You must call this subroutine explicitly in your
21281 program's startup code.
21283 @item handle_exception
21284 @findex handle_exception
21285 @cindex remote serial stub, main routine
21286 This is the central workhorse, but your program never calls it
21287 explicitly---the setup code arranges for @code{handle_exception} to
21288 run when a trap is triggered.
21290 @code{handle_exception} takes control when your program stops during
21291 execution (for example, on a breakpoint), and mediates communications
21292 with @value{GDBN} on the host machine. This is where the communications
21293 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21294 representative on the target machine. It begins by sending summary
21295 information on the state of your program, then continues to execute,
21296 retrieving and transmitting any information @value{GDBN} needs, until you
21297 execute a @value{GDBN} command that makes your program resume; at that point,
21298 @code{handle_exception} returns control to your own code on the target
21302 @cindex @code{breakpoint} subroutine, remote
21303 Use this auxiliary subroutine to make your program contain a
21304 breakpoint. Depending on the particular situation, this may be the only
21305 way for @value{GDBN} to get control. For instance, if your target
21306 machine has some sort of interrupt button, you won't need to call this;
21307 pressing the interrupt button transfers control to
21308 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21309 simply receiving characters on the serial port may also trigger a trap;
21310 again, in that situation, you don't need to call @code{breakpoint} from
21311 your own program---simply running @samp{target remote} from the host
21312 @value{GDBN} session gets control.
21314 Call @code{breakpoint} if none of these is true, or if you simply want
21315 to make certain your program stops at a predetermined point for the
21316 start of your debugging session.
21319 @node Bootstrapping
21320 @subsection What You Must Do for the Stub
21322 @cindex remote stub, support routines
21323 The debugging stubs that come with @value{GDBN} are set up for a particular
21324 chip architecture, but they have no information about the rest of your
21325 debugging target machine.
21327 First of all you need to tell the stub how to communicate with the
21331 @item int getDebugChar()
21332 @findex getDebugChar
21333 Write this subroutine to read a single character from the serial port.
21334 It may be identical to @code{getchar} for your target system; a
21335 different name is used to allow you to distinguish the two if you wish.
21337 @item void putDebugChar(int)
21338 @findex putDebugChar
21339 Write this subroutine to write a single character to the serial port.
21340 It may be identical to @code{putchar} for your target system; a
21341 different name is used to allow you to distinguish the two if you wish.
21344 @cindex control C, and remote debugging
21345 @cindex interrupting remote targets
21346 If you want @value{GDBN} to be able to stop your program while it is
21347 running, you need to use an interrupt-driven serial driver, and arrange
21348 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21349 character). That is the character which @value{GDBN} uses to tell the
21350 remote system to stop.
21352 Getting the debugging target to return the proper status to @value{GDBN}
21353 probably requires changes to the standard stub; one quick and dirty way
21354 is to just execute a breakpoint instruction (the ``dirty'' part is that
21355 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21357 Other routines you need to supply are:
21360 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21361 @findex exceptionHandler
21362 Write this function to install @var{exception_address} in the exception
21363 handling tables. You need to do this because the stub does not have any
21364 way of knowing what the exception handling tables on your target system
21365 are like (for example, the processor's table might be in @sc{rom},
21366 containing entries which point to a table in @sc{ram}).
21367 The @var{exception_number} specifies the exception which should be changed;
21368 its meaning is architecture-dependent (for example, different numbers
21369 might represent divide by zero, misaligned access, etc). When this
21370 exception occurs, control should be transferred directly to
21371 @var{exception_address}, and the processor state (stack, registers,
21372 and so on) should be just as it is when a processor exception occurs. So if
21373 you want to use a jump instruction to reach @var{exception_address}, it
21374 should be a simple jump, not a jump to subroutine.
21376 For the 386, @var{exception_address} should be installed as an interrupt
21377 gate so that interrupts are masked while the handler runs. The gate
21378 should be at privilege level 0 (the most privileged level). The
21379 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21380 help from @code{exceptionHandler}.
21382 @item void flush_i_cache()
21383 @findex flush_i_cache
21384 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21385 instruction cache, if any, on your target machine. If there is no
21386 instruction cache, this subroutine may be a no-op.
21388 On target machines that have instruction caches, @value{GDBN} requires this
21389 function to make certain that the state of your program is stable.
21393 You must also make sure this library routine is available:
21396 @item void *memset(void *, int, int)
21398 This is the standard library function @code{memset} that sets an area of
21399 memory to a known value. If you have one of the free versions of
21400 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21401 either obtain it from your hardware manufacturer, or write your own.
21404 If you do not use the GNU C compiler, you may need other standard
21405 library subroutines as well; this varies from one stub to another,
21406 but in general the stubs are likely to use any of the common library
21407 subroutines which @code{@value{NGCC}} generates as inline code.
21410 @node Debug Session
21411 @subsection Putting it All Together
21413 @cindex remote serial debugging summary
21414 In summary, when your program is ready to debug, you must follow these
21419 Make sure you have defined the supporting low-level routines
21420 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21422 @code{getDebugChar}, @code{putDebugChar},
21423 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21427 Insert these lines in your program's startup code, before the main
21428 procedure is called:
21435 On some machines, when a breakpoint trap is raised, the hardware
21436 automatically makes the PC point to the instruction after the
21437 breakpoint. If your machine doesn't do that, you may need to adjust
21438 @code{handle_exception} to arrange for it to return to the instruction
21439 after the breakpoint on this first invocation, so that your program
21440 doesn't keep hitting the initial breakpoint instead of making
21444 For the 680x0 stub only, you need to provide a variable called
21445 @code{exceptionHook}. Normally you just use:
21448 void (*exceptionHook)() = 0;
21452 but if before calling @code{set_debug_traps}, you set it to point to a
21453 function in your program, that function is called when
21454 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21455 error). The function indicated by @code{exceptionHook} is called with
21456 one parameter: an @code{int} which is the exception number.
21459 Compile and link together: your program, the @value{GDBN} debugging stub for
21460 your target architecture, and the supporting subroutines.
21463 Make sure you have a serial connection between your target machine and
21464 the @value{GDBN} host, and identify the serial port on the host.
21467 @c The "remote" target now provides a `load' command, so we should
21468 @c document that. FIXME.
21469 Download your program to your target machine (or get it there by
21470 whatever means the manufacturer provides), and start it.
21473 Start @value{GDBN} on the host, and connect to the target
21474 (@pxref{Connecting,,Connecting to a Remote Target}).
21478 @node Configurations
21479 @chapter Configuration-Specific Information
21481 While nearly all @value{GDBN} commands are available for all native and
21482 cross versions of the debugger, there are some exceptions. This chapter
21483 describes things that are only available in certain configurations.
21485 There are three major categories of configurations: native
21486 configurations, where the host and target are the same, embedded
21487 operating system configurations, which are usually the same for several
21488 different processor architectures, and bare embedded processors, which
21489 are quite different from each other.
21494 * Embedded Processors::
21501 This section describes details specific to particular native
21505 * BSD libkvm Interface:: Debugging BSD kernel memory images
21506 * SVR4 Process Information:: SVR4 process information
21507 * DJGPP Native:: Features specific to the DJGPP port
21508 * Cygwin Native:: Features specific to the Cygwin port
21509 * Hurd Native:: Features specific to @sc{gnu} Hurd
21510 * Darwin:: Features specific to Darwin
21513 @node BSD libkvm Interface
21514 @subsection BSD libkvm Interface
21517 @cindex kernel memory image
21518 @cindex kernel crash dump
21520 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21521 interface that provides a uniform interface for accessing kernel virtual
21522 memory images, including live systems and crash dumps. @value{GDBN}
21523 uses this interface to allow you to debug live kernels and kernel crash
21524 dumps on many native BSD configurations. This is implemented as a
21525 special @code{kvm} debugging target. For debugging a live system, load
21526 the currently running kernel into @value{GDBN} and connect to the
21530 (@value{GDBP}) @b{target kvm}
21533 For debugging crash dumps, provide the file name of the crash dump as an
21537 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21540 Once connected to the @code{kvm} target, the following commands are
21546 Set current context from the @dfn{Process Control Block} (PCB) address.
21549 Set current context from proc address. This command isn't available on
21550 modern FreeBSD systems.
21553 @node SVR4 Process Information
21554 @subsection SVR4 Process Information
21556 @cindex examine process image
21557 @cindex process info via @file{/proc}
21559 Many versions of SVR4 and compatible systems provide a facility called
21560 @samp{/proc} that can be used to examine the image of a running
21561 process using file-system subroutines.
21563 If @value{GDBN} is configured for an operating system with this
21564 facility, the command @code{info proc} is available to report
21565 information about the process running your program, or about any
21566 process running on your system. This includes, as of this writing,
21567 @sc{gnu}/Linux and Solaris, for example.
21569 This command may also work on core files that were created on a system
21570 that has the @samp{/proc} facility.
21576 @itemx info proc @var{process-id}
21577 Summarize available information about any running process. If a
21578 process ID is specified by @var{process-id}, display information about
21579 that process; otherwise display information about the program being
21580 debugged. The summary includes the debugged process ID, the command
21581 line used to invoke it, its current working directory, and its
21582 executable file's absolute file name.
21584 On some systems, @var{process-id} can be of the form
21585 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21586 within a process. If the optional @var{pid} part is missing, it means
21587 a thread from the process being debugged (the leading @samp{/} still
21588 needs to be present, or else @value{GDBN} will interpret the number as
21589 a process ID rather than a thread ID).
21591 @item info proc cmdline
21592 @cindex info proc cmdline
21593 Show the original command line of the process. This command is
21594 specific to @sc{gnu}/Linux.
21596 @item info proc cwd
21597 @cindex info proc cwd
21598 Show the current working directory of the process. This command is
21599 specific to @sc{gnu}/Linux.
21601 @item info proc exe
21602 @cindex info proc exe
21603 Show the name of executable of the process. This command is specific
21606 @item info proc mappings
21607 @cindex memory address space mappings
21608 Report the memory address space ranges accessible in the program, with
21609 information on whether the process has read, write, or execute access
21610 rights to each range. On @sc{gnu}/Linux systems, each memory range
21611 includes the object file which is mapped to that range, instead of the
21612 memory access rights to that range.
21614 @item info proc stat
21615 @itemx info proc status
21616 @cindex process detailed status information
21617 These subcommands are specific to @sc{gnu}/Linux systems. They show
21618 the process-related information, including the user ID and group ID;
21619 how many threads are there in the process; its virtual memory usage;
21620 the signals that are pending, blocked, and ignored; its TTY; its
21621 consumption of system and user time; its stack size; its @samp{nice}
21622 value; etc. For more information, see the @samp{proc} man page
21623 (type @kbd{man 5 proc} from your shell prompt).
21625 @item info proc all
21626 Show all the information about the process described under all of the
21627 above @code{info proc} subcommands.
21630 @comment These sub-options of 'info proc' were not included when
21631 @comment procfs.c was re-written. Keep their descriptions around
21632 @comment against the day when someone finds the time to put them back in.
21633 @kindex info proc times
21634 @item info proc times
21635 Starting time, user CPU time, and system CPU time for your program and
21638 @kindex info proc id
21640 Report on the process IDs related to your program: its own process ID,
21641 the ID of its parent, the process group ID, and the session ID.
21644 @item set procfs-trace
21645 @kindex set procfs-trace
21646 @cindex @code{procfs} API calls
21647 This command enables and disables tracing of @code{procfs} API calls.
21649 @item show procfs-trace
21650 @kindex show procfs-trace
21651 Show the current state of @code{procfs} API call tracing.
21653 @item set procfs-file @var{file}
21654 @kindex set procfs-file
21655 Tell @value{GDBN} to write @code{procfs} API trace to the named
21656 @var{file}. @value{GDBN} appends the trace info to the previous
21657 contents of the file. The default is to display the trace on the
21660 @item show procfs-file
21661 @kindex show procfs-file
21662 Show the file to which @code{procfs} API trace is written.
21664 @item proc-trace-entry
21665 @itemx proc-trace-exit
21666 @itemx proc-untrace-entry
21667 @itemx proc-untrace-exit
21668 @kindex proc-trace-entry
21669 @kindex proc-trace-exit
21670 @kindex proc-untrace-entry
21671 @kindex proc-untrace-exit
21672 These commands enable and disable tracing of entries into and exits
21673 from the @code{syscall} interface.
21676 @kindex info pidlist
21677 @cindex process list, QNX Neutrino
21678 For QNX Neutrino only, this command displays the list of all the
21679 processes and all the threads within each process.
21682 @kindex info meminfo
21683 @cindex mapinfo list, QNX Neutrino
21684 For QNX Neutrino only, this command displays the list of all mapinfos.
21688 @subsection Features for Debugging @sc{djgpp} Programs
21689 @cindex @sc{djgpp} debugging
21690 @cindex native @sc{djgpp} debugging
21691 @cindex MS-DOS-specific commands
21694 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21695 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21696 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21697 top of real-mode DOS systems and their emulations.
21699 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21700 defines a few commands specific to the @sc{djgpp} port. This
21701 subsection describes those commands.
21706 This is a prefix of @sc{djgpp}-specific commands which print
21707 information about the target system and important OS structures.
21710 @cindex MS-DOS system info
21711 @cindex free memory information (MS-DOS)
21712 @item info dos sysinfo
21713 This command displays assorted information about the underlying
21714 platform: the CPU type and features, the OS version and flavor, the
21715 DPMI version, and the available conventional and DPMI memory.
21720 @cindex segment descriptor tables
21721 @cindex descriptor tables display
21723 @itemx info dos ldt
21724 @itemx info dos idt
21725 These 3 commands display entries from, respectively, Global, Local,
21726 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21727 tables are data structures which store a descriptor for each segment
21728 that is currently in use. The segment's selector is an index into a
21729 descriptor table; the table entry for that index holds the
21730 descriptor's base address and limit, and its attributes and access
21733 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21734 segment (used for both data and the stack), and a DOS segment (which
21735 allows access to DOS/BIOS data structures and absolute addresses in
21736 conventional memory). However, the DPMI host will usually define
21737 additional segments in order to support the DPMI environment.
21739 @cindex garbled pointers
21740 These commands allow to display entries from the descriptor tables.
21741 Without an argument, all entries from the specified table are
21742 displayed. An argument, which should be an integer expression, means
21743 display a single entry whose index is given by the argument. For
21744 example, here's a convenient way to display information about the
21745 debugged program's data segment:
21748 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21749 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21753 This comes in handy when you want to see whether a pointer is outside
21754 the data segment's limit (i.e.@: @dfn{garbled}).
21756 @cindex page tables display (MS-DOS)
21758 @itemx info dos pte
21759 These two commands display entries from, respectively, the Page
21760 Directory and the Page Tables. Page Directories and Page Tables are
21761 data structures which control how virtual memory addresses are mapped
21762 into physical addresses. A Page Table includes an entry for every
21763 page of memory that is mapped into the program's address space; there
21764 may be several Page Tables, each one holding up to 4096 entries. A
21765 Page Directory has up to 4096 entries, one each for every Page Table
21766 that is currently in use.
21768 Without an argument, @kbd{info dos pde} displays the entire Page
21769 Directory, and @kbd{info dos pte} displays all the entries in all of
21770 the Page Tables. An argument, an integer expression, given to the
21771 @kbd{info dos pde} command means display only that entry from the Page
21772 Directory table. An argument given to the @kbd{info dos pte} command
21773 means display entries from a single Page Table, the one pointed to by
21774 the specified entry in the Page Directory.
21776 @cindex direct memory access (DMA) on MS-DOS
21777 These commands are useful when your program uses @dfn{DMA} (Direct
21778 Memory Access), which needs physical addresses to program the DMA
21781 These commands are supported only with some DPMI servers.
21783 @cindex physical address from linear address
21784 @item info dos address-pte @var{addr}
21785 This command displays the Page Table entry for a specified linear
21786 address. The argument @var{addr} is a linear address which should
21787 already have the appropriate segment's base address added to it,
21788 because this command accepts addresses which may belong to @emph{any}
21789 segment. For example, here's how to display the Page Table entry for
21790 the page where a variable @code{i} is stored:
21793 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21794 @exdent @code{Page Table entry for address 0x11a00d30:}
21795 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21799 This says that @code{i} is stored at offset @code{0xd30} from the page
21800 whose physical base address is @code{0x02698000}, and shows all the
21801 attributes of that page.
21803 Note that you must cast the addresses of variables to a @code{char *},
21804 since otherwise the value of @code{__djgpp_base_address}, the base
21805 address of all variables and functions in a @sc{djgpp} program, will
21806 be added using the rules of C pointer arithmetics: if @code{i} is
21807 declared an @code{int}, @value{GDBN} will add 4 times the value of
21808 @code{__djgpp_base_address} to the address of @code{i}.
21810 Here's another example, it displays the Page Table entry for the
21814 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21815 @exdent @code{Page Table entry for address 0x29110:}
21816 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21820 (The @code{+ 3} offset is because the transfer buffer's address is the
21821 3rd member of the @code{_go32_info_block} structure.) The output
21822 clearly shows that this DPMI server maps the addresses in conventional
21823 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21824 linear (@code{0x29110}) addresses are identical.
21826 This command is supported only with some DPMI servers.
21829 @cindex DOS serial data link, remote debugging
21830 In addition to native debugging, the DJGPP port supports remote
21831 debugging via a serial data link. The following commands are specific
21832 to remote serial debugging in the DJGPP port of @value{GDBN}.
21835 @kindex set com1base
21836 @kindex set com1irq
21837 @kindex set com2base
21838 @kindex set com2irq
21839 @kindex set com3base
21840 @kindex set com3irq
21841 @kindex set com4base
21842 @kindex set com4irq
21843 @item set com1base @var{addr}
21844 This command sets the base I/O port address of the @file{COM1} serial
21847 @item set com1irq @var{irq}
21848 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21849 for the @file{COM1} serial port.
21851 There are similar commands @samp{set com2base}, @samp{set com3irq},
21852 etc.@: for setting the port address and the @code{IRQ} lines for the
21855 @kindex show com1base
21856 @kindex show com1irq
21857 @kindex show com2base
21858 @kindex show com2irq
21859 @kindex show com3base
21860 @kindex show com3irq
21861 @kindex show com4base
21862 @kindex show com4irq
21863 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21864 display the current settings of the base address and the @code{IRQ}
21865 lines used by the COM ports.
21868 @kindex info serial
21869 @cindex DOS serial port status
21870 This command prints the status of the 4 DOS serial ports. For each
21871 port, it prints whether it's active or not, its I/O base address and
21872 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21873 counts of various errors encountered so far.
21877 @node Cygwin Native
21878 @subsection Features for Debugging MS Windows PE Executables
21879 @cindex MS Windows debugging
21880 @cindex native Cygwin debugging
21881 @cindex Cygwin-specific commands
21883 @value{GDBN} supports native debugging of MS Windows programs, including
21884 DLLs with and without symbolic debugging information.
21886 @cindex Ctrl-BREAK, MS-Windows
21887 @cindex interrupt debuggee on MS-Windows
21888 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21889 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21890 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21891 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21892 sequence, which can be used to interrupt the debuggee even if it
21895 There are various additional Cygwin-specific commands, described in
21896 this section. Working with DLLs that have no debugging symbols is
21897 described in @ref{Non-debug DLL Symbols}.
21902 This is a prefix of MS Windows-specific commands which print
21903 information about the target system and important OS structures.
21905 @item info w32 selector
21906 This command displays information returned by
21907 the Win32 API @code{GetThreadSelectorEntry} function.
21908 It takes an optional argument that is evaluated to
21909 a long value to give the information about this given selector.
21910 Without argument, this command displays information
21911 about the six segment registers.
21913 @item info w32 thread-information-block
21914 This command displays thread specific information stored in the
21915 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21916 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21918 @kindex signal-event
21919 @item signal-event @var{id}
21920 This command signals an event with user-provided @var{id}. Used to resume
21921 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21923 To use it, create or edit the following keys in
21924 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21925 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21926 (for x86_64 versions):
21930 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21931 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21932 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21934 The first @code{%ld} will be replaced by the process ID of the
21935 crashing process, the second @code{%ld} will be replaced by the ID of
21936 the event that blocks the crashing process, waiting for @value{GDBN}
21940 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21941 make the system run debugger specified by the Debugger key
21942 automatically, @code{0} will cause a dialog box with ``OK'' and
21943 ``Cancel'' buttons to appear, which allows the user to either
21944 terminate the crashing process (OK) or debug it (Cancel).
21947 @kindex set cygwin-exceptions
21948 @cindex debugging the Cygwin DLL
21949 @cindex Cygwin DLL, debugging
21950 @item set cygwin-exceptions @var{mode}
21951 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21952 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21953 @value{GDBN} will delay recognition of exceptions, and may ignore some
21954 exceptions which seem to be caused by internal Cygwin DLL
21955 ``bookkeeping''. This option is meant primarily for debugging the
21956 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21957 @value{GDBN} users with false @code{SIGSEGV} signals.
21959 @kindex show cygwin-exceptions
21960 @item show cygwin-exceptions
21961 Displays whether @value{GDBN} will break on exceptions that happen
21962 inside the Cygwin DLL itself.
21964 @kindex set new-console
21965 @item set new-console @var{mode}
21966 If @var{mode} is @code{on} the debuggee will
21967 be started in a new console on next start.
21968 If @var{mode} is @code{off}, the debuggee will
21969 be started in the same console as the debugger.
21971 @kindex show new-console
21972 @item show new-console
21973 Displays whether a new console is used
21974 when the debuggee is started.
21976 @kindex set new-group
21977 @item set new-group @var{mode}
21978 This boolean value controls whether the debuggee should
21979 start a new group or stay in the same group as the debugger.
21980 This affects the way the Windows OS handles
21983 @kindex show new-group
21984 @item show new-group
21985 Displays current value of new-group boolean.
21987 @kindex set debugevents
21988 @item set debugevents
21989 This boolean value adds debug output concerning kernel events related
21990 to the debuggee seen by the debugger. This includes events that
21991 signal thread and process creation and exit, DLL loading and
21992 unloading, console interrupts, and debugging messages produced by the
21993 Windows @code{OutputDebugString} API call.
21995 @kindex set debugexec
21996 @item set debugexec
21997 This boolean value adds debug output concerning execute events
21998 (such as resume thread) seen by the debugger.
22000 @kindex set debugexceptions
22001 @item set debugexceptions
22002 This boolean value adds debug output concerning exceptions in the
22003 debuggee seen by the debugger.
22005 @kindex set debugmemory
22006 @item set debugmemory
22007 This boolean value adds debug output concerning debuggee memory reads
22008 and writes by the debugger.
22012 This boolean values specifies whether the debuggee is called
22013 via a shell or directly (default value is on).
22017 Displays if the debuggee will be started with a shell.
22022 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22025 @node Non-debug DLL Symbols
22026 @subsubsection Support for DLLs without Debugging Symbols
22027 @cindex DLLs with no debugging symbols
22028 @cindex Minimal symbols and DLLs
22030 Very often on windows, some of the DLLs that your program relies on do
22031 not include symbolic debugging information (for example,
22032 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22033 symbols in a DLL, it relies on the minimal amount of symbolic
22034 information contained in the DLL's export table. This section
22035 describes working with such symbols, known internally to @value{GDBN} as
22036 ``minimal symbols''.
22038 Note that before the debugged program has started execution, no DLLs
22039 will have been loaded. The easiest way around this problem is simply to
22040 start the program --- either by setting a breakpoint or letting the
22041 program run once to completion.
22043 @subsubsection DLL Name Prefixes
22045 In keeping with the naming conventions used by the Microsoft debugging
22046 tools, DLL export symbols are made available with a prefix based on the
22047 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22048 also entered into the symbol table, so @code{CreateFileA} is often
22049 sufficient. In some cases there will be name clashes within a program
22050 (particularly if the executable itself includes full debugging symbols)
22051 necessitating the use of the fully qualified name when referring to the
22052 contents of the DLL. Use single-quotes around the name to avoid the
22053 exclamation mark (``!'') being interpreted as a language operator.
22055 Note that the internal name of the DLL may be all upper-case, even
22056 though the file name of the DLL is lower-case, or vice-versa. Since
22057 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22058 some confusion. If in doubt, try the @code{info functions} and
22059 @code{info variables} commands or even @code{maint print msymbols}
22060 (@pxref{Symbols}). Here's an example:
22063 (@value{GDBP}) info function CreateFileA
22064 All functions matching regular expression "CreateFileA":
22066 Non-debugging symbols:
22067 0x77e885f4 CreateFileA
22068 0x77e885f4 KERNEL32!CreateFileA
22072 (@value{GDBP}) info function !
22073 All functions matching regular expression "!":
22075 Non-debugging symbols:
22076 0x6100114c cygwin1!__assert
22077 0x61004034 cygwin1!_dll_crt0@@0
22078 0x61004240 cygwin1!dll_crt0(per_process *)
22082 @subsubsection Working with Minimal Symbols
22084 Symbols extracted from a DLL's export table do not contain very much
22085 type information. All that @value{GDBN} can do is guess whether a symbol
22086 refers to a function or variable depending on the linker section that
22087 contains the symbol. Also note that the actual contents of the memory
22088 contained in a DLL are not available unless the program is running. This
22089 means that you cannot examine the contents of a variable or disassemble
22090 a function within a DLL without a running program.
22092 Variables are generally treated as pointers and dereferenced
22093 automatically. For this reason, it is often necessary to prefix a
22094 variable name with the address-of operator (``&'') and provide explicit
22095 type information in the command. Here's an example of the type of
22099 (@value{GDBP}) print 'cygwin1!__argv'
22100 'cygwin1!__argv' has unknown type; cast it to its declared type
22104 (@value{GDBP}) x 'cygwin1!__argv'
22105 'cygwin1!__argv' has unknown type; cast it to its declared type
22108 And two possible solutions:
22111 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22112 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22116 (@value{GDBP}) x/2x &'cygwin1!__argv'
22117 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22118 (@value{GDBP}) x/x 0x10021608
22119 0x10021608: 0x0022fd98
22120 (@value{GDBP}) x/s 0x0022fd98
22121 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22124 Setting a break point within a DLL is possible even before the program
22125 starts execution. However, under these circumstances, @value{GDBN} can't
22126 examine the initial instructions of the function in order to skip the
22127 function's frame set-up code. You can work around this by using ``*&''
22128 to set the breakpoint at a raw memory address:
22131 (@value{GDBP}) break *&'python22!PyOS_Readline'
22132 Breakpoint 1 at 0x1e04eff0
22135 The author of these extensions is not entirely convinced that setting a
22136 break point within a shared DLL like @file{kernel32.dll} is completely
22140 @subsection Commands Specific to @sc{gnu} Hurd Systems
22141 @cindex @sc{gnu} Hurd debugging
22143 This subsection describes @value{GDBN} commands specific to the
22144 @sc{gnu} Hurd native debugging.
22149 @kindex set signals@r{, Hurd command}
22150 @kindex set sigs@r{, Hurd command}
22151 This command toggles the state of inferior signal interception by
22152 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22153 affected by this command. @code{sigs} is a shorthand alias for
22158 @kindex show signals@r{, Hurd command}
22159 @kindex show sigs@r{, Hurd command}
22160 Show the current state of intercepting inferior's signals.
22162 @item set signal-thread
22163 @itemx set sigthread
22164 @kindex set signal-thread
22165 @kindex set sigthread
22166 This command tells @value{GDBN} which thread is the @code{libc} signal
22167 thread. That thread is run when a signal is delivered to a running
22168 process. @code{set sigthread} is the shorthand alias of @code{set
22171 @item show signal-thread
22172 @itemx show sigthread
22173 @kindex show signal-thread
22174 @kindex show sigthread
22175 These two commands show which thread will run when the inferior is
22176 delivered a signal.
22179 @kindex set stopped@r{, Hurd command}
22180 This commands tells @value{GDBN} that the inferior process is stopped,
22181 as with the @code{SIGSTOP} signal. The stopped process can be
22182 continued by delivering a signal to it.
22185 @kindex show stopped@r{, Hurd command}
22186 This command shows whether @value{GDBN} thinks the debuggee is
22189 @item set exceptions
22190 @kindex set exceptions@r{, Hurd command}
22191 Use this command to turn off trapping of exceptions in the inferior.
22192 When exception trapping is off, neither breakpoints nor
22193 single-stepping will work. To restore the default, set exception
22196 @item show exceptions
22197 @kindex show exceptions@r{, Hurd command}
22198 Show the current state of trapping exceptions in the inferior.
22200 @item set task pause
22201 @kindex set task@r{, Hurd commands}
22202 @cindex task attributes (@sc{gnu} Hurd)
22203 @cindex pause current task (@sc{gnu} Hurd)
22204 This command toggles task suspension when @value{GDBN} has control.
22205 Setting it to on takes effect immediately, and the task is suspended
22206 whenever @value{GDBN} gets control. Setting it to off will take
22207 effect the next time the inferior is continued. If this option is set
22208 to off, you can use @code{set thread default pause on} or @code{set
22209 thread pause on} (see below) to pause individual threads.
22211 @item show task pause
22212 @kindex show task@r{, Hurd commands}
22213 Show the current state of task suspension.
22215 @item set task detach-suspend-count
22216 @cindex task suspend count
22217 @cindex detach from task, @sc{gnu} Hurd
22218 This command sets the suspend count the task will be left with when
22219 @value{GDBN} detaches from it.
22221 @item show task detach-suspend-count
22222 Show the suspend count the task will be left with when detaching.
22224 @item set task exception-port
22225 @itemx set task excp
22226 @cindex task exception port, @sc{gnu} Hurd
22227 This command sets the task exception port to which @value{GDBN} will
22228 forward exceptions. The argument should be the value of the @dfn{send
22229 rights} of the task. @code{set task excp} is a shorthand alias.
22231 @item set noninvasive
22232 @cindex noninvasive task options
22233 This command switches @value{GDBN} to a mode that is the least
22234 invasive as far as interfering with the inferior is concerned. This
22235 is the same as using @code{set task pause}, @code{set exceptions}, and
22236 @code{set signals} to values opposite to the defaults.
22238 @item info send-rights
22239 @itemx info receive-rights
22240 @itemx info port-rights
22241 @itemx info port-sets
22242 @itemx info dead-names
22245 @cindex send rights, @sc{gnu} Hurd
22246 @cindex receive rights, @sc{gnu} Hurd
22247 @cindex port rights, @sc{gnu} Hurd
22248 @cindex port sets, @sc{gnu} Hurd
22249 @cindex dead names, @sc{gnu} Hurd
22250 These commands display information about, respectively, send rights,
22251 receive rights, port rights, port sets, and dead names of a task.
22252 There are also shorthand aliases: @code{info ports} for @code{info
22253 port-rights} and @code{info psets} for @code{info port-sets}.
22255 @item set thread pause
22256 @kindex set thread@r{, Hurd command}
22257 @cindex thread properties, @sc{gnu} Hurd
22258 @cindex pause current thread (@sc{gnu} Hurd)
22259 This command toggles current thread suspension when @value{GDBN} has
22260 control. Setting it to on takes effect immediately, and the current
22261 thread is suspended whenever @value{GDBN} gets control. Setting it to
22262 off will take effect the next time the inferior is continued.
22263 Normally, this command has no effect, since when @value{GDBN} has
22264 control, the whole task is suspended. However, if you used @code{set
22265 task pause off} (see above), this command comes in handy to suspend
22266 only the current thread.
22268 @item show thread pause
22269 @kindex show thread@r{, Hurd command}
22270 This command shows the state of current thread suspension.
22272 @item set thread run
22273 This command sets whether the current thread is allowed to run.
22275 @item show thread run
22276 Show whether the current thread is allowed to run.
22278 @item set thread detach-suspend-count
22279 @cindex thread suspend count, @sc{gnu} Hurd
22280 @cindex detach from thread, @sc{gnu} Hurd
22281 This command sets the suspend count @value{GDBN} will leave on a
22282 thread when detaching. This number is relative to the suspend count
22283 found by @value{GDBN} when it notices the thread; use @code{set thread
22284 takeover-suspend-count} to force it to an absolute value.
22286 @item show thread detach-suspend-count
22287 Show the suspend count @value{GDBN} will leave on the thread when
22290 @item set thread exception-port
22291 @itemx set thread excp
22292 Set the thread exception port to which to forward exceptions. This
22293 overrides the port set by @code{set task exception-port} (see above).
22294 @code{set thread excp} is the shorthand alias.
22296 @item set thread takeover-suspend-count
22297 Normally, @value{GDBN}'s thread suspend counts are relative to the
22298 value @value{GDBN} finds when it notices each thread. This command
22299 changes the suspend counts to be absolute instead.
22301 @item set thread default
22302 @itemx show thread default
22303 @cindex thread default settings, @sc{gnu} Hurd
22304 Each of the above @code{set thread} commands has a @code{set thread
22305 default} counterpart (e.g., @code{set thread default pause}, @code{set
22306 thread default exception-port}, etc.). The @code{thread default}
22307 variety of commands sets the default thread properties for all
22308 threads; you can then change the properties of individual threads with
22309 the non-default commands.
22316 @value{GDBN} provides the following commands specific to the Darwin target:
22319 @item set debug darwin @var{num}
22320 @kindex set debug darwin
22321 When set to a non zero value, enables debugging messages specific to
22322 the Darwin support. Higher values produce more verbose output.
22324 @item show debug darwin
22325 @kindex show debug darwin
22326 Show the current state of Darwin messages.
22328 @item set debug mach-o @var{num}
22329 @kindex set debug mach-o
22330 When set to a non zero value, enables debugging messages while
22331 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22332 file format used on Darwin for object and executable files.) Higher
22333 values produce more verbose output. This is a command to diagnose
22334 problems internal to @value{GDBN} and should not be needed in normal
22337 @item show debug mach-o
22338 @kindex show debug mach-o
22339 Show the current state of Mach-O file messages.
22341 @item set mach-exceptions on
22342 @itemx set mach-exceptions off
22343 @kindex set mach-exceptions
22344 On Darwin, faults are first reported as a Mach exception and are then
22345 mapped to a Posix signal. Use this command to turn on trapping of
22346 Mach exceptions in the inferior. This might be sometimes useful to
22347 better understand the cause of a fault. The default is off.
22349 @item show mach-exceptions
22350 @kindex show mach-exceptions
22351 Show the current state of exceptions trapping.
22356 @section Embedded Operating Systems
22358 This section describes configurations involving the debugging of
22359 embedded operating systems that are available for several different
22362 @value{GDBN} includes the ability to debug programs running on
22363 various real-time operating systems.
22365 @node Embedded Processors
22366 @section Embedded Processors
22368 This section goes into details specific to particular embedded
22371 @cindex send command to simulator
22372 Whenever a specific embedded processor has a simulator, @value{GDBN}
22373 allows to send an arbitrary command to the simulator.
22376 @item sim @var{command}
22377 @kindex sim@r{, a command}
22378 Send an arbitrary @var{command} string to the simulator. Consult the
22379 documentation for the specific simulator in use for information about
22380 acceptable commands.
22385 * ARC:: Synopsys ARC
22387 * M68K:: Motorola M68K
22388 * MicroBlaze:: Xilinx MicroBlaze
22389 * MIPS Embedded:: MIPS Embedded
22390 * PowerPC Embedded:: PowerPC Embedded
22393 * Super-H:: Renesas Super-H
22397 @subsection Synopsys ARC
22398 @cindex Synopsys ARC
22399 @cindex ARC specific commands
22405 @value{GDBN} provides the following ARC-specific commands:
22408 @item set debug arc
22409 @kindex set debug arc
22410 Control the level of ARC specific debug messages. Use 0 for no messages (the
22411 default), 1 for debug messages, and 2 for even more debug messages.
22413 @item show debug arc
22414 @kindex show debug arc
22415 Show the level of ARC specific debugging in operation.
22417 @item maint print arc arc-instruction @var{address}
22418 @kindex maint print arc arc-instruction
22419 Print internal disassembler information about instruction at a given address.
22426 @value{GDBN} provides the following ARM-specific commands:
22429 @item set arm disassembler
22431 This commands selects from a list of disassembly styles. The
22432 @code{"std"} style is the standard style.
22434 @item show arm disassembler
22436 Show the current disassembly style.
22438 @item set arm apcs32
22439 @cindex ARM 32-bit mode
22440 This command toggles ARM operation mode between 32-bit and 26-bit.
22442 @item show arm apcs32
22443 Display the current usage of the ARM 32-bit mode.
22445 @item set arm fpu @var{fputype}
22446 This command sets the ARM floating-point unit (FPU) type. The
22447 argument @var{fputype} can be one of these:
22451 Determine the FPU type by querying the OS ABI.
22453 Software FPU, with mixed-endian doubles on little-endian ARM
22456 GCC-compiled FPA co-processor.
22458 Software FPU with pure-endian doubles.
22464 Show the current type of the FPU.
22467 This command forces @value{GDBN} to use the specified ABI.
22470 Show the currently used ABI.
22472 @item set arm fallback-mode (arm|thumb|auto)
22473 @value{GDBN} uses the symbol table, when available, to determine
22474 whether instructions are ARM or Thumb. This command controls
22475 @value{GDBN}'s default behavior when the symbol table is not
22476 available. The default is @samp{auto}, which causes @value{GDBN} to
22477 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22480 @item show arm fallback-mode
22481 Show the current fallback instruction mode.
22483 @item set arm force-mode (arm|thumb|auto)
22484 This command overrides use of the symbol table to determine whether
22485 instructions are ARM or Thumb. The default is @samp{auto}, which
22486 causes @value{GDBN} to use the symbol table and then the setting
22487 of @samp{set arm fallback-mode}.
22489 @item show arm force-mode
22490 Show the current forced instruction mode.
22492 @item set debug arm
22493 Toggle whether to display ARM-specific debugging messages from the ARM
22494 target support subsystem.
22496 @item show debug arm
22497 Show whether ARM-specific debugging messages are enabled.
22501 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22502 The @value{GDBN} ARM simulator accepts the following optional arguments.
22505 @item --swi-support=@var{type}
22506 Tell the simulator which SWI interfaces to support. The argument
22507 @var{type} may be a comma separated list of the following values.
22508 The default value is @code{all}.
22523 The Motorola m68k configuration includes ColdFire support.
22526 @subsection MicroBlaze
22527 @cindex Xilinx MicroBlaze
22528 @cindex XMD, Xilinx Microprocessor Debugger
22530 The MicroBlaze is a soft-core processor supported on various Xilinx
22531 FPGAs, such as Spartan or Virtex series. Boards with these processors
22532 usually have JTAG ports which connect to a host system running the Xilinx
22533 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22534 This host system is used to download the configuration bitstream to
22535 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22536 communicates with the target board using the JTAG interface and
22537 presents a @code{gdbserver} interface to the board. By default
22538 @code{xmd} uses port @code{1234}. (While it is possible to change
22539 this default port, it requires the use of undocumented @code{xmd}
22540 commands. Contact Xilinx support if you need to do this.)
22542 Use these GDB commands to connect to the MicroBlaze target processor.
22545 @item target remote :1234
22546 Use this command to connect to the target if you are running @value{GDBN}
22547 on the same system as @code{xmd}.
22549 @item target remote @var{xmd-host}:1234
22550 Use this command to connect to the target if it is connected to @code{xmd}
22551 running on a different system named @var{xmd-host}.
22554 Use this command to download a program to the MicroBlaze target.
22556 @item set debug microblaze @var{n}
22557 Enable MicroBlaze-specific debugging messages if non-zero.
22559 @item show debug microblaze @var{n}
22560 Show MicroBlaze-specific debugging level.
22563 @node MIPS Embedded
22564 @subsection @acronym{MIPS} Embedded
22567 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22570 @item set mipsfpu double
22571 @itemx set mipsfpu single
22572 @itemx set mipsfpu none
22573 @itemx set mipsfpu auto
22574 @itemx show mipsfpu
22575 @kindex set mipsfpu
22576 @kindex show mipsfpu
22577 @cindex @acronym{MIPS} remote floating point
22578 @cindex floating point, @acronym{MIPS} remote
22579 If your target board does not support the @acronym{MIPS} floating point
22580 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22581 need this, you may wish to put the command in your @value{GDBN} init
22582 file). This tells @value{GDBN} how to find the return value of
22583 functions which return floating point values. It also allows
22584 @value{GDBN} to avoid saving the floating point registers when calling
22585 functions on the board. If you are using a floating point coprocessor
22586 with only single precision floating point support, as on the @sc{r4650}
22587 processor, use the command @samp{set mipsfpu single}. The default
22588 double precision floating point coprocessor may be selected using
22589 @samp{set mipsfpu double}.
22591 In previous versions the only choices were double precision or no
22592 floating point, so @samp{set mipsfpu on} will select double precision
22593 and @samp{set mipsfpu off} will select no floating point.
22595 As usual, you can inquire about the @code{mipsfpu} variable with
22596 @samp{show mipsfpu}.
22599 @node PowerPC Embedded
22600 @subsection PowerPC Embedded
22602 @cindex DVC register
22603 @value{GDBN} supports using the DVC (Data Value Compare) register to
22604 implement in hardware simple hardware watchpoint conditions of the form:
22607 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22608 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22611 The DVC register will be automatically used when @value{GDBN} detects
22612 such pattern in a condition expression, and the created watchpoint uses one
22613 debug register (either the @code{exact-watchpoints} option is on and the
22614 variable is scalar, or the variable has a length of one byte). This feature
22615 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22618 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22619 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22620 in which case watchpoints using only one debug register are created when
22621 watching variables of scalar types.
22623 You can create an artificial array to watch an arbitrary memory
22624 region using one of the following commands (@pxref{Expressions}):
22627 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22628 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22631 PowerPC embedded processors support masked watchpoints. See the discussion
22632 about the @code{mask} argument in @ref{Set Watchpoints}.
22634 @cindex ranged breakpoint
22635 PowerPC embedded processors support hardware accelerated
22636 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22637 the inferior whenever it executes an instruction at any address within
22638 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22639 use the @code{break-range} command.
22641 @value{GDBN} provides the following PowerPC-specific commands:
22644 @kindex break-range
22645 @item break-range @var{start-location}, @var{end-location}
22646 Set a breakpoint for an address range given by
22647 @var{start-location} and @var{end-location}, which can specify a function name,
22648 a line number, an offset of lines from the current line or from the start
22649 location, or an address of an instruction (see @ref{Specify Location},
22650 for a list of all the possible ways to specify a @var{location}.)
22651 The breakpoint will stop execution of the inferior whenever it
22652 executes an instruction at any address within the specified range,
22653 (including @var{start-location} and @var{end-location}.)
22655 @kindex set powerpc
22656 @item set powerpc soft-float
22657 @itemx show powerpc soft-float
22658 Force @value{GDBN} to use (or not use) a software floating point calling
22659 convention. By default, @value{GDBN} selects the calling convention based
22660 on the selected architecture and the provided executable file.
22662 @item set powerpc vector-abi
22663 @itemx show powerpc vector-abi
22664 Force @value{GDBN} to use the specified calling convention for vector
22665 arguments and return values. The valid options are @samp{auto};
22666 @samp{generic}, to avoid vector registers even if they are present;
22667 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22668 registers. By default, @value{GDBN} selects the calling convention
22669 based on the selected architecture and the provided executable file.
22671 @item set powerpc exact-watchpoints
22672 @itemx show powerpc exact-watchpoints
22673 Allow @value{GDBN} to use only one debug register when watching a variable
22674 of scalar type, thus assuming that the variable is accessed through the
22675 address of its first byte.
22680 @subsection Atmel AVR
22683 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22684 following AVR-specific commands:
22687 @item info io_registers
22688 @kindex info io_registers@r{, AVR}
22689 @cindex I/O registers (Atmel AVR)
22690 This command displays information about the AVR I/O registers. For
22691 each register, @value{GDBN} prints its number and value.
22698 When configured for debugging CRIS, @value{GDBN} provides the
22699 following CRIS-specific commands:
22702 @item set cris-version @var{ver}
22703 @cindex CRIS version
22704 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22705 The CRIS version affects register names and sizes. This command is useful in
22706 case autodetection of the CRIS version fails.
22708 @item show cris-version
22709 Show the current CRIS version.
22711 @item set cris-dwarf2-cfi
22712 @cindex DWARF-2 CFI and CRIS
22713 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22714 Change to @samp{off} when using @code{gcc-cris} whose version is below
22717 @item show cris-dwarf2-cfi
22718 Show the current state of using DWARF-2 CFI.
22720 @item set cris-mode @var{mode}
22722 Set the current CRIS mode to @var{mode}. It should only be changed when
22723 debugging in guru mode, in which case it should be set to
22724 @samp{guru} (the default is @samp{normal}).
22726 @item show cris-mode
22727 Show the current CRIS mode.
22731 @subsection Renesas Super-H
22734 For the Renesas Super-H processor, @value{GDBN} provides these
22738 @item set sh calling-convention @var{convention}
22739 @kindex set sh calling-convention
22740 Set the calling-convention used when calling functions from @value{GDBN}.
22741 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22742 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22743 convention. If the DWARF-2 information of the called function specifies
22744 that the function follows the Renesas calling convention, the function
22745 is called using the Renesas calling convention. If the calling convention
22746 is set to @samp{renesas}, the Renesas calling convention is always used,
22747 regardless of the DWARF-2 information. This can be used to override the
22748 default of @samp{gcc} if debug information is missing, or the compiler
22749 does not emit the DWARF-2 calling convention entry for a function.
22751 @item show sh calling-convention
22752 @kindex show sh calling-convention
22753 Show the current calling convention setting.
22758 @node Architectures
22759 @section Architectures
22761 This section describes characteristics of architectures that affect
22762 all uses of @value{GDBN} with the architecture, both native and cross.
22769 * HPPA:: HP PA architecture
22770 * SPU:: Cell Broadband Engine SPU architecture
22777 @subsection AArch64
22778 @cindex AArch64 support
22780 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22781 following special commands:
22784 @item set debug aarch64
22785 @kindex set debug aarch64
22786 This command determines whether AArch64 architecture-specific debugging
22787 messages are to be displayed.
22789 @item show debug aarch64
22790 Show whether AArch64 debugging messages are displayed.
22795 @subsection x86 Architecture-specific Issues
22798 @item set struct-convention @var{mode}
22799 @kindex set struct-convention
22800 @cindex struct return convention
22801 @cindex struct/union returned in registers
22802 Set the convention used by the inferior to return @code{struct}s and
22803 @code{union}s from functions to @var{mode}. Possible values of
22804 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22805 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22806 are returned on the stack, while @code{"reg"} means that a
22807 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22808 be returned in a register.
22810 @item show struct-convention
22811 @kindex show struct-convention
22812 Show the current setting of the convention to return @code{struct}s
22817 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22818 @cindex Intel Memory Protection Extensions (MPX).
22820 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22821 @footnote{The register named with capital letters represent the architecture
22822 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22823 which are the lower bound and upper bound. Bounds are effective addresses or
22824 memory locations. The upper bounds are architecturally represented in 1's
22825 complement form. A bound having lower bound = 0, and upper bound = 0
22826 (1's complement of all bits set) will allow access to the entire address space.
22828 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22829 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22830 display the upper bound performing the complement of one operation on the
22831 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22832 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22833 can also be noted that the upper bounds are inclusive.
22835 As an example, assume that the register BND0 holds bounds for a pointer having
22836 access allowed for the range between 0x32 and 0x71. The values present on
22837 bnd0raw and bnd registers are presented as follows:
22840 bnd0raw = @{0x32, 0xffffffff8e@}
22841 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22844 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22845 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22846 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22847 Python, the display includes the memory size, in bits, accessible to
22850 Bounds can also be stored in bounds tables, which are stored in
22851 application memory. These tables store bounds for pointers by specifying
22852 the bounds pointer's value along with its bounds. Evaluating and changing
22853 bounds located in bound tables is therefore interesting while investigating
22854 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22857 @item show mpx bound @var{pointer}
22858 @kindex show mpx bound
22859 Display bounds of the given @var{pointer}.
22861 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22862 @kindex set mpx bound
22863 Set the bounds of a pointer in the bound table.
22864 This command takes three parameters: @var{pointer} is the pointers
22865 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22866 for lower and upper bounds respectively.
22869 When you call an inferior function on an Intel MPX enabled program,
22870 GDB sets the inferior's bound registers to the init (disabled) state
22871 before calling the function. As a consequence, bounds checks for the
22872 pointer arguments passed to the function will always pass.
22874 This is necessary because when you call an inferior function, the
22875 program is usually in the middle of the execution of other function.
22876 Since at that point bound registers are in an arbitrary state, not
22877 clearing them would lead to random bound violations in the called
22880 You can still examine the influence of the bound registers on the
22881 execution of the called function by stopping the execution of the
22882 called function at its prologue, setting bound registers, and
22883 continuing the execution. For example:
22887 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
22888 $ print upper (a, b, c, d, 1)
22889 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
22891 @{lbound = 0x0, ubound = ffffffff@} : size -1
22894 At this last step the value of bnd0 can be changed for investigation of bound
22895 violations caused along the execution of the call. In order to know how to
22896 set the bound registers or bound table for the call consult the ABI.
22901 See the following section.
22904 @subsection @acronym{MIPS}
22906 @cindex stack on Alpha
22907 @cindex stack on @acronym{MIPS}
22908 @cindex Alpha stack
22909 @cindex @acronym{MIPS} stack
22910 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22911 sometimes requires @value{GDBN} to search backward in the object code to
22912 find the beginning of a function.
22914 @cindex response time, @acronym{MIPS} debugging
22915 To improve response time (especially for embedded applications, where
22916 @value{GDBN} may be restricted to a slow serial line for this search)
22917 you may want to limit the size of this search, using one of these
22921 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22922 @item set heuristic-fence-post @var{limit}
22923 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22924 search for the beginning of a function. A value of @var{0} (the
22925 default) means there is no limit. However, except for @var{0}, the
22926 larger the limit the more bytes @code{heuristic-fence-post} must search
22927 and therefore the longer it takes to run. You should only need to use
22928 this command when debugging a stripped executable.
22930 @item show heuristic-fence-post
22931 Display the current limit.
22935 These commands are available @emph{only} when @value{GDBN} is configured
22936 for debugging programs on Alpha or @acronym{MIPS} processors.
22938 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22942 @item set mips abi @var{arg}
22943 @kindex set mips abi
22944 @cindex set ABI for @acronym{MIPS}
22945 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22946 values of @var{arg} are:
22950 The default ABI associated with the current binary (this is the
22960 @item show mips abi
22961 @kindex show mips abi
22962 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22964 @item set mips compression @var{arg}
22965 @kindex set mips compression
22966 @cindex code compression, @acronym{MIPS}
22967 Tell @value{GDBN} which @acronym{MIPS} compressed
22968 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22969 inferior. @value{GDBN} uses this for code disassembly and other
22970 internal interpretation purposes. This setting is only referred to
22971 when no executable has been associated with the debugging session or
22972 the executable does not provide information about the encoding it uses.
22973 Otherwise this setting is automatically updated from information
22974 provided by the executable.
22976 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22977 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22978 executables containing @acronym{MIPS16} code frequently are not
22979 identified as such.
22981 This setting is ``sticky''; that is, it retains its value across
22982 debugging sessions until reset either explicitly with this command or
22983 implicitly from an executable.
22985 The compiler and/or assembler typically add symbol table annotations to
22986 identify functions compiled for the @acronym{MIPS16} or
22987 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22988 are present, @value{GDBN} uses them in preference to the global
22989 compressed @acronym{ISA} encoding setting.
22991 @item show mips compression
22992 @kindex show mips compression
22993 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22994 @value{GDBN} to debug the inferior.
22997 @itemx show mipsfpu
22998 @xref{MIPS Embedded, set mipsfpu}.
23000 @item set mips mask-address @var{arg}
23001 @kindex set mips mask-address
23002 @cindex @acronym{MIPS} addresses, masking
23003 This command determines whether the most-significant 32 bits of 64-bit
23004 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23005 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23006 setting, which lets @value{GDBN} determine the correct value.
23008 @item show mips mask-address
23009 @kindex show mips mask-address
23010 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23013 @item set remote-mips64-transfers-32bit-regs
23014 @kindex set remote-mips64-transfers-32bit-regs
23015 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23016 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23017 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23018 and 64 bits for other registers, set this option to @samp{on}.
23020 @item show remote-mips64-transfers-32bit-regs
23021 @kindex show remote-mips64-transfers-32bit-regs
23022 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23024 @item set debug mips
23025 @kindex set debug mips
23026 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23027 target code in @value{GDBN}.
23029 @item show debug mips
23030 @kindex show debug mips
23031 Show the current setting of @acronym{MIPS} debugging messages.
23037 @cindex HPPA support
23039 When @value{GDBN} is debugging the HP PA architecture, it provides the
23040 following special commands:
23043 @item set debug hppa
23044 @kindex set debug hppa
23045 This command determines whether HPPA architecture-specific debugging
23046 messages are to be displayed.
23048 @item show debug hppa
23049 Show whether HPPA debugging messages are displayed.
23051 @item maint print unwind @var{address}
23052 @kindex maint print unwind@r{, HPPA}
23053 This command displays the contents of the unwind table entry at the
23054 given @var{address}.
23060 @subsection Cell Broadband Engine SPU architecture
23061 @cindex Cell Broadband Engine
23064 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23065 it provides the following special commands:
23068 @item info spu event
23070 Display SPU event facility status. Shows current event mask
23071 and pending event status.
23073 @item info spu signal
23074 Display SPU signal notification facility status. Shows pending
23075 signal-control word and signal notification mode of both signal
23076 notification channels.
23078 @item info spu mailbox
23079 Display SPU mailbox facility status. Shows all pending entries,
23080 in order of processing, in each of the SPU Write Outbound,
23081 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23084 Display MFC DMA status. Shows all pending commands in the MFC
23085 DMA queue. For each entry, opcode, tag, class IDs, effective
23086 and local store addresses and transfer size are shown.
23088 @item info spu proxydma
23089 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23090 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23091 and local store addresses and transfer size are shown.
23095 When @value{GDBN} is debugging a combined PowerPC/SPU application
23096 on the Cell Broadband Engine, it provides in addition the following
23100 @item set spu stop-on-load @var{arg}
23102 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23103 will give control to the user when a new SPE thread enters its @code{main}
23104 function. The default is @code{off}.
23106 @item show spu stop-on-load
23108 Show whether to stop for new SPE threads.
23110 @item set spu auto-flush-cache @var{arg}
23111 Set whether to automatically flush the software-managed cache. When set to
23112 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23113 cache to be flushed whenever SPE execution stops. This provides a consistent
23114 view of PowerPC memory that is accessed via the cache. If an application
23115 does not use the software-managed cache, this option has no effect.
23117 @item show spu auto-flush-cache
23118 Show whether to automatically flush the software-managed cache.
23123 @subsection PowerPC
23124 @cindex PowerPC architecture
23126 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23127 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23128 numbers stored in the floating point registers. These values must be stored
23129 in two consecutive registers, always starting at an even register like
23130 @code{f0} or @code{f2}.
23132 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23133 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23134 @code{f2} and @code{f3} for @code{$dl1} and so on.
23136 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23137 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23140 @subsection Nios II
23141 @cindex Nios II architecture
23143 When @value{GDBN} is debugging the Nios II architecture,
23144 it provides the following special commands:
23148 @item set debug nios2
23149 @kindex set debug nios2
23150 This command turns on and off debugging messages for the Nios II
23151 target code in @value{GDBN}.
23153 @item show debug nios2
23154 @kindex show debug nios2
23155 Show the current setting of Nios II debugging messages.
23159 @subsection Sparc64
23160 @cindex Sparc64 support
23161 @cindex Application Data Integrity
23162 @subsubsection ADI Support
23164 The M7 processor supports an Application Data Integrity (ADI) feature that
23165 detects invalid data accesses. When software allocates memory and enables
23166 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23167 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23168 the 4-bit version in every cacheline of that data. Hardware saves the latter
23169 in spare bits in the cache and memory hierarchy. On each load and store,
23170 the processor compares the upper 4 VA (virtual address) bits to the
23171 cacheline's version. If there is a mismatch, the processor generates a
23172 version mismatch trap which can be either precise or disrupting. The trap
23173 is an error condition which the kernel delivers to the process as a SIGSEGV
23176 Note that only 64-bit applications can use ADI and need to be built with
23179 Values of the ADI version tags, which are in granularity of a
23180 cacheline (64 bytes), can be viewed or modified.
23184 @kindex adi examine
23185 @item adi (examine | x) [ / @var{n} ] @var{addr}
23187 The @code{adi examine} command displays the value of one ADI version tag per
23190 @var{n} is a decimal integer specifying the number in bytes; the default
23191 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23192 block size, to display.
23194 @var{addr} is the address in user address space where you want @value{GDBN}
23195 to begin displaying the ADI version tags.
23197 Below is an example of displaying ADI versions of variable "shmaddr".
23200 (@value{GDBP}) adi x/100 shmaddr
23201 0xfff800010002c000: 0 0
23205 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23207 The @code{adi assign} command is used to assign new ADI version tag
23210 @var{n} is a decimal integer specifying the number in bytes;
23211 the default is 1. It specifies how much ADI version information, at the
23212 ratio of 1:ADI block size, to modify.
23214 @var{addr} is the address in user address space where you want @value{GDBN}
23215 to begin modifying the ADI version tags.
23217 @var{tag} is the new ADI version tag.
23219 For example, do the following to modify then verify ADI versions of
23220 variable "shmaddr":
23223 (@value{GDBP}) adi a/100 shmaddr = 7
23224 (@value{GDBP}) adi x/100 shmaddr
23225 0xfff800010002c000: 7 7
23230 @node Controlling GDB
23231 @chapter Controlling @value{GDBN}
23233 You can alter the way @value{GDBN} interacts with you by using the
23234 @code{set} command. For commands controlling how @value{GDBN} displays
23235 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23240 * Editing:: Command editing
23241 * Command History:: Command history
23242 * Screen Size:: Screen size
23243 * Numbers:: Numbers
23244 * ABI:: Configuring the current ABI
23245 * Auto-loading:: Automatically loading associated files
23246 * Messages/Warnings:: Optional warnings and messages
23247 * Debugging Output:: Optional messages about internal happenings
23248 * Other Misc Settings:: Other Miscellaneous Settings
23256 @value{GDBN} indicates its readiness to read a command by printing a string
23257 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23258 can change the prompt string with the @code{set prompt} command. For
23259 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23260 the prompt in one of the @value{GDBN} sessions so that you can always tell
23261 which one you are talking to.
23263 @emph{Note:} @code{set prompt} does not add a space for you after the
23264 prompt you set. This allows you to set a prompt which ends in a space
23265 or a prompt that does not.
23269 @item set prompt @var{newprompt}
23270 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23272 @kindex show prompt
23274 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23277 Versions of @value{GDBN} that ship with Python scripting enabled have
23278 prompt extensions. The commands for interacting with these extensions
23282 @kindex set extended-prompt
23283 @item set extended-prompt @var{prompt}
23284 Set an extended prompt that allows for substitutions.
23285 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23286 substitution. Any escape sequences specified as part of the prompt
23287 string are replaced with the corresponding strings each time the prompt
23293 set extended-prompt Current working directory: \w (gdb)
23296 Note that when an extended-prompt is set, it takes control of the
23297 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23299 @kindex show extended-prompt
23300 @item show extended-prompt
23301 Prints the extended prompt. Any escape sequences specified as part of
23302 the prompt string with @code{set extended-prompt}, are replaced with the
23303 corresponding strings each time the prompt is displayed.
23307 @section Command Editing
23309 @cindex command line editing
23311 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23312 @sc{gnu} library provides consistent behavior for programs which provide a
23313 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23314 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23315 substitution, and a storage and recall of command history across
23316 debugging sessions.
23318 You may control the behavior of command line editing in @value{GDBN} with the
23319 command @code{set}.
23322 @kindex set editing
23325 @itemx set editing on
23326 Enable command line editing (enabled by default).
23328 @item set editing off
23329 Disable command line editing.
23331 @kindex show editing
23333 Show whether command line editing is enabled.
23336 @ifset SYSTEM_READLINE
23337 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23339 @ifclear SYSTEM_READLINE
23340 @xref{Command Line Editing},
23342 for more details about the Readline
23343 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23344 encouraged to read that chapter.
23346 @node Command History
23347 @section Command History
23348 @cindex command history
23350 @value{GDBN} can keep track of the commands you type during your
23351 debugging sessions, so that you can be certain of precisely what
23352 happened. Use these commands to manage the @value{GDBN} command
23355 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23356 package, to provide the history facility.
23357 @ifset SYSTEM_READLINE
23358 @xref{Using History Interactively, , , history, GNU History Library},
23360 @ifclear SYSTEM_READLINE
23361 @xref{Using History Interactively},
23363 for the detailed description of the History library.
23365 To issue a command to @value{GDBN} without affecting certain aspects of
23366 the state which is seen by users, prefix it with @samp{server }
23367 (@pxref{Server Prefix}). This
23368 means that this command will not affect the command history, nor will it
23369 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23370 pressed on a line by itself.
23372 @cindex @code{server}, command prefix
23373 The server prefix does not affect the recording of values into the value
23374 history; to print a value without recording it into the value history,
23375 use the @code{output} command instead of the @code{print} command.
23377 Here is the description of @value{GDBN} commands related to command
23381 @cindex history substitution
23382 @cindex history file
23383 @kindex set history filename
23384 @cindex @env{GDBHISTFILE}, environment variable
23385 @item set history filename @var{fname}
23386 Set the name of the @value{GDBN} command history file to @var{fname}.
23387 This is the file where @value{GDBN} reads an initial command history
23388 list, and where it writes the command history from this session when it
23389 exits. You can access this list through history expansion or through
23390 the history command editing characters listed below. This file defaults
23391 to the value of the environment variable @code{GDBHISTFILE}, or to
23392 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23395 @cindex save command history
23396 @kindex set history save
23397 @item set history save
23398 @itemx set history save on
23399 Record command history in a file, whose name may be specified with the
23400 @code{set history filename} command. By default, this option is disabled.
23402 @item set history save off
23403 Stop recording command history in a file.
23405 @cindex history size
23406 @kindex set history size
23407 @cindex @env{GDBHISTSIZE}, environment variable
23408 @item set history size @var{size}
23409 @itemx set history size unlimited
23410 Set the number of commands which @value{GDBN} keeps in its history list.
23411 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23412 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23413 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23414 either a negative number or the empty string, then the number of commands
23415 @value{GDBN} keeps in the history list is unlimited.
23417 @cindex remove duplicate history
23418 @kindex set history remove-duplicates
23419 @item set history remove-duplicates @var{count}
23420 @itemx set history remove-duplicates unlimited
23421 Control the removal of duplicate history entries in the command history list.
23422 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23423 history entries and remove the first entry that is a duplicate of the current
23424 entry being added to the command history list. If @var{count} is
23425 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23426 removal of duplicate history entries is disabled.
23428 Only history entries added during the current session are considered for
23429 removal. This option is set to 0 by default.
23433 History expansion assigns special meaning to the character @kbd{!}.
23434 @ifset SYSTEM_READLINE
23435 @xref{Event Designators, , , history, GNU History Library},
23437 @ifclear SYSTEM_READLINE
23438 @xref{Event Designators},
23442 @cindex history expansion, turn on/off
23443 Since @kbd{!} is also the logical not operator in C, history expansion
23444 is off by default. If you decide to enable history expansion with the
23445 @code{set history expansion on} command, you may sometimes need to
23446 follow @kbd{!} (when it is used as logical not, in an expression) with
23447 a space or a tab to prevent it from being expanded. The readline
23448 history facilities do not attempt substitution on the strings
23449 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23451 The commands to control history expansion are:
23454 @item set history expansion on
23455 @itemx set history expansion
23456 @kindex set history expansion
23457 Enable history expansion. History expansion is off by default.
23459 @item set history expansion off
23460 Disable history expansion.
23463 @kindex show history
23465 @itemx show history filename
23466 @itemx show history save
23467 @itemx show history size
23468 @itemx show history expansion
23469 These commands display the state of the @value{GDBN} history parameters.
23470 @code{show history} by itself displays all four states.
23475 @kindex show commands
23476 @cindex show last commands
23477 @cindex display command history
23478 @item show commands
23479 Display the last ten commands in the command history.
23481 @item show commands @var{n}
23482 Print ten commands centered on command number @var{n}.
23484 @item show commands +
23485 Print ten commands just after the commands last printed.
23489 @section Screen Size
23490 @cindex size of screen
23491 @cindex screen size
23494 @cindex pauses in output
23496 Certain commands to @value{GDBN} may produce large amounts of
23497 information output to the screen. To help you read all of it,
23498 @value{GDBN} pauses and asks you for input at the end of each page of
23499 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23500 to discard the remaining output. Also, the screen width setting
23501 determines when to wrap lines of output. Depending on what is being
23502 printed, @value{GDBN} tries to break the line at a readable place,
23503 rather than simply letting it overflow onto the following line.
23505 Normally @value{GDBN} knows the size of the screen from the terminal
23506 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23507 together with the value of the @code{TERM} environment variable and the
23508 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23509 you can override it with the @code{set height} and @code{set
23516 @kindex show height
23517 @item set height @var{lpp}
23518 @itemx set height unlimited
23520 @itemx set width @var{cpl}
23521 @itemx set width unlimited
23523 These @code{set} commands specify a screen height of @var{lpp} lines and
23524 a screen width of @var{cpl} characters. The associated @code{show}
23525 commands display the current settings.
23527 If you specify a height of either @code{unlimited} or zero lines,
23528 @value{GDBN} does not pause during output no matter how long the
23529 output is. This is useful if output is to a file or to an editor
23532 Likewise, you can specify @samp{set width unlimited} or @samp{set
23533 width 0} to prevent @value{GDBN} from wrapping its output.
23535 @item set pagination on
23536 @itemx set pagination off
23537 @kindex set pagination
23538 Turn the output pagination on or off; the default is on. Turning
23539 pagination off is the alternative to @code{set height unlimited}. Note that
23540 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23541 Options, -batch}) also automatically disables pagination.
23543 @item show pagination
23544 @kindex show pagination
23545 Show the current pagination mode.
23550 @cindex number representation
23551 @cindex entering numbers
23553 You can always enter numbers in octal, decimal, or hexadecimal in
23554 @value{GDBN} by the usual conventions: octal numbers begin with
23555 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23556 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23557 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23558 10; likewise, the default display for numbers---when no particular
23559 format is specified---is base 10. You can change the default base for
23560 both input and output with the commands described below.
23563 @kindex set input-radix
23564 @item set input-radix @var{base}
23565 Set the default base for numeric input. Supported choices
23566 for @var{base} are decimal 8, 10, or 16. The base must itself be
23567 specified either unambiguously or using the current input radix; for
23571 set input-radix 012
23572 set input-radix 10.
23573 set input-radix 0xa
23577 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23578 leaves the input radix unchanged, no matter what it was, since
23579 @samp{10}, being without any leading or trailing signs of its base, is
23580 interpreted in the current radix. Thus, if the current radix is 16,
23581 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23584 @kindex set output-radix
23585 @item set output-radix @var{base}
23586 Set the default base for numeric display. Supported choices
23587 for @var{base} are decimal 8, 10, or 16. The base must itself be
23588 specified either unambiguously or using the current input radix.
23590 @kindex show input-radix
23591 @item show input-radix
23592 Display the current default base for numeric input.
23594 @kindex show output-radix
23595 @item show output-radix
23596 Display the current default base for numeric display.
23598 @item set radix @r{[}@var{base}@r{]}
23602 These commands set and show the default base for both input and output
23603 of numbers. @code{set radix} sets the radix of input and output to
23604 the same base; without an argument, it resets the radix back to its
23605 default value of 10.
23610 @section Configuring the Current ABI
23612 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23613 application automatically. However, sometimes you need to override its
23614 conclusions. Use these commands to manage @value{GDBN}'s view of the
23620 @cindex Newlib OS ABI and its influence on the longjmp handling
23622 One @value{GDBN} configuration can debug binaries for multiple operating
23623 system targets, either via remote debugging or native emulation.
23624 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23625 but you can override its conclusion using the @code{set osabi} command.
23626 One example where this is useful is in debugging of binaries which use
23627 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23628 not have the same identifying marks that the standard C library for your
23631 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23632 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23633 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23634 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23638 Show the OS ABI currently in use.
23641 With no argument, show the list of registered available OS ABI's.
23643 @item set osabi @var{abi}
23644 Set the current OS ABI to @var{abi}.
23647 @cindex float promotion
23649 Generally, the way that an argument of type @code{float} is passed to a
23650 function depends on whether the function is prototyped. For a prototyped
23651 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23652 according to the architecture's convention for @code{float}. For unprototyped
23653 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23654 @code{double} and then passed.
23656 Unfortunately, some forms of debug information do not reliably indicate whether
23657 a function is prototyped. If @value{GDBN} calls a function that is not marked
23658 as prototyped, it consults @kbd{set coerce-float-to-double}.
23661 @kindex set coerce-float-to-double
23662 @item set coerce-float-to-double
23663 @itemx set coerce-float-to-double on
23664 Arguments of type @code{float} will be promoted to @code{double} when passed
23665 to an unprototyped function. This is the default setting.
23667 @item set coerce-float-to-double off
23668 Arguments of type @code{float} will be passed directly to unprototyped
23671 @kindex show coerce-float-to-double
23672 @item show coerce-float-to-double
23673 Show the current setting of promoting @code{float} to @code{double}.
23677 @kindex show cp-abi
23678 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23679 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23680 used to build your application. @value{GDBN} only fully supports
23681 programs with a single C@t{++} ABI; if your program contains code using
23682 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23683 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23684 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23685 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23686 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23687 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23692 Show the C@t{++} ABI currently in use.
23695 With no argument, show the list of supported C@t{++} ABI's.
23697 @item set cp-abi @var{abi}
23698 @itemx set cp-abi auto
23699 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23703 @section Automatically loading associated files
23704 @cindex auto-loading
23706 @value{GDBN} sometimes reads files with commands and settings automatically,
23707 without being explicitly told so by the user. We call this feature
23708 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23709 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23710 results or introduce security risks (e.g., if the file comes from untrusted
23714 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23715 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23717 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23718 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23721 There are various kinds of files @value{GDBN} can automatically load.
23722 In addition to these files, @value{GDBN} supports auto-loading code written
23723 in various extension languages. @xref{Auto-loading extensions}.
23725 Note that loading of these associated files (including the local @file{.gdbinit}
23726 file) requires accordingly configured @code{auto-load safe-path}
23727 (@pxref{Auto-loading safe path}).
23729 For these reasons, @value{GDBN} includes commands and options to let you
23730 control when to auto-load files and which files should be auto-loaded.
23733 @anchor{set auto-load off}
23734 @kindex set auto-load off
23735 @item set auto-load off
23736 Globally disable loading of all auto-loaded files.
23737 You may want to use this command with the @samp{-iex} option
23738 (@pxref{Option -init-eval-command}) such as:
23740 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23743 Be aware that system init file (@pxref{System-wide configuration})
23744 and init files from your home directory (@pxref{Home Directory Init File})
23745 still get read (as they come from generally trusted directories).
23746 To prevent @value{GDBN} from auto-loading even those init files, use the
23747 @option{-nx} option (@pxref{Mode Options}), in addition to
23748 @code{set auto-load no}.
23750 @anchor{show auto-load}
23751 @kindex show auto-load
23752 @item show auto-load
23753 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23757 (gdb) show auto-load
23758 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23759 libthread-db: Auto-loading of inferior specific libthread_db is on.
23760 local-gdbinit: Auto-loading of .gdbinit script from current directory
23762 python-scripts: Auto-loading of Python scripts is on.
23763 safe-path: List of directories from which it is safe to auto-load files
23764 is $debugdir:$datadir/auto-load.
23765 scripts-directory: List of directories from which to load auto-loaded scripts
23766 is $debugdir:$datadir/auto-load.
23769 @anchor{info auto-load}
23770 @kindex info auto-load
23771 @item info auto-load
23772 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23776 (gdb) info auto-load
23779 Yes /home/user/gdb/gdb-gdb.gdb
23780 libthread-db: No auto-loaded libthread-db.
23781 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23785 Yes /home/user/gdb/gdb-gdb.py
23789 These are @value{GDBN} control commands for the auto-loading:
23791 @multitable @columnfractions .5 .5
23792 @item @xref{set auto-load off}.
23793 @tab Disable auto-loading globally.
23794 @item @xref{show auto-load}.
23795 @tab Show setting of all kinds of files.
23796 @item @xref{info auto-load}.
23797 @tab Show state of all kinds of files.
23798 @item @xref{set auto-load gdb-scripts}.
23799 @tab Control for @value{GDBN} command scripts.
23800 @item @xref{show auto-load gdb-scripts}.
23801 @tab Show setting of @value{GDBN} command scripts.
23802 @item @xref{info auto-load gdb-scripts}.
23803 @tab Show state of @value{GDBN} command scripts.
23804 @item @xref{set auto-load python-scripts}.
23805 @tab Control for @value{GDBN} Python scripts.
23806 @item @xref{show auto-load python-scripts}.
23807 @tab Show setting of @value{GDBN} Python scripts.
23808 @item @xref{info auto-load python-scripts}.
23809 @tab Show state of @value{GDBN} Python scripts.
23810 @item @xref{set auto-load guile-scripts}.
23811 @tab Control for @value{GDBN} Guile scripts.
23812 @item @xref{show auto-load guile-scripts}.
23813 @tab Show setting of @value{GDBN} Guile scripts.
23814 @item @xref{info auto-load guile-scripts}.
23815 @tab Show state of @value{GDBN} Guile scripts.
23816 @item @xref{set auto-load scripts-directory}.
23817 @tab Control for @value{GDBN} auto-loaded scripts location.
23818 @item @xref{show auto-load scripts-directory}.
23819 @tab Show @value{GDBN} auto-loaded scripts location.
23820 @item @xref{add-auto-load-scripts-directory}.
23821 @tab Add directory for auto-loaded scripts location list.
23822 @item @xref{set auto-load local-gdbinit}.
23823 @tab Control for init file in the current directory.
23824 @item @xref{show auto-load local-gdbinit}.
23825 @tab Show setting of init file in the current directory.
23826 @item @xref{info auto-load local-gdbinit}.
23827 @tab Show state of init file in the current directory.
23828 @item @xref{set auto-load libthread-db}.
23829 @tab Control for thread debugging library.
23830 @item @xref{show auto-load libthread-db}.
23831 @tab Show setting of thread debugging library.
23832 @item @xref{info auto-load libthread-db}.
23833 @tab Show state of thread debugging library.
23834 @item @xref{set auto-load safe-path}.
23835 @tab Control directories trusted for automatic loading.
23836 @item @xref{show auto-load safe-path}.
23837 @tab Show directories trusted for automatic loading.
23838 @item @xref{add-auto-load-safe-path}.
23839 @tab Add directory trusted for automatic loading.
23842 @node Init File in the Current Directory
23843 @subsection Automatically loading init file in the current directory
23844 @cindex auto-loading init file in the current directory
23846 By default, @value{GDBN} reads and executes the canned sequences of commands
23847 from init file (if any) in the current working directory,
23848 see @ref{Init File in the Current Directory during Startup}.
23850 Note that loading of this local @file{.gdbinit} file also requires accordingly
23851 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23854 @anchor{set auto-load local-gdbinit}
23855 @kindex set auto-load local-gdbinit
23856 @item set auto-load local-gdbinit [on|off]
23857 Enable or disable the auto-loading of canned sequences of commands
23858 (@pxref{Sequences}) found in init file in the current directory.
23860 @anchor{show auto-load local-gdbinit}
23861 @kindex show auto-load local-gdbinit
23862 @item show auto-load local-gdbinit
23863 Show whether auto-loading of canned sequences of commands from init file in the
23864 current directory is enabled or disabled.
23866 @anchor{info auto-load local-gdbinit}
23867 @kindex info auto-load local-gdbinit
23868 @item info auto-load local-gdbinit
23869 Print whether canned sequences of commands from init file in the
23870 current directory have been auto-loaded.
23873 @node libthread_db.so.1 file
23874 @subsection Automatically loading thread debugging library
23875 @cindex auto-loading libthread_db.so.1
23877 This feature is currently present only on @sc{gnu}/Linux native hosts.
23879 @value{GDBN} reads in some cases thread debugging library from places specific
23880 to the inferior (@pxref{set libthread-db-search-path}).
23882 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23883 without checking this @samp{set auto-load libthread-db} switch as system
23884 libraries have to be trusted in general. In all other cases of
23885 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23886 auto-load libthread-db} is enabled before trying to open such thread debugging
23889 Note that loading of this debugging library also requires accordingly configured
23890 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23893 @anchor{set auto-load libthread-db}
23894 @kindex set auto-load libthread-db
23895 @item set auto-load libthread-db [on|off]
23896 Enable or disable the auto-loading of inferior specific thread debugging library.
23898 @anchor{show auto-load libthread-db}
23899 @kindex show auto-load libthread-db
23900 @item show auto-load libthread-db
23901 Show whether auto-loading of inferior specific thread debugging library is
23902 enabled or disabled.
23904 @anchor{info auto-load libthread-db}
23905 @kindex info auto-load libthread-db
23906 @item info auto-load libthread-db
23907 Print the list of all loaded inferior specific thread debugging libraries and
23908 for each such library print list of inferior @var{pid}s using it.
23911 @node Auto-loading safe path
23912 @subsection Security restriction for auto-loading
23913 @cindex auto-loading safe-path
23915 As the files of inferior can come from untrusted source (such as submitted by
23916 an application user) @value{GDBN} does not always load any files automatically.
23917 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23918 directories trusted for loading files not explicitly requested by user.
23919 Each directory can also be a shell wildcard pattern.
23921 If the path is not set properly you will see a warning and the file will not
23926 Reading symbols from /home/user/gdb/gdb...done.
23927 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23928 declined by your `auto-load safe-path' set
23929 to "$debugdir:$datadir/auto-load".
23930 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23931 declined by your `auto-load safe-path' set
23932 to "$debugdir:$datadir/auto-load".
23936 To instruct @value{GDBN} to go ahead and use the init files anyway,
23937 invoke @value{GDBN} like this:
23940 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23943 The list of trusted directories is controlled by the following commands:
23946 @anchor{set auto-load safe-path}
23947 @kindex set auto-load safe-path
23948 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23949 Set the list of directories (and their subdirectories) trusted for automatic
23950 loading and execution of scripts. You can also enter a specific trusted file.
23951 Each directory can also be a shell wildcard pattern; wildcards do not match
23952 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23953 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23954 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23955 its default value as specified during @value{GDBN} compilation.
23957 The list of directories uses path separator (@samp{:} on GNU and Unix
23958 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23959 to the @env{PATH} environment variable.
23961 @anchor{show auto-load safe-path}
23962 @kindex show auto-load safe-path
23963 @item show auto-load safe-path
23964 Show the list of directories trusted for automatic loading and execution of
23967 @anchor{add-auto-load-safe-path}
23968 @kindex add-auto-load-safe-path
23969 @item add-auto-load-safe-path
23970 Add an entry (or list of entries) to the list of directories trusted for
23971 automatic loading and execution of scripts. Multiple entries may be delimited
23972 by the host platform path separator in use.
23975 This variable defaults to what @code{--with-auto-load-dir} has been configured
23976 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23977 substitution applies the same as for @ref{set auto-load scripts-directory}.
23978 The default @code{set auto-load safe-path} value can be also overriden by
23979 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23981 Setting this variable to @file{/} disables this security protection,
23982 corresponding @value{GDBN} configuration option is
23983 @option{--without-auto-load-safe-path}.
23984 This variable is supposed to be set to the system directories writable by the
23985 system superuser only. Users can add their source directories in init files in
23986 their home directories (@pxref{Home Directory Init File}). See also deprecated
23987 init file in the current directory
23988 (@pxref{Init File in the Current Directory during Startup}).
23990 To force @value{GDBN} to load the files it declined to load in the previous
23991 example, you could use one of the following ways:
23994 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23995 Specify this trusted directory (or a file) as additional component of the list.
23996 You have to specify also any existing directories displayed by
23997 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23999 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24000 Specify this directory as in the previous case but just for a single
24001 @value{GDBN} session.
24003 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24004 Disable auto-loading safety for a single @value{GDBN} session.
24005 This assumes all the files you debug during this @value{GDBN} session will come
24006 from trusted sources.
24008 @item @kbd{./configure --without-auto-load-safe-path}
24009 During compilation of @value{GDBN} you may disable any auto-loading safety.
24010 This assumes all the files you will ever debug with this @value{GDBN} come from
24014 On the other hand you can also explicitly forbid automatic files loading which
24015 also suppresses any such warning messages:
24018 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24019 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24021 @item @file{~/.gdbinit}: @samp{set auto-load no}
24022 Disable auto-loading globally for the user
24023 (@pxref{Home Directory Init File}). While it is improbable, you could also
24024 use system init file instead (@pxref{System-wide configuration}).
24027 This setting applies to the file names as entered by user. If no entry matches
24028 @value{GDBN} tries as a last resort to also resolve all the file names into
24029 their canonical form (typically resolving symbolic links) and compare the
24030 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24031 own before starting the comparison so a canonical form of directories is
24032 recommended to be entered.
24034 @node Auto-loading verbose mode
24035 @subsection Displaying files tried for auto-load
24036 @cindex auto-loading verbose mode
24038 For better visibility of all the file locations where you can place scripts to
24039 be auto-loaded with inferior --- or to protect yourself against accidental
24040 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24041 all the files attempted to be loaded. Both existing and non-existing files may
24044 For example the list of directories from which it is safe to auto-load files
24045 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24046 may not be too obvious while setting it up.
24049 (gdb) set debug auto-load on
24050 (gdb) file ~/src/t/true
24051 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24052 for objfile "/tmp/true".
24053 auto-load: Updating directories of "/usr:/opt".
24054 auto-load: Using directory "/usr".
24055 auto-load: Using directory "/opt".
24056 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24057 by your `auto-load safe-path' set to "/usr:/opt".
24061 @anchor{set debug auto-load}
24062 @kindex set debug auto-load
24063 @item set debug auto-load [on|off]
24064 Set whether to print the filenames attempted to be auto-loaded.
24066 @anchor{show debug auto-load}
24067 @kindex show debug auto-load
24068 @item show debug auto-load
24069 Show whether printing of the filenames attempted to be auto-loaded is turned
24073 @node Messages/Warnings
24074 @section Optional Warnings and Messages
24076 @cindex verbose operation
24077 @cindex optional warnings
24078 By default, @value{GDBN} is silent about its inner workings. If you are
24079 running on a slow machine, you may want to use the @code{set verbose}
24080 command. This makes @value{GDBN} tell you when it does a lengthy
24081 internal operation, so you will not think it has crashed.
24083 Currently, the messages controlled by @code{set verbose} are those
24084 which announce that the symbol table for a source file is being read;
24085 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24088 @kindex set verbose
24089 @item set verbose on
24090 Enables @value{GDBN} output of certain informational messages.
24092 @item set verbose off
24093 Disables @value{GDBN} output of certain informational messages.
24095 @kindex show verbose
24097 Displays whether @code{set verbose} is on or off.
24100 By default, if @value{GDBN} encounters bugs in the symbol table of an
24101 object file, it is silent; but if you are debugging a compiler, you may
24102 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24107 @kindex set complaints
24108 @item set complaints @var{limit}
24109 Permits @value{GDBN} to output @var{limit} complaints about each type of
24110 unusual symbols before becoming silent about the problem. Set
24111 @var{limit} to zero to suppress all complaints; set it to a large number
24112 to prevent complaints from being suppressed.
24114 @kindex show complaints
24115 @item show complaints
24116 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24120 @anchor{confirmation requests}
24121 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24122 lot of stupid questions to confirm certain commands. For example, if
24123 you try to run a program which is already running:
24127 The program being debugged has been started already.
24128 Start it from the beginning? (y or n)
24131 If you are willing to unflinchingly face the consequences of your own
24132 commands, you can disable this ``feature'':
24136 @kindex set confirm
24138 @cindex confirmation
24139 @cindex stupid questions
24140 @item set confirm off
24141 Disables confirmation requests. Note that running @value{GDBN} with
24142 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24143 automatically disables confirmation requests.
24145 @item set confirm on
24146 Enables confirmation requests (the default).
24148 @kindex show confirm
24150 Displays state of confirmation requests.
24154 @cindex command tracing
24155 If you need to debug user-defined commands or sourced files you may find it
24156 useful to enable @dfn{command tracing}. In this mode each command will be
24157 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24158 quantity denoting the call depth of each command.
24161 @kindex set trace-commands
24162 @cindex command scripts, debugging
24163 @item set trace-commands on
24164 Enable command tracing.
24165 @item set trace-commands off
24166 Disable command tracing.
24167 @item show trace-commands
24168 Display the current state of command tracing.
24171 @node Debugging Output
24172 @section Optional Messages about Internal Happenings
24173 @cindex optional debugging messages
24175 @value{GDBN} has commands that enable optional debugging messages from
24176 various @value{GDBN} subsystems; normally these commands are of
24177 interest to @value{GDBN} maintainers, or when reporting a bug. This
24178 section documents those commands.
24181 @kindex set exec-done-display
24182 @item set exec-done-display
24183 Turns on or off the notification of asynchronous commands'
24184 completion. When on, @value{GDBN} will print a message when an
24185 asynchronous command finishes its execution. The default is off.
24186 @kindex show exec-done-display
24187 @item show exec-done-display
24188 Displays the current setting of asynchronous command completion
24191 @cindex ARM AArch64
24192 @item set debug aarch64
24193 Turns on or off display of debugging messages related to ARM AArch64.
24194 The default is off.
24196 @item show debug aarch64
24197 Displays the current state of displaying debugging messages related to
24199 @cindex gdbarch debugging info
24200 @cindex architecture debugging info
24201 @item set debug arch
24202 Turns on or off display of gdbarch debugging info. The default is off
24203 @item show debug arch
24204 Displays the current state of displaying gdbarch debugging info.
24205 @item set debug aix-solib
24206 @cindex AIX shared library debugging
24207 Control display of debugging messages from the AIX shared library
24208 support module. The default is off.
24209 @item show debug aix-thread
24210 Show the current state of displaying AIX shared library debugging messages.
24211 @item set debug aix-thread
24212 @cindex AIX threads
24213 Display debugging messages about inner workings of the AIX thread
24215 @item show debug aix-thread
24216 Show the current state of AIX thread debugging info display.
24217 @item set debug check-physname
24219 Check the results of the ``physname'' computation. When reading DWARF
24220 debugging information for C@t{++}, @value{GDBN} attempts to compute
24221 each entity's name. @value{GDBN} can do this computation in two
24222 different ways, depending on exactly what information is present.
24223 When enabled, this setting causes @value{GDBN} to compute the names
24224 both ways and display any discrepancies.
24225 @item show debug check-physname
24226 Show the current state of ``physname'' checking.
24227 @item set debug coff-pe-read
24228 @cindex COFF/PE exported symbols
24229 Control display of debugging messages related to reading of COFF/PE
24230 exported symbols. The default is off.
24231 @item show debug coff-pe-read
24232 Displays the current state of displaying debugging messages related to
24233 reading of COFF/PE exported symbols.
24234 @item set debug dwarf-die
24236 Dump DWARF DIEs after they are read in.
24237 The value is the number of nesting levels to print.
24238 A value of zero turns off the display.
24239 @item show debug dwarf-die
24240 Show the current state of DWARF DIE debugging.
24241 @item set debug dwarf-line
24242 @cindex DWARF Line Tables
24243 Turns on or off display of debugging messages related to reading
24244 DWARF line tables. The default is 0 (off).
24245 A value of 1 provides basic information.
24246 A value greater than 1 provides more verbose information.
24247 @item show debug dwarf-line
24248 Show the current state of DWARF line table debugging.
24249 @item set debug dwarf-read
24250 @cindex DWARF Reading
24251 Turns on or off display of debugging messages related to reading
24252 DWARF debug info. The default is 0 (off).
24253 A value of 1 provides basic information.
24254 A value greater than 1 provides more verbose information.
24255 @item show debug dwarf-read
24256 Show the current state of DWARF reader debugging.
24257 @item set debug displaced
24258 @cindex displaced stepping debugging info
24259 Turns on or off display of @value{GDBN} debugging info for the
24260 displaced stepping support. The default is off.
24261 @item show debug displaced
24262 Displays the current state of displaying @value{GDBN} debugging info
24263 related to displaced stepping.
24264 @item set debug event
24265 @cindex event debugging info
24266 Turns on or off display of @value{GDBN} event debugging info. The
24268 @item show debug event
24269 Displays the current state of displaying @value{GDBN} event debugging
24271 @item set debug expression
24272 @cindex expression debugging info
24273 Turns on or off display of debugging info about @value{GDBN}
24274 expression parsing. The default is off.
24275 @item show debug expression
24276 Displays the current state of displaying debugging info about
24277 @value{GDBN} expression parsing.
24278 @item set debug fbsd-lwp
24279 @cindex FreeBSD LWP debug messages
24280 Turns on or off debugging messages from the FreeBSD LWP debug support.
24281 @item show debug fbsd-lwp
24282 Show the current state of FreeBSD LWP debugging messages.
24283 @item set debug frame
24284 @cindex frame debugging info
24285 Turns on or off display of @value{GDBN} frame debugging info. The
24287 @item show debug frame
24288 Displays the current state of displaying @value{GDBN} frame debugging
24290 @item set debug gnu-nat
24291 @cindex @sc{gnu}/Hurd debug messages
24292 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24293 @item show debug gnu-nat
24294 Show the current state of @sc{gnu}/Hurd debugging messages.
24295 @item set debug infrun
24296 @cindex inferior debugging info
24297 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24298 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24299 for implementing operations such as single-stepping the inferior.
24300 @item show debug infrun
24301 Displays the current state of @value{GDBN} inferior debugging.
24302 @item set debug jit
24303 @cindex just-in-time compilation, debugging messages
24304 Turn on or off debugging messages from JIT debug support.
24305 @item show debug jit
24306 Displays the current state of @value{GDBN} JIT debugging.
24307 @item set debug lin-lwp
24308 @cindex @sc{gnu}/Linux LWP debug messages
24309 @cindex Linux lightweight processes
24310 Turn on or off debugging messages from the Linux LWP debug support.
24311 @item show debug lin-lwp
24312 Show the current state of Linux LWP debugging messages.
24313 @item set debug linux-namespaces
24314 @cindex @sc{gnu}/Linux namespaces debug messages
24315 Turn on or off debugging messages from the Linux namespaces debug support.
24316 @item show debug linux-namespaces
24317 Show the current state of Linux namespaces debugging messages.
24318 @item set debug mach-o
24319 @cindex Mach-O symbols processing
24320 Control display of debugging messages related to Mach-O symbols
24321 processing. The default is off.
24322 @item show debug mach-o
24323 Displays the current state of displaying debugging messages related to
24324 reading of COFF/PE exported symbols.
24325 @item set debug notification
24326 @cindex remote async notification debugging info
24327 Turn on or off debugging messages about remote async notification.
24328 The default is off.
24329 @item show debug notification
24330 Displays the current state of remote async notification debugging messages.
24331 @item set debug observer
24332 @cindex observer debugging info
24333 Turns on or off display of @value{GDBN} observer debugging. This
24334 includes info such as the notification of observable events.
24335 @item show debug observer
24336 Displays the current state of observer debugging.
24337 @item set debug overload
24338 @cindex C@t{++} overload debugging info
24339 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24340 info. This includes info such as ranking of functions, etc. The default
24342 @item show debug overload
24343 Displays the current state of displaying @value{GDBN} C@t{++} overload
24345 @cindex expression parser, debugging info
24346 @cindex debug expression parser
24347 @item set debug parser
24348 Turns on or off the display of expression parser debugging output.
24349 Internally, this sets the @code{yydebug} variable in the expression
24350 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24351 details. The default is off.
24352 @item show debug parser
24353 Show the current state of expression parser debugging.
24354 @cindex packets, reporting on stdout
24355 @cindex serial connections, debugging
24356 @cindex debug remote protocol
24357 @cindex remote protocol debugging
24358 @cindex display remote packets
24359 @item set debug remote
24360 Turns on or off display of reports on all packets sent back and forth across
24361 the serial line to the remote machine. The info is printed on the
24362 @value{GDBN} standard output stream. The default is off.
24363 @item show debug remote
24364 Displays the state of display of remote packets.
24366 @item set debug separate-debug-file
24367 Turns on or off display of debug output about separate debug file search.
24368 @item show debug separate-debug-file
24369 Displays the state of separate debug file search debug output.
24371 @item set debug serial
24372 Turns on or off display of @value{GDBN} serial debugging info. The
24374 @item show debug serial
24375 Displays the current state of displaying @value{GDBN} serial debugging
24377 @item set debug solib-frv
24378 @cindex FR-V shared-library debugging
24379 Turn on or off debugging messages for FR-V shared-library code.
24380 @item show debug solib-frv
24381 Display the current state of FR-V shared-library code debugging
24383 @item set debug symbol-lookup
24384 @cindex symbol lookup
24385 Turns on or off display of debugging messages related to symbol lookup.
24386 The default is 0 (off).
24387 A value of 1 provides basic information.
24388 A value greater than 1 provides more verbose information.
24389 @item show debug symbol-lookup
24390 Show the current state of symbol lookup debugging messages.
24391 @item set debug symfile
24392 @cindex symbol file functions
24393 Turns on or off display of debugging messages related to symbol file functions.
24394 The default is off. @xref{Files}.
24395 @item show debug symfile
24396 Show the current state of symbol file debugging messages.
24397 @item set debug symtab-create
24398 @cindex symbol table creation
24399 Turns on or off display of debugging messages related to symbol table creation.
24400 The default is 0 (off).
24401 A value of 1 provides basic information.
24402 A value greater than 1 provides more verbose information.
24403 @item show debug symtab-create
24404 Show the current state of symbol table creation debugging.
24405 @item set debug target
24406 @cindex target debugging info
24407 Turns on or off display of @value{GDBN} target debugging info. This info
24408 includes what is going on at the target level of GDB, as it happens. The
24409 default is 0. Set it to 1 to track events, and to 2 to also track the
24410 value of large memory transfers.
24411 @item show debug target
24412 Displays the current state of displaying @value{GDBN} target debugging
24414 @item set debug timestamp
24415 @cindex timestampping debugging info
24416 Turns on or off display of timestamps with @value{GDBN} debugging info.
24417 When enabled, seconds and microseconds are displayed before each debugging
24419 @item show debug timestamp
24420 Displays the current state of displaying timestamps with @value{GDBN}
24422 @item set debug varobj
24423 @cindex variable object debugging info
24424 Turns on or off display of @value{GDBN} variable object debugging
24425 info. The default is off.
24426 @item show debug varobj
24427 Displays the current state of displaying @value{GDBN} variable object
24429 @item set debug xml
24430 @cindex XML parser debugging
24431 Turn on or off debugging messages for built-in XML parsers.
24432 @item show debug xml
24433 Displays the current state of XML debugging messages.
24436 @node Other Misc Settings
24437 @section Other Miscellaneous Settings
24438 @cindex miscellaneous settings
24441 @kindex set interactive-mode
24442 @item set interactive-mode
24443 If @code{on}, forces @value{GDBN} to assume that GDB was started
24444 in a terminal. In practice, this means that @value{GDBN} should wait
24445 for the user to answer queries generated by commands entered at
24446 the command prompt. If @code{off}, forces @value{GDBN} to operate
24447 in the opposite mode, and it uses the default answers to all queries.
24448 If @code{auto} (the default), @value{GDBN} tries to determine whether
24449 its standard input is a terminal, and works in interactive-mode if it
24450 is, non-interactively otherwise.
24452 In the vast majority of cases, the debugger should be able to guess
24453 correctly which mode should be used. But this setting can be useful
24454 in certain specific cases, such as running a MinGW @value{GDBN}
24455 inside a cygwin window.
24457 @kindex show interactive-mode
24458 @item show interactive-mode
24459 Displays whether the debugger is operating in interactive mode or not.
24462 @node Extending GDB
24463 @chapter Extending @value{GDBN}
24464 @cindex extending GDB
24466 @value{GDBN} provides several mechanisms for extension.
24467 @value{GDBN} also provides the ability to automatically load
24468 extensions when it reads a file for debugging. This allows the
24469 user to automatically customize @value{GDBN} for the program
24473 * Sequences:: Canned Sequences of @value{GDBN} Commands
24474 * Python:: Extending @value{GDBN} using Python
24475 * Guile:: Extending @value{GDBN} using Guile
24476 * Auto-loading extensions:: Automatically loading extensions
24477 * Multiple Extension Languages:: Working with multiple extension languages
24478 * Aliases:: Creating new spellings of existing commands
24481 To facilitate the use of extension languages, @value{GDBN} is capable
24482 of evaluating the contents of a file. When doing so, @value{GDBN}
24483 can recognize which extension language is being used by looking at
24484 the filename extension. Files with an unrecognized filename extension
24485 are always treated as a @value{GDBN} Command Files.
24486 @xref{Command Files,, Command files}.
24488 You can control how @value{GDBN} evaluates these files with the following
24492 @kindex set script-extension
24493 @kindex show script-extension
24494 @item set script-extension off
24495 All scripts are always evaluated as @value{GDBN} Command Files.
24497 @item set script-extension soft
24498 The debugger determines the scripting language based on filename
24499 extension. If this scripting language is supported, @value{GDBN}
24500 evaluates the script using that language. Otherwise, it evaluates
24501 the file as a @value{GDBN} Command File.
24503 @item set script-extension strict
24504 The debugger determines the scripting language based on filename
24505 extension, and evaluates the script using that language. If the
24506 language is not supported, then the evaluation fails.
24508 @item show script-extension
24509 Display the current value of the @code{script-extension} option.
24514 @section Canned Sequences of Commands
24516 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24517 Command Lists}), @value{GDBN} provides two ways to store sequences of
24518 commands for execution as a unit: user-defined commands and command
24522 * Define:: How to define your own commands
24523 * Hooks:: Hooks for user-defined commands
24524 * Command Files:: How to write scripts of commands to be stored in a file
24525 * Output:: Commands for controlled output
24526 * Auto-loading sequences:: Controlling auto-loaded command files
24530 @subsection User-defined Commands
24532 @cindex user-defined command
24533 @cindex arguments, to user-defined commands
24534 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24535 which you assign a new name as a command. This is done with the
24536 @code{define} command. User commands may accept an unlimited number of arguments
24537 separated by whitespace. Arguments are accessed within the user command
24538 via @code{$arg0@dots{}$argN}. A trivial example:
24542 print $arg0 + $arg1 + $arg2
24547 To execute the command use:
24554 This defines the command @code{adder}, which prints the sum of
24555 its three arguments. Note the arguments are text substitutions, so they may
24556 reference variables, use complex expressions, or even perform inferior
24559 @cindex argument count in user-defined commands
24560 @cindex how many arguments (user-defined commands)
24561 In addition, @code{$argc} may be used to find out how many arguments have
24567 print $arg0 + $arg1
24570 print $arg0 + $arg1 + $arg2
24575 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24576 to process a variable number of arguments:
24583 eval "set $sum = $sum + $arg%d", $i
24593 @item define @var{commandname}
24594 Define a command named @var{commandname}. If there is already a command
24595 by that name, you are asked to confirm that you want to redefine it.
24596 The argument @var{commandname} may be a bare command name consisting of letters,
24597 numbers, dashes, and underscores. It may also start with any predefined
24598 prefix command. For example, @samp{define target my-target} creates
24599 a user-defined @samp{target my-target} command.
24601 The definition of the command is made up of other @value{GDBN} command lines,
24602 which are given following the @code{define} command. The end of these
24603 commands is marked by a line containing @code{end}.
24606 @kindex end@r{ (user-defined commands)}
24607 @item document @var{commandname}
24608 Document the user-defined command @var{commandname}, so that it can be
24609 accessed by @code{help}. The command @var{commandname} must already be
24610 defined. This command reads lines of documentation just as @code{define}
24611 reads the lines of the command definition, ending with @code{end}.
24612 After the @code{document} command is finished, @code{help} on command
24613 @var{commandname} displays the documentation you have written.
24615 You may use the @code{document} command again to change the
24616 documentation of a command. Redefining the command with @code{define}
24617 does not change the documentation.
24619 @kindex dont-repeat
24620 @cindex don't repeat command
24622 Used inside a user-defined command, this tells @value{GDBN} that this
24623 command should not be repeated when the user hits @key{RET}
24624 (@pxref{Command Syntax, repeat last command}).
24626 @kindex help user-defined
24627 @item help user-defined
24628 List all user-defined commands and all python commands defined in class
24629 COMAND_USER. The first line of the documentation or docstring is
24634 @itemx show user @var{commandname}
24635 Display the @value{GDBN} commands used to define @var{commandname} (but
24636 not its documentation). If no @var{commandname} is given, display the
24637 definitions for all user-defined commands.
24638 This does not work for user-defined python commands.
24640 @cindex infinite recursion in user-defined commands
24641 @kindex show max-user-call-depth
24642 @kindex set max-user-call-depth
24643 @item show max-user-call-depth
24644 @itemx set max-user-call-depth
24645 The value of @code{max-user-call-depth} controls how many recursion
24646 levels are allowed in user-defined commands before @value{GDBN} suspects an
24647 infinite recursion and aborts the command.
24648 This does not apply to user-defined python commands.
24651 In addition to the above commands, user-defined commands frequently
24652 use control flow commands, described in @ref{Command Files}.
24654 When user-defined commands are executed, the
24655 commands of the definition are not printed. An error in any command
24656 stops execution of the user-defined command.
24658 If used interactively, commands that would ask for confirmation proceed
24659 without asking when used inside a user-defined command. Many @value{GDBN}
24660 commands that normally print messages to say what they are doing omit the
24661 messages when used in a user-defined command.
24664 @subsection User-defined Command Hooks
24665 @cindex command hooks
24666 @cindex hooks, for commands
24667 @cindex hooks, pre-command
24670 You may define @dfn{hooks}, which are a special kind of user-defined
24671 command. Whenever you run the command @samp{foo}, if the user-defined
24672 command @samp{hook-foo} exists, it is executed (with no arguments)
24673 before that command.
24675 @cindex hooks, post-command
24677 A hook may also be defined which is run after the command you executed.
24678 Whenever you run the command @samp{foo}, if the user-defined command
24679 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24680 that command. Post-execution hooks may exist simultaneously with
24681 pre-execution hooks, for the same command.
24683 It is valid for a hook to call the command which it hooks. If this
24684 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24686 @c It would be nice if hookpost could be passed a parameter indicating
24687 @c if the command it hooks executed properly or not. FIXME!
24689 @kindex stop@r{, a pseudo-command}
24690 In addition, a pseudo-command, @samp{stop} exists. Defining
24691 (@samp{hook-stop}) makes the associated commands execute every time
24692 execution stops in your program: before breakpoint commands are run,
24693 displays are printed, or the stack frame is printed.
24695 For example, to ignore @code{SIGALRM} signals while
24696 single-stepping, but treat them normally during normal execution,
24701 handle SIGALRM nopass
24705 handle SIGALRM pass
24708 define hook-continue
24709 handle SIGALRM pass
24713 As a further example, to hook at the beginning and end of the @code{echo}
24714 command, and to add extra text to the beginning and end of the message,
24722 define hookpost-echo
24726 (@value{GDBP}) echo Hello World
24727 <<<---Hello World--->>>
24732 You can define a hook for any single-word command in @value{GDBN}, but
24733 not for command aliases; you should define a hook for the basic command
24734 name, e.g.@: @code{backtrace} rather than @code{bt}.
24735 @c FIXME! So how does Joe User discover whether a command is an alias
24737 You can hook a multi-word command by adding @code{hook-} or
24738 @code{hookpost-} to the last word of the command, e.g.@:
24739 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24741 If an error occurs during the execution of your hook, execution of
24742 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24743 (before the command that you actually typed had a chance to run).
24745 If you try to define a hook which does not match any known command, you
24746 get a warning from the @code{define} command.
24748 @node Command Files
24749 @subsection Command Files
24751 @cindex command files
24752 @cindex scripting commands
24753 A command file for @value{GDBN} is a text file made of lines that are
24754 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24755 also be included. An empty line in a command file does nothing; it
24756 does not mean to repeat the last command, as it would from the
24759 You can request the execution of a command file with the @code{source}
24760 command. Note that the @code{source} command is also used to evaluate
24761 scripts that are not Command Files. The exact behavior can be configured
24762 using the @code{script-extension} setting.
24763 @xref{Extending GDB,, Extending GDB}.
24767 @cindex execute commands from a file
24768 @item source [-s] [-v] @var{filename}
24769 Execute the command file @var{filename}.
24772 The lines in a command file are generally executed sequentially,
24773 unless the order of execution is changed by one of the
24774 @emph{flow-control commands} described below. The commands are not
24775 printed as they are executed. An error in any command terminates
24776 execution of the command file and control is returned to the console.
24778 @value{GDBN} first searches for @var{filename} in the current directory.
24779 If the file is not found there, and @var{filename} does not specify a
24780 directory, then @value{GDBN} also looks for the file on the source search path
24781 (specified with the @samp{directory} command);
24782 except that @file{$cdir} is not searched because the compilation directory
24783 is not relevant to scripts.
24785 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24786 on the search path even if @var{filename} specifies a directory.
24787 The search is done by appending @var{filename} to each element of the
24788 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24789 and the search path contains @file{/home/user} then @value{GDBN} will
24790 look for the script @file{/home/user/mylib/myscript}.
24791 The search is also done if @var{filename} is an absolute path.
24792 For example, if @var{filename} is @file{/tmp/myscript} and
24793 the search path contains @file{/home/user} then @value{GDBN} will
24794 look for the script @file{/home/user/tmp/myscript}.
24795 For DOS-like systems, if @var{filename} contains a drive specification,
24796 it is stripped before concatenation. For example, if @var{filename} is
24797 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24798 will look for the script @file{c:/tmp/myscript}.
24800 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24801 each command as it is executed. The option must be given before
24802 @var{filename}, and is interpreted as part of the filename anywhere else.
24804 Commands that would ask for confirmation if used interactively proceed
24805 without asking when used in a command file. Many @value{GDBN} commands that
24806 normally print messages to say what they are doing omit the messages
24807 when called from command files.
24809 @value{GDBN} also accepts command input from standard input. In this
24810 mode, normal output goes to standard output and error output goes to
24811 standard error. Errors in a command file supplied on standard input do
24812 not terminate execution of the command file---execution continues with
24816 gdb < cmds > log 2>&1
24819 (The syntax above will vary depending on the shell used.) This example
24820 will execute commands from the file @file{cmds}. All output and errors
24821 would be directed to @file{log}.
24823 Since commands stored on command files tend to be more general than
24824 commands typed interactively, they frequently need to deal with
24825 complicated situations, such as different or unexpected values of
24826 variables and symbols, changes in how the program being debugged is
24827 built, etc. @value{GDBN} provides a set of flow-control commands to
24828 deal with these complexities. Using these commands, you can write
24829 complex scripts that loop over data structures, execute commands
24830 conditionally, etc.
24837 This command allows to include in your script conditionally executed
24838 commands. The @code{if} command takes a single argument, which is an
24839 expression to evaluate. It is followed by a series of commands that
24840 are executed only if the expression is true (its value is nonzero).
24841 There can then optionally be an @code{else} line, followed by a series
24842 of commands that are only executed if the expression was false. The
24843 end of the list is marked by a line containing @code{end}.
24847 This command allows to write loops. Its syntax is similar to
24848 @code{if}: the command takes a single argument, which is an expression
24849 to evaluate, and must be followed by the commands to execute, one per
24850 line, terminated by an @code{end}. These commands are called the
24851 @dfn{body} of the loop. The commands in the body of @code{while} are
24852 executed repeatedly as long as the expression evaluates to true.
24856 This command exits the @code{while} loop in whose body it is included.
24857 Execution of the script continues after that @code{while}s @code{end}
24860 @kindex loop_continue
24861 @item loop_continue
24862 This command skips the execution of the rest of the body of commands
24863 in the @code{while} loop in whose body it is included. Execution
24864 branches to the beginning of the @code{while} loop, where it evaluates
24865 the controlling expression.
24867 @kindex end@r{ (if/else/while commands)}
24869 Terminate the block of commands that are the body of @code{if},
24870 @code{else}, or @code{while} flow-control commands.
24875 @subsection Commands for Controlled Output
24877 During the execution of a command file or a user-defined command, normal
24878 @value{GDBN} output is suppressed; the only output that appears is what is
24879 explicitly printed by the commands in the definition. This section
24880 describes three commands useful for generating exactly the output you
24885 @item echo @var{text}
24886 @c I do not consider backslash-space a standard C escape sequence
24887 @c because it is not in ANSI.
24888 Print @var{text}. Nonprinting characters can be included in
24889 @var{text} using C escape sequences, such as @samp{\n} to print a
24890 newline. @strong{No newline is printed unless you specify one.}
24891 In addition to the standard C escape sequences, a backslash followed
24892 by a space stands for a space. This is useful for displaying a
24893 string with spaces at the beginning or the end, since leading and
24894 trailing spaces are otherwise trimmed from all arguments.
24895 To print @samp{@w{ }and foo =@w{ }}, use the command
24896 @samp{echo \@w{ }and foo = \@w{ }}.
24898 A backslash at the end of @var{text} can be used, as in C, to continue
24899 the command onto subsequent lines. For example,
24902 echo This is some text\n\
24903 which is continued\n\
24904 onto several lines.\n
24907 produces the same output as
24910 echo This is some text\n
24911 echo which is continued\n
24912 echo onto several lines.\n
24916 @item output @var{expression}
24917 Print the value of @var{expression} and nothing but that value: no
24918 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24919 value history either. @xref{Expressions, ,Expressions}, for more information
24922 @item output/@var{fmt} @var{expression}
24923 Print the value of @var{expression} in format @var{fmt}. You can use
24924 the same formats as for @code{print}. @xref{Output Formats,,Output
24925 Formats}, for more information.
24928 @item printf @var{template}, @var{expressions}@dots{}
24929 Print the values of one or more @var{expressions} under the control of
24930 the string @var{template}. To print several values, make
24931 @var{expressions} be a comma-separated list of individual expressions,
24932 which may be either numbers or pointers. Their values are printed as
24933 specified by @var{template}, exactly as a C program would do by
24934 executing the code below:
24937 printf (@var{template}, @var{expressions}@dots{});
24940 As in @code{C} @code{printf}, ordinary characters in @var{template}
24941 are printed verbatim, while @dfn{conversion specification} introduced
24942 by the @samp{%} character cause subsequent @var{expressions} to be
24943 evaluated, their values converted and formatted according to type and
24944 style information encoded in the conversion specifications, and then
24947 For example, you can print two values in hex like this:
24950 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24953 @code{printf} supports all the standard @code{C} conversion
24954 specifications, including the flags and modifiers between the @samp{%}
24955 character and the conversion letter, with the following exceptions:
24959 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24962 The modifier @samp{*} is not supported for specifying precision or
24966 The @samp{'} flag (for separation of digits into groups according to
24967 @code{LC_NUMERIC'}) is not supported.
24970 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24974 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24977 The conversion letters @samp{a} and @samp{A} are not supported.
24981 Note that the @samp{ll} type modifier is supported only if the
24982 underlying @code{C} implementation used to build @value{GDBN} supports
24983 the @code{long long int} type, and the @samp{L} type modifier is
24984 supported only if @code{long double} type is available.
24986 As in @code{C}, @code{printf} supports simple backslash-escape
24987 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24988 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24989 single character. Octal and hexadecimal escape sequences are not
24992 Additionally, @code{printf} supports conversion specifications for DFP
24993 (@dfn{Decimal Floating Point}) types using the following length modifiers
24994 together with a floating point specifier.
24999 @samp{H} for printing @code{Decimal32} types.
25002 @samp{D} for printing @code{Decimal64} types.
25005 @samp{DD} for printing @code{Decimal128} types.
25008 If the underlying @code{C} implementation used to build @value{GDBN} has
25009 support for the three length modifiers for DFP types, other modifiers
25010 such as width and precision will also be available for @value{GDBN} to use.
25012 In case there is no such @code{C} support, no additional modifiers will be
25013 available and the value will be printed in the standard way.
25015 Here's an example of printing DFP types using the above conversion letters:
25017 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25022 @item eval @var{template}, @var{expressions}@dots{}
25023 Convert the values of one or more @var{expressions} under the control of
25024 the string @var{template} to a command line, and call it.
25028 @node Auto-loading sequences
25029 @subsection Controlling auto-loading native @value{GDBN} scripts
25030 @cindex native script auto-loading
25032 When a new object file is read (for example, due to the @code{file}
25033 command, or because the inferior has loaded a shared library),
25034 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25035 @xref{Auto-loading extensions}.
25037 Auto-loading can be enabled or disabled,
25038 and the list of auto-loaded scripts can be printed.
25041 @anchor{set auto-load gdb-scripts}
25042 @kindex set auto-load gdb-scripts
25043 @item set auto-load gdb-scripts [on|off]
25044 Enable or disable the auto-loading of canned sequences of commands scripts.
25046 @anchor{show auto-load gdb-scripts}
25047 @kindex show auto-load gdb-scripts
25048 @item show auto-load gdb-scripts
25049 Show whether auto-loading of canned sequences of commands scripts is enabled or
25052 @anchor{info auto-load gdb-scripts}
25053 @kindex info auto-load gdb-scripts
25054 @cindex print list of auto-loaded canned sequences of commands scripts
25055 @item info auto-load gdb-scripts [@var{regexp}]
25056 Print the list of all canned sequences of commands scripts that @value{GDBN}
25060 If @var{regexp} is supplied only canned sequences of commands scripts with
25061 matching names are printed.
25063 @c Python docs live in a separate file.
25064 @include python.texi
25066 @c Guile docs live in a separate file.
25067 @include guile.texi
25069 @node Auto-loading extensions
25070 @section Auto-loading extensions
25071 @cindex auto-loading extensions
25073 @value{GDBN} provides two mechanisms for automatically loading extensions
25074 when a new object file is read (for example, due to the @code{file}
25075 command, or because the inferior has loaded a shared library):
25076 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25077 section of modern file formats like ELF.
25080 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25081 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25082 * Which flavor to choose?::
25085 The auto-loading feature is useful for supplying application-specific
25086 debugging commands and features.
25088 Auto-loading can be enabled or disabled,
25089 and the list of auto-loaded scripts can be printed.
25090 See the @samp{auto-loading} section of each extension language
25091 for more information.
25092 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25093 For Python files see @ref{Python Auto-loading}.
25095 Note that loading of this script file also requires accordingly configured
25096 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25098 @node objfile-gdbdotext file
25099 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25100 @cindex @file{@var{objfile}-gdb.gdb}
25101 @cindex @file{@var{objfile}-gdb.py}
25102 @cindex @file{@var{objfile}-gdb.scm}
25104 When a new object file is read, @value{GDBN} looks for a file named
25105 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25106 where @var{objfile} is the object file's name and
25107 where @var{ext} is the file extension for the extension language:
25110 @item @file{@var{objfile}-gdb.gdb}
25111 GDB's own command language
25112 @item @file{@var{objfile}-gdb.py}
25114 @item @file{@var{objfile}-gdb.scm}
25118 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25119 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25120 components, and appending the @file{-gdb.@var{ext}} suffix.
25121 If this file exists and is readable, @value{GDBN} will evaluate it as a
25122 script in the specified extension language.
25124 If this file does not exist, then @value{GDBN} will look for
25125 @var{script-name} file in all of the directories as specified below.
25127 Note that loading of these files requires an accordingly configured
25128 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25130 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25131 scripts normally according to its @file{.exe} filename. But if no scripts are
25132 found @value{GDBN} also tries script filenames matching the object file without
25133 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25134 is attempted on any platform. This makes the script filenames compatible
25135 between Unix and MS-Windows hosts.
25138 @anchor{set auto-load scripts-directory}
25139 @kindex set auto-load scripts-directory
25140 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25141 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25142 may be delimited by the host platform path separator in use
25143 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25145 Each entry here needs to be covered also by the security setting
25146 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25148 @anchor{with-auto-load-dir}
25149 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25150 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25151 configuration option @option{--with-auto-load-dir}.
25153 Any reference to @file{$debugdir} will get replaced by
25154 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25155 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25156 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25157 @file{$datadir} must be placed as a directory component --- either alone or
25158 delimited by @file{/} or @file{\} directory separators, depending on the host
25161 The list of directories uses path separator (@samp{:} on GNU and Unix
25162 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25163 to the @env{PATH} environment variable.
25165 @anchor{show auto-load scripts-directory}
25166 @kindex show auto-load scripts-directory
25167 @item show auto-load scripts-directory
25168 Show @value{GDBN} auto-loaded scripts location.
25170 @anchor{add-auto-load-scripts-directory}
25171 @kindex add-auto-load-scripts-directory
25172 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25173 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25174 Multiple entries may be delimited by the host platform path separator in use.
25177 @value{GDBN} does not track which files it has already auto-loaded this way.
25178 @value{GDBN} will load the associated script every time the corresponding
25179 @var{objfile} is opened.
25180 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25181 is evaluated more than once.
25183 @node dotdebug_gdb_scripts section
25184 @subsection The @code{.debug_gdb_scripts} section
25185 @cindex @code{.debug_gdb_scripts} section
25187 For systems using file formats like ELF and COFF,
25188 when @value{GDBN} loads a new object file
25189 it will look for a special section named @code{.debug_gdb_scripts}.
25190 If this section exists, its contents is a list of null-terminated entries
25191 specifying scripts to load. Each entry begins with a non-null prefix byte that
25192 specifies the kind of entry, typically the extension language and whether the
25193 script is in a file or inlined in @code{.debug_gdb_scripts}.
25195 The following entries are supported:
25198 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25199 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25200 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25201 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25204 @subsubsection Script File Entries
25206 If the entry specifies a file, @value{GDBN} will look for the file first
25207 in the current directory and then along the source search path
25208 (@pxref{Source Path, ,Specifying Source Directories}),
25209 except that @file{$cdir} is not searched, since the compilation
25210 directory is not relevant to scripts.
25212 File entries can be placed in section @code{.debug_gdb_scripts} with,
25213 for example, this GCC macro for Python scripts.
25216 /* Note: The "MS" section flags are to remove duplicates. */
25217 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25219 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25220 .byte 1 /* Python */\n\
25221 .asciz \"" script_name "\"\n\
25227 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25228 Then one can reference the macro in a header or source file like this:
25231 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25234 The script name may include directories if desired.
25236 Note that loading of this script file also requires accordingly configured
25237 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25239 If the macro invocation is put in a header, any application or library
25240 using this header will get a reference to the specified script,
25241 and with the use of @code{"MS"} attributes on the section, the linker
25242 will remove duplicates.
25244 @subsubsection Script Text Entries
25246 Script text entries allow to put the executable script in the entry
25247 itself instead of loading it from a file.
25248 The first line of the entry, everything after the prefix byte and up to
25249 the first newline (@code{0xa}) character, is the script name, and must not
25250 contain any kind of space character, e.g., spaces or tabs.
25251 The rest of the entry, up to the trailing null byte, is the script to
25252 execute in the specified language. The name needs to be unique among
25253 all script names, as @value{GDBN} executes each script only once based
25256 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25260 #include "symcat.h"
25261 #include "gdb/section-scripts.h"
25263 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25264 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25265 ".ascii \"gdb.inlined-script\\n\"\n"
25266 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25267 ".ascii \" def __init__ (self):\\n\"\n"
25268 ".ascii \" super (test_cmd, self).__init__ ("
25269 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25270 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25271 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25272 ".ascii \"test_cmd ()\\n\"\n"
25278 Loading of inlined scripts requires a properly configured
25279 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25280 The path to specify in @code{auto-load safe-path} is the path of the file
25281 containing the @code{.debug_gdb_scripts} section.
25283 @node Which flavor to choose?
25284 @subsection Which flavor to choose?
25286 Given the multiple ways of auto-loading extensions, it might not always
25287 be clear which one to choose. This section provides some guidance.
25290 Benefits of the @file{-gdb.@var{ext}} way:
25294 Can be used with file formats that don't support multiple sections.
25297 Ease of finding scripts for public libraries.
25299 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25300 in the source search path.
25301 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25302 isn't a source directory in which to find the script.
25305 Doesn't require source code additions.
25309 Benefits of the @code{.debug_gdb_scripts} way:
25313 Works with static linking.
25315 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25316 trigger their loading. When an application is statically linked the only
25317 objfile available is the executable, and it is cumbersome to attach all the
25318 scripts from all the input libraries to the executable's
25319 @file{-gdb.@var{ext}} script.
25322 Works with classes that are entirely inlined.
25324 Some classes can be entirely inlined, and thus there may not be an associated
25325 shared library to attach a @file{-gdb.@var{ext}} script to.
25328 Scripts needn't be copied out of the source tree.
25330 In some circumstances, apps can be built out of large collections of internal
25331 libraries, and the build infrastructure necessary to install the
25332 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25333 cumbersome. It may be easier to specify the scripts in the
25334 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25335 top of the source tree to the source search path.
25338 @node Multiple Extension Languages
25339 @section Multiple Extension Languages
25341 The Guile and Python extension languages do not share any state,
25342 and generally do not interfere with each other.
25343 There are some things to be aware of, however.
25345 @subsection Python comes first
25347 Python was @value{GDBN}'s first extension language, and to avoid breaking
25348 existing behaviour Python comes first. This is generally solved by the
25349 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25350 extension languages, and when it makes a call to an extension language,
25351 (say to pretty-print a value), it tries each in turn until an extension
25352 language indicates it has performed the request (e.g., has returned the
25353 pretty-printed form of a value).
25354 This extends to errors while performing such requests: If an error happens
25355 while, for example, trying to pretty-print an object then the error is
25356 reported and any following extension languages are not tried.
25359 @section Creating new spellings of existing commands
25360 @cindex aliases for commands
25362 It is often useful to define alternate spellings of existing commands.
25363 For example, if a new @value{GDBN} command defined in Python has
25364 a long name to type, it is handy to have an abbreviated version of it
25365 that involves less typing.
25367 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25368 of the @samp{step} command even though it is otherwise an ambiguous
25369 abbreviation of other commands like @samp{set} and @samp{show}.
25371 Aliases are also used to provide shortened or more common versions
25372 of multi-word commands. For example, @value{GDBN} provides the
25373 @samp{tty} alias of the @samp{set inferior-tty} command.
25375 You can define a new alias with the @samp{alias} command.
25380 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25384 @var{ALIAS} specifies the name of the new alias.
25385 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25388 @var{COMMAND} specifies the name of an existing command
25389 that is being aliased.
25391 The @samp{-a} option specifies that the new alias is an abbreviation
25392 of the command. Abbreviations are not shown in command
25393 lists displayed by the @samp{help} command.
25395 The @samp{--} option specifies the end of options,
25396 and is useful when @var{ALIAS} begins with a dash.
25398 Here is a simple example showing how to make an abbreviation
25399 of a command so that there is less to type.
25400 Suppose you were tired of typing @samp{disas}, the current
25401 shortest unambiguous abbreviation of the @samp{disassemble} command
25402 and you wanted an even shorter version named @samp{di}.
25403 The following will accomplish this.
25406 (gdb) alias -a di = disas
25409 Note that aliases are different from user-defined commands.
25410 With a user-defined command, you also need to write documentation
25411 for it with the @samp{document} command.
25412 An alias automatically picks up the documentation of the existing command.
25414 Here is an example where we make @samp{elms} an abbreviation of
25415 @samp{elements} in the @samp{set print elements} command.
25416 This is to show that you can make an abbreviation of any part
25420 (gdb) alias -a set print elms = set print elements
25421 (gdb) alias -a show print elms = show print elements
25422 (gdb) set p elms 20
25424 Limit on string chars or array elements to print is 200.
25427 Note that if you are defining an alias of a @samp{set} command,
25428 and you want to have an alias for the corresponding @samp{show}
25429 command, then you need to define the latter separately.
25431 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25432 @var{ALIAS}, just as they are normally.
25435 (gdb) alias -a set pr elms = set p ele
25438 Finally, here is an example showing the creation of a one word
25439 alias for a more complex command.
25440 This creates alias @samp{spe} of the command @samp{set print elements}.
25443 (gdb) alias spe = set print elements
25448 @chapter Command Interpreters
25449 @cindex command interpreters
25451 @value{GDBN} supports multiple command interpreters, and some command
25452 infrastructure to allow users or user interface writers to switch
25453 between interpreters or run commands in other interpreters.
25455 @value{GDBN} currently supports two command interpreters, the console
25456 interpreter (sometimes called the command-line interpreter or @sc{cli})
25457 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25458 describes both of these interfaces in great detail.
25460 By default, @value{GDBN} will start with the console interpreter.
25461 However, the user may choose to start @value{GDBN} with another
25462 interpreter by specifying the @option{-i} or @option{--interpreter}
25463 startup options. Defined interpreters include:
25467 @cindex console interpreter
25468 The traditional console or command-line interpreter. This is the most often
25469 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25470 @value{GDBN} will use this interpreter.
25473 @cindex mi interpreter
25474 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25475 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25476 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25480 @cindex mi2 interpreter
25481 The current @sc{gdb/mi} interface.
25484 @cindex mi1 interpreter
25485 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25489 @cindex invoke another interpreter
25491 @kindex interpreter-exec
25492 You may execute commands in any interpreter from the current
25493 interpreter using the appropriate command. If you are running the
25494 console interpreter, simply use the @code{interpreter-exec} command:
25497 interpreter-exec mi "-data-list-register-names"
25500 @sc{gdb/mi} has a similar command, although it is only available in versions of
25501 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25503 Note that @code{interpreter-exec} only changes the interpreter for the
25504 duration of the specified command. It does not change the interpreter
25507 @cindex start a new independent interpreter
25509 Although you may only choose a single interpreter at startup, it is
25510 possible to run an independent interpreter on a specified input/output
25511 device (usually a tty).
25513 For example, consider a debugger GUI or IDE that wants to provide a
25514 @value{GDBN} console view. It may do so by embedding a terminal
25515 emulator widget in its GUI, starting @value{GDBN} in the traditional
25516 command-line mode with stdin/stdout/stderr redirected to that
25517 terminal, and then creating an MI interpreter running on a specified
25518 input/output device. The console interpreter created by @value{GDBN}
25519 at startup handles commands the user types in the terminal widget,
25520 while the GUI controls and synchronizes state with @value{GDBN} using
25521 the separate MI interpreter.
25523 To start a new secondary @dfn{user interface} running MI, use the
25524 @code{new-ui} command:
25527 @cindex new user interface
25529 new-ui @var{interpreter} @var{tty}
25532 The @var{interpreter} parameter specifies the interpreter to run.
25533 This accepts the same values as the @code{interpreter-exec} command.
25534 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25535 @var{tty} parameter specifies the name of the bidirectional file the
25536 interpreter uses for input/output, usually the name of a
25537 pseudoterminal slave on Unix systems. For example:
25540 (@value{GDBP}) new-ui mi /dev/pts/9
25544 runs an MI interpreter on @file{/dev/pts/9}.
25547 @chapter @value{GDBN} Text User Interface
25549 @cindex Text User Interface
25552 * TUI Overview:: TUI overview
25553 * TUI Keys:: TUI key bindings
25554 * TUI Single Key Mode:: TUI single key mode
25555 * TUI Commands:: TUI-specific commands
25556 * TUI Configuration:: TUI configuration variables
25559 The @value{GDBN} Text User Interface (TUI) is a terminal
25560 interface which uses the @code{curses} library to show the source
25561 file, the assembly output, the program registers and @value{GDBN}
25562 commands in separate text windows. The TUI mode is supported only
25563 on platforms where a suitable version of the @code{curses} library
25566 The TUI mode is enabled by default when you invoke @value{GDBN} as
25567 @samp{@value{GDBP} -tui}.
25568 You can also switch in and out of TUI mode while @value{GDBN} runs by
25569 using various TUI commands and key bindings, such as @command{tui
25570 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25571 @ref{TUI Keys, ,TUI Key Bindings}.
25574 @section TUI Overview
25576 In TUI mode, @value{GDBN} can display several text windows:
25580 This window is the @value{GDBN} command window with the @value{GDBN}
25581 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25582 managed using readline.
25585 The source window shows the source file of the program. The current
25586 line and active breakpoints are displayed in this window.
25589 The assembly window shows the disassembly output of the program.
25592 This window shows the processor registers. Registers are highlighted
25593 when their values change.
25596 The source and assembly windows show the current program position
25597 by highlighting the current line and marking it with a @samp{>} marker.
25598 Breakpoints are indicated with two markers. The first marker
25599 indicates the breakpoint type:
25603 Breakpoint which was hit at least once.
25606 Breakpoint which was never hit.
25609 Hardware breakpoint which was hit at least once.
25612 Hardware breakpoint which was never hit.
25615 The second marker indicates whether the breakpoint is enabled or not:
25619 Breakpoint is enabled.
25622 Breakpoint is disabled.
25625 The source, assembly and register windows are updated when the current
25626 thread changes, when the frame changes, or when the program counter
25629 These windows are not all visible at the same time. The command
25630 window is always visible. The others can be arranged in several
25641 source and assembly,
25644 source and registers, or
25647 assembly and registers.
25650 A status line above the command window shows the following information:
25654 Indicates the current @value{GDBN} target.
25655 (@pxref{Targets, ,Specifying a Debugging Target}).
25658 Gives the current process or thread number.
25659 When no process is being debugged, this field is set to @code{No process}.
25662 Gives the current function name for the selected frame.
25663 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25664 When there is no symbol corresponding to the current program counter,
25665 the string @code{??} is displayed.
25668 Indicates the current line number for the selected frame.
25669 When the current line number is not known, the string @code{??} is displayed.
25672 Indicates the current program counter address.
25676 @section TUI Key Bindings
25677 @cindex TUI key bindings
25679 The TUI installs several key bindings in the readline keymaps
25680 @ifset SYSTEM_READLINE
25681 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25683 @ifclear SYSTEM_READLINE
25684 (@pxref{Command Line Editing}).
25686 The following key bindings are installed for both TUI mode and the
25687 @value{GDBN} standard mode.
25696 Enter or leave the TUI mode. When leaving the TUI mode,
25697 the curses window management stops and @value{GDBN} operates using
25698 its standard mode, writing on the terminal directly. When reentering
25699 the TUI mode, control is given back to the curses windows.
25700 The screen is then refreshed.
25704 Use a TUI layout with only one window. The layout will
25705 either be @samp{source} or @samp{assembly}. When the TUI mode
25706 is not active, it will switch to the TUI mode.
25708 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25712 Use a TUI layout with at least two windows. When the current
25713 layout already has two windows, the next layout with two windows is used.
25714 When a new layout is chosen, one window will always be common to the
25715 previous layout and the new one.
25717 Think of it as the Emacs @kbd{C-x 2} binding.
25721 Change the active window. The TUI associates several key bindings
25722 (like scrolling and arrow keys) with the active window. This command
25723 gives the focus to the next TUI window.
25725 Think of it as the Emacs @kbd{C-x o} binding.
25729 Switch in and out of the TUI SingleKey mode that binds single
25730 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25733 The following key bindings only work in the TUI mode:
25738 Scroll the active window one page up.
25742 Scroll the active window one page down.
25746 Scroll the active window one line up.
25750 Scroll the active window one line down.
25754 Scroll the active window one column left.
25758 Scroll the active window one column right.
25762 Refresh the screen.
25765 Because the arrow keys scroll the active window in the TUI mode, they
25766 are not available for their normal use by readline unless the command
25767 window has the focus. When another window is active, you must use
25768 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25769 and @kbd{C-f} to control the command window.
25771 @node TUI Single Key Mode
25772 @section TUI Single Key Mode
25773 @cindex TUI single key mode
25775 The TUI also provides a @dfn{SingleKey} mode, which binds several
25776 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25777 switch into this mode, where the following key bindings are used:
25780 @kindex c @r{(SingleKey TUI key)}
25784 @kindex d @r{(SingleKey TUI key)}
25788 @kindex f @r{(SingleKey TUI key)}
25792 @kindex n @r{(SingleKey TUI key)}
25796 @kindex o @r{(SingleKey TUI key)}
25798 nexti. The shortcut letter @samp{o} stands for ``step Over''.
25800 @kindex q @r{(SingleKey TUI key)}
25802 exit the SingleKey mode.
25804 @kindex r @r{(SingleKey TUI key)}
25808 @kindex s @r{(SingleKey TUI key)}
25812 @kindex i @r{(SingleKey TUI key)}
25814 stepi. The shortcut letter @samp{i} stands for ``step Into''.
25816 @kindex u @r{(SingleKey TUI key)}
25820 @kindex v @r{(SingleKey TUI key)}
25824 @kindex w @r{(SingleKey TUI key)}
25829 Other keys temporarily switch to the @value{GDBN} command prompt.
25830 The key that was pressed is inserted in the editing buffer so that
25831 it is possible to type most @value{GDBN} commands without interaction
25832 with the TUI SingleKey mode. Once the command is entered the TUI
25833 SingleKey mode is restored. The only way to permanently leave
25834 this mode is by typing @kbd{q} or @kbd{C-x s}.
25838 @section TUI-specific Commands
25839 @cindex TUI commands
25841 The TUI has specific commands to control the text windows.
25842 These commands are always available, even when @value{GDBN} is not in
25843 the TUI mode. When @value{GDBN} is in the standard mode, most
25844 of these commands will automatically switch to the TUI mode.
25846 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25847 terminal, or @value{GDBN} has been started with the machine interface
25848 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25849 these commands will fail with an error, because it would not be
25850 possible or desirable to enable curses window management.
25855 Activate TUI mode. The last active TUI window layout will be used if
25856 TUI mode has prevsiouly been used in the current debugging session,
25857 otherwise a default layout is used.
25860 @kindex tui disable
25861 Disable TUI mode, returning to the console interpreter.
25865 List and give the size of all displayed windows.
25867 @item layout @var{name}
25869 Changes which TUI windows are displayed. In each layout the command
25870 window is always displayed, the @var{name} parameter controls which
25871 additional windows are displayed, and can be any of the following:
25875 Display the next layout.
25878 Display the previous layout.
25881 Display the source and command windows.
25884 Display the assembly and command windows.
25887 Display the source, assembly, and command windows.
25890 When in @code{src} layout display the register, source, and command
25891 windows. When in @code{asm} or @code{split} layout display the
25892 register, assembler, and command windows.
25895 @item focus @var{name}
25897 Changes which TUI window is currently active for scrolling. The
25898 @var{name} parameter can be any of the following:
25902 Make the next window active for scrolling.
25905 Make the previous window active for scrolling.
25908 Make the source window active for scrolling.
25911 Make the assembly window active for scrolling.
25914 Make the register window active for scrolling.
25917 Make the command window active for scrolling.
25922 Refresh the screen. This is similar to typing @kbd{C-L}.
25924 @item tui reg @var{group}
25926 Changes the register group displayed in the tui register window to
25927 @var{group}. If the register window is not currently displayed this
25928 command will cause the register window to be displayed. The list of
25929 register groups, as well as their order is target specific. The
25930 following groups are available on most targets:
25933 Repeatedly selecting this group will cause the display to cycle
25934 through all of the available register groups.
25937 Repeatedly selecting this group will cause the display to cycle
25938 through all of the available register groups in the reverse order to
25942 Display the general registers.
25944 Display the floating point registers.
25946 Display the system registers.
25948 Display the vector registers.
25950 Display all registers.
25955 Update the source window and the current execution point.
25957 @item winheight @var{name} +@var{count}
25958 @itemx winheight @var{name} -@var{count}
25960 Change the height of the window @var{name} by @var{count}
25961 lines. Positive counts increase the height, while negative counts
25962 decrease it. The @var{name} parameter can be one of @code{src} (the
25963 source window), @code{cmd} (the command window), @code{asm} (the
25964 disassembly window), or @code{regs} (the register display window).
25966 @item tabset @var{nchars}
25968 Set the width of tab stops to be @var{nchars} characters. This
25969 setting affects the display of TAB characters in the source and
25973 @node TUI Configuration
25974 @section TUI Configuration Variables
25975 @cindex TUI configuration variables
25977 Several configuration variables control the appearance of TUI windows.
25980 @item set tui border-kind @var{kind}
25981 @kindex set tui border-kind
25982 Select the border appearance for the source, assembly and register windows.
25983 The possible values are the following:
25986 Use a space character to draw the border.
25989 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25992 Use the Alternate Character Set to draw the border. The border is
25993 drawn using character line graphics if the terminal supports them.
25996 @item set tui border-mode @var{mode}
25997 @kindex set tui border-mode
25998 @itemx set tui active-border-mode @var{mode}
25999 @kindex set tui active-border-mode
26000 Select the display attributes for the borders of the inactive windows
26001 or the active window. The @var{mode} can be one of the following:
26004 Use normal attributes to display the border.
26010 Use reverse video mode.
26013 Use half bright mode.
26015 @item half-standout
26016 Use half bright and standout mode.
26019 Use extra bright or bold mode.
26021 @item bold-standout
26022 Use extra bright or bold and standout mode.
26027 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26030 @cindex @sc{gnu} Emacs
26031 A special interface allows you to use @sc{gnu} Emacs to view (and
26032 edit) the source files for the program you are debugging with
26035 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26036 executable file you want to debug as an argument. This command starts
26037 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26038 created Emacs buffer.
26039 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26041 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26046 All ``terminal'' input and output goes through an Emacs buffer, called
26049 This applies both to @value{GDBN} commands and their output, and to the input
26050 and output done by the program you are debugging.
26052 This is useful because it means that you can copy the text of previous
26053 commands and input them again; you can even use parts of the output
26056 All the facilities of Emacs' Shell mode are available for interacting
26057 with your program. In particular, you can send signals the usual
26058 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26062 @value{GDBN} displays source code through Emacs.
26064 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26065 source file for that frame and puts an arrow (@samp{=>}) at the
26066 left margin of the current line. Emacs uses a separate buffer for
26067 source display, and splits the screen to show both your @value{GDBN} session
26070 Explicit @value{GDBN} @code{list} or search commands still produce output as
26071 usual, but you probably have no reason to use them from Emacs.
26074 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26075 a graphical mode, enabled by default, which provides further buffers
26076 that can control the execution and describe the state of your program.
26077 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26079 If you specify an absolute file name when prompted for the @kbd{M-x
26080 gdb} argument, then Emacs sets your current working directory to where
26081 your program resides. If you only specify the file name, then Emacs
26082 sets your current working directory to the directory associated
26083 with the previous buffer. In this case, @value{GDBN} may find your
26084 program by searching your environment's @code{PATH} variable, but on
26085 some operating systems it might not find the source. So, although the
26086 @value{GDBN} input and output session proceeds normally, the auxiliary
26087 buffer does not display the current source and line of execution.
26089 The initial working directory of @value{GDBN} is printed on the top
26090 line of the GUD buffer and this serves as a default for the commands
26091 that specify files for @value{GDBN} to operate on. @xref{Files,
26092 ,Commands to Specify Files}.
26094 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26095 need to call @value{GDBN} by a different name (for example, if you
26096 keep several configurations around, with different names) you can
26097 customize the Emacs variable @code{gud-gdb-command-name} to run the
26100 In the GUD buffer, you can use these special Emacs commands in
26101 addition to the standard Shell mode commands:
26105 Describe the features of Emacs' GUD Mode.
26108 Execute to another source line, like the @value{GDBN} @code{step} command; also
26109 update the display window to show the current file and location.
26112 Execute to next source line in this function, skipping all function
26113 calls, like the @value{GDBN} @code{next} command. Then update the display window
26114 to show the current file and location.
26117 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26118 display window accordingly.
26121 Execute until exit from the selected stack frame, like the @value{GDBN}
26122 @code{finish} command.
26125 Continue execution of your program, like the @value{GDBN} @code{continue}
26129 Go up the number of frames indicated by the numeric argument
26130 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26131 like the @value{GDBN} @code{up} command.
26134 Go down the number of frames indicated by the numeric argument, like the
26135 @value{GDBN} @code{down} command.
26138 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26139 tells @value{GDBN} to set a breakpoint on the source line point is on.
26141 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26142 separate frame which shows a backtrace when the GUD buffer is current.
26143 Move point to any frame in the stack and type @key{RET} to make it
26144 become the current frame and display the associated source in the
26145 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26146 selected frame become the current one. In graphical mode, the
26147 speedbar displays watch expressions.
26149 If you accidentally delete the source-display buffer, an easy way to get
26150 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26151 request a frame display; when you run under Emacs, this recreates
26152 the source buffer if necessary to show you the context of the current
26155 The source files displayed in Emacs are in ordinary Emacs buffers
26156 which are visiting the source files in the usual way. You can edit
26157 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26158 communicates with Emacs in terms of line numbers. If you add or
26159 delete lines from the text, the line numbers that @value{GDBN} knows cease
26160 to correspond properly with the code.
26162 A more detailed description of Emacs' interaction with @value{GDBN} is
26163 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26167 @chapter The @sc{gdb/mi} Interface
26169 @unnumberedsec Function and Purpose
26171 @cindex @sc{gdb/mi}, its purpose
26172 @sc{gdb/mi} is a line based machine oriented text interface to
26173 @value{GDBN} and is activated by specifying using the
26174 @option{--interpreter} command line option (@pxref{Mode Options}). It
26175 is specifically intended to support the development of systems which
26176 use the debugger as just one small component of a larger system.
26178 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26179 in the form of a reference manual.
26181 Note that @sc{gdb/mi} is still under construction, so some of the
26182 features described below are incomplete and subject to change
26183 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26185 @unnumberedsec Notation and Terminology
26187 @cindex notational conventions, for @sc{gdb/mi}
26188 This chapter uses the following notation:
26192 @code{|} separates two alternatives.
26195 @code{[ @var{something} ]} indicates that @var{something} is optional:
26196 it may or may not be given.
26199 @code{( @var{group} )*} means that @var{group} inside the parentheses
26200 may repeat zero or more times.
26203 @code{( @var{group} )+} means that @var{group} inside the parentheses
26204 may repeat one or more times.
26207 @code{"@var{string}"} means a literal @var{string}.
26211 @heading Dependencies
26215 * GDB/MI General Design::
26216 * GDB/MI Command Syntax::
26217 * GDB/MI Compatibility with CLI::
26218 * GDB/MI Development and Front Ends::
26219 * GDB/MI Output Records::
26220 * GDB/MI Simple Examples::
26221 * GDB/MI Command Description Format::
26222 * GDB/MI Breakpoint Commands::
26223 * GDB/MI Catchpoint Commands::
26224 * GDB/MI Program Context::
26225 * GDB/MI Thread Commands::
26226 * GDB/MI Ada Tasking Commands::
26227 * GDB/MI Program Execution::
26228 * GDB/MI Stack Manipulation::
26229 * GDB/MI Variable Objects::
26230 * GDB/MI Data Manipulation::
26231 * GDB/MI Tracepoint Commands::
26232 * GDB/MI Symbol Query::
26233 * GDB/MI File Commands::
26235 * GDB/MI Kod Commands::
26236 * GDB/MI Memory Overlay Commands::
26237 * GDB/MI Signal Handling Commands::
26239 * GDB/MI Target Manipulation::
26240 * GDB/MI File Transfer Commands::
26241 * GDB/MI Ada Exceptions Commands::
26242 * GDB/MI Support Commands::
26243 * GDB/MI Miscellaneous Commands::
26246 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26247 @node GDB/MI General Design
26248 @section @sc{gdb/mi} General Design
26249 @cindex GDB/MI General Design
26251 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26252 parts---commands sent to @value{GDBN}, responses to those commands
26253 and notifications. Each command results in exactly one response,
26254 indicating either successful completion of the command, or an error.
26255 For the commands that do not resume the target, the response contains the
26256 requested information. For the commands that resume the target, the
26257 response only indicates whether the target was successfully resumed.
26258 Notifications is the mechanism for reporting changes in the state of the
26259 target, or in @value{GDBN} state, that cannot conveniently be associated with
26260 a command and reported as part of that command response.
26262 The important examples of notifications are:
26266 Exec notifications. These are used to report changes in
26267 target state---when a target is resumed, or stopped. It would not
26268 be feasible to include this information in response of resuming
26269 commands, because one resume commands can result in multiple events in
26270 different threads. Also, quite some time may pass before any event
26271 happens in the target, while a frontend needs to know whether the resuming
26272 command itself was successfully executed.
26275 Console output, and status notifications. Console output
26276 notifications are used to report output of CLI commands, as well as
26277 diagnostics for other commands. Status notifications are used to
26278 report the progress of a long-running operation. Naturally, including
26279 this information in command response would mean no output is produced
26280 until the command is finished, which is undesirable.
26283 General notifications. Commands may have various side effects on
26284 the @value{GDBN} or target state beyond their official purpose. For example,
26285 a command may change the selected thread. Although such changes can
26286 be included in command response, using notification allows for more
26287 orthogonal frontend design.
26291 There's no guarantee that whenever an MI command reports an error,
26292 @value{GDBN} or the target are in any specific state, and especially,
26293 the state is not reverted to the state before the MI command was
26294 processed. Therefore, whenever an MI command results in an error,
26295 we recommend that the frontend refreshes all the information shown in
26296 the user interface.
26300 * Context management::
26301 * Asynchronous and non-stop modes::
26305 @node Context management
26306 @subsection Context management
26308 @subsubsection Threads and Frames
26310 In most cases when @value{GDBN} accesses the target, this access is
26311 done in context of a specific thread and frame (@pxref{Frames}).
26312 Often, even when accessing global data, the target requires that a thread
26313 be specified. The CLI interface maintains the selected thread and frame,
26314 and supplies them to target on each command. This is convenient,
26315 because a command line user would not want to specify that information
26316 explicitly on each command, and because user interacts with
26317 @value{GDBN} via a single terminal, so no confusion is possible as
26318 to what thread and frame are the current ones.
26320 In the case of MI, the concept of selected thread and frame is less
26321 useful. First, a frontend can easily remember this information
26322 itself. Second, a graphical frontend can have more than one window,
26323 each one used for debugging a different thread, and the frontend might
26324 want to access additional threads for internal purposes. This
26325 increases the risk that by relying on implicitly selected thread, the
26326 frontend may be operating on a wrong one. Therefore, each MI command
26327 should explicitly specify which thread and frame to operate on. To
26328 make it possible, each MI command accepts the @samp{--thread} and
26329 @samp{--frame} options, the value to each is @value{GDBN} global
26330 identifier for thread and frame to operate on.
26332 Usually, each top-level window in a frontend allows the user to select
26333 a thread and a frame, and remembers the user selection for further
26334 operations. However, in some cases @value{GDBN} may suggest that the
26335 current thread or frame be changed. For example, when stopping on a
26336 breakpoint it is reasonable to switch to the thread where breakpoint is
26337 hit. For another example, if the user issues the CLI @samp{thread} or
26338 @samp{frame} commands via the frontend, it is desirable to change the
26339 frontend's selection to the one specified by user. @value{GDBN}
26340 communicates the suggestion to change current thread and frame using the
26341 @samp{=thread-selected} notification.
26343 Note that historically, MI shares the selected thread with CLI, so
26344 frontends used the @code{-thread-select} to execute commands in the
26345 right context. However, getting this to work right is cumbersome. The
26346 simplest way is for frontend to emit @code{-thread-select} command
26347 before every command. This doubles the number of commands that need
26348 to be sent. The alternative approach is to suppress @code{-thread-select}
26349 if the selected thread in @value{GDBN} is supposed to be identical to the
26350 thread the frontend wants to operate on. However, getting this
26351 optimization right can be tricky. In particular, if the frontend
26352 sends several commands to @value{GDBN}, and one of the commands changes the
26353 selected thread, then the behaviour of subsequent commands will
26354 change. So, a frontend should either wait for response from such
26355 problematic commands, or explicitly add @code{-thread-select} for
26356 all subsequent commands. No frontend is known to do this exactly
26357 right, so it is suggested to just always pass the @samp{--thread} and
26358 @samp{--frame} options.
26360 @subsubsection Language
26362 The execution of several commands depends on which language is selected.
26363 By default, the current language (@pxref{show language}) is used.
26364 But for commands known to be language-sensitive, it is recommended
26365 to use the @samp{--language} option. This option takes one argument,
26366 which is the name of the language to use while executing the command.
26370 -data-evaluate-expression --language c "sizeof (void*)"
26375 The valid language names are the same names accepted by the
26376 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26377 @samp{local} or @samp{unknown}.
26379 @node Asynchronous and non-stop modes
26380 @subsection Asynchronous command execution and non-stop mode
26382 On some targets, @value{GDBN} is capable of processing MI commands
26383 even while the target is running. This is called @dfn{asynchronous
26384 command execution} (@pxref{Background Execution}). The frontend may
26385 specify a preferrence for asynchronous execution using the
26386 @code{-gdb-set mi-async 1} command, which should be emitted before
26387 either running the executable or attaching to the target. After the
26388 frontend has started the executable or attached to the target, it can
26389 find if asynchronous execution is enabled using the
26390 @code{-list-target-features} command.
26393 @item -gdb-set mi-async on
26394 @item -gdb-set mi-async off
26395 Set whether MI is in asynchronous mode.
26397 When @code{off}, which is the default, MI execution commands (e.g.,
26398 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26399 for the program to stop before processing further commands.
26401 When @code{on}, MI execution commands are background execution
26402 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26403 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26404 MI commands even while the target is running.
26406 @item -gdb-show mi-async
26407 Show whether MI asynchronous mode is enabled.
26410 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26411 @code{target-async} instead of @code{mi-async}, and it had the effect
26412 of both putting MI in asynchronous mode and making CLI background
26413 commands possible. CLI background commands are now always possible
26414 ``out of the box'' if the target supports them. The old spelling is
26415 kept as a deprecated alias for backwards compatibility.
26417 Even if @value{GDBN} can accept a command while target is running,
26418 many commands that access the target do not work when the target is
26419 running. Therefore, asynchronous command execution is most useful
26420 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26421 it is possible to examine the state of one thread, while other threads
26424 When a given thread is running, MI commands that try to access the
26425 target in the context of that thread may not work, or may work only on
26426 some targets. In particular, commands that try to operate on thread's
26427 stack will not work, on any target. Commands that read memory, or
26428 modify breakpoints, may work or not work, depending on the target. Note
26429 that even commands that operate on global state, such as @code{print},
26430 @code{set}, and breakpoint commands, still access the target in the
26431 context of a specific thread, so frontend should try to find a
26432 stopped thread and perform the operation on that thread (using the
26433 @samp{--thread} option).
26435 Which commands will work in the context of a running thread is
26436 highly target dependent. However, the two commands
26437 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26438 to find the state of a thread, will always work.
26440 @node Thread groups
26441 @subsection Thread groups
26442 @value{GDBN} may be used to debug several processes at the same time.
26443 On some platfroms, @value{GDBN} may support debugging of several
26444 hardware systems, each one having several cores with several different
26445 processes running on each core. This section describes the MI
26446 mechanism to support such debugging scenarios.
26448 The key observation is that regardless of the structure of the
26449 target, MI can have a global list of threads, because most commands that
26450 accept the @samp{--thread} option do not need to know what process that
26451 thread belongs to. Therefore, it is not necessary to introduce
26452 neither additional @samp{--process} option, nor an notion of the
26453 current process in the MI interface. The only strictly new feature
26454 that is required is the ability to find how the threads are grouped
26457 To allow the user to discover such grouping, and to support arbitrary
26458 hierarchy of machines/cores/processes, MI introduces the concept of a
26459 @dfn{thread group}. Thread group is a collection of threads and other
26460 thread groups. A thread group always has a string identifier, a type,
26461 and may have additional attributes specific to the type. A new
26462 command, @code{-list-thread-groups}, returns the list of top-level
26463 thread groups, which correspond to processes that @value{GDBN} is
26464 debugging at the moment. By passing an identifier of a thread group
26465 to the @code{-list-thread-groups} command, it is possible to obtain
26466 the members of specific thread group.
26468 To allow the user to easily discover processes, and other objects, he
26469 wishes to debug, a concept of @dfn{available thread group} is
26470 introduced. Available thread group is an thread group that
26471 @value{GDBN} is not debugging, but that can be attached to, using the
26472 @code{-target-attach} command. The list of available top-level thread
26473 groups can be obtained using @samp{-list-thread-groups --available}.
26474 In general, the content of a thread group may be only retrieved only
26475 after attaching to that thread group.
26477 Thread groups are related to inferiors (@pxref{Inferiors and
26478 Programs}). Each inferior corresponds to a thread group of a special
26479 type @samp{process}, and some additional operations are permitted on
26480 such thread groups.
26482 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26483 @node GDB/MI Command Syntax
26484 @section @sc{gdb/mi} Command Syntax
26487 * GDB/MI Input Syntax::
26488 * GDB/MI Output Syntax::
26491 @node GDB/MI Input Syntax
26492 @subsection @sc{gdb/mi} Input Syntax
26494 @cindex input syntax for @sc{gdb/mi}
26495 @cindex @sc{gdb/mi}, input syntax
26497 @item @var{command} @expansion{}
26498 @code{@var{cli-command} | @var{mi-command}}
26500 @item @var{cli-command} @expansion{}
26501 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26502 @var{cli-command} is any existing @value{GDBN} CLI command.
26504 @item @var{mi-command} @expansion{}
26505 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26506 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26508 @item @var{token} @expansion{}
26509 "any sequence of digits"
26511 @item @var{option} @expansion{}
26512 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26514 @item @var{parameter} @expansion{}
26515 @code{@var{non-blank-sequence} | @var{c-string}}
26517 @item @var{operation} @expansion{}
26518 @emph{any of the operations described in this chapter}
26520 @item @var{non-blank-sequence} @expansion{}
26521 @emph{anything, provided it doesn't contain special characters such as
26522 "-", @var{nl}, """ and of course " "}
26524 @item @var{c-string} @expansion{}
26525 @code{""" @var{seven-bit-iso-c-string-content} """}
26527 @item @var{nl} @expansion{}
26536 The CLI commands are still handled by the @sc{mi} interpreter; their
26537 output is described below.
26540 The @code{@var{token}}, when present, is passed back when the command
26544 Some @sc{mi} commands accept optional arguments as part of the parameter
26545 list. Each option is identified by a leading @samp{-} (dash) and may be
26546 followed by an optional argument parameter. Options occur first in the
26547 parameter list and can be delimited from normal parameters using
26548 @samp{--} (this is useful when some parameters begin with a dash).
26555 We want easy access to the existing CLI syntax (for debugging).
26558 We want it to be easy to spot a @sc{mi} operation.
26561 @node GDB/MI Output Syntax
26562 @subsection @sc{gdb/mi} Output Syntax
26564 @cindex output syntax of @sc{gdb/mi}
26565 @cindex @sc{gdb/mi}, output syntax
26566 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26567 followed, optionally, by a single result record. This result record
26568 is for the most recent command. The sequence of output records is
26569 terminated by @samp{(gdb)}.
26571 If an input command was prefixed with a @code{@var{token}} then the
26572 corresponding output for that command will also be prefixed by that same
26576 @item @var{output} @expansion{}
26577 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26579 @item @var{result-record} @expansion{}
26580 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26582 @item @var{out-of-band-record} @expansion{}
26583 @code{@var{async-record} | @var{stream-record}}
26585 @item @var{async-record} @expansion{}
26586 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26588 @item @var{exec-async-output} @expansion{}
26589 @code{[ @var{token} ] "*" @var{async-output nl}}
26591 @item @var{status-async-output} @expansion{}
26592 @code{[ @var{token} ] "+" @var{async-output nl}}
26594 @item @var{notify-async-output} @expansion{}
26595 @code{[ @var{token} ] "=" @var{async-output nl}}
26597 @item @var{async-output} @expansion{}
26598 @code{@var{async-class} ( "," @var{result} )*}
26600 @item @var{result-class} @expansion{}
26601 @code{"done" | "running" | "connected" | "error" | "exit"}
26603 @item @var{async-class} @expansion{}
26604 @code{"stopped" | @var{others}} (where @var{others} will be added
26605 depending on the needs---this is still in development).
26607 @item @var{result} @expansion{}
26608 @code{ @var{variable} "=" @var{value}}
26610 @item @var{variable} @expansion{}
26611 @code{ @var{string} }
26613 @item @var{value} @expansion{}
26614 @code{ @var{const} | @var{tuple} | @var{list} }
26616 @item @var{const} @expansion{}
26617 @code{@var{c-string}}
26619 @item @var{tuple} @expansion{}
26620 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26622 @item @var{list} @expansion{}
26623 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26624 @var{result} ( "," @var{result} )* "]" }
26626 @item @var{stream-record} @expansion{}
26627 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26629 @item @var{console-stream-output} @expansion{}
26630 @code{"~" @var{c-string nl}}
26632 @item @var{target-stream-output} @expansion{}
26633 @code{"@@" @var{c-string nl}}
26635 @item @var{log-stream-output} @expansion{}
26636 @code{"&" @var{c-string nl}}
26638 @item @var{nl} @expansion{}
26641 @item @var{token} @expansion{}
26642 @emph{any sequence of digits}.
26650 All output sequences end in a single line containing a period.
26653 The @code{@var{token}} is from the corresponding request. Note that
26654 for all async output, while the token is allowed by the grammar and
26655 may be output by future versions of @value{GDBN} for select async
26656 output messages, it is generally omitted. Frontends should treat
26657 all async output as reporting general changes in the state of the
26658 target and there should be no need to associate async output to any
26662 @cindex status output in @sc{gdb/mi}
26663 @var{status-async-output} contains on-going status information about the
26664 progress of a slow operation. It can be discarded. All status output is
26665 prefixed by @samp{+}.
26668 @cindex async output in @sc{gdb/mi}
26669 @var{exec-async-output} contains asynchronous state change on the target
26670 (stopped, started, disappeared). All async output is prefixed by
26674 @cindex notify output in @sc{gdb/mi}
26675 @var{notify-async-output} contains supplementary information that the
26676 client should handle (e.g., a new breakpoint information). All notify
26677 output is prefixed by @samp{=}.
26680 @cindex console output in @sc{gdb/mi}
26681 @var{console-stream-output} is output that should be displayed as is in the
26682 console. It is the textual response to a CLI command. All the console
26683 output is prefixed by @samp{~}.
26686 @cindex target output in @sc{gdb/mi}
26687 @var{target-stream-output} is the output produced by the target program.
26688 All the target output is prefixed by @samp{@@}.
26691 @cindex log output in @sc{gdb/mi}
26692 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26693 instance messages that should be displayed as part of an error log. All
26694 the log output is prefixed by @samp{&}.
26697 @cindex list output in @sc{gdb/mi}
26698 New @sc{gdb/mi} commands should only output @var{lists} containing
26704 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26705 details about the various output records.
26707 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26708 @node GDB/MI Compatibility with CLI
26709 @section @sc{gdb/mi} Compatibility with CLI
26711 @cindex compatibility, @sc{gdb/mi} and CLI
26712 @cindex @sc{gdb/mi}, compatibility with CLI
26714 For the developers convenience CLI commands can be entered directly,
26715 but there may be some unexpected behaviour. For example, commands
26716 that query the user will behave as if the user replied yes, breakpoint
26717 command lists are not executed and some CLI commands, such as
26718 @code{if}, @code{when} and @code{define}, prompt for further input with
26719 @samp{>}, which is not valid MI output.
26721 This feature may be removed at some stage in the future and it is
26722 recommended that front ends use the @code{-interpreter-exec} command
26723 (@pxref{-interpreter-exec}).
26725 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26726 @node GDB/MI Development and Front Ends
26727 @section @sc{gdb/mi} Development and Front Ends
26728 @cindex @sc{gdb/mi} development
26730 The application which takes the MI output and presents the state of the
26731 program being debugged to the user is called a @dfn{front end}.
26733 Although @sc{gdb/mi} is still incomplete, it is currently being used
26734 by a variety of front ends to @value{GDBN}. This makes it difficult
26735 to introduce new functionality without breaking existing usage. This
26736 section tries to minimize the problems by describing how the protocol
26739 Some changes in MI need not break a carefully designed front end, and
26740 for these the MI version will remain unchanged. The following is a
26741 list of changes that may occur within one level, so front ends should
26742 parse MI output in a way that can handle them:
26746 New MI commands may be added.
26749 New fields may be added to the output of any MI command.
26752 The range of values for fields with specified values, e.g.,
26753 @code{in_scope} (@pxref{-var-update}) may be extended.
26755 @c The format of field's content e.g type prefix, may change so parse it
26756 @c at your own risk. Yes, in general?
26758 @c The order of fields may change? Shouldn't really matter but it might
26759 @c resolve inconsistencies.
26762 If the changes are likely to break front ends, the MI version level
26763 will be increased by one. This will allow the front end to parse the
26764 output according to the MI version. Apart from mi0, new versions of
26765 @value{GDBN} will not support old versions of MI and it will be the
26766 responsibility of the front end to work with the new one.
26768 @c Starting with mi3, add a new command -mi-version that prints the MI
26771 The best way to avoid unexpected changes in MI that might break your front
26772 end is to make your project known to @value{GDBN} developers and
26773 follow development on @email{gdb@@sourceware.org} and
26774 @email{gdb-patches@@sourceware.org}.
26775 @cindex mailing lists
26777 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26778 @node GDB/MI Output Records
26779 @section @sc{gdb/mi} Output Records
26782 * GDB/MI Result Records::
26783 * GDB/MI Stream Records::
26784 * GDB/MI Async Records::
26785 * GDB/MI Breakpoint Information::
26786 * GDB/MI Frame Information::
26787 * GDB/MI Thread Information::
26788 * GDB/MI Ada Exception Information::
26791 @node GDB/MI Result Records
26792 @subsection @sc{gdb/mi} Result Records
26794 @cindex result records in @sc{gdb/mi}
26795 @cindex @sc{gdb/mi}, result records
26796 In addition to a number of out-of-band notifications, the response to a
26797 @sc{gdb/mi} command includes one of the following result indications:
26801 @item "^done" [ "," @var{results} ]
26802 The synchronous operation was successful, @code{@var{results}} are the return
26807 This result record is equivalent to @samp{^done}. Historically, it
26808 was output instead of @samp{^done} if the command has resumed the
26809 target. This behaviour is maintained for backward compatibility, but
26810 all frontends should treat @samp{^done} and @samp{^running}
26811 identically and rely on the @samp{*running} output record to determine
26812 which threads are resumed.
26816 @value{GDBN} has connected to a remote target.
26818 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26820 The operation failed. The @code{msg=@var{c-string}} variable contains
26821 the corresponding error message.
26823 If present, the @code{code=@var{c-string}} variable provides an error
26824 code on which consumers can rely on to detect the corresponding
26825 error condition. At present, only one error code is defined:
26828 @item "undefined-command"
26829 Indicates that the command causing the error does not exist.
26834 @value{GDBN} has terminated.
26838 @node GDB/MI Stream Records
26839 @subsection @sc{gdb/mi} Stream Records
26841 @cindex @sc{gdb/mi}, stream records
26842 @cindex stream records in @sc{gdb/mi}
26843 @value{GDBN} internally maintains a number of output streams: the console, the
26844 target, and the log. The output intended for each of these streams is
26845 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26847 Each stream record begins with a unique @dfn{prefix character} which
26848 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26849 Syntax}). In addition to the prefix, each stream record contains a
26850 @code{@var{string-output}}. This is either raw text (with an implicit new
26851 line) or a quoted C string (which does not contain an implicit newline).
26854 @item "~" @var{string-output}
26855 The console output stream contains text that should be displayed in the
26856 CLI console window. It contains the textual responses to CLI commands.
26858 @item "@@" @var{string-output}
26859 The target output stream contains any textual output from the running
26860 target. This is only present when GDB's event loop is truly
26861 asynchronous, which is currently only the case for remote targets.
26863 @item "&" @var{string-output}
26864 The log stream contains debugging messages being produced by @value{GDBN}'s
26868 @node GDB/MI Async Records
26869 @subsection @sc{gdb/mi} Async Records
26871 @cindex async records in @sc{gdb/mi}
26872 @cindex @sc{gdb/mi}, async records
26873 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26874 additional changes that have occurred. Those changes can either be a
26875 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26876 target activity (e.g., target stopped).
26878 The following is the list of possible async records:
26882 @item *running,thread-id="@var{thread}"
26883 The target is now running. The @var{thread} field can be the global
26884 thread ID of the the thread that is now running, and it can be
26885 @samp{all} if all threads are running. The frontend should assume
26886 that no interaction with a running thread is possible after this
26887 notification is produced. The frontend should not assume that this
26888 notification is output only once for any command. @value{GDBN} may
26889 emit this notification several times, either for different threads,
26890 because it cannot resume all threads together, or even for a single
26891 thread, if the thread must be stepped though some code before letting
26894 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26895 The target has stopped. The @var{reason} field can have one of the
26899 @item breakpoint-hit
26900 A breakpoint was reached.
26901 @item watchpoint-trigger
26902 A watchpoint was triggered.
26903 @item read-watchpoint-trigger
26904 A read watchpoint was triggered.
26905 @item access-watchpoint-trigger
26906 An access watchpoint was triggered.
26907 @item function-finished
26908 An -exec-finish or similar CLI command was accomplished.
26909 @item location-reached
26910 An -exec-until or similar CLI command was accomplished.
26911 @item watchpoint-scope
26912 A watchpoint has gone out of scope.
26913 @item end-stepping-range
26914 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26915 similar CLI command was accomplished.
26916 @item exited-signalled
26917 The inferior exited because of a signal.
26919 The inferior exited.
26920 @item exited-normally
26921 The inferior exited normally.
26922 @item signal-received
26923 A signal was received by the inferior.
26925 The inferior has stopped due to a library being loaded or unloaded.
26926 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26927 set or when a @code{catch load} or @code{catch unload} catchpoint is
26928 in use (@pxref{Set Catchpoints}).
26930 The inferior has forked. This is reported when @code{catch fork}
26931 (@pxref{Set Catchpoints}) has been used.
26933 The inferior has vforked. This is reported in when @code{catch vfork}
26934 (@pxref{Set Catchpoints}) has been used.
26935 @item syscall-entry
26936 The inferior entered a system call. This is reported when @code{catch
26937 syscall} (@pxref{Set Catchpoints}) has been used.
26938 @item syscall-return
26939 The inferior returned from a system call. This is reported when
26940 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26942 The inferior called @code{exec}. This is reported when @code{catch exec}
26943 (@pxref{Set Catchpoints}) has been used.
26946 The @var{id} field identifies the global thread ID of the thread
26947 that directly caused the stop -- for example by hitting a breakpoint.
26948 Depending on whether all-stop
26949 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26950 stop all threads, or only the thread that directly triggered the stop.
26951 If all threads are stopped, the @var{stopped} field will have the
26952 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26953 field will be a list of thread identifiers. Presently, this list will
26954 always include a single thread, but frontend should be prepared to see
26955 several threads in the list. The @var{core} field reports the
26956 processor core on which the stop event has happened. This field may be absent
26957 if such information is not available.
26959 @item =thread-group-added,id="@var{id}"
26960 @itemx =thread-group-removed,id="@var{id}"
26961 A thread group was either added or removed. The @var{id} field
26962 contains the @value{GDBN} identifier of the thread group. When a thread
26963 group is added, it generally might not be associated with a running
26964 process. When a thread group is removed, its id becomes invalid and
26965 cannot be used in any way.
26967 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26968 A thread group became associated with a running program,
26969 either because the program was just started or the thread group
26970 was attached to a program. The @var{id} field contains the
26971 @value{GDBN} identifier of the thread group. The @var{pid} field
26972 contains process identifier, specific to the operating system.
26974 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26975 A thread group is no longer associated with a running program,
26976 either because the program has exited, or because it was detached
26977 from. The @var{id} field contains the @value{GDBN} identifier of the
26978 thread group. The @var{code} field is the exit code of the inferior; it exists
26979 only when the inferior exited with some code.
26981 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26982 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26983 A thread either was created, or has exited. The @var{id} field
26984 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26985 field identifies the thread group this thread belongs to.
26987 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
26988 Informs that the selected thread or frame were changed. This notification
26989 is not emitted as result of the @code{-thread-select} or
26990 @code{-stack-select-frame} commands, but is emitted whenever an MI command
26991 that is not documented to change the selected thread and frame actually
26992 changes them. In particular, invoking, directly or indirectly
26993 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
26994 will generate this notification. Changing the thread or frame from another
26995 user interface (see @ref{Interpreters}) will also generate this notification.
26997 The @var{frame} field is only present if the newly selected thread is
26998 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27000 We suggest that in response to this notification, front ends
27001 highlight the selected thread and cause subsequent commands to apply to
27004 @item =library-loaded,...
27005 Reports that a new library file was loaded by the program. This
27006 notification has 5 fields---@var{id}, @var{target-name},
27007 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27008 opaque identifier of the library. For remote debugging case,
27009 @var{target-name} and @var{host-name} fields give the name of the
27010 library file on the target, and on the host respectively. For native
27011 debugging, both those fields have the same value. The
27012 @var{symbols-loaded} field is emitted only for backward compatibility
27013 and should not be relied on to convey any useful information. The
27014 @var{thread-group} field, if present, specifies the id of the thread
27015 group in whose context the library was loaded. If the field is
27016 absent, it means the library was loaded in the context of all present
27017 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27020 @item =library-unloaded,...
27021 Reports that a library was unloaded by the program. This notification
27022 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27023 the same meaning as for the @code{=library-loaded} notification.
27024 The @var{thread-group} field, if present, specifies the id of the
27025 thread group in whose context the library was unloaded. If the field is
27026 absent, it means the library was unloaded in the context of all present
27029 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27030 @itemx =traceframe-changed,end
27031 Reports that the trace frame was changed and its new number is
27032 @var{tfnum}. The number of the tracepoint associated with this trace
27033 frame is @var{tpnum}.
27035 @item =tsv-created,name=@var{name},initial=@var{initial}
27036 Reports that the new trace state variable @var{name} is created with
27037 initial value @var{initial}.
27039 @item =tsv-deleted,name=@var{name}
27040 @itemx =tsv-deleted
27041 Reports that the trace state variable @var{name} is deleted or all
27042 trace state variables are deleted.
27044 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27045 Reports that the trace state variable @var{name} is modified with
27046 the initial value @var{initial}. The current value @var{current} of
27047 trace state variable is optional and is reported if the current
27048 value of trace state variable is known.
27050 @item =breakpoint-created,bkpt=@{...@}
27051 @itemx =breakpoint-modified,bkpt=@{...@}
27052 @itemx =breakpoint-deleted,id=@var{number}
27053 Reports that a breakpoint was created, modified, or deleted,
27054 respectively. Only user-visible breakpoints are reported to the MI
27057 The @var{bkpt} argument is of the same form as returned by the various
27058 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27059 @var{number} is the ordinal number of the breakpoint.
27061 Note that if a breakpoint is emitted in the result record of a
27062 command, then it will not also be emitted in an async record.
27064 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27065 @itemx =record-stopped,thread-group="@var{id}"
27066 Execution log recording was either started or stopped on an
27067 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27068 group corresponding to the affected inferior.
27070 The @var{method} field indicates the method used to record execution. If the
27071 method in use supports multiple recording formats, @var{format} will be present
27072 and contain the currently used format. @xref{Process Record and Replay},
27073 for existing method and format values.
27075 @item =cmd-param-changed,param=@var{param},value=@var{value}
27076 Reports that a parameter of the command @code{set @var{param}} is
27077 changed to @var{value}. In the multi-word @code{set} command,
27078 the @var{param} is the whole parameter list to @code{set} command.
27079 For example, In command @code{set check type on}, @var{param}
27080 is @code{check type} and @var{value} is @code{on}.
27082 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27083 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27084 written in an inferior. The @var{id} is the identifier of the
27085 thread group corresponding to the affected inferior. The optional
27086 @code{type="code"} part is reported if the memory written to holds
27090 @node GDB/MI Breakpoint Information
27091 @subsection @sc{gdb/mi} Breakpoint Information
27093 When @value{GDBN} reports information about a breakpoint, a
27094 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27099 The breakpoint number. For a breakpoint that represents one location
27100 of a multi-location breakpoint, this will be a dotted pair, like
27104 The type of the breakpoint. For ordinary breakpoints this will be
27105 @samp{breakpoint}, but many values are possible.
27108 If the type of the breakpoint is @samp{catchpoint}, then this
27109 indicates the exact type of catchpoint.
27112 This is the breakpoint disposition---either @samp{del}, meaning that
27113 the breakpoint will be deleted at the next stop, or @samp{keep},
27114 meaning that the breakpoint will not be deleted.
27117 This indicates whether the breakpoint is enabled, in which case the
27118 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27119 Note that this is not the same as the field @code{enable}.
27122 The address of the breakpoint. This may be a hexidecimal number,
27123 giving the address; or the string @samp{<PENDING>}, for a pending
27124 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27125 multiple locations. This field will not be present if no address can
27126 be determined. For example, a watchpoint does not have an address.
27129 If known, the function in which the breakpoint appears.
27130 If not known, this field is not present.
27133 The name of the source file which contains this function, if known.
27134 If not known, this field is not present.
27137 The full file name of the source file which contains this function, if
27138 known. If not known, this field is not present.
27141 The line number at which this breakpoint appears, if known.
27142 If not known, this field is not present.
27145 If the source file is not known, this field may be provided. If
27146 provided, this holds the address of the breakpoint, possibly followed
27150 If this breakpoint is pending, this field is present and holds the
27151 text used to set the breakpoint, as entered by the user.
27154 Where this breakpoint's condition is evaluated, either @samp{host} or
27158 If this is a thread-specific breakpoint, then this identifies the
27159 thread in which the breakpoint can trigger.
27162 If this breakpoint is restricted to a particular Ada task, then this
27163 field will hold the task identifier.
27166 If the breakpoint is conditional, this is the condition expression.
27169 The ignore count of the breakpoint.
27172 The enable count of the breakpoint.
27174 @item traceframe-usage
27177 @item static-tracepoint-marker-string-id
27178 For a static tracepoint, the name of the static tracepoint marker.
27181 For a masked watchpoint, this is the mask.
27184 A tracepoint's pass count.
27186 @item original-location
27187 The location of the breakpoint as originally specified by the user.
27188 This field is optional.
27191 The number of times the breakpoint has been hit.
27194 This field is only given for tracepoints. This is either @samp{y},
27195 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27199 Some extra data, the exact contents of which are type-dependent.
27203 For example, here is what the output of @code{-break-insert}
27204 (@pxref{GDB/MI Breakpoint Commands}) might be:
27207 -> -break-insert main
27208 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27209 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27210 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27215 @node GDB/MI Frame Information
27216 @subsection @sc{gdb/mi} Frame Information
27218 Response from many MI commands includes an information about stack
27219 frame. This information is a tuple that may have the following
27224 The level of the stack frame. The innermost frame has the level of
27225 zero. This field is always present.
27228 The name of the function corresponding to the frame. This field may
27229 be absent if @value{GDBN} is unable to determine the function name.
27232 The code address for the frame. This field is always present.
27235 The name of the source files that correspond to the frame's code
27236 address. This field may be absent.
27239 The source line corresponding to the frames' code address. This field
27243 The name of the binary file (either executable or shared library) the
27244 corresponds to the frame's code address. This field may be absent.
27248 @node GDB/MI Thread Information
27249 @subsection @sc{gdb/mi} Thread Information
27251 Whenever @value{GDBN} has to report an information about a thread, it
27252 uses a tuple with the following fields. The fields are always present unless
27257 The global numeric id assigned to the thread by @value{GDBN}.
27260 The target-specific string identifying the thread.
27263 Additional information about the thread provided by the target.
27264 It is supposed to be human-readable and not interpreted by the
27265 frontend. This field is optional.
27268 The name of the thread. If the user specified a name using the
27269 @code{thread name} command, then this name is given. Otherwise, if
27270 @value{GDBN} can extract the thread name from the target, then that
27271 name is given. If @value{GDBN} cannot find the thread name, then this
27275 The execution state of the thread, either @samp{stopped} or @samp{running},
27276 depending on whether the thread is presently running.
27279 The stack frame currently executing in the thread. This field is only present
27280 if the thread is stopped. Its format is documented in
27281 @ref{GDB/MI Frame Information}.
27284 The value of this field is an integer number of the processor core the
27285 thread was last seen on. This field is optional.
27288 @node GDB/MI Ada Exception Information
27289 @subsection @sc{gdb/mi} Ada Exception Information
27291 Whenever a @code{*stopped} record is emitted because the program
27292 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27293 @value{GDBN} provides the name of the exception that was raised via
27294 the @code{exception-name} field. Also, for exceptions that were raised
27295 with an exception message, @value{GDBN} provides that message via
27296 the @code{exception-message} field.
27298 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27299 @node GDB/MI Simple Examples
27300 @section Simple Examples of @sc{gdb/mi} Interaction
27301 @cindex @sc{gdb/mi}, simple examples
27303 This subsection presents several simple examples of interaction using
27304 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27305 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27306 the output received from @sc{gdb/mi}.
27308 Note the line breaks shown in the examples are here only for
27309 readability, they don't appear in the real output.
27311 @subheading Setting a Breakpoint
27313 Setting a breakpoint generates synchronous output which contains detailed
27314 information of the breakpoint.
27317 -> -break-insert main
27318 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27319 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27320 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27325 @subheading Program Execution
27327 Program execution generates asynchronous records and MI gives the
27328 reason that execution stopped.
27334 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27335 frame=@{addr="0x08048564",func="main",
27336 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27337 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27342 <- *stopped,reason="exited-normally"
27346 @subheading Quitting @value{GDBN}
27348 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27356 Please note that @samp{^exit} is printed immediately, but it might
27357 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27358 performs necessary cleanups, including killing programs being debugged
27359 or disconnecting from debug hardware, so the frontend should wait till
27360 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27361 fails to exit in reasonable time.
27363 @subheading A Bad Command
27365 Here's what happens if you pass a non-existent command:
27369 <- ^error,msg="Undefined MI command: rubbish"
27374 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27375 @node GDB/MI Command Description Format
27376 @section @sc{gdb/mi} Command Description Format
27378 The remaining sections describe blocks of commands. Each block of
27379 commands is laid out in a fashion similar to this section.
27381 @subheading Motivation
27383 The motivation for this collection of commands.
27385 @subheading Introduction
27387 A brief introduction to this collection of commands as a whole.
27389 @subheading Commands
27391 For each command in the block, the following is described:
27393 @subsubheading Synopsis
27396 -command @var{args}@dots{}
27399 @subsubheading Result
27401 @subsubheading @value{GDBN} Command
27403 The corresponding @value{GDBN} CLI command(s), if any.
27405 @subsubheading Example
27407 Example(s) formatted for readability. Some of the described commands have
27408 not been implemented yet and these are labeled N.A.@: (not available).
27411 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27412 @node GDB/MI Breakpoint Commands
27413 @section @sc{gdb/mi} Breakpoint Commands
27415 @cindex breakpoint commands for @sc{gdb/mi}
27416 @cindex @sc{gdb/mi}, breakpoint commands
27417 This section documents @sc{gdb/mi} commands for manipulating
27420 @subheading The @code{-break-after} Command
27421 @findex -break-after
27423 @subsubheading Synopsis
27426 -break-after @var{number} @var{count}
27429 The breakpoint number @var{number} is not in effect until it has been
27430 hit @var{count} times. To see how this is reflected in the output of
27431 the @samp{-break-list} command, see the description of the
27432 @samp{-break-list} command below.
27434 @subsubheading @value{GDBN} Command
27436 The corresponding @value{GDBN} command is @samp{ignore}.
27438 @subsubheading Example
27443 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27444 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27445 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27453 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27454 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27455 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27456 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27457 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27458 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27459 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27460 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27461 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27462 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27467 @subheading The @code{-break-catch} Command
27468 @findex -break-catch
27471 @subheading The @code{-break-commands} Command
27472 @findex -break-commands
27474 @subsubheading Synopsis
27477 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27480 Specifies the CLI commands that should be executed when breakpoint
27481 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27482 are the commands. If no command is specified, any previously-set
27483 commands are cleared. @xref{Break Commands}. Typical use of this
27484 functionality is tracing a program, that is, printing of values of
27485 some variables whenever breakpoint is hit and then continuing.
27487 @subsubheading @value{GDBN} Command
27489 The corresponding @value{GDBN} command is @samp{commands}.
27491 @subsubheading Example
27496 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27497 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27498 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27501 -break-commands 1 "print v" "continue"
27506 @subheading The @code{-break-condition} Command
27507 @findex -break-condition
27509 @subsubheading Synopsis
27512 -break-condition @var{number} @var{expr}
27515 Breakpoint @var{number} will stop the program only if the condition in
27516 @var{expr} is true. The condition becomes part of the
27517 @samp{-break-list} output (see the description of the @samp{-break-list}
27520 @subsubheading @value{GDBN} Command
27522 The corresponding @value{GDBN} command is @samp{condition}.
27524 @subsubheading Example
27528 -break-condition 1 1
27532 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27533 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27534 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27535 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27536 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27537 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27538 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27539 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27540 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27541 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27545 @subheading The @code{-break-delete} Command
27546 @findex -break-delete
27548 @subsubheading Synopsis
27551 -break-delete ( @var{breakpoint} )+
27554 Delete the breakpoint(s) whose number(s) are specified in the argument
27555 list. This is obviously reflected in the breakpoint list.
27557 @subsubheading @value{GDBN} Command
27559 The corresponding @value{GDBN} command is @samp{delete}.
27561 @subsubheading Example
27569 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27570 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27571 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27572 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27573 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27574 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27575 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27580 @subheading The @code{-break-disable} Command
27581 @findex -break-disable
27583 @subsubheading Synopsis
27586 -break-disable ( @var{breakpoint} )+
27589 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27590 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27592 @subsubheading @value{GDBN} Command
27594 The corresponding @value{GDBN} command is @samp{disable}.
27596 @subsubheading Example
27604 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27605 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27606 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27607 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27608 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27609 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27610 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27611 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27612 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27613 line="5",thread-groups=["i1"],times="0"@}]@}
27617 @subheading The @code{-break-enable} Command
27618 @findex -break-enable
27620 @subsubheading Synopsis
27623 -break-enable ( @var{breakpoint} )+
27626 Enable (previously disabled) @var{breakpoint}(s).
27628 @subsubheading @value{GDBN} Command
27630 The corresponding @value{GDBN} command is @samp{enable}.
27632 @subsubheading Example
27640 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27641 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27642 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27643 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27644 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27645 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27646 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27647 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27648 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27649 line="5",thread-groups=["i1"],times="0"@}]@}
27653 @subheading The @code{-break-info} Command
27654 @findex -break-info
27656 @subsubheading Synopsis
27659 -break-info @var{breakpoint}
27663 Get information about a single breakpoint.
27665 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27666 Information}, for details on the format of each breakpoint in the
27669 @subsubheading @value{GDBN} Command
27671 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27673 @subsubheading Example
27676 @subheading The @code{-break-insert} Command
27677 @findex -break-insert
27678 @anchor{-break-insert}
27680 @subsubheading Synopsis
27683 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27684 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27685 [ -p @var{thread-id} ] [ @var{location} ]
27689 If specified, @var{location}, can be one of:
27692 @item linespec location
27693 A linespec location. @xref{Linespec Locations}.
27695 @item explicit location
27696 An explicit location. @sc{gdb/mi} explicit locations are
27697 analogous to the CLI's explicit locations using the option names
27698 listed below. @xref{Explicit Locations}.
27701 @item --source @var{filename}
27702 The source file name of the location. This option requires the use
27703 of either @samp{--function} or @samp{--line}.
27705 @item --function @var{function}
27706 The name of a function or method.
27708 @item --label @var{label}
27709 The name of a label.
27711 @item --line @var{lineoffset}
27712 An absolute or relative line offset from the start of the location.
27715 @item address location
27716 An address location, *@var{address}. @xref{Address Locations}.
27720 The possible optional parameters of this command are:
27724 Insert a temporary breakpoint.
27726 Insert a hardware breakpoint.
27728 If @var{location} cannot be parsed (for example if it
27729 refers to unknown files or functions), create a pending
27730 breakpoint. Without this flag, @value{GDBN} will report
27731 an error, and won't create a breakpoint, if @var{location}
27734 Create a disabled breakpoint.
27736 Create a tracepoint. @xref{Tracepoints}. When this parameter
27737 is used together with @samp{-h}, a fast tracepoint is created.
27738 @item -c @var{condition}
27739 Make the breakpoint conditional on @var{condition}.
27740 @item -i @var{ignore-count}
27741 Initialize the @var{ignore-count}.
27742 @item -p @var{thread-id}
27743 Restrict the breakpoint to the thread with the specified global
27747 @subsubheading Result
27749 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27750 resulting breakpoint.
27752 Note: this format is open to change.
27753 @c An out-of-band breakpoint instead of part of the result?
27755 @subsubheading @value{GDBN} Command
27757 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27758 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27760 @subsubheading Example
27765 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27766 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27769 -break-insert -t foo
27770 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27771 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27775 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27776 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27777 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27778 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27779 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27780 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27781 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27782 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27783 addr="0x0001072c", func="main",file="recursive2.c",
27784 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27786 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27787 addr="0x00010774",func="foo",file="recursive2.c",
27788 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27791 @c -break-insert -r foo.*
27792 @c ~int foo(int, int);
27793 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27794 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27799 @subheading The @code{-dprintf-insert} Command
27800 @findex -dprintf-insert
27802 @subsubheading Synopsis
27805 -dprintf-insert [ -t ] [ -f ] [ -d ]
27806 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27807 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27812 If supplied, @var{location} may be specified the same way as for
27813 the @code{-break-insert} command. @xref{-break-insert}.
27815 The possible optional parameters of this command are:
27819 Insert a temporary breakpoint.
27821 If @var{location} cannot be parsed (for example, if it
27822 refers to unknown files or functions), create a pending
27823 breakpoint. Without this flag, @value{GDBN} will report
27824 an error, and won't create a breakpoint, if @var{location}
27827 Create a disabled breakpoint.
27828 @item -c @var{condition}
27829 Make the breakpoint conditional on @var{condition}.
27830 @item -i @var{ignore-count}
27831 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27832 to @var{ignore-count}.
27833 @item -p @var{thread-id}
27834 Restrict the breakpoint to the thread with the specified global
27838 @subsubheading Result
27840 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27841 resulting breakpoint.
27843 @c An out-of-band breakpoint instead of part of the result?
27845 @subsubheading @value{GDBN} Command
27847 The corresponding @value{GDBN} command is @samp{dprintf}.
27849 @subsubheading Example
27853 4-dprintf-insert foo "At foo entry\n"
27854 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27855 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27856 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27857 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27858 original-location="foo"@}
27860 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27861 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27862 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27863 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27864 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27865 original-location="mi-dprintf.c:26"@}
27869 @subheading The @code{-break-list} Command
27870 @findex -break-list
27872 @subsubheading Synopsis
27878 Displays the list of inserted breakpoints, showing the following fields:
27882 number of the breakpoint
27884 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27886 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27889 is the breakpoint enabled or no: @samp{y} or @samp{n}
27891 memory location at which the breakpoint is set
27893 logical location of the breakpoint, expressed by function name, file
27895 @item Thread-groups
27896 list of thread groups to which this breakpoint applies
27898 number of times the breakpoint has been hit
27901 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27902 @code{body} field is an empty list.
27904 @subsubheading @value{GDBN} Command
27906 The corresponding @value{GDBN} command is @samp{info break}.
27908 @subsubheading Example
27913 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27914 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27915 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27916 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27917 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27918 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27919 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27920 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27921 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27923 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27924 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27925 line="13",thread-groups=["i1"],times="0"@}]@}
27929 Here's an example of the result when there are no breakpoints:
27934 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27935 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27936 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27937 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27938 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27939 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27940 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27945 @subheading The @code{-break-passcount} Command
27946 @findex -break-passcount
27948 @subsubheading Synopsis
27951 -break-passcount @var{tracepoint-number} @var{passcount}
27954 Set the passcount for tracepoint @var{tracepoint-number} to
27955 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27956 is not a tracepoint, error is emitted. This corresponds to CLI
27957 command @samp{passcount}.
27959 @subheading The @code{-break-watch} Command
27960 @findex -break-watch
27962 @subsubheading Synopsis
27965 -break-watch [ -a | -r ]
27968 Create a watchpoint. With the @samp{-a} option it will create an
27969 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27970 read from or on a write to the memory location. With the @samp{-r}
27971 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27972 trigger only when the memory location is accessed for reading. Without
27973 either of the options, the watchpoint created is a regular watchpoint,
27974 i.e., it will trigger when the memory location is accessed for writing.
27975 @xref{Set Watchpoints, , Setting Watchpoints}.
27977 Note that @samp{-break-list} will report a single list of watchpoints and
27978 breakpoints inserted.
27980 @subsubheading @value{GDBN} Command
27982 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27985 @subsubheading Example
27987 Setting a watchpoint on a variable in the @code{main} function:
27992 ^done,wpt=@{number="2",exp="x"@}
27997 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27998 value=@{old="-268439212",new="55"@},
27999 frame=@{func="main",args=[],file="recursive2.c",
28000 fullname="/home/foo/bar/recursive2.c",line="5"@}
28004 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28005 the program execution twice: first for the variable changing value, then
28006 for the watchpoint going out of scope.
28011 ^done,wpt=@{number="5",exp="C"@}
28016 *stopped,reason="watchpoint-trigger",
28017 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28018 frame=@{func="callee4",args=[],
28019 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28020 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28025 *stopped,reason="watchpoint-scope",wpnum="5",
28026 frame=@{func="callee3",args=[@{name="strarg",
28027 value="0x11940 \"A string argument.\""@}],
28028 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28029 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28033 Listing breakpoints and watchpoints, at different points in the program
28034 execution. Note that once the watchpoint goes out of scope, it is
28040 ^done,wpt=@{number="2",exp="C"@}
28043 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28044 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28045 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28046 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28047 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28048 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28049 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28050 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28051 addr="0x00010734",func="callee4",
28052 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28053 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28055 bkpt=@{number="2",type="watchpoint",disp="keep",
28056 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28061 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28062 value=@{old="-276895068",new="3"@},
28063 frame=@{func="callee4",args=[],
28064 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28065 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28068 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28069 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28070 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28071 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28072 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28073 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28074 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28075 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28076 addr="0x00010734",func="callee4",
28077 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28078 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28080 bkpt=@{number="2",type="watchpoint",disp="keep",
28081 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28085 ^done,reason="watchpoint-scope",wpnum="2",
28086 frame=@{func="callee3",args=[@{name="strarg",
28087 value="0x11940 \"A string argument.\""@}],
28088 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28089 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28092 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28093 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28094 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28095 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28096 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28097 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28098 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28099 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28100 addr="0x00010734",func="callee4",
28101 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28102 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28103 thread-groups=["i1"],times="1"@}]@}
28108 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28109 @node GDB/MI Catchpoint Commands
28110 @section @sc{gdb/mi} Catchpoint Commands
28112 This section documents @sc{gdb/mi} commands for manipulating
28116 * Shared Library GDB/MI Catchpoint Commands::
28117 * Ada Exception GDB/MI Catchpoint Commands::
28120 @node Shared Library GDB/MI Catchpoint Commands
28121 @subsection Shared Library @sc{gdb/mi} Catchpoints
28123 @subheading The @code{-catch-load} Command
28124 @findex -catch-load
28126 @subsubheading Synopsis
28129 -catch-load [ -t ] [ -d ] @var{regexp}
28132 Add a catchpoint for library load events. If the @samp{-t} option is used,
28133 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28134 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28135 in a disabled state. The @samp{regexp} argument is a regular
28136 expression used to match the name of the loaded library.
28139 @subsubheading @value{GDBN} Command
28141 The corresponding @value{GDBN} command is @samp{catch load}.
28143 @subsubheading Example
28146 -catch-load -t foo.so
28147 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28148 what="load of library matching foo.so",catch-type="load",times="0"@}
28153 @subheading The @code{-catch-unload} Command
28154 @findex -catch-unload
28156 @subsubheading Synopsis
28159 -catch-unload [ -t ] [ -d ] @var{regexp}
28162 Add a catchpoint for library unload events. If the @samp{-t} option is
28163 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28164 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28165 created in a disabled state. The @samp{regexp} argument is a regular
28166 expression used to match the name of the unloaded library.
28168 @subsubheading @value{GDBN} Command
28170 The corresponding @value{GDBN} command is @samp{catch unload}.
28172 @subsubheading Example
28175 -catch-unload -d bar.so
28176 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28177 what="load of library matching bar.so",catch-type="unload",times="0"@}
28181 @node Ada Exception GDB/MI Catchpoint Commands
28182 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28184 The following @sc{gdb/mi} commands can be used to create catchpoints
28185 that stop the execution when Ada exceptions are being raised.
28187 @subheading The @code{-catch-assert} Command
28188 @findex -catch-assert
28190 @subsubheading Synopsis
28193 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28196 Add a catchpoint for failed Ada assertions.
28198 The possible optional parameters for this command are:
28201 @item -c @var{condition}
28202 Make the catchpoint conditional on @var{condition}.
28204 Create a disabled catchpoint.
28206 Create a temporary catchpoint.
28209 @subsubheading @value{GDBN} Command
28211 The corresponding @value{GDBN} command is @samp{catch assert}.
28213 @subsubheading Example
28217 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28218 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28219 thread-groups=["i1"],times="0",
28220 original-location="__gnat_debug_raise_assert_failure"@}
28224 @subheading The @code{-catch-exception} Command
28225 @findex -catch-exception
28227 @subsubheading Synopsis
28230 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28234 Add a catchpoint stopping when Ada exceptions are raised.
28235 By default, the command stops the program when any Ada exception
28236 gets raised. But it is also possible, by using some of the
28237 optional parameters described below, to create more selective
28240 The possible optional parameters for this command are:
28243 @item -c @var{condition}
28244 Make the catchpoint conditional on @var{condition}.
28246 Create a disabled catchpoint.
28247 @item -e @var{exception-name}
28248 Only stop when @var{exception-name} is raised. This option cannot
28249 be used combined with @samp{-u}.
28251 Create a temporary catchpoint.
28253 Stop only when an unhandled exception gets raised. This option
28254 cannot be used combined with @samp{-e}.
28257 @subsubheading @value{GDBN} Command
28259 The corresponding @value{GDBN} commands are @samp{catch exception}
28260 and @samp{catch exception unhandled}.
28262 @subsubheading Example
28265 -catch-exception -e Program_Error
28266 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28267 enabled="y",addr="0x0000000000404874",
28268 what="`Program_Error' Ada exception", thread-groups=["i1"],
28269 times="0",original-location="__gnat_debug_raise_exception"@}
28273 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28274 @node GDB/MI Program Context
28275 @section @sc{gdb/mi} Program Context
28277 @subheading The @code{-exec-arguments} Command
28278 @findex -exec-arguments
28281 @subsubheading Synopsis
28284 -exec-arguments @var{args}
28287 Set the inferior program arguments, to be used in the next
28290 @subsubheading @value{GDBN} Command
28292 The corresponding @value{GDBN} command is @samp{set args}.
28294 @subsubheading Example
28298 -exec-arguments -v word
28305 @subheading The @code{-exec-show-arguments} Command
28306 @findex -exec-show-arguments
28308 @subsubheading Synopsis
28311 -exec-show-arguments
28314 Print the arguments of the program.
28316 @subsubheading @value{GDBN} Command
28318 The corresponding @value{GDBN} command is @samp{show args}.
28320 @subsubheading Example
28325 @subheading The @code{-environment-cd} Command
28326 @findex -environment-cd
28328 @subsubheading Synopsis
28331 -environment-cd @var{pathdir}
28334 Set @value{GDBN}'s working directory.
28336 @subsubheading @value{GDBN} Command
28338 The corresponding @value{GDBN} command is @samp{cd}.
28340 @subsubheading Example
28344 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28350 @subheading The @code{-environment-directory} Command
28351 @findex -environment-directory
28353 @subsubheading Synopsis
28356 -environment-directory [ -r ] [ @var{pathdir} ]+
28359 Add directories @var{pathdir} to beginning of search path for source files.
28360 If the @samp{-r} option is used, the search path is reset to the default
28361 search path. If directories @var{pathdir} are supplied in addition to the
28362 @samp{-r} option, the search path is first reset and then addition
28364 Multiple directories may be specified, separated by blanks. Specifying
28365 multiple directories in a single command
28366 results in the directories added to the beginning of the
28367 search path in the same order they were presented in the command.
28368 If blanks are needed as
28369 part of a directory name, double-quotes should be used around
28370 the name. In the command output, the path will show up separated
28371 by the system directory-separator character. The directory-separator
28372 character must not be used
28373 in any directory name.
28374 If no directories are specified, the current search path is displayed.
28376 @subsubheading @value{GDBN} Command
28378 The corresponding @value{GDBN} command is @samp{dir}.
28380 @subsubheading Example
28384 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28385 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28387 -environment-directory ""
28388 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28390 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28391 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28393 -environment-directory -r
28394 ^done,source-path="$cdir:$cwd"
28399 @subheading The @code{-environment-path} Command
28400 @findex -environment-path
28402 @subsubheading Synopsis
28405 -environment-path [ -r ] [ @var{pathdir} ]+
28408 Add directories @var{pathdir} to beginning of search path for object files.
28409 If the @samp{-r} option is used, the search path is reset to the original
28410 search path that existed at gdb start-up. If directories @var{pathdir} are
28411 supplied in addition to the
28412 @samp{-r} option, the search path is first reset and then addition
28414 Multiple directories may be specified, separated by blanks. Specifying
28415 multiple directories in a single command
28416 results in the directories added to the beginning of the
28417 search path in the same order they were presented in the command.
28418 If blanks are needed as
28419 part of a directory name, double-quotes should be used around
28420 the name. In the command output, the path will show up separated
28421 by the system directory-separator character. The directory-separator
28422 character must not be used
28423 in any directory name.
28424 If no directories are specified, the current path is displayed.
28427 @subsubheading @value{GDBN} Command
28429 The corresponding @value{GDBN} command is @samp{path}.
28431 @subsubheading Example
28436 ^done,path="/usr/bin"
28438 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28439 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28441 -environment-path -r /usr/local/bin
28442 ^done,path="/usr/local/bin:/usr/bin"
28447 @subheading The @code{-environment-pwd} Command
28448 @findex -environment-pwd
28450 @subsubheading Synopsis
28456 Show the current working directory.
28458 @subsubheading @value{GDBN} Command
28460 The corresponding @value{GDBN} command is @samp{pwd}.
28462 @subsubheading Example
28467 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28471 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28472 @node GDB/MI Thread Commands
28473 @section @sc{gdb/mi} Thread Commands
28476 @subheading The @code{-thread-info} Command
28477 @findex -thread-info
28479 @subsubheading Synopsis
28482 -thread-info [ @var{thread-id} ]
28485 Reports information about either a specific thread, if the
28486 @var{thread-id} parameter is present, or about all threads.
28487 @var{thread-id} is the thread's global thread ID. When printing
28488 information about all threads, also reports the global ID of the
28491 @subsubheading @value{GDBN} Command
28493 The @samp{info thread} command prints the same information
28496 @subsubheading Result
28498 The result contains the following attributes:
28502 A list of threads. The format of the elements of the list is described in
28503 @ref{GDB/MI Thread Information}.
28505 @item current-thread-id
28506 The global id of the currently selected thread. This field is omitted if there
28507 is no selected thread (for example, when the selected inferior is not running,
28508 and therefore has no threads) or if a @var{thread-id} argument was passed to
28513 @subsubheading Example
28518 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28519 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28520 args=[]@},state="running"@},
28521 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28522 frame=@{level="0",addr="0x0804891f",func="foo",
28523 args=[@{name="i",value="10"@}],
28524 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28525 state="running"@}],
28526 current-thread-id="1"
28530 @subheading The @code{-thread-list-ids} Command
28531 @findex -thread-list-ids
28533 @subsubheading Synopsis
28539 Produces a list of the currently known global @value{GDBN} thread ids.
28540 At the end of the list it also prints the total number of such
28543 This command is retained for historical reasons, the
28544 @code{-thread-info} command should be used instead.
28546 @subsubheading @value{GDBN} Command
28548 Part of @samp{info threads} supplies the same information.
28550 @subsubheading Example
28555 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28556 current-thread-id="1",number-of-threads="3"
28561 @subheading The @code{-thread-select} Command
28562 @findex -thread-select
28564 @subsubheading Synopsis
28567 -thread-select @var{thread-id}
28570 Make thread with global thread number @var{thread-id} the current
28571 thread. It prints the number of the new current thread, and the
28572 topmost frame for that thread.
28574 This command is deprecated in favor of explicitly using the
28575 @samp{--thread} option to each command.
28577 @subsubheading @value{GDBN} Command
28579 The corresponding @value{GDBN} command is @samp{thread}.
28581 @subsubheading Example
28588 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28589 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28593 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28594 number-of-threads="3"
28597 ^done,new-thread-id="3",
28598 frame=@{level="0",func="vprintf",
28599 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28600 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28604 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28605 @node GDB/MI Ada Tasking Commands
28606 @section @sc{gdb/mi} Ada Tasking Commands
28608 @subheading The @code{-ada-task-info} Command
28609 @findex -ada-task-info
28611 @subsubheading Synopsis
28614 -ada-task-info [ @var{task-id} ]
28617 Reports information about either a specific Ada task, if the
28618 @var{task-id} parameter is present, or about all Ada tasks.
28620 @subsubheading @value{GDBN} Command
28622 The @samp{info tasks} command prints the same information
28623 about all Ada tasks (@pxref{Ada Tasks}).
28625 @subsubheading Result
28627 The result is a table of Ada tasks. The following columns are
28628 defined for each Ada task:
28632 This field exists only for the current thread. It has the value @samp{*}.
28635 The identifier that @value{GDBN} uses to refer to the Ada task.
28638 The identifier that the target uses to refer to the Ada task.
28641 The global thread identifier of the thread corresponding to the Ada
28644 This field should always exist, as Ada tasks are always implemented
28645 on top of a thread. But if @value{GDBN} cannot find this corresponding
28646 thread for any reason, the field is omitted.
28649 This field exists only when the task was created by another task.
28650 In this case, it provides the ID of the parent task.
28653 The base priority of the task.
28656 The current state of the task. For a detailed description of the
28657 possible states, see @ref{Ada Tasks}.
28660 The name of the task.
28664 @subsubheading Example
28668 ^done,tasks=@{nr_rows="3",nr_cols="8",
28669 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28670 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28671 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28672 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28673 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28674 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28675 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28676 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28677 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28678 state="Child Termination Wait",name="main_task"@}]@}
28682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28683 @node GDB/MI Program Execution
28684 @section @sc{gdb/mi} Program Execution
28686 These are the asynchronous commands which generate the out-of-band
28687 record @samp{*stopped}. Currently @value{GDBN} only really executes
28688 asynchronously with remote targets and this interaction is mimicked in
28691 @subheading The @code{-exec-continue} Command
28692 @findex -exec-continue
28694 @subsubheading Synopsis
28697 -exec-continue [--reverse] [--all|--thread-group N]
28700 Resumes the execution of the inferior program, which will continue
28701 to execute until it reaches a debugger stop event. If the
28702 @samp{--reverse} option is specified, execution resumes in reverse until
28703 it reaches a stop event. Stop events may include
28706 breakpoints or watchpoints
28708 signals or exceptions
28710 the end of the process (or its beginning under @samp{--reverse})
28712 the end or beginning of a replay log if one is being used.
28714 In all-stop mode (@pxref{All-Stop
28715 Mode}), may resume only one thread, or all threads, depending on the
28716 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28717 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28718 ignored in all-stop mode. If the @samp{--thread-group} options is
28719 specified, then all threads in that thread group are resumed.
28721 @subsubheading @value{GDBN} Command
28723 The corresponding @value{GDBN} corresponding is @samp{continue}.
28725 @subsubheading Example
28732 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28733 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28739 @subheading The @code{-exec-finish} Command
28740 @findex -exec-finish
28742 @subsubheading Synopsis
28745 -exec-finish [--reverse]
28748 Resumes the execution of the inferior program until the current
28749 function is exited. Displays the results returned by the function.
28750 If the @samp{--reverse} option is specified, resumes the reverse
28751 execution of the inferior program until the point where current
28752 function was called.
28754 @subsubheading @value{GDBN} Command
28756 The corresponding @value{GDBN} command is @samp{finish}.
28758 @subsubheading Example
28760 Function returning @code{void}.
28767 *stopped,reason="function-finished",frame=@{func="main",args=[],
28768 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28772 Function returning other than @code{void}. The name of the internal
28773 @value{GDBN} variable storing the result is printed, together with the
28780 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28781 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28782 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28783 gdb-result-var="$1",return-value="0"
28788 @subheading The @code{-exec-interrupt} Command
28789 @findex -exec-interrupt
28791 @subsubheading Synopsis
28794 -exec-interrupt [--all|--thread-group N]
28797 Interrupts the background execution of the target. Note how the token
28798 associated with the stop message is the one for the execution command
28799 that has been interrupted. The token for the interrupt itself only
28800 appears in the @samp{^done} output. If the user is trying to
28801 interrupt a non-running program, an error message will be printed.
28803 Note that when asynchronous execution is enabled, this command is
28804 asynchronous just like other execution commands. That is, first the
28805 @samp{^done} response will be printed, and the target stop will be
28806 reported after that using the @samp{*stopped} notification.
28808 In non-stop mode, only the context thread is interrupted by default.
28809 All threads (in all inferiors) will be interrupted if the
28810 @samp{--all} option is specified. If the @samp{--thread-group}
28811 option is specified, all threads in that group will be interrupted.
28813 @subsubheading @value{GDBN} Command
28815 The corresponding @value{GDBN} command is @samp{interrupt}.
28817 @subsubheading Example
28828 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28829 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28830 fullname="/home/foo/bar/try.c",line="13"@}
28835 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28839 @subheading The @code{-exec-jump} Command
28842 @subsubheading Synopsis
28845 -exec-jump @var{location}
28848 Resumes execution of the inferior program at the location specified by
28849 parameter. @xref{Specify Location}, for a description of the
28850 different forms of @var{location}.
28852 @subsubheading @value{GDBN} Command
28854 The corresponding @value{GDBN} command is @samp{jump}.
28856 @subsubheading Example
28859 -exec-jump foo.c:10
28860 *running,thread-id="all"
28865 @subheading The @code{-exec-next} Command
28868 @subsubheading Synopsis
28871 -exec-next [--reverse]
28874 Resumes execution of the inferior program, stopping when the beginning
28875 of the next source line is reached.
28877 If the @samp{--reverse} option is specified, resumes reverse execution
28878 of the inferior program, stopping at the beginning of the previous
28879 source line. If you issue this command on the first line of a
28880 function, it will take you back to the caller of that function, to the
28881 source line where the function was called.
28884 @subsubheading @value{GDBN} Command
28886 The corresponding @value{GDBN} command is @samp{next}.
28888 @subsubheading Example
28894 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28899 @subheading The @code{-exec-next-instruction} Command
28900 @findex -exec-next-instruction
28902 @subsubheading Synopsis
28905 -exec-next-instruction [--reverse]
28908 Executes one machine instruction. If the instruction is a function
28909 call, continues until the function returns. If the program stops at an
28910 instruction in the middle of a source line, the address will be
28913 If the @samp{--reverse} option is specified, resumes reverse execution
28914 of the inferior program, stopping at the previous instruction. If the
28915 previously executed instruction was a return from another function,
28916 it will continue to execute in reverse until the call to that function
28917 (from the current stack frame) is reached.
28919 @subsubheading @value{GDBN} Command
28921 The corresponding @value{GDBN} command is @samp{nexti}.
28923 @subsubheading Example
28927 -exec-next-instruction
28931 *stopped,reason="end-stepping-range",
28932 addr="0x000100d4",line="5",file="hello.c"
28937 @subheading The @code{-exec-return} Command
28938 @findex -exec-return
28940 @subsubheading Synopsis
28946 Makes current function return immediately. Doesn't execute the inferior.
28947 Displays the new current frame.
28949 @subsubheading @value{GDBN} Command
28951 The corresponding @value{GDBN} command is @samp{return}.
28953 @subsubheading Example
28957 200-break-insert callee4
28958 200^done,bkpt=@{number="1",addr="0x00010734",
28959 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28964 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28965 frame=@{func="callee4",args=[],
28966 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28967 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28973 111^done,frame=@{level="0",func="callee3",
28974 args=[@{name="strarg",
28975 value="0x11940 \"A string argument.\""@}],
28976 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28977 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28982 @subheading The @code{-exec-run} Command
28985 @subsubheading Synopsis
28988 -exec-run [ --all | --thread-group N ] [ --start ]
28991 Starts execution of the inferior from the beginning. The inferior
28992 executes until either a breakpoint is encountered or the program
28993 exits. In the latter case the output will include an exit code, if
28994 the program has exited exceptionally.
28996 When neither the @samp{--all} nor the @samp{--thread-group} option
28997 is specified, the current inferior is started. If the
28998 @samp{--thread-group} option is specified, it should refer to a thread
28999 group of type @samp{process}, and that thread group will be started.
29000 If the @samp{--all} option is specified, then all inferiors will be started.
29002 Using the @samp{--start} option instructs the debugger to stop
29003 the execution at the start of the inferior's main subprogram,
29004 following the same behavior as the @code{start} command
29005 (@pxref{Starting}).
29007 @subsubheading @value{GDBN} Command
29009 The corresponding @value{GDBN} command is @samp{run}.
29011 @subsubheading Examples
29016 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29021 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29022 frame=@{func="main",args=[],file="recursive2.c",
29023 fullname="/home/foo/bar/recursive2.c",line="4"@}
29028 Program exited normally:
29036 *stopped,reason="exited-normally"
29041 Program exited exceptionally:
29049 *stopped,reason="exited",exit-code="01"
29053 Another way the program can terminate is if it receives a signal such as
29054 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29058 *stopped,reason="exited-signalled",signal-name="SIGINT",
29059 signal-meaning="Interrupt"
29063 @c @subheading -exec-signal
29066 @subheading The @code{-exec-step} Command
29069 @subsubheading Synopsis
29072 -exec-step [--reverse]
29075 Resumes execution of the inferior program, stopping when the beginning
29076 of the next source line is reached, if the next source line is not a
29077 function call. If it is, stop at the first instruction of the called
29078 function. If the @samp{--reverse} option is specified, resumes reverse
29079 execution of the inferior program, stopping at the beginning of the
29080 previously executed source line.
29082 @subsubheading @value{GDBN} Command
29084 The corresponding @value{GDBN} command is @samp{step}.
29086 @subsubheading Example
29088 Stepping into a function:
29094 *stopped,reason="end-stepping-range",
29095 frame=@{func="foo",args=[@{name="a",value="10"@},
29096 @{name="b",value="0"@}],file="recursive2.c",
29097 fullname="/home/foo/bar/recursive2.c",line="11"@}
29107 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29112 @subheading The @code{-exec-step-instruction} Command
29113 @findex -exec-step-instruction
29115 @subsubheading Synopsis
29118 -exec-step-instruction [--reverse]
29121 Resumes the inferior which executes one machine instruction. If the
29122 @samp{--reverse} option is specified, resumes reverse execution of the
29123 inferior program, stopping at the previously executed instruction.
29124 The output, once @value{GDBN} has stopped, will vary depending on
29125 whether we have stopped in the middle of a source line or not. In the
29126 former case, the address at which the program stopped will be printed
29129 @subsubheading @value{GDBN} Command
29131 The corresponding @value{GDBN} command is @samp{stepi}.
29133 @subsubheading Example
29137 -exec-step-instruction
29141 *stopped,reason="end-stepping-range",
29142 frame=@{func="foo",args=[],file="try.c",
29143 fullname="/home/foo/bar/try.c",line="10"@}
29145 -exec-step-instruction
29149 *stopped,reason="end-stepping-range",
29150 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29151 fullname="/home/foo/bar/try.c",line="10"@}
29156 @subheading The @code{-exec-until} Command
29157 @findex -exec-until
29159 @subsubheading Synopsis
29162 -exec-until [ @var{location} ]
29165 Executes the inferior until the @var{location} specified in the
29166 argument is reached. If there is no argument, the inferior executes
29167 until a source line greater than the current one is reached. The
29168 reason for stopping in this case will be @samp{location-reached}.
29170 @subsubheading @value{GDBN} Command
29172 The corresponding @value{GDBN} command is @samp{until}.
29174 @subsubheading Example
29178 -exec-until recursive2.c:6
29182 *stopped,reason="location-reached",frame=@{func="main",args=[],
29183 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29188 @subheading -file-clear
29189 Is this going away????
29192 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29193 @node GDB/MI Stack Manipulation
29194 @section @sc{gdb/mi} Stack Manipulation Commands
29196 @subheading The @code{-enable-frame-filters} Command
29197 @findex -enable-frame-filters
29200 -enable-frame-filters
29203 @value{GDBN} allows Python-based frame filters to affect the output of
29204 the MI commands relating to stack traces. As there is no way to
29205 implement this in a fully backward-compatible way, a front end must
29206 request that this functionality be enabled.
29208 Once enabled, this feature cannot be disabled.
29210 Note that if Python support has not been compiled into @value{GDBN},
29211 this command will still succeed (and do nothing).
29213 @subheading The @code{-stack-info-frame} Command
29214 @findex -stack-info-frame
29216 @subsubheading Synopsis
29222 Get info on the selected frame.
29224 @subsubheading @value{GDBN} Command
29226 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29227 (without arguments).
29229 @subsubheading Example
29234 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29235 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29236 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29240 @subheading The @code{-stack-info-depth} Command
29241 @findex -stack-info-depth
29243 @subsubheading Synopsis
29246 -stack-info-depth [ @var{max-depth} ]
29249 Return the depth of the stack. If the integer argument @var{max-depth}
29250 is specified, do not count beyond @var{max-depth} frames.
29252 @subsubheading @value{GDBN} Command
29254 There's no equivalent @value{GDBN} command.
29256 @subsubheading Example
29258 For a stack with frame levels 0 through 11:
29265 -stack-info-depth 4
29268 -stack-info-depth 12
29271 -stack-info-depth 11
29274 -stack-info-depth 13
29279 @anchor{-stack-list-arguments}
29280 @subheading The @code{-stack-list-arguments} Command
29281 @findex -stack-list-arguments
29283 @subsubheading Synopsis
29286 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29287 [ @var{low-frame} @var{high-frame} ]
29290 Display a list of the arguments for the frames between @var{low-frame}
29291 and @var{high-frame} (inclusive). If @var{low-frame} and
29292 @var{high-frame} are not provided, list the arguments for the whole
29293 call stack. If the two arguments are equal, show the single frame
29294 at the corresponding level. It is an error if @var{low-frame} is
29295 larger than the actual number of frames. On the other hand,
29296 @var{high-frame} may be larger than the actual number of frames, in
29297 which case only existing frames will be returned.
29299 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29300 the variables; if it is 1 or @code{--all-values}, print also their
29301 values; and if it is 2 or @code{--simple-values}, print the name,
29302 type and value for simple data types, and the name and type for arrays,
29303 structures and unions. If the option @code{--no-frame-filters} is
29304 supplied, then Python frame filters will not be executed.
29306 If the @code{--skip-unavailable} option is specified, arguments that
29307 are not available are not listed. Partially available arguments
29308 are still displayed, however.
29310 Use of this command to obtain arguments in a single frame is
29311 deprecated in favor of the @samp{-stack-list-variables} command.
29313 @subsubheading @value{GDBN} Command
29315 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29316 @samp{gdb_get_args} command which partially overlaps with the
29317 functionality of @samp{-stack-list-arguments}.
29319 @subsubheading Example
29326 frame=@{level="0",addr="0x00010734",func="callee4",
29327 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29328 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29329 frame=@{level="1",addr="0x0001076c",func="callee3",
29330 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29331 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29332 frame=@{level="2",addr="0x0001078c",func="callee2",
29333 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29334 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29335 frame=@{level="3",addr="0x000107b4",func="callee1",
29336 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29337 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29338 frame=@{level="4",addr="0x000107e0",func="main",
29339 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29340 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29342 -stack-list-arguments 0
29345 frame=@{level="0",args=[]@},
29346 frame=@{level="1",args=[name="strarg"]@},
29347 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29348 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29349 frame=@{level="4",args=[]@}]
29351 -stack-list-arguments 1
29354 frame=@{level="0",args=[]@},
29356 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29357 frame=@{level="2",args=[
29358 @{name="intarg",value="2"@},
29359 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29360 @{frame=@{level="3",args=[
29361 @{name="intarg",value="2"@},
29362 @{name="strarg",value="0x11940 \"A string argument.\""@},
29363 @{name="fltarg",value="3.5"@}]@},
29364 frame=@{level="4",args=[]@}]
29366 -stack-list-arguments 0 2 2
29367 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29369 -stack-list-arguments 1 2 2
29370 ^done,stack-args=[frame=@{level="2",
29371 args=[@{name="intarg",value="2"@},
29372 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29376 @c @subheading -stack-list-exception-handlers
29379 @anchor{-stack-list-frames}
29380 @subheading The @code{-stack-list-frames} Command
29381 @findex -stack-list-frames
29383 @subsubheading Synopsis
29386 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29389 List the frames currently on the stack. For each frame it displays the
29394 The frame number, 0 being the topmost frame, i.e., the innermost function.
29396 The @code{$pc} value for that frame.
29400 File name of the source file where the function lives.
29401 @item @var{fullname}
29402 The full file name of the source file where the function lives.
29404 Line number corresponding to the @code{$pc}.
29406 The shared library where this function is defined. This is only given
29407 if the frame's function is not known.
29410 If invoked without arguments, this command prints a backtrace for the
29411 whole stack. If given two integer arguments, it shows the frames whose
29412 levels are between the two arguments (inclusive). If the two arguments
29413 are equal, it shows the single frame at the corresponding level. It is
29414 an error if @var{low-frame} is larger than the actual number of
29415 frames. On the other hand, @var{high-frame} may be larger than the
29416 actual number of frames, in which case only existing frames will be
29417 returned. If the option @code{--no-frame-filters} is supplied, then
29418 Python frame filters will not be executed.
29420 @subsubheading @value{GDBN} Command
29422 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29424 @subsubheading Example
29426 Full stack backtrace:
29432 [frame=@{level="0",addr="0x0001076c",func="foo",
29433 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29434 frame=@{level="1",addr="0x000107a4",func="foo",
29435 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29436 frame=@{level="2",addr="0x000107a4",func="foo",
29437 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29438 frame=@{level="3",addr="0x000107a4",func="foo",
29439 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29440 frame=@{level="4",addr="0x000107a4",func="foo",
29441 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29442 frame=@{level="5",addr="0x000107a4",func="foo",
29443 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29444 frame=@{level="6",addr="0x000107a4",func="foo",
29445 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29446 frame=@{level="7",addr="0x000107a4",func="foo",
29447 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29448 frame=@{level="8",addr="0x000107a4",func="foo",
29449 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29450 frame=@{level="9",addr="0x000107a4",func="foo",
29451 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29452 frame=@{level="10",addr="0x000107a4",func="foo",
29453 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29454 frame=@{level="11",addr="0x00010738",func="main",
29455 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29459 Show frames between @var{low_frame} and @var{high_frame}:
29463 -stack-list-frames 3 5
29465 [frame=@{level="3",addr="0x000107a4",func="foo",
29466 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29467 frame=@{level="4",addr="0x000107a4",func="foo",
29468 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29469 frame=@{level="5",addr="0x000107a4",func="foo",
29470 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29474 Show a single frame:
29478 -stack-list-frames 3 3
29480 [frame=@{level="3",addr="0x000107a4",func="foo",
29481 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29486 @subheading The @code{-stack-list-locals} Command
29487 @findex -stack-list-locals
29488 @anchor{-stack-list-locals}
29490 @subsubheading Synopsis
29493 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29496 Display the local variable names for the selected frame. If
29497 @var{print-values} is 0 or @code{--no-values}, print only the names of
29498 the variables; if it is 1 or @code{--all-values}, print also their
29499 values; and if it is 2 or @code{--simple-values}, print the name,
29500 type and value for simple data types, and the name and type for arrays,
29501 structures and unions. In this last case, a frontend can immediately
29502 display the value of simple data types and create variable objects for
29503 other data types when the user wishes to explore their values in
29504 more detail. If the option @code{--no-frame-filters} is supplied, then
29505 Python frame filters will not be executed.
29507 If the @code{--skip-unavailable} option is specified, local variables
29508 that are not available are not listed. Partially available local
29509 variables are still displayed, however.
29511 This command is deprecated in favor of the
29512 @samp{-stack-list-variables} command.
29514 @subsubheading @value{GDBN} Command
29516 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29518 @subsubheading Example
29522 -stack-list-locals 0
29523 ^done,locals=[name="A",name="B",name="C"]
29525 -stack-list-locals --all-values
29526 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29527 @{name="C",value="@{1, 2, 3@}"@}]
29528 -stack-list-locals --simple-values
29529 ^done,locals=[@{name="A",type="int",value="1"@},
29530 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29534 @anchor{-stack-list-variables}
29535 @subheading The @code{-stack-list-variables} Command
29536 @findex -stack-list-variables
29538 @subsubheading Synopsis
29541 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29544 Display the names of local variables and function arguments for the selected frame. If
29545 @var{print-values} is 0 or @code{--no-values}, print only the names of
29546 the variables; if it is 1 or @code{--all-values}, print also their
29547 values; and if it is 2 or @code{--simple-values}, print the name,
29548 type and value for simple data types, and the name and type for arrays,
29549 structures and unions. If the option @code{--no-frame-filters} is
29550 supplied, then Python frame filters will not be executed.
29552 If the @code{--skip-unavailable} option is specified, local variables
29553 and arguments that are not available are not listed. Partially
29554 available arguments and local variables are still displayed, however.
29556 @subsubheading Example
29560 -stack-list-variables --thread 1 --frame 0 --all-values
29561 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29566 @subheading The @code{-stack-select-frame} Command
29567 @findex -stack-select-frame
29569 @subsubheading Synopsis
29572 -stack-select-frame @var{framenum}
29575 Change the selected frame. Select a different frame @var{framenum} on
29578 This command in deprecated in favor of passing the @samp{--frame}
29579 option to every command.
29581 @subsubheading @value{GDBN} Command
29583 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29584 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29586 @subsubheading Example
29590 -stack-select-frame 2
29595 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29596 @node GDB/MI Variable Objects
29597 @section @sc{gdb/mi} Variable Objects
29601 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29603 For the implementation of a variable debugger window (locals, watched
29604 expressions, etc.), we are proposing the adaptation of the existing code
29605 used by @code{Insight}.
29607 The two main reasons for that are:
29611 It has been proven in practice (it is already on its second generation).
29614 It will shorten development time (needless to say how important it is
29618 The original interface was designed to be used by Tcl code, so it was
29619 slightly changed so it could be used through @sc{gdb/mi}. This section
29620 describes the @sc{gdb/mi} operations that will be available and gives some
29621 hints about their use.
29623 @emph{Note}: In addition to the set of operations described here, we
29624 expect the @sc{gui} implementation of a variable window to require, at
29625 least, the following operations:
29628 @item @code{-gdb-show} @code{output-radix}
29629 @item @code{-stack-list-arguments}
29630 @item @code{-stack-list-locals}
29631 @item @code{-stack-select-frame}
29636 @subheading Introduction to Variable Objects
29638 @cindex variable objects in @sc{gdb/mi}
29640 Variable objects are "object-oriented" MI interface for examining and
29641 changing values of expressions. Unlike some other MI interfaces that
29642 work with expressions, variable objects are specifically designed for
29643 simple and efficient presentation in the frontend. A variable object
29644 is identified by string name. When a variable object is created, the
29645 frontend specifies the expression for that variable object. The
29646 expression can be a simple variable, or it can be an arbitrary complex
29647 expression, and can even involve CPU registers. After creating a
29648 variable object, the frontend can invoke other variable object
29649 operations---for example to obtain or change the value of a variable
29650 object, or to change display format.
29652 Variable objects have hierarchical tree structure. Any variable object
29653 that corresponds to a composite type, such as structure in C, has
29654 a number of child variable objects, for example corresponding to each
29655 element of a structure. A child variable object can itself have
29656 children, recursively. Recursion ends when we reach
29657 leaf variable objects, which always have built-in types. Child variable
29658 objects are created only by explicit request, so if a frontend
29659 is not interested in the children of a particular variable object, no
29660 child will be created.
29662 For a leaf variable object it is possible to obtain its value as a
29663 string, or set the value from a string. String value can be also
29664 obtained for a non-leaf variable object, but it's generally a string
29665 that only indicates the type of the object, and does not list its
29666 contents. Assignment to a non-leaf variable object is not allowed.
29668 A frontend does not need to read the values of all variable objects each time
29669 the program stops. Instead, MI provides an update command that lists all
29670 variable objects whose values has changed since the last update
29671 operation. This considerably reduces the amount of data that must
29672 be transferred to the frontend. As noted above, children variable
29673 objects are created on demand, and only leaf variable objects have a
29674 real value. As result, gdb will read target memory only for leaf
29675 variables that frontend has created.
29677 The automatic update is not always desirable. For example, a frontend
29678 might want to keep a value of some expression for future reference,
29679 and never update it. For another example, fetching memory is
29680 relatively slow for embedded targets, so a frontend might want
29681 to disable automatic update for the variables that are either not
29682 visible on the screen, or ``closed''. This is possible using so
29683 called ``frozen variable objects''. Such variable objects are never
29684 implicitly updated.
29686 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29687 fixed variable object, the expression is parsed when the variable
29688 object is created, including associating identifiers to specific
29689 variables. The meaning of expression never changes. For a floating
29690 variable object the values of variables whose names appear in the
29691 expressions are re-evaluated every time in the context of the current
29692 frame. Consider this example:
29697 struct work_state state;
29704 If a fixed variable object for the @code{state} variable is created in
29705 this function, and we enter the recursive call, the variable
29706 object will report the value of @code{state} in the top-level
29707 @code{do_work} invocation. On the other hand, a floating variable
29708 object will report the value of @code{state} in the current frame.
29710 If an expression specified when creating a fixed variable object
29711 refers to a local variable, the variable object becomes bound to the
29712 thread and frame in which the variable object is created. When such
29713 variable object is updated, @value{GDBN} makes sure that the
29714 thread/frame combination the variable object is bound to still exists,
29715 and re-evaluates the variable object in context of that thread/frame.
29717 The following is the complete set of @sc{gdb/mi} operations defined to
29718 access this functionality:
29720 @multitable @columnfractions .4 .6
29721 @item @strong{Operation}
29722 @tab @strong{Description}
29724 @item @code{-enable-pretty-printing}
29725 @tab enable Python-based pretty-printing
29726 @item @code{-var-create}
29727 @tab create a variable object
29728 @item @code{-var-delete}
29729 @tab delete the variable object and/or its children
29730 @item @code{-var-set-format}
29731 @tab set the display format of this variable
29732 @item @code{-var-show-format}
29733 @tab show the display format of this variable
29734 @item @code{-var-info-num-children}
29735 @tab tells how many children this object has
29736 @item @code{-var-list-children}
29737 @tab return a list of the object's children
29738 @item @code{-var-info-type}
29739 @tab show the type of this variable object
29740 @item @code{-var-info-expression}
29741 @tab print parent-relative expression that this variable object represents
29742 @item @code{-var-info-path-expression}
29743 @tab print full expression that this variable object represents
29744 @item @code{-var-show-attributes}
29745 @tab is this variable editable? does it exist here?
29746 @item @code{-var-evaluate-expression}
29747 @tab get the value of this variable
29748 @item @code{-var-assign}
29749 @tab set the value of this variable
29750 @item @code{-var-update}
29751 @tab update the variable and its children
29752 @item @code{-var-set-frozen}
29753 @tab set frozeness attribute
29754 @item @code{-var-set-update-range}
29755 @tab set range of children to display on update
29758 In the next subsection we describe each operation in detail and suggest
29759 how it can be used.
29761 @subheading Description And Use of Operations on Variable Objects
29763 @subheading The @code{-enable-pretty-printing} Command
29764 @findex -enable-pretty-printing
29767 -enable-pretty-printing
29770 @value{GDBN} allows Python-based visualizers to affect the output of the
29771 MI variable object commands. However, because there was no way to
29772 implement this in a fully backward-compatible way, a front end must
29773 request that this functionality be enabled.
29775 Once enabled, this feature cannot be disabled.
29777 Note that if Python support has not been compiled into @value{GDBN},
29778 this command will still succeed (and do nothing).
29780 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29781 may work differently in future versions of @value{GDBN}.
29783 @subheading The @code{-var-create} Command
29784 @findex -var-create
29786 @subsubheading Synopsis
29789 -var-create @{@var{name} | "-"@}
29790 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29793 This operation creates a variable object, which allows the monitoring of
29794 a variable, the result of an expression, a memory cell or a CPU
29797 The @var{name} parameter is the string by which the object can be
29798 referenced. It must be unique. If @samp{-} is specified, the varobj
29799 system will generate a string ``varNNNNNN'' automatically. It will be
29800 unique provided that one does not specify @var{name} of that format.
29801 The command fails if a duplicate name is found.
29803 The frame under which the expression should be evaluated can be
29804 specified by @var{frame-addr}. A @samp{*} indicates that the current
29805 frame should be used. A @samp{@@} indicates that a floating variable
29806 object must be created.
29808 @var{expression} is any expression valid on the current language set (must not
29809 begin with a @samp{*}), or one of the following:
29813 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29816 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29819 @samp{$@var{regname}} --- a CPU register name
29822 @cindex dynamic varobj
29823 A varobj's contents may be provided by a Python-based pretty-printer. In this
29824 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29825 have slightly different semantics in some cases. If the
29826 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29827 will never create a dynamic varobj. This ensures backward
29828 compatibility for existing clients.
29830 @subsubheading Result
29832 This operation returns attributes of the newly-created varobj. These
29837 The name of the varobj.
29840 The number of children of the varobj. This number is not necessarily
29841 reliable for a dynamic varobj. Instead, you must examine the
29842 @samp{has_more} attribute.
29845 The varobj's scalar value. For a varobj whose type is some sort of
29846 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29847 will not be interesting.
29850 The varobj's type. This is a string representation of the type, as
29851 would be printed by the @value{GDBN} CLI. If @samp{print object}
29852 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29853 @emph{actual} (derived) type of the object is shown rather than the
29854 @emph{declared} one.
29857 If a variable object is bound to a specific thread, then this is the
29858 thread's global identifier.
29861 For a dynamic varobj, this indicates whether there appear to be any
29862 children available. For a non-dynamic varobj, this will be 0.
29865 This attribute will be present and have the value @samp{1} if the
29866 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29867 then this attribute will not be present.
29870 A dynamic varobj can supply a display hint to the front end. The
29871 value comes directly from the Python pretty-printer object's
29872 @code{display_hint} method. @xref{Pretty Printing API}.
29875 Typical output will look like this:
29878 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29879 has_more="@var{has_more}"
29883 @subheading The @code{-var-delete} Command
29884 @findex -var-delete
29886 @subsubheading Synopsis
29889 -var-delete [ -c ] @var{name}
29892 Deletes a previously created variable object and all of its children.
29893 With the @samp{-c} option, just deletes the children.
29895 Returns an error if the object @var{name} is not found.
29898 @subheading The @code{-var-set-format} Command
29899 @findex -var-set-format
29901 @subsubheading Synopsis
29904 -var-set-format @var{name} @var{format-spec}
29907 Sets the output format for the value of the object @var{name} to be
29910 @anchor{-var-set-format}
29911 The syntax for the @var{format-spec} is as follows:
29914 @var{format-spec} @expansion{}
29915 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29918 The natural format is the default format choosen automatically
29919 based on the variable type (like decimal for an @code{int}, hex
29920 for pointers, etc.).
29922 The zero-hexadecimal format has a representation similar to hexadecimal
29923 but with padding zeroes to the left of the value. For example, a 32-bit
29924 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29925 zero-hexadecimal format.
29927 For a variable with children, the format is set only on the
29928 variable itself, and the children are not affected.
29930 @subheading The @code{-var-show-format} Command
29931 @findex -var-show-format
29933 @subsubheading Synopsis
29936 -var-show-format @var{name}
29939 Returns the format used to display the value of the object @var{name}.
29942 @var{format} @expansion{}
29947 @subheading The @code{-var-info-num-children} Command
29948 @findex -var-info-num-children
29950 @subsubheading Synopsis
29953 -var-info-num-children @var{name}
29956 Returns the number of children of a variable object @var{name}:
29962 Note that this number is not completely reliable for a dynamic varobj.
29963 It will return the current number of children, but more children may
29967 @subheading The @code{-var-list-children} Command
29968 @findex -var-list-children
29970 @subsubheading Synopsis
29973 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29975 @anchor{-var-list-children}
29977 Return a list of the children of the specified variable object and
29978 create variable objects for them, if they do not already exist. With
29979 a single argument or if @var{print-values} has a value of 0 or
29980 @code{--no-values}, print only the names of the variables; if
29981 @var{print-values} is 1 or @code{--all-values}, also print their
29982 values; and if it is 2 or @code{--simple-values} print the name and
29983 value for simple data types and just the name for arrays, structures
29986 @var{from} and @var{to}, if specified, indicate the range of children
29987 to report. If @var{from} or @var{to} is less than zero, the range is
29988 reset and all children will be reported. Otherwise, children starting
29989 at @var{from} (zero-based) and up to and excluding @var{to} will be
29992 If a child range is requested, it will only affect the current call to
29993 @code{-var-list-children}, but not future calls to @code{-var-update}.
29994 For this, you must instead use @code{-var-set-update-range}. The
29995 intent of this approach is to enable a front end to implement any
29996 update approach it likes; for example, scrolling a view may cause the
29997 front end to request more children with @code{-var-list-children}, and
29998 then the front end could call @code{-var-set-update-range} with a
29999 different range to ensure that future updates are restricted to just
30002 For each child the following results are returned:
30007 Name of the variable object created for this child.
30010 The expression to be shown to the user by the front end to designate this child.
30011 For example this may be the name of a structure member.
30013 For a dynamic varobj, this value cannot be used to form an
30014 expression. There is no way to do this at all with a dynamic varobj.
30016 For C/C@t{++} structures there are several pseudo children returned to
30017 designate access qualifiers. For these pseudo children @var{exp} is
30018 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30019 type and value are not present.
30021 A dynamic varobj will not report the access qualifying
30022 pseudo-children, regardless of the language. This information is not
30023 available at all with a dynamic varobj.
30026 Number of children this child has. For a dynamic varobj, this will be
30030 The type of the child. If @samp{print object}
30031 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30032 @emph{actual} (derived) type of the object is shown rather than the
30033 @emph{declared} one.
30036 If values were requested, this is the value.
30039 If this variable object is associated with a thread, this is the
30040 thread's global thread id. Otherwise this result is not present.
30043 If the variable object is frozen, this variable will be present with a value of 1.
30046 A dynamic varobj can supply a display hint to the front end. The
30047 value comes directly from the Python pretty-printer object's
30048 @code{display_hint} method. @xref{Pretty Printing API}.
30051 This attribute will be present and have the value @samp{1} if the
30052 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30053 then this attribute will not be present.
30057 The result may have its own attributes:
30061 A dynamic varobj can supply a display hint to the front end. The
30062 value comes directly from the Python pretty-printer object's
30063 @code{display_hint} method. @xref{Pretty Printing API}.
30066 This is an integer attribute which is nonzero if there are children
30067 remaining after the end of the selected range.
30070 @subsubheading Example
30074 -var-list-children n
30075 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30076 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30078 -var-list-children --all-values n
30079 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30080 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30084 @subheading The @code{-var-info-type} Command
30085 @findex -var-info-type
30087 @subsubheading Synopsis
30090 -var-info-type @var{name}
30093 Returns the type of the specified variable @var{name}. The type is
30094 returned as a string in the same format as it is output by the
30098 type=@var{typename}
30102 @subheading The @code{-var-info-expression} Command
30103 @findex -var-info-expression
30105 @subsubheading Synopsis
30108 -var-info-expression @var{name}
30111 Returns a string that is suitable for presenting this
30112 variable object in user interface. The string is generally
30113 not valid expression in the current language, and cannot be evaluated.
30115 For example, if @code{a} is an array, and variable object
30116 @code{A} was created for @code{a}, then we'll get this output:
30119 (gdb) -var-info-expression A.1
30120 ^done,lang="C",exp="1"
30124 Here, the value of @code{lang} is the language name, which can be
30125 found in @ref{Supported Languages}.
30127 Note that the output of the @code{-var-list-children} command also
30128 includes those expressions, so the @code{-var-info-expression} command
30131 @subheading The @code{-var-info-path-expression} Command
30132 @findex -var-info-path-expression
30134 @subsubheading Synopsis
30137 -var-info-path-expression @var{name}
30140 Returns an expression that can be evaluated in the current
30141 context and will yield the same value that a variable object has.
30142 Compare this with the @code{-var-info-expression} command, which
30143 result can be used only for UI presentation. Typical use of
30144 the @code{-var-info-path-expression} command is creating a
30145 watchpoint from a variable object.
30147 This command is currently not valid for children of a dynamic varobj,
30148 and will give an error when invoked on one.
30150 For example, suppose @code{C} is a C@t{++} class, derived from class
30151 @code{Base}, and that the @code{Base} class has a member called
30152 @code{m_size}. Assume a variable @code{c} is has the type of
30153 @code{C} and a variable object @code{C} was created for variable
30154 @code{c}. Then, we'll get this output:
30156 (gdb) -var-info-path-expression C.Base.public.m_size
30157 ^done,path_expr=((Base)c).m_size)
30160 @subheading The @code{-var-show-attributes} Command
30161 @findex -var-show-attributes
30163 @subsubheading Synopsis
30166 -var-show-attributes @var{name}
30169 List attributes of the specified variable object @var{name}:
30172 status=@var{attr} [ ( ,@var{attr} )* ]
30176 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30178 @subheading The @code{-var-evaluate-expression} Command
30179 @findex -var-evaluate-expression
30181 @subsubheading Synopsis
30184 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30187 Evaluates the expression that is represented by the specified variable
30188 object and returns its value as a string. The format of the string
30189 can be specified with the @samp{-f} option. The possible values of
30190 this option are the same as for @code{-var-set-format}
30191 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30192 the current display format will be used. The current display format
30193 can be changed using the @code{-var-set-format} command.
30199 Note that one must invoke @code{-var-list-children} for a variable
30200 before the value of a child variable can be evaluated.
30202 @subheading The @code{-var-assign} Command
30203 @findex -var-assign
30205 @subsubheading Synopsis
30208 -var-assign @var{name} @var{expression}
30211 Assigns the value of @var{expression} to the variable object specified
30212 by @var{name}. The object must be @samp{editable}. If the variable's
30213 value is altered by the assign, the variable will show up in any
30214 subsequent @code{-var-update} list.
30216 @subsubheading Example
30224 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30228 @subheading The @code{-var-update} Command
30229 @findex -var-update
30231 @subsubheading Synopsis
30234 -var-update [@var{print-values}] @{@var{name} | "*"@}
30237 Reevaluate the expressions corresponding to the variable object
30238 @var{name} and all its direct and indirect children, and return the
30239 list of variable objects whose values have changed; @var{name} must
30240 be a root variable object. Here, ``changed'' means that the result of
30241 @code{-var-evaluate-expression} before and after the
30242 @code{-var-update} is different. If @samp{*} is used as the variable
30243 object names, all existing variable objects are updated, except
30244 for frozen ones (@pxref{-var-set-frozen}). The option
30245 @var{print-values} determines whether both names and values, or just
30246 names are printed. The possible values of this option are the same
30247 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30248 recommended to use the @samp{--all-values} option, to reduce the
30249 number of MI commands needed on each program stop.
30251 With the @samp{*} parameter, if a variable object is bound to a
30252 currently running thread, it will not be updated, without any
30255 If @code{-var-set-update-range} was previously used on a varobj, then
30256 only the selected range of children will be reported.
30258 @code{-var-update} reports all the changed varobjs in a tuple named
30261 Each item in the change list is itself a tuple holding:
30265 The name of the varobj.
30268 If values were requested for this update, then this field will be
30269 present and will hold the value of the varobj.
30272 @anchor{-var-update}
30273 This field is a string which may take one of three values:
30277 The variable object's current value is valid.
30280 The variable object does not currently hold a valid value but it may
30281 hold one in the future if its associated expression comes back into
30285 The variable object no longer holds a valid value.
30286 This can occur when the executable file being debugged has changed,
30287 either through recompilation or by using the @value{GDBN} @code{file}
30288 command. The front end should normally choose to delete these variable
30292 In the future new values may be added to this list so the front should
30293 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30296 This is only present if the varobj is still valid. If the type
30297 changed, then this will be the string @samp{true}; otherwise it will
30300 When a varobj's type changes, its children are also likely to have
30301 become incorrect. Therefore, the varobj's children are automatically
30302 deleted when this attribute is @samp{true}. Also, the varobj's update
30303 range, when set using the @code{-var-set-update-range} command, is
30307 If the varobj's type changed, then this field will be present and will
30310 @item new_num_children
30311 For a dynamic varobj, if the number of children changed, or if the
30312 type changed, this will be the new number of children.
30314 The @samp{numchild} field in other varobj responses is generally not
30315 valid for a dynamic varobj -- it will show the number of children that
30316 @value{GDBN} knows about, but because dynamic varobjs lazily
30317 instantiate their children, this will not reflect the number of
30318 children which may be available.
30320 The @samp{new_num_children} attribute only reports changes to the
30321 number of children known by @value{GDBN}. This is the only way to
30322 detect whether an update has removed children (which necessarily can
30323 only happen at the end of the update range).
30326 The display hint, if any.
30329 This is an integer value, which will be 1 if there are more children
30330 available outside the varobj's update range.
30333 This attribute will be present and have the value @samp{1} if the
30334 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30335 then this attribute will not be present.
30338 If new children were added to a dynamic varobj within the selected
30339 update range (as set by @code{-var-set-update-range}), then they will
30340 be listed in this attribute.
30343 @subsubheading Example
30350 -var-update --all-values var1
30351 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30352 type_changed="false"@}]
30356 @subheading The @code{-var-set-frozen} Command
30357 @findex -var-set-frozen
30358 @anchor{-var-set-frozen}
30360 @subsubheading Synopsis
30363 -var-set-frozen @var{name} @var{flag}
30366 Set the frozenness flag on the variable object @var{name}. The
30367 @var{flag} parameter should be either @samp{1} to make the variable
30368 frozen or @samp{0} to make it unfrozen. If a variable object is
30369 frozen, then neither itself, nor any of its children, are
30370 implicitly updated by @code{-var-update} of
30371 a parent variable or by @code{-var-update *}. Only
30372 @code{-var-update} of the variable itself will update its value and
30373 values of its children. After a variable object is unfrozen, it is
30374 implicitly updated by all subsequent @code{-var-update} operations.
30375 Unfreezing a variable does not update it, only subsequent
30376 @code{-var-update} does.
30378 @subsubheading Example
30382 -var-set-frozen V 1
30387 @subheading The @code{-var-set-update-range} command
30388 @findex -var-set-update-range
30389 @anchor{-var-set-update-range}
30391 @subsubheading Synopsis
30394 -var-set-update-range @var{name} @var{from} @var{to}
30397 Set the range of children to be returned by future invocations of
30398 @code{-var-update}.
30400 @var{from} and @var{to} indicate the range of children to report. If
30401 @var{from} or @var{to} is less than zero, the range is reset and all
30402 children will be reported. Otherwise, children starting at @var{from}
30403 (zero-based) and up to and excluding @var{to} will be reported.
30405 @subsubheading Example
30409 -var-set-update-range V 1 2
30413 @subheading The @code{-var-set-visualizer} command
30414 @findex -var-set-visualizer
30415 @anchor{-var-set-visualizer}
30417 @subsubheading Synopsis
30420 -var-set-visualizer @var{name} @var{visualizer}
30423 Set a visualizer for the variable object @var{name}.
30425 @var{visualizer} is the visualizer to use. The special value
30426 @samp{None} means to disable any visualizer in use.
30428 If not @samp{None}, @var{visualizer} must be a Python expression.
30429 This expression must evaluate to a callable object which accepts a
30430 single argument. @value{GDBN} will call this object with the value of
30431 the varobj @var{name} as an argument (this is done so that the same
30432 Python pretty-printing code can be used for both the CLI and MI).
30433 When called, this object must return an object which conforms to the
30434 pretty-printing interface (@pxref{Pretty Printing API}).
30436 The pre-defined function @code{gdb.default_visualizer} may be used to
30437 select a visualizer by following the built-in process
30438 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30439 a varobj is created, and so ordinarily is not needed.
30441 This feature is only available if Python support is enabled. The MI
30442 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30443 can be used to check this.
30445 @subsubheading Example
30447 Resetting the visualizer:
30451 -var-set-visualizer V None
30455 Reselecting the default (type-based) visualizer:
30459 -var-set-visualizer V gdb.default_visualizer
30463 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30464 can be used to instantiate this class for a varobj:
30468 -var-set-visualizer V "lambda val: SomeClass()"
30472 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30473 @node GDB/MI Data Manipulation
30474 @section @sc{gdb/mi} Data Manipulation
30476 @cindex data manipulation, in @sc{gdb/mi}
30477 @cindex @sc{gdb/mi}, data manipulation
30478 This section describes the @sc{gdb/mi} commands that manipulate data:
30479 examine memory and registers, evaluate expressions, etc.
30481 For details about what an addressable memory unit is,
30482 @pxref{addressable memory unit}.
30484 @c REMOVED FROM THE INTERFACE.
30485 @c @subheading -data-assign
30486 @c Change the value of a program variable. Plenty of side effects.
30487 @c @subsubheading GDB Command
30489 @c @subsubheading Example
30492 @subheading The @code{-data-disassemble} Command
30493 @findex -data-disassemble
30495 @subsubheading Synopsis
30499 [ -s @var{start-addr} -e @var{end-addr} ]
30500 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30508 @item @var{start-addr}
30509 is the beginning address (or @code{$pc})
30510 @item @var{end-addr}
30512 @item @var{filename}
30513 is the name of the file to disassemble
30514 @item @var{linenum}
30515 is the line number to disassemble around
30517 is the number of disassembly lines to be produced. If it is -1,
30518 the whole function will be disassembled, in case no @var{end-addr} is
30519 specified. If @var{end-addr} is specified as a non-zero value, and
30520 @var{lines} is lower than the number of disassembly lines between
30521 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30522 displayed; if @var{lines} is higher than the number of lines between
30523 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30528 @item 0 disassembly only
30529 @item 1 mixed source and disassembly (deprecated)
30530 @item 2 disassembly with raw opcodes
30531 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30532 @item 4 mixed source and disassembly
30533 @item 5 mixed source and disassembly with raw opcodes
30536 Modes 1 and 3 are deprecated. The output is ``source centric''
30537 which hasn't proved useful in practice.
30538 @xref{Machine Code}, for a discussion of the difference between
30539 @code{/m} and @code{/s} output of the @code{disassemble} command.
30542 @subsubheading Result
30544 The result of the @code{-data-disassemble} command will be a list named
30545 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30546 used with the @code{-data-disassemble} command.
30548 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30553 The address at which this instruction was disassembled.
30556 The name of the function this instruction is within.
30559 The decimal offset in bytes from the start of @samp{func-name}.
30562 The text disassembly for this @samp{address}.
30565 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30566 bytes for the @samp{inst} field.
30570 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30571 @samp{src_and_asm_line}, each of which has the following fields:
30575 The line number within @samp{file}.
30578 The file name from the compilation unit. This might be an absolute
30579 file name or a relative file name depending on the compile command
30583 Absolute file name of @samp{file}. It is converted to a canonical form
30584 using the source file search path
30585 (@pxref{Source Path, ,Specifying Source Directories})
30586 and after resolving all the symbolic links.
30588 If the source file is not found this field will contain the path as
30589 present in the debug information.
30591 @item line_asm_insn
30592 This is a list of tuples containing the disassembly for @samp{line} in
30593 @samp{file}. The fields of each tuple are the same as for
30594 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30595 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30600 Note that whatever included in the @samp{inst} field, is not
30601 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30604 @subsubheading @value{GDBN} Command
30606 The corresponding @value{GDBN} command is @samp{disassemble}.
30608 @subsubheading Example
30610 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30614 -data-disassemble -s $pc -e "$pc + 20" -- 0
30617 @{address="0x000107c0",func-name="main",offset="4",
30618 inst="mov 2, %o0"@},
30619 @{address="0x000107c4",func-name="main",offset="8",
30620 inst="sethi %hi(0x11800), %o2"@},
30621 @{address="0x000107c8",func-name="main",offset="12",
30622 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30623 @{address="0x000107cc",func-name="main",offset="16",
30624 inst="sethi %hi(0x11800), %o2"@},
30625 @{address="0x000107d0",func-name="main",offset="20",
30626 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30630 Disassemble the whole @code{main} function. Line 32 is part of
30634 -data-disassemble -f basics.c -l 32 -- 0
30636 @{address="0x000107bc",func-name="main",offset="0",
30637 inst="save %sp, -112, %sp"@},
30638 @{address="0x000107c0",func-name="main",offset="4",
30639 inst="mov 2, %o0"@},
30640 @{address="0x000107c4",func-name="main",offset="8",
30641 inst="sethi %hi(0x11800), %o2"@},
30643 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30644 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30648 Disassemble 3 instructions from the start of @code{main}:
30652 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30654 @{address="0x000107bc",func-name="main",offset="0",
30655 inst="save %sp, -112, %sp"@},
30656 @{address="0x000107c0",func-name="main",offset="4",
30657 inst="mov 2, %o0"@},
30658 @{address="0x000107c4",func-name="main",offset="8",
30659 inst="sethi %hi(0x11800), %o2"@}]
30663 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30667 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30669 src_and_asm_line=@{line="31",
30670 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30671 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30672 line_asm_insn=[@{address="0x000107bc",
30673 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30674 src_and_asm_line=@{line="32",
30675 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30676 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30677 line_asm_insn=[@{address="0x000107c0",
30678 func-name="main",offset="4",inst="mov 2, %o0"@},
30679 @{address="0x000107c4",func-name="main",offset="8",
30680 inst="sethi %hi(0x11800), %o2"@}]@}]
30685 @subheading The @code{-data-evaluate-expression} Command
30686 @findex -data-evaluate-expression
30688 @subsubheading Synopsis
30691 -data-evaluate-expression @var{expr}
30694 Evaluate @var{expr} as an expression. The expression could contain an
30695 inferior function call. The function call will execute synchronously.
30696 If the expression contains spaces, it must be enclosed in double quotes.
30698 @subsubheading @value{GDBN} Command
30700 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30701 @samp{call}. In @code{gdbtk} only, there's a corresponding
30702 @samp{gdb_eval} command.
30704 @subsubheading Example
30706 In the following example, the numbers that precede the commands are the
30707 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30708 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30712 211-data-evaluate-expression A
30715 311-data-evaluate-expression &A
30716 311^done,value="0xefffeb7c"
30718 411-data-evaluate-expression A+3
30721 511-data-evaluate-expression "A + 3"
30727 @subheading The @code{-data-list-changed-registers} Command
30728 @findex -data-list-changed-registers
30730 @subsubheading Synopsis
30733 -data-list-changed-registers
30736 Display a list of the registers that have changed.
30738 @subsubheading @value{GDBN} Command
30740 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30741 has the corresponding command @samp{gdb_changed_register_list}.
30743 @subsubheading Example
30745 On a PPC MBX board:
30753 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30754 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30757 -data-list-changed-registers
30758 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30759 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30760 "24","25","26","27","28","30","31","64","65","66","67","69"]
30765 @subheading The @code{-data-list-register-names} Command
30766 @findex -data-list-register-names
30768 @subsubheading Synopsis
30771 -data-list-register-names [ ( @var{regno} )+ ]
30774 Show a list of register names for the current target. If no arguments
30775 are given, it shows a list of the names of all the registers. If
30776 integer numbers are given as arguments, it will print a list of the
30777 names of the registers corresponding to the arguments. To ensure
30778 consistency between a register name and its number, the output list may
30779 include empty register names.
30781 @subsubheading @value{GDBN} Command
30783 @value{GDBN} does not have a command which corresponds to
30784 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30785 corresponding command @samp{gdb_regnames}.
30787 @subsubheading Example
30789 For the PPC MBX board:
30792 -data-list-register-names
30793 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30794 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30795 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30796 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30797 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30798 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30799 "", "pc","ps","cr","lr","ctr","xer"]
30801 -data-list-register-names 1 2 3
30802 ^done,register-names=["r1","r2","r3"]
30806 @subheading The @code{-data-list-register-values} Command
30807 @findex -data-list-register-values
30809 @subsubheading Synopsis
30812 -data-list-register-values
30813 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30816 Display the registers' contents. The format according to which the
30817 registers' contents are to be returned is given by @var{fmt}, followed
30818 by an optional list of numbers specifying the registers to display. A
30819 missing list of numbers indicates that the contents of all the
30820 registers must be returned. The @code{--skip-unavailable} option
30821 indicates that only the available registers are to be returned.
30823 Allowed formats for @var{fmt} are:
30840 @subsubheading @value{GDBN} Command
30842 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30843 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30845 @subsubheading Example
30847 For a PPC MBX board (note: line breaks are for readability only, they
30848 don't appear in the actual output):
30852 -data-list-register-values r 64 65
30853 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30854 @{number="65",value="0x00029002"@}]
30856 -data-list-register-values x
30857 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30858 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30859 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30860 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30861 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30862 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30863 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30864 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30865 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30866 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30867 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30868 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30869 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30870 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30871 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30872 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30873 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30874 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30875 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30876 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30877 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30878 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30879 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30880 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30881 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30882 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30883 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30884 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30885 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30886 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30887 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30888 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30889 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30890 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30891 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30892 @{number="69",value="0x20002b03"@}]
30897 @subheading The @code{-data-read-memory} Command
30898 @findex -data-read-memory
30900 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30902 @subsubheading Synopsis
30905 -data-read-memory [ -o @var{byte-offset} ]
30906 @var{address} @var{word-format} @var{word-size}
30907 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30914 @item @var{address}
30915 An expression specifying the address of the first memory word to be
30916 read. Complex expressions containing embedded white space should be
30917 quoted using the C convention.
30919 @item @var{word-format}
30920 The format to be used to print the memory words. The notation is the
30921 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30924 @item @var{word-size}
30925 The size of each memory word in bytes.
30927 @item @var{nr-rows}
30928 The number of rows in the output table.
30930 @item @var{nr-cols}
30931 The number of columns in the output table.
30934 If present, indicates that each row should include an @sc{ascii} dump. The
30935 value of @var{aschar} is used as a padding character when a byte is not a
30936 member of the printable @sc{ascii} character set (printable @sc{ascii}
30937 characters are those whose code is between 32 and 126, inclusively).
30939 @item @var{byte-offset}
30940 An offset to add to the @var{address} before fetching memory.
30943 This command displays memory contents as a table of @var{nr-rows} by
30944 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30945 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30946 (returned as @samp{total-bytes}). Should less than the requested number
30947 of bytes be returned by the target, the missing words are identified
30948 using @samp{N/A}. The number of bytes read from the target is returned
30949 in @samp{nr-bytes} and the starting address used to read memory in
30952 The address of the next/previous row or page is available in
30953 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30956 @subsubheading @value{GDBN} Command
30958 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30959 @samp{gdb_get_mem} memory read command.
30961 @subsubheading Example
30963 Read six bytes of memory starting at @code{bytes+6} but then offset by
30964 @code{-6} bytes. Format as three rows of two columns. One byte per
30965 word. Display each word in hex.
30969 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30970 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30971 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30972 prev-page="0x0000138a",memory=[
30973 @{addr="0x00001390",data=["0x00","0x01"]@},
30974 @{addr="0x00001392",data=["0x02","0x03"]@},
30975 @{addr="0x00001394",data=["0x04","0x05"]@}]
30979 Read two bytes of memory starting at address @code{shorts + 64} and
30980 display as a single word formatted in decimal.
30984 5-data-read-memory shorts+64 d 2 1 1
30985 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30986 next-row="0x00001512",prev-row="0x0000150e",
30987 next-page="0x00001512",prev-page="0x0000150e",memory=[
30988 @{addr="0x00001510",data=["128"]@}]
30992 Read thirty two bytes of memory starting at @code{bytes+16} and format
30993 as eight rows of four columns. Include a string encoding with @samp{x}
30994 used as the non-printable character.
30998 4-data-read-memory bytes+16 x 1 8 4 x
30999 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31000 next-row="0x000013c0",prev-row="0x0000139c",
31001 next-page="0x000013c0",prev-page="0x00001380",memory=[
31002 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31003 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31004 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31005 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31006 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31007 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31008 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31009 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31013 @subheading The @code{-data-read-memory-bytes} Command
31014 @findex -data-read-memory-bytes
31016 @subsubheading Synopsis
31019 -data-read-memory-bytes [ -o @var{offset} ]
31020 @var{address} @var{count}
31027 @item @var{address}
31028 An expression specifying the address of the first addressable memory unit
31029 to be read. Complex expressions containing embedded white space should be
31030 quoted using the C convention.
31033 The number of addressable memory units to read. This should be an integer
31037 The offset relative to @var{address} at which to start reading. This
31038 should be an integer literal. This option is provided so that a frontend
31039 is not required to first evaluate address and then perform address
31040 arithmetics itself.
31044 This command attempts to read all accessible memory regions in the
31045 specified range. First, all regions marked as unreadable in the memory
31046 map (if one is defined) will be skipped. @xref{Memory Region
31047 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31048 regions. For each one, if reading full region results in an errors,
31049 @value{GDBN} will try to read a subset of the region.
31051 In general, every single memory unit in the region may be readable or not,
31052 and the only way to read every readable unit is to try a read at
31053 every address, which is not practical. Therefore, @value{GDBN} will
31054 attempt to read all accessible memory units at either beginning or the end
31055 of the region, using a binary division scheme. This heuristic works
31056 well for reading accross a memory map boundary. Note that if a region
31057 has a readable range that is neither at the beginning or the end,
31058 @value{GDBN} will not read it.
31060 The result record (@pxref{GDB/MI Result Records}) that is output of
31061 the command includes a field named @samp{memory} whose content is a
31062 list of tuples. Each tuple represent a successfully read memory block
31063 and has the following fields:
31067 The start address of the memory block, as hexadecimal literal.
31070 The end address of the memory block, as hexadecimal literal.
31073 The offset of the memory block, as hexadecimal literal, relative to
31074 the start address passed to @code{-data-read-memory-bytes}.
31077 The contents of the memory block, in hex.
31083 @subsubheading @value{GDBN} Command
31085 The corresponding @value{GDBN} command is @samp{x}.
31087 @subsubheading Example
31091 -data-read-memory-bytes &a 10
31092 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31094 contents="01000000020000000300"@}]
31099 @subheading The @code{-data-write-memory-bytes} Command
31100 @findex -data-write-memory-bytes
31102 @subsubheading Synopsis
31105 -data-write-memory-bytes @var{address} @var{contents}
31106 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31113 @item @var{address}
31114 An expression specifying the address of the first addressable memory unit
31115 to be written. Complex expressions containing embedded white space should
31116 be quoted using the C convention.
31118 @item @var{contents}
31119 The hex-encoded data to write. It is an error if @var{contents} does
31120 not represent an integral number of addressable memory units.
31123 Optional argument indicating the number of addressable memory units to be
31124 written. If @var{count} is greater than @var{contents}' length,
31125 @value{GDBN} will repeatedly write @var{contents} until it fills
31126 @var{count} memory units.
31130 @subsubheading @value{GDBN} Command
31132 There's no corresponding @value{GDBN} command.
31134 @subsubheading Example
31138 -data-write-memory-bytes &a "aabbccdd"
31145 -data-write-memory-bytes &a "aabbccdd" 16e
31150 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31151 @node GDB/MI Tracepoint Commands
31152 @section @sc{gdb/mi} Tracepoint Commands
31154 The commands defined in this section implement MI support for
31155 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31157 @subheading The @code{-trace-find} Command
31158 @findex -trace-find
31160 @subsubheading Synopsis
31163 -trace-find @var{mode} [@var{parameters}@dots{}]
31166 Find a trace frame using criteria defined by @var{mode} and
31167 @var{parameters}. The following table lists permissible
31168 modes and their parameters. For details of operation, see @ref{tfind}.
31173 No parameters are required. Stops examining trace frames.
31176 An integer is required as parameter. Selects tracepoint frame with
31179 @item tracepoint-number
31180 An integer is required as parameter. Finds next
31181 trace frame that corresponds to tracepoint with the specified number.
31184 An address is required as parameter. Finds
31185 next trace frame that corresponds to any tracepoint at the specified
31188 @item pc-inside-range
31189 Two addresses are required as parameters. Finds next trace
31190 frame that corresponds to a tracepoint at an address inside the
31191 specified range. Both bounds are considered to be inside the range.
31193 @item pc-outside-range
31194 Two addresses are required as parameters. Finds
31195 next trace frame that corresponds to a tracepoint at an address outside
31196 the specified range. Both bounds are considered to be inside the range.
31199 Line specification is required as parameter. @xref{Specify Location}.
31200 Finds next trace frame that corresponds to a tracepoint at
31201 the specified location.
31205 If @samp{none} was passed as @var{mode}, the response does not
31206 have fields. Otherwise, the response may have the following fields:
31210 This field has either @samp{0} or @samp{1} as the value, depending
31211 on whether a matching tracepoint was found.
31214 The index of the found traceframe. This field is present iff
31215 the @samp{found} field has value of @samp{1}.
31218 The index of the found tracepoint. This field is present iff
31219 the @samp{found} field has value of @samp{1}.
31222 The information about the frame corresponding to the found trace
31223 frame. This field is present only if a trace frame was found.
31224 @xref{GDB/MI Frame Information}, for description of this field.
31228 @subsubheading @value{GDBN} Command
31230 The corresponding @value{GDBN} command is @samp{tfind}.
31232 @subheading -trace-define-variable
31233 @findex -trace-define-variable
31235 @subsubheading Synopsis
31238 -trace-define-variable @var{name} [ @var{value} ]
31241 Create trace variable @var{name} if it does not exist. If
31242 @var{value} is specified, sets the initial value of the specified
31243 trace variable to that value. Note that the @var{name} should start
31244 with the @samp{$} character.
31246 @subsubheading @value{GDBN} Command
31248 The corresponding @value{GDBN} command is @samp{tvariable}.
31250 @subheading The @code{-trace-frame-collected} Command
31251 @findex -trace-frame-collected
31253 @subsubheading Synopsis
31256 -trace-frame-collected
31257 [--var-print-values @var{var_pval}]
31258 [--comp-print-values @var{comp_pval}]
31259 [--registers-format @var{regformat}]
31260 [--memory-contents]
31263 This command returns the set of collected objects, register names,
31264 trace state variable names, memory ranges and computed expressions
31265 that have been collected at a particular trace frame. The optional
31266 parameters to the command affect the output format in different ways.
31267 See the output description table below for more details.
31269 The reported names can be used in the normal manner to create
31270 varobjs and inspect the objects themselves. The items returned by
31271 this command are categorized so that it is clear which is a variable,
31272 which is a register, which is a trace state variable, which is a
31273 memory range and which is a computed expression.
31275 For instance, if the actions were
31277 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31278 collect *(int*)0xaf02bef0@@40
31282 the object collected in its entirety would be @code{myVar}. The
31283 object @code{myArray} would be partially collected, because only the
31284 element at index @code{myIndex} would be collected. The remaining
31285 objects would be computed expressions.
31287 An example output would be:
31291 -trace-frame-collected
31293 explicit-variables=[@{name="myVar",value="1"@}],
31294 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31295 @{name="myObj.field",value="0"@},
31296 @{name="myPtr->field",value="1"@},
31297 @{name="myCount + 2",value="3"@},
31298 @{name="$tvar1 + 1",value="43970027"@}],
31299 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31300 @{number="1",value="0x0"@},
31301 @{number="2",value="0x4"@},
31303 @{number="125",value="0x0"@}],
31304 tvars=[@{name="$tvar1",current="43970026"@}],
31305 memory=[@{address="0x0000000000602264",length="4"@},
31306 @{address="0x0000000000615bc0",length="4"@}]
31313 @item explicit-variables
31314 The set of objects that have been collected in their entirety (as
31315 opposed to collecting just a few elements of an array or a few struct
31316 members). For each object, its name and value are printed.
31317 The @code{--var-print-values} option affects how or whether the value
31318 field is output. If @var{var_pval} is 0, then print only the names;
31319 if it is 1, print also their values; and if it is 2, print the name,
31320 type and value for simple data types, and the name and type for
31321 arrays, structures and unions.
31323 @item computed-expressions
31324 The set of computed expressions that have been collected at the
31325 current trace frame. The @code{--comp-print-values} option affects
31326 this set like the @code{--var-print-values} option affects the
31327 @code{explicit-variables} set. See above.
31330 The registers that have been collected at the current trace frame.
31331 For each register collected, the name and current value are returned.
31332 The value is formatted according to the @code{--registers-format}
31333 option. See the @command{-data-list-register-values} command for a
31334 list of the allowed formats. The default is @samp{x}.
31337 The trace state variables that have been collected at the current
31338 trace frame. For each trace state variable collected, the name and
31339 current value are returned.
31342 The set of memory ranges that have been collected at the current trace
31343 frame. Its content is a list of tuples. Each tuple represents a
31344 collected memory range and has the following fields:
31348 The start address of the memory range, as hexadecimal literal.
31351 The length of the memory range, as decimal literal.
31354 The contents of the memory block, in hex. This field is only present
31355 if the @code{--memory-contents} option is specified.
31361 @subsubheading @value{GDBN} Command
31363 There is no corresponding @value{GDBN} command.
31365 @subsubheading Example
31367 @subheading -trace-list-variables
31368 @findex -trace-list-variables
31370 @subsubheading Synopsis
31373 -trace-list-variables
31376 Return a table of all defined trace variables. Each element of the
31377 table has the following fields:
31381 The name of the trace variable. This field is always present.
31384 The initial value. This is a 64-bit signed integer. This
31385 field is always present.
31388 The value the trace variable has at the moment. This is a 64-bit
31389 signed integer. This field is absent iff current value is
31390 not defined, for example if the trace was never run, or is
31395 @subsubheading @value{GDBN} Command
31397 The corresponding @value{GDBN} command is @samp{tvariables}.
31399 @subsubheading Example
31403 -trace-list-variables
31404 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31405 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31406 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31407 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31408 body=[variable=@{name="$trace_timestamp",initial="0"@}
31409 variable=@{name="$foo",initial="10",current="15"@}]@}
31413 @subheading -trace-save
31414 @findex -trace-save
31416 @subsubheading Synopsis
31419 -trace-save [ -r ] [ -ctf ] @var{filename}
31422 Saves the collected trace data to @var{filename}. Without the
31423 @samp{-r} option, the data is downloaded from the target and saved
31424 in a local file. With the @samp{-r} option the target is asked
31425 to perform the save.
31427 By default, this command will save the trace in the tfile format. You can
31428 supply the optional @samp{-ctf} argument to save it the CTF format. See
31429 @ref{Trace Files} for more information about CTF.
31431 @subsubheading @value{GDBN} Command
31433 The corresponding @value{GDBN} command is @samp{tsave}.
31436 @subheading -trace-start
31437 @findex -trace-start
31439 @subsubheading Synopsis
31445 Starts a tracing experiment. The result of this command does not
31448 @subsubheading @value{GDBN} Command
31450 The corresponding @value{GDBN} command is @samp{tstart}.
31452 @subheading -trace-status
31453 @findex -trace-status
31455 @subsubheading Synopsis
31461 Obtains the status of a tracing experiment. The result may include
31462 the following fields:
31467 May have a value of either @samp{0}, when no tracing operations are
31468 supported, @samp{1}, when all tracing operations are supported, or
31469 @samp{file} when examining trace file. In the latter case, examining
31470 of trace frame is possible but new tracing experiement cannot be
31471 started. This field is always present.
31474 May have a value of either @samp{0} or @samp{1} depending on whether
31475 tracing experiement is in progress on target. This field is present
31476 if @samp{supported} field is not @samp{0}.
31479 Report the reason why the tracing was stopped last time. This field
31480 may be absent iff tracing was never stopped on target yet. The
31481 value of @samp{request} means the tracing was stopped as result of
31482 the @code{-trace-stop} command. The value of @samp{overflow} means
31483 the tracing buffer is full. The value of @samp{disconnection} means
31484 tracing was automatically stopped when @value{GDBN} has disconnected.
31485 The value of @samp{passcount} means tracing was stopped when a
31486 tracepoint was passed a maximal number of times for that tracepoint.
31487 This field is present if @samp{supported} field is not @samp{0}.
31489 @item stopping-tracepoint
31490 The number of tracepoint whose passcount as exceeded. This field is
31491 present iff the @samp{stop-reason} field has the value of
31495 @itemx frames-created
31496 The @samp{frames} field is a count of the total number of trace frames
31497 in the trace buffer, while @samp{frames-created} is the total created
31498 during the run, including ones that were discarded, such as when a
31499 circular trace buffer filled up. Both fields are optional.
31503 These fields tell the current size of the tracing buffer and the
31504 remaining space. These fields are optional.
31507 The value of the circular trace buffer flag. @code{1} means that the
31508 trace buffer is circular and old trace frames will be discarded if
31509 necessary to make room, @code{0} means that the trace buffer is linear
31513 The value of the disconnected tracing flag. @code{1} means that
31514 tracing will continue after @value{GDBN} disconnects, @code{0} means
31515 that the trace run will stop.
31518 The filename of the trace file being examined. This field is
31519 optional, and only present when examining a trace file.
31523 @subsubheading @value{GDBN} Command
31525 The corresponding @value{GDBN} command is @samp{tstatus}.
31527 @subheading -trace-stop
31528 @findex -trace-stop
31530 @subsubheading Synopsis
31536 Stops a tracing experiment. The result of this command has the same
31537 fields as @code{-trace-status}, except that the @samp{supported} and
31538 @samp{running} fields are not output.
31540 @subsubheading @value{GDBN} Command
31542 The corresponding @value{GDBN} command is @samp{tstop}.
31545 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31546 @node GDB/MI Symbol Query
31547 @section @sc{gdb/mi} Symbol Query Commands
31551 @subheading The @code{-symbol-info-address} Command
31552 @findex -symbol-info-address
31554 @subsubheading Synopsis
31557 -symbol-info-address @var{symbol}
31560 Describe where @var{symbol} is stored.
31562 @subsubheading @value{GDBN} Command
31564 The corresponding @value{GDBN} command is @samp{info address}.
31566 @subsubheading Example
31570 @subheading The @code{-symbol-info-file} Command
31571 @findex -symbol-info-file
31573 @subsubheading Synopsis
31579 Show the file for the symbol.
31581 @subsubheading @value{GDBN} Command
31583 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31584 @samp{gdb_find_file}.
31586 @subsubheading Example
31590 @subheading The @code{-symbol-info-function} Command
31591 @findex -symbol-info-function
31593 @subsubheading Synopsis
31596 -symbol-info-function
31599 Show which function the symbol lives in.
31601 @subsubheading @value{GDBN} Command
31603 @samp{gdb_get_function} in @code{gdbtk}.
31605 @subsubheading Example
31609 @subheading The @code{-symbol-info-line} Command
31610 @findex -symbol-info-line
31612 @subsubheading Synopsis
31618 Show the core addresses of the code for a source line.
31620 @subsubheading @value{GDBN} Command
31622 The corresponding @value{GDBN} command is @samp{info line}.
31623 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31625 @subsubheading Example
31629 @subheading The @code{-symbol-info-symbol} Command
31630 @findex -symbol-info-symbol
31632 @subsubheading Synopsis
31635 -symbol-info-symbol @var{addr}
31638 Describe what symbol is at location @var{addr}.
31640 @subsubheading @value{GDBN} Command
31642 The corresponding @value{GDBN} command is @samp{info symbol}.
31644 @subsubheading Example
31648 @subheading The @code{-symbol-list-functions} Command
31649 @findex -symbol-list-functions
31651 @subsubheading Synopsis
31654 -symbol-list-functions
31657 List the functions in the executable.
31659 @subsubheading @value{GDBN} Command
31661 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31662 @samp{gdb_search} in @code{gdbtk}.
31664 @subsubheading Example
31669 @subheading The @code{-symbol-list-lines} Command
31670 @findex -symbol-list-lines
31672 @subsubheading Synopsis
31675 -symbol-list-lines @var{filename}
31678 Print the list of lines that contain code and their associated program
31679 addresses for the given source filename. The entries are sorted in
31680 ascending PC order.
31682 @subsubheading @value{GDBN} Command
31684 There is no corresponding @value{GDBN} command.
31686 @subsubheading Example
31689 -symbol-list-lines basics.c
31690 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31696 @subheading The @code{-symbol-list-types} Command
31697 @findex -symbol-list-types
31699 @subsubheading Synopsis
31705 List all the type names.
31707 @subsubheading @value{GDBN} Command
31709 The corresponding commands are @samp{info types} in @value{GDBN},
31710 @samp{gdb_search} in @code{gdbtk}.
31712 @subsubheading Example
31716 @subheading The @code{-symbol-list-variables} Command
31717 @findex -symbol-list-variables
31719 @subsubheading Synopsis
31722 -symbol-list-variables
31725 List all the global and static variable names.
31727 @subsubheading @value{GDBN} Command
31729 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31731 @subsubheading Example
31735 @subheading The @code{-symbol-locate} Command
31736 @findex -symbol-locate
31738 @subsubheading Synopsis
31744 @subsubheading @value{GDBN} Command
31746 @samp{gdb_loc} in @code{gdbtk}.
31748 @subsubheading Example
31752 @subheading The @code{-symbol-type} Command
31753 @findex -symbol-type
31755 @subsubheading Synopsis
31758 -symbol-type @var{variable}
31761 Show type of @var{variable}.
31763 @subsubheading @value{GDBN} Command
31765 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31766 @samp{gdb_obj_variable}.
31768 @subsubheading Example
31773 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31774 @node GDB/MI File Commands
31775 @section @sc{gdb/mi} File Commands
31777 This section describes the GDB/MI commands to specify executable file names
31778 and to read in and obtain symbol table information.
31780 @subheading The @code{-file-exec-and-symbols} Command
31781 @findex -file-exec-and-symbols
31783 @subsubheading Synopsis
31786 -file-exec-and-symbols @var{file}
31789 Specify the executable file to be debugged. This file is the one from
31790 which the symbol table is also read. If no file is specified, the
31791 command clears the executable and symbol information. If breakpoints
31792 are set when using this command with no arguments, @value{GDBN} will produce
31793 error messages. Otherwise, no output is produced, except a completion
31796 @subsubheading @value{GDBN} Command
31798 The corresponding @value{GDBN} command is @samp{file}.
31800 @subsubheading Example
31804 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31810 @subheading The @code{-file-exec-file} Command
31811 @findex -file-exec-file
31813 @subsubheading Synopsis
31816 -file-exec-file @var{file}
31819 Specify the executable file to be debugged. Unlike
31820 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31821 from this file. If used without argument, @value{GDBN} clears the information
31822 about the executable file. No output is produced, except a completion
31825 @subsubheading @value{GDBN} Command
31827 The corresponding @value{GDBN} command is @samp{exec-file}.
31829 @subsubheading Example
31833 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31840 @subheading The @code{-file-list-exec-sections} Command
31841 @findex -file-list-exec-sections
31843 @subsubheading Synopsis
31846 -file-list-exec-sections
31849 List the sections of the current executable file.
31851 @subsubheading @value{GDBN} Command
31853 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31854 information as this command. @code{gdbtk} has a corresponding command
31855 @samp{gdb_load_info}.
31857 @subsubheading Example
31862 @subheading The @code{-file-list-exec-source-file} Command
31863 @findex -file-list-exec-source-file
31865 @subsubheading Synopsis
31868 -file-list-exec-source-file
31871 List the line number, the current source file, and the absolute path
31872 to the current source file for the current executable. The macro
31873 information field has a value of @samp{1} or @samp{0} depending on
31874 whether or not the file includes preprocessor macro information.
31876 @subsubheading @value{GDBN} Command
31878 The @value{GDBN} equivalent is @samp{info source}
31880 @subsubheading Example
31884 123-file-list-exec-source-file
31885 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31890 @subheading The @code{-file-list-exec-source-files} Command
31891 @findex -file-list-exec-source-files
31893 @subsubheading Synopsis
31896 -file-list-exec-source-files
31899 List the source files for the current executable.
31901 It will always output both the filename and fullname (absolute file
31902 name) of a source file.
31904 @subsubheading @value{GDBN} Command
31906 The @value{GDBN} equivalent is @samp{info sources}.
31907 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31909 @subsubheading Example
31912 -file-list-exec-source-files
31914 @{file=foo.c,fullname=/home/foo.c@},
31915 @{file=/home/bar.c,fullname=/home/bar.c@},
31916 @{file=gdb_could_not_find_fullpath.c@}]
31920 @subheading The @code{-file-list-shared-libraries} Command
31921 @findex -file-list-shared-libraries
31923 @subsubheading Synopsis
31926 -file-list-shared-libraries [ @var{regexp} ]
31929 List the shared libraries in the program.
31930 With a regular expression @var{regexp}, only those libraries whose
31931 names match @var{regexp} are listed.
31933 @subsubheading @value{GDBN} Command
31935 The corresponding @value{GDBN} command is @samp{info shared}. The fields
31936 have a similar meaning to the @code{=library-loaded} notification.
31937 The @code{ranges} field specifies the multiple segments belonging to this
31938 library. Each range has the following fields:
31942 The address defining the inclusive lower bound of the segment.
31944 The address defining the exclusive upper bound of the segment.
31947 @subsubheading Example
31950 -file-list-exec-source-files
31951 ^done,shared-libraries=[
31952 @{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"@}]@},
31953 @{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"@}]@}]
31959 @subheading The @code{-file-list-symbol-files} Command
31960 @findex -file-list-symbol-files
31962 @subsubheading Synopsis
31965 -file-list-symbol-files
31970 @subsubheading @value{GDBN} Command
31972 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31974 @subsubheading Example
31979 @subheading The @code{-file-symbol-file} Command
31980 @findex -file-symbol-file
31982 @subsubheading Synopsis
31985 -file-symbol-file @var{file}
31988 Read symbol table info from the specified @var{file} argument. When
31989 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31990 produced, except for a completion notification.
31992 @subsubheading @value{GDBN} Command
31994 The corresponding @value{GDBN} command is @samp{symbol-file}.
31996 @subsubheading Example
32000 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32006 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32007 @node GDB/MI Memory Overlay Commands
32008 @section @sc{gdb/mi} Memory Overlay Commands
32010 The memory overlay commands are not implemented.
32012 @c @subheading -overlay-auto
32014 @c @subheading -overlay-list-mapping-state
32016 @c @subheading -overlay-list-overlays
32018 @c @subheading -overlay-map
32020 @c @subheading -overlay-off
32022 @c @subheading -overlay-on
32024 @c @subheading -overlay-unmap
32026 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32027 @node GDB/MI Signal Handling Commands
32028 @section @sc{gdb/mi} Signal Handling Commands
32030 Signal handling commands are not implemented.
32032 @c @subheading -signal-handle
32034 @c @subheading -signal-list-handle-actions
32036 @c @subheading -signal-list-signal-types
32040 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32041 @node GDB/MI Target Manipulation
32042 @section @sc{gdb/mi} Target Manipulation Commands
32045 @subheading The @code{-target-attach} Command
32046 @findex -target-attach
32048 @subsubheading Synopsis
32051 -target-attach @var{pid} | @var{gid} | @var{file}
32054 Attach to a process @var{pid} or a file @var{file} outside of
32055 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32056 group, the id previously returned by
32057 @samp{-list-thread-groups --available} must be used.
32059 @subsubheading @value{GDBN} Command
32061 The corresponding @value{GDBN} command is @samp{attach}.
32063 @subsubheading Example
32067 =thread-created,id="1"
32068 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32074 @subheading The @code{-target-compare-sections} Command
32075 @findex -target-compare-sections
32077 @subsubheading Synopsis
32080 -target-compare-sections [ @var{section} ]
32083 Compare data of section @var{section} on target to the exec file.
32084 Without the argument, all sections are compared.
32086 @subsubheading @value{GDBN} Command
32088 The @value{GDBN} equivalent is @samp{compare-sections}.
32090 @subsubheading Example
32095 @subheading The @code{-target-detach} Command
32096 @findex -target-detach
32098 @subsubheading Synopsis
32101 -target-detach [ @var{pid} | @var{gid} ]
32104 Detach from the remote target which normally resumes its execution.
32105 If either @var{pid} or @var{gid} is specified, detaches from either
32106 the specified process, or specified thread group. There's no output.
32108 @subsubheading @value{GDBN} Command
32110 The corresponding @value{GDBN} command is @samp{detach}.
32112 @subsubheading Example
32122 @subheading The @code{-target-disconnect} Command
32123 @findex -target-disconnect
32125 @subsubheading Synopsis
32131 Disconnect from the remote target. There's no output and the target is
32132 generally not resumed.
32134 @subsubheading @value{GDBN} Command
32136 The corresponding @value{GDBN} command is @samp{disconnect}.
32138 @subsubheading Example
32148 @subheading The @code{-target-download} Command
32149 @findex -target-download
32151 @subsubheading Synopsis
32157 Loads the executable onto the remote target.
32158 It prints out an update message every half second, which includes the fields:
32162 The name of the section.
32164 The size of what has been sent so far for that section.
32166 The size of the section.
32168 The total size of what was sent so far (the current and the previous sections).
32170 The size of the overall executable to download.
32174 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32175 @sc{gdb/mi} Output Syntax}).
32177 In addition, it prints the name and size of the sections, as they are
32178 downloaded. These messages include the following fields:
32182 The name of the section.
32184 The size of the section.
32186 The size of the overall executable to download.
32190 At the end, a summary is printed.
32192 @subsubheading @value{GDBN} Command
32194 The corresponding @value{GDBN} command is @samp{load}.
32196 @subsubheading Example
32198 Note: each status message appears on a single line. Here the messages
32199 have been broken down so that they can fit onto a page.
32204 +download,@{section=".text",section-size="6668",total-size="9880"@}
32205 +download,@{section=".text",section-sent="512",section-size="6668",
32206 total-sent="512",total-size="9880"@}
32207 +download,@{section=".text",section-sent="1024",section-size="6668",
32208 total-sent="1024",total-size="9880"@}
32209 +download,@{section=".text",section-sent="1536",section-size="6668",
32210 total-sent="1536",total-size="9880"@}
32211 +download,@{section=".text",section-sent="2048",section-size="6668",
32212 total-sent="2048",total-size="9880"@}
32213 +download,@{section=".text",section-sent="2560",section-size="6668",
32214 total-sent="2560",total-size="9880"@}
32215 +download,@{section=".text",section-sent="3072",section-size="6668",
32216 total-sent="3072",total-size="9880"@}
32217 +download,@{section=".text",section-sent="3584",section-size="6668",
32218 total-sent="3584",total-size="9880"@}
32219 +download,@{section=".text",section-sent="4096",section-size="6668",
32220 total-sent="4096",total-size="9880"@}
32221 +download,@{section=".text",section-sent="4608",section-size="6668",
32222 total-sent="4608",total-size="9880"@}
32223 +download,@{section=".text",section-sent="5120",section-size="6668",
32224 total-sent="5120",total-size="9880"@}
32225 +download,@{section=".text",section-sent="5632",section-size="6668",
32226 total-sent="5632",total-size="9880"@}
32227 +download,@{section=".text",section-sent="6144",section-size="6668",
32228 total-sent="6144",total-size="9880"@}
32229 +download,@{section=".text",section-sent="6656",section-size="6668",
32230 total-sent="6656",total-size="9880"@}
32231 +download,@{section=".init",section-size="28",total-size="9880"@}
32232 +download,@{section=".fini",section-size="28",total-size="9880"@}
32233 +download,@{section=".data",section-size="3156",total-size="9880"@}
32234 +download,@{section=".data",section-sent="512",section-size="3156",
32235 total-sent="7236",total-size="9880"@}
32236 +download,@{section=".data",section-sent="1024",section-size="3156",
32237 total-sent="7748",total-size="9880"@}
32238 +download,@{section=".data",section-sent="1536",section-size="3156",
32239 total-sent="8260",total-size="9880"@}
32240 +download,@{section=".data",section-sent="2048",section-size="3156",
32241 total-sent="8772",total-size="9880"@}
32242 +download,@{section=".data",section-sent="2560",section-size="3156",
32243 total-sent="9284",total-size="9880"@}
32244 +download,@{section=".data",section-sent="3072",section-size="3156",
32245 total-sent="9796",total-size="9880"@}
32246 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32253 @subheading The @code{-target-exec-status} Command
32254 @findex -target-exec-status
32256 @subsubheading Synopsis
32259 -target-exec-status
32262 Provide information on the state of the target (whether it is running or
32263 not, for instance).
32265 @subsubheading @value{GDBN} Command
32267 There's no equivalent @value{GDBN} command.
32269 @subsubheading Example
32273 @subheading The @code{-target-list-available-targets} Command
32274 @findex -target-list-available-targets
32276 @subsubheading Synopsis
32279 -target-list-available-targets
32282 List the possible targets to connect to.
32284 @subsubheading @value{GDBN} Command
32286 The corresponding @value{GDBN} command is @samp{help target}.
32288 @subsubheading Example
32292 @subheading The @code{-target-list-current-targets} Command
32293 @findex -target-list-current-targets
32295 @subsubheading Synopsis
32298 -target-list-current-targets
32301 Describe the current target.
32303 @subsubheading @value{GDBN} Command
32305 The corresponding information is printed by @samp{info file} (among
32308 @subsubheading Example
32312 @subheading The @code{-target-list-parameters} Command
32313 @findex -target-list-parameters
32315 @subsubheading Synopsis
32318 -target-list-parameters
32324 @subsubheading @value{GDBN} Command
32328 @subsubheading Example
32331 @subheading The @code{-target-flash-erase} Command
32332 @findex -target-flash-erase
32334 @subsubheading Synopsis
32337 -target-flash-erase
32340 Erases all known flash memory regions on the target.
32342 The corresponding @value{GDBN} command is @samp{flash-erase}.
32344 The output is a list of flash regions that have been erased, with starting
32345 addresses and memory region sizes.
32349 -target-flash-erase
32350 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32354 @subheading The @code{-target-select} Command
32355 @findex -target-select
32357 @subsubheading Synopsis
32360 -target-select @var{type} @var{parameters @dots{}}
32363 Connect @value{GDBN} to the remote target. This command takes two args:
32367 The type of target, for instance @samp{remote}, etc.
32368 @item @var{parameters}
32369 Device names, host names and the like. @xref{Target Commands, ,
32370 Commands for Managing Targets}, for more details.
32373 The output is a connection notification, followed by the address at
32374 which the target program is, in the following form:
32377 ^connected,addr="@var{address}",func="@var{function name}",
32378 args=[@var{arg list}]
32381 @subsubheading @value{GDBN} Command
32383 The corresponding @value{GDBN} command is @samp{target}.
32385 @subsubheading Example
32389 -target-select remote /dev/ttya
32390 ^connected,addr="0xfe00a300",func="??",args=[]
32394 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32395 @node GDB/MI File Transfer Commands
32396 @section @sc{gdb/mi} File Transfer Commands
32399 @subheading The @code{-target-file-put} Command
32400 @findex -target-file-put
32402 @subsubheading Synopsis
32405 -target-file-put @var{hostfile} @var{targetfile}
32408 Copy file @var{hostfile} from the host system (the machine running
32409 @value{GDBN}) to @var{targetfile} on the target system.
32411 @subsubheading @value{GDBN} Command
32413 The corresponding @value{GDBN} command is @samp{remote put}.
32415 @subsubheading Example
32419 -target-file-put localfile remotefile
32425 @subheading The @code{-target-file-get} Command
32426 @findex -target-file-get
32428 @subsubheading Synopsis
32431 -target-file-get @var{targetfile} @var{hostfile}
32434 Copy file @var{targetfile} from the target system to @var{hostfile}
32435 on the host system.
32437 @subsubheading @value{GDBN} Command
32439 The corresponding @value{GDBN} command is @samp{remote get}.
32441 @subsubheading Example
32445 -target-file-get remotefile localfile
32451 @subheading The @code{-target-file-delete} Command
32452 @findex -target-file-delete
32454 @subsubheading Synopsis
32457 -target-file-delete @var{targetfile}
32460 Delete @var{targetfile} from the target system.
32462 @subsubheading @value{GDBN} Command
32464 The corresponding @value{GDBN} command is @samp{remote delete}.
32466 @subsubheading Example
32470 -target-file-delete remotefile
32476 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32477 @node GDB/MI Ada Exceptions Commands
32478 @section Ada Exceptions @sc{gdb/mi} Commands
32480 @subheading The @code{-info-ada-exceptions} Command
32481 @findex -info-ada-exceptions
32483 @subsubheading Synopsis
32486 -info-ada-exceptions [ @var{regexp}]
32489 List all Ada exceptions defined within the program being debugged.
32490 With a regular expression @var{regexp}, only those exceptions whose
32491 names match @var{regexp} are listed.
32493 @subsubheading @value{GDBN} Command
32495 The corresponding @value{GDBN} command is @samp{info exceptions}.
32497 @subsubheading Result
32499 The result is a table of Ada exceptions. The following columns are
32500 defined for each exception:
32504 The name of the exception.
32507 The address of the exception.
32511 @subsubheading Example
32514 -info-ada-exceptions aint
32515 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32516 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32517 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32518 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32519 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32522 @subheading Catching Ada Exceptions
32524 The commands describing how to ask @value{GDBN} to stop when a program
32525 raises an exception are described at @ref{Ada Exception GDB/MI
32526 Catchpoint Commands}.
32529 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32530 @node GDB/MI Support Commands
32531 @section @sc{gdb/mi} Support Commands
32533 Since new commands and features get regularly added to @sc{gdb/mi},
32534 some commands are available to help front-ends query the debugger
32535 about support for these capabilities. Similarly, it is also possible
32536 to query @value{GDBN} about target support of certain features.
32538 @subheading The @code{-info-gdb-mi-command} Command
32539 @cindex @code{-info-gdb-mi-command}
32540 @findex -info-gdb-mi-command
32542 @subsubheading Synopsis
32545 -info-gdb-mi-command @var{cmd_name}
32548 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32550 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32551 is technically not part of the command name (@pxref{GDB/MI Input
32552 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32553 for ease of use, this command also accepts the form with the leading
32556 @subsubheading @value{GDBN} Command
32558 There is no corresponding @value{GDBN} command.
32560 @subsubheading Result
32562 The result is a tuple. There is currently only one field:
32566 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32567 @code{"false"} otherwise.
32571 @subsubheading Example
32573 Here is an example where the @sc{gdb/mi} command does not exist:
32576 -info-gdb-mi-command unsupported-command
32577 ^done,command=@{exists="false"@}
32581 And here is an example where the @sc{gdb/mi} command is known
32585 -info-gdb-mi-command symbol-list-lines
32586 ^done,command=@{exists="true"@}
32589 @subheading The @code{-list-features} Command
32590 @findex -list-features
32591 @cindex supported @sc{gdb/mi} features, list
32593 Returns a list of particular features of the MI protocol that
32594 this version of gdb implements. A feature can be a command,
32595 or a new field in an output of some command, or even an
32596 important bugfix. While a frontend can sometimes detect presence
32597 of a feature at runtime, it is easier to perform detection at debugger
32600 The command returns a list of strings, with each string naming an
32601 available feature. Each returned string is just a name, it does not
32602 have any internal structure. The list of possible feature names
32608 (gdb) -list-features
32609 ^done,result=["feature1","feature2"]
32612 The current list of features is:
32615 @item frozen-varobjs
32616 Indicates support for the @code{-var-set-frozen} command, as well
32617 as possible presense of the @code{frozen} field in the output
32618 of @code{-varobj-create}.
32619 @item pending-breakpoints
32620 Indicates support for the @option{-f} option to the @code{-break-insert}
32623 Indicates Python scripting support, Python-based
32624 pretty-printing commands, and possible presence of the
32625 @samp{display_hint} field in the output of @code{-var-list-children}
32627 Indicates support for the @code{-thread-info} command.
32628 @item data-read-memory-bytes
32629 Indicates support for the @code{-data-read-memory-bytes} and the
32630 @code{-data-write-memory-bytes} commands.
32631 @item breakpoint-notifications
32632 Indicates that changes to breakpoints and breakpoints created via the
32633 CLI will be announced via async records.
32634 @item ada-task-info
32635 Indicates support for the @code{-ada-task-info} command.
32636 @item language-option
32637 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32638 option (@pxref{Context management}).
32639 @item info-gdb-mi-command
32640 Indicates support for the @code{-info-gdb-mi-command} command.
32641 @item undefined-command-error-code
32642 Indicates support for the "undefined-command" error code in error result
32643 records, produced when trying to execute an undefined @sc{gdb/mi} command
32644 (@pxref{GDB/MI Result Records}).
32645 @item exec-run-start-option
32646 Indicates that the @code{-exec-run} command supports the @option{--start}
32647 option (@pxref{GDB/MI Program Execution}).
32650 @subheading The @code{-list-target-features} Command
32651 @findex -list-target-features
32653 Returns a list of particular features that are supported by the
32654 target. Those features affect the permitted MI commands, but
32655 unlike the features reported by the @code{-list-features} command, the
32656 features depend on which target GDB is using at the moment. Whenever
32657 a target can change, due to commands such as @code{-target-select},
32658 @code{-target-attach} or @code{-exec-run}, the list of target features
32659 may change, and the frontend should obtain it again.
32663 (gdb) -list-target-features
32664 ^done,result=["async"]
32667 The current list of features is:
32671 Indicates that the target is capable of asynchronous command
32672 execution, which means that @value{GDBN} will accept further commands
32673 while the target is running.
32676 Indicates that the target is capable of reverse execution.
32677 @xref{Reverse Execution}, for more information.
32681 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32682 @node GDB/MI Miscellaneous Commands
32683 @section Miscellaneous @sc{gdb/mi} Commands
32685 @c @subheading -gdb-complete
32687 @subheading The @code{-gdb-exit} Command
32690 @subsubheading Synopsis
32696 Exit @value{GDBN} immediately.
32698 @subsubheading @value{GDBN} Command
32700 Approximately corresponds to @samp{quit}.
32702 @subsubheading Example
32712 @subheading The @code{-exec-abort} Command
32713 @findex -exec-abort
32715 @subsubheading Synopsis
32721 Kill the inferior running program.
32723 @subsubheading @value{GDBN} Command
32725 The corresponding @value{GDBN} command is @samp{kill}.
32727 @subsubheading Example
32732 @subheading The @code{-gdb-set} Command
32735 @subsubheading Synopsis
32741 Set an internal @value{GDBN} variable.
32742 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32744 @subsubheading @value{GDBN} Command
32746 The corresponding @value{GDBN} command is @samp{set}.
32748 @subsubheading Example
32758 @subheading The @code{-gdb-show} Command
32761 @subsubheading Synopsis
32767 Show the current value of a @value{GDBN} variable.
32769 @subsubheading @value{GDBN} Command
32771 The corresponding @value{GDBN} command is @samp{show}.
32773 @subsubheading Example
32782 @c @subheading -gdb-source
32785 @subheading The @code{-gdb-version} Command
32786 @findex -gdb-version
32788 @subsubheading Synopsis
32794 Show version information for @value{GDBN}. Used mostly in testing.
32796 @subsubheading @value{GDBN} Command
32798 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32799 default shows this information when you start an interactive session.
32801 @subsubheading Example
32803 @c This example modifies the actual output from GDB to avoid overfull
32809 ~Copyright 2000 Free Software Foundation, Inc.
32810 ~GDB is free software, covered by the GNU General Public License, and
32811 ~you are welcome to change it and/or distribute copies of it under
32812 ~ certain conditions.
32813 ~Type "show copying" to see the conditions.
32814 ~There is absolutely no warranty for GDB. Type "show warranty" for
32816 ~This GDB was configured as
32817 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32822 @subheading The @code{-list-thread-groups} Command
32823 @findex -list-thread-groups
32825 @subheading Synopsis
32828 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32831 Lists thread groups (@pxref{Thread groups}). When a single thread
32832 group is passed as the argument, lists the children of that group.
32833 When several thread group are passed, lists information about those
32834 thread groups. Without any parameters, lists information about all
32835 top-level thread groups.
32837 Normally, thread groups that are being debugged are reported.
32838 With the @samp{--available} option, @value{GDBN} reports thread groups
32839 available on the target.
32841 The output of this command may have either a @samp{threads} result or
32842 a @samp{groups} result. The @samp{thread} result has a list of tuples
32843 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32844 Information}). The @samp{groups} result has a list of tuples as value,
32845 each tuple describing a thread group. If top-level groups are
32846 requested (that is, no parameter is passed), or when several groups
32847 are passed, the output always has a @samp{groups} result. The format
32848 of the @samp{group} result is described below.
32850 To reduce the number of roundtrips it's possible to list thread groups
32851 together with their children, by passing the @samp{--recurse} option
32852 and the recursion depth. Presently, only recursion depth of 1 is
32853 permitted. If this option is present, then every reported thread group
32854 will also include its children, either as @samp{group} or
32855 @samp{threads} field.
32857 In general, any combination of option and parameters is permitted, with
32858 the following caveats:
32862 When a single thread group is passed, the output will typically
32863 be the @samp{threads} result. Because threads may not contain
32864 anything, the @samp{recurse} option will be ignored.
32867 When the @samp{--available} option is passed, limited information may
32868 be available. In particular, the list of threads of a process might
32869 be inaccessible. Further, specifying specific thread groups might
32870 not give any performance advantage over listing all thread groups.
32871 The frontend should assume that @samp{-list-thread-groups --available}
32872 is always an expensive operation and cache the results.
32876 The @samp{groups} result is a list of tuples, where each tuple may
32877 have the following fields:
32881 Identifier of the thread group. This field is always present.
32882 The identifier is an opaque string; frontends should not try to
32883 convert it to an integer, even though it might look like one.
32886 The type of the thread group. At present, only @samp{process} is a
32890 The target-specific process identifier. This field is only present
32891 for thread groups of type @samp{process} and only if the process exists.
32894 The exit code of this group's last exited thread, formatted in octal.
32895 This field is only present for thread groups of type @samp{process} and
32896 only if the process is not running.
32899 The number of children this thread group has. This field may be
32900 absent for an available thread group.
32903 This field has a list of tuples as value, each tuple describing a
32904 thread. It may be present if the @samp{--recurse} option is
32905 specified, and it's actually possible to obtain the threads.
32908 This field is a list of integers, each identifying a core that one
32909 thread of the group is running on. This field may be absent if
32910 such information is not available.
32913 The name of the executable file that corresponds to this thread group.
32914 The field is only present for thread groups of type @samp{process},
32915 and only if there is a corresponding executable file.
32919 @subheading Example
32923 -list-thread-groups
32924 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32925 -list-thread-groups 17
32926 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32927 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32928 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32929 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32930 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32931 -list-thread-groups --available
32932 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32933 -list-thread-groups --available --recurse 1
32934 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32935 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32936 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32937 -list-thread-groups --available --recurse 1 17 18
32938 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32939 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32940 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32943 @subheading The @code{-info-os} Command
32946 @subsubheading Synopsis
32949 -info-os [ @var{type} ]
32952 If no argument is supplied, the command returns a table of available
32953 operating-system-specific information types. If one of these types is
32954 supplied as an argument @var{type}, then the command returns a table
32955 of data of that type.
32957 The types of information available depend on the target operating
32960 @subsubheading @value{GDBN} Command
32962 The corresponding @value{GDBN} command is @samp{info os}.
32964 @subsubheading Example
32966 When run on a @sc{gnu}/Linux system, the output will look something
32972 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32973 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32974 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32975 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32976 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32978 item=@{col0="files",col1="Listing of all file descriptors",
32979 col2="File descriptors"@},
32980 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32981 col2="Kernel modules"@},
32982 item=@{col0="msg",col1="Listing of all message queues",
32983 col2="Message queues"@},
32984 item=@{col0="processes",col1="Listing of all processes",
32985 col2="Processes"@},
32986 item=@{col0="procgroups",col1="Listing of all process groups",
32987 col2="Process groups"@},
32988 item=@{col0="semaphores",col1="Listing of all semaphores",
32989 col2="Semaphores"@},
32990 item=@{col0="shm",col1="Listing of all shared-memory regions",
32991 col2="Shared-memory regions"@},
32992 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32994 item=@{col0="threads",col1="Listing of all threads",
32998 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32999 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33000 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33001 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33002 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33003 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33004 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33005 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33007 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33008 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33012 (Note that the MI output here includes a @code{"Title"} column that
33013 does not appear in command-line @code{info os}; this column is useful
33014 for MI clients that want to enumerate the types of data, such as in a
33015 popup menu, but is needless clutter on the command line, and
33016 @code{info os} omits it.)
33018 @subheading The @code{-add-inferior} Command
33019 @findex -add-inferior
33021 @subheading Synopsis
33027 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33028 inferior is not associated with any executable. Such association may
33029 be established with the @samp{-file-exec-and-symbols} command
33030 (@pxref{GDB/MI File Commands}). The command response has a single
33031 field, @samp{inferior}, whose value is the identifier of the
33032 thread group corresponding to the new inferior.
33034 @subheading Example
33039 ^done,inferior="i3"
33042 @subheading The @code{-interpreter-exec} Command
33043 @findex -interpreter-exec
33045 @subheading Synopsis
33048 -interpreter-exec @var{interpreter} @var{command}
33050 @anchor{-interpreter-exec}
33052 Execute the specified @var{command} in the given @var{interpreter}.
33054 @subheading @value{GDBN} Command
33056 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33058 @subheading Example
33062 -interpreter-exec console "break main"
33063 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33064 &"During symbol reading, bad structure-type format.\n"
33065 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33070 @subheading The @code{-inferior-tty-set} Command
33071 @findex -inferior-tty-set
33073 @subheading Synopsis
33076 -inferior-tty-set /dev/pts/1
33079 Set terminal for future runs of the program being debugged.
33081 @subheading @value{GDBN} Command
33083 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33085 @subheading Example
33089 -inferior-tty-set /dev/pts/1
33094 @subheading The @code{-inferior-tty-show} Command
33095 @findex -inferior-tty-show
33097 @subheading Synopsis
33103 Show terminal for future runs of program being debugged.
33105 @subheading @value{GDBN} Command
33107 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33109 @subheading Example
33113 -inferior-tty-set /dev/pts/1
33117 ^done,inferior_tty_terminal="/dev/pts/1"
33121 @subheading The @code{-enable-timings} Command
33122 @findex -enable-timings
33124 @subheading Synopsis
33127 -enable-timings [yes | no]
33130 Toggle the printing of the wallclock, user and system times for an MI
33131 command as a field in its output. This command is to help frontend
33132 developers optimize the performance of their code. No argument is
33133 equivalent to @samp{yes}.
33135 @subheading @value{GDBN} Command
33139 @subheading Example
33147 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33148 addr="0x080484ed",func="main",file="myprog.c",
33149 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33151 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33159 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33160 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33161 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33162 fullname="/home/nickrob/myprog.c",line="73"@}
33167 @chapter @value{GDBN} Annotations
33169 This chapter describes annotations in @value{GDBN}. Annotations were
33170 designed to interface @value{GDBN} to graphical user interfaces or other
33171 similar programs which want to interact with @value{GDBN} at a
33172 relatively high level.
33174 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33178 This is Edition @value{EDITION}, @value{DATE}.
33182 * Annotations Overview:: What annotations are; the general syntax.
33183 * Server Prefix:: Issuing a command without affecting user state.
33184 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33185 * Errors:: Annotations for error messages.
33186 * Invalidation:: Some annotations describe things now invalid.
33187 * Annotations for Running::
33188 Whether the program is running, how it stopped, etc.
33189 * Source Annotations:: Annotations describing source code.
33192 @node Annotations Overview
33193 @section What is an Annotation?
33194 @cindex annotations
33196 Annotations start with a newline character, two @samp{control-z}
33197 characters, and the name of the annotation. If there is no additional
33198 information associated with this annotation, the name of the annotation
33199 is followed immediately by a newline. If there is additional
33200 information, the name of the annotation is followed by a space, the
33201 additional information, and a newline. The additional information
33202 cannot contain newline characters.
33204 Any output not beginning with a newline and two @samp{control-z}
33205 characters denotes literal output from @value{GDBN}. Currently there is
33206 no need for @value{GDBN} to output a newline followed by two
33207 @samp{control-z} characters, but if there was such a need, the
33208 annotations could be extended with an @samp{escape} annotation which
33209 means those three characters as output.
33211 The annotation @var{level}, which is specified using the
33212 @option{--annotate} command line option (@pxref{Mode Options}), controls
33213 how much information @value{GDBN} prints together with its prompt,
33214 values of expressions, source lines, and other types of output. Level 0
33215 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33216 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33217 for programs that control @value{GDBN}, and level 2 annotations have
33218 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33219 Interface, annotate, GDB's Obsolete Annotations}).
33222 @kindex set annotate
33223 @item set annotate @var{level}
33224 The @value{GDBN} command @code{set annotate} sets the level of
33225 annotations to the specified @var{level}.
33227 @item show annotate
33228 @kindex show annotate
33229 Show the current annotation level.
33232 This chapter describes level 3 annotations.
33234 A simple example of starting up @value{GDBN} with annotations is:
33237 $ @kbd{gdb --annotate=3}
33239 Copyright 2003 Free Software Foundation, Inc.
33240 GDB is free software, covered by the GNU General Public License,
33241 and you are welcome to change it and/or distribute copies of it
33242 under certain conditions.
33243 Type "show copying" to see the conditions.
33244 There is absolutely no warranty for GDB. Type "show warranty"
33246 This GDB was configured as "i386-pc-linux-gnu"
33257 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33258 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33259 denotes a @samp{control-z} character) are annotations; the rest is
33260 output from @value{GDBN}.
33262 @node Server Prefix
33263 @section The Server Prefix
33264 @cindex server prefix
33266 If you prefix a command with @samp{server } then it will not affect
33267 the command history, nor will it affect @value{GDBN}'s notion of which
33268 command to repeat if @key{RET} is pressed on a line by itself. This
33269 means that commands can be run behind a user's back by a front-end in
33270 a transparent manner.
33272 The @code{server } prefix does not affect the recording of values into
33273 the value history; to print a value without recording it into the
33274 value history, use the @code{output} command instead of the
33275 @code{print} command.
33277 Using this prefix also disables confirmation requests
33278 (@pxref{confirmation requests}).
33281 @section Annotation for @value{GDBN} Input
33283 @cindex annotations for prompts
33284 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33285 to know when to send output, when the output from a given command is
33288 Different kinds of input each have a different @dfn{input type}. Each
33289 input type has three annotations: a @code{pre-} annotation, which
33290 denotes the beginning of any prompt which is being output, a plain
33291 annotation, which denotes the end of the prompt, and then a @code{post-}
33292 annotation which denotes the end of any echo which may (or may not) be
33293 associated with the input. For example, the @code{prompt} input type
33294 features the following annotations:
33302 The input types are
33305 @findex pre-prompt annotation
33306 @findex prompt annotation
33307 @findex post-prompt annotation
33309 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33311 @findex pre-commands annotation
33312 @findex commands annotation
33313 @findex post-commands annotation
33315 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33316 command. The annotations are repeated for each command which is input.
33318 @findex pre-overload-choice annotation
33319 @findex overload-choice annotation
33320 @findex post-overload-choice annotation
33321 @item overload-choice
33322 When @value{GDBN} wants the user to select between various overloaded functions.
33324 @findex pre-query annotation
33325 @findex query annotation
33326 @findex post-query annotation
33328 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33330 @findex pre-prompt-for-continue annotation
33331 @findex prompt-for-continue annotation
33332 @findex post-prompt-for-continue annotation
33333 @item prompt-for-continue
33334 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33335 expect this to work well; instead use @code{set height 0} to disable
33336 prompting. This is because the counting of lines is buggy in the
33337 presence of annotations.
33342 @cindex annotations for errors, warnings and interrupts
33344 @findex quit annotation
33349 This annotation occurs right before @value{GDBN} responds to an interrupt.
33351 @findex error annotation
33356 This annotation occurs right before @value{GDBN} responds to an error.
33358 Quit and error annotations indicate that any annotations which @value{GDBN} was
33359 in the middle of may end abruptly. For example, if a
33360 @code{value-history-begin} annotation is followed by a @code{error}, one
33361 cannot expect to receive the matching @code{value-history-end}. One
33362 cannot expect not to receive it either, however; an error annotation
33363 does not necessarily mean that @value{GDBN} is immediately returning all the way
33366 @findex error-begin annotation
33367 A quit or error annotation may be preceded by
33373 Any output between that and the quit or error annotation is the error
33376 Warning messages are not yet annotated.
33377 @c If we want to change that, need to fix warning(), type_error(),
33378 @c range_error(), and possibly other places.
33381 @section Invalidation Notices
33383 @cindex annotations for invalidation messages
33384 The following annotations say that certain pieces of state may have
33388 @findex frames-invalid annotation
33389 @item ^Z^Zframes-invalid
33391 The frames (for example, output from the @code{backtrace} command) may
33394 @findex breakpoints-invalid annotation
33395 @item ^Z^Zbreakpoints-invalid
33397 The breakpoints may have changed. For example, the user just added or
33398 deleted a breakpoint.
33401 @node Annotations for Running
33402 @section Running the Program
33403 @cindex annotations for running programs
33405 @findex starting annotation
33406 @findex stopping annotation
33407 When the program starts executing due to a @value{GDBN} command such as
33408 @code{step} or @code{continue},
33414 is output. When the program stops,
33420 is output. Before the @code{stopped} annotation, a variety of
33421 annotations describe how the program stopped.
33424 @findex exited annotation
33425 @item ^Z^Zexited @var{exit-status}
33426 The program exited, and @var{exit-status} is the exit status (zero for
33427 successful exit, otherwise nonzero).
33429 @findex signalled annotation
33430 @findex signal-name annotation
33431 @findex signal-name-end annotation
33432 @findex signal-string annotation
33433 @findex signal-string-end annotation
33434 @item ^Z^Zsignalled
33435 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33436 annotation continues:
33442 ^Z^Zsignal-name-end
33446 ^Z^Zsignal-string-end
33451 where @var{name} is the name of the signal, such as @code{SIGILL} or
33452 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33453 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33454 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33455 user's benefit and have no particular format.
33457 @findex signal annotation
33459 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33460 just saying that the program received the signal, not that it was
33461 terminated with it.
33463 @findex breakpoint annotation
33464 @item ^Z^Zbreakpoint @var{number}
33465 The program hit breakpoint number @var{number}.
33467 @findex watchpoint annotation
33468 @item ^Z^Zwatchpoint @var{number}
33469 The program hit watchpoint number @var{number}.
33472 @node Source Annotations
33473 @section Displaying Source
33474 @cindex annotations for source display
33476 @findex source annotation
33477 The following annotation is used instead of displaying source code:
33480 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33483 where @var{filename} is an absolute file name indicating which source
33484 file, @var{line} is the line number within that file (where 1 is the
33485 first line in the file), @var{character} is the character position
33486 within the file (where 0 is the first character in the file) (for most
33487 debug formats this will necessarily point to the beginning of a line),
33488 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33489 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33490 @var{addr} is the address in the target program associated with the
33491 source which is being displayed. The @var{addr} is in the form @samp{0x}
33492 followed by one or more lowercase hex digits (note that this does not
33493 depend on the language).
33495 @node JIT Interface
33496 @chapter JIT Compilation Interface
33497 @cindex just-in-time compilation
33498 @cindex JIT compilation interface
33500 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33501 interface. A JIT compiler is a program or library that generates native
33502 executable code at runtime and executes it, usually in order to achieve good
33503 performance while maintaining platform independence.
33505 Programs that use JIT compilation are normally difficult to debug because
33506 portions of their code are generated at runtime, instead of being loaded from
33507 object files, which is where @value{GDBN} normally finds the program's symbols
33508 and debug information. In order to debug programs that use JIT compilation,
33509 @value{GDBN} has an interface that allows the program to register in-memory
33510 symbol files with @value{GDBN} at runtime.
33512 If you are using @value{GDBN} to debug a program that uses this interface, then
33513 it should work transparently so long as you have not stripped the binary. If
33514 you are developing a JIT compiler, then the interface is documented in the rest
33515 of this chapter. At this time, the only known client of this interface is the
33518 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33519 JIT compiler communicates with @value{GDBN} by writing data into a global
33520 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33521 attaches, it reads a linked list of symbol files from the global variable to
33522 find existing code, and puts a breakpoint in the function so that it can find
33523 out about additional code.
33526 * Declarations:: Relevant C struct declarations
33527 * Registering Code:: Steps to register code
33528 * Unregistering Code:: Steps to unregister code
33529 * Custom Debug Info:: Emit debug information in a custom format
33533 @section JIT Declarations
33535 These are the relevant struct declarations that a C program should include to
33536 implement the interface:
33546 struct jit_code_entry
33548 struct jit_code_entry *next_entry;
33549 struct jit_code_entry *prev_entry;
33550 const char *symfile_addr;
33551 uint64_t symfile_size;
33554 struct jit_descriptor
33557 /* This type should be jit_actions_t, but we use uint32_t
33558 to be explicit about the bitwidth. */
33559 uint32_t action_flag;
33560 struct jit_code_entry *relevant_entry;
33561 struct jit_code_entry *first_entry;
33564 /* GDB puts a breakpoint in this function. */
33565 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33567 /* Make sure to specify the version statically, because the
33568 debugger may check the version before we can set it. */
33569 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33572 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33573 modifications to this global data properly, which can easily be done by putting
33574 a global mutex around modifications to these structures.
33576 @node Registering Code
33577 @section Registering Code
33579 To register code with @value{GDBN}, the JIT should follow this protocol:
33583 Generate an object file in memory with symbols and other desired debug
33584 information. The file must include the virtual addresses of the sections.
33587 Create a code entry for the file, which gives the start and size of the symbol
33591 Add it to the linked list in the JIT descriptor.
33594 Point the relevant_entry field of the descriptor at the entry.
33597 Set @code{action_flag} to @code{JIT_REGISTER} and call
33598 @code{__jit_debug_register_code}.
33601 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33602 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33603 new code. However, the linked list must still be maintained in order to allow
33604 @value{GDBN} to attach to a running process and still find the symbol files.
33606 @node Unregistering Code
33607 @section Unregistering Code
33609 If code is freed, then the JIT should use the following protocol:
33613 Remove the code entry corresponding to the code from the linked list.
33616 Point the @code{relevant_entry} field of the descriptor at the code entry.
33619 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33620 @code{__jit_debug_register_code}.
33623 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33624 and the JIT will leak the memory used for the associated symbol files.
33626 @node Custom Debug Info
33627 @section Custom Debug Info
33628 @cindex custom JIT debug info
33629 @cindex JIT debug info reader
33631 Generating debug information in platform-native file formats (like ELF
33632 or COFF) may be an overkill for JIT compilers; especially if all the
33633 debug info is used for is displaying a meaningful backtrace. The
33634 issue can be resolved by having the JIT writers decide on a debug info
33635 format and also provide a reader that parses the debug info generated
33636 by the JIT compiler. This section gives a brief overview on writing
33637 such a parser. More specific details can be found in the source file
33638 @file{gdb/jit-reader.in}, which is also installed as a header at
33639 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33641 The reader is implemented as a shared object (so this functionality is
33642 not available on platforms which don't allow loading shared objects at
33643 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33644 @code{jit-reader-unload} are provided, to be used to load and unload
33645 the readers from a preconfigured directory. Once loaded, the shared
33646 object is used the parse the debug information emitted by the JIT
33650 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33651 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33654 @node Using JIT Debug Info Readers
33655 @subsection Using JIT Debug Info Readers
33656 @kindex jit-reader-load
33657 @kindex jit-reader-unload
33659 Readers can be loaded and unloaded using the @code{jit-reader-load}
33660 and @code{jit-reader-unload} commands.
33663 @item jit-reader-load @var{reader}
33664 Load the JIT reader named @var{reader}, which is a shared
33665 object specified as either an absolute or a relative file name. In
33666 the latter case, @value{GDBN} will try to load the reader from a
33667 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33668 system (here @var{libdir} is the system library directory, often
33669 @file{/usr/local/lib}).
33671 Only one reader can be active at a time; trying to load a second
33672 reader when one is already loaded will result in @value{GDBN}
33673 reporting an error. A new JIT reader can be loaded by first unloading
33674 the current one using @code{jit-reader-unload} and then invoking
33675 @code{jit-reader-load}.
33677 @item jit-reader-unload
33678 Unload the currently loaded JIT reader.
33682 @node Writing JIT Debug Info Readers
33683 @subsection Writing JIT Debug Info Readers
33684 @cindex writing JIT debug info readers
33686 As mentioned, a reader is essentially a shared object conforming to a
33687 certain ABI. This ABI is described in @file{jit-reader.h}.
33689 @file{jit-reader.h} defines the structures, macros and functions
33690 required to write a reader. It is installed (along with
33691 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33692 the system include directory.
33694 Readers need to be released under a GPL compatible license. A reader
33695 can be declared as released under such a license by placing the macro
33696 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33698 The entry point for readers is the symbol @code{gdb_init_reader},
33699 which is expected to be a function with the prototype
33701 @findex gdb_init_reader
33703 extern struct gdb_reader_funcs *gdb_init_reader (void);
33706 @cindex @code{struct gdb_reader_funcs}
33708 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33709 functions. These functions are executed to read the debug info
33710 generated by the JIT compiler (@code{read}), to unwind stack frames
33711 (@code{unwind}) and to create canonical frame IDs
33712 (@code{get_Frame_id}). It also has a callback that is called when the
33713 reader is being unloaded (@code{destroy}). The struct looks like this
33716 struct gdb_reader_funcs
33718 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33719 int reader_version;
33721 /* For use by the reader. */
33724 gdb_read_debug_info *read;
33725 gdb_unwind_frame *unwind;
33726 gdb_get_frame_id *get_frame_id;
33727 gdb_destroy_reader *destroy;
33731 @cindex @code{struct gdb_symbol_callbacks}
33732 @cindex @code{struct gdb_unwind_callbacks}
33734 The callbacks are provided with another set of callbacks by
33735 @value{GDBN} to do their job. For @code{read}, these callbacks are
33736 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33737 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33738 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33739 files and new symbol tables inside those object files. @code{struct
33740 gdb_unwind_callbacks} has callbacks to read registers off the current
33741 frame and to write out the values of the registers in the previous
33742 frame. Both have a callback (@code{target_read}) to read bytes off the
33743 target's address space.
33745 @node In-Process Agent
33746 @chapter In-Process Agent
33747 @cindex debugging agent
33748 The traditional debugging model is conceptually low-speed, but works fine,
33749 because most bugs can be reproduced in debugging-mode execution. However,
33750 as multi-core or many-core processors are becoming mainstream, and
33751 multi-threaded programs become more and more popular, there should be more
33752 and more bugs that only manifest themselves at normal-mode execution, for
33753 example, thread races, because debugger's interference with the program's
33754 timing may conceal the bugs. On the other hand, in some applications,
33755 it is not feasible for the debugger to interrupt the program's execution
33756 long enough for the developer to learn anything helpful about its behavior.
33757 If the program's correctness depends on its real-time behavior, delays
33758 introduced by a debugger might cause the program to fail, even when the
33759 code itself is correct. It is useful to be able to observe the program's
33760 behavior without interrupting it.
33762 Therefore, traditional debugging model is too intrusive to reproduce
33763 some bugs. In order to reduce the interference with the program, we can
33764 reduce the number of operations performed by debugger. The
33765 @dfn{In-Process Agent}, a shared library, is running within the same
33766 process with inferior, and is able to perform some debugging operations
33767 itself. As a result, debugger is only involved when necessary, and
33768 performance of debugging can be improved accordingly. Note that
33769 interference with program can be reduced but can't be removed completely,
33770 because the in-process agent will still stop or slow down the program.
33772 The in-process agent can interpret and execute Agent Expressions
33773 (@pxref{Agent Expressions}) during performing debugging operations. The
33774 agent expressions can be used for different purposes, such as collecting
33775 data in tracepoints, and condition evaluation in breakpoints.
33777 @anchor{Control Agent}
33778 You can control whether the in-process agent is used as an aid for
33779 debugging with the following commands:
33782 @kindex set agent on
33784 Causes the in-process agent to perform some operations on behalf of the
33785 debugger. Just which operations requested by the user will be done
33786 by the in-process agent depends on the its capabilities. For example,
33787 if you request to evaluate breakpoint conditions in the in-process agent,
33788 and the in-process agent has such capability as well, then breakpoint
33789 conditions will be evaluated in the in-process agent.
33791 @kindex set agent off
33792 @item set agent off
33793 Disables execution of debugging operations by the in-process agent. All
33794 of the operations will be performed by @value{GDBN}.
33798 Display the current setting of execution of debugging operations by
33799 the in-process agent.
33803 * In-Process Agent Protocol::
33806 @node In-Process Agent Protocol
33807 @section In-Process Agent Protocol
33808 @cindex in-process agent protocol
33810 The in-process agent is able to communicate with both @value{GDBN} and
33811 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33812 used for communications between @value{GDBN} or GDBserver and the IPA.
33813 In general, @value{GDBN} or GDBserver sends commands
33814 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33815 in-process agent replies back with the return result of the command, or
33816 some other information. The data sent to in-process agent is composed
33817 of primitive data types, such as 4-byte or 8-byte type, and composite
33818 types, which are called objects (@pxref{IPA Protocol Objects}).
33821 * IPA Protocol Objects::
33822 * IPA Protocol Commands::
33825 @node IPA Protocol Objects
33826 @subsection IPA Protocol Objects
33827 @cindex ipa protocol objects
33829 The commands sent to and results received from agent may contain some
33830 complex data types called @dfn{objects}.
33832 The in-process agent is running on the same machine with @value{GDBN}
33833 or GDBserver, so it doesn't have to handle as much differences between
33834 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33835 However, there are still some differences of two ends in two processes:
33839 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33840 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33842 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33843 GDBserver is compiled with one, and in-process agent is compiled with
33847 Here are the IPA Protocol Objects:
33851 agent expression object. It represents an agent expression
33852 (@pxref{Agent Expressions}).
33853 @anchor{agent expression object}
33855 tracepoint action object. It represents a tracepoint action
33856 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33857 memory, static trace data and to evaluate expression.
33858 @anchor{tracepoint action object}
33860 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33861 @anchor{tracepoint object}
33865 The following table describes important attributes of each IPA protocol
33868 @multitable @columnfractions .30 .20 .50
33869 @headitem Name @tab Size @tab Description
33870 @item @emph{agent expression object} @tab @tab
33871 @item length @tab 4 @tab length of bytes code
33872 @item byte code @tab @var{length} @tab contents of byte code
33873 @item @emph{tracepoint action for collecting memory} @tab @tab
33874 @item 'M' @tab 1 @tab type of tracepoint action
33875 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33876 address of the lowest byte to collect, otherwise @var{addr} is the offset
33877 of @var{basereg} for memory collecting.
33878 @item len @tab 8 @tab length of memory for collecting
33879 @item basereg @tab 4 @tab the register number containing the starting
33880 memory address for collecting.
33881 @item @emph{tracepoint action for collecting registers} @tab @tab
33882 @item 'R' @tab 1 @tab type of tracepoint action
33883 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33884 @item 'L' @tab 1 @tab type of tracepoint action
33885 @item @emph{tracepoint action for expression evaluation} @tab @tab
33886 @item 'X' @tab 1 @tab type of tracepoint action
33887 @item agent expression @tab length of @tab @ref{agent expression object}
33888 @item @emph{tracepoint object} @tab @tab
33889 @item number @tab 4 @tab number of tracepoint
33890 @item address @tab 8 @tab address of tracepoint inserted on
33891 @item type @tab 4 @tab type of tracepoint
33892 @item enabled @tab 1 @tab enable or disable of tracepoint
33893 @item step_count @tab 8 @tab step
33894 @item pass_count @tab 8 @tab pass
33895 @item numactions @tab 4 @tab number of tracepoint actions
33896 @item hit count @tab 8 @tab hit count
33897 @item trace frame usage @tab 8 @tab trace frame usage
33898 @item compiled_cond @tab 8 @tab compiled condition
33899 @item orig_size @tab 8 @tab orig size
33900 @item condition @tab 4 if condition is NULL otherwise length of
33901 @ref{agent expression object}
33902 @tab zero if condition is NULL, otherwise is
33903 @ref{agent expression object}
33904 @item actions @tab variable
33905 @tab numactions number of @ref{tracepoint action object}
33908 @node IPA Protocol Commands
33909 @subsection IPA Protocol Commands
33910 @cindex ipa protocol commands
33912 The spaces in each command are delimiters to ease reading this commands
33913 specification. They don't exist in real commands.
33917 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33918 Installs a new fast tracepoint described by @var{tracepoint_object}
33919 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33920 head of @dfn{jumppad}, which is used to jump to data collection routine
33925 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33926 @var{target_address} is address of tracepoint in the inferior.
33927 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33928 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33929 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33930 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33937 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33938 is about to kill inferiors.
33946 @item probe_marker_at:@var{address}
33947 Asks in-process agent to probe the marker at @var{address}.
33954 @item unprobe_marker_at:@var{address}
33955 Asks in-process agent to unprobe the marker at @var{address}.
33959 @chapter Reporting Bugs in @value{GDBN}
33960 @cindex bugs in @value{GDBN}
33961 @cindex reporting bugs in @value{GDBN}
33963 Your bug reports play an essential role in making @value{GDBN} reliable.
33965 Reporting a bug may help you by bringing a solution to your problem, or it
33966 may not. But in any case the principal function of a bug report is to help
33967 the entire community by making the next version of @value{GDBN} work better. Bug
33968 reports are your contribution to the maintenance of @value{GDBN}.
33970 In order for a bug report to serve its purpose, you must include the
33971 information that enables us to fix the bug.
33974 * Bug Criteria:: Have you found a bug?
33975 * Bug Reporting:: How to report bugs
33979 @section Have You Found a Bug?
33980 @cindex bug criteria
33982 If you are not sure whether you have found a bug, here are some guidelines:
33985 @cindex fatal signal
33986 @cindex debugger crash
33987 @cindex crash of debugger
33989 If the debugger gets a fatal signal, for any input whatever, that is a
33990 @value{GDBN} bug. Reliable debuggers never crash.
33992 @cindex error on valid input
33994 If @value{GDBN} produces an error message for valid input, that is a
33995 bug. (Note that if you're cross debugging, the problem may also be
33996 somewhere in the connection to the target.)
33998 @cindex invalid input
34000 If @value{GDBN} does not produce an error message for invalid input,
34001 that is a bug. However, you should note that your idea of
34002 ``invalid input'' might be our idea of ``an extension'' or ``support
34003 for traditional practice''.
34006 If you are an experienced user of debugging tools, your suggestions
34007 for improvement of @value{GDBN} are welcome in any case.
34010 @node Bug Reporting
34011 @section How to Report Bugs
34012 @cindex bug reports
34013 @cindex @value{GDBN} bugs, reporting
34015 A number of companies and individuals offer support for @sc{gnu} products.
34016 If you obtained @value{GDBN} from a support organization, we recommend you
34017 contact that organization first.
34019 You can find contact information for many support companies and
34020 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34022 @c should add a web page ref...
34025 @ifset BUGURL_DEFAULT
34026 In any event, we also recommend that you submit bug reports for
34027 @value{GDBN}. The preferred method is to submit them directly using
34028 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34029 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34032 @strong{Do not send bug reports to @samp{info-gdb}, or to
34033 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34034 not want to receive bug reports. Those that do have arranged to receive
34037 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34038 serves as a repeater. The mailing list and the newsgroup carry exactly
34039 the same messages. Often people think of posting bug reports to the
34040 newsgroup instead of mailing them. This appears to work, but it has one
34041 problem which can be crucial: a newsgroup posting often lacks a mail
34042 path back to the sender. Thus, if we need to ask for more information,
34043 we may be unable to reach you. For this reason, it is better to send
34044 bug reports to the mailing list.
34046 @ifclear BUGURL_DEFAULT
34047 In any event, we also recommend that you submit bug reports for
34048 @value{GDBN} to @value{BUGURL}.
34052 The fundamental principle of reporting bugs usefully is this:
34053 @strong{report all the facts}. If you are not sure whether to state a
34054 fact or leave it out, state it!
34056 Often people omit facts because they think they know what causes the
34057 problem and assume that some details do not matter. Thus, you might
34058 assume that the name of the variable you use in an example does not matter.
34059 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34060 stray memory reference which happens to fetch from the location where that
34061 name is stored in memory; perhaps, if the name were different, the contents
34062 of that location would fool the debugger into doing the right thing despite
34063 the bug. Play it safe and give a specific, complete example. That is the
34064 easiest thing for you to do, and the most helpful.
34066 Keep in mind that the purpose of a bug report is to enable us to fix the
34067 bug. It may be that the bug has been reported previously, but neither
34068 you nor we can know that unless your bug report is complete and
34071 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34072 bell?'' Those bug reports are useless, and we urge everyone to
34073 @emph{refuse to respond to them} except to chide the sender to report
34076 To enable us to fix the bug, you should include all these things:
34080 The version of @value{GDBN}. @value{GDBN} announces it if you start
34081 with no arguments; you can also print it at any time using @code{show
34084 Without this, we will not know whether there is any point in looking for
34085 the bug in the current version of @value{GDBN}.
34088 The type of machine you are using, and the operating system name and
34092 The details of the @value{GDBN} build-time configuration.
34093 @value{GDBN} shows these details if you invoke it with the
34094 @option{--configuration} command-line option, or if you type
34095 @code{show configuration} at @value{GDBN}'s prompt.
34098 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34099 ``@value{GCC}--2.8.1''.
34102 What compiler (and its version) was used to compile the program you are
34103 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34104 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34105 to get this information; for other compilers, see the documentation for
34109 The command arguments you gave the compiler to compile your example and
34110 observe the bug. For example, did you use @samp{-O}? To guarantee
34111 you will not omit something important, list them all. A copy of the
34112 Makefile (or the output from make) is sufficient.
34114 If we were to try to guess the arguments, we would probably guess wrong
34115 and then we might not encounter the bug.
34118 A complete input script, and all necessary source files, that will
34122 A description of what behavior you observe that you believe is
34123 incorrect. For example, ``It gets a fatal signal.''
34125 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34126 will certainly notice it. But if the bug is incorrect output, we might
34127 not notice unless it is glaringly wrong. You might as well not give us
34128 a chance to make a mistake.
34130 Even if the problem you experience is a fatal signal, you should still
34131 say so explicitly. Suppose something strange is going on, such as, your
34132 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34133 the C library on your system. (This has happened!) Your copy might
34134 crash and ours would not. If you told us to expect a crash, then when
34135 ours fails to crash, we would know that the bug was not happening for
34136 us. If you had not told us to expect a crash, then we would not be able
34137 to draw any conclusion from our observations.
34140 @cindex recording a session script
34141 To collect all this information, you can use a session recording program
34142 such as @command{script}, which is available on many Unix systems.
34143 Just run your @value{GDBN} session inside @command{script} and then
34144 include the @file{typescript} file with your bug report.
34146 Another way to record a @value{GDBN} session is to run @value{GDBN}
34147 inside Emacs and then save the entire buffer to a file.
34150 If you wish to suggest changes to the @value{GDBN} source, send us context
34151 diffs. If you even discuss something in the @value{GDBN} source, refer to
34152 it by context, not by line number.
34154 The line numbers in our development sources will not match those in your
34155 sources. Your line numbers would convey no useful information to us.
34159 Here are some things that are not necessary:
34163 A description of the envelope of the bug.
34165 Often people who encounter a bug spend a lot of time investigating
34166 which changes to the input file will make the bug go away and which
34167 changes will not affect it.
34169 This is often time consuming and not very useful, because the way we
34170 will find the bug is by running a single example under the debugger
34171 with breakpoints, not by pure deduction from a series of examples.
34172 We recommend that you save your time for something else.
34174 Of course, if you can find a simpler example to report @emph{instead}
34175 of the original one, that is a convenience for us. Errors in the
34176 output will be easier to spot, running under the debugger will take
34177 less time, and so on.
34179 However, simplification is not vital; if you do not want to do this,
34180 report the bug anyway and send us the entire test case you used.
34183 A patch for the bug.
34185 A patch for the bug does help us if it is a good one. But do not omit
34186 the necessary information, such as the test case, on the assumption that
34187 a patch is all we need. We might see problems with your patch and decide
34188 to fix the problem another way, or we might not understand it at all.
34190 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34191 construct an example that will make the program follow a certain path
34192 through the code. If you do not send us the example, we will not be able
34193 to construct one, so we will not be able to verify that the bug is fixed.
34195 And if we cannot understand what bug you are trying to fix, or why your
34196 patch should be an improvement, we will not install it. A test case will
34197 help us to understand.
34200 A guess about what the bug is or what it depends on.
34202 Such guesses are usually wrong. Even we cannot guess right about such
34203 things without first using the debugger to find the facts.
34206 @c The readline documentation is distributed with the readline code
34207 @c and consists of the two following files:
34210 @c Use -I with makeinfo to point to the appropriate directory,
34211 @c environment var TEXINPUTS with TeX.
34212 @ifclear SYSTEM_READLINE
34213 @include rluser.texi
34214 @include hsuser.texi
34218 @appendix In Memoriam
34220 The @value{GDBN} project mourns the loss of the following long-time
34225 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34226 to Free Software in general. Outside of @value{GDBN}, he was known in
34227 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34229 @item Michael Snyder
34230 Michael was one of the Global Maintainers of the @value{GDBN} project,
34231 with contributions recorded as early as 1996, until 2011. In addition
34232 to his day to day participation, he was a large driving force behind
34233 adding Reverse Debugging to @value{GDBN}.
34236 Beyond their technical contributions to the project, they were also
34237 enjoyable members of the Free Software Community. We will miss them.
34239 @node Formatting Documentation
34240 @appendix Formatting Documentation
34242 @cindex @value{GDBN} reference card
34243 @cindex reference card
34244 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34245 for printing with PostScript or Ghostscript, in the @file{gdb}
34246 subdirectory of the main source directory@footnote{In
34247 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34248 release.}. If you can use PostScript or Ghostscript with your printer,
34249 you can print the reference card immediately with @file{refcard.ps}.
34251 The release also includes the source for the reference card. You
34252 can format it, using @TeX{}, by typing:
34258 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34259 mode on US ``letter'' size paper;
34260 that is, on a sheet 11 inches wide by 8.5 inches
34261 high. You will need to specify this form of printing as an option to
34262 your @sc{dvi} output program.
34264 @cindex documentation
34266 All the documentation for @value{GDBN} comes as part of the machine-readable
34267 distribution. The documentation is written in Texinfo format, which is
34268 a documentation system that uses a single source file to produce both
34269 on-line information and a printed manual. You can use one of the Info
34270 formatting commands to create the on-line version of the documentation
34271 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34273 @value{GDBN} includes an already formatted copy of the on-line Info
34274 version of this manual in the @file{gdb} subdirectory. The main Info
34275 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34276 subordinate files matching @samp{gdb.info*} in the same directory. If
34277 necessary, you can print out these files, or read them with any editor;
34278 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34279 Emacs or the standalone @code{info} program, available as part of the
34280 @sc{gnu} Texinfo distribution.
34282 If you want to format these Info files yourself, you need one of the
34283 Info formatting programs, such as @code{texinfo-format-buffer} or
34286 If you have @code{makeinfo} installed, and are in the top level
34287 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34288 version @value{GDBVN}), you can make the Info file by typing:
34295 If you want to typeset and print copies of this manual, you need @TeX{},
34296 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34297 Texinfo definitions file.
34299 @TeX{} is a typesetting program; it does not print files directly, but
34300 produces output files called @sc{dvi} files. To print a typeset
34301 document, you need a program to print @sc{dvi} files. If your system
34302 has @TeX{} installed, chances are it has such a program. The precise
34303 command to use depends on your system; @kbd{lpr -d} is common; another
34304 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34305 require a file name without any extension or a @samp{.dvi} extension.
34307 @TeX{} also requires a macro definitions file called
34308 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34309 written in Texinfo format. On its own, @TeX{} cannot either read or
34310 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34311 and is located in the @file{gdb-@var{version-number}/texinfo}
34314 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34315 typeset and print this manual. First switch to the @file{gdb}
34316 subdirectory of the main source directory (for example, to
34317 @file{gdb-@value{GDBVN}/gdb}) and type:
34323 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34325 @node Installing GDB
34326 @appendix Installing @value{GDBN}
34327 @cindex installation
34330 * Requirements:: Requirements for building @value{GDBN}
34331 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34332 * Separate Objdir:: Compiling @value{GDBN} in another directory
34333 * Config Names:: Specifying names for hosts and targets
34334 * Configure Options:: Summary of options for configure
34335 * System-wide configuration:: Having a system-wide init file
34339 @section Requirements for Building @value{GDBN}
34340 @cindex building @value{GDBN}, requirements for
34342 Building @value{GDBN} requires various tools and packages to be available.
34343 Other packages will be used only if they are found.
34345 @heading Tools/Packages Necessary for Building @value{GDBN}
34347 @item ISO C90 compiler
34348 @value{GDBN} is written in ISO C90. It should be buildable with any
34349 working C90 compiler, e.g.@: GCC.
34353 @heading Tools/Packages Optional for Building @value{GDBN}
34357 @value{GDBN} can use the Expat XML parsing library. This library may be
34358 included with your operating system distribution; if it is not, you
34359 can get the latest version from @url{http://expat.sourceforge.net}.
34360 The @file{configure} script will search for this library in several
34361 standard locations; if it is installed in an unusual path, you can
34362 use the @option{--with-libexpat-prefix} option to specify its location.
34368 Remote protocol memory maps (@pxref{Memory Map Format})
34370 Target descriptions (@pxref{Target Descriptions})
34372 Remote shared library lists (@xref{Library List Format},
34373 or alternatively @pxref{Library List Format for SVR4 Targets})
34375 MS-Windows shared libraries (@pxref{Shared Libraries})
34377 Traceframe info (@pxref{Traceframe Info Format})
34379 Branch trace (@pxref{Branch Trace Format},
34380 @pxref{Branch Trace Configuration Format})
34385 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
34386 library. This library may be included with your operating system
34387 distribution; if it is not, you can get the latest version from
34388 @url{http://www.mpfr.org}. The @file{configure} script will search
34389 for this library in several standard locations; if it is installed
34390 in an unusual path, you can use the @option{--with-libmpfr-prefix}
34391 option to specify its location.
34393 GNU MPFR is used to emulate target floating-point arithmetic during
34394 expression evaluation when the target uses different floating-point
34395 formats than the host. If GNU MPFR it is not available, @value{GDBN}
34396 will fall back to using host floating-point arithmetic.
34399 @cindex compressed debug sections
34400 @value{GDBN} will use the @samp{zlib} library, if available, to read
34401 compressed debug sections. Some linkers, such as GNU gold, are capable
34402 of producing binaries with compressed debug sections. If @value{GDBN}
34403 is compiled with @samp{zlib}, it will be able to read the debug
34404 information in such binaries.
34406 The @samp{zlib} library is likely included with your operating system
34407 distribution; if it is not, you can get the latest version from
34408 @url{http://zlib.net}.
34411 @value{GDBN}'s features related to character sets (@pxref{Character
34412 Sets}) require a functioning @code{iconv} implementation. If you are
34413 on a GNU system, then this is provided by the GNU C Library. Some
34414 other systems also provide a working @code{iconv}.
34416 If @value{GDBN} is using the @code{iconv} program which is installed
34417 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34418 This is done with @option{--with-iconv-bin} which specifies the
34419 directory that contains the @code{iconv} program.
34421 On systems without @code{iconv}, you can install GNU Libiconv. If you
34422 have previously installed Libiconv, you can use the
34423 @option{--with-libiconv-prefix} option to configure.
34425 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34426 arrange to build Libiconv if a directory named @file{libiconv} appears
34427 in the top-most source directory. If Libiconv is built this way, and
34428 if the operating system does not provide a suitable @code{iconv}
34429 implementation, then the just-built library will automatically be used
34430 by @value{GDBN}. One easy way to set this up is to download GNU
34431 Libiconv, unpack it, and then rename the directory holding the
34432 Libiconv source code to @samp{libiconv}.
34435 @node Running Configure
34436 @section Invoking the @value{GDBN} @file{configure} Script
34437 @cindex configuring @value{GDBN}
34438 @value{GDBN} comes with a @file{configure} script that automates the process
34439 of preparing @value{GDBN} for installation; you can then use @code{make} to
34440 build the @code{gdb} program.
34442 @c irrelevant in info file; it's as current as the code it lives with.
34443 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34444 look at the @file{README} file in the sources; we may have improved the
34445 installation procedures since publishing this manual.}
34448 The @value{GDBN} distribution includes all the source code you need for
34449 @value{GDBN} in a single directory, whose name is usually composed by
34450 appending the version number to @samp{gdb}.
34452 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34453 @file{gdb-@value{GDBVN}} directory. That directory contains:
34456 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34457 script for configuring @value{GDBN} and all its supporting libraries
34459 @item gdb-@value{GDBVN}/gdb
34460 the source specific to @value{GDBN} itself
34462 @item gdb-@value{GDBVN}/bfd
34463 source for the Binary File Descriptor library
34465 @item gdb-@value{GDBVN}/include
34466 @sc{gnu} include files
34468 @item gdb-@value{GDBVN}/libiberty
34469 source for the @samp{-liberty} free software library
34471 @item gdb-@value{GDBVN}/opcodes
34472 source for the library of opcode tables and disassemblers
34474 @item gdb-@value{GDBVN}/readline
34475 source for the @sc{gnu} command-line interface
34477 @item gdb-@value{GDBVN}/glob
34478 source for the @sc{gnu} filename pattern-matching subroutine
34480 @item gdb-@value{GDBVN}/mmalloc
34481 source for the @sc{gnu} memory-mapped malloc package
34484 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34485 from the @file{gdb-@var{version-number}} source directory, which in
34486 this example is the @file{gdb-@value{GDBVN}} directory.
34488 First switch to the @file{gdb-@var{version-number}} source directory
34489 if you are not already in it; then run @file{configure}. Pass the
34490 identifier for the platform on which @value{GDBN} will run as an
34496 cd gdb-@value{GDBVN}
34497 ./configure @var{host}
34502 where @var{host} is an identifier such as @samp{sun4} or
34503 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34504 (You can often leave off @var{host}; @file{configure} tries to guess the
34505 correct value by examining your system.)
34507 Running @samp{configure @var{host}} and then running @code{make} builds the
34508 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34509 libraries, then @code{gdb} itself. The configured source files, and the
34510 binaries, are left in the corresponding source directories.
34513 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34514 system does not recognize this automatically when you run a different
34515 shell, you may need to run @code{sh} on it explicitly:
34518 sh configure @var{host}
34521 If you run @file{configure} from a directory that contains source
34522 directories for multiple libraries or programs, such as the
34523 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34525 creates configuration files for every directory level underneath (unless
34526 you tell it not to, with the @samp{--norecursion} option).
34528 You should run the @file{configure} script from the top directory in the
34529 source tree, the @file{gdb-@var{version-number}} directory. If you run
34530 @file{configure} from one of the subdirectories, you will configure only
34531 that subdirectory. That is usually not what you want. In particular,
34532 if you run the first @file{configure} from the @file{gdb} subdirectory
34533 of the @file{gdb-@var{version-number}} directory, you will omit the
34534 configuration of @file{bfd}, @file{readline}, and other sibling
34535 directories of the @file{gdb} subdirectory. This leads to build errors
34536 about missing include files such as @file{bfd/bfd.h}.
34538 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34539 However, you should make sure that the shell on your path (named by
34540 the @samp{SHELL} environment variable) is publicly readable. Remember
34541 that @value{GDBN} uses the shell to start your program---some systems refuse to
34542 let @value{GDBN} debug child processes whose programs are not readable.
34544 @node Separate Objdir
34545 @section Compiling @value{GDBN} in Another Directory
34547 If you want to run @value{GDBN} versions for several host or target machines,
34548 you need a different @code{gdb} compiled for each combination of
34549 host and target. @file{configure} is designed to make this easy by
34550 allowing you to generate each configuration in a separate subdirectory,
34551 rather than in the source directory. If your @code{make} program
34552 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34553 @code{make} in each of these directories builds the @code{gdb}
34554 program specified there.
34556 To build @code{gdb} in a separate directory, run @file{configure}
34557 with the @samp{--srcdir} option to specify where to find the source.
34558 (You also need to specify a path to find @file{configure}
34559 itself from your working directory. If the path to @file{configure}
34560 would be the same as the argument to @samp{--srcdir}, you can leave out
34561 the @samp{--srcdir} option; it is assumed.)
34563 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34564 separate directory for a Sun 4 like this:
34568 cd gdb-@value{GDBVN}
34571 ../gdb-@value{GDBVN}/configure sun4
34576 When @file{configure} builds a configuration using a remote source
34577 directory, it creates a tree for the binaries with the same structure
34578 (and using the same names) as the tree under the source directory. In
34579 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34580 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34581 @file{gdb-sun4/gdb}.
34583 Make sure that your path to the @file{configure} script has just one
34584 instance of @file{gdb} in it. If your path to @file{configure} looks
34585 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34586 one subdirectory of @value{GDBN}, not the whole package. This leads to
34587 build errors about missing include files such as @file{bfd/bfd.h}.
34589 One popular reason to build several @value{GDBN} configurations in separate
34590 directories is to configure @value{GDBN} for cross-compiling (where
34591 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34592 programs that run on another machine---the @dfn{target}).
34593 You specify a cross-debugging target by
34594 giving the @samp{--target=@var{target}} option to @file{configure}.
34596 When you run @code{make} to build a program or library, you must run
34597 it in a configured directory---whatever directory you were in when you
34598 called @file{configure} (or one of its subdirectories).
34600 The @code{Makefile} that @file{configure} generates in each source
34601 directory also runs recursively. If you type @code{make} in a source
34602 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34603 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34604 will build all the required libraries, and then build GDB.
34606 When you have multiple hosts or targets configured in separate
34607 directories, you can run @code{make} on them in parallel (for example,
34608 if they are NFS-mounted on each of the hosts); they will not interfere
34612 @section Specifying Names for Hosts and Targets
34614 The specifications used for hosts and targets in the @file{configure}
34615 script are based on a three-part naming scheme, but some short predefined
34616 aliases are also supported. The full naming scheme encodes three pieces
34617 of information in the following pattern:
34620 @var{architecture}-@var{vendor}-@var{os}
34623 For example, you can use the alias @code{sun4} as a @var{host} argument,
34624 or as the value for @var{target} in a @code{--target=@var{target}}
34625 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34627 The @file{configure} script accompanying @value{GDBN} does not provide
34628 any query facility to list all supported host and target names or
34629 aliases. @file{configure} calls the Bourne shell script
34630 @code{config.sub} to map abbreviations to full names; you can read the
34631 script, if you wish, or you can use it to test your guesses on
34632 abbreviations---for example:
34635 % sh config.sub i386-linux
34637 % sh config.sub alpha-linux
34638 alpha-unknown-linux-gnu
34639 % sh config.sub hp9k700
34641 % sh config.sub sun4
34642 sparc-sun-sunos4.1.1
34643 % sh config.sub sun3
34644 m68k-sun-sunos4.1.1
34645 % sh config.sub i986v
34646 Invalid configuration `i986v': machine `i986v' not recognized
34650 @code{config.sub} is also distributed in the @value{GDBN} source
34651 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34653 @node Configure Options
34654 @section @file{configure} Options
34656 Here is a summary of the @file{configure} options and arguments that
34657 are most often useful for building @value{GDBN}. @file{configure} also has
34658 several other options not listed here. @inforef{What Configure
34659 Does,,configure.info}, for a full explanation of @file{configure}.
34662 configure @r{[}--help@r{]}
34663 @r{[}--prefix=@var{dir}@r{]}
34664 @r{[}--exec-prefix=@var{dir}@r{]}
34665 @r{[}--srcdir=@var{dirname}@r{]}
34666 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34667 @r{[}--target=@var{target}@r{]}
34672 You may introduce options with a single @samp{-} rather than
34673 @samp{--} if you prefer; but you may abbreviate option names if you use
34678 Display a quick summary of how to invoke @file{configure}.
34680 @item --prefix=@var{dir}
34681 Configure the source to install programs and files under directory
34684 @item --exec-prefix=@var{dir}
34685 Configure the source to install programs under directory
34688 @c avoid splitting the warning from the explanation:
34690 @item --srcdir=@var{dirname}
34691 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34692 @code{make} that implements the @code{VPATH} feature.}@*
34693 Use this option to make configurations in directories separate from the
34694 @value{GDBN} source directories. Among other things, you can use this to
34695 build (or maintain) several configurations simultaneously, in separate
34696 directories. @file{configure} writes configuration-specific files in
34697 the current directory, but arranges for them to use the source in the
34698 directory @var{dirname}. @file{configure} creates directories under
34699 the working directory in parallel to the source directories below
34702 @item --norecursion
34703 Configure only the directory level where @file{configure} is executed; do not
34704 propagate configuration to subdirectories.
34706 @item --target=@var{target}
34707 Configure @value{GDBN} for cross-debugging programs running on the specified
34708 @var{target}. Without this option, @value{GDBN} is configured to debug
34709 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34711 There is no convenient way to generate a list of all available targets.
34713 @item @var{host} @dots{}
34714 Configure @value{GDBN} to run on the specified @var{host}.
34716 There is no convenient way to generate a list of all available hosts.
34719 There are many other options available as well, but they are generally
34720 needed for special purposes only.
34722 @node System-wide configuration
34723 @section System-wide configuration and settings
34724 @cindex system-wide init file
34726 @value{GDBN} can be configured to have a system-wide init file;
34727 this file will be read and executed at startup (@pxref{Startup, , What
34728 @value{GDBN} does during startup}).
34730 Here is the corresponding configure option:
34733 @item --with-system-gdbinit=@var{file}
34734 Specify that the default location of the system-wide init file is
34738 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34739 it may be subject to relocation. Two possible cases:
34743 If the default location of this init file contains @file{$prefix},
34744 it will be subject to relocation. Suppose that the configure options
34745 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34746 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34747 init file is looked for as @file{$install/etc/gdbinit} instead of
34748 @file{$prefix/etc/gdbinit}.
34751 By contrast, if the default location does not contain the prefix,
34752 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34753 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34754 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34755 wherever @value{GDBN} is installed.
34758 If the configured location of the system-wide init file (as given by the
34759 @option{--with-system-gdbinit} option at configure time) is in the
34760 data-directory (as specified by @option{--with-gdb-datadir} at configure
34761 time) or in one of its subdirectories, then @value{GDBN} will look for the
34762 system-wide init file in the directory specified by the
34763 @option{--data-directory} command-line option.
34764 Note that the system-wide init file is only read once, during @value{GDBN}
34765 initialization. If the data-directory is changed after @value{GDBN} has
34766 started with the @code{set data-directory} command, the file will not be
34770 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34773 @node System-wide Configuration Scripts
34774 @subsection Installed System-wide Configuration Scripts
34775 @cindex system-wide configuration scripts
34777 The @file{system-gdbinit} directory, located inside the data-directory
34778 (as specified by @option{--with-gdb-datadir} at configure time) contains
34779 a number of scripts which can be used as system-wide init files. To
34780 automatically source those scripts at startup, @value{GDBN} should be
34781 configured with @option{--with-system-gdbinit}. Otherwise, any user
34782 should be able to source them by hand as needed.
34784 The following scripts are currently available:
34787 @item @file{elinos.py}
34789 @cindex ELinOS system-wide configuration script
34790 This script is useful when debugging a program on an ELinOS target.
34791 It takes advantage of the environment variables defined in a standard
34792 ELinOS environment in order to determine the location of the system
34793 shared libraries, and then sets the @samp{solib-absolute-prefix}
34794 and @samp{solib-search-path} variables appropriately.
34796 @item @file{wrs-linux.py}
34797 @pindex wrs-linux.py
34798 @cindex Wind River Linux system-wide configuration script
34799 This script is useful when debugging a program on a target running
34800 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34801 the host-side sysroot used by the target system.
34805 @node Maintenance Commands
34806 @appendix Maintenance Commands
34807 @cindex maintenance commands
34808 @cindex internal commands
34810 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34811 includes a number of commands intended for @value{GDBN} developers,
34812 that are not documented elsewhere in this manual. These commands are
34813 provided here for reference. (For commands that turn on debugging
34814 messages, see @ref{Debugging Output}.)
34817 @kindex maint agent
34818 @kindex maint agent-eval
34819 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34820 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34821 Translate the given @var{expression} into remote agent bytecodes.
34822 This command is useful for debugging the Agent Expression mechanism
34823 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34824 expression useful for data collection, such as by tracepoints, while
34825 @samp{maint agent-eval} produces an expression that evaluates directly
34826 to a result. For instance, a collection expression for @code{globa +
34827 globb} will include bytecodes to record four bytes of memory at each
34828 of the addresses of @code{globa} and @code{globb}, while discarding
34829 the result of the addition, while an evaluation expression will do the
34830 addition and return the sum.
34831 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34832 If not, generate remote agent bytecode for current frame PC address.
34834 @kindex maint agent-printf
34835 @item maint agent-printf @var{format},@var{expr},...
34836 Translate the given format string and list of argument expressions
34837 into remote agent bytecodes and display them as a disassembled list.
34838 This command is useful for debugging the agent version of dynamic
34839 printf (@pxref{Dynamic Printf}).
34841 @kindex maint info breakpoints
34842 @item @anchor{maint info breakpoints}maint info breakpoints
34843 Using the same format as @samp{info breakpoints}, display both the
34844 breakpoints you've set explicitly, and those @value{GDBN} is using for
34845 internal purposes. Internal breakpoints are shown with negative
34846 breakpoint numbers. The type column identifies what kind of breakpoint
34851 Normal, explicitly set breakpoint.
34854 Normal, explicitly set watchpoint.
34857 Internal breakpoint, used to handle correctly stepping through
34858 @code{longjmp} calls.
34860 @item longjmp resume
34861 Internal breakpoint at the target of a @code{longjmp}.
34864 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34867 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34870 Shared library events.
34874 @kindex maint info btrace
34875 @item maint info btrace
34876 Pint information about raw branch tracing data.
34878 @kindex maint btrace packet-history
34879 @item maint btrace packet-history
34880 Print the raw branch trace packets that are used to compute the
34881 execution history for the @samp{record btrace} command. Both the
34882 information and the format in which it is printed depend on the btrace
34887 For the BTS recording format, print a list of blocks of sequential
34888 code. For each block, the following information is printed:
34892 Newer blocks have higher numbers. The oldest block has number zero.
34893 @item Lowest @samp{PC}
34894 @item Highest @samp{PC}
34898 For the Intel Processor Trace recording format, print a list of
34899 Intel Processor Trace packets. For each packet, the following
34900 information is printed:
34903 @item Packet number
34904 Newer packets have higher numbers. The oldest packet has number zero.
34906 The packet's offset in the trace stream.
34907 @item Packet opcode and payload
34911 @kindex maint btrace clear-packet-history
34912 @item maint btrace clear-packet-history
34913 Discards the cached packet history printed by the @samp{maint btrace
34914 packet-history} command. The history will be computed again when
34917 @kindex maint btrace clear
34918 @item maint btrace clear
34919 Discard the branch trace data. The data will be fetched anew and the
34920 branch trace will be recomputed when needed.
34922 This implicitly truncates the branch trace to a single branch trace
34923 buffer. When updating branch trace incrementally, the branch trace
34924 available to @value{GDBN} may be bigger than a single branch trace
34927 @kindex maint set btrace pt skip-pad
34928 @item maint set btrace pt skip-pad
34929 @kindex maint show btrace pt skip-pad
34930 @item maint show btrace pt skip-pad
34931 Control whether @value{GDBN} will skip PAD packets when computing the
34934 @kindex set displaced-stepping
34935 @kindex show displaced-stepping
34936 @cindex displaced stepping support
34937 @cindex out-of-line single-stepping
34938 @item set displaced-stepping
34939 @itemx show displaced-stepping
34940 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34941 if the target supports it. Displaced stepping is a way to single-step
34942 over breakpoints without removing them from the inferior, by executing
34943 an out-of-line copy of the instruction that was originally at the
34944 breakpoint location. It is also known as out-of-line single-stepping.
34947 @item set displaced-stepping on
34948 If the target architecture supports it, @value{GDBN} will use
34949 displaced stepping to step over breakpoints.
34951 @item set displaced-stepping off
34952 @value{GDBN} will not use displaced stepping to step over breakpoints,
34953 even if such is supported by the target architecture.
34955 @cindex non-stop mode, and @samp{set displaced-stepping}
34956 @item set displaced-stepping auto
34957 This is the default mode. @value{GDBN} will use displaced stepping
34958 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34959 architecture supports displaced stepping.
34962 @kindex maint check-psymtabs
34963 @item maint check-psymtabs
34964 Check the consistency of currently expanded psymtabs versus symtabs.
34965 Use this to check, for example, whether a symbol is in one but not the other.
34967 @kindex maint check-symtabs
34968 @item maint check-symtabs
34969 Check the consistency of currently expanded symtabs.
34971 @kindex maint expand-symtabs
34972 @item maint expand-symtabs [@var{regexp}]
34973 Expand symbol tables.
34974 If @var{regexp} is specified, only expand symbol tables for file
34975 names matching @var{regexp}.
34977 @kindex maint set catch-demangler-crashes
34978 @kindex maint show catch-demangler-crashes
34979 @cindex demangler crashes
34980 @item maint set catch-demangler-crashes [on|off]
34981 @itemx maint show catch-demangler-crashes
34982 Control whether @value{GDBN} should attempt to catch crashes in the
34983 symbol name demangler. The default is to attempt to catch crashes.
34984 If enabled, the first time a crash is caught, a core file is created,
34985 the offending symbol is displayed and the user is presented with the
34986 option to terminate the current session.
34988 @kindex maint cplus first_component
34989 @item maint cplus first_component @var{name}
34990 Print the first C@t{++} class/namespace component of @var{name}.
34992 @kindex maint cplus namespace
34993 @item maint cplus namespace
34994 Print the list of possible C@t{++} namespaces.
34996 @kindex maint deprecate
34997 @kindex maint undeprecate
34998 @cindex deprecated commands
34999 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35000 @itemx maint undeprecate @var{command}
35001 Deprecate or undeprecate the named @var{command}. Deprecated commands
35002 cause @value{GDBN} to issue a warning when you use them. The optional
35003 argument @var{replacement} says which newer command should be used in
35004 favor of the deprecated one; if it is given, @value{GDBN} will mention
35005 the replacement as part of the warning.
35007 @kindex maint dump-me
35008 @item maint dump-me
35009 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35010 Cause a fatal signal in the debugger and force it to dump its core.
35011 This is supported only on systems which support aborting a program
35012 with the @code{SIGQUIT} signal.
35014 @kindex maint internal-error
35015 @kindex maint internal-warning
35016 @kindex maint demangler-warning
35017 @cindex demangler crashes
35018 @item maint internal-error @r{[}@var{message-text}@r{]}
35019 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35020 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35022 Cause @value{GDBN} to call the internal function @code{internal_error},
35023 @code{internal_warning} or @code{demangler_warning} and hence behave
35024 as though an internal problem has been detected. In addition to
35025 reporting the internal problem, these functions give the user the
35026 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35027 and @code{internal_warning}) create a core file of the current
35028 @value{GDBN} session.
35030 These commands take an optional parameter @var{message-text} that is
35031 used as the text of the error or warning message.
35033 Here's an example of using @code{internal-error}:
35036 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35037 @dots{}/maint.c:121: internal-error: testing, 1, 2
35038 A problem internal to GDB has been detected. Further
35039 debugging may prove unreliable.
35040 Quit this debugging session? (y or n) @kbd{n}
35041 Create a core file? (y or n) @kbd{n}
35045 @cindex @value{GDBN} internal error
35046 @cindex internal errors, control of @value{GDBN} behavior
35047 @cindex demangler crashes
35049 @kindex maint set internal-error
35050 @kindex maint show internal-error
35051 @kindex maint set internal-warning
35052 @kindex maint show internal-warning
35053 @kindex maint set demangler-warning
35054 @kindex maint show demangler-warning
35055 @item maint set internal-error @var{action} [ask|yes|no]
35056 @itemx maint show internal-error @var{action}
35057 @itemx maint set internal-warning @var{action} [ask|yes|no]
35058 @itemx maint show internal-warning @var{action}
35059 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35060 @itemx maint show demangler-warning @var{action}
35061 When @value{GDBN} reports an internal problem (error or warning) it
35062 gives the user the opportunity to both quit @value{GDBN} and create a
35063 core file of the current @value{GDBN} session. These commands let you
35064 override the default behaviour for each particular @var{action},
35065 described in the table below.
35069 You can specify that @value{GDBN} should always (yes) or never (no)
35070 quit. The default is to ask the user what to do.
35073 You can specify that @value{GDBN} should always (yes) or never (no)
35074 create a core file. The default is to ask the user what to do. Note
35075 that there is no @code{corefile} option for @code{demangler-warning}:
35076 demangler warnings always create a core file and this cannot be
35080 @kindex maint packet
35081 @item maint packet @var{text}
35082 If @value{GDBN} is talking to an inferior via the serial protocol,
35083 then this command sends the string @var{text} to the inferior, and
35084 displays the response packet. @value{GDBN} supplies the initial
35085 @samp{$} character, the terminating @samp{#} character, and the
35088 @kindex maint print architecture
35089 @item maint print architecture @r{[}@var{file}@r{]}
35090 Print the entire architecture configuration. The optional argument
35091 @var{file} names the file where the output goes.
35093 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35094 @item maint print c-tdesc
35095 Print the target description (@pxref{Target Descriptions}) as
35096 a C source file. By default, the target description is for the current
35097 target, but if the optional argument @var{file} is provided, that file
35098 is used to produce the description. The @var{file} should be an XML
35099 document, of the form described in @ref{Target Description Format}.
35100 The created source file is built into @value{GDBN} when @value{GDBN} is
35101 built again. This command is used by developers after they add or
35102 modify XML target descriptions.
35104 @kindex maint check xml-descriptions
35105 @item maint check xml-descriptions @var{dir}
35106 Check that the target descriptions dynamically created by @value{GDBN}
35107 equal the descriptions created from XML files found in @var{dir}.
35109 @kindex maint print dummy-frames
35110 @item maint print dummy-frames
35111 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35114 (@value{GDBP}) @kbd{b add}
35116 (@value{GDBP}) @kbd{print add(2,3)}
35117 Breakpoint 2, add (a=2, b=3) at @dots{}
35119 The program being debugged stopped while in a function called from GDB.
35121 (@value{GDBP}) @kbd{maint print dummy-frames}
35122 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35126 Takes an optional file parameter.
35128 @kindex maint print registers
35129 @kindex maint print raw-registers
35130 @kindex maint print cooked-registers
35131 @kindex maint print register-groups
35132 @kindex maint print remote-registers
35133 @item maint print registers @r{[}@var{file}@r{]}
35134 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35135 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35136 @itemx maint print register-groups @r{[}@var{file}@r{]}
35137 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35138 Print @value{GDBN}'s internal register data structures.
35140 The command @code{maint print raw-registers} includes the contents of
35141 the raw register cache; the command @code{maint print
35142 cooked-registers} includes the (cooked) value of all registers,
35143 including registers which aren't available on the target nor visible
35144 to user; the command @code{maint print register-groups} includes the
35145 groups that each register is a member of; and the command @code{maint
35146 print remote-registers} includes the remote target's register numbers
35147 and offsets in the `G' packets.
35149 These commands take an optional parameter, a file name to which to
35150 write the information.
35152 @kindex maint print reggroups
35153 @item maint print reggroups @r{[}@var{file}@r{]}
35154 Print @value{GDBN}'s internal register group data structures. The
35155 optional argument @var{file} tells to what file to write the
35158 The register groups info looks like this:
35161 (@value{GDBP}) @kbd{maint print reggroups}
35174 This command forces @value{GDBN} to flush its internal register cache.
35176 @kindex maint print objfiles
35177 @cindex info for known object files
35178 @item maint print objfiles @r{[}@var{regexp}@r{]}
35179 Print a dump of all known object files.
35180 If @var{regexp} is specified, only print object files whose names
35181 match @var{regexp}. For each object file, this command prints its name,
35182 address in memory, and all of its psymtabs and symtabs.
35184 @kindex maint print user-registers
35185 @cindex user registers
35186 @item maint print user-registers
35187 List all currently available @dfn{user registers}. User registers
35188 typically provide alternate names for actual hardware registers. They
35189 include the four ``standard'' registers @code{$fp}, @code{$pc},
35190 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35191 registers can be used in expressions in the same way as the canonical
35192 register names, but only the latter are listed by the @code{info
35193 registers} and @code{maint print registers} commands.
35195 @kindex maint print section-scripts
35196 @cindex info for known .debug_gdb_scripts-loaded scripts
35197 @item maint print section-scripts [@var{regexp}]
35198 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35199 If @var{regexp} is specified, only print scripts loaded by object files
35200 matching @var{regexp}.
35201 For each script, this command prints its name as specified in the objfile,
35202 and the full path if known.
35203 @xref{dotdebug_gdb_scripts section}.
35205 @kindex maint print statistics
35206 @cindex bcache statistics
35207 @item maint print statistics
35208 This command prints, for each object file in the program, various data
35209 about that object file followed by the byte cache (@dfn{bcache})
35210 statistics for the object file. The objfile data includes the number
35211 of minimal, partial, full, and stabs symbols, the number of types
35212 defined by the objfile, the number of as yet unexpanded psym tables,
35213 the number of line tables and string tables, and the amount of memory
35214 used by the various tables. The bcache statistics include the counts,
35215 sizes, and counts of duplicates of all and unique objects, max,
35216 average, and median entry size, total memory used and its overhead and
35217 savings, and various measures of the hash table size and chain
35220 @kindex maint print target-stack
35221 @cindex target stack description
35222 @item maint print target-stack
35223 A @dfn{target} is an interface between the debugger and a particular
35224 kind of file or process. Targets can be stacked in @dfn{strata},
35225 so that more than one target can potentially respond to a request.
35226 In particular, memory accesses will walk down the stack of targets
35227 until they find a target that is interested in handling that particular
35230 This command prints a short description of each layer that was pushed on
35231 the @dfn{target stack}, starting from the top layer down to the bottom one.
35233 @kindex maint print type
35234 @cindex type chain of a data type
35235 @item maint print type @var{expr}
35236 Print the type chain for a type specified by @var{expr}. The argument
35237 can be either a type name or a symbol. If it is a symbol, the type of
35238 that symbol is described. The type chain produced by this command is
35239 a recursive definition of the data type as stored in @value{GDBN}'s
35240 data structures, including its flags and contained types.
35242 @kindex maint selftest
35244 @item maint selftest @r{[}@var{filter}@r{]}
35245 Run any self tests that were compiled in to @value{GDBN}. This will
35246 print a message showing how many tests were run, and how many failed.
35247 If a @var{filter} is passed, only the tests with @var{filter} in their
35250 @kindex "maint info selftests"
35252 @item maint info selftests
35253 List the selftests compiled in to @value{GDBN}.
35255 @kindex maint set dwarf always-disassemble
35256 @kindex maint show dwarf always-disassemble
35257 @item maint set dwarf always-disassemble
35258 @item maint show dwarf always-disassemble
35259 Control the behavior of @code{info address} when using DWARF debugging
35262 The default is @code{off}, which means that @value{GDBN} should try to
35263 describe a variable's location in an easily readable format. When
35264 @code{on}, @value{GDBN} will instead display the DWARF location
35265 expression in an assembly-like format. Note that some locations are
35266 too complex for @value{GDBN} to describe simply; in this case you will
35267 always see the disassembly form.
35269 Here is an example of the resulting disassembly:
35272 (gdb) info addr argc
35273 Symbol "argc" is a complex DWARF expression:
35277 For more information on these expressions, see
35278 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35280 @kindex maint set dwarf max-cache-age
35281 @kindex maint show dwarf max-cache-age
35282 @item maint set dwarf max-cache-age
35283 @itemx maint show dwarf max-cache-age
35284 Control the DWARF compilation unit cache.
35286 @cindex DWARF compilation units cache
35287 In object files with inter-compilation-unit references, such as those
35288 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35289 reader needs to frequently refer to previously read compilation units.
35290 This setting controls how long a compilation unit will remain in the
35291 cache if it is not referenced. A higher limit means that cached
35292 compilation units will be stored in memory longer, and more total
35293 memory will be used. Setting it to zero disables caching, which will
35294 slow down @value{GDBN} startup, but reduce memory consumption.
35296 @kindex maint set profile
35297 @kindex maint show profile
35298 @cindex profiling GDB
35299 @item maint set profile
35300 @itemx maint show profile
35301 Control profiling of @value{GDBN}.
35303 Profiling will be disabled until you use the @samp{maint set profile}
35304 command to enable it. When you enable profiling, the system will begin
35305 collecting timing and execution count data; when you disable profiling or
35306 exit @value{GDBN}, the results will be written to a log file. Remember that
35307 if you use profiling, @value{GDBN} will overwrite the profiling log file
35308 (often called @file{gmon.out}). If you have a record of important profiling
35309 data in a @file{gmon.out} file, be sure to move it to a safe location.
35311 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35312 compiled with the @samp{-pg} compiler option.
35314 @kindex maint set show-debug-regs
35315 @kindex maint show show-debug-regs
35316 @cindex hardware debug registers
35317 @item maint set show-debug-regs
35318 @itemx maint show show-debug-regs
35319 Control whether to show variables that mirror the hardware debug
35320 registers. Use @code{on} to enable, @code{off} to disable. If
35321 enabled, the debug registers values are shown when @value{GDBN} inserts or
35322 removes a hardware breakpoint or watchpoint, and when the inferior
35323 triggers a hardware-assisted breakpoint or watchpoint.
35325 @kindex maint set show-all-tib
35326 @kindex maint show show-all-tib
35327 @item maint set show-all-tib
35328 @itemx maint show show-all-tib
35329 Control whether to show all non zero areas within a 1k block starting
35330 at thread local base, when using the @samp{info w32 thread-information-block}
35333 @kindex maint set target-async
35334 @kindex maint show target-async
35335 @item maint set target-async
35336 @itemx maint show target-async
35337 This controls whether @value{GDBN} targets operate in synchronous or
35338 asynchronous mode (@pxref{Background Execution}). Normally the
35339 default is asynchronous, if it is available; but this can be changed
35340 to more easily debug problems occurring only in synchronous mode.
35342 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35343 @kindex maint show target-non-stop
35344 @item maint set target-non-stop
35345 @itemx maint show target-non-stop
35347 This controls whether @value{GDBN} targets always operate in non-stop
35348 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35349 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35350 if supported by the target.
35353 @item maint set target-non-stop auto
35354 This is the default mode. @value{GDBN} controls the target in
35355 non-stop mode if the target supports it.
35357 @item maint set target-non-stop on
35358 @value{GDBN} controls the target in non-stop mode even if the target
35359 does not indicate support.
35361 @item maint set target-non-stop off
35362 @value{GDBN} does not control the target in non-stop mode even if the
35363 target supports it.
35366 @kindex maint set per-command
35367 @kindex maint show per-command
35368 @item maint set per-command
35369 @itemx maint show per-command
35370 @cindex resources used by commands
35372 @value{GDBN} can display the resources used by each command.
35373 This is useful in debugging performance problems.
35376 @item maint set per-command space [on|off]
35377 @itemx maint show per-command space
35378 Enable or disable the printing of the memory used by GDB for each command.
35379 If enabled, @value{GDBN} will display how much memory each command
35380 took, following the command's own output.
35381 This can also be requested by invoking @value{GDBN} with the
35382 @option{--statistics} command-line switch (@pxref{Mode Options}).
35384 @item maint set per-command time [on|off]
35385 @itemx maint show per-command time
35386 Enable or disable the printing of the execution time of @value{GDBN}
35388 If enabled, @value{GDBN} will display how much time it
35389 took to execute each command, following the command's own output.
35390 Both CPU time and wallclock time are printed.
35391 Printing both is useful when trying to determine whether the cost is
35392 CPU or, e.g., disk/network latency.
35393 Note that the CPU time printed is for @value{GDBN} only, it does not include
35394 the execution time of the inferior because there's no mechanism currently
35395 to compute how much time was spent by @value{GDBN} and how much time was
35396 spent by the program been debugged.
35397 This can also be requested by invoking @value{GDBN} with the
35398 @option{--statistics} command-line switch (@pxref{Mode Options}).
35400 @item maint set per-command symtab [on|off]
35401 @itemx maint show per-command symtab
35402 Enable or disable the printing of basic symbol table statistics
35404 If enabled, @value{GDBN} will display the following information:
35408 number of symbol tables
35410 number of primary symbol tables
35412 number of blocks in the blockvector
35416 @kindex maint space
35417 @cindex memory used by commands
35418 @item maint space @var{value}
35419 An alias for @code{maint set per-command space}.
35420 A non-zero value enables it, zero disables it.
35423 @cindex time of command execution
35424 @item maint time @var{value}
35425 An alias for @code{maint set per-command time}.
35426 A non-zero value enables it, zero disables it.
35428 @kindex maint translate-address
35429 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35430 Find the symbol stored at the location specified by the address
35431 @var{addr} and an optional section name @var{section}. If found,
35432 @value{GDBN} prints the name of the closest symbol and an offset from
35433 the symbol's location to the specified address. This is similar to
35434 the @code{info address} command (@pxref{Symbols}), except that this
35435 command also allows to find symbols in other sections.
35437 If section was not specified, the section in which the symbol was found
35438 is also printed. For dynamically linked executables, the name of
35439 executable or shared library containing the symbol is printed as well.
35443 The following command is useful for non-interactive invocations of
35444 @value{GDBN}, such as in the test suite.
35447 @item set watchdog @var{nsec}
35448 @kindex set watchdog
35449 @cindex watchdog timer
35450 @cindex timeout for commands
35451 Set the maximum number of seconds @value{GDBN} will wait for the
35452 target operation to finish. If this time expires, @value{GDBN}
35453 reports and error and the command is aborted.
35455 @item show watchdog
35456 Show the current setting of the target wait timeout.
35459 @node Remote Protocol
35460 @appendix @value{GDBN} Remote Serial Protocol
35465 * Stop Reply Packets::
35466 * General Query Packets::
35467 * Architecture-Specific Protocol Details::
35468 * Tracepoint Packets::
35469 * Host I/O Packets::
35471 * Notification Packets::
35472 * Remote Non-Stop::
35473 * Packet Acknowledgment::
35475 * File-I/O Remote Protocol Extension::
35476 * Library List Format::
35477 * Library List Format for SVR4 Targets::
35478 * Memory Map Format::
35479 * Thread List Format::
35480 * Traceframe Info Format::
35481 * Branch Trace Format::
35482 * Branch Trace Configuration Format::
35488 There may be occasions when you need to know something about the
35489 protocol---for example, if there is only one serial port to your target
35490 machine, you might want your program to do something special if it
35491 recognizes a packet meant for @value{GDBN}.
35493 In the examples below, @samp{->} and @samp{<-} are used to indicate
35494 transmitted and received data, respectively.
35496 @cindex protocol, @value{GDBN} remote serial
35497 @cindex serial protocol, @value{GDBN} remote
35498 @cindex remote serial protocol
35499 All @value{GDBN} commands and responses (other than acknowledgments
35500 and notifications, see @ref{Notification Packets}) are sent as a
35501 @var{packet}. A @var{packet} is introduced with the character
35502 @samp{$}, the actual @var{packet-data}, and the terminating character
35503 @samp{#} followed by a two-digit @var{checksum}:
35506 @code{$}@var{packet-data}@code{#}@var{checksum}
35510 @cindex checksum, for @value{GDBN} remote
35512 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35513 characters between the leading @samp{$} and the trailing @samp{#} (an
35514 eight bit unsigned checksum).
35516 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35517 specification also included an optional two-digit @var{sequence-id}:
35520 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35523 @cindex sequence-id, for @value{GDBN} remote
35525 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35526 has never output @var{sequence-id}s. Stubs that handle packets added
35527 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35529 When either the host or the target machine receives a packet, the first
35530 response expected is an acknowledgment: either @samp{+} (to indicate
35531 the package was received correctly) or @samp{-} (to request
35535 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35540 The @samp{+}/@samp{-} acknowledgments can be disabled
35541 once a connection is established.
35542 @xref{Packet Acknowledgment}, for details.
35544 The host (@value{GDBN}) sends @var{command}s, and the target (the
35545 debugging stub incorporated in your program) sends a @var{response}. In
35546 the case of step and continue @var{command}s, the response is only sent
35547 when the operation has completed, and the target has again stopped all
35548 threads in all attached processes. This is the default all-stop mode
35549 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35550 execution mode; see @ref{Remote Non-Stop}, for details.
35552 @var{packet-data} consists of a sequence of characters with the
35553 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35556 @cindex remote protocol, field separator
35557 Fields within the packet should be separated using @samp{,} @samp{;} or
35558 @samp{:}. Except where otherwise noted all numbers are represented in
35559 @sc{hex} with leading zeros suppressed.
35561 Implementors should note that prior to @value{GDBN} 5.0, the character
35562 @samp{:} could not appear as the third character in a packet (as it
35563 would potentially conflict with the @var{sequence-id}).
35565 @cindex remote protocol, binary data
35566 @anchor{Binary Data}
35567 Binary data in most packets is encoded either as two hexadecimal
35568 digits per byte of binary data. This allowed the traditional remote
35569 protocol to work over connections which were only seven-bit clean.
35570 Some packets designed more recently assume an eight-bit clean
35571 connection, and use a more efficient encoding to send and receive
35574 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35575 as an escape character. Any escaped byte is transmitted as the escape
35576 character followed by the original character XORed with @code{0x20}.
35577 For example, the byte @code{0x7d} would be transmitted as the two
35578 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35579 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35580 @samp{@}}) must always be escaped. Responses sent by the stub
35581 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35582 is not interpreted as the start of a run-length encoded sequence
35585 Response @var{data} can be run-length encoded to save space.
35586 Run-length encoding replaces runs of identical characters with one
35587 instance of the repeated character, followed by a @samp{*} and a
35588 repeat count. The repeat count is itself sent encoded, to avoid
35589 binary characters in @var{data}: a value of @var{n} is sent as
35590 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35591 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35592 code 32) for a repeat count of 3. (This is because run-length
35593 encoding starts to win for counts 3 or more.) Thus, for example,
35594 @samp{0* } is a run-length encoding of ``0000'': the space character
35595 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35598 The printable characters @samp{#} and @samp{$} or with a numeric value
35599 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35600 seven repeats (@samp{$}) can be expanded using a repeat count of only
35601 five (@samp{"}). For example, @samp{00000000} can be encoded as
35604 The error response returned for some packets includes a two character
35605 error number. That number is not well defined.
35607 @cindex empty response, for unsupported packets
35608 For any @var{command} not supported by the stub, an empty response
35609 (@samp{$#00}) should be returned. That way it is possible to extend the
35610 protocol. A newer @value{GDBN} can tell if a packet is supported based
35613 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35614 commands for register access, and the @samp{m} and @samp{M} commands
35615 for memory access. Stubs that only control single-threaded targets
35616 can implement run control with the @samp{c} (continue), and @samp{s}
35617 (step) commands. Stubs that support multi-threading targets should
35618 support the @samp{vCont} command. All other commands are optional.
35623 The following table provides a complete list of all currently defined
35624 @var{command}s and their corresponding response @var{data}.
35625 @xref{File-I/O Remote Protocol Extension}, for details about the File
35626 I/O extension of the remote protocol.
35628 Each packet's description has a template showing the packet's overall
35629 syntax, followed by an explanation of the packet's meaning. We
35630 include spaces in some of the templates for clarity; these are not
35631 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35632 separate its components. For example, a template like @samp{foo
35633 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35634 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35635 @var{baz}. @value{GDBN} does not transmit a space character between the
35636 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35639 @cindex @var{thread-id}, in remote protocol
35640 @anchor{thread-id syntax}
35641 Several packets and replies include a @var{thread-id} field to identify
35642 a thread. Normally these are positive numbers with a target-specific
35643 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35644 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35647 In addition, the remote protocol supports a multiprocess feature in
35648 which the @var{thread-id} syntax is extended to optionally include both
35649 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35650 The @var{pid} (process) and @var{tid} (thread) components each have the
35651 format described above: a positive number with target-specific
35652 interpretation formatted as a big-endian hex string, literal @samp{-1}
35653 to indicate all processes or threads (respectively), or @samp{0} to
35654 indicate an arbitrary process or thread. Specifying just a process, as
35655 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35656 error to specify all processes but a specific thread, such as
35657 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35658 for those packets and replies explicitly documented to include a process
35659 ID, rather than a @var{thread-id}.
35661 The multiprocess @var{thread-id} syntax extensions are only used if both
35662 @value{GDBN} and the stub report support for the @samp{multiprocess}
35663 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35666 Note that all packet forms beginning with an upper- or lower-case
35667 letter, other than those described here, are reserved for future use.
35669 Here are the packet descriptions.
35674 @cindex @samp{!} packet
35675 @anchor{extended mode}
35676 Enable extended mode. In extended mode, the remote server is made
35677 persistent. The @samp{R} packet is used to restart the program being
35683 The remote target both supports and has enabled extended mode.
35687 @cindex @samp{?} packet
35689 Indicate the reason the target halted. The reply is the same as for
35690 step and continue. This packet has a special interpretation when the
35691 target is in non-stop mode; see @ref{Remote Non-Stop}.
35694 @xref{Stop Reply Packets}, for the reply specifications.
35696 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35697 @cindex @samp{A} packet
35698 Initialized @code{argv[]} array passed into program. @var{arglen}
35699 specifies the number of bytes in the hex encoded byte stream
35700 @var{arg}. See @code{gdbserver} for more details.
35705 The arguments were set.
35711 @cindex @samp{b} packet
35712 (Don't use this packet; its behavior is not well-defined.)
35713 Change the serial line speed to @var{baud}.
35715 JTC: @emph{When does the transport layer state change? When it's
35716 received, or after the ACK is transmitted. In either case, there are
35717 problems if the command or the acknowledgment packet is dropped.}
35719 Stan: @emph{If people really wanted to add something like this, and get
35720 it working for the first time, they ought to modify ser-unix.c to send
35721 some kind of out-of-band message to a specially-setup stub and have the
35722 switch happen "in between" packets, so that from remote protocol's point
35723 of view, nothing actually happened.}
35725 @item B @var{addr},@var{mode}
35726 @cindex @samp{B} packet
35727 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35728 breakpoint at @var{addr}.
35730 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35731 (@pxref{insert breakpoint or watchpoint packet}).
35733 @cindex @samp{bc} packet
35736 Backward continue. Execute the target system in reverse. No parameter.
35737 @xref{Reverse Execution}, for more information.
35740 @xref{Stop Reply Packets}, for the reply specifications.
35742 @cindex @samp{bs} packet
35745 Backward single step. Execute one instruction in reverse. No parameter.
35746 @xref{Reverse Execution}, for more information.
35749 @xref{Stop Reply Packets}, for the reply specifications.
35751 @item c @r{[}@var{addr}@r{]}
35752 @cindex @samp{c} packet
35753 Continue at @var{addr}, which is the address to resume. If @var{addr}
35754 is omitted, resume at current address.
35756 This packet is deprecated for multi-threading support. @xref{vCont
35760 @xref{Stop Reply Packets}, for the reply specifications.
35762 @item C @var{sig}@r{[};@var{addr}@r{]}
35763 @cindex @samp{C} packet
35764 Continue with signal @var{sig} (hex signal number). If
35765 @samp{;@var{addr}} is omitted, resume at same address.
35767 This packet is deprecated for multi-threading support. @xref{vCont
35771 @xref{Stop Reply Packets}, for the reply specifications.
35774 @cindex @samp{d} packet
35777 Don't use this packet; instead, define a general set packet
35778 (@pxref{General Query Packets}).
35782 @cindex @samp{D} packet
35783 The first form of the packet is used to detach @value{GDBN} from the
35784 remote system. It is sent to the remote target
35785 before @value{GDBN} disconnects via the @code{detach} command.
35787 The second form, including a process ID, is used when multiprocess
35788 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35789 detach only a specific process. The @var{pid} is specified as a
35790 big-endian hex string.
35800 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35801 @cindex @samp{F} packet
35802 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35803 This is part of the File-I/O protocol extension. @xref{File-I/O
35804 Remote Protocol Extension}, for the specification.
35807 @anchor{read registers packet}
35808 @cindex @samp{g} packet
35809 Read general registers.
35813 @item @var{XX@dots{}}
35814 Each byte of register data is described by two hex digits. The bytes
35815 with the register are transmitted in target byte order. The size of
35816 each register and their position within the @samp{g} packet are
35817 determined by the @value{GDBN} internal gdbarch functions
35818 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35820 When reading registers from a trace frame (@pxref{Analyze Collected
35821 Data,,Using the Collected Data}), the stub may also return a string of
35822 literal @samp{x}'s in place of the register data digits, to indicate
35823 that the corresponding register has not been collected, thus its value
35824 is unavailable. For example, for an architecture with 4 registers of
35825 4 bytes each, the following reply indicates to @value{GDBN} that
35826 registers 0 and 2 have not been collected, while registers 1 and 3
35827 have been collected, and both have zero value:
35831 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35838 @item G @var{XX@dots{}}
35839 @cindex @samp{G} packet
35840 Write general registers. @xref{read registers packet}, for a
35841 description of the @var{XX@dots{}} data.
35851 @item H @var{op} @var{thread-id}
35852 @cindex @samp{H} packet
35853 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35854 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35855 should be @samp{c} for step and continue operations (note that this
35856 is deprecated, supporting the @samp{vCont} command is a better
35857 option), and @samp{g} for other operations. The thread designator
35858 @var{thread-id} has the format and interpretation described in
35859 @ref{thread-id syntax}.
35870 @c 'H': How restrictive (or permissive) is the thread model. If a
35871 @c thread is selected and stopped, are other threads allowed
35872 @c to continue to execute? As I mentioned above, I think the
35873 @c semantics of each command when a thread is selected must be
35874 @c described. For example:
35876 @c 'g': If the stub supports threads and a specific thread is
35877 @c selected, returns the register block from that thread;
35878 @c otherwise returns current registers.
35880 @c 'G' If the stub supports threads and a specific thread is
35881 @c selected, sets the registers of the register block of
35882 @c that thread; otherwise sets current registers.
35884 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35885 @anchor{cycle step packet}
35886 @cindex @samp{i} packet
35887 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35888 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35889 step starting at that address.
35892 @cindex @samp{I} packet
35893 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35897 @cindex @samp{k} packet
35900 The exact effect of this packet is not specified.
35902 For a bare-metal target, it may power cycle or reset the target
35903 system. For that reason, the @samp{k} packet has no reply.
35905 For a single-process target, it may kill that process if possible.
35907 A multiple-process target may choose to kill just one process, or all
35908 that are under @value{GDBN}'s control. For more precise control, use
35909 the vKill packet (@pxref{vKill packet}).
35911 If the target system immediately closes the connection in response to
35912 @samp{k}, @value{GDBN} does not consider the lack of packet
35913 acknowledgment to be an error, and assumes the kill was successful.
35915 If connected using @kbd{target extended-remote}, and the target does
35916 not close the connection in response to a kill request, @value{GDBN}
35917 probes the target state as if a new connection was opened
35918 (@pxref{? packet}).
35920 @item m @var{addr},@var{length}
35921 @cindex @samp{m} packet
35922 Read @var{length} addressable memory units starting at address @var{addr}
35923 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35924 any particular boundary.
35926 The stub need not use any particular size or alignment when gathering
35927 data from memory for the response; even if @var{addr} is word-aligned
35928 and @var{length} is a multiple of the word size, the stub is free to
35929 use byte accesses, or not. For this reason, this packet may not be
35930 suitable for accessing memory-mapped I/O devices.
35931 @cindex alignment of remote memory accesses
35932 @cindex size of remote memory accesses
35933 @cindex memory, alignment and size of remote accesses
35937 @item @var{XX@dots{}}
35938 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35939 The reply may contain fewer addressable memory units than requested if the
35940 server was able to read only part of the region of memory.
35945 @item M @var{addr},@var{length}:@var{XX@dots{}}
35946 @cindex @samp{M} packet
35947 Write @var{length} addressable memory units starting at address @var{addr}
35948 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35949 byte is transmitted as a two-digit hexadecimal number.
35956 for an error (this includes the case where only part of the data was
35961 @cindex @samp{p} packet
35962 Read the value of register @var{n}; @var{n} is in hex.
35963 @xref{read registers packet}, for a description of how the returned
35964 register value is encoded.
35968 @item @var{XX@dots{}}
35969 the register's value
35973 Indicating an unrecognized @var{query}.
35976 @item P @var{n@dots{}}=@var{r@dots{}}
35977 @anchor{write register packet}
35978 @cindex @samp{P} packet
35979 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35980 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35981 digits for each byte in the register (target byte order).
35991 @item q @var{name} @var{params}@dots{}
35992 @itemx Q @var{name} @var{params}@dots{}
35993 @cindex @samp{q} packet
35994 @cindex @samp{Q} packet
35995 General query (@samp{q}) and set (@samp{Q}). These packets are
35996 described fully in @ref{General Query Packets}.
35999 @cindex @samp{r} packet
36000 Reset the entire system.
36002 Don't use this packet; use the @samp{R} packet instead.
36005 @cindex @samp{R} packet
36006 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36007 This packet is only available in extended mode (@pxref{extended mode}).
36009 The @samp{R} packet has no reply.
36011 @item s @r{[}@var{addr}@r{]}
36012 @cindex @samp{s} packet
36013 Single step, resuming at @var{addr}. If
36014 @var{addr} is omitted, resume at same address.
36016 This packet is deprecated for multi-threading support. @xref{vCont
36020 @xref{Stop Reply Packets}, for the reply specifications.
36022 @item S @var{sig}@r{[};@var{addr}@r{]}
36023 @anchor{step with signal packet}
36024 @cindex @samp{S} packet
36025 Step with signal. This is analogous to the @samp{C} packet, but
36026 requests a single-step, rather than a normal resumption of execution.
36028 This packet is deprecated for multi-threading support. @xref{vCont
36032 @xref{Stop Reply Packets}, for the reply specifications.
36034 @item t @var{addr}:@var{PP},@var{MM}
36035 @cindex @samp{t} packet
36036 Search backwards starting at address @var{addr} for a match with pattern
36037 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36038 There must be at least 3 digits in @var{addr}.
36040 @item T @var{thread-id}
36041 @cindex @samp{T} packet
36042 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36047 thread is still alive
36053 Packets starting with @samp{v} are identified by a multi-letter name,
36054 up to the first @samp{;} or @samp{?} (or the end of the packet).
36056 @item vAttach;@var{pid}
36057 @cindex @samp{vAttach} packet
36058 Attach to a new process with the specified process ID @var{pid}.
36059 The process ID is a
36060 hexadecimal integer identifying the process. In all-stop mode, all
36061 threads in the attached process are stopped; in non-stop mode, it may be
36062 attached without being stopped if that is supported by the target.
36064 @c In non-stop mode, on a successful vAttach, the stub should set the
36065 @c current thread to a thread of the newly-attached process. After
36066 @c attaching, GDB queries for the attached process's thread ID with qC.
36067 @c Also note that, from a user perspective, whether or not the
36068 @c target is stopped on attach in non-stop mode depends on whether you
36069 @c use the foreground or background version of the attach command, not
36070 @c on what vAttach does; GDB does the right thing with respect to either
36071 @c stopping or restarting threads.
36073 This packet is only available in extended mode (@pxref{extended mode}).
36079 @item @r{Any stop packet}
36080 for success in all-stop mode (@pxref{Stop Reply Packets})
36082 for success in non-stop mode (@pxref{Remote Non-Stop})
36085 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36086 @cindex @samp{vCont} packet
36087 @anchor{vCont packet}
36088 Resume the inferior, specifying different actions for each thread.
36090 For each inferior thread, the leftmost action with a matching
36091 @var{thread-id} is applied. Threads that don't match any action
36092 remain in their current state. Thread IDs are specified using the
36093 syntax described in @ref{thread-id syntax}. If multiprocess
36094 extensions (@pxref{multiprocess extensions}) are supported, actions
36095 can be specified to match all threads in a process by using the
36096 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36097 @var{thread-id} matches all threads. Specifying no actions is an
36100 Currently supported actions are:
36106 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36110 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36113 @item r @var{start},@var{end}
36114 Step once, and then keep stepping as long as the thread stops at
36115 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36116 The remote stub reports a stop reply when either the thread goes out
36117 of the range or is stopped due to an unrelated reason, such as hitting
36118 a breakpoint. @xref{range stepping}.
36120 If the range is empty (@var{start} == @var{end}), then the action
36121 becomes equivalent to the @samp{s} action. In other words,
36122 single-step once, and report the stop (even if the stepped instruction
36123 jumps to @var{start}).
36125 (A stop reply may be sent at any point even if the PC is still within
36126 the stepping range; for example, it is valid to implement this packet
36127 in a degenerate way as a single instruction step operation.)
36131 The optional argument @var{addr} normally associated with the
36132 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36133 not supported in @samp{vCont}.
36135 The @samp{t} action is only relevant in non-stop mode
36136 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36137 A stop reply should be generated for any affected thread not already stopped.
36138 When a thread is stopped by means of a @samp{t} action,
36139 the corresponding stop reply should indicate that the thread has stopped with
36140 signal @samp{0}, regardless of whether the target uses some other signal
36141 as an implementation detail.
36143 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36144 @samp{r} actions for threads that are already running. Conversely,
36145 the server must ignore @samp{t} actions for threads that are already
36148 @emph{Note:} In non-stop mode, a thread is considered running until
36149 @value{GDBN} acknowleges an asynchronous stop notification for it with
36150 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36152 The stub must support @samp{vCont} if it reports support for
36153 multiprocess extensions (@pxref{multiprocess extensions}).
36156 @xref{Stop Reply Packets}, for the reply specifications.
36159 @cindex @samp{vCont?} packet
36160 Request a list of actions supported by the @samp{vCont} packet.
36164 @item vCont@r{[};@var{action}@dots{}@r{]}
36165 The @samp{vCont} packet is supported. Each @var{action} is a supported
36166 command in the @samp{vCont} packet.
36168 The @samp{vCont} packet is not supported.
36171 @anchor{vCtrlC packet}
36173 @cindex @samp{vCtrlC} packet
36174 Interrupt remote target as if a control-C was pressed on the remote
36175 terminal. This is the equivalent to reacting to the @code{^C}
36176 (@samp{\003}, the control-C character) character in all-stop mode
36177 while the target is running, except this works in non-stop mode.
36178 @xref{interrupting remote targets}, for more info on the all-stop
36189 @item vFile:@var{operation}:@var{parameter}@dots{}
36190 @cindex @samp{vFile} packet
36191 Perform a file operation on the target system. For details,
36192 see @ref{Host I/O Packets}.
36194 @item vFlashErase:@var{addr},@var{length}
36195 @cindex @samp{vFlashErase} packet
36196 Direct the stub to erase @var{length} bytes of flash starting at
36197 @var{addr}. The region may enclose any number of flash blocks, but
36198 its start and end must fall on block boundaries, as indicated by the
36199 flash block size appearing in the memory map (@pxref{Memory Map
36200 Format}). @value{GDBN} groups flash memory programming operations
36201 together, and sends a @samp{vFlashDone} request after each group; the
36202 stub is allowed to delay erase operation until the @samp{vFlashDone}
36203 packet is received.
36213 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36214 @cindex @samp{vFlashWrite} packet
36215 Direct the stub to write data to flash address @var{addr}. The data
36216 is passed in binary form using the same encoding as for the @samp{X}
36217 packet (@pxref{Binary Data}). The memory ranges specified by
36218 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36219 not overlap, and must appear in order of increasing addresses
36220 (although @samp{vFlashErase} packets for higher addresses may already
36221 have been received; the ordering is guaranteed only between
36222 @samp{vFlashWrite} packets). If a packet writes to an address that was
36223 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36224 target-specific method, the results are unpredictable.
36232 for vFlashWrite addressing non-flash memory
36238 @cindex @samp{vFlashDone} packet
36239 Indicate to the stub that flash programming operation is finished.
36240 The stub is permitted to delay or batch the effects of a group of
36241 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36242 @samp{vFlashDone} packet is received. The contents of the affected
36243 regions of flash memory are unpredictable until the @samp{vFlashDone}
36244 request is completed.
36246 @item vKill;@var{pid}
36247 @cindex @samp{vKill} packet
36248 @anchor{vKill packet}
36249 Kill the process with the specified process ID @var{pid}, which is a
36250 hexadecimal integer identifying the process. This packet is used in
36251 preference to @samp{k} when multiprocess protocol extensions are
36252 supported; see @ref{multiprocess extensions}.
36262 @item vMustReplyEmpty
36263 @cindex @samp{vMustReplyEmpty} packet
36264 The correct reply to an unknown @samp{v} packet is to return the empty
36265 string, however, some older versions of @command{gdbserver} would
36266 incorrectly return @samp{OK} for unknown @samp{v} packets.
36268 The @samp{vMustReplyEmpty} is used as a feature test to check how
36269 @command{gdbserver} handles unknown packets, it is important that this
36270 packet be handled in the same way as other unknown @samp{v} packets.
36271 If this packet is handled differently to other unknown @samp{v}
36272 packets then it is possile that @value{GDBN} may run into problems in
36273 other areas, specifically around use of @samp{vFile:setfs:}.
36275 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36276 @cindex @samp{vRun} packet
36277 Run the program @var{filename}, passing it each @var{argument} on its
36278 command line. The file and arguments are hex-encoded strings. If
36279 @var{filename} is an empty string, the stub may use a default program
36280 (e.g.@: the last program run). The program is created in the stopped
36283 @c FIXME: What about non-stop mode?
36285 This packet is only available in extended mode (@pxref{extended mode}).
36291 @item @r{Any stop packet}
36292 for success (@pxref{Stop Reply Packets})
36296 @cindex @samp{vStopped} packet
36297 @xref{Notification Packets}.
36299 @item X @var{addr},@var{length}:@var{XX@dots{}}
36301 @cindex @samp{X} packet
36302 Write data to memory, where the data is transmitted in binary.
36303 Memory is specified by its address @var{addr} and number of addressable memory
36304 units @var{length} (@pxref{addressable memory unit});
36305 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36315 @item z @var{type},@var{addr},@var{kind}
36316 @itemx Z @var{type},@var{addr},@var{kind}
36317 @anchor{insert breakpoint or watchpoint packet}
36318 @cindex @samp{z} packet
36319 @cindex @samp{Z} packets
36320 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36321 watchpoint starting at address @var{address} of kind @var{kind}.
36323 Each breakpoint and watchpoint packet @var{type} is documented
36326 @emph{Implementation notes: A remote target shall return an empty string
36327 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36328 remote target shall support either both or neither of a given
36329 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36330 avoid potential problems with duplicate packets, the operations should
36331 be implemented in an idempotent way.}
36333 @item z0,@var{addr},@var{kind}
36334 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36335 @cindex @samp{z0} packet
36336 @cindex @samp{Z0} packet
36337 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36338 @var{addr} of type @var{kind}.
36340 A software breakpoint is implemented by replacing the instruction at
36341 @var{addr} with a software breakpoint or trap instruction. The
36342 @var{kind} is target-specific and typically indicates the size of the
36343 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36344 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36345 architectures have additional meanings for @var{kind}
36346 (@pxref{Architecture-Specific Protocol Details}); if no
36347 architecture-specific value is being used, it should be @samp{0}.
36348 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36349 conditional expressions in bytecode form that should be evaluated on
36350 the target's side. These are the conditions that should be taken into
36351 consideration when deciding if the breakpoint trigger should be
36352 reported back to @value{GDBN}.
36354 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36355 for how to best report a software breakpoint event to @value{GDBN}.
36357 The @var{cond_list} parameter is comprised of a series of expressions,
36358 concatenated without separators. Each expression has the following form:
36362 @item X @var{len},@var{expr}
36363 @var{len} is the length of the bytecode expression and @var{expr} is the
36364 actual conditional expression in bytecode form.
36368 The optional @var{cmd_list} parameter introduces commands that may be
36369 run on the target, rather than being reported back to @value{GDBN}.
36370 The parameter starts with a numeric flag @var{persist}; if the flag is
36371 nonzero, then the breakpoint may remain active and the commands
36372 continue to be run even when @value{GDBN} disconnects from the target.
36373 Following this flag is a series of expressions concatenated with no
36374 separators. Each expression has the following form:
36378 @item X @var{len},@var{expr}
36379 @var{len} is the length of the bytecode expression and @var{expr} is the
36380 actual commands expression in bytecode form.
36384 @emph{Implementation note: It is possible for a target to copy or move
36385 code that contains software breakpoints (e.g., when implementing
36386 overlays). The behavior of this packet, in the presence of such a
36387 target, is not defined.}
36399 @item z1,@var{addr},@var{kind}
36400 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36401 @cindex @samp{z1} packet
36402 @cindex @samp{Z1} packet
36403 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36404 address @var{addr}.
36406 A hardware breakpoint is implemented using a mechanism that is not
36407 dependent on being able to modify the target's memory. The
36408 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36409 same meaning as in @samp{Z0} packets.
36411 @emph{Implementation note: A hardware breakpoint is not affected by code
36424 @item z2,@var{addr},@var{kind}
36425 @itemx Z2,@var{addr},@var{kind}
36426 @cindex @samp{z2} packet
36427 @cindex @samp{Z2} packet
36428 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36429 The number of bytes to watch is specified by @var{kind}.
36441 @item z3,@var{addr},@var{kind}
36442 @itemx Z3,@var{addr},@var{kind}
36443 @cindex @samp{z3} packet
36444 @cindex @samp{Z3} packet
36445 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36446 The number of bytes to watch is specified by @var{kind}.
36458 @item z4,@var{addr},@var{kind}
36459 @itemx Z4,@var{addr},@var{kind}
36460 @cindex @samp{z4} packet
36461 @cindex @samp{Z4} packet
36462 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36463 The number of bytes to watch is specified by @var{kind}.
36477 @node Stop Reply Packets
36478 @section Stop Reply Packets
36479 @cindex stop reply packets
36481 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36482 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36483 receive any of the below as a reply. Except for @samp{?}
36484 and @samp{vStopped}, that reply is only returned
36485 when the target halts. In the below the exact meaning of @dfn{signal
36486 number} is defined by the header @file{include/gdb/signals.h} in the
36487 @value{GDBN} source code.
36489 In non-stop mode, the server will simply reply @samp{OK} to commands
36490 such as @samp{vCont}; any stop will be the subject of a future
36491 notification. @xref{Remote Non-Stop}.
36493 As in the description of request packets, we include spaces in the
36494 reply templates for clarity; these are not part of the reply packet's
36495 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36501 The program received signal number @var{AA} (a two-digit hexadecimal
36502 number). This is equivalent to a @samp{T} response with no
36503 @var{n}:@var{r} pairs.
36505 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36506 @cindex @samp{T} packet reply
36507 The program received signal number @var{AA} (a two-digit hexadecimal
36508 number). This is equivalent to an @samp{S} response, except that the
36509 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36510 and other information directly in the stop reply packet, reducing
36511 round-trip latency. Single-step and breakpoint traps are reported
36512 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36516 If @var{n} is a hexadecimal number, it is a register number, and the
36517 corresponding @var{r} gives that register's value. The data @var{r} is a
36518 series of bytes in target byte order, with each byte given by a
36519 two-digit hex number.
36522 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36523 the stopped thread, as specified in @ref{thread-id syntax}.
36526 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36527 the core on which the stop event was detected.
36530 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36531 specific event that stopped the target. The currently defined stop
36532 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36533 signal. At most one stop reason should be present.
36536 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36537 and go on to the next; this allows us to extend the protocol in the
36541 The currently defined stop reasons are:
36547 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36550 @item syscall_entry
36551 @itemx syscall_return
36552 The packet indicates a syscall entry or return, and @var{r} is the
36553 syscall number, in hex.
36555 @cindex shared library events, remote reply
36557 The packet indicates that the loaded libraries have changed.
36558 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36559 list of loaded libraries. The @var{r} part is ignored.
36561 @cindex replay log events, remote reply
36563 The packet indicates that the target cannot continue replaying
36564 logged execution events, because it has reached the end (or the
36565 beginning when executing backward) of the log. The value of @var{r}
36566 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36567 for more information.
36570 @anchor{swbreak stop reason}
36571 The packet indicates a software breakpoint instruction was executed,
36572 irrespective of whether it was @value{GDBN} that planted the
36573 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36574 part must be left empty.
36576 On some architectures, such as x86, at the architecture level, when a
36577 breakpoint instruction executes the program counter points at the
36578 breakpoint address plus an offset. On such targets, the stub is
36579 responsible for adjusting the PC to point back at the breakpoint
36582 This packet should not be sent by default; older @value{GDBN} versions
36583 did not support it. @value{GDBN} requests it, by supplying an
36584 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36585 remote stub must also supply the appropriate @samp{qSupported} feature
36586 indicating support.
36588 This packet is required for correct non-stop mode operation.
36591 The packet indicates the target stopped for a hardware breakpoint.
36592 The @var{r} part must be left empty.
36594 The same remarks about @samp{qSupported} and non-stop mode above
36597 @cindex fork events, remote reply
36599 The packet indicates that @code{fork} was called, and @var{r}
36600 is the thread ID of the new child process. Refer to
36601 @ref{thread-id syntax} for the format of the @var{thread-id}
36602 field. This packet is only applicable to targets that support
36605 This packet should not be sent by default; older @value{GDBN} versions
36606 did not support it. @value{GDBN} requests it, by supplying an
36607 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36608 remote stub must also supply the appropriate @samp{qSupported} feature
36609 indicating support.
36611 @cindex vfork events, remote reply
36613 The packet indicates that @code{vfork} was called, and @var{r}
36614 is the thread ID of the new child process. Refer to
36615 @ref{thread-id syntax} for the format of the @var{thread-id}
36616 field. This packet is only applicable to targets that support
36619 This packet should not be sent by default; older @value{GDBN} versions
36620 did not support it. @value{GDBN} requests it, by supplying an
36621 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36622 remote stub must also supply the appropriate @samp{qSupported} feature
36623 indicating support.
36625 @cindex vforkdone events, remote reply
36627 The packet indicates that a child process created by a vfork
36628 has either called @code{exec} or terminated, so that the
36629 address spaces of the parent and child process are no longer
36630 shared. The @var{r} part is ignored. This packet is only
36631 applicable to targets that support vforkdone events.
36633 This packet should not be sent by default; older @value{GDBN} versions
36634 did not support it. @value{GDBN} requests it, by supplying an
36635 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36636 remote stub must also supply the appropriate @samp{qSupported} feature
36637 indicating support.
36639 @cindex exec events, remote reply
36641 The packet indicates that @code{execve} was called, and @var{r}
36642 is the absolute pathname of the file that was executed, in hex.
36643 This packet is only applicable to targets that support exec events.
36645 This packet should not be sent by default; older @value{GDBN} versions
36646 did not support it. @value{GDBN} requests it, by supplying an
36647 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36648 remote stub must also supply the appropriate @samp{qSupported} feature
36649 indicating support.
36651 @cindex thread create event, remote reply
36652 @anchor{thread create event}
36654 The packet indicates that the thread was just created. The new thread
36655 is stopped until @value{GDBN} sets it running with a resumption packet
36656 (@pxref{vCont packet}). This packet should not be sent by default;
36657 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36658 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36659 @var{r} part is ignored.
36664 @itemx W @var{AA} ; process:@var{pid}
36665 The process exited, and @var{AA} is the exit status. This is only
36666 applicable to certain targets.
36668 The second form of the response, including the process ID of the
36669 exited process, can be used only when @value{GDBN} has reported
36670 support for multiprocess protocol extensions; see @ref{multiprocess
36671 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36675 @itemx X @var{AA} ; process:@var{pid}
36676 The process terminated with signal @var{AA}.
36678 The second form of the response, including the process ID of the
36679 terminated process, can be used only when @value{GDBN} has reported
36680 support for multiprocess protocol extensions; see @ref{multiprocess
36681 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36684 @anchor{thread exit event}
36685 @cindex thread exit event, remote reply
36686 @item w @var{AA} ; @var{tid}
36688 The thread exited, and @var{AA} is the exit status. This response
36689 should not be sent by default; @value{GDBN} requests it with the
36690 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36691 @var{AA} is formatted as a big-endian hex string.
36694 There are no resumed threads left in the target. In other words, even
36695 though the process is alive, the last resumed thread has exited. For
36696 example, say the target process has two threads: thread 1 and thread
36697 2. The client leaves thread 1 stopped, and resumes thread 2, which
36698 subsequently exits. At this point, even though the process is still
36699 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36700 executing either. The @samp{N} stop reply thus informs the client
36701 that it can stop waiting for stop replies. This packet should not be
36702 sent by default; older @value{GDBN} versions did not support it.
36703 @value{GDBN} requests it, by supplying an appropriate
36704 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36705 also supply the appropriate @samp{qSupported} feature indicating
36708 @item O @var{XX}@dots{}
36709 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36710 written as the program's console output. This can happen at any time
36711 while the program is running and the debugger should continue to wait
36712 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36714 @item F @var{call-id},@var{parameter}@dots{}
36715 @var{call-id} is the identifier which says which host system call should
36716 be called. This is just the name of the function. Translation into the
36717 correct system call is only applicable as it's defined in @value{GDBN}.
36718 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36721 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36722 this very system call.
36724 The target replies with this packet when it expects @value{GDBN} to
36725 call a host system call on behalf of the target. @value{GDBN} replies
36726 with an appropriate @samp{F} packet and keeps up waiting for the next
36727 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36728 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36729 Protocol Extension}, for more details.
36733 @node General Query Packets
36734 @section General Query Packets
36735 @cindex remote query requests
36737 Packets starting with @samp{q} are @dfn{general query packets};
36738 packets starting with @samp{Q} are @dfn{general set packets}. General
36739 query and set packets are a semi-unified form for retrieving and
36740 sending information to and from the stub.
36742 The initial letter of a query or set packet is followed by a name
36743 indicating what sort of thing the packet applies to. For example,
36744 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36745 definitions with the stub. These packet names follow some
36750 The name must not contain commas, colons or semicolons.
36752 Most @value{GDBN} query and set packets have a leading upper case
36755 The names of custom vendor packets should use a company prefix, in
36756 lower case, followed by a period. For example, packets designed at
36757 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36758 foos) or @samp{Qacme.bar} (for setting bars).
36761 The name of a query or set packet should be separated from any
36762 parameters by a @samp{:}; the parameters themselves should be
36763 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36764 full packet name, and check for a separator or the end of the packet,
36765 in case two packet names share a common prefix. New packets should not begin
36766 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36767 packets predate these conventions, and have arguments without any terminator
36768 for the packet name; we suspect they are in widespread use in places that
36769 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36770 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36773 Like the descriptions of the other packets, each description here
36774 has a template showing the packet's overall syntax, followed by an
36775 explanation of the packet's meaning. We include spaces in some of the
36776 templates for clarity; these are not part of the packet's syntax. No
36777 @value{GDBN} packet uses spaces to separate its components.
36779 Here are the currently defined query and set packets:
36785 Turn on or off the agent as a helper to perform some debugging operations
36786 delegated from @value{GDBN} (@pxref{Control Agent}).
36788 @item QAllow:@var{op}:@var{val}@dots{}
36789 @cindex @samp{QAllow} packet
36790 Specify which operations @value{GDBN} expects to request of the
36791 target, as a semicolon-separated list of operation name and value
36792 pairs. Possible values for @var{op} include @samp{WriteReg},
36793 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36794 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36795 indicating that @value{GDBN} will not request the operation, or 1,
36796 indicating that it may. (The target can then use this to set up its
36797 own internals optimally, for instance if the debugger never expects to
36798 insert breakpoints, it may not need to install its own trap handler.)
36801 @cindex current thread, remote request
36802 @cindex @samp{qC} packet
36803 Return the current thread ID.
36807 @item QC @var{thread-id}
36808 Where @var{thread-id} is a thread ID as documented in
36809 @ref{thread-id syntax}.
36810 @item @r{(anything else)}
36811 Any other reply implies the old thread ID.
36814 @item qCRC:@var{addr},@var{length}
36815 @cindex CRC of memory block, remote request
36816 @cindex @samp{qCRC} packet
36817 @anchor{qCRC packet}
36818 Compute the CRC checksum of a block of memory using CRC-32 defined in
36819 IEEE 802.3. The CRC is computed byte at a time, taking the most
36820 significant bit of each byte first. The initial pattern code
36821 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36823 @emph{Note:} This is the same CRC used in validating separate debug
36824 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36825 Files}). However the algorithm is slightly different. When validating
36826 separate debug files, the CRC is computed taking the @emph{least}
36827 significant bit of each byte first, and the final result is inverted to
36828 detect trailing zeros.
36833 An error (such as memory fault)
36834 @item C @var{crc32}
36835 The specified memory region's checksum is @var{crc32}.
36838 @item QDisableRandomization:@var{value}
36839 @cindex disable address space randomization, remote request
36840 @cindex @samp{QDisableRandomization} packet
36841 Some target operating systems will randomize the virtual address space
36842 of the inferior process as a security feature, but provide a feature
36843 to disable such randomization, e.g.@: to allow for a more deterministic
36844 debugging experience. On such systems, this packet with a @var{value}
36845 of 1 directs the target to disable address space randomization for
36846 processes subsequently started via @samp{vRun} packets, while a packet
36847 with a @var{value} of 0 tells the target to enable address space
36850 This packet is only available in extended mode (@pxref{extended mode}).
36855 The request succeeded.
36858 An error occurred. The error number @var{nn} is given as hex digits.
36861 An empty reply indicates that @samp{QDisableRandomization} is not supported
36865 This packet is not probed by default; the remote stub must request it,
36866 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36867 This should only be done on targets that actually support disabling
36868 address space randomization.
36870 @item QStartupWithShell:@var{value}
36871 @cindex startup with shell, remote request
36872 @cindex @samp{QStartupWithShell} packet
36873 On UNIX-like targets, it is possible to start the inferior using a
36874 shell program. This is the default behavior on both @value{GDBN} and
36875 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
36876 used to inform @command{gdbserver} whether it should start the
36877 inferior using a shell or not.
36879 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
36880 to start the inferior. If @var{value} is @samp{1},
36881 @command{gdbserver} will use a shell to start the inferior. All other
36882 values are considered an error.
36884 This packet is only available in extended mode (@pxref{extended
36890 The request succeeded.
36893 An error occurred. The error number @var{nn} is given as hex digits.
36896 This packet is not probed by default; the remote stub must request it,
36897 by supplying an appropriate @samp{qSupported} response
36898 (@pxref{qSupported}). This should only be done on targets that
36899 actually support starting the inferior using a shell.
36901 Use of this packet is controlled by the @code{set startup-with-shell}
36902 command; @pxref{set startup-with-shell}.
36904 @item QEnvironmentHexEncoded:@var{hex-value}
36905 @anchor{QEnvironmentHexEncoded}
36906 @cindex set environment variable, remote request
36907 @cindex @samp{QEnvironmentHexEncoded} packet
36908 On UNIX-like targets, it is possible to set environment variables that
36909 will be passed to the inferior during the startup process. This
36910 packet is used to inform @command{gdbserver} of an environment
36911 variable that has been defined by the user on @value{GDBN} (@pxref{set
36914 The packet is composed by @var{hex-value}, an hex encoded
36915 representation of the @var{name=value} format representing an
36916 environment variable. The name of the environment variable is
36917 represented by @var{name}, and the value to be assigned to the
36918 environment variable is represented by @var{value}. If the variable
36919 has no value (i.e., the value is @code{null}), then @var{value} will
36922 This packet is only available in extended mode (@pxref{extended
36928 The request succeeded.
36931 This packet is not probed by default; the remote stub must request it,
36932 by supplying an appropriate @samp{qSupported} response
36933 (@pxref{qSupported}). This should only be done on targets that
36934 actually support passing environment variables to the starting
36937 This packet is related to the @code{set environment} command;
36938 @pxref{set environment}.
36940 @item QEnvironmentUnset:@var{hex-value}
36941 @anchor{QEnvironmentUnset}
36942 @cindex unset environment variable, remote request
36943 @cindex @samp{QEnvironmentUnset} packet
36944 On UNIX-like targets, it is possible to unset environment variables
36945 before starting the inferior in the remote target. This packet is
36946 used to inform @command{gdbserver} of an environment variable that has
36947 been unset by the user on @value{GDBN} (@pxref{unset environment}).
36949 The packet is composed by @var{hex-value}, an hex encoded
36950 representation of the name of the environment variable to be unset.
36952 This packet is only available in extended mode (@pxref{extended
36958 The request succeeded.
36961 This packet is not probed by default; the remote stub must request it,
36962 by supplying an appropriate @samp{qSupported} response
36963 (@pxref{qSupported}). This should only be done on targets that
36964 actually support passing environment variables to the starting
36967 This packet is related to the @code{unset environment} command;
36968 @pxref{unset environment}.
36970 @item QEnvironmentReset
36971 @anchor{QEnvironmentReset}
36972 @cindex reset environment, remote request
36973 @cindex @samp{QEnvironmentReset} packet
36974 On UNIX-like targets, this packet is used to reset the state of
36975 environment variables in the remote target before starting the
36976 inferior. In this context, reset means unsetting all environment
36977 variables that were previously set by the user (i.e., were not
36978 initially present in the environment). It is sent to
36979 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
36980 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
36981 (@pxref{QEnvironmentUnset}) packets.
36983 This packet is only available in extended mode (@pxref{extended
36989 The request succeeded.
36992 This packet is not probed by default; the remote stub must request it,
36993 by supplying an appropriate @samp{qSupported} response
36994 (@pxref{qSupported}). This should only be done on targets that
36995 actually support passing environment variables to the starting
36998 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
36999 @anchor{QSetWorkingDir packet}
37000 @cindex set working directory, remote request
37001 @cindex @samp{QSetWorkingDir} packet
37002 This packet is used to inform the remote server of the intended
37003 current working directory for programs that are going to be executed.
37005 The packet is composed by @var{directory}, an hex encoded
37006 representation of the directory that the remote inferior will use as
37007 its current working directory. If @var{directory} is an empty string,
37008 the remote server should reset the inferior's current working
37009 directory to its original, empty value.
37011 This packet is only available in extended mode (@pxref{extended
37017 The request succeeded.
37021 @itemx qsThreadInfo
37022 @cindex list active threads, remote request
37023 @cindex @samp{qfThreadInfo} packet
37024 @cindex @samp{qsThreadInfo} packet
37025 Obtain a list of all active thread IDs from the target (OS). Since there
37026 may be too many active threads to fit into one reply packet, this query
37027 works iteratively: it may require more than one query/reply sequence to
37028 obtain the entire list of threads. The first query of the sequence will
37029 be the @samp{qfThreadInfo} query; subsequent queries in the
37030 sequence will be the @samp{qsThreadInfo} query.
37032 NOTE: This packet replaces the @samp{qL} query (see below).
37036 @item m @var{thread-id}
37038 @item m @var{thread-id},@var{thread-id}@dots{}
37039 a comma-separated list of thread IDs
37041 (lower case letter @samp{L}) denotes end of list.
37044 In response to each query, the target will reply with a list of one or
37045 more thread IDs, separated by commas.
37046 @value{GDBN} will respond to each reply with a request for more thread
37047 ids (using the @samp{qs} form of the query), until the target responds
37048 with @samp{l} (lower-case ell, for @dfn{last}).
37049 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37052 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37053 initial connection with the remote target, and the very first thread ID
37054 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37055 message. Therefore, the stub should ensure that the first thread ID in
37056 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37058 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37059 @cindex get thread-local storage address, remote request
37060 @cindex @samp{qGetTLSAddr} packet
37061 Fetch the address associated with thread local storage specified
37062 by @var{thread-id}, @var{offset}, and @var{lm}.
37064 @var{thread-id} is the thread ID associated with the
37065 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37067 @var{offset} is the (big endian, hex encoded) offset associated with the
37068 thread local variable. (This offset is obtained from the debug
37069 information associated with the variable.)
37071 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37072 load module associated with the thread local storage. For example,
37073 a @sc{gnu}/Linux system will pass the link map address of the shared
37074 object associated with the thread local storage under consideration.
37075 Other operating environments may choose to represent the load module
37076 differently, so the precise meaning of this parameter will vary.
37080 @item @var{XX}@dots{}
37081 Hex encoded (big endian) bytes representing the address of the thread
37082 local storage requested.
37085 An error occurred. The error number @var{nn} is given as hex digits.
37088 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37091 @item qGetTIBAddr:@var{thread-id}
37092 @cindex get thread information block address
37093 @cindex @samp{qGetTIBAddr} packet
37094 Fetch address of the Windows OS specific Thread Information Block.
37096 @var{thread-id} is the thread ID associated with the thread.
37100 @item @var{XX}@dots{}
37101 Hex encoded (big endian) bytes representing the linear address of the
37102 thread information block.
37105 An error occured. This means that either the thread was not found, or the
37106 address could not be retrieved.
37109 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37112 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37113 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37114 digit) is one to indicate the first query and zero to indicate a
37115 subsequent query; @var{threadcount} (two hex digits) is the maximum
37116 number of threads the response packet can contain; and @var{nextthread}
37117 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37118 returned in the response as @var{argthread}.
37120 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37124 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37125 Where: @var{count} (two hex digits) is the number of threads being
37126 returned; @var{done} (one hex digit) is zero to indicate more threads
37127 and one indicates no further threads; @var{argthreadid} (eight hex
37128 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37129 is a sequence of thread IDs, @var{threadid} (eight hex
37130 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37134 @cindex section offsets, remote request
37135 @cindex @samp{qOffsets} packet
37136 Get section offsets that the target used when relocating the downloaded
37141 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37142 Relocate the @code{Text} section by @var{xxx} from its original address.
37143 Relocate the @code{Data} section by @var{yyy} from its original address.
37144 If the object file format provides segment information (e.g.@: @sc{elf}
37145 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37146 segments by the supplied offsets.
37148 @emph{Note: while a @code{Bss} offset may be included in the response,
37149 @value{GDBN} ignores this and instead applies the @code{Data} offset
37150 to the @code{Bss} section.}
37152 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37153 Relocate the first segment of the object file, which conventionally
37154 contains program code, to a starting address of @var{xxx}. If
37155 @samp{DataSeg} is specified, relocate the second segment, which
37156 conventionally contains modifiable data, to a starting address of
37157 @var{yyy}. @value{GDBN} will report an error if the object file
37158 does not contain segment information, or does not contain at least
37159 as many segments as mentioned in the reply. Extra segments are
37160 kept at fixed offsets relative to the last relocated segment.
37163 @item qP @var{mode} @var{thread-id}
37164 @cindex thread information, remote request
37165 @cindex @samp{qP} packet
37166 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37167 encoded 32 bit mode; @var{thread-id} is a thread ID
37168 (@pxref{thread-id syntax}).
37170 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37173 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37177 @cindex non-stop mode, remote request
37178 @cindex @samp{QNonStop} packet
37180 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37181 @xref{Remote Non-Stop}, for more information.
37186 The request succeeded.
37189 An error occurred. The error number @var{nn} is given as hex digits.
37192 An empty reply indicates that @samp{QNonStop} is not supported by
37196 This packet is not probed by default; the remote stub must request it,
37197 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37198 Use of this packet is controlled by the @code{set non-stop} command;
37199 @pxref{Non-Stop Mode}.
37201 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37202 @itemx QCatchSyscalls:0
37203 @cindex catch syscalls from inferior, remote request
37204 @cindex @samp{QCatchSyscalls} packet
37205 @anchor{QCatchSyscalls}
37206 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37207 catching syscalls from the inferior process.
37209 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37210 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37211 is listed, every system call should be reported.
37213 Note that if a syscall not in the list is reported, @value{GDBN} will
37214 still filter the event according to its own list from all corresponding
37215 @code{catch syscall} commands. However, it is more efficient to only
37216 report the requested syscalls.
37218 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37219 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37221 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37222 kept for the new process too. On targets where exec may affect syscall
37223 numbers, for example with exec between 32 and 64-bit processes, the
37224 client should send a new packet with the new syscall list.
37229 The request succeeded.
37232 An error occurred. @var{nn} are hex digits.
37235 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37239 Use of this packet is controlled by the @code{set remote catch-syscalls}
37240 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37241 This packet is not probed by default; the remote stub must request it,
37242 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37244 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37245 @cindex pass signals to inferior, remote request
37246 @cindex @samp{QPassSignals} packet
37247 @anchor{QPassSignals}
37248 Each listed @var{signal} should be passed directly to the inferior process.
37249 Signals are numbered identically to continue packets and stop replies
37250 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37251 strictly greater than the previous item. These signals do not need to stop
37252 the inferior, or be reported to @value{GDBN}. All other signals should be
37253 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37254 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37255 new list. This packet improves performance when using @samp{handle
37256 @var{signal} nostop noprint pass}.
37261 The request succeeded.
37264 An error occurred. The error number @var{nn} is given as hex digits.
37267 An empty reply indicates that @samp{QPassSignals} is not supported by
37271 Use of this packet is controlled by the @code{set remote pass-signals}
37272 command (@pxref{Remote Configuration, set remote pass-signals}).
37273 This packet is not probed by default; the remote stub must request it,
37274 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37276 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37277 @cindex signals the inferior may see, remote request
37278 @cindex @samp{QProgramSignals} packet
37279 @anchor{QProgramSignals}
37280 Each listed @var{signal} may be delivered to the inferior process.
37281 Others should be silently discarded.
37283 In some cases, the remote stub may need to decide whether to deliver a
37284 signal to the program or not without @value{GDBN} involvement. One
37285 example of that is while detaching --- the program's threads may have
37286 stopped for signals that haven't yet had a chance of being reported to
37287 @value{GDBN}, and so the remote stub can use the signal list specified
37288 by this packet to know whether to deliver or ignore those pending
37291 This does not influence whether to deliver a signal as requested by a
37292 resumption packet (@pxref{vCont packet}).
37294 Signals are numbered identically to continue packets and stop replies
37295 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37296 strictly greater than the previous item. Multiple
37297 @samp{QProgramSignals} packets do not combine; any earlier
37298 @samp{QProgramSignals} list is completely replaced by the new list.
37303 The request succeeded.
37306 An error occurred. The error number @var{nn} is given as hex digits.
37309 An empty reply indicates that @samp{QProgramSignals} is not supported
37313 Use of this packet is controlled by the @code{set remote program-signals}
37314 command (@pxref{Remote Configuration, set remote program-signals}).
37315 This packet is not probed by default; the remote stub must request it,
37316 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37318 @anchor{QThreadEvents}
37319 @item QThreadEvents:1
37320 @itemx QThreadEvents:0
37321 @cindex thread create/exit events, remote request
37322 @cindex @samp{QThreadEvents} packet
37324 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37325 reporting of thread create and exit events. @xref{thread create
37326 event}, for the reply specifications. For example, this is used in
37327 non-stop mode when @value{GDBN} stops a set of threads and
37328 synchronously waits for the their corresponding stop replies. Without
37329 exit events, if one of the threads exits, @value{GDBN} would hang
37330 forever not knowing that it should no longer expect a stop for that
37331 same thread. @value{GDBN} does not enable this feature unless the
37332 stub reports that it supports it by including @samp{QThreadEvents+} in
37333 its @samp{qSupported} reply.
37338 The request succeeded.
37341 An error occurred. The error number @var{nn} is given as hex digits.
37344 An empty reply indicates that @samp{QThreadEvents} is not supported by
37348 Use of this packet is controlled by the @code{set remote thread-events}
37349 command (@pxref{Remote Configuration, set remote thread-events}).
37351 @item qRcmd,@var{command}
37352 @cindex execute remote command, remote request
37353 @cindex @samp{qRcmd} packet
37354 @var{command} (hex encoded) is passed to the local interpreter for
37355 execution. Invalid commands should be reported using the output
37356 string. Before the final result packet, the target may also respond
37357 with a number of intermediate @samp{O@var{output}} console output
37358 packets. @emph{Implementors should note that providing access to a
37359 stubs's interpreter may have security implications}.
37364 A command response with no output.
37366 A command response with the hex encoded output string @var{OUTPUT}.
37368 Indicate a badly formed request.
37370 An empty reply indicates that @samp{qRcmd} is not recognized.
37373 (Note that the @code{qRcmd} packet's name is separated from the
37374 command by a @samp{,}, not a @samp{:}, contrary to the naming
37375 conventions above. Please don't use this packet as a model for new
37378 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37379 @cindex searching memory, in remote debugging
37381 @cindex @samp{qSearch:memory} packet
37383 @cindex @samp{qSearch memory} packet
37384 @anchor{qSearch memory}
37385 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37386 Both @var{address} and @var{length} are encoded in hex;
37387 @var{search-pattern} is a sequence of bytes, also hex encoded.
37392 The pattern was not found.
37394 The pattern was found at @var{address}.
37396 A badly formed request or an error was encountered while searching memory.
37398 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37401 @item QStartNoAckMode
37402 @cindex @samp{QStartNoAckMode} packet
37403 @anchor{QStartNoAckMode}
37404 Request that the remote stub disable the normal @samp{+}/@samp{-}
37405 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37410 The stub has switched to no-acknowledgment mode.
37411 @value{GDBN} acknowledges this reponse,
37412 but neither the stub nor @value{GDBN} shall send or expect further
37413 @samp{+}/@samp{-} acknowledgments in the current connection.
37415 An empty reply indicates that the stub does not support no-acknowledgment mode.
37418 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37419 @cindex supported packets, remote query
37420 @cindex features of the remote protocol
37421 @cindex @samp{qSupported} packet
37422 @anchor{qSupported}
37423 Tell the remote stub about features supported by @value{GDBN}, and
37424 query the stub for features it supports. This packet allows
37425 @value{GDBN} and the remote stub to take advantage of each others'
37426 features. @samp{qSupported} also consolidates multiple feature probes
37427 at startup, to improve @value{GDBN} performance---a single larger
37428 packet performs better than multiple smaller probe packets on
37429 high-latency links. Some features may enable behavior which must not
37430 be on by default, e.g.@: because it would confuse older clients or
37431 stubs. Other features may describe packets which could be
37432 automatically probed for, but are not. These features must be
37433 reported before @value{GDBN} will use them. This ``default
37434 unsupported'' behavior is not appropriate for all packets, but it
37435 helps to keep the initial connection time under control with new
37436 versions of @value{GDBN} which support increasing numbers of packets.
37440 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37441 The stub supports or does not support each returned @var{stubfeature},
37442 depending on the form of each @var{stubfeature} (see below for the
37445 An empty reply indicates that @samp{qSupported} is not recognized,
37446 or that no features needed to be reported to @value{GDBN}.
37449 The allowed forms for each feature (either a @var{gdbfeature} in the
37450 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37454 @item @var{name}=@var{value}
37455 The remote protocol feature @var{name} is supported, and associated
37456 with the specified @var{value}. The format of @var{value} depends
37457 on the feature, but it must not include a semicolon.
37459 The remote protocol feature @var{name} is supported, and does not
37460 need an associated value.
37462 The remote protocol feature @var{name} is not supported.
37464 The remote protocol feature @var{name} may be supported, and
37465 @value{GDBN} should auto-detect support in some other way when it is
37466 needed. This form will not be used for @var{gdbfeature} notifications,
37467 but may be used for @var{stubfeature} responses.
37470 Whenever the stub receives a @samp{qSupported} request, the
37471 supplied set of @value{GDBN} features should override any previous
37472 request. This allows @value{GDBN} to put the stub in a known
37473 state, even if the stub had previously been communicating with
37474 a different version of @value{GDBN}.
37476 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37481 This feature indicates whether @value{GDBN} supports multiprocess
37482 extensions to the remote protocol. @value{GDBN} does not use such
37483 extensions unless the stub also reports that it supports them by
37484 including @samp{multiprocess+} in its @samp{qSupported} reply.
37485 @xref{multiprocess extensions}, for details.
37488 This feature indicates that @value{GDBN} supports the XML target
37489 description. If the stub sees @samp{xmlRegisters=} with target
37490 specific strings separated by a comma, it will report register
37494 This feature indicates whether @value{GDBN} supports the
37495 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37496 instruction reply packet}).
37499 This feature indicates whether @value{GDBN} supports the swbreak stop
37500 reason in stop replies. @xref{swbreak stop reason}, for details.
37503 This feature indicates whether @value{GDBN} supports the hwbreak stop
37504 reason in stop replies. @xref{swbreak stop reason}, for details.
37507 This feature indicates whether @value{GDBN} supports fork event
37508 extensions to the remote protocol. @value{GDBN} does not use such
37509 extensions unless the stub also reports that it supports them by
37510 including @samp{fork-events+} in its @samp{qSupported} reply.
37513 This feature indicates whether @value{GDBN} supports vfork event
37514 extensions to the remote protocol. @value{GDBN} does not use such
37515 extensions unless the stub also reports that it supports them by
37516 including @samp{vfork-events+} in its @samp{qSupported} reply.
37519 This feature indicates whether @value{GDBN} supports exec event
37520 extensions to the remote protocol. @value{GDBN} does not use such
37521 extensions unless the stub also reports that it supports them by
37522 including @samp{exec-events+} in its @samp{qSupported} reply.
37524 @item vContSupported
37525 This feature indicates whether @value{GDBN} wants to know the
37526 supported actions in the reply to @samp{vCont?} packet.
37529 Stubs should ignore any unknown values for
37530 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37531 packet supports receiving packets of unlimited length (earlier
37532 versions of @value{GDBN} may reject overly long responses). Additional values
37533 for @var{gdbfeature} may be defined in the future to let the stub take
37534 advantage of new features in @value{GDBN}, e.g.@: incompatible
37535 improvements in the remote protocol---the @samp{multiprocess} feature is
37536 an example of such a feature. The stub's reply should be independent
37537 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37538 describes all the features it supports, and then the stub replies with
37539 all the features it supports.
37541 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37542 responses, as long as each response uses one of the standard forms.
37544 Some features are flags. A stub which supports a flag feature
37545 should respond with a @samp{+} form response. Other features
37546 require values, and the stub should respond with an @samp{=}
37549 Each feature has a default value, which @value{GDBN} will use if
37550 @samp{qSupported} is not available or if the feature is not mentioned
37551 in the @samp{qSupported} response. The default values are fixed; a
37552 stub is free to omit any feature responses that match the defaults.
37554 Not all features can be probed, but for those which can, the probing
37555 mechanism is useful: in some cases, a stub's internal
37556 architecture may not allow the protocol layer to know some information
37557 about the underlying target in advance. This is especially common in
37558 stubs which may be configured for multiple targets.
37560 These are the currently defined stub features and their properties:
37562 @multitable @columnfractions 0.35 0.2 0.12 0.2
37563 @c NOTE: The first row should be @headitem, but we do not yet require
37564 @c a new enough version of Texinfo (4.7) to use @headitem.
37566 @tab Value Required
37570 @item @samp{PacketSize}
37575 @item @samp{qXfer:auxv:read}
37580 @item @samp{qXfer:btrace:read}
37585 @item @samp{qXfer:btrace-conf:read}
37590 @item @samp{qXfer:exec-file:read}
37595 @item @samp{qXfer:features:read}
37600 @item @samp{qXfer:libraries:read}
37605 @item @samp{qXfer:libraries-svr4:read}
37610 @item @samp{augmented-libraries-svr4-read}
37615 @item @samp{qXfer:memory-map:read}
37620 @item @samp{qXfer:sdata:read}
37625 @item @samp{qXfer:spu:read}
37630 @item @samp{qXfer:spu:write}
37635 @item @samp{qXfer:siginfo:read}
37640 @item @samp{qXfer:siginfo:write}
37645 @item @samp{qXfer:threads:read}
37650 @item @samp{qXfer:traceframe-info:read}
37655 @item @samp{qXfer:uib:read}
37660 @item @samp{qXfer:fdpic:read}
37665 @item @samp{Qbtrace:off}
37670 @item @samp{Qbtrace:bts}
37675 @item @samp{Qbtrace:pt}
37680 @item @samp{Qbtrace-conf:bts:size}
37685 @item @samp{Qbtrace-conf:pt:size}
37690 @item @samp{QNonStop}
37695 @item @samp{QCatchSyscalls}
37700 @item @samp{QPassSignals}
37705 @item @samp{QStartNoAckMode}
37710 @item @samp{multiprocess}
37715 @item @samp{ConditionalBreakpoints}
37720 @item @samp{ConditionalTracepoints}
37725 @item @samp{ReverseContinue}
37730 @item @samp{ReverseStep}
37735 @item @samp{TracepointSource}
37740 @item @samp{QAgent}
37745 @item @samp{QAllow}
37750 @item @samp{QDisableRandomization}
37755 @item @samp{EnableDisableTracepoints}
37760 @item @samp{QTBuffer:size}
37765 @item @samp{tracenz}
37770 @item @samp{BreakpointCommands}
37775 @item @samp{swbreak}
37780 @item @samp{hwbreak}
37785 @item @samp{fork-events}
37790 @item @samp{vfork-events}
37795 @item @samp{exec-events}
37800 @item @samp{QThreadEvents}
37805 @item @samp{no-resumed}
37812 These are the currently defined stub features, in more detail:
37815 @cindex packet size, remote protocol
37816 @item PacketSize=@var{bytes}
37817 The remote stub can accept packets up to at least @var{bytes} in
37818 length. @value{GDBN} will send packets up to this size for bulk
37819 transfers, and will never send larger packets. This is a limit on the
37820 data characters in the packet, including the frame and checksum.
37821 There is no trailing NUL byte in a remote protocol packet; if the stub
37822 stores packets in a NUL-terminated format, it should allow an extra
37823 byte in its buffer for the NUL. If this stub feature is not supported,
37824 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37826 @item qXfer:auxv:read
37827 The remote stub understands the @samp{qXfer:auxv:read} packet
37828 (@pxref{qXfer auxiliary vector read}).
37830 @item qXfer:btrace:read
37831 The remote stub understands the @samp{qXfer:btrace:read}
37832 packet (@pxref{qXfer btrace read}).
37834 @item qXfer:btrace-conf:read
37835 The remote stub understands the @samp{qXfer:btrace-conf:read}
37836 packet (@pxref{qXfer btrace-conf read}).
37838 @item qXfer:exec-file:read
37839 The remote stub understands the @samp{qXfer:exec-file:read} packet
37840 (@pxref{qXfer executable filename read}).
37842 @item qXfer:features:read
37843 The remote stub understands the @samp{qXfer:features:read} packet
37844 (@pxref{qXfer target description read}).
37846 @item qXfer:libraries:read
37847 The remote stub understands the @samp{qXfer:libraries:read} packet
37848 (@pxref{qXfer library list read}).
37850 @item qXfer:libraries-svr4:read
37851 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37852 (@pxref{qXfer svr4 library list read}).
37854 @item augmented-libraries-svr4-read
37855 The remote stub understands the augmented form of the
37856 @samp{qXfer:libraries-svr4:read} packet
37857 (@pxref{qXfer svr4 library list read}).
37859 @item qXfer:memory-map:read
37860 The remote stub understands the @samp{qXfer:memory-map:read} packet
37861 (@pxref{qXfer memory map read}).
37863 @item qXfer:sdata:read
37864 The remote stub understands the @samp{qXfer:sdata:read} packet
37865 (@pxref{qXfer sdata read}).
37867 @item qXfer:spu:read
37868 The remote stub understands the @samp{qXfer:spu:read} packet
37869 (@pxref{qXfer spu read}).
37871 @item qXfer:spu:write
37872 The remote stub understands the @samp{qXfer:spu:write} packet
37873 (@pxref{qXfer spu write}).
37875 @item qXfer:siginfo:read
37876 The remote stub understands the @samp{qXfer:siginfo:read} packet
37877 (@pxref{qXfer siginfo read}).
37879 @item qXfer:siginfo:write
37880 The remote stub understands the @samp{qXfer:siginfo:write} packet
37881 (@pxref{qXfer siginfo write}).
37883 @item qXfer:threads:read
37884 The remote stub understands the @samp{qXfer:threads:read} packet
37885 (@pxref{qXfer threads read}).
37887 @item qXfer:traceframe-info:read
37888 The remote stub understands the @samp{qXfer:traceframe-info:read}
37889 packet (@pxref{qXfer traceframe info read}).
37891 @item qXfer:uib:read
37892 The remote stub understands the @samp{qXfer:uib:read}
37893 packet (@pxref{qXfer unwind info block}).
37895 @item qXfer:fdpic:read
37896 The remote stub understands the @samp{qXfer:fdpic:read}
37897 packet (@pxref{qXfer fdpic loadmap read}).
37900 The remote stub understands the @samp{QNonStop} packet
37901 (@pxref{QNonStop}).
37903 @item QCatchSyscalls
37904 The remote stub understands the @samp{QCatchSyscalls} packet
37905 (@pxref{QCatchSyscalls}).
37908 The remote stub understands the @samp{QPassSignals} packet
37909 (@pxref{QPassSignals}).
37911 @item QStartNoAckMode
37912 The remote stub understands the @samp{QStartNoAckMode} packet and
37913 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37916 @anchor{multiprocess extensions}
37917 @cindex multiprocess extensions, in remote protocol
37918 The remote stub understands the multiprocess extensions to the remote
37919 protocol syntax. The multiprocess extensions affect the syntax of
37920 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37921 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37922 replies. Note that reporting this feature indicates support for the
37923 syntactic extensions only, not that the stub necessarily supports
37924 debugging of more than one process at a time. The stub must not use
37925 multiprocess extensions in packet replies unless @value{GDBN} has also
37926 indicated it supports them in its @samp{qSupported} request.
37928 @item qXfer:osdata:read
37929 The remote stub understands the @samp{qXfer:osdata:read} packet
37930 ((@pxref{qXfer osdata read}).
37932 @item ConditionalBreakpoints
37933 The target accepts and implements evaluation of conditional expressions
37934 defined for breakpoints. The target will only report breakpoint triggers
37935 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37937 @item ConditionalTracepoints
37938 The remote stub accepts and implements conditional expressions defined
37939 for tracepoints (@pxref{Tracepoint Conditions}).
37941 @item ReverseContinue
37942 The remote stub accepts and implements the reverse continue packet
37946 The remote stub accepts and implements the reverse step packet
37949 @item TracepointSource
37950 The remote stub understands the @samp{QTDPsrc} packet that supplies
37951 the source form of tracepoint definitions.
37954 The remote stub understands the @samp{QAgent} packet.
37957 The remote stub understands the @samp{QAllow} packet.
37959 @item QDisableRandomization
37960 The remote stub understands the @samp{QDisableRandomization} packet.
37962 @item StaticTracepoint
37963 @cindex static tracepoints, in remote protocol
37964 The remote stub supports static tracepoints.
37966 @item InstallInTrace
37967 @anchor{install tracepoint in tracing}
37968 The remote stub supports installing tracepoint in tracing.
37970 @item EnableDisableTracepoints
37971 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37972 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37973 to be enabled and disabled while a trace experiment is running.
37975 @item QTBuffer:size
37976 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37977 packet that allows to change the size of the trace buffer.
37980 @cindex string tracing, in remote protocol
37981 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37982 See @ref{Bytecode Descriptions} for details about the bytecode.
37984 @item BreakpointCommands
37985 @cindex breakpoint commands, in remote protocol
37986 The remote stub supports running a breakpoint's command list itself,
37987 rather than reporting the hit to @value{GDBN}.
37990 The remote stub understands the @samp{Qbtrace:off} packet.
37993 The remote stub understands the @samp{Qbtrace:bts} packet.
37996 The remote stub understands the @samp{Qbtrace:pt} packet.
37998 @item Qbtrace-conf:bts:size
37999 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38001 @item Qbtrace-conf:pt:size
38002 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38005 The remote stub reports the @samp{swbreak} stop reason for memory
38009 The remote stub reports the @samp{hwbreak} stop reason for hardware
38013 The remote stub reports the @samp{fork} stop reason for fork events.
38016 The remote stub reports the @samp{vfork} stop reason for vfork events
38017 and vforkdone events.
38020 The remote stub reports the @samp{exec} stop reason for exec events.
38022 @item vContSupported
38023 The remote stub reports the supported actions in the reply to
38024 @samp{vCont?} packet.
38026 @item QThreadEvents
38027 The remote stub understands the @samp{QThreadEvents} packet.
38030 The remote stub reports the @samp{N} stop reply.
38035 @cindex symbol lookup, remote request
38036 @cindex @samp{qSymbol} packet
38037 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38038 requests. Accept requests from the target for the values of symbols.
38043 The target does not need to look up any (more) symbols.
38044 @item qSymbol:@var{sym_name}
38045 The target requests the value of symbol @var{sym_name} (hex encoded).
38046 @value{GDBN} may provide the value by using the
38047 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38051 @item qSymbol:@var{sym_value}:@var{sym_name}
38052 Set the value of @var{sym_name} to @var{sym_value}.
38054 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38055 target has previously requested.
38057 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38058 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38064 The target does not need to look up any (more) symbols.
38065 @item qSymbol:@var{sym_name}
38066 The target requests the value of a new symbol @var{sym_name} (hex
38067 encoded). @value{GDBN} will continue to supply the values of symbols
38068 (if available), until the target ceases to request them.
38073 @itemx QTDisconnected
38080 @itemx qTMinFTPILen
38082 @xref{Tracepoint Packets}.
38084 @item qThreadExtraInfo,@var{thread-id}
38085 @cindex thread attributes info, remote request
38086 @cindex @samp{qThreadExtraInfo} packet
38087 Obtain from the target OS a printable string description of thread
38088 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38089 for the forms of @var{thread-id}. This
38090 string may contain anything that the target OS thinks is interesting
38091 for @value{GDBN} to tell the user about the thread. The string is
38092 displayed in @value{GDBN}'s @code{info threads} display. Some
38093 examples of possible thread extra info strings are @samp{Runnable}, or
38094 @samp{Blocked on Mutex}.
38098 @item @var{XX}@dots{}
38099 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38100 comprising the printable string containing the extra information about
38101 the thread's attributes.
38104 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38105 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38106 conventions above. Please don't use this packet as a model for new
38125 @xref{Tracepoint Packets}.
38127 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38128 @cindex read special object, remote request
38129 @cindex @samp{qXfer} packet
38130 @anchor{qXfer read}
38131 Read uninterpreted bytes from the target's special data area
38132 identified by the keyword @var{object}. Request @var{length} bytes
38133 starting at @var{offset} bytes into the data. The content and
38134 encoding of @var{annex} is specific to @var{object}; it can supply
38135 additional details about what data to access.
38140 Data @var{data} (@pxref{Binary Data}) has been read from the
38141 target. There may be more data at a higher address (although
38142 it is permitted to return @samp{m} even for the last valid
38143 block of data, as long as at least one byte of data was read).
38144 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38148 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38149 There is no more data to be read. It is possible for @var{data} to
38150 have fewer bytes than the @var{length} in the request.
38153 The @var{offset} in the request is at the end of the data.
38154 There is no more data to be read.
38157 The request was malformed, or @var{annex} was invalid.
38160 The offset was invalid, or there was an error encountered reading the data.
38161 The @var{nn} part is a hex-encoded @code{errno} value.
38164 An empty reply indicates the @var{object} string was not recognized by
38165 the stub, or that the object does not support reading.
38168 Here are the specific requests of this form defined so far. All the
38169 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38170 formats, listed above.
38173 @item qXfer:auxv:read::@var{offset},@var{length}
38174 @anchor{qXfer auxiliary vector read}
38175 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38176 auxiliary vector}. Note @var{annex} must be empty.
38178 This packet is not probed by default; the remote stub must request it,
38179 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38181 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38182 @anchor{qXfer btrace read}
38184 Return a description of the current branch trace.
38185 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38186 packet may have one of the following values:
38190 Returns all available branch trace.
38193 Returns all available branch trace if the branch trace changed since
38194 the last read request.
38197 Returns the new branch trace since the last read request. Adds a new
38198 block to the end of the trace that begins at zero and ends at the source
38199 location of the first branch in the trace buffer. This extra block is
38200 used to stitch traces together.
38202 If the trace buffer overflowed, returns an error indicating the overflow.
38205 This packet is not probed by default; the remote stub must request it
38206 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38208 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38209 @anchor{qXfer btrace-conf read}
38211 Return a description of the current branch trace configuration.
38212 @xref{Branch Trace Configuration Format}.
38214 This packet is not probed by default; the remote stub must request it
38215 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38217 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38218 @anchor{qXfer executable filename read}
38219 Return the full absolute name of the file that was executed to create
38220 a process running on the remote system. The annex specifies the
38221 numeric process ID of the process to query, encoded as a hexadecimal
38222 number. If the annex part is empty the remote stub should return the
38223 filename corresponding to the currently executing process.
38225 This packet is not probed by default; the remote stub must request it,
38226 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38228 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38229 @anchor{qXfer target description read}
38230 Access the @dfn{target description}. @xref{Target Descriptions}. The
38231 annex specifies which XML document to access. The main description is
38232 always loaded from the @samp{target.xml} annex.
38234 This packet is not probed by default; the remote stub must request it,
38235 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38237 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38238 @anchor{qXfer library list read}
38239 Access the target's list of loaded libraries. @xref{Library List Format}.
38240 The annex part of the generic @samp{qXfer} packet must be empty
38241 (@pxref{qXfer read}).
38243 Targets which maintain a list of libraries in the program's memory do
38244 not need to implement this packet; it is designed for platforms where
38245 the operating system manages the list of loaded libraries.
38247 This packet is not probed by default; the remote stub must request it,
38248 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38250 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38251 @anchor{qXfer svr4 library list read}
38252 Access the target's list of loaded libraries when the target is an SVR4
38253 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38254 of the generic @samp{qXfer} packet must be empty unless the remote
38255 stub indicated it supports the augmented form of this packet
38256 by supplying an appropriate @samp{qSupported} response
38257 (@pxref{qXfer read}, @ref{qSupported}).
38259 This packet is optional for better performance on SVR4 targets.
38260 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38262 This packet is not probed by default; the remote stub must request it,
38263 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38265 If the remote stub indicates it supports the augmented form of this
38266 packet then the annex part of the generic @samp{qXfer} packet may
38267 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38268 arguments. The currently supported arguments are:
38271 @item start=@var{address}
38272 A hexadecimal number specifying the address of the @samp{struct
38273 link_map} to start reading the library list from. If unset or zero
38274 then the first @samp{struct link_map} in the library list will be
38275 chosen as the starting point.
38277 @item prev=@var{address}
38278 A hexadecimal number specifying the address of the @samp{struct
38279 link_map} immediately preceding the @samp{struct link_map}
38280 specified by the @samp{start} argument. If unset or zero then
38281 the remote stub will expect that no @samp{struct link_map}
38282 exists prior to the starting point.
38286 Arguments that are not understood by the remote stub will be silently
38289 @item qXfer:memory-map:read::@var{offset},@var{length}
38290 @anchor{qXfer memory map read}
38291 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38292 annex part of the generic @samp{qXfer} packet must be empty
38293 (@pxref{qXfer read}).
38295 This packet is not probed by default; the remote stub must request it,
38296 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38298 @item qXfer:sdata:read::@var{offset},@var{length}
38299 @anchor{qXfer sdata read}
38301 Read contents of the extra collected static tracepoint marker
38302 information. The annex part of the generic @samp{qXfer} packet must
38303 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38306 This packet is not probed by default; the remote stub must request it,
38307 by supplying an appropriate @samp{qSupported} response
38308 (@pxref{qSupported}).
38310 @item qXfer:siginfo:read::@var{offset},@var{length}
38311 @anchor{qXfer siginfo read}
38312 Read contents of the extra signal information on the target
38313 system. The annex part of the generic @samp{qXfer} packet must be
38314 empty (@pxref{qXfer read}).
38316 This packet is not probed by default; the remote stub must request it,
38317 by supplying an appropriate @samp{qSupported} response
38318 (@pxref{qSupported}).
38320 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38321 @anchor{qXfer spu read}
38322 Read contents of an @code{spufs} file on the target system. The
38323 annex specifies which file to read; it must be of the form
38324 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38325 in the target process, and @var{name} identifes the @code{spufs} file
38326 in that context to be accessed.
38328 This packet is not probed by default; the remote stub must request it,
38329 by supplying an appropriate @samp{qSupported} response
38330 (@pxref{qSupported}).
38332 @item qXfer:threads:read::@var{offset},@var{length}
38333 @anchor{qXfer threads read}
38334 Access the list of threads on target. @xref{Thread List Format}. The
38335 annex part of the generic @samp{qXfer} packet must be empty
38336 (@pxref{qXfer read}).
38338 This packet is not probed by default; the remote stub must request it,
38339 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38341 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38342 @anchor{qXfer traceframe info read}
38344 Return a description of the current traceframe's contents.
38345 @xref{Traceframe Info Format}. The annex part of the generic
38346 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38348 This packet is not probed by default; the remote stub must request it,
38349 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38351 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38352 @anchor{qXfer unwind info block}
38354 Return the unwind information block for @var{pc}. This packet is used
38355 on OpenVMS/ia64 to ask the kernel unwind information.
38357 This packet is not probed by default.
38359 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38360 @anchor{qXfer fdpic loadmap read}
38361 Read contents of @code{loadmap}s on the target system. The
38362 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38363 executable @code{loadmap} or interpreter @code{loadmap} to read.
38365 This packet is not probed by default; the remote stub must request it,
38366 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38368 @item qXfer:osdata:read::@var{offset},@var{length}
38369 @anchor{qXfer osdata read}
38370 Access the target's @dfn{operating system information}.
38371 @xref{Operating System Information}.
38375 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38376 @cindex write data into object, remote request
38377 @anchor{qXfer write}
38378 Write uninterpreted bytes into the target's special data area
38379 identified by the keyword @var{object}, starting at @var{offset} bytes
38380 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38381 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38382 is specific to @var{object}; it can supply additional details about what data
38388 @var{nn} (hex encoded) is the number of bytes written.
38389 This may be fewer bytes than supplied in the request.
38392 The request was malformed, or @var{annex} was invalid.
38395 The offset was invalid, or there was an error encountered writing the data.
38396 The @var{nn} part is a hex-encoded @code{errno} value.
38399 An empty reply indicates the @var{object} string was not
38400 recognized by the stub, or that the object does not support writing.
38403 Here are the specific requests of this form defined so far. All the
38404 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38405 formats, listed above.
38408 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38409 @anchor{qXfer siginfo write}
38410 Write @var{data} to the extra signal information on the target system.
38411 The annex part of the generic @samp{qXfer} packet must be
38412 empty (@pxref{qXfer write}).
38414 This packet is not probed by default; the remote stub must request it,
38415 by supplying an appropriate @samp{qSupported} response
38416 (@pxref{qSupported}).
38418 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38419 @anchor{qXfer spu write}
38420 Write @var{data} to an @code{spufs} file on the target system. The
38421 annex specifies which file to write; it must be of the form
38422 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38423 in the target process, and @var{name} identifes the @code{spufs} file
38424 in that context to be accessed.
38426 This packet is not probed by default; the remote stub must request it,
38427 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38430 @item qXfer:@var{object}:@var{operation}:@dots{}
38431 Requests of this form may be added in the future. When a stub does
38432 not recognize the @var{object} keyword, or its support for
38433 @var{object} does not recognize the @var{operation} keyword, the stub
38434 must respond with an empty packet.
38436 @item qAttached:@var{pid}
38437 @cindex query attached, remote request
38438 @cindex @samp{qAttached} packet
38439 Return an indication of whether the remote server attached to an
38440 existing process or created a new process. When the multiprocess
38441 protocol extensions are supported (@pxref{multiprocess extensions}),
38442 @var{pid} is an integer in hexadecimal format identifying the target
38443 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38444 the query packet will be simplified as @samp{qAttached}.
38446 This query is used, for example, to know whether the remote process
38447 should be detached or killed when a @value{GDBN} session is ended with
38448 the @code{quit} command.
38453 The remote server attached to an existing process.
38455 The remote server created a new process.
38457 A badly formed request or an error was encountered.
38461 Enable branch tracing for the current thread using Branch Trace Store.
38466 Branch tracing has been enabled.
38468 A badly formed request or an error was encountered.
38472 Enable branch tracing for the current thread using Intel Processor Trace.
38477 Branch tracing has been enabled.
38479 A badly formed request or an error was encountered.
38483 Disable branch tracing for the current thread.
38488 Branch tracing has been disabled.
38490 A badly formed request or an error was encountered.
38493 @item Qbtrace-conf:bts:size=@var{value}
38494 Set the requested ring buffer size for new threads that use the
38495 btrace recording method in bts format.
38500 The ring buffer size has been set.
38502 A badly formed request or an error was encountered.
38505 @item Qbtrace-conf:pt:size=@var{value}
38506 Set the requested ring buffer size for new threads that use the
38507 btrace recording method in pt format.
38512 The ring buffer size has been set.
38514 A badly formed request or an error was encountered.
38519 @node Architecture-Specific Protocol Details
38520 @section Architecture-Specific Protocol Details
38522 This section describes how the remote protocol is applied to specific
38523 target architectures. Also see @ref{Standard Target Features}, for
38524 details of XML target descriptions for each architecture.
38527 * ARM-Specific Protocol Details::
38528 * MIPS-Specific Protocol Details::
38531 @node ARM-Specific Protocol Details
38532 @subsection @acronym{ARM}-specific Protocol Details
38535 * ARM Breakpoint Kinds::
38538 @node ARM Breakpoint Kinds
38539 @subsubsection @acronym{ARM} Breakpoint Kinds
38540 @cindex breakpoint kinds, @acronym{ARM}
38542 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38547 16-bit Thumb mode breakpoint.
38550 32-bit Thumb mode (Thumb-2) breakpoint.
38553 32-bit @acronym{ARM} mode breakpoint.
38557 @node MIPS-Specific Protocol Details
38558 @subsection @acronym{MIPS}-specific Protocol Details
38561 * MIPS Register packet Format::
38562 * MIPS Breakpoint Kinds::
38565 @node MIPS Register packet Format
38566 @subsubsection @acronym{MIPS} Register Packet Format
38567 @cindex register packet format, @acronym{MIPS}
38569 The following @code{g}/@code{G} packets have previously been defined.
38570 In the below, some thirty-two bit registers are transferred as
38571 sixty-four bits. Those registers should be zero/sign extended (which?)
38572 to fill the space allocated. Register bytes are transferred in target
38573 byte order. The two nibbles within a register byte are transferred
38574 most-significant -- least-significant.
38579 All registers are transferred as thirty-two bit quantities in the order:
38580 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38581 registers; fsr; fir; fp.
38584 All registers are transferred as sixty-four bit quantities (including
38585 thirty-two bit registers such as @code{sr}). The ordering is the same
38590 @node MIPS Breakpoint Kinds
38591 @subsubsection @acronym{MIPS} Breakpoint Kinds
38592 @cindex breakpoint kinds, @acronym{MIPS}
38594 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38599 16-bit @acronym{MIPS16} mode breakpoint.
38602 16-bit @acronym{microMIPS} mode breakpoint.
38605 32-bit standard @acronym{MIPS} mode breakpoint.
38608 32-bit @acronym{microMIPS} mode breakpoint.
38612 @node Tracepoint Packets
38613 @section Tracepoint Packets
38614 @cindex tracepoint packets
38615 @cindex packets, tracepoint
38617 Here we describe the packets @value{GDBN} uses to implement
38618 tracepoints (@pxref{Tracepoints}).
38622 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38623 @cindex @samp{QTDP} packet
38624 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38625 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38626 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38627 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38628 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38629 the number of bytes that the target should copy elsewhere to make room
38630 for the tracepoint. If an @samp{X} is present, it introduces a
38631 tracepoint condition, which consists of a hexadecimal length, followed
38632 by a comma and hex-encoded bytes, in a manner similar to action
38633 encodings as described below. If the trailing @samp{-} is present,
38634 further @samp{QTDP} packets will follow to specify this tracepoint's
38640 The packet was understood and carried out.
38642 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38644 The packet was not recognized.
38647 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38648 Define actions to be taken when a tracepoint is hit. The @var{n} and
38649 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38650 this tracepoint. This packet may only be sent immediately after
38651 another @samp{QTDP} packet that ended with a @samp{-}. If the
38652 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38653 specifying more actions for this tracepoint.
38655 In the series of action packets for a given tracepoint, at most one
38656 can have an @samp{S} before its first @var{action}. If such a packet
38657 is sent, it and the following packets define ``while-stepping''
38658 actions. Any prior packets define ordinary actions --- that is, those
38659 taken when the tracepoint is first hit. If no action packet has an
38660 @samp{S}, then all the packets in the series specify ordinary
38661 tracepoint actions.
38663 The @samp{@var{action}@dots{}} portion of the packet is a series of
38664 actions, concatenated without separators. Each action has one of the
38670 Collect the registers whose bits are set in @var{mask},
38671 a hexadecimal number whose @var{i}'th bit is set if register number
38672 @var{i} should be collected. (The least significant bit is numbered
38673 zero.) Note that @var{mask} may be any number of digits long; it may
38674 not fit in a 32-bit word.
38676 @item M @var{basereg},@var{offset},@var{len}
38677 Collect @var{len} bytes of memory starting at the address in register
38678 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38679 @samp{-1}, then the range has a fixed address: @var{offset} is the
38680 address of the lowest byte to collect. The @var{basereg},
38681 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38682 values (the @samp{-1} value for @var{basereg} is a special case).
38684 @item X @var{len},@var{expr}
38685 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38686 it directs. The agent expression @var{expr} is as described in
38687 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38688 two-digit hex number in the packet; @var{len} is the number of bytes
38689 in the expression (and thus one-half the number of hex digits in the
38694 Any number of actions may be packed together in a single @samp{QTDP}
38695 packet, as long as the packet does not exceed the maximum packet
38696 length (400 bytes, for many stubs). There may be only one @samp{R}
38697 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38698 actions. Any registers referred to by @samp{M} and @samp{X} actions
38699 must be collected by a preceding @samp{R} action. (The
38700 ``while-stepping'' actions are treated as if they were attached to a
38701 separate tracepoint, as far as these restrictions are concerned.)
38706 The packet was understood and carried out.
38708 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38710 The packet was not recognized.
38713 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38714 @cindex @samp{QTDPsrc} packet
38715 Specify a source string of tracepoint @var{n} at address @var{addr}.
38716 This is useful to get accurate reproduction of the tracepoints
38717 originally downloaded at the beginning of the trace run. The @var{type}
38718 is the name of the tracepoint part, such as @samp{cond} for the
38719 tracepoint's conditional expression (see below for a list of types), while
38720 @var{bytes} is the string, encoded in hexadecimal.
38722 @var{start} is the offset of the @var{bytes} within the overall source
38723 string, while @var{slen} is the total length of the source string.
38724 This is intended for handling source strings that are longer than will
38725 fit in a single packet.
38726 @c Add detailed example when this info is moved into a dedicated
38727 @c tracepoint descriptions section.
38729 The available string types are @samp{at} for the location,
38730 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38731 @value{GDBN} sends a separate packet for each command in the action
38732 list, in the same order in which the commands are stored in the list.
38734 The target does not need to do anything with source strings except
38735 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38738 Although this packet is optional, and @value{GDBN} will only send it
38739 if the target replies with @samp{TracepointSource} @xref{General
38740 Query Packets}, it makes both disconnected tracing and trace files
38741 much easier to use. Otherwise the user must be careful that the
38742 tracepoints in effect while looking at trace frames are identical to
38743 the ones in effect during the trace run; even a small discrepancy
38744 could cause @samp{tdump} not to work, or a particular trace frame not
38747 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38748 @cindex define trace state variable, remote request
38749 @cindex @samp{QTDV} packet
38750 Create a new trace state variable, number @var{n}, with an initial
38751 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38752 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38753 the option of not using this packet for initial values of zero; the
38754 target should simply create the trace state variables as they are
38755 mentioned in expressions. The value @var{builtin} should be 1 (one)
38756 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38757 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38758 @samp{qTsV} packet had it set. The contents of @var{name} is the
38759 hex-encoded name (without the leading @samp{$}) of the trace state
38762 @item QTFrame:@var{n}
38763 @cindex @samp{QTFrame} packet
38764 Select the @var{n}'th tracepoint frame from the buffer, and use the
38765 register and memory contents recorded there to answer subsequent
38766 request packets from @value{GDBN}.
38768 A successful reply from the stub indicates that the stub has found the
38769 requested frame. The response is a series of parts, concatenated
38770 without separators, describing the frame we selected. Each part has
38771 one of the following forms:
38775 The selected frame is number @var{n} in the trace frame buffer;
38776 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38777 was no frame matching the criteria in the request packet.
38780 The selected trace frame records a hit of tracepoint number @var{t};
38781 @var{t} is a hexadecimal number.
38785 @item QTFrame:pc:@var{addr}
38786 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38787 currently selected frame whose PC is @var{addr};
38788 @var{addr} is a hexadecimal number.
38790 @item QTFrame:tdp:@var{t}
38791 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38792 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38793 is a hexadecimal number.
38795 @item QTFrame:range:@var{start}:@var{end}
38796 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38797 currently selected frame whose PC is between @var{start} (inclusive)
38798 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38801 @item QTFrame:outside:@var{start}:@var{end}
38802 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38803 frame @emph{outside} the given range of addresses (exclusive).
38806 @cindex @samp{qTMinFTPILen} packet
38807 This packet requests the minimum length of instruction at which a fast
38808 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38809 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38810 it depends on the target system being able to create trampolines in
38811 the first 64K of memory, which might or might not be possible for that
38812 system. So the reply to this packet will be 4 if it is able to
38819 The minimum instruction length is currently unknown.
38821 The minimum instruction length is @var{length}, where @var{length}
38822 is a hexadecimal number greater or equal to 1. A reply
38823 of 1 means that a fast tracepoint may be placed on any instruction
38824 regardless of size.
38826 An error has occurred.
38828 An empty reply indicates that the request is not supported by the stub.
38832 @cindex @samp{QTStart} packet
38833 Begin the tracepoint experiment. Begin collecting data from
38834 tracepoint hits in the trace frame buffer. This packet supports the
38835 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38836 instruction reply packet}).
38839 @cindex @samp{QTStop} packet
38840 End the tracepoint experiment. Stop collecting trace frames.
38842 @item QTEnable:@var{n}:@var{addr}
38844 @cindex @samp{QTEnable} packet
38845 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38846 experiment. If the tracepoint was previously disabled, then collection
38847 of data from it will resume.
38849 @item QTDisable:@var{n}:@var{addr}
38851 @cindex @samp{QTDisable} packet
38852 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38853 experiment. No more data will be collected from the tracepoint unless
38854 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38857 @cindex @samp{QTinit} packet
38858 Clear the table of tracepoints, and empty the trace frame buffer.
38860 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38861 @cindex @samp{QTro} packet
38862 Establish the given ranges of memory as ``transparent''. The stub
38863 will answer requests for these ranges from memory's current contents,
38864 if they were not collected as part of the tracepoint hit.
38866 @value{GDBN} uses this to mark read-only regions of memory, like those
38867 containing program code. Since these areas never change, they should
38868 still have the same contents they did when the tracepoint was hit, so
38869 there's no reason for the stub to refuse to provide their contents.
38871 @item QTDisconnected:@var{value}
38872 @cindex @samp{QTDisconnected} packet
38873 Set the choice to what to do with the tracing run when @value{GDBN}
38874 disconnects from the target. A @var{value} of 1 directs the target to
38875 continue the tracing run, while 0 tells the target to stop tracing if
38876 @value{GDBN} is no longer in the picture.
38879 @cindex @samp{qTStatus} packet
38880 Ask the stub if there is a trace experiment running right now.
38882 The reply has the form:
38886 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38887 @var{running} is a single digit @code{1} if the trace is presently
38888 running, or @code{0} if not. It is followed by semicolon-separated
38889 optional fields that an agent may use to report additional status.
38893 If the trace is not running, the agent may report any of several
38894 explanations as one of the optional fields:
38899 No trace has been run yet.
38901 @item tstop[:@var{text}]:0
38902 The trace was stopped by a user-originated stop command. The optional
38903 @var{text} field is a user-supplied string supplied as part of the
38904 stop command (for instance, an explanation of why the trace was
38905 stopped manually). It is hex-encoded.
38908 The trace stopped because the trace buffer filled up.
38910 @item tdisconnected:0
38911 The trace stopped because @value{GDBN} disconnected from the target.
38913 @item tpasscount:@var{tpnum}
38914 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38916 @item terror:@var{text}:@var{tpnum}
38917 The trace stopped because tracepoint @var{tpnum} had an error. The
38918 string @var{text} is available to describe the nature of the error
38919 (for instance, a divide by zero in the condition expression); it
38923 The trace stopped for some other reason.
38927 Additional optional fields supply statistical and other information.
38928 Although not required, they are extremely useful for users monitoring
38929 the progress of a trace run. If a trace has stopped, and these
38930 numbers are reported, they must reflect the state of the just-stopped
38935 @item tframes:@var{n}
38936 The number of trace frames in the buffer.
38938 @item tcreated:@var{n}
38939 The total number of trace frames created during the run. This may
38940 be larger than the trace frame count, if the buffer is circular.
38942 @item tsize:@var{n}
38943 The total size of the trace buffer, in bytes.
38945 @item tfree:@var{n}
38946 The number of bytes still unused in the buffer.
38948 @item circular:@var{n}
38949 The value of the circular trace buffer flag. @code{1} means that the
38950 trace buffer is circular and old trace frames will be discarded if
38951 necessary to make room, @code{0} means that the trace buffer is linear
38954 @item disconn:@var{n}
38955 The value of the disconnected tracing flag. @code{1} means that
38956 tracing will continue after @value{GDBN} disconnects, @code{0} means
38957 that the trace run will stop.
38961 @item qTP:@var{tp}:@var{addr}
38962 @cindex tracepoint status, remote request
38963 @cindex @samp{qTP} packet
38964 Ask the stub for the current state of tracepoint number @var{tp} at
38965 address @var{addr}.
38969 @item V@var{hits}:@var{usage}
38970 The tracepoint has been hit @var{hits} times so far during the trace
38971 run, and accounts for @var{usage} in the trace buffer. Note that
38972 @code{while-stepping} steps are not counted as separate hits, but the
38973 steps' space consumption is added into the usage number.
38977 @item qTV:@var{var}
38978 @cindex trace state variable value, remote request
38979 @cindex @samp{qTV} packet
38980 Ask the stub for the value of the trace state variable number @var{var}.
38985 The value of the variable is @var{value}. This will be the current
38986 value of the variable if the user is examining a running target, or a
38987 saved value if the variable was collected in the trace frame that the
38988 user is looking at. Note that multiple requests may result in
38989 different reply values, such as when requesting values while the
38990 program is running.
38993 The value of the variable is unknown. This would occur, for example,
38994 if the user is examining a trace frame in which the requested variable
38999 @cindex @samp{qTfP} packet
39001 @cindex @samp{qTsP} packet
39002 These packets request data about tracepoints that are being used by
39003 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39004 of data, and multiple @code{qTsP} to get additional pieces. Replies
39005 to these packets generally take the form of the @code{QTDP} packets
39006 that define tracepoints. (FIXME add detailed syntax)
39009 @cindex @samp{qTfV} packet
39011 @cindex @samp{qTsV} packet
39012 These packets request data about trace state variables that are on the
39013 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39014 and multiple @code{qTsV} to get additional variables. Replies to
39015 these packets follow the syntax of the @code{QTDV} packets that define
39016 trace state variables.
39022 @cindex @samp{qTfSTM} packet
39023 @cindex @samp{qTsSTM} packet
39024 These packets request data about static tracepoint markers that exist
39025 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39026 first piece of data, and multiple @code{qTsSTM} to get additional
39027 pieces. Replies to these packets take the following form:
39031 @item m @var{address}:@var{id}:@var{extra}
39033 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39034 a comma-separated list of markers
39036 (lower case letter @samp{L}) denotes end of list.
39038 An error occurred. The error number @var{nn} is given as hex digits.
39040 An empty reply indicates that the request is not supported by the
39044 The @var{address} is encoded in hex;
39045 @var{id} and @var{extra} are strings encoded in hex.
39047 In response to each query, the target will reply with a list of one or
39048 more markers, separated by commas. @value{GDBN} will respond to each
39049 reply with a request for more markers (using the @samp{qs} form of the
39050 query), until the target responds with @samp{l} (lower-case ell, for
39053 @item qTSTMat:@var{address}
39055 @cindex @samp{qTSTMat} packet
39056 This packets requests data about static tracepoint markers in the
39057 target program at @var{address}. Replies to this packet follow the
39058 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39059 tracepoint markers.
39061 @item QTSave:@var{filename}
39062 @cindex @samp{QTSave} packet
39063 This packet directs the target to save trace data to the file name
39064 @var{filename} in the target's filesystem. The @var{filename} is encoded
39065 as a hex string; the interpretation of the file name (relative vs
39066 absolute, wild cards, etc) is up to the target.
39068 @item qTBuffer:@var{offset},@var{len}
39069 @cindex @samp{qTBuffer} packet
39070 Return up to @var{len} bytes of the current contents of trace buffer,
39071 starting at @var{offset}. The trace buffer is treated as if it were
39072 a contiguous collection of traceframes, as per the trace file format.
39073 The reply consists as many hex-encoded bytes as the target can deliver
39074 in a packet; it is not an error to return fewer than were asked for.
39075 A reply consisting of just @code{l} indicates that no bytes are
39078 @item QTBuffer:circular:@var{value}
39079 This packet directs the target to use a circular trace buffer if
39080 @var{value} is 1, or a linear buffer if the value is 0.
39082 @item QTBuffer:size:@var{size}
39083 @anchor{QTBuffer-size}
39084 @cindex @samp{QTBuffer size} packet
39085 This packet directs the target to make the trace buffer be of size
39086 @var{size} if possible. A value of @code{-1} tells the target to
39087 use whatever size it prefers.
39089 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39090 @cindex @samp{QTNotes} packet
39091 This packet adds optional textual notes to the trace run. Allowable
39092 types include @code{user}, @code{notes}, and @code{tstop}, the
39093 @var{text} fields are arbitrary strings, hex-encoded.
39097 @subsection Relocate instruction reply packet
39098 When installing fast tracepoints in memory, the target may need to
39099 relocate the instruction currently at the tracepoint address to a
39100 different address in memory. For most instructions, a simple copy is
39101 enough, but, for example, call instructions that implicitly push the
39102 return address on the stack, and relative branches or other
39103 PC-relative instructions require offset adjustment, so that the effect
39104 of executing the instruction at a different address is the same as if
39105 it had executed in the original location.
39107 In response to several of the tracepoint packets, the target may also
39108 respond with a number of intermediate @samp{qRelocInsn} request
39109 packets before the final result packet, to have @value{GDBN} handle
39110 this relocation operation. If a packet supports this mechanism, its
39111 documentation will explicitly say so. See for example the above
39112 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39113 format of the request is:
39116 @item qRelocInsn:@var{from};@var{to}
39118 This requests @value{GDBN} to copy instruction at address @var{from}
39119 to address @var{to}, possibly adjusted so that executing the
39120 instruction at @var{to} has the same effect as executing it at
39121 @var{from}. @value{GDBN} writes the adjusted instruction to target
39122 memory starting at @var{to}.
39127 @item qRelocInsn:@var{adjusted_size}
39128 Informs the stub the relocation is complete. The @var{adjusted_size} is
39129 the length in bytes of resulting relocated instruction sequence.
39131 A badly formed request was detected, or an error was encountered while
39132 relocating the instruction.
39135 @node Host I/O Packets
39136 @section Host I/O Packets
39137 @cindex Host I/O, remote protocol
39138 @cindex file transfer, remote protocol
39140 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39141 operations on the far side of a remote link. For example, Host I/O is
39142 used to upload and download files to a remote target with its own
39143 filesystem. Host I/O uses the same constant values and data structure
39144 layout as the target-initiated File-I/O protocol. However, the
39145 Host I/O packets are structured differently. The target-initiated
39146 protocol relies on target memory to store parameters and buffers.
39147 Host I/O requests are initiated by @value{GDBN}, and the
39148 target's memory is not involved. @xref{File-I/O Remote Protocol
39149 Extension}, for more details on the target-initiated protocol.
39151 The Host I/O request packets all encode a single operation along with
39152 its arguments. They have this format:
39156 @item vFile:@var{operation}: @var{parameter}@dots{}
39157 @var{operation} is the name of the particular request; the target
39158 should compare the entire packet name up to the second colon when checking
39159 for a supported operation. The format of @var{parameter} depends on
39160 the operation. Numbers are always passed in hexadecimal. Negative
39161 numbers have an explicit minus sign (i.e.@: two's complement is not
39162 used). Strings (e.g.@: filenames) are encoded as a series of
39163 hexadecimal bytes. The last argument to a system call may be a
39164 buffer of escaped binary data (@pxref{Binary Data}).
39168 The valid responses to Host I/O packets are:
39172 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39173 @var{result} is the integer value returned by this operation, usually
39174 non-negative for success and -1 for errors. If an error has occured,
39175 @var{errno} will be included in the result specifying a
39176 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39177 operations which return data, @var{attachment} supplies the data as a
39178 binary buffer. Binary buffers in response packets are escaped in the
39179 normal way (@pxref{Binary Data}). See the individual packet
39180 documentation for the interpretation of @var{result} and
39184 An empty response indicates that this operation is not recognized.
39188 These are the supported Host I/O operations:
39191 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39192 Open a file at @var{filename} and return a file descriptor for it, or
39193 return -1 if an error occurs. The @var{filename} is a string,
39194 @var{flags} is an integer indicating a mask of open flags
39195 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39196 of mode bits to use if the file is created (@pxref{mode_t Values}).
39197 @xref{open}, for details of the open flags and mode values.
39199 @item vFile:close: @var{fd}
39200 Close the open file corresponding to @var{fd} and return 0, or
39201 -1 if an error occurs.
39203 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39204 Read data from the open file corresponding to @var{fd}. Up to
39205 @var{count} bytes will be read from the file, starting at @var{offset}
39206 relative to the start of the file. The target may read fewer bytes;
39207 common reasons include packet size limits and an end-of-file
39208 condition. The number of bytes read is returned. Zero should only be
39209 returned for a successful read at the end of the file, or if
39210 @var{count} was zero.
39212 The data read should be returned as a binary attachment on success.
39213 If zero bytes were read, the response should include an empty binary
39214 attachment (i.e.@: a trailing semicolon). The return value is the
39215 number of target bytes read; the binary attachment may be longer if
39216 some characters were escaped.
39218 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39219 Write @var{data} (a binary buffer) to the open file corresponding
39220 to @var{fd}. Start the write at @var{offset} from the start of the
39221 file. Unlike many @code{write} system calls, there is no
39222 separate @var{count} argument; the length of @var{data} in the
39223 packet is used. @samp{vFile:write} returns the number of bytes written,
39224 which may be shorter than the length of @var{data}, or -1 if an
39227 @item vFile:fstat: @var{fd}
39228 Get information about the open file corresponding to @var{fd}.
39229 On success the information is returned as a binary attachment
39230 and the return value is the size of this attachment in bytes.
39231 If an error occurs the return value is -1. The format of the
39232 returned binary attachment is as described in @ref{struct stat}.
39234 @item vFile:unlink: @var{filename}
39235 Delete the file at @var{filename} on the target. Return 0,
39236 or -1 if an error occurs. The @var{filename} is a string.
39238 @item vFile:readlink: @var{filename}
39239 Read value of symbolic link @var{filename} on the target. Return
39240 the number of bytes read, or -1 if an error occurs.
39242 The data read should be returned as a binary attachment on success.
39243 If zero bytes were read, the response should include an empty binary
39244 attachment (i.e.@: a trailing semicolon). The return value is the
39245 number of target bytes read; the binary attachment may be longer if
39246 some characters were escaped.
39248 @item vFile:setfs: @var{pid}
39249 Select the filesystem on which @code{vFile} operations with
39250 @var{filename} arguments will operate. This is required for
39251 @value{GDBN} to be able to access files on remote targets where
39252 the remote stub does not share a common filesystem with the
39255 If @var{pid} is nonzero, select the filesystem as seen by process
39256 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39257 the remote stub. Return 0 on success, or -1 if an error occurs.
39258 If @code{vFile:setfs:} indicates success, the selected filesystem
39259 remains selected until the next successful @code{vFile:setfs:}
39265 @section Interrupts
39266 @cindex interrupts (remote protocol)
39267 @anchor{interrupting remote targets}
39269 In all-stop mode, when a program on the remote target is running,
39270 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39271 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39272 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39274 The precise meaning of @code{BREAK} is defined by the transport
39275 mechanism and may, in fact, be undefined. @value{GDBN} does not
39276 currently define a @code{BREAK} mechanism for any of the network
39277 interfaces except for TCP, in which case @value{GDBN} sends the
39278 @code{telnet} BREAK sequence.
39280 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39281 transport mechanisms. It is represented by sending the single byte
39282 @code{0x03} without any of the usual packet overhead described in
39283 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39284 transmitted as part of a packet, it is considered to be packet data
39285 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39286 (@pxref{X packet}), used for binary downloads, may include an unescaped
39287 @code{0x03} as part of its packet.
39289 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39290 When Linux kernel receives this sequence from serial port,
39291 it stops execution and connects to gdb.
39293 In non-stop mode, because packet resumptions are asynchronous
39294 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39295 command to the remote stub, even when the target is running. For that
39296 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39297 packet}) with the usual packet framing instead of the single byte
39300 Stubs are not required to recognize these interrupt mechanisms and the
39301 precise meaning associated with receipt of the interrupt is
39302 implementation defined. If the target supports debugging of multiple
39303 threads and/or processes, it should attempt to interrupt all
39304 currently-executing threads and processes.
39305 If the stub is successful at interrupting the
39306 running program, it should send one of the stop
39307 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39308 of successfully stopping the program in all-stop mode, and a stop reply
39309 for each stopped thread in non-stop mode.
39310 Interrupts received while the
39311 program is stopped are queued and the program will be interrupted when
39312 it is resumed next time.
39314 @node Notification Packets
39315 @section Notification Packets
39316 @cindex notification packets
39317 @cindex packets, notification
39319 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39320 packets that require no acknowledgment. Both the GDB and the stub
39321 may send notifications (although the only notifications defined at
39322 present are sent by the stub). Notifications carry information
39323 without incurring the round-trip latency of an acknowledgment, and so
39324 are useful for low-impact communications where occasional packet loss
39327 A notification packet has the form @samp{% @var{data} #
39328 @var{checksum}}, where @var{data} is the content of the notification,
39329 and @var{checksum} is a checksum of @var{data}, computed and formatted
39330 as for ordinary @value{GDBN} packets. A notification's @var{data}
39331 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39332 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39333 to acknowledge the notification's receipt or to report its corruption.
39335 Every notification's @var{data} begins with a name, which contains no
39336 colon characters, followed by a colon character.
39338 Recipients should silently ignore corrupted notifications and
39339 notifications they do not understand. Recipients should restart
39340 timeout periods on receipt of a well-formed notification, whether or
39341 not they understand it.
39343 Senders should only send the notifications described here when this
39344 protocol description specifies that they are permitted. In the
39345 future, we may extend the protocol to permit existing notifications in
39346 new contexts; this rule helps older senders avoid confusing newer
39349 (Older versions of @value{GDBN} ignore bytes received until they see
39350 the @samp{$} byte that begins an ordinary packet, so new stubs may
39351 transmit notifications without fear of confusing older clients. There
39352 are no notifications defined for @value{GDBN} to send at the moment, but we
39353 assume that most older stubs would ignore them, as well.)
39355 Each notification is comprised of three parts:
39357 @item @var{name}:@var{event}
39358 The notification packet is sent by the side that initiates the
39359 exchange (currently, only the stub does that), with @var{event}
39360 carrying the specific information about the notification, and
39361 @var{name} specifying the name of the notification.
39363 The acknowledge sent by the other side, usually @value{GDBN}, to
39364 acknowledge the exchange and request the event.
39367 The purpose of an asynchronous notification mechanism is to report to
39368 @value{GDBN} that something interesting happened in the remote stub.
39370 The remote stub may send notification @var{name}:@var{event}
39371 at any time, but @value{GDBN} acknowledges the notification when
39372 appropriate. The notification event is pending before @value{GDBN}
39373 acknowledges. Only one notification at a time may be pending; if
39374 additional events occur before @value{GDBN} has acknowledged the
39375 previous notification, they must be queued by the stub for later
39376 synchronous transmission in response to @var{ack} packets from
39377 @value{GDBN}. Because the notification mechanism is unreliable,
39378 the stub is permitted to resend a notification if it believes
39379 @value{GDBN} may not have received it.
39381 Specifically, notifications may appear when @value{GDBN} is not
39382 otherwise reading input from the stub, or when @value{GDBN} is
39383 expecting to read a normal synchronous response or a
39384 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39385 Notification packets are distinct from any other communication from
39386 the stub so there is no ambiguity.
39388 After receiving a notification, @value{GDBN} shall acknowledge it by
39389 sending a @var{ack} packet as a regular, synchronous request to the
39390 stub. Such acknowledgment is not required to happen immediately, as
39391 @value{GDBN} is permitted to send other, unrelated packets to the
39392 stub first, which the stub should process normally.
39394 Upon receiving a @var{ack} packet, if the stub has other queued
39395 events to report to @value{GDBN}, it shall respond by sending a
39396 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39397 packet to solicit further responses; again, it is permitted to send
39398 other, unrelated packets as well which the stub should process
39401 If the stub receives a @var{ack} packet and there are no additional
39402 @var{event} to report, the stub shall return an @samp{OK} response.
39403 At this point, @value{GDBN} has finished processing a notification
39404 and the stub has completed sending any queued events. @value{GDBN}
39405 won't accept any new notifications until the final @samp{OK} is
39406 received . If further notification events occur, the stub shall send
39407 a new notification, @value{GDBN} shall accept the notification, and
39408 the process shall be repeated.
39410 The process of asynchronous notification can be illustrated by the
39413 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39416 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39418 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39423 The following notifications are defined:
39424 @multitable @columnfractions 0.12 0.12 0.38 0.38
39433 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39434 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39435 for information on how these notifications are acknowledged by
39437 @tab Report an asynchronous stop event in non-stop mode.
39441 @node Remote Non-Stop
39442 @section Remote Protocol Support for Non-Stop Mode
39444 @value{GDBN}'s remote protocol supports non-stop debugging of
39445 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39446 supports non-stop mode, it should report that to @value{GDBN} by including
39447 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39449 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39450 establishing a new connection with the stub. Entering non-stop mode
39451 does not alter the state of any currently-running threads, but targets
39452 must stop all threads in any already-attached processes when entering
39453 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39454 probe the target state after a mode change.
39456 In non-stop mode, when an attached process encounters an event that
39457 would otherwise be reported with a stop reply, it uses the
39458 asynchronous notification mechanism (@pxref{Notification Packets}) to
39459 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39460 in all processes are stopped when a stop reply is sent, in non-stop
39461 mode only the thread reporting the stop event is stopped. That is,
39462 when reporting a @samp{S} or @samp{T} response to indicate completion
39463 of a step operation, hitting a breakpoint, or a fault, only the
39464 affected thread is stopped; any other still-running threads continue
39465 to run. When reporting a @samp{W} or @samp{X} response, all running
39466 threads belonging to other attached processes continue to run.
39468 In non-stop mode, the target shall respond to the @samp{?} packet as
39469 follows. First, any incomplete stop reply notification/@samp{vStopped}
39470 sequence in progress is abandoned. The target must begin a new
39471 sequence reporting stop events for all stopped threads, whether or not
39472 it has previously reported those events to @value{GDBN}. The first
39473 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39474 subsequent stop replies are sent as responses to @samp{vStopped} packets
39475 using the mechanism described above. The target must not send
39476 asynchronous stop reply notifications until the sequence is complete.
39477 If all threads are running when the target receives the @samp{?} packet,
39478 or if the target is not attached to any process, it shall respond
39481 If the stub supports non-stop mode, it should also support the
39482 @samp{swbreak} stop reason if software breakpoints are supported, and
39483 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39484 (@pxref{swbreak stop reason}). This is because given the asynchronous
39485 nature of non-stop mode, between the time a thread hits a breakpoint
39486 and the time the event is finally processed by @value{GDBN}, the
39487 breakpoint may have already been removed from the target. Due to
39488 this, @value{GDBN} needs to be able to tell whether a trap stop was
39489 caused by a delayed breakpoint event, which should be ignored, as
39490 opposed to a random trap signal, which should be reported to the user.
39491 Note the @samp{swbreak} feature implies that the target is responsible
39492 for adjusting the PC when a software breakpoint triggers, if
39493 necessary, such as on the x86 architecture.
39495 @node Packet Acknowledgment
39496 @section Packet Acknowledgment
39498 @cindex acknowledgment, for @value{GDBN} remote
39499 @cindex packet acknowledgment, for @value{GDBN} remote
39500 By default, when either the host or the target machine receives a packet,
39501 the first response expected is an acknowledgment: either @samp{+} (to indicate
39502 the package was received correctly) or @samp{-} (to request retransmission).
39503 This mechanism allows the @value{GDBN} remote protocol to operate over
39504 unreliable transport mechanisms, such as a serial line.
39506 In cases where the transport mechanism is itself reliable (such as a pipe or
39507 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39508 It may be desirable to disable them in that case to reduce communication
39509 overhead, or for other reasons. This can be accomplished by means of the
39510 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39512 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39513 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39514 and response format still includes the normal checksum, as described in
39515 @ref{Overview}, but the checksum may be ignored by the receiver.
39517 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39518 no-acknowledgment mode, it should report that to @value{GDBN}
39519 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39520 @pxref{qSupported}.
39521 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39522 disabled via the @code{set remote noack-packet off} command
39523 (@pxref{Remote Configuration}),
39524 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39525 Only then may the stub actually turn off packet acknowledgments.
39526 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39527 response, which can be safely ignored by the stub.
39529 Note that @code{set remote noack-packet} command only affects negotiation
39530 between @value{GDBN} and the stub when subsequent connections are made;
39531 it does not affect the protocol acknowledgment state for any current
39533 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39534 new connection is established,
39535 there is also no protocol request to re-enable the acknowledgments
39536 for the current connection, once disabled.
39541 Example sequence of a target being re-started. Notice how the restart
39542 does not get any direct output:
39547 @emph{target restarts}
39550 <- @code{T001:1234123412341234}
39554 Example sequence of a target being stepped by a single instruction:
39557 -> @code{G1445@dots{}}
39562 <- @code{T001:1234123412341234}
39566 <- @code{1455@dots{}}
39570 @node File-I/O Remote Protocol Extension
39571 @section File-I/O Remote Protocol Extension
39572 @cindex File-I/O remote protocol extension
39575 * File-I/O Overview::
39576 * Protocol Basics::
39577 * The F Request Packet::
39578 * The F Reply Packet::
39579 * The Ctrl-C Message::
39581 * List of Supported Calls::
39582 * Protocol-specific Representation of Datatypes::
39584 * File-I/O Examples::
39587 @node File-I/O Overview
39588 @subsection File-I/O Overview
39589 @cindex file-i/o overview
39591 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39592 target to use the host's file system and console I/O to perform various
39593 system calls. System calls on the target system are translated into a
39594 remote protocol packet to the host system, which then performs the needed
39595 actions and returns a response packet to the target system.
39596 This simulates file system operations even on targets that lack file systems.
39598 The protocol is defined to be independent of both the host and target systems.
39599 It uses its own internal representation of datatypes and values. Both
39600 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39601 translating the system-dependent value representations into the internal
39602 protocol representations when data is transmitted.
39604 The communication is synchronous. A system call is possible only when
39605 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39606 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39607 the target is stopped to allow deterministic access to the target's
39608 memory. Therefore File-I/O is not interruptible by target signals. On
39609 the other hand, it is possible to interrupt File-I/O by a user interrupt
39610 (@samp{Ctrl-C}) within @value{GDBN}.
39612 The target's request to perform a host system call does not finish
39613 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39614 after finishing the system call, the target returns to continuing the
39615 previous activity (continue, step). No additional continue or step
39616 request from @value{GDBN} is required.
39619 (@value{GDBP}) continue
39620 <- target requests 'system call X'
39621 target is stopped, @value{GDBN} executes system call
39622 -> @value{GDBN} returns result
39623 ... target continues, @value{GDBN} returns to wait for the target
39624 <- target hits breakpoint and sends a Txx packet
39627 The protocol only supports I/O on the console and to regular files on
39628 the host file system. Character or block special devices, pipes,
39629 named pipes, sockets or any other communication method on the host
39630 system are not supported by this protocol.
39632 File I/O is not supported in non-stop mode.
39634 @node Protocol Basics
39635 @subsection Protocol Basics
39636 @cindex protocol basics, file-i/o
39638 The File-I/O protocol uses the @code{F} packet as the request as well
39639 as reply packet. Since a File-I/O system call can only occur when
39640 @value{GDBN} is waiting for a response from the continuing or stepping target,
39641 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39642 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39643 This @code{F} packet contains all information needed to allow @value{GDBN}
39644 to call the appropriate host system call:
39648 A unique identifier for the requested system call.
39651 All parameters to the system call. Pointers are given as addresses
39652 in the target memory address space. Pointers to strings are given as
39653 pointer/length pair. Numerical values are given as they are.
39654 Numerical control flags are given in a protocol-specific representation.
39658 At this point, @value{GDBN} has to perform the following actions.
39662 If the parameters include pointer values to data needed as input to a
39663 system call, @value{GDBN} requests this data from the target with a
39664 standard @code{m} packet request. This additional communication has to be
39665 expected by the target implementation and is handled as any other @code{m}
39669 @value{GDBN} translates all value from protocol representation to host
39670 representation as needed. Datatypes are coerced into the host types.
39673 @value{GDBN} calls the system call.
39676 It then coerces datatypes back to protocol representation.
39679 If the system call is expected to return data in buffer space specified
39680 by pointer parameters to the call, the data is transmitted to the
39681 target using a @code{M} or @code{X} packet. This packet has to be expected
39682 by the target implementation and is handled as any other @code{M} or @code{X}
39687 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39688 necessary information for the target to continue. This at least contains
39695 @code{errno}, if has been changed by the system call.
39702 After having done the needed type and value coercion, the target continues
39703 the latest continue or step action.
39705 @node The F Request Packet
39706 @subsection The @code{F} Request Packet
39707 @cindex file-i/o request packet
39708 @cindex @code{F} request packet
39710 The @code{F} request packet has the following format:
39713 @item F@var{call-id},@var{parameter@dots{}}
39715 @var{call-id} is the identifier to indicate the host system call to be called.
39716 This is just the name of the function.
39718 @var{parameter@dots{}} are the parameters to the system call.
39719 Parameters are hexadecimal integer values, either the actual values in case
39720 of scalar datatypes, pointers to target buffer space in case of compound
39721 datatypes and unspecified memory areas, or pointer/length pairs in case
39722 of string parameters. These are appended to the @var{call-id} as a
39723 comma-delimited list. All values are transmitted in ASCII
39724 string representation, pointer/length pairs separated by a slash.
39730 @node The F Reply Packet
39731 @subsection The @code{F} Reply Packet
39732 @cindex file-i/o reply packet
39733 @cindex @code{F} reply packet
39735 The @code{F} reply packet has the following format:
39739 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39741 @var{retcode} is the return code of the system call as hexadecimal value.
39743 @var{errno} is the @code{errno} set by the call, in protocol-specific
39745 This parameter can be omitted if the call was successful.
39747 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39748 case, @var{errno} must be sent as well, even if the call was successful.
39749 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39756 or, if the call was interrupted before the host call has been performed:
39763 assuming 4 is the protocol-specific representation of @code{EINTR}.
39768 @node The Ctrl-C Message
39769 @subsection The @samp{Ctrl-C} Message
39770 @cindex ctrl-c message, in file-i/o protocol
39772 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39773 reply packet (@pxref{The F Reply Packet}),
39774 the target should behave as if it had
39775 gotten a break message. The meaning for the target is ``system call
39776 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39777 (as with a break message) and return to @value{GDBN} with a @code{T02}
39780 It's important for the target to know in which
39781 state the system call was interrupted. There are two possible cases:
39785 The system call hasn't been performed on the host yet.
39788 The system call on the host has been finished.
39792 These two states can be distinguished by the target by the value of the
39793 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39794 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39795 on POSIX systems. In any other case, the target may presume that the
39796 system call has been finished --- successfully or not --- and should behave
39797 as if the break message arrived right after the system call.
39799 @value{GDBN} must behave reliably. If the system call has not been called
39800 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39801 @code{errno} in the packet. If the system call on the host has been finished
39802 before the user requests a break, the full action must be finished by
39803 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39804 The @code{F} packet may only be sent when either nothing has happened
39805 or the full action has been completed.
39808 @subsection Console I/O
39809 @cindex console i/o as part of file-i/o
39811 By default and if not explicitly closed by the target system, the file
39812 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39813 on the @value{GDBN} console is handled as any other file output operation
39814 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39815 by @value{GDBN} so that after the target read request from file descriptor
39816 0 all following typing is buffered until either one of the following
39821 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39823 system call is treated as finished.
39826 The user presses @key{RET}. This is treated as end of input with a trailing
39830 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39831 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39835 If the user has typed more characters than fit in the buffer given to
39836 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39837 either another @code{read(0, @dots{})} is requested by the target, or debugging
39838 is stopped at the user's request.
39841 @node List of Supported Calls
39842 @subsection List of Supported Calls
39843 @cindex list of supported file-i/o calls
39860 @unnumberedsubsubsec open
39861 @cindex open, file-i/o system call
39866 int open(const char *pathname, int flags);
39867 int open(const char *pathname, int flags, mode_t mode);
39871 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39874 @var{flags} is the bitwise @code{OR} of the following values:
39878 If the file does not exist it will be created. The host
39879 rules apply as far as file ownership and time stamps
39883 When used with @code{O_CREAT}, if the file already exists it is
39884 an error and open() fails.
39887 If the file already exists and the open mode allows
39888 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39889 truncated to zero length.
39892 The file is opened in append mode.
39895 The file is opened for reading only.
39898 The file is opened for writing only.
39901 The file is opened for reading and writing.
39905 Other bits are silently ignored.
39909 @var{mode} is the bitwise @code{OR} of the following values:
39913 User has read permission.
39916 User has write permission.
39919 Group has read permission.
39922 Group has write permission.
39925 Others have read permission.
39928 Others have write permission.
39932 Other bits are silently ignored.
39935 @item Return value:
39936 @code{open} returns the new file descriptor or -1 if an error
39943 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39946 @var{pathname} refers to a directory.
39949 The requested access is not allowed.
39952 @var{pathname} was too long.
39955 A directory component in @var{pathname} does not exist.
39958 @var{pathname} refers to a device, pipe, named pipe or socket.
39961 @var{pathname} refers to a file on a read-only filesystem and
39962 write access was requested.
39965 @var{pathname} is an invalid pointer value.
39968 No space on device to create the file.
39971 The process already has the maximum number of files open.
39974 The limit on the total number of files open on the system
39978 The call was interrupted by the user.
39984 @unnumberedsubsubsec close
39985 @cindex close, file-i/o system call
39994 @samp{Fclose,@var{fd}}
39996 @item Return value:
39997 @code{close} returns zero on success, or -1 if an error occurred.
40003 @var{fd} isn't a valid open file descriptor.
40006 The call was interrupted by the user.
40012 @unnumberedsubsubsec read
40013 @cindex read, file-i/o system call
40018 int read(int fd, void *buf, unsigned int count);
40022 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40024 @item Return value:
40025 On success, the number of bytes read is returned.
40026 Zero indicates end of file. If count is zero, read
40027 returns zero as well. On error, -1 is returned.
40033 @var{fd} is not a valid file descriptor or is not open for
40037 @var{bufptr} is an invalid pointer value.
40040 The call was interrupted by the user.
40046 @unnumberedsubsubsec write
40047 @cindex write, file-i/o system call
40052 int write(int fd, const void *buf, unsigned int count);
40056 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40058 @item Return value:
40059 On success, the number of bytes written are returned.
40060 Zero indicates nothing was written. On error, -1
40067 @var{fd} is not a valid file descriptor or is not open for
40071 @var{bufptr} is an invalid pointer value.
40074 An attempt was made to write a file that exceeds the
40075 host-specific maximum file size allowed.
40078 No space on device to write the data.
40081 The call was interrupted by the user.
40087 @unnumberedsubsubsec lseek
40088 @cindex lseek, file-i/o system call
40093 long lseek (int fd, long offset, int flag);
40097 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40099 @var{flag} is one of:
40103 The offset is set to @var{offset} bytes.
40106 The offset is set to its current location plus @var{offset}
40110 The offset is set to the size of the file plus @var{offset}
40114 @item Return value:
40115 On success, the resulting unsigned offset in bytes from
40116 the beginning of the file is returned. Otherwise, a
40117 value of -1 is returned.
40123 @var{fd} is not a valid open file descriptor.
40126 @var{fd} is associated with the @value{GDBN} console.
40129 @var{flag} is not a proper value.
40132 The call was interrupted by the user.
40138 @unnumberedsubsubsec rename
40139 @cindex rename, file-i/o system call
40144 int rename(const char *oldpath, const char *newpath);
40148 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40150 @item Return value:
40151 On success, zero is returned. On error, -1 is returned.
40157 @var{newpath} is an existing directory, but @var{oldpath} is not a
40161 @var{newpath} is a non-empty directory.
40164 @var{oldpath} or @var{newpath} is a directory that is in use by some
40168 An attempt was made to make a directory a subdirectory
40172 A component used as a directory in @var{oldpath} or new
40173 path is not a directory. Or @var{oldpath} is a directory
40174 and @var{newpath} exists but is not a directory.
40177 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40180 No access to the file or the path of the file.
40184 @var{oldpath} or @var{newpath} was too long.
40187 A directory component in @var{oldpath} or @var{newpath} does not exist.
40190 The file is on a read-only filesystem.
40193 The device containing the file has no room for the new
40197 The call was interrupted by the user.
40203 @unnumberedsubsubsec unlink
40204 @cindex unlink, file-i/o system call
40209 int unlink(const char *pathname);
40213 @samp{Funlink,@var{pathnameptr}/@var{len}}
40215 @item Return value:
40216 On success, zero is returned. On error, -1 is returned.
40222 No access to the file or the path of the file.
40225 The system does not allow unlinking of directories.
40228 The file @var{pathname} cannot be unlinked because it's
40229 being used by another process.
40232 @var{pathnameptr} is an invalid pointer value.
40235 @var{pathname} was too long.
40238 A directory component in @var{pathname} does not exist.
40241 A component of the path is not a directory.
40244 The file is on a read-only filesystem.
40247 The call was interrupted by the user.
40253 @unnumberedsubsubsec stat/fstat
40254 @cindex fstat, file-i/o system call
40255 @cindex stat, file-i/o system call
40260 int stat(const char *pathname, struct stat *buf);
40261 int fstat(int fd, struct stat *buf);
40265 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40266 @samp{Ffstat,@var{fd},@var{bufptr}}
40268 @item Return value:
40269 On success, zero is returned. On error, -1 is returned.
40275 @var{fd} is not a valid open file.
40278 A directory component in @var{pathname} does not exist or the
40279 path is an empty string.
40282 A component of the path is not a directory.
40285 @var{pathnameptr} is an invalid pointer value.
40288 No access to the file or the path of the file.
40291 @var{pathname} was too long.
40294 The call was interrupted by the user.
40300 @unnumberedsubsubsec gettimeofday
40301 @cindex gettimeofday, file-i/o system call
40306 int gettimeofday(struct timeval *tv, void *tz);
40310 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40312 @item Return value:
40313 On success, 0 is returned, -1 otherwise.
40319 @var{tz} is a non-NULL pointer.
40322 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40328 @unnumberedsubsubsec isatty
40329 @cindex isatty, file-i/o system call
40334 int isatty(int fd);
40338 @samp{Fisatty,@var{fd}}
40340 @item Return value:
40341 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40347 The call was interrupted by the user.
40352 Note that the @code{isatty} call is treated as a special case: it returns
40353 1 to the target if the file descriptor is attached
40354 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40355 would require implementing @code{ioctl} and would be more complex than
40360 @unnumberedsubsubsec system
40361 @cindex system, file-i/o system call
40366 int system(const char *command);
40370 @samp{Fsystem,@var{commandptr}/@var{len}}
40372 @item Return value:
40373 If @var{len} is zero, the return value indicates whether a shell is
40374 available. A zero return value indicates a shell is not available.
40375 For non-zero @var{len}, the value returned is -1 on error and the
40376 return status of the command otherwise. Only the exit status of the
40377 command is returned, which is extracted from the host's @code{system}
40378 return value by calling @code{WEXITSTATUS(retval)}. In case
40379 @file{/bin/sh} could not be executed, 127 is returned.
40385 The call was interrupted by the user.
40390 @value{GDBN} takes over the full task of calling the necessary host calls
40391 to perform the @code{system} call. The return value of @code{system} on
40392 the host is simplified before it's returned
40393 to the target. Any termination signal information from the child process
40394 is discarded, and the return value consists
40395 entirely of the exit status of the called command.
40397 Due to security concerns, the @code{system} call is by default refused
40398 by @value{GDBN}. The user has to allow this call explicitly with the
40399 @code{set remote system-call-allowed 1} command.
40402 @item set remote system-call-allowed
40403 @kindex set remote system-call-allowed
40404 Control whether to allow the @code{system} calls in the File I/O
40405 protocol for the remote target. The default is zero (disabled).
40407 @item show remote system-call-allowed
40408 @kindex show remote system-call-allowed
40409 Show whether the @code{system} calls are allowed in the File I/O
40413 @node Protocol-specific Representation of Datatypes
40414 @subsection Protocol-specific Representation of Datatypes
40415 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40418 * Integral Datatypes::
40420 * Memory Transfer::
40425 @node Integral Datatypes
40426 @unnumberedsubsubsec Integral Datatypes
40427 @cindex integral datatypes, in file-i/o protocol
40429 The integral datatypes used in the system calls are @code{int},
40430 @code{unsigned int}, @code{long}, @code{unsigned long},
40431 @code{mode_t}, and @code{time_t}.
40433 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40434 implemented as 32 bit values in this protocol.
40436 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40438 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40439 in @file{limits.h}) to allow range checking on host and target.
40441 @code{time_t} datatypes are defined as seconds since the Epoch.
40443 All integral datatypes transferred as part of a memory read or write of a
40444 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40447 @node Pointer Values
40448 @unnumberedsubsubsec Pointer Values
40449 @cindex pointer values, in file-i/o protocol
40451 Pointers to target data are transmitted as they are. An exception
40452 is made for pointers to buffers for which the length isn't
40453 transmitted as part of the function call, namely strings. Strings
40454 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40461 which is a pointer to data of length 18 bytes at position 0x1aaf.
40462 The length is defined as the full string length in bytes, including
40463 the trailing null byte. For example, the string @code{"hello world"}
40464 at address 0x123456 is transmitted as
40470 @node Memory Transfer
40471 @unnumberedsubsubsec Memory Transfer
40472 @cindex memory transfer, in file-i/o protocol
40474 Structured data which is transferred using a memory read or write (for
40475 example, a @code{struct stat}) is expected to be in a protocol-specific format
40476 with all scalar multibyte datatypes being big endian. Translation to
40477 this representation needs to be done both by the target before the @code{F}
40478 packet is sent, and by @value{GDBN} before
40479 it transfers memory to the target. Transferred pointers to structured
40480 data should point to the already-coerced data at any time.
40484 @unnumberedsubsubsec struct stat
40485 @cindex struct stat, in file-i/o protocol
40487 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40488 is defined as follows:
40492 unsigned int st_dev; /* device */
40493 unsigned int st_ino; /* inode */
40494 mode_t st_mode; /* protection */
40495 unsigned int st_nlink; /* number of hard links */
40496 unsigned int st_uid; /* user ID of owner */
40497 unsigned int st_gid; /* group ID of owner */
40498 unsigned int st_rdev; /* device type (if inode device) */
40499 unsigned long st_size; /* total size, in bytes */
40500 unsigned long st_blksize; /* blocksize for filesystem I/O */
40501 unsigned long st_blocks; /* number of blocks allocated */
40502 time_t st_atime; /* time of last access */
40503 time_t st_mtime; /* time of last modification */
40504 time_t st_ctime; /* time of last change */
40508 The integral datatypes conform to the definitions given in the
40509 appropriate section (see @ref{Integral Datatypes}, for details) so this
40510 structure is of size 64 bytes.
40512 The values of several fields have a restricted meaning and/or
40518 A value of 0 represents a file, 1 the console.
40521 No valid meaning for the target. Transmitted unchanged.
40524 Valid mode bits are described in @ref{Constants}. Any other
40525 bits have currently no meaning for the target.
40530 No valid meaning for the target. Transmitted unchanged.
40535 These values have a host and file system dependent
40536 accuracy. Especially on Windows hosts, the file system may not
40537 support exact timing values.
40540 The target gets a @code{struct stat} of the above representation and is
40541 responsible for coercing it to the target representation before
40544 Note that due to size differences between the host, target, and protocol
40545 representations of @code{struct stat} members, these members could eventually
40546 get truncated on the target.
40548 @node struct timeval
40549 @unnumberedsubsubsec struct timeval
40550 @cindex struct timeval, in file-i/o protocol
40552 The buffer of type @code{struct timeval} used by the File-I/O protocol
40553 is defined as follows:
40557 time_t tv_sec; /* second */
40558 long tv_usec; /* microsecond */
40562 The integral datatypes conform to the definitions given in the
40563 appropriate section (see @ref{Integral Datatypes}, for details) so this
40564 structure is of size 8 bytes.
40567 @subsection Constants
40568 @cindex constants, in file-i/o protocol
40570 The following values are used for the constants inside of the
40571 protocol. @value{GDBN} and target are responsible for translating these
40572 values before and after the call as needed.
40583 @unnumberedsubsubsec Open Flags
40584 @cindex open flags, in file-i/o protocol
40586 All values are given in hexadecimal representation.
40598 @node mode_t Values
40599 @unnumberedsubsubsec mode_t Values
40600 @cindex mode_t values, in file-i/o protocol
40602 All values are given in octal representation.
40619 @unnumberedsubsubsec Errno Values
40620 @cindex errno values, in file-i/o protocol
40622 All values are given in decimal representation.
40647 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40648 any error value not in the list of supported error numbers.
40651 @unnumberedsubsubsec Lseek Flags
40652 @cindex lseek flags, in file-i/o protocol
40661 @unnumberedsubsubsec Limits
40662 @cindex limits, in file-i/o protocol
40664 All values are given in decimal representation.
40667 INT_MIN -2147483648
40669 UINT_MAX 4294967295
40670 LONG_MIN -9223372036854775808
40671 LONG_MAX 9223372036854775807
40672 ULONG_MAX 18446744073709551615
40675 @node File-I/O Examples
40676 @subsection File-I/O Examples
40677 @cindex file-i/o examples
40679 Example sequence of a write call, file descriptor 3, buffer is at target
40680 address 0x1234, 6 bytes should be written:
40683 <- @code{Fwrite,3,1234,6}
40684 @emph{request memory read from target}
40687 @emph{return "6 bytes written"}
40691 Example sequence of a read call, file descriptor 3, buffer is at target
40692 address 0x1234, 6 bytes should be read:
40695 <- @code{Fread,3,1234,6}
40696 @emph{request memory write to target}
40697 -> @code{X1234,6:XXXXXX}
40698 @emph{return "6 bytes read"}
40702 Example sequence of a read call, call fails on the host due to invalid
40703 file descriptor (@code{EBADF}):
40706 <- @code{Fread,3,1234,6}
40710 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40714 <- @code{Fread,3,1234,6}
40719 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40723 <- @code{Fread,3,1234,6}
40724 -> @code{X1234,6:XXXXXX}
40728 @node Library List Format
40729 @section Library List Format
40730 @cindex library list format, remote protocol
40732 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40733 same process as your application to manage libraries. In this case,
40734 @value{GDBN} can use the loader's symbol table and normal memory
40735 operations to maintain a list of shared libraries. On other
40736 platforms, the operating system manages loaded libraries.
40737 @value{GDBN} can not retrieve the list of currently loaded libraries
40738 through memory operations, so it uses the @samp{qXfer:libraries:read}
40739 packet (@pxref{qXfer library list read}) instead. The remote stub
40740 queries the target's operating system and reports which libraries
40743 The @samp{qXfer:libraries:read} packet returns an XML document which
40744 lists loaded libraries and their offsets. Each library has an
40745 associated name and one or more segment or section base addresses,
40746 which report where the library was loaded in memory.
40748 For the common case of libraries that are fully linked binaries, the
40749 library should have a list of segments. If the target supports
40750 dynamic linking of a relocatable object file, its library XML element
40751 should instead include a list of allocated sections. The segment or
40752 section bases are start addresses, not relocation offsets; they do not
40753 depend on the library's link-time base addresses.
40755 @value{GDBN} must be linked with the Expat library to support XML
40756 library lists. @xref{Expat}.
40758 A simple memory map, with one loaded library relocated by a single
40759 offset, looks like this:
40763 <library name="/lib/libc.so.6">
40764 <segment address="0x10000000"/>
40769 Another simple memory map, with one loaded library with three
40770 allocated sections (.text, .data, .bss), looks like this:
40774 <library name="sharedlib.o">
40775 <section address="0x10000000"/>
40776 <section address="0x20000000"/>
40777 <section address="0x30000000"/>
40782 The format of a library list is described by this DTD:
40785 <!-- library-list: Root element with versioning -->
40786 <!ELEMENT library-list (library)*>
40787 <!ATTLIST library-list version CDATA #FIXED "1.0">
40788 <!ELEMENT library (segment*, section*)>
40789 <!ATTLIST library name CDATA #REQUIRED>
40790 <!ELEMENT segment EMPTY>
40791 <!ATTLIST segment address CDATA #REQUIRED>
40792 <!ELEMENT section EMPTY>
40793 <!ATTLIST section address CDATA #REQUIRED>
40796 In addition, segments and section descriptors cannot be mixed within a
40797 single library element, and you must supply at least one segment or
40798 section for each library.
40800 @node Library List Format for SVR4 Targets
40801 @section Library List Format for SVR4 Targets
40802 @cindex library list format, remote protocol
40804 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40805 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40806 shared libraries. Still a special library list provided by this packet is
40807 more efficient for the @value{GDBN} remote protocol.
40809 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40810 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40811 target, the following parameters are reported:
40815 @code{name}, the absolute file name from the @code{l_name} field of
40816 @code{struct link_map}.
40818 @code{lm} with address of @code{struct link_map} used for TLS
40819 (Thread Local Storage) access.
40821 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40822 @code{struct link_map}. For prelinked libraries this is not an absolute
40823 memory address. It is a displacement of absolute memory address against
40824 address the file was prelinked to during the library load.
40826 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40829 Additionally the single @code{main-lm} attribute specifies address of
40830 @code{struct link_map} used for the main executable. This parameter is used
40831 for TLS access and its presence is optional.
40833 @value{GDBN} must be linked with the Expat library to support XML
40834 SVR4 library lists. @xref{Expat}.
40836 A simple memory map, with two loaded libraries (which do not use prelink),
40840 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40841 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40843 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40845 </library-list-svr>
40848 The format of an SVR4 library list is described by this DTD:
40851 <!-- library-list-svr4: Root element with versioning -->
40852 <!ELEMENT library-list-svr4 (library)*>
40853 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40854 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40855 <!ELEMENT library EMPTY>
40856 <!ATTLIST library name CDATA #REQUIRED>
40857 <!ATTLIST library lm CDATA #REQUIRED>
40858 <!ATTLIST library l_addr CDATA #REQUIRED>
40859 <!ATTLIST library l_ld CDATA #REQUIRED>
40862 @node Memory Map Format
40863 @section Memory Map Format
40864 @cindex memory map format
40866 To be able to write into flash memory, @value{GDBN} needs to obtain a
40867 memory map from the target. This section describes the format of the
40870 The memory map is obtained using the @samp{qXfer:memory-map:read}
40871 (@pxref{qXfer memory map read}) packet and is an XML document that
40872 lists memory regions.
40874 @value{GDBN} must be linked with the Expat library to support XML
40875 memory maps. @xref{Expat}.
40877 The top-level structure of the document is shown below:
40880 <?xml version="1.0"?>
40881 <!DOCTYPE memory-map
40882 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40883 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40889 Each region can be either:
40894 A region of RAM starting at @var{addr} and extending for @var{length}
40898 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40903 A region of read-only memory:
40906 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40911 A region of flash memory, with erasure blocks @var{blocksize}
40915 <memory type="flash" start="@var{addr}" length="@var{length}">
40916 <property name="blocksize">@var{blocksize}</property>
40922 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40923 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40924 packets to write to addresses in such ranges.
40926 The formal DTD for memory map format is given below:
40929 <!-- ................................................... -->
40930 <!-- Memory Map XML DTD ................................ -->
40931 <!-- File: memory-map.dtd .............................. -->
40932 <!-- .................................... .............. -->
40933 <!-- memory-map.dtd -->
40934 <!-- memory-map: Root element with versioning -->
40935 <!ELEMENT memory-map (memory)*>
40936 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40937 <!ELEMENT memory (property)*>
40938 <!-- memory: Specifies a memory region,
40939 and its type, or device. -->
40940 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
40941 start CDATA #REQUIRED
40942 length CDATA #REQUIRED>
40943 <!-- property: Generic attribute tag -->
40944 <!ELEMENT property (#PCDATA | property)*>
40945 <!ATTLIST property name (blocksize) #REQUIRED>
40948 @node Thread List Format
40949 @section Thread List Format
40950 @cindex thread list format
40952 To efficiently update the list of threads and their attributes,
40953 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40954 (@pxref{qXfer threads read}) and obtains the XML document with
40955 the following structure:
40958 <?xml version="1.0"?>
40960 <thread id="id" core="0" name="name">
40961 ... description ...
40966 Each @samp{thread} element must have the @samp{id} attribute that
40967 identifies the thread (@pxref{thread-id syntax}). The
40968 @samp{core} attribute, if present, specifies which processor core
40969 the thread was last executing on. The @samp{name} attribute, if
40970 present, specifies the human-readable name of the thread. The content
40971 of the of @samp{thread} element is interpreted as human-readable
40972 auxiliary information. The @samp{handle} attribute, if present,
40973 is a hex encoded representation of the thread handle.
40976 @node Traceframe Info Format
40977 @section Traceframe Info Format
40978 @cindex traceframe info format
40980 To be able to know which objects in the inferior can be examined when
40981 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40982 memory ranges, registers and trace state variables that have been
40983 collected in a traceframe.
40985 This list is obtained using the @samp{qXfer:traceframe-info:read}
40986 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40988 @value{GDBN} must be linked with the Expat library to support XML
40989 traceframe info discovery. @xref{Expat}.
40991 The top-level structure of the document is shown below:
40994 <?xml version="1.0"?>
40995 <!DOCTYPE traceframe-info
40996 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40997 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41003 Each traceframe block can be either:
41008 A region of collected memory starting at @var{addr} and extending for
41009 @var{length} bytes from there:
41012 <memory start="@var{addr}" length="@var{length}"/>
41016 A block indicating trace state variable numbered @var{number} has been
41020 <tvar id="@var{number}"/>
41025 The formal DTD for the traceframe info format is given below:
41028 <!ELEMENT traceframe-info (memory | tvar)* >
41029 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41031 <!ELEMENT memory EMPTY>
41032 <!ATTLIST memory start CDATA #REQUIRED
41033 length CDATA #REQUIRED>
41035 <!ATTLIST tvar id CDATA #REQUIRED>
41038 @node Branch Trace Format
41039 @section Branch Trace Format
41040 @cindex branch trace format
41042 In order to display the branch trace of an inferior thread,
41043 @value{GDBN} needs to obtain the list of branches. This list is
41044 represented as list of sequential code blocks that are connected via
41045 branches. The code in each block has been executed sequentially.
41047 This list is obtained using the @samp{qXfer:btrace:read}
41048 (@pxref{qXfer btrace read}) packet and is an XML document.
41050 @value{GDBN} must be linked with the Expat library to support XML
41051 traceframe info discovery. @xref{Expat}.
41053 The top-level structure of the document is shown below:
41056 <?xml version="1.0"?>
41058 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41059 "http://sourceware.org/gdb/gdb-btrace.dtd">
41068 A block of sequentially executed instructions starting at @var{begin}
41069 and ending at @var{end}:
41072 <block begin="@var{begin}" end="@var{end}"/>
41077 The formal DTD for the branch trace format is given below:
41080 <!ELEMENT btrace (block* | pt) >
41081 <!ATTLIST btrace version CDATA #FIXED "1.0">
41083 <!ELEMENT block EMPTY>
41084 <!ATTLIST block begin CDATA #REQUIRED
41085 end CDATA #REQUIRED>
41087 <!ELEMENT pt (pt-config?, raw?)>
41089 <!ELEMENT pt-config (cpu?)>
41091 <!ELEMENT cpu EMPTY>
41092 <!ATTLIST cpu vendor CDATA #REQUIRED
41093 family CDATA #REQUIRED
41094 model CDATA #REQUIRED
41095 stepping CDATA #REQUIRED>
41097 <!ELEMENT raw (#PCDATA)>
41100 @node Branch Trace Configuration Format
41101 @section Branch Trace Configuration Format
41102 @cindex branch trace configuration format
41104 For each inferior thread, @value{GDBN} can obtain the branch trace
41105 configuration using the @samp{qXfer:btrace-conf:read}
41106 (@pxref{qXfer btrace-conf read}) packet.
41108 The configuration describes the branch trace format and configuration
41109 settings for that format. The following information is described:
41113 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41116 The size of the @acronym{BTS} ring buffer in bytes.
41119 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41123 The size of the @acronym{Intel PT} ring buffer in bytes.
41127 @value{GDBN} must be linked with the Expat library to support XML
41128 branch trace configuration discovery. @xref{Expat}.
41130 The formal DTD for the branch trace configuration format is given below:
41133 <!ELEMENT btrace-conf (bts?, pt?)>
41134 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41136 <!ELEMENT bts EMPTY>
41137 <!ATTLIST bts size CDATA #IMPLIED>
41139 <!ELEMENT pt EMPTY>
41140 <!ATTLIST pt size CDATA #IMPLIED>
41143 @include agentexpr.texi
41145 @node Target Descriptions
41146 @appendix Target Descriptions
41147 @cindex target descriptions
41149 One of the challenges of using @value{GDBN} to debug embedded systems
41150 is that there are so many minor variants of each processor
41151 architecture in use. It is common practice for vendors to start with
41152 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41153 and then make changes to adapt it to a particular market niche. Some
41154 architectures have hundreds of variants, available from dozens of
41155 vendors. This leads to a number of problems:
41159 With so many different customized processors, it is difficult for
41160 the @value{GDBN} maintainers to keep up with the changes.
41162 Since individual variants may have short lifetimes or limited
41163 audiences, it may not be worthwhile to carry information about every
41164 variant in the @value{GDBN} source tree.
41166 When @value{GDBN} does support the architecture of the embedded system
41167 at hand, the task of finding the correct architecture name to give the
41168 @command{set architecture} command can be error-prone.
41171 To address these problems, the @value{GDBN} remote protocol allows a
41172 target system to not only identify itself to @value{GDBN}, but to
41173 actually describe its own features. This lets @value{GDBN} support
41174 processor variants it has never seen before --- to the extent that the
41175 descriptions are accurate, and that @value{GDBN} understands them.
41177 @value{GDBN} must be linked with the Expat library to support XML
41178 target descriptions. @xref{Expat}.
41181 * Retrieving Descriptions:: How descriptions are fetched from a target.
41182 * Target Description Format:: The contents of a target description.
41183 * Predefined Target Types:: Standard types available for target
41185 * Enum Target Types:: How to define enum target types.
41186 * Standard Target Features:: Features @value{GDBN} knows about.
41189 @node Retrieving Descriptions
41190 @section Retrieving Descriptions
41192 Target descriptions can be read from the target automatically, or
41193 specified by the user manually. The default behavior is to read the
41194 description from the target. @value{GDBN} retrieves it via the remote
41195 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41196 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41197 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41198 XML document, of the form described in @ref{Target Description
41201 Alternatively, you can specify a file to read for the target description.
41202 If a file is set, the target will not be queried. The commands to
41203 specify a file are:
41206 @cindex set tdesc filename
41207 @item set tdesc filename @var{path}
41208 Read the target description from @var{path}.
41210 @cindex unset tdesc filename
41211 @item unset tdesc filename
41212 Do not read the XML target description from a file. @value{GDBN}
41213 will use the description supplied by the current target.
41215 @cindex show tdesc filename
41216 @item show tdesc filename
41217 Show the filename to read for a target description, if any.
41221 @node Target Description Format
41222 @section Target Description Format
41223 @cindex target descriptions, XML format
41225 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41226 document which complies with the Document Type Definition provided in
41227 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41228 means you can use generally available tools like @command{xmllint} to
41229 check that your feature descriptions are well-formed and valid.
41230 However, to help people unfamiliar with XML write descriptions for
41231 their targets, we also describe the grammar here.
41233 Target descriptions can identify the architecture of the remote target
41234 and (for some architectures) provide information about custom register
41235 sets. They can also identify the OS ABI of the remote target.
41236 @value{GDBN} can use this information to autoconfigure for your
41237 target, or to warn you if you connect to an unsupported target.
41239 Here is a simple target description:
41242 <target version="1.0">
41243 <architecture>i386:x86-64</architecture>
41248 This minimal description only says that the target uses
41249 the x86-64 architecture.
41251 A target description has the following overall form, with [ ] marking
41252 optional elements and @dots{} marking repeatable elements. The elements
41253 are explained further below.
41256 <?xml version="1.0"?>
41257 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41258 <target version="1.0">
41259 @r{[}@var{architecture}@r{]}
41260 @r{[}@var{osabi}@r{]}
41261 @r{[}@var{compatible}@r{]}
41262 @r{[}@var{feature}@dots{}@r{]}
41267 The description is generally insensitive to whitespace and line
41268 breaks, under the usual common-sense rules. The XML version
41269 declaration and document type declaration can generally be omitted
41270 (@value{GDBN} does not require them), but specifying them may be
41271 useful for XML validation tools. The @samp{version} attribute for
41272 @samp{<target>} may also be omitted, but we recommend
41273 including it; if future versions of @value{GDBN} use an incompatible
41274 revision of @file{gdb-target.dtd}, they will detect and report
41275 the version mismatch.
41277 @subsection Inclusion
41278 @cindex target descriptions, inclusion
41281 @cindex <xi:include>
41284 It can sometimes be valuable to split a target description up into
41285 several different annexes, either for organizational purposes, or to
41286 share files between different possible target descriptions. You can
41287 divide a description into multiple files by replacing any element of
41288 the target description with an inclusion directive of the form:
41291 <xi:include href="@var{document}"/>
41295 When @value{GDBN} encounters an element of this form, it will retrieve
41296 the named XML @var{document}, and replace the inclusion directive with
41297 the contents of that document. If the current description was read
41298 using @samp{qXfer}, then so will be the included document;
41299 @var{document} will be interpreted as the name of an annex. If the
41300 current description was read from a file, @value{GDBN} will look for
41301 @var{document} as a file in the same directory where it found the
41302 original description.
41304 @subsection Architecture
41305 @cindex <architecture>
41307 An @samp{<architecture>} element has this form:
41310 <architecture>@var{arch}</architecture>
41313 @var{arch} is one of the architectures from the set accepted by
41314 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41317 @cindex @code{<osabi>}
41319 This optional field was introduced in @value{GDBN} version 7.0.
41320 Previous versions of @value{GDBN} ignore it.
41322 An @samp{<osabi>} element has this form:
41325 <osabi>@var{abi-name}</osabi>
41328 @var{abi-name} is an OS ABI name from the same selection accepted by
41329 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41331 @subsection Compatible Architecture
41332 @cindex @code{<compatible>}
41334 This optional field was introduced in @value{GDBN} version 7.0.
41335 Previous versions of @value{GDBN} ignore it.
41337 A @samp{<compatible>} element has this form:
41340 <compatible>@var{arch}</compatible>
41343 @var{arch} is one of the architectures from the set accepted by
41344 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41346 A @samp{<compatible>} element is used to specify that the target
41347 is able to run binaries in some other than the main target architecture
41348 given by the @samp{<architecture>} element. For example, on the
41349 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41350 or @code{powerpc:common64}, but the system is able to run binaries
41351 in the @code{spu} architecture as well. The way to describe this
41352 capability with @samp{<compatible>} is as follows:
41355 <architecture>powerpc:common</architecture>
41356 <compatible>spu</compatible>
41359 @subsection Features
41362 Each @samp{<feature>} describes some logical portion of the target
41363 system. Features are currently used to describe available CPU
41364 registers and the types of their contents. A @samp{<feature>} element
41368 <feature name="@var{name}">
41369 @r{[}@var{type}@dots{}@r{]}
41375 Each feature's name should be unique within the description. The name
41376 of a feature does not matter unless @value{GDBN} has some special
41377 knowledge of the contents of that feature; if it does, the feature
41378 should have its standard name. @xref{Standard Target Features}.
41382 Any register's value is a collection of bits which @value{GDBN} must
41383 interpret. The default interpretation is a two's complement integer,
41384 but other types can be requested by name in the register description.
41385 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41386 Target Types}), and the description can define additional composite
41389 Each type element must have an @samp{id} attribute, which gives
41390 a unique (within the containing @samp{<feature>}) name to the type.
41391 Types must be defined before they are used.
41394 Some targets offer vector registers, which can be treated as arrays
41395 of scalar elements. These types are written as @samp{<vector>} elements,
41396 specifying the array element type, @var{type}, and the number of elements,
41400 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41404 If a register's value is usefully viewed in multiple ways, define it
41405 with a union type containing the useful representations. The
41406 @samp{<union>} element contains one or more @samp{<field>} elements,
41407 each of which has a @var{name} and a @var{type}:
41410 <union id="@var{id}">
41411 <field name="@var{name}" type="@var{type}"/>
41418 If a register's value is composed from several separate values, define
41419 it with either a structure type or a flags type.
41420 A flags type may only contain bitfields.
41421 A structure type may either contain only bitfields or contain no bitfields.
41422 If the value contains only bitfields, its total size in bytes must be
41425 Non-bitfield values have a @var{name} and @var{type}.
41428 <struct id="@var{id}">
41429 <field name="@var{name}" type="@var{type}"/>
41434 Both @var{name} and @var{type} values are required.
41435 No implicit padding is added.
41437 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41440 <struct id="@var{id}" size="@var{size}">
41441 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41447 <flags id="@var{id}" size="@var{size}">
41448 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41453 The @var{name} value is required.
41454 Bitfield values may be named with the empty string, @samp{""},
41455 in which case the field is ``filler'' and its value is not printed.
41456 Not all bits need to be specified, so ``filler'' fields are optional.
41458 The @var{start} and @var{end} values are required, and @var{type}
41460 The field's @var{start} must be less than or equal to its @var{end},
41461 and zero represents the least significant bit.
41463 The default value of @var{type} is @code{bool} for single bit fields,
41464 and an unsigned integer otherwise.
41466 Which to choose? Structures or flags?
41468 Registers defined with @samp{flags} have these advantages over
41469 defining them with @samp{struct}:
41473 Arithmetic may be performed on them as if they were integers.
41475 They are printed in a more readable fashion.
41478 Registers defined with @samp{struct} have one advantage over
41479 defining them with @samp{flags}:
41483 One can fetch individual fields like in @samp{C}.
41486 (gdb) print $my_struct_reg.field3
41492 @subsection Registers
41495 Each register is represented as an element with this form:
41498 <reg name="@var{name}"
41499 bitsize="@var{size}"
41500 @r{[}regnum="@var{num}"@r{]}
41501 @r{[}save-restore="@var{save-restore}"@r{]}
41502 @r{[}type="@var{type}"@r{]}
41503 @r{[}group="@var{group}"@r{]}/>
41507 The components are as follows:
41512 The register's name; it must be unique within the target description.
41515 The register's size, in bits.
41518 The register's number. If omitted, a register's number is one greater
41519 than that of the previous register (either in the current feature or in
41520 a preceding feature); the first register in the target description
41521 defaults to zero. This register number is used to read or write
41522 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41523 packets, and registers appear in the @code{g} and @code{G} packets
41524 in order of increasing register number.
41527 Whether the register should be preserved across inferior function
41528 calls; this must be either @code{yes} or @code{no}. The default is
41529 @code{yes}, which is appropriate for most registers except for
41530 some system control registers; this is not related to the target's
41534 The type of the register. It may be a predefined type, a type
41535 defined in the current feature, or one of the special types @code{int}
41536 and @code{float}. @code{int} is an integer type of the correct size
41537 for @var{bitsize}, and @code{float} is a floating point type (in the
41538 architecture's normal floating point format) of the correct size for
41539 @var{bitsize}. The default is @code{int}.
41542 The register group to which this register belongs. It must
41543 be either @code{general}, @code{float}, or @code{vector}. If no
41544 @var{group} is specified, @value{GDBN} will not display the register
41545 in @code{info registers}.
41549 @node Predefined Target Types
41550 @section Predefined Target Types
41551 @cindex target descriptions, predefined types
41553 Type definitions in the self-description can build up composite types
41554 from basic building blocks, but can not define fundamental types. Instead,
41555 standard identifiers are provided by @value{GDBN} for the fundamental
41556 types. The currently supported types are:
41561 Boolean type, occupying a single bit.
41568 Signed integer types holding the specified number of bits.
41575 Unsigned integer types holding the specified number of bits.
41579 Pointers to unspecified code and data. The program counter and
41580 any dedicated return address register may be marked as code
41581 pointers; printing a code pointer converts it into a symbolic
41582 address. The stack pointer and any dedicated address registers
41583 may be marked as data pointers.
41586 Single precision IEEE floating point.
41589 Double precision IEEE floating point.
41592 The 12-byte extended precision format used by ARM FPA registers.
41595 The 10-byte extended precision format used by x87 registers.
41598 32bit @sc{eflags} register used by x86.
41601 32bit @sc{mxcsr} register used by x86.
41605 @node Enum Target Types
41606 @section Enum Target Types
41607 @cindex target descriptions, enum types
41609 Enum target types are useful in @samp{struct} and @samp{flags}
41610 register descriptions. @xref{Target Description Format}.
41612 Enum types have a name, size and a list of name/value pairs.
41615 <enum id="@var{id}" size="@var{size}">
41616 <evalue name="@var{name}" value="@var{value}"/>
41621 Enums must be defined before they are used.
41624 <enum id="levels_type" size="4">
41625 <evalue name="low" value="0"/>
41626 <evalue name="high" value="1"/>
41628 <flags id="flags_type" size="4">
41629 <field name="X" start="0"/>
41630 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41632 <reg name="flags" bitsize="32" type="flags_type"/>
41635 Given that description, a value of 3 for the @samp{flags} register
41636 would be printed as:
41639 (gdb) info register flags
41640 flags 0x3 [ X LEVEL=high ]
41643 @node Standard Target Features
41644 @section Standard Target Features
41645 @cindex target descriptions, standard features
41647 A target description must contain either no registers or all the
41648 target's registers. If the description contains no registers, then
41649 @value{GDBN} will assume a default register layout, selected based on
41650 the architecture. If the description contains any registers, the
41651 default layout will not be used; the standard registers must be
41652 described in the target description, in such a way that @value{GDBN}
41653 can recognize them.
41655 This is accomplished by giving specific names to feature elements
41656 which contain standard registers. @value{GDBN} will look for features
41657 with those names and verify that they contain the expected registers;
41658 if any known feature is missing required registers, or if any required
41659 feature is missing, @value{GDBN} will reject the target
41660 description. You can add additional registers to any of the
41661 standard features --- @value{GDBN} will display them just as if
41662 they were added to an unrecognized feature.
41664 This section lists the known features and their expected contents.
41665 Sample XML documents for these features are included in the
41666 @value{GDBN} source tree, in the directory @file{gdb/features}.
41668 Names recognized by @value{GDBN} should include the name of the
41669 company or organization which selected the name, and the overall
41670 architecture to which the feature applies; so e.g.@: the feature
41671 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41673 The names of registers are not case sensitive for the purpose
41674 of recognizing standard features, but @value{GDBN} will only display
41675 registers using the capitalization used in the description.
41678 * AArch64 Features::
41682 * MicroBlaze Features::
41686 * Nios II Features::
41687 * PowerPC Features::
41688 * S/390 and System z Features::
41694 @node AArch64 Features
41695 @subsection AArch64 Features
41696 @cindex target descriptions, AArch64 features
41698 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41699 targets. It should contain registers @samp{x0} through @samp{x30},
41700 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41702 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41703 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41707 @subsection ARC Features
41708 @cindex target descriptions, ARC Features
41710 ARC processors are highly configurable, so even core registers and their number
41711 are not completely predetermined. In addition flags and PC registers which are
41712 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41713 that one of the core registers features is present.
41714 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41716 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41717 targets with a normal register file. It should contain registers @samp{r0}
41718 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41719 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41720 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41721 @samp{ilink} and extension core registers are not available to read/write, when
41722 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41724 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41725 ARC HS targets with a reduced register file. It should contain registers
41726 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41727 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41728 This feature may contain register @samp{ilink} and any of extension core
41729 registers @samp{r32} through @samp{r59/acch}.
41731 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41732 targets with a normal register file. It should contain registers @samp{r0}
41733 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41734 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41735 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41736 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41737 registers are not available when debugging GNU/Linux applications. The only
41738 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41739 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41740 ARC v2, but @samp{ilink2} is optional on ARCompact.
41742 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41743 targets. It should contain registers @samp{pc} and @samp{status32}.
41746 @subsection ARM Features
41747 @cindex target descriptions, ARM features
41749 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41751 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41752 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41754 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41755 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41756 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41759 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41760 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41762 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41763 it should contain at least registers @samp{wR0} through @samp{wR15} and
41764 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41765 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41767 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41768 should contain at least registers @samp{d0} through @samp{d15}. If
41769 they are present, @samp{d16} through @samp{d31} should also be included.
41770 @value{GDBN} will synthesize the single-precision registers from
41771 halves of the double-precision registers.
41773 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41774 need to contain registers; it instructs @value{GDBN} to display the
41775 VFP double-precision registers as vectors and to synthesize the
41776 quad-precision registers from pairs of double-precision registers.
41777 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41778 be present and include 32 double-precision registers.
41780 @node i386 Features
41781 @subsection i386 Features
41782 @cindex target descriptions, i386 features
41784 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41785 targets. It should describe the following registers:
41789 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41791 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41793 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41794 @samp{fs}, @samp{gs}
41796 @samp{st0} through @samp{st7}
41798 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41799 @samp{foseg}, @samp{fooff} and @samp{fop}
41802 The register sets may be different, depending on the target.
41804 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41805 describe registers:
41809 @samp{xmm0} through @samp{xmm7} for i386
41811 @samp{xmm0} through @samp{xmm15} for amd64
41816 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41817 @samp{org.gnu.gdb.i386.sse} feature. It should
41818 describe the upper 128 bits of @sc{ymm} registers:
41822 @samp{ymm0h} through @samp{ymm7h} for i386
41824 @samp{ymm0h} through @samp{ymm15h} for amd64
41827 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41828 Memory Protection Extension (MPX). It should describe the following registers:
41832 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41834 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41837 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41838 describe a single register, @samp{orig_eax}.
41840 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
41841 describe two system registers: @samp{fs_base} and @samp{gs_base}.
41843 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41844 @samp{org.gnu.gdb.i386.avx} feature. It should
41845 describe additional @sc{xmm} registers:
41849 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41852 It should describe the upper 128 bits of additional @sc{ymm} registers:
41856 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41860 describe the upper 256 bits of @sc{zmm} registers:
41864 @samp{zmm0h} through @samp{zmm7h} for i386.
41866 @samp{zmm0h} through @samp{zmm15h} for amd64.
41870 describe the additional @sc{zmm} registers:
41874 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41877 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
41878 describe a single register, @samp{pkru}. It is a 32-bit register
41879 valid for i386 and amd64.
41881 @node MicroBlaze Features
41882 @subsection MicroBlaze Features
41883 @cindex target descriptions, MicroBlaze features
41885 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41886 targets. It should contain registers @samp{r0} through @samp{r31},
41887 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41888 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41889 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41891 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41892 If present, it should contain registers @samp{rshr} and @samp{rslr}
41894 @node MIPS Features
41895 @subsection @acronym{MIPS} Features
41896 @cindex target descriptions, @acronym{MIPS} features
41898 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41899 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41900 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41903 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41904 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41905 registers. They may be 32-bit or 64-bit depending on the target.
41907 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41908 it may be optional in a future version of @value{GDBN}. It should
41909 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41910 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41912 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41913 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41914 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41915 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41917 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41918 contain a single register, @samp{restart}, which is used by the
41919 Linux kernel to control restartable syscalls.
41921 @node M68K Features
41922 @subsection M68K Features
41923 @cindex target descriptions, M68K features
41926 @item @samp{org.gnu.gdb.m68k.core}
41927 @itemx @samp{org.gnu.gdb.coldfire.core}
41928 @itemx @samp{org.gnu.gdb.fido.core}
41929 One of those features must be always present.
41930 The feature that is present determines which flavor of m68k is
41931 used. The feature that is present should contain registers
41932 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41933 @samp{sp}, @samp{ps} and @samp{pc}.
41935 @item @samp{org.gnu.gdb.coldfire.fp}
41936 This feature is optional. If present, it should contain registers
41937 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41941 @node NDS32 Features
41942 @subsection NDS32 Features
41943 @cindex target descriptions, NDS32 features
41945 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
41946 targets. It should contain at least registers @samp{r0} through
41947 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
41950 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
41951 it should contain 64-bit double-precision floating-point registers
41952 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
41953 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
41955 @emph{Note:} The first sixteen 64-bit double-precision floating-point
41956 registers are overlapped with the thirty-two 32-bit single-precision
41957 floating-point registers. The 32-bit single-precision registers, if
41958 not being listed explicitly, will be synthesized from halves of the
41959 overlapping 64-bit double-precision registers. Listing 32-bit
41960 single-precision registers explicitly is deprecated, and the
41961 support to it could be totally removed some day.
41963 @node Nios II Features
41964 @subsection Nios II Features
41965 @cindex target descriptions, Nios II features
41967 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
41968 targets. It should contain the 32 core registers (@samp{zero},
41969 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
41970 @samp{pc}, and the 16 control registers (@samp{status} through
41973 @node PowerPC Features
41974 @subsection PowerPC Features
41975 @cindex target descriptions, PowerPC features
41977 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41978 targets. It should contain registers @samp{r0} through @samp{r31},
41979 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41980 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41982 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41983 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41985 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41986 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41989 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41990 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41991 will combine these registers with the floating point registers
41992 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41993 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41994 through @samp{vs63}, the set of vector registers for POWER7.
41996 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41997 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41998 @samp{spefscr}. SPE targets should provide 32-bit registers in
41999 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42000 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42001 these to present registers @samp{ev0} through @samp{ev31} to the
42004 @node S/390 and System z Features
42005 @subsection S/390 and System z Features
42006 @cindex target descriptions, S/390 features
42007 @cindex target descriptions, System z features
42009 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42010 System z targets. It should contain the PSW and the 16 general
42011 registers. In particular, System z targets should provide the 64-bit
42012 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42013 S/390 targets should provide the 32-bit versions of these registers.
42014 A System z target that runs in 31-bit addressing mode should provide
42015 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42016 register's upper halves @samp{r0h} through @samp{r15h}, and their
42017 lower halves @samp{r0l} through @samp{r15l}.
42019 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42020 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42023 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42024 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42026 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42027 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42028 targets and 32-bit otherwise. In addition, the feature may contain
42029 the @samp{last_break} register, whose width depends on the addressing
42030 mode, as well as the @samp{system_call} register, which is always
42033 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42034 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42035 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42037 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42038 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42039 combined by @value{GDBN} with the floating point registers @samp{f0}
42040 through @samp{f15} to present the 128-bit wide vector registers
42041 @samp{v0} through @samp{v15}. In addition, this feature should
42042 contain the 128-bit wide vector registers @samp{v16} through
42045 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42046 the 64-bit wide guarded-storage-control registers @samp{gsd},
42047 @samp{gssm}, and @samp{gsepla}.
42049 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42050 the 64-bit wide guarded-storage broadcast control registers
42051 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42053 @node Sparc Features
42054 @subsection Sparc Features
42055 @cindex target descriptions, sparc32 features
42056 @cindex target descriptions, sparc64 features
42057 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42058 targets. It should describe the following registers:
42062 @samp{g0} through @samp{g7}
42064 @samp{o0} through @samp{o7}
42066 @samp{l0} through @samp{l7}
42068 @samp{i0} through @samp{i7}
42071 They may be 32-bit or 64-bit depending on the target.
42073 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42074 targets. It should describe the following registers:
42078 @samp{f0} through @samp{f31}
42080 @samp{f32} through @samp{f62} for sparc64
42083 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42084 targets. It should describe the following registers:
42088 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42089 @samp{fsr}, and @samp{csr} for sparc32
42091 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42095 @node TIC6x Features
42096 @subsection TMS320C6x Features
42097 @cindex target descriptions, TIC6x features
42098 @cindex target descriptions, TMS320C6x features
42099 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42100 targets. It should contain registers @samp{A0} through @samp{A15},
42101 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42103 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42104 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42105 through @samp{B31}.
42107 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42108 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42110 @node Operating System Information
42111 @appendix Operating System Information
42112 @cindex operating system information
42118 Users of @value{GDBN} often wish to obtain information about the state of
42119 the operating system running on the target---for example the list of
42120 processes, or the list of open files. This section describes the
42121 mechanism that makes it possible. This mechanism is similar to the
42122 target features mechanism (@pxref{Target Descriptions}), but focuses
42123 on a different aspect of target.
42125 Operating system information is retrived from the target via the
42126 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42127 read}). The object name in the request should be @samp{osdata}, and
42128 the @var{annex} identifies the data to be fetched.
42131 @appendixsection Process list
42132 @cindex operating system information, process list
42134 When requesting the process list, the @var{annex} field in the
42135 @samp{qXfer} request should be @samp{processes}. The returned data is
42136 an XML document. The formal syntax of this document is defined in
42137 @file{gdb/features/osdata.dtd}.
42139 An example document is:
42142 <?xml version="1.0"?>
42143 <!DOCTYPE target SYSTEM "osdata.dtd">
42144 <osdata type="processes">
42146 <column name="pid">1</column>
42147 <column name="user">root</column>
42148 <column name="command">/sbin/init</column>
42149 <column name="cores">1,2,3</column>
42154 Each item should include a column whose name is @samp{pid}. The value
42155 of that column should identify the process on the target. The
42156 @samp{user} and @samp{command} columns are optional, and will be
42157 displayed by @value{GDBN}. The @samp{cores} column, if present,
42158 should contain a comma-separated list of cores that this process
42159 is running on. Target may provide additional columns,
42160 which @value{GDBN} currently ignores.
42162 @node Trace File Format
42163 @appendix Trace File Format
42164 @cindex trace file format
42166 The trace file comes in three parts: a header, a textual description
42167 section, and a trace frame section with binary data.
42169 The header has the form @code{\x7fTRACE0\n}. The first byte is
42170 @code{0x7f} so as to indicate that the file contains binary data,
42171 while the @code{0} is a version number that may have different values
42174 The description section consists of multiple lines of @sc{ascii} text
42175 separated by newline characters (@code{0xa}). The lines may include a
42176 variety of optional descriptive or context-setting information, such
42177 as tracepoint definitions or register set size. @value{GDBN} will
42178 ignore any line that it does not recognize. An empty line marks the end
42183 Specifies the size of a register block in bytes. This is equal to the
42184 size of a @code{g} packet payload in the remote protocol. @var{size}
42185 is an ascii decimal number. There should be only one such line in
42186 a single trace file.
42188 @item status @var{status}
42189 Trace status. @var{status} has the same format as a @code{qTStatus}
42190 remote packet reply. There should be only one such line in a single trace
42193 @item tp @var{payload}
42194 Tracepoint definition. The @var{payload} has the same format as
42195 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42196 may take multiple lines of definition, corresponding to the multiple
42199 @item tsv @var{payload}
42200 Trace state variable definition. The @var{payload} has the same format as
42201 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42202 may take multiple lines of definition, corresponding to the multiple
42205 @item tdesc @var{payload}
42206 Target description in XML format. The @var{payload} is a single line of
42207 the XML file. All such lines should be concatenated together to get
42208 the original XML file. This file is in the same format as @code{qXfer}
42209 @code{features} payload, and corresponds to the main @code{target.xml}
42210 file. Includes are not allowed.
42214 The trace frame section consists of a number of consecutive frames.
42215 Each frame begins with a two-byte tracepoint number, followed by a
42216 four-byte size giving the amount of data in the frame. The data in
42217 the frame consists of a number of blocks, each introduced by a
42218 character indicating its type (at least register, memory, and trace
42219 state variable). The data in this section is raw binary, not a
42220 hexadecimal or other encoding; its endianness matches the target's
42223 @c FIXME bi-arch may require endianness/arch info in description section
42226 @item R @var{bytes}
42227 Register block. The number and ordering of bytes matches that of a
42228 @code{g} packet in the remote protocol. Note that these are the
42229 actual bytes, in target order, not a hexadecimal encoding.
42231 @item M @var{address} @var{length} @var{bytes}...
42232 Memory block. This is a contiguous block of memory, at the 8-byte
42233 address @var{address}, with a 2-byte length @var{length}, followed by
42234 @var{length} bytes.
42236 @item V @var{number} @var{value}
42237 Trace state variable block. This records the 8-byte signed value
42238 @var{value} of trace state variable numbered @var{number}.
42242 Future enhancements of the trace file format may include additional types
42245 @node Index Section Format
42246 @appendix @code{.gdb_index} section format
42247 @cindex .gdb_index section format
42248 @cindex index section format
42250 This section documents the index section that is created by @code{save
42251 gdb-index} (@pxref{Index Files}). The index section is
42252 DWARF-specific; some knowledge of DWARF is assumed in this
42255 The mapped index file format is designed to be directly
42256 @code{mmap}able on any architecture. In most cases, a datum is
42257 represented using a little-endian 32-bit integer value, called an
42258 @code{offset_type}. Big endian machines must byte-swap the values
42259 before using them. Exceptions to this rule are noted. The data is
42260 laid out such that alignment is always respected.
42262 A mapped index consists of several areas, laid out in order.
42266 The file header. This is a sequence of values, of @code{offset_type}
42267 unless otherwise noted:
42271 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42272 Version 4 uses a different hashing function from versions 5 and 6.
42273 Version 6 includes symbols for inlined functions, whereas versions 4
42274 and 5 do not. Version 7 adds attributes to the CU indices in the
42275 symbol table. Version 8 specifies that symbols from DWARF type units
42276 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42277 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42279 @value{GDBN} will only read version 4, 5, or 6 indices
42280 by specifying @code{set use-deprecated-index-sections on}.
42281 GDB has a workaround for potentially broken version 7 indices so it is
42282 currently not flagged as deprecated.
42285 The offset, from the start of the file, of the CU list.
42288 The offset, from the start of the file, of the types CU list. Note
42289 that this area can be empty, in which case this offset will be equal
42290 to the next offset.
42293 The offset, from the start of the file, of the address area.
42296 The offset, from the start of the file, of the symbol table.
42299 The offset, from the start of the file, of the constant pool.
42303 The CU list. This is a sequence of pairs of 64-bit little-endian
42304 values, sorted by the CU offset. The first element in each pair is
42305 the offset of a CU in the @code{.debug_info} section. The second
42306 element in each pair is the length of that CU. References to a CU
42307 elsewhere in the map are done using a CU index, which is just the
42308 0-based index into this table. Note that if there are type CUs, then
42309 conceptually CUs and type CUs form a single list for the purposes of
42313 The types CU list. This is a sequence of triplets of 64-bit
42314 little-endian values. In a triplet, the first value is the CU offset,
42315 the second value is the type offset in the CU, and the third value is
42316 the type signature. The types CU list is not sorted.
42319 The address area. The address area consists of a sequence of address
42320 entries. Each address entry has three elements:
42324 The low address. This is a 64-bit little-endian value.
42327 The high address. This is a 64-bit little-endian value. Like
42328 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42331 The CU index. This is an @code{offset_type} value.
42335 The symbol table. This is an open-addressed hash table. The size of
42336 the hash table is always a power of 2.
42338 Each slot in the hash table consists of a pair of @code{offset_type}
42339 values. The first value is the offset of the symbol's name in the
42340 constant pool. The second value is the offset of the CU vector in the
42343 If both values are 0, then this slot in the hash table is empty. This
42344 is ok because while 0 is a valid constant pool index, it cannot be a
42345 valid index for both a string and a CU vector.
42347 The hash value for a table entry is computed by applying an
42348 iterative hash function to the symbol's name. Starting with an
42349 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42350 the string is incorporated into the hash using the formula depending on the
42355 The formula is @code{r = r * 67 + c - 113}.
42357 @item Versions 5 to 7
42358 The formula is @code{r = r * 67 + tolower (c) - 113}.
42361 The terminating @samp{\0} is not incorporated into the hash.
42363 The step size used in the hash table is computed via
42364 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42365 value, and @samp{size} is the size of the hash table. The step size
42366 is used to find the next candidate slot when handling a hash
42369 The names of C@t{++} symbols in the hash table are canonicalized. We
42370 don't currently have a simple description of the canonicalization
42371 algorithm; if you intend to create new index sections, you must read
42375 The constant pool. This is simply a bunch of bytes. It is organized
42376 so that alignment is correct: CU vectors are stored first, followed by
42379 A CU vector in the constant pool is a sequence of @code{offset_type}
42380 values. The first value is the number of CU indices in the vector.
42381 Each subsequent value is the index and symbol attributes of a CU in
42382 the CU list. This element in the hash table is used to indicate which
42383 CUs define the symbol and how the symbol is used.
42384 See below for the format of each CU index+attributes entry.
42386 A string in the constant pool is zero-terminated.
42389 Attributes were added to CU index values in @code{.gdb_index} version 7.
42390 If a symbol has multiple uses within a CU then there is one
42391 CU index+attributes value for each use.
42393 The format of each CU index+attributes entry is as follows
42399 This is the index of the CU in the CU list.
42401 These bits are reserved for future purposes and must be zero.
42403 The kind of the symbol in the CU.
42407 This value is reserved and should not be used.
42408 By reserving zero the full @code{offset_type} value is backwards compatible
42409 with previous versions of the index.
42411 The symbol is a type.
42413 The symbol is a variable or an enum value.
42415 The symbol is a function.
42417 Any other kind of symbol.
42419 These values are reserved.
42423 This bit is zero if the value is global and one if it is static.
42425 The determination of whether a symbol is global or static is complicated.
42426 The authorative reference is the file @file{dwarf2read.c} in
42427 @value{GDBN} sources.
42431 This pseudo-code describes the computation of a symbol's kind and
42432 global/static attributes in the index.
42435 is_external = get_attribute (die, DW_AT_external);
42436 language = get_attribute (cu_die, DW_AT_language);
42439 case DW_TAG_typedef:
42440 case DW_TAG_base_type:
42441 case DW_TAG_subrange_type:
42445 case DW_TAG_enumerator:
42447 is_static = language != CPLUS;
42449 case DW_TAG_subprogram:
42451 is_static = ! (is_external || language == ADA);
42453 case DW_TAG_constant:
42455 is_static = ! is_external;
42457 case DW_TAG_variable:
42459 is_static = ! is_external;
42461 case DW_TAG_namespace:
42465 case DW_TAG_class_type:
42466 case DW_TAG_interface_type:
42467 case DW_TAG_structure_type:
42468 case DW_TAG_union_type:
42469 case DW_TAG_enumeration_type:
42471 is_static = language != CPLUS;
42479 @appendix Manual pages
42483 * gdb man:: The GNU Debugger man page
42484 * gdbserver man:: Remote Server for the GNU Debugger man page
42485 * gcore man:: Generate a core file of a running program
42486 * gdbinit man:: gdbinit scripts
42492 @c man title gdb The GNU Debugger
42494 @c man begin SYNOPSIS gdb
42495 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42496 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42497 [@option{-b}@w{ }@var{bps}]
42498 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42499 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42500 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42501 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42502 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42505 @c man begin DESCRIPTION gdb
42506 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42507 going on ``inside'' another program while it executes -- or what another
42508 program was doing at the moment it crashed.
42510 @value{GDBN} can do four main kinds of things (plus other things in support of
42511 these) to help you catch bugs in the act:
42515 Start your program, specifying anything that might affect its behavior.
42518 Make your program stop on specified conditions.
42521 Examine what has happened, when your program has stopped.
42524 Change things in your program, so you can experiment with correcting the
42525 effects of one bug and go on to learn about another.
42528 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42531 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42532 commands from the terminal until you tell it to exit with the @value{GDBN}
42533 command @code{quit}. You can get online help from @value{GDBN} itself
42534 by using the command @code{help}.
42536 You can run @code{gdb} with no arguments or options; but the most
42537 usual way to start @value{GDBN} is with one argument or two, specifying an
42538 executable program as the argument:
42544 You can also start with both an executable program and a core file specified:
42550 You can, instead, specify a process ID as a second argument, if you want
42551 to debug a running process:
42559 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42560 named @file{1234}; @value{GDBN} does check for a core file first).
42561 With option @option{-p} you can omit the @var{program} filename.
42563 Here are some of the most frequently needed @value{GDBN} commands:
42565 @c pod2man highlights the right hand side of the @item lines.
42567 @item break [@var{file}:]@var{function}
42568 Set a breakpoint at @var{function} (in @var{file}).
42570 @item run [@var{arglist}]
42571 Start your program (with @var{arglist}, if specified).
42574 Backtrace: display the program stack.
42576 @item print @var{expr}
42577 Display the value of an expression.
42580 Continue running your program (after stopping, e.g. at a breakpoint).
42583 Execute next program line (after stopping); step @emph{over} any
42584 function calls in the line.
42586 @item edit [@var{file}:]@var{function}
42587 look at the program line where it is presently stopped.
42589 @item list [@var{file}:]@var{function}
42590 type the text of the program in the vicinity of where it is presently stopped.
42593 Execute next program line (after stopping); step @emph{into} any
42594 function calls in the line.
42596 @item help [@var{name}]
42597 Show information about @value{GDBN} command @var{name}, or general information
42598 about using @value{GDBN}.
42601 Exit from @value{GDBN}.
42605 For full details on @value{GDBN},
42606 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42607 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42608 as the @code{gdb} entry in the @code{info} program.
42612 @c man begin OPTIONS gdb
42613 Any arguments other than options specify an executable
42614 file and core file (or process ID); that is, the first argument
42615 encountered with no
42616 associated option flag is equivalent to a @option{-se} option, and the second,
42617 if any, is equivalent to a @option{-c} option if it's the name of a file.
42619 both long and short forms; both are shown here. The long forms are also
42620 recognized if you truncate them, so long as enough of the option is
42621 present to be unambiguous. (If you prefer, you can flag option
42622 arguments with @option{+} rather than @option{-}, though we illustrate the
42623 more usual convention.)
42625 All the options and command line arguments you give are processed
42626 in sequential order. The order makes a difference when the @option{-x}
42632 List all options, with brief explanations.
42634 @item -symbols=@var{file}
42635 @itemx -s @var{file}
42636 Read symbol table from file @var{file}.
42639 Enable writing into executable and core files.
42641 @item -exec=@var{file}
42642 @itemx -e @var{file}
42643 Use file @var{file} as the executable file to execute when
42644 appropriate, and for examining pure data in conjunction with a core
42647 @item -se=@var{file}
42648 Read symbol table from file @var{file} and use it as the executable
42651 @item -core=@var{file}
42652 @itemx -c @var{file}
42653 Use file @var{file} as a core dump to examine.
42655 @item -command=@var{file}
42656 @itemx -x @var{file}
42657 Execute @value{GDBN} commands from file @var{file}.
42659 @item -ex @var{command}
42660 Execute given @value{GDBN} @var{command}.
42662 @item -directory=@var{directory}
42663 @itemx -d @var{directory}
42664 Add @var{directory} to the path to search for source files.
42667 Do not execute commands from @file{~/.gdbinit}.
42671 Do not execute commands from any @file{.gdbinit} initialization files.
42675 ``Quiet''. Do not print the introductory and copyright messages. These
42676 messages are also suppressed in batch mode.
42679 Run in batch mode. Exit with status @code{0} after processing all the command
42680 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42681 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42682 commands in the command files.
42684 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42685 download and run a program on another computer; in order to make this
42686 more useful, the message
42689 Program exited normally.
42693 (which is ordinarily issued whenever a program running under @value{GDBN} control
42694 terminates) is not issued when running in batch mode.
42696 @item -cd=@var{directory}
42697 Run @value{GDBN} using @var{directory} as its working directory,
42698 instead of the current directory.
42702 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42703 @value{GDBN} to output the full file name and line number in a standard,
42704 recognizable fashion each time a stack frame is displayed (which
42705 includes each time the program stops). This recognizable format looks
42706 like two @samp{\032} characters, followed by the file name, line number
42707 and character position separated by colons, and a newline. The
42708 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42709 characters as a signal to display the source code for the frame.
42712 Set the line speed (baud rate or bits per second) of any serial
42713 interface used by @value{GDBN} for remote debugging.
42715 @item -tty=@var{device}
42716 Run using @var{device} for your program's standard input and output.
42720 @c man begin SEEALSO gdb
42722 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42723 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42724 documentation are properly installed at your site, the command
42731 should give you access to the complete manual.
42733 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42734 Richard M. Stallman and Roland H. Pesch, July 1991.
42738 @node gdbserver man
42739 @heading gdbserver man
42741 @c man title gdbserver Remote Server for the GNU Debugger
42743 @c man begin SYNOPSIS gdbserver
42744 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42746 gdbserver --attach @var{comm} @var{pid}
42748 gdbserver --multi @var{comm}
42752 @c man begin DESCRIPTION gdbserver
42753 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42754 than the one which is running the program being debugged.
42757 @subheading Usage (server (target) side)
42760 Usage (server (target) side):
42763 First, you need to have a copy of the program you want to debug put onto
42764 the target system. The program can be stripped to save space if needed, as
42765 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42766 the @value{GDBN} running on the host system.
42768 To use the server, you log on to the target system, and run the @command{gdbserver}
42769 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42770 your program, and (c) its arguments. The general syntax is:
42773 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42776 For example, using a serial port, you might say:
42780 @c @file would wrap it as F</dev/com1>.
42781 target> gdbserver /dev/com1 emacs foo.txt
42784 target> gdbserver @file{/dev/com1} emacs foo.txt
42788 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42789 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42790 waits patiently for the host @value{GDBN} to communicate with it.
42792 To use a TCP connection, you could say:
42795 target> gdbserver host:2345 emacs foo.txt
42798 This says pretty much the same thing as the last example, except that we are
42799 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42800 that we are expecting to see a TCP connection from @code{host} to local TCP port
42801 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42802 want for the port number as long as it does not conflict with any existing TCP
42803 ports on the target system. This same port number must be used in the host
42804 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42805 you chose a port number that conflicts with another service, @command{gdbserver} will
42806 print an error message and exit.
42808 @command{gdbserver} can also attach to running programs.
42809 This is accomplished via the @option{--attach} argument. The syntax is:
42812 target> gdbserver --attach @var{comm} @var{pid}
42815 @var{pid} is the process ID of a currently running process. It isn't
42816 necessary to point @command{gdbserver} at a binary for the running process.
42818 To start @code{gdbserver} without supplying an initial command to run
42819 or process ID to attach, use the @option{--multi} command line option.
42820 In such case you should connect using @kbd{target extended-remote} to start
42821 the program you want to debug.
42824 target> gdbserver --multi @var{comm}
42828 @subheading Usage (host side)
42834 You need an unstripped copy of the target program on your host system, since
42835 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42836 would, with the target program as the first argument. (You may need to use the
42837 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42838 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42839 new command you need to know about is @code{target remote}
42840 (or @code{target extended-remote}). Its argument is either
42841 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42842 descriptor. For example:
42846 @c @file would wrap it as F</dev/ttyb>.
42847 (gdb) target remote /dev/ttyb
42850 (gdb) target remote @file{/dev/ttyb}
42855 communicates with the server via serial line @file{/dev/ttyb}, and:
42858 (gdb) target remote the-target:2345
42862 communicates via a TCP connection to port 2345 on host `the-target', where
42863 you previously started up @command{gdbserver} with the same port number. Note that for
42864 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42865 command, otherwise you may get an error that looks something like
42866 `Connection refused'.
42868 @command{gdbserver} can also debug multiple inferiors at once,
42871 the @value{GDBN} manual in node @code{Inferiors and Programs}
42872 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42875 @ref{Inferiors and Programs}.
42877 In such case use the @code{extended-remote} @value{GDBN} command variant:
42880 (gdb) target extended-remote the-target:2345
42883 The @command{gdbserver} option @option{--multi} may or may not be used in such
42887 @c man begin OPTIONS gdbserver
42888 There are three different modes for invoking @command{gdbserver}:
42893 Debug a specific program specified by its program name:
42896 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42899 The @var{comm} parameter specifies how should the server communicate
42900 with @value{GDBN}; it is either a device name (to use a serial line),
42901 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42902 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42903 debug in @var{prog}. Any remaining arguments will be passed to the
42904 program verbatim. When the program exits, @value{GDBN} will close the
42905 connection, and @code{gdbserver} will exit.
42908 Debug a specific program by specifying the process ID of a running
42912 gdbserver --attach @var{comm} @var{pid}
42915 The @var{comm} parameter is as described above. Supply the process ID
42916 of a running program in @var{pid}; @value{GDBN} will do everything
42917 else. Like with the previous mode, when the process @var{pid} exits,
42918 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42921 Multi-process mode -- debug more than one program/process:
42924 gdbserver --multi @var{comm}
42927 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42928 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42929 close the connection when a process being debugged exits, so you can
42930 debug several processes in the same session.
42933 In each of the modes you may specify these options:
42938 List all options, with brief explanations.
42941 This option causes @command{gdbserver} to print its version number and exit.
42944 @command{gdbserver} will attach to a running program. The syntax is:
42947 target> gdbserver --attach @var{comm} @var{pid}
42950 @var{pid} is the process ID of a currently running process. It isn't
42951 necessary to point @command{gdbserver} at a binary for the running process.
42954 To start @code{gdbserver} without supplying an initial command to run
42955 or process ID to attach, use this command line option.
42956 Then you can connect using @kbd{target extended-remote} and start
42957 the program you want to debug. The syntax is:
42960 target> gdbserver --multi @var{comm}
42964 Instruct @code{gdbserver} to display extra status information about the debugging
42966 This option is intended for @code{gdbserver} development and for bug reports to
42969 @item --remote-debug
42970 Instruct @code{gdbserver} to display remote protocol debug output.
42971 This option is intended for @code{gdbserver} development and for bug reports to
42974 @item --debug-format=option1@r{[},option2,...@r{]}
42975 Instruct @code{gdbserver} to include extra information in each line
42976 of debugging output.
42977 @xref{Other Command-Line Arguments for gdbserver}.
42980 Specify a wrapper to launch programs
42981 for debugging. The option should be followed by the name of the
42982 wrapper, then any command-line arguments to pass to the wrapper, then
42983 @kbd{--} indicating the end of the wrapper arguments.
42986 By default, @command{gdbserver} keeps the listening TCP port open, so that
42987 additional connections are possible. However, if you start @code{gdbserver}
42988 with the @option{--once} option, it will stop listening for any further
42989 connection attempts after connecting to the first @value{GDBN} session.
42991 @c --disable-packet is not documented for users.
42993 @c --disable-randomization and --no-disable-randomization are superseded by
42994 @c QDisableRandomization.
42999 @c man begin SEEALSO gdbserver
43001 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43002 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43003 documentation are properly installed at your site, the command
43009 should give you access to the complete manual.
43011 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43012 Richard M. Stallman and Roland H. Pesch, July 1991.
43019 @c man title gcore Generate a core file of a running program
43022 @c man begin SYNOPSIS gcore
43023 gcore [-o @var{filename}] @var{pid}
43027 @c man begin DESCRIPTION gcore
43028 Generate a core dump of a running program with process ID @var{pid}.
43029 Produced file is equivalent to a kernel produced core file as if the process
43030 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43031 limit). Unlike after a crash, after @command{gcore} the program remains
43032 running without any change.
43035 @c man begin OPTIONS gcore
43037 @item -o @var{filename}
43038 The optional argument
43039 @var{filename} specifies the file name where to put the core dump.
43040 If not specified, the file name defaults to @file{core.@var{pid}},
43041 where @var{pid} is the running program process ID.
43045 @c man begin SEEALSO gcore
43047 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43048 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43049 documentation are properly installed at your site, the command
43056 should give you access to the complete manual.
43058 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43059 Richard M. Stallman and Roland H. Pesch, July 1991.
43066 @c man title gdbinit GDB initialization scripts
43069 @c man begin SYNOPSIS gdbinit
43070 @ifset SYSTEM_GDBINIT
43071 @value{SYSTEM_GDBINIT}
43080 @c man begin DESCRIPTION gdbinit
43081 These files contain @value{GDBN} commands to automatically execute during
43082 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43085 the @value{GDBN} manual in node @code{Sequences}
43086 -- shell command @code{info -f gdb -n Sequences}.
43092 Please read more in
43094 the @value{GDBN} manual in node @code{Startup}
43095 -- shell command @code{info -f gdb -n Startup}.
43102 @ifset SYSTEM_GDBINIT
43103 @item @value{SYSTEM_GDBINIT}
43105 @ifclear SYSTEM_GDBINIT
43106 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43108 System-wide initialization file. It is executed unless user specified
43109 @value{GDBN} option @code{-nx} or @code{-n}.
43112 the @value{GDBN} manual in node @code{System-wide configuration}
43113 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43116 @ref{System-wide configuration}.
43120 User initialization file. It is executed unless user specified
43121 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43124 Initialization file for current directory. It may need to be enabled with
43125 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43128 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43129 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43132 @ref{Init File in the Current Directory}.
43137 @c man begin SEEALSO gdbinit
43139 gdb(1), @code{info -f gdb -n Startup}
43141 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43142 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43143 documentation are properly installed at your site, the command
43149 should give you access to the complete manual.
43151 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43152 Richard M. Stallman and Roland H. Pesch, July 1991.
43158 @node GNU Free Documentation License
43159 @appendix GNU Free Documentation License
43162 @node Concept Index
43163 @unnumbered Concept Index
43167 @node Command and Variable Index
43168 @unnumbered Command, Variable, and Function Index
43173 % I think something like @@colophon should be in texinfo. In the
43175 \long\def\colophon{\hbox to0pt{}\vfill
43176 \centerline{The body of this manual is set in}
43177 \centerline{\fontname\tenrm,}
43178 \centerline{with headings in {\bf\fontname\tenbf}}
43179 \centerline{and examples in {\tt\fontname\tentt}.}
43180 \centerline{{\it\fontname\tenit\/},}
43181 \centerline{{\bf\fontname\tenbf}, and}
43182 \centerline{{\sl\fontname\tensl\/}}
43183 \centerline{are used for emphasis.}\vfill}
43185 % Blame: doc@@cygnus.com, 1991.