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.
1041 @anchor{--readnever}
1042 @cindex @code{--readnever}, command-line option
1043 Do not read each symbol file's symbolic debug information. This makes
1044 startup faster but at the expense of not being able to perform
1045 symbolic debugging. DWARF unwind information is also not read,
1046 meaning backtraces may become incomplete or inaccurate. One use of
1047 this is when a user simply wants to do the following sequence: attach,
1048 dump core, detach. Loading the debugging information in this case is
1049 an unnecessary cause of delay.
1053 @subsection Choosing Modes
1055 You can run @value{GDBN} in various alternative modes---for example, in
1056 batch mode or quiet mode.
1064 Do not execute commands found in any initialization file.
1065 There are three init files, loaded in the following order:
1068 @item @file{system.gdbinit}
1069 This is the system-wide init file.
1070 Its location is specified with the @code{--with-system-gdbinit}
1071 configure option (@pxref{System-wide configuration}).
1072 It is loaded first when @value{GDBN} starts, before command line options
1073 have been processed.
1074 @item @file{~/.gdbinit}
1075 This is the init file in your home directory.
1076 It is loaded next, after @file{system.gdbinit}, and before
1077 command options have been processed.
1078 @item @file{./.gdbinit}
1079 This is the init file in the current directory.
1080 It is loaded last, after command line options other than @code{-x} and
1081 @code{-ex} have been processed. Command line options @code{-x} and
1082 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1085 For further documentation on startup processing, @xref{Startup}.
1086 For documentation on how to write command files,
1087 @xref{Command Files,,Command Files}.
1092 Do not execute commands found in @file{~/.gdbinit}, the init file
1093 in your home directory.
1099 @cindex @code{--quiet}
1100 @cindex @code{--silent}
1102 ``Quiet''. Do not print the introductory and copyright messages. These
1103 messages are also suppressed in batch mode.
1106 @cindex @code{--batch}
1107 Run in batch mode. Exit with status @code{0} after processing all the
1108 command files specified with @samp{-x} (and all commands from
1109 initialization files, if not inhibited with @samp{-n}). Exit with
1110 nonzero status if an error occurs in executing the @value{GDBN} commands
1111 in the command files. Batch mode also disables pagination, sets unlimited
1112 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1113 off} were in effect (@pxref{Messages/Warnings}).
1115 Batch mode may be useful for running @value{GDBN} as a filter, for
1116 example to download and run a program on another computer; in order to
1117 make this more useful, the message
1120 Program exited normally.
1124 (which is ordinarily issued whenever a program running under
1125 @value{GDBN} control terminates) is not issued when running in batch
1129 @cindex @code{--batch-silent}
1130 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1131 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1132 unaffected). This is much quieter than @samp{-silent} and would be useless
1133 for an interactive session.
1135 This is particularly useful when using targets that give @samp{Loading section}
1136 messages, for example.
1138 Note that targets that give their output via @value{GDBN}, as opposed to
1139 writing directly to @code{stdout}, will also be made silent.
1141 @item -return-child-result
1142 @cindex @code{--return-child-result}
1143 The return code from @value{GDBN} will be the return code from the child
1144 process (the process being debugged), with the following exceptions:
1148 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1149 internal error. In this case the exit code is the same as it would have been
1150 without @samp{-return-child-result}.
1152 The user quits with an explicit value. E.g., @samp{quit 1}.
1154 The child process never runs, or is not allowed to terminate, in which case
1155 the exit code will be -1.
1158 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1159 when @value{GDBN} is being used as a remote program loader or simulator
1164 @cindex @code{--nowindows}
1166 ``No windows''. If @value{GDBN} comes with a graphical user interface
1167 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1168 interface. If no GUI is available, this option has no effect.
1172 @cindex @code{--windows}
1174 If @value{GDBN} includes a GUI, then this option requires it to be
1177 @item -cd @var{directory}
1179 Run @value{GDBN} using @var{directory} as its working directory,
1180 instead of the current directory.
1182 @item -data-directory @var{directory}
1183 @itemx -D @var{directory}
1184 @cindex @code{--data-directory}
1186 Run @value{GDBN} using @var{directory} as its data directory.
1187 The data directory is where @value{GDBN} searches for its
1188 auxiliary files. @xref{Data Files}.
1192 @cindex @code{--fullname}
1194 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1195 subprocess. It tells @value{GDBN} to output the full file name and line
1196 number in a standard, recognizable fashion each time a stack frame is
1197 displayed (which includes each time your program stops). This
1198 recognizable format looks like two @samp{\032} characters, followed by
1199 the file name, line number and character position separated by colons,
1200 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1201 @samp{\032} characters as a signal to display the source code for the
1204 @item -annotate @var{level}
1205 @cindex @code{--annotate}
1206 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1207 effect is identical to using @samp{set annotate @var{level}}
1208 (@pxref{Annotations}). The annotation @var{level} controls how much
1209 information @value{GDBN} prints together with its prompt, values of
1210 expressions, source lines, and other types of output. Level 0 is the
1211 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1212 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1213 that control @value{GDBN}, and level 2 has been deprecated.
1215 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1219 @cindex @code{--args}
1220 Change interpretation of command line so that arguments following the
1221 executable file are passed as command line arguments to the inferior.
1222 This option stops option processing.
1224 @item -baud @var{bps}
1226 @cindex @code{--baud}
1228 Set the line speed (baud rate or bits per second) of any serial
1229 interface used by @value{GDBN} for remote debugging.
1231 @item -l @var{timeout}
1233 Set the timeout (in seconds) of any communication used by @value{GDBN}
1234 for remote debugging.
1236 @item -tty @var{device}
1237 @itemx -t @var{device}
1238 @cindex @code{--tty}
1240 Run using @var{device} for your program's standard input and output.
1241 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1243 @c resolve the situation of these eventually
1245 @cindex @code{--tui}
1246 Activate the @dfn{Text User Interface} when starting. The Text User
1247 Interface manages several text windows on the terminal, showing
1248 source, assembly, registers and @value{GDBN} command outputs
1249 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1250 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1251 Using @value{GDBN} under @sc{gnu} Emacs}).
1253 @item -interpreter @var{interp}
1254 @cindex @code{--interpreter}
1255 Use the interpreter @var{interp} for interface with the controlling
1256 program or device. This option is meant to be set by programs which
1257 communicate with @value{GDBN} using it as a back end.
1258 @xref{Interpreters, , Command Interpreters}.
1260 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1261 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1262 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1263 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1264 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1265 @sc{gdb/mi} interfaces are no longer supported.
1268 @cindex @code{--write}
1269 Open the executable and core files for both reading and writing. This
1270 is equivalent to the @samp{set write on} command inside @value{GDBN}
1274 @cindex @code{--statistics}
1275 This option causes @value{GDBN} to print statistics about time and
1276 memory usage after it completes each command and returns to the prompt.
1279 @cindex @code{--version}
1280 This option causes @value{GDBN} to print its version number and
1281 no-warranty blurb, and exit.
1283 @item -configuration
1284 @cindex @code{--configuration}
1285 This option causes @value{GDBN} to print details about its build-time
1286 configuration parameters, and then exit. These details can be
1287 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1292 @subsection What @value{GDBN} Does During Startup
1293 @cindex @value{GDBN} startup
1295 Here's the description of what @value{GDBN} does during session startup:
1299 Sets up the command interpreter as specified by the command line
1300 (@pxref{Mode Options, interpreter}).
1304 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1305 used when building @value{GDBN}; @pxref{System-wide configuration,
1306 ,System-wide configuration and settings}) and executes all the commands in
1309 @anchor{Home Directory Init File}
1311 Reads the init file (if any) in your home directory@footnote{On
1312 DOS/Windows systems, the home directory is the one pointed to by the
1313 @code{HOME} environment variable.} and executes all the commands in
1316 @anchor{Option -init-eval-command}
1318 Executes commands and command files specified by the @samp{-iex} and
1319 @samp{-ix} options in their specified order. Usually you should use the
1320 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1321 settings before @value{GDBN} init files get executed and before inferior
1325 Processes command line options and operands.
1327 @anchor{Init File in the Current Directory during Startup}
1329 Reads and executes the commands from init file (if any) in the current
1330 working directory as long as @samp{set auto-load local-gdbinit} is set to
1331 @samp{on} (@pxref{Init File in the Current Directory}).
1332 This is only done if the current directory is
1333 different from your home directory. Thus, you can have more than one
1334 init file, one generic in your home directory, and another, specific
1335 to the program you are debugging, in the directory where you invoke
1339 If the command line specified a program to debug, or a process to
1340 attach to, or a core file, @value{GDBN} loads any auto-loaded
1341 scripts provided for the program or for its loaded shared libraries.
1342 @xref{Auto-loading}.
1344 If you wish to disable the auto-loading during startup,
1345 you must do something like the following:
1348 $ gdb -iex "set auto-load python-scripts off" myprogram
1351 Option @samp{-ex} does not work because the auto-loading is then turned
1355 Executes commands and command files specified by the @samp{-ex} and
1356 @samp{-x} options in their specified order. @xref{Command Files}, for
1357 more details about @value{GDBN} command files.
1360 Reads the command history recorded in the @dfn{history file}.
1361 @xref{Command History}, for more details about the command history and the
1362 files where @value{GDBN} records it.
1365 Init files use the same syntax as @dfn{command files} (@pxref{Command
1366 Files}) and are processed by @value{GDBN} in the same way. The init
1367 file in your home directory can set options (such as @samp{set
1368 complaints}) that affect subsequent processing of command line options
1369 and operands. Init files are not executed if you use the @samp{-nx}
1370 option (@pxref{Mode Options, ,Choosing Modes}).
1372 To display the list of init files loaded by gdb at startup, you
1373 can use @kbd{gdb --help}.
1375 @cindex init file name
1376 @cindex @file{.gdbinit}
1377 @cindex @file{gdb.ini}
1378 The @value{GDBN} init files are normally called @file{.gdbinit}.
1379 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1380 the limitations of file names imposed by DOS filesystems. The Windows
1381 port of @value{GDBN} uses the standard name, but if it finds a
1382 @file{gdb.ini} file in your home directory, it warns you about that
1383 and suggests to rename the file to the standard name.
1387 @section Quitting @value{GDBN}
1388 @cindex exiting @value{GDBN}
1389 @cindex leaving @value{GDBN}
1392 @kindex quit @r{[}@var{expression}@r{]}
1393 @kindex q @r{(@code{quit})}
1394 @item quit @r{[}@var{expression}@r{]}
1396 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1397 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1398 do not supply @var{expression}, @value{GDBN} will terminate normally;
1399 otherwise it will terminate using the result of @var{expression} as the
1404 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1405 terminates the action of any @value{GDBN} command that is in progress and
1406 returns to @value{GDBN} command level. It is safe to type the interrupt
1407 character at any time because @value{GDBN} does not allow it to take effect
1408 until a time when it is safe.
1410 If you have been using @value{GDBN} to control an attached process or
1411 device, you can release it with the @code{detach} command
1412 (@pxref{Attach, ,Debugging an Already-running Process}).
1414 @node Shell Commands
1415 @section Shell Commands
1417 If you need to execute occasional shell commands during your
1418 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1419 just use the @code{shell} command.
1424 @cindex shell escape
1425 @item shell @var{command-string}
1426 @itemx !@var{command-string}
1427 Invoke a standard shell to execute @var{command-string}.
1428 Note that no space is needed between @code{!} and @var{command-string}.
1429 If it exists, the environment variable @code{SHELL} determines which
1430 shell to run. Otherwise @value{GDBN} uses the default shell
1431 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1434 The utility @code{make} is often needed in development environments.
1435 You do not have to use the @code{shell} command for this purpose in
1440 @cindex calling make
1441 @item make @var{make-args}
1442 Execute the @code{make} program with the specified
1443 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1446 @node Logging Output
1447 @section Logging Output
1448 @cindex logging @value{GDBN} output
1449 @cindex save @value{GDBN} output to a file
1451 You may want to save the output of @value{GDBN} commands to a file.
1452 There are several commands to control @value{GDBN}'s logging.
1456 @item set logging on
1458 @item set logging off
1460 @cindex logging file name
1461 @item set logging file @var{file}
1462 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1463 @item set logging overwrite [on|off]
1464 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1465 you want @code{set logging on} to overwrite the logfile instead.
1466 @item set logging redirect [on|off]
1467 By default, @value{GDBN} output will go to both the terminal and the logfile.
1468 Set @code{redirect} if you want output to go only to the log file.
1469 @kindex show logging
1471 Show the current values of the logging settings.
1475 @chapter @value{GDBN} Commands
1477 You can abbreviate a @value{GDBN} command to the first few letters of the command
1478 name, if that abbreviation is unambiguous; and you can repeat certain
1479 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1480 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1481 show you the alternatives available, if there is more than one possibility).
1484 * Command Syntax:: How to give commands to @value{GDBN}
1485 * Completion:: Command completion
1486 * Help:: How to ask @value{GDBN} for help
1489 @node Command Syntax
1490 @section Command Syntax
1492 A @value{GDBN} command is a single line of input. There is no limit on
1493 how long it can be. It starts with a command name, which is followed by
1494 arguments whose meaning depends on the command name. For example, the
1495 command @code{step} accepts an argument which is the number of times to
1496 step, as in @samp{step 5}. You can also use the @code{step} command
1497 with no arguments. Some commands do not allow any arguments.
1499 @cindex abbreviation
1500 @value{GDBN} command names may always be truncated if that abbreviation is
1501 unambiguous. Other possible command abbreviations are listed in the
1502 documentation for individual commands. In some cases, even ambiguous
1503 abbreviations are allowed; for example, @code{s} is specially defined as
1504 equivalent to @code{step} even though there are other commands whose
1505 names start with @code{s}. You can test abbreviations by using them as
1506 arguments to the @code{help} command.
1508 @cindex repeating commands
1509 @kindex RET @r{(repeat last command)}
1510 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1511 repeat the previous command. Certain commands (for example, @code{run})
1512 will not repeat this way; these are commands whose unintentional
1513 repetition might cause trouble and which you are unlikely to want to
1514 repeat. User-defined commands can disable this feature; see
1515 @ref{Define, dont-repeat}.
1517 The @code{list} and @code{x} commands, when you repeat them with
1518 @key{RET}, construct new arguments rather than repeating
1519 exactly as typed. This permits easy scanning of source or memory.
1521 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1522 output, in a way similar to the common utility @code{more}
1523 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1524 @key{RET} too many in this situation, @value{GDBN} disables command
1525 repetition after any command that generates this sort of display.
1527 @kindex # @r{(a comment)}
1529 Any text from a @kbd{#} to the end of the line is a comment; it does
1530 nothing. This is useful mainly in command files (@pxref{Command
1531 Files,,Command Files}).
1533 @cindex repeating command sequences
1534 @kindex Ctrl-o @r{(operate-and-get-next)}
1535 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1536 commands. This command accepts the current line, like @key{RET}, and
1537 then fetches the next line relative to the current line from the history
1541 @section Command Completion
1544 @cindex word completion
1545 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1546 only one possibility; it can also show you what the valid possibilities
1547 are for the next word in a command, at any time. This works for @value{GDBN}
1548 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1550 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1551 of a word. If there is only one possibility, @value{GDBN} fills in the
1552 word, and waits for you to finish the command (or press @key{RET} to
1553 enter it). For example, if you type
1555 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1556 @c complete accuracy in these examples; space introduced for clarity.
1557 @c If texinfo enhancements make it unnecessary, it would be nice to
1558 @c replace " @key" by "@key" in the following...
1560 (@value{GDBP}) info bre @key{TAB}
1564 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1565 the only @code{info} subcommand beginning with @samp{bre}:
1568 (@value{GDBP}) info breakpoints
1572 You can either press @key{RET} at this point, to run the @code{info
1573 breakpoints} command, or backspace and enter something else, if
1574 @samp{breakpoints} does not look like the command you expected. (If you
1575 were sure you wanted @code{info breakpoints} in the first place, you
1576 might as well just type @key{RET} immediately after @samp{info bre},
1577 to exploit command abbreviations rather than command completion).
1579 If there is more than one possibility for the next word when you press
1580 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1581 characters and try again, or just press @key{TAB} a second time;
1582 @value{GDBN} displays all the possible completions for that word. For
1583 example, you might want to set a breakpoint on a subroutine whose name
1584 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1585 just sounds the bell. Typing @key{TAB} again displays all the
1586 function names in your program that begin with those characters, for
1590 (@value{GDBP}) b make_ @key{TAB}
1591 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1592 make_a_section_from_file make_environ
1593 make_abs_section make_function_type
1594 make_blockvector make_pointer_type
1595 make_cleanup make_reference_type
1596 make_command make_symbol_completion_list
1597 (@value{GDBP}) b make_
1601 After displaying the available possibilities, @value{GDBN} copies your
1602 partial input (@samp{b make_} in the example) so you can finish the
1605 If you just want to see the list of alternatives in the first place, you
1606 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1607 means @kbd{@key{META} ?}. You can type this either by holding down a
1608 key designated as the @key{META} shift on your keyboard (if there is
1609 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1611 If the number of possible completions is large, @value{GDBN} will
1612 print as much of the list as it has collected, as well as a message
1613 indicating that the list may be truncated.
1616 (@value{GDBP}) b m@key{TAB}@key{TAB}
1618 <... the rest of the possible completions ...>
1619 *** List may be truncated, max-completions reached. ***
1624 This behavior can be controlled with the following commands:
1627 @kindex set max-completions
1628 @item set max-completions @var{limit}
1629 @itemx set max-completions unlimited
1630 Set the maximum number of completion candidates. @value{GDBN} will
1631 stop looking for more completions once it collects this many candidates.
1632 This is useful when completing on things like function names as collecting
1633 all the possible candidates can be time consuming.
1634 The default value is 200. A value of zero disables tab-completion.
1635 Note that setting either no limit or a very large limit can make
1637 @kindex show max-completions
1638 @item show max-completions
1639 Show the maximum number of candidates that @value{GDBN} will collect and show
1643 @cindex quotes in commands
1644 @cindex completion of quoted strings
1645 Sometimes the string you need, while logically a ``word'', may contain
1646 parentheses or other characters that @value{GDBN} normally excludes from
1647 its notion of a word. To permit word completion to work in this
1648 situation, you may enclose words in @code{'} (single quote marks) in
1649 @value{GDBN} commands.
1651 A likely situation where you might need this is in typing an
1652 expression that involves a C@t{++} symbol name with template
1653 parameters. This is because when completing expressions, GDB treats
1654 the @samp{<} character as word delimiter, assuming that it's the
1655 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1658 For example, when you want to call a C@t{++} template function
1659 interactively using the @code{print} or @code{call} commands, you may
1660 need to distinguish whether you mean the version of @code{name} that
1661 was specialized for @code{int}, @code{name<int>()}, or the version
1662 that was specialized for @code{float}, @code{name<float>()}. To use
1663 the word-completion facilities in this situation, type a single quote
1664 @code{'} at the beginning of the function name. This alerts
1665 @value{GDBN} that it may need to consider more information than usual
1666 when you press @key{TAB} or @kbd{M-?} to request word completion:
1669 (@value{GDBP}) p 'func< @kbd{M-?}
1670 func<int>() func<float>()
1671 (@value{GDBP}) p 'func<
1674 When setting breakpoints however (@pxref{Specify Location}), you don't
1675 usually need to type a quote before the function name, because
1676 @value{GDBN} understands that you want to set a breakpoint on a
1680 (@value{GDBP}) b func< @kbd{M-?}
1681 func<int>() func<float>()
1682 (@value{GDBP}) b func<
1685 This is true even in the case of typing the name of C@t{++} overloaded
1686 functions (multiple definitions of the same function, distinguished by
1687 argument type). For example, when you want to set a breakpoint you
1688 don't need to distinguish whether you mean the version of @code{name}
1689 that takes an @code{int} parameter, @code{name(int)}, or the version
1690 that takes a @code{float} parameter, @code{name(float)}.
1693 (@value{GDBP}) b bubble( @kbd{M-?}
1694 bubble(int) bubble(double)
1695 (@value{GDBP}) b bubble(dou @kbd{M-?}
1699 See @ref{quoting names} for a description of other scenarios that
1702 For more information about overloaded functions, see @ref{C Plus Plus
1703 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1704 overload-resolution off} to disable overload resolution;
1705 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1707 @cindex completion of structure field names
1708 @cindex structure field name completion
1709 @cindex completion of union field names
1710 @cindex union field name completion
1711 When completing in an expression which looks up a field in a
1712 structure, @value{GDBN} also tries@footnote{The completer can be
1713 confused by certain kinds of invalid expressions. Also, it only
1714 examines the static type of the expression, not the dynamic type.} to
1715 limit completions to the field names available in the type of the
1719 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1720 magic to_fputs to_rewind
1721 to_data to_isatty to_write
1722 to_delete to_put to_write_async_safe
1727 This is because the @code{gdb_stdout} is a variable of the type
1728 @code{struct ui_file} that is defined in @value{GDBN} sources as
1735 ui_file_flush_ftype *to_flush;
1736 ui_file_write_ftype *to_write;
1737 ui_file_write_async_safe_ftype *to_write_async_safe;
1738 ui_file_fputs_ftype *to_fputs;
1739 ui_file_read_ftype *to_read;
1740 ui_file_delete_ftype *to_delete;
1741 ui_file_isatty_ftype *to_isatty;
1742 ui_file_rewind_ftype *to_rewind;
1743 ui_file_put_ftype *to_put;
1750 @section Getting Help
1751 @cindex online documentation
1754 You can always ask @value{GDBN} itself for information on its commands,
1755 using the command @code{help}.
1758 @kindex h @r{(@code{help})}
1761 You can use @code{help} (abbreviated @code{h}) with no arguments to
1762 display a short list of named classes of commands:
1766 List of classes of commands:
1768 aliases -- Aliases of other commands
1769 breakpoints -- Making program stop at certain points
1770 data -- Examining data
1771 files -- Specifying and examining files
1772 internals -- Maintenance commands
1773 obscure -- Obscure features
1774 running -- Running the program
1775 stack -- Examining the stack
1776 status -- Status inquiries
1777 support -- Support facilities
1778 tracepoints -- Tracing of program execution without
1779 stopping the program
1780 user-defined -- User-defined commands
1782 Type "help" followed by a class name for a list of
1783 commands in that class.
1784 Type "help" followed by command name for full
1786 Command name abbreviations are allowed if unambiguous.
1789 @c the above line break eliminates huge line overfull...
1791 @item help @var{class}
1792 Using one of the general help classes as an argument, you can get a
1793 list of the individual commands in that class. For example, here is the
1794 help display for the class @code{status}:
1797 (@value{GDBP}) help status
1802 @c Line break in "show" line falsifies real output, but needed
1803 @c to fit in smallbook page size.
1804 info -- Generic command for showing things
1805 about the program being debugged
1806 show -- Generic command for showing things
1809 Type "help" followed by command name for full
1811 Command name abbreviations are allowed if unambiguous.
1815 @item help @var{command}
1816 With a command name as @code{help} argument, @value{GDBN} displays a
1817 short paragraph on how to use that command.
1820 @item apropos @var{args}
1821 The @code{apropos} command searches through all of the @value{GDBN}
1822 commands, and their documentation, for the regular expression specified in
1823 @var{args}. It prints out all matches found. For example:
1834 alias -- Define a new command that is an alias of an existing command
1835 aliases -- Aliases of other commands
1836 d -- Delete some breakpoints or auto-display expressions
1837 del -- Delete some breakpoints or auto-display expressions
1838 delete -- Delete some breakpoints or auto-display expressions
1843 @item complete @var{args}
1844 The @code{complete @var{args}} command lists all the possible completions
1845 for the beginning of a command. Use @var{args} to specify the beginning of the
1846 command you want completed. For example:
1852 @noindent results in:
1863 @noindent This is intended for use by @sc{gnu} Emacs.
1866 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1867 and @code{show} to inquire about the state of your program, or the state
1868 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1869 manual introduces each of them in the appropriate context. The listings
1870 under @code{info} and under @code{show} in the Command, Variable, and
1871 Function Index point to all the sub-commands. @xref{Command and Variable
1877 @kindex i @r{(@code{info})}
1879 This command (abbreviated @code{i}) is for describing the state of your
1880 program. For example, you can show the arguments passed to a function
1881 with @code{info args}, list the registers currently in use with @code{info
1882 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1883 You can get a complete list of the @code{info} sub-commands with
1884 @w{@code{help info}}.
1888 You can assign the result of an expression to an environment variable with
1889 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1890 @code{set prompt $}.
1894 In contrast to @code{info}, @code{show} is for describing the state of
1895 @value{GDBN} itself.
1896 You can change most of the things you can @code{show}, by using the
1897 related command @code{set}; for example, you can control what number
1898 system is used for displays with @code{set radix}, or simply inquire
1899 which is currently in use with @code{show radix}.
1902 To display all the settable parameters and their current
1903 values, you can use @code{show} with no arguments; you may also use
1904 @code{info set}. Both commands produce the same display.
1905 @c FIXME: "info set" violates the rule that "info" is for state of
1906 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1907 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1911 Here are several miscellaneous @code{show} subcommands, all of which are
1912 exceptional in lacking corresponding @code{set} commands:
1915 @kindex show version
1916 @cindex @value{GDBN} version number
1918 Show what version of @value{GDBN} is running. You should include this
1919 information in @value{GDBN} bug-reports. If multiple versions of
1920 @value{GDBN} are in use at your site, you may need to determine which
1921 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1922 commands are introduced, and old ones may wither away. Also, many
1923 system vendors ship variant versions of @value{GDBN}, and there are
1924 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1925 The version number is the same as the one announced when you start
1928 @kindex show copying
1929 @kindex info copying
1930 @cindex display @value{GDBN} copyright
1933 Display information about permission for copying @value{GDBN}.
1935 @kindex show warranty
1936 @kindex info warranty
1938 @itemx info warranty
1939 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1940 if your version of @value{GDBN} comes with one.
1942 @kindex show configuration
1943 @item show configuration
1944 Display detailed information about the way @value{GDBN} was configured
1945 when it was built. This displays the optional arguments passed to the
1946 @file{configure} script and also configuration parameters detected
1947 automatically by @command{configure}. When reporting a @value{GDBN}
1948 bug (@pxref{GDB Bugs}), it is important to include this information in
1954 @chapter Running Programs Under @value{GDBN}
1956 When you run a program under @value{GDBN}, you must first generate
1957 debugging information when you compile it.
1959 You may start @value{GDBN} with its arguments, if any, in an environment
1960 of your choice. If you are doing native debugging, you may redirect
1961 your program's input and output, debug an already running process, or
1962 kill a child process.
1965 * Compilation:: Compiling for debugging
1966 * Starting:: Starting your program
1967 * Arguments:: Your program's arguments
1968 * Environment:: Your program's environment
1970 * Working Directory:: Your program's working directory
1971 * Input/Output:: Your program's input and output
1972 * Attach:: Debugging an already-running process
1973 * Kill Process:: Killing the child process
1975 * Inferiors and Programs:: Debugging multiple inferiors and programs
1976 * Threads:: Debugging programs with multiple threads
1977 * Forks:: Debugging forks
1978 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1982 @section Compiling for Debugging
1984 In order to debug a program effectively, you need to generate
1985 debugging information when you compile it. This debugging information
1986 is stored in the object file; it describes the data type of each
1987 variable or function and the correspondence between source line numbers
1988 and addresses in the executable code.
1990 To request debugging information, specify the @samp{-g} option when you run
1993 Programs that are to be shipped to your customers are compiled with
1994 optimizations, using the @samp{-O} compiler option. However, some
1995 compilers are unable to handle the @samp{-g} and @samp{-O} options
1996 together. Using those compilers, you cannot generate optimized
1997 executables containing debugging information.
1999 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2000 without @samp{-O}, making it possible to debug optimized code. We
2001 recommend that you @emph{always} use @samp{-g} whenever you compile a
2002 program. You may think your program is correct, but there is no sense
2003 in pushing your luck. For more information, see @ref{Optimized Code}.
2005 Older versions of the @sc{gnu} C compiler permitted a variant option
2006 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2007 format; if your @sc{gnu} C compiler has this option, do not use it.
2009 @value{GDBN} knows about preprocessor macros and can show you their
2010 expansion (@pxref{Macros}). Most compilers do not include information
2011 about preprocessor macros in the debugging information if you specify
2012 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2013 the @sc{gnu} C compiler, provides macro information if you are using
2014 the DWARF debugging format, and specify the option @option{-g3}.
2016 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2017 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2018 information on @value{NGCC} options affecting debug information.
2020 You will have the best debugging experience if you use the latest
2021 version of the DWARF debugging format that your compiler supports.
2022 DWARF is currently the most expressive and best supported debugging
2023 format in @value{GDBN}.
2027 @section Starting your Program
2033 @kindex r @r{(@code{run})}
2036 Use the @code{run} command to start your program under @value{GDBN}.
2037 You must first specify the program name with an argument to
2038 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2039 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2040 command (@pxref{Files, ,Commands to Specify Files}).
2044 If you are running your program in an execution environment that
2045 supports processes, @code{run} creates an inferior process and makes
2046 that process run your program. In some environments without processes,
2047 @code{run} jumps to the start of your program. Other targets,
2048 like @samp{remote}, are always running. If you get an error
2049 message like this one:
2052 The "remote" target does not support "run".
2053 Try "help target" or "continue".
2057 then use @code{continue} to run your program. You may need @code{load}
2058 first (@pxref{load}).
2060 The execution of a program is affected by certain information it
2061 receives from its superior. @value{GDBN} provides ways to specify this
2062 information, which you must do @emph{before} starting your program. (You
2063 can change it after starting your program, but such changes only affect
2064 your program the next time you start it.) This information may be
2065 divided into four categories:
2068 @item The @emph{arguments.}
2069 Specify the arguments to give your program as the arguments of the
2070 @code{run} command. If a shell is available on your target, the shell
2071 is used to pass the arguments, so that you may use normal conventions
2072 (such as wildcard expansion or variable substitution) in describing
2074 In Unix systems, you can control which shell is used with the
2075 @code{SHELL} environment variable. If you do not define @code{SHELL},
2076 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2077 use of any shell with the @code{set startup-with-shell} command (see
2080 @item The @emph{environment.}
2081 Your program normally inherits its environment from @value{GDBN}, but you can
2082 use the @value{GDBN} commands @code{set environment} and @code{unset
2083 environment} to change parts of the environment that affect
2084 your program. @xref{Environment, ,Your Program's Environment}.
2086 @item The @emph{working directory.}
2087 You can set your program's working directory with the command
2088 @kbd{set cwd}. If you do not set any working directory with this
2089 command, your program will inherit @value{GDBN}'s working directory if
2090 native debugging, or the remote server's working directory if remote
2091 debugging. @xref{Working Directory, ,Your Program's Working
2094 @item The @emph{standard input and output.}
2095 Your program normally uses the same device for standard input and
2096 standard output as @value{GDBN} is using. You can redirect input and output
2097 in the @code{run} command line, or you can use the @code{tty} command to
2098 set a different device for your program.
2099 @xref{Input/Output, ,Your Program's Input and Output}.
2102 @emph{Warning:} While input and output redirection work, you cannot use
2103 pipes to pass the output of the program you are debugging to another
2104 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2108 When you issue the @code{run} command, your program begins to execute
2109 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2110 of how to arrange for your program to stop. Once your program has
2111 stopped, you may call functions in your program, using the @code{print}
2112 or @code{call} commands. @xref{Data, ,Examining Data}.
2114 If the modification time of your symbol file has changed since the last
2115 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2116 table, and reads it again. When it does this, @value{GDBN} tries to retain
2117 your current breakpoints.
2122 @cindex run to main procedure
2123 The name of the main procedure can vary from language to language.
2124 With C or C@t{++}, the main procedure name is always @code{main}, but
2125 other languages such as Ada do not require a specific name for their
2126 main procedure. The debugger provides a convenient way to start the
2127 execution of the program and to stop at the beginning of the main
2128 procedure, depending on the language used.
2130 The @samp{start} command does the equivalent of setting a temporary
2131 breakpoint at the beginning of the main procedure and then invoking
2132 the @samp{run} command.
2134 @cindex elaboration phase
2135 Some programs contain an @dfn{elaboration} phase where some startup code is
2136 executed before the main procedure is called. This depends on the
2137 languages used to write your program. In C@t{++}, for instance,
2138 constructors for static and global objects are executed before
2139 @code{main} is called. It is therefore possible that the debugger stops
2140 before reaching the main procedure. However, the temporary breakpoint
2141 will remain to halt execution.
2143 Specify the arguments to give to your program as arguments to the
2144 @samp{start} command. These arguments will be given verbatim to the
2145 underlying @samp{run} command. Note that the same arguments will be
2146 reused if no argument is provided during subsequent calls to
2147 @samp{start} or @samp{run}.
2149 It is sometimes necessary to debug the program during elaboration. In
2150 these cases, using the @code{start} command would stop the execution
2151 of your program too late, as the program would have already completed
2152 the elaboration phase. Under these circumstances, either insert
2153 breakpoints in your elaboration code before running your program or
2154 use the @code{starti} command.
2158 @cindex run to first instruction
2159 The @samp{starti} command does the equivalent of setting a temporary
2160 breakpoint at the first instruction of a program's execution and then
2161 invoking the @samp{run} command. For programs containing an
2162 elaboration phase, the @code{starti} command will stop execution at
2163 the start of the elaboration phase.
2165 @anchor{set exec-wrapper}
2166 @kindex set exec-wrapper
2167 @item set exec-wrapper @var{wrapper}
2168 @itemx show exec-wrapper
2169 @itemx unset exec-wrapper
2170 When @samp{exec-wrapper} is set, the specified wrapper is used to
2171 launch programs for debugging. @value{GDBN} starts your program
2172 with a shell command of the form @kbd{exec @var{wrapper}
2173 @var{program}}. Quoting is added to @var{program} and its
2174 arguments, but not to @var{wrapper}, so you should add quotes if
2175 appropriate for your shell. The wrapper runs until it executes
2176 your program, and then @value{GDBN} takes control.
2178 You can use any program that eventually calls @code{execve} with
2179 its arguments as a wrapper. Several standard Unix utilities do
2180 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2181 with @code{exec "$@@"} will also work.
2183 For example, you can use @code{env} to pass an environment variable to
2184 the debugged program, without setting the variable in your shell's
2188 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2192 This command is available when debugging locally on most targets, excluding
2193 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2195 @kindex set startup-with-shell
2196 @anchor{set startup-with-shell}
2197 @item set startup-with-shell
2198 @itemx set startup-with-shell on
2199 @itemx set startup-with-shell off
2200 @itemx show startup-with-shell
2201 On Unix systems, by default, if a shell is available on your target,
2202 @value{GDBN}) uses it to start your program. Arguments of the
2203 @code{run} command are passed to the shell, which does variable
2204 substitution, expands wildcard characters and performs redirection of
2205 I/O. In some circumstances, it may be useful to disable such use of a
2206 shell, for example, when debugging the shell itself or diagnosing
2207 startup failures such as:
2211 Starting program: ./a.out
2212 During startup program terminated with signal SIGSEGV, Segmentation fault.
2216 which indicates the shell or the wrapper specified with
2217 @samp{exec-wrapper} crashed, not your program. Most often, this is
2218 caused by something odd in your shell's non-interactive mode
2219 initialization file---such as @file{.cshrc} for C-shell,
2220 $@file{.zshenv} for the Z shell, or the file specified in the
2221 @samp{BASH_ENV} environment variable for BASH.
2223 @anchor{set auto-connect-native-target}
2224 @kindex set auto-connect-native-target
2225 @item set auto-connect-native-target
2226 @itemx set auto-connect-native-target on
2227 @itemx set auto-connect-native-target off
2228 @itemx show auto-connect-native-target
2230 By default, if not connected to any target yet (e.g., with
2231 @code{target remote}), the @code{run} command starts your program as a
2232 native process under @value{GDBN}, on your local machine. If you're
2233 sure you don't want to debug programs on your local machine, you can
2234 tell @value{GDBN} to not connect to the native target automatically
2235 with the @code{set auto-connect-native-target off} command.
2237 If @code{on}, which is the default, and if @value{GDBN} is not
2238 connected to a target already, the @code{run} command automaticaly
2239 connects to the native target, if one is available.
2241 If @code{off}, and if @value{GDBN} is not connected to a target
2242 already, the @code{run} command fails with an error:
2246 Don't know how to run. Try "help target".
2249 If @value{GDBN} is already connected to a target, @value{GDBN} always
2250 uses it with the @code{run} command.
2252 In any case, you can explicitly connect to the native target with the
2253 @code{target native} command. For example,
2256 (@value{GDBP}) set auto-connect-native-target off
2258 Don't know how to run. Try "help target".
2259 (@value{GDBP}) target native
2261 Starting program: ./a.out
2262 [Inferior 1 (process 10421) exited normally]
2265 In case you connected explicitly to the @code{native} target,
2266 @value{GDBN} remains connected even if all inferiors exit, ready for
2267 the next @code{run} command. Use the @code{disconnect} command to
2270 Examples of other commands that likewise respect the
2271 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2272 proc}, @code{info os}.
2274 @kindex set disable-randomization
2275 @item set disable-randomization
2276 @itemx set disable-randomization on
2277 This option (enabled by default in @value{GDBN}) will turn off the native
2278 randomization of the virtual address space of the started program. This option
2279 is useful for multiple debugging sessions to make the execution better
2280 reproducible and memory addresses reusable across debugging sessions.
2282 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2283 On @sc{gnu}/Linux you can get the same behavior using
2286 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2289 @item set disable-randomization off
2290 Leave the behavior of the started executable unchanged. Some bugs rear their
2291 ugly heads only when the program is loaded at certain addresses. If your bug
2292 disappears when you run the program under @value{GDBN}, that might be because
2293 @value{GDBN} by default disables the address randomization on platforms, such
2294 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2295 disable-randomization off} to try to reproduce such elusive bugs.
2297 On targets where it is available, virtual address space randomization
2298 protects the programs against certain kinds of security attacks. In these
2299 cases the attacker needs to know the exact location of a concrete executable
2300 code. Randomizing its location makes it impossible to inject jumps misusing
2301 a code at its expected addresses.
2303 Prelinking shared libraries provides a startup performance advantage but it
2304 makes addresses in these libraries predictable for privileged processes by
2305 having just unprivileged access at the target system. Reading the shared
2306 library binary gives enough information for assembling the malicious code
2307 misusing it. Still even a prelinked shared library can get loaded at a new
2308 random address just requiring the regular relocation process during the
2309 startup. Shared libraries not already prelinked are always loaded at
2310 a randomly chosen address.
2312 Position independent executables (PIE) contain position independent code
2313 similar to the shared libraries and therefore such executables get loaded at
2314 a randomly chosen address upon startup. PIE executables always load even
2315 already prelinked shared libraries at a random address. You can build such
2316 executable using @command{gcc -fPIE -pie}.
2318 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2319 (as long as the randomization is enabled).
2321 @item show disable-randomization
2322 Show the current setting of the explicit disable of the native randomization of
2323 the virtual address space of the started program.
2328 @section Your Program's Arguments
2330 @cindex arguments (to your program)
2331 The arguments to your program can be specified by the arguments of the
2333 They are passed to a shell, which expands wildcard characters and
2334 performs redirection of I/O, and thence to your program. Your
2335 @code{SHELL} environment variable (if it exists) specifies what shell
2336 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2337 the default shell (@file{/bin/sh} on Unix).
2339 On non-Unix systems, the program is usually invoked directly by
2340 @value{GDBN}, which emulates I/O redirection via the appropriate system
2341 calls, and the wildcard characters are expanded by the startup code of
2342 the program, not by the shell.
2344 @code{run} with no arguments uses the same arguments used by the previous
2345 @code{run}, or those set by the @code{set args} command.
2350 Specify the arguments to be used the next time your program is run. If
2351 @code{set args} has no arguments, @code{run} executes your program
2352 with no arguments. Once you have run your program with arguments,
2353 using @code{set args} before the next @code{run} is the only way to run
2354 it again without arguments.
2358 Show the arguments to give your program when it is started.
2362 @section Your Program's Environment
2364 @cindex environment (of your program)
2365 The @dfn{environment} consists of a set of environment variables and
2366 their values. Environment variables conventionally record such things as
2367 your user name, your home directory, your terminal type, and your search
2368 path for programs to run. Usually you set up environment variables with
2369 the shell and they are inherited by all the other programs you run. When
2370 debugging, it can be useful to try running your program with a modified
2371 environment without having to start @value{GDBN} over again.
2375 @item path @var{directory}
2376 Add @var{directory} to the front of the @code{PATH} environment variable
2377 (the search path for executables) that will be passed to your program.
2378 The value of @code{PATH} used by @value{GDBN} does not change.
2379 You may specify several directory names, separated by whitespace or by a
2380 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2381 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2382 is moved to the front, so it is searched sooner.
2384 You can use the string @samp{$cwd} to refer to whatever is the current
2385 working directory at the time @value{GDBN} searches the path. If you
2386 use @samp{.} instead, it refers to the directory where you executed the
2387 @code{path} command. @value{GDBN} replaces @samp{.} in the
2388 @var{directory} argument (with the current path) before adding
2389 @var{directory} to the search path.
2390 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2391 @c document that, since repeating it would be a no-op.
2395 Display the list of search paths for executables (the @code{PATH}
2396 environment variable).
2398 @kindex show environment
2399 @item show environment @r{[}@var{varname}@r{]}
2400 Print the value of environment variable @var{varname} to be given to
2401 your program when it starts. If you do not supply @var{varname},
2402 print the names and values of all environment variables to be given to
2403 your program. You can abbreviate @code{environment} as @code{env}.
2405 @kindex set environment
2406 @anchor{set environment}
2407 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2408 Set environment variable @var{varname} to @var{value}. The value
2409 changes for your program (and the shell @value{GDBN} uses to launch
2410 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2411 values of environment variables are just strings, and any
2412 interpretation is supplied by your program itself. The @var{value}
2413 parameter is optional; if it is eliminated, the variable is set to a
2415 @c "any string" here does not include leading, trailing
2416 @c blanks. Gnu asks: does anyone care?
2418 For example, this command:
2425 tells the debugged program, when subsequently run, that its user is named
2426 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2427 are not actually required.)
2429 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2430 which also inherits the environment set with @code{set environment}.
2431 If necessary, you can avoid that by using the @samp{env} program as a
2432 wrapper instead of using @code{set environment}. @xref{set
2433 exec-wrapper}, for an example doing just that.
2435 Environment variables that are set by the user are also transmitted to
2436 @command{gdbserver} to be used when starting the remote inferior.
2437 @pxref{QEnvironmentHexEncoded}.
2439 @kindex unset environment
2440 @anchor{unset environment}
2441 @item unset environment @var{varname}
2442 Remove variable @var{varname} from the environment to be passed to your
2443 program. This is different from @samp{set env @var{varname} =};
2444 @code{unset environment} removes the variable from the environment,
2445 rather than assigning it an empty value.
2447 Environment variables that are unset by the user are also unset on
2448 @command{gdbserver} when starting the remote inferior.
2449 @pxref{QEnvironmentUnset}.
2452 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2453 the shell indicated by your @code{SHELL} environment variable if it
2454 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2455 names a shell that runs an initialization file when started
2456 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2457 for the Z shell, or the file specified in the @samp{BASH_ENV}
2458 environment variable for BASH---any variables you set in that file
2459 affect your program. You may wish to move setting of environment
2460 variables to files that are only run when you sign on, such as
2461 @file{.login} or @file{.profile}.
2463 @node Working Directory
2464 @section Your Program's Working Directory
2466 @cindex working directory (of your program)
2467 Each time you start your program with @code{run}, the inferior will be
2468 initialized with the current working directory specified by the
2469 @kbd{set cwd} command. If no directory has been specified by this
2470 command, then the inferior will inherit @value{GDBN}'s current working
2471 directory as its working directory if native debugging, or it will
2472 inherit the remote server's current working directory if remote
2477 @cindex change inferior's working directory
2478 @anchor{set cwd command}
2479 @item set cwd @r{[}@var{directory}@r{]}
2480 Set the inferior's working directory to @var{directory}, which will be
2481 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2482 argument has been specified, the command clears the setting and resets
2483 it to an empty state. This setting has no effect on @value{GDBN}'s
2484 working directory, and it only takes effect the next time you start
2485 the inferior. The @file{~} in @var{directory} is a short for the
2486 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2487 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2488 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2491 You can also change @value{GDBN}'s current working directory by using
2492 the @code{cd} command.
2496 @cindex show inferior's working directory
2498 Show the inferior's working directory. If no directory has been
2499 specified by @kbd{set cwd}, then the default inferior's working
2500 directory is the same as @value{GDBN}'s working directory.
2503 @cindex change @value{GDBN}'s working directory
2505 @item cd @r{[}@var{directory}@r{]}
2506 Set the @value{GDBN} working directory to @var{directory}. If not
2507 given, @var{directory} uses @file{'~'}.
2509 The @value{GDBN} working directory serves as a default for the
2510 commands that specify files for @value{GDBN} to operate on.
2511 @xref{Files, ,Commands to Specify Files}.
2512 @xref{set cwd command}
2516 Print the @value{GDBN} working directory.
2519 It is generally impossible to find the current working directory of
2520 the process being debugged (since a program can change its directory
2521 during its run). If you work on a system where @value{GDBN} is
2522 configured with the @file{/proc} support, you can use the @code{info
2523 proc} command (@pxref{SVR4 Process Information}) to find out the
2524 current working directory of the debuggee.
2527 @section Your Program's Input and Output
2532 By default, the program you run under @value{GDBN} does input and output to
2533 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2534 to its own terminal modes to interact with you, but it records the terminal
2535 modes your program was using and switches back to them when you continue
2536 running your program.
2539 @kindex info terminal
2541 Displays information recorded by @value{GDBN} about the terminal modes your
2545 You can redirect your program's input and/or output using shell
2546 redirection with the @code{run} command. For example,
2553 starts your program, diverting its output to the file @file{outfile}.
2556 @cindex controlling terminal
2557 Another way to specify where your program should do input and output is
2558 with the @code{tty} command. This command accepts a file name as
2559 argument, and causes this file to be the default for future @code{run}
2560 commands. It also resets the controlling terminal for the child
2561 process, for future @code{run} commands. For example,
2568 directs that processes started with subsequent @code{run} commands
2569 default to do input and output on the terminal @file{/dev/ttyb} and have
2570 that as their controlling terminal.
2572 An explicit redirection in @code{run} overrides the @code{tty} command's
2573 effect on the input/output device, but not its effect on the controlling
2576 When you use the @code{tty} command or redirect input in the @code{run}
2577 command, only the input @emph{for your program} is affected. The input
2578 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2579 for @code{set inferior-tty}.
2581 @cindex inferior tty
2582 @cindex set inferior controlling terminal
2583 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2584 display the name of the terminal that will be used for future runs of your
2588 @item set inferior-tty [ @var{tty} ]
2589 @kindex set inferior-tty
2590 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2591 restores the default behavior, which is to use the same terminal as
2594 @item show inferior-tty
2595 @kindex show inferior-tty
2596 Show the current tty for the program being debugged.
2600 @section Debugging an Already-running Process
2605 @item attach @var{process-id}
2606 This command attaches to a running process---one that was started
2607 outside @value{GDBN}. (@code{info files} shows your active
2608 targets.) The command takes as argument a process ID. The usual way to
2609 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2610 or with the @samp{jobs -l} shell command.
2612 @code{attach} does not repeat if you press @key{RET} a second time after
2613 executing the command.
2616 To use @code{attach}, your program must be running in an environment
2617 which supports processes; for example, @code{attach} does not work for
2618 programs on bare-board targets that lack an operating system. You must
2619 also have permission to send the process a signal.
2621 When you use @code{attach}, the debugger finds the program running in
2622 the process first by looking in the current working directory, then (if
2623 the program is not found) by using the source file search path
2624 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2625 the @code{file} command to load the program. @xref{Files, ,Commands to
2628 The first thing @value{GDBN} does after arranging to debug the specified
2629 process is to stop it. You can examine and modify an attached process
2630 with all the @value{GDBN} commands that are ordinarily available when
2631 you start processes with @code{run}. You can insert breakpoints; you
2632 can step and continue; you can modify storage. If you would rather the
2633 process continue running, you may use the @code{continue} command after
2634 attaching @value{GDBN} to the process.
2639 When you have finished debugging the attached process, you can use the
2640 @code{detach} command to release it from @value{GDBN} control. Detaching
2641 the process continues its execution. After the @code{detach} command,
2642 that process and @value{GDBN} become completely independent once more, and you
2643 are ready to @code{attach} another process or start one with @code{run}.
2644 @code{detach} does not repeat if you press @key{RET} again after
2645 executing the command.
2648 If you exit @value{GDBN} while you have an attached process, you detach
2649 that process. If you use the @code{run} command, you kill that process.
2650 By default, @value{GDBN} asks for confirmation if you try to do either of these
2651 things; you can control whether or not you need to confirm by using the
2652 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2656 @section Killing the Child Process
2661 Kill the child process in which your program is running under @value{GDBN}.
2664 This command is useful if you wish to debug a core dump instead of a
2665 running process. @value{GDBN} ignores any core dump file while your program
2668 On some operating systems, a program cannot be executed outside @value{GDBN}
2669 while you have breakpoints set on it inside @value{GDBN}. You can use the
2670 @code{kill} command in this situation to permit running your program
2671 outside the debugger.
2673 The @code{kill} command is also useful if you wish to recompile and
2674 relink your program, since on many systems it is impossible to modify an
2675 executable file while it is running in a process. In this case, when you
2676 next type @code{run}, @value{GDBN} notices that the file has changed, and
2677 reads the symbol table again (while trying to preserve your current
2678 breakpoint settings).
2680 @node Inferiors and Programs
2681 @section Debugging Multiple Inferiors and Programs
2683 @value{GDBN} lets you run and debug multiple programs in a single
2684 session. In addition, @value{GDBN} on some systems may let you run
2685 several programs simultaneously (otherwise you have to exit from one
2686 before starting another). In the most general case, you can have
2687 multiple threads of execution in each of multiple processes, launched
2688 from multiple executables.
2691 @value{GDBN} represents the state of each program execution with an
2692 object called an @dfn{inferior}. An inferior typically corresponds to
2693 a process, but is more general and applies also to targets that do not
2694 have processes. Inferiors may be created before a process runs, and
2695 may be retained after a process exits. Inferiors have unique
2696 identifiers that are different from process ids. Usually each
2697 inferior will also have its own distinct address space, although some
2698 embedded targets may have several inferiors running in different parts
2699 of a single address space. Each inferior may in turn have multiple
2700 threads running in it.
2702 To find out what inferiors exist at any moment, use @w{@code{info
2706 @kindex info inferiors
2707 @item info inferiors
2708 Print a list of all inferiors currently being managed by @value{GDBN}.
2710 @value{GDBN} displays for each inferior (in this order):
2714 the inferior number assigned by @value{GDBN}
2717 the target system's inferior identifier
2720 the name of the executable the inferior is running.
2725 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2726 indicates the current inferior.
2730 @c end table here to get a little more width for example
2733 (@value{GDBP}) info inferiors
2734 Num Description Executable
2735 2 process 2307 hello
2736 * 1 process 3401 goodbye
2739 To switch focus between inferiors, use the @code{inferior} command:
2742 @kindex inferior @var{infno}
2743 @item inferior @var{infno}
2744 Make inferior number @var{infno} the current inferior. The argument
2745 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2746 in the first field of the @samp{info inferiors} display.
2749 @vindex $_inferior@r{, convenience variable}
2750 The debugger convenience variable @samp{$_inferior} contains the
2751 number of the current inferior. You may find this useful in writing
2752 breakpoint conditional expressions, command scripts, and so forth.
2753 @xref{Convenience Vars,, Convenience Variables}, for general
2754 information on convenience variables.
2756 You can get multiple executables into a debugging session via the
2757 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2758 systems @value{GDBN} can add inferiors to the debug session
2759 automatically by following calls to @code{fork} and @code{exec}. To
2760 remove inferiors from the debugging session use the
2761 @w{@code{remove-inferiors}} command.
2764 @kindex add-inferior
2765 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2766 Adds @var{n} inferiors to be run using @var{executable} as the
2767 executable; @var{n} defaults to 1. If no executable is specified,
2768 the inferiors begins empty, with no program. You can still assign or
2769 change the program assigned to the inferior at any time by using the
2770 @code{file} command with the executable name as its argument.
2772 @kindex clone-inferior
2773 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2774 Adds @var{n} inferiors ready to execute the same program as inferior
2775 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2776 number of the current inferior. This is a convenient command when you
2777 want to run another instance of the inferior you are debugging.
2780 (@value{GDBP}) info inferiors
2781 Num Description Executable
2782 * 1 process 29964 helloworld
2783 (@value{GDBP}) clone-inferior
2786 (@value{GDBP}) info inferiors
2787 Num Description Executable
2789 * 1 process 29964 helloworld
2792 You can now simply switch focus to inferior 2 and run it.
2794 @kindex remove-inferiors
2795 @item remove-inferiors @var{infno}@dots{}
2796 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2797 possible to remove an inferior that is running with this command. For
2798 those, use the @code{kill} or @code{detach} command first.
2802 To quit debugging one of the running inferiors that is not the current
2803 inferior, you can either detach from it by using the @w{@code{detach
2804 inferior}} command (allowing it to run independently), or kill it
2805 using the @w{@code{kill inferiors}} command:
2808 @kindex detach inferiors @var{infno}@dots{}
2809 @item detach inferior @var{infno}@dots{}
2810 Detach from the inferior or inferiors identified by @value{GDBN}
2811 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2812 still stays on the list of inferiors shown by @code{info inferiors},
2813 but its Description will show @samp{<null>}.
2815 @kindex kill inferiors @var{infno}@dots{}
2816 @item kill inferiors @var{infno}@dots{}
2817 Kill the inferior or inferiors identified by @value{GDBN} inferior
2818 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2819 stays on the list of inferiors shown by @code{info inferiors}, but its
2820 Description will show @samp{<null>}.
2823 After the successful completion of a command such as @code{detach},
2824 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2825 a normal process exit, the inferior is still valid and listed with
2826 @code{info inferiors}, ready to be restarted.
2829 To be notified when inferiors are started or exit under @value{GDBN}'s
2830 control use @w{@code{set print inferior-events}}:
2833 @kindex set print inferior-events
2834 @cindex print messages on inferior start and exit
2835 @item set print inferior-events
2836 @itemx set print inferior-events on
2837 @itemx set print inferior-events off
2838 The @code{set print inferior-events} command allows you to enable or
2839 disable printing of messages when @value{GDBN} notices that new
2840 inferiors have started or that inferiors have exited or have been
2841 detached. By default, these messages will not be printed.
2843 @kindex show print inferior-events
2844 @item show print inferior-events
2845 Show whether messages will be printed when @value{GDBN} detects that
2846 inferiors have started, exited or have been detached.
2849 Many commands will work the same with multiple programs as with a
2850 single program: e.g., @code{print myglobal} will simply display the
2851 value of @code{myglobal} in the current inferior.
2854 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2855 get more info about the relationship of inferiors, programs, address
2856 spaces in a debug session. You can do that with the @w{@code{maint
2857 info program-spaces}} command.
2860 @kindex maint info program-spaces
2861 @item maint info program-spaces
2862 Print a list of all program spaces currently being managed by
2865 @value{GDBN} displays for each program space (in this order):
2869 the program space number assigned by @value{GDBN}
2872 the name of the executable loaded into the program space, with e.g.,
2873 the @code{file} command.
2878 An asterisk @samp{*} preceding the @value{GDBN} program space number
2879 indicates the current program space.
2881 In addition, below each program space line, @value{GDBN} prints extra
2882 information that isn't suitable to display in tabular form. For
2883 example, the list of inferiors bound to the program space.
2886 (@value{GDBP}) maint info program-spaces
2890 Bound inferiors: ID 1 (process 21561)
2893 Here we can see that no inferior is running the program @code{hello},
2894 while @code{process 21561} is running the program @code{goodbye}. On
2895 some targets, it is possible that multiple inferiors are bound to the
2896 same program space. The most common example is that of debugging both
2897 the parent and child processes of a @code{vfork} call. For example,
2900 (@value{GDBP}) maint info program-spaces
2903 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2906 Here, both inferior 2 and inferior 1 are running in the same program
2907 space as a result of inferior 1 having executed a @code{vfork} call.
2911 @section Debugging Programs with Multiple Threads
2913 @cindex threads of execution
2914 @cindex multiple threads
2915 @cindex switching threads
2916 In some operating systems, such as GNU/Linux and Solaris, a single program
2917 may have more than one @dfn{thread} of execution. The precise semantics
2918 of threads differ from one operating system to another, but in general
2919 the threads of a single program are akin to multiple processes---except
2920 that they share one address space (that is, they can all examine and
2921 modify the same variables). On the other hand, each thread has its own
2922 registers and execution stack, and perhaps private memory.
2924 @value{GDBN} provides these facilities for debugging multi-thread
2928 @item automatic notification of new threads
2929 @item @samp{thread @var{thread-id}}, a command to switch among threads
2930 @item @samp{info threads}, a command to inquire about existing threads
2931 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2932 a command to apply a command to a list of threads
2933 @item thread-specific breakpoints
2934 @item @samp{set print thread-events}, which controls printing of
2935 messages on thread start and exit.
2936 @item @samp{set libthread-db-search-path @var{path}}, which lets
2937 the user specify which @code{libthread_db} to use if the default choice
2938 isn't compatible with the program.
2941 @cindex focus of debugging
2942 @cindex current thread
2943 The @value{GDBN} thread debugging facility allows you to observe all
2944 threads while your program runs---but whenever @value{GDBN} takes
2945 control, one thread in particular is always the focus of debugging.
2946 This thread is called the @dfn{current thread}. Debugging commands show
2947 program information from the perspective of the current thread.
2949 @cindex @code{New} @var{systag} message
2950 @cindex thread identifier (system)
2951 @c FIXME-implementors!! It would be more helpful if the [New...] message
2952 @c included GDB's numeric thread handle, so you could just go to that
2953 @c thread without first checking `info threads'.
2954 Whenever @value{GDBN} detects a new thread in your program, it displays
2955 the target system's identification for the thread with a message in the
2956 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2957 whose form varies depending on the particular system. For example, on
2958 @sc{gnu}/Linux, you might see
2961 [New Thread 0x41e02940 (LWP 25582)]
2965 when @value{GDBN} notices a new thread. In contrast, on other systems,
2966 the @var{systag} is simply something like @samp{process 368}, with no
2969 @c FIXME!! (1) Does the [New...] message appear even for the very first
2970 @c thread of a program, or does it only appear for the
2971 @c second---i.e.@: when it becomes obvious we have a multithread
2973 @c (2) *Is* there necessarily a first thread always? Or do some
2974 @c multithread systems permit starting a program with multiple
2975 @c threads ab initio?
2977 @anchor{thread numbers}
2978 @cindex thread number, per inferior
2979 @cindex thread identifier (GDB)
2980 For debugging purposes, @value{GDBN} associates its own thread number
2981 ---always a single integer---with each thread of an inferior. This
2982 number is unique between all threads of an inferior, but not unique
2983 between threads of different inferiors.
2985 @cindex qualified thread ID
2986 You can refer to a given thread in an inferior using the qualified
2987 @var{inferior-num}.@var{thread-num} syntax, also known as
2988 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2989 number and @var{thread-num} being the thread number of the given
2990 inferior. For example, thread @code{2.3} refers to thread number 3 of
2991 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2992 then @value{GDBN} infers you're referring to a thread of the current
2995 Until you create a second inferior, @value{GDBN} does not show the
2996 @var{inferior-num} part of thread IDs, even though you can always use
2997 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2998 of inferior 1, the initial inferior.
3000 @anchor{thread ID lists}
3001 @cindex thread ID lists
3002 Some commands accept a space-separated @dfn{thread ID list} as
3003 argument. A list element can be:
3007 A thread ID as shown in the first field of the @samp{info threads}
3008 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3012 A range of thread numbers, again with or without an inferior
3013 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3014 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3017 All threads of an inferior, specified with a star wildcard, with or
3018 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3019 @samp{1.*}) or @code{*}. The former refers to all threads of the
3020 given inferior, and the latter form without an inferior qualifier
3021 refers to all threads of the current inferior.
3025 For example, if the current inferior is 1, and inferior 7 has one
3026 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3027 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3028 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3029 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3033 @anchor{global thread numbers}
3034 @cindex global thread number
3035 @cindex global thread identifier (GDB)
3036 In addition to a @emph{per-inferior} number, each thread is also
3037 assigned a unique @emph{global} number, also known as @dfn{global
3038 thread ID}, a single integer. Unlike the thread number component of
3039 the thread ID, no two threads have the same global ID, even when
3040 you're debugging multiple inferiors.
3042 From @value{GDBN}'s perspective, a process always has at least one
3043 thread. In other words, @value{GDBN} assigns a thread number to the
3044 program's ``main thread'' even if the program is not multi-threaded.
3046 @vindex $_thread@r{, convenience variable}
3047 @vindex $_gthread@r{, convenience variable}
3048 The debugger convenience variables @samp{$_thread} and
3049 @samp{$_gthread} contain, respectively, the per-inferior thread number
3050 and the global thread number of the current thread. You may find this
3051 useful in writing breakpoint conditional expressions, command scripts,
3052 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3053 general information on convenience variables.
3055 If @value{GDBN} detects the program is multi-threaded, it augments the
3056 usual message about stopping at a breakpoint with the ID and name of
3057 the thread that hit the breakpoint.
3060 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3063 Likewise when the program receives a signal:
3066 Thread 1 "main" received signal SIGINT, Interrupt.
3070 @kindex info threads
3071 @item info threads @r{[}@var{thread-id-list}@r{]}
3073 Display information about one or more threads. With no arguments
3074 displays information about all threads. You can specify the list of
3075 threads that you want to display using the thread ID list syntax
3076 (@pxref{thread ID lists}).
3078 @value{GDBN} displays for each thread (in this order):
3082 the per-inferior thread number assigned by @value{GDBN}
3085 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3086 option was specified
3089 the target system's thread identifier (@var{systag})
3092 the thread's name, if one is known. A thread can either be named by
3093 the user (see @code{thread name}, below), or, in some cases, by the
3097 the current stack frame summary for that thread
3101 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3102 indicates the current thread.
3106 @c end table here to get a little more width for example
3109 (@value{GDBP}) info threads
3111 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3112 2 process 35 thread 23 0x34e5 in sigpause ()
3113 3 process 35 thread 27 0x34e5 in sigpause ()
3117 If you're debugging multiple inferiors, @value{GDBN} displays thread
3118 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3119 Otherwise, only @var{thread-num} is shown.
3121 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3122 indicating each thread's global thread ID:
3125 (@value{GDBP}) info threads
3126 Id GId Target Id Frame
3127 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3128 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3129 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3130 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3133 On Solaris, you can display more information about user threads with a
3134 Solaris-specific command:
3137 @item maint info sol-threads
3138 @kindex maint info sol-threads
3139 @cindex thread info (Solaris)
3140 Display info on Solaris user threads.
3144 @kindex thread @var{thread-id}
3145 @item thread @var{thread-id}
3146 Make thread ID @var{thread-id} the current thread. The command
3147 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3148 the first field of the @samp{info threads} display, with or without an
3149 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3151 @value{GDBN} responds by displaying the system identifier of the
3152 thread you selected, and its current stack frame summary:
3155 (@value{GDBP}) thread 2
3156 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3157 #0 some_function (ignore=0x0) at example.c:8
3158 8 printf ("hello\n");
3162 As with the @samp{[New @dots{}]} message, the form of the text after
3163 @samp{Switching to} depends on your system's conventions for identifying
3166 @kindex thread apply
3167 @cindex apply command to several threads
3168 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3169 The @code{thread apply} command allows you to apply the named
3170 @var{command} to one or more threads. Specify the threads that you
3171 want affected using the thread ID list syntax (@pxref{thread ID
3172 lists}), or specify @code{all} to apply to all threads. To apply a
3173 command to all threads in descending order, type @kbd{thread apply all
3174 @var{command}}. To apply a command to all threads in ascending order,
3175 type @kbd{thread apply all -ascending @var{command}}.
3179 @cindex name a thread
3180 @item thread name [@var{name}]
3181 This command assigns a name to the current thread. If no argument is
3182 given, any existing user-specified name is removed. The thread name
3183 appears in the @samp{info threads} display.
3185 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3186 determine the name of the thread as given by the OS. On these
3187 systems, a name specified with @samp{thread name} will override the
3188 system-give name, and removing the user-specified name will cause
3189 @value{GDBN} to once again display the system-specified name.
3192 @cindex search for a thread
3193 @item thread find [@var{regexp}]
3194 Search for and display thread ids whose name or @var{systag}
3195 matches the supplied regular expression.
3197 As well as being the complement to the @samp{thread name} command,
3198 this command also allows you to identify a thread by its target
3199 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3203 (@value{GDBN}) thread find 26688
3204 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3205 (@value{GDBN}) info thread 4
3207 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3210 @kindex set print thread-events
3211 @cindex print messages on thread start and exit
3212 @item set print thread-events
3213 @itemx set print thread-events on
3214 @itemx set print thread-events off
3215 The @code{set print thread-events} command allows you to enable or
3216 disable printing of messages when @value{GDBN} notices that new threads have
3217 started or that threads have exited. By default, these messages will
3218 be printed if detection of these events is supported by the target.
3219 Note that these messages cannot be disabled on all targets.
3221 @kindex show print thread-events
3222 @item show print thread-events
3223 Show whether messages will be printed when @value{GDBN} detects that threads
3224 have started and exited.
3227 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3228 more information about how @value{GDBN} behaves when you stop and start
3229 programs with multiple threads.
3231 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3232 watchpoints in programs with multiple threads.
3234 @anchor{set libthread-db-search-path}
3236 @kindex set libthread-db-search-path
3237 @cindex search path for @code{libthread_db}
3238 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3239 If this variable is set, @var{path} is a colon-separated list of
3240 directories @value{GDBN} will use to search for @code{libthread_db}.
3241 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3242 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3243 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3246 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3247 @code{libthread_db} library to obtain information about threads in the
3248 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3249 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3250 specific thread debugging library loading is enabled
3251 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3253 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3254 refers to the default system directories that are
3255 normally searched for loading shared libraries. The @samp{$sdir} entry
3256 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3257 (@pxref{libthread_db.so.1 file}).
3259 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3260 refers to the directory from which @code{libpthread}
3261 was loaded in the inferior process.
3263 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3264 @value{GDBN} attempts to initialize it with the current inferior process.
3265 If this initialization fails (which could happen because of a version
3266 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3267 will unload @code{libthread_db}, and continue with the next directory.
3268 If none of @code{libthread_db} libraries initialize successfully,
3269 @value{GDBN} will issue a warning and thread debugging will be disabled.
3271 Setting @code{libthread-db-search-path} is currently implemented
3272 only on some platforms.
3274 @kindex show libthread-db-search-path
3275 @item show libthread-db-search-path
3276 Display current libthread_db search path.
3278 @kindex set debug libthread-db
3279 @kindex show debug libthread-db
3280 @cindex debugging @code{libthread_db}
3281 @item set debug libthread-db
3282 @itemx show debug libthread-db
3283 Turns on or off display of @code{libthread_db}-related events.
3284 Use @code{1} to enable, @code{0} to disable.
3288 @section Debugging Forks
3290 @cindex fork, debugging programs which call
3291 @cindex multiple processes
3292 @cindex processes, multiple
3293 On most systems, @value{GDBN} has no special support for debugging
3294 programs which create additional processes using the @code{fork}
3295 function. When a program forks, @value{GDBN} will continue to debug the
3296 parent process and the child process will run unimpeded. If you have
3297 set a breakpoint in any code which the child then executes, the child
3298 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3299 will cause it to terminate.
3301 However, if you want to debug the child process there is a workaround
3302 which isn't too painful. Put a call to @code{sleep} in the code which
3303 the child process executes after the fork. It may be useful to sleep
3304 only if a certain environment variable is set, or a certain file exists,
3305 so that the delay need not occur when you don't want to run @value{GDBN}
3306 on the child. While the child is sleeping, use the @code{ps} program to
3307 get its process ID. Then tell @value{GDBN} (a new invocation of
3308 @value{GDBN} if you are also debugging the parent process) to attach to
3309 the child process (@pxref{Attach}). From that point on you can debug
3310 the child process just like any other process which you attached to.
3312 On some systems, @value{GDBN} provides support for debugging programs
3313 that create additional processes using the @code{fork} or @code{vfork}
3314 functions. On @sc{gnu}/Linux platforms, this feature is supported
3315 with kernel version 2.5.46 and later.
3317 The fork debugging commands are supported in native mode and when
3318 connected to @code{gdbserver} in either @code{target remote} mode or
3319 @code{target extended-remote} mode.
3321 By default, when a program forks, @value{GDBN} will continue to debug
3322 the parent process and the child process will run unimpeded.
3324 If you want to follow the child process instead of the parent process,
3325 use the command @w{@code{set follow-fork-mode}}.
3328 @kindex set follow-fork-mode
3329 @item set follow-fork-mode @var{mode}
3330 Set the debugger response to a program call of @code{fork} or
3331 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3332 process. The @var{mode} argument can be:
3336 The original process is debugged after a fork. The child process runs
3337 unimpeded. This is the default.
3340 The new process is debugged after a fork. The parent process runs
3345 @kindex show follow-fork-mode
3346 @item show follow-fork-mode
3347 Display the current debugger response to a @code{fork} or @code{vfork} call.
3350 @cindex debugging multiple processes
3351 On Linux, if you want to debug both the parent and child processes, use the
3352 command @w{@code{set detach-on-fork}}.
3355 @kindex set detach-on-fork
3356 @item set detach-on-fork @var{mode}
3357 Tells gdb whether to detach one of the processes after a fork, or
3358 retain debugger control over them both.
3362 The child process (or parent process, depending on the value of
3363 @code{follow-fork-mode}) will be detached and allowed to run
3364 independently. This is the default.
3367 Both processes will be held under the control of @value{GDBN}.
3368 One process (child or parent, depending on the value of
3369 @code{follow-fork-mode}) is debugged as usual, while the other
3374 @kindex show detach-on-fork
3375 @item show detach-on-fork
3376 Show whether detach-on-fork mode is on/off.
3379 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3380 will retain control of all forked processes (including nested forks).
3381 You can list the forked processes under the control of @value{GDBN} by
3382 using the @w{@code{info inferiors}} command, and switch from one fork
3383 to another by using the @code{inferior} command (@pxref{Inferiors and
3384 Programs, ,Debugging Multiple Inferiors and Programs}).
3386 To quit debugging one of the forked processes, you can either detach
3387 from it by using the @w{@code{detach inferiors}} command (allowing it
3388 to run independently), or kill it using the @w{@code{kill inferiors}}
3389 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3392 If you ask to debug a child process and a @code{vfork} is followed by an
3393 @code{exec}, @value{GDBN} executes the new target up to the first
3394 breakpoint in the new target. If you have a breakpoint set on
3395 @code{main} in your original program, the breakpoint will also be set on
3396 the child process's @code{main}.
3398 On some systems, when a child process is spawned by @code{vfork}, you
3399 cannot debug the child or parent until an @code{exec} call completes.
3401 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3402 call executes, the new target restarts. To restart the parent
3403 process, use the @code{file} command with the parent executable name
3404 as its argument. By default, after an @code{exec} call executes,
3405 @value{GDBN} discards the symbols of the previous executable image.
3406 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3410 @kindex set follow-exec-mode
3411 @item set follow-exec-mode @var{mode}
3413 Set debugger response to a program call of @code{exec}. An
3414 @code{exec} call replaces the program image of a process.
3416 @code{follow-exec-mode} can be:
3420 @value{GDBN} creates a new inferior and rebinds the process to this
3421 new inferior. The program the process was running before the
3422 @code{exec} call can be restarted afterwards by restarting the
3428 (@value{GDBP}) info inferiors
3430 Id Description Executable
3433 process 12020 is executing new program: prog2
3434 Program exited normally.
3435 (@value{GDBP}) info inferiors
3436 Id Description Executable
3442 @value{GDBN} keeps the process bound to the same inferior. The new
3443 executable image replaces the previous executable loaded in the
3444 inferior. Restarting the inferior after the @code{exec} call, with
3445 e.g., the @code{run} command, restarts the executable the process was
3446 running after the @code{exec} call. This is the default mode.
3451 (@value{GDBP}) info inferiors
3452 Id Description Executable
3455 process 12020 is executing new program: prog2
3456 Program exited normally.
3457 (@value{GDBP}) info inferiors
3458 Id Description Executable
3465 @code{follow-exec-mode} is supported in native mode and
3466 @code{target extended-remote} mode.
3468 You can use the @code{catch} command to make @value{GDBN} stop whenever
3469 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3470 Catchpoints, ,Setting Catchpoints}.
3472 @node Checkpoint/Restart
3473 @section Setting a @emph{Bookmark} to Return to Later
3478 @cindex snapshot of a process
3479 @cindex rewind program state
3481 On certain operating systems@footnote{Currently, only
3482 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3483 program's state, called a @dfn{checkpoint}, and come back to it
3486 Returning to a checkpoint effectively undoes everything that has
3487 happened in the program since the @code{checkpoint} was saved. This
3488 includes changes in memory, registers, and even (within some limits)
3489 system state. Effectively, it is like going back in time to the
3490 moment when the checkpoint was saved.
3492 Thus, if you're stepping thru a program and you think you're
3493 getting close to the point where things go wrong, you can save
3494 a checkpoint. Then, if you accidentally go too far and miss
3495 the critical statement, instead of having to restart your program
3496 from the beginning, you can just go back to the checkpoint and
3497 start again from there.
3499 This can be especially useful if it takes a lot of time or
3500 steps to reach the point where you think the bug occurs.
3502 To use the @code{checkpoint}/@code{restart} method of debugging:
3507 Save a snapshot of the debugged program's current execution state.
3508 The @code{checkpoint} command takes no arguments, but each checkpoint
3509 is assigned a small integer id, similar to a breakpoint id.
3511 @kindex info checkpoints
3512 @item info checkpoints
3513 List the checkpoints that have been saved in the current debugging
3514 session. For each checkpoint, the following information will be
3521 @item Source line, or label
3524 @kindex restart @var{checkpoint-id}
3525 @item restart @var{checkpoint-id}
3526 Restore the program state that was saved as checkpoint number
3527 @var{checkpoint-id}. All program variables, registers, stack frames
3528 etc.@: will be returned to the values that they had when the checkpoint
3529 was saved. In essence, gdb will ``wind back the clock'' to the point
3530 in time when the checkpoint was saved.
3532 Note that breakpoints, @value{GDBN} variables, command history etc.
3533 are not affected by restoring a checkpoint. In general, a checkpoint
3534 only restores things that reside in the program being debugged, not in
3537 @kindex delete checkpoint @var{checkpoint-id}
3538 @item delete checkpoint @var{checkpoint-id}
3539 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3543 Returning to a previously saved checkpoint will restore the user state
3544 of the program being debugged, plus a significant subset of the system
3545 (OS) state, including file pointers. It won't ``un-write'' data from
3546 a file, but it will rewind the file pointer to the previous location,
3547 so that the previously written data can be overwritten. For files
3548 opened in read mode, the pointer will also be restored so that the
3549 previously read data can be read again.
3551 Of course, characters that have been sent to a printer (or other
3552 external device) cannot be ``snatched back'', and characters received
3553 from eg.@: a serial device can be removed from internal program buffers,
3554 but they cannot be ``pushed back'' into the serial pipeline, ready to
3555 be received again. Similarly, the actual contents of files that have
3556 been changed cannot be restored (at this time).
3558 However, within those constraints, you actually can ``rewind'' your
3559 program to a previously saved point in time, and begin debugging it
3560 again --- and you can change the course of events so as to debug a
3561 different execution path this time.
3563 @cindex checkpoints and process id
3564 Finally, there is one bit of internal program state that will be
3565 different when you return to a checkpoint --- the program's process
3566 id. Each checkpoint will have a unique process id (or @var{pid}),
3567 and each will be different from the program's original @var{pid}.
3568 If your program has saved a local copy of its process id, this could
3569 potentially pose a problem.
3571 @subsection A Non-obvious Benefit of Using Checkpoints
3573 On some systems such as @sc{gnu}/Linux, address space randomization
3574 is performed on new processes for security reasons. This makes it
3575 difficult or impossible to set a breakpoint, or watchpoint, on an
3576 absolute address if you have to restart the program, since the
3577 absolute location of a symbol will change from one execution to the
3580 A checkpoint, however, is an @emph{identical} copy of a process.
3581 Therefore if you create a checkpoint at (eg.@:) the start of main,
3582 and simply return to that checkpoint instead of restarting the
3583 process, you can avoid the effects of address randomization and
3584 your symbols will all stay in the same place.
3587 @chapter Stopping and Continuing
3589 The principal purposes of using a debugger are so that you can stop your
3590 program before it terminates; or so that, if your program runs into
3591 trouble, you can investigate and find out why.
3593 Inside @value{GDBN}, your program may stop for any of several reasons,
3594 such as a signal, a breakpoint, or reaching a new line after a
3595 @value{GDBN} command such as @code{step}. You may then examine and
3596 change variables, set new breakpoints or remove old ones, and then
3597 continue execution. Usually, the messages shown by @value{GDBN} provide
3598 ample explanation of the status of your program---but you can also
3599 explicitly request this information at any time.
3602 @kindex info program
3604 Display information about the status of your program: whether it is
3605 running or not, what process it is, and why it stopped.
3609 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3610 * Continuing and Stepping:: Resuming execution
3611 * Skipping Over Functions and Files::
3612 Skipping over functions and files
3614 * Thread Stops:: Stopping and starting multi-thread programs
3618 @section Breakpoints, Watchpoints, and Catchpoints
3621 A @dfn{breakpoint} makes your program stop whenever a certain point in
3622 the program is reached. For each breakpoint, you can add conditions to
3623 control in finer detail whether your program stops. You can set
3624 breakpoints with the @code{break} command and its variants (@pxref{Set
3625 Breaks, ,Setting Breakpoints}), to specify the place where your program
3626 should stop by line number, function name or exact address in the
3629 On some systems, you can set breakpoints in shared libraries before
3630 the executable is run.
3633 @cindex data breakpoints
3634 @cindex memory tracing
3635 @cindex breakpoint on memory address
3636 @cindex breakpoint on variable modification
3637 A @dfn{watchpoint} is a special breakpoint that stops your program
3638 when the value of an expression changes. The expression may be a value
3639 of a variable, or it could involve values of one or more variables
3640 combined by operators, such as @samp{a + b}. This is sometimes called
3641 @dfn{data breakpoints}. You must use a different command to set
3642 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3643 from that, you can manage a watchpoint like any other breakpoint: you
3644 enable, disable, and delete both breakpoints and watchpoints using the
3647 You can arrange to have values from your program displayed automatically
3648 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3652 @cindex breakpoint on events
3653 A @dfn{catchpoint} is another special breakpoint that stops your program
3654 when a certain kind of event occurs, such as the throwing of a C@t{++}
3655 exception or the loading of a library. As with watchpoints, you use a
3656 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3657 Catchpoints}), but aside from that, you can manage a catchpoint like any
3658 other breakpoint. (To stop when your program receives a signal, use the
3659 @code{handle} command; see @ref{Signals, ,Signals}.)
3661 @cindex breakpoint numbers
3662 @cindex numbers for breakpoints
3663 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3664 catchpoint when you create it; these numbers are successive integers
3665 starting with one. In many of the commands for controlling various
3666 features of breakpoints you use the breakpoint number to say which
3667 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3668 @dfn{disabled}; if disabled, it has no effect on your program until you
3671 @cindex breakpoint ranges
3672 @cindex breakpoint lists
3673 @cindex ranges of breakpoints
3674 @cindex lists of breakpoints
3675 Some @value{GDBN} commands accept a space-separated list of breakpoints
3676 on which to operate. A list element can be either a single breakpoint number,
3677 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3678 When a breakpoint list is given to a command, all breakpoints in that list
3682 * Set Breaks:: Setting breakpoints
3683 * Set Watchpoints:: Setting watchpoints
3684 * Set Catchpoints:: Setting catchpoints
3685 * Delete Breaks:: Deleting breakpoints
3686 * Disabling:: Disabling breakpoints
3687 * Conditions:: Break conditions
3688 * Break Commands:: Breakpoint command lists
3689 * Dynamic Printf:: Dynamic printf
3690 * Save Breakpoints:: How to save breakpoints in a file
3691 * Static Probe Points:: Listing static probe points
3692 * Error in Breakpoints:: ``Cannot insert breakpoints''
3693 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3697 @subsection Setting Breakpoints
3699 @c FIXME LMB what does GDB do if no code on line of breakpt?
3700 @c consider in particular declaration with/without initialization.
3702 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3705 @kindex b @r{(@code{break})}
3706 @vindex $bpnum@r{, convenience variable}
3707 @cindex latest breakpoint
3708 Breakpoints are set with the @code{break} command (abbreviated
3709 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3710 number of the breakpoint you've set most recently; see @ref{Convenience
3711 Vars,, Convenience Variables}, for a discussion of what you can do with
3712 convenience variables.
3715 @item break @var{location}
3716 Set a breakpoint at the given @var{location}, which can specify a
3717 function name, a line number, or an address of an instruction.
3718 (@xref{Specify Location}, for a list of all the possible ways to
3719 specify a @var{location}.) The breakpoint will stop your program just
3720 before it executes any of the code in the specified @var{location}.
3722 When using source languages that permit overloading of symbols, such as
3723 C@t{++}, a function name may refer to more than one possible place to break.
3724 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3727 It is also possible to insert a breakpoint that will stop the program
3728 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3729 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3732 When called without any arguments, @code{break} sets a breakpoint at
3733 the next instruction to be executed in the selected stack frame
3734 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3735 innermost, this makes your program stop as soon as control
3736 returns to that frame. This is similar to the effect of a
3737 @code{finish} command in the frame inside the selected frame---except
3738 that @code{finish} does not leave an active breakpoint. If you use
3739 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3740 the next time it reaches the current location; this may be useful
3743 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3744 least one instruction has been executed. If it did not do this, you
3745 would be unable to proceed past a breakpoint without first disabling the
3746 breakpoint. This rule applies whether or not the breakpoint already
3747 existed when your program stopped.
3749 @item break @dots{} if @var{cond}
3750 Set a breakpoint with condition @var{cond}; evaluate the expression
3751 @var{cond} each time the breakpoint is reached, and stop only if the
3752 value is nonzero---that is, if @var{cond} evaluates as true.
3753 @samp{@dots{}} stands for one of the possible arguments described
3754 above (or no argument) specifying where to break. @xref{Conditions,
3755 ,Break Conditions}, for more information on breakpoint conditions.
3758 @item tbreak @var{args}
3759 Set a breakpoint enabled only for one stop. The @var{args} are the
3760 same as for the @code{break} command, and the breakpoint is set in the same
3761 way, but the breakpoint is automatically deleted after the first time your
3762 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3765 @cindex hardware breakpoints
3766 @item hbreak @var{args}
3767 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3768 @code{break} command and the breakpoint is set in the same way, but the
3769 breakpoint requires hardware support and some target hardware may not
3770 have this support. The main purpose of this is EPROM/ROM code
3771 debugging, so you can set a breakpoint at an instruction without
3772 changing the instruction. This can be used with the new trap-generation
3773 provided by SPARClite DSU and most x86-based targets. These targets
3774 will generate traps when a program accesses some data or instruction
3775 address that is assigned to the debug registers. However the hardware
3776 breakpoint registers can take a limited number of breakpoints. For
3777 example, on the DSU, only two data breakpoints can be set at a time, and
3778 @value{GDBN} will reject this command if more than two are used. Delete
3779 or disable unused hardware breakpoints before setting new ones
3780 (@pxref{Disabling, ,Disabling Breakpoints}).
3781 @xref{Conditions, ,Break Conditions}.
3782 For remote targets, you can restrict the number of hardware
3783 breakpoints @value{GDBN} will use, see @ref{set remote
3784 hardware-breakpoint-limit}.
3787 @item thbreak @var{args}
3788 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3789 are the same as for the @code{hbreak} command and the breakpoint is set in
3790 the same way. However, like the @code{tbreak} command,
3791 the breakpoint is automatically deleted after the
3792 first time your program stops there. Also, like the @code{hbreak}
3793 command, the breakpoint requires hardware support and some target hardware
3794 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3795 See also @ref{Conditions, ,Break Conditions}.
3798 @cindex regular expression
3799 @cindex breakpoints at functions matching a regexp
3800 @cindex set breakpoints in many functions
3801 @item rbreak @var{regex}
3802 Set breakpoints on all functions matching the regular expression
3803 @var{regex}. This command sets an unconditional breakpoint on all
3804 matches, printing a list of all breakpoints it set. Once these
3805 breakpoints are set, they are treated just like the breakpoints set with
3806 the @code{break} command. You can delete them, disable them, or make
3807 them conditional the same way as any other breakpoint.
3809 The syntax of the regular expression is the standard one used with tools
3810 like @file{grep}. Note that this is different from the syntax used by
3811 shells, so for instance @code{foo*} matches all functions that include
3812 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3813 @code{.*} leading and trailing the regular expression you supply, so to
3814 match only functions that begin with @code{foo}, use @code{^foo}.
3816 @cindex non-member C@t{++} functions, set breakpoint in
3817 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3818 breakpoints on overloaded functions that are not members of any special
3821 @cindex set breakpoints on all functions
3822 The @code{rbreak} command can be used to set breakpoints in
3823 @strong{all} the functions in a program, like this:
3826 (@value{GDBP}) rbreak .
3829 @item rbreak @var{file}:@var{regex}
3830 If @code{rbreak} is called with a filename qualification, it limits
3831 the search for functions matching the given regular expression to the
3832 specified @var{file}. This can be used, for example, to set breakpoints on
3833 every function in a given file:
3836 (@value{GDBP}) rbreak file.c:.
3839 The colon separating the filename qualifier from the regex may
3840 optionally be surrounded by spaces.
3842 @kindex info breakpoints
3843 @cindex @code{$_} and @code{info breakpoints}
3844 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3845 @itemx info break @r{[}@var{list}@dots{}@r{]}
3846 Print a table of all breakpoints, watchpoints, and catchpoints set and
3847 not deleted. Optional argument @var{n} means print information only
3848 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3849 For each breakpoint, following columns are printed:
3852 @item Breakpoint Numbers
3854 Breakpoint, watchpoint, or catchpoint.
3856 Whether the breakpoint is marked to be disabled or deleted when hit.
3857 @item Enabled or Disabled
3858 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3859 that are not enabled.
3861 Where the breakpoint is in your program, as a memory address. For a
3862 pending breakpoint whose address is not yet known, this field will
3863 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3864 library that has the symbol or line referred by breakpoint is loaded.
3865 See below for details. A breakpoint with several locations will
3866 have @samp{<MULTIPLE>} in this field---see below for details.
3868 Where the breakpoint is in the source for your program, as a file and
3869 line number. For a pending breakpoint, the original string passed to
3870 the breakpoint command will be listed as it cannot be resolved until
3871 the appropriate shared library is loaded in the future.
3875 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3876 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3877 @value{GDBN} on the host's side. If it is ``target'', then the condition
3878 is evaluated by the target. The @code{info break} command shows
3879 the condition on the line following the affected breakpoint, together with
3880 its condition evaluation mode in between parentheses.
3882 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3883 allowed to have a condition specified for it. The condition is not parsed for
3884 validity until a shared library is loaded that allows the pending
3885 breakpoint to resolve to a valid location.
3888 @code{info break} with a breakpoint
3889 number @var{n} as argument lists only that breakpoint. The
3890 convenience variable @code{$_} and the default examining-address for
3891 the @code{x} command are set to the address of the last breakpoint
3892 listed (@pxref{Memory, ,Examining Memory}).
3895 @code{info break} displays a count of the number of times the breakpoint
3896 has been hit. This is especially useful in conjunction with the
3897 @code{ignore} command. You can ignore a large number of breakpoint
3898 hits, look at the breakpoint info to see how many times the breakpoint
3899 was hit, and then run again, ignoring one less than that number. This
3900 will get you quickly to the last hit of that breakpoint.
3903 For a breakpoints with an enable count (xref) greater than 1,
3904 @code{info break} also displays that count.
3908 @value{GDBN} allows you to set any number of breakpoints at the same place in
3909 your program. There is nothing silly or meaningless about this. When
3910 the breakpoints are conditional, this is even useful
3911 (@pxref{Conditions, ,Break Conditions}).
3913 @cindex multiple locations, breakpoints
3914 @cindex breakpoints, multiple locations
3915 It is possible that a breakpoint corresponds to several locations
3916 in your program. Examples of this situation are:
3920 Multiple functions in the program may have the same name.
3923 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3924 instances of the function body, used in different cases.
3927 For a C@t{++} template function, a given line in the function can
3928 correspond to any number of instantiations.
3931 For an inlined function, a given source line can correspond to
3932 several places where that function is inlined.
3935 In all those cases, @value{GDBN} will insert a breakpoint at all
3936 the relevant locations.
3938 A breakpoint with multiple locations is displayed in the breakpoint
3939 table using several rows---one header row, followed by one row for
3940 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3941 address column. The rows for individual locations contain the actual
3942 addresses for locations, and show the functions to which those
3943 locations belong. The number column for a location is of the form
3944 @var{breakpoint-number}.@var{location-number}.
3949 Num Type Disp Enb Address What
3950 1 breakpoint keep y <MULTIPLE>
3952 breakpoint already hit 1 time
3953 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3954 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3957 You cannot delete the individual locations from a breakpoint. However,
3958 each location can be individually enabled or disabled by passing
3959 @var{breakpoint-number}.@var{location-number} as argument to the
3960 @code{enable} and @code{disable} commands. It's also possible to
3961 @code{enable} and @code{disable} a range of @var{location-number}
3962 locations using a @var{breakpoint-number} and two @var{location-number}s,
3963 in increasing order, separated by a hyphen, like
3964 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
3965 in which case @value{GDBN} acts on all the locations in the range (inclusive).
3966 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
3967 all of the locations that belong to that breakpoint.
3969 @cindex pending breakpoints
3970 It's quite common to have a breakpoint inside a shared library.
3971 Shared libraries can be loaded and unloaded explicitly,
3972 and possibly repeatedly, as the program is executed. To support
3973 this use case, @value{GDBN} updates breakpoint locations whenever
3974 any shared library is loaded or unloaded. Typically, you would
3975 set a breakpoint in a shared library at the beginning of your
3976 debugging session, when the library is not loaded, and when the
3977 symbols from the library are not available. When you try to set
3978 breakpoint, @value{GDBN} will ask you if you want to set
3979 a so called @dfn{pending breakpoint}---breakpoint whose address
3980 is not yet resolved.
3982 After the program is run, whenever a new shared library is loaded,
3983 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3984 shared library contains the symbol or line referred to by some
3985 pending breakpoint, that breakpoint is resolved and becomes an
3986 ordinary breakpoint. When a library is unloaded, all breakpoints
3987 that refer to its symbols or source lines become pending again.
3989 This logic works for breakpoints with multiple locations, too. For
3990 example, if you have a breakpoint in a C@t{++} template function, and
3991 a newly loaded shared library has an instantiation of that template,
3992 a new location is added to the list of locations for the breakpoint.
3994 Except for having unresolved address, pending breakpoints do not
3995 differ from regular breakpoints. You can set conditions or commands,
3996 enable and disable them and perform other breakpoint operations.
3998 @value{GDBN} provides some additional commands for controlling what
3999 happens when the @samp{break} command cannot resolve breakpoint
4000 address specification to an address:
4002 @kindex set breakpoint pending
4003 @kindex show breakpoint pending
4005 @item set breakpoint pending auto
4006 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4007 location, it queries you whether a pending breakpoint should be created.
4009 @item set breakpoint pending on
4010 This indicates that an unrecognized breakpoint location should automatically
4011 result in a pending breakpoint being created.
4013 @item set breakpoint pending off
4014 This indicates that pending breakpoints are not to be created. Any
4015 unrecognized breakpoint location results in an error. This setting does
4016 not affect any pending breakpoints previously created.
4018 @item show breakpoint pending
4019 Show the current behavior setting for creating pending breakpoints.
4022 The settings above only affect the @code{break} command and its
4023 variants. Once breakpoint is set, it will be automatically updated
4024 as shared libraries are loaded and unloaded.
4026 @cindex automatic hardware breakpoints
4027 For some targets, @value{GDBN} can automatically decide if hardware or
4028 software breakpoints should be used, depending on whether the
4029 breakpoint address is read-only or read-write. This applies to
4030 breakpoints set with the @code{break} command as well as to internal
4031 breakpoints set by commands like @code{next} and @code{finish}. For
4032 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4035 You can control this automatic behaviour with the following commands:
4037 @kindex set breakpoint auto-hw
4038 @kindex show breakpoint auto-hw
4040 @item set breakpoint auto-hw on
4041 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4042 will try to use the target memory map to decide if software or hardware
4043 breakpoint must be used.
4045 @item set breakpoint auto-hw off
4046 This indicates @value{GDBN} should not automatically select breakpoint
4047 type. If the target provides a memory map, @value{GDBN} will warn when
4048 trying to set software breakpoint at a read-only address.
4051 @value{GDBN} normally implements breakpoints by replacing the program code
4052 at the breakpoint address with a special instruction, which, when
4053 executed, given control to the debugger. By default, the program
4054 code is so modified only when the program is resumed. As soon as
4055 the program stops, @value{GDBN} restores the original instructions. This
4056 behaviour guards against leaving breakpoints inserted in the
4057 target should gdb abrubptly disconnect. However, with slow remote
4058 targets, inserting and removing breakpoint can reduce the performance.
4059 This behavior can be controlled with the following commands::
4061 @kindex set breakpoint always-inserted
4062 @kindex show breakpoint always-inserted
4064 @item set breakpoint always-inserted off
4065 All breakpoints, including newly added by the user, are inserted in
4066 the target only when the target is resumed. All breakpoints are
4067 removed from the target when it stops. This is the default mode.
4069 @item set breakpoint always-inserted on
4070 Causes all breakpoints to be inserted in the target at all times. If
4071 the user adds a new breakpoint, or changes an existing breakpoint, the
4072 breakpoints in the target are updated immediately. A breakpoint is
4073 removed from the target only when breakpoint itself is deleted.
4076 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4077 when a breakpoint breaks. If the condition is true, then the process being
4078 debugged stops, otherwise the process is resumed.
4080 If the target supports evaluating conditions on its end, @value{GDBN} may
4081 download the breakpoint, together with its conditions, to it.
4083 This feature can be controlled via the following commands:
4085 @kindex set breakpoint condition-evaluation
4086 @kindex show breakpoint condition-evaluation
4088 @item set breakpoint condition-evaluation host
4089 This option commands @value{GDBN} to evaluate the breakpoint
4090 conditions on the host's side. Unconditional breakpoints are sent to
4091 the target which in turn receives the triggers and reports them back to GDB
4092 for condition evaluation. This is the standard evaluation mode.
4094 @item set breakpoint condition-evaluation target
4095 This option commands @value{GDBN} to download breakpoint conditions
4096 to the target at the moment of their insertion. The target
4097 is responsible for evaluating the conditional expression and reporting
4098 breakpoint stop events back to @value{GDBN} whenever the condition
4099 is true. Due to limitations of target-side evaluation, some conditions
4100 cannot be evaluated there, e.g., conditions that depend on local data
4101 that is only known to the host. Examples include
4102 conditional expressions involving convenience variables, complex types
4103 that cannot be handled by the agent expression parser and expressions
4104 that are too long to be sent over to the target, specially when the
4105 target is a remote system. In these cases, the conditions will be
4106 evaluated by @value{GDBN}.
4108 @item set breakpoint condition-evaluation auto
4109 This is the default mode. If the target supports evaluating breakpoint
4110 conditions on its end, @value{GDBN} will download breakpoint conditions to
4111 the target (limitations mentioned previously apply). If the target does
4112 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4113 to evaluating all these conditions on the host's side.
4117 @cindex negative breakpoint numbers
4118 @cindex internal @value{GDBN} breakpoints
4119 @value{GDBN} itself sometimes sets breakpoints in your program for
4120 special purposes, such as proper handling of @code{longjmp} (in C
4121 programs). These internal breakpoints are assigned negative numbers,
4122 starting with @code{-1}; @samp{info breakpoints} does not display them.
4123 You can see these breakpoints with the @value{GDBN} maintenance command
4124 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4127 @node Set Watchpoints
4128 @subsection Setting Watchpoints
4130 @cindex setting watchpoints
4131 You can use a watchpoint to stop execution whenever the value of an
4132 expression changes, without having to predict a particular place where
4133 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4134 The expression may be as simple as the value of a single variable, or
4135 as complex as many variables combined by operators. Examples include:
4139 A reference to the value of a single variable.
4142 An address cast to an appropriate data type. For example,
4143 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4144 address (assuming an @code{int} occupies 4 bytes).
4147 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4148 expression can use any operators valid in the program's native
4149 language (@pxref{Languages}).
4152 You can set a watchpoint on an expression even if the expression can
4153 not be evaluated yet. For instance, you can set a watchpoint on
4154 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4155 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4156 the expression produces a valid value. If the expression becomes
4157 valid in some other way than changing a variable (e.g.@: if the memory
4158 pointed to by @samp{*global_ptr} becomes readable as the result of a
4159 @code{malloc} call), @value{GDBN} may not stop until the next time
4160 the expression changes.
4162 @cindex software watchpoints
4163 @cindex hardware watchpoints
4164 Depending on your system, watchpoints may be implemented in software or
4165 hardware. @value{GDBN} does software watchpointing by single-stepping your
4166 program and testing the variable's value each time, which is hundreds of
4167 times slower than normal execution. (But this may still be worth it, to
4168 catch errors where you have no clue what part of your program is the
4171 On some systems, such as most PowerPC or x86-based targets,
4172 @value{GDBN} includes support for hardware watchpoints, which do not
4173 slow down the running of your program.
4177 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4178 Set a watchpoint for an expression. @value{GDBN} will break when the
4179 expression @var{expr} is written into by the program and its value
4180 changes. The simplest (and the most popular) use of this command is
4181 to watch the value of a single variable:
4184 (@value{GDBP}) watch foo
4187 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4188 argument, @value{GDBN} breaks only when the thread identified by
4189 @var{thread-id} changes the value of @var{expr}. If any other threads
4190 change the value of @var{expr}, @value{GDBN} will not break. Note
4191 that watchpoints restricted to a single thread in this way only work
4192 with Hardware Watchpoints.
4194 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4195 (see below). The @code{-location} argument tells @value{GDBN} to
4196 instead watch the memory referred to by @var{expr}. In this case,
4197 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4198 and watch the memory at that address. The type of the result is used
4199 to determine the size of the watched memory. If the expression's
4200 result does not have an address, then @value{GDBN} will print an
4203 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4204 of masked watchpoints, if the current architecture supports this
4205 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4206 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4207 to an address to watch. The mask specifies that some bits of an address
4208 (the bits which are reset in the mask) should be ignored when matching
4209 the address accessed by the inferior against the watchpoint address.
4210 Thus, a masked watchpoint watches many addresses simultaneously---those
4211 addresses whose unmasked bits are identical to the unmasked bits in the
4212 watchpoint address. The @code{mask} argument implies @code{-location}.
4216 (@value{GDBP}) watch foo mask 0xffff00ff
4217 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4221 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4222 Set a watchpoint that will break when the value of @var{expr} is read
4226 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4227 Set a watchpoint that will break when @var{expr} is either read from
4228 or written into by the program.
4230 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4231 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4232 This command prints a list of watchpoints, using the same format as
4233 @code{info break} (@pxref{Set Breaks}).
4236 If you watch for a change in a numerically entered address you need to
4237 dereference it, as the address itself is just a constant number which will
4238 never change. @value{GDBN} refuses to create a watchpoint that watches
4239 a never-changing value:
4242 (@value{GDBP}) watch 0x600850
4243 Cannot watch constant value 0x600850.
4244 (@value{GDBP}) watch *(int *) 0x600850
4245 Watchpoint 1: *(int *) 6293584
4248 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4249 watchpoints execute very quickly, and the debugger reports a change in
4250 value at the exact instruction where the change occurs. If @value{GDBN}
4251 cannot set a hardware watchpoint, it sets a software watchpoint, which
4252 executes more slowly and reports the change in value at the next
4253 @emph{statement}, not the instruction, after the change occurs.
4255 @cindex use only software watchpoints
4256 You can force @value{GDBN} to use only software watchpoints with the
4257 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4258 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4259 the underlying system supports them. (Note that hardware-assisted
4260 watchpoints that were set @emph{before} setting
4261 @code{can-use-hw-watchpoints} to zero will still use the hardware
4262 mechanism of watching expression values.)
4265 @item set can-use-hw-watchpoints
4266 @kindex set can-use-hw-watchpoints
4267 Set whether or not to use hardware watchpoints.
4269 @item show can-use-hw-watchpoints
4270 @kindex show can-use-hw-watchpoints
4271 Show the current mode of using hardware watchpoints.
4274 For remote targets, you can restrict the number of hardware
4275 watchpoints @value{GDBN} will use, see @ref{set remote
4276 hardware-breakpoint-limit}.
4278 When you issue the @code{watch} command, @value{GDBN} reports
4281 Hardware watchpoint @var{num}: @var{expr}
4285 if it was able to set a hardware watchpoint.
4287 Currently, the @code{awatch} and @code{rwatch} commands can only set
4288 hardware watchpoints, because accesses to data that don't change the
4289 value of the watched expression cannot be detected without examining
4290 every instruction as it is being executed, and @value{GDBN} does not do
4291 that currently. If @value{GDBN} finds that it is unable to set a
4292 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4293 will print a message like this:
4296 Expression cannot be implemented with read/access watchpoint.
4299 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4300 data type of the watched expression is wider than what a hardware
4301 watchpoint on the target machine can handle. For example, some systems
4302 can only watch regions that are up to 4 bytes wide; on such systems you
4303 cannot set hardware watchpoints for an expression that yields a
4304 double-precision floating-point number (which is typically 8 bytes
4305 wide). As a work-around, it might be possible to break the large region
4306 into a series of smaller ones and watch them with separate watchpoints.
4308 If you set too many hardware watchpoints, @value{GDBN} might be unable
4309 to insert all of them when you resume the execution of your program.
4310 Since the precise number of active watchpoints is unknown until such
4311 time as the program is about to be resumed, @value{GDBN} might not be
4312 able to warn you about this when you set the watchpoints, and the
4313 warning will be printed only when the program is resumed:
4316 Hardware watchpoint @var{num}: Could not insert watchpoint
4320 If this happens, delete or disable some of the watchpoints.
4322 Watching complex expressions that reference many variables can also
4323 exhaust the resources available for hardware-assisted watchpoints.
4324 That's because @value{GDBN} needs to watch every variable in the
4325 expression with separately allocated resources.
4327 If you call a function interactively using @code{print} or @code{call},
4328 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4329 kind of breakpoint or the call completes.
4331 @value{GDBN} automatically deletes watchpoints that watch local
4332 (automatic) variables, or expressions that involve such variables, when
4333 they go out of scope, that is, when the execution leaves the block in
4334 which these variables were defined. In particular, when the program
4335 being debugged terminates, @emph{all} local variables go out of scope,
4336 and so only watchpoints that watch global variables remain set. If you
4337 rerun the program, you will need to set all such watchpoints again. One
4338 way of doing that would be to set a code breakpoint at the entry to the
4339 @code{main} function and when it breaks, set all the watchpoints.
4341 @cindex watchpoints and threads
4342 @cindex threads and watchpoints
4343 In multi-threaded programs, watchpoints will detect changes to the
4344 watched expression from every thread.
4347 @emph{Warning:} In multi-threaded programs, software watchpoints
4348 have only limited usefulness. If @value{GDBN} creates a software
4349 watchpoint, it can only watch the value of an expression @emph{in a
4350 single thread}. If you are confident that the expression can only
4351 change due to the current thread's activity (and if you are also
4352 confident that no other thread can become current), then you can use
4353 software watchpoints as usual. However, @value{GDBN} may not notice
4354 when a non-current thread's activity changes the expression. (Hardware
4355 watchpoints, in contrast, watch an expression in all threads.)
4358 @xref{set remote hardware-watchpoint-limit}.
4360 @node Set Catchpoints
4361 @subsection Setting Catchpoints
4362 @cindex catchpoints, setting
4363 @cindex exception handlers
4364 @cindex event handling
4366 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4367 kinds of program events, such as C@t{++} exceptions or the loading of a
4368 shared library. Use the @code{catch} command to set a catchpoint.
4372 @item catch @var{event}
4373 Stop when @var{event} occurs. The @var{event} can be any of the following:
4376 @item throw @r{[}@var{regexp}@r{]}
4377 @itemx rethrow @r{[}@var{regexp}@r{]}
4378 @itemx catch @r{[}@var{regexp}@r{]}
4380 @kindex catch rethrow
4382 @cindex stop on C@t{++} exceptions
4383 The throwing, re-throwing, or catching of a C@t{++} exception.
4385 If @var{regexp} is given, then only exceptions whose type matches the
4386 regular expression will be caught.
4388 @vindex $_exception@r{, convenience variable}
4389 The convenience variable @code{$_exception} is available at an
4390 exception-related catchpoint, on some systems. This holds the
4391 exception being thrown.
4393 There are currently some limitations to C@t{++} exception handling in
4398 The support for these commands is system-dependent. Currently, only
4399 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4403 The regular expression feature and the @code{$_exception} convenience
4404 variable rely on the presence of some SDT probes in @code{libstdc++}.
4405 If these probes are not present, then these features cannot be used.
4406 These probes were first available in the GCC 4.8 release, but whether
4407 or not they are available in your GCC also depends on how it was
4411 The @code{$_exception} convenience variable is only valid at the
4412 instruction at which an exception-related catchpoint is set.
4415 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4416 location in the system library which implements runtime exception
4417 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4418 (@pxref{Selection}) to get to your code.
4421 If you call a function interactively, @value{GDBN} normally returns
4422 control to you when the function has finished executing. If the call
4423 raises an exception, however, the call may bypass the mechanism that
4424 returns control to you and cause your program either to abort or to
4425 simply continue running until it hits a breakpoint, catches a signal
4426 that @value{GDBN} is listening for, or exits. This is the case even if
4427 you set a catchpoint for the exception; catchpoints on exceptions are
4428 disabled within interactive calls. @xref{Calling}, for information on
4429 controlling this with @code{set unwind-on-terminating-exception}.
4432 You cannot raise an exception interactively.
4435 You cannot install an exception handler interactively.
4439 @kindex catch exception
4440 @cindex Ada exception catching
4441 @cindex catch Ada exceptions
4442 An Ada exception being raised. If an exception name is specified
4443 at the end of the command (eg @code{catch exception Program_Error}),
4444 the debugger will stop only when this specific exception is raised.
4445 Otherwise, the debugger stops execution when any Ada exception is raised.
4447 When inserting an exception catchpoint on a user-defined exception whose
4448 name is identical to one of the exceptions defined by the language, the
4449 fully qualified name must be used as the exception name. Otherwise,
4450 @value{GDBN} will assume that it should stop on the pre-defined exception
4451 rather than the user-defined one. For instance, assuming an exception
4452 called @code{Constraint_Error} is defined in package @code{Pck}, then
4453 the command to use to catch such exceptions is @kbd{catch exception
4454 Pck.Constraint_Error}.
4456 @item exception unhandled
4457 @kindex catch exception unhandled
4458 An exception that was raised but is not handled by the program.
4461 @kindex catch assert
4462 A failed Ada assertion.
4466 @cindex break on fork/exec
4467 A call to @code{exec}.
4470 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4471 @kindex catch syscall
4472 @cindex break on a system call.
4473 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4474 syscall is a mechanism for application programs to request a service
4475 from the operating system (OS) or one of the OS system services.
4476 @value{GDBN} can catch some or all of the syscalls issued by the
4477 debuggee, and show the related information for each syscall. If no
4478 argument is specified, calls to and returns from all system calls
4481 @var{name} can be any system call name that is valid for the
4482 underlying OS. Just what syscalls are valid depends on the OS. On
4483 GNU and Unix systems, you can find the full list of valid syscall
4484 names on @file{/usr/include/asm/unistd.h}.
4486 @c For MS-Windows, the syscall names and the corresponding numbers
4487 @c can be found, e.g., on this URL:
4488 @c http://www.metasploit.com/users/opcode/syscalls.html
4489 @c but we don't support Windows syscalls yet.
4491 Normally, @value{GDBN} knows in advance which syscalls are valid for
4492 each OS, so you can use the @value{GDBN} command-line completion
4493 facilities (@pxref{Completion,, command completion}) to list the
4496 You may also specify the system call numerically. A syscall's
4497 number is the value passed to the OS's syscall dispatcher to
4498 identify the requested service. When you specify the syscall by its
4499 name, @value{GDBN} uses its database of syscalls to convert the name
4500 into the corresponding numeric code, but using the number directly
4501 may be useful if @value{GDBN}'s database does not have the complete
4502 list of syscalls on your system (e.g., because @value{GDBN} lags
4503 behind the OS upgrades).
4505 You may specify a group of related syscalls to be caught at once using
4506 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4507 instance, on some platforms @value{GDBN} allows you to catch all
4508 network related syscalls, by passing the argument @code{group:network}
4509 to @code{catch syscall}. Note that not all syscall groups are
4510 available in every system. You can use the command completion
4511 facilities (@pxref{Completion,, command completion}) to list the
4512 syscall groups available on your environment.
4514 The example below illustrates how this command works if you don't provide
4518 (@value{GDBP}) catch syscall
4519 Catchpoint 1 (syscall)
4521 Starting program: /tmp/catch-syscall
4523 Catchpoint 1 (call to syscall 'close'), \
4524 0xffffe424 in __kernel_vsyscall ()
4528 Catchpoint 1 (returned from syscall 'close'), \
4529 0xffffe424 in __kernel_vsyscall ()
4533 Here is an example of catching a system call by name:
4536 (@value{GDBP}) catch syscall chroot
4537 Catchpoint 1 (syscall 'chroot' [61])
4539 Starting program: /tmp/catch-syscall
4541 Catchpoint 1 (call to syscall 'chroot'), \
4542 0xffffe424 in __kernel_vsyscall ()
4546 Catchpoint 1 (returned from syscall 'chroot'), \
4547 0xffffe424 in __kernel_vsyscall ()
4551 An example of specifying a system call numerically. In the case
4552 below, the syscall number has a corresponding entry in the XML
4553 file, so @value{GDBN} finds its name and prints it:
4556 (@value{GDBP}) catch syscall 252
4557 Catchpoint 1 (syscall(s) 'exit_group')
4559 Starting program: /tmp/catch-syscall
4561 Catchpoint 1 (call to syscall 'exit_group'), \
4562 0xffffe424 in __kernel_vsyscall ()
4566 Program exited normally.
4570 Here is an example of catching a syscall group:
4573 (@value{GDBP}) catch syscall group:process
4574 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4575 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4576 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4578 Starting program: /tmp/catch-syscall
4580 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4581 from /lib64/ld-linux-x86-64.so.2
4587 However, there can be situations when there is no corresponding name
4588 in XML file for that syscall number. In this case, @value{GDBN} prints
4589 a warning message saying that it was not able to find the syscall name,
4590 but the catchpoint will be set anyway. See the example below:
4593 (@value{GDBP}) catch syscall 764
4594 warning: The number '764' does not represent a known syscall.
4595 Catchpoint 2 (syscall 764)
4599 If you configure @value{GDBN} using the @samp{--without-expat} option,
4600 it will not be able to display syscall names. Also, if your
4601 architecture does not have an XML file describing its system calls,
4602 you will not be able to see the syscall names. It is important to
4603 notice that these two features are used for accessing the syscall
4604 name database. In either case, you will see a warning like this:
4607 (@value{GDBP}) catch syscall
4608 warning: Could not open "syscalls/i386-linux.xml"
4609 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4610 GDB will not be able to display syscall names.
4611 Catchpoint 1 (syscall)
4615 Of course, the file name will change depending on your architecture and system.
4617 Still using the example above, you can also try to catch a syscall by its
4618 number. In this case, you would see something like:
4621 (@value{GDBP}) catch syscall 252
4622 Catchpoint 1 (syscall(s) 252)
4625 Again, in this case @value{GDBN} would not be able to display syscall's names.
4629 A call to @code{fork}.
4633 A call to @code{vfork}.
4635 @item load @r{[}regexp@r{]}
4636 @itemx unload @r{[}regexp@r{]}
4638 @kindex catch unload
4639 The loading or unloading of a shared library. If @var{regexp} is
4640 given, then the catchpoint will stop only if the regular expression
4641 matches one of the affected libraries.
4643 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4644 @kindex catch signal
4645 The delivery of a signal.
4647 With no arguments, this catchpoint will catch any signal that is not
4648 used internally by @value{GDBN}, specifically, all signals except
4649 @samp{SIGTRAP} and @samp{SIGINT}.
4651 With the argument @samp{all}, all signals, including those used by
4652 @value{GDBN}, will be caught. This argument cannot be used with other
4655 Otherwise, the arguments are a list of signal names as given to
4656 @code{handle} (@pxref{Signals}). Only signals specified in this list
4659 One reason that @code{catch signal} can be more useful than
4660 @code{handle} is that you can attach commands and conditions to the
4663 When a signal is caught by a catchpoint, the signal's @code{stop} and
4664 @code{print} settings, as specified by @code{handle}, are ignored.
4665 However, whether the signal is still delivered to the inferior depends
4666 on the @code{pass} setting; this can be changed in the catchpoint's
4671 @item tcatch @var{event}
4673 Set a catchpoint that is enabled only for one stop. The catchpoint is
4674 automatically deleted after the first time the event is caught.
4678 Use the @code{info break} command to list the current catchpoints.
4682 @subsection Deleting Breakpoints
4684 @cindex clearing breakpoints, watchpoints, catchpoints
4685 @cindex deleting breakpoints, watchpoints, catchpoints
4686 It is often necessary to eliminate a breakpoint, watchpoint, or
4687 catchpoint once it has done its job and you no longer want your program
4688 to stop there. This is called @dfn{deleting} the breakpoint. A
4689 breakpoint that has been deleted no longer exists; it is forgotten.
4691 With the @code{clear} command you can delete breakpoints according to
4692 where they are in your program. With the @code{delete} command you can
4693 delete individual breakpoints, watchpoints, or catchpoints by specifying
4694 their breakpoint numbers.
4696 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4697 automatically ignores breakpoints on the first instruction to be executed
4698 when you continue execution without changing the execution address.
4703 Delete any breakpoints at the next instruction to be executed in the
4704 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4705 the innermost frame is selected, this is a good way to delete a
4706 breakpoint where your program just stopped.
4708 @item clear @var{location}
4709 Delete any breakpoints set at the specified @var{location}.
4710 @xref{Specify Location}, for the various forms of @var{location}; the
4711 most useful ones are listed below:
4714 @item clear @var{function}
4715 @itemx clear @var{filename}:@var{function}
4716 Delete any breakpoints set at entry to the named @var{function}.
4718 @item clear @var{linenum}
4719 @itemx clear @var{filename}:@var{linenum}
4720 Delete any breakpoints set at or within the code of the specified
4721 @var{linenum} of the specified @var{filename}.
4724 @cindex delete breakpoints
4726 @kindex d @r{(@code{delete})}
4727 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4728 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4729 list specified as argument. If no argument is specified, delete all
4730 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4731 confirm off}). You can abbreviate this command as @code{d}.
4735 @subsection Disabling Breakpoints
4737 @cindex enable/disable a breakpoint
4738 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4739 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4740 it had been deleted, but remembers the information on the breakpoint so
4741 that you can @dfn{enable} it again later.
4743 You disable and enable breakpoints, watchpoints, and catchpoints with
4744 the @code{enable} and @code{disable} commands, optionally specifying
4745 one or more breakpoint numbers as arguments. Use @code{info break} to
4746 print a list of all breakpoints, watchpoints, and catchpoints if you
4747 do not know which numbers to use.
4749 Disabling and enabling a breakpoint that has multiple locations
4750 affects all of its locations.
4752 A breakpoint, watchpoint, or catchpoint can have any of several
4753 different states of enablement:
4757 Enabled. The breakpoint stops your program. A breakpoint set
4758 with the @code{break} command starts out in this state.
4760 Disabled. The breakpoint has no effect on your program.
4762 Enabled once. The breakpoint stops your program, but then becomes
4765 Enabled for a count. The breakpoint stops your program for the next
4766 N times, then becomes disabled.
4768 Enabled for deletion. The breakpoint stops your program, but
4769 immediately after it does so it is deleted permanently. A breakpoint
4770 set with the @code{tbreak} command starts out in this state.
4773 You can use the following commands to enable or disable breakpoints,
4774 watchpoints, and catchpoints:
4778 @kindex dis @r{(@code{disable})}
4779 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4780 Disable the specified breakpoints---or all breakpoints, if none are
4781 listed. A disabled breakpoint has no effect but is not forgotten. All
4782 options such as ignore-counts, conditions and commands are remembered in
4783 case the breakpoint is enabled again later. You may abbreviate
4784 @code{disable} as @code{dis}.
4787 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4788 Enable the specified breakpoints (or all defined breakpoints). They
4789 become effective once again in stopping your program.
4791 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4792 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4793 of these breakpoints immediately after stopping your program.
4795 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4796 Enable the specified breakpoints temporarily. @value{GDBN} records
4797 @var{count} with each of the specified breakpoints, and decrements a
4798 breakpoint's count when it is hit. When any count reaches 0,
4799 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4800 count (@pxref{Conditions, ,Break Conditions}), that will be
4801 decremented to 0 before @var{count} is affected.
4803 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4804 Enable the specified breakpoints to work once, then die. @value{GDBN}
4805 deletes any of these breakpoints as soon as your program stops there.
4806 Breakpoints set by the @code{tbreak} command start out in this state.
4809 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4810 @c confusing: tbreak is also initially enabled.
4811 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4812 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4813 subsequently, they become disabled or enabled only when you use one of
4814 the commands above. (The command @code{until} can set and delete a
4815 breakpoint of its own, but it does not change the state of your other
4816 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4820 @subsection Break Conditions
4821 @cindex conditional breakpoints
4822 @cindex breakpoint conditions
4824 @c FIXME what is scope of break condition expr? Context where wanted?
4825 @c in particular for a watchpoint?
4826 The simplest sort of breakpoint breaks every time your program reaches a
4827 specified place. You can also specify a @dfn{condition} for a
4828 breakpoint. A condition is just a Boolean expression in your
4829 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4830 a condition evaluates the expression each time your program reaches it,
4831 and your program stops only if the condition is @emph{true}.
4833 This is the converse of using assertions for program validation; in that
4834 situation, you want to stop when the assertion is violated---that is,
4835 when the condition is false. In C, if you want to test an assertion expressed
4836 by the condition @var{assert}, you should set the condition
4837 @samp{! @var{assert}} on the appropriate breakpoint.
4839 Conditions are also accepted for watchpoints; you may not need them,
4840 since a watchpoint is inspecting the value of an expression anyhow---but
4841 it might be simpler, say, to just set a watchpoint on a variable name,
4842 and specify a condition that tests whether the new value is an interesting
4845 Break conditions can have side effects, and may even call functions in
4846 your program. This can be useful, for example, to activate functions
4847 that log program progress, or to use your own print functions to
4848 format special data structures. The effects are completely predictable
4849 unless there is another enabled breakpoint at the same address. (In
4850 that case, @value{GDBN} might see the other breakpoint first and stop your
4851 program without checking the condition of this one.) Note that
4852 breakpoint commands are usually more convenient and flexible than break
4854 purpose of performing side effects when a breakpoint is reached
4855 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4857 Breakpoint conditions can also be evaluated on the target's side if
4858 the target supports it. Instead of evaluating the conditions locally,
4859 @value{GDBN} encodes the expression into an agent expression
4860 (@pxref{Agent Expressions}) suitable for execution on the target,
4861 independently of @value{GDBN}. Global variables become raw memory
4862 locations, locals become stack accesses, and so forth.
4864 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4865 when its condition evaluates to true. This mechanism may provide faster
4866 response times depending on the performance characteristics of the target
4867 since it does not need to keep @value{GDBN} informed about
4868 every breakpoint trigger, even those with false conditions.
4870 Break conditions can be specified when a breakpoint is set, by using
4871 @samp{if} in the arguments to the @code{break} command. @xref{Set
4872 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4873 with the @code{condition} command.
4875 You can also use the @code{if} keyword with the @code{watch} command.
4876 The @code{catch} command does not recognize the @code{if} keyword;
4877 @code{condition} is the only way to impose a further condition on a
4882 @item condition @var{bnum} @var{expression}
4883 Specify @var{expression} as the break condition for breakpoint,
4884 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4885 breakpoint @var{bnum} stops your program only if the value of
4886 @var{expression} is true (nonzero, in C). When you use
4887 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4888 syntactic correctness, and to determine whether symbols in it have
4889 referents in the context of your breakpoint. If @var{expression} uses
4890 symbols not referenced in the context of the breakpoint, @value{GDBN}
4891 prints an error message:
4894 No symbol "foo" in current context.
4899 not actually evaluate @var{expression} at the time the @code{condition}
4900 command (or a command that sets a breakpoint with a condition, like
4901 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4903 @item condition @var{bnum}
4904 Remove the condition from breakpoint number @var{bnum}. It becomes
4905 an ordinary unconditional breakpoint.
4908 @cindex ignore count (of breakpoint)
4909 A special case of a breakpoint condition is to stop only when the
4910 breakpoint has been reached a certain number of times. This is so
4911 useful that there is a special way to do it, using the @dfn{ignore
4912 count} of the breakpoint. Every breakpoint has an ignore count, which
4913 is an integer. Most of the time, the ignore count is zero, and
4914 therefore has no effect. But if your program reaches a breakpoint whose
4915 ignore count is positive, then instead of stopping, it just decrements
4916 the ignore count by one and continues. As a result, if the ignore count
4917 value is @var{n}, the breakpoint does not stop the next @var{n} times
4918 your program reaches it.
4922 @item ignore @var{bnum} @var{count}
4923 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4924 The next @var{count} times the breakpoint is reached, your program's
4925 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4928 To make the breakpoint stop the next time it is reached, specify
4931 When you use @code{continue} to resume execution of your program from a
4932 breakpoint, you can specify an ignore count directly as an argument to
4933 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4934 Stepping,,Continuing and Stepping}.
4936 If a breakpoint has a positive ignore count and a condition, the
4937 condition is not checked. Once the ignore count reaches zero,
4938 @value{GDBN} resumes checking the condition.
4940 You could achieve the effect of the ignore count with a condition such
4941 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4942 is decremented each time. @xref{Convenience Vars, ,Convenience
4946 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4949 @node Break Commands
4950 @subsection Breakpoint Command Lists
4952 @cindex breakpoint commands
4953 You can give any breakpoint (or watchpoint or catchpoint) a series of
4954 commands to execute when your program stops due to that breakpoint. For
4955 example, you might want to print the values of certain expressions, or
4956 enable other breakpoints.
4960 @kindex end@r{ (breakpoint commands)}
4961 @item commands @r{[}@var{list}@dots{}@r{]}
4962 @itemx @dots{} @var{command-list} @dots{}
4964 Specify a list of commands for the given breakpoints. The commands
4965 themselves appear on the following lines. Type a line containing just
4966 @code{end} to terminate the commands.
4968 To remove all commands from a breakpoint, type @code{commands} and
4969 follow it immediately with @code{end}; that is, give no commands.
4971 With no argument, @code{commands} refers to the last breakpoint,
4972 watchpoint, or catchpoint set (not to the breakpoint most recently
4973 encountered). If the most recent breakpoints were set with a single
4974 command, then the @code{commands} will apply to all the breakpoints
4975 set by that command. This applies to breakpoints set by
4976 @code{rbreak}, and also applies when a single @code{break} command
4977 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4981 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4982 disabled within a @var{command-list}.
4984 You can use breakpoint commands to start your program up again. Simply
4985 use the @code{continue} command, or @code{step}, or any other command
4986 that resumes execution.
4988 Any other commands in the command list, after a command that resumes
4989 execution, are ignored. This is because any time you resume execution
4990 (even with a simple @code{next} or @code{step}), you may encounter
4991 another breakpoint---which could have its own command list, leading to
4992 ambiguities about which list to execute.
4995 If the first command you specify in a command list is @code{silent}, the
4996 usual message about stopping at a breakpoint is not printed. This may
4997 be desirable for breakpoints that are to print a specific message and
4998 then continue. If none of the remaining commands print anything, you
4999 see no sign that the breakpoint was reached. @code{silent} is
5000 meaningful only at the beginning of a breakpoint command list.
5002 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5003 print precisely controlled output, and are often useful in silent
5004 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5006 For example, here is how you could use breakpoint commands to print the
5007 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5013 printf "x is %d\n",x
5018 One application for breakpoint commands is to compensate for one bug so
5019 you can test for another. Put a breakpoint just after the erroneous line
5020 of code, give it a condition to detect the case in which something
5021 erroneous has been done, and give it commands to assign correct values
5022 to any variables that need them. End with the @code{continue} command
5023 so that your program does not stop, and start with the @code{silent}
5024 command so that no output is produced. Here is an example:
5035 @node Dynamic Printf
5036 @subsection Dynamic Printf
5038 @cindex dynamic printf
5040 The dynamic printf command @code{dprintf} combines a breakpoint with
5041 formatted printing of your program's data to give you the effect of
5042 inserting @code{printf} calls into your program on-the-fly, without
5043 having to recompile it.
5045 In its most basic form, the output goes to the GDB console. However,
5046 you can set the variable @code{dprintf-style} for alternate handling.
5047 For instance, you can ask to format the output by calling your
5048 program's @code{printf} function. This has the advantage that the
5049 characters go to the program's output device, so they can recorded in
5050 redirects to files and so forth.
5052 If you are doing remote debugging with a stub or agent, you can also
5053 ask to have the printf handled by the remote agent. In addition to
5054 ensuring that the output goes to the remote program's device along
5055 with any other output the program might produce, you can also ask that
5056 the dprintf remain active even after disconnecting from the remote
5057 target. Using the stub/agent is also more efficient, as it can do
5058 everything without needing to communicate with @value{GDBN}.
5062 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5063 Whenever execution reaches @var{location}, print the values of one or
5064 more @var{expressions} under the control of the string @var{template}.
5065 To print several values, separate them with commas.
5067 @item set dprintf-style @var{style}
5068 Set the dprintf output to be handled in one of several different
5069 styles enumerated below. A change of style affects all existing
5070 dynamic printfs immediately. (If you need individual control over the
5071 print commands, simply define normal breakpoints with
5072 explicitly-supplied command lists.)
5076 @kindex dprintf-style gdb
5077 Handle the output using the @value{GDBN} @code{printf} command.
5080 @kindex dprintf-style call
5081 Handle the output by calling a function in your program (normally
5085 @kindex dprintf-style agent
5086 Have the remote debugging agent (such as @code{gdbserver}) handle
5087 the output itself. This style is only available for agents that
5088 support running commands on the target.
5091 @item set dprintf-function @var{function}
5092 Set the function to call if the dprintf style is @code{call}. By
5093 default its value is @code{printf}. You may set it to any expression.
5094 that @value{GDBN} can evaluate to a function, as per the @code{call}
5097 @item set dprintf-channel @var{channel}
5098 Set a ``channel'' for dprintf. If set to a non-empty value,
5099 @value{GDBN} will evaluate it as an expression and pass the result as
5100 a first argument to the @code{dprintf-function}, in the manner of
5101 @code{fprintf} and similar functions. Otherwise, the dprintf format
5102 string will be the first argument, in the manner of @code{printf}.
5104 As an example, if you wanted @code{dprintf} output to go to a logfile
5105 that is a standard I/O stream assigned to the variable @code{mylog},
5106 you could do the following:
5109 (gdb) set dprintf-style call
5110 (gdb) set dprintf-function fprintf
5111 (gdb) set dprintf-channel mylog
5112 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5113 Dprintf 1 at 0x123456: file main.c, line 25.
5115 1 dprintf keep y 0x00123456 in main at main.c:25
5116 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5121 Note that the @code{info break} displays the dynamic printf commands
5122 as normal breakpoint commands; you can thus easily see the effect of
5123 the variable settings.
5125 @item set disconnected-dprintf on
5126 @itemx set disconnected-dprintf off
5127 @kindex set disconnected-dprintf
5128 Choose whether @code{dprintf} commands should continue to run if
5129 @value{GDBN} has disconnected from the target. This only applies
5130 if the @code{dprintf-style} is @code{agent}.
5132 @item show disconnected-dprintf off
5133 @kindex show disconnected-dprintf
5134 Show the current choice for disconnected @code{dprintf}.
5138 @value{GDBN} does not check the validity of function and channel,
5139 relying on you to supply values that are meaningful for the contexts
5140 in which they are being used. For instance, the function and channel
5141 may be the values of local variables, but if that is the case, then
5142 all enabled dynamic prints must be at locations within the scope of
5143 those locals. If evaluation fails, @value{GDBN} will report an error.
5145 @node Save Breakpoints
5146 @subsection How to save breakpoints to a file
5148 To save breakpoint definitions to a file use the @w{@code{save
5149 breakpoints}} command.
5152 @kindex save breakpoints
5153 @cindex save breakpoints to a file for future sessions
5154 @item save breakpoints [@var{filename}]
5155 This command saves all current breakpoint definitions together with
5156 their commands and ignore counts, into a file @file{@var{filename}}
5157 suitable for use in a later debugging session. This includes all
5158 types of breakpoints (breakpoints, watchpoints, catchpoints,
5159 tracepoints). To read the saved breakpoint definitions, use the
5160 @code{source} command (@pxref{Command Files}). Note that watchpoints
5161 with expressions involving local variables may fail to be recreated
5162 because it may not be possible to access the context where the
5163 watchpoint is valid anymore. Because the saved breakpoint definitions
5164 are simply a sequence of @value{GDBN} commands that recreate the
5165 breakpoints, you can edit the file in your favorite editing program,
5166 and remove the breakpoint definitions you're not interested in, or
5167 that can no longer be recreated.
5170 @node Static Probe Points
5171 @subsection Static Probe Points
5173 @cindex static probe point, SystemTap
5174 @cindex static probe point, DTrace
5175 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5176 for Statically Defined Tracing, and the probes are designed to have a tiny
5177 runtime code and data footprint, and no dynamic relocations.
5179 Currently, the following types of probes are supported on
5180 ELF-compatible systems:
5184 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5185 @acronym{SDT} probes@footnote{See
5186 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5187 for more information on how to add @code{SystemTap} @acronym{SDT}
5188 probes in your applications.}. @code{SystemTap} probes are usable
5189 from assembly, C and C@t{++} languages@footnote{See
5190 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5191 for a good reference on how the @acronym{SDT} probes are implemented.}.
5193 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5194 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5198 @cindex semaphores on static probe points
5199 Some @code{SystemTap} probes have an associated semaphore variable;
5200 for instance, this happens automatically if you defined your probe
5201 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5202 @value{GDBN} will automatically enable it when you specify a
5203 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5204 breakpoint at a probe's location by some other method (e.g.,
5205 @code{break file:line}), then @value{GDBN} will not automatically set
5206 the semaphore. @code{DTrace} probes do not support semaphores.
5208 You can examine the available static static probes using @code{info
5209 probes}, with optional arguments:
5213 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5214 If given, @var{type} is either @code{stap} for listing
5215 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5216 probes. If omitted all probes are listed regardless of their types.
5218 If given, @var{provider} is a regular expression used to match against provider
5219 names when selecting which probes to list. If omitted, probes by all
5220 probes from all providers are listed.
5222 If given, @var{name} is a regular expression to match against probe names
5223 when selecting which probes to list. If omitted, probe names are not
5224 considered when deciding whether to display them.
5226 If given, @var{objfile} is a regular expression used to select which
5227 object files (executable or shared libraries) to examine. If not
5228 given, all object files are considered.
5230 @item info probes all
5231 List the available static probes, from all types.
5234 @cindex enabling and disabling probes
5235 Some probe points can be enabled and/or disabled. The effect of
5236 enabling or disabling a probe depends on the type of probe being
5237 handled. Some @code{DTrace} probes can be enabled or
5238 disabled, but @code{SystemTap} probes cannot be disabled.
5240 You can enable (or disable) one or more probes using the following
5241 commands, with optional arguments:
5244 @kindex enable probes
5245 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5246 If given, @var{provider} is a regular expression used to match against
5247 provider names when selecting which probes to enable. If omitted,
5248 all probes from all providers are enabled.
5250 If given, @var{name} is a regular expression to match against probe
5251 names when selecting which probes to enable. If omitted, probe names
5252 are not considered when deciding whether to enable them.
5254 If given, @var{objfile} is a regular expression used to select which
5255 object files (executable or shared libraries) to examine. If not
5256 given, all object files are considered.
5258 @kindex disable probes
5259 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5260 See the @code{enable probes} command above for a description of the
5261 optional arguments accepted by this command.
5264 @vindex $_probe_arg@r{, convenience variable}
5265 A probe may specify up to twelve arguments. These are available at the
5266 point at which the probe is defined---that is, when the current PC is
5267 at the probe's location. The arguments are available using the
5268 convenience variables (@pxref{Convenience Vars})
5269 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5270 probes each probe argument is an integer of the appropriate size;
5271 types are not preserved. In @code{DTrace} probes types are preserved
5272 provided that they are recognized as such by @value{GDBN}; otherwise
5273 the value of the probe argument will be a long integer. The
5274 convenience variable @code{$_probe_argc} holds the number of arguments
5275 at the current probe point.
5277 These variables are always available, but attempts to access them at
5278 any location other than a probe point will cause @value{GDBN} to give
5282 @c @ifclear BARETARGET
5283 @node Error in Breakpoints
5284 @subsection ``Cannot insert breakpoints''
5286 If you request too many active hardware-assisted breakpoints and
5287 watchpoints, you will see this error message:
5289 @c FIXME: the precise wording of this message may change; the relevant
5290 @c source change is not committed yet (Sep 3, 1999).
5292 Stopped; cannot insert breakpoints.
5293 You may have requested too many hardware breakpoints and watchpoints.
5297 This message is printed when you attempt to resume the program, since
5298 only then @value{GDBN} knows exactly how many hardware breakpoints and
5299 watchpoints it needs to insert.
5301 When this message is printed, you need to disable or remove some of the
5302 hardware-assisted breakpoints and watchpoints, and then continue.
5304 @node Breakpoint-related Warnings
5305 @subsection ``Breakpoint address adjusted...''
5306 @cindex breakpoint address adjusted
5308 Some processor architectures place constraints on the addresses at
5309 which breakpoints may be placed. For architectures thus constrained,
5310 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5311 with the constraints dictated by the architecture.
5313 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5314 a VLIW architecture in which a number of RISC-like instructions may be
5315 bundled together for parallel execution. The FR-V architecture
5316 constrains the location of a breakpoint instruction within such a
5317 bundle to the instruction with the lowest address. @value{GDBN}
5318 honors this constraint by adjusting a breakpoint's address to the
5319 first in the bundle.
5321 It is not uncommon for optimized code to have bundles which contain
5322 instructions from different source statements, thus it may happen that
5323 a breakpoint's address will be adjusted from one source statement to
5324 another. Since this adjustment may significantly alter @value{GDBN}'s
5325 breakpoint related behavior from what the user expects, a warning is
5326 printed when the breakpoint is first set and also when the breakpoint
5329 A warning like the one below is printed when setting a breakpoint
5330 that's been subject to address adjustment:
5333 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5336 Such warnings are printed both for user settable and @value{GDBN}'s
5337 internal breakpoints. If you see one of these warnings, you should
5338 verify that a breakpoint set at the adjusted address will have the
5339 desired affect. If not, the breakpoint in question may be removed and
5340 other breakpoints may be set which will have the desired behavior.
5341 E.g., it may be sufficient to place the breakpoint at a later
5342 instruction. A conditional breakpoint may also be useful in some
5343 cases to prevent the breakpoint from triggering too often.
5345 @value{GDBN} will also issue a warning when stopping at one of these
5346 adjusted breakpoints:
5349 warning: Breakpoint 1 address previously adjusted from 0x00010414
5353 When this warning is encountered, it may be too late to take remedial
5354 action except in cases where the breakpoint is hit earlier or more
5355 frequently than expected.
5357 @node Continuing and Stepping
5358 @section Continuing and Stepping
5362 @cindex resuming execution
5363 @dfn{Continuing} means resuming program execution until your program
5364 completes normally. In contrast, @dfn{stepping} means executing just
5365 one more ``step'' of your program, where ``step'' may mean either one
5366 line of source code, or one machine instruction (depending on what
5367 particular command you use). Either when continuing or when stepping,
5368 your program may stop even sooner, due to a breakpoint or a signal. (If
5369 it stops due to a signal, you may want to use @code{handle}, or use
5370 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5371 or you may step into the signal's handler (@pxref{stepping and signal
5376 @kindex c @r{(@code{continue})}
5377 @kindex fg @r{(resume foreground execution)}
5378 @item continue @r{[}@var{ignore-count}@r{]}
5379 @itemx c @r{[}@var{ignore-count}@r{]}
5380 @itemx fg @r{[}@var{ignore-count}@r{]}
5381 Resume program execution, at the address where your program last stopped;
5382 any breakpoints set at that address are bypassed. The optional argument
5383 @var{ignore-count} allows you to specify a further number of times to
5384 ignore a breakpoint at this location; its effect is like that of
5385 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5387 The argument @var{ignore-count} is meaningful only when your program
5388 stopped due to a breakpoint. At other times, the argument to
5389 @code{continue} is ignored.
5391 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5392 debugged program is deemed to be the foreground program) are provided
5393 purely for convenience, and have exactly the same behavior as
5397 To resume execution at a different place, you can use @code{return}
5398 (@pxref{Returning, ,Returning from a Function}) to go back to the
5399 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5400 Different Address}) to go to an arbitrary location in your program.
5402 A typical technique for using stepping is to set a breakpoint
5403 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5404 beginning of the function or the section of your program where a problem
5405 is believed to lie, run your program until it stops at that breakpoint,
5406 and then step through the suspect area, examining the variables that are
5407 interesting, until you see the problem happen.
5411 @kindex s @r{(@code{step})}
5413 Continue running your program until control reaches a different source
5414 line, then stop it and return control to @value{GDBN}. This command is
5415 abbreviated @code{s}.
5418 @c "without debugging information" is imprecise; actually "without line
5419 @c numbers in the debugging information". (gcc -g1 has debugging info but
5420 @c not line numbers). But it seems complex to try to make that
5421 @c distinction here.
5422 @emph{Warning:} If you use the @code{step} command while control is
5423 within a function that was compiled without debugging information,
5424 execution proceeds until control reaches a function that does have
5425 debugging information. Likewise, it will not step into a function which
5426 is compiled without debugging information. To step through functions
5427 without debugging information, use the @code{stepi} command, described
5431 The @code{step} command only stops at the first instruction of a source
5432 line. This prevents the multiple stops that could otherwise occur in
5433 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5434 to stop if a function that has debugging information is called within
5435 the line. In other words, @code{step} @emph{steps inside} any functions
5436 called within the line.
5438 Also, the @code{step} command only enters a function if there is line
5439 number information for the function. Otherwise it acts like the
5440 @code{next} command. This avoids problems when using @code{cc -gl}
5441 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5442 was any debugging information about the routine.
5444 @item step @var{count}
5445 Continue running as in @code{step}, but do so @var{count} times. If a
5446 breakpoint is reached, or a signal not related to stepping occurs before
5447 @var{count} steps, stepping stops right away.
5450 @kindex n @r{(@code{next})}
5451 @item next @r{[}@var{count}@r{]}
5452 Continue to the next source line in the current (innermost) stack frame.
5453 This is similar to @code{step}, but function calls that appear within
5454 the line of code are executed without stopping. Execution stops when
5455 control reaches a different line of code at the original stack level
5456 that was executing when you gave the @code{next} command. This command
5457 is abbreviated @code{n}.
5459 An argument @var{count} is a repeat count, as for @code{step}.
5462 @c FIX ME!! Do we delete this, or is there a way it fits in with
5463 @c the following paragraph? --- Vctoria
5465 @c @code{next} within a function that lacks debugging information acts like
5466 @c @code{step}, but any function calls appearing within the code of the
5467 @c function are executed without stopping.
5469 The @code{next} command only stops at the first instruction of a
5470 source line. This prevents multiple stops that could otherwise occur in
5471 @code{switch} statements, @code{for} loops, etc.
5473 @kindex set step-mode
5475 @cindex functions without line info, and stepping
5476 @cindex stepping into functions with no line info
5477 @itemx set step-mode on
5478 The @code{set step-mode on} command causes the @code{step} command to
5479 stop at the first instruction of a function which contains no debug line
5480 information rather than stepping over it.
5482 This is useful in cases where you may be interested in inspecting the
5483 machine instructions of a function which has no symbolic info and do not
5484 want @value{GDBN} to automatically skip over this function.
5486 @item set step-mode off
5487 Causes the @code{step} command to step over any functions which contains no
5488 debug information. This is the default.
5490 @item show step-mode
5491 Show whether @value{GDBN} will stop in or step over functions without
5492 source line debug information.
5495 @kindex fin @r{(@code{finish})}
5497 Continue running until just after function in the selected stack frame
5498 returns. Print the returned value (if any). This command can be
5499 abbreviated as @code{fin}.
5501 Contrast this with the @code{return} command (@pxref{Returning,
5502 ,Returning from a Function}).
5505 @kindex u @r{(@code{until})}
5506 @cindex run until specified location
5509 Continue running until a source line past the current line, in the
5510 current stack frame, is reached. This command is used to avoid single
5511 stepping through a loop more than once. It is like the @code{next}
5512 command, except that when @code{until} encounters a jump, it
5513 automatically continues execution until the program counter is greater
5514 than the address of the jump.
5516 This means that when you reach the end of a loop after single stepping
5517 though it, @code{until} makes your program continue execution until it
5518 exits the loop. In contrast, a @code{next} command at the end of a loop
5519 simply steps back to the beginning of the loop, which forces you to step
5520 through the next iteration.
5522 @code{until} always stops your program if it attempts to exit the current
5525 @code{until} may produce somewhat counterintuitive results if the order
5526 of machine code does not match the order of the source lines. For
5527 example, in the following excerpt from a debugging session, the @code{f}
5528 (@code{frame}) command shows that execution is stopped at line
5529 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5533 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5535 (@value{GDBP}) until
5536 195 for ( ; argc > 0; NEXTARG) @{
5539 This happened because, for execution efficiency, the compiler had
5540 generated code for the loop closure test at the end, rather than the
5541 start, of the loop---even though the test in a C @code{for}-loop is
5542 written before the body of the loop. The @code{until} command appeared
5543 to step back to the beginning of the loop when it advanced to this
5544 expression; however, it has not really gone to an earlier
5545 statement---not in terms of the actual machine code.
5547 @code{until} with no argument works by means of single
5548 instruction stepping, and hence is slower than @code{until} with an
5551 @item until @var{location}
5552 @itemx u @var{location}
5553 Continue running your program until either the specified @var{location} is
5554 reached, or the current stack frame returns. The location is any of
5555 the forms described in @ref{Specify Location}.
5556 This form of the command uses temporary breakpoints, and
5557 hence is quicker than @code{until} without an argument. The specified
5558 location is actually reached only if it is in the current frame. This
5559 implies that @code{until} can be used to skip over recursive function
5560 invocations. For instance in the code below, if the current location is
5561 line @code{96}, issuing @code{until 99} will execute the program up to
5562 line @code{99} in the same invocation of factorial, i.e., after the inner
5563 invocations have returned.
5566 94 int factorial (int value)
5568 96 if (value > 1) @{
5569 97 value *= factorial (value - 1);
5576 @kindex advance @var{location}
5577 @item advance @var{location}
5578 Continue running the program up to the given @var{location}. An argument is
5579 required, which should be of one of the forms described in
5580 @ref{Specify Location}.
5581 Execution will also stop upon exit from the current stack
5582 frame. This command is similar to @code{until}, but @code{advance} will
5583 not skip over recursive function calls, and the target location doesn't
5584 have to be in the same frame as the current one.
5588 @kindex si @r{(@code{stepi})}
5590 @itemx stepi @var{arg}
5592 Execute one machine instruction, then stop and return to the debugger.
5594 It is often useful to do @samp{display/i $pc} when stepping by machine
5595 instructions. This makes @value{GDBN} automatically display the next
5596 instruction to be executed, each time your program stops. @xref{Auto
5597 Display,, Automatic Display}.
5599 An argument is a repeat count, as in @code{step}.
5603 @kindex ni @r{(@code{nexti})}
5605 @itemx nexti @var{arg}
5607 Execute one machine instruction, but if it is a function call,
5608 proceed until the function returns.
5610 An argument is a repeat count, as in @code{next}.
5614 @anchor{range stepping}
5615 @cindex range stepping
5616 @cindex target-assisted range stepping
5617 By default, and if available, @value{GDBN} makes use of
5618 target-assisted @dfn{range stepping}. In other words, whenever you
5619 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5620 tells the target to step the corresponding range of instruction
5621 addresses instead of issuing multiple single-steps. This speeds up
5622 line stepping, particularly for remote targets. Ideally, there should
5623 be no reason you would want to turn range stepping off. However, it's
5624 possible that a bug in the debug info, a bug in the remote stub (for
5625 remote targets), or even a bug in @value{GDBN} could make line
5626 stepping behave incorrectly when target-assisted range stepping is
5627 enabled. You can use the following command to turn off range stepping
5631 @kindex set range-stepping
5632 @kindex show range-stepping
5633 @item set range-stepping
5634 @itemx show range-stepping
5635 Control whether range stepping is enabled.
5637 If @code{on}, and the target supports it, @value{GDBN} tells the
5638 target to step a range of addresses itself, instead of issuing
5639 multiple single-steps. If @code{off}, @value{GDBN} always issues
5640 single-steps, even if range stepping is supported by the target. The
5641 default is @code{on}.
5645 @node Skipping Over Functions and Files
5646 @section Skipping Over Functions and Files
5647 @cindex skipping over functions and files
5649 The program you are debugging may contain some functions which are
5650 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5651 skip a function, all functions in a file or a particular function in
5652 a particular file when stepping.
5654 For example, consider the following C function:
5665 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5666 are not interested in stepping through @code{boring}. If you run @code{step}
5667 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5668 step over both @code{foo} and @code{boring}!
5670 One solution is to @code{step} into @code{boring} and use the @code{finish}
5671 command to immediately exit it. But this can become tedious if @code{boring}
5672 is called from many places.
5674 A more flexible solution is to execute @kbd{skip boring}. This instructs
5675 @value{GDBN} never to step into @code{boring}. Now when you execute
5676 @code{step} at line 103, you'll step over @code{boring} and directly into
5679 Functions may be skipped by providing either a function name, linespec
5680 (@pxref{Specify Location}), regular expression that matches the function's
5681 name, file name or a @code{glob}-style pattern that matches the file name.
5683 On Posix systems the form of the regular expression is
5684 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5685 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5686 expression is whatever is provided by the @code{regcomp} function of
5687 the underlying system.
5688 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5689 description of @code{glob}-style patterns.
5693 @item skip @r{[}@var{options}@r{]}
5694 The basic form of the @code{skip} command takes zero or more options
5695 that specify what to skip.
5696 The @var{options} argument is any useful combination of the following:
5699 @item -file @var{file}
5700 @itemx -fi @var{file}
5701 Functions in @var{file} will be skipped over when stepping.
5703 @item -gfile @var{file-glob-pattern}
5704 @itemx -gfi @var{file-glob-pattern}
5705 @cindex skipping over files via glob-style patterns
5706 Functions in files matching @var{file-glob-pattern} will be skipped
5710 (gdb) skip -gfi utils/*.c
5713 @item -function @var{linespec}
5714 @itemx -fu @var{linespec}
5715 Functions named by @var{linespec} or the function containing the line
5716 named by @var{linespec} will be skipped over when stepping.
5717 @xref{Specify Location}.
5719 @item -rfunction @var{regexp}
5720 @itemx -rfu @var{regexp}
5721 @cindex skipping over functions via regular expressions
5722 Functions whose name matches @var{regexp} will be skipped over when stepping.
5724 This form is useful for complex function names.
5725 For example, there is generally no need to step into C@t{++} @code{std::string}
5726 constructors or destructors. Plus with C@t{++} templates it can be hard to
5727 write out the full name of the function, and often it doesn't matter what
5728 the template arguments are. Specifying the function to be skipped as a
5729 regular expression makes this easier.
5732 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5735 If you want to skip every templated C@t{++} constructor and destructor
5736 in the @code{std} namespace you can do:
5739 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5743 If no options are specified, the function you're currently debugging
5746 @kindex skip function
5747 @item skip function @r{[}@var{linespec}@r{]}
5748 After running this command, the function named by @var{linespec} or the
5749 function containing the line named by @var{linespec} will be skipped over when
5750 stepping. @xref{Specify Location}.
5752 If you do not specify @var{linespec}, the function you're currently debugging
5755 (If you have a function called @code{file} that you want to skip, use
5756 @kbd{skip function file}.)
5759 @item skip file @r{[}@var{filename}@r{]}
5760 After running this command, any function whose source lives in @var{filename}
5761 will be skipped over when stepping.
5764 (gdb) skip file boring.c
5765 File boring.c will be skipped when stepping.
5768 If you do not specify @var{filename}, functions whose source lives in the file
5769 you're currently debugging will be skipped.
5772 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5773 These are the commands for managing your list of skips:
5777 @item info skip @r{[}@var{range}@r{]}
5778 Print details about the specified skip(s). If @var{range} is not specified,
5779 print a table with details about all functions and files marked for skipping.
5780 @code{info skip} prints the following information about each skip:
5784 A number identifying this skip.
5785 @item Enabled or Disabled
5786 Enabled skips are marked with @samp{y}.
5787 Disabled skips are marked with @samp{n}.
5789 If the file name is a @samp{glob} pattern this is @samp{y}.
5790 Otherwise it is @samp{n}.
5792 The name or @samp{glob} pattern of the file to be skipped.
5793 If no file is specified this is @samp{<none>}.
5795 If the function name is a @samp{regular expression} this is @samp{y}.
5796 Otherwise it is @samp{n}.
5798 The name or regular expression of the function to skip.
5799 If no function is specified this is @samp{<none>}.
5803 @item skip delete @r{[}@var{range}@r{]}
5804 Delete the specified skip(s). If @var{range} is not specified, delete all
5808 @item skip enable @r{[}@var{range}@r{]}
5809 Enable the specified skip(s). If @var{range} is not specified, enable all
5812 @kindex skip disable
5813 @item skip disable @r{[}@var{range}@r{]}
5814 Disable the specified skip(s). If @var{range} is not specified, disable all
5823 A signal is an asynchronous event that can happen in a program. The
5824 operating system defines the possible kinds of signals, and gives each
5825 kind a name and a number. For example, in Unix @code{SIGINT} is the
5826 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5827 @code{SIGSEGV} is the signal a program gets from referencing a place in
5828 memory far away from all the areas in use; @code{SIGALRM} occurs when
5829 the alarm clock timer goes off (which happens only if your program has
5830 requested an alarm).
5832 @cindex fatal signals
5833 Some signals, including @code{SIGALRM}, are a normal part of the
5834 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5835 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5836 program has not specified in advance some other way to handle the signal.
5837 @code{SIGINT} does not indicate an error in your program, but it is normally
5838 fatal so it can carry out the purpose of the interrupt: to kill the program.
5840 @value{GDBN} has the ability to detect any occurrence of a signal in your
5841 program. You can tell @value{GDBN} in advance what to do for each kind of
5844 @cindex handling signals
5845 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5846 @code{SIGALRM} be silently passed to your program
5847 (so as not to interfere with their role in the program's functioning)
5848 but to stop your program immediately whenever an error signal happens.
5849 You can change these settings with the @code{handle} command.
5852 @kindex info signals
5856 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5857 handle each one. You can use this to see the signal numbers of all
5858 the defined types of signals.
5860 @item info signals @var{sig}
5861 Similar, but print information only about the specified signal number.
5863 @code{info handle} is an alias for @code{info signals}.
5865 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5866 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5867 for details about this command.
5870 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5871 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5872 can be the number of a signal or its name (with or without the
5873 @samp{SIG} at the beginning); a list of signal numbers of the form
5874 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5875 known signals. Optional arguments @var{keywords}, described below,
5876 say what change to make.
5880 The keywords allowed by the @code{handle} command can be abbreviated.
5881 Their full names are:
5885 @value{GDBN} should not stop your program when this signal happens. It may
5886 still print a message telling you that the signal has come in.
5889 @value{GDBN} should stop your program when this signal happens. This implies
5890 the @code{print} keyword as well.
5893 @value{GDBN} should print a message when this signal happens.
5896 @value{GDBN} should not mention the occurrence of the signal at all. This
5897 implies the @code{nostop} keyword as well.
5901 @value{GDBN} should allow your program to see this signal; your program
5902 can handle the signal, or else it may terminate if the signal is fatal
5903 and not handled. @code{pass} and @code{noignore} are synonyms.
5907 @value{GDBN} should not allow your program to see this signal.
5908 @code{nopass} and @code{ignore} are synonyms.
5912 When a signal stops your program, the signal is not visible to the
5914 continue. Your program sees the signal then, if @code{pass} is in
5915 effect for the signal in question @emph{at that time}. In other words,
5916 after @value{GDBN} reports a signal, you can use the @code{handle}
5917 command with @code{pass} or @code{nopass} to control whether your
5918 program sees that signal when you continue.
5920 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5921 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5922 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5925 You can also use the @code{signal} command to prevent your program from
5926 seeing a signal, or cause it to see a signal it normally would not see,
5927 or to give it any signal at any time. For example, if your program stopped
5928 due to some sort of memory reference error, you might store correct
5929 values into the erroneous variables and continue, hoping to see more
5930 execution; but your program would probably terminate immediately as
5931 a result of the fatal signal once it saw the signal. To prevent this,
5932 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5935 @cindex stepping and signal handlers
5936 @anchor{stepping and signal handlers}
5938 @value{GDBN} optimizes for stepping the mainline code. If a signal
5939 that has @code{handle nostop} and @code{handle pass} set arrives while
5940 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5941 in progress, @value{GDBN} lets the signal handler run and then resumes
5942 stepping the mainline code once the signal handler returns. In other
5943 words, @value{GDBN} steps over the signal handler. This prevents
5944 signals that you've specified as not interesting (with @code{handle
5945 nostop}) from changing the focus of debugging unexpectedly. Note that
5946 the signal handler itself may still hit a breakpoint, stop for another
5947 signal that has @code{handle stop} in effect, or for any other event
5948 that normally results in stopping the stepping command sooner. Also
5949 note that @value{GDBN} still informs you that the program received a
5950 signal if @code{handle print} is set.
5952 @anchor{stepping into signal handlers}
5954 If you set @code{handle pass} for a signal, and your program sets up a
5955 handler for it, then issuing a stepping command, such as @code{step}
5956 or @code{stepi}, when your program is stopped due to the signal will
5957 step @emph{into} the signal handler (if the target supports that).
5959 Likewise, if you use the @code{queue-signal} command to queue a signal
5960 to be delivered to the current thread when execution of the thread
5961 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5962 stepping command will step into the signal handler.
5964 Here's an example, using @code{stepi} to step to the first instruction
5965 of @code{SIGUSR1}'s handler:
5968 (@value{GDBP}) handle SIGUSR1
5969 Signal Stop Print Pass to program Description
5970 SIGUSR1 Yes Yes Yes User defined signal 1
5974 Program received signal SIGUSR1, User defined signal 1.
5975 main () sigusr1.c:28
5978 sigusr1_handler () at sigusr1.c:9
5982 The same, but using @code{queue-signal} instead of waiting for the
5983 program to receive the signal first:
5988 (@value{GDBP}) queue-signal SIGUSR1
5990 sigusr1_handler () at sigusr1.c:9
5995 @cindex extra signal information
5996 @anchor{extra signal information}
5998 On some targets, @value{GDBN} can inspect extra signal information
5999 associated with the intercepted signal, before it is actually
6000 delivered to the program being debugged. This information is exported
6001 by the convenience variable @code{$_siginfo}, and consists of data
6002 that is passed by the kernel to the signal handler at the time of the
6003 receipt of a signal. The data type of the information itself is
6004 target dependent. You can see the data type using the @code{ptype
6005 $_siginfo} command. On Unix systems, it typically corresponds to the
6006 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6009 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6010 referenced address that raised a segmentation fault.
6014 (@value{GDBP}) continue
6015 Program received signal SIGSEGV, Segmentation fault.
6016 0x0000000000400766 in main ()
6018 (@value{GDBP}) ptype $_siginfo
6025 struct @{...@} _kill;
6026 struct @{...@} _timer;
6028 struct @{...@} _sigchld;
6029 struct @{...@} _sigfault;
6030 struct @{...@} _sigpoll;
6033 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6037 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6038 $1 = (void *) 0x7ffff7ff7000
6042 Depending on target support, @code{$_siginfo} may also be writable.
6044 @cindex Intel MPX boundary violations
6045 @cindex boundary violations, Intel MPX
6046 On some targets, a @code{SIGSEGV} can be caused by a boundary
6047 violation, i.e., accessing an address outside of the allowed range.
6048 In those cases @value{GDBN} may displays additional information,
6049 depending on how @value{GDBN} has been told to handle the signal.
6050 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6051 kind: "Upper" or "Lower", the memory address accessed and the
6052 bounds, while with @code{handle nostop SIGSEGV} no additional
6053 information is displayed.
6055 The usual output of a segfault is:
6057 Program received signal SIGSEGV, Segmentation fault
6058 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6059 68 value = *(p + len);
6062 While a bound violation is presented as:
6064 Program received signal SIGSEGV, Segmentation fault
6065 Upper bound violation while accessing address 0x7fffffffc3b3
6066 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6067 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6068 68 value = *(p + len);
6072 @section Stopping and Starting Multi-thread Programs
6074 @cindex stopped threads
6075 @cindex threads, stopped
6077 @cindex continuing threads
6078 @cindex threads, continuing
6080 @value{GDBN} supports debugging programs with multiple threads
6081 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6082 are two modes of controlling execution of your program within the
6083 debugger. In the default mode, referred to as @dfn{all-stop mode},
6084 when any thread in your program stops (for example, at a breakpoint
6085 or while being stepped), all other threads in the program are also stopped by
6086 @value{GDBN}. On some targets, @value{GDBN} also supports
6087 @dfn{non-stop mode}, in which other threads can continue to run freely while
6088 you examine the stopped thread in the debugger.
6091 * All-Stop Mode:: All threads stop when GDB takes control
6092 * Non-Stop Mode:: Other threads continue to execute
6093 * Background Execution:: Running your program asynchronously
6094 * Thread-Specific Breakpoints:: Controlling breakpoints
6095 * Interrupted System Calls:: GDB may interfere with system calls
6096 * Observer Mode:: GDB does not alter program behavior
6100 @subsection All-Stop Mode
6102 @cindex all-stop mode
6104 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6105 @emph{all} threads of execution stop, not just the current thread. This
6106 allows you to examine the overall state of the program, including
6107 switching between threads, without worrying that things may change
6110 Conversely, whenever you restart the program, @emph{all} threads start
6111 executing. @emph{This is true even when single-stepping} with commands
6112 like @code{step} or @code{next}.
6114 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6115 Since thread scheduling is up to your debugging target's operating
6116 system (not controlled by @value{GDBN}), other threads may
6117 execute more than one statement while the current thread completes a
6118 single step. Moreover, in general other threads stop in the middle of a
6119 statement, rather than at a clean statement boundary, when the program
6122 You might even find your program stopped in another thread after
6123 continuing or even single-stepping. This happens whenever some other
6124 thread runs into a breakpoint, a signal, or an exception before the
6125 first thread completes whatever you requested.
6127 @cindex automatic thread selection
6128 @cindex switching threads automatically
6129 @cindex threads, automatic switching
6130 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6131 signal, it automatically selects the thread where that breakpoint or
6132 signal happened. @value{GDBN} alerts you to the context switch with a
6133 message such as @samp{[Switching to Thread @var{n}]} to identify the
6136 On some OSes, you can modify @value{GDBN}'s default behavior by
6137 locking the OS scheduler to allow only a single thread to run.
6140 @item set scheduler-locking @var{mode}
6141 @cindex scheduler locking mode
6142 @cindex lock scheduler
6143 Set the scheduler locking mode. It applies to normal execution,
6144 record mode, and replay mode. If it is @code{off}, then there is no
6145 locking and any thread may run at any time. If @code{on}, then only
6146 the current thread may run when the inferior is resumed. The
6147 @code{step} mode optimizes for single-stepping; it prevents other
6148 threads from preempting the current thread while you are stepping, so
6149 that the focus of debugging does not change unexpectedly. Other
6150 threads never get a chance to run when you step, and they are
6151 completely free to run when you use commands like @samp{continue},
6152 @samp{until}, or @samp{finish}. However, unless another thread hits a
6153 breakpoint during its timeslice, @value{GDBN} does not change the
6154 current thread away from the thread that you are debugging. The
6155 @code{replay} mode behaves like @code{off} in record mode and like
6156 @code{on} in replay mode.
6158 @item show scheduler-locking
6159 Display the current scheduler locking mode.
6162 @cindex resume threads of multiple processes simultaneously
6163 By default, when you issue one of the execution commands such as
6164 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6165 threads of the current inferior to run. For example, if @value{GDBN}
6166 is attached to two inferiors, each with two threads, the
6167 @code{continue} command resumes only the two threads of the current
6168 inferior. This is useful, for example, when you debug a program that
6169 forks and you want to hold the parent stopped (so that, for instance,
6170 it doesn't run to exit), while you debug the child. In other
6171 situations, you may not be interested in inspecting the current state
6172 of any of the processes @value{GDBN} is attached to, and you may want
6173 to resume them all until some breakpoint is hit. In the latter case,
6174 you can instruct @value{GDBN} to allow all threads of all the
6175 inferiors to run with the @w{@code{set schedule-multiple}} command.
6178 @kindex set schedule-multiple
6179 @item set schedule-multiple
6180 Set the mode for allowing threads of multiple processes to be resumed
6181 when an execution command is issued. When @code{on}, all threads of
6182 all processes are allowed to run. When @code{off}, only the threads
6183 of the current process are resumed. The default is @code{off}. The
6184 @code{scheduler-locking} mode takes precedence when set to @code{on},
6185 or while you are stepping and set to @code{step}.
6187 @item show schedule-multiple
6188 Display the current mode for resuming the execution of threads of
6193 @subsection Non-Stop Mode
6195 @cindex non-stop mode
6197 @c This section is really only a place-holder, and needs to be expanded
6198 @c with more details.
6200 For some multi-threaded targets, @value{GDBN} supports an optional
6201 mode of operation in which you can examine stopped program threads in
6202 the debugger while other threads continue to execute freely. This
6203 minimizes intrusion when debugging live systems, such as programs
6204 where some threads have real-time constraints or must continue to
6205 respond to external events. This is referred to as @dfn{non-stop} mode.
6207 In non-stop mode, when a thread stops to report a debugging event,
6208 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6209 threads as well, in contrast to the all-stop mode behavior. Additionally,
6210 execution commands such as @code{continue} and @code{step} apply by default
6211 only to the current thread in non-stop mode, rather than all threads as
6212 in all-stop mode. This allows you to control threads explicitly in
6213 ways that are not possible in all-stop mode --- for example, stepping
6214 one thread while allowing others to run freely, stepping
6215 one thread while holding all others stopped, or stepping several threads
6216 independently and simultaneously.
6218 To enter non-stop mode, use this sequence of commands before you run
6219 or attach to your program:
6222 # If using the CLI, pagination breaks non-stop.
6225 # Finally, turn it on!
6229 You can use these commands to manipulate the non-stop mode setting:
6232 @kindex set non-stop
6233 @item set non-stop on
6234 Enable selection of non-stop mode.
6235 @item set non-stop off
6236 Disable selection of non-stop mode.
6237 @kindex show non-stop
6239 Show the current non-stop enablement setting.
6242 Note these commands only reflect whether non-stop mode is enabled,
6243 not whether the currently-executing program is being run in non-stop mode.
6244 In particular, the @code{set non-stop} preference is only consulted when
6245 @value{GDBN} starts or connects to the target program, and it is generally
6246 not possible to switch modes once debugging has started. Furthermore,
6247 since not all targets support non-stop mode, even when you have enabled
6248 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6251 In non-stop mode, all execution commands apply only to the current thread
6252 by default. That is, @code{continue} only continues one thread.
6253 To continue all threads, issue @code{continue -a} or @code{c -a}.
6255 You can use @value{GDBN}'s background execution commands
6256 (@pxref{Background Execution}) to run some threads in the background
6257 while you continue to examine or step others from @value{GDBN}.
6258 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6259 always executed asynchronously in non-stop mode.
6261 Suspending execution is done with the @code{interrupt} command when
6262 running in the background, or @kbd{Ctrl-c} during foreground execution.
6263 In all-stop mode, this stops the whole process;
6264 but in non-stop mode the interrupt applies only to the current thread.
6265 To stop the whole program, use @code{interrupt -a}.
6267 Other execution commands do not currently support the @code{-a} option.
6269 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6270 that thread current, as it does in all-stop mode. This is because the
6271 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6272 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6273 changed to a different thread just as you entered a command to operate on the
6274 previously current thread.
6276 @node Background Execution
6277 @subsection Background Execution
6279 @cindex foreground execution
6280 @cindex background execution
6281 @cindex asynchronous execution
6282 @cindex execution, foreground, background and asynchronous
6284 @value{GDBN}'s execution commands have two variants: the normal
6285 foreground (synchronous) behavior, and a background
6286 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6287 the program to report that some thread has stopped before prompting for
6288 another command. In background execution, @value{GDBN} immediately gives
6289 a command prompt so that you can issue other commands while your program runs.
6291 If the target doesn't support async mode, @value{GDBN} issues an error
6292 message if you attempt to use the background execution commands.
6294 To specify background execution, add a @code{&} to the command. For example,
6295 the background form of the @code{continue} command is @code{continue&}, or
6296 just @code{c&}. The execution commands that accept background execution
6302 @xref{Starting, , Starting your Program}.
6306 @xref{Attach, , Debugging an Already-running Process}.
6310 @xref{Continuing and Stepping, step}.
6314 @xref{Continuing and Stepping, stepi}.
6318 @xref{Continuing and Stepping, next}.
6322 @xref{Continuing and Stepping, nexti}.
6326 @xref{Continuing and Stepping, continue}.
6330 @xref{Continuing and Stepping, finish}.
6334 @xref{Continuing and Stepping, until}.
6338 Background execution is especially useful in conjunction with non-stop
6339 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6340 However, you can also use these commands in the normal all-stop mode with
6341 the restriction that you cannot issue another execution command until the
6342 previous one finishes. Examples of commands that are valid in all-stop
6343 mode while the program is running include @code{help} and @code{info break}.
6345 You can interrupt your program while it is running in the background by
6346 using the @code{interrupt} command.
6353 Suspend execution of the running program. In all-stop mode,
6354 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6355 only the current thread. To stop the whole program in non-stop mode,
6356 use @code{interrupt -a}.
6359 @node Thread-Specific Breakpoints
6360 @subsection Thread-Specific Breakpoints
6362 When your program has multiple threads (@pxref{Threads,, Debugging
6363 Programs with Multiple Threads}), you can choose whether to set
6364 breakpoints on all threads, or on a particular thread.
6367 @cindex breakpoints and threads
6368 @cindex thread breakpoints
6369 @kindex break @dots{} thread @var{thread-id}
6370 @item break @var{location} thread @var{thread-id}
6371 @itemx break @var{location} thread @var{thread-id} if @dots{}
6372 @var{location} specifies source lines; there are several ways of
6373 writing them (@pxref{Specify Location}), but the effect is always to
6374 specify some source line.
6376 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6377 to specify that you only want @value{GDBN} to stop the program when a
6378 particular thread reaches this breakpoint. The @var{thread-id} specifier
6379 is one of the thread identifiers assigned by @value{GDBN}, shown
6380 in the first column of the @samp{info threads} display.
6382 If you do not specify @samp{thread @var{thread-id}} when you set a
6383 breakpoint, the breakpoint applies to @emph{all} threads of your
6386 You can use the @code{thread} qualifier on conditional breakpoints as
6387 well; in this case, place @samp{thread @var{thread-id}} before or
6388 after the breakpoint condition, like this:
6391 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6396 Thread-specific breakpoints are automatically deleted when
6397 @value{GDBN} detects the corresponding thread is no longer in the
6398 thread list. For example:
6402 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6405 There are several ways for a thread to disappear, such as a regular
6406 thread exit, but also when you detach from the process with the
6407 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6408 Process}), or if @value{GDBN} loses the remote connection
6409 (@pxref{Remote Debugging}), etc. Note that with some targets,
6410 @value{GDBN} is only able to detect a thread has exited when the user
6411 explictly asks for the thread list with the @code{info threads}
6414 @node Interrupted System Calls
6415 @subsection Interrupted System Calls
6417 @cindex thread breakpoints and system calls
6418 @cindex system calls and thread breakpoints
6419 @cindex premature return from system calls
6420 There is an unfortunate side effect when using @value{GDBN} to debug
6421 multi-threaded programs. If one thread stops for a
6422 breakpoint, or for some other reason, and another thread is blocked in a
6423 system call, then the system call may return prematurely. This is a
6424 consequence of the interaction between multiple threads and the signals
6425 that @value{GDBN} uses to implement breakpoints and other events that
6428 To handle this problem, your program should check the return value of
6429 each system call and react appropriately. This is good programming
6432 For example, do not write code like this:
6438 The call to @code{sleep} will return early if a different thread stops
6439 at a breakpoint or for some other reason.
6441 Instead, write this:
6446 unslept = sleep (unslept);
6449 A system call is allowed to return early, so the system is still
6450 conforming to its specification. But @value{GDBN} does cause your
6451 multi-threaded program to behave differently than it would without
6454 Also, @value{GDBN} uses internal breakpoints in the thread library to
6455 monitor certain events such as thread creation and thread destruction.
6456 When such an event happens, a system call in another thread may return
6457 prematurely, even though your program does not appear to stop.
6460 @subsection Observer Mode
6462 If you want to build on non-stop mode and observe program behavior
6463 without any chance of disruption by @value{GDBN}, you can set
6464 variables to disable all of the debugger's attempts to modify state,
6465 whether by writing memory, inserting breakpoints, etc. These operate
6466 at a low level, intercepting operations from all commands.
6468 When all of these are set to @code{off}, then @value{GDBN} is said to
6469 be @dfn{observer mode}. As a convenience, the variable
6470 @code{observer} can be set to disable these, plus enable non-stop
6473 Note that @value{GDBN} will not prevent you from making nonsensical
6474 combinations of these settings. For instance, if you have enabled
6475 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6476 then breakpoints that work by writing trap instructions into the code
6477 stream will still not be able to be placed.
6482 @item set observer on
6483 @itemx set observer off
6484 When set to @code{on}, this disables all the permission variables
6485 below (except for @code{insert-fast-tracepoints}), plus enables
6486 non-stop debugging. Setting this to @code{off} switches back to
6487 normal debugging, though remaining in non-stop mode.
6490 Show whether observer mode is on or off.
6492 @kindex may-write-registers
6493 @item set may-write-registers on
6494 @itemx set may-write-registers off
6495 This controls whether @value{GDBN} will attempt to alter the values of
6496 registers, such as with assignment expressions in @code{print}, or the
6497 @code{jump} command. It defaults to @code{on}.
6499 @item show may-write-registers
6500 Show the current permission to write registers.
6502 @kindex may-write-memory
6503 @item set may-write-memory on
6504 @itemx set may-write-memory off
6505 This controls whether @value{GDBN} will attempt to alter the contents
6506 of memory, such as with assignment expressions in @code{print}. It
6507 defaults to @code{on}.
6509 @item show may-write-memory
6510 Show the current permission to write memory.
6512 @kindex may-insert-breakpoints
6513 @item set may-insert-breakpoints on
6514 @itemx set may-insert-breakpoints off
6515 This controls whether @value{GDBN} will attempt to insert breakpoints.
6516 This affects all breakpoints, including internal breakpoints defined
6517 by @value{GDBN}. It defaults to @code{on}.
6519 @item show may-insert-breakpoints
6520 Show the current permission to insert breakpoints.
6522 @kindex may-insert-tracepoints
6523 @item set may-insert-tracepoints on
6524 @itemx set may-insert-tracepoints off
6525 This controls whether @value{GDBN} will attempt to insert (regular)
6526 tracepoints at the beginning of a tracing experiment. It affects only
6527 non-fast tracepoints, fast tracepoints being under the control of
6528 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6530 @item show may-insert-tracepoints
6531 Show the current permission to insert tracepoints.
6533 @kindex may-insert-fast-tracepoints
6534 @item set may-insert-fast-tracepoints on
6535 @itemx set may-insert-fast-tracepoints off
6536 This controls whether @value{GDBN} will attempt to insert fast
6537 tracepoints at the beginning of a tracing experiment. It affects only
6538 fast tracepoints, regular (non-fast) tracepoints being under the
6539 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6541 @item show may-insert-fast-tracepoints
6542 Show the current permission to insert fast tracepoints.
6544 @kindex may-interrupt
6545 @item set may-interrupt on
6546 @itemx set may-interrupt off
6547 This controls whether @value{GDBN} will attempt to interrupt or stop
6548 program execution. When this variable is @code{off}, the
6549 @code{interrupt} command will have no effect, nor will
6550 @kbd{Ctrl-c}. It defaults to @code{on}.
6552 @item show may-interrupt
6553 Show the current permission to interrupt or stop the program.
6557 @node Reverse Execution
6558 @chapter Running programs backward
6559 @cindex reverse execution
6560 @cindex running programs backward
6562 When you are debugging a program, it is not unusual to realize that
6563 you have gone too far, and some event of interest has already happened.
6564 If the target environment supports it, @value{GDBN} can allow you to
6565 ``rewind'' the program by running it backward.
6567 A target environment that supports reverse execution should be able
6568 to ``undo'' the changes in machine state that have taken place as the
6569 program was executing normally. Variables, registers etc.@: should
6570 revert to their previous values. Obviously this requires a great
6571 deal of sophistication on the part of the target environment; not
6572 all target environments can support reverse execution.
6574 When a program is executed in reverse, the instructions that
6575 have most recently been executed are ``un-executed'', in reverse
6576 order. The program counter runs backward, following the previous
6577 thread of execution in reverse. As each instruction is ``un-executed'',
6578 the values of memory and/or registers that were changed by that
6579 instruction are reverted to their previous states. After executing
6580 a piece of source code in reverse, all side effects of that code
6581 should be ``undone'', and all variables should be returned to their
6582 prior values@footnote{
6583 Note that some side effects are easier to undo than others. For instance,
6584 memory and registers are relatively easy, but device I/O is hard. Some
6585 targets may be able undo things like device I/O, and some may not.
6587 The contract between @value{GDBN} and the reverse executing target
6588 requires only that the target do something reasonable when
6589 @value{GDBN} tells it to execute backwards, and then report the
6590 results back to @value{GDBN}. Whatever the target reports back to
6591 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6592 assumes that the memory and registers that the target reports are in a
6593 consistant state, but @value{GDBN} accepts whatever it is given.
6596 If you are debugging in a target environment that supports
6597 reverse execution, @value{GDBN} provides the following commands.
6600 @kindex reverse-continue
6601 @kindex rc @r{(@code{reverse-continue})}
6602 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6603 @itemx rc @r{[}@var{ignore-count}@r{]}
6604 Beginning at the point where your program last stopped, start executing
6605 in reverse. Reverse execution will stop for breakpoints and synchronous
6606 exceptions (signals), just like normal execution. Behavior of
6607 asynchronous signals depends on the target environment.
6609 @kindex reverse-step
6610 @kindex rs @r{(@code{step})}
6611 @item reverse-step @r{[}@var{count}@r{]}
6612 Run the program backward until control reaches the start of a
6613 different source line; then stop it, and return control to @value{GDBN}.
6615 Like the @code{step} command, @code{reverse-step} will only stop
6616 at the beginning of a source line. It ``un-executes'' the previously
6617 executed source line. If the previous source line included calls to
6618 debuggable functions, @code{reverse-step} will step (backward) into
6619 the called function, stopping at the beginning of the @emph{last}
6620 statement in the called function (typically a return statement).
6622 Also, as with the @code{step} command, if non-debuggable functions are
6623 called, @code{reverse-step} will run thru them backward without stopping.
6625 @kindex reverse-stepi
6626 @kindex rsi @r{(@code{reverse-stepi})}
6627 @item reverse-stepi @r{[}@var{count}@r{]}
6628 Reverse-execute one machine instruction. Note that the instruction
6629 to be reverse-executed is @emph{not} the one pointed to by the program
6630 counter, but the instruction executed prior to that one. For instance,
6631 if the last instruction was a jump, @code{reverse-stepi} will take you
6632 back from the destination of the jump to the jump instruction itself.
6634 @kindex reverse-next
6635 @kindex rn @r{(@code{reverse-next})}
6636 @item reverse-next @r{[}@var{count}@r{]}
6637 Run backward to the beginning of the previous line executed in
6638 the current (innermost) stack frame. If the line contains function
6639 calls, they will be ``un-executed'' without stopping. Starting from
6640 the first line of a function, @code{reverse-next} will take you back
6641 to the caller of that function, @emph{before} the function was called,
6642 just as the normal @code{next} command would take you from the last
6643 line of a function back to its return to its caller
6644 @footnote{Unless the code is too heavily optimized.}.
6646 @kindex reverse-nexti
6647 @kindex rni @r{(@code{reverse-nexti})}
6648 @item reverse-nexti @r{[}@var{count}@r{]}
6649 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6650 in reverse, except that called functions are ``un-executed'' atomically.
6651 That is, if the previously executed instruction was a return from
6652 another function, @code{reverse-nexti} will continue to execute
6653 in reverse until the call to that function (from the current stack
6656 @kindex reverse-finish
6657 @item reverse-finish
6658 Just as the @code{finish} command takes you to the point where the
6659 current function returns, @code{reverse-finish} takes you to the point
6660 where it was called. Instead of ending up at the end of the current
6661 function invocation, you end up at the beginning.
6663 @kindex set exec-direction
6664 @item set exec-direction
6665 Set the direction of target execution.
6666 @item set exec-direction reverse
6667 @cindex execute forward or backward in time
6668 @value{GDBN} will perform all execution commands in reverse, until the
6669 exec-direction mode is changed to ``forward''. Affected commands include
6670 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6671 command cannot be used in reverse mode.
6672 @item set exec-direction forward
6673 @value{GDBN} will perform all execution commands in the normal fashion.
6674 This is the default.
6678 @node Process Record and Replay
6679 @chapter Recording Inferior's Execution and Replaying It
6680 @cindex process record and replay
6681 @cindex recording inferior's execution and replaying it
6683 On some platforms, @value{GDBN} provides a special @dfn{process record
6684 and replay} target that can record a log of the process execution, and
6685 replay it later with both forward and reverse execution commands.
6688 When this target is in use, if the execution log includes the record
6689 for the next instruction, @value{GDBN} will debug in @dfn{replay
6690 mode}. In the replay mode, the inferior does not really execute code
6691 instructions. Instead, all the events that normally happen during
6692 code execution are taken from the execution log. While code is not
6693 really executed in replay mode, the values of registers (including the
6694 program counter register) and the memory of the inferior are still
6695 changed as they normally would. Their contents are taken from the
6699 If the record for the next instruction is not in the execution log,
6700 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6701 inferior executes normally, and @value{GDBN} records the execution log
6704 The process record and replay target supports reverse execution
6705 (@pxref{Reverse Execution}), even if the platform on which the
6706 inferior runs does not. However, the reverse execution is limited in
6707 this case by the range of the instructions recorded in the execution
6708 log. In other words, reverse execution on platforms that don't
6709 support it directly can only be done in the replay mode.
6711 When debugging in the reverse direction, @value{GDBN} will work in
6712 replay mode as long as the execution log includes the record for the
6713 previous instruction; otherwise, it will work in record mode, if the
6714 platform supports reverse execution, or stop if not.
6716 For architecture environments that support process record and replay,
6717 @value{GDBN} provides the following commands:
6720 @kindex target record
6721 @kindex target record-full
6722 @kindex target record-btrace
6725 @kindex record btrace
6726 @kindex record btrace bts
6727 @kindex record btrace pt
6733 @kindex rec btrace bts
6734 @kindex rec btrace pt
6737 @item record @var{method}
6738 This command starts the process record and replay target. The
6739 recording method can be specified as parameter. Without a parameter
6740 the command uses the @code{full} recording method. The following
6741 recording methods are available:
6745 Full record/replay recording using @value{GDBN}'s software record and
6746 replay implementation. This method allows replaying and reverse
6749 @item btrace @var{format}
6750 Hardware-supported instruction recording. This method does not record
6751 data. Further, the data is collected in a ring buffer so old data will
6752 be overwritten when the buffer is full. It allows limited reverse
6753 execution. Variables and registers are not available during reverse
6754 execution. In remote debugging, recording continues on disconnect.
6755 Recorded data can be inspected after reconnecting. The recording may
6756 be stopped using @code{record stop}.
6758 The recording format can be specified as parameter. Without a parameter
6759 the command chooses the recording format. The following recording
6760 formats are available:
6764 @cindex branch trace store
6765 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6766 this format, the processor stores a from/to record for each executed
6767 branch in the btrace ring buffer.
6770 @cindex Intel Processor Trace
6771 Use the @dfn{Intel Processor Trace} recording format. In this
6772 format, the processor stores the execution trace in a compressed form
6773 that is afterwards decoded by @value{GDBN}.
6775 The trace can be recorded with very low overhead. The compressed
6776 trace format also allows small trace buffers to already contain a big
6777 number of instructions compared to @acronym{BTS}.
6779 Decoding the recorded execution trace, on the other hand, is more
6780 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6781 increased number of instructions to process. You should increase the
6782 buffer-size with care.
6785 Not all recording formats may be available on all processors.
6788 The process record and replay target can only debug a process that is
6789 already running. Therefore, you need first to start the process with
6790 the @kbd{run} or @kbd{start} commands, and then start the recording
6791 with the @kbd{record @var{method}} command.
6793 @cindex displaced stepping, and process record and replay
6794 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6795 will be automatically disabled when process record and replay target
6796 is started. That's because the process record and replay target
6797 doesn't support displaced stepping.
6799 @cindex non-stop mode, and process record and replay
6800 @cindex asynchronous execution, and process record and replay
6801 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6802 the asynchronous execution mode (@pxref{Background Execution}), not
6803 all recording methods are available. The @code{full} recording method
6804 does not support these two modes.
6809 Stop the process record and replay target. When process record and
6810 replay target stops, the entire execution log will be deleted and the
6811 inferior will either be terminated, or will remain in its final state.
6813 When you stop the process record and replay target in record mode (at
6814 the end of the execution log), the inferior will be stopped at the
6815 next instruction that would have been recorded. In other words, if
6816 you record for a while and then stop recording, the inferior process
6817 will be left in the same state as if the recording never happened.
6819 On the other hand, if the process record and replay target is stopped
6820 while in replay mode (that is, not at the end of the execution log,
6821 but at some earlier point), the inferior process will become ``live''
6822 at that earlier state, and it will then be possible to continue the
6823 usual ``live'' debugging of the process from that state.
6825 When the inferior process exits, or @value{GDBN} detaches from it,
6826 process record and replay target will automatically stop itself.
6830 Go to a specific location in the execution log. There are several
6831 ways to specify the location to go to:
6834 @item record goto begin
6835 @itemx record goto start
6836 Go to the beginning of the execution log.
6838 @item record goto end
6839 Go to the end of the execution log.
6841 @item record goto @var{n}
6842 Go to instruction number @var{n} in the execution log.
6846 @item record save @var{filename}
6847 Save the execution log to a file @file{@var{filename}}.
6848 Default filename is @file{gdb_record.@var{process_id}}, where
6849 @var{process_id} is the process ID of the inferior.
6851 This command may not be available for all recording methods.
6853 @kindex record restore
6854 @item record restore @var{filename}
6855 Restore the execution log from a file @file{@var{filename}}.
6856 File must have been created with @code{record save}.
6858 @kindex set record full
6859 @item set record full insn-number-max @var{limit}
6860 @itemx set record full insn-number-max unlimited
6861 Set the limit of instructions to be recorded for the @code{full}
6862 recording method. Default value is 200000.
6864 If @var{limit} is a positive number, then @value{GDBN} will start
6865 deleting instructions from the log once the number of the record
6866 instructions becomes greater than @var{limit}. For every new recorded
6867 instruction, @value{GDBN} will delete the earliest recorded
6868 instruction to keep the number of recorded instructions at the limit.
6869 (Since deleting recorded instructions loses information, @value{GDBN}
6870 lets you control what happens when the limit is reached, by means of
6871 the @code{stop-at-limit} option, described below.)
6873 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6874 delete recorded instructions from the execution log. The number of
6875 recorded instructions is limited only by the available memory.
6877 @kindex show record full
6878 @item show record full insn-number-max
6879 Show the limit of instructions to be recorded with the @code{full}
6882 @item set record full stop-at-limit
6883 Control the behavior of the @code{full} recording method when the
6884 number of recorded instructions reaches the limit. If ON (the
6885 default), @value{GDBN} will stop when the limit is reached for the
6886 first time and ask you whether you want to stop the inferior or
6887 continue running it and recording the execution log. If you decide
6888 to continue recording, each new recorded instruction will cause the
6889 oldest one to be deleted.
6891 If this option is OFF, @value{GDBN} will automatically delete the
6892 oldest record to make room for each new one, without asking.
6894 @item show record full stop-at-limit
6895 Show the current setting of @code{stop-at-limit}.
6897 @item set record full memory-query
6898 Control the behavior when @value{GDBN} is unable to record memory
6899 changes caused by an instruction for the @code{full} recording method.
6900 If ON, @value{GDBN} will query whether to stop the inferior in that
6903 If this option is OFF (the default), @value{GDBN} will automatically
6904 ignore the effect of such instructions on memory. Later, when
6905 @value{GDBN} replays this execution log, it will mark the log of this
6906 instruction as not accessible, and it will not affect the replay
6909 @item show record full memory-query
6910 Show the current setting of @code{memory-query}.
6912 @kindex set record btrace
6913 The @code{btrace} record target does not trace data. As a
6914 convenience, when replaying, @value{GDBN} reads read-only memory off
6915 the live program directly, assuming that the addresses of the
6916 read-only areas don't change. This for example makes it possible to
6917 disassemble code while replaying, but not to print variables.
6918 In some cases, being able to inspect variables might be useful.
6919 You can use the following command for that:
6921 @item set record btrace replay-memory-access
6922 Control the behavior of the @code{btrace} recording method when
6923 accessing memory during replay. If @code{read-only} (the default),
6924 @value{GDBN} will only allow accesses to read-only memory.
6925 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6926 and to read-write memory. Beware that the accessed memory corresponds
6927 to the live target and not necessarily to the current replay
6930 @kindex show record btrace
6931 @item show record btrace replay-memory-access
6932 Show the current setting of @code{replay-memory-access}.
6934 @kindex set record btrace bts
6935 @item set record btrace bts buffer-size @var{size}
6936 @itemx set record btrace bts buffer-size unlimited
6937 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6938 format. Default is 64KB.
6940 If @var{size} is a positive number, then @value{GDBN} will try to
6941 allocate a buffer of at least @var{size} bytes for each new thread
6942 that uses the btrace recording method and the @acronym{BTS} format.
6943 The actually obtained buffer size may differ from the requested
6944 @var{size}. Use the @code{info record} command to see the actual
6945 buffer size for each thread that uses the btrace recording method and
6946 the @acronym{BTS} format.
6948 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6949 allocate a buffer of 4MB.
6951 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6952 also need longer to process the branch trace data before it can be used.
6954 @item show record btrace bts buffer-size @var{size}
6955 Show the current setting of the requested ring buffer size for branch
6956 tracing in @acronym{BTS} format.
6958 @kindex set record btrace pt
6959 @item set record btrace pt buffer-size @var{size}
6960 @itemx set record btrace pt buffer-size unlimited
6961 Set the requested ring buffer size for branch tracing in Intel
6962 Processor Trace format. Default is 16KB.
6964 If @var{size} is a positive number, then @value{GDBN} will try to
6965 allocate a buffer of at least @var{size} bytes for each new thread
6966 that uses the btrace recording method and the Intel Processor Trace
6967 format. The actually obtained buffer size may differ from the
6968 requested @var{size}. Use the @code{info record} command to see the
6969 actual buffer size for each thread.
6971 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6972 allocate a buffer of 4MB.
6974 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6975 also need longer to process the branch trace data before it can be used.
6977 @item show record btrace pt buffer-size @var{size}
6978 Show the current setting of the requested ring buffer size for branch
6979 tracing in Intel Processor Trace format.
6983 Show various statistics about the recording depending on the recording
6988 For the @code{full} recording method, it shows the state of process
6989 record and its in-memory execution log buffer, including:
6993 Whether in record mode or replay mode.
6995 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6997 Highest recorded instruction number.
6999 Current instruction about to be replayed (if in replay mode).
7001 Number of instructions contained in the execution log.
7003 Maximum number of instructions that may be contained in the execution log.
7007 For the @code{btrace} recording method, it shows:
7013 Number of instructions that have been recorded.
7015 Number of blocks of sequential control-flow formed by the recorded
7018 Whether in record mode or replay mode.
7021 For the @code{bts} recording format, it also shows:
7024 Size of the perf ring buffer.
7027 For the @code{pt} recording format, it also shows:
7030 Size of the perf ring buffer.
7034 @kindex record delete
7037 When record target runs in replay mode (``in the past''), delete the
7038 subsequent execution log and begin to record a new execution log starting
7039 from the current address. This means you will abandon the previously
7040 recorded ``future'' and begin recording a new ``future''.
7042 @kindex record instruction-history
7043 @kindex rec instruction-history
7044 @item record instruction-history
7045 Disassembles instructions from the recorded execution log. By
7046 default, ten instructions are disassembled. This can be changed using
7047 the @code{set record instruction-history-size} command. Instructions
7048 are printed in execution order.
7050 It can also print mixed source+disassembly if you specify the the
7051 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7052 as well as in symbolic form by specifying the @code{/r} modifier.
7054 The current position marker is printed for the instruction at the
7055 current program counter value. This instruction can appear multiple
7056 times in the trace and the current position marker will be printed
7057 every time. To omit the current position marker, specify the
7060 To better align the printed instructions when the trace contains
7061 instructions from more than one function, the function name may be
7062 omitted by specifying the @code{/f} modifier.
7064 Speculatively executed instructions are prefixed with @samp{?}. This
7065 feature is not available for all recording formats.
7067 There are several ways to specify what part of the execution log to
7071 @item record instruction-history @var{insn}
7072 Disassembles ten instructions starting from instruction number
7075 @item record instruction-history @var{insn}, +/-@var{n}
7076 Disassembles @var{n} instructions around instruction number
7077 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7078 @var{n} instructions after instruction number @var{insn}. If
7079 @var{n} is preceded with @code{-}, disassembles @var{n}
7080 instructions before instruction number @var{insn}.
7082 @item record instruction-history
7083 Disassembles ten more instructions after the last disassembly.
7085 @item record instruction-history -
7086 Disassembles ten more instructions before the last disassembly.
7088 @item record instruction-history @var{begin}, @var{end}
7089 Disassembles instructions beginning with instruction number
7090 @var{begin} until instruction number @var{end}. The instruction
7091 number @var{end} is included.
7094 This command may not be available for all recording methods.
7097 @item set record instruction-history-size @var{size}
7098 @itemx set record instruction-history-size unlimited
7099 Define how many instructions to disassemble in the @code{record
7100 instruction-history} command. The default value is 10.
7101 A @var{size} of @code{unlimited} means unlimited instructions.
7104 @item show record instruction-history-size
7105 Show how many instructions to disassemble in the @code{record
7106 instruction-history} command.
7108 @kindex record function-call-history
7109 @kindex rec function-call-history
7110 @item record function-call-history
7111 Prints the execution history at function granularity. It prints one
7112 line for each sequence of instructions that belong to the same
7113 function giving the name of that function, the source lines
7114 for this instruction sequence (if the @code{/l} modifier is
7115 specified), and the instructions numbers that form the sequence (if
7116 the @code{/i} modifier is specified). The function names are indented
7117 to reflect the call stack depth if the @code{/c} modifier is
7118 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7122 (@value{GDBP}) @b{list 1, 10}
7133 (@value{GDBP}) @b{record function-call-history /ilc}
7134 1 bar inst 1,4 at foo.c:6,8
7135 2 foo inst 5,10 at foo.c:2,3
7136 3 bar inst 11,13 at foo.c:9,10
7139 By default, ten lines are printed. This can be changed using the
7140 @code{set record function-call-history-size} command. Functions are
7141 printed in execution order. There are several ways to specify what
7145 @item record function-call-history @var{func}
7146 Prints ten functions starting from function number @var{func}.
7148 @item record function-call-history @var{func}, +/-@var{n}
7149 Prints @var{n} functions around function number @var{func}. If
7150 @var{n} is preceded with @code{+}, prints @var{n} functions after
7151 function number @var{func}. If @var{n} is preceded with @code{-},
7152 prints @var{n} functions before function number @var{func}.
7154 @item record function-call-history
7155 Prints ten more functions after the last ten-line print.
7157 @item record function-call-history -
7158 Prints ten more functions before the last ten-line print.
7160 @item record function-call-history @var{begin}, @var{end}
7161 Prints functions beginning with function number @var{begin} until
7162 function number @var{end}. The function number @var{end} is included.
7165 This command may not be available for all recording methods.
7167 @item set record function-call-history-size @var{size}
7168 @itemx set record function-call-history-size unlimited
7169 Define how many lines to print in the
7170 @code{record function-call-history} command. The default value is 10.
7171 A size of @code{unlimited} means unlimited lines.
7173 @item show record function-call-history-size
7174 Show how many lines to print in the
7175 @code{record function-call-history} command.
7180 @chapter Examining the Stack
7182 When your program has stopped, the first thing you need to know is where it
7183 stopped and how it got there.
7186 Each time your program performs a function call, information about the call
7188 That information includes the location of the call in your program,
7189 the arguments of the call,
7190 and the local variables of the function being called.
7191 The information is saved in a block of data called a @dfn{stack frame}.
7192 The stack frames are allocated in a region of memory called the @dfn{call
7195 When your program stops, the @value{GDBN} commands for examining the
7196 stack allow you to see all of this information.
7198 @cindex selected frame
7199 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7200 @value{GDBN} commands refer implicitly to the selected frame. In
7201 particular, whenever you ask @value{GDBN} for the value of a variable in
7202 your program, the value is found in the selected frame. There are
7203 special @value{GDBN} commands to select whichever frame you are
7204 interested in. @xref{Selection, ,Selecting a Frame}.
7206 When your program stops, @value{GDBN} automatically selects the
7207 currently executing frame and describes it briefly, similar to the
7208 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7211 * Frames:: Stack frames
7212 * Backtrace:: Backtraces
7213 * Selection:: Selecting a frame
7214 * Frame Info:: Information on a frame
7215 * Frame Filter Management:: Managing frame filters
7220 @section Stack Frames
7222 @cindex frame, definition
7224 The call stack is divided up into contiguous pieces called @dfn{stack
7225 frames}, or @dfn{frames} for short; each frame is the data associated
7226 with one call to one function. The frame contains the arguments given
7227 to the function, the function's local variables, and the address at
7228 which the function is executing.
7230 @cindex initial frame
7231 @cindex outermost frame
7232 @cindex innermost frame
7233 When your program is started, the stack has only one frame, that of the
7234 function @code{main}. This is called the @dfn{initial} frame or the
7235 @dfn{outermost} frame. Each time a function is called, a new frame is
7236 made. Each time a function returns, the frame for that function invocation
7237 is eliminated. If a function is recursive, there can be many frames for
7238 the same function. The frame for the function in which execution is
7239 actually occurring is called the @dfn{innermost} frame. This is the most
7240 recently created of all the stack frames that still exist.
7242 @cindex frame pointer
7243 Inside your program, stack frames are identified by their addresses. A
7244 stack frame consists of many bytes, each of which has its own address; each
7245 kind of computer has a convention for choosing one byte whose
7246 address serves as the address of the frame. Usually this address is kept
7247 in a register called the @dfn{frame pointer register}
7248 (@pxref{Registers, $fp}) while execution is going on in that frame.
7250 @cindex frame number
7251 @value{GDBN} assigns numbers to all existing stack frames, starting with
7252 zero for the innermost frame, one for the frame that called it,
7253 and so on upward. These numbers do not really exist in your program;
7254 they are assigned by @value{GDBN} to give you a way of designating stack
7255 frames in @value{GDBN} commands.
7257 @c The -fomit-frame-pointer below perennially causes hbox overflow
7258 @c underflow problems.
7259 @cindex frameless execution
7260 Some compilers provide a way to compile functions so that they operate
7261 without stack frames. (For example, the @value{NGCC} option
7263 @samp{-fomit-frame-pointer}
7265 generates functions without a frame.)
7266 This is occasionally done with heavily used library functions to save
7267 the frame setup time. @value{GDBN} has limited facilities for dealing
7268 with these function invocations. If the innermost function invocation
7269 has no stack frame, @value{GDBN} nevertheless regards it as though
7270 it had a separate frame, which is numbered zero as usual, allowing
7271 correct tracing of the function call chain. However, @value{GDBN} has
7272 no provision for frameless functions elsewhere in the stack.
7278 @cindex call stack traces
7279 A backtrace is a summary of how your program got where it is. It shows one
7280 line per frame, for many frames, starting with the currently executing
7281 frame (frame zero), followed by its caller (frame one), and on up the
7284 @anchor{backtrace-command}
7287 @kindex bt @r{(@code{backtrace})}
7290 Print a backtrace of the entire stack: one line per frame for all
7291 frames in the stack.
7293 You can stop the backtrace at any time by typing the system interrupt
7294 character, normally @kbd{Ctrl-c}.
7296 @item backtrace @var{n}
7298 Similar, but print only the innermost @var{n} frames.
7300 @item backtrace -@var{n}
7302 Similar, but print only the outermost @var{n} frames.
7304 @item backtrace full
7306 @itemx bt full @var{n}
7307 @itemx bt full -@var{n}
7308 Print the values of the local variables also. As described above,
7309 @var{n} specifies the number of frames to print.
7311 @item backtrace no-filters
7312 @itemx bt no-filters
7313 @itemx bt no-filters @var{n}
7314 @itemx bt no-filters -@var{n}
7315 @itemx bt no-filters full
7316 @itemx bt no-filters full @var{n}
7317 @itemx bt no-filters full -@var{n}
7318 Do not run Python frame filters on this backtrace. @xref{Frame
7319 Filter API}, for more information. Additionally use @ref{disable
7320 frame-filter all} to turn off all frame filters. This is only
7321 relevant when @value{GDBN} has been configured with @code{Python}
7327 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7328 are additional aliases for @code{backtrace}.
7330 @cindex multiple threads, backtrace
7331 In a multi-threaded program, @value{GDBN} by default shows the
7332 backtrace only for the current thread. To display the backtrace for
7333 several or all of the threads, use the command @code{thread apply}
7334 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7335 apply all backtrace}, @value{GDBN} will display the backtrace for all
7336 the threads; this is handy when you debug a core dump of a
7337 multi-threaded program.
7339 Each line in the backtrace shows the frame number and the function name.
7340 The program counter value is also shown---unless you use @code{set
7341 print address off}. The backtrace also shows the source file name and
7342 line number, as well as the arguments to the function. The program
7343 counter value is omitted if it is at the beginning of the code for that
7346 Here is an example of a backtrace. It was made with the command
7347 @samp{bt 3}, so it shows the innermost three frames.
7351 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7353 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7354 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7356 (More stack frames follow...)
7361 The display for frame zero does not begin with a program counter
7362 value, indicating that your program has stopped at the beginning of the
7363 code for line @code{993} of @code{builtin.c}.
7366 The value of parameter @code{data} in frame 1 has been replaced by
7367 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7368 only if it is a scalar (integer, pointer, enumeration, etc). See command
7369 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7370 on how to configure the way function parameter values are printed.
7372 @cindex optimized out, in backtrace
7373 @cindex function call arguments, optimized out
7374 If your program was compiled with optimizations, some compilers will
7375 optimize away arguments passed to functions if those arguments are
7376 never used after the call. Such optimizations generate code that
7377 passes arguments through registers, but doesn't store those arguments
7378 in the stack frame. @value{GDBN} has no way of displaying such
7379 arguments in stack frames other than the innermost one. Here's what
7380 such a backtrace might look like:
7384 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7386 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7387 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7389 (More stack frames follow...)
7394 The values of arguments that were not saved in their stack frames are
7395 shown as @samp{<optimized out>}.
7397 If you need to display the values of such optimized-out arguments,
7398 either deduce that from other variables whose values depend on the one
7399 you are interested in, or recompile without optimizations.
7401 @cindex backtrace beyond @code{main} function
7402 @cindex program entry point
7403 @cindex startup code, and backtrace
7404 Most programs have a standard user entry point---a place where system
7405 libraries and startup code transition into user code. For C this is
7406 @code{main}@footnote{
7407 Note that embedded programs (the so-called ``free-standing''
7408 environment) are not required to have a @code{main} function as the
7409 entry point. They could even have multiple entry points.}.
7410 When @value{GDBN} finds the entry function in a backtrace
7411 it will terminate the backtrace, to avoid tracing into highly
7412 system-specific (and generally uninteresting) code.
7414 If you need to examine the startup code, or limit the number of levels
7415 in a backtrace, you can change this behavior:
7418 @item set backtrace past-main
7419 @itemx set backtrace past-main on
7420 @kindex set backtrace
7421 Backtraces will continue past the user entry point.
7423 @item set backtrace past-main off
7424 Backtraces will stop when they encounter the user entry point. This is the
7427 @item show backtrace past-main
7428 @kindex show backtrace
7429 Display the current user entry point backtrace policy.
7431 @item set backtrace past-entry
7432 @itemx set backtrace past-entry on
7433 Backtraces will continue past the internal entry point of an application.
7434 This entry point is encoded by the linker when the application is built,
7435 and is likely before the user entry point @code{main} (or equivalent) is called.
7437 @item set backtrace past-entry off
7438 Backtraces will stop when they encounter the internal entry point of an
7439 application. This is the default.
7441 @item show backtrace past-entry
7442 Display the current internal entry point backtrace policy.
7444 @item set backtrace limit @var{n}
7445 @itemx set backtrace limit 0
7446 @itemx set backtrace limit unlimited
7447 @cindex backtrace limit
7448 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7449 or zero means unlimited levels.
7451 @item show backtrace limit
7452 Display the current limit on backtrace levels.
7455 You can control how file names are displayed.
7458 @item set filename-display
7459 @itemx set filename-display relative
7460 @cindex filename-display
7461 Display file names relative to the compilation directory. This is the default.
7463 @item set filename-display basename
7464 Display only basename of a filename.
7466 @item set filename-display absolute
7467 Display an absolute filename.
7469 @item show filename-display
7470 Show the current way to display filenames.
7474 @section Selecting a Frame
7476 Most commands for examining the stack and other data in your program work on
7477 whichever stack frame is selected at the moment. Here are the commands for
7478 selecting a stack frame; all of them finish by printing a brief description
7479 of the stack frame just selected.
7482 @kindex frame@r{, selecting}
7483 @kindex f @r{(@code{frame})}
7486 Select frame number @var{n}. Recall that frame zero is the innermost
7487 (currently executing) frame, frame one is the frame that called the
7488 innermost one, and so on. The highest-numbered frame is the one for
7491 @item frame @var{stack-addr} [ @var{pc-addr} ]
7492 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7493 Select the frame at address @var{stack-addr}. This is useful mainly if the
7494 chaining of stack frames has been damaged by a bug, making it
7495 impossible for @value{GDBN} to assign numbers properly to all frames. In
7496 addition, this can be useful when your program has multiple stacks and
7497 switches between them. The optional @var{pc-addr} can also be given to
7498 specify the value of PC for the stack frame.
7502 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7503 numbers @var{n}, this advances toward the outermost frame, to higher
7504 frame numbers, to frames that have existed longer.
7507 @kindex do @r{(@code{down})}
7509 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7510 positive numbers @var{n}, this advances toward the innermost frame, to
7511 lower frame numbers, to frames that were created more recently.
7512 You may abbreviate @code{down} as @code{do}.
7515 All of these commands end by printing two lines of output describing the
7516 frame. The first line shows the frame number, the function name, the
7517 arguments, and the source file and line number of execution in that
7518 frame. The second line shows the text of that source line.
7526 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7528 10 read_input_file (argv[i]);
7532 After such a printout, the @code{list} command with no arguments
7533 prints ten lines centered on the point of execution in the frame.
7534 You can also edit the program at the point of execution with your favorite
7535 editing program by typing @code{edit}.
7536 @xref{List, ,Printing Source Lines},
7540 @kindex select-frame
7542 The @code{select-frame} command is a variant of @code{frame} that does
7543 not display the new frame after selecting it. This command is
7544 intended primarily for use in @value{GDBN} command scripts, where the
7545 output might be unnecessary and distracting.
7547 @kindex down-silently
7549 @item up-silently @var{n}
7550 @itemx down-silently @var{n}
7551 These two commands are variants of @code{up} and @code{down},
7552 respectively; they differ in that they do their work silently, without
7553 causing display of the new frame. They are intended primarily for use
7554 in @value{GDBN} command scripts, where the output might be unnecessary and
7559 @section Information About a Frame
7561 There are several other commands to print information about the selected
7567 When used without any argument, this command does not change which
7568 frame is selected, but prints a brief description of the currently
7569 selected stack frame. It can be abbreviated @code{f}. With an
7570 argument, this command is used to select a stack frame.
7571 @xref{Selection, ,Selecting a Frame}.
7574 @kindex info f @r{(@code{info frame})}
7577 This command prints a verbose description of the selected stack frame,
7582 the address of the frame
7584 the address of the next frame down (called by this frame)
7586 the address of the next frame up (caller of this frame)
7588 the language in which the source code corresponding to this frame is written
7590 the address of the frame's arguments
7592 the address of the frame's local variables
7594 the program counter saved in it (the address of execution in the caller frame)
7596 which registers were saved in the frame
7599 @noindent The verbose description is useful when
7600 something has gone wrong that has made the stack format fail to fit
7601 the usual conventions.
7603 @item info frame @var{addr}
7604 @itemx info f @var{addr}
7605 Print a verbose description of the frame at address @var{addr}, without
7606 selecting that frame. The selected frame remains unchanged by this
7607 command. This requires the same kind of address (more than one for some
7608 architectures) that you specify in the @code{frame} command.
7609 @xref{Selection, ,Selecting a Frame}.
7613 Print the arguments of the selected frame, each on a separate line.
7617 Print the local variables of the selected frame, each on a separate
7618 line. These are all variables (declared either static or automatic)
7619 accessible at the point of execution of the selected frame.
7623 @node Frame Filter Management
7624 @section Management of Frame Filters.
7625 @cindex managing frame filters
7627 Frame filters are Python based utilities to manage and decorate the
7628 output of frames. @xref{Frame Filter API}, for further information.
7630 Managing frame filters is performed by several commands available
7631 within @value{GDBN}, detailed here.
7634 @kindex info frame-filter
7635 @item info frame-filter
7636 Print a list of installed frame filters from all dictionaries, showing
7637 their name, priority and enabled status.
7639 @kindex disable frame-filter
7640 @anchor{disable frame-filter all}
7641 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7642 Disable a frame filter in the dictionary matching
7643 @var{filter-dictionary} and @var{filter-name}. The
7644 @var{filter-dictionary} may be @code{all}, @code{global},
7645 @code{progspace}, or the name of the object file where the frame filter
7646 dictionary resides. When @code{all} is specified, all frame filters
7647 across all dictionaries are disabled. The @var{filter-name} is the name
7648 of the frame filter and is used when @code{all} is not the option for
7649 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7650 may be enabled again later.
7652 @kindex enable frame-filter
7653 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7654 Enable a frame filter in the dictionary matching
7655 @var{filter-dictionary} and @var{filter-name}. The
7656 @var{filter-dictionary} may be @code{all}, @code{global},
7657 @code{progspace} or the name of the object file where the frame filter
7658 dictionary resides. When @code{all} is specified, all frame filters across
7659 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7660 filter and is used when @code{all} is not the option for
7661 @var{filter-dictionary}.
7666 (gdb) info frame-filter
7668 global frame-filters:
7669 Priority Enabled Name
7670 1000 No PrimaryFunctionFilter
7673 progspace /build/test frame-filters:
7674 Priority Enabled Name
7675 100 Yes ProgspaceFilter
7677 objfile /build/test frame-filters:
7678 Priority Enabled Name
7679 999 Yes BuildProgra Filter
7681 (gdb) disable frame-filter /build/test BuildProgramFilter
7682 (gdb) info frame-filter
7684 global frame-filters:
7685 Priority Enabled Name
7686 1000 No PrimaryFunctionFilter
7689 progspace /build/test frame-filters:
7690 Priority Enabled Name
7691 100 Yes ProgspaceFilter
7693 objfile /build/test frame-filters:
7694 Priority Enabled Name
7695 999 No BuildProgramFilter
7697 (gdb) enable frame-filter global PrimaryFunctionFilter
7698 (gdb) info frame-filter
7700 global frame-filters:
7701 Priority Enabled Name
7702 1000 Yes PrimaryFunctionFilter
7705 progspace /build/test frame-filters:
7706 Priority Enabled Name
7707 100 Yes ProgspaceFilter
7709 objfile /build/test frame-filters:
7710 Priority Enabled Name
7711 999 No BuildProgramFilter
7714 @kindex set frame-filter priority
7715 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7716 Set the @var{priority} of a frame filter in the dictionary matching
7717 @var{filter-dictionary}, and the frame filter name matching
7718 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7719 @code{progspace} or the name of the object file where the frame filter
7720 dictionary resides. The @var{priority} is an integer.
7722 @kindex show frame-filter priority
7723 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7724 Show the @var{priority} of a frame filter in the dictionary matching
7725 @var{filter-dictionary}, and the frame filter name matching
7726 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7727 @code{progspace} or the name of the object file where the frame filter
7733 (gdb) info frame-filter
7735 global frame-filters:
7736 Priority Enabled Name
7737 1000 Yes PrimaryFunctionFilter
7740 progspace /build/test frame-filters:
7741 Priority Enabled Name
7742 100 Yes ProgspaceFilter
7744 objfile /build/test frame-filters:
7745 Priority Enabled Name
7746 999 No BuildProgramFilter
7748 (gdb) set frame-filter priority global Reverse 50
7749 (gdb) info frame-filter
7751 global frame-filters:
7752 Priority Enabled Name
7753 1000 Yes PrimaryFunctionFilter
7756 progspace /build/test frame-filters:
7757 Priority Enabled Name
7758 100 Yes ProgspaceFilter
7760 objfile /build/test frame-filters:
7761 Priority Enabled Name
7762 999 No BuildProgramFilter
7767 @chapter Examining Source Files
7769 @value{GDBN} can print parts of your program's source, since the debugging
7770 information recorded in the program tells @value{GDBN} what source files were
7771 used to build it. When your program stops, @value{GDBN} spontaneously prints
7772 the line where it stopped. Likewise, when you select a stack frame
7773 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7774 execution in that frame has stopped. You can print other portions of
7775 source files by explicit command.
7777 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7778 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7779 @value{GDBN} under @sc{gnu} Emacs}.
7782 * List:: Printing source lines
7783 * Specify Location:: How to specify code locations
7784 * Edit:: Editing source files
7785 * Search:: Searching source files
7786 * Source Path:: Specifying source directories
7787 * Machine Code:: Source and machine code
7791 @section Printing Source Lines
7794 @kindex l @r{(@code{list})}
7795 To print lines from a source file, use the @code{list} command
7796 (abbreviated @code{l}). By default, ten lines are printed.
7797 There are several ways to specify what part of the file you want to
7798 print; see @ref{Specify Location}, for the full list.
7800 Here are the forms of the @code{list} command most commonly used:
7803 @item list @var{linenum}
7804 Print lines centered around line number @var{linenum} in the
7805 current source file.
7807 @item list @var{function}
7808 Print lines centered around the beginning of function
7812 Print more lines. If the last lines printed were printed with a
7813 @code{list} command, this prints lines following the last lines
7814 printed; however, if the last line printed was a solitary line printed
7815 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7816 Stack}), this prints lines centered around that line.
7819 Print lines just before the lines last printed.
7822 @cindex @code{list}, how many lines to display
7823 By default, @value{GDBN} prints ten source lines with any of these forms of
7824 the @code{list} command. You can change this using @code{set listsize}:
7827 @kindex set listsize
7828 @item set listsize @var{count}
7829 @itemx set listsize unlimited
7830 Make the @code{list} command display @var{count} source lines (unless
7831 the @code{list} argument explicitly specifies some other number).
7832 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7834 @kindex show listsize
7836 Display the number of lines that @code{list} prints.
7839 Repeating a @code{list} command with @key{RET} discards the argument,
7840 so it is equivalent to typing just @code{list}. This is more useful
7841 than listing the same lines again. An exception is made for an
7842 argument of @samp{-}; that argument is preserved in repetition so that
7843 each repetition moves up in the source file.
7845 In general, the @code{list} command expects you to supply zero, one or two
7846 @dfn{locations}. Locations specify source lines; there are several ways
7847 of writing them (@pxref{Specify Location}), but the effect is always
7848 to specify some source line.
7850 Here is a complete description of the possible arguments for @code{list}:
7853 @item list @var{location}
7854 Print lines centered around the line specified by @var{location}.
7856 @item list @var{first},@var{last}
7857 Print lines from @var{first} to @var{last}. Both arguments are
7858 locations. When a @code{list} command has two locations, and the
7859 source file of the second location is omitted, this refers to
7860 the same source file as the first location.
7862 @item list ,@var{last}
7863 Print lines ending with @var{last}.
7865 @item list @var{first},
7866 Print lines starting with @var{first}.
7869 Print lines just after the lines last printed.
7872 Print lines just before the lines last printed.
7875 As described in the preceding table.
7878 @node Specify Location
7879 @section Specifying a Location
7880 @cindex specifying location
7882 @cindex source location
7885 * Linespec Locations:: Linespec locations
7886 * Explicit Locations:: Explicit locations
7887 * Address Locations:: Address locations
7890 Several @value{GDBN} commands accept arguments that specify a location
7891 of your program's code. Since @value{GDBN} is a source-level
7892 debugger, a location usually specifies some line in the source code.
7893 Locations may be specified using three different formats:
7894 linespec locations, explicit locations, or address locations.
7896 @node Linespec Locations
7897 @subsection Linespec Locations
7898 @cindex linespec locations
7900 A @dfn{linespec} is a colon-separated list of source location parameters such
7901 as file name, function name, etc. Here are all the different ways of
7902 specifying a linespec:
7906 Specifies the line number @var{linenum} of the current source file.
7909 @itemx +@var{offset}
7910 Specifies the line @var{offset} lines before or after the @dfn{current
7911 line}. For the @code{list} command, the current line is the last one
7912 printed; for the breakpoint commands, this is the line at which
7913 execution stopped in the currently selected @dfn{stack frame}
7914 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7915 used as the second of the two linespecs in a @code{list} command,
7916 this specifies the line @var{offset} lines up or down from the first
7919 @item @var{filename}:@var{linenum}
7920 Specifies the line @var{linenum} in the source file @var{filename}.
7921 If @var{filename} is a relative file name, then it will match any
7922 source file name with the same trailing components. For example, if
7923 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7924 name of @file{/build/trunk/gcc/expr.c}, but not
7925 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7927 @item @var{function}
7928 Specifies the line that begins the body of the function @var{function}.
7929 For example, in C, this is the line with the open brace.
7931 By default, in C@t{++} and Ada, @var{function} is interpreted as
7932 specifying all functions named @var{function} in all scopes. For
7933 C@t{++}, this means in all namespaces and classes. For Ada, this
7934 means in all packages.
7936 For example, assuming a program with C@t{++} symbols named
7937 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
7938 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
7940 Commands that accept a linespec let you override this with the
7941 @code{-qualified} option. For example, @w{@kbd{break -qualified
7942 func}} sets a breakpoint on a free-function named @code{func} ignoring
7943 any C@t{++} class methods and namespace functions called @code{func}.
7945 @xref{Explicit Locations}.
7947 @item @var{function}:@var{label}
7948 Specifies the line where @var{label} appears in @var{function}.
7950 @item @var{filename}:@var{function}
7951 Specifies the line that begins the body of the function @var{function}
7952 in the file @var{filename}. You only need the file name with a
7953 function name to avoid ambiguity when there are identically named
7954 functions in different source files.
7957 Specifies the line at which the label named @var{label} appears
7958 in the function corresponding to the currently selected stack frame.
7959 If there is no current selected stack frame (for instance, if the inferior
7960 is not running), then @value{GDBN} will not search for a label.
7962 @cindex breakpoint at static probe point
7963 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7964 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7965 applications to embed static probes. @xref{Static Probe Points}, for more
7966 information on finding and using static probes. This form of linespec
7967 specifies the location of such a static probe.
7969 If @var{objfile} is given, only probes coming from that shared library
7970 or executable matching @var{objfile} as a regular expression are considered.
7971 If @var{provider} is given, then only probes from that provider are considered.
7972 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7973 each one of those probes.
7976 @node Explicit Locations
7977 @subsection Explicit Locations
7978 @cindex explicit locations
7980 @dfn{Explicit locations} allow the user to directly specify the source
7981 location's parameters using option-value pairs.
7983 Explicit locations are useful when several functions, labels, or
7984 file names have the same name (base name for files) in the program's
7985 sources. In these cases, explicit locations point to the source
7986 line you meant more accurately and unambiguously. Also, using
7987 explicit locations might be faster in large programs.
7989 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7990 defined in the file named @file{foo} or the label @code{bar} in a function
7991 named @code{foo}. @value{GDBN} must search either the file system or
7992 the symbol table to know.
7994 The list of valid explicit location options is summarized in the
7998 @item -source @var{filename}
7999 The value specifies the source file name. To differentiate between
8000 files with the same base name, prepend as many directories as is necessary
8001 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8002 @value{GDBN} will use the first file it finds with the given base
8003 name. This option requires the use of either @code{-function} or @code{-line}.
8005 @item -function @var{function}
8006 The value specifies the name of a function. Operations
8007 on function locations unmodified by other options (such as @code{-label}
8008 or @code{-line}) refer to the line that begins the body of the function.
8009 In C, for example, this is the line with the open brace.
8011 By default, in C@t{++} and Ada, @var{function} is interpreted as
8012 specifying all functions named @var{function} in all scopes. For
8013 C@t{++}, this means in all namespaces and classes. For Ada, this
8014 means in all packages.
8016 For example, assuming a program with C@t{++} symbols named
8017 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8018 -function func}} and @w{@kbd{break -function B::func}} set a
8019 breakpoint on both symbols.
8021 You can use the @kbd{-qualified} flag to override this (see below).
8025 This flag makes @value{GDBN} interpret a function name specified with
8026 @kbd{-function} as a complete fully-qualified name.
8028 For example, assuming a C@t{++} program with symbols named
8029 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8030 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8032 (Note: the @kbd{-qualified} option can precede a linespec as well
8033 (@pxref{Linespec Locations}), so the particular example above could be
8034 simplified as @w{@kbd{break -qualified B::func}}.)
8036 @item -label @var{label}
8037 The value specifies the name of a label. When the function
8038 name is not specified, the label is searched in the function of the currently
8039 selected stack frame.
8041 @item -line @var{number}
8042 The value specifies a line offset for the location. The offset may either
8043 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8044 the command. When specified without any other options, the line offset is
8045 relative to the current line.
8048 Explicit location options may be abbreviated by omitting any non-unique
8049 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8051 @node Address Locations
8052 @subsection Address Locations
8053 @cindex address locations
8055 @dfn{Address locations} indicate a specific program address. They have
8056 the generalized form *@var{address}.
8058 For line-oriented commands, such as @code{list} and @code{edit}, this
8059 specifies a source line that contains @var{address}. For @code{break} and
8060 other breakpoint-oriented commands, this can be used to set breakpoints in
8061 parts of your program which do not have debugging information or
8064 Here @var{address} may be any expression valid in the current working
8065 language (@pxref{Languages, working language}) that specifies a code
8066 address. In addition, as a convenience, @value{GDBN} extends the
8067 semantics of expressions used in locations to cover several situations
8068 that frequently occur during debugging. Here are the various forms
8072 @item @var{expression}
8073 Any expression valid in the current working language.
8075 @item @var{funcaddr}
8076 An address of a function or procedure derived from its name. In C,
8077 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8078 simply the function's name @var{function} (and actually a special case
8079 of a valid expression). In Pascal and Modula-2, this is
8080 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8081 (although the Pascal form also works).
8083 This form specifies the address of the function's first instruction,
8084 before the stack frame and arguments have been set up.
8086 @item '@var{filename}':@var{funcaddr}
8087 Like @var{funcaddr} above, but also specifies the name of the source
8088 file explicitly. This is useful if the name of the function does not
8089 specify the function unambiguously, e.g., if there are several
8090 functions with identical names in different source files.
8094 @section Editing Source Files
8095 @cindex editing source files
8098 @kindex e @r{(@code{edit})}
8099 To edit the lines in a source file, use the @code{edit} command.
8100 The editing program of your choice
8101 is invoked with the current line set to
8102 the active line in the program.
8103 Alternatively, there are several ways to specify what part of the file you
8104 want to print if you want to see other parts of the program:
8107 @item edit @var{location}
8108 Edit the source file specified by @code{location}. Editing starts at
8109 that @var{location}, e.g., at the specified source line of the
8110 specified file. @xref{Specify Location}, for all the possible forms
8111 of the @var{location} argument; here are the forms of the @code{edit}
8112 command most commonly used:
8115 @item edit @var{number}
8116 Edit the current source file with @var{number} as the active line number.
8118 @item edit @var{function}
8119 Edit the file containing @var{function} at the beginning of its definition.
8124 @subsection Choosing your Editor
8125 You can customize @value{GDBN} to use any editor you want
8127 The only restriction is that your editor (say @code{ex}), recognizes the
8128 following command-line syntax:
8130 ex +@var{number} file
8132 The optional numeric value +@var{number} specifies the number of the line in
8133 the file where to start editing.}.
8134 By default, it is @file{@value{EDITOR}}, but you can change this
8135 by setting the environment variable @code{EDITOR} before using
8136 @value{GDBN}. For example, to configure @value{GDBN} to use the
8137 @code{vi} editor, you could use these commands with the @code{sh} shell:
8143 or in the @code{csh} shell,
8145 setenv EDITOR /usr/bin/vi
8150 @section Searching Source Files
8151 @cindex searching source files
8153 There are two commands for searching through the current source file for a
8158 @kindex forward-search
8159 @kindex fo @r{(@code{forward-search})}
8160 @item forward-search @var{regexp}
8161 @itemx search @var{regexp}
8162 The command @samp{forward-search @var{regexp}} checks each line,
8163 starting with the one following the last line listed, for a match for
8164 @var{regexp}. It lists the line that is found. You can use the
8165 synonym @samp{search @var{regexp}} or abbreviate the command name as
8168 @kindex reverse-search
8169 @item reverse-search @var{regexp}
8170 The command @samp{reverse-search @var{regexp}} checks each line, starting
8171 with the one before the last line listed and going backward, for a match
8172 for @var{regexp}. It lists the line that is found. You can abbreviate
8173 this command as @code{rev}.
8177 @section Specifying Source Directories
8180 @cindex directories for source files
8181 Executable programs sometimes do not record the directories of the source
8182 files from which they were compiled, just the names. Even when they do,
8183 the directories could be moved between the compilation and your debugging
8184 session. @value{GDBN} has a list of directories to search for source files;
8185 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8186 it tries all the directories in the list, in the order they are present
8187 in the list, until it finds a file with the desired name.
8189 For example, suppose an executable references the file
8190 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8191 @file{/mnt/cross}. The file is first looked up literally; if this
8192 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8193 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8194 message is printed. @value{GDBN} does not look up the parts of the
8195 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8196 Likewise, the subdirectories of the source path are not searched: if
8197 the source path is @file{/mnt/cross}, and the binary refers to
8198 @file{foo.c}, @value{GDBN} would not find it under
8199 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8201 Plain file names, relative file names with leading directories, file
8202 names containing dots, etc.@: are all treated as described above; for
8203 instance, if the source path is @file{/mnt/cross}, and the source file
8204 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8205 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8206 that---@file{/mnt/cross/foo.c}.
8208 Note that the executable search path is @emph{not} used to locate the
8211 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8212 any information it has cached about where source files are found and where
8213 each line is in the file.
8217 When you start @value{GDBN}, its source path includes only @samp{cdir}
8218 and @samp{cwd}, in that order.
8219 To add other directories, use the @code{directory} command.
8221 The search path is used to find both program source files and @value{GDBN}
8222 script files (read using the @samp{-command} option and @samp{source} command).
8224 In addition to the source path, @value{GDBN} provides a set of commands
8225 that manage a list of source path substitution rules. A @dfn{substitution
8226 rule} specifies how to rewrite source directories stored in the program's
8227 debug information in case the sources were moved to a different
8228 directory between compilation and debugging. A rule is made of
8229 two strings, the first specifying what needs to be rewritten in
8230 the path, and the second specifying how it should be rewritten.
8231 In @ref{set substitute-path}, we name these two parts @var{from} and
8232 @var{to} respectively. @value{GDBN} does a simple string replacement
8233 of @var{from} with @var{to} at the start of the directory part of the
8234 source file name, and uses that result instead of the original file
8235 name to look up the sources.
8237 Using the previous example, suppose the @file{foo-1.0} tree has been
8238 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8239 @value{GDBN} to replace @file{/usr/src} in all source path names with
8240 @file{/mnt/cross}. The first lookup will then be
8241 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8242 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8243 substitution rule, use the @code{set substitute-path} command
8244 (@pxref{set substitute-path}).
8246 To avoid unexpected substitution results, a rule is applied only if the
8247 @var{from} part of the directory name ends at a directory separator.
8248 For instance, a rule substituting @file{/usr/source} into
8249 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8250 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8251 is applied only at the beginning of the directory name, this rule will
8252 not be applied to @file{/root/usr/source/baz.c} either.
8254 In many cases, you can achieve the same result using the @code{directory}
8255 command. However, @code{set substitute-path} can be more efficient in
8256 the case where the sources are organized in a complex tree with multiple
8257 subdirectories. With the @code{directory} command, you need to add each
8258 subdirectory of your project. If you moved the entire tree while
8259 preserving its internal organization, then @code{set substitute-path}
8260 allows you to direct the debugger to all the sources with one single
8263 @code{set substitute-path} is also more than just a shortcut command.
8264 The source path is only used if the file at the original location no
8265 longer exists. On the other hand, @code{set substitute-path} modifies
8266 the debugger behavior to look at the rewritten location instead. So, if
8267 for any reason a source file that is not relevant to your executable is
8268 located at the original location, a substitution rule is the only
8269 method available to point @value{GDBN} at the new location.
8271 @cindex @samp{--with-relocated-sources}
8272 @cindex default source path substitution
8273 You can configure a default source path substitution rule by
8274 configuring @value{GDBN} with the
8275 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8276 should be the name of a directory under @value{GDBN}'s configured
8277 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8278 directory names in debug information under @var{dir} will be adjusted
8279 automatically if the installed @value{GDBN} is moved to a new
8280 location. This is useful if @value{GDBN}, libraries or executables
8281 with debug information and corresponding source code are being moved
8285 @item directory @var{dirname} @dots{}
8286 @item dir @var{dirname} @dots{}
8287 Add directory @var{dirname} to the front of the source path. Several
8288 directory names may be given to this command, separated by @samp{:}
8289 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8290 part of absolute file names) or
8291 whitespace. You may specify a directory that is already in the source
8292 path; this moves it forward, so @value{GDBN} searches it sooner.
8296 @vindex $cdir@r{, convenience variable}
8297 @vindex $cwd@r{, convenience variable}
8298 @cindex compilation directory
8299 @cindex current directory
8300 @cindex working directory
8301 @cindex directory, current
8302 @cindex directory, compilation
8303 You can use the string @samp{$cdir} to refer to the compilation
8304 directory (if one is recorded), and @samp{$cwd} to refer to the current
8305 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8306 tracks the current working directory as it changes during your @value{GDBN}
8307 session, while the latter is immediately expanded to the current
8308 directory at the time you add an entry to the source path.
8311 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8313 @c RET-repeat for @code{directory} is explicitly disabled, but since
8314 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8316 @item set directories @var{path-list}
8317 @kindex set directories
8318 Set the source path to @var{path-list}.
8319 @samp{$cdir:$cwd} are added if missing.
8321 @item show directories
8322 @kindex show directories
8323 Print the source path: show which directories it contains.
8325 @anchor{set substitute-path}
8326 @item set substitute-path @var{from} @var{to}
8327 @kindex set substitute-path
8328 Define a source path substitution rule, and add it at the end of the
8329 current list of existing substitution rules. If a rule with the same
8330 @var{from} was already defined, then the old rule is also deleted.
8332 For example, if the file @file{/foo/bar/baz.c} was moved to
8333 @file{/mnt/cross/baz.c}, then the command
8336 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8340 will tell @value{GDBN} to replace @samp{/foo/bar} with
8341 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8342 @file{baz.c} even though it was moved.
8344 In the case when more than one substitution rule have been defined,
8345 the rules are evaluated one by one in the order where they have been
8346 defined. The first one matching, if any, is selected to perform
8349 For instance, if we had entered the following commands:
8352 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8353 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8357 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8358 @file{/mnt/include/defs.h} by using the first rule. However, it would
8359 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8360 @file{/mnt/src/lib/foo.c}.
8363 @item unset substitute-path [path]
8364 @kindex unset substitute-path
8365 If a path is specified, search the current list of substitution rules
8366 for a rule that would rewrite that path. Delete that rule if found.
8367 A warning is emitted by the debugger if no rule could be found.
8369 If no path is specified, then all substitution rules are deleted.
8371 @item show substitute-path [path]
8372 @kindex show substitute-path
8373 If a path is specified, then print the source path substitution rule
8374 which would rewrite that path, if any.
8376 If no path is specified, then print all existing source path substitution
8381 If your source path is cluttered with directories that are no longer of
8382 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8383 versions of source. You can correct the situation as follows:
8387 Use @code{directory} with no argument to reset the source path to its default value.
8390 Use @code{directory} with suitable arguments to reinstall the
8391 directories you want in the source path. You can add all the
8392 directories in one command.
8396 @section Source and Machine Code
8397 @cindex source line and its code address
8399 You can use the command @code{info line} to map source lines to program
8400 addresses (and vice versa), and the command @code{disassemble} to display
8401 a range of addresses as machine instructions. You can use the command
8402 @code{set disassemble-next-line} to set whether to disassemble next
8403 source line when execution stops. When run under @sc{gnu} Emacs
8404 mode, the @code{info line} command causes the arrow to point to the
8405 line specified. Also, @code{info line} prints addresses in symbolic form as
8410 @item info line @var{location}
8411 Print the starting and ending addresses of the compiled code for
8412 source line @var{location}. You can specify source lines in any of
8413 the ways documented in @ref{Specify Location}.
8416 For example, we can use @code{info line} to discover the location of
8417 the object code for the first line of function
8418 @code{m4_changequote}:
8420 @c FIXME: I think this example should also show the addresses in
8421 @c symbolic form, as they usually would be displayed.
8423 (@value{GDBP}) info line m4_changequote
8424 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8428 @cindex code address and its source line
8429 We can also inquire (using @code{*@var{addr}} as the form for
8430 @var{location}) what source line covers a particular address:
8432 (@value{GDBP}) info line *0x63ff
8433 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8436 @cindex @code{$_} and @code{info line}
8437 @cindex @code{x} command, default address
8438 @kindex x@r{(examine), and} info line
8439 After @code{info line}, the default address for the @code{x} command
8440 is changed to the starting address of the line, so that @samp{x/i} is
8441 sufficient to begin examining the machine code (@pxref{Memory,
8442 ,Examining Memory}). Also, this address is saved as the value of the
8443 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8448 @cindex assembly instructions
8449 @cindex instructions, assembly
8450 @cindex machine instructions
8451 @cindex listing machine instructions
8453 @itemx disassemble /m
8454 @itemx disassemble /s
8455 @itemx disassemble /r
8456 This specialized command dumps a range of memory as machine
8457 instructions. It can also print mixed source+disassembly by specifying
8458 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8459 as well as in symbolic form by specifying the @code{/r} modifier.
8460 The default memory range is the function surrounding the
8461 program counter of the selected frame. A single argument to this
8462 command is a program counter value; @value{GDBN} dumps the function
8463 surrounding this value. When two arguments are given, they should
8464 be separated by a comma, possibly surrounded by whitespace. The
8465 arguments specify a range of addresses to dump, in one of two forms:
8468 @item @var{start},@var{end}
8469 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8470 @item @var{start},+@var{length}
8471 the addresses from @var{start} (inclusive) to
8472 @code{@var{start}+@var{length}} (exclusive).
8476 When 2 arguments are specified, the name of the function is also
8477 printed (since there could be several functions in the given range).
8479 The argument(s) can be any expression yielding a numeric value, such as
8480 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8482 If the range of memory being disassembled contains current program counter,
8483 the instruction at that location is shown with a @code{=>} marker.
8486 The following example shows the disassembly of a range of addresses of
8487 HP PA-RISC 2.0 code:
8490 (@value{GDBP}) disas 0x32c4, 0x32e4
8491 Dump of assembler code from 0x32c4 to 0x32e4:
8492 0x32c4 <main+204>: addil 0,dp
8493 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8494 0x32cc <main+212>: ldil 0x3000,r31
8495 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8496 0x32d4 <main+220>: ldo 0(r31),rp
8497 0x32d8 <main+224>: addil -0x800,dp
8498 0x32dc <main+228>: ldo 0x588(r1),r26
8499 0x32e0 <main+232>: ldil 0x3000,r31
8500 End of assembler dump.
8503 Here is an example showing mixed source+assembly for Intel x86
8504 with @code{/m} or @code{/s}, when the program is stopped just after
8505 function prologue in a non-optimized function with no inline code.
8508 (@value{GDBP}) disas /m main
8509 Dump of assembler code for function main:
8511 0x08048330 <+0>: push %ebp
8512 0x08048331 <+1>: mov %esp,%ebp
8513 0x08048333 <+3>: sub $0x8,%esp
8514 0x08048336 <+6>: and $0xfffffff0,%esp
8515 0x08048339 <+9>: sub $0x10,%esp
8517 6 printf ("Hello.\n");
8518 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8519 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8523 0x08048348 <+24>: mov $0x0,%eax
8524 0x0804834d <+29>: leave
8525 0x0804834e <+30>: ret
8527 End of assembler dump.
8530 The @code{/m} option is deprecated as its output is not useful when
8531 there is either inlined code or re-ordered code.
8532 The @code{/s} option is the preferred choice.
8533 Here is an example for AMD x86-64 showing the difference between
8534 @code{/m} output and @code{/s} output.
8535 This example has one inline function defined in a header file,
8536 and the code is compiled with @samp{-O2} optimization.
8537 Note how the @code{/m} output is missing the disassembly of
8538 several instructions that are present in the @code{/s} output.
8568 (@value{GDBP}) disas /m main
8569 Dump of assembler code for function main:
8573 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8574 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8578 0x000000000040041d <+29>: xor %eax,%eax
8579 0x000000000040041f <+31>: retq
8580 0x0000000000400420 <+32>: add %eax,%eax
8581 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8583 End of assembler dump.
8584 (@value{GDBP}) disas /s main
8585 Dump of assembler code for function main:
8589 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8593 0x0000000000400406 <+6>: test %eax,%eax
8594 0x0000000000400408 <+8>: js 0x400420 <main+32>
8599 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8600 0x000000000040040d <+13>: test %eax,%eax
8601 0x000000000040040f <+15>: mov $0x1,%eax
8602 0x0000000000400414 <+20>: cmovne %edx,%eax
8606 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8610 0x000000000040041d <+29>: xor %eax,%eax
8611 0x000000000040041f <+31>: retq
8615 0x0000000000400420 <+32>: add %eax,%eax
8616 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8617 End of assembler dump.
8620 Here is another example showing raw instructions in hex for AMD x86-64,
8623 (gdb) disas /r 0x400281,+10
8624 Dump of assembler code from 0x400281 to 0x40028b:
8625 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8626 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8627 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8628 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8629 End of assembler dump.
8632 Addresses cannot be specified as a location (@pxref{Specify Location}).
8633 So, for example, if you want to disassemble function @code{bar}
8634 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8635 and not @samp{disassemble foo.c:bar}.
8637 Some architectures have more than one commonly-used set of instruction
8638 mnemonics or other syntax.
8640 For programs that were dynamically linked and use shared libraries,
8641 instructions that call functions or branch to locations in the shared
8642 libraries might show a seemingly bogus location---it's actually a
8643 location of the relocation table. On some architectures, @value{GDBN}
8644 might be able to resolve these to actual function names.
8647 @kindex set disassembler-options
8648 @cindex disassembler options
8649 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8650 This command controls the passing of target specific information to
8651 the disassembler. For a list of valid options, please refer to the
8652 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8653 manual and/or the output of @kbd{objdump --help}
8654 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8655 The default value is the empty string.
8657 If it is necessary to specify more than one disassembler option, then
8658 multiple options can be placed together into a comma separated list.
8659 Currently this command is only supported on targets ARM, PowerPC
8662 @kindex show disassembler-options
8663 @item show disassembler-options
8664 Show the current setting of the disassembler options.
8668 @kindex set disassembly-flavor
8669 @cindex Intel disassembly flavor
8670 @cindex AT&T disassembly flavor
8671 @item set disassembly-flavor @var{instruction-set}
8672 Select the instruction set to use when disassembling the
8673 program via the @code{disassemble} or @code{x/i} commands.
8675 Currently this command is only defined for the Intel x86 family. You
8676 can set @var{instruction-set} to either @code{intel} or @code{att}.
8677 The default is @code{att}, the AT&T flavor used by default by Unix
8678 assemblers for x86-based targets.
8680 @kindex show disassembly-flavor
8681 @item show disassembly-flavor
8682 Show the current setting of the disassembly flavor.
8686 @kindex set disassemble-next-line
8687 @kindex show disassemble-next-line
8688 @item set disassemble-next-line
8689 @itemx show disassemble-next-line
8690 Control whether or not @value{GDBN} will disassemble the next source
8691 line or instruction when execution stops. If ON, @value{GDBN} will
8692 display disassembly of the next source line when execution of the
8693 program being debugged stops. This is @emph{in addition} to
8694 displaying the source line itself, which @value{GDBN} always does if
8695 possible. If the next source line cannot be displayed for some reason
8696 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8697 info in the debug info), @value{GDBN} will display disassembly of the
8698 next @emph{instruction} instead of showing the next source line. If
8699 AUTO, @value{GDBN} will display disassembly of next instruction only
8700 if the source line cannot be displayed. This setting causes
8701 @value{GDBN} to display some feedback when you step through a function
8702 with no line info or whose source file is unavailable. The default is
8703 OFF, which means never display the disassembly of the next line or
8709 @chapter Examining Data
8711 @cindex printing data
8712 @cindex examining data
8715 The usual way to examine data in your program is with the @code{print}
8716 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8717 evaluates and prints the value of an expression of the language your
8718 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8719 Different Languages}). It may also print the expression using a
8720 Python-based pretty-printer (@pxref{Pretty Printing}).
8723 @item print @var{expr}
8724 @itemx print /@var{f} @var{expr}
8725 @var{expr} is an expression (in the source language). By default the
8726 value of @var{expr} is printed in a format appropriate to its data type;
8727 you can choose a different format by specifying @samp{/@var{f}}, where
8728 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8732 @itemx print /@var{f}
8733 @cindex reprint the last value
8734 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8735 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8736 conveniently inspect the same value in an alternative format.
8739 A more low-level way of examining data is with the @code{x} command.
8740 It examines data in memory at a specified address and prints it in a
8741 specified format. @xref{Memory, ,Examining Memory}.
8743 If you are interested in information about types, or about how the
8744 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8745 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8748 @cindex exploring hierarchical data structures
8750 Another way of examining values of expressions and type information is
8751 through the Python extension command @code{explore} (available only if
8752 the @value{GDBN} build is configured with @code{--with-python}). It
8753 offers an interactive way to start at the highest level (or, the most
8754 abstract level) of the data type of an expression (or, the data type
8755 itself) and explore all the way down to leaf scalar values/fields
8756 embedded in the higher level data types.
8759 @item explore @var{arg}
8760 @var{arg} is either an expression (in the source language), or a type
8761 visible in the current context of the program being debugged.
8764 The working of the @code{explore} command can be illustrated with an
8765 example. If a data type @code{struct ComplexStruct} is defined in your
8775 struct ComplexStruct
8777 struct SimpleStruct *ss_p;
8783 followed by variable declarations as
8786 struct SimpleStruct ss = @{ 10, 1.11 @};
8787 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8791 then, the value of the variable @code{cs} can be explored using the
8792 @code{explore} command as follows.
8796 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8797 the following fields:
8799 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8800 arr = <Enter 1 to explore this field of type `int [10]'>
8802 Enter the field number of choice:
8806 Since the fields of @code{cs} are not scalar values, you are being
8807 prompted to chose the field you want to explore. Let's say you choose
8808 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8809 pointer, you will be asked if it is pointing to a single value. From
8810 the declaration of @code{cs} above, it is indeed pointing to a single
8811 value, hence you enter @code{y}. If you enter @code{n}, then you will
8812 be asked if it were pointing to an array of values, in which case this
8813 field will be explored as if it were an array.
8816 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8817 Continue exploring it as a pointer to a single value [y/n]: y
8818 The value of `*(cs.ss_p)' is a struct/class of type `struct
8819 SimpleStruct' with the following fields:
8821 i = 10 .. (Value of type `int')
8822 d = 1.1100000000000001 .. (Value of type `double')
8824 Press enter to return to parent value:
8828 If the field @code{arr} of @code{cs} was chosen for exploration by
8829 entering @code{1} earlier, then since it is as array, you will be
8830 prompted to enter the index of the element in the array that you want
8834 `cs.arr' is an array of `int'.
8835 Enter the index of the element you want to explore in `cs.arr': 5
8837 `(cs.arr)[5]' is a scalar value of type `int'.
8841 Press enter to return to parent value:
8844 In general, at any stage of exploration, you can go deeper towards the
8845 leaf values by responding to the prompts appropriately, or hit the
8846 return key to return to the enclosing data structure (the @i{higher}
8847 level data structure).
8849 Similar to exploring values, you can use the @code{explore} command to
8850 explore types. Instead of specifying a value (which is typically a
8851 variable name or an expression valid in the current context of the
8852 program being debugged), you specify a type name. If you consider the
8853 same example as above, your can explore the type
8854 @code{struct ComplexStruct} by passing the argument
8855 @code{struct ComplexStruct} to the @code{explore} command.
8858 (gdb) explore struct ComplexStruct
8862 By responding to the prompts appropriately in the subsequent interactive
8863 session, you can explore the type @code{struct ComplexStruct} in a
8864 manner similar to how the value @code{cs} was explored in the above
8867 The @code{explore} command also has two sub-commands,
8868 @code{explore value} and @code{explore type}. The former sub-command is
8869 a way to explicitly specify that value exploration of the argument is
8870 being invoked, while the latter is a way to explicitly specify that type
8871 exploration of the argument is being invoked.
8874 @item explore value @var{expr}
8875 @cindex explore value
8876 This sub-command of @code{explore} explores the value of the
8877 expression @var{expr} (if @var{expr} is an expression valid in the
8878 current context of the program being debugged). The behavior of this
8879 command is identical to that of the behavior of the @code{explore}
8880 command being passed the argument @var{expr}.
8882 @item explore type @var{arg}
8883 @cindex explore type
8884 This sub-command of @code{explore} explores the type of @var{arg} (if
8885 @var{arg} is a type visible in the current context of program being
8886 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8887 is an expression valid in the current context of the program being
8888 debugged). If @var{arg} is a type, then the behavior of this command is
8889 identical to that of the @code{explore} command being passed the
8890 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8891 this command will be identical to that of the @code{explore} command
8892 being passed the type of @var{arg} as the argument.
8896 * Expressions:: Expressions
8897 * Ambiguous Expressions:: Ambiguous Expressions
8898 * Variables:: Program variables
8899 * Arrays:: Artificial arrays
8900 * Output Formats:: Output formats
8901 * Memory:: Examining memory
8902 * Auto Display:: Automatic display
8903 * Print Settings:: Print settings
8904 * Pretty Printing:: Python pretty printing
8905 * Value History:: Value history
8906 * Convenience Vars:: Convenience variables
8907 * Convenience Funs:: Convenience functions
8908 * Registers:: Registers
8909 * Floating Point Hardware:: Floating point hardware
8910 * Vector Unit:: Vector Unit
8911 * OS Information:: Auxiliary data provided by operating system
8912 * Memory Region Attributes:: Memory region attributes
8913 * Dump/Restore Files:: Copy between memory and a file
8914 * Core File Generation:: Cause a program dump its core
8915 * Character Sets:: Debugging programs that use a different
8916 character set than GDB does
8917 * Caching Target Data:: Data caching for targets
8918 * Searching Memory:: Searching memory for a sequence of bytes
8919 * Value Sizes:: Managing memory allocated for values
8923 @section Expressions
8926 @code{print} and many other @value{GDBN} commands accept an expression and
8927 compute its value. Any kind of constant, variable or operator defined
8928 by the programming language you are using is valid in an expression in
8929 @value{GDBN}. This includes conditional expressions, function calls,
8930 casts, and string constants. It also includes preprocessor macros, if
8931 you compiled your program to include this information; see
8934 @cindex arrays in expressions
8935 @value{GDBN} supports array constants in expressions input by
8936 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8937 you can use the command @code{print @{1, 2, 3@}} to create an array
8938 of three integers. If you pass an array to a function or assign it
8939 to a program variable, @value{GDBN} copies the array to memory that
8940 is @code{malloc}ed in the target program.
8942 Because C is so widespread, most of the expressions shown in examples in
8943 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8944 Languages}, for information on how to use expressions in other
8947 In this section, we discuss operators that you can use in @value{GDBN}
8948 expressions regardless of your programming language.
8950 @cindex casts, in expressions
8951 Casts are supported in all languages, not just in C, because it is so
8952 useful to cast a number into a pointer in order to examine a structure
8953 at that address in memory.
8954 @c FIXME: casts supported---Mod2 true?
8956 @value{GDBN} supports these operators, in addition to those common
8957 to programming languages:
8961 @samp{@@} is a binary operator for treating parts of memory as arrays.
8962 @xref{Arrays, ,Artificial Arrays}, for more information.
8965 @samp{::} allows you to specify a variable in terms of the file or
8966 function where it is defined. @xref{Variables, ,Program Variables}.
8968 @cindex @{@var{type}@}
8969 @cindex type casting memory
8970 @cindex memory, viewing as typed object
8971 @cindex casts, to view memory
8972 @item @{@var{type}@} @var{addr}
8973 Refers to an object of type @var{type} stored at address @var{addr} in
8974 memory. The address @var{addr} may be any expression whose value is
8975 an integer or pointer (but parentheses are required around binary
8976 operators, just as in a cast). This construct is allowed regardless
8977 of what kind of data is normally supposed to reside at @var{addr}.
8980 @node Ambiguous Expressions
8981 @section Ambiguous Expressions
8982 @cindex ambiguous expressions
8984 Expressions can sometimes contain some ambiguous elements. For instance,
8985 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8986 a single function name to be defined several times, for application in
8987 different contexts. This is called @dfn{overloading}. Another example
8988 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8989 templates and is typically instantiated several times, resulting in
8990 the same function name being defined in different contexts.
8992 In some cases and depending on the language, it is possible to adjust
8993 the expression to remove the ambiguity. For instance in C@t{++}, you
8994 can specify the signature of the function you want to break on, as in
8995 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8996 qualified name of your function often makes the expression unambiguous
8999 When an ambiguity that needs to be resolved is detected, the debugger
9000 has the capability to display a menu of numbered choices for each
9001 possibility, and then waits for the selection with the prompt @samp{>}.
9002 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9003 aborts the current command. If the command in which the expression was
9004 used allows more than one choice to be selected, the next option in the
9005 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9008 For example, the following session excerpt shows an attempt to set a
9009 breakpoint at the overloaded symbol @code{String::after}.
9010 We choose three particular definitions of that function name:
9012 @c FIXME! This is likely to change to show arg type lists, at least
9015 (@value{GDBP}) b String::after
9018 [2] file:String.cc; line number:867
9019 [3] file:String.cc; line number:860
9020 [4] file:String.cc; line number:875
9021 [5] file:String.cc; line number:853
9022 [6] file:String.cc; line number:846
9023 [7] file:String.cc; line number:735
9025 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9026 Breakpoint 2 at 0xb344: file String.cc, line 875.
9027 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9028 Multiple breakpoints were set.
9029 Use the "delete" command to delete unwanted
9036 @kindex set multiple-symbols
9037 @item set multiple-symbols @var{mode}
9038 @cindex multiple-symbols menu
9040 This option allows you to adjust the debugger behavior when an expression
9043 By default, @var{mode} is set to @code{all}. If the command with which
9044 the expression is used allows more than one choice, then @value{GDBN}
9045 automatically selects all possible choices. For instance, inserting
9046 a breakpoint on a function using an ambiguous name results in a breakpoint
9047 inserted on each possible match. However, if a unique choice must be made,
9048 then @value{GDBN} uses the menu to help you disambiguate the expression.
9049 For instance, printing the address of an overloaded function will result
9050 in the use of the menu.
9052 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9053 when an ambiguity is detected.
9055 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9056 an error due to the ambiguity and the command is aborted.
9058 @kindex show multiple-symbols
9059 @item show multiple-symbols
9060 Show the current value of the @code{multiple-symbols} setting.
9064 @section Program Variables
9066 The most common kind of expression to use is the name of a variable
9069 Variables in expressions are understood in the selected stack frame
9070 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9074 global (or file-static)
9081 visible according to the scope rules of the
9082 programming language from the point of execution in that frame
9085 @noindent This means that in the function
9100 you can examine and use the variable @code{a} whenever your program is
9101 executing within the function @code{foo}, but you can only use or
9102 examine the variable @code{b} while your program is executing inside
9103 the block where @code{b} is declared.
9105 @cindex variable name conflict
9106 There is an exception: you can refer to a variable or function whose
9107 scope is a single source file even if the current execution point is not
9108 in this file. But it is possible to have more than one such variable or
9109 function with the same name (in different source files). If that
9110 happens, referring to that name has unpredictable effects. If you wish,
9111 you can specify a static variable in a particular function or file by
9112 using the colon-colon (@code{::}) notation:
9114 @cindex colon-colon, context for variables/functions
9116 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9117 @cindex @code{::}, context for variables/functions
9120 @var{file}::@var{variable}
9121 @var{function}::@var{variable}
9125 Here @var{file} or @var{function} is the name of the context for the
9126 static @var{variable}. In the case of file names, you can use quotes to
9127 make sure @value{GDBN} parses the file name as a single word---for example,
9128 to print a global value of @code{x} defined in @file{f2.c}:
9131 (@value{GDBP}) p 'f2.c'::x
9134 The @code{::} notation is normally used for referring to
9135 static variables, since you typically disambiguate uses of local variables
9136 in functions by selecting the appropriate frame and using the
9137 simple name of the variable. However, you may also use this notation
9138 to refer to local variables in frames enclosing the selected frame:
9147 process (a); /* Stop here */
9158 For example, if there is a breakpoint at the commented line,
9159 here is what you might see
9160 when the program stops after executing the call @code{bar(0)}:
9165 (@value{GDBP}) p bar::a
9168 #2 0x080483d0 in foo (a=5) at foobar.c:12
9171 (@value{GDBP}) p bar::a
9175 @cindex C@t{++} scope resolution
9176 These uses of @samp{::} are very rarely in conflict with the very
9177 similar use of the same notation in C@t{++}. When they are in
9178 conflict, the C@t{++} meaning takes precedence; however, this can be
9179 overridden by quoting the file or function name with single quotes.
9181 For example, suppose the program is stopped in a method of a class
9182 that has a field named @code{includefile}, and there is also an
9183 include file named @file{includefile} that defines a variable,
9187 (@value{GDBP}) p includefile
9189 (@value{GDBP}) p includefile::some_global
9190 A syntax error in expression, near `'.
9191 (@value{GDBP}) p 'includefile'::some_global
9195 @cindex wrong values
9196 @cindex variable values, wrong
9197 @cindex function entry/exit, wrong values of variables
9198 @cindex optimized code, wrong values of variables
9200 @emph{Warning:} Occasionally, a local variable may appear to have the
9201 wrong value at certain points in a function---just after entry to a new
9202 scope, and just before exit.
9204 You may see this problem when you are stepping by machine instructions.
9205 This is because, on most machines, it takes more than one instruction to
9206 set up a stack frame (including local variable definitions); if you are
9207 stepping by machine instructions, variables may appear to have the wrong
9208 values until the stack frame is completely built. On exit, it usually
9209 also takes more than one machine instruction to destroy a stack frame;
9210 after you begin stepping through that group of instructions, local
9211 variable definitions may be gone.
9213 This may also happen when the compiler does significant optimizations.
9214 To be sure of always seeing accurate values, turn off all optimization
9217 @cindex ``No symbol "foo" in current context''
9218 Another possible effect of compiler optimizations is to optimize
9219 unused variables out of existence, or assign variables to registers (as
9220 opposed to memory addresses). Depending on the support for such cases
9221 offered by the debug info format used by the compiler, @value{GDBN}
9222 might not be able to display values for such local variables. If that
9223 happens, @value{GDBN} will print a message like this:
9226 No symbol "foo" in current context.
9229 To solve such problems, either recompile without optimizations, or use a
9230 different debug info format, if the compiler supports several such
9231 formats. @xref{Compilation}, for more information on choosing compiler
9232 options. @xref{C, ,C and C@t{++}}, for more information about debug
9233 info formats that are best suited to C@t{++} programs.
9235 If you ask to print an object whose contents are unknown to
9236 @value{GDBN}, e.g., because its data type is not completely specified
9237 by the debug information, @value{GDBN} will say @samp{<incomplete
9238 type>}. @xref{Symbols, incomplete type}, for more about this.
9240 @cindex no debug info variables
9241 If you try to examine or use the value of a (global) variable for
9242 which @value{GDBN} has no type information, e.g., because the program
9243 includes no debug information, @value{GDBN} displays an error message.
9244 @xref{Symbols, unknown type}, for more about unknown types. If you
9245 cast the variable to its declared type, @value{GDBN} gets the
9246 variable's value using the cast-to type as the variable's type. For
9247 example, in a C program:
9250 (@value{GDBP}) p var
9251 'var' has unknown type; cast it to its declared type
9252 (@value{GDBP}) p (float) var
9256 If you append @kbd{@@entry} string to a function parameter name you get its
9257 value at the time the function got called. If the value is not available an
9258 error message is printed. Entry values are available only with some compilers.
9259 Entry values are normally also printed at the function parameter list according
9260 to @ref{set print entry-values}.
9263 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9269 (gdb) print i@@entry
9273 Strings are identified as arrays of @code{char} values without specified
9274 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9275 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9276 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9277 defines literal string type @code{"char"} as @code{char} without a sign.
9282 signed char var1[] = "A";
9285 You get during debugging
9290 $2 = @{65 'A', 0 '\0'@}
9294 @section Artificial Arrays
9296 @cindex artificial array
9298 @kindex @@@r{, referencing memory as an array}
9299 It is often useful to print out several successive objects of the
9300 same type in memory; a section of an array, or an array of
9301 dynamically determined size for which only a pointer exists in the
9304 You can do this by referring to a contiguous span of memory as an
9305 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9306 operand of @samp{@@} should be the first element of the desired array
9307 and be an individual object. The right operand should be the desired length
9308 of the array. The result is an array value whose elements are all of
9309 the type of the left argument. The first element is actually the left
9310 argument; the second element comes from bytes of memory immediately
9311 following those that hold the first element, and so on. Here is an
9312 example. If a program says
9315 int *array = (int *) malloc (len * sizeof (int));
9319 you can print the contents of @code{array} with
9325 The left operand of @samp{@@} must reside in memory. Array values made
9326 with @samp{@@} in this way behave just like other arrays in terms of
9327 subscripting, and are coerced to pointers when used in expressions.
9328 Artificial arrays most often appear in expressions via the value history
9329 (@pxref{Value History, ,Value History}), after printing one out.
9331 Another way to create an artificial array is to use a cast.
9332 This re-interprets a value as if it were an array.
9333 The value need not be in memory:
9335 (@value{GDBP}) p/x (short[2])0x12345678
9336 $1 = @{0x1234, 0x5678@}
9339 As a convenience, if you leave the array length out (as in
9340 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9341 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9343 (@value{GDBP}) p/x (short[])0x12345678
9344 $2 = @{0x1234, 0x5678@}
9347 Sometimes the artificial array mechanism is not quite enough; in
9348 moderately complex data structures, the elements of interest may not
9349 actually be adjacent---for example, if you are interested in the values
9350 of pointers in an array. One useful work-around in this situation is
9351 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9352 Variables}) as a counter in an expression that prints the first
9353 interesting value, and then repeat that expression via @key{RET}. For
9354 instance, suppose you have an array @code{dtab} of pointers to
9355 structures, and you are interested in the values of a field @code{fv}
9356 in each structure. Here is an example of what you might type:
9366 @node Output Formats
9367 @section Output Formats
9369 @cindex formatted output
9370 @cindex output formats
9371 By default, @value{GDBN} prints a value according to its data type. Sometimes
9372 this is not what you want. For example, you might want to print a number
9373 in hex, or a pointer in decimal. Or you might want to view data in memory
9374 at a certain address as a character string or as an instruction. To do
9375 these things, specify an @dfn{output format} when you print a value.
9377 The simplest use of output formats is to say how to print a value
9378 already computed. This is done by starting the arguments of the
9379 @code{print} command with a slash and a format letter. The format
9380 letters supported are:
9384 Regard the bits of the value as an integer, and print the integer in
9388 Print as integer in signed decimal.
9391 Print as integer in unsigned decimal.
9394 Print as integer in octal.
9397 Print as integer in binary. The letter @samp{t} stands for ``two''.
9398 @footnote{@samp{b} cannot be used because these format letters are also
9399 used with the @code{x} command, where @samp{b} stands for ``byte'';
9400 see @ref{Memory,,Examining Memory}.}
9403 @cindex unknown address, locating
9404 @cindex locate address
9405 Print as an address, both absolute in hexadecimal and as an offset from
9406 the nearest preceding symbol. You can use this format used to discover
9407 where (in what function) an unknown address is located:
9410 (@value{GDBP}) p/a 0x54320
9411 $3 = 0x54320 <_initialize_vx+396>
9415 The command @code{info symbol 0x54320} yields similar results.
9416 @xref{Symbols, info symbol}.
9419 Regard as an integer and print it as a character constant. This
9420 prints both the numerical value and its character representation. The
9421 character representation is replaced with the octal escape @samp{\nnn}
9422 for characters outside the 7-bit @sc{ascii} range.
9424 Without this format, @value{GDBN} displays @code{char},
9425 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9426 constants. Single-byte members of vectors are displayed as integer
9430 Regard the bits of the value as a floating point number and print
9431 using typical floating point syntax.
9434 @cindex printing strings
9435 @cindex printing byte arrays
9436 Regard as a string, if possible. With this format, pointers to single-byte
9437 data are displayed as null-terminated strings and arrays of single-byte data
9438 are displayed as fixed-length strings. Other values are displayed in their
9441 Without this format, @value{GDBN} displays pointers to and arrays of
9442 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9443 strings. Single-byte members of a vector are displayed as an integer
9447 Like @samp{x} formatting, the value is treated as an integer and
9448 printed as hexadecimal, but leading zeros are printed to pad the value
9449 to the size of the integer type.
9452 @cindex raw printing
9453 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9454 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9455 Printing}). This typically results in a higher-level display of the
9456 value's contents. The @samp{r} format bypasses any Python
9457 pretty-printer which might exist.
9460 For example, to print the program counter in hex (@pxref{Registers}), type
9467 Note that no space is required before the slash; this is because command
9468 names in @value{GDBN} cannot contain a slash.
9470 To reprint the last value in the value history with a different format,
9471 you can use the @code{print} command with just a format and no
9472 expression. For example, @samp{p/x} reprints the last value in hex.
9475 @section Examining Memory
9477 You can use the command @code{x} (for ``examine'') to examine memory in
9478 any of several formats, independently of your program's data types.
9480 @cindex examining memory
9482 @kindex x @r{(examine memory)}
9483 @item x/@var{nfu} @var{addr}
9486 Use the @code{x} command to examine memory.
9489 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9490 much memory to display and how to format it; @var{addr} is an
9491 expression giving the address where you want to start displaying memory.
9492 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9493 Several commands set convenient defaults for @var{addr}.
9496 @item @var{n}, the repeat count
9497 The repeat count is a decimal integer; the default is 1. It specifies
9498 how much memory (counting by units @var{u}) to display. If a negative
9499 number is specified, memory is examined backward from @var{addr}.
9500 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9503 @item @var{f}, the display format
9504 The display format is one of the formats used by @code{print}
9505 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9506 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9507 The default is @samp{x} (hexadecimal) initially. The default changes
9508 each time you use either @code{x} or @code{print}.
9510 @item @var{u}, the unit size
9511 The unit size is any of
9517 Halfwords (two bytes).
9519 Words (four bytes). This is the initial default.
9521 Giant words (eight bytes).
9524 Each time you specify a unit size with @code{x}, that size becomes the
9525 default unit the next time you use @code{x}. For the @samp{i} format,
9526 the unit size is ignored and is normally not written. For the @samp{s} format,
9527 the unit size defaults to @samp{b}, unless it is explicitly given.
9528 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9529 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9530 Note that the results depend on the programming language of the
9531 current compilation unit. If the language is C, the @samp{s}
9532 modifier will use the UTF-16 encoding while @samp{w} will use
9533 UTF-32. The encoding is set by the programming language and cannot
9536 @item @var{addr}, starting display address
9537 @var{addr} is the address where you want @value{GDBN} to begin displaying
9538 memory. The expression need not have a pointer value (though it may);
9539 it is always interpreted as an integer address of a byte of memory.
9540 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9541 @var{addr} is usually just after the last address examined---but several
9542 other commands also set the default address: @code{info breakpoints} (to
9543 the address of the last breakpoint listed), @code{info line} (to the
9544 starting address of a line), and @code{print} (if you use it to display
9545 a value from memory).
9548 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9549 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9550 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9551 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9552 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9554 You can also specify a negative repeat count to examine memory backward
9555 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9556 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9558 Since the letters indicating unit sizes are all distinct from the
9559 letters specifying output formats, you do not have to remember whether
9560 unit size or format comes first; either order works. The output
9561 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9562 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9564 Even though the unit size @var{u} is ignored for the formats @samp{s}
9565 and @samp{i}, you might still want to use a count @var{n}; for example,
9566 @samp{3i} specifies that you want to see three machine instructions,
9567 including any operands. For convenience, especially when used with
9568 the @code{display} command, the @samp{i} format also prints branch delay
9569 slot instructions, if any, beyond the count specified, which immediately
9570 follow the last instruction that is within the count. The command
9571 @code{disassemble} gives an alternative way of inspecting machine
9572 instructions; see @ref{Machine Code,,Source and Machine Code}.
9574 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9575 the command displays null-terminated strings or instructions before the given
9576 address as many as the absolute value of the given number. For the @samp{i}
9577 format, we use line number information in the debug info to accurately locate
9578 instruction boundaries while disassembling backward. If line info is not
9579 available, the command stops examining memory with an error message.
9581 All the defaults for the arguments to @code{x} are designed to make it
9582 easy to continue scanning memory with minimal specifications each time
9583 you use @code{x}. For example, after you have inspected three machine
9584 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9585 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9586 the repeat count @var{n} is used again; the other arguments default as
9587 for successive uses of @code{x}.
9589 When examining machine instructions, the instruction at current program
9590 counter is shown with a @code{=>} marker. For example:
9593 (@value{GDBP}) x/5i $pc-6
9594 0x804837f <main+11>: mov %esp,%ebp
9595 0x8048381 <main+13>: push %ecx
9596 0x8048382 <main+14>: sub $0x4,%esp
9597 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9598 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9601 @cindex @code{$_}, @code{$__}, and value history
9602 The addresses and contents printed by the @code{x} command are not saved
9603 in the value history because there is often too much of them and they
9604 would get in the way. Instead, @value{GDBN} makes these values available for
9605 subsequent use in expressions as values of the convenience variables
9606 @code{$_} and @code{$__}. After an @code{x} command, the last address
9607 examined is available for use in expressions in the convenience variable
9608 @code{$_}. The contents of that address, as examined, are available in
9609 the convenience variable @code{$__}.
9611 If the @code{x} command has a repeat count, the address and contents saved
9612 are from the last memory unit printed; this is not the same as the last
9613 address printed if several units were printed on the last line of output.
9615 @anchor{addressable memory unit}
9616 @cindex addressable memory unit
9617 Most targets have an addressable memory unit size of 8 bits. This means
9618 that to each memory address are associated 8 bits of data. Some
9619 targets, however, have other addressable memory unit sizes.
9620 Within @value{GDBN} and this document, the term
9621 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9622 when explicitly referring to a chunk of data of that size. The word
9623 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9624 the addressable memory unit size of the target. For most systems,
9625 addressable memory unit is a synonym of byte.
9627 @cindex remote memory comparison
9628 @cindex target memory comparison
9629 @cindex verify remote memory image
9630 @cindex verify target memory image
9631 When you are debugging a program running on a remote target machine
9632 (@pxref{Remote Debugging}), you may wish to verify the program's image
9633 in the remote machine's memory against the executable file you
9634 downloaded to the target. Or, on any target, you may want to check
9635 whether the program has corrupted its own read-only sections. The
9636 @code{compare-sections} command is provided for such situations.
9639 @kindex compare-sections
9640 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9641 Compare the data of a loadable section @var{section-name} in the
9642 executable file of the program being debugged with the same section in
9643 the target machine's memory, and report any mismatches. With no
9644 arguments, compares all loadable sections. With an argument of
9645 @code{-r}, compares all loadable read-only sections.
9647 Note: for remote targets, this command can be accelerated if the
9648 target supports computing the CRC checksum of a block of memory
9649 (@pxref{qCRC packet}).
9653 @section Automatic Display
9654 @cindex automatic display
9655 @cindex display of expressions
9657 If you find that you want to print the value of an expression frequently
9658 (to see how it changes), you might want to add it to the @dfn{automatic
9659 display list} so that @value{GDBN} prints its value each time your program stops.
9660 Each expression added to the list is given a number to identify it;
9661 to remove an expression from the list, you specify that number.
9662 The automatic display looks like this:
9666 3: bar[5] = (struct hack *) 0x3804
9670 This display shows item numbers, expressions and their current values. As with
9671 displays you request manually using @code{x} or @code{print}, you can
9672 specify the output format you prefer; in fact, @code{display} decides
9673 whether to use @code{print} or @code{x} depending your format
9674 specification---it uses @code{x} if you specify either the @samp{i}
9675 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9679 @item display @var{expr}
9680 Add the expression @var{expr} to the list of expressions to display
9681 each time your program stops. @xref{Expressions, ,Expressions}.
9683 @code{display} does not repeat if you press @key{RET} again after using it.
9685 @item display/@var{fmt} @var{expr}
9686 For @var{fmt} specifying only a display format and not a size or
9687 count, add the expression @var{expr} to the auto-display list but
9688 arrange to display it each time in the specified format @var{fmt}.
9689 @xref{Output Formats,,Output Formats}.
9691 @item display/@var{fmt} @var{addr}
9692 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9693 number of units, add the expression @var{addr} as a memory address to
9694 be examined each time your program stops. Examining means in effect
9695 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9698 For example, @samp{display/i $pc} can be helpful, to see the machine
9699 instruction about to be executed each time execution stops (@samp{$pc}
9700 is a common name for the program counter; @pxref{Registers, ,Registers}).
9703 @kindex delete display
9705 @item undisplay @var{dnums}@dots{}
9706 @itemx delete display @var{dnums}@dots{}
9707 Remove items from the list of expressions to display. Specify the
9708 numbers of the displays that you want affected with the command
9709 argument @var{dnums}. It can be a single display number, one of the
9710 numbers shown in the first field of the @samp{info display} display;
9711 or it could be a range of display numbers, as in @code{2-4}.
9713 @code{undisplay} does not repeat if you press @key{RET} after using it.
9714 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9716 @kindex disable display
9717 @item disable display @var{dnums}@dots{}
9718 Disable the display of item numbers @var{dnums}. A disabled display
9719 item is not printed automatically, but is not forgotten. It may be
9720 enabled again later. Specify the numbers of the displays that you
9721 want affected with the command argument @var{dnums}. It can be a
9722 single display number, one of the numbers shown in the first field of
9723 the @samp{info display} display; or it could be a range of display
9724 numbers, as in @code{2-4}.
9726 @kindex enable display
9727 @item enable display @var{dnums}@dots{}
9728 Enable display of item numbers @var{dnums}. It becomes effective once
9729 again in auto display of its expression, until you specify otherwise.
9730 Specify the numbers of the displays that you want affected with the
9731 command argument @var{dnums}. It can be a single display number, one
9732 of the numbers shown in the first field of the @samp{info display}
9733 display; or it could be a range of display numbers, as in @code{2-4}.
9736 Display the current values of the expressions on the list, just as is
9737 done when your program stops.
9739 @kindex info display
9741 Print the list of expressions previously set up to display
9742 automatically, each one with its item number, but without showing the
9743 values. This includes disabled expressions, which are marked as such.
9744 It also includes expressions which would not be displayed right now
9745 because they refer to automatic variables not currently available.
9748 @cindex display disabled out of scope
9749 If a display expression refers to local variables, then it does not make
9750 sense outside the lexical context for which it was set up. Such an
9751 expression is disabled when execution enters a context where one of its
9752 variables is not defined. For example, if you give the command
9753 @code{display last_char} while inside a function with an argument
9754 @code{last_char}, @value{GDBN} displays this argument while your program
9755 continues to stop inside that function. When it stops elsewhere---where
9756 there is no variable @code{last_char}---the display is disabled
9757 automatically. The next time your program stops where @code{last_char}
9758 is meaningful, you can enable the display expression once again.
9760 @node Print Settings
9761 @section Print Settings
9763 @cindex format options
9764 @cindex print settings
9765 @value{GDBN} provides the following ways to control how arrays, structures,
9766 and symbols are printed.
9769 These settings are useful for debugging programs in any language:
9773 @item set print address
9774 @itemx set print address on
9775 @cindex print/don't print memory addresses
9776 @value{GDBN} prints memory addresses showing the location of stack
9777 traces, structure values, pointer values, breakpoints, and so forth,
9778 even when it also displays the contents of those addresses. The default
9779 is @code{on}. For example, this is what a stack frame display looks like with
9780 @code{set print address on}:
9785 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9787 530 if (lquote != def_lquote)
9791 @item set print address off
9792 Do not print addresses when displaying their contents. For example,
9793 this is the same stack frame displayed with @code{set print address off}:
9797 (@value{GDBP}) set print addr off
9799 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9800 530 if (lquote != def_lquote)
9804 You can use @samp{set print address off} to eliminate all machine
9805 dependent displays from the @value{GDBN} interface. For example, with
9806 @code{print address off}, you should get the same text for backtraces on
9807 all machines---whether or not they involve pointer arguments.
9810 @item show print address
9811 Show whether or not addresses are to be printed.
9814 When @value{GDBN} prints a symbolic address, it normally prints the
9815 closest earlier symbol plus an offset. If that symbol does not uniquely
9816 identify the address (for example, it is a name whose scope is a single
9817 source file), you may need to clarify. One way to do this is with
9818 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9819 you can set @value{GDBN} to print the source file and line number when
9820 it prints a symbolic address:
9823 @item set print symbol-filename on
9824 @cindex source file and line of a symbol
9825 @cindex symbol, source file and line
9826 Tell @value{GDBN} to print the source file name and line number of a
9827 symbol in the symbolic form of an address.
9829 @item set print symbol-filename off
9830 Do not print source file name and line number of a symbol. This is the
9833 @item show print symbol-filename
9834 Show whether or not @value{GDBN} will print the source file name and
9835 line number of a symbol in the symbolic form of an address.
9838 Another situation where it is helpful to show symbol filenames and line
9839 numbers is when disassembling code; @value{GDBN} shows you the line
9840 number and source file that corresponds to each instruction.
9842 Also, you may wish to see the symbolic form only if the address being
9843 printed is reasonably close to the closest earlier symbol:
9846 @item set print max-symbolic-offset @var{max-offset}
9847 @itemx set print max-symbolic-offset unlimited
9848 @cindex maximum value for offset of closest symbol
9849 Tell @value{GDBN} to only display the symbolic form of an address if the
9850 offset between the closest earlier symbol and the address is less than
9851 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9852 to always print the symbolic form of an address if any symbol precedes
9853 it. Zero is equivalent to @code{unlimited}.
9855 @item show print max-symbolic-offset
9856 Ask how large the maximum offset is that @value{GDBN} prints in a
9860 @cindex wild pointer, interpreting
9861 @cindex pointer, finding referent
9862 If you have a pointer and you are not sure where it points, try
9863 @samp{set print symbol-filename on}. Then you can determine the name
9864 and source file location of the variable where it points, using
9865 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9866 For example, here @value{GDBN} shows that a variable @code{ptt} points
9867 at another variable @code{t}, defined in @file{hi2.c}:
9870 (@value{GDBP}) set print symbol-filename on
9871 (@value{GDBP}) p/a ptt
9872 $4 = 0xe008 <t in hi2.c>
9876 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9877 does not show the symbol name and filename of the referent, even with
9878 the appropriate @code{set print} options turned on.
9881 You can also enable @samp{/a}-like formatting all the time using
9882 @samp{set print symbol on}:
9885 @item set print symbol on
9886 Tell @value{GDBN} to print the symbol corresponding to an address, if
9889 @item set print symbol off
9890 Tell @value{GDBN} not to print the symbol corresponding to an
9891 address. In this mode, @value{GDBN} will still print the symbol
9892 corresponding to pointers to functions. This is the default.
9894 @item show print symbol
9895 Show whether @value{GDBN} will display the symbol corresponding to an
9899 Other settings control how different kinds of objects are printed:
9902 @item set print array
9903 @itemx set print array on
9904 @cindex pretty print arrays
9905 Pretty print arrays. This format is more convenient to read,
9906 but uses more space. The default is off.
9908 @item set print array off
9909 Return to compressed format for arrays.
9911 @item show print array
9912 Show whether compressed or pretty format is selected for displaying
9915 @cindex print array indexes
9916 @item set print array-indexes
9917 @itemx set print array-indexes on
9918 Print the index of each element when displaying arrays. May be more
9919 convenient to locate a given element in the array or quickly find the
9920 index of a given element in that printed array. The default is off.
9922 @item set print array-indexes off
9923 Stop printing element indexes when displaying arrays.
9925 @item show print array-indexes
9926 Show whether the index of each element is printed when displaying
9929 @item set print elements @var{number-of-elements}
9930 @itemx set print elements unlimited
9931 @cindex number of array elements to print
9932 @cindex limit on number of printed array elements
9933 Set a limit on how many elements of an array @value{GDBN} will print.
9934 If @value{GDBN} is printing a large array, it stops printing after it has
9935 printed the number of elements set by the @code{set print elements} command.
9936 This limit also applies to the display of strings.
9937 When @value{GDBN} starts, this limit is set to 200.
9938 Setting @var{number-of-elements} to @code{unlimited} or zero means
9939 that the number of elements to print is unlimited.
9941 @item show print elements
9942 Display the number of elements of a large array that @value{GDBN} will print.
9943 If the number is 0, then the printing is unlimited.
9945 @item set print frame-arguments @var{value}
9946 @kindex set print frame-arguments
9947 @cindex printing frame argument values
9948 @cindex print all frame argument values
9949 @cindex print frame argument values for scalars only
9950 @cindex do not print frame argument values
9951 This command allows to control how the values of arguments are printed
9952 when the debugger prints a frame (@pxref{Frames}). The possible
9957 The values of all arguments are printed.
9960 Print the value of an argument only if it is a scalar. The value of more
9961 complex arguments such as arrays, structures, unions, etc, is replaced
9962 by @code{@dots{}}. This is the default. Here is an example where
9963 only scalar arguments are shown:
9966 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9971 None of the argument values are printed. Instead, the value of each argument
9972 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9975 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9980 By default, only scalar arguments are printed. This command can be used
9981 to configure the debugger to print the value of all arguments, regardless
9982 of their type. However, it is often advantageous to not print the value
9983 of more complex parameters. For instance, it reduces the amount of
9984 information printed in each frame, making the backtrace more readable.
9985 Also, it improves performance when displaying Ada frames, because
9986 the computation of large arguments can sometimes be CPU-intensive,
9987 especially in large applications. Setting @code{print frame-arguments}
9988 to @code{scalars} (the default) or @code{none} avoids this computation,
9989 thus speeding up the display of each Ada frame.
9991 @item show print frame-arguments
9992 Show how the value of arguments should be displayed when printing a frame.
9994 @item set print raw frame-arguments on
9995 Print frame arguments in raw, non pretty-printed, form.
9997 @item set print raw frame-arguments off
9998 Print frame arguments in pretty-printed form, if there is a pretty-printer
9999 for the value (@pxref{Pretty Printing}),
10000 otherwise print the value in raw form.
10001 This is the default.
10003 @item show print raw frame-arguments
10004 Show whether to print frame arguments in raw form.
10006 @anchor{set print entry-values}
10007 @item set print entry-values @var{value}
10008 @kindex set print entry-values
10009 Set printing of frame argument values at function entry. In some cases
10010 @value{GDBN} can determine the value of function argument which was passed by
10011 the function caller, even if the value was modified inside the called function
10012 and therefore is different. With optimized code, the current value could be
10013 unavailable, but the entry value may still be known.
10015 The default value is @code{default} (see below for its description). Older
10016 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10017 this feature will behave in the @code{default} setting the same way as with the
10020 This functionality is currently supported only by DWARF 2 debugging format and
10021 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10022 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10025 The @var{value} parameter can be one of the following:
10029 Print only actual parameter values, never print values from function entry
10033 #0 different (val=6)
10034 #0 lost (val=<optimized out>)
10036 #0 invalid (val=<optimized out>)
10040 Print only parameter values from function entry point. The actual parameter
10041 values are never printed.
10043 #0 equal (val@@entry=5)
10044 #0 different (val@@entry=5)
10045 #0 lost (val@@entry=5)
10046 #0 born (val@@entry=<optimized out>)
10047 #0 invalid (val@@entry=<optimized out>)
10051 Print only parameter values from function entry point. If value from function
10052 entry point is not known while the actual value is known, print the actual
10053 value for such parameter.
10055 #0 equal (val@@entry=5)
10056 #0 different (val@@entry=5)
10057 #0 lost (val@@entry=5)
10059 #0 invalid (val@@entry=<optimized out>)
10063 Print actual parameter values. If actual parameter value is not known while
10064 value from function entry point is known, print the entry point value for such
10068 #0 different (val=6)
10069 #0 lost (val@@entry=5)
10071 #0 invalid (val=<optimized out>)
10075 Always print both the actual parameter value and its value from function entry
10076 point, even if values of one or both are not available due to compiler
10079 #0 equal (val=5, val@@entry=5)
10080 #0 different (val=6, val@@entry=5)
10081 #0 lost (val=<optimized out>, val@@entry=5)
10082 #0 born (val=10, val@@entry=<optimized out>)
10083 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10087 Print the actual parameter value if it is known and also its value from
10088 function entry point if it is known. If neither is known, print for the actual
10089 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10090 values are known and identical, print the shortened
10091 @code{param=param@@entry=VALUE} notation.
10093 #0 equal (val=val@@entry=5)
10094 #0 different (val=6, val@@entry=5)
10095 #0 lost (val@@entry=5)
10097 #0 invalid (val=<optimized out>)
10101 Always print the actual parameter value. Print also its value from function
10102 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10103 if both values are known and identical, print the shortened
10104 @code{param=param@@entry=VALUE} notation.
10106 #0 equal (val=val@@entry=5)
10107 #0 different (val=6, val@@entry=5)
10108 #0 lost (val=<optimized out>, val@@entry=5)
10110 #0 invalid (val=<optimized out>)
10114 For analysis messages on possible failures of frame argument values at function
10115 entry resolution see @ref{set debug entry-values}.
10117 @item show print entry-values
10118 Show the method being used for printing of frame argument values at function
10121 @item set print repeats @var{number-of-repeats}
10122 @itemx set print repeats unlimited
10123 @cindex repeated array elements
10124 Set the threshold for suppressing display of repeated array
10125 elements. When the number of consecutive identical elements of an
10126 array exceeds the threshold, @value{GDBN} prints the string
10127 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10128 identical repetitions, instead of displaying the identical elements
10129 themselves. Setting the threshold to @code{unlimited} or zero will
10130 cause all elements to be individually printed. The default threshold
10133 @item show print repeats
10134 Display the current threshold for printing repeated identical
10137 @item set print null-stop
10138 @cindex @sc{null} elements in arrays
10139 Cause @value{GDBN} to stop printing the characters of an array when the first
10140 @sc{null} is encountered. This is useful when large arrays actually
10141 contain only short strings.
10142 The default is off.
10144 @item show print null-stop
10145 Show whether @value{GDBN} stops printing an array on the first
10146 @sc{null} character.
10148 @item set print pretty on
10149 @cindex print structures in indented form
10150 @cindex indentation in structure display
10151 Cause @value{GDBN} to print structures in an indented format with one member
10152 per line, like this:
10167 @item set print pretty off
10168 Cause @value{GDBN} to print structures in a compact format, like this:
10172 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10173 meat = 0x54 "Pork"@}
10178 This is the default format.
10180 @item show print pretty
10181 Show which format @value{GDBN} is using to print structures.
10183 @item set print sevenbit-strings on
10184 @cindex eight-bit characters in strings
10185 @cindex octal escapes in strings
10186 Print using only seven-bit characters; if this option is set,
10187 @value{GDBN} displays any eight-bit characters (in strings or
10188 character values) using the notation @code{\}@var{nnn}. This setting is
10189 best if you are working in English (@sc{ascii}) and you use the
10190 high-order bit of characters as a marker or ``meta'' bit.
10192 @item set print sevenbit-strings off
10193 Print full eight-bit characters. This allows the use of more
10194 international character sets, and is the default.
10196 @item show print sevenbit-strings
10197 Show whether or not @value{GDBN} is printing only seven-bit characters.
10199 @item set print union on
10200 @cindex unions in structures, printing
10201 Tell @value{GDBN} to print unions which are contained in structures
10202 and other unions. This is the default setting.
10204 @item set print union off
10205 Tell @value{GDBN} not to print unions which are contained in
10206 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10209 @item show print union
10210 Ask @value{GDBN} whether or not it will print unions which are contained in
10211 structures and other unions.
10213 For example, given the declarations
10216 typedef enum @{Tree, Bug@} Species;
10217 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10218 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10229 struct thing foo = @{Tree, @{Acorn@}@};
10233 with @code{set print union on} in effect @samp{p foo} would print
10236 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10240 and with @code{set print union off} in effect it would print
10243 $1 = @{it = Tree, form = @{...@}@}
10247 @code{set print union} affects programs written in C-like languages
10253 These settings are of interest when debugging C@t{++} programs:
10256 @cindex demangling C@t{++} names
10257 @item set print demangle
10258 @itemx set print demangle on
10259 Print C@t{++} names in their source form rather than in the encoded
10260 (``mangled'') form passed to the assembler and linker for type-safe
10261 linkage. The default is on.
10263 @item show print demangle
10264 Show whether C@t{++} names are printed in mangled or demangled form.
10266 @item set print asm-demangle
10267 @itemx set print asm-demangle on
10268 Print C@t{++} names in their source form rather than their mangled form, even
10269 in assembler code printouts such as instruction disassemblies.
10270 The default is off.
10272 @item show print asm-demangle
10273 Show whether C@t{++} names in assembly listings are printed in mangled
10276 @cindex C@t{++} symbol decoding style
10277 @cindex symbol decoding style, C@t{++}
10278 @kindex set demangle-style
10279 @item set demangle-style @var{style}
10280 Choose among several encoding schemes used by different compilers to
10281 represent C@t{++} names. The choices for @var{style} are currently:
10285 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10286 This is the default.
10289 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10292 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10295 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10298 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10299 @strong{Warning:} this setting alone is not sufficient to allow
10300 debugging @code{cfront}-generated executables. @value{GDBN} would
10301 require further enhancement to permit that.
10304 If you omit @var{style}, you will see a list of possible formats.
10306 @item show demangle-style
10307 Display the encoding style currently in use for decoding C@t{++} symbols.
10309 @item set print object
10310 @itemx set print object on
10311 @cindex derived type of an object, printing
10312 @cindex display derived types
10313 When displaying a pointer to an object, identify the @emph{actual}
10314 (derived) type of the object rather than the @emph{declared} type, using
10315 the virtual function table. Note that the virtual function table is
10316 required---this feature can only work for objects that have run-time
10317 type identification; a single virtual method in the object's declared
10318 type is sufficient. Note that this setting is also taken into account when
10319 working with variable objects via MI (@pxref{GDB/MI}).
10321 @item set print object off
10322 Display only the declared type of objects, without reference to the
10323 virtual function table. This is the default setting.
10325 @item show print object
10326 Show whether actual, or declared, object types are displayed.
10328 @item set print static-members
10329 @itemx set print static-members on
10330 @cindex static members of C@t{++} objects
10331 Print static members when displaying a C@t{++} object. The default is on.
10333 @item set print static-members off
10334 Do not print static members when displaying a C@t{++} object.
10336 @item show print static-members
10337 Show whether C@t{++} static members are printed or not.
10339 @item set print pascal_static-members
10340 @itemx set print pascal_static-members on
10341 @cindex static members of Pascal objects
10342 @cindex Pascal objects, static members display
10343 Print static members when displaying a Pascal object. The default is on.
10345 @item set print pascal_static-members off
10346 Do not print static members when displaying a Pascal object.
10348 @item show print pascal_static-members
10349 Show whether Pascal static members are printed or not.
10351 @c These don't work with HP ANSI C++ yet.
10352 @item set print vtbl
10353 @itemx set print vtbl on
10354 @cindex pretty print C@t{++} virtual function tables
10355 @cindex virtual functions (C@t{++}) display
10356 @cindex VTBL display
10357 Pretty print C@t{++} virtual function tables. The default is off.
10358 (The @code{vtbl} commands do not work on programs compiled with the HP
10359 ANSI C@t{++} compiler (@code{aCC}).)
10361 @item set print vtbl off
10362 Do not pretty print C@t{++} virtual function tables.
10364 @item show print vtbl
10365 Show whether C@t{++} virtual function tables are pretty printed, or not.
10368 @node Pretty Printing
10369 @section Pretty Printing
10371 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10372 Python code. It greatly simplifies the display of complex objects. This
10373 mechanism works for both MI and the CLI.
10376 * Pretty-Printer Introduction:: Introduction to pretty-printers
10377 * Pretty-Printer Example:: An example pretty-printer
10378 * Pretty-Printer Commands:: Pretty-printer commands
10381 @node Pretty-Printer Introduction
10382 @subsection Pretty-Printer Introduction
10384 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10385 registered for the value. If there is then @value{GDBN} invokes the
10386 pretty-printer to print the value. Otherwise the value is printed normally.
10388 Pretty-printers are normally named. This makes them easy to manage.
10389 The @samp{info pretty-printer} command will list all the installed
10390 pretty-printers with their names.
10391 If a pretty-printer can handle multiple data types, then its
10392 @dfn{subprinters} are the printers for the individual data types.
10393 Each such subprinter has its own name.
10394 The format of the name is @var{printer-name};@var{subprinter-name}.
10396 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10397 Typically they are automatically loaded and registered when the corresponding
10398 debug information is loaded, thus making them available without having to
10399 do anything special.
10401 There are three places where a pretty-printer can be registered.
10405 Pretty-printers registered globally are available when debugging
10409 Pretty-printers registered with a program space are available only
10410 when debugging that program.
10411 @xref{Progspaces In Python}, for more details on program spaces in Python.
10414 Pretty-printers registered with an objfile are loaded and unloaded
10415 with the corresponding objfile (e.g., shared library).
10416 @xref{Objfiles In Python}, for more details on objfiles in Python.
10419 @xref{Selecting Pretty-Printers}, for further information on how
10420 pretty-printers are selected,
10422 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10425 @node Pretty-Printer Example
10426 @subsection Pretty-Printer Example
10428 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10431 (@value{GDBP}) print s
10433 static npos = 4294967295,
10435 <std::allocator<char>> = @{
10436 <__gnu_cxx::new_allocator<char>> = @{
10437 <No data fields>@}, <No data fields>
10439 members of std::basic_string<char, std::char_traits<char>,
10440 std::allocator<char> >::_Alloc_hider:
10441 _M_p = 0x804a014 "abcd"
10446 With a pretty-printer for @code{std::string} only the contents are printed:
10449 (@value{GDBP}) print s
10453 @node Pretty-Printer Commands
10454 @subsection Pretty-Printer Commands
10455 @cindex pretty-printer commands
10458 @kindex info pretty-printer
10459 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10460 Print the list of installed pretty-printers.
10461 This includes disabled pretty-printers, which are marked as such.
10463 @var{object-regexp} is a regular expression matching the objects
10464 whose pretty-printers to list.
10465 Objects can be @code{global}, the program space's file
10466 (@pxref{Progspaces In Python}),
10467 and the object files within that program space (@pxref{Objfiles In Python}).
10468 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10469 looks up a printer from these three objects.
10471 @var{name-regexp} is a regular expression matching the name of the printers
10474 @kindex disable pretty-printer
10475 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10476 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10477 A disabled pretty-printer is not forgotten, it may be enabled again later.
10479 @kindex enable pretty-printer
10480 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10481 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10486 Suppose we have three pretty-printers installed: one from library1.so
10487 named @code{foo} that prints objects of type @code{foo}, and
10488 another from library2.so named @code{bar} that prints two types of objects,
10489 @code{bar1} and @code{bar2}.
10492 (gdb) info pretty-printer
10499 (gdb) info pretty-printer library2
10504 (gdb) disable pretty-printer library1
10506 2 of 3 printers enabled
10507 (gdb) info pretty-printer
10514 (gdb) disable pretty-printer library2 bar:bar1
10516 1 of 3 printers enabled
10517 (gdb) info pretty-printer library2
10524 (gdb) disable pretty-printer library2 bar
10526 0 of 3 printers enabled
10527 (gdb) info pretty-printer library2
10536 Note that for @code{bar} the entire printer can be disabled,
10537 as can each individual subprinter.
10539 @node Value History
10540 @section Value History
10542 @cindex value history
10543 @cindex history of values printed by @value{GDBN}
10544 Values printed by the @code{print} command are saved in the @value{GDBN}
10545 @dfn{value history}. This allows you to refer to them in other expressions.
10546 Values are kept until the symbol table is re-read or discarded
10547 (for example with the @code{file} or @code{symbol-file} commands).
10548 When the symbol table changes, the value history is discarded,
10549 since the values may contain pointers back to the types defined in the
10554 @cindex history number
10555 The values printed are given @dfn{history numbers} by which you can
10556 refer to them. These are successive integers starting with one.
10557 @code{print} shows you the history number assigned to a value by
10558 printing @samp{$@var{num} = } before the value; here @var{num} is the
10561 To refer to any previous value, use @samp{$} followed by the value's
10562 history number. The way @code{print} labels its output is designed to
10563 remind you of this. Just @code{$} refers to the most recent value in
10564 the history, and @code{$$} refers to the value before that.
10565 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10566 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10567 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10569 For example, suppose you have just printed a pointer to a structure and
10570 want to see the contents of the structure. It suffices to type
10576 If you have a chain of structures where the component @code{next} points
10577 to the next one, you can print the contents of the next one with this:
10584 You can print successive links in the chain by repeating this
10585 command---which you can do by just typing @key{RET}.
10587 Note that the history records values, not expressions. If the value of
10588 @code{x} is 4 and you type these commands:
10596 then the value recorded in the value history by the @code{print} command
10597 remains 4 even though the value of @code{x} has changed.
10600 @kindex show values
10602 Print the last ten values in the value history, with their item numbers.
10603 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10604 values} does not change the history.
10606 @item show values @var{n}
10607 Print ten history values centered on history item number @var{n}.
10609 @item show values +
10610 Print ten history values just after the values last printed. If no more
10611 values are available, @code{show values +} produces no display.
10614 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10615 same effect as @samp{show values +}.
10617 @node Convenience Vars
10618 @section Convenience Variables
10620 @cindex convenience variables
10621 @cindex user-defined variables
10622 @value{GDBN} provides @dfn{convenience variables} that you can use within
10623 @value{GDBN} to hold on to a value and refer to it later. These variables
10624 exist entirely within @value{GDBN}; they are not part of your program, and
10625 setting a convenience variable has no direct effect on further execution
10626 of your program. That is why you can use them freely.
10628 Convenience variables are prefixed with @samp{$}. Any name preceded by
10629 @samp{$} can be used for a convenience variable, unless it is one of
10630 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10631 (Value history references, in contrast, are @emph{numbers} preceded
10632 by @samp{$}. @xref{Value History, ,Value History}.)
10634 You can save a value in a convenience variable with an assignment
10635 expression, just as you would set a variable in your program.
10639 set $foo = *object_ptr
10643 would save in @code{$foo} the value contained in the object pointed to by
10646 Using a convenience variable for the first time creates it, but its
10647 value is @code{void} until you assign a new value. You can alter the
10648 value with another assignment at any time.
10650 Convenience variables have no fixed types. You can assign a convenience
10651 variable any type of value, including structures and arrays, even if
10652 that variable already has a value of a different type. The convenience
10653 variable, when used as an expression, has the type of its current value.
10656 @kindex show convenience
10657 @cindex show all user variables and functions
10658 @item show convenience
10659 Print a list of convenience variables used so far, and their values,
10660 as well as a list of the convenience functions.
10661 Abbreviated @code{show conv}.
10663 @kindex init-if-undefined
10664 @cindex convenience variables, initializing
10665 @item init-if-undefined $@var{variable} = @var{expression}
10666 Set a convenience variable if it has not already been set. This is useful
10667 for user-defined commands that keep some state. It is similar, in concept,
10668 to using local static variables with initializers in C (except that
10669 convenience variables are global). It can also be used to allow users to
10670 override default values used in a command script.
10672 If the variable is already defined then the expression is not evaluated so
10673 any side-effects do not occur.
10676 One of the ways to use a convenience variable is as a counter to be
10677 incremented or a pointer to be advanced. For example, to print
10678 a field from successive elements of an array of structures:
10682 print bar[$i++]->contents
10686 Repeat that command by typing @key{RET}.
10688 Some convenience variables are created automatically by @value{GDBN} and given
10689 values likely to be useful.
10692 @vindex $_@r{, convenience variable}
10694 The variable @code{$_} is automatically set by the @code{x} command to
10695 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10696 commands which provide a default address for @code{x} to examine also
10697 set @code{$_} to that address; these commands include @code{info line}
10698 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10699 except when set by the @code{x} command, in which case it is a pointer
10700 to the type of @code{$__}.
10702 @vindex $__@r{, convenience variable}
10704 The variable @code{$__} is automatically set by the @code{x} command
10705 to the value found in the last address examined. Its type is chosen
10706 to match the format in which the data was printed.
10709 @vindex $_exitcode@r{, convenience variable}
10710 When the program being debugged terminates normally, @value{GDBN}
10711 automatically sets this variable to the exit code of the program, and
10712 resets @code{$_exitsignal} to @code{void}.
10715 @vindex $_exitsignal@r{, convenience variable}
10716 When the program being debugged dies due to an uncaught signal,
10717 @value{GDBN} automatically sets this variable to that signal's number,
10718 and resets @code{$_exitcode} to @code{void}.
10720 To distinguish between whether the program being debugged has exited
10721 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10722 @code{$_exitsignal} is not @code{void}), the convenience function
10723 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10724 Functions}). For example, considering the following source code:
10727 #include <signal.h>
10730 main (int argc, char *argv[])
10737 A valid way of telling whether the program being debugged has exited
10738 or signalled would be:
10741 (@value{GDBP}) define has_exited_or_signalled
10742 Type commands for definition of ``has_exited_or_signalled''.
10743 End with a line saying just ``end''.
10744 >if $_isvoid ($_exitsignal)
10745 >echo The program has exited\n
10747 >echo The program has signalled\n
10753 Program terminated with signal SIGALRM, Alarm clock.
10754 The program no longer exists.
10755 (@value{GDBP}) has_exited_or_signalled
10756 The program has signalled
10759 As can be seen, @value{GDBN} correctly informs that the program being
10760 debugged has signalled, since it calls @code{raise} and raises a
10761 @code{SIGALRM} signal. If the program being debugged had not called
10762 @code{raise}, then @value{GDBN} would report a normal exit:
10765 (@value{GDBP}) has_exited_or_signalled
10766 The program has exited
10770 The variable @code{$_exception} is set to the exception object being
10771 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10774 @itemx $_probe_arg0@dots{}$_probe_arg11
10775 Arguments to a static probe. @xref{Static Probe Points}.
10778 @vindex $_sdata@r{, inspect, convenience variable}
10779 The variable @code{$_sdata} contains extra collected static tracepoint
10780 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10781 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10782 if extra static tracepoint data has not been collected.
10785 @vindex $_siginfo@r{, convenience variable}
10786 The variable @code{$_siginfo} contains extra signal information
10787 (@pxref{extra signal information}). Note that @code{$_siginfo}
10788 could be empty, if the application has not yet received any signals.
10789 For example, it will be empty before you execute the @code{run} command.
10792 @vindex $_tlb@r{, convenience variable}
10793 The variable @code{$_tlb} is automatically set when debugging
10794 applications running on MS-Windows in native mode or connected to
10795 gdbserver that supports the @code{qGetTIBAddr} request.
10796 @xref{General Query Packets}.
10797 This variable contains the address of the thread information block.
10800 The number of the current inferior. @xref{Inferiors and
10801 Programs, ,Debugging Multiple Inferiors and Programs}.
10804 The thread number of the current thread. @xref{thread numbers}.
10807 The global number of the current thread. @xref{global thread numbers}.
10811 @node Convenience Funs
10812 @section Convenience Functions
10814 @cindex convenience functions
10815 @value{GDBN} also supplies some @dfn{convenience functions}. These
10816 have a syntax similar to convenience variables. A convenience
10817 function can be used in an expression just like an ordinary function;
10818 however, a convenience function is implemented internally to
10821 These functions do not require @value{GDBN} to be configured with
10822 @code{Python} support, which means that they are always available.
10826 @item $_isvoid (@var{expr})
10827 @findex $_isvoid@r{, convenience function}
10828 Return one if the expression @var{expr} is @code{void}. Otherwise it
10831 A @code{void} expression is an expression where the type of the result
10832 is @code{void}. For example, you can examine a convenience variable
10833 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10837 (@value{GDBP}) print $_exitcode
10839 (@value{GDBP}) print $_isvoid ($_exitcode)
10842 Starting program: ./a.out
10843 [Inferior 1 (process 29572) exited normally]
10844 (@value{GDBP}) print $_exitcode
10846 (@value{GDBP}) print $_isvoid ($_exitcode)
10850 In the example above, we used @code{$_isvoid} to check whether
10851 @code{$_exitcode} is @code{void} before and after the execution of the
10852 program being debugged. Before the execution there is no exit code to
10853 be examined, therefore @code{$_exitcode} is @code{void}. After the
10854 execution the program being debugged returned zero, therefore
10855 @code{$_exitcode} is zero, which means that it is not @code{void}
10858 The @code{void} expression can also be a call of a function from the
10859 program being debugged. For example, given the following function:
10868 The result of calling it inside @value{GDBN} is @code{void}:
10871 (@value{GDBP}) print foo ()
10873 (@value{GDBP}) print $_isvoid (foo ())
10875 (@value{GDBP}) set $v = foo ()
10876 (@value{GDBP}) print $v
10878 (@value{GDBP}) print $_isvoid ($v)
10884 These functions require @value{GDBN} to be configured with
10885 @code{Python} support.
10889 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10890 @findex $_memeq@r{, convenience function}
10891 Returns one if the @var{length} bytes at the addresses given by
10892 @var{buf1} and @var{buf2} are equal.
10893 Otherwise it returns zero.
10895 @item $_regex(@var{str}, @var{regex})
10896 @findex $_regex@r{, convenience function}
10897 Returns one if the string @var{str} matches the regular expression
10898 @var{regex}. Otherwise it returns zero.
10899 The syntax of the regular expression is that specified by @code{Python}'s
10900 regular expression support.
10902 @item $_streq(@var{str1}, @var{str2})
10903 @findex $_streq@r{, convenience function}
10904 Returns one if the strings @var{str1} and @var{str2} are equal.
10905 Otherwise it returns zero.
10907 @item $_strlen(@var{str})
10908 @findex $_strlen@r{, convenience function}
10909 Returns the length of string @var{str}.
10911 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10912 @findex $_caller_is@r{, convenience function}
10913 Returns one if the calling function's name is equal to @var{name}.
10914 Otherwise it returns zero.
10916 If the optional argument @var{number_of_frames} is provided,
10917 it is the number of frames up in the stack to look.
10925 at testsuite/gdb.python/py-caller-is.c:21
10926 #1 0x00000000004005a0 in middle_func ()
10927 at testsuite/gdb.python/py-caller-is.c:27
10928 #2 0x00000000004005ab in top_func ()
10929 at testsuite/gdb.python/py-caller-is.c:33
10930 #3 0x00000000004005b6 in main ()
10931 at testsuite/gdb.python/py-caller-is.c:39
10932 (gdb) print $_caller_is ("middle_func")
10934 (gdb) print $_caller_is ("top_func", 2)
10938 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10939 @findex $_caller_matches@r{, convenience function}
10940 Returns one if the calling function's name matches the regular expression
10941 @var{regexp}. Otherwise it returns zero.
10943 If the optional argument @var{number_of_frames} is provided,
10944 it is the number of frames up in the stack to look.
10947 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10948 @findex $_any_caller_is@r{, convenience function}
10949 Returns one if any calling function's name is equal to @var{name}.
10950 Otherwise it returns zero.
10952 If the optional argument @var{number_of_frames} is provided,
10953 it is the number of frames up in the stack to look.
10956 This function differs from @code{$_caller_is} in that this function
10957 checks all stack frames from the immediate caller to the frame specified
10958 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10959 frame specified by @var{number_of_frames}.
10961 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10962 @findex $_any_caller_matches@r{, convenience function}
10963 Returns one if any calling function's name matches the regular expression
10964 @var{regexp}. Otherwise it returns zero.
10966 If the optional argument @var{number_of_frames} is provided,
10967 it is the number of frames up in the stack to look.
10970 This function differs from @code{$_caller_matches} in that this function
10971 checks all stack frames from the immediate caller to the frame specified
10972 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10973 frame specified by @var{number_of_frames}.
10975 @item $_as_string(@var{value})
10976 @findex $_as_string@r{, convenience function}
10977 Return the string representation of @var{value}.
10979 This function is useful to obtain the textual label (enumerator) of an
10980 enumeration value. For example, assuming the variable @var{node} is of
10981 an enumerated type:
10984 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10985 Visiting node of type NODE_INTEGER
10990 @value{GDBN} provides the ability to list and get help on
10991 convenience functions.
10994 @item help function
10995 @kindex help function
10996 @cindex show all convenience functions
10997 Print a list of all convenience functions.
11004 You can refer to machine register contents, in expressions, as variables
11005 with names starting with @samp{$}. The names of registers are different
11006 for each machine; use @code{info registers} to see the names used on
11010 @kindex info registers
11011 @item info registers
11012 Print the names and values of all registers except floating-point
11013 and vector registers (in the selected stack frame).
11015 @kindex info all-registers
11016 @cindex floating point registers
11017 @item info all-registers
11018 Print the names and values of all registers, including floating-point
11019 and vector registers (in the selected stack frame).
11021 @item info registers @var{regname} @dots{}
11022 Print the @dfn{relativized} value of each specified register @var{regname}.
11023 As discussed in detail below, register values are normally relative to
11024 the selected stack frame. The @var{regname} may be any register name valid on
11025 the machine you are using, with or without the initial @samp{$}.
11028 @anchor{standard registers}
11029 @cindex stack pointer register
11030 @cindex program counter register
11031 @cindex process status register
11032 @cindex frame pointer register
11033 @cindex standard registers
11034 @value{GDBN} has four ``standard'' register names that are available (in
11035 expressions) on most machines---whenever they do not conflict with an
11036 architecture's canonical mnemonics for registers. The register names
11037 @code{$pc} and @code{$sp} are used for the program counter register and
11038 the stack pointer. @code{$fp} is used for a register that contains a
11039 pointer to the current stack frame, and @code{$ps} is used for a
11040 register that contains the processor status. For example,
11041 you could print the program counter in hex with
11048 or print the instruction to be executed next with
11055 or add four to the stack pointer@footnote{This is a way of removing
11056 one word from the stack, on machines where stacks grow downward in
11057 memory (most machines, nowadays). This assumes that the innermost
11058 stack frame is selected; setting @code{$sp} is not allowed when other
11059 stack frames are selected. To pop entire frames off the stack,
11060 regardless of machine architecture, use @code{return};
11061 see @ref{Returning, ,Returning from a Function}.} with
11067 Whenever possible, these four standard register names are available on
11068 your machine even though the machine has different canonical mnemonics,
11069 so long as there is no conflict. The @code{info registers} command
11070 shows the canonical names. For example, on the SPARC, @code{info
11071 registers} displays the processor status register as @code{$psr} but you
11072 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11073 is an alias for the @sc{eflags} register.
11075 @value{GDBN} always considers the contents of an ordinary register as an
11076 integer when the register is examined in this way. Some machines have
11077 special registers which can hold nothing but floating point; these
11078 registers are considered to have floating point values. There is no way
11079 to refer to the contents of an ordinary register as floating point value
11080 (although you can @emph{print} it as a floating point value with
11081 @samp{print/f $@var{regname}}).
11083 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11084 means that the data format in which the register contents are saved by
11085 the operating system is not the same one that your program normally
11086 sees. For example, the registers of the 68881 floating point
11087 coprocessor are always saved in ``extended'' (raw) format, but all C
11088 programs expect to work with ``double'' (virtual) format. In such
11089 cases, @value{GDBN} normally works with the virtual format only (the format
11090 that makes sense for your program), but the @code{info registers} command
11091 prints the data in both formats.
11093 @cindex SSE registers (x86)
11094 @cindex MMX registers (x86)
11095 Some machines have special registers whose contents can be interpreted
11096 in several different ways. For example, modern x86-based machines
11097 have SSE and MMX registers that can hold several values packed
11098 together in several different formats. @value{GDBN} refers to such
11099 registers in @code{struct} notation:
11102 (@value{GDBP}) print $xmm1
11104 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11105 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11106 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11107 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11108 v4_int32 = @{0, 20657912, 11, 13@},
11109 v2_int64 = @{88725056443645952, 55834574859@},
11110 uint128 = 0x0000000d0000000b013b36f800000000
11115 To set values of such registers, you need to tell @value{GDBN} which
11116 view of the register you wish to change, as if you were assigning
11117 value to a @code{struct} member:
11120 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11123 Normally, register values are relative to the selected stack frame
11124 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11125 value that the register would contain if all stack frames farther in
11126 were exited and their saved registers restored. In order to see the
11127 true contents of hardware registers, you must select the innermost
11128 frame (with @samp{frame 0}).
11130 @cindex caller-saved registers
11131 @cindex call-clobbered registers
11132 @cindex volatile registers
11133 @cindex <not saved> values
11134 Usually ABIs reserve some registers as not needed to be saved by the
11135 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11136 registers). It may therefore not be possible for @value{GDBN} to know
11137 the value a register had before the call (in other words, in the outer
11138 frame), if the register value has since been changed by the callee.
11139 @value{GDBN} tries to deduce where the inner frame saved
11140 (``callee-saved'') registers, from the debug info, unwind info, or the
11141 machine code generated by your compiler. If some register is not
11142 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11143 its own knowledge of the ABI, or because the debug/unwind info
11144 explicitly says the register's value is undefined), @value{GDBN}
11145 displays @w{@samp{<not saved>}} as the register's value. With targets
11146 that @value{GDBN} has no knowledge of the register saving convention,
11147 if a register was not saved by the callee, then its value and location
11148 in the outer frame are assumed to be the same of the inner frame.
11149 This is usually harmless, because if the register is call-clobbered,
11150 the caller either does not care what is in the register after the
11151 call, or has code to restore the value that it does care about. Note,
11152 however, that if you change such a register in the outer frame, you
11153 may also be affecting the inner frame. Also, the more ``outer'' the
11154 frame is you're looking at, the more likely a call-clobbered
11155 register's value is to be wrong, in the sense that it doesn't actually
11156 represent the value the register had just before the call.
11158 @node Floating Point Hardware
11159 @section Floating Point Hardware
11160 @cindex floating point
11162 Depending on the configuration, @value{GDBN} may be able to give
11163 you more information about the status of the floating point hardware.
11168 Display hardware-dependent information about the floating
11169 point unit. The exact contents and layout vary depending on the
11170 floating point chip. Currently, @samp{info float} is supported on
11171 the ARM and x86 machines.
11175 @section Vector Unit
11176 @cindex vector unit
11178 Depending on the configuration, @value{GDBN} may be able to give you
11179 more information about the status of the vector unit.
11182 @kindex info vector
11184 Display information about the vector unit. The exact contents and
11185 layout vary depending on the hardware.
11188 @node OS Information
11189 @section Operating System Auxiliary Information
11190 @cindex OS information
11192 @value{GDBN} provides interfaces to useful OS facilities that can help
11193 you debug your program.
11195 @cindex auxiliary vector
11196 @cindex vector, auxiliary
11197 Some operating systems supply an @dfn{auxiliary vector} to programs at
11198 startup. This is akin to the arguments and environment that you
11199 specify for a program, but contains a system-dependent variety of
11200 binary values that tell system libraries important details about the
11201 hardware, operating system, and process. Each value's purpose is
11202 identified by an integer tag; the meanings are well-known but system-specific.
11203 Depending on the configuration and operating system facilities,
11204 @value{GDBN} may be able to show you this information. For remote
11205 targets, this functionality may further depend on the remote stub's
11206 support of the @samp{qXfer:auxv:read} packet, see
11207 @ref{qXfer auxiliary vector read}.
11212 Display the auxiliary vector of the inferior, which can be either a
11213 live process or a core dump file. @value{GDBN} prints each tag value
11214 numerically, and also shows names and text descriptions for recognized
11215 tags. Some values in the vector are numbers, some bit masks, and some
11216 pointers to strings or other data. @value{GDBN} displays each value in the
11217 most appropriate form for a recognized tag, and in hexadecimal for
11218 an unrecognized tag.
11221 On some targets, @value{GDBN} can access operating system-specific
11222 information and show it to you. The types of information available
11223 will differ depending on the type of operating system running on the
11224 target. The mechanism used to fetch the data is described in
11225 @ref{Operating System Information}. For remote targets, this
11226 functionality depends on the remote stub's support of the
11227 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11231 @item info os @var{infotype}
11233 Display OS information of the requested type.
11235 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11237 @anchor{linux info os infotypes}
11239 @kindex info os cpus
11241 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11242 the available fields from /proc/cpuinfo. For each supported architecture
11243 different fields are available. Two common entries are processor which gives
11244 CPU number and bogomips; a system constant that is calculated during
11245 kernel initialization.
11247 @kindex info os files
11249 Display the list of open file descriptors on the target. For each
11250 file descriptor, @value{GDBN} prints the identifier of the process
11251 owning the descriptor, the command of the owning process, the value
11252 of the descriptor, and the target of the descriptor.
11254 @kindex info os modules
11256 Display the list of all loaded kernel modules on the target. For each
11257 module, @value{GDBN} prints the module name, the size of the module in
11258 bytes, the number of times the module is used, the dependencies of the
11259 module, the status of the module, and the address of the loaded module
11262 @kindex info os msg
11264 Display the list of all System V message queues on the target. For each
11265 message queue, @value{GDBN} prints the message queue key, the message
11266 queue identifier, the access permissions, the current number of bytes
11267 on the queue, the current number of messages on the queue, the processes
11268 that last sent and received a message on the queue, the user and group
11269 of the owner and creator of the message queue, the times at which a
11270 message was last sent and received on the queue, and the time at which
11271 the message queue was last changed.
11273 @kindex info os processes
11275 Display the list of processes on the target. For each process,
11276 @value{GDBN} prints the process identifier, the name of the user, the
11277 command corresponding to the process, and the list of processor cores
11278 that the process is currently running on. (To understand what these
11279 properties mean, for this and the following info types, please consult
11280 the general @sc{gnu}/Linux documentation.)
11282 @kindex info os procgroups
11284 Display the list of process groups on the target. For each process,
11285 @value{GDBN} prints the identifier of the process group that it belongs
11286 to, the command corresponding to the process group leader, the process
11287 identifier, and the command line of the process. The list is sorted
11288 first by the process group identifier, then by the process identifier,
11289 so that processes belonging to the same process group are grouped together
11290 and the process group leader is listed first.
11292 @kindex info os semaphores
11294 Display the list of all System V semaphore sets on the target. For each
11295 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11296 set identifier, the access permissions, the number of semaphores in the
11297 set, the user and group of the owner and creator of the semaphore set,
11298 and the times at which the semaphore set was operated upon and changed.
11300 @kindex info os shm
11302 Display the list of all System V shared-memory regions on the target.
11303 For each shared-memory region, @value{GDBN} prints the region key,
11304 the shared-memory identifier, the access permissions, the size of the
11305 region, the process that created the region, the process that last
11306 attached to or detached from the region, the current number of live
11307 attaches to the region, and the times at which the region was last
11308 attached to, detach from, and changed.
11310 @kindex info os sockets
11312 Display the list of Internet-domain sockets on the target. For each
11313 socket, @value{GDBN} prints the address and port of the local and
11314 remote endpoints, the current state of the connection, the creator of
11315 the socket, the IP address family of the socket, and the type of the
11318 @kindex info os threads
11320 Display the list of threads running on the target. For each thread,
11321 @value{GDBN} prints the identifier of the process that the thread
11322 belongs to, the command of the process, the thread identifier, and the
11323 processor core that it is currently running on. The main thread of a
11324 process is not listed.
11328 If @var{infotype} is omitted, then list the possible values for
11329 @var{infotype} and the kind of OS information available for each
11330 @var{infotype}. If the target does not return a list of possible
11331 types, this command will report an error.
11334 @node Memory Region Attributes
11335 @section Memory Region Attributes
11336 @cindex memory region attributes
11338 @dfn{Memory region attributes} allow you to describe special handling
11339 required by regions of your target's memory. @value{GDBN} uses
11340 attributes to determine whether to allow certain types of memory
11341 accesses; whether to use specific width accesses; and whether to cache
11342 target memory. By default the description of memory regions is
11343 fetched from the target (if the current target supports this), but the
11344 user can override the fetched regions.
11346 Defined memory regions can be individually enabled and disabled. When a
11347 memory region is disabled, @value{GDBN} uses the default attributes when
11348 accessing memory in that region. Similarly, if no memory regions have
11349 been defined, @value{GDBN} uses the default attributes when accessing
11352 When a memory region is defined, it is given a number to identify it;
11353 to enable, disable, or remove a memory region, you specify that number.
11357 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11358 Define a memory region bounded by @var{lower} and @var{upper} with
11359 attributes @var{attributes}@dots{}, and add it to the list of regions
11360 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11361 case: it is treated as the target's maximum memory address.
11362 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11365 Discard any user changes to the memory regions and use target-supplied
11366 regions, if available, or no regions if the target does not support.
11369 @item delete mem @var{nums}@dots{}
11370 Remove memory regions @var{nums}@dots{} from the list of regions
11371 monitored by @value{GDBN}.
11373 @kindex disable mem
11374 @item disable mem @var{nums}@dots{}
11375 Disable monitoring of memory regions @var{nums}@dots{}.
11376 A disabled memory region is not forgotten.
11377 It may be enabled again later.
11380 @item enable mem @var{nums}@dots{}
11381 Enable monitoring of memory regions @var{nums}@dots{}.
11385 Print a table of all defined memory regions, with the following columns
11389 @item Memory Region Number
11390 @item Enabled or Disabled.
11391 Enabled memory regions are marked with @samp{y}.
11392 Disabled memory regions are marked with @samp{n}.
11395 The address defining the inclusive lower bound of the memory region.
11398 The address defining the exclusive upper bound of the memory region.
11401 The list of attributes set for this memory region.
11406 @subsection Attributes
11408 @subsubsection Memory Access Mode
11409 The access mode attributes set whether @value{GDBN} may make read or
11410 write accesses to a memory region.
11412 While these attributes prevent @value{GDBN} from performing invalid
11413 memory accesses, they do nothing to prevent the target system, I/O DMA,
11414 etc.@: from accessing memory.
11418 Memory is read only.
11420 Memory is write only.
11422 Memory is read/write. This is the default.
11425 @subsubsection Memory Access Size
11426 The access size attribute tells @value{GDBN} to use specific sized
11427 accesses in the memory region. Often memory mapped device registers
11428 require specific sized accesses. If no access size attribute is
11429 specified, @value{GDBN} may use accesses of any size.
11433 Use 8 bit memory accesses.
11435 Use 16 bit memory accesses.
11437 Use 32 bit memory accesses.
11439 Use 64 bit memory accesses.
11442 @c @subsubsection Hardware/Software Breakpoints
11443 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11444 @c will use hardware or software breakpoints for the internal breakpoints
11445 @c used by the step, next, finish, until, etc. commands.
11449 @c Always use hardware breakpoints
11450 @c @item swbreak (default)
11453 @subsubsection Data Cache
11454 The data cache attributes set whether @value{GDBN} will cache target
11455 memory. While this generally improves performance by reducing debug
11456 protocol overhead, it can lead to incorrect results because @value{GDBN}
11457 does not know about volatile variables or memory mapped device
11462 Enable @value{GDBN} to cache target memory.
11464 Disable @value{GDBN} from caching target memory. This is the default.
11467 @subsection Memory Access Checking
11468 @value{GDBN} can be instructed to refuse accesses to memory that is
11469 not explicitly described. This can be useful if accessing such
11470 regions has undesired effects for a specific target, or to provide
11471 better error checking. The following commands control this behaviour.
11474 @kindex set mem inaccessible-by-default
11475 @item set mem inaccessible-by-default [on|off]
11476 If @code{on} is specified, make @value{GDBN} treat memory not
11477 explicitly described by the memory ranges as non-existent and refuse accesses
11478 to such memory. The checks are only performed if there's at least one
11479 memory range defined. If @code{off} is specified, make @value{GDBN}
11480 treat the memory not explicitly described by the memory ranges as RAM.
11481 The default value is @code{on}.
11482 @kindex show mem inaccessible-by-default
11483 @item show mem inaccessible-by-default
11484 Show the current handling of accesses to unknown memory.
11488 @c @subsubsection Memory Write Verification
11489 @c The memory write verification attributes set whether @value{GDBN}
11490 @c will re-reads data after each write to verify the write was successful.
11494 @c @item noverify (default)
11497 @node Dump/Restore Files
11498 @section Copy Between Memory and a File
11499 @cindex dump/restore files
11500 @cindex append data to a file
11501 @cindex dump data to a file
11502 @cindex restore data from a file
11504 You can use the commands @code{dump}, @code{append}, and
11505 @code{restore} to copy data between target memory and a file. The
11506 @code{dump} and @code{append} commands write data to a file, and the
11507 @code{restore} command reads data from a file back into the inferior's
11508 memory. Files may be in binary, Motorola S-record, Intel hex,
11509 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11510 append to binary files, and cannot read from Verilog Hex files.
11515 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11516 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11517 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11518 or the value of @var{expr}, to @var{filename} in the given format.
11520 The @var{format} parameter may be any one of:
11527 Motorola S-record format.
11529 Tektronix Hex format.
11531 Verilog Hex format.
11534 @value{GDBN} uses the same definitions of these formats as the
11535 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11536 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11540 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11541 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11542 Append the contents of memory from @var{start_addr} to @var{end_addr},
11543 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11544 (@value{GDBN} can only append data to files in raw binary form.)
11547 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11548 Restore the contents of file @var{filename} into memory. The
11549 @code{restore} command can automatically recognize any known @sc{bfd}
11550 file format, except for raw binary. To restore a raw binary file you
11551 must specify the optional keyword @code{binary} after the filename.
11553 If @var{bias} is non-zero, its value will be added to the addresses
11554 contained in the file. Binary files always start at address zero, so
11555 they will be restored at address @var{bias}. Other bfd files have
11556 a built-in location; they will be restored at offset @var{bias}
11557 from that location.
11559 If @var{start} and/or @var{end} are non-zero, then only data between
11560 file offset @var{start} and file offset @var{end} will be restored.
11561 These offsets are relative to the addresses in the file, before
11562 the @var{bias} argument is applied.
11566 @node Core File Generation
11567 @section How to Produce a Core File from Your Program
11568 @cindex dump core from inferior
11570 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11571 image of a running process and its process status (register values
11572 etc.). Its primary use is post-mortem debugging of a program that
11573 crashed while it ran outside a debugger. A program that crashes
11574 automatically produces a core file, unless this feature is disabled by
11575 the user. @xref{Files}, for information on invoking @value{GDBN} in
11576 the post-mortem debugging mode.
11578 Occasionally, you may wish to produce a core file of the program you
11579 are debugging in order to preserve a snapshot of its state.
11580 @value{GDBN} has a special command for that.
11584 @kindex generate-core-file
11585 @item generate-core-file [@var{file}]
11586 @itemx gcore [@var{file}]
11587 Produce a core dump of the inferior process. The optional argument
11588 @var{file} specifies the file name where to put the core dump. If not
11589 specified, the file name defaults to @file{core.@var{pid}}, where
11590 @var{pid} is the inferior process ID.
11592 Note that this command is implemented only for some systems (as of
11593 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11595 On @sc{gnu}/Linux, this command can take into account the value of the
11596 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11597 dump (@pxref{set use-coredump-filter}).
11599 @kindex set use-coredump-filter
11600 @anchor{set use-coredump-filter}
11601 @item set use-coredump-filter on
11602 @itemx set use-coredump-filter off
11603 Enable or disable the use of the file
11604 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11605 files. This file is used by the Linux kernel to decide what types of
11606 memory mappings will be dumped or ignored when generating a core dump
11607 file. @var{pid} is the process ID of a currently running process.
11609 To make use of this feature, you have to write in the
11610 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11611 which is a bit mask representing the memory mapping types. If a bit
11612 is set in the bit mask, then the memory mappings of the corresponding
11613 types will be dumped; otherwise, they will be ignored. This
11614 configuration is inherited by child processes. For more information
11615 about the bits that can be set in the
11616 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11617 manpage of @code{core(5)}.
11619 By default, this option is @code{on}. If this option is turned
11620 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11621 and instead uses the same default value as the Linux kernel in order
11622 to decide which pages will be dumped in the core dump file. This
11623 value is currently @code{0x33}, which means that bits @code{0}
11624 (anonymous private mappings), @code{1} (anonymous shared mappings),
11625 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11626 This will cause these memory mappings to be dumped automatically.
11629 @node Character Sets
11630 @section Character Sets
11631 @cindex character sets
11633 @cindex translating between character sets
11634 @cindex host character set
11635 @cindex target character set
11637 If the program you are debugging uses a different character set to
11638 represent characters and strings than the one @value{GDBN} uses itself,
11639 @value{GDBN} can automatically translate between the character sets for
11640 you. The character set @value{GDBN} uses we call the @dfn{host
11641 character set}; the one the inferior program uses we call the
11642 @dfn{target character set}.
11644 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11645 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11646 remote protocol (@pxref{Remote Debugging}) to debug a program
11647 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11648 then the host character set is Latin-1, and the target character set is
11649 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11650 target-charset EBCDIC-US}, then @value{GDBN} translates between
11651 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11652 character and string literals in expressions.
11654 @value{GDBN} has no way to automatically recognize which character set
11655 the inferior program uses; you must tell it, using the @code{set
11656 target-charset} command, described below.
11658 Here are the commands for controlling @value{GDBN}'s character set
11662 @item set target-charset @var{charset}
11663 @kindex set target-charset
11664 Set the current target character set to @var{charset}. To display the
11665 list of supported target character sets, type
11666 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11668 @item set host-charset @var{charset}
11669 @kindex set host-charset
11670 Set the current host character set to @var{charset}.
11672 By default, @value{GDBN} uses a host character set appropriate to the
11673 system it is running on; you can override that default using the
11674 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11675 automatically determine the appropriate host character set. In this
11676 case, @value{GDBN} uses @samp{UTF-8}.
11678 @value{GDBN} can only use certain character sets as its host character
11679 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11680 @value{GDBN} will list the host character sets it supports.
11682 @item set charset @var{charset}
11683 @kindex set charset
11684 Set the current host and target character sets to @var{charset}. As
11685 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11686 @value{GDBN} will list the names of the character sets that can be used
11687 for both host and target.
11690 @kindex show charset
11691 Show the names of the current host and target character sets.
11693 @item show host-charset
11694 @kindex show host-charset
11695 Show the name of the current host character set.
11697 @item show target-charset
11698 @kindex show target-charset
11699 Show the name of the current target character set.
11701 @item set target-wide-charset @var{charset}
11702 @kindex set target-wide-charset
11703 Set the current target's wide character set to @var{charset}. This is
11704 the character set used by the target's @code{wchar_t} type. To
11705 display the list of supported wide character sets, type
11706 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11708 @item show target-wide-charset
11709 @kindex show target-wide-charset
11710 Show the name of the current target's wide character set.
11713 Here is an example of @value{GDBN}'s character set support in action.
11714 Assume that the following source code has been placed in the file
11715 @file{charset-test.c}:
11721 = @{72, 101, 108, 108, 111, 44, 32, 119,
11722 111, 114, 108, 100, 33, 10, 0@};
11723 char ibm1047_hello[]
11724 = @{200, 133, 147, 147, 150, 107, 64, 166,
11725 150, 153, 147, 132, 90, 37, 0@};
11729 printf ("Hello, world!\n");
11733 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11734 containing the string @samp{Hello, world!} followed by a newline,
11735 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11737 We compile the program, and invoke the debugger on it:
11740 $ gcc -g charset-test.c -o charset-test
11741 $ gdb -nw charset-test
11742 GNU gdb 2001-12-19-cvs
11743 Copyright 2001 Free Software Foundation, Inc.
11748 We can use the @code{show charset} command to see what character sets
11749 @value{GDBN} is currently using to interpret and display characters and
11753 (@value{GDBP}) show charset
11754 The current host and target character set is `ISO-8859-1'.
11758 For the sake of printing this manual, let's use @sc{ascii} as our
11759 initial character set:
11761 (@value{GDBP}) set charset ASCII
11762 (@value{GDBP}) show charset
11763 The current host and target character set is `ASCII'.
11767 Let's assume that @sc{ascii} is indeed the correct character set for our
11768 host system --- in other words, let's assume that if @value{GDBN} prints
11769 characters using the @sc{ascii} character set, our terminal will display
11770 them properly. Since our current target character set is also
11771 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11774 (@value{GDBP}) print ascii_hello
11775 $1 = 0x401698 "Hello, world!\n"
11776 (@value{GDBP}) print ascii_hello[0]
11781 @value{GDBN} uses the target character set for character and string
11782 literals you use in expressions:
11785 (@value{GDBP}) print '+'
11790 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11793 @value{GDBN} relies on the user to tell it which character set the
11794 target program uses. If we print @code{ibm1047_hello} while our target
11795 character set is still @sc{ascii}, we get jibberish:
11798 (@value{GDBP}) print ibm1047_hello
11799 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11800 (@value{GDBP}) print ibm1047_hello[0]
11805 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11806 @value{GDBN} tells us the character sets it supports:
11809 (@value{GDBP}) set target-charset
11810 ASCII EBCDIC-US IBM1047 ISO-8859-1
11811 (@value{GDBP}) set target-charset
11814 We can select @sc{ibm1047} as our target character set, and examine the
11815 program's strings again. Now the @sc{ascii} string is wrong, but
11816 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11817 target character set, @sc{ibm1047}, to the host character set,
11818 @sc{ascii}, and they display correctly:
11821 (@value{GDBP}) set target-charset IBM1047
11822 (@value{GDBP}) show charset
11823 The current host character set is `ASCII'.
11824 The current target character set is `IBM1047'.
11825 (@value{GDBP}) print ascii_hello
11826 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11827 (@value{GDBP}) print ascii_hello[0]
11829 (@value{GDBP}) print ibm1047_hello
11830 $8 = 0x4016a8 "Hello, world!\n"
11831 (@value{GDBP}) print ibm1047_hello[0]
11836 As above, @value{GDBN} uses the target character set for character and
11837 string literals you use in expressions:
11840 (@value{GDBP}) print '+'
11845 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11848 @node Caching Target Data
11849 @section Caching Data of Targets
11850 @cindex caching data of targets
11852 @value{GDBN} caches data exchanged between the debugger and a target.
11853 Each cache is associated with the address space of the inferior.
11854 @xref{Inferiors and Programs}, about inferior and address space.
11855 Such caching generally improves performance in remote debugging
11856 (@pxref{Remote Debugging}), because it reduces the overhead of the
11857 remote protocol by bundling memory reads and writes into large chunks.
11858 Unfortunately, simply caching everything would lead to incorrect results,
11859 since @value{GDBN} does not necessarily know anything about volatile
11860 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11861 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11863 Therefore, by default, @value{GDBN} only caches data
11864 known to be on the stack@footnote{In non-stop mode, it is moderately
11865 rare for a running thread to modify the stack of a stopped thread
11866 in a way that would interfere with a backtrace, and caching of
11867 stack reads provides a significant speed up of remote backtraces.} or
11868 in the code segment.
11869 Other regions of memory can be explicitly marked as
11870 cacheable; @pxref{Memory Region Attributes}.
11873 @kindex set remotecache
11874 @item set remotecache on
11875 @itemx set remotecache off
11876 This option no longer does anything; it exists for compatibility
11879 @kindex show remotecache
11880 @item show remotecache
11881 Show the current state of the obsolete remotecache flag.
11883 @kindex set stack-cache
11884 @item set stack-cache on
11885 @itemx set stack-cache off
11886 Enable or disable caching of stack accesses. When @code{on}, use
11887 caching. By default, this option is @code{on}.
11889 @kindex show stack-cache
11890 @item show stack-cache
11891 Show the current state of data caching for memory accesses.
11893 @kindex set code-cache
11894 @item set code-cache on
11895 @itemx set code-cache off
11896 Enable or disable caching of code segment accesses. When @code{on},
11897 use caching. By default, this option is @code{on}. This improves
11898 performance of disassembly in remote debugging.
11900 @kindex show code-cache
11901 @item show code-cache
11902 Show the current state of target memory cache for code segment
11905 @kindex info dcache
11906 @item info dcache @r{[}line@r{]}
11907 Print the information about the performance of data cache of the
11908 current inferior's address space. The information displayed
11909 includes the dcache width and depth, and for each cache line, its
11910 number, address, and how many times it was referenced. This
11911 command is useful for debugging the data cache operation.
11913 If a line number is specified, the contents of that line will be
11916 @item set dcache size @var{size}
11917 @cindex dcache size
11918 @kindex set dcache size
11919 Set maximum number of entries in dcache (dcache depth above).
11921 @item set dcache line-size @var{line-size}
11922 @cindex dcache line-size
11923 @kindex set dcache line-size
11924 Set number of bytes each dcache entry caches (dcache width above).
11925 Must be a power of 2.
11927 @item show dcache size
11928 @kindex show dcache size
11929 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11931 @item show dcache line-size
11932 @kindex show dcache line-size
11933 Show default size of dcache lines.
11937 @node Searching Memory
11938 @section Search Memory
11939 @cindex searching memory
11941 Memory can be searched for a particular sequence of bytes with the
11942 @code{find} command.
11946 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11947 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11948 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11949 etc. The search begins at address @var{start_addr} and continues for either
11950 @var{len} bytes or through to @var{end_addr} inclusive.
11953 @var{s} and @var{n} are optional parameters.
11954 They may be specified in either order, apart or together.
11957 @item @var{s}, search query size
11958 The size of each search query value.
11964 halfwords (two bytes)
11968 giant words (eight bytes)
11971 All values are interpreted in the current language.
11972 This means, for example, that if the current source language is C/C@t{++}
11973 then searching for the string ``hello'' includes the trailing '\0'.
11974 The null terminator can be removed from searching by using casts,
11975 e.g.: @samp{@{char[5]@}"hello"}.
11977 If the value size is not specified, it is taken from the
11978 value's type in the current language.
11979 This is useful when one wants to specify the search
11980 pattern as a mixture of types.
11981 Note that this means, for example, that in the case of C-like languages
11982 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11983 which is typically four bytes.
11985 @item @var{n}, maximum number of finds
11986 The maximum number of matches to print. The default is to print all finds.
11989 You can use strings as search values. Quote them with double-quotes
11991 The string value is copied into the search pattern byte by byte,
11992 regardless of the endianness of the target and the size specification.
11994 The address of each match found is printed as well as a count of the
11995 number of matches found.
11997 The address of the last value found is stored in convenience variable
11999 A count of the number of matches is stored in @samp{$numfound}.
12001 For example, if stopped at the @code{printf} in this function:
12007 static char hello[] = "hello-hello";
12008 static struct @{ char c; short s; int i; @}
12009 __attribute__ ((packed)) mixed
12010 = @{ 'c', 0x1234, 0x87654321 @};
12011 printf ("%s\n", hello);
12016 you get during debugging:
12019 (gdb) find &hello[0], +sizeof(hello), "hello"
12020 0x804956d <hello.1620+6>
12022 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12023 0x8049567 <hello.1620>
12024 0x804956d <hello.1620+6>
12026 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12027 0x8049567 <hello.1620>
12028 0x804956d <hello.1620+6>
12030 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12031 0x8049567 <hello.1620>
12033 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12034 0x8049560 <mixed.1625>
12036 (gdb) print $numfound
12039 $2 = (void *) 0x8049560
12043 @section Value Sizes
12045 Whenever @value{GDBN} prints a value memory will be allocated within
12046 @value{GDBN} to hold the contents of the value. It is possible in
12047 some languages with dynamic typing systems, that an invalid program
12048 may indicate a value that is incorrectly large, this in turn may cause
12049 @value{GDBN} to try and allocate an overly large ammount of memory.
12052 @kindex set max-value-size
12053 @item set max-value-size @var{bytes}
12054 @itemx set max-value-size unlimited
12055 Set the maximum size of memory that @value{GDBN} will allocate for the
12056 contents of a value to @var{bytes}, trying to display a value that
12057 requires more memory than that will result in an error.
12059 Setting this variable does not effect values that have already been
12060 allocated within @value{GDBN}, only future allocations.
12062 There's a minimum size that @code{max-value-size} can be set to in
12063 order that @value{GDBN} can still operate correctly, this minimum is
12064 currently 16 bytes.
12066 The limit applies to the results of some subexpressions as well as to
12067 complete expressions. For example, an expression denoting a simple
12068 integer component, such as @code{x.y.z}, may fail if the size of
12069 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12070 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12071 @var{A} is an array variable with non-constant size, will generally
12072 succeed regardless of the bounds on @var{A}, as long as the component
12073 size is less than @var{bytes}.
12075 The default value of @code{max-value-size} is currently 64k.
12077 @kindex show max-value-size
12078 @item show max-value-size
12079 Show the maximum size of memory, in bytes, that @value{GDBN} will
12080 allocate for the contents of a value.
12083 @node Optimized Code
12084 @chapter Debugging Optimized Code
12085 @cindex optimized code, debugging
12086 @cindex debugging optimized code
12088 Almost all compilers support optimization. With optimization
12089 disabled, the compiler generates assembly code that corresponds
12090 directly to your source code, in a simplistic way. As the compiler
12091 applies more powerful optimizations, the generated assembly code
12092 diverges from your original source code. With help from debugging
12093 information generated by the compiler, @value{GDBN} can map from
12094 the running program back to constructs from your original source.
12096 @value{GDBN} is more accurate with optimization disabled. If you
12097 can recompile without optimization, it is easier to follow the
12098 progress of your program during debugging. But, there are many cases
12099 where you may need to debug an optimized version.
12101 When you debug a program compiled with @samp{-g -O}, remember that the
12102 optimizer has rearranged your code; the debugger shows you what is
12103 really there. Do not be too surprised when the execution path does not
12104 exactly match your source file! An extreme example: if you define a
12105 variable, but never use it, @value{GDBN} never sees that
12106 variable---because the compiler optimizes it out of existence.
12108 Some things do not work as well with @samp{-g -O} as with just
12109 @samp{-g}, particularly on machines with instruction scheduling. If in
12110 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12111 please report it to us as a bug (including a test case!).
12112 @xref{Variables}, for more information about debugging optimized code.
12115 * Inline Functions:: How @value{GDBN} presents inlining
12116 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12119 @node Inline Functions
12120 @section Inline Functions
12121 @cindex inline functions, debugging
12123 @dfn{Inlining} is an optimization that inserts a copy of the function
12124 body directly at each call site, instead of jumping to a shared
12125 routine. @value{GDBN} displays inlined functions just like
12126 non-inlined functions. They appear in backtraces. You can view their
12127 arguments and local variables, step into them with @code{step}, skip
12128 them with @code{next}, and escape from them with @code{finish}.
12129 You can check whether a function was inlined by using the
12130 @code{info frame} command.
12132 For @value{GDBN} to support inlined functions, the compiler must
12133 record information about inlining in the debug information ---
12134 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12135 other compilers do also. @value{GDBN} only supports inlined functions
12136 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12137 do not emit two required attributes (@samp{DW_AT_call_file} and
12138 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12139 function calls with earlier versions of @value{NGCC}. It instead
12140 displays the arguments and local variables of inlined functions as
12141 local variables in the caller.
12143 The body of an inlined function is directly included at its call site;
12144 unlike a non-inlined function, there are no instructions devoted to
12145 the call. @value{GDBN} still pretends that the call site and the
12146 start of the inlined function are different instructions. Stepping to
12147 the call site shows the call site, and then stepping again shows
12148 the first line of the inlined function, even though no additional
12149 instructions are executed.
12151 This makes source-level debugging much clearer; you can see both the
12152 context of the call and then the effect of the call. Only stepping by
12153 a single instruction using @code{stepi} or @code{nexti} does not do
12154 this; single instruction steps always show the inlined body.
12156 There are some ways that @value{GDBN} does not pretend that inlined
12157 function calls are the same as normal calls:
12161 Setting breakpoints at the call site of an inlined function may not
12162 work, because the call site does not contain any code. @value{GDBN}
12163 may incorrectly move the breakpoint to the next line of the enclosing
12164 function, after the call. This limitation will be removed in a future
12165 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12166 or inside the inlined function instead.
12169 @value{GDBN} cannot locate the return value of inlined calls after
12170 using the @code{finish} command. This is a limitation of compiler-generated
12171 debugging information; after @code{finish}, you can step to the next line
12172 and print a variable where your program stored the return value.
12176 @node Tail Call Frames
12177 @section Tail Call Frames
12178 @cindex tail call frames, debugging
12180 Function @code{B} can call function @code{C} in its very last statement. In
12181 unoptimized compilation the call of @code{C} is immediately followed by return
12182 instruction at the end of @code{B} code. Optimizing compiler may replace the
12183 call and return in function @code{B} into one jump to function @code{C}
12184 instead. Such use of a jump instruction is called @dfn{tail call}.
12186 During execution of function @code{C}, there will be no indication in the
12187 function call stack frames that it was tail-called from @code{B}. If function
12188 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12189 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12190 some cases @value{GDBN} can determine that @code{C} was tail-called from
12191 @code{B}, and it will then create fictitious call frame for that, with the
12192 return address set up as if @code{B} called @code{C} normally.
12194 This functionality is currently supported only by DWARF 2 debugging format and
12195 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12196 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12199 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12200 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12204 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12206 Stack level 1, frame at 0x7fffffffda30:
12207 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12208 tail call frame, caller of frame at 0x7fffffffda30
12209 source language c++.
12210 Arglist at unknown address.
12211 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12214 The detection of all the possible code path executions can find them ambiguous.
12215 There is no execution history stored (possible @ref{Reverse Execution} is never
12216 used for this purpose) and the last known caller could have reached the known
12217 callee by multiple different jump sequences. In such case @value{GDBN} still
12218 tries to show at least all the unambiguous top tail callers and all the
12219 unambiguous bottom tail calees, if any.
12222 @anchor{set debug entry-values}
12223 @item set debug entry-values
12224 @kindex set debug entry-values
12225 When set to on, enables printing of analysis messages for both frame argument
12226 values at function entry and tail calls. It will show all the possible valid
12227 tail calls code paths it has considered. It will also print the intersection
12228 of them with the final unambiguous (possibly partial or even empty) code path
12231 @item show debug entry-values
12232 @kindex show debug entry-values
12233 Show the current state of analysis messages printing for both frame argument
12234 values at function entry and tail calls.
12237 The analysis messages for tail calls can for example show why the virtual tail
12238 call frame for function @code{c} has not been recognized (due to the indirect
12239 reference by variable @code{x}):
12242 static void __attribute__((noinline, noclone)) c (void);
12243 void (*x) (void) = c;
12244 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12245 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12246 int main (void) @{ x (); return 0; @}
12248 Breakpoint 1, DW_OP_entry_value resolving cannot find
12249 DW_TAG_call_site 0x40039a in main
12251 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12254 #1 0x000000000040039a in main () at t.c:5
12257 Another possibility is an ambiguous virtual tail call frames resolution:
12261 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12262 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12263 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12264 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12265 static void __attribute__((noinline, noclone)) b (void)
12266 @{ if (i) c (); else e (); @}
12267 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12268 int main (void) @{ a (); return 0; @}
12270 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12271 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12272 tailcall: reduced: 0x4004d2(a) |
12275 #1 0x00000000004004d2 in a () at t.c:8
12276 #2 0x0000000000400395 in main () at t.c:9
12279 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12280 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12282 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12283 @ifset HAVE_MAKEINFO_CLICK
12284 @set ARROW @click{}
12285 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12286 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12288 @ifclear HAVE_MAKEINFO_CLICK
12290 @set CALLSEQ1B @value{CALLSEQ1A}
12291 @set CALLSEQ2B @value{CALLSEQ2A}
12294 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12295 The code can have possible execution paths @value{CALLSEQ1B} or
12296 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12298 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12299 has found. It then finds another possible calling sequcen - that one is
12300 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12301 printed as the @code{reduced:} calling sequence. That one could have many
12302 futher @code{compare:} and @code{reduced:} statements as long as there remain
12303 any non-ambiguous sequence entries.
12305 For the frame of function @code{b} in both cases there are different possible
12306 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12307 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12308 therefore this one is displayed to the user while the ambiguous frames are
12311 There can be also reasons why printing of frame argument values at function
12316 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12317 static void __attribute__((noinline, noclone)) a (int i);
12318 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12319 static void __attribute__((noinline, noclone)) a (int i)
12320 @{ if (i) b (i - 1); else c (0); @}
12321 int main (void) @{ a (5); return 0; @}
12324 #0 c (i=i@@entry=0) at t.c:2
12325 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12326 function "a" at 0x400420 can call itself via tail calls
12327 i=<optimized out>) at t.c:6
12328 #2 0x000000000040036e in main () at t.c:7
12331 @value{GDBN} cannot find out from the inferior state if and how many times did
12332 function @code{a} call itself (via function @code{b}) as these calls would be
12333 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12334 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12335 prints @code{<optimized out>} instead.
12338 @chapter C Preprocessor Macros
12340 Some languages, such as C and C@t{++}, provide a way to define and invoke
12341 ``preprocessor macros'' which expand into strings of tokens.
12342 @value{GDBN} can evaluate expressions containing macro invocations, show
12343 the result of macro expansion, and show a macro's definition, including
12344 where it was defined.
12346 You may need to compile your program specially to provide @value{GDBN}
12347 with information about preprocessor macros. Most compilers do not
12348 include macros in their debugging information, even when you compile
12349 with the @option{-g} flag. @xref{Compilation}.
12351 A program may define a macro at one point, remove that definition later,
12352 and then provide a different definition after that. Thus, at different
12353 points in the program, a macro may have different definitions, or have
12354 no definition at all. If there is a current stack frame, @value{GDBN}
12355 uses the macros in scope at that frame's source code line. Otherwise,
12356 @value{GDBN} uses the macros in scope at the current listing location;
12359 Whenever @value{GDBN} evaluates an expression, it always expands any
12360 macro invocations present in the expression. @value{GDBN} also provides
12361 the following commands for working with macros explicitly.
12365 @kindex macro expand
12366 @cindex macro expansion, showing the results of preprocessor
12367 @cindex preprocessor macro expansion, showing the results of
12368 @cindex expanding preprocessor macros
12369 @item macro expand @var{expression}
12370 @itemx macro exp @var{expression}
12371 Show the results of expanding all preprocessor macro invocations in
12372 @var{expression}. Since @value{GDBN} simply expands macros, but does
12373 not parse the result, @var{expression} need not be a valid expression;
12374 it can be any string of tokens.
12377 @item macro expand-once @var{expression}
12378 @itemx macro exp1 @var{expression}
12379 @cindex expand macro once
12380 @i{(This command is not yet implemented.)} Show the results of
12381 expanding those preprocessor macro invocations that appear explicitly in
12382 @var{expression}. Macro invocations appearing in that expansion are
12383 left unchanged. This command allows you to see the effect of a
12384 particular macro more clearly, without being confused by further
12385 expansions. Since @value{GDBN} simply expands macros, but does not
12386 parse the result, @var{expression} need not be a valid expression; it
12387 can be any string of tokens.
12390 @cindex macro definition, showing
12391 @cindex definition of a macro, showing
12392 @cindex macros, from debug info
12393 @item info macro [-a|-all] [--] @var{macro}
12394 Show the current definition or all definitions of the named @var{macro},
12395 and describe the source location or compiler command-line where that
12396 definition was established. The optional double dash is to signify the end of
12397 argument processing and the beginning of @var{macro} for non C-like macros where
12398 the macro may begin with a hyphen.
12400 @kindex info macros
12401 @item info macros @var{location}
12402 Show all macro definitions that are in effect at the location specified
12403 by @var{location}, and describe the source location or compiler
12404 command-line where those definitions were established.
12406 @kindex macro define
12407 @cindex user-defined macros
12408 @cindex defining macros interactively
12409 @cindex macros, user-defined
12410 @item macro define @var{macro} @var{replacement-list}
12411 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12412 Introduce a definition for a preprocessor macro named @var{macro},
12413 invocations of which are replaced by the tokens given in
12414 @var{replacement-list}. The first form of this command defines an
12415 ``object-like'' macro, which takes no arguments; the second form
12416 defines a ``function-like'' macro, which takes the arguments given in
12419 A definition introduced by this command is in scope in every
12420 expression evaluated in @value{GDBN}, until it is removed with the
12421 @code{macro undef} command, described below. The definition overrides
12422 all definitions for @var{macro} present in the program being debugged,
12423 as well as any previous user-supplied definition.
12425 @kindex macro undef
12426 @item macro undef @var{macro}
12427 Remove any user-supplied definition for the macro named @var{macro}.
12428 This command only affects definitions provided with the @code{macro
12429 define} command, described above; it cannot remove definitions present
12430 in the program being debugged.
12434 List all the macros defined using the @code{macro define} command.
12437 @cindex macros, example of debugging with
12438 Here is a transcript showing the above commands in action. First, we
12439 show our source files:
12444 #include "sample.h"
12447 #define ADD(x) (M + x)
12452 printf ("Hello, world!\n");
12454 printf ("We're so creative.\n");
12456 printf ("Goodbye, world!\n");
12463 Now, we compile the program using the @sc{gnu} C compiler,
12464 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12465 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12466 and @option{-gdwarf-4}; we recommend always choosing the most recent
12467 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12468 includes information about preprocessor macros in the debugging
12472 $ gcc -gdwarf-2 -g3 sample.c -o sample
12476 Now, we start @value{GDBN} on our sample program:
12480 GNU gdb 2002-05-06-cvs
12481 Copyright 2002 Free Software Foundation, Inc.
12482 GDB is free software, @dots{}
12486 We can expand macros and examine their definitions, even when the
12487 program is not running. @value{GDBN} uses the current listing position
12488 to decide which macro definitions are in scope:
12491 (@value{GDBP}) list main
12494 5 #define ADD(x) (M + x)
12499 10 printf ("Hello, world!\n");
12501 12 printf ("We're so creative.\n");
12502 (@value{GDBP}) info macro ADD
12503 Defined at /home/jimb/gdb/macros/play/sample.c:5
12504 #define ADD(x) (M + x)
12505 (@value{GDBP}) info macro Q
12506 Defined at /home/jimb/gdb/macros/play/sample.h:1
12507 included at /home/jimb/gdb/macros/play/sample.c:2
12509 (@value{GDBP}) macro expand ADD(1)
12510 expands to: (42 + 1)
12511 (@value{GDBP}) macro expand-once ADD(1)
12512 expands to: once (M + 1)
12516 In the example above, note that @code{macro expand-once} expands only
12517 the macro invocation explicit in the original text --- the invocation of
12518 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12519 which was introduced by @code{ADD}.
12521 Once the program is running, @value{GDBN} uses the macro definitions in
12522 force at the source line of the current stack frame:
12525 (@value{GDBP}) break main
12526 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12528 Starting program: /home/jimb/gdb/macros/play/sample
12530 Breakpoint 1, main () at sample.c:10
12531 10 printf ("Hello, world!\n");
12535 At line 10, the definition of the macro @code{N} at line 9 is in force:
12538 (@value{GDBP}) info macro N
12539 Defined at /home/jimb/gdb/macros/play/sample.c:9
12541 (@value{GDBP}) macro expand N Q M
12542 expands to: 28 < 42
12543 (@value{GDBP}) print N Q M
12548 As we step over directives that remove @code{N}'s definition, and then
12549 give it a new definition, @value{GDBN} finds the definition (or lack
12550 thereof) in force at each point:
12553 (@value{GDBP}) next
12555 12 printf ("We're so creative.\n");
12556 (@value{GDBP}) info macro N
12557 The symbol `N' has no definition as a C/C++ preprocessor macro
12558 at /home/jimb/gdb/macros/play/sample.c:12
12559 (@value{GDBP}) next
12561 14 printf ("Goodbye, world!\n");
12562 (@value{GDBP}) info macro N
12563 Defined at /home/jimb/gdb/macros/play/sample.c:13
12565 (@value{GDBP}) macro expand N Q M
12566 expands to: 1729 < 42
12567 (@value{GDBP}) print N Q M
12572 In addition to source files, macros can be defined on the compilation command
12573 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12574 such a way, @value{GDBN} displays the location of their definition as line zero
12575 of the source file submitted to the compiler.
12578 (@value{GDBP}) info macro __STDC__
12579 Defined at /home/jimb/gdb/macros/play/sample.c:0
12586 @chapter Tracepoints
12587 @c This chapter is based on the documentation written by Michael
12588 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12590 @cindex tracepoints
12591 In some applications, it is not feasible for the debugger to interrupt
12592 the program's execution long enough for the developer to learn
12593 anything helpful about its behavior. If the program's correctness
12594 depends on its real-time behavior, delays introduced by a debugger
12595 might cause the program to change its behavior drastically, or perhaps
12596 fail, even when the code itself is correct. It is useful to be able
12597 to observe the program's behavior without interrupting it.
12599 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12600 specify locations in the program, called @dfn{tracepoints}, and
12601 arbitrary expressions to evaluate when those tracepoints are reached.
12602 Later, using the @code{tfind} command, you can examine the values
12603 those expressions had when the program hit the tracepoints. The
12604 expressions may also denote objects in memory---structures or arrays,
12605 for example---whose values @value{GDBN} should record; while visiting
12606 a particular tracepoint, you may inspect those objects as if they were
12607 in memory at that moment. However, because @value{GDBN} records these
12608 values without interacting with you, it can do so quickly and
12609 unobtrusively, hopefully not disturbing the program's behavior.
12611 The tracepoint facility is currently available only for remote
12612 targets. @xref{Targets}. In addition, your remote target must know
12613 how to collect trace data. This functionality is implemented in the
12614 remote stub; however, none of the stubs distributed with @value{GDBN}
12615 support tracepoints as of this writing. The format of the remote
12616 packets used to implement tracepoints are described in @ref{Tracepoint
12619 It is also possible to get trace data from a file, in a manner reminiscent
12620 of corefiles; you specify the filename, and use @code{tfind} to search
12621 through the file. @xref{Trace Files}, for more details.
12623 This chapter describes the tracepoint commands and features.
12626 * Set Tracepoints::
12627 * Analyze Collected Data::
12628 * Tracepoint Variables::
12632 @node Set Tracepoints
12633 @section Commands to Set Tracepoints
12635 Before running such a @dfn{trace experiment}, an arbitrary number of
12636 tracepoints can be set. A tracepoint is actually a special type of
12637 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12638 standard breakpoint commands. For instance, as with breakpoints,
12639 tracepoint numbers are successive integers starting from one, and many
12640 of the commands associated with tracepoints take the tracepoint number
12641 as their argument, to identify which tracepoint to work on.
12643 For each tracepoint, you can specify, in advance, some arbitrary set
12644 of data that you want the target to collect in the trace buffer when
12645 it hits that tracepoint. The collected data can include registers,
12646 local variables, or global data. Later, you can use @value{GDBN}
12647 commands to examine the values these data had at the time the
12648 tracepoint was hit.
12650 Tracepoints do not support every breakpoint feature. Ignore counts on
12651 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12652 commands when they are hit. Tracepoints may not be thread-specific
12655 @cindex fast tracepoints
12656 Some targets may support @dfn{fast tracepoints}, which are inserted in
12657 a different way (such as with a jump instead of a trap), that is
12658 faster but possibly restricted in where they may be installed.
12660 @cindex static tracepoints
12661 @cindex markers, static tracepoints
12662 @cindex probing markers, static tracepoints
12663 Regular and fast tracepoints are dynamic tracing facilities, meaning
12664 that they can be used to insert tracepoints at (almost) any location
12665 in the target. Some targets may also support controlling @dfn{static
12666 tracepoints} from @value{GDBN}. With static tracing, a set of
12667 instrumentation points, also known as @dfn{markers}, are embedded in
12668 the target program, and can be activated or deactivated by name or
12669 address. These are usually placed at locations which facilitate
12670 investigating what the target is actually doing. @value{GDBN}'s
12671 support for static tracing includes being able to list instrumentation
12672 points, and attach them with @value{GDBN} defined high level
12673 tracepoints that expose the whole range of convenience of
12674 @value{GDBN}'s tracepoints support. Namely, support for collecting
12675 registers values and values of global or local (to the instrumentation
12676 point) variables; tracepoint conditions and trace state variables.
12677 The act of installing a @value{GDBN} static tracepoint on an
12678 instrumentation point, or marker, is referred to as @dfn{probing} a
12679 static tracepoint marker.
12681 @code{gdbserver} supports tracepoints on some target systems.
12682 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12684 This section describes commands to set tracepoints and associated
12685 conditions and actions.
12688 * Create and Delete Tracepoints::
12689 * Enable and Disable Tracepoints::
12690 * Tracepoint Passcounts::
12691 * Tracepoint Conditions::
12692 * Trace State Variables::
12693 * Tracepoint Actions::
12694 * Listing Tracepoints::
12695 * Listing Static Tracepoint Markers::
12696 * Starting and Stopping Trace Experiments::
12697 * Tracepoint Restrictions::
12700 @node Create and Delete Tracepoints
12701 @subsection Create and Delete Tracepoints
12704 @cindex set tracepoint
12706 @item trace @var{location}
12707 The @code{trace} command is very similar to the @code{break} command.
12708 Its argument @var{location} can be any valid location.
12709 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12710 which is a point in the target program where the debugger will briefly stop,
12711 collect some data, and then allow the program to continue. Setting a tracepoint
12712 or changing its actions takes effect immediately if the remote stub
12713 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12715 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12716 these changes don't take effect until the next @code{tstart}
12717 command, and once a trace experiment is running, further changes will
12718 not have any effect until the next trace experiment starts. In addition,
12719 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12720 address is not yet resolved. (This is similar to pending breakpoints.)
12721 Pending tracepoints are not downloaded to the target and not installed
12722 until they are resolved. The resolution of pending tracepoints requires
12723 @value{GDBN} support---when debugging with the remote target, and
12724 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12725 tracing}), pending tracepoints can not be resolved (and downloaded to
12726 the remote stub) while @value{GDBN} is disconnected.
12728 Here are some examples of using the @code{trace} command:
12731 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12733 (@value{GDBP}) @b{trace +2} // 2 lines forward
12735 (@value{GDBP}) @b{trace my_function} // first source line of function
12737 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12739 (@value{GDBP}) @b{trace *0x2117c4} // an address
12743 You can abbreviate @code{trace} as @code{tr}.
12745 @item trace @var{location} if @var{cond}
12746 Set a tracepoint with condition @var{cond}; evaluate the expression
12747 @var{cond} each time the tracepoint is reached, and collect data only
12748 if the value is nonzero---that is, if @var{cond} evaluates as true.
12749 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12750 information on tracepoint conditions.
12752 @item ftrace @var{location} [ if @var{cond} ]
12753 @cindex set fast tracepoint
12754 @cindex fast tracepoints, setting
12756 The @code{ftrace} command sets a fast tracepoint. For targets that
12757 support them, fast tracepoints will use a more efficient but possibly
12758 less general technique to trigger data collection, such as a jump
12759 instruction instead of a trap, or some sort of hardware support. It
12760 may not be possible to create a fast tracepoint at the desired
12761 location, in which case the command will exit with an explanatory
12764 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12767 On 32-bit x86-architecture systems, fast tracepoints normally need to
12768 be placed at an instruction that is 5 bytes or longer, but can be
12769 placed at 4-byte instructions if the low 64K of memory of the target
12770 program is available to install trampolines. Some Unix-type systems,
12771 such as @sc{gnu}/Linux, exclude low addresses from the program's
12772 address space; but for instance with the Linux kernel it is possible
12773 to let @value{GDBN} use this area by doing a @command{sysctl} command
12774 to set the @code{mmap_min_addr} kernel parameter, as in
12777 sudo sysctl -w vm.mmap_min_addr=32768
12781 which sets the low address to 32K, which leaves plenty of room for
12782 trampolines. The minimum address should be set to a page boundary.
12784 @item strace @var{location} [ if @var{cond} ]
12785 @cindex set static tracepoint
12786 @cindex static tracepoints, setting
12787 @cindex probe static tracepoint marker
12789 The @code{strace} command sets a static tracepoint. For targets that
12790 support it, setting a static tracepoint probes a static
12791 instrumentation point, or marker, found at @var{location}. It may not
12792 be possible to set a static tracepoint at the desired location, in
12793 which case the command will exit with an explanatory message.
12795 @value{GDBN} handles arguments to @code{strace} exactly as for
12796 @code{trace}, with the addition that the user can also specify
12797 @code{-m @var{marker}} as @var{location}. This probes the marker
12798 identified by the @var{marker} string identifier. This identifier
12799 depends on the static tracepoint backend library your program is
12800 using. You can find all the marker identifiers in the @samp{ID} field
12801 of the @code{info static-tracepoint-markers} command output.
12802 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12803 Markers}. For example, in the following small program using the UST
12809 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12814 the marker id is composed of joining the first two arguments to the
12815 @code{trace_mark} call with a slash, which translates to:
12818 (@value{GDBP}) info static-tracepoint-markers
12819 Cnt Enb ID Address What
12820 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12826 so you may probe the marker above with:
12829 (@value{GDBP}) strace -m ust/bar33
12832 Static tracepoints accept an extra collect action --- @code{collect
12833 $_sdata}. This collects arbitrary user data passed in the probe point
12834 call to the tracing library. In the UST example above, you'll see
12835 that the third argument to @code{trace_mark} is a printf-like format
12836 string. The user data is then the result of running that formating
12837 string against the following arguments. Note that @code{info
12838 static-tracepoint-markers} command output lists that format string in
12839 the @samp{Data:} field.
12841 You can inspect this data when analyzing the trace buffer, by printing
12842 the $_sdata variable like any other variable available to
12843 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12846 @cindex last tracepoint number
12847 @cindex recent tracepoint number
12848 @cindex tracepoint number
12849 The convenience variable @code{$tpnum} records the tracepoint number
12850 of the most recently set tracepoint.
12852 @kindex delete tracepoint
12853 @cindex tracepoint deletion
12854 @item delete tracepoint @r{[}@var{num}@r{]}
12855 Permanently delete one or more tracepoints. With no argument, the
12856 default is to delete all tracepoints. Note that the regular
12857 @code{delete} command can remove tracepoints also.
12862 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12864 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12868 You can abbreviate this command as @code{del tr}.
12871 @node Enable and Disable Tracepoints
12872 @subsection Enable and Disable Tracepoints
12874 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12877 @kindex disable tracepoint
12878 @item disable tracepoint @r{[}@var{num}@r{]}
12879 Disable tracepoint @var{num}, or all tracepoints if no argument
12880 @var{num} is given. A disabled tracepoint will have no effect during
12881 a trace experiment, but it is not forgotten. You can re-enable
12882 a disabled tracepoint using the @code{enable tracepoint} command.
12883 If the command is issued during a trace experiment and the debug target
12884 has support for disabling tracepoints during a trace experiment, then the
12885 change will be effective immediately. Otherwise, it will be applied to the
12886 next trace experiment.
12888 @kindex enable tracepoint
12889 @item enable tracepoint @r{[}@var{num}@r{]}
12890 Enable tracepoint @var{num}, or all tracepoints. If this command is
12891 issued during a trace experiment and the debug target supports enabling
12892 tracepoints during a trace experiment, then the enabled tracepoints will
12893 become effective immediately. Otherwise, they will become effective the
12894 next time a trace experiment is run.
12897 @node Tracepoint Passcounts
12898 @subsection Tracepoint Passcounts
12902 @cindex tracepoint pass count
12903 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12904 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12905 automatically stop a trace experiment. If a tracepoint's passcount is
12906 @var{n}, then the trace experiment will be automatically stopped on
12907 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12908 @var{num} is not specified, the @code{passcount} command sets the
12909 passcount of the most recently defined tracepoint. If no passcount is
12910 given, the trace experiment will run until stopped explicitly by the
12916 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12917 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12919 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12920 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12921 (@value{GDBP}) @b{trace foo}
12922 (@value{GDBP}) @b{pass 3}
12923 (@value{GDBP}) @b{trace bar}
12924 (@value{GDBP}) @b{pass 2}
12925 (@value{GDBP}) @b{trace baz}
12926 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12927 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12928 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12929 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12933 @node Tracepoint Conditions
12934 @subsection Tracepoint Conditions
12935 @cindex conditional tracepoints
12936 @cindex tracepoint conditions
12938 The simplest sort of tracepoint collects data every time your program
12939 reaches a specified place. You can also specify a @dfn{condition} for
12940 a tracepoint. A condition is just a Boolean expression in your
12941 programming language (@pxref{Expressions, ,Expressions}). A
12942 tracepoint with a condition evaluates the expression each time your
12943 program reaches it, and data collection happens only if the condition
12946 Tracepoint conditions can be specified when a tracepoint is set, by
12947 using @samp{if} in the arguments to the @code{trace} command.
12948 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12949 also be set or changed at any time with the @code{condition} command,
12950 just as with breakpoints.
12952 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12953 the conditional expression itself. Instead, @value{GDBN} encodes the
12954 expression into an agent expression (@pxref{Agent Expressions})
12955 suitable for execution on the target, independently of @value{GDBN}.
12956 Global variables become raw memory locations, locals become stack
12957 accesses, and so forth.
12959 For instance, suppose you have a function that is usually called
12960 frequently, but should not be called after an error has occurred. You
12961 could use the following tracepoint command to collect data about calls
12962 of that function that happen while the error code is propagating
12963 through the program; an unconditional tracepoint could end up
12964 collecting thousands of useless trace frames that you would have to
12968 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12971 @node Trace State Variables
12972 @subsection Trace State Variables
12973 @cindex trace state variables
12975 A @dfn{trace state variable} is a special type of variable that is
12976 created and managed by target-side code. The syntax is the same as
12977 that for GDB's convenience variables (a string prefixed with ``$''),
12978 but they are stored on the target. They must be created explicitly,
12979 using a @code{tvariable} command. They are always 64-bit signed
12982 Trace state variables are remembered by @value{GDBN}, and downloaded
12983 to the target along with tracepoint information when the trace
12984 experiment starts. There are no intrinsic limits on the number of
12985 trace state variables, beyond memory limitations of the target.
12987 @cindex convenience variables, and trace state variables
12988 Although trace state variables are managed by the target, you can use
12989 them in print commands and expressions as if they were convenience
12990 variables; @value{GDBN} will get the current value from the target
12991 while the trace experiment is running. Trace state variables share
12992 the same namespace as other ``$'' variables, which means that you
12993 cannot have trace state variables with names like @code{$23} or
12994 @code{$pc}, nor can you have a trace state variable and a convenience
12995 variable with the same name.
12999 @item tvariable $@var{name} [ = @var{expression} ]
13001 The @code{tvariable} command creates a new trace state variable named
13002 @code{$@var{name}}, and optionally gives it an initial value of
13003 @var{expression}. The @var{expression} is evaluated when this command is
13004 entered; the result will be converted to an integer if possible,
13005 otherwise @value{GDBN} will report an error. A subsequent
13006 @code{tvariable} command specifying the same name does not create a
13007 variable, but instead assigns the supplied initial value to the
13008 existing variable of that name, overwriting any previous initial
13009 value. The default initial value is 0.
13011 @item info tvariables
13012 @kindex info tvariables
13013 List all the trace state variables along with their initial values.
13014 Their current values may also be displayed, if the trace experiment is
13017 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13018 @kindex delete tvariable
13019 Delete the given trace state variables, or all of them if no arguments
13024 @node Tracepoint Actions
13025 @subsection Tracepoint Action Lists
13029 @cindex tracepoint actions
13030 @item actions @r{[}@var{num}@r{]}
13031 This command will prompt for a list of actions to be taken when the
13032 tracepoint is hit. If the tracepoint number @var{num} is not
13033 specified, this command sets the actions for the one that was most
13034 recently defined (so that you can define a tracepoint and then say
13035 @code{actions} without bothering about its number). You specify the
13036 actions themselves on the following lines, one action at a time, and
13037 terminate the actions list with a line containing just @code{end}. So
13038 far, the only defined actions are @code{collect}, @code{teval}, and
13039 @code{while-stepping}.
13041 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13042 Commands, ,Breakpoint Command Lists}), except that only the defined
13043 actions are allowed; any other @value{GDBN} command is rejected.
13045 @cindex remove actions from a tracepoint
13046 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13047 and follow it immediately with @samp{end}.
13050 (@value{GDBP}) @b{collect @var{data}} // collect some data
13052 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13054 (@value{GDBP}) @b{end} // signals the end of actions.
13057 In the following example, the action list begins with @code{collect}
13058 commands indicating the things to be collected when the tracepoint is
13059 hit. Then, in order to single-step and collect additional data
13060 following the tracepoint, a @code{while-stepping} command is used,
13061 followed by the list of things to be collected after each step in a
13062 sequence of single steps. The @code{while-stepping} command is
13063 terminated by its own separate @code{end} command. Lastly, the action
13064 list is terminated by an @code{end} command.
13067 (@value{GDBP}) @b{trace foo}
13068 (@value{GDBP}) @b{actions}
13069 Enter actions for tracepoint 1, one per line:
13072 > while-stepping 12
13073 > collect $pc, arr[i]
13078 @kindex collect @r{(tracepoints)}
13079 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13080 Collect values of the given expressions when the tracepoint is hit.
13081 This command accepts a comma-separated list of any valid expressions.
13082 In addition to global, static, or local variables, the following
13083 special arguments are supported:
13087 Collect all registers.
13090 Collect all function arguments.
13093 Collect all local variables.
13096 Collect the return address. This is helpful if you want to see more
13099 @emph{Note:} The return address location can not always be reliably
13100 determined up front, and the wrong address / registers may end up
13101 collected instead. On some architectures the reliability is higher
13102 for tracepoints at function entry, while on others it's the opposite.
13103 When this happens, backtracing will stop because the return address is
13104 found unavailable (unless another collect rule happened to match it).
13107 Collects the number of arguments from the static probe at which the
13108 tracepoint is located.
13109 @xref{Static Probe Points}.
13111 @item $_probe_arg@var{n}
13112 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13113 from the static probe at which the tracepoint is located.
13114 @xref{Static Probe Points}.
13117 @vindex $_sdata@r{, collect}
13118 Collect static tracepoint marker specific data. Only available for
13119 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13120 Lists}. On the UST static tracepoints library backend, an
13121 instrumentation point resembles a @code{printf} function call. The
13122 tracing library is able to collect user specified data formatted to a
13123 character string using the format provided by the programmer that
13124 instrumented the program. Other backends have similar mechanisms.
13125 Here's an example of a UST marker call:
13128 const char master_name[] = "$your_name";
13129 trace_mark(channel1, marker1, "hello %s", master_name)
13132 In this case, collecting @code{$_sdata} collects the string
13133 @samp{hello $yourname}. When analyzing the trace buffer, you can
13134 inspect @samp{$_sdata} like any other variable available to
13138 You can give several consecutive @code{collect} commands, each one
13139 with a single argument, or one @code{collect} command with several
13140 arguments separated by commas; the effect is the same.
13142 The optional @var{mods} changes the usual handling of the arguments.
13143 @code{s} requests that pointers to chars be handled as strings, in
13144 particular collecting the contents of the memory being pointed at, up
13145 to the first zero. The upper bound is by default the value of the
13146 @code{print elements} variable; if @code{s} is followed by a decimal
13147 number, that is the upper bound instead. So for instance
13148 @samp{collect/s25 mystr} collects as many as 25 characters at
13151 The command @code{info scope} (@pxref{Symbols, info scope}) is
13152 particularly useful for figuring out what data to collect.
13154 @kindex teval @r{(tracepoints)}
13155 @item teval @var{expr1}, @var{expr2}, @dots{}
13156 Evaluate the given expressions when the tracepoint is hit. This
13157 command accepts a comma-separated list of expressions. The results
13158 are discarded, so this is mainly useful for assigning values to trace
13159 state variables (@pxref{Trace State Variables}) without adding those
13160 values to the trace buffer, as would be the case if the @code{collect}
13163 @kindex while-stepping @r{(tracepoints)}
13164 @item while-stepping @var{n}
13165 Perform @var{n} single-step instruction traces after the tracepoint,
13166 collecting new data after each step. The @code{while-stepping}
13167 command is followed by the list of what to collect while stepping
13168 (followed by its own @code{end} command):
13171 > while-stepping 12
13172 > collect $regs, myglobal
13178 Note that @code{$pc} is not automatically collected by
13179 @code{while-stepping}; you need to explicitly collect that register if
13180 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13183 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13184 @kindex set default-collect
13185 @cindex default collection action
13186 This variable is a list of expressions to collect at each tracepoint
13187 hit. It is effectively an additional @code{collect} action prepended
13188 to every tracepoint action list. The expressions are parsed
13189 individually for each tracepoint, so for instance a variable named
13190 @code{xyz} may be interpreted as a global for one tracepoint, and a
13191 local for another, as appropriate to the tracepoint's location.
13193 @item show default-collect
13194 @kindex show default-collect
13195 Show the list of expressions that are collected by default at each
13200 @node Listing Tracepoints
13201 @subsection Listing Tracepoints
13204 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13205 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13206 @cindex information about tracepoints
13207 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13208 Display information about the tracepoint @var{num}. If you don't
13209 specify a tracepoint number, displays information about all the
13210 tracepoints defined so far. The format is similar to that used for
13211 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13212 command, simply restricting itself to tracepoints.
13214 A tracepoint's listing may include additional information specific to
13219 its passcount as given by the @code{passcount @var{n}} command
13222 the state about installed on target of each location
13226 (@value{GDBP}) @b{info trace}
13227 Num Type Disp Enb Address What
13228 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13230 collect globfoo, $regs
13235 2 tracepoint keep y <MULTIPLE>
13237 2.1 y 0x0804859c in func4 at change-loc.h:35
13238 installed on target
13239 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13240 installed on target
13241 2.3 y <PENDING> set_tracepoint
13242 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13243 not installed on target
13248 This command can be abbreviated @code{info tp}.
13251 @node Listing Static Tracepoint Markers
13252 @subsection Listing Static Tracepoint Markers
13255 @kindex info static-tracepoint-markers
13256 @cindex information about static tracepoint markers
13257 @item info static-tracepoint-markers
13258 Display information about all static tracepoint markers defined in the
13261 For each marker, the following columns are printed:
13265 An incrementing counter, output to help readability. This is not a
13268 The marker ID, as reported by the target.
13269 @item Enabled or Disabled
13270 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13271 that are not enabled.
13273 Where the marker is in your program, as a memory address.
13275 Where the marker is in the source for your program, as a file and line
13276 number. If the debug information included in the program does not
13277 allow @value{GDBN} to locate the source of the marker, this column
13278 will be left blank.
13282 In addition, the following information may be printed for each marker:
13286 User data passed to the tracing library by the marker call. In the
13287 UST backend, this is the format string passed as argument to the
13289 @item Static tracepoints probing the marker
13290 The list of static tracepoints attached to the marker.
13294 (@value{GDBP}) info static-tracepoint-markers
13295 Cnt ID Enb Address What
13296 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13297 Data: number1 %d number2 %d
13298 Probed by static tracepoints: #2
13299 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13305 @node Starting and Stopping Trace Experiments
13306 @subsection Starting and Stopping Trace Experiments
13309 @kindex tstart [ @var{notes} ]
13310 @cindex start a new trace experiment
13311 @cindex collected data discarded
13313 This command starts the trace experiment, and begins collecting data.
13314 It has the side effect of discarding all the data collected in the
13315 trace buffer during the previous trace experiment. If any arguments
13316 are supplied, they are taken as a note and stored with the trace
13317 experiment's state. The notes may be arbitrary text, and are
13318 especially useful with disconnected tracing in a multi-user context;
13319 the notes can explain what the trace is doing, supply user contact
13320 information, and so forth.
13322 @kindex tstop [ @var{notes} ]
13323 @cindex stop a running trace experiment
13325 This command stops the trace experiment. If any arguments are
13326 supplied, they are recorded with the experiment as a note. This is
13327 useful if you are stopping a trace started by someone else, for
13328 instance if the trace is interfering with the system's behavior and
13329 needs to be stopped quickly.
13331 @strong{Note}: a trace experiment and data collection may stop
13332 automatically if any tracepoint's passcount is reached
13333 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13336 @cindex status of trace data collection
13337 @cindex trace experiment, status of
13339 This command displays the status of the current trace data
13343 Here is an example of the commands we described so far:
13346 (@value{GDBP}) @b{trace gdb_c_test}
13347 (@value{GDBP}) @b{actions}
13348 Enter actions for tracepoint #1, one per line.
13349 > collect $regs,$locals,$args
13350 > while-stepping 11
13354 (@value{GDBP}) @b{tstart}
13355 [time passes @dots{}]
13356 (@value{GDBP}) @b{tstop}
13359 @anchor{disconnected tracing}
13360 @cindex disconnected tracing
13361 You can choose to continue running the trace experiment even if
13362 @value{GDBN} disconnects from the target, voluntarily or
13363 involuntarily. For commands such as @code{detach}, the debugger will
13364 ask what you want to do with the trace. But for unexpected
13365 terminations (@value{GDBN} crash, network outage), it would be
13366 unfortunate to lose hard-won trace data, so the variable
13367 @code{disconnected-tracing} lets you decide whether the trace should
13368 continue running without @value{GDBN}.
13371 @item set disconnected-tracing on
13372 @itemx set disconnected-tracing off
13373 @kindex set disconnected-tracing
13374 Choose whether a tracing run should continue to run if @value{GDBN}
13375 has disconnected from the target. Note that @code{detach} or
13376 @code{quit} will ask you directly what to do about a running trace no
13377 matter what this variable's setting, so the variable is mainly useful
13378 for handling unexpected situations, such as loss of the network.
13380 @item show disconnected-tracing
13381 @kindex show disconnected-tracing
13382 Show the current choice for disconnected tracing.
13386 When you reconnect to the target, the trace experiment may or may not
13387 still be running; it might have filled the trace buffer in the
13388 meantime, or stopped for one of the other reasons. If it is running,
13389 it will continue after reconnection.
13391 Upon reconnection, the target will upload information about the
13392 tracepoints in effect. @value{GDBN} will then compare that
13393 information to the set of tracepoints currently defined, and attempt
13394 to match them up, allowing for the possibility that the numbers may
13395 have changed due to creation and deletion in the meantime. If one of
13396 the target's tracepoints does not match any in @value{GDBN}, the
13397 debugger will create a new tracepoint, so that you have a number with
13398 which to specify that tracepoint. This matching-up process is
13399 necessarily heuristic, and it may result in useless tracepoints being
13400 created; you may simply delete them if they are of no use.
13402 @cindex circular trace buffer
13403 If your target agent supports a @dfn{circular trace buffer}, then you
13404 can run a trace experiment indefinitely without filling the trace
13405 buffer; when space runs out, the agent deletes already-collected trace
13406 frames, oldest first, until there is enough room to continue
13407 collecting. This is especially useful if your tracepoints are being
13408 hit too often, and your trace gets terminated prematurely because the
13409 buffer is full. To ask for a circular trace buffer, simply set
13410 @samp{circular-trace-buffer} to on. You can set this at any time,
13411 including during tracing; if the agent can do it, it will change
13412 buffer handling on the fly, otherwise it will not take effect until
13416 @item set circular-trace-buffer on
13417 @itemx set circular-trace-buffer off
13418 @kindex set circular-trace-buffer
13419 Choose whether a tracing run should use a linear or circular buffer
13420 for trace data. A linear buffer will not lose any trace data, but may
13421 fill up prematurely, while a circular buffer will discard old trace
13422 data, but it will have always room for the latest tracepoint hits.
13424 @item show circular-trace-buffer
13425 @kindex show circular-trace-buffer
13426 Show the current choice for the trace buffer. Note that this may not
13427 match the agent's current buffer handling, nor is it guaranteed to
13428 match the setting that might have been in effect during a past run,
13429 for instance if you are looking at frames from a trace file.
13434 @item set trace-buffer-size @var{n}
13435 @itemx set trace-buffer-size unlimited
13436 @kindex set trace-buffer-size
13437 Request that the target use a trace buffer of @var{n} bytes. Not all
13438 targets will honor the request; they may have a compiled-in size for
13439 the trace buffer, or some other limitation. Set to a value of
13440 @code{unlimited} or @code{-1} to let the target use whatever size it
13441 likes. This is also the default.
13443 @item show trace-buffer-size
13444 @kindex show trace-buffer-size
13445 Show the current requested size for the trace buffer. Note that this
13446 will only match the actual size if the target supports size-setting,
13447 and was able to handle the requested size. For instance, if the
13448 target can only change buffer size between runs, this variable will
13449 not reflect the change until the next run starts. Use @code{tstatus}
13450 to get a report of the actual buffer size.
13454 @item set trace-user @var{text}
13455 @kindex set trace-user
13457 @item show trace-user
13458 @kindex show trace-user
13460 @item set trace-notes @var{text}
13461 @kindex set trace-notes
13462 Set the trace run's notes.
13464 @item show trace-notes
13465 @kindex show trace-notes
13466 Show the trace run's notes.
13468 @item set trace-stop-notes @var{text}
13469 @kindex set trace-stop-notes
13470 Set the trace run's stop notes. The handling of the note is as for
13471 @code{tstop} arguments; the set command is convenient way to fix a
13472 stop note that is mistaken or incomplete.
13474 @item show trace-stop-notes
13475 @kindex show trace-stop-notes
13476 Show the trace run's stop notes.
13480 @node Tracepoint Restrictions
13481 @subsection Tracepoint Restrictions
13483 @cindex tracepoint restrictions
13484 There are a number of restrictions on the use of tracepoints. As
13485 described above, tracepoint data gathering occurs on the target
13486 without interaction from @value{GDBN}. Thus the full capabilities of
13487 the debugger are not available during data gathering, and then at data
13488 examination time, you will be limited by only having what was
13489 collected. The following items describe some common problems, but it
13490 is not exhaustive, and you may run into additional difficulties not
13496 Tracepoint expressions are intended to gather objects (lvalues). Thus
13497 the full flexibility of GDB's expression evaluator is not available.
13498 You cannot call functions, cast objects to aggregate types, access
13499 convenience variables or modify values (except by assignment to trace
13500 state variables). Some language features may implicitly call
13501 functions (for instance Objective-C fields with accessors), and therefore
13502 cannot be collected either.
13505 Collection of local variables, either individually or in bulk with
13506 @code{$locals} or @code{$args}, during @code{while-stepping} may
13507 behave erratically. The stepping action may enter a new scope (for
13508 instance by stepping into a function), or the location of the variable
13509 may change (for instance it is loaded into a register). The
13510 tracepoint data recorded uses the location information for the
13511 variables that is correct for the tracepoint location. When the
13512 tracepoint is created, it is not possible, in general, to determine
13513 where the steps of a @code{while-stepping} sequence will advance the
13514 program---particularly if a conditional branch is stepped.
13517 Collection of an incompletely-initialized or partially-destroyed object
13518 may result in something that @value{GDBN} cannot display, or displays
13519 in a misleading way.
13522 When @value{GDBN} displays a pointer to character it automatically
13523 dereferences the pointer to also display characters of the string
13524 being pointed to. However, collecting the pointer during tracing does
13525 not automatically collect the string. You need to explicitly
13526 dereference the pointer and provide size information if you want to
13527 collect not only the pointer, but the memory pointed to. For example,
13528 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13532 It is not possible to collect a complete stack backtrace at a
13533 tracepoint. Instead, you may collect the registers and a few hundred
13534 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13535 (adjust to use the name of the actual stack pointer register on your
13536 target architecture, and the amount of stack you wish to capture).
13537 Then the @code{backtrace} command will show a partial backtrace when
13538 using a trace frame. The number of stack frames that can be examined
13539 depends on the sizes of the frames in the collected stack. Note that
13540 if you ask for a block so large that it goes past the bottom of the
13541 stack, the target agent may report an error trying to read from an
13545 If you do not collect registers at a tracepoint, @value{GDBN} can
13546 infer that the value of @code{$pc} must be the same as the address of
13547 the tracepoint and use that when you are looking at a trace frame
13548 for that tracepoint. However, this cannot work if the tracepoint has
13549 multiple locations (for instance if it was set in a function that was
13550 inlined), or if it has a @code{while-stepping} loop. In those cases
13551 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13556 @node Analyze Collected Data
13557 @section Using the Collected Data
13559 After the tracepoint experiment ends, you use @value{GDBN} commands
13560 for examining the trace data. The basic idea is that each tracepoint
13561 collects a trace @dfn{snapshot} every time it is hit and another
13562 snapshot every time it single-steps. All these snapshots are
13563 consecutively numbered from zero and go into a buffer, and you can
13564 examine them later. The way you examine them is to @dfn{focus} on a
13565 specific trace snapshot. When the remote stub is focused on a trace
13566 snapshot, it will respond to all @value{GDBN} requests for memory and
13567 registers by reading from the buffer which belongs to that snapshot,
13568 rather than from @emph{real} memory or registers of the program being
13569 debugged. This means that @strong{all} @value{GDBN} commands
13570 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13571 behave as if we were currently debugging the program state as it was
13572 when the tracepoint occurred. Any requests for data that are not in
13573 the buffer will fail.
13576 * tfind:: How to select a trace snapshot
13577 * tdump:: How to display all data for a snapshot
13578 * save tracepoints:: How to save tracepoints for a future run
13582 @subsection @code{tfind @var{n}}
13585 @cindex select trace snapshot
13586 @cindex find trace snapshot
13587 The basic command for selecting a trace snapshot from the buffer is
13588 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13589 counting from zero. If no argument @var{n} is given, the next
13590 snapshot is selected.
13592 Here are the various forms of using the @code{tfind} command.
13596 Find the first snapshot in the buffer. This is a synonym for
13597 @code{tfind 0} (since 0 is the number of the first snapshot).
13600 Stop debugging trace snapshots, resume @emph{live} debugging.
13603 Same as @samp{tfind none}.
13606 No argument means find the next trace snapshot or find the first
13607 one if no trace snapshot is selected.
13610 Find the previous trace snapshot before the current one. This permits
13611 retracing earlier steps.
13613 @item tfind tracepoint @var{num}
13614 Find the next snapshot associated with tracepoint @var{num}. Search
13615 proceeds forward from the last examined trace snapshot. If no
13616 argument @var{num} is given, it means find the next snapshot collected
13617 for the same tracepoint as the current snapshot.
13619 @item tfind pc @var{addr}
13620 Find the next snapshot associated with the value @var{addr} of the
13621 program counter. Search proceeds forward from the last examined trace
13622 snapshot. If no argument @var{addr} is given, it means find the next
13623 snapshot with the same value of PC as the current snapshot.
13625 @item tfind outside @var{addr1}, @var{addr2}
13626 Find the next snapshot whose PC is outside the given range of
13627 addresses (exclusive).
13629 @item tfind range @var{addr1}, @var{addr2}
13630 Find the next snapshot whose PC is between @var{addr1} and
13631 @var{addr2} (inclusive).
13633 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13634 Find the next snapshot associated with the source line @var{n}. If
13635 the optional argument @var{file} is given, refer to line @var{n} in
13636 that source file. Search proceeds forward from the last examined
13637 trace snapshot. If no argument @var{n} is given, it means find the
13638 next line other than the one currently being examined; thus saying
13639 @code{tfind line} repeatedly can appear to have the same effect as
13640 stepping from line to line in a @emph{live} debugging session.
13643 The default arguments for the @code{tfind} commands are specifically
13644 designed to make it easy to scan through the trace buffer. For
13645 instance, @code{tfind} with no argument selects the next trace
13646 snapshot, and @code{tfind -} with no argument selects the previous
13647 trace snapshot. So, by giving one @code{tfind} command, and then
13648 simply hitting @key{RET} repeatedly you can examine all the trace
13649 snapshots in order. Or, by saying @code{tfind -} and then hitting
13650 @key{RET} repeatedly you can examine the snapshots in reverse order.
13651 The @code{tfind line} command with no argument selects the snapshot
13652 for the next source line executed. The @code{tfind pc} command with
13653 no argument selects the next snapshot with the same program counter
13654 (PC) as the current frame. The @code{tfind tracepoint} command with
13655 no argument selects the next trace snapshot collected by the same
13656 tracepoint as the current one.
13658 In addition to letting you scan through the trace buffer manually,
13659 these commands make it easy to construct @value{GDBN} scripts that
13660 scan through the trace buffer and print out whatever collected data
13661 you are interested in. Thus, if we want to examine the PC, FP, and SP
13662 registers from each trace frame in the buffer, we can say this:
13665 (@value{GDBP}) @b{tfind start}
13666 (@value{GDBP}) @b{while ($trace_frame != -1)}
13667 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13668 $trace_frame, $pc, $sp, $fp
13672 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13673 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13674 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13675 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13676 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13677 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13678 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13679 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13680 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13681 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13682 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13685 Or, if we want to examine the variable @code{X} at each source line in
13689 (@value{GDBP}) @b{tfind start}
13690 (@value{GDBP}) @b{while ($trace_frame != -1)}
13691 > printf "Frame %d, X == %d\n", $trace_frame, X
13701 @subsection @code{tdump}
13703 @cindex dump all data collected at tracepoint
13704 @cindex tracepoint data, display
13706 This command takes no arguments. It prints all the data collected at
13707 the current trace snapshot.
13710 (@value{GDBP}) @b{trace 444}
13711 (@value{GDBP}) @b{actions}
13712 Enter actions for tracepoint #2, one per line:
13713 > collect $regs, $locals, $args, gdb_long_test
13716 (@value{GDBP}) @b{tstart}
13718 (@value{GDBP}) @b{tfind line 444}
13719 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13721 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13723 (@value{GDBP}) @b{tdump}
13724 Data collected at tracepoint 2, trace frame 1:
13725 d0 0xc4aa0085 -995491707
13729 d4 0x71aea3d 119204413
13732 d7 0x380035 3670069
13733 a0 0x19e24a 1696330
13734 a1 0x3000668 50333288
13736 a3 0x322000 3284992
13737 a4 0x3000698 50333336
13738 a5 0x1ad3cc 1758156
13739 fp 0x30bf3c 0x30bf3c
13740 sp 0x30bf34 0x30bf34
13742 pc 0x20b2c8 0x20b2c8
13746 p = 0x20e5b4 "gdb-test"
13753 gdb_long_test = 17 '\021'
13758 @code{tdump} works by scanning the tracepoint's current collection
13759 actions and printing the value of each expression listed. So
13760 @code{tdump} can fail, if after a run, you change the tracepoint's
13761 actions to mention variables that were not collected during the run.
13763 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13764 uses the collected value of @code{$pc} to distinguish between trace
13765 frames that were collected at the tracepoint hit, and frames that were
13766 collected while stepping. This allows it to correctly choose whether
13767 to display the basic list of collections, or the collections from the
13768 body of the while-stepping loop. However, if @code{$pc} was not collected,
13769 then @code{tdump} will always attempt to dump using the basic collection
13770 list, and may fail if a while-stepping frame does not include all the
13771 same data that is collected at the tracepoint hit.
13772 @c This is getting pretty arcane, example would be good.
13774 @node save tracepoints
13775 @subsection @code{save tracepoints @var{filename}}
13776 @kindex save tracepoints
13777 @kindex save-tracepoints
13778 @cindex save tracepoints for future sessions
13780 This command saves all current tracepoint definitions together with
13781 their actions and passcounts, into a file @file{@var{filename}}
13782 suitable for use in a later debugging session. To read the saved
13783 tracepoint definitions, use the @code{source} command (@pxref{Command
13784 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13785 alias for @w{@code{save tracepoints}}
13787 @node Tracepoint Variables
13788 @section Convenience Variables for Tracepoints
13789 @cindex tracepoint variables
13790 @cindex convenience variables for tracepoints
13793 @vindex $trace_frame
13794 @item (int) $trace_frame
13795 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13796 snapshot is selected.
13798 @vindex $tracepoint
13799 @item (int) $tracepoint
13800 The tracepoint for the current trace snapshot.
13802 @vindex $trace_line
13803 @item (int) $trace_line
13804 The line number for the current trace snapshot.
13806 @vindex $trace_file
13807 @item (char []) $trace_file
13808 The source file for the current trace snapshot.
13810 @vindex $trace_func
13811 @item (char []) $trace_func
13812 The name of the function containing @code{$tracepoint}.
13815 Note: @code{$trace_file} is not suitable for use in @code{printf},
13816 use @code{output} instead.
13818 Here's a simple example of using these convenience variables for
13819 stepping through all the trace snapshots and printing some of their
13820 data. Note that these are not the same as trace state variables,
13821 which are managed by the target.
13824 (@value{GDBP}) @b{tfind start}
13826 (@value{GDBP}) @b{while $trace_frame != -1}
13827 > output $trace_file
13828 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13834 @section Using Trace Files
13835 @cindex trace files
13837 In some situations, the target running a trace experiment may no
13838 longer be available; perhaps it crashed, or the hardware was needed
13839 for a different activity. To handle these cases, you can arrange to
13840 dump the trace data into a file, and later use that file as a source
13841 of trace data, via the @code{target tfile} command.
13846 @item tsave [ -r ] @var{filename}
13847 @itemx tsave [-ctf] @var{dirname}
13848 Save the trace data to @var{filename}. By default, this command
13849 assumes that @var{filename} refers to the host filesystem, so if
13850 necessary @value{GDBN} will copy raw trace data up from the target and
13851 then save it. If the target supports it, you can also supply the
13852 optional argument @code{-r} (``remote'') to direct the target to save
13853 the data directly into @var{filename} in its own filesystem, which may be
13854 more efficient if the trace buffer is very large. (Note, however, that
13855 @code{target tfile} can only read from files accessible to the host.)
13856 By default, this command will save trace frame in tfile format.
13857 You can supply the optional argument @code{-ctf} to save data in CTF
13858 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13859 that can be shared by multiple debugging and tracing tools. Please go to
13860 @indicateurl{http://www.efficios.com/ctf} to get more information.
13862 @kindex target tfile
13866 @item target tfile @var{filename}
13867 @itemx target ctf @var{dirname}
13868 Use the file named @var{filename} or directory named @var{dirname} as
13869 a source of trace data. Commands that examine data work as they do with
13870 a live target, but it is not possible to run any new trace experiments.
13871 @code{tstatus} will report the state of the trace run at the moment
13872 the data was saved, as well as the current trace frame you are examining.
13873 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13877 (@value{GDBP}) target ctf ctf.ctf
13878 (@value{GDBP}) tfind
13879 Found trace frame 0, tracepoint 2
13880 39 ++a; /* set tracepoint 1 here */
13881 (@value{GDBP}) tdump
13882 Data collected at tracepoint 2, trace frame 0:
13886 c = @{"123", "456", "789", "123", "456", "789"@}
13887 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13895 @chapter Debugging Programs That Use Overlays
13898 If your program is too large to fit completely in your target system's
13899 memory, you can sometimes use @dfn{overlays} to work around this
13900 problem. @value{GDBN} provides some support for debugging programs that
13904 * How Overlays Work:: A general explanation of overlays.
13905 * Overlay Commands:: Managing overlays in @value{GDBN}.
13906 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13907 mapped by asking the inferior.
13908 * Overlay Sample Program:: A sample program using overlays.
13911 @node How Overlays Work
13912 @section How Overlays Work
13913 @cindex mapped overlays
13914 @cindex unmapped overlays
13915 @cindex load address, overlay's
13916 @cindex mapped address
13917 @cindex overlay area
13919 Suppose you have a computer whose instruction address space is only 64
13920 kilobytes long, but which has much more memory which can be accessed by
13921 other means: special instructions, segment registers, or memory
13922 management hardware, for example. Suppose further that you want to
13923 adapt a program which is larger than 64 kilobytes to run on this system.
13925 One solution is to identify modules of your program which are relatively
13926 independent, and need not call each other directly; call these modules
13927 @dfn{overlays}. Separate the overlays from the main program, and place
13928 their machine code in the larger memory. Place your main program in
13929 instruction memory, but leave at least enough space there to hold the
13930 largest overlay as well.
13932 Now, to call a function located in an overlay, you must first copy that
13933 overlay's machine code from the large memory into the space set aside
13934 for it in the instruction memory, and then jump to its entry point
13937 @c NB: In the below the mapped area's size is greater or equal to the
13938 @c size of all overlays. This is intentional to remind the developer
13939 @c that overlays don't necessarily need to be the same size.
13943 Data Instruction Larger
13944 Address Space Address Space Address Space
13945 +-----------+ +-----------+ +-----------+
13947 +-----------+ +-----------+ +-----------+<-- overlay 1
13948 | program | | main | .----| overlay 1 | load address
13949 | variables | | program | | +-----------+
13950 | and heap | | | | | |
13951 +-----------+ | | | +-----------+<-- overlay 2
13952 | | +-----------+ | | | load address
13953 +-----------+ | | | .-| overlay 2 |
13955 mapped --->+-----------+ | | +-----------+
13956 address | | | | | |
13957 | overlay | <-' | | |
13958 | area | <---' +-----------+<-- overlay 3
13959 | | <---. | | load address
13960 +-----------+ `--| overlay 3 |
13967 @anchor{A code overlay}A code overlay
13971 The diagram (@pxref{A code overlay}) shows a system with separate data
13972 and instruction address spaces. To map an overlay, the program copies
13973 its code from the larger address space to the instruction address space.
13974 Since the overlays shown here all use the same mapped address, only one
13975 may be mapped at a time. For a system with a single address space for
13976 data and instructions, the diagram would be similar, except that the
13977 program variables and heap would share an address space with the main
13978 program and the overlay area.
13980 An overlay loaded into instruction memory and ready for use is called a
13981 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13982 instruction memory. An overlay not present (or only partially present)
13983 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13984 is its address in the larger memory. The mapped address is also called
13985 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13986 called the @dfn{load memory address}, or @dfn{LMA}.
13988 Unfortunately, overlays are not a completely transparent way to adapt a
13989 program to limited instruction memory. They introduce a new set of
13990 global constraints you must keep in mind as you design your program:
13995 Before calling or returning to a function in an overlay, your program
13996 must make sure that overlay is actually mapped. Otherwise, the call or
13997 return will transfer control to the right address, but in the wrong
13998 overlay, and your program will probably crash.
14001 If the process of mapping an overlay is expensive on your system, you
14002 will need to choose your overlays carefully to minimize their effect on
14003 your program's performance.
14006 The executable file you load onto your system must contain each
14007 overlay's instructions, appearing at the overlay's load address, not its
14008 mapped address. However, each overlay's instructions must be relocated
14009 and its symbols defined as if the overlay were at its mapped address.
14010 You can use GNU linker scripts to specify different load and relocation
14011 addresses for pieces of your program; see @ref{Overlay Description,,,
14012 ld.info, Using ld: the GNU linker}.
14015 The procedure for loading executable files onto your system must be able
14016 to load their contents into the larger address space as well as the
14017 instruction and data spaces.
14021 The overlay system described above is rather simple, and could be
14022 improved in many ways:
14027 If your system has suitable bank switch registers or memory management
14028 hardware, you could use those facilities to make an overlay's load area
14029 contents simply appear at their mapped address in instruction space.
14030 This would probably be faster than copying the overlay to its mapped
14031 area in the usual way.
14034 If your overlays are small enough, you could set aside more than one
14035 overlay area, and have more than one overlay mapped at a time.
14038 You can use overlays to manage data, as well as instructions. In
14039 general, data overlays are even less transparent to your design than
14040 code overlays: whereas code overlays only require care when you call or
14041 return to functions, data overlays require care every time you access
14042 the data. Also, if you change the contents of a data overlay, you
14043 must copy its contents back out to its load address before you can copy a
14044 different data overlay into the same mapped area.
14049 @node Overlay Commands
14050 @section Overlay Commands
14052 To use @value{GDBN}'s overlay support, each overlay in your program must
14053 correspond to a separate section of the executable file. The section's
14054 virtual memory address and load memory address must be the overlay's
14055 mapped and load addresses. Identifying overlays with sections allows
14056 @value{GDBN} to determine the appropriate address of a function or
14057 variable, depending on whether the overlay is mapped or not.
14059 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14060 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14065 Disable @value{GDBN}'s overlay support. When overlay support is
14066 disabled, @value{GDBN} assumes that all functions and variables are
14067 always present at their mapped addresses. By default, @value{GDBN}'s
14068 overlay support is disabled.
14070 @item overlay manual
14071 @cindex manual overlay debugging
14072 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14073 relies on you to tell it which overlays are mapped, and which are not,
14074 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14075 commands described below.
14077 @item overlay map-overlay @var{overlay}
14078 @itemx overlay map @var{overlay}
14079 @cindex map an overlay
14080 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14081 be the name of the object file section containing the overlay. When an
14082 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14083 functions and variables at their mapped addresses. @value{GDBN} assumes
14084 that any other overlays whose mapped ranges overlap that of
14085 @var{overlay} are now unmapped.
14087 @item overlay unmap-overlay @var{overlay}
14088 @itemx overlay unmap @var{overlay}
14089 @cindex unmap an overlay
14090 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14091 must be the name of the object file section containing the overlay.
14092 When an overlay is unmapped, @value{GDBN} assumes it can find the
14093 overlay's functions and variables at their load addresses.
14096 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14097 consults a data structure the overlay manager maintains in the inferior
14098 to see which overlays are mapped. For details, see @ref{Automatic
14099 Overlay Debugging}.
14101 @item overlay load-target
14102 @itemx overlay load
14103 @cindex reloading the overlay table
14104 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14105 re-reads the table @value{GDBN} automatically each time the inferior
14106 stops, so this command should only be necessary if you have changed the
14107 overlay mapping yourself using @value{GDBN}. This command is only
14108 useful when using automatic overlay debugging.
14110 @item overlay list-overlays
14111 @itemx overlay list
14112 @cindex listing mapped overlays
14113 Display a list of the overlays currently mapped, along with their mapped
14114 addresses, load addresses, and sizes.
14118 Normally, when @value{GDBN} prints a code address, it includes the name
14119 of the function the address falls in:
14122 (@value{GDBP}) print main
14123 $3 = @{int ()@} 0x11a0 <main>
14126 When overlay debugging is enabled, @value{GDBN} recognizes code in
14127 unmapped overlays, and prints the names of unmapped functions with
14128 asterisks around them. For example, if @code{foo} is a function in an
14129 unmapped overlay, @value{GDBN} prints it this way:
14132 (@value{GDBP}) overlay list
14133 No sections are mapped.
14134 (@value{GDBP}) print foo
14135 $5 = @{int (int)@} 0x100000 <*foo*>
14138 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14142 (@value{GDBP}) overlay list
14143 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14144 mapped at 0x1016 - 0x104a
14145 (@value{GDBP}) print foo
14146 $6 = @{int (int)@} 0x1016 <foo>
14149 When overlay debugging is enabled, @value{GDBN} can find the correct
14150 address for functions and variables in an overlay, whether or not the
14151 overlay is mapped. This allows most @value{GDBN} commands, like
14152 @code{break} and @code{disassemble}, to work normally, even on unmapped
14153 code. However, @value{GDBN}'s breakpoint support has some limitations:
14157 @cindex breakpoints in overlays
14158 @cindex overlays, setting breakpoints in
14159 You can set breakpoints in functions in unmapped overlays, as long as
14160 @value{GDBN} can write to the overlay at its load address.
14162 @value{GDBN} can not set hardware or simulator-based breakpoints in
14163 unmapped overlays. However, if you set a breakpoint at the end of your
14164 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14165 you are using manual overlay management), @value{GDBN} will re-set its
14166 breakpoints properly.
14170 @node Automatic Overlay Debugging
14171 @section Automatic Overlay Debugging
14172 @cindex automatic overlay debugging
14174 @value{GDBN} can automatically track which overlays are mapped and which
14175 are not, given some simple co-operation from the overlay manager in the
14176 inferior. If you enable automatic overlay debugging with the
14177 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14178 looks in the inferior's memory for certain variables describing the
14179 current state of the overlays.
14181 Here are the variables your overlay manager must define to support
14182 @value{GDBN}'s automatic overlay debugging:
14186 @item @code{_ovly_table}:
14187 This variable must be an array of the following structures:
14192 /* The overlay's mapped address. */
14195 /* The size of the overlay, in bytes. */
14196 unsigned long size;
14198 /* The overlay's load address. */
14201 /* Non-zero if the overlay is currently mapped;
14203 unsigned long mapped;
14207 @item @code{_novlys}:
14208 This variable must be a four-byte signed integer, holding the total
14209 number of elements in @code{_ovly_table}.
14213 To decide whether a particular overlay is mapped or not, @value{GDBN}
14214 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14215 @code{lma} members equal the VMA and LMA of the overlay's section in the
14216 executable file. When @value{GDBN} finds a matching entry, it consults
14217 the entry's @code{mapped} member to determine whether the overlay is
14220 In addition, your overlay manager may define a function called
14221 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14222 will silently set a breakpoint there. If the overlay manager then
14223 calls this function whenever it has changed the overlay table, this
14224 will enable @value{GDBN} to accurately keep track of which overlays
14225 are in program memory, and update any breakpoints that may be set
14226 in overlays. This will allow breakpoints to work even if the
14227 overlays are kept in ROM or other non-writable memory while they
14228 are not being executed.
14230 @node Overlay Sample Program
14231 @section Overlay Sample Program
14232 @cindex overlay example program
14234 When linking a program which uses overlays, you must place the overlays
14235 at their load addresses, while relocating them to run at their mapped
14236 addresses. To do this, you must write a linker script (@pxref{Overlay
14237 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14238 since linker scripts are specific to a particular host system, target
14239 architecture, and target memory layout, this manual cannot provide
14240 portable sample code demonstrating @value{GDBN}'s overlay support.
14242 However, the @value{GDBN} source distribution does contain an overlaid
14243 program, with linker scripts for a few systems, as part of its test
14244 suite. The program consists of the following files from
14245 @file{gdb/testsuite/gdb.base}:
14249 The main program file.
14251 A simple overlay manager, used by @file{overlays.c}.
14256 Overlay modules, loaded and used by @file{overlays.c}.
14259 Linker scripts for linking the test program on the @code{d10v-elf}
14260 and @code{m32r-elf} targets.
14263 You can build the test program using the @code{d10v-elf} GCC
14264 cross-compiler like this:
14267 $ d10v-elf-gcc -g -c overlays.c
14268 $ d10v-elf-gcc -g -c ovlymgr.c
14269 $ d10v-elf-gcc -g -c foo.c
14270 $ d10v-elf-gcc -g -c bar.c
14271 $ d10v-elf-gcc -g -c baz.c
14272 $ d10v-elf-gcc -g -c grbx.c
14273 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14274 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14277 The build process is identical for any other architecture, except that
14278 you must substitute the appropriate compiler and linker script for the
14279 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14283 @chapter Using @value{GDBN} with Different Languages
14286 Although programming languages generally have common aspects, they are
14287 rarely expressed in the same manner. For instance, in ANSI C,
14288 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14289 Modula-2, it is accomplished by @code{p^}. Values can also be
14290 represented (and displayed) differently. Hex numbers in C appear as
14291 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14293 @cindex working language
14294 Language-specific information is built into @value{GDBN} for some languages,
14295 allowing you to express operations like the above in your program's
14296 native language, and allowing @value{GDBN} to output values in a manner
14297 consistent with the syntax of your program's native language. The
14298 language you use to build expressions is called the @dfn{working
14302 * Setting:: Switching between source languages
14303 * Show:: Displaying the language
14304 * Checks:: Type and range checks
14305 * Supported Languages:: Supported languages
14306 * Unsupported Languages:: Unsupported languages
14310 @section Switching Between Source Languages
14312 There are two ways to control the working language---either have @value{GDBN}
14313 set it automatically, or select it manually yourself. You can use the
14314 @code{set language} command for either purpose. On startup, @value{GDBN}
14315 defaults to setting the language automatically. The working language is
14316 used to determine how expressions you type are interpreted, how values
14319 In addition to the working language, every source file that
14320 @value{GDBN} knows about has its own working language. For some object
14321 file formats, the compiler might indicate which language a particular
14322 source file is in. However, most of the time @value{GDBN} infers the
14323 language from the name of the file. The language of a source file
14324 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14325 show each frame appropriately for its own language. There is no way to
14326 set the language of a source file from within @value{GDBN}, but you can
14327 set the language associated with a filename extension. @xref{Show, ,
14328 Displaying the Language}.
14330 This is most commonly a problem when you use a program, such
14331 as @code{cfront} or @code{f2c}, that generates C but is written in
14332 another language. In that case, make the
14333 program use @code{#line} directives in its C output; that way
14334 @value{GDBN} will know the correct language of the source code of the original
14335 program, and will display that source code, not the generated C code.
14338 * Filenames:: Filename extensions and languages.
14339 * Manually:: Setting the working language manually
14340 * Automatically:: Having @value{GDBN} infer the source language
14344 @subsection List of Filename Extensions and Languages
14346 If a source file name ends in one of the following extensions, then
14347 @value{GDBN} infers that its language is the one indicated.
14365 C@t{++} source file
14371 Objective-C source file
14375 Fortran source file
14378 Modula-2 source file
14382 Assembler source file. This actually behaves almost like C, but
14383 @value{GDBN} does not skip over function prologues when stepping.
14386 In addition, you may set the language associated with a filename
14387 extension. @xref{Show, , Displaying the Language}.
14390 @subsection Setting the Working Language
14392 If you allow @value{GDBN} to set the language automatically,
14393 expressions are interpreted the same way in your debugging session and
14396 @kindex set language
14397 If you wish, you may set the language manually. To do this, issue the
14398 command @samp{set language @var{lang}}, where @var{lang} is the name of
14399 a language, such as
14400 @code{c} or @code{modula-2}.
14401 For a list of the supported languages, type @samp{set language}.
14403 Setting the language manually prevents @value{GDBN} from updating the working
14404 language automatically. This can lead to confusion if you try
14405 to debug a program when the working language is not the same as the
14406 source language, when an expression is acceptable to both
14407 languages---but means different things. For instance, if the current
14408 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14416 might not have the effect you intended. In C, this means to add
14417 @code{b} and @code{c} and place the result in @code{a}. The result
14418 printed would be the value of @code{a}. In Modula-2, this means to compare
14419 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14421 @node Automatically
14422 @subsection Having @value{GDBN} Infer the Source Language
14424 To have @value{GDBN} set the working language automatically, use
14425 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14426 then infers the working language. That is, when your program stops in a
14427 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14428 working language to the language recorded for the function in that
14429 frame. If the language for a frame is unknown (that is, if the function
14430 or block corresponding to the frame was defined in a source file that
14431 does not have a recognized extension), the current working language is
14432 not changed, and @value{GDBN} issues a warning.
14434 This may not seem necessary for most programs, which are written
14435 entirely in one source language. However, program modules and libraries
14436 written in one source language can be used by a main program written in
14437 a different source language. Using @samp{set language auto} in this
14438 case frees you from having to set the working language manually.
14441 @section Displaying the Language
14443 The following commands help you find out which language is the
14444 working language, and also what language source files were written in.
14447 @item show language
14448 @anchor{show language}
14449 @kindex show language
14450 Display the current working language. This is the
14451 language you can use with commands such as @code{print} to
14452 build and compute expressions that may involve variables in your program.
14455 @kindex info frame@r{, show the source language}
14456 Display the source language for this frame. This language becomes the
14457 working language if you use an identifier from this frame.
14458 @xref{Frame Info, ,Information about a Frame}, to identify the other
14459 information listed here.
14462 @kindex info source@r{, show the source language}
14463 Display the source language of this source file.
14464 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14465 information listed here.
14468 In unusual circumstances, you may have source files with extensions
14469 not in the standard list. You can then set the extension associated
14470 with a language explicitly:
14473 @item set extension-language @var{ext} @var{language}
14474 @kindex set extension-language
14475 Tell @value{GDBN} that source files with extension @var{ext} are to be
14476 assumed as written in the source language @var{language}.
14478 @item info extensions
14479 @kindex info extensions
14480 List all the filename extensions and the associated languages.
14484 @section Type and Range Checking
14486 Some languages are designed to guard you against making seemingly common
14487 errors through a series of compile- and run-time checks. These include
14488 checking the type of arguments to functions and operators and making
14489 sure mathematical overflows are caught at run time. Checks such as
14490 these help to ensure a program's correctness once it has been compiled
14491 by eliminating type mismatches and providing active checks for range
14492 errors when your program is running.
14494 By default @value{GDBN} checks for these errors according to the
14495 rules of the current source language. Although @value{GDBN} does not check
14496 the statements in your program, it can check expressions entered directly
14497 into @value{GDBN} for evaluation via the @code{print} command, for example.
14500 * Type Checking:: An overview of type checking
14501 * Range Checking:: An overview of range checking
14504 @cindex type checking
14505 @cindex checks, type
14506 @node Type Checking
14507 @subsection An Overview of Type Checking
14509 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14510 arguments to operators and functions have to be of the correct type,
14511 otherwise an error occurs. These checks prevent type mismatch
14512 errors from ever causing any run-time problems. For example,
14515 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14517 (@value{GDBP}) print obj.my_method (0)
14520 (@value{GDBP}) print obj.my_method (0x1234)
14521 Cannot resolve method klass::my_method to any overloaded instance
14524 The second example fails because in C@t{++} the integer constant
14525 @samp{0x1234} is not type-compatible with the pointer parameter type.
14527 For the expressions you use in @value{GDBN} commands, you can tell
14528 @value{GDBN} to not enforce strict type checking or
14529 to treat any mismatches as errors and abandon the expression;
14530 When type checking is disabled, @value{GDBN} successfully evaluates
14531 expressions like the second example above.
14533 Even if type checking is off, there may be other reasons
14534 related to type that prevent @value{GDBN} from evaluating an expression.
14535 For instance, @value{GDBN} does not know how to add an @code{int} and
14536 a @code{struct foo}. These particular type errors have nothing to do
14537 with the language in use and usually arise from expressions which make
14538 little sense to evaluate anyway.
14540 @value{GDBN} provides some additional commands for controlling type checking:
14542 @kindex set check type
14543 @kindex show check type
14545 @item set check type on
14546 @itemx set check type off
14547 Set strict type checking on or off. If any type mismatches occur in
14548 evaluating an expression while type checking is on, @value{GDBN} prints a
14549 message and aborts evaluation of the expression.
14551 @item show check type
14552 Show the current setting of type checking and whether @value{GDBN}
14553 is enforcing strict type checking rules.
14556 @cindex range checking
14557 @cindex checks, range
14558 @node Range Checking
14559 @subsection An Overview of Range Checking
14561 In some languages (such as Modula-2), it is an error to exceed the
14562 bounds of a type; this is enforced with run-time checks. Such range
14563 checking is meant to ensure program correctness by making sure
14564 computations do not overflow, or indices on an array element access do
14565 not exceed the bounds of the array.
14567 For expressions you use in @value{GDBN} commands, you can tell
14568 @value{GDBN} to treat range errors in one of three ways: ignore them,
14569 always treat them as errors and abandon the expression, or issue
14570 warnings but evaluate the expression anyway.
14572 A range error can result from numerical overflow, from exceeding an
14573 array index bound, or when you type a constant that is not a member
14574 of any type. Some languages, however, do not treat overflows as an
14575 error. In many implementations of C, mathematical overflow causes the
14576 result to ``wrap around'' to lower values---for example, if @var{m} is
14577 the largest integer value, and @var{s} is the smallest, then
14580 @var{m} + 1 @result{} @var{s}
14583 This, too, is specific to individual languages, and in some cases
14584 specific to individual compilers or machines. @xref{Supported Languages, ,
14585 Supported Languages}, for further details on specific languages.
14587 @value{GDBN} provides some additional commands for controlling the range checker:
14589 @kindex set check range
14590 @kindex show check range
14592 @item set check range auto
14593 Set range checking on or off based on the current working language.
14594 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14597 @item set check range on
14598 @itemx set check range off
14599 Set range checking on or off, overriding the default setting for the
14600 current working language. A warning is issued if the setting does not
14601 match the language default. If a range error occurs and range checking is on,
14602 then a message is printed and evaluation of the expression is aborted.
14604 @item set check range warn
14605 Output messages when the @value{GDBN} range checker detects a range error,
14606 but attempt to evaluate the expression anyway. Evaluating the
14607 expression may still be impossible for other reasons, such as accessing
14608 memory that the process does not own (a typical example from many Unix
14612 Show the current setting of the range checker, and whether or not it is
14613 being set automatically by @value{GDBN}.
14616 @node Supported Languages
14617 @section Supported Languages
14619 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14620 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14621 @c This is false ...
14622 Some @value{GDBN} features may be used in expressions regardless of the
14623 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14624 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14625 ,Expressions}) can be used with the constructs of any supported
14628 The following sections detail to what degree each source language is
14629 supported by @value{GDBN}. These sections are not meant to be language
14630 tutorials or references, but serve only as a reference guide to what the
14631 @value{GDBN} expression parser accepts, and what input and output
14632 formats should look like for different languages. There are many good
14633 books written on each of these languages; please look to these for a
14634 language reference or tutorial.
14637 * C:: C and C@t{++}
14640 * Objective-C:: Objective-C
14641 * OpenCL C:: OpenCL C
14642 * Fortran:: Fortran
14645 * Modula-2:: Modula-2
14650 @subsection C and C@t{++}
14652 @cindex C and C@t{++}
14653 @cindex expressions in C or C@t{++}
14655 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14656 to both languages. Whenever this is the case, we discuss those languages
14660 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14661 @cindex @sc{gnu} C@t{++}
14662 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14663 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14664 effectively, you must compile your C@t{++} programs with a supported
14665 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14666 compiler (@code{aCC}).
14669 * C Operators:: C and C@t{++} operators
14670 * C Constants:: C and C@t{++} constants
14671 * C Plus Plus Expressions:: C@t{++} expressions
14672 * C Defaults:: Default settings for C and C@t{++}
14673 * C Checks:: C and C@t{++} type and range checks
14674 * Debugging C:: @value{GDBN} and C
14675 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14676 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14680 @subsubsection C and C@t{++} Operators
14682 @cindex C and C@t{++} operators
14684 Operators must be defined on values of specific types. For instance,
14685 @code{+} is defined on numbers, but not on structures. Operators are
14686 often defined on groups of types.
14688 For the purposes of C and C@t{++}, the following definitions hold:
14693 @emph{Integral types} include @code{int} with any of its storage-class
14694 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14697 @emph{Floating-point types} include @code{float}, @code{double}, and
14698 @code{long double} (if supported by the target platform).
14701 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14704 @emph{Scalar types} include all of the above.
14709 The following operators are supported. They are listed here
14710 in order of increasing precedence:
14714 The comma or sequencing operator. Expressions in a comma-separated list
14715 are evaluated from left to right, with the result of the entire
14716 expression being the last expression evaluated.
14719 Assignment. The value of an assignment expression is the value
14720 assigned. Defined on scalar types.
14723 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14724 and translated to @w{@code{@var{a} = @var{a op b}}}.
14725 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14726 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14727 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14730 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14731 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14732 should be of an integral type.
14735 Logical @sc{or}. Defined on integral types.
14738 Logical @sc{and}. Defined on integral types.
14741 Bitwise @sc{or}. Defined on integral types.
14744 Bitwise exclusive-@sc{or}. Defined on integral types.
14747 Bitwise @sc{and}. Defined on integral types.
14750 Equality and inequality. Defined on scalar types. The value of these
14751 expressions is 0 for false and non-zero for true.
14753 @item <@r{, }>@r{, }<=@r{, }>=
14754 Less than, greater than, less than or equal, greater than or equal.
14755 Defined on scalar types. The value of these expressions is 0 for false
14756 and non-zero for true.
14759 left shift, and right shift. Defined on integral types.
14762 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14765 Addition and subtraction. Defined on integral types, floating-point types and
14768 @item *@r{, }/@r{, }%
14769 Multiplication, division, and modulus. Multiplication and division are
14770 defined on integral and floating-point types. Modulus is defined on
14774 Increment and decrement. When appearing before a variable, the
14775 operation is performed before the variable is used in an expression;
14776 when appearing after it, the variable's value is used before the
14777 operation takes place.
14780 Pointer dereferencing. Defined on pointer types. Same precedence as
14784 Address operator. Defined on variables. Same precedence as @code{++}.
14786 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14787 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14788 to examine the address
14789 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14793 Negative. Defined on integral and floating-point types. Same
14794 precedence as @code{++}.
14797 Logical negation. Defined on integral types. Same precedence as
14801 Bitwise complement operator. Defined on integral types. Same precedence as
14806 Structure member, and pointer-to-structure member. For convenience,
14807 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14808 pointer based on the stored type information.
14809 Defined on @code{struct} and @code{union} data.
14812 Dereferences of pointers to members.
14815 Array indexing. @code{@var{a}[@var{i}]} is defined as
14816 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14819 Function parameter list. Same precedence as @code{->}.
14822 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14823 and @code{class} types.
14826 Doubled colons also represent the @value{GDBN} scope operator
14827 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14831 If an operator is redefined in the user code, @value{GDBN} usually
14832 attempts to invoke the redefined version instead of using the operator's
14833 predefined meaning.
14836 @subsubsection C and C@t{++} Constants
14838 @cindex C and C@t{++} constants
14840 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14845 Integer constants are a sequence of digits. Octal constants are
14846 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14847 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14848 @samp{l}, specifying that the constant should be treated as a
14852 Floating point constants are a sequence of digits, followed by a decimal
14853 point, followed by a sequence of digits, and optionally followed by an
14854 exponent. An exponent is of the form:
14855 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14856 sequence of digits. The @samp{+} is optional for positive exponents.
14857 A floating-point constant may also end with a letter @samp{f} or
14858 @samp{F}, specifying that the constant should be treated as being of
14859 the @code{float} (as opposed to the default @code{double}) type; or with
14860 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14864 Enumerated constants consist of enumerated identifiers, or their
14865 integral equivalents.
14868 Character constants are a single character surrounded by single quotes
14869 (@code{'}), or a number---the ordinal value of the corresponding character
14870 (usually its @sc{ascii} value). Within quotes, the single character may
14871 be represented by a letter or by @dfn{escape sequences}, which are of
14872 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14873 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14874 @samp{@var{x}} is a predefined special character---for example,
14875 @samp{\n} for newline.
14877 Wide character constants can be written by prefixing a character
14878 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14879 form of @samp{x}. The target wide character set is used when
14880 computing the value of this constant (@pxref{Character Sets}).
14883 String constants are a sequence of character constants surrounded by
14884 double quotes (@code{"}). Any valid character constant (as described
14885 above) may appear. Double quotes within the string must be preceded by
14886 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14889 Wide string constants can be written by prefixing a string constant
14890 with @samp{L}, as in C. The target wide character set is used when
14891 computing the value of this constant (@pxref{Character Sets}).
14894 Pointer constants are an integral value. You can also write pointers
14895 to constants using the C operator @samp{&}.
14898 Array constants are comma-separated lists surrounded by braces @samp{@{}
14899 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14900 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14901 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14904 @node C Plus Plus Expressions
14905 @subsubsection C@t{++} Expressions
14907 @cindex expressions in C@t{++}
14908 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14910 @cindex debugging C@t{++} programs
14911 @cindex C@t{++} compilers
14912 @cindex debug formats and C@t{++}
14913 @cindex @value{NGCC} and C@t{++}
14915 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14916 the proper compiler and the proper debug format. Currently,
14917 @value{GDBN} works best when debugging C@t{++} code that is compiled
14918 with the most recent version of @value{NGCC} possible. The DWARF
14919 debugging format is preferred; @value{NGCC} defaults to this on most
14920 popular platforms. Other compilers and/or debug formats are likely to
14921 work badly or not at all when using @value{GDBN} to debug C@t{++}
14922 code. @xref{Compilation}.
14927 @cindex member functions
14929 Member function calls are allowed; you can use expressions like
14932 count = aml->GetOriginal(x, y)
14935 @vindex this@r{, inside C@t{++} member functions}
14936 @cindex namespace in C@t{++}
14938 While a member function is active (in the selected stack frame), your
14939 expressions have the same namespace available as the member function;
14940 that is, @value{GDBN} allows implicit references to the class instance
14941 pointer @code{this} following the same rules as C@t{++}. @code{using}
14942 declarations in the current scope are also respected by @value{GDBN}.
14944 @cindex call overloaded functions
14945 @cindex overloaded functions, calling
14946 @cindex type conversions in C@t{++}
14948 You can call overloaded functions; @value{GDBN} resolves the function
14949 call to the right definition, with some restrictions. @value{GDBN} does not
14950 perform overload resolution involving user-defined type conversions,
14951 calls to constructors, or instantiations of templates that do not exist
14952 in the program. It also cannot handle ellipsis argument lists or
14955 It does perform integral conversions and promotions, floating-point
14956 promotions, arithmetic conversions, pointer conversions, conversions of
14957 class objects to base classes, and standard conversions such as those of
14958 functions or arrays to pointers; it requires an exact match on the
14959 number of function arguments.
14961 Overload resolution is always performed, unless you have specified
14962 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14963 ,@value{GDBN} Features for C@t{++}}.
14965 You must specify @code{set overload-resolution off} in order to use an
14966 explicit function signature to call an overloaded function, as in
14968 p 'foo(char,int)'('x', 13)
14971 The @value{GDBN} command-completion facility can simplify this;
14972 see @ref{Completion, ,Command Completion}.
14974 @cindex reference declarations
14976 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
14977 references; you can use them in expressions just as you do in C@t{++}
14978 source---they are automatically dereferenced.
14980 In the parameter list shown when @value{GDBN} displays a frame, the values of
14981 reference variables are not displayed (unlike other variables); this
14982 avoids clutter, since references are often used for large structures.
14983 The @emph{address} of a reference variable is always shown, unless
14984 you have specified @samp{set print address off}.
14987 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14988 expressions can use it just as expressions in your program do. Since
14989 one scope may be defined in another, you can use @code{::} repeatedly if
14990 necessary, for example in an expression like
14991 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14992 resolving name scope by reference to source files, in both C and C@t{++}
14993 debugging (@pxref{Variables, ,Program Variables}).
14996 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15001 @subsubsection C and C@t{++} Defaults
15003 @cindex C and C@t{++} defaults
15005 If you allow @value{GDBN} to set range checking automatically, it
15006 defaults to @code{off} whenever the working language changes to
15007 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15008 selects the working language.
15010 If you allow @value{GDBN} to set the language automatically, it
15011 recognizes source files whose names end with @file{.c}, @file{.C}, or
15012 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15013 these files, it sets the working language to C or C@t{++}.
15014 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15015 for further details.
15018 @subsubsection C and C@t{++} Type and Range Checks
15020 @cindex C and C@t{++} checks
15022 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15023 checking is used. However, if you turn type checking off, @value{GDBN}
15024 will allow certain non-standard conversions, such as promoting integer
15025 constants to pointers.
15027 Range checking, if turned on, is done on mathematical operations. Array
15028 indices are not checked, since they are often used to index a pointer
15029 that is not itself an array.
15032 @subsubsection @value{GDBN} and C
15034 The @code{set print union} and @code{show print union} commands apply to
15035 the @code{union} type. When set to @samp{on}, any @code{union} that is
15036 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15037 appears as @samp{@{...@}}.
15039 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15040 with pointers and a memory allocation function. @xref{Expressions,
15043 @node Debugging C Plus Plus
15044 @subsubsection @value{GDBN} Features for C@t{++}
15046 @cindex commands for C@t{++}
15048 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15049 designed specifically for use with C@t{++}. Here is a summary:
15052 @cindex break in overloaded functions
15053 @item @r{breakpoint menus}
15054 When you want a breakpoint in a function whose name is overloaded,
15055 @value{GDBN} has the capability to display a menu of possible breakpoint
15056 locations to help you specify which function definition you want.
15057 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15059 @cindex overloading in C@t{++}
15060 @item rbreak @var{regex}
15061 Setting breakpoints using regular expressions is helpful for setting
15062 breakpoints on overloaded functions that are not members of any special
15064 @xref{Set Breaks, ,Setting Breakpoints}.
15066 @cindex C@t{++} exception handling
15068 @itemx catch rethrow
15070 Debug C@t{++} exception handling using these commands. @xref{Set
15071 Catchpoints, , Setting Catchpoints}.
15073 @cindex inheritance
15074 @item ptype @var{typename}
15075 Print inheritance relationships as well as other information for type
15077 @xref{Symbols, ,Examining the Symbol Table}.
15079 @item info vtbl @var{expression}.
15080 The @code{info vtbl} command can be used to display the virtual
15081 method tables of the object computed by @var{expression}. This shows
15082 one entry per virtual table; there may be multiple virtual tables when
15083 multiple inheritance is in use.
15085 @cindex C@t{++} demangling
15086 @item demangle @var{name}
15087 Demangle @var{name}.
15088 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15090 @cindex C@t{++} symbol display
15091 @item set print demangle
15092 @itemx show print demangle
15093 @itemx set print asm-demangle
15094 @itemx show print asm-demangle
15095 Control whether C@t{++} symbols display in their source form, both when
15096 displaying code as C@t{++} source and when displaying disassemblies.
15097 @xref{Print Settings, ,Print Settings}.
15099 @item set print object
15100 @itemx show print object
15101 Choose whether to print derived (actual) or declared types of objects.
15102 @xref{Print Settings, ,Print Settings}.
15104 @item set print vtbl
15105 @itemx show print vtbl
15106 Control the format for printing virtual function tables.
15107 @xref{Print Settings, ,Print Settings}.
15108 (The @code{vtbl} commands do not work on programs compiled with the HP
15109 ANSI C@t{++} compiler (@code{aCC}).)
15111 @kindex set overload-resolution
15112 @cindex overloaded functions, overload resolution
15113 @item set overload-resolution on
15114 Enable overload resolution for C@t{++} expression evaluation. The default
15115 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15116 and searches for a function whose signature matches the argument types,
15117 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15118 Expressions, ,C@t{++} Expressions}, for details).
15119 If it cannot find a match, it emits a message.
15121 @item set overload-resolution off
15122 Disable overload resolution for C@t{++} expression evaluation. For
15123 overloaded functions that are not class member functions, @value{GDBN}
15124 chooses the first function of the specified name that it finds in the
15125 symbol table, whether or not its arguments are of the correct type. For
15126 overloaded functions that are class member functions, @value{GDBN}
15127 searches for a function whose signature @emph{exactly} matches the
15130 @kindex show overload-resolution
15131 @item show overload-resolution
15132 Show the current setting of overload resolution.
15134 @item @r{Overloaded symbol names}
15135 You can specify a particular definition of an overloaded symbol, using
15136 the same notation that is used to declare such symbols in C@t{++}: type
15137 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15138 also use the @value{GDBN} command-line word completion facilities to list the
15139 available choices, or to finish the type list for you.
15140 @xref{Completion,, Command Completion}, for details on how to do this.
15142 @item @r{Breakpoints in functions with ABI tags}
15144 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15145 correspond to changes in the ABI of a type, function, or variable that
15146 would not otherwise be reflected in a mangled name. See
15147 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15150 The ABI tags are visible in C@t{++} demangled names. For example, a
15151 function that returns a std::string:
15154 std::string function(int);
15158 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15159 tag, and @value{GDBN} displays the symbol like this:
15162 function[abi:cxx11](int)
15165 You can set a breakpoint on such functions simply as if they had no
15169 (gdb) b function(int)
15170 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15171 (gdb) info breakpoints
15172 Num Type Disp Enb Address What
15173 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15177 On the rare occasion you need to disambiguate between different ABI
15178 tags, you can do so by simply including the ABI tag in the function
15182 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15186 @node Decimal Floating Point
15187 @subsubsection Decimal Floating Point format
15188 @cindex decimal floating point format
15190 @value{GDBN} can examine, set and perform computations with numbers in
15191 decimal floating point format, which in the C language correspond to the
15192 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15193 specified by the extension to support decimal floating-point arithmetic.
15195 There are two encodings in use, depending on the architecture: BID (Binary
15196 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15197 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15200 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15201 to manipulate decimal floating point numbers, it is not possible to convert
15202 (using a cast, for example) integers wider than 32-bit to decimal float.
15204 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15205 point computations, error checking in decimal float operations ignores
15206 underflow, overflow and divide by zero exceptions.
15208 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15209 to inspect @code{_Decimal128} values stored in floating point registers.
15210 See @ref{PowerPC,,PowerPC} for more details.
15216 @value{GDBN} can be used to debug programs written in D and compiled with
15217 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15218 specific feature --- dynamic arrays.
15223 @cindex Go (programming language)
15224 @value{GDBN} can be used to debug programs written in Go and compiled with
15225 @file{gccgo} or @file{6g} compilers.
15227 Here is a summary of the Go-specific features and restrictions:
15230 @cindex current Go package
15231 @item The current Go package
15232 The name of the current package does not need to be specified when
15233 specifying global variables and functions.
15235 For example, given the program:
15239 var myglob = "Shall we?"
15245 When stopped inside @code{main} either of these work:
15249 (gdb) p main.myglob
15252 @cindex builtin Go types
15253 @item Builtin Go types
15254 The @code{string} type is recognized by @value{GDBN} and is printed
15257 @cindex builtin Go functions
15258 @item Builtin Go functions
15259 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15260 function and handles it internally.
15262 @cindex restrictions on Go expressions
15263 @item Restrictions on Go expressions
15264 All Go operators are supported except @code{&^}.
15265 The Go @code{_} ``blank identifier'' is not supported.
15266 Automatic dereferencing of pointers is not supported.
15270 @subsection Objective-C
15272 @cindex Objective-C
15273 This section provides information about some commands and command
15274 options that are useful for debugging Objective-C code. See also
15275 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15276 few more commands specific to Objective-C support.
15279 * Method Names in Commands::
15280 * The Print Command with Objective-C::
15283 @node Method Names in Commands
15284 @subsubsection Method Names in Commands
15286 The following commands have been extended to accept Objective-C method
15287 names as line specifications:
15289 @kindex clear@r{, and Objective-C}
15290 @kindex break@r{, and Objective-C}
15291 @kindex info line@r{, and Objective-C}
15292 @kindex jump@r{, and Objective-C}
15293 @kindex list@r{, and Objective-C}
15297 @item @code{info line}
15302 A fully qualified Objective-C method name is specified as
15305 -[@var{Class} @var{methodName}]
15308 where the minus sign is used to indicate an instance method and a
15309 plus sign (not shown) is used to indicate a class method. The class
15310 name @var{Class} and method name @var{methodName} are enclosed in
15311 brackets, similar to the way messages are specified in Objective-C
15312 source code. For example, to set a breakpoint at the @code{create}
15313 instance method of class @code{Fruit} in the program currently being
15317 break -[Fruit create]
15320 To list ten program lines around the @code{initialize} class method,
15324 list +[NSText initialize]
15327 In the current version of @value{GDBN}, the plus or minus sign is
15328 required. In future versions of @value{GDBN}, the plus or minus
15329 sign will be optional, but you can use it to narrow the search. It
15330 is also possible to specify just a method name:
15336 You must specify the complete method name, including any colons. If
15337 your program's source files contain more than one @code{create} method,
15338 you'll be presented with a numbered list of classes that implement that
15339 method. Indicate your choice by number, or type @samp{0} to exit if
15342 As another example, to clear a breakpoint established at the
15343 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15346 clear -[NSWindow makeKeyAndOrderFront:]
15349 @node The Print Command with Objective-C
15350 @subsubsection The Print Command With Objective-C
15351 @cindex Objective-C, print objects
15352 @kindex print-object
15353 @kindex po @r{(@code{print-object})}
15355 The print command has also been extended to accept methods. For example:
15358 print -[@var{object} hash]
15361 @cindex print an Objective-C object description
15362 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15364 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15365 and print the result. Also, an additional command has been added,
15366 @code{print-object} or @code{po} for short, which is meant to print
15367 the description of an object. However, this command may only work
15368 with certain Objective-C libraries that have a particular hook
15369 function, @code{_NSPrintForDebugger}, defined.
15372 @subsection OpenCL C
15375 This section provides information about @value{GDBN}s OpenCL C support.
15378 * OpenCL C Datatypes::
15379 * OpenCL C Expressions::
15380 * OpenCL C Operators::
15383 @node OpenCL C Datatypes
15384 @subsubsection OpenCL C Datatypes
15386 @cindex OpenCL C Datatypes
15387 @value{GDBN} supports the builtin scalar and vector datatypes specified
15388 by OpenCL 1.1. In addition the half- and double-precision floating point
15389 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15390 extensions are also known to @value{GDBN}.
15392 @node OpenCL C Expressions
15393 @subsubsection OpenCL C Expressions
15395 @cindex OpenCL C Expressions
15396 @value{GDBN} supports accesses to vector components including the access as
15397 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15398 supported by @value{GDBN} can be used as well.
15400 @node OpenCL C Operators
15401 @subsubsection OpenCL C Operators
15403 @cindex OpenCL C Operators
15404 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15408 @subsection Fortran
15409 @cindex Fortran-specific support in @value{GDBN}
15411 @value{GDBN} can be used to debug programs written in Fortran, but it
15412 currently supports only the features of Fortran 77 language.
15414 @cindex trailing underscore, in Fortran symbols
15415 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15416 among them) append an underscore to the names of variables and
15417 functions. When you debug programs compiled by those compilers, you
15418 will need to refer to variables and functions with a trailing
15422 * Fortran Operators:: Fortran operators and expressions
15423 * Fortran Defaults:: Default settings for Fortran
15424 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15427 @node Fortran Operators
15428 @subsubsection Fortran Operators and Expressions
15430 @cindex Fortran operators and expressions
15432 Operators must be defined on values of specific types. For instance,
15433 @code{+} is defined on numbers, but not on characters or other non-
15434 arithmetic types. Operators are often defined on groups of types.
15438 The exponentiation operator. It raises the first operand to the power
15442 The range operator. Normally used in the form of array(low:high) to
15443 represent a section of array.
15446 The access component operator. Normally used to access elements in derived
15447 types. Also suitable for unions. As unions aren't part of regular Fortran,
15448 this can only happen when accessing a register that uses a gdbarch-defined
15452 @node Fortran Defaults
15453 @subsubsection Fortran Defaults
15455 @cindex Fortran Defaults
15457 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15458 default uses case-insensitive matches for Fortran symbols. You can
15459 change that with the @samp{set case-insensitive} command, see
15460 @ref{Symbols}, for the details.
15462 @node Special Fortran Commands
15463 @subsubsection Special Fortran Commands
15465 @cindex Special Fortran commands
15467 @value{GDBN} has some commands to support Fortran-specific features,
15468 such as displaying common blocks.
15471 @cindex @code{COMMON} blocks, Fortran
15472 @kindex info common
15473 @item info common @r{[}@var{common-name}@r{]}
15474 This command prints the values contained in the Fortran @code{COMMON}
15475 block whose name is @var{common-name}. With no argument, the names of
15476 all @code{COMMON} blocks visible at the current program location are
15483 @cindex Pascal support in @value{GDBN}, limitations
15484 Debugging Pascal programs which use sets, subranges, file variables, or
15485 nested functions does not currently work. @value{GDBN} does not support
15486 entering expressions, printing values, or similar features using Pascal
15489 The Pascal-specific command @code{set print pascal_static-members}
15490 controls whether static members of Pascal objects are displayed.
15491 @xref{Print Settings, pascal_static-members}.
15496 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15497 Programming Language}. Type- and value-printing, and expression
15498 parsing, are reasonably complete. However, there are a few
15499 peculiarities and holes to be aware of.
15503 Linespecs (@pxref{Specify Location}) are never relative to the current
15504 crate. Instead, they act as if there were a global namespace of
15505 crates, somewhat similar to the way @code{extern crate} behaves.
15507 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15508 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15509 to set a breakpoint in a function named @samp{f} in a crate named
15512 As a consequence of this approach, linespecs also cannot refer to
15513 items using @samp{self::} or @samp{super::}.
15516 Because @value{GDBN} implements Rust name-lookup semantics in
15517 expressions, it will sometimes prepend the current crate to a name.
15518 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15519 @samp{K}, then @code{print ::x::y} will try to find the symbol
15522 However, since it is useful to be able to refer to other crates when
15523 debugging, @value{GDBN} provides the @code{extern} extension to
15524 circumvent this. To use the extension, just put @code{extern} before
15525 a path expression to refer to the otherwise unavailable ``global''
15528 In the above example, if you wanted to refer to the symbol @samp{y} in
15529 the crate @samp{x}, you would use @code{print extern x::y}.
15532 The Rust expression evaluator does not support ``statement-like''
15533 expressions such as @code{if} or @code{match}, or lambda expressions.
15536 Tuple expressions are not implemented.
15539 The Rust expression evaluator does not currently implement the
15540 @code{Drop} trait. Objects that may be created by the evaluator will
15541 never be destroyed.
15544 @value{GDBN} does not implement type inference for generics. In order
15545 to call generic functions or otherwise refer to generic items, you
15546 will have to specify the type parameters manually.
15549 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15550 cases this does not cause any problems. However, in an expression
15551 context, completing a generic function name will give syntactically
15552 invalid results. This happens because Rust requires the @samp{::}
15553 operator between the function name and its generic arguments. For
15554 example, @value{GDBN} might provide a completion like
15555 @code{crate::f<u32>}, where the parser would require
15556 @code{crate::f::<u32>}.
15559 As of this writing, the Rust compiler (version 1.8) has a few holes in
15560 the debugging information it generates. These holes prevent certain
15561 features from being implemented by @value{GDBN}:
15565 Method calls cannot be made via traits.
15568 Trait objects cannot be created or inspected.
15571 Operator overloading is not implemented.
15574 When debugging in a monomorphized function, you cannot use the generic
15578 The type @code{Self} is not available.
15581 @code{use} statements are not available, so some names may not be
15582 available in the crate.
15587 @subsection Modula-2
15589 @cindex Modula-2, @value{GDBN} support
15591 The extensions made to @value{GDBN} to support Modula-2 only support
15592 output from the @sc{gnu} Modula-2 compiler (which is currently being
15593 developed). Other Modula-2 compilers are not currently supported, and
15594 attempting to debug executables produced by them is most likely
15595 to give an error as @value{GDBN} reads in the executable's symbol
15598 @cindex expressions in Modula-2
15600 * M2 Operators:: Built-in operators
15601 * Built-In Func/Proc:: Built-in functions and procedures
15602 * M2 Constants:: Modula-2 constants
15603 * M2 Types:: Modula-2 types
15604 * M2 Defaults:: Default settings for Modula-2
15605 * Deviations:: Deviations from standard Modula-2
15606 * M2 Checks:: Modula-2 type and range checks
15607 * M2 Scope:: The scope operators @code{::} and @code{.}
15608 * GDB/M2:: @value{GDBN} and Modula-2
15612 @subsubsection Operators
15613 @cindex Modula-2 operators
15615 Operators must be defined on values of specific types. For instance,
15616 @code{+} is defined on numbers, but not on structures. Operators are
15617 often defined on groups of types. For the purposes of Modula-2, the
15618 following definitions hold:
15623 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15627 @emph{Character types} consist of @code{CHAR} and its subranges.
15630 @emph{Floating-point types} consist of @code{REAL}.
15633 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15637 @emph{Scalar types} consist of all of the above.
15640 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15643 @emph{Boolean types} consist of @code{BOOLEAN}.
15647 The following operators are supported, and appear in order of
15648 increasing precedence:
15652 Function argument or array index separator.
15655 Assignment. The value of @var{var} @code{:=} @var{value} is
15659 Less than, greater than on integral, floating-point, or enumerated
15663 Less than or equal to, greater than or equal to
15664 on integral, floating-point and enumerated types, or set inclusion on
15665 set types. Same precedence as @code{<}.
15667 @item =@r{, }<>@r{, }#
15668 Equality and two ways of expressing inequality, valid on scalar types.
15669 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15670 available for inequality, since @code{#} conflicts with the script
15674 Set membership. Defined on set types and the types of their members.
15675 Same precedence as @code{<}.
15678 Boolean disjunction. Defined on boolean types.
15681 Boolean conjunction. Defined on boolean types.
15684 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15687 Addition and subtraction on integral and floating-point types, or union
15688 and difference on set types.
15691 Multiplication on integral and floating-point types, or set intersection
15695 Division on floating-point types, or symmetric set difference on set
15696 types. Same precedence as @code{*}.
15699 Integer division and remainder. Defined on integral types. Same
15700 precedence as @code{*}.
15703 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15706 Pointer dereferencing. Defined on pointer types.
15709 Boolean negation. Defined on boolean types. Same precedence as
15713 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15714 precedence as @code{^}.
15717 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15720 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15724 @value{GDBN} and Modula-2 scope operators.
15728 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15729 treats the use of the operator @code{IN}, or the use of operators
15730 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15731 @code{<=}, and @code{>=} on sets as an error.
15735 @node Built-In Func/Proc
15736 @subsubsection Built-in Functions and Procedures
15737 @cindex Modula-2 built-ins
15739 Modula-2 also makes available several built-in procedures and functions.
15740 In describing these, the following metavariables are used:
15745 represents an @code{ARRAY} variable.
15748 represents a @code{CHAR} constant or variable.
15751 represents a variable or constant of integral type.
15754 represents an identifier that belongs to a set. Generally used in the
15755 same function with the metavariable @var{s}. The type of @var{s} should
15756 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15759 represents a variable or constant of integral or floating-point type.
15762 represents a variable or constant of floating-point type.
15768 represents a variable.
15771 represents a variable or constant of one of many types. See the
15772 explanation of the function for details.
15775 All Modula-2 built-in procedures also return a result, described below.
15779 Returns the absolute value of @var{n}.
15782 If @var{c} is a lower case letter, it returns its upper case
15783 equivalent, otherwise it returns its argument.
15786 Returns the character whose ordinal value is @var{i}.
15789 Decrements the value in the variable @var{v} by one. Returns the new value.
15791 @item DEC(@var{v},@var{i})
15792 Decrements the value in the variable @var{v} by @var{i}. Returns the
15795 @item EXCL(@var{m},@var{s})
15796 Removes the element @var{m} from the set @var{s}. Returns the new
15799 @item FLOAT(@var{i})
15800 Returns the floating point equivalent of the integer @var{i}.
15802 @item HIGH(@var{a})
15803 Returns the index of the last member of @var{a}.
15806 Increments the value in the variable @var{v} by one. Returns the new value.
15808 @item INC(@var{v},@var{i})
15809 Increments the value in the variable @var{v} by @var{i}. Returns the
15812 @item INCL(@var{m},@var{s})
15813 Adds the element @var{m} to the set @var{s} if it is not already
15814 there. Returns the new set.
15817 Returns the maximum value of the type @var{t}.
15820 Returns the minimum value of the type @var{t}.
15823 Returns boolean TRUE if @var{i} is an odd number.
15826 Returns the ordinal value of its argument. For example, the ordinal
15827 value of a character is its @sc{ascii} value (on machines supporting
15828 the @sc{ascii} character set). The argument @var{x} must be of an
15829 ordered type, which include integral, character and enumerated types.
15831 @item SIZE(@var{x})
15832 Returns the size of its argument. The argument @var{x} can be a
15833 variable or a type.
15835 @item TRUNC(@var{r})
15836 Returns the integral part of @var{r}.
15838 @item TSIZE(@var{x})
15839 Returns the size of its argument. The argument @var{x} can be a
15840 variable or a type.
15842 @item VAL(@var{t},@var{i})
15843 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15847 @emph{Warning:} Sets and their operations are not yet supported, so
15848 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15852 @cindex Modula-2 constants
15854 @subsubsection Constants
15856 @value{GDBN} allows you to express the constants of Modula-2 in the following
15862 Integer constants are simply a sequence of digits. When used in an
15863 expression, a constant is interpreted to be type-compatible with the
15864 rest of the expression. Hexadecimal integers are specified by a
15865 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15868 Floating point constants appear as a sequence of digits, followed by a
15869 decimal point and another sequence of digits. An optional exponent can
15870 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15871 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15872 digits of the floating point constant must be valid decimal (base 10)
15876 Character constants consist of a single character enclosed by a pair of
15877 like quotes, either single (@code{'}) or double (@code{"}). They may
15878 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15879 followed by a @samp{C}.
15882 String constants consist of a sequence of characters enclosed by a
15883 pair of like quotes, either single (@code{'}) or double (@code{"}).
15884 Escape sequences in the style of C are also allowed. @xref{C
15885 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15889 Enumerated constants consist of an enumerated identifier.
15892 Boolean constants consist of the identifiers @code{TRUE} and
15896 Pointer constants consist of integral values only.
15899 Set constants are not yet supported.
15903 @subsubsection Modula-2 Types
15904 @cindex Modula-2 types
15906 Currently @value{GDBN} can print the following data types in Modula-2
15907 syntax: array types, record types, set types, pointer types, procedure
15908 types, enumerated types, subrange types and base types. You can also
15909 print the contents of variables declared using these type.
15910 This section gives a number of simple source code examples together with
15911 sample @value{GDBN} sessions.
15913 The first example contains the following section of code:
15922 and you can request @value{GDBN} to interrogate the type and value of
15923 @code{r} and @code{s}.
15926 (@value{GDBP}) print s
15928 (@value{GDBP}) ptype s
15930 (@value{GDBP}) print r
15932 (@value{GDBP}) ptype r
15937 Likewise if your source code declares @code{s} as:
15941 s: SET ['A'..'Z'] ;
15945 then you may query the type of @code{s} by:
15948 (@value{GDBP}) ptype s
15949 type = SET ['A'..'Z']
15953 Note that at present you cannot interactively manipulate set
15954 expressions using the debugger.
15956 The following example shows how you might declare an array in Modula-2
15957 and how you can interact with @value{GDBN} to print its type and contents:
15961 s: ARRAY [-10..10] OF CHAR ;
15965 (@value{GDBP}) ptype s
15966 ARRAY [-10..10] OF CHAR
15969 Note that the array handling is not yet complete and although the type
15970 is printed correctly, expression handling still assumes that all
15971 arrays have a lower bound of zero and not @code{-10} as in the example
15974 Here are some more type related Modula-2 examples:
15978 colour = (blue, red, yellow, green) ;
15979 t = [blue..yellow] ;
15987 The @value{GDBN} interaction shows how you can query the data type
15988 and value of a variable.
15991 (@value{GDBP}) print s
15993 (@value{GDBP}) ptype t
15994 type = [blue..yellow]
15998 In this example a Modula-2 array is declared and its contents
15999 displayed. Observe that the contents are written in the same way as
16000 their @code{C} counterparts.
16004 s: ARRAY [1..5] OF CARDINAL ;
16010 (@value{GDBP}) print s
16011 $1 = @{1, 0, 0, 0, 0@}
16012 (@value{GDBP}) ptype s
16013 type = ARRAY [1..5] OF CARDINAL
16016 The Modula-2 language interface to @value{GDBN} also understands
16017 pointer types as shown in this example:
16021 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16028 and you can request that @value{GDBN} describes the type of @code{s}.
16031 (@value{GDBP}) ptype s
16032 type = POINTER TO ARRAY [1..5] OF CARDINAL
16035 @value{GDBN} handles compound types as we can see in this example.
16036 Here we combine array types, record types, pointer types and subrange
16047 myarray = ARRAY myrange OF CARDINAL ;
16048 myrange = [-2..2] ;
16050 s: POINTER TO ARRAY myrange OF foo ;
16054 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16058 (@value{GDBP}) ptype s
16059 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16062 f3 : ARRAY [-2..2] OF CARDINAL;
16067 @subsubsection Modula-2 Defaults
16068 @cindex Modula-2 defaults
16070 If type and range checking are set automatically by @value{GDBN}, they
16071 both default to @code{on} whenever the working language changes to
16072 Modula-2. This happens regardless of whether you or @value{GDBN}
16073 selected the working language.
16075 If you allow @value{GDBN} to set the language automatically, then entering
16076 code compiled from a file whose name ends with @file{.mod} sets the
16077 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16078 Infer the Source Language}, for further details.
16081 @subsubsection Deviations from Standard Modula-2
16082 @cindex Modula-2, deviations from
16084 A few changes have been made to make Modula-2 programs easier to debug.
16085 This is done primarily via loosening its type strictness:
16089 Unlike in standard Modula-2, pointer constants can be formed by
16090 integers. This allows you to modify pointer variables during
16091 debugging. (In standard Modula-2, the actual address contained in a
16092 pointer variable is hidden from you; it can only be modified
16093 through direct assignment to another pointer variable or expression that
16094 returned a pointer.)
16097 C escape sequences can be used in strings and characters to represent
16098 non-printable characters. @value{GDBN} prints out strings with these
16099 escape sequences embedded. Single non-printable characters are
16100 printed using the @samp{CHR(@var{nnn})} format.
16103 The assignment operator (@code{:=}) returns the value of its right-hand
16107 All built-in procedures both modify @emph{and} return their argument.
16111 @subsubsection Modula-2 Type and Range Checks
16112 @cindex Modula-2 checks
16115 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16118 @c FIXME remove warning when type/range checks added
16120 @value{GDBN} considers two Modula-2 variables type equivalent if:
16124 They are of types that have been declared equivalent via a @code{TYPE
16125 @var{t1} = @var{t2}} statement
16128 They have been declared on the same line. (Note: This is true of the
16129 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16132 As long as type checking is enabled, any attempt to combine variables
16133 whose types are not equivalent is an error.
16135 Range checking is done on all mathematical operations, assignment, array
16136 index bounds, and all built-in functions and procedures.
16139 @subsubsection The Scope Operators @code{::} and @code{.}
16141 @cindex @code{.}, Modula-2 scope operator
16142 @cindex colon, doubled as scope operator
16144 @vindex colon-colon@r{, in Modula-2}
16145 @c Info cannot handle :: but TeX can.
16148 @vindex ::@r{, in Modula-2}
16151 There are a few subtle differences between the Modula-2 scope operator
16152 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16157 @var{module} . @var{id}
16158 @var{scope} :: @var{id}
16162 where @var{scope} is the name of a module or a procedure,
16163 @var{module} the name of a module, and @var{id} is any declared
16164 identifier within your program, except another module.
16166 Using the @code{::} operator makes @value{GDBN} search the scope
16167 specified by @var{scope} for the identifier @var{id}. If it is not
16168 found in the specified scope, then @value{GDBN} searches all scopes
16169 enclosing the one specified by @var{scope}.
16171 Using the @code{.} operator makes @value{GDBN} search the current scope for
16172 the identifier specified by @var{id} that was imported from the
16173 definition module specified by @var{module}. With this operator, it is
16174 an error if the identifier @var{id} was not imported from definition
16175 module @var{module}, or if @var{id} is not an identifier in
16179 @subsubsection @value{GDBN} and Modula-2
16181 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16182 Five subcommands of @code{set print} and @code{show print} apply
16183 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16184 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16185 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16186 analogue in Modula-2.
16188 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16189 with any language, is not useful with Modula-2. Its
16190 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16191 created in Modula-2 as they can in C or C@t{++}. However, because an
16192 address can be specified by an integral constant, the construct
16193 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16195 @cindex @code{#} in Modula-2
16196 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16197 interpreted as the beginning of a comment. Use @code{<>} instead.
16203 The extensions made to @value{GDBN} for Ada only support
16204 output from the @sc{gnu} Ada (GNAT) compiler.
16205 Other Ada compilers are not currently supported, and
16206 attempting to debug executables produced by them is most likely
16210 @cindex expressions in Ada
16212 * Ada Mode Intro:: General remarks on the Ada syntax
16213 and semantics supported by Ada mode
16215 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16216 * Additions to Ada:: Extensions of the Ada expression syntax.
16217 * Overloading support for Ada:: Support for expressions involving overloaded
16219 * Stopping Before Main Program:: Debugging the program during elaboration.
16220 * Ada Exceptions:: Ada Exceptions
16221 * Ada Tasks:: Listing and setting breakpoints in tasks.
16222 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16223 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16225 * Ada Glitches:: Known peculiarities of Ada mode.
16228 @node Ada Mode Intro
16229 @subsubsection Introduction
16230 @cindex Ada mode, general
16232 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16233 syntax, with some extensions.
16234 The philosophy behind the design of this subset is
16238 That @value{GDBN} should provide basic literals and access to operations for
16239 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16240 leaving more sophisticated computations to subprograms written into the
16241 program (which therefore may be called from @value{GDBN}).
16244 That type safety and strict adherence to Ada language restrictions
16245 are not particularly important to the @value{GDBN} user.
16248 That brevity is important to the @value{GDBN} user.
16251 Thus, for brevity, the debugger acts as if all names declared in
16252 user-written packages are directly visible, even if they are not visible
16253 according to Ada rules, thus making it unnecessary to fully qualify most
16254 names with their packages, regardless of context. Where this causes
16255 ambiguity, @value{GDBN} asks the user's intent.
16257 The debugger will start in Ada mode if it detects an Ada main program.
16258 As for other languages, it will enter Ada mode when stopped in a program that
16259 was translated from an Ada source file.
16261 While in Ada mode, you may use `@t{--}' for comments. This is useful
16262 mostly for documenting command files. The standard @value{GDBN} comment
16263 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16264 middle (to allow based literals).
16266 @node Omissions from Ada
16267 @subsubsection Omissions from Ada
16268 @cindex Ada, omissions from
16270 Here are the notable omissions from the subset:
16274 Only a subset of the attributes are supported:
16278 @t{'First}, @t{'Last}, and @t{'Length}
16279 on array objects (not on types and subtypes).
16282 @t{'Min} and @t{'Max}.
16285 @t{'Pos} and @t{'Val}.
16291 @t{'Range} on array objects (not subtypes), but only as the right
16292 operand of the membership (@code{in}) operator.
16295 @t{'Access}, @t{'Unchecked_Access}, and
16296 @t{'Unrestricted_Access} (a GNAT extension).
16304 @code{Characters.Latin_1} are not available and
16305 concatenation is not implemented. Thus, escape characters in strings are
16306 not currently available.
16309 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16310 equality of representations. They will generally work correctly
16311 for strings and arrays whose elements have integer or enumeration types.
16312 They may not work correctly for arrays whose element
16313 types have user-defined equality, for arrays of real values
16314 (in particular, IEEE-conformant floating point, because of negative
16315 zeroes and NaNs), and for arrays whose elements contain unused bits with
16316 indeterminate values.
16319 The other component-by-component array operations (@code{and}, @code{or},
16320 @code{xor}, @code{not}, and relational tests other than equality)
16321 are not implemented.
16324 @cindex array aggregates (Ada)
16325 @cindex record aggregates (Ada)
16326 @cindex aggregates (Ada)
16327 There is limited support for array and record aggregates. They are
16328 permitted only on the right sides of assignments, as in these examples:
16331 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16332 (@value{GDBP}) set An_Array := (1, others => 0)
16333 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16334 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16335 (@value{GDBP}) set A_Record := (1, "Peter", True);
16336 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16340 discriminant's value by assigning an aggregate has an
16341 undefined effect if that discriminant is used within the record.
16342 However, you can first modify discriminants by directly assigning to
16343 them (which normally would not be allowed in Ada), and then performing an
16344 aggregate assignment. For example, given a variable @code{A_Rec}
16345 declared to have a type such as:
16348 type Rec (Len : Small_Integer := 0) is record
16350 Vals : IntArray (1 .. Len);
16354 you can assign a value with a different size of @code{Vals} with two
16358 (@value{GDBP}) set A_Rec.Len := 4
16359 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16362 As this example also illustrates, @value{GDBN} is very loose about the usual
16363 rules concerning aggregates. You may leave out some of the
16364 components of an array or record aggregate (such as the @code{Len}
16365 component in the assignment to @code{A_Rec} above); they will retain their
16366 original values upon assignment. You may freely use dynamic values as
16367 indices in component associations. You may even use overlapping or
16368 redundant component associations, although which component values are
16369 assigned in such cases is not defined.
16372 Calls to dispatching subprograms are not implemented.
16375 The overloading algorithm is much more limited (i.e., less selective)
16376 than that of real Ada. It makes only limited use of the context in
16377 which a subexpression appears to resolve its meaning, and it is much
16378 looser in its rules for allowing type matches. As a result, some
16379 function calls will be ambiguous, and the user will be asked to choose
16380 the proper resolution.
16383 The @code{new} operator is not implemented.
16386 Entry calls are not implemented.
16389 Aside from printing, arithmetic operations on the native VAX floating-point
16390 formats are not supported.
16393 It is not possible to slice a packed array.
16396 The names @code{True} and @code{False}, when not part of a qualified name,
16397 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16399 Should your program
16400 redefine these names in a package or procedure (at best a dubious practice),
16401 you will have to use fully qualified names to access their new definitions.
16404 @node Additions to Ada
16405 @subsubsection Additions to Ada
16406 @cindex Ada, deviations from
16408 As it does for other languages, @value{GDBN} makes certain generic
16409 extensions to Ada (@pxref{Expressions}):
16413 If the expression @var{E} is a variable residing in memory (typically
16414 a local variable or array element) and @var{N} is a positive integer,
16415 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16416 @var{N}-1 adjacent variables following it in memory as an array. In
16417 Ada, this operator is generally not necessary, since its prime use is
16418 in displaying parts of an array, and slicing will usually do this in
16419 Ada. However, there are occasional uses when debugging programs in
16420 which certain debugging information has been optimized away.
16423 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16424 appears in function or file @var{B}.'' When @var{B} is a file name,
16425 you must typically surround it in single quotes.
16428 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16429 @var{type} that appears at address @var{addr}.''
16432 A name starting with @samp{$} is a convenience variable
16433 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16436 In addition, @value{GDBN} provides a few other shortcuts and outright
16437 additions specific to Ada:
16441 The assignment statement is allowed as an expression, returning
16442 its right-hand operand as its value. Thus, you may enter
16445 (@value{GDBP}) set x := y + 3
16446 (@value{GDBP}) print A(tmp := y + 1)
16450 The semicolon is allowed as an ``operator,'' returning as its value
16451 the value of its right-hand operand.
16452 This allows, for example,
16453 complex conditional breaks:
16456 (@value{GDBP}) break f
16457 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16461 Rather than use catenation and symbolic character names to introduce special
16462 characters into strings, one may instead use a special bracket notation,
16463 which is also used to print strings. A sequence of characters of the form
16464 @samp{["@var{XX}"]} within a string or character literal denotes the
16465 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16466 sequence of characters @samp{["""]} also denotes a single quotation mark
16467 in strings. For example,
16469 "One line.["0a"]Next line.["0a"]"
16472 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16476 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16477 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16481 (@value{GDBP}) print 'max(x, y)
16485 When printing arrays, @value{GDBN} uses positional notation when the
16486 array has a lower bound of 1, and uses a modified named notation otherwise.
16487 For example, a one-dimensional array of three integers with a lower bound
16488 of 3 might print as
16495 That is, in contrast to valid Ada, only the first component has a @code{=>}
16499 You may abbreviate attributes in expressions with any unique,
16500 multi-character subsequence of
16501 their names (an exact match gets preference).
16502 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16503 in place of @t{a'length}.
16506 @cindex quoting Ada internal identifiers
16507 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16508 to lower case. The GNAT compiler uses upper-case characters for
16509 some of its internal identifiers, which are normally of no interest to users.
16510 For the rare occasions when you actually have to look at them,
16511 enclose them in angle brackets to avoid the lower-case mapping.
16514 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16518 Printing an object of class-wide type or dereferencing an
16519 access-to-class-wide value will display all the components of the object's
16520 specific type (as indicated by its run-time tag). Likewise, component
16521 selection on such a value will operate on the specific type of the
16526 @node Overloading support for Ada
16527 @subsubsection Overloading support for Ada
16528 @cindex overloading, Ada
16530 The debugger supports limited overloading. Given a subprogram call in which
16531 the function symbol has multiple definitions, it will use the number of
16532 actual parameters and some information about their types to attempt to narrow
16533 the set of definitions. It also makes very limited use of context, preferring
16534 procedures to functions in the context of the @code{call} command, and
16535 functions to procedures elsewhere.
16537 If, after narrowing, the set of matching definitions still contains more than
16538 one definition, @value{GDBN} will display a menu to query which one it should
16542 (@value{GDBP}) print f(1)
16543 Multiple matches for f
16545 [1] foo.f (integer) return boolean at foo.adb:23
16546 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16550 In this case, just select one menu entry either to cancel expression evaluation
16551 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16552 instance (type the corresponding number and press @key{RET}).
16554 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16559 @kindex set ada print-signatures
16560 @item set ada print-signatures
16561 Control whether parameter types and return types are displayed in overloads
16562 selection menus. It is @code{on} by default.
16563 @xref{Overloading support for Ada}.
16565 @kindex show ada print-signatures
16566 @item show ada print-signatures
16567 Show the current setting for displaying parameter types and return types in
16568 overloads selection menu.
16569 @xref{Overloading support for Ada}.
16573 @node Stopping Before Main Program
16574 @subsubsection Stopping at the Very Beginning
16576 @cindex breakpointing Ada elaboration code
16577 It is sometimes necessary to debug the program during elaboration, and
16578 before reaching the main procedure.
16579 As defined in the Ada Reference
16580 Manual, the elaboration code is invoked from a procedure called
16581 @code{adainit}. To run your program up to the beginning of
16582 elaboration, simply use the following two commands:
16583 @code{tbreak adainit} and @code{run}.
16585 @node Ada Exceptions
16586 @subsubsection Ada Exceptions
16588 A command is provided to list all Ada exceptions:
16591 @kindex info exceptions
16592 @item info exceptions
16593 @itemx info exceptions @var{regexp}
16594 The @code{info exceptions} command allows you to list all Ada exceptions
16595 defined within the program being debugged, as well as their addresses.
16596 With a regular expression, @var{regexp}, as argument, only those exceptions
16597 whose names match @var{regexp} are listed.
16600 Below is a small example, showing how the command can be used, first
16601 without argument, and next with a regular expression passed as an
16605 (@value{GDBP}) info exceptions
16606 All defined Ada exceptions:
16607 constraint_error: 0x613da0
16608 program_error: 0x613d20
16609 storage_error: 0x613ce0
16610 tasking_error: 0x613ca0
16611 const.aint_global_e: 0x613b00
16612 (@value{GDBP}) info exceptions const.aint
16613 All Ada exceptions matching regular expression "const.aint":
16614 constraint_error: 0x613da0
16615 const.aint_global_e: 0x613b00
16618 It is also possible to ask @value{GDBN} to stop your program's execution
16619 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16622 @subsubsection Extensions for Ada Tasks
16623 @cindex Ada, tasking
16625 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16626 @value{GDBN} provides the following task-related commands:
16631 This command shows a list of current Ada tasks, as in the following example:
16638 (@value{GDBP}) info tasks
16639 ID TID P-ID Pri State Name
16640 1 8088000 0 15 Child Activation Wait main_task
16641 2 80a4000 1 15 Accept Statement b
16642 3 809a800 1 15 Child Activation Wait a
16643 * 4 80ae800 3 15 Runnable c
16648 In this listing, the asterisk before the last task indicates it to be the
16649 task currently being inspected.
16653 Represents @value{GDBN}'s internal task number.
16659 The parent's task ID (@value{GDBN}'s internal task number).
16662 The base priority of the task.
16665 Current state of the task.
16669 The task has been created but has not been activated. It cannot be
16673 The task is not blocked for any reason known to Ada. (It may be waiting
16674 for a mutex, though.) It is conceptually "executing" in normal mode.
16677 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16678 that were waiting on terminate alternatives have been awakened and have
16679 terminated themselves.
16681 @item Child Activation Wait
16682 The task is waiting for created tasks to complete activation.
16684 @item Accept Statement
16685 The task is waiting on an accept or selective wait statement.
16687 @item Waiting on entry call
16688 The task is waiting on an entry call.
16690 @item Async Select Wait
16691 The task is waiting to start the abortable part of an asynchronous
16695 The task is waiting on a select statement with only a delay
16698 @item Child Termination Wait
16699 The task is sleeping having completed a master within itself, and is
16700 waiting for the tasks dependent on that master to become terminated or
16701 waiting on a terminate Phase.
16703 @item Wait Child in Term Alt
16704 The task is sleeping waiting for tasks on terminate alternatives to
16705 finish terminating.
16707 @item Accepting RV with @var{taskno}
16708 The task is accepting a rendez-vous with the task @var{taskno}.
16712 Name of the task in the program.
16716 @kindex info task @var{taskno}
16717 @item info task @var{taskno}
16718 This command shows detailled informations on the specified task, as in
16719 the following example:
16724 (@value{GDBP}) info tasks
16725 ID TID P-ID Pri State Name
16726 1 8077880 0 15 Child Activation Wait main_task
16727 * 2 807c468 1 15 Runnable task_1
16728 (@value{GDBP}) info task 2
16729 Ada Task: 0x807c468
16732 Parent: 1 (main_task)
16738 @kindex task@r{ (Ada)}
16739 @cindex current Ada task ID
16740 This command prints the ID of the current task.
16746 (@value{GDBP}) info tasks
16747 ID TID P-ID Pri State Name
16748 1 8077870 0 15 Child Activation Wait main_task
16749 * 2 807c458 1 15 Runnable t
16750 (@value{GDBP}) task
16751 [Current task is 2]
16754 @item task @var{taskno}
16755 @cindex Ada task switching
16756 This command is like the @code{thread @var{thread-id}}
16757 command (@pxref{Threads}). It switches the context of debugging
16758 from the current task to the given task.
16764 (@value{GDBP}) info tasks
16765 ID TID P-ID Pri State Name
16766 1 8077870 0 15 Child Activation Wait main_task
16767 * 2 807c458 1 15 Runnable t
16768 (@value{GDBP}) task 1
16769 [Switching to task 1]
16770 #0 0x8067726 in pthread_cond_wait ()
16772 #0 0x8067726 in pthread_cond_wait ()
16773 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16774 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16775 #3 0x806153e in system.tasking.stages.activate_tasks ()
16776 #4 0x804aacc in un () at un.adb:5
16779 @item break @var{location} task @var{taskno}
16780 @itemx break @var{location} task @var{taskno} if @dots{}
16781 @cindex breakpoints and tasks, in Ada
16782 @cindex task breakpoints, in Ada
16783 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16784 These commands are like the @code{break @dots{} thread @dots{}}
16785 command (@pxref{Thread Stops}). The
16786 @var{location} argument specifies source lines, as described
16787 in @ref{Specify Location}.
16789 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16790 to specify that you only want @value{GDBN} to stop the program when a
16791 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16792 numeric task identifiers assigned by @value{GDBN}, shown in the first
16793 column of the @samp{info tasks} display.
16795 If you do not specify @samp{task @var{taskno}} when you set a
16796 breakpoint, the breakpoint applies to @emph{all} tasks of your
16799 You can use the @code{task} qualifier on conditional breakpoints as
16800 well; in this case, place @samp{task @var{taskno}} before the
16801 breakpoint condition (before the @code{if}).
16809 (@value{GDBP}) info tasks
16810 ID TID P-ID Pri State Name
16811 1 140022020 0 15 Child Activation Wait main_task
16812 2 140045060 1 15 Accept/Select Wait t2
16813 3 140044840 1 15 Runnable t1
16814 * 4 140056040 1 15 Runnable t3
16815 (@value{GDBP}) b 15 task 2
16816 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16817 (@value{GDBP}) cont
16822 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16824 (@value{GDBP}) info tasks
16825 ID TID P-ID Pri State Name
16826 1 140022020 0 15 Child Activation Wait main_task
16827 * 2 140045060 1 15 Runnable t2
16828 3 140044840 1 15 Runnable t1
16829 4 140056040 1 15 Delay Sleep t3
16833 @node Ada Tasks and Core Files
16834 @subsubsection Tasking Support when Debugging Core Files
16835 @cindex Ada tasking and core file debugging
16837 When inspecting a core file, as opposed to debugging a live program,
16838 tasking support may be limited or even unavailable, depending on
16839 the platform being used.
16840 For instance, on x86-linux, the list of tasks is available, but task
16841 switching is not supported.
16843 On certain platforms, the debugger needs to perform some
16844 memory writes in order to provide Ada tasking support. When inspecting
16845 a core file, this means that the core file must be opened with read-write
16846 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16847 Under these circumstances, you should make a backup copy of the core
16848 file before inspecting it with @value{GDBN}.
16850 @node Ravenscar Profile
16851 @subsubsection Tasking Support when using the Ravenscar Profile
16852 @cindex Ravenscar Profile
16854 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16855 specifically designed for systems with safety-critical real-time
16859 @kindex set ravenscar task-switching on
16860 @cindex task switching with program using Ravenscar Profile
16861 @item set ravenscar task-switching on
16862 Allows task switching when debugging a program that uses the Ravenscar
16863 Profile. This is the default.
16865 @kindex set ravenscar task-switching off
16866 @item set ravenscar task-switching off
16867 Turn off task switching when debugging a program that uses the Ravenscar
16868 Profile. This is mostly intended to disable the code that adds support
16869 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16870 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16871 To be effective, this command should be run before the program is started.
16873 @kindex show ravenscar task-switching
16874 @item show ravenscar task-switching
16875 Show whether it is possible to switch from task to task in a program
16876 using the Ravenscar Profile.
16881 @subsubsection Known Peculiarities of Ada Mode
16882 @cindex Ada, problems
16884 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16885 we know of several problems with and limitations of Ada mode in
16887 some of which will be fixed with planned future releases of the debugger
16888 and the GNU Ada compiler.
16892 Static constants that the compiler chooses not to materialize as objects in
16893 storage are invisible to the debugger.
16896 Named parameter associations in function argument lists are ignored (the
16897 argument lists are treated as positional).
16900 Many useful library packages are currently invisible to the debugger.
16903 Fixed-point arithmetic, conversions, input, and output is carried out using
16904 floating-point arithmetic, and may give results that only approximate those on
16908 The GNAT compiler never generates the prefix @code{Standard} for any of
16909 the standard symbols defined by the Ada language. @value{GDBN} knows about
16910 this: it will strip the prefix from names when you use it, and will never
16911 look for a name you have so qualified among local symbols, nor match against
16912 symbols in other packages or subprograms. If you have
16913 defined entities anywhere in your program other than parameters and
16914 local variables whose simple names match names in @code{Standard},
16915 GNAT's lack of qualification here can cause confusion. When this happens,
16916 you can usually resolve the confusion
16917 by qualifying the problematic names with package
16918 @code{Standard} explicitly.
16921 Older versions of the compiler sometimes generate erroneous debugging
16922 information, resulting in the debugger incorrectly printing the value
16923 of affected entities. In some cases, the debugger is able to work
16924 around an issue automatically. In other cases, the debugger is able
16925 to work around the issue, but the work-around has to be specifically
16928 @kindex set ada trust-PAD-over-XVS
16929 @kindex show ada trust-PAD-over-XVS
16932 @item set ada trust-PAD-over-XVS on
16933 Configure GDB to strictly follow the GNAT encoding when computing the
16934 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16935 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16936 a complete description of the encoding used by the GNAT compiler).
16937 This is the default.
16939 @item set ada trust-PAD-over-XVS off
16940 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16941 sometimes prints the wrong value for certain entities, changing @code{ada
16942 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16943 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16944 @code{off}, but this incurs a slight performance penalty, so it is
16945 recommended to leave this setting to @code{on} unless necessary.
16949 @cindex GNAT descriptive types
16950 @cindex GNAT encoding
16951 Internally, the debugger also relies on the compiler following a number
16952 of conventions known as the @samp{GNAT Encoding}, all documented in
16953 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16954 how the debugging information should be generated for certain types.
16955 In particular, this convention makes use of @dfn{descriptive types},
16956 which are artificial types generated purely to help the debugger.
16958 These encodings were defined at a time when the debugging information
16959 format used was not powerful enough to describe some of the more complex
16960 types available in Ada. Since DWARF allows us to express nearly all
16961 Ada features, the long-term goal is to slowly replace these descriptive
16962 types by their pure DWARF equivalent. To facilitate that transition,
16963 a new maintenance option is available to force the debugger to ignore
16964 those descriptive types. It allows the user to quickly evaluate how
16965 well @value{GDBN} works without them.
16969 @kindex maint ada set ignore-descriptive-types
16970 @item maintenance ada set ignore-descriptive-types [on|off]
16971 Control whether the debugger should ignore descriptive types.
16972 The default is not to ignore descriptives types (@code{off}).
16974 @kindex maint ada show ignore-descriptive-types
16975 @item maintenance ada show ignore-descriptive-types
16976 Show if descriptive types are ignored by @value{GDBN}.
16980 @node Unsupported Languages
16981 @section Unsupported Languages
16983 @cindex unsupported languages
16984 @cindex minimal language
16985 In addition to the other fully-supported programming languages,
16986 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16987 It does not represent a real programming language, but provides a set
16988 of capabilities close to what the C or assembly languages provide.
16989 This should allow most simple operations to be performed while debugging
16990 an application that uses a language currently not supported by @value{GDBN}.
16992 If the language is set to @code{auto}, @value{GDBN} will automatically
16993 select this language if the current frame corresponds to an unsupported
16997 @chapter Examining the Symbol Table
16999 The commands described in this chapter allow you to inquire about the
17000 symbols (names of variables, functions and types) defined in your
17001 program. This information is inherent in the text of your program and
17002 does not change as your program executes. @value{GDBN} finds it in your
17003 program's symbol table, in the file indicated when you started @value{GDBN}
17004 (@pxref{File Options, ,Choosing Files}), or by one of the
17005 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17007 @cindex symbol names
17008 @cindex names of symbols
17009 @cindex quoting names
17010 @anchor{quoting names}
17011 Occasionally, you may need to refer to symbols that contain unusual
17012 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17013 most frequent case is in referring to static variables in other
17014 source files (@pxref{Variables,,Program Variables}). File names
17015 are recorded in object files as debugging symbols, but @value{GDBN} would
17016 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17017 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17018 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17025 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17028 @cindex case-insensitive symbol names
17029 @cindex case sensitivity in symbol names
17030 @kindex set case-sensitive
17031 @item set case-sensitive on
17032 @itemx set case-sensitive off
17033 @itemx set case-sensitive auto
17034 Normally, when @value{GDBN} looks up symbols, it matches their names
17035 with case sensitivity determined by the current source language.
17036 Occasionally, you may wish to control that. The command @code{set
17037 case-sensitive} lets you do that by specifying @code{on} for
17038 case-sensitive matches or @code{off} for case-insensitive ones. If
17039 you specify @code{auto}, case sensitivity is reset to the default
17040 suitable for the source language. The default is case-sensitive
17041 matches for all languages except for Fortran, for which the default is
17042 case-insensitive matches.
17044 @kindex show case-sensitive
17045 @item show case-sensitive
17046 This command shows the current setting of case sensitivity for symbols
17049 @kindex set print type methods
17050 @item set print type methods
17051 @itemx set print type methods on
17052 @itemx set print type methods off
17053 Normally, when @value{GDBN} prints a class, it displays any methods
17054 declared in that class. You can control this behavior either by
17055 passing the appropriate flag to @code{ptype}, or using @command{set
17056 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17057 display the methods; this is the default. Specifying @code{off} will
17058 cause @value{GDBN} to omit the methods.
17060 @kindex show print type methods
17061 @item show print type methods
17062 This command shows the current setting of method display when printing
17065 @kindex set print type typedefs
17066 @item set print type typedefs
17067 @itemx set print type typedefs on
17068 @itemx set print type typedefs off
17070 Normally, when @value{GDBN} prints a class, it displays any typedefs
17071 defined in that class. You can control this behavior either by
17072 passing the appropriate flag to @code{ptype}, or using @command{set
17073 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17074 display the typedef definitions; this is the default. Specifying
17075 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17076 Note that this controls whether the typedef definition itself is
17077 printed, not whether typedef names are substituted when printing other
17080 @kindex show print type typedefs
17081 @item show print type typedefs
17082 This command shows the current setting of typedef display when
17085 @kindex info address
17086 @cindex address of a symbol
17087 @item info address @var{symbol}
17088 Describe where the data for @var{symbol} is stored. For a register
17089 variable, this says which register it is kept in. For a non-register
17090 local variable, this prints the stack-frame offset at which the variable
17093 Note the contrast with @samp{print &@var{symbol}}, which does not work
17094 at all for a register variable, and for a stack local variable prints
17095 the exact address of the current instantiation of the variable.
17097 @kindex info symbol
17098 @cindex symbol from address
17099 @cindex closest symbol and offset for an address
17100 @item info symbol @var{addr}
17101 Print the name of a symbol which is stored at the address @var{addr}.
17102 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17103 nearest symbol and an offset from it:
17106 (@value{GDBP}) info symbol 0x54320
17107 _initialize_vx + 396 in section .text
17111 This is the opposite of the @code{info address} command. You can use
17112 it to find out the name of a variable or a function given its address.
17114 For dynamically linked executables, the name of executable or shared
17115 library containing the symbol is also printed:
17118 (@value{GDBP}) info symbol 0x400225
17119 _start + 5 in section .text of /tmp/a.out
17120 (@value{GDBP}) info symbol 0x2aaaac2811cf
17121 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17126 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17127 Demangle @var{name}.
17128 If @var{language} is provided it is the name of the language to demangle
17129 @var{name} in. Otherwise @var{name} is demangled in the current language.
17131 The @samp{--} option specifies the end of options,
17132 and is useful when @var{name} begins with a dash.
17134 The parameter @code{demangle-style} specifies how to interpret the kind
17135 of mangling used. @xref{Print Settings}.
17138 @item whatis[/@var{flags}] [@var{arg}]
17139 Print the data type of @var{arg}, which can be either an expression
17140 or a name of a data type. With no argument, print the data type of
17141 @code{$}, the last value in the value history.
17143 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17144 is not actually evaluated, and any side-effecting operations (such as
17145 assignments or function calls) inside it do not take place.
17147 If @var{arg} is a variable or an expression, @code{whatis} prints its
17148 literal type as it is used in the source code. If the type was
17149 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17150 the data type underlying the @code{typedef}. If the type of the
17151 variable or the expression is a compound data type, such as
17152 @code{struct} or @code{class}, @code{whatis} never prints their
17153 fields or methods. It just prints the @code{struct}/@code{class}
17154 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17155 such a compound data type, use @code{ptype}.
17157 If @var{arg} is a type name that was defined using @code{typedef},
17158 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17159 Unrolling means that @code{whatis} will show the underlying type used
17160 in the @code{typedef} declaration of @var{arg}. However, if that
17161 underlying type is also a @code{typedef}, @code{whatis} will not
17164 For C code, the type names may also have the form @samp{class
17165 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17166 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17168 @var{flags} can be used to modify how the type is displayed.
17169 Available flags are:
17173 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17174 parameters and typedefs defined in a class when printing the class'
17175 members. The @code{/r} flag disables this.
17178 Do not print methods defined in the class.
17181 Print methods defined in the class. This is the default, but the flag
17182 exists in case you change the default with @command{set print type methods}.
17185 Do not print typedefs defined in the class. Note that this controls
17186 whether the typedef definition itself is printed, not whether typedef
17187 names are substituted when printing other types.
17190 Print typedefs defined in the class. This is the default, but the flag
17191 exists in case you change the default with @command{set print type typedefs}.
17195 @item ptype[/@var{flags}] [@var{arg}]
17196 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17197 detailed description of the type, instead of just the name of the type.
17198 @xref{Expressions, ,Expressions}.
17200 Contrary to @code{whatis}, @code{ptype} always unrolls any
17201 @code{typedef}s in its argument declaration, whether the argument is
17202 a variable, expression, or a data type. This means that @code{ptype}
17203 of a variable or an expression will not print literally its type as
17204 present in the source code---use @code{whatis} for that. @code{typedef}s at
17205 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17206 fields, methods and inner @code{class typedef}s of @code{struct}s,
17207 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17209 For example, for this variable declaration:
17212 typedef double real_t;
17213 struct complex @{ real_t real; double imag; @};
17214 typedef struct complex complex_t;
17216 real_t *real_pointer_var;
17220 the two commands give this output:
17224 (@value{GDBP}) whatis var
17226 (@value{GDBP}) ptype var
17227 type = struct complex @{
17231 (@value{GDBP}) whatis complex_t
17232 type = struct complex
17233 (@value{GDBP}) whatis struct complex
17234 type = struct complex
17235 (@value{GDBP}) ptype struct complex
17236 type = struct complex @{
17240 (@value{GDBP}) whatis real_pointer_var
17242 (@value{GDBP}) ptype real_pointer_var
17248 As with @code{whatis}, using @code{ptype} without an argument refers to
17249 the type of @code{$}, the last value in the value history.
17251 @cindex incomplete type
17252 Sometimes, programs use opaque data types or incomplete specifications
17253 of complex data structure. If the debug information included in the
17254 program does not allow @value{GDBN} to display a full declaration of
17255 the data type, it will say @samp{<incomplete type>}. For example,
17256 given these declarations:
17260 struct foo *fooptr;
17264 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17267 (@value{GDBP}) ptype foo
17268 $1 = <incomplete type>
17272 ``Incomplete type'' is C terminology for data types that are not
17273 completely specified.
17275 @cindex unknown type
17276 Othertimes, information about a variable's type is completely absent
17277 from the debug information included in the program. This most often
17278 happens when the program or library where the variable is defined
17279 includes no debug information at all. @value{GDBN} knows the variable
17280 exists from inspecting the linker/loader symbol table (e.g., the ELF
17281 dynamic symbol table), but such symbols do not contain type
17282 information. Inspecting the type of a (global) variable for which
17283 @value{GDBN} has no type information shows:
17286 (@value{GDBP}) ptype var
17287 type = <data variable, no debug info>
17290 @xref{Variables, no debug info variables}, for how to print the values
17294 @item info types @var{regexp}
17296 Print a brief description of all types whose names match the regular
17297 expression @var{regexp} (or all types in your program, if you supply
17298 no argument). Each complete typename is matched as though it were a
17299 complete line; thus, @samp{i type value} gives information on all
17300 types in your program whose names include the string @code{value}, but
17301 @samp{i type ^value$} gives information only on types whose complete
17302 name is @code{value}.
17304 This command differs from @code{ptype} in two ways: first, like
17305 @code{whatis}, it does not print a detailed description; second, it
17306 lists all source files where a type is defined.
17308 @kindex info type-printers
17309 @item info type-printers
17310 Versions of @value{GDBN} that ship with Python scripting enabled may
17311 have ``type printers'' available. When using @command{ptype} or
17312 @command{whatis}, these printers are consulted when the name of a type
17313 is needed. @xref{Type Printing API}, for more information on writing
17316 @code{info type-printers} displays all the available type printers.
17318 @kindex enable type-printer
17319 @kindex disable type-printer
17320 @item enable type-printer @var{name}@dots{}
17321 @item disable type-printer @var{name}@dots{}
17322 These commands can be used to enable or disable type printers.
17325 @cindex local variables
17326 @item info scope @var{location}
17327 List all the variables local to a particular scope. This command
17328 accepts a @var{location} argument---a function name, a source line, or
17329 an address preceded by a @samp{*}, and prints all the variables local
17330 to the scope defined by that location. (@xref{Specify Location}, for
17331 details about supported forms of @var{location}.) For example:
17334 (@value{GDBP}) @b{info scope command_line_handler}
17335 Scope for command_line_handler:
17336 Symbol rl is an argument at stack/frame offset 8, length 4.
17337 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17338 Symbol linelength is in static storage at address 0x150a1c, length 4.
17339 Symbol p is a local variable in register $esi, length 4.
17340 Symbol p1 is a local variable in register $ebx, length 4.
17341 Symbol nline is a local variable in register $edx, length 4.
17342 Symbol repeat is a local variable at frame offset -8, length 4.
17346 This command is especially useful for determining what data to collect
17347 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17350 @kindex info source
17352 Show information about the current source file---that is, the source file for
17353 the function containing the current point of execution:
17356 the name of the source file, and the directory containing it,
17358 the directory it was compiled in,
17360 its length, in lines,
17362 which programming language it is written in,
17364 if the debug information provides it, the program that compiled the file
17365 (which may include, e.g., the compiler version and command line arguments),
17367 whether the executable includes debugging information for that file, and
17368 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17370 whether the debugging information includes information about
17371 preprocessor macros.
17375 @kindex info sources
17377 Print the names of all source files in your program for which there is
17378 debugging information, organized into two lists: files whose symbols
17379 have already been read, and files whose symbols will be read when needed.
17381 @kindex info functions
17382 @item info functions
17383 Print the names and data types of all defined functions.
17385 @item info functions @var{regexp}
17386 Print the names and data types of all defined functions
17387 whose names contain a match for regular expression @var{regexp}.
17388 Thus, @samp{info fun step} finds all functions whose names
17389 include @code{step}; @samp{info fun ^step} finds those whose names
17390 start with @code{step}. If a function name contains characters
17391 that conflict with the regular expression language (e.g.@:
17392 @samp{operator*()}), they may be quoted with a backslash.
17394 @kindex info variables
17395 @item info variables
17396 Print the names and data types of all variables that are defined
17397 outside of functions (i.e.@: excluding local variables).
17399 @item info variables @var{regexp}
17400 Print the names and data types of all variables (except for local
17401 variables) whose names contain a match for regular expression
17404 @kindex info classes
17405 @cindex Objective-C, classes and selectors
17407 @itemx info classes @var{regexp}
17408 Display all Objective-C classes in your program, or
17409 (with the @var{regexp} argument) all those matching a particular regular
17412 @kindex info selectors
17413 @item info selectors
17414 @itemx info selectors @var{regexp}
17415 Display all Objective-C selectors in your program, or
17416 (with the @var{regexp} argument) all those matching a particular regular
17420 This was never implemented.
17421 @kindex info methods
17423 @itemx info methods @var{regexp}
17424 The @code{info methods} command permits the user to examine all defined
17425 methods within C@t{++} program, or (with the @var{regexp} argument) a
17426 specific set of methods found in the various C@t{++} classes. Many
17427 C@t{++} classes provide a large number of methods. Thus, the output
17428 from the @code{ptype} command can be overwhelming and hard to use. The
17429 @code{info-methods} command filters the methods, printing only those
17430 which match the regular-expression @var{regexp}.
17433 @cindex opaque data types
17434 @kindex set opaque-type-resolution
17435 @item set opaque-type-resolution on
17436 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17437 declared as a pointer to a @code{struct}, @code{class}, or
17438 @code{union}---for example, @code{struct MyType *}---that is used in one
17439 source file although the full declaration of @code{struct MyType} is in
17440 another source file. The default is on.
17442 A change in the setting of this subcommand will not take effect until
17443 the next time symbols for a file are loaded.
17445 @item set opaque-type-resolution off
17446 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17447 is printed as follows:
17449 @{<no data fields>@}
17452 @kindex show opaque-type-resolution
17453 @item show opaque-type-resolution
17454 Show whether opaque types are resolved or not.
17456 @kindex set print symbol-loading
17457 @cindex print messages when symbols are loaded
17458 @item set print symbol-loading
17459 @itemx set print symbol-loading full
17460 @itemx set print symbol-loading brief
17461 @itemx set print symbol-loading off
17462 The @code{set print symbol-loading} command allows you to control the
17463 printing of messages when @value{GDBN} loads symbol information.
17464 By default a message is printed for the executable and one for each
17465 shared library, and normally this is what you want. However, when
17466 debugging apps with large numbers of shared libraries these messages
17468 When set to @code{brief} a message is printed for each executable,
17469 and when @value{GDBN} loads a collection of shared libraries at once
17470 it will only print one message regardless of the number of shared
17471 libraries. When set to @code{off} no messages are printed.
17473 @kindex show print symbol-loading
17474 @item show print symbol-loading
17475 Show whether messages will be printed when a @value{GDBN} command
17476 entered from the keyboard causes symbol information to be loaded.
17478 @kindex maint print symbols
17479 @cindex symbol dump
17480 @kindex maint print psymbols
17481 @cindex partial symbol dump
17482 @kindex maint print msymbols
17483 @cindex minimal symbol dump
17484 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17485 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17486 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17487 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17488 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17489 Write a dump of debugging symbol data into the file @var{filename} or
17490 the terminal if @var{filename} is unspecified.
17491 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17493 If @code{-pc @var{address}} is specified, only dump symbols for the file
17494 with code at that address. Note that @var{address} may be a symbol like
17496 If @code{-source @var{source}} is specified, only dump symbols for that
17499 These commands are used to debug the @value{GDBN} symbol-reading code.
17500 These commands do not modify internal @value{GDBN} state, therefore
17501 @samp{maint print symbols} will only print symbols for already expanded symbol
17503 You can use the command @code{info sources} to find out which files these are.
17504 If you use @samp{maint print psymbols} instead, the dump shows information
17505 about symbols that @value{GDBN} only knows partially---that is, symbols
17506 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17507 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17510 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17511 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17513 @kindex maint info symtabs
17514 @kindex maint info psymtabs
17515 @cindex listing @value{GDBN}'s internal symbol tables
17516 @cindex symbol tables, listing @value{GDBN}'s internal
17517 @cindex full symbol tables, listing @value{GDBN}'s internal
17518 @cindex partial symbol tables, listing @value{GDBN}'s internal
17519 @item maint info symtabs @r{[} @var{regexp} @r{]}
17520 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17522 List the @code{struct symtab} or @code{struct partial_symtab}
17523 structures whose names match @var{regexp}. If @var{regexp} is not
17524 given, list them all. The output includes expressions which you can
17525 copy into a @value{GDBN} debugging this one to examine a particular
17526 structure in more detail. For example:
17529 (@value{GDBP}) maint info psymtabs dwarf2read
17530 @{ objfile /home/gnu/build/gdb/gdb
17531 ((struct objfile *) 0x82e69d0)
17532 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17533 ((struct partial_symtab *) 0x8474b10)
17536 text addresses 0x814d3c8 -- 0x8158074
17537 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17538 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17539 dependencies (none)
17542 (@value{GDBP}) maint info symtabs
17546 We see that there is one partial symbol table whose filename contains
17547 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17548 and we see that @value{GDBN} has not read in any symtabs yet at all.
17549 If we set a breakpoint on a function, that will cause @value{GDBN} to
17550 read the symtab for the compilation unit containing that function:
17553 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17554 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17556 (@value{GDBP}) maint info symtabs
17557 @{ objfile /home/gnu/build/gdb/gdb
17558 ((struct objfile *) 0x82e69d0)
17559 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17560 ((struct symtab *) 0x86c1f38)
17563 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17564 linetable ((struct linetable *) 0x8370fa0)
17565 debugformat DWARF 2
17571 @kindex maint info line-table
17572 @cindex listing @value{GDBN}'s internal line tables
17573 @cindex line tables, listing @value{GDBN}'s internal
17574 @item maint info line-table @r{[} @var{regexp} @r{]}
17576 List the @code{struct linetable} from all @code{struct symtab}
17577 instances whose name matches @var{regexp}. If @var{regexp} is not
17578 given, list the @code{struct linetable} from all @code{struct symtab}.
17580 @kindex maint set symbol-cache-size
17581 @cindex symbol cache size
17582 @item maint set symbol-cache-size @var{size}
17583 Set the size of the symbol cache to @var{size}.
17584 The default size is intended to be good enough for debugging
17585 most applications. This option exists to allow for experimenting
17586 with different sizes.
17588 @kindex maint show symbol-cache-size
17589 @item maint show symbol-cache-size
17590 Show the size of the symbol cache.
17592 @kindex maint print symbol-cache
17593 @cindex symbol cache, printing its contents
17594 @item maint print symbol-cache
17595 Print the contents of the symbol cache.
17596 This is useful when debugging symbol cache issues.
17598 @kindex maint print symbol-cache-statistics
17599 @cindex symbol cache, printing usage statistics
17600 @item maint print symbol-cache-statistics
17601 Print symbol cache usage statistics.
17602 This helps determine how well the cache is being utilized.
17604 @kindex maint flush-symbol-cache
17605 @cindex symbol cache, flushing
17606 @item maint flush-symbol-cache
17607 Flush the contents of the symbol cache, all entries are removed.
17608 This command is useful when debugging the symbol cache.
17609 It is also useful when collecting performance data.
17614 @chapter Altering Execution
17616 Once you think you have found an error in your program, you might want to
17617 find out for certain whether correcting the apparent error would lead to
17618 correct results in the rest of the run. You can find the answer by
17619 experiment, using the @value{GDBN} features for altering execution of the
17622 For example, you can store new values into variables or memory
17623 locations, give your program a signal, restart it at a different
17624 address, or even return prematurely from a function.
17627 * Assignment:: Assignment to variables
17628 * Jumping:: Continuing at a different address
17629 * Signaling:: Giving your program a signal
17630 * Returning:: Returning from a function
17631 * Calling:: Calling your program's functions
17632 * Patching:: Patching your program
17633 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17637 @section Assignment to Variables
17640 @cindex setting variables
17641 To alter the value of a variable, evaluate an assignment expression.
17642 @xref{Expressions, ,Expressions}. For example,
17649 stores the value 4 into the variable @code{x}, and then prints the
17650 value of the assignment expression (which is 4).
17651 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17652 information on operators in supported languages.
17654 @kindex set variable
17655 @cindex variables, setting
17656 If you are not interested in seeing the value of the assignment, use the
17657 @code{set} command instead of the @code{print} command. @code{set} is
17658 really the same as @code{print} except that the expression's value is
17659 not printed and is not put in the value history (@pxref{Value History,
17660 ,Value History}). The expression is evaluated only for its effects.
17662 If the beginning of the argument string of the @code{set} command
17663 appears identical to a @code{set} subcommand, use the @code{set
17664 variable} command instead of just @code{set}. This command is identical
17665 to @code{set} except for its lack of subcommands. For example, if your
17666 program has a variable @code{width}, you get an error if you try to set
17667 a new value with just @samp{set width=13}, because @value{GDBN} has the
17668 command @code{set width}:
17671 (@value{GDBP}) whatis width
17673 (@value{GDBP}) p width
17675 (@value{GDBP}) set width=47
17676 Invalid syntax in expression.
17680 The invalid expression, of course, is @samp{=47}. In
17681 order to actually set the program's variable @code{width}, use
17684 (@value{GDBP}) set var width=47
17687 Because the @code{set} command has many subcommands that can conflict
17688 with the names of program variables, it is a good idea to use the
17689 @code{set variable} command instead of just @code{set}. For example, if
17690 your program has a variable @code{g}, you run into problems if you try
17691 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17692 the command @code{set gnutarget}, abbreviated @code{set g}:
17696 (@value{GDBP}) whatis g
17700 (@value{GDBP}) set g=4
17704 The program being debugged has been started already.
17705 Start it from the beginning? (y or n) y
17706 Starting program: /home/smith/cc_progs/a.out
17707 "/home/smith/cc_progs/a.out": can't open to read symbols:
17708 Invalid bfd target.
17709 (@value{GDBP}) show g
17710 The current BFD target is "=4".
17715 The program variable @code{g} did not change, and you silently set the
17716 @code{gnutarget} to an invalid value. In order to set the variable
17720 (@value{GDBP}) set var g=4
17723 @value{GDBN} allows more implicit conversions in assignments than C; you can
17724 freely store an integer value into a pointer variable or vice versa,
17725 and you can convert any structure to any other structure that is the
17726 same length or shorter.
17727 @comment FIXME: how do structs align/pad in these conversions?
17728 @comment /doc@cygnus.com 18dec1990
17730 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17731 construct to generate a value of specified type at a specified address
17732 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17733 to memory location @code{0x83040} as an integer (which implies a certain size
17734 and representation in memory), and
17737 set @{int@}0x83040 = 4
17741 stores the value 4 into that memory location.
17744 @section Continuing at a Different Address
17746 Ordinarily, when you continue your program, you do so at the place where
17747 it stopped, with the @code{continue} command. You can instead continue at
17748 an address of your own choosing, with the following commands:
17752 @kindex j @r{(@code{jump})}
17753 @item jump @var{location}
17754 @itemx j @var{location}
17755 Resume execution at @var{location}. Execution stops again immediately
17756 if there is a breakpoint there. @xref{Specify Location}, for a description
17757 of the different forms of @var{location}. It is common
17758 practice to use the @code{tbreak} command in conjunction with
17759 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17761 The @code{jump} command does not change the current stack frame, or
17762 the stack pointer, or the contents of any memory location or any
17763 register other than the program counter. If @var{location} is in
17764 a different function from the one currently executing, the results may
17765 be bizarre if the two functions expect different patterns of arguments or
17766 of local variables. For this reason, the @code{jump} command requests
17767 confirmation if the specified line is not in the function currently
17768 executing. However, even bizarre results are predictable if you are
17769 well acquainted with the machine-language code of your program.
17772 On many systems, you can get much the same effect as the @code{jump}
17773 command by storing a new value into the register @code{$pc}. The
17774 difference is that this does not start your program running; it only
17775 changes the address of where it @emph{will} run when you continue. For
17783 makes the next @code{continue} command or stepping command execute at
17784 address @code{0x485}, rather than at the address where your program stopped.
17785 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17787 The most common occasion to use the @code{jump} command is to back
17788 up---perhaps with more breakpoints set---over a portion of a program
17789 that has already executed, in order to examine its execution in more
17794 @section Giving your Program a Signal
17795 @cindex deliver a signal to a program
17799 @item signal @var{signal}
17800 Resume execution where your program is stopped, but immediately give it the
17801 signal @var{signal}. The @var{signal} can be the name or the number of a
17802 signal. For example, on many systems @code{signal 2} and @code{signal
17803 SIGINT} are both ways of sending an interrupt signal.
17805 Alternatively, if @var{signal} is zero, continue execution without
17806 giving a signal. This is useful when your program stopped on account of
17807 a signal and would ordinarily see the signal when resumed with the
17808 @code{continue} command; @samp{signal 0} causes it to resume without a
17811 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17812 delivered to the currently selected thread, not the thread that last
17813 reported a stop. This includes the situation where a thread was
17814 stopped due to a signal. So if you want to continue execution
17815 suppressing the signal that stopped a thread, you should select that
17816 same thread before issuing the @samp{signal 0} command. If you issue
17817 the @samp{signal 0} command with another thread as the selected one,
17818 @value{GDBN} detects that and asks for confirmation.
17820 Invoking the @code{signal} command is not the same as invoking the
17821 @code{kill} utility from the shell. Sending a signal with @code{kill}
17822 causes @value{GDBN} to decide what to do with the signal depending on
17823 the signal handling tables (@pxref{Signals}). The @code{signal} command
17824 passes the signal directly to your program.
17826 @code{signal} does not repeat when you press @key{RET} a second time
17827 after executing the command.
17829 @kindex queue-signal
17830 @item queue-signal @var{signal}
17831 Queue @var{signal} to be delivered immediately to the current thread
17832 when execution of the thread resumes. The @var{signal} can be the name or
17833 the number of a signal. For example, on many systems @code{signal 2} and
17834 @code{signal SIGINT} are both ways of sending an interrupt signal.
17835 The handling of the signal must be set to pass the signal to the program,
17836 otherwise @value{GDBN} will report an error.
17837 You can control the handling of signals from @value{GDBN} with the
17838 @code{handle} command (@pxref{Signals}).
17840 Alternatively, if @var{signal} is zero, any currently queued signal
17841 for the current thread is discarded and when execution resumes no signal
17842 will be delivered. This is useful when your program stopped on account
17843 of a signal and would ordinarily see the signal when resumed with the
17844 @code{continue} command.
17846 This command differs from the @code{signal} command in that the signal
17847 is just queued, execution is not resumed. And @code{queue-signal} cannot
17848 be used to pass a signal whose handling state has been set to @code{nopass}
17853 @xref{stepping into signal handlers}, for information on how stepping
17854 commands behave when the thread has a signal queued.
17857 @section Returning from a Function
17860 @cindex returning from a function
17863 @itemx return @var{expression}
17864 You can cancel execution of a function call with the @code{return}
17865 command. If you give an
17866 @var{expression} argument, its value is used as the function's return
17870 When you use @code{return}, @value{GDBN} discards the selected stack frame
17871 (and all frames within it). You can think of this as making the
17872 discarded frame return prematurely. If you wish to specify a value to
17873 be returned, give that value as the argument to @code{return}.
17875 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17876 Frame}), and any other frames inside of it, leaving its caller as the
17877 innermost remaining frame. That frame becomes selected. The
17878 specified value is stored in the registers used for returning values
17881 The @code{return} command does not resume execution; it leaves the
17882 program stopped in the state that would exist if the function had just
17883 returned. In contrast, the @code{finish} command (@pxref{Continuing
17884 and Stepping, ,Continuing and Stepping}) resumes execution until the
17885 selected stack frame returns naturally.
17887 @value{GDBN} needs to know how the @var{expression} argument should be set for
17888 the inferior. The concrete registers assignment depends on the OS ABI and the
17889 type being returned by the selected stack frame. For example it is common for
17890 OS ABI to return floating point values in FPU registers while integer values in
17891 CPU registers. Still some ABIs return even floating point values in CPU
17892 registers. Larger integer widths (such as @code{long long int}) also have
17893 specific placement rules. @value{GDBN} already knows the OS ABI from its
17894 current target so it needs to find out also the type being returned to make the
17895 assignment into the right register(s).
17897 Normally, the selected stack frame has debug info. @value{GDBN} will always
17898 use the debug info instead of the implicit type of @var{expression} when the
17899 debug info is available. For example, if you type @kbd{return -1}, and the
17900 function in the current stack frame is declared to return a @code{long long
17901 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17902 into a @code{long long int}:
17905 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17907 (@value{GDBP}) return -1
17908 Make func return now? (y or n) y
17909 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17910 43 printf ("result=%lld\n", func ());
17914 However, if the selected stack frame does not have a debug info, e.g., if the
17915 function was compiled without debug info, @value{GDBN} has to find out the type
17916 to return from user. Specifying a different type by mistake may set the value
17917 in different inferior registers than the caller code expects. For example,
17918 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17919 of a @code{long long int} result for a debug info less function (on 32-bit
17920 architectures). Therefore the user is required to specify the return type by
17921 an appropriate cast explicitly:
17924 Breakpoint 2, 0x0040050b in func ()
17925 (@value{GDBP}) return -1
17926 Return value type not available for selected stack frame.
17927 Please use an explicit cast of the value to return.
17928 (@value{GDBP}) return (long long int) -1
17929 Make selected stack frame return now? (y or n) y
17930 #0 0x00400526 in main ()
17935 @section Calling Program Functions
17938 @cindex calling functions
17939 @cindex inferior functions, calling
17940 @item print @var{expr}
17941 Evaluate the expression @var{expr} and display the resulting value.
17942 The expression may include calls to functions in the program being
17946 @item call @var{expr}
17947 Evaluate the expression @var{expr} without displaying @code{void}
17950 You can use this variant of the @code{print} command if you want to
17951 execute a function from your program that does not return anything
17952 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17953 with @code{void} returned values that @value{GDBN} will otherwise
17954 print. If the result is not void, it is printed and saved in the
17958 It is possible for the function you call via the @code{print} or
17959 @code{call} command to generate a signal (e.g., if there's a bug in
17960 the function, or if you passed it incorrect arguments). What happens
17961 in that case is controlled by the @code{set unwindonsignal} command.
17963 Similarly, with a C@t{++} program it is possible for the function you
17964 call via the @code{print} or @code{call} command to generate an
17965 exception that is not handled due to the constraints of the dummy
17966 frame. In this case, any exception that is raised in the frame, but has
17967 an out-of-frame exception handler will not be found. GDB builds a
17968 dummy-frame for the inferior function call, and the unwinder cannot
17969 seek for exception handlers outside of this dummy-frame. What happens
17970 in that case is controlled by the
17971 @code{set unwind-on-terminating-exception} command.
17974 @item set unwindonsignal
17975 @kindex set unwindonsignal
17976 @cindex unwind stack in called functions
17977 @cindex call dummy stack unwinding
17978 Set unwinding of the stack if a signal is received while in a function
17979 that @value{GDBN} called in the program being debugged. If set to on,
17980 @value{GDBN} unwinds the stack it created for the call and restores
17981 the context to what it was before the call. If set to off (the
17982 default), @value{GDBN} stops in the frame where the signal was
17985 @item show unwindonsignal
17986 @kindex show unwindonsignal
17987 Show the current setting of stack unwinding in the functions called by
17990 @item set unwind-on-terminating-exception
17991 @kindex set unwind-on-terminating-exception
17992 @cindex unwind stack in called functions with unhandled exceptions
17993 @cindex call dummy stack unwinding on unhandled exception.
17994 Set unwinding of the stack if a C@t{++} exception is raised, but left
17995 unhandled while in a function that @value{GDBN} called in the program being
17996 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17997 it created for the call and restores the context to what it was before
17998 the call. If set to off, @value{GDBN} the exception is delivered to
17999 the default C@t{++} exception handler and the inferior terminated.
18001 @item show unwind-on-terminating-exception
18002 @kindex show unwind-on-terminating-exception
18003 Show the current setting of stack unwinding in the functions called by
18008 @subsection Calling functions with no debug info
18010 @cindex no debug info functions
18011 Sometimes, a function you wish to call is missing debug information.
18012 In such case, @value{GDBN} does not know the type of the function,
18013 including the types of the function's parameters. To avoid calling
18014 the inferior function incorrectly, which could result in the called
18015 function functioning erroneously and even crash, @value{GDBN} refuses
18016 to call the function unless you tell it the type of the function.
18018 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18019 to do that. The simplest is to cast the call to the function's
18020 declared return type. For example:
18023 (@value{GDBP}) p getenv ("PATH")
18024 'getenv' has unknown return type; cast the call to its declared return type
18025 (@value{GDBP}) p (char *) getenv ("PATH")
18026 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18029 Casting the return type of a no-debug function is equivalent to
18030 casting the function to a pointer to a prototyped function that has a
18031 prototype that matches the types of the passed-in arguments, and
18032 calling that. I.e., the call above is equivalent to:
18035 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18039 and given this prototyped C or C++ function with float parameters:
18042 float multiply (float v1, float v2) @{ return v1 * v2; @}
18046 these calls are equivalent:
18049 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18050 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18053 If the function you wish to call is declared as unprototyped (i.e.@:
18054 old K&R style), you must use the cast-to-function-pointer syntax, so
18055 that @value{GDBN} knows that it needs to apply default argument
18056 promotions (promote float arguments to double). @xref{ABI, float
18057 promotion}. For example, given this unprototyped C function with
18058 float parameters, and no debug info:
18062 multiply_noproto (v1, v2)
18070 you call it like this:
18073 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18077 @section Patching Programs
18079 @cindex patching binaries
18080 @cindex writing into executables
18081 @cindex writing into corefiles
18083 By default, @value{GDBN} opens the file containing your program's
18084 executable code (or the corefile) read-only. This prevents accidental
18085 alterations to machine code; but it also prevents you from intentionally
18086 patching your program's binary.
18088 If you'd like to be able to patch the binary, you can specify that
18089 explicitly with the @code{set write} command. For example, you might
18090 want to turn on internal debugging flags, or even to make emergency
18096 @itemx set write off
18097 If you specify @samp{set write on}, @value{GDBN} opens executable and
18098 core files for both reading and writing; if you specify @kbd{set write
18099 off} (the default), @value{GDBN} opens them read-only.
18101 If you have already loaded a file, you must load it again (using the
18102 @code{exec-file} or @code{core-file} command) after changing @code{set
18103 write}, for your new setting to take effect.
18107 Display whether executable files and core files are opened for writing
18108 as well as reading.
18111 @node Compiling and Injecting Code
18112 @section Compiling and injecting code in @value{GDBN}
18113 @cindex injecting code
18114 @cindex writing into executables
18115 @cindex compiling code
18117 @value{GDBN} supports on-demand compilation and code injection into
18118 programs running under @value{GDBN}. GCC 5.0 or higher built with
18119 @file{libcc1.so} must be installed for this functionality to be enabled.
18120 This functionality is implemented with the following commands.
18123 @kindex compile code
18124 @item compile code @var{source-code}
18125 @itemx compile code -raw @var{--} @var{source-code}
18126 Compile @var{source-code} with the compiler language found as the current
18127 language in @value{GDBN} (@pxref{Languages}). If compilation and
18128 injection is not supported with the current language specified in
18129 @value{GDBN}, or the compiler does not support this feature, an error
18130 message will be printed. If @var{source-code} compiles and links
18131 successfully, @value{GDBN} will load the object-code emitted,
18132 and execute it within the context of the currently selected inferior.
18133 It is important to note that the compiled code is executed immediately.
18134 After execution, the compiled code is removed from @value{GDBN} and any
18135 new types or variables you have defined will be deleted.
18137 The command allows you to specify @var{source-code} in two ways.
18138 The simplest method is to provide a single line of code to the command.
18142 compile code printf ("hello world\n");
18145 If you specify options on the command line as well as source code, they
18146 may conflict. The @samp{--} delimiter can be used to separate options
18147 from actual source code. E.g.:
18150 compile code -r -- printf ("hello world\n");
18153 Alternatively you can enter source code as multiple lines of text. To
18154 enter this mode, invoke the @samp{compile code} command without any text
18155 following the command. This will start the multiple-line editor and
18156 allow you to type as many lines of source code as required. When you
18157 have completed typing, enter @samp{end} on its own line to exit the
18162 >printf ("hello\n");
18163 >printf ("world\n");
18167 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18168 provided @var{source-code} in a callable scope. In this case, you must
18169 specify the entry point of the code by defining a function named
18170 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18171 inferior. Using @samp{-raw} option may be needed for example when
18172 @var{source-code} requires @samp{#include} lines which may conflict with
18173 inferior symbols otherwise.
18175 @kindex compile file
18176 @item compile file @var{filename}
18177 @itemx compile file -raw @var{filename}
18178 Like @code{compile code}, but take the source code from @var{filename}.
18181 compile file /home/user/example.c
18186 @item compile print @var{expr}
18187 @itemx compile print /@var{f} @var{expr}
18188 Compile and execute @var{expr} with the compiler language found as the
18189 current language in @value{GDBN} (@pxref{Languages}). By default the
18190 value of @var{expr} is printed in a format appropriate to its data type;
18191 you can choose a different format by specifying @samp{/@var{f}}, where
18192 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18195 @item compile print
18196 @itemx compile print /@var{f}
18197 @cindex reprint the last value
18198 Alternatively you can enter the expression (source code producing it) as
18199 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18200 command without any text following the command. This will start the
18201 multiple-line editor.
18205 The process of compiling and injecting the code can be inspected using:
18208 @anchor{set debug compile}
18209 @item set debug compile
18210 @cindex compile command debugging info
18211 Turns on or off display of @value{GDBN} process of compiling and
18212 injecting the code. The default is off.
18214 @item show debug compile
18215 Displays the current state of displaying @value{GDBN} process of
18216 compiling and injecting the code.
18219 @subsection Compilation options for the @code{compile} command
18221 @value{GDBN} needs to specify the right compilation options for the code
18222 to be injected, in part to make its ABI compatible with the inferior
18223 and in part to make the injected code compatible with @value{GDBN}'s
18227 The options used, in increasing precedence:
18230 @item target architecture and OS options (@code{gdbarch})
18231 These options depend on target processor type and target operating
18232 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18233 (@code{-m64}) compilation option.
18235 @item compilation options recorded in the target
18236 @value{NGCC} (since version 4.7) stores the options used for compilation
18237 into @code{DW_AT_producer} part of DWARF debugging information according
18238 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18239 explicitly specify @code{-g} during inferior compilation otherwise
18240 @value{NGCC} produces no DWARF. This feature is only relevant for
18241 platforms where @code{-g} produces DWARF by default, otherwise one may
18242 try to enforce DWARF by using @code{-gdwarf-4}.
18244 @item compilation options set by @code{set compile-args}
18248 You can override compilation options using the following command:
18251 @item set compile-args
18252 @cindex compile command options override
18253 Set compilation options used for compiling and injecting code with the
18254 @code{compile} commands. These options override any conflicting ones
18255 from the target architecture and/or options stored during inferior
18258 @item show compile-args
18259 Displays the current state of compilation options override.
18260 This does not show all the options actually used during compilation,
18261 use @ref{set debug compile} for that.
18264 @subsection Caveats when using the @code{compile} command
18266 There are a few caveats to keep in mind when using the @code{compile}
18267 command. As the caveats are different per language, the table below
18268 highlights specific issues on a per language basis.
18271 @item C code examples and caveats
18272 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18273 attempt to compile the source code with a @samp{C} compiler. The source
18274 code provided to the @code{compile} command will have much the same
18275 access to variables and types as it normally would if it were part of
18276 the program currently being debugged in @value{GDBN}.
18278 Below is a sample program that forms the basis of the examples that
18279 follow. This program has been compiled and loaded into @value{GDBN},
18280 much like any other normal debugging session.
18283 void function1 (void)
18286 printf ("function 1\n");
18289 void function2 (void)
18304 For the purposes of the examples in this section, the program above has
18305 been compiled, loaded into @value{GDBN}, stopped at the function
18306 @code{main}, and @value{GDBN} is awaiting input from the user.
18308 To access variables and types for any program in @value{GDBN}, the
18309 program must be compiled and packaged with debug information. The
18310 @code{compile} command is not an exception to this rule. Without debug
18311 information, you can still use the @code{compile} command, but you will
18312 be very limited in what variables and types you can access.
18314 So with that in mind, the example above has been compiled with debug
18315 information enabled. The @code{compile} command will have access to
18316 all variables and types (except those that may have been optimized
18317 out). Currently, as @value{GDBN} has stopped the program in the
18318 @code{main} function, the @code{compile} command would have access to
18319 the variable @code{k}. You could invoke the @code{compile} command
18320 and type some source code to set the value of @code{k}. You can also
18321 read it, or do anything with that variable you would normally do in
18322 @code{C}. Be aware that changes to inferior variables in the
18323 @code{compile} command are persistent. In the following example:
18326 compile code k = 3;
18330 the variable @code{k} is now 3. It will retain that value until
18331 something else in the example program changes it, or another
18332 @code{compile} command changes it.
18334 Normal scope and access rules apply to source code compiled and
18335 injected by the @code{compile} command. In the example, the variables
18336 @code{j} and @code{k} are not accessible yet, because the program is
18337 currently stopped in the @code{main} function, where these variables
18338 are not in scope. Therefore, the following command
18341 compile code j = 3;
18345 will result in a compilation error message.
18347 Once the program is continued, execution will bring these variables in
18348 scope, and they will become accessible; then the code you specify via
18349 the @code{compile} command will be able to access them.
18351 You can create variables and types with the @code{compile} command as
18352 part of your source code. Variables and types that are created as part
18353 of the @code{compile} command are not visible to the rest of the program for
18354 the duration of its run. This example is valid:
18357 compile code int ff = 5; printf ("ff is %d\n", ff);
18360 However, if you were to type the following into @value{GDBN} after that
18361 command has completed:
18364 compile code printf ("ff is %d\n'', ff);
18368 a compiler error would be raised as the variable @code{ff} no longer
18369 exists. Object code generated and injected by the @code{compile}
18370 command is removed when its execution ends. Caution is advised
18371 when assigning to program variables values of variables created by the
18372 code submitted to the @code{compile} command. This example is valid:
18375 compile code int ff = 5; k = ff;
18378 The value of the variable @code{ff} is assigned to @code{k}. The variable
18379 @code{k} does not require the existence of @code{ff} to maintain the value
18380 it has been assigned. However, pointers require particular care in
18381 assignment. If the source code compiled with the @code{compile} command
18382 changed the address of a pointer in the example program, perhaps to a
18383 variable created in the @code{compile} command, that pointer would point
18384 to an invalid location when the command exits. The following example
18385 would likely cause issues with your debugged program:
18388 compile code int ff = 5; p = &ff;
18391 In this example, @code{p} would point to @code{ff} when the
18392 @code{compile} command is executing the source code provided to it.
18393 However, as variables in the (example) program persist with their
18394 assigned values, the variable @code{p} would point to an invalid
18395 location when the command exists. A general rule should be followed
18396 in that you should either assign @code{NULL} to any assigned pointers,
18397 or restore a valid location to the pointer before the command exits.
18399 Similar caution must be exercised with any structs, unions, and typedefs
18400 defined in @code{compile} command. Types defined in the @code{compile}
18401 command will no longer be available in the next @code{compile} command.
18402 Therefore, if you cast a variable to a type defined in the
18403 @code{compile} command, care must be taken to ensure that any future
18404 need to resolve the type can be achieved.
18407 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18408 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18409 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18410 Compilation failed.
18411 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18415 Variables that have been optimized away by the compiler are not
18416 accessible to the code submitted to the @code{compile} command.
18417 Access to those variables will generate a compiler error which @value{GDBN}
18418 will print to the console.
18421 @subsection Compiler search for the @code{compile} command
18423 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18424 which may not be obvious for remote targets of different architecture
18425 than where @value{GDBN} is running. Environment variable @code{PATH} on
18426 @value{GDBN} host is searched for @value{NGCC} binary matching the
18427 target architecture and operating system. This search can be overriden
18428 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18429 taken from shell that executed @value{GDBN}, it is not the value set by
18430 @value{GDBN} command @code{set environment}). @xref{Environment}.
18433 Specifically @code{PATH} is searched for binaries matching regular expression
18434 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18435 debugged. @var{arch} is processor name --- multiarch is supported, so for
18436 example both @code{i386} and @code{x86_64} targets look for pattern
18437 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18438 for pattern @code{s390x?}. @var{os} is currently supported only for
18439 pattern @code{linux(-gnu)?}.
18441 On Posix hosts the compiler driver @value{GDBN} needs to find also
18442 shared library @file{libcc1.so} from the compiler. It is searched in
18443 default shared library search path (overridable with usual environment
18444 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18445 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18446 according to the installation of the found compiler --- as possibly
18447 specified by the @code{set compile-gcc} command.
18450 @item set compile-gcc
18451 @cindex compile command driver filename override
18452 Set compilation command used for compiling and injecting code with the
18453 @code{compile} commands. If this option is not set (it is set to
18454 an empty string), the search described above will occur --- that is the
18457 @item show compile-gcc
18458 Displays the current compile command @value{NGCC} driver filename.
18459 If set, it is the main command @command{gcc}, found usually for example
18460 under name @file{x86_64-linux-gnu-gcc}.
18464 @chapter @value{GDBN} Files
18466 @value{GDBN} needs to know the file name of the program to be debugged,
18467 both in order to read its symbol table and in order to start your
18468 program. To debug a core dump of a previous run, you must also tell
18469 @value{GDBN} the name of the core dump file.
18472 * Files:: Commands to specify files
18473 * File Caching:: Information about @value{GDBN}'s file caching
18474 * Separate Debug Files:: Debugging information in separate files
18475 * MiniDebugInfo:: Debugging information in a special section
18476 * Index Files:: Index files speed up GDB
18477 * Symbol Errors:: Errors reading symbol files
18478 * Data Files:: GDB data files
18482 @section Commands to Specify Files
18484 @cindex symbol table
18485 @cindex core dump file
18487 You may want to specify executable and core dump file names. The usual
18488 way to do this is at start-up time, using the arguments to
18489 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18490 Out of @value{GDBN}}).
18492 Occasionally it is necessary to change to a different file during a
18493 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18494 specify a file you want to use. Or you are debugging a remote target
18495 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18496 Program}). In these situations the @value{GDBN} commands to specify
18497 new files are useful.
18500 @cindex executable file
18502 @item file @var{filename}
18503 Use @var{filename} as the program to be debugged. It is read for its
18504 symbols and for the contents of pure memory. It is also the program
18505 executed when you use the @code{run} command. If you do not specify a
18506 directory and the file is not found in the @value{GDBN} working directory,
18507 @value{GDBN} uses the environment variable @code{PATH} as a list of
18508 directories to search, just as the shell does when looking for a program
18509 to run. You can change the value of this variable, for both @value{GDBN}
18510 and your program, using the @code{path} command.
18512 @cindex unlinked object files
18513 @cindex patching object files
18514 You can load unlinked object @file{.o} files into @value{GDBN} using
18515 the @code{file} command. You will not be able to ``run'' an object
18516 file, but you can disassemble functions and inspect variables. Also,
18517 if the underlying BFD functionality supports it, you could use
18518 @kbd{gdb -write} to patch object files using this technique. Note
18519 that @value{GDBN} can neither interpret nor modify relocations in this
18520 case, so branches and some initialized variables will appear to go to
18521 the wrong place. But this feature is still handy from time to time.
18524 @code{file} with no argument makes @value{GDBN} discard any information it
18525 has on both executable file and the symbol table.
18528 @item exec-file @r{[} @var{filename} @r{]}
18529 Specify that the program to be run (but not the symbol table) is found
18530 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18531 if necessary to locate your program. Omitting @var{filename} means to
18532 discard information on the executable file.
18534 @kindex symbol-file
18535 @item symbol-file @r{[} @var{filename} @r{]}
18536 Read symbol table information from file @var{filename}. @code{PATH} is
18537 searched when necessary. Use the @code{file} command to get both symbol
18538 table and program to run from the same file.
18540 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18541 program's symbol table.
18543 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18544 some breakpoints and auto-display expressions. This is because they may
18545 contain pointers to the internal data recording symbols and data types,
18546 which are part of the old symbol table data being discarded inside
18549 @code{symbol-file} does not repeat if you press @key{RET} again after
18552 When @value{GDBN} is configured for a particular environment, it
18553 understands debugging information in whatever format is the standard
18554 generated for that environment; you may use either a @sc{gnu} compiler, or
18555 other compilers that adhere to the local conventions.
18556 Best results are usually obtained from @sc{gnu} compilers; for example,
18557 using @code{@value{NGCC}} you can generate debugging information for
18560 For most kinds of object files, with the exception of old SVR3 systems
18561 using COFF, the @code{symbol-file} command does not normally read the
18562 symbol table in full right away. Instead, it scans the symbol table
18563 quickly to find which source files and which symbols are present. The
18564 details are read later, one source file at a time, as they are needed.
18566 The purpose of this two-stage reading strategy is to make @value{GDBN}
18567 start up faster. For the most part, it is invisible except for
18568 occasional pauses while the symbol table details for a particular source
18569 file are being read. (The @code{set verbose} command can turn these
18570 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18571 Warnings and Messages}.)
18573 We have not implemented the two-stage strategy for COFF yet. When the
18574 symbol table is stored in COFF format, @code{symbol-file} reads the
18575 symbol table data in full right away. Note that ``stabs-in-COFF''
18576 still does the two-stage strategy, since the debug info is actually
18580 @cindex reading symbols immediately
18581 @cindex symbols, reading immediately
18582 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18583 @itemx file @r{[} -readnow @r{]} @var{filename}
18584 You can override the @value{GDBN} two-stage strategy for reading symbol
18585 tables by using the @samp{-readnow} option with any of the commands that
18586 load symbol table information, if you want to be sure @value{GDBN} has the
18587 entire symbol table available.
18589 @cindex @code{-readnever}, option for symbol-file command
18590 @cindex never read symbols
18591 @cindex symbols, never read
18592 @item symbol-file @r{[} -readnever @r{]} @var{filename}
18593 @itemx file @r{[} -readnever @r{]} @var{filename}
18594 You can instruct @value{GDBN} to never read the symbolic information
18595 contained in @var{filename} by using the @samp{-readnever} option.
18596 @xref{--readnever}.
18598 @c FIXME: for now no mention of directories, since this seems to be in
18599 @c flux. 13mar1992 status is that in theory GDB would look either in
18600 @c current dir or in same dir as myprog; but issues like competing
18601 @c GDB's, or clutter in system dirs, mean that in practice right now
18602 @c only current dir is used. FFish says maybe a special GDB hierarchy
18603 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18607 @item core-file @r{[}@var{filename}@r{]}
18609 Specify the whereabouts of a core dump file to be used as the ``contents
18610 of memory''. Traditionally, core files contain only some parts of the
18611 address space of the process that generated them; @value{GDBN} can access the
18612 executable file itself for other parts.
18614 @code{core-file} with no argument specifies that no core file is
18617 Note that the core file is ignored when your program is actually running
18618 under @value{GDBN}. So, if you have been running your program and you
18619 wish to debug a core file instead, you must kill the subprocess in which
18620 the program is running. To do this, use the @code{kill} command
18621 (@pxref{Kill Process, ,Killing the Child Process}).
18623 @kindex add-symbol-file
18624 @cindex dynamic linking
18625 @item add-symbol-file @var{filename} @var{address}
18626 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{|} -readnever @r{]}
18627 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18628 The @code{add-symbol-file} command reads additional symbol table
18629 information from the file @var{filename}. You would use this command
18630 when @var{filename} has been dynamically loaded (by some other means)
18631 into the program that is running. The @var{address} should give the memory
18632 address at which the file has been loaded; @value{GDBN} cannot figure
18633 this out for itself. You can additionally specify an arbitrary number
18634 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18635 section name and base address for that section. You can specify any
18636 @var{address} as an expression.
18638 The symbol table of the file @var{filename} is added to the symbol table
18639 originally read with the @code{symbol-file} command. You can use the
18640 @code{add-symbol-file} command any number of times; the new symbol data
18641 thus read is kept in addition to the old.
18643 Changes can be reverted using the command @code{remove-symbol-file}.
18645 @cindex relocatable object files, reading symbols from
18646 @cindex object files, relocatable, reading symbols from
18647 @cindex reading symbols from relocatable object files
18648 @cindex symbols, reading from relocatable object files
18649 @cindex @file{.o} files, reading symbols from
18650 Although @var{filename} is typically a shared library file, an
18651 executable file, or some other object file which has been fully
18652 relocated for loading into a process, you can also load symbolic
18653 information from relocatable @file{.o} files, as long as:
18657 the file's symbolic information refers only to linker symbols defined in
18658 that file, not to symbols defined by other object files,
18660 every section the file's symbolic information refers to has actually
18661 been loaded into the inferior, as it appears in the file, and
18663 you can determine the address at which every section was loaded, and
18664 provide these to the @code{add-symbol-file} command.
18668 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18669 relocatable files into an already running program; such systems
18670 typically make the requirements above easy to meet. However, it's
18671 important to recognize that many native systems use complex link
18672 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18673 assembly, for example) that make the requirements difficult to meet. In
18674 general, one cannot assume that using @code{add-symbol-file} to read a
18675 relocatable object file's symbolic information will have the same effect
18676 as linking the relocatable object file into the program in the normal
18679 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18681 @kindex remove-symbol-file
18682 @item remove-symbol-file @var{filename}
18683 @item remove-symbol-file -a @var{address}
18684 Remove a symbol file added via the @code{add-symbol-file} command. The
18685 file to remove can be identified by its @var{filename} or by an @var{address}
18686 that lies within the boundaries of this symbol file in memory. Example:
18689 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18690 add symbol table from file "/home/user/gdb/mylib.so" at
18691 .text_addr = 0x7ffff7ff9480
18693 Reading symbols from /home/user/gdb/mylib.so...done.
18694 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18695 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18700 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18702 @kindex add-symbol-file-from-memory
18703 @cindex @code{syscall DSO}
18704 @cindex load symbols from memory
18705 @item add-symbol-file-from-memory @var{address}
18706 Load symbols from the given @var{address} in a dynamically loaded
18707 object file whose image is mapped directly into the inferior's memory.
18708 For example, the Linux kernel maps a @code{syscall DSO} into each
18709 process's address space; this DSO provides kernel-specific code for
18710 some system calls. The argument can be any expression whose
18711 evaluation yields the address of the file's shared object file header.
18712 For this command to work, you must have used @code{symbol-file} or
18713 @code{exec-file} commands in advance.
18716 @item section @var{section} @var{addr}
18717 The @code{section} command changes the base address of the named
18718 @var{section} of the exec file to @var{addr}. This can be used if the
18719 exec file does not contain section addresses, (such as in the
18720 @code{a.out} format), or when the addresses specified in the file
18721 itself are wrong. Each section must be changed separately. The
18722 @code{info files} command, described below, lists all the sections and
18726 @kindex info target
18729 @code{info files} and @code{info target} are synonymous; both print the
18730 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18731 including the names of the executable and core dump files currently in
18732 use by @value{GDBN}, and the files from which symbols were loaded. The
18733 command @code{help target} lists all possible targets rather than
18736 @kindex maint info sections
18737 @item maint info sections
18738 Another command that can give you extra information about program sections
18739 is @code{maint info sections}. In addition to the section information
18740 displayed by @code{info files}, this command displays the flags and file
18741 offset of each section in the executable and core dump files. In addition,
18742 @code{maint info sections} provides the following command options (which
18743 may be arbitrarily combined):
18747 Display sections for all loaded object files, including shared libraries.
18748 @item @var{sections}
18749 Display info only for named @var{sections}.
18750 @item @var{section-flags}
18751 Display info only for sections for which @var{section-flags} are true.
18752 The section flags that @value{GDBN} currently knows about are:
18755 Section will have space allocated in the process when loaded.
18756 Set for all sections except those containing debug information.
18758 Section will be loaded from the file into the child process memory.
18759 Set for pre-initialized code and data, clear for @code{.bss} sections.
18761 Section needs to be relocated before loading.
18763 Section cannot be modified by the child process.
18765 Section contains executable code only.
18767 Section contains data only (no executable code).
18769 Section will reside in ROM.
18771 Section contains data for constructor/destructor lists.
18773 Section is not empty.
18775 An instruction to the linker to not output the section.
18776 @item COFF_SHARED_LIBRARY
18777 A notification to the linker that the section contains
18778 COFF shared library information.
18780 Section contains common symbols.
18783 @kindex set trust-readonly-sections
18784 @cindex read-only sections
18785 @item set trust-readonly-sections on
18786 Tell @value{GDBN} that readonly sections in your object file
18787 really are read-only (i.e.@: that their contents will not change).
18788 In that case, @value{GDBN} can fetch values from these sections
18789 out of the object file, rather than from the target program.
18790 For some targets (notably embedded ones), this can be a significant
18791 enhancement to debugging performance.
18793 The default is off.
18795 @item set trust-readonly-sections off
18796 Tell @value{GDBN} not to trust readonly sections. This means that
18797 the contents of the section might change while the program is running,
18798 and must therefore be fetched from the target when needed.
18800 @item show trust-readonly-sections
18801 Show the current setting of trusting readonly sections.
18804 All file-specifying commands allow both absolute and relative file names
18805 as arguments. @value{GDBN} always converts the file name to an absolute file
18806 name and remembers it that way.
18808 @cindex shared libraries
18809 @anchor{Shared Libraries}
18810 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18811 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18812 DSBT (TIC6X) shared libraries.
18814 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18815 shared libraries. @xref{Expat}.
18817 @value{GDBN} automatically loads symbol definitions from shared libraries
18818 when you use the @code{run} command, or when you examine a core file.
18819 (Before you issue the @code{run} command, @value{GDBN} does not understand
18820 references to a function in a shared library, however---unless you are
18821 debugging a core file).
18823 @c FIXME: some @value{GDBN} release may permit some refs to undef
18824 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18825 @c FIXME...lib; check this from time to time when updating manual
18827 There are times, however, when you may wish to not automatically load
18828 symbol definitions from shared libraries, such as when they are
18829 particularly large or there are many of them.
18831 To control the automatic loading of shared library symbols, use the
18835 @kindex set auto-solib-add
18836 @item set auto-solib-add @var{mode}
18837 If @var{mode} is @code{on}, symbols from all shared object libraries
18838 will be loaded automatically when the inferior begins execution, you
18839 attach to an independently started inferior, or when the dynamic linker
18840 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18841 is @code{off}, symbols must be loaded manually, using the
18842 @code{sharedlibrary} command. The default value is @code{on}.
18844 @cindex memory used for symbol tables
18845 If your program uses lots of shared libraries with debug info that
18846 takes large amounts of memory, you can decrease the @value{GDBN}
18847 memory footprint by preventing it from automatically loading the
18848 symbols from shared libraries. To that end, type @kbd{set
18849 auto-solib-add off} before running the inferior, then load each
18850 library whose debug symbols you do need with @kbd{sharedlibrary
18851 @var{regexp}}, where @var{regexp} is a regular expression that matches
18852 the libraries whose symbols you want to be loaded.
18854 @kindex show auto-solib-add
18855 @item show auto-solib-add
18856 Display the current autoloading mode.
18859 @cindex load shared library
18860 To explicitly load shared library symbols, use the @code{sharedlibrary}
18864 @kindex info sharedlibrary
18866 @item info share @var{regex}
18867 @itemx info sharedlibrary @var{regex}
18868 Print the names of the shared libraries which are currently loaded
18869 that match @var{regex}. If @var{regex} is omitted then print
18870 all shared libraries that are loaded.
18873 @item info dll @var{regex}
18874 This is an alias of @code{info sharedlibrary}.
18876 @kindex sharedlibrary
18878 @item sharedlibrary @var{regex}
18879 @itemx share @var{regex}
18880 Load shared object library symbols for files matching a
18881 Unix regular expression.
18882 As with files loaded automatically, it only loads shared libraries
18883 required by your program for a core file or after typing @code{run}. If
18884 @var{regex} is omitted all shared libraries required by your program are
18887 @item nosharedlibrary
18888 @kindex nosharedlibrary
18889 @cindex unload symbols from shared libraries
18890 Unload all shared object library symbols. This discards all symbols
18891 that have been loaded from all shared libraries. Symbols from shared
18892 libraries that were loaded by explicit user requests are not
18896 Sometimes you may wish that @value{GDBN} stops and gives you control
18897 when any of shared library events happen. The best way to do this is
18898 to use @code{catch load} and @code{catch unload} (@pxref{Set
18901 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18902 command for this. This command exists for historical reasons. It is
18903 less useful than setting a catchpoint, because it does not allow for
18904 conditions or commands as a catchpoint does.
18907 @item set stop-on-solib-events
18908 @kindex set stop-on-solib-events
18909 This command controls whether @value{GDBN} should give you control
18910 when the dynamic linker notifies it about some shared library event.
18911 The most common event of interest is loading or unloading of a new
18914 @item show stop-on-solib-events
18915 @kindex show stop-on-solib-events
18916 Show whether @value{GDBN} stops and gives you control when shared
18917 library events happen.
18920 Shared libraries are also supported in many cross or remote debugging
18921 configurations. @value{GDBN} needs to have access to the target's libraries;
18922 this can be accomplished either by providing copies of the libraries
18923 on the host system, or by asking @value{GDBN} to automatically retrieve the
18924 libraries from the target. If copies of the target libraries are
18925 provided, they need to be the same as the target libraries, although the
18926 copies on the target can be stripped as long as the copies on the host are
18929 @cindex where to look for shared libraries
18930 For remote debugging, you need to tell @value{GDBN} where the target
18931 libraries are, so that it can load the correct copies---otherwise, it
18932 may try to load the host's libraries. @value{GDBN} has two variables
18933 to specify the search directories for target libraries.
18936 @cindex prefix for executable and shared library file names
18937 @cindex system root, alternate
18938 @kindex set solib-absolute-prefix
18939 @kindex set sysroot
18940 @item set sysroot @var{path}
18941 Use @var{path} as the system root for the program being debugged. Any
18942 absolute shared library paths will be prefixed with @var{path}; many
18943 runtime loaders store the absolute paths to the shared library in the
18944 target program's memory. When starting processes remotely, and when
18945 attaching to already-running processes (local or remote), their
18946 executable filenames will be prefixed with @var{path} if reported to
18947 @value{GDBN} as absolute by the operating system. If you use
18948 @code{set sysroot} to find executables and shared libraries, they need
18949 to be laid out in the same way that they are on the target, with
18950 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18953 If @var{path} starts with the sequence @file{target:} and the target
18954 system is remote then @value{GDBN} will retrieve the target binaries
18955 from the remote system. This is only supported when using a remote
18956 target that supports the @code{remote get} command (@pxref{File
18957 Transfer,,Sending files to a remote system}). The part of @var{path}
18958 following the initial @file{target:} (if present) is used as system
18959 root prefix on the remote file system. If @var{path} starts with the
18960 sequence @file{remote:} this is converted to the sequence
18961 @file{target:} by @code{set sysroot}@footnote{Historically the
18962 functionality to retrieve binaries from the remote system was
18963 provided by prefixing @var{path} with @file{remote:}}. If you want
18964 to specify a local system root using a directory that happens to be
18965 named @file{target:} or @file{remote:}, you need to use some
18966 equivalent variant of the name like @file{./target:}.
18968 For targets with an MS-DOS based filesystem, such as MS-Windows and
18969 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18970 absolute file name with @var{path}. But first, on Unix hosts,
18971 @value{GDBN} converts all backslash directory separators into forward
18972 slashes, because the backslash is not a directory separator on Unix:
18975 c:\foo\bar.dll @result{} c:/foo/bar.dll
18978 Then, @value{GDBN} attempts prefixing the target file name with
18979 @var{path}, and looks for the resulting file name in the host file
18983 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18986 If that does not find the binary, @value{GDBN} tries removing
18987 the @samp{:} character from the drive spec, both for convenience, and,
18988 for the case of the host file system not supporting file names with
18992 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18995 This makes it possible to have a system root that mirrors a target
18996 with more than one drive. E.g., you may want to setup your local
18997 copies of the target system shared libraries like so (note @samp{c} vs
19001 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19002 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19003 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19007 and point the system root at @file{/path/to/sysroot}, so that
19008 @value{GDBN} can find the correct copies of both
19009 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19011 If that still does not find the binary, @value{GDBN} tries
19012 removing the whole drive spec from the target file name:
19015 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19018 This last lookup makes it possible to not care about the drive name,
19019 if you don't want or need to.
19021 The @code{set solib-absolute-prefix} command is an alias for @code{set
19024 @cindex default system root
19025 @cindex @samp{--with-sysroot}
19026 You can set the default system root by using the configure-time
19027 @samp{--with-sysroot} option. If the system root is inside
19028 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19029 @samp{--exec-prefix}), then the default system root will be updated
19030 automatically if the installed @value{GDBN} is moved to a new
19033 @kindex show sysroot
19035 Display the current executable and shared library prefix.
19037 @kindex set solib-search-path
19038 @item set solib-search-path @var{path}
19039 If this variable is set, @var{path} is a colon-separated list of
19040 directories to search for shared libraries. @samp{solib-search-path}
19041 is used after @samp{sysroot} fails to locate the library, or if the
19042 path to the library is relative instead of absolute. If you want to
19043 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19044 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19045 finding your host's libraries. @samp{sysroot} is preferred; setting
19046 it to a nonexistent directory may interfere with automatic loading
19047 of shared library symbols.
19049 @kindex show solib-search-path
19050 @item show solib-search-path
19051 Display the current shared library search path.
19053 @cindex DOS file-name semantics of file names.
19054 @kindex set target-file-system-kind (unix|dos-based|auto)
19055 @kindex show target-file-system-kind
19056 @item set target-file-system-kind @var{kind}
19057 Set assumed file system kind for target reported file names.
19059 Shared library file names as reported by the target system may not
19060 make sense as is on the system @value{GDBN} is running on. For
19061 example, when remote debugging a target that has MS-DOS based file
19062 system semantics, from a Unix host, the target may be reporting to
19063 @value{GDBN} a list of loaded shared libraries with file names such as
19064 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19065 drive letters, so the @samp{c:\} prefix is not normally understood as
19066 indicating an absolute file name, and neither is the backslash
19067 normally considered a directory separator character. In that case,
19068 the native file system would interpret this whole absolute file name
19069 as a relative file name with no directory components. This would make
19070 it impossible to point @value{GDBN} at a copy of the remote target's
19071 shared libraries on the host using @code{set sysroot}, and impractical
19072 with @code{set solib-search-path}. Setting
19073 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19074 to interpret such file names similarly to how the target would, and to
19075 map them to file names valid on @value{GDBN}'s native file system
19076 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19077 to one of the supported file system kinds. In that case, @value{GDBN}
19078 tries to determine the appropriate file system variant based on the
19079 current target's operating system (@pxref{ABI, ,Configuring the
19080 Current ABI}). The supported file system settings are:
19084 Instruct @value{GDBN} to assume the target file system is of Unix
19085 kind. Only file names starting the forward slash (@samp{/}) character
19086 are considered absolute, and the directory separator character is also
19090 Instruct @value{GDBN} to assume the target file system is DOS based.
19091 File names starting with either a forward slash, or a drive letter
19092 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19093 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19094 considered directory separators.
19097 Instruct @value{GDBN} to use the file system kind associated with the
19098 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19099 This is the default.
19103 @cindex file name canonicalization
19104 @cindex base name differences
19105 When processing file names provided by the user, @value{GDBN}
19106 frequently needs to compare them to the file names recorded in the
19107 program's debug info. Normally, @value{GDBN} compares just the
19108 @dfn{base names} of the files as strings, which is reasonably fast
19109 even for very large programs. (The base name of a file is the last
19110 portion of its name, after stripping all the leading directories.)
19111 This shortcut in comparison is based upon the assumption that files
19112 cannot have more than one base name. This is usually true, but
19113 references to files that use symlinks or similar filesystem
19114 facilities violate that assumption. If your program records files
19115 using such facilities, or if you provide file names to @value{GDBN}
19116 using symlinks etc., you can set @code{basenames-may-differ} to
19117 @code{true} to instruct @value{GDBN} to completely canonicalize each
19118 pair of file names it needs to compare. This will make file-name
19119 comparisons accurate, but at a price of a significant slowdown.
19122 @item set basenames-may-differ
19123 @kindex set basenames-may-differ
19124 Set whether a source file may have multiple base names.
19126 @item show basenames-may-differ
19127 @kindex show basenames-may-differ
19128 Show whether a source file may have multiple base names.
19132 @section File Caching
19133 @cindex caching of opened files
19134 @cindex caching of bfd objects
19136 To speed up file loading, and reduce memory usage, @value{GDBN} will
19137 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19138 BFD, bfd, The Binary File Descriptor Library}. The following commands
19139 allow visibility and control of the caching behavior.
19142 @kindex maint info bfds
19143 @item maint info bfds
19144 This prints information about each @code{bfd} object that is known to
19147 @kindex maint set bfd-sharing
19148 @kindex maint show bfd-sharing
19149 @kindex bfd caching
19150 @item maint set bfd-sharing
19151 @item maint show bfd-sharing
19152 Control whether @code{bfd} objects can be shared. When sharing is
19153 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19154 than reopening the same file. Turning sharing off does not cause
19155 already shared @code{bfd} objects to be unshared, but all future files
19156 that are opened will create a new @code{bfd} object. Similarly,
19157 re-enabling sharing does not cause multiple existing @code{bfd}
19158 objects to be collapsed into a single shared @code{bfd} object.
19160 @kindex set debug bfd-cache @var{level}
19161 @kindex bfd caching
19162 @item set debug bfd-cache @var{level}
19163 Turns on debugging of the bfd cache, setting the level to @var{level}.
19165 @kindex show debug bfd-cache
19166 @kindex bfd caching
19167 @item show debug bfd-cache
19168 Show the current debugging level of the bfd cache.
19171 @node Separate Debug Files
19172 @section Debugging Information in Separate Files
19173 @cindex separate debugging information files
19174 @cindex debugging information in separate files
19175 @cindex @file{.debug} subdirectories
19176 @cindex debugging information directory, global
19177 @cindex global debugging information directories
19178 @cindex build ID, and separate debugging files
19179 @cindex @file{.build-id} directory
19181 @value{GDBN} allows you to put a program's debugging information in a
19182 file separate from the executable itself, in a way that allows
19183 @value{GDBN} to find and load the debugging information automatically.
19184 Since debugging information can be very large---sometimes larger
19185 than the executable code itself---some systems distribute debugging
19186 information for their executables in separate files, which users can
19187 install only when they need to debug a problem.
19189 @value{GDBN} supports two ways of specifying the separate debug info
19194 The executable contains a @dfn{debug link} that specifies the name of
19195 the separate debug info file. The separate debug file's name is
19196 usually @file{@var{executable}.debug}, where @var{executable} is the
19197 name of the corresponding executable file without leading directories
19198 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19199 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19200 checksum for the debug file, which @value{GDBN} uses to validate that
19201 the executable and the debug file came from the same build.
19204 The executable contains a @dfn{build ID}, a unique bit string that is
19205 also present in the corresponding debug info file. (This is supported
19206 only on some operating systems, when using the ELF or PE file formats
19207 for binary files and the @sc{gnu} Binutils.) For more details about
19208 this feature, see the description of the @option{--build-id}
19209 command-line option in @ref{Options, , Command Line Options, ld.info,
19210 The GNU Linker}. The debug info file's name is not specified
19211 explicitly by the build ID, but can be computed from the build ID, see
19215 Depending on the way the debug info file is specified, @value{GDBN}
19216 uses two different methods of looking for the debug file:
19220 For the ``debug link'' method, @value{GDBN} looks up the named file in
19221 the directory of the executable file, then in a subdirectory of that
19222 directory named @file{.debug}, and finally under each one of the global debug
19223 directories, in a subdirectory whose name is identical to the leading
19224 directories of the executable's absolute file name.
19227 For the ``build ID'' method, @value{GDBN} looks in the
19228 @file{.build-id} subdirectory of each one of the global debug directories for
19229 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19230 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19231 are the rest of the bit string. (Real build ID strings are 32 or more
19232 hex characters, not 10.)
19235 So, for example, suppose you ask @value{GDBN} to debug
19236 @file{/usr/bin/ls}, which has a debug link that specifies the
19237 file @file{ls.debug}, and a build ID whose value in hex is
19238 @code{abcdef1234}. If the list of the global debug directories includes
19239 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19240 debug information files, in the indicated order:
19244 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19246 @file{/usr/bin/ls.debug}
19248 @file{/usr/bin/.debug/ls.debug}
19250 @file{/usr/lib/debug/usr/bin/ls.debug}.
19253 @anchor{debug-file-directory}
19254 Global debugging info directories default to what is set by @value{GDBN}
19255 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19256 you can also set the global debugging info directories, and view the list
19257 @value{GDBN} is currently using.
19261 @kindex set debug-file-directory
19262 @item set debug-file-directory @var{directories}
19263 Set the directories which @value{GDBN} searches for separate debugging
19264 information files to @var{directory}. Multiple path components can be set
19265 concatenating them by a path separator.
19267 @kindex show debug-file-directory
19268 @item show debug-file-directory
19269 Show the directories @value{GDBN} searches for separate debugging
19274 @cindex @code{.gnu_debuglink} sections
19275 @cindex debug link sections
19276 A debug link is a special section of the executable file named
19277 @code{.gnu_debuglink}. The section must contain:
19281 A filename, with any leading directory components removed, followed by
19284 zero to three bytes of padding, as needed to reach the next four-byte
19285 boundary within the section, and
19287 a four-byte CRC checksum, stored in the same endianness used for the
19288 executable file itself. The checksum is computed on the debugging
19289 information file's full contents by the function given below, passing
19290 zero as the @var{crc} argument.
19293 Any executable file format can carry a debug link, as long as it can
19294 contain a section named @code{.gnu_debuglink} with the contents
19297 @cindex @code{.note.gnu.build-id} sections
19298 @cindex build ID sections
19299 The build ID is a special section in the executable file (and in other
19300 ELF binary files that @value{GDBN} may consider). This section is
19301 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19302 It contains unique identification for the built files---the ID remains
19303 the same across multiple builds of the same build tree. The default
19304 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19305 content for the build ID string. The same section with an identical
19306 value is present in the original built binary with symbols, in its
19307 stripped variant, and in the separate debugging information file.
19309 The debugging information file itself should be an ordinary
19310 executable, containing a full set of linker symbols, sections, and
19311 debugging information. The sections of the debugging information file
19312 should have the same names, addresses, and sizes as the original file,
19313 but they need not contain any data---much like a @code{.bss} section
19314 in an ordinary executable.
19316 The @sc{gnu} binary utilities (Binutils) package includes the
19317 @samp{objcopy} utility that can produce
19318 the separated executable / debugging information file pairs using the
19319 following commands:
19322 @kbd{objcopy --only-keep-debug foo foo.debug}
19327 These commands remove the debugging
19328 information from the executable file @file{foo} and place it in the file
19329 @file{foo.debug}. You can use the first, second or both methods to link the
19334 The debug link method needs the following additional command to also leave
19335 behind a debug link in @file{foo}:
19338 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19341 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19342 a version of the @code{strip} command such that the command @kbd{strip foo -f
19343 foo.debug} has the same functionality as the two @code{objcopy} commands and
19344 the @code{ln -s} command above, together.
19347 Build ID gets embedded into the main executable using @code{ld --build-id} or
19348 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19349 compatibility fixes for debug files separation are present in @sc{gnu} binary
19350 utilities (Binutils) package since version 2.18.
19355 @cindex CRC algorithm definition
19356 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19357 IEEE 802.3 using the polynomial:
19359 @c TexInfo requires naked braces for multi-digit exponents for Tex
19360 @c output, but this causes HTML output to barf. HTML has to be set using
19361 @c raw commands. So we end up having to specify this equation in 2
19366 <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>
19367 + <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
19373 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19374 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19378 The function is computed byte at a time, taking the least
19379 significant bit of each byte first. The initial pattern
19380 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19381 the final result is inverted to ensure trailing zeros also affect the
19384 @emph{Note:} This is the same CRC polynomial as used in handling the
19385 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19386 However in the case of the Remote Serial Protocol, the CRC is computed
19387 @emph{most} significant bit first, and the result is not inverted, so
19388 trailing zeros have no effect on the CRC value.
19390 To complete the description, we show below the code of the function
19391 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19392 initially supplied @code{crc} argument means that an initial call to
19393 this function passing in zero will start computing the CRC using
19396 @kindex gnu_debuglink_crc32
19399 gnu_debuglink_crc32 (unsigned long crc,
19400 unsigned char *buf, size_t len)
19402 static const unsigned long crc32_table[256] =
19404 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19405 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19406 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19407 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19408 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19409 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19410 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19411 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19412 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19413 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19414 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19415 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19416 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19417 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19418 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19419 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19420 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19421 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19422 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19423 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19424 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19425 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19426 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19427 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19428 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19429 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19430 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19431 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19432 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19433 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19434 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19435 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19436 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19437 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19438 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19439 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19440 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19441 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19442 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19443 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19444 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19445 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19446 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19447 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19448 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19449 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19450 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19451 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19452 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19453 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19454 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19457 unsigned char *end;
19459 crc = ~crc & 0xffffffff;
19460 for (end = buf + len; buf < end; ++buf)
19461 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19462 return ~crc & 0xffffffff;
19467 This computation does not apply to the ``build ID'' method.
19469 @node MiniDebugInfo
19470 @section Debugging information in a special section
19471 @cindex separate debug sections
19472 @cindex @samp{.gnu_debugdata} section
19474 Some systems ship pre-built executables and libraries that have a
19475 special @samp{.gnu_debugdata} section. This feature is called
19476 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19477 is used to supply extra symbols for backtraces.
19479 The intent of this section is to provide extra minimal debugging
19480 information for use in simple backtraces. It is not intended to be a
19481 replacement for full separate debugging information (@pxref{Separate
19482 Debug Files}). The example below shows the intended use; however,
19483 @value{GDBN} does not currently put restrictions on what sort of
19484 debugging information might be included in the section.
19486 @value{GDBN} has support for this extension. If the section exists,
19487 then it is used provided that no other source of debugging information
19488 can be found, and that @value{GDBN} was configured with LZMA support.
19490 This section can be easily created using @command{objcopy} and other
19491 standard utilities:
19494 # Extract the dynamic symbols from the main binary, there is no need
19495 # to also have these in the normal symbol table.
19496 nm -D @var{binary} --format=posix --defined-only \
19497 | awk '@{ print $1 @}' | sort > dynsyms
19499 # Extract all the text (i.e. function) symbols from the debuginfo.
19500 # (Note that we actually also accept "D" symbols, for the benefit
19501 # of platforms like PowerPC64 that use function descriptors.)
19502 nm @var{binary} --format=posix --defined-only \
19503 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19506 # Keep all the function symbols not already in the dynamic symbol
19508 comm -13 dynsyms funcsyms > keep_symbols
19510 # Separate full debug info into debug binary.
19511 objcopy --only-keep-debug @var{binary} debug
19513 # Copy the full debuginfo, keeping only a minimal set of symbols and
19514 # removing some unnecessary sections.
19515 objcopy -S --remove-section .gdb_index --remove-section .comment \
19516 --keep-symbols=keep_symbols debug mini_debuginfo
19518 # Drop the full debug info from the original binary.
19519 strip --strip-all -R .comment @var{binary}
19521 # Inject the compressed data into the .gnu_debugdata section of the
19524 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19528 @section Index Files Speed Up @value{GDBN}
19529 @cindex index files
19530 @cindex @samp{.gdb_index} section
19532 When @value{GDBN} finds a symbol file, it scans the symbols in the
19533 file in order to construct an internal symbol table. This lets most
19534 @value{GDBN} operations work quickly---at the cost of a delay early
19535 on. For large programs, this delay can be quite lengthy, so
19536 @value{GDBN} provides a way to build an index, which speeds up
19539 The index is stored as a section in the symbol file. @value{GDBN} can
19540 write the index to a file, then you can put it into the symbol file
19541 using @command{objcopy}.
19543 To create an index file, use the @code{save gdb-index} command:
19546 @item save gdb-index @var{directory}
19547 @kindex save gdb-index
19548 Create an index file for each symbol file currently known by
19549 @value{GDBN}. Each file is named after its corresponding symbol file,
19550 with @samp{.gdb-index} appended, and is written into the given
19554 Once you have created an index file you can merge it into your symbol
19555 file, here named @file{symfile}, using @command{objcopy}:
19558 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19559 --set-section-flags .gdb_index=readonly symfile symfile
19562 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19563 sections that have been deprecated. Usually they are deprecated because
19564 they are missing a new feature or have performance issues.
19565 To tell @value{GDBN} to use a deprecated index section anyway
19566 specify @code{set use-deprecated-index-sections on}.
19567 The default is @code{off}.
19568 This can speed up startup, but may result in some functionality being lost.
19569 @xref{Index Section Format}.
19571 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19572 must be done before gdb reads the file. The following will not work:
19575 $ gdb -ex "set use-deprecated-index-sections on" <program>
19578 Instead you must do, for example,
19581 $ gdb -iex "set use-deprecated-index-sections on" <program>
19584 There are currently some limitation on indices. They only work when
19585 for DWARF debugging information, not stabs. And, they do not
19586 currently work for programs using Ada.
19588 @node Symbol Errors
19589 @section Errors Reading Symbol Files
19591 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19592 such as symbol types it does not recognize, or known bugs in compiler
19593 output. By default, @value{GDBN} does not notify you of such problems, since
19594 they are relatively common and primarily of interest to people
19595 debugging compilers. If you are interested in seeing information
19596 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19597 only one message about each such type of problem, no matter how many
19598 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19599 to see how many times the problems occur, with the @code{set
19600 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19603 The messages currently printed, and their meanings, include:
19606 @item inner block not inside outer block in @var{symbol}
19608 The symbol information shows where symbol scopes begin and end
19609 (such as at the start of a function or a block of statements). This
19610 error indicates that an inner scope block is not fully contained
19611 in its outer scope blocks.
19613 @value{GDBN} circumvents the problem by treating the inner block as if it had
19614 the same scope as the outer block. In the error message, @var{symbol}
19615 may be shown as ``@code{(don't know)}'' if the outer block is not a
19618 @item block at @var{address} out of order
19620 The symbol information for symbol scope blocks should occur in
19621 order of increasing addresses. This error indicates that it does not
19624 @value{GDBN} does not circumvent this problem, and has trouble
19625 locating symbols in the source file whose symbols it is reading. (You
19626 can often determine what source file is affected by specifying
19627 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19630 @item bad block start address patched
19632 The symbol information for a symbol scope block has a start address
19633 smaller than the address of the preceding source line. This is known
19634 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19636 @value{GDBN} circumvents the problem by treating the symbol scope block as
19637 starting on the previous source line.
19639 @item bad string table offset in symbol @var{n}
19642 Symbol number @var{n} contains a pointer into the string table which is
19643 larger than the size of the string table.
19645 @value{GDBN} circumvents the problem by considering the symbol to have the
19646 name @code{foo}, which may cause other problems if many symbols end up
19649 @item unknown symbol type @code{0x@var{nn}}
19651 The symbol information contains new data types that @value{GDBN} does
19652 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19653 uncomprehended information, in hexadecimal.
19655 @value{GDBN} circumvents the error by ignoring this symbol information.
19656 This usually allows you to debug your program, though certain symbols
19657 are not accessible. If you encounter such a problem and feel like
19658 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19659 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19660 and examine @code{*bufp} to see the symbol.
19662 @item stub type has NULL name
19664 @value{GDBN} could not find the full definition for a struct or class.
19666 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19667 The symbol information for a C@t{++} member function is missing some
19668 information that recent versions of the compiler should have output for
19671 @item info mismatch between compiler and debugger
19673 @value{GDBN} could not parse a type specification output by the compiler.
19678 @section GDB Data Files
19680 @cindex prefix for data files
19681 @value{GDBN} will sometimes read an auxiliary data file. These files
19682 are kept in a directory known as the @dfn{data directory}.
19684 You can set the data directory's name, and view the name @value{GDBN}
19685 is currently using.
19688 @kindex set data-directory
19689 @item set data-directory @var{directory}
19690 Set the directory which @value{GDBN} searches for auxiliary data files
19691 to @var{directory}.
19693 @kindex show data-directory
19694 @item show data-directory
19695 Show the directory @value{GDBN} searches for auxiliary data files.
19698 @cindex default data directory
19699 @cindex @samp{--with-gdb-datadir}
19700 You can set the default data directory by using the configure-time
19701 @samp{--with-gdb-datadir} option. If the data directory is inside
19702 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19703 @samp{--exec-prefix}), then the default data directory will be updated
19704 automatically if the installed @value{GDBN} is moved to a new
19707 The data directory may also be specified with the
19708 @code{--data-directory} command line option.
19709 @xref{Mode Options}.
19712 @chapter Specifying a Debugging Target
19714 @cindex debugging target
19715 A @dfn{target} is the execution environment occupied by your program.
19717 Often, @value{GDBN} runs in the same host environment as your program;
19718 in that case, the debugging target is specified as a side effect when
19719 you use the @code{file} or @code{core} commands. When you need more
19720 flexibility---for example, running @value{GDBN} on a physically separate
19721 host, or controlling a standalone system over a serial port or a
19722 realtime system over a TCP/IP connection---you can use the @code{target}
19723 command to specify one of the target types configured for @value{GDBN}
19724 (@pxref{Target Commands, ,Commands for Managing Targets}).
19726 @cindex target architecture
19727 It is possible to build @value{GDBN} for several different @dfn{target
19728 architectures}. When @value{GDBN} is built like that, you can choose
19729 one of the available architectures with the @kbd{set architecture}
19733 @kindex set architecture
19734 @kindex show architecture
19735 @item set architecture @var{arch}
19736 This command sets the current target architecture to @var{arch}. The
19737 value of @var{arch} can be @code{"auto"}, in addition to one of the
19738 supported architectures.
19740 @item show architecture
19741 Show the current target architecture.
19743 @item set processor
19745 @kindex set processor
19746 @kindex show processor
19747 These are alias commands for, respectively, @code{set architecture}
19748 and @code{show architecture}.
19752 * Active Targets:: Active targets
19753 * Target Commands:: Commands for managing targets
19754 * Byte Order:: Choosing target byte order
19757 @node Active Targets
19758 @section Active Targets
19760 @cindex stacking targets
19761 @cindex active targets
19762 @cindex multiple targets
19764 There are multiple classes of targets such as: processes, executable files or
19765 recording sessions. Core files belong to the process class, making core file
19766 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19767 on multiple active targets, one in each class. This allows you to (for
19768 example) start a process and inspect its activity, while still having access to
19769 the executable file after the process finishes. Or if you start process
19770 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19771 presented a virtual layer of the recording target, while the process target
19772 remains stopped at the chronologically last point of the process execution.
19774 Use the @code{core-file} and @code{exec-file} commands to select a new core
19775 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19776 specify as a target a process that is already running, use the @code{attach}
19777 command (@pxref{Attach, ,Debugging an Already-running Process}).
19779 @node Target Commands
19780 @section Commands for Managing Targets
19783 @item target @var{type} @var{parameters}
19784 Connects the @value{GDBN} host environment to a target machine or
19785 process. A target is typically a protocol for talking to debugging
19786 facilities. You use the argument @var{type} to specify the type or
19787 protocol of the target machine.
19789 Further @var{parameters} are interpreted by the target protocol, but
19790 typically include things like device names or host names to connect
19791 with, process numbers, and baud rates.
19793 The @code{target} command does not repeat if you press @key{RET} again
19794 after executing the command.
19796 @kindex help target
19798 Displays the names of all targets available. To display targets
19799 currently selected, use either @code{info target} or @code{info files}
19800 (@pxref{Files, ,Commands to Specify Files}).
19802 @item help target @var{name}
19803 Describe a particular target, including any parameters necessary to
19806 @kindex set gnutarget
19807 @item set gnutarget @var{args}
19808 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19809 knows whether it is reading an @dfn{executable},
19810 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19811 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19812 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19815 @emph{Warning:} To specify a file format with @code{set gnutarget},
19816 you must know the actual BFD name.
19820 @xref{Files, , Commands to Specify Files}.
19822 @kindex show gnutarget
19823 @item show gnutarget
19824 Use the @code{show gnutarget} command to display what file format
19825 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19826 @value{GDBN} will determine the file format for each file automatically,
19827 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19830 @cindex common targets
19831 Here are some common targets (available, or not, depending on the GDB
19836 @item target exec @var{program}
19837 @cindex executable file target
19838 An executable file. @samp{target exec @var{program}} is the same as
19839 @samp{exec-file @var{program}}.
19841 @item target core @var{filename}
19842 @cindex core dump file target
19843 A core dump file. @samp{target core @var{filename}} is the same as
19844 @samp{core-file @var{filename}}.
19846 @item target remote @var{medium}
19847 @cindex remote target
19848 A remote system connected to @value{GDBN} via a serial line or network
19849 connection. This command tells @value{GDBN} to use its own remote
19850 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19852 For example, if you have a board connected to @file{/dev/ttya} on the
19853 machine running @value{GDBN}, you could say:
19856 target remote /dev/ttya
19859 @code{target remote} supports the @code{load} command. This is only
19860 useful if you have some other way of getting the stub to the target
19861 system, and you can put it somewhere in memory where it won't get
19862 clobbered by the download.
19864 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19865 @cindex built-in simulator target
19866 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19874 works; however, you cannot assume that a specific memory map, device
19875 drivers, or even basic I/O is available, although some simulators do
19876 provide these. For info about any processor-specific simulator details,
19877 see the appropriate section in @ref{Embedded Processors, ,Embedded
19880 @item target native
19881 @cindex native target
19882 Setup for local/native process debugging. Useful to make the
19883 @code{run} command spawn native processes (likewise @code{attach},
19884 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19885 (@pxref{set auto-connect-native-target}).
19889 Different targets are available on different configurations of @value{GDBN};
19890 your configuration may have more or fewer targets.
19892 Many remote targets require you to download the executable's code once
19893 you've successfully established a connection. You may wish to control
19894 various aspects of this process.
19899 @kindex set hash@r{, for remote monitors}
19900 @cindex hash mark while downloading
19901 This command controls whether a hash mark @samp{#} is displayed while
19902 downloading a file to the remote monitor. If on, a hash mark is
19903 displayed after each S-record is successfully downloaded to the
19907 @kindex show hash@r{, for remote monitors}
19908 Show the current status of displaying the hash mark.
19910 @item set debug monitor
19911 @kindex set debug monitor
19912 @cindex display remote monitor communications
19913 Enable or disable display of communications messages between
19914 @value{GDBN} and the remote monitor.
19916 @item show debug monitor
19917 @kindex show debug monitor
19918 Show the current status of displaying communications between
19919 @value{GDBN} and the remote monitor.
19924 @kindex load @var{filename} @var{offset}
19925 @item load @var{filename} @var{offset}
19927 Depending on what remote debugging facilities are configured into
19928 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19929 is meant to make @var{filename} (an executable) available for debugging
19930 on the remote system---by downloading, or dynamic linking, for example.
19931 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19932 the @code{add-symbol-file} command.
19934 If your @value{GDBN} does not have a @code{load} command, attempting to
19935 execute it gets the error message ``@code{You can't do that when your
19936 target is @dots{}}''
19938 The file is loaded at whatever address is specified in the executable.
19939 For some object file formats, you can specify the load address when you
19940 link the program; for other formats, like a.out, the object file format
19941 specifies a fixed address.
19942 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19944 It is also possible to tell @value{GDBN} to load the executable file at a
19945 specific offset described by the optional argument @var{offset}. When
19946 @var{offset} is provided, @var{filename} must also be provided.
19948 Depending on the remote side capabilities, @value{GDBN} may be able to
19949 load programs into flash memory.
19951 @code{load} does not repeat if you press @key{RET} again after using it.
19956 @kindex flash-erase
19958 @anchor{flash-erase}
19960 Erases all known flash memory regions on the target.
19965 @section Choosing Target Byte Order
19967 @cindex choosing target byte order
19968 @cindex target byte order
19970 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19971 offer the ability to run either big-endian or little-endian byte
19972 orders. Usually the executable or symbol will include a bit to
19973 designate the endian-ness, and you will not need to worry about
19974 which to use. However, you may still find it useful to adjust
19975 @value{GDBN}'s idea of processor endian-ness manually.
19979 @item set endian big
19980 Instruct @value{GDBN} to assume the target is big-endian.
19982 @item set endian little
19983 Instruct @value{GDBN} to assume the target is little-endian.
19985 @item set endian auto
19986 Instruct @value{GDBN} to use the byte order associated with the
19990 Display @value{GDBN}'s current idea of the target byte order.
19994 Note that these commands merely adjust interpretation of symbolic
19995 data on the host, and that they have absolutely no effect on the
19999 @node Remote Debugging
20000 @chapter Debugging Remote Programs
20001 @cindex remote debugging
20003 If you are trying to debug a program running on a machine that cannot run
20004 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20005 For example, you might use remote debugging on an operating system kernel,
20006 or on a small system which does not have a general purpose operating system
20007 powerful enough to run a full-featured debugger.
20009 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20010 to make this work with particular debugging targets. In addition,
20011 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20012 but not specific to any particular target system) which you can use if you
20013 write the remote stubs---the code that runs on the remote system to
20014 communicate with @value{GDBN}.
20016 Other remote targets may be available in your
20017 configuration of @value{GDBN}; use @code{help target} to list them.
20020 * Connecting:: Connecting to a remote target
20021 * File Transfer:: Sending files to a remote system
20022 * Server:: Using the gdbserver program
20023 * Remote Configuration:: Remote configuration
20024 * Remote Stub:: Implementing a remote stub
20028 @section Connecting to a Remote Target
20029 @cindex remote debugging, connecting
20030 @cindex @code{gdbserver}, connecting
20031 @cindex remote debugging, types of connections
20032 @cindex @code{gdbserver}, types of connections
20033 @cindex @code{gdbserver}, @code{target remote} mode
20034 @cindex @code{gdbserver}, @code{target extended-remote} mode
20036 This section describes how to connect to a remote target, including the
20037 types of connections and their differences, how to set up executable and
20038 symbol files on the host and target, and the commands used for
20039 connecting to and disconnecting from the remote target.
20041 @subsection Types of Remote Connections
20043 @value{GDBN} supports two types of remote connections, @code{target remote}
20044 mode and @code{target extended-remote} mode. Note that many remote targets
20045 support only @code{target remote} mode. There are several major
20046 differences between the two types of connections, enumerated here:
20050 @cindex remote debugging, detach and program exit
20051 @item Result of detach or program exit
20052 @strong{With target remote mode:} When the debugged program exits or you
20053 detach from it, @value{GDBN} disconnects from the target. When using
20054 @code{gdbserver}, @code{gdbserver} will exit.
20056 @strong{With target extended-remote mode:} When the debugged program exits or
20057 you detach from it, @value{GDBN} remains connected to the target, even
20058 though no program is running. You can rerun the program, attach to a
20059 running program, or use @code{monitor} commands specific to the target.
20061 When using @code{gdbserver} in this case, it does not exit unless it was
20062 invoked using the @option{--once} option. If the @option{--once} option
20063 was not used, you can ask @code{gdbserver} to exit using the
20064 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20066 @item Specifying the program to debug
20067 For both connection types you use the @code{file} command to specify the
20068 program on the host system. If you are using @code{gdbserver} there are
20069 some differences in how to specify the location of the program on the
20072 @strong{With target remote mode:} You must either specify the program to debug
20073 on the @code{gdbserver} command line or use the @option{--attach} option
20074 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20076 @cindex @option{--multi}, @code{gdbserver} option
20077 @strong{With target extended-remote mode:} You may specify the program to debug
20078 on the @code{gdbserver} command line, or you can load the program or attach
20079 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20081 @anchor{--multi Option in Types of Remote Connnections}
20082 You can start @code{gdbserver} without supplying an initial command to run
20083 or process ID to attach. To do this, use the @option{--multi} command line
20084 option. Then you can connect using @code{target extended-remote} and start
20085 the program you want to debug (see below for details on using the
20086 @code{run} command in this scenario). Note that the conditions under which
20087 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20088 (@code{target remote} or @code{target extended-remote}). The
20089 @option{--multi} option to @code{gdbserver} has no influence on that.
20091 @item The @code{run} command
20092 @strong{With target remote mode:} The @code{run} command is not
20093 supported. Once a connection has been established, you can use all
20094 the usual @value{GDBN} commands to examine and change data. The
20095 remote program is already running, so you can use commands like
20096 @kbd{step} and @kbd{continue}.
20098 @strong{With target extended-remote mode:} The @code{run} command is
20099 supported. The @code{run} command uses the value set by
20100 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20101 the program to run. Command line arguments are supported, except for
20102 wildcard expansion and I/O redirection (@pxref{Arguments}).
20104 If you specify the program to debug on the command line, then the
20105 @code{run} command is not required to start execution, and you can
20106 resume using commands like @kbd{step} and @kbd{continue} as with
20107 @code{target remote} mode.
20109 @anchor{Attaching in Types of Remote Connections}
20111 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20112 not supported. To attach to a running program using @code{gdbserver}, you
20113 must use the @option{--attach} option (@pxref{Running gdbserver}).
20115 @strong{With target extended-remote mode:} To attach to a running program,
20116 you may use the @code{attach} command after the connection has been
20117 established. If you are using @code{gdbserver}, you may also invoke
20118 @code{gdbserver} using the @option{--attach} option
20119 (@pxref{Running gdbserver}).
20123 @anchor{Host and target files}
20124 @subsection Host and Target Files
20125 @cindex remote debugging, symbol files
20126 @cindex symbol files, remote debugging
20128 @value{GDBN}, running on the host, needs access to symbol and debugging
20129 information for your program running on the target. This requires
20130 access to an unstripped copy of your program, and possibly any associated
20131 symbol files. Note that this section applies equally to both @code{target
20132 remote} mode and @code{target extended-remote} mode.
20134 Some remote targets (@pxref{qXfer executable filename read}, and
20135 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20136 the same connection used to communicate with @value{GDBN}. With such a
20137 target, if the remote program is unstripped, the only command you need is
20138 @code{target remote} (or @code{target extended-remote}).
20140 If the remote program is stripped, or the target does not support remote
20141 program file access, start up @value{GDBN} using the name of the local
20142 unstripped copy of your program as the first argument, or use the
20143 @code{file} command. Use @code{set sysroot} to specify the location (on
20144 the host) of target libraries (unless your @value{GDBN} was compiled with
20145 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20146 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20149 The symbol file and target libraries must exactly match the executable
20150 and libraries on the target, with one exception: the files on the host
20151 system should not be stripped, even if the files on the target system
20152 are. Mismatched or missing files will lead to confusing results
20153 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20154 files may also prevent @code{gdbserver} from debugging multi-threaded
20157 @subsection Remote Connection Commands
20158 @cindex remote connection commands
20159 @value{GDBN} can communicate with the target over a serial line, or
20160 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20161 each case, @value{GDBN} uses the same protocol for debugging your
20162 program; only the medium carrying the debugging packets varies. The
20163 @code{target remote} and @code{target extended-remote} commands
20164 establish a connection to the target. Both commands accept the same
20165 arguments, which indicate the medium to use:
20169 @item target remote @var{serial-device}
20170 @itemx target extended-remote @var{serial-device}
20171 @cindex serial line, @code{target remote}
20172 Use @var{serial-device} to communicate with the target. For example,
20173 to use a serial line connected to the device named @file{/dev/ttyb}:
20176 target remote /dev/ttyb
20179 If you're using a serial line, you may want to give @value{GDBN} the
20180 @samp{--baud} option, or use the @code{set serial baud} command
20181 (@pxref{Remote Configuration, set serial baud}) before the
20182 @code{target} command.
20184 @item target remote @code{@var{host}:@var{port}}
20185 @itemx target remote @code{tcp:@var{host}:@var{port}}
20186 @itemx target extended-remote @code{@var{host}:@var{port}}
20187 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20188 @cindex @acronym{TCP} port, @code{target remote}
20189 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20190 The @var{host} may be either a host name or a numeric @acronym{IP}
20191 address; @var{port} must be a decimal number. The @var{host} could be
20192 the target machine itself, if it is directly connected to the net, or
20193 it might be a terminal server which in turn has a serial line to the
20196 For example, to connect to port 2828 on a terminal server named
20200 target remote manyfarms:2828
20203 If your remote target is actually running on the same machine as your
20204 debugger session (e.g.@: a simulator for your target running on the
20205 same host), you can omit the hostname. For example, to connect to
20206 port 1234 on your local machine:
20209 target remote :1234
20213 Note that the colon is still required here.
20215 @item target remote @code{udp:@var{host}:@var{port}}
20216 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20217 @cindex @acronym{UDP} port, @code{target remote}
20218 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20219 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20222 target remote udp:manyfarms:2828
20225 When using a @acronym{UDP} connection for remote debugging, you should
20226 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20227 can silently drop packets on busy or unreliable networks, which will
20228 cause havoc with your debugging session.
20230 @item target remote | @var{command}
20231 @itemx target extended-remote | @var{command}
20232 @cindex pipe, @code{target remote} to
20233 Run @var{command} in the background and communicate with it using a
20234 pipe. The @var{command} is a shell command, to be parsed and expanded
20235 by the system's command shell, @code{/bin/sh}; it should expect remote
20236 protocol packets on its standard input, and send replies on its
20237 standard output. You could use this to run a stand-alone simulator
20238 that speaks the remote debugging protocol, to make net connections
20239 using programs like @code{ssh}, or for other similar tricks.
20241 If @var{command} closes its standard output (perhaps by exiting),
20242 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20243 program has already exited, this will have no effect.)
20247 @cindex interrupting remote programs
20248 @cindex remote programs, interrupting
20249 Whenever @value{GDBN} is waiting for the remote program, if you type the
20250 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20251 program. This may or may not succeed, depending in part on the hardware
20252 and the serial drivers the remote system uses. If you type the
20253 interrupt character once again, @value{GDBN} displays this prompt:
20256 Interrupted while waiting for the program.
20257 Give up (and stop debugging it)? (y or n)
20260 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20261 the remote debugging session. (If you decide you want to try again later,
20262 you can use @kbd{target remote} again to connect once more.) If you type
20263 @kbd{n}, @value{GDBN} goes back to waiting.
20265 In @code{target extended-remote} mode, typing @kbd{n} will leave
20266 @value{GDBN} connected to the target.
20269 @kindex detach (remote)
20271 When you have finished debugging the remote program, you can use the
20272 @code{detach} command to release it from @value{GDBN} control.
20273 Detaching from the target normally resumes its execution, but the results
20274 will depend on your particular remote stub. After the @code{detach}
20275 command in @code{target remote} mode, @value{GDBN} is free to connect to
20276 another target. In @code{target extended-remote} mode, @value{GDBN} is
20277 still connected to the target.
20281 The @code{disconnect} command closes the connection to the target, and
20282 the target is generally not resumed. It will wait for @value{GDBN}
20283 (this instance or another one) to connect and continue debugging. After
20284 the @code{disconnect} command, @value{GDBN} is again free to connect to
20287 @cindex send command to remote monitor
20288 @cindex extend @value{GDBN} for remote targets
20289 @cindex add new commands for external monitor
20291 @item monitor @var{cmd}
20292 This command allows you to send arbitrary commands directly to the
20293 remote monitor. Since @value{GDBN} doesn't care about the commands it
20294 sends like this, this command is the way to extend @value{GDBN}---you
20295 can add new commands that only the external monitor will understand
20299 @node File Transfer
20300 @section Sending files to a remote system
20301 @cindex remote target, file transfer
20302 @cindex file transfer
20303 @cindex sending files to remote systems
20305 Some remote targets offer the ability to transfer files over the same
20306 connection used to communicate with @value{GDBN}. This is convenient
20307 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20308 running @code{gdbserver} over a network interface. For other targets,
20309 e.g.@: embedded devices with only a single serial port, this may be
20310 the only way to upload or download files.
20312 Not all remote targets support these commands.
20316 @item remote put @var{hostfile} @var{targetfile}
20317 Copy file @var{hostfile} from the host system (the machine running
20318 @value{GDBN}) to @var{targetfile} on the target system.
20321 @item remote get @var{targetfile} @var{hostfile}
20322 Copy file @var{targetfile} from the target system to @var{hostfile}
20323 on the host system.
20325 @kindex remote delete
20326 @item remote delete @var{targetfile}
20327 Delete @var{targetfile} from the target system.
20332 @section Using the @code{gdbserver} Program
20335 @cindex remote connection without stubs
20336 @code{gdbserver} is a control program for Unix-like systems, which
20337 allows you to connect your program with a remote @value{GDBN} via
20338 @code{target remote} or @code{target extended-remote}---but without
20339 linking in the usual debugging stub.
20341 @code{gdbserver} is not a complete replacement for the debugging stubs,
20342 because it requires essentially the same operating-system facilities
20343 that @value{GDBN} itself does. In fact, a system that can run
20344 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20345 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20346 because it is a much smaller program than @value{GDBN} itself. It is
20347 also easier to port than all of @value{GDBN}, so you may be able to get
20348 started more quickly on a new system by using @code{gdbserver}.
20349 Finally, if you develop code for real-time systems, you may find that
20350 the tradeoffs involved in real-time operation make it more convenient to
20351 do as much development work as possible on another system, for example
20352 by cross-compiling. You can use @code{gdbserver} to make a similar
20353 choice for debugging.
20355 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20356 or a TCP connection, using the standard @value{GDBN} remote serial
20360 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20361 Do not run @code{gdbserver} connected to any public network; a
20362 @value{GDBN} connection to @code{gdbserver} provides access to the
20363 target system with the same privileges as the user running
20367 @anchor{Running gdbserver}
20368 @subsection Running @code{gdbserver}
20369 @cindex arguments, to @code{gdbserver}
20370 @cindex @code{gdbserver}, command-line arguments
20372 Run @code{gdbserver} on the target system. You need a copy of the
20373 program you want to debug, including any libraries it requires.
20374 @code{gdbserver} does not need your program's symbol table, so you can
20375 strip the program if necessary to save space. @value{GDBN} on the host
20376 system does all the symbol handling.
20378 To use the server, you must tell it how to communicate with @value{GDBN};
20379 the name of your program; and the arguments for your program. The usual
20383 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20386 @var{comm} is either a device name (to use a serial line), or a TCP
20387 hostname and portnumber, or @code{-} or @code{stdio} to use
20388 stdin/stdout of @code{gdbserver}.
20389 For example, to debug Emacs with the argument
20390 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20394 target> gdbserver /dev/com1 emacs foo.txt
20397 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20400 To use a TCP connection instead of a serial line:
20403 target> gdbserver host:2345 emacs foo.txt
20406 The only difference from the previous example is the first argument,
20407 specifying that you are communicating with the host @value{GDBN} via
20408 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20409 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20410 (Currently, the @samp{host} part is ignored.) You can choose any number
20411 you want for the port number as long as it does not conflict with any
20412 TCP ports already in use on the target system (for example, @code{23} is
20413 reserved for @code{telnet}).@footnote{If you choose a port number that
20414 conflicts with another service, @code{gdbserver} prints an error message
20415 and exits.} You must use the same port number with the host @value{GDBN}
20416 @code{target remote} command.
20418 The @code{stdio} connection is useful when starting @code{gdbserver}
20422 (gdb) target remote | ssh -T hostname gdbserver - hello
20425 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20426 and we don't want escape-character handling. Ssh does this by default when
20427 a command is provided, the flag is provided to make it explicit.
20428 You could elide it if you want to.
20430 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20431 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20432 display through a pipe connected to gdbserver.
20433 Both @code{stdout} and @code{stderr} use the same pipe.
20435 @anchor{Attaching to a program}
20436 @subsubsection Attaching to a Running Program
20437 @cindex attach to a program, @code{gdbserver}
20438 @cindex @option{--attach}, @code{gdbserver} option
20440 On some targets, @code{gdbserver} can also attach to running programs.
20441 This is accomplished via the @code{--attach} argument. The syntax is:
20444 target> gdbserver --attach @var{comm} @var{pid}
20447 @var{pid} is the process ID of a currently running process. It isn't
20448 necessary to point @code{gdbserver} at a binary for the running process.
20450 In @code{target extended-remote} mode, you can also attach using the
20451 @value{GDBN} attach command
20452 (@pxref{Attaching in Types of Remote Connections}).
20455 You can debug processes by name instead of process ID if your target has the
20456 @code{pidof} utility:
20459 target> gdbserver --attach @var{comm} `pidof @var{program}`
20462 In case more than one copy of @var{program} is running, or @var{program}
20463 has multiple threads, most versions of @code{pidof} support the
20464 @code{-s} option to only return the first process ID.
20466 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20468 This section applies only when @code{gdbserver} is run to listen on a TCP
20471 @code{gdbserver} normally terminates after all of its debugged processes have
20472 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20473 extended-remote}, @code{gdbserver} stays running even with no processes left.
20474 @value{GDBN} normally terminates the spawned debugged process on its exit,
20475 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20476 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20477 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20478 stays running even in the @kbd{target remote} mode.
20480 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20481 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20482 completeness, at most one @value{GDBN} can be connected at a time.
20484 @cindex @option{--once}, @code{gdbserver} option
20485 By default, @code{gdbserver} keeps the listening TCP port open, so that
20486 subsequent connections are possible. However, if you start @code{gdbserver}
20487 with the @option{--once} option, it will stop listening for any further
20488 connection attempts after connecting to the first @value{GDBN} session. This
20489 means no further connections to @code{gdbserver} will be possible after the
20490 first one. It also means @code{gdbserver} will terminate after the first
20491 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20492 connections and even in the @kbd{target extended-remote} mode. The
20493 @option{--once} option allows reusing the same port number for connecting to
20494 multiple instances of @code{gdbserver} running on the same host, since each
20495 instance closes its port after the first connection.
20497 @anchor{Other Command-Line Arguments for gdbserver}
20498 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20500 You can use the @option{--multi} option to start @code{gdbserver} without
20501 specifying a program to debug or a process to attach to. Then you can
20502 attach in @code{target extended-remote} mode and run or attach to a
20503 program. For more information,
20504 @pxref{--multi Option in Types of Remote Connnections}.
20506 @cindex @option{--debug}, @code{gdbserver} option
20507 The @option{--debug} option tells @code{gdbserver} to display extra
20508 status information about the debugging process.
20509 @cindex @option{--remote-debug}, @code{gdbserver} option
20510 The @option{--remote-debug} option tells @code{gdbserver} to display
20511 remote protocol debug output. These options are intended for
20512 @code{gdbserver} development and for bug reports to the developers.
20514 @cindex @option{--debug-format}, @code{gdbserver} option
20515 The @option{--debug-format=option1[,option2,...]} option tells
20516 @code{gdbserver} to include additional information in each output.
20517 Possible options are:
20521 Turn off all extra information in debugging output.
20523 Turn on all extra information in debugging output.
20525 Include a timestamp in each line of debugging output.
20528 Options are processed in order. Thus, for example, if @option{none}
20529 appears last then no additional information is added to debugging output.
20531 @cindex @option{--wrapper}, @code{gdbserver} option
20532 The @option{--wrapper} option specifies a wrapper to launch programs
20533 for debugging. The option should be followed by the name of the
20534 wrapper, then any command-line arguments to pass to the wrapper, then
20535 @kbd{--} indicating the end of the wrapper arguments.
20537 @code{gdbserver} runs the specified wrapper program with a combined
20538 command line including the wrapper arguments, then the name of the
20539 program to debug, then any arguments to the program. The wrapper
20540 runs until it executes your program, and then @value{GDBN} gains control.
20542 You can use any program that eventually calls @code{execve} with
20543 its arguments as a wrapper. Several standard Unix utilities do
20544 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20545 with @code{exec "$@@"} will also work.
20547 For example, you can use @code{env} to pass an environment variable to
20548 the debugged program, without setting the variable in @code{gdbserver}'s
20552 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20555 @cindex @option{--selftest}
20556 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20559 $ gdbserver --selftest
20560 Ran 2 unit tests, 0 failed
20563 These tests are disabled in release.
20564 @subsection Connecting to @code{gdbserver}
20566 The basic procedure for connecting to the remote target is:
20570 Run @value{GDBN} on the host system.
20573 Make sure you have the necessary symbol files
20574 (@pxref{Host and target files}).
20575 Load symbols for your application using the @code{file} command before you
20576 connect. Use @code{set sysroot} to locate target libraries (unless your
20577 @value{GDBN} was compiled with the correct sysroot using
20578 @code{--with-sysroot}).
20581 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20582 For TCP connections, you must start up @code{gdbserver} prior to using
20583 the @code{target} command. Otherwise you may get an error whose
20584 text depends on the host system, but which usually looks something like
20585 @samp{Connection refused}. Don't use the @code{load}
20586 command in @value{GDBN} when using @code{target remote} mode, since the
20587 program is already on the target.
20591 @anchor{Monitor Commands for gdbserver}
20592 @subsection Monitor Commands for @code{gdbserver}
20593 @cindex monitor commands, for @code{gdbserver}
20595 During a @value{GDBN} session using @code{gdbserver}, you can use the
20596 @code{monitor} command to send special requests to @code{gdbserver}.
20597 Here are the available commands.
20601 List the available monitor commands.
20603 @item monitor set debug 0
20604 @itemx monitor set debug 1
20605 Disable or enable general debugging messages.
20607 @item monitor set remote-debug 0
20608 @itemx monitor set remote-debug 1
20609 Disable or enable specific debugging messages associated with the remote
20610 protocol (@pxref{Remote Protocol}).
20612 @item monitor set debug-format option1@r{[},option2,...@r{]}
20613 Specify additional text to add to debugging messages.
20614 Possible options are:
20618 Turn off all extra information in debugging output.
20620 Turn on all extra information in debugging output.
20622 Include a timestamp in each line of debugging output.
20625 Options are processed in order. Thus, for example, if @option{none}
20626 appears last then no additional information is added to debugging output.
20628 @item monitor set libthread-db-search-path [PATH]
20629 @cindex gdbserver, search path for @code{libthread_db}
20630 When this command is issued, @var{path} is a colon-separated list of
20631 directories to search for @code{libthread_db} (@pxref{Threads,,set
20632 libthread-db-search-path}). If you omit @var{path},
20633 @samp{libthread-db-search-path} will be reset to its default value.
20635 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20636 not supported in @code{gdbserver}.
20639 Tell gdbserver to exit immediately. This command should be followed by
20640 @code{disconnect} to close the debugging session. @code{gdbserver} will
20641 detach from any attached processes and kill any processes it created.
20642 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20643 of a multi-process mode debug session.
20647 @subsection Tracepoints support in @code{gdbserver}
20648 @cindex tracepoints support in @code{gdbserver}
20650 On some targets, @code{gdbserver} supports tracepoints, fast
20651 tracepoints and static tracepoints.
20653 For fast or static tracepoints to work, a special library called the
20654 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20655 This library is built and distributed as an integral part of
20656 @code{gdbserver}. In addition, support for static tracepoints
20657 requires building the in-process agent library with static tracepoints
20658 support. At present, the UST (LTTng Userspace Tracer,
20659 @url{http://lttng.org/ust}) tracing engine is supported. This support
20660 is automatically available if UST development headers are found in the
20661 standard include path when @code{gdbserver} is built, or if
20662 @code{gdbserver} was explicitly configured using @option{--with-ust}
20663 to point at such headers. You can explicitly disable the support
20664 using @option{--with-ust=no}.
20666 There are several ways to load the in-process agent in your program:
20669 @item Specifying it as dependency at link time
20671 You can link your program dynamically with the in-process agent
20672 library. On most systems, this is accomplished by adding
20673 @code{-linproctrace} to the link command.
20675 @item Using the system's preloading mechanisms
20677 You can force loading the in-process agent at startup time by using
20678 your system's support for preloading shared libraries. Many Unixes
20679 support the concept of preloading user defined libraries. In most
20680 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20681 in the environment. See also the description of @code{gdbserver}'s
20682 @option{--wrapper} command line option.
20684 @item Using @value{GDBN} to force loading the agent at run time
20686 On some systems, you can force the inferior to load a shared library,
20687 by calling a dynamic loader function in the inferior that takes care
20688 of dynamically looking up and loading a shared library. On most Unix
20689 systems, the function is @code{dlopen}. You'll use the @code{call}
20690 command for that. For example:
20693 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20696 Note that on most Unix systems, for the @code{dlopen} function to be
20697 available, the program needs to be linked with @code{-ldl}.
20700 On systems that have a userspace dynamic loader, like most Unix
20701 systems, when you connect to @code{gdbserver} using @code{target
20702 remote}, you'll find that the program is stopped at the dynamic
20703 loader's entry point, and no shared library has been loaded in the
20704 program's address space yet, including the in-process agent. In that
20705 case, before being able to use any of the fast or static tracepoints
20706 features, you need to let the loader run and load the shared
20707 libraries. The simplest way to do that is to run the program to the
20708 main procedure. E.g., if debugging a C or C@t{++} program, start
20709 @code{gdbserver} like so:
20712 $ gdbserver :9999 myprogram
20715 Start GDB and connect to @code{gdbserver} like so, and run to main:
20719 (@value{GDBP}) target remote myhost:9999
20720 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20721 (@value{GDBP}) b main
20722 (@value{GDBP}) continue
20725 The in-process tracing agent library should now be loaded into the
20726 process; you can confirm it with the @code{info sharedlibrary}
20727 command, which will list @file{libinproctrace.so} as loaded in the
20728 process. You are now ready to install fast tracepoints, list static
20729 tracepoint markers, probe static tracepoints markers, and start
20732 @node Remote Configuration
20733 @section Remote Configuration
20736 @kindex show remote
20737 This section documents the configuration options available when
20738 debugging remote programs. For the options related to the File I/O
20739 extensions of the remote protocol, see @ref{system,
20740 system-call-allowed}.
20743 @item set remoteaddresssize @var{bits}
20744 @cindex address size for remote targets
20745 @cindex bits in remote address
20746 Set the maximum size of address in a memory packet to the specified
20747 number of bits. @value{GDBN} will mask off the address bits above
20748 that number, when it passes addresses to the remote target. The
20749 default value is the number of bits in the target's address.
20751 @item show remoteaddresssize
20752 Show the current value of remote address size in bits.
20754 @item set serial baud @var{n}
20755 @cindex baud rate for remote targets
20756 Set the baud rate for the remote serial I/O to @var{n} baud. The
20757 value is used to set the speed of the serial port used for debugging
20760 @item show serial baud
20761 Show the current speed of the remote connection.
20763 @item set serial parity @var{parity}
20764 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20765 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20767 @item show serial parity
20768 Show the current parity of the serial port.
20770 @item set remotebreak
20771 @cindex interrupt remote programs
20772 @cindex BREAK signal instead of Ctrl-C
20773 @anchor{set remotebreak}
20774 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20775 when you type @kbd{Ctrl-c} to interrupt the program running
20776 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20777 character instead. The default is off, since most remote systems
20778 expect to see @samp{Ctrl-C} as the interrupt signal.
20780 @item show remotebreak
20781 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20782 interrupt the remote program.
20784 @item set remoteflow on
20785 @itemx set remoteflow off
20786 @kindex set remoteflow
20787 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20788 on the serial port used to communicate to the remote target.
20790 @item show remoteflow
20791 @kindex show remoteflow
20792 Show the current setting of hardware flow control.
20794 @item set remotelogbase @var{base}
20795 Set the base (a.k.a.@: radix) of logging serial protocol
20796 communications to @var{base}. Supported values of @var{base} are:
20797 @code{ascii}, @code{octal}, and @code{hex}. The default is
20800 @item show remotelogbase
20801 Show the current setting of the radix for logging remote serial
20804 @item set remotelogfile @var{file}
20805 @cindex record serial communications on file
20806 Record remote serial communications on the named @var{file}. The
20807 default is not to record at all.
20809 @item show remotelogfile.
20810 Show the current setting of the file name on which to record the
20811 serial communications.
20813 @item set remotetimeout @var{num}
20814 @cindex timeout for serial communications
20815 @cindex remote timeout
20816 Set the timeout limit to wait for the remote target to respond to
20817 @var{num} seconds. The default is 2 seconds.
20819 @item show remotetimeout
20820 Show the current number of seconds to wait for the remote target
20823 @cindex limit hardware breakpoints and watchpoints
20824 @cindex remote target, limit break- and watchpoints
20825 @anchor{set remote hardware-watchpoint-limit}
20826 @anchor{set remote hardware-breakpoint-limit}
20827 @item set remote hardware-watchpoint-limit @var{limit}
20828 @itemx set remote hardware-breakpoint-limit @var{limit}
20829 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20830 watchpoints. A limit of -1, the default, is treated as unlimited.
20832 @cindex limit hardware watchpoints length
20833 @cindex remote target, limit watchpoints length
20834 @anchor{set remote hardware-watchpoint-length-limit}
20835 @item set remote hardware-watchpoint-length-limit @var{limit}
20836 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20837 a remote hardware watchpoint. A limit of -1, the default, is treated
20840 @item show remote hardware-watchpoint-length-limit
20841 Show the current limit (in bytes) of the maximum length of
20842 a remote hardware watchpoint.
20844 @item set remote exec-file @var{filename}
20845 @itemx show remote exec-file
20846 @anchor{set remote exec-file}
20847 @cindex executable file, for remote target
20848 Select the file used for @code{run} with @code{target
20849 extended-remote}. This should be set to a filename valid on the
20850 target system. If it is not set, the target will use a default
20851 filename (e.g.@: the last program run).
20853 @item set remote interrupt-sequence
20854 @cindex interrupt remote programs
20855 @cindex select Ctrl-C, BREAK or BREAK-g
20856 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20857 @samp{BREAK-g} as the
20858 sequence to the remote target in order to interrupt the execution.
20859 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20860 is high level of serial line for some certain time.
20861 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20862 It is @code{BREAK} signal followed by character @code{g}.
20864 @item show interrupt-sequence
20865 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20866 is sent by @value{GDBN} to interrupt the remote program.
20867 @code{BREAK-g} is BREAK signal followed by @code{g} and
20868 also known as Magic SysRq g.
20870 @item set remote interrupt-on-connect
20871 @cindex send interrupt-sequence on start
20872 Specify whether interrupt-sequence is sent to remote target when
20873 @value{GDBN} connects to it. This is mostly needed when you debug
20874 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20875 which is known as Magic SysRq g in order to connect @value{GDBN}.
20877 @item show interrupt-on-connect
20878 Show whether interrupt-sequence is sent
20879 to remote target when @value{GDBN} connects to it.
20883 @item set tcp auto-retry on
20884 @cindex auto-retry, for remote TCP target
20885 Enable auto-retry for remote TCP connections. This is useful if the remote
20886 debugging agent is launched in parallel with @value{GDBN}; there is a race
20887 condition because the agent may not become ready to accept the connection
20888 before @value{GDBN} attempts to connect. When auto-retry is
20889 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20890 to establish the connection using the timeout specified by
20891 @code{set tcp connect-timeout}.
20893 @item set tcp auto-retry off
20894 Do not auto-retry failed TCP connections.
20896 @item show tcp auto-retry
20897 Show the current auto-retry setting.
20899 @item set tcp connect-timeout @var{seconds}
20900 @itemx set tcp connect-timeout unlimited
20901 @cindex connection timeout, for remote TCP target
20902 @cindex timeout, for remote target connection
20903 Set the timeout for establishing a TCP connection to the remote target to
20904 @var{seconds}. The timeout affects both polling to retry failed connections
20905 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20906 that are merely slow to complete, and represents an approximate cumulative
20907 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20908 @value{GDBN} will keep attempting to establish a connection forever,
20909 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20911 @item show tcp connect-timeout
20912 Show the current connection timeout setting.
20915 @cindex remote packets, enabling and disabling
20916 The @value{GDBN} remote protocol autodetects the packets supported by
20917 your debugging stub. If you need to override the autodetection, you
20918 can use these commands to enable or disable individual packets. Each
20919 packet can be set to @samp{on} (the remote target supports this
20920 packet), @samp{off} (the remote target does not support this packet),
20921 or @samp{auto} (detect remote target support for this packet). They
20922 all default to @samp{auto}. For more information about each packet,
20923 see @ref{Remote Protocol}.
20925 During normal use, you should not have to use any of these commands.
20926 If you do, that may be a bug in your remote debugging stub, or a bug
20927 in @value{GDBN}. You may want to report the problem to the
20928 @value{GDBN} developers.
20930 For each packet @var{name}, the command to enable or disable the
20931 packet is @code{set remote @var{name}-packet}. The available settings
20934 @multitable @columnfractions 0.28 0.32 0.25
20937 @tab Related Features
20939 @item @code{fetch-register}
20941 @tab @code{info registers}
20943 @item @code{set-register}
20947 @item @code{binary-download}
20949 @tab @code{load}, @code{set}
20951 @item @code{read-aux-vector}
20952 @tab @code{qXfer:auxv:read}
20953 @tab @code{info auxv}
20955 @item @code{symbol-lookup}
20956 @tab @code{qSymbol}
20957 @tab Detecting multiple threads
20959 @item @code{attach}
20960 @tab @code{vAttach}
20963 @item @code{verbose-resume}
20965 @tab Stepping or resuming multiple threads
20971 @item @code{software-breakpoint}
20975 @item @code{hardware-breakpoint}
20979 @item @code{write-watchpoint}
20983 @item @code{read-watchpoint}
20987 @item @code{access-watchpoint}
20991 @item @code{pid-to-exec-file}
20992 @tab @code{qXfer:exec-file:read}
20993 @tab @code{attach}, @code{run}
20995 @item @code{target-features}
20996 @tab @code{qXfer:features:read}
20997 @tab @code{set architecture}
20999 @item @code{library-info}
21000 @tab @code{qXfer:libraries:read}
21001 @tab @code{info sharedlibrary}
21003 @item @code{memory-map}
21004 @tab @code{qXfer:memory-map:read}
21005 @tab @code{info mem}
21007 @item @code{read-sdata-object}
21008 @tab @code{qXfer:sdata:read}
21009 @tab @code{print $_sdata}
21011 @item @code{read-spu-object}
21012 @tab @code{qXfer:spu:read}
21013 @tab @code{info spu}
21015 @item @code{write-spu-object}
21016 @tab @code{qXfer:spu:write}
21017 @tab @code{info spu}
21019 @item @code{read-siginfo-object}
21020 @tab @code{qXfer:siginfo:read}
21021 @tab @code{print $_siginfo}
21023 @item @code{write-siginfo-object}
21024 @tab @code{qXfer:siginfo:write}
21025 @tab @code{set $_siginfo}
21027 @item @code{threads}
21028 @tab @code{qXfer:threads:read}
21029 @tab @code{info threads}
21031 @item @code{get-thread-local-@*storage-address}
21032 @tab @code{qGetTLSAddr}
21033 @tab Displaying @code{__thread} variables
21035 @item @code{get-thread-information-block-address}
21036 @tab @code{qGetTIBAddr}
21037 @tab Display MS-Windows Thread Information Block.
21039 @item @code{search-memory}
21040 @tab @code{qSearch:memory}
21043 @item @code{supported-packets}
21044 @tab @code{qSupported}
21045 @tab Remote communications parameters
21047 @item @code{catch-syscalls}
21048 @tab @code{QCatchSyscalls}
21049 @tab @code{catch syscall}
21051 @item @code{pass-signals}
21052 @tab @code{QPassSignals}
21053 @tab @code{handle @var{signal}}
21055 @item @code{program-signals}
21056 @tab @code{QProgramSignals}
21057 @tab @code{handle @var{signal}}
21059 @item @code{hostio-close-packet}
21060 @tab @code{vFile:close}
21061 @tab @code{remote get}, @code{remote put}
21063 @item @code{hostio-open-packet}
21064 @tab @code{vFile:open}
21065 @tab @code{remote get}, @code{remote put}
21067 @item @code{hostio-pread-packet}
21068 @tab @code{vFile:pread}
21069 @tab @code{remote get}, @code{remote put}
21071 @item @code{hostio-pwrite-packet}
21072 @tab @code{vFile:pwrite}
21073 @tab @code{remote get}, @code{remote put}
21075 @item @code{hostio-unlink-packet}
21076 @tab @code{vFile:unlink}
21077 @tab @code{remote delete}
21079 @item @code{hostio-readlink-packet}
21080 @tab @code{vFile:readlink}
21083 @item @code{hostio-fstat-packet}
21084 @tab @code{vFile:fstat}
21087 @item @code{hostio-setfs-packet}
21088 @tab @code{vFile:setfs}
21091 @item @code{noack-packet}
21092 @tab @code{QStartNoAckMode}
21093 @tab Packet acknowledgment
21095 @item @code{osdata}
21096 @tab @code{qXfer:osdata:read}
21097 @tab @code{info os}
21099 @item @code{query-attached}
21100 @tab @code{qAttached}
21101 @tab Querying remote process attach state.
21103 @item @code{trace-buffer-size}
21104 @tab @code{QTBuffer:size}
21105 @tab @code{set trace-buffer-size}
21107 @item @code{trace-status}
21108 @tab @code{qTStatus}
21109 @tab @code{tstatus}
21111 @item @code{traceframe-info}
21112 @tab @code{qXfer:traceframe-info:read}
21113 @tab Traceframe info
21115 @item @code{install-in-trace}
21116 @tab @code{InstallInTrace}
21117 @tab Install tracepoint in tracing
21119 @item @code{disable-randomization}
21120 @tab @code{QDisableRandomization}
21121 @tab @code{set disable-randomization}
21123 @item @code{startup-with-shell}
21124 @tab @code{QStartupWithShell}
21125 @tab @code{set startup-with-shell}
21127 @item @code{environment-hex-encoded}
21128 @tab @code{QEnvironmentHexEncoded}
21129 @tab @code{set environment}
21131 @item @code{environment-unset}
21132 @tab @code{QEnvironmentUnset}
21133 @tab @code{unset environment}
21135 @item @code{environment-reset}
21136 @tab @code{QEnvironmentReset}
21137 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21139 @item @code{set-working-dir}
21140 @tab @code{QSetWorkingDir}
21141 @tab @code{set cwd}
21143 @item @code{conditional-breakpoints-packet}
21144 @tab @code{Z0 and Z1}
21145 @tab @code{Support for target-side breakpoint condition evaluation}
21147 @item @code{multiprocess-extensions}
21148 @tab @code{multiprocess extensions}
21149 @tab Debug multiple processes and remote process PID awareness
21151 @item @code{swbreak-feature}
21152 @tab @code{swbreak stop reason}
21155 @item @code{hwbreak-feature}
21156 @tab @code{hwbreak stop reason}
21159 @item @code{fork-event-feature}
21160 @tab @code{fork stop reason}
21163 @item @code{vfork-event-feature}
21164 @tab @code{vfork stop reason}
21167 @item @code{exec-event-feature}
21168 @tab @code{exec stop reason}
21171 @item @code{thread-events}
21172 @tab @code{QThreadEvents}
21173 @tab Tracking thread lifetime.
21175 @item @code{no-resumed-stop-reply}
21176 @tab @code{no resumed thread left stop reply}
21177 @tab Tracking thread lifetime.
21182 @section Implementing a Remote Stub
21184 @cindex debugging stub, example
21185 @cindex remote stub, example
21186 @cindex stub example, remote debugging
21187 The stub files provided with @value{GDBN} implement the target side of the
21188 communication protocol, and the @value{GDBN} side is implemented in the
21189 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21190 these subroutines to communicate, and ignore the details. (If you're
21191 implementing your own stub file, you can still ignore the details: start
21192 with one of the existing stub files. @file{sparc-stub.c} is the best
21193 organized, and therefore the easiest to read.)
21195 @cindex remote serial debugging, overview
21196 To debug a program running on another machine (the debugging
21197 @dfn{target} machine), you must first arrange for all the usual
21198 prerequisites for the program to run by itself. For example, for a C
21203 A startup routine to set up the C runtime environment; these usually
21204 have a name like @file{crt0}. The startup routine may be supplied by
21205 your hardware supplier, or you may have to write your own.
21208 A C subroutine library to support your program's
21209 subroutine calls, notably managing input and output.
21212 A way of getting your program to the other machine---for example, a
21213 download program. These are often supplied by the hardware
21214 manufacturer, but you may have to write your own from hardware
21218 The next step is to arrange for your program to use a serial port to
21219 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21220 machine). In general terms, the scheme looks like this:
21224 @value{GDBN} already understands how to use this protocol; when everything
21225 else is set up, you can simply use the @samp{target remote} command
21226 (@pxref{Targets,,Specifying a Debugging Target}).
21228 @item On the target,
21229 you must link with your program a few special-purpose subroutines that
21230 implement the @value{GDBN} remote serial protocol. The file containing these
21231 subroutines is called a @dfn{debugging stub}.
21233 On certain remote targets, you can use an auxiliary program
21234 @code{gdbserver} instead of linking a stub into your program.
21235 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21238 The debugging stub is specific to the architecture of the remote
21239 machine; for example, use @file{sparc-stub.c} to debug programs on
21242 @cindex remote serial stub list
21243 These working remote stubs are distributed with @value{GDBN}:
21248 @cindex @file{i386-stub.c}
21251 For Intel 386 and compatible architectures.
21254 @cindex @file{m68k-stub.c}
21255 @cindex Motorola 680x0
21257 For Motorola 680x0 architectures.
21260 @cindex @file{sh-stub.c}
21263 For Renesas SH architectures.
21266 @cindex @file{sparc-stub.c}
21268 For @sc{sparc} architectures.
21270 @item sparcl-stub.c
21271 @cindex @file{sparcl-stub.c}
21274 For Fujitsu @sc{sparclite} architectures.
21278 The @file{README} file in the @value{GDBN} distribution may list other
21279 recently added stubs.
21282 * Stub Contents:: What the stub can do for you
21283 * Bootstrapping:: What you must do for the stub
21284 * Debug Session:: Putting it all together
21287 @node Stub Contents
21288 @subsection What the Stub Can Do for You
21290 @cindex remote serial stub
21291 The debugging stub for your architecture supplies these three
21295 @item set_debug_traps
21296 @findex set_debug_traps
21297 @cindex remote serial stub, initialization
21298 This routine arranges for @code{handle_exception} to run when your
21299 program stops. You must call this subroutine explicitly in your
21300 program's startup code.
21302 @item handle_exception
21303 @findex handle_exception
21304 @cindex remote serial stub, main routine
21305 This is the central workhorse, but your program never calls it
21306 explicitly---the setup code arranges for @code{handle_exception} to
21307 run when a trap is triggered.
21309 @code{handle_exception} takes control when your program stops during
21310 execution (for example, on a breakpoint), and mediates communications
21311 with @value{GDBN} on the host machine. This is where the communications
21312 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21313 representative on the target machine. It begins by sending summary
21314 information on the state of your program, then continues to execute,
21315 retrieving and transmitting any information @value{GDBN} needs, until you
21316 execute a @value{GDBN} command that makes your program resume; at that point,
21317 @code{handle_exception} returns control to your own code on the target
21321 @cindex @code{breakpoint} subroutine, remote
21322 Use this auxiliary subroutine to make your program contain a
21323 breakpoint. Depending on the particular situation, this may be the only
21324 way for @value{GDBN} to get control. For instance, if your target
21325 machine has some sort of interrupt button, you won't need to call this;
21326 pressing the interrupt button transfers control to
21327 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21328 simply receiving characters on the serial port may also trigger a trap;
21329 again, in that situation, you don't need to call @code{breakpoint} from
21330 your own program---simply running @samp{target remote} from the host
21331 @value{GDBN} session gets control.
21333 Call @code{breakpoint} if none of these is true, or if you simply want
21334 to make certain your program stops at a predetermined point for the
21335 start of your debugging session.
21338 @node Bootstrapping
21339 @subsection What You Must Do for the Stub
21341 @cindex remote stub, support routines
21342 The debugging stubs that come with @value{GDBN} are set up for a particular
21343 chip architecture, but they have no information about the rest of your
21344 debugging target machine.
21346 First of all you need to tell the stub how to communicate with the
21350 @item int getDebugChar()
21351 @findex getDebugChar
21352 Write this subroutine to read a single character from the serial port.
21353 It may be identical to @code{getchar} for your target system; a
21354 different name is used to allow you to distinguish the two if you wish.
21356 @item void putDebugChar(int)
21357 @findex putDebugChar
21358 Write this subroutine to write a single character to the serial port.
21359 It may be identical to @code{putchar} for your target system; a
21360 different name is used to allow you to distinguish the two if you wish.
21363 @cindex control C, and remote debugging
21364 @cindex interrupting remote targets
21365 If you want @value{GDBN} to be able to stop your program while it is
21366 running, you need to use an interrupt-driven serial driver, and arrange
21367 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21368 character). That is the character which @value{GDBN} uses to tell the
21369 remote system to stop.
21371 Getting the debugging target to return the proper status to @value{GDBN}
21372 probably requires changes to the standard stub; one quick and dirty way
21373 is to just execute a breakpoint instruction (the ``dirty'' part is that
21374 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21376 Other routines you need to supply are:
21379 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21380 @findex exceptionHandler
21381 Write this function to install @var{exception_address} in the exception
21382 handling tables. You need to do this because the stub does not have any
21383 way of knowing what the exception handling tables on your target system
21384 are like (for example, the processor's table might be in @sc{rom},
21385 containing entries which point to a table in @sc{ram}).
21386 The @var{exception_number} specifies the exception which should be changed;
21387 its meaning is architecture-dependent (for example, different numbers
21388 might represent divide by zero, misaligned access, etc). When this
21389 exception occurs, control should be transferred directly to
21390 @var{exception_address}, and the processor state (stack, registers,
21391 and so on) should be just as it is when a processor exception occurs. So if
21392 you want to use a jump instruction to reach @var{exception_address}, it
21393 should be a simple jump, not a jump to subroutine.
21395 For the 386, @var{exception_address} should be installed as an interrupt
21396 gate so that interrupts are masked while the handler runs. The gate
21397 should be at privilege level 0 (the most privileged level). The
21398 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21399 help from @code{exceptionHandler}.
21401 @item void flush_i_cache()
21402 @findex flush_i_cache
21403 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21404 instruction cache, if any, on your target machine. If there is no
21405 instruction cache, this subroutine may be a no-op.
21407 On target machines that have instruction caches, @value{GDBN} requires this
21408 function to make certain that the state of your program is stable.
21412 You must also make sure this library routine is available:
21415 @item void *memset(void *, int, int)
21417 This is the standard library function @code{memset} that sets an area of
21418 memory to a known value. If you have one of the free versions of
21419 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21420 either obtain it from your hardware manufacturer, or write your own.
21423 If you do not use the GNU C compiler, you may need other standard
21424 library subroutines as well; this varies from one stub to another,
21425 but in general the stubs are likely to use any of the common library
21426 subroutines which @code{@value{NGCC}} generates as inline code.
21429 @node Debug Session
21430 @subsection Putting it All Together
21432 @cindex remote serial debugging summary
21433 In summary, when your program is ready to debug, you must follow these
21438 Make sure you have defined the supporting low-level routines
21439 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21441 @code{getDebugChar}, @code{putDebugChar},
21442 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21446 Insert these lines in your program's startup code, before the main
21447 procedure is called:
21454 On some machines, when a breakpoint trap is raised, the hardware
21455 automatically makes the PC point to the instruction after the
21456 breakpoint. If your machine doesn't do that, you may need to adjust
21457 @code{handle_exception} to arrange for it to return to the instruction
21458 after the breakpoint on this first invocation, so that your program
21459 doesn't keep hitting the initial breakpoint instead of making
21463 For the 680x0 stub only, you need to provide a variable called
21464 @code{exceptionHook}. Normally you just use:
21467 void (*exceptionHook)() = 0;
21471 but if before calling @code{set_debug_traps}, you set it to point to a
21472 function in your program, that function is called when
21473 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21474 error). The function indicated by @code{exceptionHook} is called with
21475 one parameter: an @code{int} which is the exception number.
21478 Compile and link together: your program, the @value{GDBN} debugging stub for
21479 your target architecture, and the supporting subroutines.
21482 Make sure you have a serial connection between your target machine and
21483 the @value{GDBN} host, and identify the serial port on the host.
21486 @c The "remote" target now provides a `load' command, so we should
21487 @c document that. FIXME.
21488 Download your program to your target machine (or get it there by
21489 whatever means the manufacturer provides), and start it.
21492 Start @value{GDBN} on the host, and connect to the target
21493 (@pxref{Connecting,,Connecting to a Remote Target}).
21497 @node Configurations
21498 @chapter Configuration-Specific Information
21500 While nearly all @value{GDBN} commands are available for all native and
21501 cross versions of the debugger, there are some exceptions. This chapter
21502 describes things that are only available in certain configurations.
21504 There are three major categories of configurations: native
21505 configurations, where the host and target are the same, embedded
21506 operating system configurations, which are usually the same for several
21507 different processor architectures, and bare embedded processors, which
21508 are quite different from each other.
21513 * Embedded Processors::
21520 This section describes details specific to particular native
21524 * BSD libkvm Interface:: Debugging BSD kernel memory images
21525 * SVR4 Process Information:: SVR4 process information
21526 * DJGPP Native:: Features specific to the DJGPP port
21527 * Cygwin Native:: Features specific to the Cygwin port
21528 * Hurd Native:: Features specific to @sc{gnu} Hurd
21529 * Darwin:: Features specific to Darwin
21532 @node BSD libkvm Interface
21533 @subsection BSD libkvm Interface
21536 @cindex kernel memory image
21537 @cindex kernel crash dump
21539 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21540 interface that provides a uniform interface for accessing kernel virtual
21541 memory images, including live systems and crash dumps. @value{GDBN}
21542 uses this interface to allow you to debug live kernels and kernel crash
21543 dumps on many native BSD configurations. This is implemented as a
21544 special @code{kvm} debugging target. For debugging a live system, load
21545 the currently running kernel into @value{GDBN} and connect to the
21549 (@value{GDBP}) @b{target kvm}
21552 For debugging crash dumps, provide the file name of the crash dump as an
21556 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21559 Once connected to the @code{kvm} target, the following commands are
21565 Set current context from the @dfn{Process Control Block} (PCB) address.
21568 Set current context from proc address. This command isn't available on
21569 modern FreeBSD systems.
21572 @node SVR4 Process Information
21573 @subsection SVR4 Process Information
21575 @cindex examine process image
21576 @cindex process info via @file{/proc}
21578 Many versions of SVR4 and compatible systems provide a facility called
21579 @samp{/proc} that can be used to examine the image of a running
21580 process using file-system subroutines.
21582 If @value{GDBN} is configured for an operating system with this
21583 facility, the command @code{info proc} is available to report
21584 information about the process running your program, or about any
21585 process running on your system. This includes, as of this writing,
21586 @sc{gnu}/Linux and Solaris, for example.
21588 This command may also work on core files that were created on a system
21589 that has the @samp{/proc} facility.
21595 @itemx info proc @var{process-id}
21596 Summarize available information about any running process. If a
21597 process ID is specified by @var{process-id}, display information about
21598 that process; otherwise display information about the program being
21599 debugged. The summary includes the debugged process ID, the command
21600 line used to invoke it, its current working directory, and its
21601 executable file's absolute file name.
21603 On some systems, @var{process-id} can be of the form
21604 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21605 within a process. If the optional @var{pid} part is missing, it means
21606 a thread from the process being debugged (the leading @samp{/} still
21607 needs to be present, or else @value{GDBN} will interpret the number as
21608 a process ID rather than a thread ID).
21610 @item info proc cmdline
21611 @cindex info proc cmdline
21612 Show the original command line of the process. This command is
21613 specific to @sc{gnu}/Linux.
21615 @item info proc cwd
21616 @cindex info proc cwd
21617 Show the current working directory of the process. This command is
21618 specific to @sc{gnu}/Linux.
21620 @item info proc exe
21621 @cindex info proc exe
21622 Show the name of executable of the process. This command is specific
21625 @item info proc mappings
21626 @cindex memory address space mappings
21627 Report the memory address space ranges accessible in the program, with
21628 information on whether the process has read, write, or execute access
21629 rights to each range. On @sc{gnu}/Linux systems, each memory range
21630 includes the object file which is mapped to that range, instead of the
21631 memory access rights to that range.
21633 @item info proc stat
21634 @itemx info proc status
21635 @cindex process detailed status information
21636 These subcommands are specific to @sc{gnu}/Linux systems. They show
21637 the process-related information, including the user ID and group ID;
21638 how many threads are there in the process; its virtual memory usage;
21639 the signals that are pending, blocked, and ignored; its TTY; its
21640 consumption of system and user time; its stack size; its @samp{nice}
21641 value; etc. For more information, see the @samp{proc} man page
21642 (type @kbd{man 5 proc} from your shell prompt).
21644 @item info proc all
21645 Show all the information about the process described under all of the
21646 above @code{info proc} subcommands.
21649 @comment These sub-options of 'info proc' were not included when
21650 @comment procfs.c was re-written. Keep their descriptions around
21651 @comment against the day when someone finds the time to put them back in.
21652 @kindex info proc times
21653 @item info proc times
21654 Starting time, user CPU time, and system CPU time for your program and
21657 @kindex info proc id
21659 Report on the process IDs related to your program: its own process ID,
21660 the ID of its parent, the process group ID, and the session ID.
21663 @item set procfs-trace
21664 @kindex set procfs-trace
21665 @cindex @code{procfs} API calls
21666 This command enables and disables tracing of @code{procfs} API calls.
21668 @item show procfs-trace
21669 @kindex show procfs-trace
21670 Show the current state of @code{procfs} API call tracing.
21672 @item set procfs-file @var{file}
21673 @kindex set procfs-file
21674 Tell @value{GDBN} to write @code{procfs} API trace to the named
21675 @var{file}. @value{GDBN} appends the trace info to the previous
21676 contents of the file. The default is to display the trace on the
21679 @item show procfs-file
21680 @kindex show procfs-file
21681 Show the file to which @code{procfs} API trace is written.
21683 @item proc-trace-entry
21684 @itemx proc-trace-exit
21685 @itemx proc-untrace-entry
21686 @itemx proc-untrace-exit
21687 @kindex proc-trace-entry
21688 @kindex proc-trace-exit
21689 @kindex proc-untrace-entry
21690 @kindex proc-untrace-exit
21691 These commands enable and disable tracing of entries into and exits
21692 from the @code{syscall} interface.
21695 @kindex info pidlist
21696 @cindex process list, QNX Neutrino
21697 For QNX Neutrino only, this command displays the list of all the
21698 processes and all the threads within each process.
21701 @kindex info meminfo
21702 @cindex mapinfo list, QNX Neutrino
21703 For QNX Neutrino only, this command displays the list of all mapinfos.
21707 @subsection Features for Debugging @sc{djgpp} Programs
21708 @cindex @sc{djgpp} debugging
21709 @cindex native @sc{djgpp} debugging
21710 @cindex MS-DOS-specific commands
21713 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21714 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21715 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21716 top of real-mode DOS systems and their emulations.
21718 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21719 defines a few commands specific to the @sc{djgpp} port. This
21720 subsection describes those commands.
21725 This is a prefix of @sc{djgpp}-specific commands which print
21726 information about the target system and important OS structures.
21729 @cindex MS-DOS system info
21730 @cindex free memory information (MS-DOS)
21731 @item info dos sysinfo
21732 This command displays assorted information about the underlying
21733 platform: the CPU type and features, the OS version and flavor, the
21734 DPMI version, and the available conventional and DPMI memory.
21739 @cindex segment descriptor tables
21740 @cindex descriptor tables display
21742 @itemx info dos ldt
21743 @itemx info dos idt
21744 These 3 commands display entries from, respectively, Global, Local,
21745 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21746 tables are data structures which store a descriptor for each segment
21747 that is currently in use. The segment's selector is an index into a
21748 descriptor table; the table entry for that index holds the
21749 descriptor's base address and limit, and its attributes and access
21752 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21753 segment (used for both data and the stack), and a DOS segment (which
21754 allows access to DOS/BIOS data structures and absolute addresses in
21755 conventional memory). However, the DPMI host will usually define
21756 additional segments in order to support the DPMI environment.
21758 @cindex garbled pointers
21759 These commands allow to display entries from the descriptor tables.
21760 Without an argument, all entries from the specified table are
21761 displayed. An argument, which should be an integer expression, means
21762 display a single entry whose index is given by the argument. For
21763 example, here's a convenient way to display information about the
21764 debugged program's data segment:
21767 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21768 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21772 This comes in handy when you want to see whether a pointer is outside
21773 the data segment's limit (i.e.@: @dfn{garbled}).
21775 @cindex page tables display (MS-DOS)
21777 @itemx info dos pte
21778 These two commands display entries from, respectively, the Page
21779 Directory and the Page Tables. Page Directories and Page Tables are
21780 data structures which control how virtual memory addresses are mapped
21781 into physical addresses. A Page Table includes an entry for every
21782 page of memory that is mapped into the program's address space; there
21783 may be several Page Tables, each one holding up to 4096 entries. A
21784 Page Directory has up to 4096 entries, one each for every Page Table
21785 that is currently in use.
21787 Without an argument, @kbd{info dos pde} displays the entire Page
21788 Directory, and @kbd{info dos pte} displays all the entries in all of
21789 the Page Tables. An argument, an integer expression, given to the
21790 @kbd{info dos pde} command means display only that entry from the Page
21791 Directory table. An argument given to the @kbd{info dos pte} command
21792 means display entries from a single Page Table, the one pointed to by
21793 the specified entry in the Page Directory.
21795 @cindex direct memory access (DMA) on MS-DOS
21796 These commands are useful when your program uses @dfn{DMA} (Direct
21797 Memory Access), which needs physical addresses to program the DMA
21800 These commands are supported only with some DPMI servers.
21802 @cindex physical address from linear address
21803 @item info dos address-pte @var{addr}
21804 This command displays the Page Table entry for a specified linear
21805 address. The argument @var{addr} is a linear address which should
21806 already have the appropriate segment's base address added to it,
21807 because this command accepts addresses which may belong to @emph{any}
21808 segment. For example, here's how to display the Page Table entry for
21809 the page where a variable @code{i} is stored:
21812 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21813 @exdent @code{Page Table entry for address 0x11a00d30:}
21814 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21818 This says that @code{i} is stored at offset @code{0xd30} from the page
21819 whose physical base address is @code{0x02698000}, and shows all the
21820 attributes of that page.
21822 Note that you must cast the addresses of variables to a @code{char *},
21823 since otherwise the value of @code{__djgpp_base_address}, the base
21824 address of all variables and functions in a @sc{djgpp} program, will
21825 be added using the rules of C pointer arithmetics: if @code{i} is
21826 declared an @code{int}, @value{GDBN} will add 4 times the value of
21827 @code{__djgpp_base_address} to the address of @code{i}.
21829 Here's another example, it displays the Page Table entry for the
21833 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21834 @exdent @code{Page Table entry for address 0x29110:}
21835 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21839 (The @code{+ 3} offset is because the transfer buffer's address is the
21840 3rd member of the @code{_go32_info_block} structure.) The output
21841 clearly shows that this DPMI server maps the addresses in conventional
21842 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21843 linear (@code{0x29110}) addresses are identical.
21845 This command is supported only with some DPMI servers.
21848 @cindex DOS serial data link, remote debugging
21849 In addition to native debugging, the DJGPP port supports remote
21850 debugging via a serial data link. The following commands are specific
21851 to remote serial debugging in the DJGPP port of @value{GDBN}.
21854 @kindex set com1base
21855 @kindex set com1irq
21856 @kindex set com2base
21857 @kindex set com2irq
21858 @kindex set com3base
21859 @kindex set com3irq
21860 @kindex set com4base
21861 @kindex set com4irq
21862 @item set com1base @var{addr}
21863 This command sets the base I/O port address of the @file{COM1} serial
21866 @item set com1irq @var{irq}
21867 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21868 for the @file{COM1} serial port.
21870 There are similar commands @samp{set com2base}, @samp{set com3irq},
21871 etc.@: for setting the port address and the @code{IRQ} lines for the
21874 @kindex show com1base
21875 @kindex show com1irq
21876 @kindex show com2base
21877 @kindex show com2irq
21878 @kindex show com3base
21879 @kindex show com3irq
21880 @kindex show com4base
21881 @kindex show com4irq
21882 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21883 display the current settings of the base address and the @code{IRQ}
21884 lines used by the COM ports.
21887 @kindex info serial
21888 @cindex DOS serial port status
21889 This command prints the status of the 4 DOS serial ports. For each
21890 port, it prints whether it's active or not, its I/O base address and
21891 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21892 counts of various errors encountered so far.
21896 @node Cygwin Native
21897 @subsection Features for Debugging MS Windows PE Executables
21898 @cindex MS Windows debugging
21899 @cindex native Cygwin debugging
21900 @cindex Cygwin-specific commands
21902 @value{GDBN} supports native debugging of MS Windows programs, including
21903 DLLs with and without symbolic debugging information.
21905 @cindex Ctrl-BREAK, MS-Windows
21906 @cindex interrupt debuggee on MS-Windows
21907 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21908 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21909 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21910 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21911 sequence, which can be used to interrupt the debuggee even if it
21914 There are various additional Cygwin-specific commands, described in
21915 this section. Working with DLLs that have no debugging symbols is
21916 described in @ref{Non-debug DLL Symbols}.
21921 This is a prefix of MS Windows-specific commands which print
21922 information about the target system and important OS structures.
21924 @item info w32 selector
21925 This command displays information returned by
21926 the Win32 API @code{GetThreadSelectorEntry} function.
21927 It takes an optional argument that is evaluated to
21928 a long value to give the information about this given selector.
21929 Without argument, this command displays information
21930 about the six segment registers.
21932 @item info w32 thread-information-block
21933 This command displays thread specific information stored in the
21934 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21935 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21937 @kindex signal-event
21938 @item signal-event @var{id}
21939 This command signals an event with user-provided @var{id}. Used to resume
21940 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21942 To use it, create or edit the following keys in
21943 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21944 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21945 (for x86_64 versions):
21949 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21950 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21951 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21953 The first @code{%ld} will be replaced by the process ID of the
21954 crashing process, the second @code{%ld} will be replaced by the ID of
21955 the event that blocks the crashing process, waiting for @value{GDBN}
21959 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21960 make the system run debugger specified by the Debugger key
21961 automatically, @code{0} will cause a dialog box with ``OK'' and
21962 ``Cancel'' buttons to appear, which allows the user to either
21963 terminate the crashing process (OK) or debug it (Cancel).
21966 @kindex set cygwin-exceptions
21967 @cindex debugging the Cygwin DLL
21968 @cindex Cygwin DLL, debugging
21969 @item set cygwin-exceptions @var{mode}
21970 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21971 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21972 @value{GDBN} will delay recognition of exceptions, and may ignore some
21973 exceptions which seem to be caused by internal Cygwin DLL
21974 ``bookkeeping''. This option is meant primarily for debugging the
21975 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21976 @value{GDBN} users with false @code{SIGSEGV} signals.
21978 @kindex show cygwin-exceptions
21979 @item show cygwin-exceptions
21980 Displays whether @value{GDBN} will break on exceptions that happen
21981 inside the Cygwin DLL itself.
21983 @kindex set new-console
21984 @item set new-console @var{mode}
21985 If @var{mode} is @code{on} the debuggee will
21986 be started in a new console on next start.
21987 If @var{mode} is @code{off}, the debuggee will
21988 be started in the same console as the debugger.
21990 @kindex show new-console
21991 @item show new-console
21992 Displays whether a new console is used
21993 when the debuggee is started.
21995 @kindex set new-group
21996 @item set new-group @var{mode}
21997 This boolean value controls whether the debuggee should
21998 start a new group or stay in the same group as the debugger.
21999 This affects the way the Windows OS handles
22002 @kindex show new-group
22003 @item show new-group
22004 Displays current value of new-group boolean.
22006 @kindex set debugevents
22007 @item set debugevents
22008 This boolean value adds debug output concerning kernel events related
22009 to the debuggee seen by the debugger. This includes events that
22010 signal thread and process creation and exit, DLL loading and
22011 unloading, console interrupts, and debugging messages produced by the
22012 Windows @code{OutputDebugString} API call.
22014 @kindex set debugexec
22015 @item set debugexec
22016 This boolean value adds debug output concerning execute events
22017 (such as resume thread) seen by the debugger.
22019 @kindex set debugexceptions
22020 @item set debugexceptions
22021 This boolean value adds debug output concerning exceptions in the
22022 debuggee seen by the debugger.
22024 @kindex set debugmemory
22025 @item set debugmemory
22026 This boolean value adds debug output concerning debuggee memory reads
22027 and writes by the debugger.
22031 This boolean values specifies whether the debuggee is called
22032 via a shell or directly (default value is on).
22036 Displays if the debuggee will be started with a shell.
22041 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22044 @node Non-debug DLL Symbols
22045 @subsubsection Support for DLLs without Debugging Symbols
22046 @cindex DLLs with no debugging symbols
22047 @cindex Minimal symbols and DLLs
22049 Very often on windows, some of the DLLs that your program relies on do
22050 not include symbolic debugging information (for example,
22051 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22052 symbols in a DLL, it relies on the minimal amount of symbolic
22053 information contained in the DLL's export table. This section
22054 describes working with such symbols, known internally to @value{GDBN} as
22055 ``minimal symbols''.
22057 Note that before the debugged program has started execution, no DLLs
22058 will have been loaded. The easiest way around this problem is simply to
22059 start the program --- either by setting a breakpoint or letting the
22060 program run once to completion.
22062 @subsubsection DLL Name Prefixes
22064 In keeping with the naming conventions used by the Microsoft debugging
22065 tools, DLL export symbols are made available with a prefix based on the
22066 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22067 also entered into the symbol table, so @code{CreateFileA} is often
22068 sufficient. In some cases there will be name clashes within a program
22069 (particularly if the executable itself includes full debugging symbols)
22070 necessitating the use of the fully qualified name when referring to the
22071 contents of the DLL. Use single-quotes around the name to avoid the
22072 exclamation mark (``!'') being interpreted as a language operator.
22074 Note that the internal name of the DLL may be all upper-case, even
22075 though the file name of the DLL is lower-case, or vice-versa. Since
22076 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22077 some confusion. If in doubt, try the @code{info functions} and
22078 @code{info variables} commands or even @code{maint print msymbols}
22079 (@pxref{Symbols}). Here's an example:
22082 (@value{GDBP}) info function CreateFileA
22083 All functions matching regular expression "CreateFileA":
22085 Non-debugging symbols:
22086 0x77e885f4 CreateFileA
22087 0x77e885f4 KERNEL32!CreateFileA
22091 (@value{GDBP}) info function !
22092 All functions matching regular expression "!":
22094 Non-debugging symbols:
22095 0x6100114c cygwin1!__assert
22096 0x61004034 cygwin1!_dll_crt0@@0
22097 0x61004240 cygwin1!dll_crt0(per_process *)
22101 @subsubsection Working with Minimal Symbols
22103 Symbols extracted from a DLL's export table do not contain very much
22104 type information. All that @value{GDBN} can do is guess whether a symbol
22105 refers to a function or variable depending on the linker section that
22106 contains the symbol. Also note that the actual contents of the memory
22107 contained in a DLL are not available unless the program is running. This
22108 means that you cannot examine the contents of a variable or disassemble
22109 a function within a DLL without a running program.
22111 Variables are generally treated as pointers and dereferenced
22112 automatically. For this reason, it is often necessary to prefix a
22113 variable name with the address-of operator (``&'') and provide explicit
22114 type information in the command. Here's an example of the type of
22118 (@value{GDBP}) print 'cygwin1!__argv'
22119 'cygwin1!__argv' has unknown type; cast it to its declared type
22123 (@value{GDBP}) x 'cygwin1!__argv'
22124 'cygwin1!__argv' has unknown type; cast it to its declared type
22127 And two possible solutions:
22130 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22131 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22135 (@value{GDBP}) x/2x &'cygwin1!__argv'
22136 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22137 (@value{GDBP}) x/x 0x10021608
22138 0x10021608: 0x0022fd98
22139 (@value{GDBP}) x/s 0x0022fd98
22140 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22143 Setting a break point within a DLL is possible even before the program
22144 starts execution. However, under these circumstances, @value{GDBN} can't
22145 examine the initial instructions of the function in order to skip the
22146 function's frame set-up code. You can work around this by using ``*&''
22147 to set the breakpoint at a raw memory address:
22150 (@value{GDBP}) break *&'python22!PyOS_Readline'
22151 Breakpoint 1 at 0x1e04eff0
22154 The author of these extensions is not entirely convinced that setting a
22155 break point within a shared DLL like @file{kernel32.dll} is completely
22159 @subsection Commands Specific to @sc{gnu} Hurd Systems
22160 @cindex @sc{gnu} Hurd debugging
22162 This subsection describes @value{GDBN} commands specific to the
22163 @sc{gnu} Hurd native debugging.
22168 @kindex set signals@r{, Hurd command}
22169 @kindex set sigs@r{, Hurd command}
22170 This command toggles the state of inferior signal interception by
22171 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22172 affected by this command. @code{sigs} is a shorthand alias for
22177 @kindex show signals@r{, Hurd command}
22178 @kindex show sigs@r{, Hurd command}
22179 Show the current state of intercepting inferior's signals.
22181 @item set signal-thread
22182 @itemx set sigthread
22183 @kindex set signal-thread
22184 @kindex set sigthread
22185 This command tells @value{GDBN} which thread is the @code{libc} signal
22186 thread. That thread is run when a signal is delivered to a running
22187 process. @code{set sigthread} is the shorthand alias of @code{set
22190 @item show signal-thread
22191 @itemx show sigthread
22192 @kindex show signal-thread
22193 @kindex show sigthread
22194 These two commands show which thread will run when the inferior is
22195 delivered a signal.
22198 @kindex set stopped@r{, Hurd command}
22199 This commands tells @value{GDBN} that the inferior process is stopped,
22200 as with the @code{SIGSTOP} signal. The stopped process can be
22201 continued by delivering a signal to it.
22204 @kindex show stopped@r{, Hurd command}
22205 This command shows whether @value{GDBN} thinks the debuggee is
22208 @item set exceptions
22209 @kindex set exceptions@r{, Hurd command}
22210 Use this command to turn off trapping of exceptions in the inferior.
22211 When exception trapping is off, neither breakpoints nor
22212 single-stepping will work. To restore the default, set exception
22215 @item show exceptions
22216 @kindex show exceptions@r{, Hurd command}
22217 Show the current state of trapping exceptions in the inferior.
22219 @item set task pause
22220 @kindex set task@r{, Hurd commands}
22221 @cindex task attributes (@sc{gnu} Hurd)
22222 @cindex pause current task (@sc{gnu} Hurd)
22223 This command toggles task suspension when @value{GDBN} has control.
22224 Setting it to on takes effect immediately, and the task is suspended
22225 whenever @value{GDBN} gets control. Setting it to off will take
22226 effect the next time the inferior is continued. If this option is set
22227 to off, you can use @code{set thread default pause on} or @code{set
22228 thread pause on} (see below) to pause individual threads.
22230 @item show task pause
22231 @kindex show task@r{, Hurd commands}
22232 Show the current state of task suspension.
22234 @item set task detach-suspend-count
22235 @cindex task suspend count
22236 @cindex detach from task, @sc{gnu} Hurd
22237 This command sets the suspend count the task will be left with when
22238 @value{GDBN} detaches from it.
22240 @item show task detach-suspend-count
22241 Show the suspend count the task will be left with when detaching.
22243 @item set task exception-port
22244 @itemx set task excp
22245 @cindex task exception port, @sc{gnu} Hurd
22246 This command sets the task exception port to which @value{GDBN} will
22247 forward exceptions. The argument should be the value of the @dfn{send
22248 rights} of the task. @code{set task excp} is a shorthand alias.
22250 @item set noninvasive
22251 @cindex noninvasive task options
22252 This command switches @value{GDBN} to a mode that is the least
22253 invasive as far as interfering with the inferior is concerned. This
22254 is the same as using @code{set task pause}, @code{set exceptions}, and
22255 @code{set signals} to values opposite to the defaults.
22257 @item info send-rights
22258 @itemx info receive-rights
22259 @itemx info port-rights
22260 @itemx info port-sets
22261 @itemx info dead-names
22264 @cindex send rights, @sc{gnu} Hurd
22265 @cindex receive rights, @sc{gnu} Hurd
22266 @cindex port rights, @sc{gnu} Hurd
22267 @cindex port sets, @sc{gnu} Hurd
22268 @cindex dead names, @sc{gnu} Hurd
22269 These commands display information about, respectively, send rights,
22270 receive rights, port rights, port sets, and dead names of a task.
22271 There are also shorthand aliases: @code{info ports} for @code{info
22272 port-rights} and @code{info psets} for @code{info port-sets}.
22274 @item set thread pause
22275 @kindex set thread@r{, Hurd command}
22276 @cindex thread properties, @sc{gnu} Hurd
22277 @cindex pause current thread (@sc{gnu} Hurd)
22278 This command toggles current thread suspension when @value{GDBN} has
22279 control. Setting it to on takes effect immediately, and the current
22280 thread is suspended whenever @value{GDBN} gets control. Setting it to
22281 off will take effect the next time the inferior is continued.
22282 Normally, this command has no effect, since when @value{GDBN} has
22283 control, the whole task is suspended. However, if you used @code{set
22284 task pause off} (see above), this command comes in handy to suspend
22285 only the current thread.
22287 @item show thread pause
22288 @kindex show thread@r{, Hurd command}
22289 This command shows the state of current thread suspension.
22291 @item set thread run
22292 This command sets whether the current thread is allowed to run.
22294 @item show thread run
22295 Show whether the current thread is allowed to run.
22297 @item set thread detach-suspend-count
22298 @cindex thread suspend count, @sc{gnu} Hurd
22299 @cindex detach from thread, @sc{gnu} Hurd
22300 This command sets the suspend count @value{GDBN} will leave on a
22301 thread when detaching. This number is relative to the suspend count
22302 found by @value{GDBN} when it notices the thread; use @code{set thread
22303 takeover-suspend-count} to force it to an absolute value.
22305 @item show thread detach-suspend-count
22306 Show the suspend count @value{GDBN} will leave on the thread when
22309 @item set thread exception-port
22310 @itemx set thread excp
22311 Set the thread exception port to which to forward exceptions. This
22312 overrides the port set by @code{set task exception-port} (see above).
22313 @code{set thread excp} is the shorthand alias.
22315 @item set thread takeover-suspend-count
22316 Normally, @value{GDBN}'s thread suspend counts are relative to the
22317 value @value{GDBN} finds when it notices each thread. This command
22318 changes the suspend counts to be absolute instead.
22320 @item set thread default
22321 @itemx show thread default
22322 @cindex thread default settings, @sc{gnu} Hurd
22323 Each of the above @code{set thread} commands has a @code{set thread
22324 default} counterpart (e.g., @code{set thread default pause}, @code{set
22325 thread default exception-port}, etc.). The @code{thread default}
22326 variety of commands sets the default thread properties for all
22327 threads; you can then change the properties of individual threads with
22328 the non-default commands.
22335 @value{GDBN} provides the following commands specific to the Darwin target:
22338 @item set debug darwin @var{num}
22339 @kindex set debug darwin
22340 When set to a non zero value, enables debugging messages specific to
22341 the Darwin support. Higher values produce more verbose output.
22343 @item show debug darwin
22344 @kindex show debug darwin
22345 Show the current state of Darwin messages.
22347 @item set debug mach-o @var{num}
22348 @kindex set debug mach-o
22349 When set to a non zero value, enables debugging messages while
22350 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22351 file format used on Darwin for object and executable files.) Higher
22352 values produce more verbose output. This is a command to diagnose
22353 problems internal to @value{GDBN} and should not be needed in normal
22356 @item show debug mach-o
22357 @kindex show debug mach-o
22358 Show the current state of Mach-O file messages.
22360 @item set mach-exceptions on
22361 @itemx set mach-exceptions off
22362 @kindex set mach-exceptions
22363 On Darwin, faults are first reported as a Mach exception and are then
22364 mapped to a Posix signal. Use this command to turn on trapping of
22365 Mach exceptions in the inferior. This might be sometimes useful to
22366 better understand the cause of a fault. The default is off.
22368 @item show mach-exceptions
22369 @kindex show mach-exceptions
22370 Show the current state of exceptions trapping.
22375 @section Embedded Operating Systems
22377 This section describes configurations involving the debugging of
22378 embedded operating systems that are available for several different
22381 @value{GDBN} includes the ability to debug programs running on
22382 various real-time operating systems.
22384 @node Embedded Processors
22385 @section Embedded Processors
22387 This section goes into details specific to particular embedded
22390 @cindex send command to simulator
22391 Whenever a specific embedded processor has a simulator, @value{GDBN}
22392 allows to send an arbitrary command to the simulator.
22395 @item sim @var{command}
22396 @kindex sim@r{, a command}
22397 Send an arbitrary @var{command} string to the simulator. Consult the
22398 documentation for the specific simulator in use for information about
22399 acceptable commands.
22404 * ARC:: Synopsys ARC
22406 * M68K:: Motorola M68K
22407 * MicroBlaze:: Xilinx MicroBlaze
22408 * MIPS Embedded:: MIPS Embedded
22409 * PowerPC Embedded:: PowerPC Embedded
22412 * Super-H:: Renesas Super-H
22416 @subsection Synopsys ARC
22417 @cindex Synopsys ARC
22418 @cindex ARC specific commands
22424 @value{GDBN} provides the following ARC-specific commands:
22427 @item set debug arc
22428 @kindex set debug arc
22429 Control the level of ARC specific debug messages. Use 0 for no messages (the
22430 default), 1 for debug messages, and 2 for even more debug messages.
22432 @item show debug arc
22433 @kindex show debug arc
22434 Show the level of ARC specific debugging in operation.
22436 @item maint print arc arc-instruction @var{address}
22437 @kindex maint print arc arc-instruction
22438 Print internal disassembler information about instruction at a given address.
22445 @value{GDBN} provides the following ARM-specific commands:
22448 @item set arm disassembler
22450 This commands selects from a list of disassembly styles. The
22451 @code{"std"} style is the standard style.
22453 @item show arm disassembler
22455 Show the current disassembly style.
22457 @item set arm apcs32
22458 @cindex ARM 32-bit mode
22459 This command toggles ARM operation mode between 32-bit and 26-bit.
22461 @item show arm apcs32
22462 Display the current usage of the ARM 32-bit mode.
22464 @item set arm fpu @var{fputype}
22465 This command sets the ARM floating-point unit (FPU) type. The
22466 argument @var{fputype} can be one of these:
22470 Determine the FPU type by querying the OS ABI.
22472 Software FPU, with mixed-endian doubles on little-endian ARM
22475 GCC-compiled FPA co-processor.
22477 Software FPU with pure-endian doubles.
22483 Show the current type of the FPU.
22486 This command forces @value{GDBN} to use the specified ABI.
22489 Show the currently used ABI.
22491 @item set arm fallback-mode (arm|thumb|auto)
22492 @value{GDBN} uses the symbol table, when available, to determine
22493 whether instructions are ARM or Thumb. This command controls
22494 @value{GDBN}'s default behavior when the symbol table is not
22495 available. The default is @samp{auto}, which causes @value{GDBN} to
22496 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22499 @item show arm fallback-mode
22500 Show the current fallback instruction mode.
22502 @item set arm force-mode (arm|thumb|auto)
22503 This command overrides use of the symbol table to determine whether
22504 instructions are ARM or Thumb. The default is @samp{auto}, which
22505 causes @value{GDBN} to use the symbol table and then the setting
22506 of @samp{set arm fallback-mode}.
22508 @item show arm force-mode
22509 Show the current forced instruction mode.
22511 @item set debug arm
22512 Toggle whether to display ARM-specific debugging messages from the ARM
22513 target support subsystem.
22515 @item show debug arm
22516 Show whether ARM-specific debugging messages are enabled.
22520 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22521 The @value{GDBN} ARM simulator accepts the following optional arguments.
22524 @item --swi-support=@var{type}
22525 Tell the simulator which SWI interfaces to support. The argument
22526 @var{type} may be a comma separated list of the following values.
22527 The default value is @code{all}.
22542 The Motorola m68k configuration includes ColdFire support.
22545 @subsection MicroBlaze
22546 @cindex Xilinx MicroBlaze
22547 @cindex XMD, Xilinx Microprocessor Debugger
22549 The MicroBlaze is a soft-core processor supported on various Xilinx
22550 FPGAs, such as Spartan or Virtex series. Boards with these processors
22551 usually have JTAG ports which connect to a host system running the Xilinx
22552 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22553 This host system is used to download the configuration bitstream to
22554 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22555 communicates with the target board using the JTAG interface and
22556 presents a @code{gdbserver} interface to the board. By default
22557 @code{xmd} uses port @code{1234}. (While it is possible to change
22558 this default port, it requires the use of undocumented @code{xmd}
22559 commands. Contact Xilinx support if you need to do this.)
22561 Use these GDB commands to connect to the MicroBlaze target processor.
22564 @item target remote :1234
22565 Use this command to connect to the target if you are running @value{GDBN}
22566 on the same system as @code{xmd}.
22568 @item target remote @var{xmd-host}:1234
22569 Use this command to connect to the target if it is connected to @code{xmd}
22570 running on a different system named @var{xmd-host}.
22573 Use this command to download a program to the MicroBlaze target.
22575 @item set debug microblaze @var{n}
22576 Enable MicroBlaze-specific debugging messages if non-zero.
22578 @item show debug microblaze @var{n}
22579 Show MicroBlaze-specific debugging level.
22582 @node MIPS Embedded
22583 @subsection @acronym{MIPS} Embedded
22586 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22589 @item set mipsfpu double
22590 @itemx set mipsfpu single
22591 @itemx set mipsfpu none
22592 @itemx set mipsfpu auto
22593 @itemx show mipsfpu
22594 @kindex set mipsfpu
22595 @kindex show mipsfpu
22596 @cindex @acronym{MIPS} remote floating point
22597 @cindex floating point, @acronym{MIPS} remote
22598 If your target board does not support the @acronym{MIPS} floating point
22599 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22600 need this, you may wish to put the command in your @value{GDBN} init
22601 file). This tells @value{GDBN} how to find the return value of
22602 functions which return floating point values. It also allows
22603 @value{GDBN} to avoid saving the floating point registers when calling
22604 functions on the board. If you are using a floating point coprocessor
22605 with only single precision floating point support, as on the @sc{r4650}
22606 processor, use the command @samp{set mipsfpu single}. The default
22607 double precision floating point coprocessor may be selected using
22608 @samp{set mipsfpu double}.
22610 In previous versions the only choices were double precision or no
22611 floating point, so @samp{set mipsfpu on} will select double precision
22612 and @samp{set mipsfpu off} will select no floating point.
22614 As usual, you can inquire about the @code{mipsfpu} variable with
22615 @samp{show mipsfpu}.
22618 @node PowerPC Embedded
22619 @subsection PowerPC Embedded
22621 @cindex DVC register
22622 @value{GDBN} supports using the DVC (Data Value Compare) register to
22623 implement in hardware simple hardware watchpoint conditions of the form:
22626 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22627 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22630 The DVC register will be automatically used when @value{GDBN} detects
22631 such pattern in a condition expression, and the created watchpoint uses one
22632 debug register (either the @code{exact-watchpoints} option is on and the
22633 variable is scalar, or the variable has a length of one byte). This feature
22634 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22637 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22638 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22639 in which case watchpoints using only one debug register are created when
22640 watching variables of scalar types.
22642 You can create an artificial array to watch an arbitrary memory
22643 region using one of the following commands (@pxref{Expressions}):
22646 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22647 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22650 PowerPC embedded processors support masked watchpoints. See the discussion
22651 about the @code{mask} argument in @ref{Set Watchpoints}.
22653 @cindex ranged breakpoint
22654 PowerPC embedded processors support hardware accelerated
22655 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22656 the inferior whenever it executes an instruction at any address within
22657 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22658 use the @code{break-range} command.
22660 @value{GDBN} provides the following PowerPC-specific commands:
22663 @kindex break-range
22664 @item break-range @var{start-location}, @var{end-location}
22665 Set a breakpoint for an address range given by
22666 @var{start-location} and @var{end-location}, which can specify a function name,
22667 a line number, an offset of lines from the current line or from the start
22668 location, or an address of an instruction (see @ref{Specify Location},
22669 for a list of all the possible ways to specify a @var{location}.)
22670 The breakpoint will stop execution of the inferior whenever it
22671 executes an instruction at any address within the specified range,
22672 (including @var{start-location} and @var{end-location}.)
22674 @kindex set powerpc
22675 @item set powerpc soft-float
22676 @itemx show powerpc soft-float
22677 Force @value{GDBN} to use (or not use) a software floating point calling
22678 convention. By default, @value{GDBN} selects the calling convention based
22679 on the selected architecture and the provided executable file.
22681 @item set powerpc vector-abi
22682 @itemx show powerpc vector-abi
22683 Force @value{GDBN} to use the specified calling convention for vector
22684 arguments and return values. The valid options are @samp{auto};
22685 @samp{generic}, to avoid vector registers even if they are present;
22686 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22687 registers. By default, @value{GDBN} selects the calling convention
22688 based on the selected architecture and the provided executable file.
22690 @item set powerpc exact-watchpoints
22691 @itemx show powerpc exact-watchpoints
22692 Allow @value{GDBN} to use only one debug register when watching a variable
22693 of scalar type, thus assuming that the variable is accessed through the
22694 address of its first byte.
22699 @subsection Atmel AVR
22702 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22703 following AVR-specific commands:
22706 @item info io_registers
22707 @kindex info io_registers@r{, AVR}
22708 @cindex I/O registers (Atmel AVR)
22709 This command displays information about the AVR I/O registers. For
22710 each register, @value{GDBN} prints its number and value.
22717 When configured for debugging CRIS, @value{GDBN} provides the
22718 following CRIS-specific commands:
22721 @item set cris-version @var{ver}
22722 @cindex CRIS version
22723 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22724 The CRIS version affects register names and sizes. This command is useful in
22725 case autodetection of the CRIS version fails.
22727 @item show cris-version
22728 Show the current CRIS version.
22730 @item set cris-dwarf2-cfi
22731 @cindex DWARF-2 CFI and CRIS
22732 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22733 Change to @samp{off} when using @code{gcc-cris} whose version is below
22736 @item show cris-dwarf2-cfi
22737 Show the current state of using DWARF-2 CFI.
22739 @item set cris-mode @var{mode}
22741 Set the current CRIS mode to @var{mode}. It should only be changed when
22742 debugging in guru mode, in which case it should be set to
22743 @samp{guru} (the default is @samp{normal}).
22745 @item show cris-mode
22746 Show the current CRIS mode.
22750 @subsection Renesas Super-H
22753 For the Renesas Super-H processor, @value{GDBN} provides these
22757 @item set sh calling-convention @var{convention}
22758 @kindex set sh calling-convention
22759 Set the calling-convention used when calling functions from @value{GDBN}.
22760 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22761 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22762 convention. If the DWARF-2 information of the called function specifies
22763 that the function follows the Renesas calling convention, the function
22764 is called using the Renesas calling convention. If the calling convention
22765 is set to @samp{renesas}, the Renesas calling convention is always used,
22766 regardless of the DWARF-2 information. This can be used to override the
22767 default of @samp{gcc} if debug information is missing, or the compiler
22768 does not emit the DWARF-2 calling convention entry for a function.
22770 @item show sh calling-convention
22771 @kindex show sh calling-convention
22772 Show the current calling convention setting.
22777 @node Architectures
22778 @section Architectures
22780 This section describes characteristics of architectures that affect
22781 all uses of @value{GDBN} with the architecture, both native and cross.
22788 * HPPA:: HP PA architecture
22789 * SPU:: Cell Broadband Engine SPU architecture
22796 @subsection AArch64
22797 @cindex AArch64 support
22799 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22800 following special commands:
22803 @item set debug aarch64
22804 @kindex set debug aarch64
22805 This command determines whether AArch64 architecture-specific debugging
22806 messages are to be displayed.
22808 @item show debug aarch64
22809 Show whether AArch64 debugging messages are displayed.
22814 @subsection x86 Architecture-specific Issues
22817 @item set struct-convention @var{mode}
22818 @kindex set struct-convention
22819 @cindex struct return convention
22820 @cindex struct/union returned in registers
22821 Set the convention used by the inferior to return @code{struct}s and
22822 @code{union}s from functions to @var{mode}. Possible values of
22823 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22824 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22825 are returned on the stack, while @code{"reg"} means that a
22826 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22827 be returned in a register.
22829 @item show struct-convention
22830 @kindex show struct-convention
22831 Show the current setting of the convention to return @code{struct}s
22836 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22837 @cindex Intel Memory Protection Extensions (MPX).
22839 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22840 @footnote{The register named with capital letters represent the architecture
22841 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22842 which are the lower bound and upper bound. Bounds are effective addresses or
22843 memory locations. The upper bounds are architecturally represented in 1's
22844 complement form. A bound having lower bound = 0, and upper bound = 0
22845 (1's complement of all bits set) will allow access to the entire address space.
22847 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22848 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22849 display the upper bound performing the complement of one operation on the
22850 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22851 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22852 can also be noted that the upper bounds are inclusive.
22854 As an example, assume that the register BND0 holds bounds for a pointer having
22855 access allowed for the range between 0x32 and 0x71. The values present on
22856 bnd0raw and bnd registers are presented as follows:
22859 bnd0raw = @{0x32, 0xffffffff8e@}
22860 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22863 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22864 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22865 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22866 Python, the display includes the memory size, in bits, accessible to
22869 Bounds can also be stored in bounds tables, which are stored in
22870 application memory. These tables store bounds for pointers by specifying
22871 the bounds pointer's value along with its bounds. Evaluating and changing
22872 bounds located in bound tables is therefore interesting while investigating
22873 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22876 @item show mpx bound @var{pointer}
22877 @kindex show mpx bound
22878 Display bounds of the given @var{pointer}.
22880 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22881 @kindex set mpx bound
22882 Set the bounds of a pointer in the bound table.
22883 This command takes three parameters: @var{pointer} is the pointers
22884 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22885 for lower and upper bounds respectively.
22888 When you call an inferior function on an Intel MPX enabled program,
22889 GDB sets the inferior's bound registers to the init (disabled) state
22890 before calling the function. As a consequence, bounds checks for the
22891 pointer arguments passed to the function will always pass.
22893 This is necessary because when you call an inferior function, the
22894 program is usually in the middle of the execution of other function.
22895 Since at that point bound registers are in an arbitrary state, not
22896 clearing them would lead to random bound violations in the called
22899 You can still examine the influence of the bound registers on the
22900 execution of the called function by stopping the execution of the
22901 called function at its prologue, setting bound registers, and
22902 continuing the execution. For example:
22906 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
22907 $ print upper (a, b, c, d, 1)
22908 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
22910 @{lbound = 0x0, ubound = ffffffff@} : size -1
22913 At this last step the value of bnd0 can be changed for investigation of bound
22914 violations caused along the execution of the call. In order to know how to
22915 set the bound registers or bound table for the call consult the ABI.
22920 See the following section.
22923 @subsection @acronym{MIPS}
22925 @cindex stack on Alpha
22926 @cindex stack on @acronym{MIPS}
22927 @cindex Alpha stack
22928 @cindex @acronym{MIPS} stack
22929 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22930 sometimes requires @value{GDBN} to search backward in the object code to
22931 find the beginning of a function.
22933 @cindex response time, @acronym{MIPS} debugging
22934 To improve response time (especially for embedded applications, where
22935 @value{GDBN} may be restricted to a slow serial line for this search)
22936 you may want to limit the size of this search, using one of these
22940 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22941 @item set heuristic-fence-post @var{limit}
22942 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22943 search for the beginning of a function. A value of @var{0} (the
22944 default) means there is no limit. However, except for @var{0}, the
22945 larger the limit the more bytes @code{heuristic-fence-post} must search
22946 and therefore the longer it takes to run. You should only need to use
22947 this command when debugging a stripped executable.
22949 @item show heuristic-fence-post
22950 Display the current limit.
22954 These commands are available @emph{only} when @value{GDBN} is configured
22955 for debugging programs on Alpha or @acronym{MIPS} processors.
22957 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22961 @item set mips abi @var{arg}
22962 @kindex set mips abi
22963 @cindex set ABI for @acronym{MIPS}
22964 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22965 values of @var{arg} are:
22969 The default ABI associated with the current binary (this is the
22979 @item show mips abi
22980 @kindex show mips abi
22981 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22983 @item set mips compression @var{arg}
22984 @kindex set mips compression
22985 @cindex code compression, @acronym{MIPS}
22986 Tell @value{GDBN} which @acronym{MIPS} compressed
22987 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22988 inferior. @value{GDBN} uses this for code disassembly and other
22989 internal interpretation purposes. This setting is only referred to
22990 when no executable has been associated with the debugging session or
22991 the executable does not provide information about the encoding it uses.
22992 Otherwise this setting is automatically updated from information
22993 provided by the executable.
22995 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22996 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22997 executables containing @acronym{MIPS16} code frequently are not
22998 identified as such.
23000 This setting is ``sticky''; that is, it retains its value across
23001 debugging sessions until reset either explicitly with this command or
23002 implicitly from an executable.
23004 The compiler and/or assembler typically add symbol table annotations to
23005 identify functions compiled for the @acronym{MIPS16} or
23006 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23007 are present, @value{GDBN} uses them in preference to the global
23008 compressed @acronym{ISA} encoding setting.
23010 @item show mips compression
23011 @kindex show mips compression
23012 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23013 @value{GDBN} to debug the inferior.
23016 @itemx show mipsfpu
23017 @xref{MIPS Embedded, set mipsfpu}.
23019 @item set mips mask-address @var{arg}
23020 @kindex set mips mask-address
23021 @cindex @acronym{MIPS} addresses, masking
23022 This command determines whether the most-significant 32 bits of 64-bit
23023 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23024 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23025 setting, which lets @value{GDBN} determine the correct value.
23027 @item show mips mask-address
23028 @kindex show mips mask-address
23029 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23032 @item set remote-mips64-transfers-32bit-regs
23033 @kindex set remote-mips64-transfers-32bit-regs
23034 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23035 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23036 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23037 and 64 bits for other registers, set this option to @samp{on}.
23039 @item show remote-mips64-transfers-32bit-regs
23040 @kindex show remote-mips64-transfers-32bit-regs
23041 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23043 @item set debug mips
23044 @kindex set debug mips
23045 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23046 target code in @value{GDBN}.
23048 @item show debug mips
23049 @kindex show debug mips
23050 Show the current setting of @acronym{MIPS} debugging messages.
23056 @cindex HPPA support
23058 When @value{GDBN} is debugging the HP PA architecture, it provides the
23059 following special commands:
23062 @item set debug hppa
23063 @kindex set debug hppa
23064 This command determines whether HPPA architecture-specific debugging
23065 messages are to be displayed.
23067 @item show debug hppa
23068 Show whether HPPA debugging messages are displayed.
23070 @item maint print unwind @var{address}
23071 @kindex maint print unwind@r{, HPPA}
23072 This command displays the contents of the unwind table entry at the
23073 given @var{address}.
23079 @subsection Cell Broadband Engine SPU architecture
23080 @cindex Cell Broadband Engine
23083 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23084 it provides the following special commands:
23087 @item info spu event
23089 Display SPU event facility status. Shows current event mask
23090 and pending event status.
23092 @item info spu signal
23093 Display SPU signal notification facility status. Shows pending
23094 signal-control word and signal notification mode of both signal
23095 notification channels.
23097 @item info spu mailbox
23098 Display SPU mailbox facility status. Shows all pending entries,
23099 in order of processing, in each of the SPU Write Outbound,
23100 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23103 Display MFC DMA status. Shows all pending commands in the MFC
23104 DMA queue. For each entry, opcode, tag, class IDs, effective
23105 and local store addresses and transfer size are shown.
23107 @item info spu proxydma
23108 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23109 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23110 and local store addresses and transfer size are shown.
23114 When @value{GDBN} is debugging a combined PowerPC/SPU application
23115 on the Cell Broadband Engine, it provides in addition the following
23119 @item set spu stop-on-load @var{arg}
23121 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23122 will give control to the user when a new SPE thread enters its @code{main}
23123 function. The default is @code{off}.
23125 @item show spu stop-on-load
23127 Show whether to stop for new SPE threads.
23129 @item set spu auto-flush-cache @var{arg}
23130 Set whether to automatically flush the software-managed cache. When set to
23131 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23132 cache to be flushed whenever SPE execution stops. This provides a consistent
23133 view of PowerPC memory that is accessed via the cache. If an application
23134 does not use the software-managed cache, this option has no effect.
23136 @item show spu auto-flush-cache
23137 Show whether to automatically flush the software-managed cache.
23142 @subsection PowerPC
23143 @cindex PowerPC architecture
23145 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23146 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23147 numbers stored in the floating point registers. These values must be stored
23148 in two consecutive registers, always starting at an even register like
23149 @code{f0} or @code{f2}.
23151 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23152 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23153 @code{f2} and @code{f3} for @code{$dl1} and so on.
23155 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23156 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23159 @subsection Nios II
23160 @cindex Nios II architecture
23162 When @value{GDBN} is debugging the Nios II architecture,
23163 it provides the following special commands:
23167 @item set debug nios2
23168 @kindex set debug nios2
23169 This command turns on and off debugging messages for the Nios II
23170 target code in @value{GDBN}.
23172 @item show debug nios2
23173 @kindex show debug nios2
23174 Show the current setting of Nios II debugging messages.
23178 @subsection Sparc64
23179 @cindex Sparc64 support
23180 @cindex Application Data Integrity
23181 @subsubsection ADI Support
23183 The M7 processor supports an Application Data Integrity (ADI) feature that
23184 detects invalid data accesses. When software allocates memory and enables
23185 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23186 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23187 the 4-bit version in every cacheline of that data. Hardware saves the latter
23188 in spare bits in the cache and memory hierarchy. On each load and store,
23189 the processor compares the upper 4 VA (virtual address) bits to the
23190 cacheline's version. If there is a mismatch, the processor generates a
23191 version mismatch trap which can be either precise or disrupting. The trap
23192 is an error condition which the kernel delivers to the process as a SIGSEGV
23195 Note that only 64-bit applications can use ADI and need to be built with
23198 Values of the ADI version tags, which are in granularity of a
23199 cacheline (64 bytes), can be viewed or modified.
23203 @kindex adi examine
23204 @item adi (examine | x) [ / @var{n} ] @var{addr}
23206 The @code{adi examine} command displays the value of one ADI version tag per
23209 @var{n} is a decimal integer specifying the number in bytes; the default
23210 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23211 block size, to display.
23213 @var{addr} is the address in user address space where you want @value{GDBN}
23214 to begin displaying the ADI version tags.
23216 Below is an example of displaying ADI versions of variable "shmaddr".
23219 (@value{GDBP}) adi x/100 shmaddr
23220 0xfff800010002c000: 0 0
23224 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23226 The @code{adi assign} command is used to assign new ADI version tag
23229 @var{n} is a decimal integer specifying the number in bytes;
23230 the default is 1. It specifies how much ADI version information, at the
23231 ratio of 1:ADI block size, to modify.
23233 @var{addr} is the address in user address space where you want @value{GDBN}
23234 to begin modifying the ADI version tags.
23236 @var{tag} is the new ADI version tag.
23238 For example, do the following to modify then verify ADI versions of
23239 variable "shmaddr":
23242 (@value{GDBP}) adi a/100 shmaddr = 7
23243 (@value{GDBP}) adi x/100 shmaddr
23244 0xfff800010002c000: 7 7
23249 @node Controlling GDB
23250 @chapter Controlling @value{GDBN}
23252 You can alter the way @value{GDBN} interacts with you by using the
23253 @code{set} command. For commands controlling how @value{GDBN} displays
23254 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23259 * Editing:: Command editing
23260 * Command History:: Command history
23261 * Screen Size:: Screen size
23262 * Numbers:: Numbers
23263 * ABI:: Configuring the current ABI
23264 * Auto-loading:: Automatically loading associated files
23265 * Messages/Warnings:: Optional warnings and messages
23266 * Debugging Output:: Optional messages about internal happenings
23267 * Other Misc Settings:: Other Miscellaneous Settings
23275 @value{GDBN} indicates its readiness to read a command by printing a string
23276 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23277 can change the prompt string with the @code{set prompt} command. For
23278 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23279 the prompt in one of the @value{GDBN} sessions so that you can always tell
23280 which one you are talking to.
23282 @emph{Note:} @code{set prompt} does not add a space for you after the
23283 prompt you set. This allows you to set a prompt which ends in a space
23284 or a prompt that does not.
23288 @item set prompt @var{newprompt}
23289 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23291 @kindex show prompt
23293 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23296 Versions of @value{GDBN} that ship with Python scripting enabled have
23297 prompt extensions. The commands for interacting with these extensions
23301 @kindex set extended-prompt
23302 @item set extended-prompt @var{prompt}
23303 Set an extended prompt that allows for substitutions.
23304 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23305 substitution. Any escape sequences specified as part of the prompt
23306 string are replaced with the corresponding strings each time the prompt
23312 set extended-prompt Current working directory: \w (gdb)
23315 Note that when an extended-prompt is set, it takes control of the
23316 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23318 @kindex show extended-prompt
23319 @item show extended-prompt
23320 Prints the extended prompt. Any escape sequences specified as part of
23321 the prompt string with @code{set extended-prompt}, are replaced with the
23322 corresponding strings each time the prompt is displayed.
23326 @section Command Editing
23328 @cindex command line editing
23330 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23331 @sc{gnu} library provides consistent behavior for programs which provide a
23332 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23333 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23334 substitution, and a storage and recall of command history across
23335 debugging sessions.
23337 You may control the behavior of command line editing in @value{GDBN} with the
23338 command @code{set}.
23341 @kindex set editing
23344 @itemx set editing on
23345 Enable command line editing (enabled by default).
23347 @item set editing off
23348 Disable command line editing.
23350 @kindex show editing
23352 Show whether command line editing is enabled.
23355 @ifset SYSTEM_READLINE
23356 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23358 @ifclear SYSTEM_READLINE
23359 @xref{Command Line Editing},
23361 for more details about the Readline
23362 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23363 encouraged to read that chapter.
23365 @node Command History
23366 @section Command History
23367 @cindex command history
23369 @value{GDBN} can keep track of the commands you type during your
23370 debugging sessions, so that you can be certain of precisely what
23371 happened. Use these commands to manage the @value{GDBN} command
23374 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23375 package, to provide the history facility.
23376 @ifset SYSTEM_READLINE
23377 @xref{Using History Interactively, , , history, GNU History Library},
23379 @ifclear SYSTEM_READLINE
23380 @xref{Using History Interactively},
23382 for the detailed description of the History library.
23384 To issue a command to @value{GDBN} without affecting certain aspects of
23385 the state which is seen by users, prefix it with @samp{server }
23386 (@pxref{Server Prefix}). This
23387 means that this command will not affect the command history, nor will it
23388 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23389 pressed on a line by itself.
23391 @cindex @code{server}, command prefix
23392 The server prefix does not affect the recording of values into the value
23393 history; to print a value without recording it into the value history,
23394 use the @code{output} command instead of the @code{print} command.
23396 Here is the description of @value{GDBN} commands related to command
23400 @cindex history substitution
23401 @cindex history file
23402 @kindex set history filename
23403 @cindex @env{GDBHISTFILE}, environment variable
23404 @item set history filename @var{fname}
23405 Set the name of the @value{GDBN} command history file to @var{fname}.
23406 This is the file where @value{GDBN} reads an initial command history
23407 list, and where it writes the command history from this session when it
23408 exits. You can access this list through history expansion or through
23409 the history command editing characters listed below. This file defaults
23410 to the value of the environment variable @code{GDBHISTFILE}, or to
23411 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23414 @cindex save command history
23415 @kindex set history save
23416 @item set history save
23417 @itemx set history save on
23418 Record command history in a file, whose name may be specified with the
23419 @code{set history filename} command. By default, this option is disabled.
23421 @item set history save off
23422 Stop recording command history in a file.
23424 @cindex history size
23425 @kindex set history size
23426 @cindex @env{GDBHISTSIZE}, environment variable
23427 @item set history size @var{size}
23428 @itemx set history size unlimited
23429 Set the number of commands which @value{GDBN} keeps in its history list.
23430 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23431 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23432 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23433 either a negative number or the empty string, then the number of commands
23434 @value{GDBN} keeps in the history list is unlimited.
23436 @cindex remove duplicate history
23437 @kindex set history remove-duplicates
23438 @item set history remove-duplicates @var{count}
23439 @itemx set history remove-duplicates unlimited
23440 Control the removal of duplicate history entries in the command history list.
23441 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23442 history entries and remove the first entry that is a duplicate of the current
23443 entry being added to the command history list. If @var{count} is
23444 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23445 removal of duplicate history entries is disabled.
23447 Only history entries added during the current session are considered for
23448 removal. This option is set to 0 by default.
23452 History expansion assigns special meaning to the character @kbd{!}.
23453 @ifset SYSTEM_READLINE
23454 @xref{Event Designators, , , history, GNU History Library},
23456 @ifclear SYSTEM_READLINE
23457 @xref{Event Designators},
23461 @cindex history expansion, turn on/off
23462 Since @kbd{!} is also the logical not operator in C, history expansion
23463 is off by default. If you decide to enable history expansion with the
23464 @code{set history expansion on} command, you may sometimes need to
23465 follow @kbd{!} (when it is used as logical not, in an expression) with
23466 a space or a tab to prevent it from being expanded. The readline
23467 history facilities do not attempt substitution on the strings
23468 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23470 The commands to control history expansion are:
23473 @item set history expansion on
23474 @itemx set history expansion
23475 @kindex set history expansion
23476 Enable history expansion. History expansion is off by default.
23478 @item set history expansion off
23479 Disable history expansion.
23482 @kindex show history
23484 @itemx show history filename
23485 @itemx show history save
23486 @itemx show history size
23487 @itemx show history expansion
23488 These commands display the state of the @value{GDBN} history parameters.
23489 @code{show history} by itself displays all four states.
23494 @kindex show commands
23495 @cindex show last commands
23496 @cindex display command history
23497 @item show commands
23498 Display the last ten commands in the command history.
23500 @item show commands @var{n}
23501 Print ten commands centered on command number @var{n}.
23503 @item show commands +
23504 Print ten commands just after the commands last printed.
23508 @section Screen Size
23509 @cindex size of screen
23510 @cindex screen size
23513 @cindex pauses in output
23515 Certain commands to @value{GDBN} may produce large amounts of
23516 information output to the screen. To help you read all of it,
23517 @value{GDBN} pauses and asks you for input at the end of each page of
23518 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23519 to discard the remaining output. Also, the screen width setting
23520 determines when to wrap lines of output. Depending on what is being
23521 printed, @value{GDBN} tries to break the line at a readable place,
23522 rather than simply letting it overflow onto the following line.
23524 Normally @value{GDBN} knows the size of the screen from the terminal
23525 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23526 together with the value of the @code{TERM} environment variable and the
23527 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23528 you can override it with the @code{set height} and @code{set
23535 @kindex show height
23536 @item set height @var{lpp}
23537 @itemx set height unlimited
23539 @itemx set width @var{cpl}
23540 @itemx set width unlimited
23542 These @code{set} commands specify a screen height of @var{lpp} lines and
23543 a screen width of @var{cpl} characters. The associated @code{show}
23544 commands display the current settings.
23546 If you specify a height of either @code{unlimited} or zero lines,
23547 @value{GDBN} does not pause during output no matter how long the
23548 output is. This is useful if output is to a file or to an editor
23551 Likewise, you can specify @samp{set width unlimited} or @samp{set
23552 width 0} to prevent @value{GDBN} from wrapping its output.
23554 @item set pagination on
23555 @itemx set pagination off
23556 @kindex set pagination
23557 Turn the output pagination on or off; the default is on. Turning
23558 pagination off is the alternative to @code{set height unlimited}. Note that
23559 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23560 Options, -batch}) also automatically disables pagination.
23562 @item show pagination
23563 @kindex show pagination
23564 Show the current pagination mode.
23569 @cindex number representation
23570 @cindex entering numbers
23572 You can always enter numbers in octal, decimal, or hexadecimal in
23573 @value{GDBN} by the usual conventions: octal numbers begin with
23574 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23575 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23576 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23577 10; likewise, the default display for numbers---when no particular
23578 format is specified---is base 10. You can change the default base for
23579 both input and output with the commands described below.
23582 @kindex set input-radix
23583 @item set input-radix @var{base}
23584 Set the default base for numeric input. Supported choices
23585 for @var{base} are decimal 8, 10, or 16. The base must itself be
23586 specified either unambiguously or using the current input radix; for
23590 set input-radix 012
23591 set input-radix 10.
23592 set input-radix 0xa
23596 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23597 leaves the input radix unchanged, no matter what it was, since
23598 @samp{10}, being without any leading or trailing signs of its base, is
23599 interpreted in the current radix. Thus, if the current radix is 16,
23600 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23603 @kindex set output-radix
23604 @item set output-radix @var{base}
23605 Set the default base for numeric display. Supported choices
23606 for @var{base} are decimal 8, 10, or 16. The base must itself be
23607 specified either unambiguously or using the current input radix.
23609 @kindex show input-radix
23610 @item show input-radix
23611 Display the current default base for numeric input.
23613 @kindex show output-radix
23614 @item show output-radix
23615 Display the current default base for numeric display.
23617 @item set radix @r{[}@var{base}@r{]}
23621 These commands set and show the default base for both input and output
23622 of numbers. @code{set radix} sets the radix of input and output to
23623 the same base; without an argument, it resets the radix back to its
23624 default value of 10.
23629 @section Configuring the Current ABI
23631 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23632 application automatically. However, sometimes you need to override its
23633 conclusions. Use these commands to manage @value{GDBN}'s view of the
23639 @cindex Newlib OS ABI and its influence on the longjmp handling
23641 One @value{GDBN} configuration can debug binaries for multiple operating
23642 system targets, either via remote debugging or native emulation.
23643 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23644 but you can override its conclusion using the @code{set osabi} command.
23645 One example where this is useful is in debugging of binaries which use
23646 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23647 not have the same identifying marks that the standard C library for your
23650 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23651 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23652 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23653 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23657 Show the OS ABI currently in use.
23660 With no argument, show the list of registered available OS ABI's.
23662 @item set osabi @var{abi}
23663 Set the current OS ABI to @var{abi}.
23666 @cindex float promotion
23668 Generally, the way that an argument of type @code{float} is passed to a
23669 function depends on whether the function is prototyped. For a prototyped
23670 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23671 according to the architecture's convention for @code{float}. For unprototyped
23672 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23673 @code{double} and then passed.
23675 Unfortunately, some forms of debug information do not reliably indicate whether
23676 a function is prototyped. If @value{GDBN} calls a function that is not marked
23677 as prototyped, it consults @kbd{set coerce-float-to-double}.
23680 @kindex set coerce-float-to-double
23681 @item set coerce-float-to-double
23682 @itemx set coerce-float-to-double on
23683 Arguments of type @code{float} will be promoted to @code{double} when passed
23684 to an unprototyped function. This is the default setting.
23686 @item set coerce-float-to-double off
23687 Arguments of type @code{float} will be passed directly to unprototyped
23690 @kindex show coerce-float-to-double
23691 @item show coerce-float-to-double
23692 Show the current setting of promoting @code{float} to @code{double}.
23696 @kindex show cp-abi
23697 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23698 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23699 used to build your application. @value{GDBN} only fully supports
23700 programs with a single C@t{++} ABI; if your program contains code using
23701 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23702 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23703 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23704 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23705 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23706 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23711 Show the C@t{++} ABI currently in use.
23714 With no argument, show the list of supported C@t{++} ABI's.
23716 @item set cp-abi @var{abi}
23717 @itemx set cp-abi auto
23718 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23722 @section Automatically loading associated files
23723 @cindex auto-loading
23725 @value{GDBN} sometimes reads files with commands and settings automatically,
23726 without being explicitly told so by the user. We call this feature
23727 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23728 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23729 results or introduce security risks (e.g., if the file comes from untrusted
23733 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23734 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23736 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23737 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23740 There are various kinds of files @value{GDBN} can automatically load.
23741 In addition to these files, @value{GDBN} supports auto-loading code written
23742 in various extension languages. @xref{Auto-loading extensions}.
23744 Note that loading of these associated files (including the local @file{.gdbinit}
23745 file) requires accordingly configured @code{auto-load safe-path}
23746 (@pxref{Auto-loading safe path}).
23748 For these reasons, @value{GDBN} includes commands and options to let you
23749 control when to auto-load files and which files should be auto-loaded.
23752 @anchor{set auto-load off}
23753 @kindex set auto-load off
23754 @item set auto-load off
23755 Globally disable loading of all auto-loaded files.
23756 You may want to use this command with the @samp{-iex} option
23757 (@pxref{Option -init-eval-command}) such as:
23759 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23762 Be aware that system init file (@pxref{System-wide configuration})
23763 and init files from your home directory (@pxref{Home Directory Init File})
23764 still get read (as they come from generally trusted directories).
23765 To prevent @value{GDBN} from auto-loading even those init files, use the
23766 @option{-nx} option (@pxref{Mode Options}), in addition to
23767 @code{set auto-load no}.
23769 @anchor{show auto-load}
23770 @kindex show auto-load
23771 @item show auto-load
23772 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23776 (gdb) show auto-load
23777 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23778 libthread-db: Auto-loading of inferior specific libthread_db is on.
23779 local-gdbinit: Auto-loading of .gdbinit script from current directory
23781 python-scripts: Auto-loading of Python scripts is on.
23782 safe-path: List of directories from which it is safe to auto-load files
23783 is $debugdir:$datadir/auto-load.
23784 scripts-directory: List of directories from which to load auto-loaded scripts
23785 is $debugdir:$datadir/auto-load.
23788 @anchor{info auto-load}
23789 @kindex info auto-load
23790 @item info auto-load
23791 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23795 (gdb) info auto-load
23798 Yes /home/user/gdb/gdb-gdb.gdb
23799 libthread-db: No auto-loaded libthread-db.
23800 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23804 Yes /home/user/gdb/gdb-gdb.py
23808 These are @value{GDBN} control commands for the auto-loading:
23810 @multitable @columnfractions .5 .5
23811 @item @xref{set auto-load off}.
23812 @tab Disable auto-loading globally.
23813 @item @xref{show auto-load}.
23814 @tab Show setting of all kinds of files.
23815 @item @xref{info auto-load}.
23816 @tab Show state of all kinds of files.
23817 @item @xref{set auto-load gdb-scripts}.
23818 @tab Control for @value{GDBN} command scripts.
23819 @item @xref{show auto-load gdb-scripts}.
23820 @tab Show setting of @value{GDBN} command scripts.
23821 @item @xref{info auto-load gdb-scripts}.
23822 @tab Show state of @value{GDBN} command scripts.
23823 @item @xref{set auto-load python-scripts}.
23824 @tab Control for @value{GDBN} Python scripts.
23825 @item @xref{show auto-load python-scripts}.
23826 @tab Show setting of @value{GDBN} Python scripts.
23827 @item @xref{info auto-load python-scripts}.
23828 @tab Show state of @value{GDBN} Python scripts.
23829 @item @xref{set auto-load guile-scripts}.
23830 @tab Control for @value{GDBN} Guile scripts.
23831 @item @xref{show auto-load guile-scripts}.
23832 @tab Show setting of @value{GDBN} Guile scripts.
23833 @item @xref{info auto-load guile-scripts}.
23834 @tab Show state of @value{GDBN} Guile scripts.
23835 @item @xref{set auto-load scripts-directory}.
23836 @tab Control for @value{GDBN} auto-loaded scripts location.
23837 @item @xref{show auto-load scripts-directory}.
23838 @tab Show @value{GDBN} auto-loaded scripts location.
23839 @item @xref{add-auto-load-scripts-directory}.
23840 @tab Add directory for auto-loaded scripts location list.
23841 @item @xref{set auto-load local-gdbinit}.
23842 @tab Control for init file in the current directory.
23843 @item @xref{show auto-load local-gdbinit}.
23844 @tab Show setting of init file in the current directory.
23845 @item @xref{info auto-load local-gdbinit}.
23846 @tab Show state of init file in the current directory.
23847 @item @xref{set auto-load libthread-db}.
23848 @tab Control for thread debugging library.
23849 @item @xref{show auto-load libthread-db}.
23850 @tab Show setting of thread debugging library.
23851 @item @xref{info auto-load libthread-db}.
23852 @tab Show state of thread debugging library.
23853 @item @xref{set auto-load safe-path}.
23854 @tab Control directories trusted for automatic loading.
23855 @item @xref{show auto-load safe-path}.
23856 @tab Show directories trusted for automatic loading.
23857 @item @xref{add-auto-load-safe-path}.
23858 @tab Add directory trusted for automatic loading.
23861 @node Init File in the Current Directory
23862 @subsection Automatically loading init file in the current directory
23863 @cindex auto-loading init file in the current directory
23865 By default, @value{GDBN} reads and executes the canned sequences of commands
23866 from init file (if any) in the current working directory,
23867 see @ref{Init File in the Current Directory during Startup}.
23869 Note that loading of this local @file{.gdbinit} file also requires accordingly
23870 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23873 @anchor{set auto-load local-gdbinit}
23874 @kindex set auto-load local-gdbinit
23875 @item set auto-load local-gdbinit [on|off]
23876 Enable or disable the auto-loading of canned sequences of commands
23877 (@pxref{Sequences}) found in init file in the current directory.
23879 @anchor{show auto-load local-gdbinit}
23880 @kindex show auto-load local-gdbinit
23881 @item show auto-load local-gdbinit
23882 Show whether auto-loading of canned sequences of commands from init file in the
23883 current directory is enabled or disabled.
23885 @anchor{info auto-load local-gdbinit}
23886 @kindex info auto-load local-gdbinit
23887 @item info auto-load local-gdbinit
23888 Print whether canned sequences of commands from init file in the
23889 current directory have been auto-loaded.
23892 @node libthread_db.so.1 file
23893 @subsection Automatically loading thread debugging library
23894 @cindex auto-loading libthread_db.so.1
23896 This feature is currently present only on @sc{gnu}/Linux native hosts.
23898 @value{GDBN} reads in some cases thread debugging library from places specific
23899 to the inferior (@pxref{set libthread-db-search-path}).
23901 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23902 without checking this @samp{set auto-load libthread-db} switch as system
23903 libraries have to be trusted in general. In all other cases of
23904 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23905 auto-load libthread-db} is enabled before trying to open such thread debugging
23908 Note that loading of this debugging library also requires accordingly configured
23909 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23912 @anchor{set auto-load libthread-db}
23913 @kindex set auto-load libthread-db
23914 @item set auto-load libthread-db [on|off]
23915 Enable or disable the auto-loading of inferior specific thread debugging library.
23917 @anchor{show auto-load libthread-db}
23918 @kindex show auto-load libthread-db
23919 @item show auto-load libthread-db
23920 Show whether auto-loading of inferior specific thread debugging library is
23921 enabled or disabled.
23923 @anchor{info auto-load libthread-db}
23924 @kindex info auto-load libthread-db
23925 @item info auto-load libthread-db
23926 Print the list of all loaded inferior specific thread debugging libraries and
23927 for each such library print list of inferior @var{pid}s using it.
23930 @node Auto-loading safe path
23931 @subsection Security restriction for auto-loading
23932 @cindex auto-loading safe-path
23934 As the files of inferior can come from untrusted source (such as submitted by
23935 an application user) @value{GDBN} does not always load any files automatically.
23936 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23937 directories trusted for loading files not explicitly requested by user.
23938 Each directory can also be a shell wildcard pattern.
23940 If the path is not set properly you will see a warning and the file will not
23945 Reading symbols from /home/user/gdb/gdb...done.
23946 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23947 declined by your `auto-load safe-path' set
23948 to "$debugdir:$datadir/auto-load".
23949 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23950 declined by your `auto-load safe-path' set
23951 to "$debugdir:$datadir/auto-load".
23955 To instruct @value{GDBN} to go ahead and use the init files anyway,
23956 invoke @value{GDBN} like this:
23959 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23962 The list of trusted directories is controlled by the following commands:
23965 @anchor{set auto-load safe-path}
23966 @kindex set auto-load safe-path
23967 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23968 Set the list of directories (and their subdirectories) trusted for automatic
23969 loading and execution of scripts. You can also enter a specific trusted file.
23970 Each directory can also be a shell wildcard pattern; wildcards do not match
23971 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23972 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23973 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23974 its default value as specified during @value{GDBN} compilation.
23976 The list of directories uses path separator (@samp{:} on GNU and Unix
23977 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23978 to the @env{PATH} environment variable.
23980 @anchor{show auto-load safe-path}
23981 @kindex show auto-load safe-path
23982 @item show auto-load safe-path
23983 Show the list of directories trusted for automatic loading and execution of
23986 @anchor{add-auto-load-safe-path}
23987 @kindex add-auto-load-safe-path
23988 @item add-auto-load-safe-path
23989 Add an entry (or list of entries) to the list of directories trusted for
23990 automatic loading and execution of scripts. Multiple entries may be delimited
23991 by the host platform path separator in use.
23994 This variable defaults to what @code{--with-auto-load-dir} has been configured
23995 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23996 substitution applies the same as for @ref{set auto-load scripts-directory}.
23997 The default @code{set auto-load safe-path} value can be also overriden by
23998 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24000 Setting this variable to @file{/} disables this security protection,
24001 corresponding @value{GDBN} configuration option is
24002 @option{--without-auto-load-safe-path}.
24003 This variable is supposed to be set to the system directories writable by the
24004 system superuser only. Users can add their source directories in init files in
24005 their home directories (@pxref{Home Directory Init File}). See also deprecated
24006 init file in the current directory
24007 (@pxref{Init File in the Current Directory during Startup}).
24009 To force @value{GDBN} to load the files it declined to load in the previous
24010 example, you could use one of the following ways:
24013 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24014 Specify this trusted directory (or a file) as additional component of the list.
24015 You have to specify also any existing directories displayed by
24016 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24018 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24019 Specify this directory as in the previous case but just for a single
24020 @value{GDBN} session.
24022 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24023 Disable auto-loading safety for a single @value{GDBN} session.
24024 This assumes all the files you debug during this @value{GDBN} session will come
24025 from trusted sources.
24027 @item @kbd{./configure --without-auto-load-safe-path}
24028 During compilation of @value{GDBN} you may disable any auto-loading safety.
24029 This assumes all the files you will ever debug with this @value{GDBN} come from
24033 On the other hand you can also explicitly forbid automatic files loading which
24034 also suppresses any such warning messages:
24037 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24038 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24040 @item @file{~/.gdbinit}: @samp{set auto-load no}
24041 Disable auto-loading globally for the user
24042 (@pxref{Home Directory Init File}). While it is improbable, you could also
24043 use system init file instead (@pxref{System-wide configuration}).
24046 This setting applies to the file names as entered by user. If no entry matches
24047 @value{GDBN} tries as a last resort to also resolve all the file names into
24048 their canonical form (typically resolving symbolic links) and compare the
24049 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24050 own before starting the comparison so a canonical form of directories is
24051 recommended to be entered.
24053 @node Auto-loading verbose mode
24054 @subsection Displaying files tried for auto-load
24055 @cindex auto-loading verbose mode
24057 For better visibility of all the file locations where you can place scripts to
24058 be auto-loaded with inferior --- or to protect yourself against accidental
24059 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24060 all the files attempted to be loaded. Both existing and non-existing files may
24063 For example the list of directories from which it is safe to auto-load files
24064 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24065 may not be too obvious while setting it up.
24068 (gdb) set debug auto-load on
24069 (gdb) file ~/src/t/true
24070 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24071 for objfile "/tmp/true".
24072 auto-load: Updating directories of "/usr:/opt".
24073 auto-load: Using directory "/usr".
24074 auto-load: Using directory "/opt".
24075 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24076 by your `auto-load safe-path' set to "/usr:/opt".
24080 @anchor{set debug auto-load}
24081 @kindex set debug auto-load
24082 @item set debug auto-load [on|off]
24083 Set whether to print the filenames attempted to be auto-loaded.
24085 @anchor{show debug auto-load}
24086 @kindex show debug auto-load
24087 @item show debug auto-load
24088 Show whether printing of the filenames attempted to be auto-loaded is turned
24092 @node Messages/Warnings
24093 @section Optional Warnings and Messages
24095 @cindex verbose operation
24096 @cindex optional warnings
24097 By default, @value{GDBN} is silent about its inner workings. If you are
24098 running on a slow machine, you may want to use the @code{set verbose}
24099 command. This makes @value{GDBN} tell you when it does a lengthy
24100 internal operation, so you will not think it has crashed.
24102 Currently, the messages controlled by @code{set verbose} are those
24103 which announce that the symbol table for a source file is being read;
24104 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24107 @kindex set verbose
24108 @item set verbose on
24109 Enables @value{GDBN} output of certain informational messages.
24111 @item set verbose off
24112 Disables @value{GDBN} output of certain informational messages.
24114 @kindex show verbose
24116 Displays whether @code{set verbose} is on or off.
24119 By default, if @value{GDBN} encounters bugs in the symbol table of an
24120 object file, it is silent; but if you are debugging a compiler, you may
24121 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24126 @kindex set complaints
24127 @item set complaints @var{limit}
24128 Permits @value{GDBN} to output @var{limit} complaints about each type of
24129 unusual symbols before becoming silent about the problem. Set
24130 @var{limit} to zero to suppress all complaints; set it to a large number
24131 to prevent complaints from being suppressed.
24133 @kindex show complaints
24134 @item show complaints
24135 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24139 @anchor{confirmation requests}
24140 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24141 lot of stupid questions to confirm certain commands. For example, if
24142 you try to run a program which is already running:
24146 The program being debugged has been started already.
24147 Start it from the beginning? (y or n)
24150 If you are willing to unflinchingly face the consequences of your own
24151 commands, you can disable this ``feature'':
24155 @kindex set confirm
24157 @cindex confirmation
24158 @cindex stupid questions
24159 @item set confirm off
24160 Disables confirmation requests. Note that running @value{GDBN} with
24161 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24162 automatically disables confirmation requests.
24164 @item set confirm on
24165 Enables confirmation requests (the default).
24167 @kindex show confirm
24169 Displays state of confirmation requests.
24173 @cindex command tracing
24174 If you need to debug user-defined commands or sourced files you may find it
24175 useful to enable @dfn{command tracing}. In this mode each command will be
24176 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24177 quantity denoting the call depth of each command.
24180 @kindex set trace-commands
24181 @cindex command scripts, debugging
24182 @item set trace-commands on
24183 Enable command tracing.
24184 @item set trace-commands off
24185 Disable command tracing.
24186 @item show trace-commands
24187 Display the current state of command tracing.
24190 @node Debugging Output
24191 @section Optional Messages about Internal Happenings
24192 @cindex optional debugging messages
24194 @value{GDBN} has commands that enable optional debugging messages from
24195 various @value{GDBN} subsystems; normally these commands are of
24196 interest to @value{GDBN} maintainers, or when reporting a bug. This
24197 section documents those commands.
24200 @kindex set exec-done-display
24201 @item set exec-done-display
24202 Turns on or off the notification of asynchronous commands'
24203 completion. When on, @value{GDBN} will print a message when an
24204 asynchronous command finishes its execution. The default is off.
24205 @kindex show exec-done-display
24206 @item show exec-done-display
24207 Displays the current setting of asynchronous command completion
24210 @cindex ARM AArch64
24211 @item set debug aarch64
24212 Turns on or off display of debugging messages related to ARM AArch64.
24213 The default is off.
24215 @item show debug aarch64
24216 Displays the current state of displaying debugging messages related to
24218 @cindex gdbarch debugging info
24219 @cindex architecture debugging info
24220 @item set debug arch
24221 Turns on or off display of gdbarch debugging info. The default is off
24222 @item show debug arch
24223 Displays the current state of displaying gdbarch debugging info.
24224 @item set debug aix-solib
24225 @cindex AIX shared library debugging
24226 Control display of debugging messages from the AIX shared library
24227 support module. The default is off.
24228 @item show debug aix-thread
24229 Show the current state of displaying AIX shared library debugging messages.
24230 @item set debug aix-thread
24231 @cindex AIX threads
24232 Display debugging messages about inner workings of the AIX thread
24234 @item show debug aix-thread
24235 Show the current state of AIX thread debugging info display.
24236 @item set debug check-physname
24238 Check the results of the ``physname'' computation. When reading DWARF
24239 debugging information for C@t{++}, @value{GDBN} attempts to compute
24240 each entity's name. @value{GDBN} can do this computation in two
24241 different ways, depending on exactly what information is present.
24242 When enabled, this setting causes @value{GDBN} to compute the names
24243 both ways and display any discrepancies.
24244 @item show debug check-physname
24245 Show the current state of ``physname'' checking.
24246 @item set debug coff-pe-read
24247 @cindex COFF/PE exported symbols
24248 Control display of debugging messages related to reading of COFF/PE
24249 exported symbols. The default is off.
24250 @item show debug coff-pe-read
24251 Displays the current state of displaying debugging messages related to
24252 reading of COFF/PE exported symbols.
24253 @item set debug dwarf-die
24255 Dump DWARF DIEs after they are read in.
24256 The value is the number of nesting levels to print.
24257 A value of zero turns off the display.
24258 @item show debug dwarf-die
24259 Show the current state of DWARF DIE debugging.
24260 @item set debug dwarf-line
24261 @cindex DWARF Line Tables
24262 Turns on or off display of debugging messages related to reading
24263 DWARF line tables. The default is 0 (off).
24264 A value of 1 provides basic information.
24265 A value greater than 1 provides more verbose information.
24266 @item show debug dwarf-line
24267 Show the current state of DWARF line table debugging.
24268 @item set debug dwarf-read
24269 @cindex DWARF Reading
24270 Turns on or off display of debugging messages related to reading
24271 DWARF debug info. The default is 0 (off).
24272 A value of 1 provides basic information.
24273 A value greater than 1 provides more verbose information.
24274 @item show debug dwarf-read
24275 Show the current state of DWARF reader debugging.
24276 @item set debug displaced
24277 @cindex displaced stepping debugging info
24278 Turns on or off display of @value{GDBN} debugging info for the
24279 displaced stepping support. The default is off.
24280 @item show debug displaced
24281 Displays the current state of displaying @value{GDBN} debugging info
24282 related to displaced stepping.
24283 @item set debug event
24284 @cindex event debugging info
24285 Turns on or off display of @value{GDBN} event debugging info. The
24287 @item show debug event
24288 Displays the current state of displaying @value{GDBN} event debugging
24290 @item set debug expression
24291 @cindex expression debugging info
24292 Turns on or off display of debugging info about @value{GDBN}
24293 expression parsing. The default is off.
24294 @item show debug expression
24295 Displays the current state of displaying debugging info about
24296 @value{GDBN} expression parsing.
24297 @item set debug fbsd-lwp
24298 @cindex FreeBSD LWP debug messages
24299 Turns on or off debugging messages from the FreeBSD LWP debug support.
24300 @item show debug fbsd-lwp
24301 Show the current state of FreeBSD LWP debugging messages.
24302 @item set debug frame
24303 @cindex frame debugging info
24304 Turns on or off display of @value{GDBN} frame debugging info. The
24306 @item show debug frame
24307 Displays the current state of displaying @value{GDBN} frame debugging
24309 @item set debug gnu-nat
24310 @cindex @sc{gnu}/Hurd debug messages
24311 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24312 @item show debug gnu-nat
24313 Show the current state of @sc{gnu}/Hurd debugging messages.
24314 @item set debug infrun
24315 @cindex inferior debugging info
24316 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24317 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24318 for implementing operations such as single-stepping the inferior.
24319 @item show debug infrun
24320 Displays the current state of @value{GDBN} inferior debugging.
24321 @item set debug jit
24322 @cindex just-in-time compilation, debugging messages
24323 Turn on or off debugging messages from JIT debug support.
24324 @item show debug jit
24325 Displays the current state of @value{GDBN} JIT debugging.
24326 @item set debug lin-lwp
24327 @cindex @sc{gnu}/Linux LWP debug messages
24328 @cindex Linux lightweight processes
24329 Turn on or off debugging messages from the Linux LWP debug support.
24330 @item show debug lin-lwp
24331 Show the current state of Linux LWP debugging messages.
24332 @item set debug linux-namespaces
24333 @cindex @sc{gnu}/Linux namespaces debug messages
24334 Turn on or off debugging messages from the Linux namespaces debug support.
24335 @item show debug linux-namespaces
24336 Show the current state of Linux namespaces debugging messages.
24337 @item set debug mach-o
24338 @cindex Mach-O symbols processing
24339 Control display of debugging messages related to Mach-O symbols
24340 processing. The default is off.
24341 @item show debug mach-o
24342 Displays the current state of displaying debugging messages related to
24343 reading of COFF/PE exported symbols.
24344 @item set debug notification
24345 @cindex remote async notification debugging info
24346 Turn on or off debugging messages about remote async notification.
24347 The default is off.
24348 @item show debug notification
24349 Displays the current state of remote async notification debugging messages.
24350 @item set debug observer
24351 @cindex observer debugging info
24352 Turns on or off display of @value{GDBN} observer debugging. This
24353 includes info such as the notification of observable events.
24354 @item show debug observer
24355 Displays the current state of observer debugging.
24356 @item set debug overload
24357 @cindex C@t{++} overload debugging info
24358 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24359 info. This includes info such as ranking of functions, etc. The default
24361 @item show debug overload
24362 Displays the current state of displaying @value{GDBN} C@t{++} overload
24364 @cindex expression parser, debugging info
24365 @cindex debug expression parser
24366 @item set debug parser
24367 Turns on or off the display of expression parser debugging output.
24368 Internally, this sets the @code{yydebug} variable in the expression
24369 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24370 details. The default is off.
24371 @item show debug parser
24372 Show the current state of expression parser debugging.
24373 @cindex packets, reporting on stdout
24374 @cindex serial connections, debugging
24375 @cindex debug remote protocol
24376 @cindex remote protocol debugging
24377 @cindex display remote packets
24378 @item set debug remote
24379 Turns on or off display of reports on all packets sent back and forth across
24380 the serial line to the remote machine. The info is printed on the
24381 @value{GDBN} standard output stream. The default is off.
24382 @item show debug remote
24383 Displays the state of display of remote packets.
24385 @item set debug separate-debug-file
24386 Turns on or off display of debug output about separate debug file search.
24387 @item show debug separate-debug-file
24388 Displays the state of separate debug file search debug output.
24390 @item set debug serial
24391 Turns on or off display of @value{GDBN} serial debugging info. The
24393 @item show debug serial
24394 Displays the current state of displaying @value{GDBN} serial debugging
24396 @item set debug solib-frv
24397 @cindex FR-V shared-library debugging
24398 Turn on or off debugging messages for FR-V shared-library code.
24399 @item show debug solib-frv
24400 Display the current state of FR-V shared-library code debugging
24402 @item set debug symbol-lookup
24403 @cindex symbol lookup
24404 Turns on or off display of debugging messages related to symbol lookup.
24405 The default is 0 (off).
24406 A value of 1 provides basic information.
24407 A value greater than 1 provides more verbose information.
24408 @item show debug symbol-lookup
24409 Show the current state of symbol lookup debugging messages.
24410 @item set debug symfile
24411 @cindex symbol file functions
24412 Turns on or off display of debugging messages related to symbol file functions.
24413 The default is off. @xref{Files}.
24414 @item show debug symfile
24415 Show the current state of symbol file debugging messages.
24416 @item set debug symtab-create
24417 @cindex symbol table creation
24418 Turns on or off display of debugging messages related to symbol table creation.
24419 The default is 0 (off).
24420 A value of 1 provides basic information.
24421 A value greater than 1 provides more verbose information.
24422 @item show debug symtab-create
24423 Show the current state of symbol table creation debugging.
24424 @item set debug target
24425 @cindex target debugging info
24426 Turns on or off display of @value{GDBN} target debugging info. This info
24427 includes what is going on at the target level of GDB, as it happens. The
24428 default is 0. Set it to 1 to track events, and to 2 to also track the
24429 value of large memory transfers.
24430 @item show debug target
24431 Displays the current state of displaying @value{GDBN} target debugging
24433 @item set debug timestamp
24434 @cindex timestampping debugging info
24435 Turns on or off display of timestamps with @value{GDBN} debugging info.
24436 When enabled, seconds and microseconds are displayed before each debugging
24438 @item show debug timestamp
24439 Displays the current state of displaying timestamps with @value{GDBN}
24441 @item set debug varobj
24442 @cindex variable object debugging info
24443 Turns on or off display of @value{GDBN} variable object debugging
24444 info. The default is off.
24445 @item show debug varobj
24446 Displays the current state of displaying @value{GDBN} variable object
24448 @item set debug xml
24449 @cindex XML parser debugging
24450 Turn on or off debugging messages for built-in XML parsers.
24451 @item show debug xml
24452 Displays the current state of XML debugging messages.
24455 @node Other Misc Settings
24456 @section Other Miscellaneous Settings
24457 @cindex miscellaneous settings
24460 @kindex set interactive-mode
24461 @item set interactive-mode
24462 If @code{on}, forces @value{GDBN} to assume that GDB was started
24463 in a terminal. In practice, this means that @value{GDBN} should wait
24464 for the user to answer queries generated by commands entered at
24465 the command prompt. If @code{off}, forces @value{GDBN} to operate
24466 in the opposite mode, and it uses the default answers to all queries.
24467 If @code{auto} (the default), @value{GDBN} tries to determine whether
24468 its standard input is a terminal, and works in interactive-mode if it
24469 is, non-interactively otherwise.
24471 In the vast majority of cases, the debugger should be able to guess
24472 correctly which mode should be used. But this setting can be useful
24473 in certain specific cases, such as running a MinGW @value{GDBN}
24474 inside a cygwin window.
24476 @kindex show interactive-mode
24477 @item show interactive-mode
24478 Displays whether the debugger is operating in interactive mode or not.
24481 @node Extending GDB
24482 @chapter Extending @value{GDBN}
24483 @cindex extending GDB
24485 @value{GDBN} provides several mechanisms for extension.
24486 @value{GDBN} also provides the ability to automatically load
24487 extensions when it reads a file for debugging. This allows the
24488 user to automatically customize @value{GDBN} for the program
24492 * Sequences:: Canned Sequences of @value{GDBN} Commands
24493 * Python:: Extending @value{GDBN} using Python
24494 * Guile:: Extending @value{GDBN} using Guile
24495 * Auto-loading extensions:: Automatically loading extensions
24496 * Multiple Extension Languages:: Working with multiple extension languages
24497 * Aliases:: Creating new spellings of existing commands
24500 To facilitate the use of extension languages, @value{GDBN} is capable
24501 of evaluating the contents of a file. When doing so, @value{GDBN}
24502 can recognize which extension language is being used by looking at
24503 the filename extension. Files with an unrecognized filename extension
24504 are always treated as a @value{GDBN} Command Files.
24505 @xref{Command Files,, Command files}.
24507 You can control how @value{GDBN} evaluates these files with the following
24511 @kindex set script-extension
24512 @kindex show script-extension
24513 @item set script-extension off
24514 All scripts are always evaluated as @value{GDBN} Command Files.
24516 @item set script-extension soft
24517 The debugger determines the scripting language based on filename
24518 extension. If this scripting language is supported, @value{GDBN}
24519 evaluates the script using that language. Otherwise, it evaluates
24520 the file as a @value{GDBN} Command File.
24522 @item set script-extension strict
24523 The debugger determines the scripting language based on filename
24524 extension, and evaluates the script using that language. If the
24525 language is not supported, then the evaluation fails.
24527 @item show script-extension
24528 Display the current value of the @code{script-extension} option.
24533 @section Canned Sequences of Commands
24535 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24536 Command Lists}), @value{GDBN} provides two ways to store sequences of
24537 commands for execution as a unit: user-defined commands and command
24541 * Define:: How to define your own commands
24542 * Hooks:: Hooks for user-defined commands
24543 * Command Files:: How to write scripts of commands to be stored in a file
24544 * Output:: Commands for controlled output
24545 * Auto-loading sequences:: Controlling auto-loaded command files
24549 @subsection User-defined Commands
24551 @cindex user-defined command
24552 @cindex arguments, to user-defined commands
24553 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24554 which you assign a new name as a command. This is done with the
24555 @code{define} command. User commands may accept an unlimited number of arguments
24556 separated by whitespace. Arguments are accessed within the user command
24557 via @code{$arg0@dots{}$argN}. A trivial example:
24561 print $arg0 + $arg1 + $arg2
24566 To execute the command use:
24573 This defines the command @code{adder}, which prints the sum of
24574 its three arguments. Note the arguments are text substitutions, so they may
24575 reference variables, use complex expressions, or even perform inferior
24578 @cindex argument count in user-defined commands
24579 @cindex how many arguments (user-defined commands)
24580 In addition, @code{$argc} may be used to find out how many arguments have
24586 print $arg0 + $arg1
24589 print $arg0 + $arg1 + $arg2
24594 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24595 to process a variable number of arguments:
24602 eval "set $sum = $sum + $arg%d", $i
24612 @item define @var{commandname}
24613 Define a command named @var{commandname}. If there is already a command
24614 by that name, you are asked to confirm that you want to redefine it.
24615 The argument @var{commandname} may be a bare command name consisting of letters,
24616 numbers, dashes, and underscores. It may also start with any predefined
24617 prefix command. For example, @samp{define target my-target} creates
24618 a user-defined @samp{target my-target} command.
24620 The definition of the command is made up of other @value{GDBN} command lines,
24621 which are given following the @code{define} command. The end of these
24622 commands is marked by a line containing @code{end}.
24625 @kindex end@r{ (user-defined commands)}
24626 @item document @var{commandname}
24627 Document the user-defined command @var{commandname}, so that it can be
24628 accessed by @code{help}. The command @var{commandname} must already be
24629 defined. This command reads lines of documentation just as @code{define}
24630 reads the lines of the command definition, ending with @code{end}.
24631 After the @code{document} command is finished, @code{help} on command
24632 @var{commandname} displays the documentation you have written.
24634 You may use the @code{document} command again to change the
24635 documentation of a command. Redefining the command with @code{define}
24636 does not change the documentation.
24638 @kindex dont-repeat
24639 @cindex don't repeat command
24641 Used inside a user-defined command, this tells @value{GDBN} that this
24642 command should not be repeated when the user hits @key{RET}
24643 (@pxref{Command Syntax, repeat last command}).
24645 @kindex help user-defined
24646 @item help user-defined
24647 List all user-defined commands and all python commands defined in class
24648 COMAND_USER. The first line of the documentation or docstring is
24653 @itemx show user @var{commandname}
24654 Display the @value{GDBN} commands used to define @var{commandname} (but
24655 not its documentation). If no @var{commandname} is given, display the
24656 definitions for all user-defined commands.
24657 This does not work for user-defined python commands.
24659 @cindex infinite recursion in user-defined commands
24660 @kindex show max-user-call-depth
24661 @kindex set max-user-call-depth
24662 @item show max-user-call-depth
24663 @itemx set max-user-call-depth
24664 The value of @code{max-user-call-depth} controls how many recursion
24665 levels are allowed in user-defined commands before @value{GDBN} suspects an
24666 infinite recursion and aborts the command.
24667 This does not apply to user-defined python commands.
24670 In addition to the above commands, user-defined commands frequently
24671 use control flow commands, described in @ref{Command Files}.
24673 When user-defined commands are executed, the
24674 commands of the definition are not printed. An error in any command
24675 stops execution of the user-defined command.
24677 If used interactively, commands that would ask for confirmation proceed
24678 without asking when used inside a user-defined command. Many @value{GDBN}
24679 commands that normally print messages to say what they are doing omit the
24680 messages when used in a user-defined command.
24683 @subsection User-defined Command Hooks
24684 @cindex command hooks
24685 @cindex hooks, for commands
24686 @cindex hooks, pre-command
24689 You may define @dfn{hooks}, which are a special kind of user-defined
24690 command. Whenever you run the command @samp{foo}, if the user-defined
24691 command @samp{hook-foo} exists, it is executed (with no arguments)
24692 before that command.
24694 @cindex hooks, post-command
24696 A hook may also be defined which is run after the command you executed.
24697 Whenever you run the command @samp{foo}, if the user-defined command
24698 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24699 that command. Post-execution hooks may exist simultaneously with
24700 pre-execution hooks, for the same command.
24702 It is valid for a hook to call the command which it hooks. If this
24703 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24705 @c It would be nice if hookpost could be passed a parameter indicating
24706 @c if the command it hooks executed properly or not. FIXME!
24708 @kindex stop@r{, a pseudo-command}
24709 In addition, a pseudo-command, @samp{stop} exists. Defining
24710 (@samp{hook-stop}) makes the associated commands execute every time
24711 execution stops in your program: before breakpoint commands are run,
24712 displays are printed, or the stack frame is printed.
24714 For example, to ignore @code{SIGALRM} signals while
24715 single-stepping, but treat them normally during normal execution,
24720 handle SIGALRM nopass
24724 handle SIGALRM pass
24727 define hook-continue
24728 handle SIGALRM pass
24732 As a further example, to hook at the beginning and end of the @code{echo}
24733 command, and to add extra text to the beginning and end of the message,
24741 define hookpost-echo
24745 (@value{GDBP}) echo Hello World
24746 <<<---Hello World--->>>
24751 You can define a hook for any single-word command in @value{GDBN}, but
24752 not for command aliases; you should define a hook for the basic command
24753 name, e.g.@: @code{backtrace} rather than @code{bt}.
24754 @c FIXME! So how does Joe User discover whether a command is an alias
24756 You can hook a multi-word command by adding @code{hook-} or
24757 @code{hookpost-} to the last word of the command, e.g.@:
24758 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24760 If an error occurs during the execution of your hook, execution of
24761 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24762 (before the command that you actually typed had a chance to run).
24764 If you try to define a hook which does not match any known command, you
24765 get a warning from the @code{define} command.
24767 @node Command Files
24768 @subsection Command Files
24770 @cindex command files
24771 @cindex scripting commands
24772 A command file for @value{GDBN} is a text file made of lines that are
24773 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24774 also be included. An empty line in a command file does nothing; it
24775 does not mean to repeat the last command, as it would from the
24778 You can request the execution of a command file with the @code{source}
24779 command. Note that the @code{source} command is also used to evaluate
24780 scripts that are not Command Files. The exact behavior can be configured
24781 using the @code{script-extension} setting.
24782 @xref{Extending GDB,, Extending GDB}.
24786 @cindex execute commands from a file
24787 @item source [-s] [-v] @var{filename}
24788 Execute the command file @var{filename}.
24791 The lines in a command file are generally executed sequentially,
24792 unless the order of execution is changed by one of the
24793 @emph{flow-control commands} described below. The commands are not
24794 printed as they are executed. An error in any command terminates
24795 execution of the command file and control is returned to the console.
24797 @value{GDBN} first searches for @var{filename} in the current directory.
24798 If the file is not found there, and @var{filename} does not specify a
24799 directory, then @value{GDBN} also looks for the file on the source search path
24800 (specified with the @samp{directory} command);
24801 except that @file{$cdir} is not searched because the compilation directory
24802 is not relevant to scripts.
24804 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24805 on the search path even if @var{filename} specifies a directory.
24806 The search is done by appending @var{filename} to each element of the
24807 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24808 and the search path contains @file{/home/user} then @value{GDBN} will
24809 look for the script @file{/home/user/mylib/myscript}.
24810 The search is also done if @var{filename} is an absolute path.
24811 For example, if @var{filename} is @file{/tmp/myscript} and
24812 the search path contains @file{/home/user} then @value{GDBN} will
24813 look for the script @file{/home/user/tmp/myscript}.
24814 For DOS-like systems, if @var{filename} contains a drive specification,
24815 it is stripped before concatenation. For example, if @var{filename} is
24816 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24817 will look for the script @file{c:/tmp/myscript}.
24819 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24820 each command as it is executed. The option must be given before
24821 @var{filename}, and is interpreted as part of the filename anywhere else.
24823 Commands that would ask for confirmation if used interactively proceed
24824 without asking when used in a command file. Many @value{GDBN} commands that
24825 normally print messages to say what they are doing omit the messages
24826 when called from command files.
24828 @value{GDBN} also accepts command input from standard input. In this
24829 mode, normal output goes to standard output and error output goes to
24830 standard error. Errors in a command file supplied on standard input do
24831 not terminate execution of the command file---execution continues with
24835 gdb < cmds > log 2>&1
24838 (The syntax above will vary depending on the shell used.) This example
24839 will execute commands from the file @file{cmds}. All output and errors
24840 would be directed to @file{log}.
24842 Since commands stored on command files tend to be more general than
24843 commands typed interactively, they frequently need to deal with
24844 complicated situations, such as different or unexpected values of
24845 variables and symbols, changes in how the program being debugged is
24846 built, etc. @value{GDBN} provides a set of flow-control commands to
24847 deal with these complexities. Using these commands, you can write
24848 complex scripts that loop over data structures, execute commands
24849 conditionally, etc.
24856 This command allows to include in your script conditionally executed
24857 commands. The @code{if} command takes a single argument, which is an
24858 expression to evaluate. It is followed by a series of commands that
24859 are executed only if the expression is true (its value is nonzero).
24860 There can then optionally be an @code{else} line, followed by a series
24861 of commands that are only executed if the expression was false. The
24862 end of the list is marked by a line containing @code{end}.
24866 This command allows to write loops. Its syntax is similar to
24867 @code{if}: the command takes a single argument, which is an expression
24868 to evaluate, and must be followed by the commands to execute, one per
24869 line, terminated by an @code{end}. These commands are called the
24870 @dfn{body} of the loop. The commands in the body of @code{while} are
24871 executed repeatedly as long as the expression evaluates to true.
24875 This command exits the @code{while} loop in whose body it is included.
24876 Execution of the script continues after that @code{while}s @code{end}
24879 @kindex loop_continue
24880 @item loop_continue
24881 This command skips the execution of the rest of the body of commands
24882 in the @code{while} loop in whose body it is included. Execution
24883 branches to the beginning of the @code{while} loop, where it evaluates
24884 the controlling expression.
24886 @kindex end@r{ (if/else/while commands)}
24888 Terminate the block of commands that are the body of @code{if},
24889 @code{else}, or @code{while} flow-control commands.
24894 @subsection Commands for Controlled Output
24896 During the execution of a command file or a user-defined command, normal
24897 @value{GDBN} output is suppressed; the only output that appears is what is
24898 explicitly printed by the commands in the definition. This section
24899 describes three commands useful for generating exactly the output you
24904 @item echo @var{text}
24905 @c I do not consider backslash-space a standard C escape sequence
24906 @c because it is not in ANSI.
24907 Print @var{text}. Nonprinting characters can be included in
24908 @var{text} using C escape sequences, such as @samp{\n} to print a
24909 newline. @strong{No newline is printed unless you specify one.}
24910 In addition to the standard C escape sequences, a backslash followed
24911 by a space stands for a space. This is useful for displaying a
24912 string with spaces at the beginning or the end, since leading and
24913 trailing spaces are otherwise trimmed from all arguments.
24914 To print @samp{@w{ }and foo =@w{ }}, use the command
24915 @samp{echo \@w{ }and foo = \@w{ }}.
24917 A backslash at the end of @var{text} can be used, as in C, to continue
24918 the command onto subsequent lines. For example,
24921 echo This is some text\n\
24922 which is continued\n\
24923 onto several lines.\n
24926 produces the same output as
24929 echo This is some text\n
24930 echo which is continued\n
24931 echo onto several lines.\n
24935 @item output @var{expression}
24936 Print the value of @var{expression} and nothing but that value: no
24937 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24938 value history either. @xref{Expressions, ,Expressions}, for more information
24941 @item output/@var{fmt} @var{expression}
24942 Print the value of @var{expression} in format @var{fmt}. You can use
24943 the same formats as for @code{print}. @xref{Output Formats,,Output
24944 Formats}, for more information.
24947 @item printf @var{template}, @var{expressions}@dots{}
24948 Print the values of one or more @var{expressions} under the control of
24949 the string @var{template}. To print several values, make
24950 @var{expressions} be a comma-separated list of individual expressions,
24951 which may be either numbers or pointers. Their values are printed as
24952 specified by @var{template}, exactly as a C program would do by
24953 executing the code below:
24956 printf (@var{template}, @var{expressions}@dots{});
24959 As in @code{C} @code{printf}, ordinary characters in @var{template}
24960 are printed verbatim, while @dfn{conversion specification} introduced
24961 by the @samp{%} character cause subsequent @var{expressions} to be
24962 evaluated, their values converted and formatted according to type and
24963 style information encoded in the conversion specifications, and then
24966 For example, you can print two values in hex like this:
24969 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24972 @code{printf} supports all the standard @code{C} conversion
24973 specifications, including the flags and modifiers between the @samp{%}
24974 character and the conversion letter, with the following exceptions:
24978 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24981 The modifier @samp{*} is not supported for specifying precision or
24985 The @samp{'} flag (for separation of digits into groups according to
24986 @code{LC_NUMERIC'}) is not supported.
24989 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24993 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24996 The conversion letters @samp{a} and @samp{A} are not supported.
25000 Note that the @samp{ll} type modifier is supported only if the
25001 underlying @code{C} implementation used to build @value{GDBN} supports
25002 the @code{long long int} type, and the @samp{L} type modifier is
25003 supported only if @code{long double} type is available.
25005 As in @code{C}, @code{printf} supports simple backslash-escape
25006 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25007 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25008 single character. Octal and hexadecimal escape sequences are not
25011 Additionally, @code{printf} supports conversion specifications for DFP
25012 (@dfn{Decimal Floating Point}) types using the following length modifiers
25013 together with a floating point specifier.
25018 @samp{H} for printing @code{Decimal32} types.
25021 @samp{D} for printing @code{Decimal64} types.
25024 @samp{DD} for printing @code{Decimal128} types.
25027 If the underlying @code{C} implementation used to build @value{GDBN} has
25028 support for the three length modifiers for DFP types, other modifiers
25029 such as width and precision will also be available for @value{GDBN} to use.
25031 In case there is no such @code{C} support, no additional modifiers will be
25032 available and the value will be printed in the standard way.
25034 Here's an example of printing DFP types using the above conversion letters:
25036 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25041 @item eval @var{template}, @var{expressions}@dots{}
25042 Convert the values of one or more @var{expressions} under the control of
25043 the string @var{template} to a command line, and call it.
25047 @node Auto-loading sequences
25048 @subsection Controlling auto-loading native @value{GDBN} scripts
25049 @cindex native script auto-loading
25051 When a new object file is read (for example, due to the @code{file}
25052 command, or because the inferior has loaded a shared library),
25053 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25054 @xref{Auto-loading extensions}.
25056 Auto-loading can be enabled or disabled,
25057 and the list of auto-loaded scripts can be printed.
25060 @anchor{set auto-load gdb-scripts}
25061 @kindex set auto-load gdb-scripts
25062 @item set auto-load gdb-scripts [on|off]
25063 Enable or disable the auto-loading of canned sequences of commands scripts.
25065 @anchor{show auto-load gdb-scripts}
25066 @kindex show auto-load gdb-scripts
25067 @item show auto-load gdb-scripts
25068 Show whether auto-loading of canned sequences of commands scripts is enabled or
25071 @anchor{info auto-load gdb-scripts}
25072 @kindex info auto-load gdb-scripts
25073 @cindex print list of auto-loaded canned sequences of commands scripts
25074 @item info auto-load gdb-scripts [@var{regexp}]
25075 Print the list of all canned sequences of commands scripts that @value{GDBN}
25079 If @var{regexp} is supplied only canned sequences of commands scripts with
25080 matching names are printed.
25082 @c Python docs live in a separate file.
25083 @include python.texi
25085 @c Guile docs live in a separate file.
25086 @include guile.texi
25088 @node Auto-loading extensions
25089 @section Auto-loading extensions
25090 @cindex auto-loading extensions
25092 @value{GDBN} provides two mechanisms for automatically loading extensions
25093 when a new object file is read (for example, due to the @code{file}
25094 command, or because the inferior has loaded a shared library):
25095 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25096 section of modern file formats like ELF.
25099 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25100 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25101 * Which flavor to choose?::
25104 The auto-loading feature is useful for supplying application-specific
25105 debugging commands and features.
25107 Auto-loading can be enabled or disabled,
25108 and the list of auto-loaded scripts can be printed.
25109 See the @samp{auto-loading} section of each extension language
25110 for more information.
25111 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25112 For Python files see @ref{Python Auto-loading}.
25114 Note that loading of this script file also requires accordingly configured
25115 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25117 @node objfile-gdbdotext file
25118 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25119 @cindex @file{@var{objfile}-gdb.gdb}
25120 @cindex @file{@var{objfile}-gdb.py}
25121 @cindex @file{@var{objfile}-gdb.scm}
25123 When a new object file is read, @value{GDBN} looks for a file named
25124 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25125 where @var{objfile} is the object file's name and
25126 where @var{ext} is the file extension for the extension language:
25129 @item @file{@var{objfile}-gdb.gdb}
25130 GDB's own command language
25131 @item @file{@var{objfile}-gdb.py}
25133 @item @file{@var{objfile}-gdb.scm}
25137 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25138 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25139 components, and appending the @file{-gdb.@var{ext}} suffix.
25140 If this file exists and is readable, @value{GDBN} will evaluate it as a
25141 script in the specified extension language.
25143 If this file does not exist, then @value{GDBN} will look for
25144 @var{script-name} file in all of the directories as specified below.
25146 Note that loading of these files requires an accordingly configured
25147 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25149 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25150 scripts normally according to its @file{.exe} filename. But if no scripts are
25151 found @value{GDBN} also tries script filenames matching the object file without
25152 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25153 is attempted on any platform. This makes the script filenames compatible
25154 between Unix and MS-Windows hosts.
25157 @anchor{set auto-load scripts-directory}
25158 @kindex set auto-load scripts-directory
25159 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25160 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25161 may be delimited by the host platform path separator in use
25162 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25164 Each entry here needs to be covered also by the security setting
25165 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25167 @anchor{with-auto-load-dir}
25168 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25169 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25170 configuration option @option{--with-auto-load-dir}.
25172 Any reference to @file{$debugdir} will get replaced by
25173 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25174 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25175 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25176 @file{$datadir} must be placed as a directory component --- either alone or
25177 delimited by @file{/} or @file{\} directory separators, depending on the host
25180 The list of directories uses path separator (@samp{:} on GNU and Unix
25181 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25182 to the @env{PATH} environment variable.
25184 @anchor{show auto-load scripts-directory}
25185 @kindex show auto-load scripts-directory
25186 @item show auto-load scripts-directory
25187 Show @value{GDBN} auto-loaded scripts location.
25189 @anchor{add-auto-load-scripts-directory}
25190 @kindex add-auto-load-scripts-directory
25191 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25192 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25193 Multiple entries may be delimited by the host platform path separator in use.
25196 @value{GDBN} does not track which files it has already auto-loaded this way.
25197 @value{GDBN} will load the associated script every time the corresponding
25198 @var{objfile} is opened.
25199 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25200 is evaluated more than once.
25202 @node dotdebug_gdb_scripts section
25203 @subsection The @code{.debug_gdb_scripts} section
25204 @cindex @code{.debug_gdb_scripts} section
25206 For systems using file formats like ELF and COFF,
25207 when @value{GDBN} loads a new object file
25208 it will look for a special section named @code{.debug_gdb_scripts}.
25209 If this section exists, its contents is a list of null-terminated entries
25210 specifying scripts to load. Each entry begins with a non-null prefix byte that
25211 specifies the kind of entry, typically the extension language and whether the
25212 script is in a file or inlined in @code{.debug_gdb_scripts}.
25214 The following entries are supported:
25217 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25218 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25219 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25220 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25223 @subsubsection Script File Entries
25225 If the entry specifies a file, @value{GDBN} will look for the file first
25226 in the current directory and then along the source search path
25227 (@pxref{Source Path, ,Specifying Source Directories}),
25228 except that @file{$cdir} is not searched, since the compilation
25229 directory is not relevant to scripts.
25231 File entries can be placed in section @code{.debug_gdb_scripts} with,
25232 for example, this GCC macro for Python scripts.
25235 /* Note: The "MS" section flags are to remove duplicates. */
25236 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25238 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25239 .byte 1 /* Python */\n\
25240 .asciz \"" script_name "\"\n\
25246 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25247 Then one can reference the macro in a header or source file like this:
25250 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25253 The script name may include directories if desired.
25255 Note that loading of this script file also requires accordingly configured
25256 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25258 If the macro invocation is put in a header, any application or library
25259 using this header will get a reference to the specified script,
25260 and with the use of @code{"MS"} attributes on the section, the linker
25261 will remove duplicates.
25263 @subsubsection Script Text Entries
25265 Script text entries allow to put the executable script in the entry
25266 itself instead of loading it from a file.
25267 The first line of the entry, everything after the prefix byte and up to
25268 the first newline (@code{0xa}) character, is the script name, and must not
25269 contain any kind of space character, e.g., spaces or tabs.
25270 The rest of the entry, up to the trailing null byte, is the script to
25271 execute in the specified language. The name needs to be unique among
25272 all script names, as @value{GDBN} executes each script only once based
25275 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25279 #include "symcat.h"
25280 #include "gdb/section-scripts.h"
25282 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25283 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25284 ".ascii \"gdb.inlined-script\\n\"\n"
25285 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25286 ".ascii \" def __init__ (self):\\n\"\n"
25287 ".ascii \" super (test_cmd, self).__init__ ("
25288 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25289 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25290 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25291 ".ascii \"test_cmd ()\\n\"\n"
25297 Loading of inlined scripts requires a properly configured
25298 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25299 The path to specify in @code{auto-load safe-path} is the path of the file
25300 containing the @code{.debug_gdb_scripts} section.
25302 @node Which flavor to choose?
25303 @subsection Which flavor to choose?
25305 Given the multiple ways of auto-loading extensions, it might not always
25306 be clear which one to choose. This section provides some guidance.
25309 Benefits of the @file{-gdb.@var{ext}} way:
25313 Can be used with file formats that don't support multiple sections.
25316 Ease of finding scripts for public libraries.
25318 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25319 in the source search path.
25320 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25321 isn't a source directory in which to find the script.
25324 Doesn't require source code additions.
25328 Benefits of the @code{.debug_gdb_scripts} way:
25332 Works with static linking.
25334 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25335 trigger their loading. When an application is statically linked the only
25336 objfile available is the executable, and it is cumbersome to attach all the
25337 scripts from all the input libraries to the executable's
25338 @file{-gdb.@var{ext}} script.
25341 Works with classes that are entirely inlined.
25343 Some classes can be entirely inlined, and thus there may not be an associated
25344 shared library to attach a @file{-gdb.@var{ext}} script to.
25347 Scripts needn't be copied out of the source tree.
25349 In some circumstances, apps can be built out of large collections of internal
25350 libraries, and the build infrastructure necessary to install the
25351 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25352 cumbersome. It may be easier to specify the scripts in the
25353 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25354 top of the source tree to the source search path.
25357 @node Multiple Extension Languages
25358 @section Multiple Extension Languages
25360 The Guile and Python extension languages do not share any state,
25361 and generally do not interfere with each other.
25362 There are some things to be aware of, however.
25364 @subsection Python comes first
25366 Python was @value{GDBN}'s first extension language, and to avoid breaking
25367 existing behaviour Python comes first. This is generally solved by the
25368 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25369 extension languages, and when it makes a call to an extension language,
25370 (say to pretty-print a value), it tries each in turn until an extension
25371 language indicates it has performed the request (e.g., has returned the
25372 pretty-printed form of a value).
25373 This extends to errors while performing such requests: If an error happens
25374 while, for example, trying to pretty-print an object then the error is
25375 reported and any following extension languages are not tried.
25378 @section Creating new spellings of existing commands
25379 @cindex aliases for commands
25381 It is often useful to define alternate spellings of existing commands.
25382 For example, if a new @value{GDBN} command defined in Python has
25383 a long name to type, it is handy to have an abbreviated version of it
25384 that involves less typing.
25386 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25387 of the @samp{step} command even though it is otherwise an ambiguous
25388 abbreviation of other commands like @samp{set} and @samp{show}.
25390 Aliases are also used to provide shortened or more common versions
25391 of multi-word commands. For example, @value{GDBN} provides the
25392 @samp{tty} alias of the @samp{set inferior-tty} command.
25394 You can define a new alias with the @samp{alias} command.
25399 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25403 @var{ALIAS} specifies the name of the new alias.
25404 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25407 @var{COMMAND} specifies the name of an existing command
25408 that is being aliased.
25410 The @samp{-a} option specifies that the new alias is an abbreviation
25411 of the command. Abbreviations are not shown in command
25412 lists displayed by the @samp{help} command.
25414 The @samp{--} option specifies the end of options,
25415 and is useful when @var{ALIAS} begins with a dash.
25417 Here is a simple example showing how to make an abbreviation
25418 of a command so that there is less to type.
25419 Suppose you were tired of typing @samp{disas}, the current
25420 shortest unambiguous abbreviation of the @samp{disassemble} command
25421 and you wanted an even shorter version named @samp{di}.
25422 The following will accomplish this.
25425 (gdb) alias -a di = disas
25428 Note that aliases are different from user-defined commands.
25429 With a user-defined command, you also need to write documentation
25430 for it with the @samp{document} command.
25431 An alias automatically picks up the documentation of the existing command.
25433 Here is an example where we make @samp{elms} an abbreviation of
25434 @samp{elements} in the @samp{set print elements} command.
25435 This is to show that you can make an abbreviation of any part
25439 (gdb) alias -a set print elms = set print elements
25440 (gdb) alias -a show print elms = show print elements
25441 (gdb) set p elms 20
25443 Limit on string chars or array elements to print is 200.
25446 Note that if you are defining an alias of a @samp{set} command,
25447 and you want to have an alias for the corresponding @samp{show}
25448 command, then you need to define the latter separately.
25450 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25451 @var{ALIAS}, just as they are normally.
25454 (gdb) alias -a set pr elms = set p ele
25457 Finally, here is an example showing the creation of a one word
25458 alias for a more complex command.
25459 This creates alias @samp{spe} of the command @samp{set print elements}.
25462 (gdb) alias spe = set print elements
25467 @chapter Command Interpreters
25468 @cindex command interpreters
25470 @value{GDBN} supports multiple command interpreters, and some command
25471 infrastructure to allow users or user interface writers to switch
25472 between interpreters or run commands in other interpreters.
25474 @value{GDBN} currently supports two command interpreters, the console
25475 interpreter (sometimes called the command-line interpreter or @sc{cli})
25476 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25477 describes both of these interfaces in great detail.
25479 By default, @value{GDBN} will start with the console interpreter.
25480 However, the user may choose to start @value{GDBN} with another
25481 interpreter by specifying the @option{-i} or @option{--interpreter}
25482 startup options. Defined interpreters include:
25486 @cindex console interpreter
25487 The traditional console or command-line interpreter. This is the most often
25488 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25489 @value{GDBN} will use this interpreter.
25492 @cindex mi interpreter
25493 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25494 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25495 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25499 @cindex mi2 interpreter
25500 The current @sc{gdb/mi} interface.
25503 @cindex mi1 interpreter
25504 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25508 @cindex invoke another interpreter
25510 @kindex interpreter-exec
25511 You may execute commands in any interpreter from the current
25512 interpreter using the appropriate command. If you are running the
25513 console interpreter, simply use the @code{interpreter-exec} command:
25516 interpreter-exec mi "-data-list-register-names"
25519 @sc{gdb/mi} has a similar command, although it is only available in versions of
25520 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25522 Note that @code{interpreter-exec} only changes the interpreter for the
25523 duration of the specified command. It does not change the interpreter
25526 @cindex start a new independent interpreter
25528 Although you may only choose a single interpreter at startup, it is
25529 possible to run an independent interpreter on a specified input/output
25530 device (usually a tty).
25532 For example, consider a debugger GUI or IDE that wants to provide a
25533 @value{GDBN} console view. It may do so by embedding a terminal
25534 emulator widget in its GUI, starting @value{GDBN} in the traditional
25535 command-line mode with stdin/stdout/stderr redirected to that
25536 terminal, and then creating an MI interpreter running on a specified
25537 input/output device. The console interpreter created by @value{GDBN}
25538 at startup handles commands the user types in the terminal widget,
25539 while the GUI controls and synchronizes state with @value{GDBN} using
25540 the separate MI interpreter.
25542 To start a new secondary @dfn{user interface} running MI, use the
25543 @code{new-ui} command:
25546 @cindex new user interface
25548 new-ui @var{interpreter} @var{tty}
25551 The @var{interpreter} parameter specifies the interpreter to run.
25552 This accepts the same values as the @code{interpreter-exec} command.
25553 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25554 @var{tty} parameter specifies the name of the bidirectional file the
25555 interpreter uses for input/output, usually the name of a
25556 pseudoterminal slave on Unix systems. For example:
25559 (@value{GDBP}) new-ui mi /dev/pts/9
25563 runs an MI interpreter on @file{/dev/pts/9}.
25566 @chapter @value{GDBN} Text User Interface
25568 @cindex Text User Interface
25571 * TUI Overview:: TUI overview
25572 * TUI Keys:: TUI key bindings
25573 * TUI Single Key Mode:: TUI single key mode
25574 * TUI Commands:: TUI-specific commands
25575 * TUI Configuration:: TUI configuration variables
25578 The @value{GDBN} Text User Interface (TUI) is a terminal
25579 interface which uses the @code{curses} library to show the source
25580 file, the assembly output, the program registers and @value{GDBN}
25581 commands in separate text windows. The TUI mode is supported only
25582 on platforms where a suitable version of the @code{curses} library
25585 The TUI mode is enabled by default when you invoke @value{GDBN} as
25586 @samp{@value{GDBP} -tui}.
25587 You can also switch in and out of TUI mode while @value{GDBN} runs by
25588 using various TUI commands and key bindings, such as @command{tui
25589 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25590 @ref{TUI Keys, ,TUI Key Bindings}.
25593 @section TUI Overview
25595 In TUI mode, @value{GDBN} can display several text windows:
25599 This window is the @value{GDBN} command window with the @value{GDBN}
25600 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25601 managed using readline.
25604 The source window shows the source file of the program. The current
25605 line and active breakpoints are displayed in this window.
25608 The assembly window shows the disassembly output of the program.
25611 This window shows the processor registers. Registers are highlighted
25612 when their values change.
25615 The source and assembly windows show the current program position
25616 by highlighting the current line and marking it with a @samp{>} marker.
25617 Breakpoints are indicated with two markers. The first marker
25618 indicates the breakpoint type:
25622 Breakpoint which was hit at least once.
25625 Breakpoint which was never hit.
25628 Hardware breakpoint which was hit at least once.
25631 Hardware breakpoint which was never hit.
25634 The second marker indicates whether the breakpoint is enabled or not:
25638 Breakpoint is enabled.
25641 Breakpoint is disabled.
25644 The source, assembly and register windows are updated when the current
25645 thread changes, when the frame changes, or when the program counter
25648 These windows are not all visible at the same time. The command
25649 window is always visible. The others can be arranged in several
25660 source and assembly,
25663 source and registers, or
25666 assembly and registers.
25669 A status line above the command window shows the following information:
25673 Indicates the current @value{GDBN} target.
25674 (@pxref{Targets, ,Specifying a Debugging Target}).
25677 Gives the current process or thread number.
25678 When no process is being debugged, this field is set to @code{No process}.
25681 Gives the current function name for the selected frame.
25682 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25683 When there is no symbol corresponding to the current program counter,
25684 the string @code{??} is displayed.
25687 Indicates the current line number for the selected frame.
25688 When the current line number is not known, the string @code{??} is displayed.
25691 Indicates the current program counter address.
25695 @section TUI Key Bindings
25696 @cindex TUI key bindings
25698 The TUI installs several key bindings in the readline keymaps
25699 @ifset SYSTEM_READLINE
25700 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25702 @ifclear SYSTEM_READLINE
25703 (@pxref{Command Line Editing}).
25705 The following key bindings are installed for both TUI mode and the
25706 @value{GDBN} standard mode.
25715 Enter or leave the TUI mode. When leaving the TUI mode,
25716 the curses window management stops and @value{GDBN} operates using
25717 its standard mode, writing on the terminal directly. When reentering
25718 the TUI mode, control is given back to the curses windows.
25719 The screen is then refreshed.
25723 Use a TUI layout with only one window. The layout will
25724 either be @samp{source} or @samp{assembly}. When the TUI mode
25725 is not active, it will switch to the TUI mode.
25727 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25731 Use a TUI layout with at least two windows. When the current
25732 layout already has two windows, the next layout with two windows is used.
25733 When a new layout is chosen, one window will always be common to the
25734 previous layout and the new one.
25736 Think of it as the Emacs @kbd{C-x 2} binding.
25740 Change the active window. The TUI associates several key bindings
25741 (like scrolling and arrow keys) with the active window. This command
25742 gives the focus to the next TUI window.
25744 Think of it as the Emacs @kbd{C-x o} binding.
25748 Switch in and out of the TUI SingleKey mode that binds single
25749 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25752 The following key bindings only work in the TUI mode:
25757 Scroll the active window one page up.
25761 Scroll the active window one page down.
25765 Scroll the active window one line up.
25769 Scroll the active window one line down.
25773 Scroll the active window one column left.
25777 Scroll the active window one column right.
25781 Refresh the screen.
25784 Because the arrow keys scroll the active window in the TUI mode, they
25785 are not available for their normal use by readline unless the command
25786 window has the focus. When another window is active, you must use
25787 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25788 and @kbd{C-f} to control the command window.
25790 @node TUI Single Key Mode
25791 @section TUI Single Key Mode
25792 @cindex TUI single key mode
25794 The TUI also provides a @dfn{SingleKey} mode, which binds several
25795 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25796 switch into this mode, where the following key bindings are used:
25799 @kindex c @r{(SingleKey TUI key)}
25803 @kindex d @r{(SingleKey TUI key)}
25807 @kindex f @r{(SingleKey TUI key)}
25811 @kindex n @r{(SingleKey TUI key)}
25815 @kindex o @r{(SingleKey TUI key)}
25817 nexti. The shortcut letter @samp{o} stands for ``step Over''.
25819 @kindex q @r{(SingleKey TUI key)}
25821 exit the SingleKey mode.
25823 @kindex r @r{(SingleKey TUI key)}
25827 @kindex s @r{(SingleKey TUI key)}
25831 @kindex i @r{(SingleKey TUI key)}
25833 stepi. The shortcut letter @samp{i} stands for ``step Into''.
25835 @kindex u @r{(SingleKey TUI key)}
25839 @kindex v @r{(SingleKey TUI key)}
25843 @kindex w @r{(SingleKey TUI key)}
25848 Other keys temporarily switch to the @value{GDBN} command prompt.
25849 The key that was pressed is inserted in the editing buffer so that
25850 it is possible to type most @value{GDBN} commands without interaction
25851 with the TUI SingleKey mode. Once the command is entered the TUI
25852 SingleKey mode is restored. The only way to permanently leave
25853 this mode is by typing @kbd{q} or @kbd{C-x s}.
25857 @section TUI-specific Commands
25858 @cindex TUI commands
25860 The TUI has specific commands to control the text windows.
25861 These commands are always available, even when @value{GDBN} is not in
25862 the TUI mode. When @value{GDBN} is in the standard mode, most
25863 of these commands will automatically switch to the TUI mode.
25865 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25866 terminal, or @value{GDBN} has been started with the machine interface
25867 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25868 these commands will fail with an error, because it would not be
25869 possible or desirable to enable curses window management.
25874 Activate TUI mode. The last active TUI window layout will be used if
25875 TUI mode has prevsiouly been used in the current debugging session,
25876 otherwise a default layout is used.
25879 @kindex tui disable
25880 Disable TUI mode, returning to the console interpreter.
25884 List and give the size of all displayed windows.
25886 @item layout @var{name}
25888 Changes which TUI windows are displayed. In each layout the command
25889 window is always displayed, the @var{name} parameter controls which
25890 additional windows are displayed, and can be any of the following:
25894 Display the next layout.
25897 Display the previous layout.
25900 Display the source and command windows.
25903 Display the assembly and command windows.
25906 Display the source, assembly, and command windows.
25909 When in @code{src} layout display the register, source, and command
25910 windows. When in @code{asm} or @code{split} layout display the
25911 register, assembler, and command windows.
25914 @item focus @var{name}
25916 Changes which TUI window is currently active for scrolling. The
25917 @var{name} parameter can be any of the following:
25921 Make the next window active for scrolling.
25924 Make the previous window active for scrolling.
25927 Make the source window active for scrolling.
25930 Make the assembly window active for scrolling.
25933 Make the register window active for scrolling.
25936 Make the command window active for scrolling.
25941 Refresh the screen. This is similar to typing @kbd{C-L}.
25943 @item tui reg @var{group}
25945 Changes the register group displayed in the tui register window to
25946 @var{group}. If the register window is not currently displayed this
25947 command will cause the register window to be displayed. The list of
25948 register groups, as well as their order is target specific. The
25949 following groups are available on most targets:
25952 Repeatedly selecting this group will cause the display to cycle
25953 through all of the available register groups.
25956 Repeatedly selecting this group will cause the display to cycle
25957 through all of the available register groups in the reverse order to
25961 Display the general registers.
25963 Display the floating point registers.
25965 Display the system registers.
25967 Display the vector registers.
25969 Display all registers.
25974 Update the source window and the current execution point.
25976 @item winheight @var{name} +@var{count}
25977 @itemx winheight @var{name} -@var{count}
25979 Change the height of the window @var{name} by @var{count}
25980 lines. Positive counts increase the height, while negative counts
25981 decrease it. The @var{name} parameter can be one of @code{src} (the
25982 source window), @code{cmd} (the command window), @code{asm} (the
25983 disassembly window), or @code{regs} (the register display window).
25985 @item tabset @var{nchars}
25987 Set the width of tab stops to be @var{nchars} characters. This
25988 setting affects the display of TAB characters in the source and
25992 @node TUI Configuration
25993 @section TUI Configuration Variables
25994 @cindex TUI configuration variables
25996 Several configuration variables control the appearance of TUI windows.
25999 @item set tui border-kind @var{kind}
26000 @kindex set tui border-kind
26001 Select the border appearance for the source, assembly and register windows.
26002 The possible values are the following:
26005 Use a space character to draw the border.
26008 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26011 Use the Alternate Character Set to draw the border. The border is
26012 drawn using character line graphics if the terminal supports them.
26015 @item set tui border-mode @var{mode}
26016 @kindex set tui border-mode
26017 @itemx set tui active-border-mode @var{mode}
26018 @kindex set tui active-border-mode
26019 Select the display attributes for the borders of the inactive windows
26020 or the active window. The @var{mode} can be one of the following:
26023 Use normal attributes to display the border.
26029 Use reverse video mode.
26032 Use half bright mode.
26034 @item half-standout
26035 Use half bright and standout mode.
26038 Use extra bright or bold mode.
26040 @item bold-standout
26041 Use extra bright or bold and standout mode.
26046 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26049 @cindex @sc{gnu} Emacs
26050 A special interface allows you to use @sc{gnu} Emacs to view (and
26051 edit) the source files for the program you are debugging with
26054 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26055 executable file you want to debug as an argument. This command starts
26056 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26057 created Emacs buffer.
26058 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26060 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26065 All ``terminal'' input and output goes through an Emacs buffer, called
26068 This applies both to @value{GDBN} commands and their output, and to the input
26069 and output done by the program you are debugging.
26071 This is useful because it means that you can copy the text of previous
26072 commands and input them again; you can even use parts of the output
26075 All the facilities of Emacs' Shell mode are available for interacting
26076 with your program. In particular, you can send signals the usual
26077 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26081 @value{GDBN} displays source code through Emacs.
26083 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26084 source file for that frame and puts an arrow (@samp{=>}) at the
26085 left margin of the current line. Emacs uses a separate buffer for
26086 source display, and splits the screen to show both your @value{GDBN} session
26089 Explicit @value{GDBN} @code{list} or search commands still produce output as
26090 usual, but you probably have no reason to use them from Emacs.
26093 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26094 a graphical mode, enabled by default, which provides further buffers
26095 that can control the execution and describe the state of your program.
26096 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26098 If you specify an absolute file name when prompted for the @kbd{M-x
26099 gdb} argument, then Emacs sets your current working directory to where
26100 your program resides. If you only specify the file name, then Emacs
26101 sets your current working directory to the directory associated
26102 with the previous buffer. In this case, @value{GDBN} may find your
26103 program by searching your environment's @code{PATH} variable, but on
26104 some operating systems it might not find the source. So, although the
26105 @value{GDBN} input and output session proceeds normally, the auxiliary
26106 buffer does not display the current source and line of execution.
26108 The initial working directory of @value{GDBN} is printed on the top
26109 line of the GUD buffer and this serves as a default for the commands
26110 that specify files for @value{GDBN} to operate on. @xref{Files,
26111 ,Commands to Specify Files}.
26113 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26114 need to call @value{GDBN} by a different name (for example, if you
26115 keep several configurations around, with different names) you can
26116 customize the Emacs variable @code{gud-gdb-command-name} to run the
26119 In the GUD buffer, you can use these special Emacs commands in
26120 addition to the standard Shell mode commands:
26124 Describe the features of Emacs' GUD Mode.
26127 Execute to another source line, like the @value{GDBN} @code{step} command; also
26128 update the display window to show the current file and location.
26131 Execute to next source line in this function, skipping all function
26132 calls, like the @value{GDBN} @code{next} command. Then update the display window
26133 to show the current file and location.
26136 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26137 display window accordingly.
26140 Execute until exit from the selected stack frame, like the @value{GDBN}
26141 @code{finish} command.
26144 Continue execution of your program, like the @value{GDBN} @code{continue}
26148 Go up the number of frames indicated by the numeric argument
26149 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26150 like the @value{GDBN} @code{up} command.
26153 Go down the number of frames indicated by the numeric argument, like the
26154 @value{GDBN} @code{down} command.
26157 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26158 tells @value{GDBN} to set a breakpoint on the source line point is on.
26160 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26161 separate frame which shows a backtrace when the GUD buffer is current.
26162 Move point to any frame in the stack and type @key{RET} to make it
26163 become the current frame and display the associated source in the
26164 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26165 selected frame become the current one. In graphical mode, the
26166 speedbar displays watch expressions.
26168 If you accidentally delete the source-display buffer, an easy way to get
26169 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26170 request a frame display; when you run under Emacs, this recreates
26171 the source buffer if necessary to show you the context of the current
26174 The source files displayed in Emacs are in ordinary Emacs buffers
26175 which are visiting the source files in the usual way. You can edit
26176 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26177 communicates with Emacs in terms of line numbers. If you add or
26178 delete lines from the text, the line numbers that @value{GDBN} knows cease
26179 to correspond properly with the code.
26181 A more detailed description of Emacs' interaction with @value{GDBN} is
26182 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26186 @chapter The @sc{gdb/mi} Interface
26188 @unnumberedsec Function and Purpose
26190 @cindex @sc{gdb/mi}, its purpose
26191 @sc{gdb/mi} is a line based machine oriented text interface to
26192 @value{GDBN} and is activated by specifying using the
26193 @option{--interpreter} command line option (@pxref{Mode Options}). It
26194 is specifically intended to support the development of systems which
26195 use the debugger as just one small component of a larger system.
26197 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26198 in the form of a reference manual.
26200 Note that @sc{gdb/mi} is still under construction, so some of the
26201 features described below are incomplete and subject to change
26202 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26204 @unnumberedsec Notation and Terminology
26206 @cindex notational conventions, for @sc{gdb/mi}
26207 This chapter uses the following notation:
26211 @code{|} separates two alternatives.
26214 @code{[ @var{something} ]} indicates that @var{something} is optional:
26215 it may or may not be given.
26218 @code{( @var{group} )*} means that @var{group} inside the parentheses
26219 may repeat zero or more times.
26222 @code{( @var{group} )+} means that @var{group} inside the parentheses
26223 may repeat one or more times.
26226 @code{"@var{string}"} means a literal @var{string}.
26230 @heading Dependencies
26234 * GDB/MI General Design::
26235 * GDB/MI Command Syntax::
26236 * GDB/MI Compatibility with CLI::
26237 * GDB/MI Development and Front Ends::
26238 * GDB/MI Output Records::
26239 * GDB/MI Simple Examples::
26240 * GDB/MI Command Description Format::
26241 * GDB/MI Breakpoint Commands::
26242 * GDB/MI Catchpoint Commands::
26243 * GDB/MI Program Context::
26244 * GDB/MI Thread Commands::
26245 * GDB/MI Ada Tasking Commands::
26246 * GDB/MI Program Execution::
26247 * GDB/MI Stack Manipulation::
26248 * GDB/MI Variable Objects::
26249 * GDB/MI Data Manipulation::
26250 * GDB/MI Tracepoint Commands::
26251 * GDB/MI Symbol Query::
26252 * GDB/MI File Commands::
26254 * GDB/MI Kod Commands::
26255 * GDB/MI Memory Overlay Commands::
26256 * GDB/MI Signal Handling Commands::
26258 * GDB/MI Target Manipulation::
26259 * GDB/MI File Transfer Commands::
26260 * GDB/MI Ada Exceptions Commands::
26261 * GDB/MI Support Commands::
26262 * GDB/MI Miscellaneous Commands::
26265 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26266 @node GDB/MI General Design
26267 @section @sc{gdb/mi} General Design
26268 @cindex GDB/MI General Design
26270 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26271 parts---commands sent to @value{GDBN}, responses to those commands
26272 and notifications. Each command results in exactly one response,
26273 indicating either successful completion of the command, or an error.
26274 For the commands that do not resume the target, the response contains the
26275 requested information. For the commands that resume the target, the
26276 response only indicates whether the target was successfully resumed.
26277 Notifications is the mechanism for reporting changes in the state of the
26278 target, or in @value{GDBN} state, that cannot conveniently be associated with
26279 a command and reported as part of that command response.
26281 The important examples of notifications are:
26285 Exec notifications. These are used to report changes in
26286 target state---when a target is resumed, or stopped. It would not
26287 be feasible to include this information in response of resuming
26288 commands, because one resume commands can result in multiple events in
26289 different threads. Also, quite some time may pass before any event
26290 happens in the target, while a frontend needs to know whether the resuming
26291 command itself was successfully executed.
26294 Console output, and status notifications. Console output
26295 notifications are used to report output of CLI commands, as well as
26296 diagnostics for other commands. Status notifications are used to
26297 report the progress of a long-running operation. Naturally, including
26298 this information in command response would mean no output is produced
26299 until the command is finished, which is undesirable.
26302 General notifications. Commands may have various side effects on
26303 the @value{GDBN} or target state beyond their official purpose. For example,
26304 a command may change the selected thread. Although such changes can
26305 be included in command response, using notification allows for more
26306 orthogonal frontend design.
26310 There's no guarantee that whenever an MI command reports an error,
26311 @value{GDBN} or the target are in any specific state, and especially,
26312 the state is not reverted to the state before the MI command was
26313 processed. Therefore, whenever an MI command results in an error,
26314 we recommend that the frontend refreshes all the information shown in
26315 the user interface.
26319 * Context management::
26320 * Asynchronous and non-stop modes::
26324 @node Context management
26325 @subsection Context management
26327 @subsubsection Threads and Frames
26329 In most cases when @value{GDBN} accesses the target, this access is
26330 done in context of a specific thread and frame (@pxref{Frames}).
26331 Often, even when accessing global data, the target requires that a thread
26332 be specified. The CLI interface maintains the selected thread and frame,
26333 and supplies them to target on each command. This is convenient,
26334 because a command line user would not want to specify that information
26335 explicitly on each command, and because user interacts with
26336 @value{GDBN} via a single terminal, so no confusion is possible as
26337 to what thread and frame are the current ones.
26339 In the case of MI, the concept of selected thread and frame is less
26340 useful. First, a frontend can easily remember this information
26341 itself. Second, a graphical frontend can have more than one window,
26342 each one used for debugging a different thread, and the frontend might
26343 want to access additional threads for internal purposes. This
26344 increases the risk that by relying on implicitly selected thread, the
26345 frontend may be operating on a wrong one. Therefore, each MI command
26346 should explicitly specify which thread and frame to operate on. To
26347 make it possible, each MI command accepts the @samp{--thread} and
26348 @samp{--frame} options, the value to each is @value{GDBN} global
26349 identifier for thread and frame to operate on.
26351 Usually, each top-level window in a frontend allows the user to select
26352 a thread and a frame, and remembers the user selection for further
26353 operations. However, in some cases @value{GDBN} may suggest that the
26354 current thread or frame be changed. For example, when stopping on a
26355 breakpoint it is reasonable to switch to the thread where breakpoint is
26356 hit. For another example, if the user issues the CLI @samp{thread} or
26357 @samp{frame} commands via the frontend, it is desirable to change the
26358 frontend's selection to the one specified by user. @value{GDBN}
26359 communicates the suggestion to change current thread and frame using the
26360 @samp{=thread-selected} notification.
26362 Note that historically, MI shares the selected thread with CLI, so
26363 frontends used the @code{-thread-select} to execute commands in the
26364 right context. However, getting this to work right is cumbersome. The
26365 simplest way is for frontend to emit @code{-thread-select} command
26366 before every command. This doubles the number of commands that need
26367 to be sent. The alternative approach is to suppress @code{-thread-select}
26368 if the selected thread in @value{GDBN} is supposed to be identical to the
26369 thread the frontend wants to operate on. However, getting this
26370 optimization right can be tricky. In particular, if the frontend
26371 sends several commands to @value{GDBN}, and one of the commands changes the
26372 selected thread, then the behaviour of subsequent commands will
26373 change. So, a frontend should either wait for response from such
26374 problematic commands, or explicitly add @code{-thread-select} for
26375 all subsequent commands. No frontend is known to do this exactly
26376 right, so it is suggested to just always pass the @samp{--thread} and
26377 @samp{--frame} options.
26379 @subsubsection Language
26381 The execution of several commands depends on which language is selected.
26382 By default, the current language (@pxref{show language}) is used.
26383 But for commands known to be language-sensitive, it is recommended
26384 to use the @samp{--language} option. This option takes one argument,
26385 which is the name of the language to use while executing the command.
26389 -data-evaluate-expression --language c "sizeof (void*)"
26394 The valid language names are the same names accepted by the
26395 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26396 @samp{local} or @samp{unknown}.
26398 @node Asynchronous and non-stop modes
26399 @subsection Asynchronous command execution and non-stop mode
26401 On some targets, @value{GDBN} is capable of processing MI commands
26402 even while the target is running. This is called @dfn{asynchronous
26403 command execution} (@pxref{Background Execution}). The frontend may
26404 specify a preferrence for asynchronous execution using the
26405 @code{-gdb-set mi-async 1} command, which should be emitted before
26406 either running the executable or attaching to the target. After the
26407 frontend has started the executable or attached to the target, it can
26408 find if asynchronous execution is enabled using the
26409 @code{-list-target-features} command.
26412 @item -gdb-set mi-async on
26413 @item -gdb-set mi-async off
26414 Set whether MI is in asynchronous mode.
26416 When @code{off}, which is the default, MI execution commands (e.g.,
26417 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26418 for the program to stop before processing further commands.
26420 When @code{on}, MI execution commands are background execution
26421 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26422 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26423 MI commands even while the target is running.
26425 @item -gdb-show mi-async
26426 Show whether MI asynchronous mode is enabled.
26429 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26430 @code{target-async} instead of @code{mi-async}, and it had the effect
26431 of both putting MI in asynchronous mode and making CLI background
26432 commands possible. CLI background commands are now always possible
26433 ``out of the box'' if the target supports them. The old spelling is
26434 kept as a deprecated alias for backwards compatibility.
26436 Even if @value{GDBN} can accept a command while target is running,
26437 many commands that access the target do not work when the target is
26438 running. Therefore, asynchronous command execution is most useful
26439 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26440 it is possible to examine the state of one thread, while other threads
26443 When a given thread is running, MI commands that try to access the
26444 target in the context of that thread may not work, or may work only on
26445 some targets. In particular, commands that try to operate on thread's
26446 stack will not work, on any target. Commands that read memory, or
26447 modify breakpoints, may work or not work, depending on the target. Note
26448 that even commands that operate on global state, such as @code{print},
26449 @code{set}, and breakpoint commands, still access the target in the
26450 context of a specific thread, so frontend should try to find a
26451 stopped thread and perform the operation on that thread (using the
26452 @samp{--thread} option).
26454 Which commands will work in the context of a running thread is
26455 highly target dependent. However, the two commands
26456 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26457 to find the state of a thread, will always work.
26459 @node Thread groups
26460 @subsection Thread groups
26461 @value{GDBN} may be used to debug several processes at the same time.
26462 On some platfroms, @value{GDBN} may support debugging of several
26463 hardware systems, each one having several cores with several different
26464 processes running on each core. This section describes the MI
26465 mechanism to support such debugging scenarios.
26467 The key observation is that regardless of the structure of the
26468 target, MI can have a global list of threads, because most commands that
26469 accept the @samp{--thread} option do not need to know what process that
26470 thread belongs to. Therefore, it is not necessary to introduce
26471 neither additional @samp{--process} option, nor an notion of the
26472 current process in the MI interface. The only strictly new feature
26473 that is required is the ability to find how the threads are grouped
26476 To allow the user to discover such grouping, and to support arbitrary
26477 hierarchy of machines/cores/processes, MI introduces the concept of a
26478 @dfn{thread group}. Thread group is a collection of threads and other
26479 thread groups. A thread group always has a string identifier, a type,
26480 and may have additional attributes specific to the type. A new
26481 command, @code{-list-thread-groups}, returns the list of top-level
26482 thread groups, which correspond to processes that @value{GDBN} is
26483 debugging at the moment. By passing an identifier of a thread group
26484 to the @code{-list-thread-groups} command, it is possible to obtain
26485 the members of specific thread group.
26487 To allow the user to easily discover processes, and other objects, he
26488 wishes to debug, a concept of @dfn{available thread group} is
26489 introduced. Available thread group is an thread group that
26490 @value{GDBN} is not debugging, but that can be attached to, using the
26491 @code{-target-attach} command. The list of available top-level thread
26492 groups can be obtained using @samp{-list-thread-groups --available}.
26493 In general, the content of a thread group may be only retrieved only
26494 after attaching to that thread group.
26496 Thread groups are related to inferiors (@pxref{Inferiors and
26497 Programs}). Each inferior corresponds to a thread group of a special
26498 type @samp{process}, and some additional operations are permitted on
26499 such thread groups.
26501 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26502 @node GDB/MI Command Syntax
26503 @section @sc{gdb/mi} Command Syntax
26506 * GDB/MI Input Syntax::
26507 * GDB/MI Output Syntax::
26510 @node GDB/MI Input Syntax
26511 @subsection @sc{gdb/mi} Input Syntax
26513 @cindex input syntax for @sc{gdb/mi}
26514 @cindex @sc{gdb/mi}, input syntax
26516 @item @var{command} @expansion{}
26517 @code{@var{cli-command} | @var{mi-command}}
26519 @item @var{cli-command} @expansion{}
26520 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26521 @var{cli-command} is any existing @value{GDBN} CLI command.
26523 @item @var{mi-command} @expansion{}
26524 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26525 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26527 @item @var{token} @expansion{}
26528 "any sequence of digits"
26530 @item @var{option} @expansion{}
26531 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26533 @item @var{parameter} @expansion{}
26534 @code{@var{non-blank-sequence} | @var{c-string}}
26536 @item @var{operation} @expansion{}
26537 @emph{any of the operations described in this chapter}
26539 @item @var{non-blank-sequence} @expansion{}
26540 @emph{anything, provided it doesn't contain special characters such as
26541 "-", @var{nl}, """ and of course " "}
26543 @item @var{c-string} @expansion{}
26544 @code{""" @var{seven-bit-iso-c-string-content} """}
26546 @item @var{nl} @expansion{}
26555 The CLI commands are still handled by the @sc{mi} interpreter; their
26556 output is described below.
26559 The @code{@var{token}}, when present, is passed back when the command
26563 Some @sc{mi} commands accept optional arguments as part of the parameter
26564 list. Each option is identified by a leading @samp{-} (dash) and may be
26565 followed by an optional argument parameter. Options occur first in the
26566 parameter list and can be delimited from normal parameters using
26567 @samp{--} (this is useful when some parameters begin with a dash).
26574 We want easy access to the existing CLI syntax (for debugging).
26577 We want it to be easy to spot a @sc{mi} operation.
26580 @node GDB/MI Output Syntax
26581 @subsection @sc{gdb/mi} Output Syntax
26583 @cindex output syntax of @sc{gdb/mi}
26584 @cindex @sc{gdb/mi}, output syntax
26585 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26586 followed, optionally, by a single result record. This result record
26587 is for the most recent command. The sequence of output records is
26588 terminated by @samp{(gdb)}.
26590 If an input command was prefixed with a @code{@var{token}} then the
26591 corresponding output for that command will also be prefixed by that same
26595 @item @var{output} @expansion{}
26596 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26598 @item @var{result-record} @expansion{}
26599 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26601 @item @var{out-of-band-record} @expansion{}
26602 @code{@var{async-record} | @var{stream-record}}
26604 @item @var{async-record} @expansion{}
26605 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26607 @item @var{exec-async-output} @expansion{}
26608 @code{[ @var{token} ] "*" @var{async-output nl}}
26610 @item @var{status-async-output} @expansion{}
26611 @code{[ @var{token} ] "+" @var{async-output nl}}
26613 @item @var{notify-async-output} @expansion{}
26614 @code{[ @var{token} ] "=" @var{async-output nl}}
26616 @item @var{async-output} @expansion{}
26617 @code{@var{async-class} ( "," @var{result} )*}
26619 @item @var{result-class} @expansion{}
26620 @code{"done" | "running" | "connected" | "error" | "exit"}
26622 @item @var{async-class} @expansion{}
26623 @code{"stopped" | @var{others}} (where @var{others} will be added
26624 depending on the needs---this is still in development).
26626 @item @var{result} @expansion{}
26627 @code{ @var{variable} "=" @var{value}}
26629 @item @var{variable} @expansion{}
26630 @code{ @var{string} }
26632 @item @var{value} @expansion{}
26633 @code{ @var{const} | @var{tuple} | @var{list} }
26635 @item @var{const} @expansion{}
26636 @code{@var{c-string}}
26638 @item @var{tuple} @expansion{}
26639 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26641 @item @var{list} @expansion{}
26642 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26643 @var{result} ( "," @var{result} )* "]" }
26645 @item @var{stream-record} @expansion{}
26646 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26648 @item @var{console-stream-output} @expansion{}
26649 @code{"~" @var{c-string nl}}
26651 @item @var{target-stream-output} @expansion{}
26652 @code{"@@" @var{c-string nl}}
26654 @item @var{log-stream-output} @expansion{}
26655 @code{"&" @var{c-string nl}}
26657 @item @var{nl} @expansion{}
26660 @item @var{token} @expansion{}
26661 @emph{any sequence of digits}.
26669 All output sequences end in a single line containing a period.
26672 The @code{@var{token}} is from the corresponding request. Note that
26673 for all async output, while the token is allowed by the grammar and
26674 may be output by future versions of @value{GDBN} for select async
26675 output messages, it is generally omitted. Frontends should treat
26676 all async output as reporting general changes in the state of the
26677 target and there should be no need to associate async output to any
26681 @cindex status output in @sc{gdb/mi}
26682 @var{status-async-output} contains on-going status information about the
26683 progress of a slow operation. It can be discarded. All status output is
26684 prefixed by @samp{+}.
26687 @cindex async output in @sc{gdb/mi}
26688 @var{exec-async-output} contains asynchronous state change on the target
26689 (stopped, started, disappeared). All async output is prefixed by
26693 @cindex notify output in @sc{gdb/mi}
26694 @var{notify-async-output} contains supplementary information that the
26695 client should handle (e.g., a new breakpoint information). All notify
26696 output is prefixed by @samp{=}.
26699 @cindex console output in @sc{gdb/mi}
26700 @var{console-stream-output} is output that should be displayed as is in the
26701 console. It is the textual response to a CLI command. All the console
26702 output is prefixed by @samp{~}.
26705 @cindex target output in @sc{gdb/mi}
26706 @var{target-stream-output} is the output produced by the target program.
26707 All the target output is prefixed by @samp{@@}.
26710 @cindex log output in @sc{gdb/mi}
26711 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26712 instance messages that should be displayed as part of an error log. All
26713 the log output is prefixed by @samp{&}.
26716 @cindex list output in @sc{gdb/mi}
26717 New @sc{gdb/mi} commands should only output @var{lists} containing
26723 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26724 details about the various output records.
26726 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26727 @node GDB/MI Compatibility with CLI
26728 @section @sc{gdb/mi} Compatibility with CLI
26730 @cindex compatibility, @sc{gdb/mi} and CLI
26731 @cindex @sc{gdb/mi}, compatibility with CLI
26733 For the developers convenience CLI commands can be entered directly,
26734 but there may be some unexpected behaviour. For example, commands
26735 that query the user will behave as if the user replied yes, breakpoint
26736 command lists are not executed and some CLI commands, such as
26737 @code{if}, @code{when} and @code{define}, prompt for further input with
26738 @samp{>}, which is not valid MI output.
26740 This feature may be removed at some stage in the future and it is
26741 recommended that front ends use the @code{-interpreter-exec} command
26742 (@pxref{-interpreter-exec}).
26744 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26745 @node GDB/MI Development and Front Ends
26746 @section @sc{gdb/mi} Development and Front Ends
26747 @cindex @sc{gdb/mi} development
26749 The application which takes the MI output and presents the state of the
26750 program being debugged to the user is called a @dfn{front end}.
26752 Although @sc{gdb/mi} is still incomplete, it is currently being used
26753 by a variety of front ends to @value{GDBN}. This makes it difficult
26754 to introduce new functionality without breaking existing usage. This
26755 section tries to minimize the problems by describing how the protocol
26758 Some changes in MI need not break a carefully designed front end, and
26759 for these the MI version will remain unchanged. The following is a
26760 list of changes that may occur within one level, so front ends should
26761 parse MI output in a way that can handle them:
26765 New MI commands may be added.
26768 New fields may be added to the output of any MI command.
26771 The range of values for fields with specified values, e.g.,
26772 @code{in_scope} (@pxref{-var-update}) may be extended.
26774 @c The format of field's content e.g type prefix, may change so parse it
26775 @c at your own risk. Yes, in general?
26777 @c The order of fields may change? Shouldn't really matter but it might
26778 @c resolve inconsistencies.
26781 If the changes are likely to break front ends, the MI version level
26782 will be increased by one. This will allow the front end to parse the
26783 output according to the MI version. Apart from mi0, new versions of
26784 @value{GDBN} will not support old versions of MI and it will be the
26785 responsibility of the front end to work with the new one.
26787 @c Starting with mi3, add a new command -mi-version that prints the MI
26790 The best way to avoid unexpected changes in MI that might break your front
26791 end is to make your project known to @value{GDBN} developers and
26792 follow development on @email{gdb@@sourceware.org} and
26793 @email{gdb-patches@@sourceware.org}.
26794 @cindex mailing lists
26796 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26797 @node GDB/MI Output Records
26798 @section @sc{gdb/mi} Output Records
26801 * GDB/MI Result Records::
26802 * GDB/MI Stream Records::
26803 * GDB/MI Async Records::
26804 * GDB/MI Breakpoint Information::
26805 * GDB/MI Frame Information::
26806 * GDB/MI Thread Information::
26807 * GDB/MI Ada Exception Information::
26810 @node GDB/MI Result Records
26811 @subsection @sc{gdb/mi} Result Records
26813 @cindex result records in @sc{gdb/mi}
26814 @cindex @sc{gdb/mi}, result records
26815 In addition to a number of out-of-band notifications, the response to a
26816 @sc{gdb/mi} command includes one of the following result indications:
26820 @item "^done" [ "," @var{results} ]
26821 The synchronous operation was successful, @code{@var{results}} are the return
26826 This result record is equivalent to @samp{^done}. Historically, it
26827 was output instead of @samp{^done} if the command has resumed the
26828 target. This behaviour is maintained for backward compatibility, but
26829 all frontends should treat @samp{^done} and @samp{^running}
26830 identically and rely on the @samp{*running} output record to determine
26831 which threads are resumed.
26835 @value{GDBN} has connected to a remote target.
26837 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26839 The operation failed. The @code{msg=@var{c-string}} variable contains
26840 the corresponding error message.
26842 If present, the @code{code=@var{c-string}} variable provides an error
26843 code on which consumers can rely on to detect the corresponding
26844 error condition. At present, only one error code is defined:
26847 @item "undefined-command"
26848 Indicates that the command causing the error does not exist.
26853 @value{GDBN} has terminated.
26857 @node GDB/MI Stream Records
26858 @subsection @sc{gdb/mi} Stream Records
26860 @cindex @sc{gdb/mi}, stream records
26861 @cindex stream records in @sc{gdb/mi}
26862 @value{GDBN} internally maintains a number of output streams: the console, the
26863 target, and the log. The output intended for each of these streams is
26864 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26866 Each stream record begins with a unique @dfn{prefix character} which
26867 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26868 Syntax}). In addition to the prefix, each stream record contains a
26869 @code{@var{string-output}}. This is either raw text (with an implicit new
26870 line) or a quoted C string (which does not contain an implicit newline).
26873 @item "~" @var{string-output}
26874 The console output stream contains text that should be displayed in the
26875 CLI console window. It contains the textual responses to CLI commands.
26877 @item "@@" @var{string-output}
26878 The target output stream contains any textual output from the running
26879 target. This is only present when GDB's event loop is truly
26880 asynchronous, which is currently only the case for remote targets.
26882 @item "&" @var{string-output}
26883 The log stream contains debugging messages being produced by @value{GDBN}'s
26887 @node GDB/MI Async Records
26888 @subsection @sc{gdb/mi} Async Records
26890 @cindex async records in @sc{gdb/mi}
26891 @cindex @sc{gdb/mi}, async records
26892 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26893 additional changes that have occurred. Those changes can either be a
26894 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26895 target activity (e.g., target stopped).
26897 The following is the list of possible async records:
26901 @item *running,thread-id="@var{thread}"
26902 The target is now running. The @var{thread} field can be the global
26903 thread ID of the the thread that is now running, and it can be
26904 @samp{all} if all threads are running. The frontend should assume
26905 that no interaction with a running thread is possible after this
26906 notification is produced. The frontend should not assume that this
26907 notification is output only once for any command. @value{GDBN} may
26908 emit this notification several times, either for different threads,
26909 because it cannot resume all threads together, or even for a single
26910 thread, if the thread must be stepped though some code before letting
26913 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26914 The target has stopped. The @var{reason} field can have one of the
26918 @item breakpoint-hit
26919 A breakpoint was reached.
26920 @item watchpoint-trigger
26921 A watchpoint was triggered.
26922 @item read-watchpoint-trigger
26923 A read watchpoint was triggered.
26924 @item access-watchpoint-trigger
26925 An access watchpoint was triggered.
26926 @item function-finished
26927 An -exec-finish or similar CLI command was accomplished.
26928 @item location-reached
26929 An -exec-until or similar CLI command was accomplished.
26930 @item watchpoint-scope
26931 A watchpoint has gone out of scope.
26932 @item end-stepping-range
26933 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26934 similar CLI command was accomplished.
26935 @item exited-signalled
26936 The inferior exited because of a signal.
26938 The inferior exited.
26939 @item exited-normally
26940 The inferior exited normally.
26941 @item signal-received
26942 A signal was received by the inferior.
26944 The inferior has stopped due to a library being loaded or unloaded.
26945 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26946 set or when a @code{catch load} or @code{catch unload} catchpoint is
26947 in use (@pxref{Set Catchpoints}).
26949 The inferior has forked. This is reported when @code{catch fork}
26950 (@pxref{Set Catchpoints}) has been used.
26952 The inferior has vforked. This is reported in when @code{catch vfork}
26953 (@pxref{Set Catchpoints}) has been used.
26954 @item syscall-entry
26955 The inferior entered a system call. This is reported when @code{catch
26956 syscall} (@pxref{Set Catchpoints}) has been used.
26957 @item syscall-return
26958 The inferior returned from a system call. This is reported when
26959 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26961 The inferior called @code{exec}. This is reported when @code{catch exec}
26962 (@pxref{Set Catchpoints}) has been used.
26965 The @var{id} field identifies the global thread ID of the thread
26966 that directly caused the stop -- for example by hitting a breakpoint.
26967 Depending on whether all-stop
26968 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26969 stop all threads, or only the thread that directly triggered the stop.
26970 If all threads are stopped, the @var{stopped} field will have the
26971 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26972 field will be a list of thread identifiers. Presently, this list will
26973 always include a single thread, but frontend should be prepared to see
26974 several threads in the list. The @var{core} field reports the
26975 processor core on which the stop event has happened. This field may be absent
26976 if such information is not available.
26978 @item =thread-group-added,id="@var{id}"
26979 @itemx =thread-group-removed,id="@var{id}"
26980 A thread group was either added or removed. The @var{id} field
26981 contains the @value{GDBN} identifier of the thread group. When a thread
26982 group is added, it generally might not be associated with a running
26983 process. When a thread group is removed, its id becomes invalid and
26984 cannot be used in any way.
26986 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26987 A thread group became associated with a running program,
26988 either because the program was just started or the thread group
26989 was attached to a program. The @var{id} field contains the
26990 @value{GDBN} identifier of the thread group. The @var{pid} field
26991 contains process identifier, specific to the operating system.
26993 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26994 A thread group is no longer associated with a running program,
26995 either because the program has exited, or because it was detached
26996 from. The @var{id} field contains the @value{GDBN} identifier of the
26997 thread group. The @var{code} field is the exit code of the inferior; it exists
26998 only when the inferior exited with some code.
27000 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27001 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27002 A thread either was created, or has exited. The @var{id} field
27003 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27004 field identifies the thread group this thread belongs to.
27006 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27007 Informs that the selected thread or frame were changed. This notification
27008 is not emitted as result of the @code{-thread-select} or
27009 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27010 that is not documented to change the selected thread and frame actually
27011 changes them. In particular, invoking, directly or indirectly
27012 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27013 will generate this notification. Changing the thread or frame from another
27014 user interface (see @ref{Interpreters}) will also generate this notification.
27016 The @var{frame} field is only present if the newly selected thread is
27017 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27019 We suggest that in response to this notification, front ends
27020 highlight the selected thread and cause subsequent commands to apply to
27023 @item =library-loaded,...
27024 Reports that a new library file was loaded by the program. This
27025 notification has 5 fields---@var{id}, @var{target-name},
27026 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27027 opaque identifier of the library. For remote debugging case,
27028 @var{target-name} and @var{host-name} fields give the name of the
27029 library file on the target, and on the host respectively. For native
27030 debugging, both those fields have the same value. The
27031 @var{symbols-loaded} field is emitted only for backward compatibility
27032 and should not be relied on to convey any useful information. The
27033 @var{thread-group} field, if present, specifies the id of the thread
27034 group in whose context the library was loaded. If the field is
27035 absent, it means the library was loaded in the context of all present
27036 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27039 @item =library-unloaded,...
27040 Reports that a library was unloaded by the program. This notification
27041 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27042 the same meaning as for the @code{=library-loaded} notification.
27043 The @var{thread-group} field, if present, specifies the id of the
27044 thread group in whose context the library was unloaded. If the field is
27045 absent, it means the library was unloaded in the context of all present
27048 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27049 @itemx =traceframe-changed,end
27050 Reports that the trace frame was changed and its new number is
27051 @var{tfnum}. The number of the tracepoint associated with this trace
27052 frame is @var{tpnum}.
27054 @item =tsv-created,name=@var{name},initial=@var{initial}
27055 Reports that the new trace state variable @var{name} is created with
27056 initial value @var{initial}.
27058 @item =tsv-deleted,name=@var{name}
27059 @itemx =tsv-deleted
27060 Reports that the trace state variable @var{name} is deleted or all
27061 trace state variables are deleted.
27063 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27064 Reports that the trace state variable @var{name} is modified with
27065 the initial value @var{initial}. The current value @var{current} of
27066 trace state variable is optional and is reported if the current
27067 value of trace state variable is known.
27069 @item =breakpoint-created,bkpt=@{...@}
27070 @itemx =breakpoint-modified,bkpt=@{...@}
27071 @itemx =breakpoint-deleted,id=@var{number}
27072 Reports that a breakpoint was created, modified, or deleted,
27073 respectively. Only user-visible breakpoints are reported to the MI
27076 The @var{bkpt} argument is of the same form as returned by the various
27077 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27078 @var{number} is the ordinal number of the breakpoint.
27080 Note that if a breakpoint is emitted in the result record of a
27081 command, then it will not also be emitted in an async record.
27083 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27084 @itemx =record-stopped,thread-group="@var{id}"
27085 Execution log recording was either started or stopped on an
27086 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27087 group corresponding to the affected inferior.
27089 The @var{method} field indicates the method used to record execution. If the
27090 method in use supports multiple recording formats, @var{format} will be present
27091 and contain the currently used format. @xref{Process Record and Replay},
27092 for existing method and format values.
27094 @item =cmd-param-changed,param=@var{param},value=@var{value}
27095 Reports that a parameter of the command @code{set @var{param}} is
27096 changed to @var{value}. In the multi-word @code{set} command,
27097 the @var{param} is the whole parameter list to @code{set} command.
27098 For example, In command @code{set check type on}, @var{param}
27099 is @code{check type} and @var{value} is @code{on}.
27101 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27102 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27103 written in an inferior. The @var{id} is the identifier of the
27104 thread group corresponding to the affected inferior. The optional
27105 @code{type="code"} part is reported if the memory written to holds
27109 @node GDB/MI Breakpoint Information
27110 @subsection @sc{gdb/mi} Breakpoint Information
27112 When @value{GDBN} reports information about a breakpoint, a
27113 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27118 The breakpoint number. For a breakpoint that represents one location
27119 of a multi-location breakpoint, this will be a dotted pair, like
27123 The type of the breakpoint. For ordinary breakpoints this will be
27124 @samp{breakpoint}, but many values are possible.
27127 If the type of the breakpoint is @samp{catchpoint}, then this
27128 indicates the exact type of catchpoint.
27131 This is the breakpoint disposition---either @samp{del}, meaning that
27132 the breakpoint will be deleted at the next stop, or @samp{keep},
27133 meaning that the breakpoint will not be deleted.
27136 This indicates whether the breakpoint is enabled, in which case the
27137 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27138 Note that this is not the same as the field @code{enable}.
27141 The address of the breakpoint. This may be a hexidecimal number,
27142 giving the address; or the string @samp{<PENDING>}, for a pending
27143 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27144 multiple locations. This field will not be present if no address can
27145 be determined. For example, a watchpoint does not have an address.
27148 If known, the function in which the breakpoint appears.
27149 If not known, this field is not present.
27152 The name of the source file which contains this function, if known.
27153 If not known, this field is not present.
27156 The full file name of the source file which contains this function, if
27157 known. If not known, this field is not present.
27160 The line number at which this breakpoint appears, if known.
27161 If not known, this field is not present.
27164 If the source file is not known, this field may be provided. If
27165 provided, this holds the address of the breakpoint, possibly followed
27169 If this breakpoint is pending, this field is present and holds the
27170 text used to set the breakpoint, as entered by the user.
27173 Where this breakpoint's condition is evaluated, either @samp{host} or
27177 If this is a thread-specific breakpoint, then this identifies the
27178 thread in which the breakpoint can trigger.
27181 If this breakpoint is restricted to a particular Ada task, then this
27182 field will hold the task identifier.
27185 If the breakpoint is conditional, this is the condition expression.
27188 The ignore count of the breakpoint.
27191 The enable count of the breakpoint.
27193 @item traceframe-usage
27196 @item static-tracepoint-marker-string-id
27197 For a static tracepoint, the name of the static tracepoint marker.
27200 For a masked watchpoint, this is the mask.
27203 A tracepoint's pass count.
27205 @item original-location
27206 The location of the breakpoint as originally specified by the user.
27207 This field is optional.
27210 The number of times the breakpoint has been hit.
27213 This field is only given for tracepoints. This is either @samp{y},
27214 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27218 Some extra data, the exact contents of which are type-dependent.
27222 For example, here is what the output of @code{-break-insert}
27223 (@pxref{GDB/MI Breakpoint Commands}) might be:
27226 -> -break-insert main
27227 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27228 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27229 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27234 @node GDB/MI Frame Information
27235 @subsection @sc{gdb/mi} Frame Information
27237 Response from many MI commands includes an information about stack
27238 frame. This information is a tuple that may have the following
27243 The level of the stack frame. The innermost frame has the level of
27244 zero. This field is always present.
27247 The name of the function corresponding to the frame. This field may
27248 be absent if @value{GDBN} is unable to determine the function name.
27251 The code address for the frame. This field is always present.
27254 The name of the source files that correspond to the frame's code
27255 address. This field may be absent.
27258 The source line corresponding to the frames' code address. This field
27262 The name of the binary file (either executable or shared library) the
27263 corresponds to the frame's code address. This field may be absent.
27267 @node GDB/MI Thread Information
27268 @subsection @sc{gdb/mi} Thread Information
27270 Whenever @value{GDBN} has to report an information about a thread, it
27271 uses a tuple with the following fields. The fields are always present unless
27276 The global numeric id assigned to the thread by @value{GDBN}.
27279 The target-specific string identifying the thread.
27282 Additional information about the thread provided by the target.
27283 It is supposed to be human-readable and not interpreted by the
27284 frontend. This field is optional.
27287 The name of the thread. If the user specified a name using the
27288 @code{thread name} command, then this name is given. Otherwise, if
27289 @value{GDBN} can extract the thread name from the target, then that
27290 name is given. If @value{GDBN} cannot find the thread name, then this
27294 The execution state of the thread, either @samp{stopped} or @samp{running},
27295 depending on whether the thread is presently running.
27298 The stack frame currently executing in the thread. This field is only present
27299 if the thread is stopped. Its format is documented in
27300 @ref{GDB/MI Frame Information}.
27303 The value of this field is an integer number of the processor core the
27304 thread was last seen on. This field is optional.
27307 @node GDB/MI Ada Exception Information
27308 @subsection @sc{gdb/mi} Ada Exception Information
27310 Whenever a @code{*stopped} record is emitted because the program
27311 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27312 @value{GDBN} provides the name of the exception that was raised via
27313 the @code{exception-name} field. Also, for exceptions that were raised
27314 with an exception message, @value{GDBN} provides that message via
27315 the @code{exception-message} field.
27317 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27318 @node GDB/MI Simple Examples
27319 @section Simple Examples of @sc{gdb/mi} Interaction
27320 @cindex @sc{gdb/mi}, simple examples
27322 This subsection presents several simple examples of interaction using
27323 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27324 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27325 the output received from @sc{gdb/mi}.
27327 Note the line breaks shown in the examples are here only for
27328 readability, they don't appear in the real output.
27330 @subheading Setting a Breakpoint
27332 Setting a breakpoint generates synchronous output which contains detailed
27333 information of the breakpoint.
27336 -> -break-insert main
27337 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27338 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27339 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27344 @subheading Program Execution
27346 Program execution generates asynchronous records and MI gives the
27347 reason that execution stopped.
27353 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27354 frame=@{addr="0x08048564",func="main",
27355 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27356 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27361 <- *stopped,reason="exited-normally"
27365 @subheading Quitting @value{GDBN}
27367 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27375 Please note that @samp{^exit} is printed immediately, but it might
27376 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27377 performs necessary cleanups, including killing programs being debugged
27378 or disconnecting from debug hardware, so the frontend should wait till
27379 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27380 fails to exit in reasonable time.
27382 @subheading A Bad Command
27384 Here's what happens if you pass a non-existent command:
27388 <- ^error,msg="Undefined MI command: rubbish"
27393 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27394 @node GDB/MI Command Description Format
27395 @section @sc{gdb/mi} Command Description Format
27397 The remaining sections describe blocks of commands. Each block of
27398 commands is laid out in a fashion similar to this section.
27400 @subheading Motivation
27402 The motivation for this collection of commands.
27404 @subheading Introduction
27406 A brief introduction to this collection of commands as a whole.
27408 @subheading Commands
27410 For each command in the block, the following is described:
27412 @subsubheading Synopsis
27415 -command @var{args}@dots{}
27418 @subsubheading Result
27420 @subsubheading @value{GDBN} Command
27422 The corresponding @value{GDBN} CLI command(s), if any.
27424 @subsubheading Example
27426 Example(s) formatted for readability. Some of the described commands have
27427 not been implemented yet and these are labeled N.A.@: (not available).
27430 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27431 @node GDB/MI Breakpoint Commands
27432 @section @sc{gdb/mi} Breakpoint Commands
27434 @cindex breakpoint commands for @sc{gdb/mi}
27435 @cindex @sc{gdb/mi}, breakpoint commands
27436 This section documents @sc{gdb/mi} commands for manipulating
27439 @subheading The @code{-break-after} Command
27440 @findex -break-after
27442 @subsubheading Synopsis
27445 -break-after @var{number} @var{count}
27448 The breakpoint number @var{number} is not in effect until it has been
27449 hit @var{count} times. To see how this is reflected in the output of
27450 the @samp{-break-list} command, see the description of the
27451 @samp{-break-list} command below.
27453 @subsubheading @value{GDBN} Command
27455 The corresponding @value{GDBN} command is @samp{ignore}.
27457 @subsubheading Example
27462 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27463 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27464 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27472 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27473 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27474 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27475 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27476 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27477 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27478 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27479 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27480 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27481 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27486 @subheading The @code{-break-catch} Command
27487 @findex -break-catch
27490 @subheading The @code{-break-commands} Command
27491 @findex -break-commands
27493 @subsubheading Synopsis
27496 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27499 Specifies the CLI commands that should be executed when breakpoint
27500 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27501 are the commands. If no command is specified, any previously-set
27502 commands are cleared. @xref{Break Commands}. Typical use of this
27503 functionality is tracing a program, that is, printing of values of
27504 some variables whenever breakpoint is hit and then continuing.
27506 @subsubheading @value{GDBN} Command
27508 The corresponding @value{GDBN} command is @samp{commands}.
27510 @subsubheading Example
27515 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27516 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27517 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27520 -break-commands 1 "print v" "continue"
27525 @subheading The @code{-break-condition} Command
27526 @findex -break-condition
27528 @subsubheading Synopsis
27531 -break-condition @var{number} @var{expr}
27534 Breakpoint @var{number} will stop the program only if the condition in
27535 @var{expr} is true. The condition becomes part of the
27536 @samp{-break-list} output (see the description of the @samp{-break-list}
27539 @subsubheading @value{GDBN} Command
27541 The corresponding @value{GDBN} command is @samp{condition}.
27543 @subsubheading Example
27547 -break-condition 1 1
27551 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27552 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27553 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27554 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27555 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27556 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27557 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27558 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27559 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27560 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27564 @subheading The @code{-break-delete} Command
27565 @findex -break-delete
27567 @subsubheading Synopsis
27570 -break-delete ( @var{breakpoint} )+
27573 Delete the breakpoint(s) whose number(s) are specified in the argument
27574 list. This is obviously reflected in the breakpoint list.
27576 @subsubheading @value{GDBN} Command
27578 The corresponding @value{GDBN} command is @samp{delete}.
27580 @subsubheading Example
27588 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27589 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27590 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27591 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27592 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27593 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27594 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27599 @subheading The @code{-break-disable} Command
27600 @findex -break-disable
27602 @subsubheading Synopsis
27605 -break-disable ( @var{breakpoint} )+
27608 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27609 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27611 @subsubheading @value{GDBN} Command
27613 The corresponding @value{GDBN} command is @samp{disable}.
27615 @subsubheading Example
27623 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27624 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27625 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27626 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27627 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27628 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27629 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27630 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27631 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27632 line="5",thread-groups=["i1"],times="0"@}]@}
27636 @subheading The @code{-break-enable} Command
27637 @findex -break-enable
27639 @subsubheading Synopsis
27642 -break-enable ( @var{breakpoint} )+
27645 Enable (previously disabled) @var{breakpoint}(s).
27647 @subsubheading @value{GDBN} Command
27649 The corresponding @value{GDBN} command is @samp{enable}.
27651 @subsubheading Example
27659 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27660 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27661 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27662 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27663 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27664 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27665 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27666 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27667 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27668 line="5",thread-groups=["i1"],times="0"@}]@}
27672 @subheading The @code{-break-info} Command
27673 @findex -break-info
27675 @subsubheading Synopsis
27678 -break-info @var{breakpoint}
27682 Get information about a single breakpoint.
27684 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27685 Information}, for details on the format of each breakpoint in the
27688 @subsubheading @value{GDBN} Command
27690 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27692 @subsubheading Example
27695 @subheading The @code{-break-insert} Command
27696 @findex -break-insert
27697 @anchor{-break-insert}
27699 @subsubheading Synopsis
27702 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27703 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27704 [ -p @var{thread-id} ] [ @var{location} ]
27708 If specified, @var{location}, can be one of:
27711 @item linespec location
27712 A linespec location. @xref{Linespec Locations}.
27714 @item explicit location
27715 An explicit location. @sc{gdb/mi} explicit locations are
27716 analogous to the CLI's explicit locations using the option names
27717 listed below. @xref{Explicit Locations}.
27720 @item --source @var{filename}
27721 The source file name of the location. This option requires the use
27722 of either @samp{--function} or @samp{--line}.
27724 @item --function @var{function}
27725 The name of a function or method.
27727 @item --label @var{label}
27728 The name of a label.
27730 @item --line @var{lineoffset}
27731 An absolute or relative line offset from the start of the location.
27734 @item address location
27735 An address location, *@var{address}. @xref{Address Locations}.
27739 The possible optional parameters of this command are:
27743 Insert a temporary breakpoint.
27745 Insert a hardware breakpoint.
27747 If @var{location} cannot be parsed (for example if it
27748 refers to unknown files or functions), create a pending
27749 breakpoint. Without this flag, @value{GDBN} will report
27750 an error, and won't create a breakpoint, if @var{location}
27753 Create a disabled breakpoint.
27755 Create a tracepoint. @xref{Tracepoints}. When this parameter
27756 is used together with @samp{-h}, a fast tracepoint is created.
27757 @item -c @var{condition}
27758 Make the breakpoint conditional on @var{condition}.
27759 @item -i @var{ignore-count}
27760 Initialize the @var{ignore-count}.
27761 @item -p @var{thread-id}
27762 Restrict the breakpoint to the thread with the specified global
27766 @subsubheading Result
27768 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27769 resulting breakpoint.
27771 Note: this format is open to change.
27772 @c An out-of-band breakpoint instead of part of the result?
27774 @subsubheading @value{GDBN} Command
27776 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27777 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27779 @subsubheading Example
27784 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27785 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27788 -break-insert -t foo
27789 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27790 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27794 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27795 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27796 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27797 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27798 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27799 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27800 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27801 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27802 addr="0x0001072c", func="main",file="recursive2.c",
27803 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27805 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27806 addr="0x00010774",func="foo",file="recursive2.c",
27807 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27810 @c -break-insert -r foo.*
27811 @c ~int foo(int, int);
27812 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27813 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27818 @subheading The @code{-dprintf-insert} Command
27819 @findex -dprintf-insert
27821 @subsubheading Synopsis
27824 -dprintf-insert [ -t ] [ -f ] [ -d ]
27825 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27826 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27831 If supplied, @var{location} may be specified the same way as for
27832 the @code{-break-insert} command. @xref{-break-insert}.
27834 The possible optional parameters of this command are:
27838 Insert a temporary breakpoint.
27840 If @var{location} cannot be parsed (for example, if it
27841 refers to unknown files or functions), create a pending
27842 breakpoint. Without this flag, @value{GDBN} will report
27843 an error, and won't create a breakpoint, if @var{location}
27846 Create a disabled breakpoint.
27847 @item -c @var{condition}
27848 Make the breakpoint conditional on @var{condition}.
27849 @item -i @var{ignore-count}
27850 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27851 to @var{ignore-count}.
27852 @item -p @var{thread-id}
27853 Restrict the breakpoint to the thread with the specified global
27857 @subsubheading Result
27859 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27860 resulting breakpoint.
27862 @c An out-of-band breakpoint instead of part of the result?
27864 @subsubheading @value{GDBN} Command
27866 The corresponding @value{GDBN} command is @samp{dprintf}.
27868 @subsubheading Example
27872 4-dprintf-insert foo "At foo entry\n"
27873 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27874 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27875 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27876 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27877 original-location="foo"@}
27879 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27880 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27881 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27882 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27883 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27884 original-location="mi-dprintf.c:26"@}
27888 @subheading The @code{-break-list} Command
27889 @findex -break-list
27891 @subsubheading Synopsis
27897 Displays the list of inserted breakpoints, showing the following fields:
27901 number of the breakpoint
27903 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27905 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27908 is the breakpoint enabled or no: @samp{y} or @samp{n}
27910 memory location at which the breakpoint is set
27912 logical location of the breakpoint, expressed by function name, file
27914 @item Thread-groups
27915 list of thread groups to which this breakpoint applies
27917 number of times the breakpoint has been hit
27920 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27921 @code{body} field is an empty list.
27923 @subsubheading @value{GDBN} Command
27925 The corresponding @value{GDBN} command is @samp{info break}.
27927 @subsubheading Example
27932 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27933 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27934 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27935 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27936 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27937 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27938 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27939 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27940 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27942 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27943 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27944 line="13",thread-groups=["i1"],times="0"@}]@}
27948 Here's an example of the result when there are no breakpoints:
27953 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27954 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27955 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27956 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27957 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27958 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27959 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27964 @subheading The @code{-break-passcount} Command
27965 @findex -break-passcount
27967 @subsubheading Synopsis
27970 -break-passcount @var{tracepoint-number} @var{passcount}
27973 Set the passcount for tracepoint @var{tracepoint-number} to
27974 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27975 is not a tracepoint, error is emitted. This corresponds to CLI
27976 command @samp{passcount}.
27978 @subheading The @code{-break-watch} Command
27979 @findex -break-watch
27981 @subsubheading Synopsis
27984 -break-watch [ -a | -r ]
27987 Create a watchpoint. With the @samp{-a} option it will create an
27988 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27989 read from or on a write to the memory location. With the @samp{-r}
27990 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27991 trigger only when the memory location is accessed for reading. Without
27992 either of the options, the watchpoint created is a regular watchpoint,
27993 i.e., it will trigger when the memory location is accessed for writing.
27994 @xref{Set Watchpoints, , Setting Watchpoints}.
27996 Note that @samp{-break-list} will report a single list of watchpoints and
27997 breakpoints inserted.
27999 @subsubheading @value{GDBN} Command
28001 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28004 @subsubheading Example
28006 Setting a watchpoint on a variable in the @code{main} function:
28011 ^done,wpt=@{number="2",exp="x"@}
28016 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28017 value=@{old="-268439212",new="55"@},
28018 frame=@{func="main",args=[],file="recursive2.c",
28019 fullname="/home/foo/bar/recursive2.c",line="5"@}
28023 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28024 the program execution twice: first for the variable changing value, then
28025 for the watchpoint going out of scope.
28030 ^done,wpt=@{number="5",exp="C"@}
28035 *stopped,reason="watchpoint-trigger",
28036 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28037 frame=@{func="callee4",args=[],
28038 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28039 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28044 *stopped,reason="watchpoint-scope",wpnum="5",
28045 frame=@{func="callee3",args=[@{name="strarg",
28046 value="0x11940 \"A string argument.\""@}],
28047 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28048 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28052 Listing breakpoints and watchpoints, at different points in the program
28053 execution. Note that once the watchpoint goes out of scope, it is
28059 ^done,wpt=@{number="2",exp="C"@}
28062 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28063 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28064 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28065 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28066 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28067 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28068 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28069 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28070 addr="0x00010734",func="callee4",
28071 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28072 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28074 bkpt=@{number="2",type="watchpoint",disp="keep",
28075 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28080 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28081 value=@{old="-276895068",new="3"@},
28082 frame=@{func="callee4",args=[],
28083 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28084 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28087 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28088 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28089 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28090 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28091 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28092 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28093 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28094 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28095 addr="0x00010734",func="callee4",
28096 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28097 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28099 bkpt=@{number="2",type="watchpoint",disp="keep",
28100 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28104 ^done,reason="watchpoint-scope",wpnum="2",
28105 frame=@{func="callee3",args=[@{name="strarg",
28106 value="0x11940 \"A string argument.\""@}],
28107 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28108 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28111 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28112 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28113 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28114 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28115 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28116 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28117 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28118 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28119 addr="0x00010734",func="callee4",
28120 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28121 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28122 thread-groups=["i1"],times="1"@}]@}
28127 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28128 @node GDB/MI Catchpoint Commands
28129 @section @sc{gdb/mi} Catchpoint Commands
28131 This section documents @sc{gdb/mi} commands for manipulating
28135 * Shared Library GDB/MI Catchpoint Commands::
28136 * Ada Exception GDB/MI Catchpoint Commands::
28139 @node Shared Library GDB/MI Catchpoint Commands
28140 @subsection Shared Library @sc{gdb/mi} Catchpoints
28142 @subheading The @code{-catch-load} Command
28143 @findex -catch-load
28145 @subsubheading Synopsis
28148 -catch-load [ -t ] [ -d ] @var{regexp}
28151 Add a catchpoint for library load events. If the @samp{-t} option is used,
28152 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28153 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28154 in a disabled state. The @samp{regexp} argument is a regular
28155 expression used to match the name of the loaded library.
28158 @subsubheading @value{GDBN} Command
28160 The corresponding @value{GDBN} command is @samp{catch load}.
28162 @subsubheading Example
28165 -catch-load -t foo.so
28166 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28167 what="load of library matching foo.so",catch-type="load",times="0"@}
28172 @subheading The @code{-catch-unload} Command
28173 @findex -catch-unload
28175 @subsubheading Synopsis
28178 -catch-unload [ -t ] [ -d ] @var{regexp}
28181 Add a catchpoint for library unload events. If the @samp{-t} option is
28182 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28183 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28184 created in a disabled state. The @samp{regexp} argument is a regular
28185 expression used to match the name of the unloaded library.
28187 @subsubheading @value{GDBN} Command
28189 The corresponding @value{GDBN} command is @samp{catch unload}.
28191 @subsubheading Example
28194 -catch-unload -d bar.so
28195 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28196 what="load of library matching bar.so",catch-type="unload",times="0"@}
28200 @node Ada Exception GDB/MI Catchpoint Commands
28201 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28203 The following @sc{gdb/mi} commands can be used to create catchpoints
28204 that stop the execution when Ada exceptions are being raised.
28206 @subheading The @code{-catch-assert} Command
28207 @findex -catch-assert
28209 @subsubheading Synopsis
28212 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28215 Add a catchpoint for failed Ada assertions.
28217 The possible optional parameters for this command are:
28220 @item -c @var{condition}
28221 Make the catchpoint conditional on @var{condition}.
28223 Create a disabled catchpoint.
28225 Create a temporary catchpoint.
28228 @subsubheading @value{GDBN} Command
28230 The corresponding @value{GDBN} command is @samp{catch assert}.
28232 @subsubheading Example
28236 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28237 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28238 thread-groups=["i1"],times="0",
28239 original-location="__gnat_debug_raise_assert_failure"@}
28243 @subheading The @code{-catch-exception} Command
28244 @findex -catch-exception
28246 @subsubheading Synopsis
28249 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28253 Add a catchpoint stopping when Ada exceptions are raised.
28254 By default, the command stops the program when any Ada exception
28255 gets raised. But it is also possible, by using some of the
28256 optional parameters described below, to create more selective
28259 The possible optional parameters for this command are:
28262 @item -c @var{condition}
28263 Make the catchpoint conditional on @var{condition}.
28265 Create a disabled catchpoint.
28266 @item -e @var{exception-name}
28267 Only stop when @var{exception-name} is raised. This option cannot
28268 be used combined with @samp{-u}.
28270 Create a temporary catchpoint.
28272 Stop only when an unhandled exception gets raised. This option
28273 cannot be used combined with @samp{-e}.
28276 @subsubheading @value{GDBN} Command
28278 The corresponding @value{GDBN} commands are @samp{catch exception}
28279 and @samp{catch exception unhandled}.
28281 @subsubheading Example
28284 -catch-exception -e Program_Error
28285 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28286 enabled="y",addr="0x0000000000404874",
28287 what="`Program_Error' Ada exception", thread-groups=["i1"],
28288 times="0",original-location="__gnat_debug_raise_exception"@}
28292 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28293 @node GDB/MI Program Context
28294 @section @sc{gdb/mi} Program Context
28296 @subheading The @code{-exec-arguments} Command
28297 @findex -exec-arguments
28300 @subsubheading Synopsis
28303 -exec-arguments @var{args}
28306 Set the inferior program arguments, to be used in the next
28309 @subsubheading @value{GDBN} Command
28311 The corresponding @value{GDBN} command is @samp{set args}.
28313 @subsubheading Example
28317 -exec-arguments -v word
28324 @subheading The @code{-exec-show-arguments} Command
28325 @findex -exec-show-arguments
28327 @subsubheading Synopsis
28330 -exec-show-arguments
28333 Print the arguments of the program.
28335 @subsubheading @value{GDBN} Command
28337 The corresponding @value{GDBN} command is @samp{show args}.
28339 @subsubheading Example
28344 @subheading The @code{-environment-cd} Command
28345 @findex -environment-cd
28347 @subsubheading Synopsis
28350 -environment-cd @var{pathdir}
28353 Set @value{GDBN}'s working directory.
28355 @subsubheading @value{GDBN} Command
28357 The corresponding @value{GDBN} command is @samp{cd}.
28359 @subsubheading Example
28363 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28369 @subheading The @code{-environment-directory} Command
28370 @findex -environment-directory
28372 @subsubheading Synopsis
28375 -environment-directory [ -r ] [ @var{pathdir} ]+
28378 Add directories @var{pathdir} to beginning of search path for source files.
28379 If the @samp{-r} option is used, the search path is reset to the default
28380 search path. If directories @var{pathdir} are supplied in addition to the
28381 @samp{-r} option, the search path is first reset and then addition
28383 Multiple directories may be specified, separated by blanks. Specifying
28384 multiple directories in a single command
28385 results in the directories added to the beginning of the
28386 search path in the same order they were presented in the command.
28387 If blanks are needed as
28388 part of a directory name, double-quotes should be used around
28389 the name. In the command output, the path will show up separated
28390 by the system directory-separator character. The directory-separator
28391 character must not be used
28392 in any directory name.
28393 If no directories are specified, the current search path is displayed.
28395 @subsubheading @value{GDBN} Command
28397 The corresponding @value{GDBN} command is @samp{dir}.
28399 @subsubheading Example
28403 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28404 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28406 -environment-directory ""
28407 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28409 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28410 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28412 -environment-directory -r
28413 ^done,source-path="$cdir:$cwd"
28418 @subheading The @code{-environment-path} Command
28419 @findex -environment-path
28421 @subsubheading Synopsis
28424 -environment-path [ -r ] [ @var{pathdir} ]+
28427 Add directories @var{pathdir} to beginning of search path for object files.
28428 If the @samp{-r} option is used, the search path is reset to the original
28429 search path that existed at gdb start-up. If directories @var{pathdir} are
28430 supplied in addition to the
28431 @samp{-r} option, the search path is first reset and then addition
28433 Multiple directories may be specified, separated by blanks. Specifying
28434 multiple directories in a single command
28435 results in the directories added to the beginning of the
28436 search path in the same order they were presented in the command.
28437 If blanks are needed as
28438 part of a directory name, double-quotes should be used around
28439 the name. In the command output, the path will show up separated
28440 by the system directory-separator character. The directory-separator
28441 character must not be used
28442 in any directory name.
28443 If no directories are specified, the current path is displayed.
28446 @subsubheading @value{GDBN} Command
28448 The corresponding @value{GDBN} command is @samp{path}.
28450 @subsubheading Example
28455 ^done,path="/usr/bin"
28457 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28458 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28460 -environment-path -r /usr/local/bin
28461 ^done,path="/usr/local/bin:/usr/bin"
28466 @subheading The @code{-environment-pwd} Command
28467 @findex -environment-pwd
28469 @subsubheading Synopsis
28475 Show the current working directory.
28477 @subsubheading @value{GDBN} Command
28479 The corresponding @value{GDBN} command is @samp{pwd}.
28481 @subsubheading Example
28486 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28490 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28491 @node GDB/MI Thread Commands
28492 @section @sc{gdb/mi} Thread Commands
28495 @subheading The @code{-thread-info} Command
28496 @findex -thread-info
28498 @subsubheading Synopsis
28501 -thread-info [ @var{thread-id} ]
28504 Reports information about either a specific thread, if the
28505 @var{thread-id} parameter is present, or about all threads.
28506 @var{thread-id} is the thread's global thread ID. When printing
28507 information about all threads, also reports the global ID of the
28510 @subsubheading @value{GDBN} Command
28512 The @samp{info thread} command prints the same information
28515 @subsubheading Result
28517 The result contains the following attributes:
28521 A list of threads. The format of the elements of the list is described in
28522 @ref{GDB/MI Thread Information}.
28524 @item current-thread-id
28525 The global id of the currently selected thread. This field is omitted if there
28526 is no selected thread (for example, when the selected inferior is not running,
28527 and therefore has no threads) or if a @var{thread-id} argument was passed to
28532 @subsubheading Example
28537 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28538 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28539 args=[]@},state="running"@},
28540 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28541 frame=@{level="0",addr="0x0804891f",func="foo",
28542 args=[@{name="i",value="10"@}],
28543 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28544 state="running"@}],
28545 current-thread-id="1"
28549 @subheading The @code{-thread-list-ids} Command
28550 @findex -thread-list-ids
28552 @subsubheading Synopsis
28558 Produces a list of the currently known global @value{GDBN} thread ids.
28559 At the end of the list it also prints the total number of such
28562 This command is retained for historical reasons, the
28563 @code{-thread-info} command should be used instead.
28565 @subsubheading @value{GDBN} Command
28567 Part of @samp{info threads} supplies the same information.
28569 @subsubheading Example
28574 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28575 current-thread-id="1",number-of-threads="3"
28580 @subheading The @code{-thread-select} Command
28581 @findex -thread-select
28583 @subsubheading Synopsis
28586 -thread-select @var{thread-id}
28589 Make thread with global thread number @var{thread-id} the current
28590 thread. It prints the number of the new current thread, and the
28591 topmost frame for that thread.
28593 This command is deprecated in favor of explicitly using the
28594 @samp{--thread} option to each command.
28596 @subsubheading @value{GDBN} Command
28598 The corresponding @value{GDBN} command is @samp{thread}.
28600 @subsubheading Example
28607 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28608 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28612 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28613 number-of-threads="3"
28616 ^done,new-thread-id="3",
28617 frame=@{level="0",func="vprintf",
28618 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28619 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28623 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28624 @node GDB/MI Ada Tasking Commands
28625 @section @sc{gdb/mi} Ada Tasking Commands
28627 @subheading The @code{-ada-task-info} Command
28628 @findex -ada-task-info
28630 @subsubheading Synopsis
28633 -ada-task-info [ @var{task-id} ]
28636 Reports information about either a specific Ada task, if the
28637 @var{task-id} parameter is present, or about all Ada tasks.
28639 @subsubheading @value{GDBN} Command
28641 The @samp{info tasks} command prints the same information
28642 about all Ada tasks (@pxref{Ada Tasks}).
28644 @subsubheading Result
28646 The result is a table of Ada tasks. The following columns are
28647 defined for each Ada task:
28651 This field exists only for the current thread. It has the value @samp{*}.
28654 The identifier that @value{GDBN} uses to refer to the Ada task.
28657 The identifier that the target uses to refer to the Ada task.
28660 The global thread identifier of the thread corresponding to the Ada
28663 This field should always exist, as Ada tasks are always implemented
28664 on top of a thread. But if @value{GDBN} cannot find this corresponding
28665 thread for any reason, the field is omitted.
28668 This field exists only when the task was created by another task.
28669 In this case, it provides the ID of the parent task.
28672 The base priority of the task.
28675 The current state of the task. For a detailed description of the
28676 possible states, see @ref{Ada Tasks}.
28679 The name of the task.
28683 @subsubheading Example
28687 ^done,tasks=@{nr_rows="3",nr_cols="8",
28688 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28689 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28690 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28691 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28692 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28693 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28694 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28695 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28696 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28697 state="Child Termination Wait",name="main_task"@}]@}
28701 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28702 @node GDB/MI Program Execution
28703 @section @sc{gdb/mi} Program Execution
28705 These are the asynchronous commands which generate the out-of-band
28706 record @samp{*stopped}. Currently @value{GDBN} only really executes
28707 asynchronously with remote targets and this interaction is mimicked in
28710 @subheading The @code{-exec-continue} Command
28711 @findex -exec-continue
28713 @subsubheading Synopsis
28716 -exec-continue [--reverse] [--all|--thread-group N]
28719 Resumes the execution of the inferior program, which will continue
28720 to execute until it reaches a debugger stop event. If the
28721 @samp{--reverse} option is specified, execution resumes in reverse until
28722 it reaches a stop event. Stop events may include
28725 breakpoints or watchpoints
28727 signals or exceptions
28729 the end of the process (or its beginning under @samp{--reverse})
28731 the end or beginning of a replay log if one is being used.
28733 In all-stop mode (@pxref{All-Stop
28734 Mode}), may resume only one thread, or all threads, depending on the
28735 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28736 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28737 ignored in all-stop mode. If the @samp{--thread-group} options is
28738 specified, then all threads in that thread group are resumed.
28740 @subsubheading @value{GDBN} Command
28742 The corresponding @value{GDBN} corresponding is @samp{continue}.
28744 @subsubheading Example
28751 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28752 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28758 @subheading The @code{-exec-finish} Command
28759 @findex -exec-finish
28761 @subsubheading Synopsis
28764 -exec-finish [--reverse]
28767 Resumes the execution of the inferior program until the current
28768 function is exited. Displays the results returned by the function.
28769 If the @samp{--reverse} option is specified, resumes the reverse
28770 execution of the inferior program until the point where current
28771 function was called.
28773 @subsubheading @value{GDBN} Command
28775 The corresponding @value{GDBN} command is @samp{finish}.
28777 @subsubheading Example
28779 Function returning @code{void}.
28786 *stopped,reason="function-finished",frame=@{func="main",args=[],
28787 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28791 Function returning other than @code{void}. The name of the internal
28792 @value{GDBN} variable storing the result is printed, together with the
28799 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28800 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28801 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28802 gdb-result-var="$1",return-value="0"
28807 @subheading The @code{-exec-interrupt} Command
28808 @findex -exec-interrupt
28810 @subsubheading Synopsis
28813 -exec-interrupt [--all|--thread-group N]
28816 Interrupts the background execution of the target. Note how the token
28817 associated with the stop message is the one for the execution command
28818 that has been interrupted. The token for the interrupt itself only
28819 appears in the @samp{^done} output. If the user is trying to
28820 interrupt a non-running program, an error message will be printed.
28822 Note that when asynchronous execution is enabled, this command is
28823 asynchronous just like other execution commands. That is, first the
28824 @samp{^done} response will be printed, and the target stop will be
28825 reported after that using the @samp{*stopped} notification.
28827 In non-stop mode, only the context thread is interrupted by default.
28828 All threads (in all inferiors) will be interrupted if the
28829 @samp{--all} option is specified. If the @samp{--thread-group}
28830 option is specified, all threads in that group will be interrupted.
28832 @subsubheading @value{GDBN} Command
28834 The corresponding @value{GDBN} command is @samp{interrupt}.
28836 @subsubheading Example
28847 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28848 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28849 fullname="/home/foo/bar/try.c",line="13"@}
28854 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28858 @subheading The @code{-exec-jump} Command
28861 @subsubheading Synopsis
28864 -exec-jump @var{location}
28867 Resumes execution of the inferior program at the location specified by
28868 parameter. @xref{Specify Location}, for a description of the
28869 different forms of @var{location}.
28871 @subsubheading @value{GDBN} Command
28873 The corresponding @value{GDBN} command is @samp{jump}.
28875 @subsubheading Example
28878 -exec-jump foo.c:10
28879 *running,thread-id="all"
28884 @subheading The @code{-exec-next} Command
28887 @subsubheading Synopsis
28890 -exec-next [--reverse]
28893 Resumes execution of the inferior program, stopping when the beginning
28894 of the next source line is reached.
28896 If the @samp{--reverse} option is specified, resumes reverse execution
28897 of the inferior program, stopping at the beginning of the previous
28898 source line. If you issue this command on the first line of a
28899 function, it will take you back to the caller of that function, to the
28900 source line where the function was called.
28903 @subsubheading @value{GDBN} Command
28905 The corresponding @value{GDBN} command is @samp{next}.
28907 @subsubheading Example
28913 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28918 @subheading The @code{-exec-next-instruction} Command
28919 @findex -exec-next-instruction
28921 @subsubheading Synopsis
28924 -exec-next-instruction [--reverse]
28927 Executes one machine instruction. If the instruction is a function
28928 call, continues until the function returns. If the program stops at an
28929 instruction in the middle of a source line, the address will be
28932 If the @samp{--reverse} option is specified, resumes reverse execution
28933 of the inferior program, stopping at the previous instruction. If the
28934 previously executed instruction was a return from another function,
28935 it will continue to execute in reverse until the call to that function
28936 (from the current stack frame) is reached.
28938 @subsubheading @value{GDBN} Command
28940 The corresponding @value{GDBN} command is @samp{nexti}.
28942 @subsubheading Example
28946 -exec-next-instruction
28950 *stopped,reason="end-stepping-range",
28951 addr="0x000100d4",line="5",file="hello.c"
28956 @subheading The @code{-exec-return} Command
28957 @findex -exec-return
28959 @subsubheading Synopsis
28965 Makes current function return immediately. Doesn't execute the inferior.
28966 Displays the new current frame.
28968 @subsubheading @value{GDBN} Command
28970 The corresponding @value{GDBN} command is @samp{return}.
28972 @subsubheading Example
28976 200-break-insert callee4
28977 200^done,bkpt=@{number="1",addr="0x00010734",
28978 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28983 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28984 frame=@{func="callee4",args=[],
28985 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28986 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28992 111^done,frame=@{level="0",func="callee3",
28993 args=[@{name="strarg",
28994 value="0x11940 \"A string argument.\""@}],
28995 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28996 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29001 @subheading The @code{-exec-run} Command
29004 @subsubheading Synopsis
29007 -exec-run [ --all | --thread-group N ] [ --start ]
29010 Starts execution of the inferior from the beginning. The inferior
29011 executes until either a breakpoint is encountered or the program
29012 exits. In the latter case the output will include an exit code, if
29013 the program has exited exceptionally.
29015 When neither the @samp{--all} nor the @samp{--thread-group} option
29016 is specified, the current inferior is started. If the
29017 @samp{--thread-group} option is specified, it should refer to a thread
29018 group of type @samp{process}, and that thread group will be started.
29019 If the @samp{--all} option is specified, then all inferiors will be started.
29021 Using the @samp{--start} option instructs the debugger to stop
29022 the execution at the start of the inferior's main subprogram,
29023 following the same behavior as the @code{start} command
29024 (@pxref{Starting}).
29026 @subsubheading @value{GDBN} Command
29028 The corresponding @value{GDBN} command is @samp{run}.
29030 @subsubheading Examples
29035 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29040 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29041 frame=@{func="main",args=[],file="recursive2.c",
29042 fullname="/home/foo/bar/recursive2.c",line="4"@}
29047 Program exited normally:
29055 *stopped,reason="exited-normally"
29060 Program exited exceptionally:
29068 *stopped,reason="exited",exit-code="01"
29072 Another way the program can terminate is if it receives a signal such as
29073 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29077 *stopped,reason="exited-signalled",signal-name="SIGINT",
29078 signal-meaning="Interrupt"
29082 @c @subheading -exec-signal
29085 @subheading The @code{-exec-step} Command
29088 @subsubheading Synopsis
29091 -exec-step [--reverse]
29094 Resumes execution of the inferior program, stopping when the beginning
29095 of the next source line is reached, if the next source line is not a
29096 function call. If it is, stop at the first instruction of the called
29097 function. If the @samp{--reverse} option is specified, resumes reverse
29098 execution of the inferior program, stopping at the beginning of the
29099 previously executed source line.
29101 @subsubheading @value{GDBN} Command
29103 The corresponding @value{GDBN} command is @samp{step}.
29105 @subsubheading Example
29107 Stepping into a function:
29113 *stopped,reason="end-stepping-range",
29114 frame=@{func="foo",args=[@{name="a",value="10"@},
29115 @{name="b",value="0"@}],file="recursive2.c",
29116 fullname="/home/foo/bar/recursive2.c",line="11"@}
29126 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29131 @subheading The @code{-exec-step-instruction} Command
29132 @findex -exec-step-instruction
29134 @subsubheading Synopsis
29137 -exec-step-instruction [--reverse]
29140 Resumes the inferior which executes one machine instruction. If the
29141 @samp{--reverse} option is specified, resumes reverse execution of the
29142 inferior program, stopping at the previously executed instruction.
29143 The output, once @value{GDBN} has stopped, will vary depending on
29144 whether we have stopped in the middle of a source line or not. In the
29145 former case, the address at which the program stopped will be printed
29148 @subsubheading @value{GDBN} Command
29150 The corresponding @value{GDBN} command is @samp{stepi}.
29152 @subsubheading Example
29156 -exec-step-instruction
29160 *stopped,reason="end-stepping-range",
29161 frame=@{func="foo",args=[],file="try.c",
29162 fullname="/home/foo/bar/try.c",line="10"@}
29164 -exec-step-instruction
29168 *stopped,reason="end-stepping-range",
29169 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29170 fullname="/home/foo/bar/try.c",line="10"@}
29175 @subheading The @code{-exec-until} Command
29176 @findex -exec-until
29178 @subsubheading Synopsis
29181 -exec-until [ @var{location} ]
29184 Executes the inferior until the @var{location} specified in the
29185 argument is reached. If there is no argument, the inferior executes
29186 until a source line greater than the current one is reached. The
29187 reason for stopping in this case will be @samp{location-reached}.
29189 @subsubheading @value{GDBN} Command
29191 The corresponding @value{GDBN} command is @samp{until}.
29193 @subsubheading Example
29197 -exec-until recursive2.c:6
29201 *stopped,reason="location-reached",frame=@{func="main",args=[],
29202 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29207 @subheading -file-clear
29208 Is this going away????
29211 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29212 @node GDB/MI Stack Manipulation
29213 @section @sc{gdb/mi} Stack Manipulation Commands
29215 @subheading The @code{-enable-frame-filters} Command
29216 @findex -enable-frame-filters
29219 -enable-frame-filters
29222 @value{GDBN} allows Python-based frame filters to affect the output of
29223 the MI commands relating to stack traces. As there is no way to
29224 implement this in a fully backward-compatible way, a front end must
29225 request that this functionality be enabled.
29227 Once enabled, this feature cannot be disabled.
29229 Note that if Python support has not been compiled into @value{GDBN},
29230 this command will still succeed (and do nothing).
29232 @subheading The @code{-stack-info-frame} Command
29233 @findex -stack-info-frame
29235 @subsubheading Synopsis
29241 Get info on the selected frame.
29243 @subsubheading @value{GDBN} Command
29245 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29246 (without arguments).
29248 @subsubheading Example
29253 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29254 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29255 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29259 @subheading The @code{-stack-info-depth} Command
29260 @findex -stack-info-depth
29262 @subsubheading Synopsis
29265 -stack-info-depth [ @var{max-depth} ]
29268 Return the depth of the stack. If the integer argument @var{max-depth}
29269 is specified, do not count beyond @var{max-depth} frames.
29271 @subsubheading @value{GDBN} Command
29273 There's no equivalent @value{GDBN} command.
29275 @subsubheading Example
29277 For a stack with frame levels 0 through 11:
29284 -stack-info-depth 4
29287 -stack-info-depth 12
29290 -stack-info-depth 11
29293 -stack-info-depth 13
29298 @anchor{-stack-list-arguments}
29299 @subheading The @code{-stack-list-arguments} Command
29300 @findex -stack-list-arguments
29302 @subsubheading Synopsis
29305 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29306 [ @var{low-frame} @var{high-frame} ]
29309 Display a list of the arguments for the frames between @var{low-frame}
29310 and @var{high-frame} (inclusive). If @var{low-frame} and
29311 @var{high-frame} are not provided, list the arguments for the whole
29312 call stack. If the two arguments are equal, show the single frame
29313 at the corresponding level. It is an error if @var{low-frame} is
29314 larger than the actual number of frames. On the other hand,
29315 @var{high-frame} may be larger than the actual number of frames, in
29316 which case only existing frames will be returned.
29318 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29319 the variables; if it is 1 or @code{--all-values}, print also their
29320 values; and if it is 2 or @code{--simple-values}, print the name,
29321 type and value for simple data types, and the name and type for arrays,
29322 structures and unions. If the option @code{--no-frame-filters} is
29323 supplied, then Python frame filters will not be executed.
29325 If the @code{--skip-unavailable} option is specified, arguments that
29326 are not available are not listed. Partially available arguments
29327 are still displayed, however.
29329 Use of this command to obtain arguments in a single frame is
29330 deprecated in favor of the @samp{-stack-list-variables} command.
29332 @subsubheading @value{GDBN} Command
29334 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29335 @samp{gdb_get_args} command which partially overlaps with the
29336 functionality of @samp{-stack-list-arguments}.
29338 @subsubheading Example
29345 frame=@{level="0",addr="0x00010734",func="callee4",
29346 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29347 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29348 frame=@{level="1",addr="0x0001076c",func="callee3",
29349 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29350 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29351 frame=@{level="2",addr="0x0001078c",func="callee2",
29352 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29353 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29354 frame=@{level="3",addr="0x000107b4",func="callee1",
29355 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29356 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29357 frame=@{level="4",addr="0x000107e0",func="main",
29358 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29359 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29361 -stack-list-arguments 0
29364 frame=@{level="0",args=[]@},
29365 frame=@{level="1",args=[name="strarg"]@},
29366 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29367 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29368 frame=@{level="4",args=[]@}]
29370 -stack-list-arguments 1
29373 frame=@{level="0",args=[]@},
29375 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29376 frame=@{level="2",args=[
29377 @{name="intarg",value="2"@},
29378 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29379 @{frame=@{level="3",args=[
29380 @{name="intarg",value="2"@},
29381 @{name="strarg",value="0x11940 \"A string argument.\""@},
29382 @{name="fltarg",value="3.5"@}]@},
29383 frame=@{level="4",args=[]@}]
29385 -stack-list-arguments 0 2 2
29386 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29388 -stack-list-arguments 1 2 2
29389 ^done,stack-args=[frame=@{level="2",
29390 args=[@{name="intarg",value="2"@},
29391 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29395 @c @subheading -stack-list-exception-handlers
29398 @anchor{-stack-list-frames}
29399 @subheading The @code{-stack-list-frames} Command
29400 @findex -stack-list-frames
29402 @subsubheading Synopsis
29405 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29408 List the frames currently on the stack. For each frame it displays the
29413 The frame number, 0 being the topmost frame, i.e., the innermost function.
29415 The @code{$pc} value for that frame.
29419 File name of the source file where the function lives.
29420 @item @var{fullname}
29421 The full file name of the source file where the function lives.
29423 Line number corresponding to the @code{$pc}.
29425 The shared library where this function is defined. This is only given
29426 if the frame's function is not known.
29429 If invoked without arguments, this command prints a backtrace for the
29430 whole stack. If given two integer arguments, it shows the frames whose
29431 levels are between the two arguments (inclusive). If the two arguments
29432 are equal, it shows the single frame at the corresponding level. It is
29433 an error if @var{low-frame} is larger than the actual number of
29434 frames. On the other hand, @var{high-frame} may be larger than the
29435 actual number of frames, in which case only existing frames will be
29436 returned. If the option @code{--no-frame-filters} is supplied, then
29437 Python frame filters will not be executed.
29439 @subsubheading @value{GDBN} Command
29441 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29443 @subsubheading Example
29445 Full stack backtrace:
29451 [frame=@{level="0",addr="0x0001076c",func="foo",
29452 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29453 frame=@{level="1",addr="0x000107a4",func="foo",
29454 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29455 frame=@{level="2",addr="0x000107a4",func="foo",
29456 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29457 frame=@{level="3",addr="0x000107a4",func="foo",
29458 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29459 frame=@{level="4",addr="0x000107a4",func="foo",
29460 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29461 frame=@{level="5",addr="0x000107a4",func="foo",
29462 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29463 frame=@{level="6",addr="0x000107a4",func="foo",
29464 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29465 frame=@{level="7",addr="0x000107a4",func="foo",
29466 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29467 frame=@{level="8",addr="0x000107a4",func="foo",
29468 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29469 frame=@{level="9",addr="0x000107a4",func="foo",
29470 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29471 frame=@{level="10",addr="0x000107a4",func="foo",
29472 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29473 frame=@{level="11",addr="0x00010738",func="main",
29474 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29478 Show frames between @var{low_frame} and @var{high_frame}:
29482 -stack-list-frames 3 5
29484 [frame=@{level="3",addr="0x000107a4",func="foo",
29485 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29486 frame=@{level="4",addr="0x000107a4",func="foo",
29487 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29488 frame=@{level="5",addr="0x000107a4",func="foo",
29489 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29493 Show a single frame:
29497 -stack-list-frames 3 3
29499 [frame=@{level="3",addr="0x000107a4",func="foo",
29500 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29505 @subheading The @code{-stack-list-locals} Command
29506 @findex -stack-list-locals
29507 @anchor{-stack-list-locals}
29509 @subsubheading Synopsis
29512 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29515 Display the local variable names for the selected frame. If
29516 @var{print-values} is 0 or @code{--no-values}, print only the names of
29517 the variables; if it is 1 or @code{--all-values}, print also their
29518 values; and if it is 2 or @code{--simple-values}, print the name,
29519 type and value for simple data types, and the name and type for arrays,
29520 structures and unions. In this last case, a frontend can immediately
29521 display the value of simple data types and create variable objects for
29522 other data types when the user wishes to explore their values in
29523 more detail. If the option @code{--no-frame-filters} is supplied, then
29524 Python frame filters will not be executed.
29526 If the @code{--skip-unavailable} option is specified, local variables
29527 that are not available are not listed. Partially available local
29528 variables are still displayed, however.
29530 This command is deprecated in favor of the
29531 @samp{-stack-list-variables} command.
29533 @subsubheading @value{GDBN} Command
29535 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29537 @subsubheading Example
29541 -stack-list-locals 0
29542 ^done,locals=[name="A",name="B",name="C"]
29544 -stack-list-locals --all-values
29545 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29546 @{name="C",value="@{1, 2, 3@}"@}]
29547 -stack-list-locals --simple-values
29548 ^done,locals=[@{name="A",type="int",value="1"@},
29549 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29553 @anchor{-stack-list-variables}
29554 @subheading The @code{-stack-list-variables} Command
29555 @findex -stack-list-variables
29557 @subsubheading Synopsis
29560 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29563 Display the names of local variables and function arguments for the selected frame. If
29564 @var{print-values} is 0 or @code{--no-values}, print only the names of
29565 the variables; if it is 1 or @code{--all-values}, print also their
29566 values; and if it is 2 or @code{--simple-values}, print the name,
29567 type and value for simple data types, and the name and type for arrays,
29568 structures and unions. If the option @code{--no-frame-filters} is
29569 supplied, then Python frame filters will not be executed.
29571 If the @code{--skip-unavailable} option is specified, local variables
29572 and arguments that are not available are not listed. Partially
29573 available arguments and local variables are still displayed, however.
29575 @subsubheading Example
29579 -stack-list-variables --thread 1 --frame 0 --all-values
29580 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29585 @subheading The @code{-stack-select-frame} Command
29586 @findex -stack-select-frame
29588 @subsubheading Synopsis
29591 -stack-select-frame @var{framenum}
29594 Change the selected frame. Select a different frame @var{framenum} on
29597 This command in deprecated in favor of passing the @samp{--frame}
29598 option to every command.
29600 @subsubheading @value{GDBN} Command
29602 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29603 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29605 @subsubheading Example
29609 -stack-select-frame 2
29614 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29615 @node GDB/MI Variable Objects
29616 @section @sc{gdb/mi} Variable Objects
29620 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29622 For the implementation of a variable debugger window (locals, watched
29623 expressions, etc.), we are proposing the adaptation of the existing code
29624 used by @code{Insight}.
29626 The two main reasons for that are:
29630 It has been proven in practice (it is already on its second generation).
29633 It will shorten development time (needless to say how important it is
29637 The original interface was designed to be used by Tcl code, so it was
29638 slightly changed so it could be used through @sc{gdb/mi}. This section
29639 describes the @sc{gdb/mi} operations that will be available and gives some
29640 hints about their use.
29642 @emph{Note}: In addition to the set of operations described here, we
29643 expect the @sc{gui} implementation of a variable window to require, at
29644 least, the following operations:
29647 @item @code{-gdb-show} @code{output-radix}
29648 @item @code{-stack-list-arguments}
29649 @item @code{-stack-list-locals}
29650 @item @code{-stack-select-frame}
29655 @subheading Introduction to Variable Objects
29657 @cindex variable objects in @sc{gdb/mi}
29659 Variable objects are "object-oriented" MI interface for examining and
29660 changing values of expressions. Unlike some other MI interfaces that
29661 work with expressions, variable objects are specifically designed for
29662 simple and efficient presentation in the frontend. A variable object
29663 is identified by string name. When a variable object is created, the
29664 frontend specifies the expression for that variable object. The
29665 expression can be a simple variable, or it can be an arbitrary complex
29666 expression, and can even involve CPU registers. After creating a
29667 variable object, the frontend can invoke other variable object
29668 operations---for example to obtain or change the value of a variable
29669 object, or to change display format.
29671 Variable objects have hierarchical tree structure. Any variable object
29672 that corresponds to a composite type, such as structure in C, has
29673 a number of child variable objects, for example corresponding to each
29674 element of a structure. A child variable object can itself have
29675 children, recursively. Recursion ends when we reach
29676 leaf variable objects, which always have built-in types. Child variable
29677 objects are created only by explicit request, so if a frontend
29678 is not interested in the children of a particular variable object, no
29679 child will be created.
29681 For a leaf variable object it is possible to obtain its value as a
29682 string, or set the value from a string. String value can be also
29683 obtained for a non-leaf variable object, but it's generally a string
29684 that only indicates the type of the object, and does not list its
29685 contents. Assignment to a non-leaf variable object is not allowed.
29687 A frontend does not need to read the values of all variable objects each time
29688 the program stops. Instead, MI provides an update command that lists all
29689 variable objects whose values has changed since the last update
29690 operation. This considerably reduces the amount of data that must
29691 be transferred to the frontend. As noted above, children variable
29692 objects are created on demand, and only leaf variable objects have a
29693 real value. As result, gdb will read target memory only for leaf
29694 variables that frontend has created.
29696 The automatic update is not always desirable. For example, a frontend
29697 might want to keep a value of some expression for future reference,
29698 and never update it. For another example, fetching memory is
29699 relatively slow for embedded targets, so a frontend might want
29700 to disable automatic update for the variables that are either not
29701 visible on the screen, or ``closed''. This is possible using so
29702 called ``frozen variable objects''. Such variable objects are never
29703 implicitly updated.
29705 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29706 fixed variable object, the expression is parsed when the variable
29707 object is created, including associating identifiers to specific
29708 variables. The meaning of expression never changes. For a floating
29709 variable object the values of variables whose names appear in the
29710 expressions are re-evaluated every time in the context of the current
29711 frame. Consider this example:
29716 struct work_state state;
29723 If a fixed variable object for the @code{state} variable is created in
29724 this function, and we enter the recursive call, the variable
29725 object will report the value of @code{state} in the top-level
29726 @code{do_work} invocation. On the other hand, a floating variable
29727 object will report the value of @code{state} in the current frame.
29729 If an expression specified when creating a fixed variable object
29730 refers to a local variable, the variable object becomes bound to the
29731 thread and frame in which the variable object is created. When such
29732 variable object is updated, @value{GDBN} makes sure that the
29733 thread/frame combination the variable object is bound to still exists,
29734 and re-evaluates the variable object in context of that thread/frame.
29736 The following is the complete set of @sc{gdb/mi} operations defined to
29737 access this functionality:
29739 @multitable @columnfractions .4 .6
29740 @item @strong{Operation}
29741 @tab @strong{Description}
29743 @item @code{-enable-pretty-printing}
29744 @tab enable Python-based pretty-printing
29745 @item @code{-var-create}
29746 @tab create a variable object
29747 @item @code{-var-delete}
29748 @tab delete the variable object and/or its children
29749 @item @code{-var-set-format}
29750 @tab set the display format of this variable
29751 @item @code{-var-show-format}
29752 @tab show the display format of this variable
29753 @item @code{-var-info-num-children}
29754 @tab tells how many children this object has
29755 @item @code{-var-list-children}
29756 @tab return a list of the object's children
29757 @item @code{-var-info-type}
29758 @tab show the type of this variable object
29759 @item @code{-var-info-expression}
29760 @tab print parent-relative expression that this variable object represents
29761 @item @code{-var-info-path-expression}
29762 @tab print full expression that this variable object represents
29763 @item @code{-var-show-attributes}
29764 @tab is this variable editable? does it exist here?
29765 @item @code{-var-evaluate-expression}
29766 @tab get the value of this variable
29767 @item @code{-var-assign}
29768 @tab set the value of this variable
29769 @item @code{-var-update}
29770 @tab update the variable and its children
29771 @item @code{-var-set-frozen}
29772 @tab set frozeness attribute
29773 @item @code{-var-set-update-range}
29774 @tab set range of children to display on update
29777 In the next subsection we describe each operation in detail and suggest
29778 how it can be used.
29780 @subheading Description And Use of Operations on Variable Objects
29782 @subheading The @code{-enable-pretty-printing} Command
29783 @findex -enable-pretty-printing
29786 -enable-pretty-printing
29789 @value{GDBN} allows Python-based visualizers to affect the output of the
29790 MI variable object commands. However, because there was no way to
29791 implement this in a fully backward-compatible way, a front end must
29792 request that this functionality be enabled.
29794 Once enabled, this feature cannot be disabled.
29796 Note that if Python support has not been compiled into @value{GDBN},
29797 this command will still succeed (and do nothing).
29799 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29800 may work differently in future versions of @value{GDBN}.
29802 @subheading The @code{-var-create} Command
29803 @findex -var-create
29805 @subsubheading Synopsis
29808 -var-create @{@var{name} | "-"@}
29809 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29812 This operation creates a variable object, which allows the monitoring of
29813 a variable, the result of an expression, a memory cell or a CPU
29816 The @var{name} parameter is the string by which the object can be
29817 referenced. It must be unique. If @samp{-} is specified, the varobj
29818 system will generate a string ``varNNNNNN'' automatically. It will be
29819 unique provided that one does not specify @var{name} of that format.
29820 The command fails if a duplicate name is found.
29822 The frame under which the expression should be evaluated can be
29823 specified by @var{frame-addr}. A @samp{*} indicates that the current
29824 frame should be used. A @samp{@@} indicates that a floating variable
29825 object must be created.
29827 @var{expression} is any expression valid on the current language set (must not
29828 begin with a @samp{*}), or one of the following:
29832 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29835 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29838 @samp{$@var{regname}} --- a CPU register name
29841 @cindex dynamic varobj
29842 A varobj's contents may be provided by a Python-based pretty-printer. In this
29843 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29844 have slightly different semantics in some cases. If the
29845 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29846 will never create a dynamic varobj. This ensures backward
29847 compatibility for existing clients.
29849 @subsubheading Result
29851 This operation returns attributes of the newly-created varobj. These
29856 The name of the varobj.
29859 The number of children of the varobj. This number is not necessarily
29860 reliable for a dynamic varobj. Instead, you must examine the
29861 @samp{has_more} attribute.
29864 The varobj's scalar value. For a varobj whose type is some sort of
29865 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29866 will not be interesting.
29869 The varobj's type. This is a string representation of the type, as
29870 would be printed by the @value{GDBN} CLI. If @samp{print object}
29871 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29872 @emph{actual} (derived) type of the object is shown rather than the
29873 @emph{declared} one.
29876 If a variable object is bound to a specific thread, then this is the
29877 thread's global identifier.
29880 For a dynamic varobj, this indicates whether there appear to be any
29881 children available. For a non-dynamic varobj, this will be 0.
29884 This attribute will be present and have the value @samp{1} if the
29885 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29886 then this attribute will not be present.
29889 A dynamic varobj can supply a display hint to the front end. The
29890 value comes directly from the Python pretty-printer object's
29891 @code{display_hint} method. @xref{Pretty Printing API}.
29894 Typical output will look like this:
29897 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29898 has_more="@var{has_more}"
29902 @subheading The @code{-var-delete} Command
29903 @findex -var-delete
29905 @subsubheading Synopsis
29908 -var-delete [ -c ] @var{name}
29911 Deletes a previously created variable object and all of its children.
29912 With the @samp{-c} option, just deletes the children.
29914 Returns an error if the object @var{name} is not found.
29917 @subheading The @code{-var-set-format} Command
29918 @findex -var-set-format
29920 @subsubheading Synopsis
29923 -var-set-format @var{name} @var{format-spec}
29926 Sets the output format for the value of the object @var{name} to be
29929 @anchor{-var-set-format}
29930 The syntax for the @var{format-spec} is as follows:
29933 @var{format-spec} @expansion{}
29934 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29937 The natural format is the default format choosen automatically
29938 based on the variable type (like decimal for an @code{int}, hex
29939 for pointers, etc.).
29941 The zero-hexadecimal format has a representation similar to hexadecimal
29942 but with padding zeroes to the left of the value. For example, a 32-bit
29943 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29944 zero-hexadecimal format.
29946 For a variable with children, the format is set only on the
29947 variable itself, and the children are not affected.
29949 @subheading The @code{-var-show-format} Command
29950 @findex -var-show-format
29952 @subsubheading Synopsis
29955 -var-show-format @var{name}
29958 Returns the format used to display the value of the object @var{name}.
29961 @var{format} @expansion{}
29966 @subheading The @code{-var-info-num-children} Command
29967 @findex -var-info-num-children
29969 @subsubheading Synopsis
29972 -var-info-num-children @var{name}
29975 Returns the number of children of a variable object @var{name}:
29981 Note that this number is not completely reliable for a dynamic varobj.
29982 It will return the current number of children, but more children may
29986 @subheading The @code{-var-list-children} Command
29987 @findex -var-list-children
29989 @subsubheading Synopsis
29992 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29994 @anchor{-var-list-children}
29996 Return a list of the children of the specified variable object and
29997 create variable objects for them, if they do not already exist. With
29998 a single argument or if @var{print-values} has a value of 0 or
29999 @code{--no-values}, print only the names of the variables; if
30000 @var{print-values} is 1 or @code{--all-values}, also print their
30001 values; and if it is 2 or @code{--simple-values} print the name and
30002 value for simple data types and just the name for arrays, structures
30005 @var{from} and @var{to}, if specified, indicate the range of children
30006 to report. If @var{from} or @var{to} is less than zero, the range is
30007 reset and all children will be reported. Otherwise, children starting
30008 at @var{from} (zero-based) and up to and excluding @var{to} will be
30011 If a child range is requested, it will only affect the current call to
30012 @code{-var-list-children}, but not future calls to @code{-var-update}.
30013 For this, you must instead use @code{-var-set-update-range}. The
30014 intent of this approach is to enable a front end to implement any
30015 update approach it likes; for example, scrolling a view may cause the
30016 front end to request more children with @code{-var-list-children}, and
30017 then the front end could call @code{-var-set-update-range} with a
30018 different range to ensure that future updates are restricted to just
30021 For each child the following results are returned:
30026 Name of the variable object created for this child.
30029 The expression to be shown to the user by the front end to designate this child.
30030 For example this may be the name of a structure member.
30032 For a dynamic varobj, this value cannot be used to form an
30033 expression. There is no way to do this at all with a dynamic varobj.
30035 For C/C@t{++} structures there are several pseudo children returned to
30036 designate access qualifiers. For these pseudo children @var{exp} is
30037 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30038 type and value are not present.
30040 A dynamic varobj will not report the access qualifying
30041 pseudo-children, regardless of the language. This information is not
30042 available at all with a dynamic varobj.
30045 Number of children this child has. For a dynamic varobj, this will be
30049 The type of the child. If @samp{print object}
30050 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30051 @emph{actual} (derived) type of the object is shown rather than the
30052 @emph{declared} one.
30055 If values were requested, this is the value.
30058 If this variable object is associated with a thread, this is the
30059 thread's global thread id. Otherwise this result is not present.
30062 If the variable object is frozen, this variable will be present with a value of 1.
30065 A dynamic varobj can supply a display hint to the front end. The
30066 value comes directly from the Python pretty-printer object's
30067 @code{display_hint} method. @xref{Pretty Printing API}.
30070 This attribute will be present and have the value @samp{1} if the
30071 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30072 then this attribute will not be present.
30076 The result may have its own attributes:
30080 A dynamic varobj can supply a display hint to the front end. The
30081 value comes directly from the Python pretty-printer object's
30082 @code{display_hint} method. @xref{Pretty Printing API}.
30085 This is an integer attribute which is nonzero if there are children
30086 remaining after the end of the selected range.
30089 @subsubheading Example
30093 -var-list-children n
30094 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30095 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30097 -var-list-children --all-values n
30098 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30099 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30103 @subheading The @code{-var-info-type} Command
30104 @findex -var-info-type
30106 @subsubheading Synopsis
30109 -var-info-type @var{name}
30112 Returns the type of the specified variable @var{name}. The type is
30113 returned as a string in the same format as it is output by the
30117 type=@var{typename}
30121 @subheading The @code{-var-info-expression} Command
30122 @findex -var-info-expression
30124 @subsubheading Synopsis
30127 -var-info-expression @var{name}
30130 Returns a string that is suitable for presenting this
30131 variable object in user interface. The string is generally
30132 not valid expression in the current language, and cannot be evaluated.
30134 For example, if @code{a} is an array, and variable object
30135 @code{A} was created for @code{a}, then we'll get this output:
30138 (gdb) -var-info-expression A.1
30139 ^done,lang="C",exp="1"
30143 Here, the value of @code{lang} is the language name, which can be
30144 found in @ref{Supported Languages}.
30146 Note that the output of the @code{-var-list-children} command also
30147 includes those expressions, so the @code{-var-info-expression} command
30150 @subheading The @code{-var-info-path-expression} Command
30151 @findex -var-info-path-expression
30153 @subsubheading Synopsis
30156 -var-info-path-expression @var{name}
30159 Returns an expression that can be evaluated in the current
30160 context and will yield the same value that a variable object has.
30161 Compare this with the @code{-var-info-expression} command, which
30162 result can be used only for UI presentation. Typical use of
30163 the @code{-var-info-path-expression} command is creating a
30164 watchpoint from a variable object.
30166 This command is currently not valid for children of a dynamic varobj,
30167 and will give an error when invoked on one.
30169 For example, suppose @code{C} is a C@t{++} class, derived from class
30170 @code{Base}, and that the @code{Base} class has a member called
30171 @code{m_size}. Assume a variable @code{c} is has the type of
30172 @code{C} and a variable object @code{C} was created for variable
30173 @code{c}. Then, we'll get this output:
30175 (gdb) -var-info-path-expression C.Base.public.m_size
30176 ^done,path_expr=((Base)c).m_size)
30179 @subheading The @code{-var-show-attributes} Command
30180 @findex -var-show-attributes
30182 @subsubheading Synopsis
30185 -var-show-attributes @var{name}
30188 List attributes of the specified variable object @var{name}:
30191 status=@var{attr} [ ( ,@var{attr} )* ]
30195 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30197 @subheading The @code{-var-evaluate-expression} Command
30198 @findex -var-evaluate-expression
30200 @subsubheading Synopsis
30203 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30206 Evaluates the expression that is represented by the specified variable
30207 object and returns its value as a string. The format of the string
30208 can be specified with the @samp{-f} option. The possible values of
30209 this option are the same as for @code{-var-set-format}
30210 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30211 the current display format will be used. The current display format
30212 can be changed using the @code{-var-set-format} command.
30218 Note that one must invoke @code{-var-list-children} for a variable
30219 before the value of a child variable can be evaluated.
30221 @subheading The @code{-var-assign} Command
30222 @findex -var-assign
30224 @subsubheading Synopsis
30227 -var-assign @var{name} @var{expression}
30230 Assigns the value of @var{expression} to the variable object specified
30231 by @var{name}. The object must be @samp{editable}. If the variable's
30232 value is altered by the assign, the variable will show up in any
30233 subsequent @code{-var-update} list.
30235 @subsubheading Example
30243 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30247 @subheading The @code{-var-update} Command
30248 @findex -var-update
30250 @subsubheading Synopsis
30253 -var-update [@var{print-values}] @{@var{name} | "*"@}
30256 Reevaluate the expressions corresponding to the variable object
30257 @var{name} and all its direct and indirect children, and return the
30258 list of variable objects whose values have changed; @var{name} must
30259 be a root variable object. Here, ``changed'' means that the result of
30260 @code{-var-evaluate-expression} before and after the
30261 @code{-var-update} is different. If @samp{*} is used as the variable
30262 object names, all existing variable objects are updated, except
30263 for frozen ones (@pxref{-var-set-frozen}). The option
30264 @var{print-values} determines whether both names and values, or just
30265 names are printed. The possible values of this option are the same
30266 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30267 recommended to use the @samp{--all-values} option, to reduce the
30268 number of MI commands needed on each program stop.
30270 With the @samp{*} parameter, if a variable object is bound to a
30271 currently running thread, it will not be updated, without any
30274 If @code{-var-set-update-range} was previously used on a varobj, then
30275 only the selected range of children will be reported.
30277 @code{-var-update} reports all the changed varobjs in a tuple named
30280 Each item in the change list is itself a tuple holding:
30284 The name of the varobj.
30287 If values were requested for this update, then this field will be
30288 present and will hold the value of the varobj.
30291 @anchor{-var-update}
30292 This field is a string which may take one of three values:
30296 The variable object's current value is valid.
30299 The variable object does not currently hold a valid value but it may
30300 hold one in the future if its associated expression comes back into
30304 The variable object no longer holds a valid value.
30305 This can occur when the executable file being debugged has changed,
30306 either through recompilation or by using the @value{GDBN} @code{file}
30307 command. The front end should normally choose to delete these variable
30311 In the future new values may be added to this list so the front should
30312 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30315 This is only present if the varobj is still valid. If the type
30316 changed, then this will be the string @samp{true}; otherwise it will
30319 When a varobj's type changes, its children are also likely to have
30320 become incorrect. Therefore, the varobj's children are automatically
30321 deleted when this attribute is @samp{true}. Also, the varobj's update
30322 range, when set using the @code{-var-set-update-range} command, is
30326 If the varobj's type changed, then this field will be present and will
30329 @item new_num_children
30330 For a dynamic varobj, if the number of children changed, or if the
30331 type changed, this will be the new number of children.
30333 The @samp{numchild} field in other varobj responses is generally not
30334 valid for a dynamic varobj -- it will show the number of children that
30335 @value{GDBN} knows about, but because dynamic varobjs lazily
30336 instantiate their children, this will not reflect the number of
30337 children which may be available.
30339 The @samp{new_num_children} attribute only reports changes to the
30340 number of children known by @value{GDBN}. This is the only way to
30341 detect whether an update has removed children (which necessarily can
30342 only happen at the end of the update range).
30345 The display hint, if any.
30348 This is an integer value, which will be 1 if there are more children
30349 available outside the varobj's update range.
30352 This attribute will be present and have the value @samp{1} if the
30353 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30354 then this attribute will not be present.
30357 If new children were added to a dynamic varobj within the selected
30358 update range (as set by @code{-var-set-update-range}), then they will
30359 be listed in this attribute.
30362 @subsubheading Example
30369 -var-update --all-values var1
30370 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30371 type_changed="false"@}]
30375 @subheading The @code{-var-set-frozen} Command
30376 @findex -var-set-frozen
30377 @anchor{-var-set-frozen}
30379 @subsubheading Synopsis
30382 -var-set-frozen @var{name} @var{flag}
30385 Set the frozenness flag on the variable object @var{name}. The
30386 @var{flag} parameter should be either @samp{1} to make the variable
30387 frozen or @samp{0} to make it unfrozen. If a variable object is
30388 frozen, then neither itself, nor any of its children, are
30389 implicitly updated by @code{-var-update} of
30390 a parent variable or by @code{-var-update *}. Only
30391 @code{-var-update} of the variable itself will update its value and
30392 values of its children. After a variable object is unfrozen, it is
30393 implicitly updated by all subsequent @code{-var-update} operations.
30394 Unfreezing a variable does not update it, only subsequent
30395 @code{-var-update} does.
30397 @subsubheading Example
30401 -var-set-frozen V 1
30406 @subheading The @code{-var-set-update-range} command
30407 @findex -var-set-update-range
30408 @anchor{-var-set-update-range}
30410 @subsubheading Synopsis
30413 -var-set-update-range @var{name} @var{from} @var{to}
30416 Set the range of children to be returned by future invocations of
30417 @code{-var-update}.
30419 @var{from} and @var{to} indicate the range of children to report. If
30420 @var{from} or @var{to} is less than zero, the range is reset and all
30421 children will be reported. Otherwise, children starting at @var{from}
30422 (zero-based) and up to and excluding @var{to} will be reported.
30424 @subsubheading Example
30428 -var-set-update-range V 1 2
30432 @subheading The @code{-var-set-visualizer} command
30433 @findex -var-set-visualizer
30434 @anchor{-var-set-visualizer}
30436 @subsubheading Synopsis
30439 -var-set-visualizer @var{name} @var{visualizer}
30442 Set a visualizer for the variable object @var{name}.
30444 @var{visualizer} is the visualizer to use. The special value
30445 @samp{None} means to disable any visualizer in use.
30447 If not @samp{None}, @var{visualizer} must be a Python expression.
30448 This expression must evaluate to a callable object which accepts a
30449 single argument. @value{GDBN} will call this object with the value of
30450 the varobj @var{name} as an argument (this is done so that the same
30451 Python pretty-printing code can be used for both the CLI and MI).
30452 When called, this object must return an object which conforms to the
30453 pretty-printing interface (@pxref{Pretty Printing API}).
30455 The pre-defined function @code{gdb.default_visualizer} may be used to
30456 select a visualizer by following the built-in process
30457 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30458 a varobj is created, and so ordinarily is not needed.
30460 This feature is only available if Python support is enabled. The MI
30461 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30462 can be used to check this.
30464 @subsubheading Example
30466 Resetting the visualizer:
30470 -var-set-visualizer V None
30474 Reselecting the default (type-based) visualizer:
30478 -var-set-visualizer V gdb.default_visualizer
30482 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30483 can be used to instantiate this class for a varobj:
30487 -var-set-visualizer V "lambda val: SomeClass()"
30491 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30492 @node GDB/MI Data Manipulation
30493 @section @sc{gdb/mi} Data Manipulation
30495 @cindex data manipulation, in @sc{gdb/mi}
30496 @cindex @sc{gdb/mi}, data manipulation
30497 This section describes the @sc{gdb/mi} commands that manipulate data:
30498 examine memory and registers, evaluate expressions, etc.
30500 For details about what an addressable memory unit is,
30501 @pxref{addressable memory unit}.
30503 @c REMOVED FROM THE INTERFACE.
30504 @c @subheading -data-assign
30505 @c Change the value of a program variable. Plenty of side effects.
30506 @c @subsubheading GDB Command
30508 @c @subsubheading Example
30511 @subheading The @code{-data-disassemble} Command
30512 @findex -data-disassemble
30514 @subsubheading Synopsis
30518 [ -s @var{start-addr} -e @var{end-addr} ]
30519 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30527 @item @var{start-addr}
30528 is the beginning address (or @code{$pc})
30529 @item @var{end-addr}
30531 @item @var{filename}
30532 is the name of the file to disassemble
30533 @item @var{linenum}
30534 is the line number to disassemble around
30536 is the number of disassembly lines to be produced. If it is -1,
30537 the whole function will be disassembled, in case no @var{end-addr} is
30538 specified. If @var{end-addr} is specified as a non-zero value, and
30539 @var{lines} is lower than the number of disassembly lines between
30540 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30541 displayed; if @var{lines} is higher than the number of lines between
30542 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30547 @item 0 disassembly only
30548 @item 1 mixed source and disassembly (deprecated)
30549 @item 2 disassembly with raw opcodes
30550 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30551 @item 4 mixed source and disassembly
30552 @item 5 mixed source and disassembly with raw opcodes
30555 Modes 1 and 3 are deprecated. The output is ``source centric''
30556 which hasn't proved useful in practice.
30557 @xref{Machine Code}, for a discussion of the difference between
30558 @code{/m} and @code{/s} output of the @code{disassemble} command.
30561 @subsubheading Result
30563 The result of the @code{-data-disassemble} command will be a list named
30564 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30565 used with the @code{-data-disassemble} command.
30567 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30572 The address at which this instruction was disassembled.
30575 The name of the function this instruction is within.
30578 The decimal offset in bytes from the start of @samp{func-name}.
30581 The text disassembly for this @samp{address}.
30584 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30585 bytes for the @samp{inst} field.
30589 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30590 @samp{src_and_asm_line}, each of which has the following fields:
30594 The line number within @samp{file}.
30597 The file name from the compilation unit. This might be an absolute
30598 file name or a relative file name depending on the compile command
30602 Absolute file name of @samp{file}. It is converted to a canonical form
30603 using the source file search path
30604 (@pxref{Source Path, ,Specifying Source Directories})
30605 and after resolving all the symbolic links.
30607 If the source file is not found this field will contain the path as
30608 present in the debug information.
30610 @item line_asm_insn
30611 This is a list of tuples containing the disassembly for @samp{line} in
30612 @samp{file}. The fields of each tuple are the same as for
30613 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30614 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30619 Note that whatever included in the @samp{inst} field, is not
30620 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30623 @subsubheading @value{GDBN} Command
30625 The corresponding @value{GDBN} command is @samp{disassemble}.
30627 @subsubheading Example
30629 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30633 -data-disassemble -s $pc -e "$pc + 20" -- 0
30636 @{address="0x000107c0",func-name="main",offset="4",
30637 inst="mov 2, %o0"@},
30638 @{address="0x000107c4",func-name="main",offset="8",
30639 inst="sethi %hi(0x11800), %o2"@},
30640 @{address="0x000107c8",func-name="main",offset="12",
30641 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30642 @{address="0x000107cc",func-name="main",offset="16",
30643 inst="sethi %hi(0x11800), %o2"@},
30644 @{address="0x000107d0",func-name="main",offset="20",
30645 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30649 Disassemble the whole @code{main} function. Line 32 is part of
30653 -data-disassemble -f basics.c -l 32 -- 0
30655 @{address="0x000107bc",func-name="main",offset="0",
30656 inst="save %sp, -112, %sp"@},
30657 @{address="0x000107c0",func-name="main",offset="4",
30658 inst="mov 2, %o0"@},
30659 @{address="0x000107c4",func-name="main",offset="8",
30660 inst="sethi %hi(0x11800), %o2"@},
30662 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30663 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30667 Disassemble 3 instructions from the start of @code{main}:
30671 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30673 @{address="0x000107bc",func-name="main",offset="0",
30674 inst="save %sp, -112, %sp"@},
30675 @{address="0x000107c0",func-name="main",offset="4",
30676 inst="mov 2, %o0"@},
30677 @{address="0x000107c4",func-name="main",offset="8",
30678 inst="sethi %hi(0x11800), %o2"@}]
30682 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30686 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30688 src_and_asm_line=@{line="31",
30689 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30690 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30691 line_asm_insn=[@{address="0x000107bc",
30692 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30693 src_and_asm_line=@{line="32",
30694 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30695 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30696 line_asm_insn=[@{address="0x000107c0",
30697 func-name="main",offset="4",inst="mov 2, %o0"@},
30698 @{address="0x000107c4",func-name="main",offset="8",
30699 inst="sethi %hi(0x11800), %o2"@}]@}]
30704 @subheading The @code{-data-evaluate-expression} Command
30705 @findex -data-evaluate-expression
30707 @subsubheading Synopsis
30710 -data-evaluate-expression @var{expr}
30713 Evaluate @var{expr} as an expression. The expression could contain an
30714 inferior function call. The function call will execute synchronously.
30715 If the expression contains spaces, it must be enclosed in double quotes.
30717 @subsubheading @value{GDBN} Command
30719 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30720 @samp{call}. In @code{gdbtk} only, there's a corresponding
30721 @samp{gdb_eval} command.
30723 @subsubheading Example
30725 In the following example, the numbers that precede the commands are the
30726 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30727 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30731 211-data-evaluate-expression A
30734 311-data-evaluate-expression &A
30735 311^done,value="0xefffeb7c"
30737 411-data-evaluate-expression A+3
30740 511-data-evaluate-expression "A + 3"
30746 @subheading The @code{-data-list-changed-registers} Command
30747 @findex -data-list-changed-registers
30749 @subsubheading Synopsis
30752 -data-list-changed-registers
30755 Display a list of the registers that have changed.
30757 @subsubheading @value{GDBN} Command
30759 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30760 has the corresponding command @samp{gdb_changed_register_list}.
30762 @subsubheading Example
30764 On a PPC MBX board:
30772 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30773 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30776 -data-list-changed-registers
30777 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30778 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30779 "24","25","26","27","28","30","31","64","65","66","67","69"]
30784 @subheading The @code{-data-list-register-names} Command
30785 @findex -data-list-register-names
30787 @subsubheading Synopsis
30790 -data-list-register-names [ ( @var{regno} )+ ]
30793 Show a list of register names for the current target. If no arguments
30794 are given, it shows a list of the names of all the registers. If
30795 integer numbers are given as arguments, it will print a list of the
30796 names of the registers corresponding to the arguments. To ensure
30797 consistency between a register name and its number, the output list may
30798 include empty register names.
30800 @subsubheading @value{GDBN} Command
30802 @value{GDBN} does not have a command which corresponds to
30803 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30804 corresponding command @samp{gdb_regnames}.
30806 @subsubheading Example
30808 For the PPC MBX board:
30811 -data-list-register-names
30812 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30813 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30814 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30815 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30816 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30817 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30818 "", "pc","ps","cr","lr","ctr","xer"]
30820 -data-list-register-names 1 2 3
30821 ^done,register-names=["r1","r2","r3"]
30825 @subheading The @code{-data-list-register-values} Command
30826 @findex -data-list-register-values
30828 @subsubheading Synopsis
30831 -data-list-register-values
30832 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30835 Display the registers' contents. The format according to which the
30836 registers' contents are to be returned is given by @var{fmt}, followed
30837 by an optional list of numbers specifying the registers to display. A
30838 missing list of numbers indicates that the contents of all the
30839 registers must be returned. The @code{--skip-unavailable} option
30840 indicates that only the available registers are to be returned.
30842 Allowed formats for @var{fmt} are:
30859 @subsubheading @value{GDBN} Command
30861 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30862 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30864 @subsubheading Example
30866 For a PPC MBX board (note: line breaks are for readability only, they
30867 don't appear in the actual output):
30871 -data-list-register-values r 64 65
30872 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30873 @{number="65",value="0x00029002"@}]
30875 -data-list-register-values x
30876 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30877 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30878 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30879 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30880 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30881 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30882 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30883 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30884 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30885 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30886 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30887 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30888 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30889 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30890 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30891 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30892 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30893 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30894 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30895 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30896 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30897 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30898 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30899 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30900 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30901 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30902 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30903 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30904 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30905 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30906 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30907 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30908 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30909 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30910 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30911 @{number="69",value="0x20002b03"@}]
30916 @subheading The @code{-data-read-memory} Command
30917 @findex -data-read-memory
30919 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30921 @subsubheading Synopsis
30924 -data-read-memory [ -o @var{byte-offset} ]
30925 @var{address} @var{word-format} @var{word-size}
30926 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30933 @item @var{address}
30934 An expression specifying the address of the first memory word to be
30935 read. Complex expressions containing embedded white space should be
30936 quoted using the C convention.
30938 @item @var{word-format}
30939 The format to be used to print the memory words. The notation is the
30940 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30943 @item @var{word-size}
30944 The size of each memory word in bytes.
30946 @item @var{nr-rows}
30947 The number of rows in the output table.
30949 @item @var{nr-cols}
30950 The number of columns in the output table.
30953 If present, indicates that each row should include an @sc{ascii} dump. The
30954 value of @var{aschar} is used as a padding character when a byte is not a
30955 member of the printable @sc{ascii} character set (printable @sc{ascii}
30956 characters are those whose code is between 32 and 126, inclusively).
30958 @item @var{byte-offset}
30959 An offset to add to the @var{address} before fetching memory.
30962 This command displays memory contents as a table of @var{nr-rows} by
30963 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30964 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30965 (returned as @samp{total-bytes}). Should less than the requested number
30966 of bytes be returned by the target, the missing words are identified
30967 using @samp{N/A}. The number of bytes read from the target is returned
30968 in @samp{nr-bytes} and the starting address used to read memory in
30971 The address of the next/previous row or page is available in
30972 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30975 @subsubheading @value{GDBN} Command
30977 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30978 @samp{gdb_get_mem} memory read command.
30980 @subsubheading Example
30982 Read six bytes of memory starting at @code{bytes+6} but then offset by
30983 @code{-6} bytes. Format as three rows of two columns. One byte per
30984 word. Display each word in hex.
30988 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30989 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30990 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30991 prev-page="0x0000138a",memory=[
30992 @{addr="0x00001390",data=["0x00","0x01"]@},
30993 @{addr="0x00001392",data=["0x02","0x03"]@},
30994 @{addr="0x00001394",data=["0x04","0x05"]@}]
30998 Read two bytes of memory starting at address @code{shorts + 64} and
30999 display as a single word formatted in decimal.
31003 5-data-read-memory shorts+64 d 2 1 1
31004 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31005 next-row="0x00001512",prev-row="0x0000150e",
31006 next-page="0x00001512",prev-page="0x0000150e",memory=[
31007 @{addr="0x00001510",data=["128"]@}]
31011 Read thirty two bytes of memory starting at @code{bytes+16} and format
31012 as eight rows of four columns. Include a string encoding with @samp{x}
31013 used as the non-printable character.
31017 4-data-read-memory bytes+16 x 1 8 4 x
31018 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31019 next-row="0x000013c0",prev-row="0x0000139c",
31020 next-page="0x000013c0",prev-page="0x00001380",memory=[
31021 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31022 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31023 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31024 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31025 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31026 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31027 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31028 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31032 @subheading The @code{-data-read-memory-bytes} Command
31033 @findex -data-read-memory-bytes
31035 @subsubheading Synopsis
31038 -data-read-memory-bytes [ -o @var{offset} ]
31039 @var{address} @var{count}
31046 @item @var{address}
31047 An expression specifying the address of the first addressable memory unit
31048 to be read. Complex expressions containing embedded white space should be
31049 quoted using the C convention.
31052 The number of addressable memory units to read. This should be an integer
31056 The offset relative to @var{address} at which to start reading. This
31057 should be an integer literal. This option is provided so that a frontend
31058 is not required to first evaluate address and then perform address
31059 arithmetics itself.
31063 This command attempts to read all accessible memory regions in the
31064 specified range. First, all regions marked as unreadable in the memory
31065 map (if one is defined) will be skipped. @xref{Memory Region
31066 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31067 regions. For each one, if reading full region results in an errors,
31068 @value{GDBN} will try to read a subset of the region.
31070 In general, every single memory unit in the region may be readable or not,
31071 and the only way to read every readable unit is to try a read at
31072 every address, which is not practical. Therefore, @value{GDBN} will
31073 attempt to read all accessible memory units at either beginning or the end
31074 of the region, using a binary division scheme. This heuristic works
31075 well for reading accross a memory map boundary. Note that if a region
31076 has a readable range that is neither at the beginning or the end,
31077 @value{GDBN} will not read it.
31079 The result record (@pxref{GDB/MI Result Records}) that is output of
31080 the command includes a field named @samp{memory} whose content is a
31081 list of tuples. Each tuple represent a successfully read memory block
31082 and has the following fields:
31086 The start address of the memory block, as hexadecimal literal.
31089 The end address of the memory block, as hexadecimal literal.
31092 The offset of the memory block, as hexadecimal literal, relative to
31093 the start address passed to @code{-data-read-memory-bytes}.
31096 The contents of the memory block, in hex.
31102 @subsubheading @value{GDBN} Command
31104 The corresponding @value{GDBN} command is @samp{x}.
31106 @subsubheading Example
31110 -data-read-memory-bytes &a 10
31111 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31113 contents="01000000020000000300"@}]
31118 @subheading The @code{-data-write-memory-bytes} Command
31119 @findex -data-write-memory-bytes
31121 @subsubheading Synopsis
31124 -data-write-memory-bytes @var{address} @var{contents}
31125 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31132 @item @var{address}
31133 An expression specifying the address of the first addressable memory unit
31134 to be written. Complex expressions containing embedded white space should
31135 be quoted using the C convention.
31137 @item @var{contents}
31138 The hex-encoded data to write. It is an error if @var{contents} does
31139 not represent an integral number of addressable memory units.
31142 Optional argument indicating the number of addressable memory units to be
31143 written. If @var{count} is greater than @var{contents}' length,
31144 @value{GDBN} will repeatedly write @var{contents} until it fills
31145 @var{count} memory units.
31149 @subsubheading @value{GDBN} Command
31151 There's no corresponding @value{GDBN} command.
31153 @subsubheading Example
31157 -data-write-memory-bytes &a "aabbccdd"
31164 -data-write-memory-bytes &a "aabbccdd" 16e
31169 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31170 @node GDB/MI Tracepoint Commands
31171 @section @sc{gdb/mi} Tracepoint Commands
31173 The commands defined in this section implement MI support for
31174 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31176 @subheading The @code{-trace-find} Command
31177 @findex -trace-find
31179 @subsubheading Synopsis
31182 -trace-find @var{mode} [@var{parameters}@dots{}]
31185 Find a trace frame using criteria defined by @var{mode} and
31186 @var{parameters}. The following table lists permissible
31187 modes and their parameters. For details of operation, see @ref{tfind}.
31192 No parameters are required. Stops examining trace frames.
31195 An integer is required as parameter. Selects tracepoint frame with
31198 @item tracepoint-number
31199 An integer is required as parameter. Finds next
31200 trace frame that corresponds to tracepoint with the specified number.
31203 An address is required as parameter. Finds
31204 next trace frame that corresponds to any tracepoint at the specified
31207 @item pc-inside-range
31208 Two addresses are required as parameters. Finds next trace
31209 frame that corresponds to a tracepoint at an address inside the
31210 specified range. Both bounds are considered to be inside the range.
31212 @item pc-outside-range
31213 Two addresses are required as parameters. Finds
31214 next trace frame that corresponds to a tracepoint at an address outside
31215 the specified range. Both bounds are considered to be inside the range.
31218 Line specification is required as parameter. @xref{Specify Location}.
31219 Finds next trace frame that corresponds to a tracepoint at
31220 the specified location.
31224 If @samp{none} was passed as @var{mode}, the response does not
31225 have fields. Otherwise, the response may have the following fields:
31229 This field has either @samp{0} or @samp{1} as the value, depending
31230 on whether a matching tracepoint was found.
31233 The index of the found traceframe. This field is present iff
31234 the @samp{found} field has value of @samp{1}.
31237 The index of the found tracepoint. This field is present iff
31238 the @samp{found} field has value of @samp{1}.
31241 The information about the frame corresponding to the found trace
31242 frame. This field is present only if a trace frame was found.
31243 @xref{GDB/MI Frame Information}, for description of this field.
31247 @subsubheading @value{GDBN} Command
31249 The corresponding @value{GDBN} command is @samp{tfind}.
31251 @subheading -trace-define-variable
31252 @findex -trace-define-variable
31254 @subsubheading Synopsis
31257 -trace-define-variable @var{name} [ @var{value} ]
31260 Create trace variable @var{name} if it does not exist. If
31261 @var{value} is specified, sets the initial value of the specified
31262 trace variable to that value. Note that the @var{name} should start
31263 with the @samp{$} character.
31265 @subsubheading @value{GDBN} Command
31267 The corresponding @value{GDBN} command is @samp{tvariable}.
31269 @subheading The @code{-trace-frame-collected} Command
31270 @findex -trace-frame-collected
31272 @subsubheading Synopsis
31275 -trace-frame-collected
31276 [--var-print-values @var{var_pval}]
31277 [--comp-print-values @var{comp_pval}]
31278 [--registers-format @var{regformat}]
31279 [--memory-contents]
31282 This command returns the set of collected objects, register names,
31283 trace state variable names, memory ranges and computed expressions
31284 that have been collected at a particular trace frame. The optional
31285 parameters to the command affect the output format in different ways.
31286 See the output description table below for more details.
31288 The reported names can be used in the normal manner to create
31289 varobjs and inspect the objects themselves. The items returned by
31290 this command are categorized so that it is clear which is a variable,
31291 which is a register, which is a trace state variable, which is a
31292 memory range and which is a computed expression.
31294 For instance, if the actions were
31296 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31297 collect *(int*)0xaf02bef0@@40
31301 the object collected in its entirety would be @code{myVar}. The
31302 object @code{myArray} would be partially collected, because only the
31303 element at index @code{myIndex} would be collected. The remaining
31304 objects would be computed expressions.
31306 An example output would be:
31310 -trace-frame-collected
31312 explicit-variables=[@{name="myVar",value="1"@}],
31313 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31314 @{name="myObj.field",value="0"@},
31315 @{name="myPtr->field",value="1"@},
31316 @{name="myCount + 2",value="3"@},
31317 @{name="$tvar1 + 1",value="43970027"@}],
31318 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31319 @{number="1",value="0x0"@},
31320 @{number="2",value="0x4"@},
31322 @{number="125",value="0x0"@}],
31323 tvars=[@{name="$tvar1",current="43970026"@}],
31324 memory=[@{address="0x0000000000602264",length="4"@},
31325 @{address="0x0000000000615bc0",length="4"@}]
31332 @item explicit-variables
31333 The set of objects that have been collected in their entirety (as
31334 opposed to collecting just a few elements of an array or a few struct
31335 members). For each object, its name and value are printed.
31336 The @code{--var-print-values} option affects how or whether the value
31337 field is output. If @var{var_pval} is 0, then print only the names;
31338 if it is 1, print also their values; and if it is 2, print the name,
31339 type and value for simple data types, and the name and type for
31340 arrays, structures and unions.
31342 @item computed-expressions
31343 The set of computed expressions that have been collected at the
31344 current trace frame. The @code{--comp-print-values} option affects
31345 this set like the @code{--var-print-values} option affects the
31346 @code{explicit-variables} set. See above.
31349 The registers that have been collected at the current trace frame.
31350 For each register collected, the name and current value are returned.
31351 The value is formatted according to the @code{--registers-format}
31352 option. See the @command{-data-list-register-values} command for a
31353 list of the allowed formats. The default is @samp{x}.
31356 The trace state variables that have been collected at the current
31357 trace frame. For each trace state variable collected, the name and
31358 current value are returned.
31361 The set of memory ranges that have been collected at the current trace
31362 frame. Its content is a list of tuples. Each tuple represents a
31363 collected memory range and has the following fields:
31367 The start address of the memory range, as hexadecimal literal.
31370 The length of the memory range, as decimal literal.
31373 The contents of the memory block, in hex. This field is only present
31374 if the @code{--memory-contents} option is specified.
31380 @subsubheading @value{GDBN} Command
31382 There is no corresponding @value{GDBN} command.
31384 @subsubheading Example
31386 @subheading -trace-list-variables
31387 @findex -trace-list-variables
31389 @subsubheading Synopsis
31392 -trace-list-variables
31395 Return a table of all defined trace variables. Each element of the
31396 table has the following fields:
31400 The name of the trace variable. This field is always present.
31403 The initial value. This is a 64-bit signed integer. This
31404 field is always present.
31407 The value the trace variable has at the moment. This is a 64-bit
31408 signed integer. This field is absent iff current value is
31409 not defined, for example if the trace was never run, or is
31414 @subsubheading @value{GDBN} Command
31416 The corresponding @value{GDBN} command is @samp{tvariables}.
31418 @subsubheading Example
31422 -trace-list-variables
31423 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31424 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31425 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31426 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31427 body=[variable=@{name="$trace_timestamp",initial="0"@}
31428 variable=@{name="$foo",initial="10",current="15"@}]@}
31432 @subheading -trace-save
31433 @findex -trace-save
31435 @subsubheading Synopsis
31438 -trace-save [ -r ] [ -ctf ] @var{filename}
31441 Saves the collected trace data to @var{filename}. Without the
31442 @samp{-r} option, the data is downloaded from the target and saved
31443 in a local file. With the @samp{-r} option the target is asked
31444 to perform the save.
31446 By default, this command will save the trace in the tfile format. You can
31447 supply the optional @samp{-ctf} argument to save it the CTF format. See
31448 @ref{Trace Files} for more information about CTF.
31450 @subsubheading @value{GDBN} Command
31452 The corresponding @value{GDBN} command is @samp{tsave}.
31455 @subheading -trace-start
31456 @findex -trace-start
31458 @subsubheading Synopsis
31464 Starts a tracing experiment. The result of this command does not
31467 @subsubheading @value{GDBN} Command
31469 The corresponding @value{GDBN} command is @samp{tstart}.
31471 @subheading -trace-status
31472 @findex -trace-status
31474 @subsubheading Synopsis
31480 Obtains the status of a tracing experiment. The result may include
31481 the following fields:
31486 May have a value of either @samp{0}, when no tracing operations are
31487 supported, @samp{1}, when all tracing operations are supported, or
31488 @samp{file} when examining trace file. In the latter case, examining
31489 of trace frame is possible but new tracing experiement cannot be
31490 started. This field is always present.
31493 May have a value of either @samp{0} or @samp{1} depending on whether
31494 tracing experiement is in progress on target. This field is present
31495 if @samp{supported} field is not @samp{0}.
31498 Report the reason why the tracing was stopped last time. This field
31499 may be absent iff tracing was never stopped on target yet. The
31500 value of @samp{request} means the tracing was stopped as result of
31501 the @code{-trace-stop} command. The value of @samp{overflow} means
31502 the tracing buffer is full. The value of @samp{disconnection} means
31503 tracing was automatically stopped when @value{GDBN} has disconnected.
31504 The value of @samp{passcount} means tracing was stopped when a
31505 tracepoint was passed a maximal number of times for that tracepoint.
31506 This field is present if @samp{supported} field is not @samp{0}.
31508 @item stopping-tracepoint
31509 The number of tracepoint whose passcount as exceeded. This field is
31510 present iff the @samp{stop-reason} field has the value of
31514 @itemx frames-created
31515 The @samp{frames} field is a count of the total number of trace frames
31516 in the trace buffer, while @samp{frames-created} is the total created
31517 during the run, including ones that were discarded, such as when a
31518 circular trace buffer filled up. Both fields are optional.
31522 These fields tell the current size of the tracing buffer and the
31523 remaining space. These fields are optional.
31526 The value of the circular trace buffer flag. @code{1} means that the
31527 trace buffer is circular and old trace frames will be discarded if
31528 necessary to make room, @code{0} means that the trace buffer is linear
31532 The value of the disconnected tracing flag. @code{1} means that
31533 tracing will continue after @value{GDBN} disconnects, @code{0} means
31534 that the trace run will stop.
31537 The filename of the trace file being examined. This field is
31538 optional, and only present when examining a trace file.
31542 @subsubheading @value{GDBN} Command
31544 The corresponding @value{GDBN} command is @samp{tstatus}.
31546 @subheading -trace-stop
31547 @findex -trace-stop
31549 @subsubheading Synopsis
31555 Stops a tracing experiment. The result of this command has the same
31556 fields as @code{-trace-status}, except that the @samp{supported} and
31557 @samp{running} fields are not output.
31559 @subsubheading @value{GDBN} Command
31561 The corresponding @value{GDBN} command is @samp{tstop}.
31564 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31565 @node GDB/MI Symbol Query
31566 @section @sc{gdb/mi} Symbol Query Commands
31570 @subheading The @code{-symbol-info-address} Command
31571 @findex -symbol-info-address
31573 @subsubheading Synopsis
31576 -symbol-info-address @var{symbol}
31579 Describe where @var{symbol} is stored.
31581 @subsubheading @value{GDBN} Command
31583 The corresponding @value{GDBN} command is @samp{info address}.
31585 @subsubheading Example
31589 @subheading The @code{-symbol-info-file} Command
31590 @findex -symbol-info-file
31592 @subsubheading Synopsis
31598 Show the file for the symbol.
31600 @subsubheading @value{GDBN} Command
31602 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31603 @samp{gdb_find_file}.
31605 @subsubheading Example
31609 @subheading The @code{-symbol-info-function} Command
31610 @findex -symbol-info-function
31612 @subsubheading Synopsis
31615 -symbol-info-function
31618 Show which function the symbol lives in.
31620 @subsubheading @value{GDBN} Command
31622 @samp{gdb_get_function} in @code{gdbtk}.
31624 @subsubheading Example
31628 @subheading The @code{-symbol-info-line} Command
31629 @findex -symbol-info-line
31631 @subsubheading Synopsis
31637 Show the core addresses of the code for a source line.
31639 @subsubheading @value{GDBN} Command
31641 The corresponding @value{GDBN} command is @samp{info line}.
31642 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31644 @subsubheading Example
31648 @subheading The @code{-symbol-info-symbol} Command
31649 @findex -symbol-info-symbol
31651 @subsubheading Synopsis
31654 -symbol-info-symbol @var{addr}
31657 Describe what symbol is at location @var{addr}.
31659 @subsubheading @value{GDBN} Command
31661 The corresponding @value{GDBN} command is @samp{info symbol}.
31663 @subsubheading Example
31667 @subheading The @code{-symbol-list-functions} Command
31668 @findex -symbol-list-functions
31670 @subsubheading Synopsis
31673 -symbol-list-functions
31676 List the functions in the executable.
31678 @subsubheading @value{GDBN} Command
31680 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31681 @samp{gdb_search} in @code{gdbtk}.
31683 @subsubheading Example
31688 @subheading The @code{-symbol-list-lines} Command
31689 @findex -symbol-list-lines
31691 @subsubheading Synopsis
31694 -symbol-list-lines @var{filename}
31697 Print the list of lines that contain code and their associated program
31698 addresses for the given source filename. The entries are sorted in
31699 ascending PC order.
31701 @subsubheading @value{GDBN} Command
31703 There is no corresponding @value{GDBN} command.
31705 @subsubheading Example
31708 -symbol-list-lines basics.c
31709 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31715 @subheading The @code{-symbol-list-types} Command
31716 @findex -symbol-list-types
31718 @subsubheading Synopsis
31724 List all the type names.
31726 @subsubheading @value{GDBN} Command
31728 The corresponding commands are @samp{info types} in @value{GDBN},
31729 @samp{gdb_search} in @code{gdbtk}.
31731 @subsubheading Example
31735 @subheading The @code{-symbol-list-variables} Command
31736 @findex -symbol-list-variables
31738 @subsubheading Synopsis
31741 -symbol-list-variables
31744 List all the global and static variable names.
31746 @subsubheading @value{GDBN} Command
31748 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31750 @subsubheading Example
31754 @subheading The @code{-symbol-locate} Command
31755 @findex -symbol-locate
31757 @subsubheading Synopsis
31763 @subsubheading @value{GDBN} Command
31765 @samp{gdb_loc} in @code{gdbtk}.
31767 @subsubheading Example
31771 @subheading The @code{-symbol-type} Command
31772 @findex -symbol-type
31774 @subsubheading Synopsis
31777 -symbol-type @var{variable}
31780 Show type of @var{variable}.
31782 @subsubheading @value{GDBN} Command
31784 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31785 @samp{gdb_obj_variable}.
31787 @subsubheading Example
31792 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31793 @node GDB/MI File Commands
31794 @section @sc{gdb/mi} File Commands
31796 This section describes the GDB/MI commands to specify executable file names
31797 and to read in and obtain symbol table information.
31799 @subheading The @code{-file-exec-and-symbols} Command
31800 @findex -file-exec-and-symbols
31802 @subsubheading Synopsis
31805 -file-exec-and-symbols @var{file}
31808 Specify the executable file to be debugged. This file is the one from
31809 which the symbol table is also read. If no file is specified, the
31810 command clears the executable and symbol information. If breakpoints
31811 are set when using this command with no arguments, @value{GDBN} will produce
31812 error messages. Otherwise, no output is produced, except a completion
31815 @subsubheading @value{GDBN} Command
31817 The corresponding @value{GDBN} command is @samp{file}.
31819 @subsubheading Example
31823 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31829 @subheading The @code{-file-exec-file} Command
31830 @findex -file-exec-file
31832 @subsubheading Synopsis
31835 -file-exec-file @var{file}
31838 Specify the executable file to be debugged. Unlike
31839 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31840 from this file. If used without argument, @value{GDBN} clears the information
31841 about the executable file. No output is produced, except a completion
31844 @subsubheading @value{GDBN} Command
31846 The corresponding @value{GDBN} command is @samp{exec-file}.
31848 @subsubheading Example
31852 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31859 @subheading The @code{-file-list-exec-sections} Command
31860 @findex -file-list-exec-sections
31862 @subsubheading Synopsis
31865 -file-list-exec-sections
31868 List the sections of the current executable file.
31870 @subsubheading @value{GDBN} Command
31872 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31873 information as this command. @code{gdbtk} has a corresponding command
31874 @samp{gdb_load_info}.
31876 @subsubheading Example
31881 @subheading The @code{-file-list-exec-source-file} Command
31882 @findex -file-list-exec-source-file
31884 @subsubheading Synopsis
31887 -file-list-exec-source-file
31890 List the line number, the current source file, and the absolute path
31891 to the current source file for the current executable. The macro
31892 information field has a value of @samp{1} or @samp{0} depending on
31893 whether or not the file includes preprocessor macro information.
31895 @subsubheading @value{GDBN} Command
31897 The @value{GDBN} equivalent is @samp{info source}
31899 @subsubheading Example
31903 123-file-list-exec-source-file
31904 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31909 @subheading The @code{-file-list-exec-source-files} Command
31910 @findex -file-list-exec-source-files
31912 @subsubheading Synopsis
31915 -file-list-exec-source-files
31918 List the source files for the current executable.
31920 It will always output both the filename and fullname (absolute file
31921 name) of a source file.
31923 @subsubheading @value{GDBN} Command
31925 The @value{GDBN} equivalent is @samp{info sources}.
31926 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31928 @subsubheading Example
31931 -file-list-exec-source-files
31933 @{file=foo.c,fullname=/home/foo.c@},
31934 @{file=/home/bar.c,fullname=/home/bar.c@},
31935 @{file=gdb_could_not_find_fullpath.c@}]
31939 @subheading The @code{-file-list-shared-libraries} Command
31940 @findex -file-list-shared-libraries
31942 @subsubheading Synopsis
31945 -file-list-shared-libraries [ @var{regexp} ]
31948 List the shared libraries in the program.
31949 With a regular expression @var{regexp}, only those libraries whose
31950 names match @var{regexp} are listed.
31952 @subsubheading @value{GDBN} Command
31954 The corresponding @value{GDBN} command is @samp{info shared}. The fields
31955 have a similar meaning to the @code{=library-loaded} notification.
31956 The @code{ranges} field specifies the multiple segments belonging to this
31957 library. Each range has the following fields:
31961 The address defining the inclusive lower bound of the segment.
31963 The address defining the exclusive upper bound of the segment.
31966 @subsubheading Example
31969 -file-list-exec-source-files
31970 ^done,shared-libraries=[
31971 @{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"@}]@},
31972 @{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"@}]@}]
31978 @subheading The @code{-file-list-symbol-files} Command
31979 @findex -file-list-symbol-files
31981 @subsubheading Synopsis
31984 -file-list-symbol-files
31989 @subsubheading @value{GDBN} Command
31991 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31993 @subsubheading Example
31998 @subheading The @code{-file-symbol-file} Command
31999 @findex -file-symbol-file
32001 @subsubheading Synopsis
32004 -file-symbol-file @var{file}
32007 Read symbol table info from the specified @var{file} argument. When
32008 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32009 produced, except for a completion notification.
32011 @subsubheading @value{GDBN} Command
32013 The corresponding @value{GDBN} command is @samp{symbol-file}.
32015 @subsubheading Example
32019 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32025 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32026 @node GDB/MI Memory Overlay Commands
32027 @section @sc{gdb/mi} Memory Overlay Commands
32029 The memory overlay commands are not implemented.
32031 @c @subheading -overlay-auto
32033 @c @subheading -overlay-list-mapping-state
32035 @c @subheading -overlay-list-overlays
32037 @c @subheading -overlay-map
32039 @c @subheading -overlay-off
32041 @c @subheading -overlay-on
32043 @c @subheading -overlay-unmap
32045 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32046 @node GDB/MI Signal Handling Commands
32047 @section @sc{gdb/mi} Signal Handling Commands
32049 Signal handling commands are not implemented.
32051 @c @subheading -signal-handle
32053 @c @subheading -signal-list-handle-actions
32055 @c @subheading -signal-list-signal-types
32059 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32060 @node GDB/MI Target Manipulation
32061 @section @sc{gdb/mi} Target Manipulation Commands
32064 @subheading The @code{-target-attach} Command
32065 @findex -target-attach
32067 @subsubheading Synopsis
32070 -target-attach @var{pid} | @var{gid} | @var{file}
32073 Attach to a process @var{pid} or a file @var{file} outside of
32074 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32075 group, the id previously returned by
32076 @samp{-list-thread-groups --available} must be used.
32078 @subsubheading @value{GDBN} Command
32080 The corresponding @value{GDBN} command is @samp{attach}.
32082 @subsubheading Example
32086 =thread-created,id="1"
32087 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32093 @subheading The @code{-target-compare-sections} Command
32094 @findex -target-compare-sections
32096 @subsubheading Synopsis
32099 -target-compare-sections [ @var{section} ]
32102 Compare data of section @var{section} on target to the exec file.
32103 Without the argument, all sections are compared.
32105 @subsubheading @value{GDBN} Command
32107 The @value{GDBN} equivalent is @samp{compare-sections}.
32109 @subsubheading Example
32114 @subheading The @code{-target-detach} Command
32115 @findex -target-detach
32117 @subsubheading Synopsis
32120 -target-detach [ @var{pid} | @var{gid} ]
32123 Detach from the remote target which normally resumes its execution.
32124 If either @var{pid} or @var{gid} is specified, detaches from either
32125 the specified process, or specified thread group. There's no output.
32127 @subsubheading @value{GDBN} Command
32129 The corresponding @value{GDBN} command is @samp{detach}.
32131 @subsubheading Example
32141 @subheading The @code{-target-disconnect} Command
32142 @findex -target-disconnect
32144 @subsubheading Synopsis
32150 Disconnect from the remote target. There's no output and the target is
32151 generally not resumed.
32153 @subsubheading @value{GDBN} Command
32155 The corresponding @value{GDBN} command is @samp{disconnect}.
32157 @subsubheading Example
32167 @subheading The @code{-target-download} Command
32168 @findex -target-download
32170 @subsubheading Synopsis
32176 Loads the executable onto the remote target.
32177 It prints out an update message every half second, which includes the fields:
32181 The name of the section.
32183 The size of what has been sent so far for that section.
32185 The size of the section.
32187 The total size of what was sent so far (the current and the previous sections).
32189 The size of the overall executable to download.
32193 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32194 @sc{gdb/mi} Output Syntax}).
32196 In addition, it prints the name and size of the sections, as they are
32197 downloaded. These messages include the following fields:
32201 The name of the section.
32203 The size of the section.
32205 The size of the overall executable to download.
32209 At the end, a summary is printed.
32211 @subsubheading @value{GDBN} Command
32213 The corresponding @value{GDBN} command is @samp{load}.
32215 @subsubheading Example
32217 Note: each status message appears on a single line. Here the messages
32218 have been broken down so that they can fit onto a page.
32223 +download,@{section=".text",section-size="6668",total-size="9880"@}
32224 +download,@{section=".text",section-sent="512",section-size="6668",
32225 total-sent="512",total-size="9880"@}
32226 +download,@{section=".text",section-sent="1024",section-size="6668",
32227 total-sent="1024",total-size="9880"@}
32228 +download,@{section=".text",section-sent="1536",section-size="6668",
32229 total-sent="1536",total-size="9880"@}
32230 +download,@{section=".text",section-sent="2048",section-size="6668",
32231 total-sent="2048",total-size="9880"@}
32232 +download,@{section=".text",section-sent="2560",section-size="6668",
32233 total-sent="2560",total-size="9880"@}
32234 +download,@{section=".text",section-sent="3072",section-size="6668",
32235 total-sent="3072",total-size="9880"@}
32236 +download,@{section=".text",section-sent="3584",section-size="6668",
32237 total-sent="3584",total-size="9880"@}
32238 +download,@{section=".text",section-sent="4096",section-size="6668",
32239 total-sent="4096",total-size="9880"@}
32240 +download,@{section=".text",section-sent="4608",section-size="6668",
32241 total-sent="4608",total-size="9880"@}
32242 +download,@{section=".text",section-sent="5120",section-size="6668",
32243 total-sent="5120",total-size="9880"@}
32244 +download,@{section=".text",section-sent="5632",section-size="6668",
32245 total-sent="5632",total-size="9880"@}
32246 +download,@{section=".text",section-sent="6144",section-size="6668",
32247 total-sent="6144",total-size="9880"@}
32248 +download,@{section=".text",section-sent="6656",section-size="6668",
32249 total-sent="6656",total-size="9880"@}
32250 +download,@{section=".init",section-size="28",total-size="9880"@}
32251 +download,@{section=".fini",section-size="28",total-size="9880"@}
32252 +download,@{section=".data",section-size="3156",total-size="9880"@}
32253 +download,@{section=".data",section-sent="512",section-size="3156",
32254 total-sent="7236",total-size="9880"@}
32255 +download,@{section=".data",section-sent="1024",section-size="3156",
32256 total-sent="7748",total-size="9880"@}
32257 +download,@{section=".data",section-sent="1536",section-size="3156",
32258 total-sent="8260",total-size="9880"@}
32259 +download,@{section=".data",section-sent="2048",section-size="3156",
32260 total-sent="8772",total-size="9880"@}
32261 +download,@{section=".data",section-sent="2560",section-size="3156",
32262 total-sent="9284",total-size="9880"@}
32263 +download,@{section=".data",section-sent="3072",section-size="3156",
32264 total-sent="9796",total-size="9880"@}
32265 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32272 @subheading The @code{-target-exec-status} Command
32273 @findex -target-exec-status
32275 @subsubheading Synopsis
32278 -target-exec-status
32281 Provide information on the state of the target (whether it is running or
32282 not, for instance).
32284 @subsubheading @value{GDBN} Command
32286 There's no equivalent @value{GDBN} command.
32288 @subsubheading Example
32292 @subheading The @code{-target-list-available-targets} Command
32293 @findex -target-list-available-targets
32295 @subsubheading Synopsis
32298 -target-list-available-targets
32301 List the possible targets to connect to.
32303 @subsubheading @value{GDBN} Command
32305 The corresponding @value{GDBN} command is @samp{help target}.
32307 @subsubheading Example
32311 @subheading The @code{-target-list-current-targets} Command
32312 @findex -target-list-current-targets
32314 @subsubheading Synopsis
32317 -target-list-current-targets
32320 Describe the current target.
32322 @subsubheading @value{GDBN} Command
32324 The corresponding information is printed by @samp{info file} (among
32327 @subsubheading Example
32331 @subheading The @code{-target-list-parameters} Command
32332 @findex -target-list-parameters
32334 @subsubheading Synopsis
32337 -target-list-parameters
32343 @subsubheading @value{GDBN} Command
32347 @subsubheading Example
32350 @subheading The @code{-target-flash-erase} Command
32351 @findex -target-flash-erase
32353 @subsubheading Synopsis
32356 -target-flash-erase
32359 Erases all known flash memory regions on the target.
32361 The corresponding @value{GDBN} command is @samp{flash-erase}.
32363 The output is a list of flash regions that have been erased, with starting
32364 addresses and memory region sizes.
32368 -target-flash-erase
32369 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32373 @subheading The @code{-target-select} Command
32374 @findex -target-select
32376 @subsubheading Synopsis
32379 -target-select @var{type} @var{parameters @dots{}}
32382 Connect @value{GDBN} to the remote target. This command takes two args:
32386 The type of target, for instance @samp{remote}, etc.
32387 @item @var{parameters}
32388 Device names, host names and the like. @xref{Target Commands, ,
32389 Commands for Managing Targets}, for more details.
32392 The output is a connection notification, followed by the address at
32393 which the target program is, in the following form:
32396 ^connected,addr="@var{address}",func="@var{function name}",
32397 args=[@var{arg list}]
32400 @subsubheading @value{GDBN} Command
32402 The corresponding @value{GDBN} command is @samp{target}.
32404 @subsubheading Example
32408 -target-select remote /dev/ttya
32409 ^connected,addr="0xfe00a300",func="??",args=[]
32413 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32414 @node GDB/MI File Transfer Commands
32415 @section @sc{gdb/mi} File Transfer Commands
32418 @subheading The @code{-target-file-put} Command
32419 @findex -target-file-put
32421 @subsubheading Synopsis
32424 -target-file-put @var{hostfile} @var{targetfile}
32427 Copy file @var{hostfile} from the host system (the machine running
32428 @value{GDBN}) to @var{targetfile} on the target system.
32430 @subsubheading @value{GDBN} Command
32432 The corresponding @value{GDBN} command is @samp{remote put}.
32434 @subsubheading Example
32438 -target-file-put localfile remotefile
32444 @subheading The @code{-target-file-get} Command
32445 @findex -target-file-get
32447 @subsubheading Synopsis
32450 -target-file-get @var{targetfile} @var{hostfile}
32453 Copy file @var{targetfile} from the target system to @var{hostfile}
32454 on the host system.
32456 @subsubheading @value{GDBN} Command
32458 The corresponding @value{GDBN} command is @samp{remote get}.
32460 @subsubheading Example
32464 -target-file-get remotefile localfile
32470 @subheading The @code{-target-file-delete} Command
32471 @findex -target-file-delete
32473 @subsubheading Synopsis
32476 -target-file-delete @var{targetfile}
32479 Delete @var{targetfile} from the target system.
32481 @subsubheading @value{GDBN} Command
32483 The corresponding @value{GDBN} command is @samp{remote delete}.
32485 @subsubheading Example
32489 -target-file-delete remotefile
32495 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32496 @node GDB/MI Ada Exceptions Commands
32497 @section Ada Exceptions @sc{gdb/mi} Commands
32499 @subheading The @code{-info-ada-exceptions} Command
32500 @findex -info-ada-exceptions
32502 @subsubheading Synopsis
32505 -info-ada-exceptions [ @var{regexp}]
32508 List all Ada exceptions defined within the program being debugged.
32509 With a regular expression @var{regexp}, only those exceptions whose
32510 names match @var{regexp} are listed.
32512 @subsubheading @value{GDBN} Command
32514 The corresponding @value{GDBN} command is @samp{info exceptions}.
32516 @subsubheading Result
32518 The result is a table of Ada exceptions. The following columns are
32519 defined for each exception:
32523 The name of the exception.
32526 The address of the exception.
32530 @subsubheading Example
32533 -info-ada-exceptions aint
32534 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32535 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32536 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32537 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32538 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32541 @subheading Catching Ada Exceptions
32543 The commands describing how to ask @value{GDBN} to stop when a program
32544 raises an exception are described at @ref{Ada Exception GDB/MI
32545 Catchpoint Commands}.
32548 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32549 @node GDB/MI Support Commands
32550 @section @sc{gdb/mi} Support Commands
32552 Since new commands and features get regularly added to @sc{gdb/mi},
32553 some commands are available to help front-ends query the debugger
32554 about support for these capabilities. Similarly, it is also possible
32555 to query @value{GDBN} about target support of certain features.
32557 @subheading The @code{-info-gdb-mi-command} Command
32558 @cindex @code{-info-gdb-mi-command}
32559 @findex -info-gdb-mi-command
32561 @subsubheading Synopsis
32564 -info-gdb-mi-command @var{cmd_name}
32567 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32569 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32570 is technically not part of the command name (@pxref{GDB/MI Input
32571 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32572 for ease of use, this command also accepts the form with the leading
32575 @subsubheading @value{GDBN} Command
32577 There is no corresponding @value{GDBN} command.
32579 @subsubheading Result
32581 The result is a tuple. There is currently only one field:
32585 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32586 @code{"false"} otherwise.
32590 @subsubheading Example
32592 Here is an example where the @sc{gdb/mi} command does not exist:
32595 -info-gdb-mi-command unsupported-command
32596 ^done,command=@{exists="false"@}
32600 And here is an example where the @sc{gdb/mi} command is known
32604 -info-gdb-mi-command symbol-list-lines
32605 ^done,command=@{exists="true"@}
32608 @subheading The @code{-list-features} Command
32609 @findex -list-features
32610 @cindex supported @sc{gdb/mi} features, list
32612 Returns a list of particular features of the MI protocol that
32613 this version of gdb implements. A feature can be a command,
32614 or a new field in an output of some command, or even an
32615 important bugfix. While a frontend can sometimes detect presence
32616 of a feature at runtime, it is easier to perform detection at debugger
32619 The command returns a list of strings, with each string naming an
32620 available feature. Each returned string is just a name, it does not
32621 have any internal structure. The list of possible feature names
32627 (gdb) -list-features
32628 ^done,result=["feature1","feature2"]
32631 The current list of features is:
32634 @item frozen-varobjs
32635 Indicates support for the @code{-var-set-frozen} command, as well
32636 as possible presense of the @code{frozen} field in the output
32637 of @code{-varobj-create}.
32638 @item pending-breakpoints
32639 Indicates support for the @option{-f} option to the @code{-break-insert}
32642 Indicates Python scripting support, Python-based
32643 pretty-printing commands, and possible presence of the
32644 @samp{display_hint} field in the output of @code{-var-list-children}
32646 Indicates support for the @code{-thread-info} command.
32647 @item data-read-memory-bytes
32648 Indicates support for the @code{-data-read-memory-bytes} and the
32649 @code{-data-write-memory-bytes} commands.
32650 @item breakpoint-notifications
32651 Indicates that changes to breakpoints and breakpoints created via the
32652 CLI will be announced via async records.
32653 @item ada-task-info
32654 Indicates support for the @code{-ada-task-info} command.
32655 @item language-option
32656 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32657 option (@pxref{Context management}).
32658 @item info-gdb-mi-command
32659 Indicates support for the @code{-info-gdb-mi-command} command.
32660 @item undefined-command-error-code
32661 Indicates support for the "undefined-command" error code in error result
32662 records, produced when trying to execute an undefined @sc{gdb/mi} command
32663 (@pxref{GDB/MI Result Records}).
32664 @item exec-run-start-option
32665 Indicates that the @code{-exec-run} command supports the @option{--start}
32666 option (@pxref{GDB/MI Program Execution}).
32669 @subheading The @code{-list-target-features} Command
32670 @findex -list-target-features
32672 Returns a list of particular features that are supported by the
32673 target. Those features affect the permitted MI commands, but
32674 unlike the features reported by the @code{-list-features} command, the
32675 features depend on which target GDB is using at the moment. Whenever
32676 a target can change, due to commands such as @code{-target-select},
32677 @code{-target-attach} or @code{-exec-run}, the list of target features
32678 may change, and the frontend should obtain it again.
32682 (gdb) -list-target-features
32683 ^done,result=["async"]
32686 The current list of features is:
32690 Indicates that the target is capable of asynchronous command
32691 execution, which means that @value{GDBN} will accept further commands
32692 while the target is running.
32695 Indicates that the target is capable of reverse execution.
32696 @xref{Reverse Execution}, for more information.
32700 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32701 @node GDB/MI Miscellaneous Commands
32702 @section Miscellaneous @sc{gdb/mi} Commands
32704 @c @subheading -gdb-complete
32706 @subheading The @code{-gdb-exit} Command
32709 @subsubheading Synopsis
32715 Exit @value{GDBN} immediately.
32717 @subsubheading @value{GDBN} Command
32719 Approximately corresponds to @samp{quit}.
32721 @subsubheading Example
32731 @subheading The @code{-exec-abort} Command
32732 @findex -exec-abort
32734 @subsubheading Synopsis
32740 Kill the inferior running program.
32742 @subsubheading @value{GDBN} Command
32744 The corresponding @value{GDBN} command is @samp{kill}.
32746 @subsubheading Example
32751 @subheading The @code{-gdb-set} Command
32754 @subsubheading Synopsis
32760 Set an internal @value{GDBN} variable.
32761 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32763 @subsubheading @value{GDBN} Command
32765 The corresponding @value{GDBN} command is @samp{set}.
32767 @subsubheading Example
32777 @subheading The @code{-gdb-show} Command
32780 @subsubheading Synopsis
32786 Show the current value of a @value{GDBN} variable.
32788 @subsubheading @value{GDBN} Command
32790 The corresponding @value{GDBN} command is @samp{show}.
32792 @subsubheading Example
32801 @c @subheading -gdb-source
32804 @subheading The @code{-gdb-version} Command
32805 @findex -gdb-version
32807 @subsubheading Synopsis
32813 Show version information for @value{GDBN}. Used mostly in testing.
32815 @subsubheading @value{GDBN} Command
32817 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32818 default shows this information when you start an interactive session.
32820 @subsubheading Example
32822 @c This example modifies the actual output from GDB to avoid overfull
32828 ~Copyright 2000 Free Software Foundation, Inc.
32829 ~GDB is free software, covered by the GNU General Public License, and
32830 ~you are welcome to change it and/or distribute copies of it under
32831 ~ certain conditions.
32832 ~Type "show copying" to see the conditions.
32833 ~There is absolutely no warranty for GDB. Type "show warranty" for
32835 ~This GDB was configured as
32836 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32841 @subheading The @code{-list-thread-groups} Command
32842 @findex -list-thread-groups
32844 @subheading Synopsis
32847 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32850 Lists thread groups (@pxref{Thread groups}). When a single thread
32851 group is passed as the argument, lists the children of that group.
32852 When several thread group are passed, lists information about those
32853 thread groups. Without any parameters, lists information about all
32854 top-level thread groups.
32856 Normally, thread groups that are being debugged are reported.
32857 With the @samp{--available} option, @value{GDBN} reports thread groups
32858 available on the target.
32860 The output of this command may have either a @samp{threads} result or
32861 a @samp{groups} result. The @samp{thread} result has a list of tuples
32862 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32863 Information}). The @samp{groups} result has a list of tuples as value,
32864 each tuple describing a thread group. If top-level groups are
32865 requested (that is, no parameter is passed), or when several groups
32866 are passed, the output always has a @samp{groups} result. The format
32867 of the @samp{group} result is described below.
32869 To reduce the number of roundtrips it's possible to list thread groups
32870 together with their children, by passing the @samp{--recurse} option
32871 and the recursion depth. Presently, only recursion depth of 1 is
32872 permitted. If this option is present, then every reported thread group
32873 will also include its children, either as @samp{group} or
32874 @samp{threads} field.
32876 In general, any combination of option and parameters is permitted, with
32877 the following caveats:
32881 When a single thread group is passed, the output will typically
32882 be the @samp{threads} result. Because threads may not contain
32883 anything, the @samp{recurse} option will be ignored.
32886 When the @samp{--available} option is passed, limited information may
32887 be available. In particular, the list of threads of a process might
32888 be inaccessible. Further, specifying specific thread groups might
32889 not give any performance advantage over listing all thread groups.
32890 The frontend should assume that @samp{-list-thread-groups --available}
32891 is always an expensive operation and cache the results.
32895 The @samp{groups} result is a list of tuples, where each tuple may
32896 have the following fields:
32900 Identifier of the thread group. This field is always present.
32901 The identifier is an opaque string; frontends should not try to
32902 convert it to an integer, even though it might look like one.
32905 The type of the thread group. At present, only @samp{process} is a
32909 The target-specific process identifier. This field is only present
32910 for thread groups of type @samp{process} and only if the process exists.
32913 The exit code of this group's last exited thread, formatted in octal.
32914 This field is only present for thread groups of type @samp{process} and
32915 only if the process is not running.
32918 The number of children this thread group has. This field may be
32919 absent for an available thread group.
32922 This field has a list of tuples as value, each tuple describing a
32923 thread. It may be present if the @samp{--recurse} option is
32924 specified, and it's actually possible to obtain the threads.
32927 This field is a list of integers, each identifying a core that one
32928 thread of the group is running on. This field may be absent if
32929 such information is not available.
32932 The name of the executable file that corresponds to this thread group.
32933 The field is only present for thread groups of type @samp{process},
32934 and only if there is a corresponding executable file.
32938 @subheading Example
32942 -list-thread-groups
32943 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32944 -list-thread-groups 17
32945 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32946 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32947 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32948 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32949 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32950 -list-thread-groups --available
32951 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32952 -list-thread-groups --available --recurse 1
32953 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32954 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32955 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32956 -list-thread-groups --available --recurse 1 17 18
32957 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32958 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32959 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32962 @subheading The @code{-info-os} Command
32965 @subsubheading Synopsis
32968 -info-os [ @var{type} ]
32971 If no argument is supplied, the command returns a table of available
32972 operating-system-specific information types. If one of these types is
32973 supplied as an argument @var{type}, then the command returns a table
32974 of data of that type.
32976 The types of information available depend on the target operating
32979 @subsubheading @value{GDBN} Command
32981 The corresponding @value{GDBN} command is @samp{info os}.
32983 @subsubheading Example
32985 When run on a @sc{gnu}/Linux system, the output will look something
32991 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32992 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32993 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32994 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32995 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32997 item=@{col0="files",col1="Listing of all file descriptors",
32998 col2="File descriptors"@},
32999 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33000 col2="Kernel modules"@},
33001 item=@{col0="msg",col1="Listing of all message queues",
33002 col2="Message queues"@},
33003 item=@{col0="processes",col1="Listing of all processes",
33004 col2="Processes"@},
33005 item=@{col0="procgroups",col1="Listing of all process groups",
33006 col2="Process groups"@},
33007 item=@{col0="semaphores",col1="Listing of all semaphores",
33008 col2="Semaphores"@},
33009 item=@{col0="shm",col1="Listing of all shared-memory regions",
33010 col2="Shared-memory regions"@},
33011 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33013 item=@{col0="threads",col1="Listing of all threads",
33017 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33018 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33019 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33020 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33021 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33022 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33023 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33024 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33026 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33027 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33031 (Note that the MI output here includes a @code{"Title"} column that
33032 does not appear in command-line @code{info os}; this column is useful
33033 for MI clients that want to enumerate the types of data, such as in a
33034 popup menu, but is needless clutter on the command line, and
33035 @code{info os} omits it.)
33037 @subheading The @code{-add-inferior} Command
33038 @findex -add-inferior
33040 @subheading Synopsis
33046 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33047 inferior is not associated with any executable. Such association may
33048 be established with the @samp{-file-exec-and-symbols} command
33049 (@pxref{GDB/MI File Commands}). The command response has a single
33050 field, @samp{inferior}, whose value is the identifier of the
33051 thread group corresponding to the new inferior.
33053 @subheading Example
33058 ^done,inferior="i3"
33061 @subheading The @code{-interpreter-exec} Command
33062 @findex -interpreter-exec
33064 @subheading Synopsis
33067 -interpreter-exec @var{interpreter} @var{command}
33069 @anchor{-interpreter-exec}
33071 Execute the specified @var{command} in the given @var{interpreter}.
33073 @subheading @value{GDBN} Command
33075 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33077 @subheading Example
33081 -interpreter-exec console "break main"
33082 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33083 &"During symbol reading, bad structure-type format.\n"
33084 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33089 @subheading The @code{-inferior-tty-set} Command
33090 @findex -inferior-tty-set
33092 @subheading Synopsis
33095 -inferior-tty-set /dev/pts/1
33098 Set terminal for future runs of the program being debugged.
33100 @subheading @value{GDBN} Command
33102 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33104 @subheading Example
33108 -inferior-tty-set /dev/pts/1
33113 @subheading The @code{-inferior-tty-show} Command
33114 @findex -inferior-tty-show
33116 @subheading Synopsis
33122 Show terminal for future runs of program being debugged.
33124 @subheading @value{GDBN} Command
33126 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33128 @subheading Example
33132 -inferior-tty-set /dev/pts/1
33136 ^done,inferior_tty_terminal="/dev/pts/1"
33140 @subheading The @code{-enable-timings} Command
33141 @findex -enable-timings
33143 @subheading Synopsis
33146 -enable-timings [yes | no]
33149 Toggle the printing of the wallclock, user and system times for an MI
33150 command as a field in its output. This command is to help frontend
33151 developers optimize the performance of their code. No argument is
33152 equivalent to @samp{yes}.
33154 @subheading @value{GDBN} Command
33158 @subheading Example
33166 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33167 addr="0x080484ed",func="main",file="myprog.c",
33168 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33170 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33178 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33179 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33180 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33181 fullname="/home/nickrob/myprog.c",line="73"@}
33186 @chapter @value{GDBN} Annotations
33188 This chapter describes annotations in @value{GDBN}. Annotations were
33189 designed to interface @value{GDBN} to graphical user interfaces or other
33190 similar programs which want to interact with @value{GDBN} at a
33191 relatively high level.
33193 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33197 This is Edition @value{EDITION}, @value{DATE}.
33201 * Annotations Overview:: What annotations are; the general syntax.
33202 * Server Prefix:: Issuing a command without affecting user state.
33203 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33204 * Errors:: Annotations for error messages.
33205 * Invalidation:: Some annotations describe things now invalid.
33206 * Annotations for Running::
33207 Whether the program is running, how it stopped, etc.
33208 * Source Annotations:: Annotations describing source code.
33211 @node Annotations Overview
33212 @section What is an Annotation?
33213 @cindex annotations
33215 Annotations start with a newline character, two @samp{control-z}
33216 characters, and the name of the annotation. If there is no additional
33217 information associated with this annotation, the name of the annotation
33218 is followed immediately by a newline. If there is additional
33219 information, the name of the annotation is followed by a space, the
33220 additional information, and a newline. The additional information
33221 cannot contain newline characters.
33223 Any output not beginning with a newline and two @samp{control-z}
33224 characters denotes literal output from @value{GDBN}. Currently there is
33225 no need for @value{GDBN} to output a newline followed by two
33226 @samp{control-z} characters, but if there was such a need, the
33227 annotations could be extended with an @samp{escape} annotation which
33228 means those three characters as output.
33230 The annotation @var{level}, which is specified using the
33231 @option{--annotate} command line option (@pxref{Mode Options}), controls
33232 how much information @value{GDBN} prints together with its prompt,
33233 values of expressions, source lines, and other types of output. Level 0
33234 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33235 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33236 for programs that control @value{GDBN}, and level 2 annotations have
33237 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33238 Interface, annotate, GDB's Obsolete Annotations}).
33241 @kindex set annotate
33242 @item set annotate @var{level}
33243 The @value{GDBN} command @code{set annotate} sets the level of
33244 annotations to the specified @var{level}.
33246 @item show annotate
33247 @kindex show annotate
33248 Show the current annotation level.
33251 This chapter describes level 3 annotations.
33253 A simple example of starting up @value{GDBN} with annotations is:
33256 $ @kbd{gdb --annotate=3}
33258 Copyright 2003 Free Software Foundation, Inc.
33259 GDB is free software, covered by the GNU General Public License,
33260 and you are welcome to change it and/or distribute copies of it
33261 under certain conditions.
33262 Type "show copying" to see the conditions.
33263 There is absolutely no warranty for GDB. Type "show warranty"
33265 This GDB was configured as "i386-pc-linux-gnu"
33276 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33277 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33278 denotes a @samp{control-z} character) are annotations; the rest is
33279 output from @value{GDBN}.
33281 @node Server Prefix
33282 @section The Server Prefix
33283 @cindex server prefix
33285 If you prefix a command with @samp{server } then it will not affect
33286 the command history, nor will it affect @value{GDBN}'s notion of which
33287 command to repeat if @key{RET} is pressed on a line by itself. This
33288 means that commands can be run behind a user's back by a front-end in
33289 a transparent manner.
33291 The @code{server } prefix does not affect the recording of values into
33292 the value history; to print a value without recording it into the
33293 value history, use the @code{output} command instead of the
33294 @code{print} command.
33296 Using this prefix also disables confirmation requests
33297 (@pxref{confirmation requests}).
33300 @section Annotation for @value{GDBN} Input
33302 @cindex annotations for prompts
33303 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33304 to know when to send output, when the output from a given command is
33307 Different kinds of input each have a different @dfn{input type}. Each
33308 input type has three annotations: a @code{pre-} annotation, which
33309 denotes the beginning of any prompt which is being output, a plain
33310 annotation, which denotes the end of the prompt, and then a @code{post-}
33311 annotation which denotes the end of any echo which may (or may not) be
33312 associated with the input. For example, the @code{prompt} input type
33313 features the following annotations:
33321 The input types are
33324 @findex pre-prompt annotation
33325 @findex prompt annotation
33326 @findex post-prompt annotation
33328 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33330 @findex pre-commands annotation
33331 @findex commands annotation
33332 @findex post-commands annotation
33334 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33335 command. The annotations are repeated for each command which is input.
33337 @findex pre-overload-choice annotation
33338 @findex overload-choice annotation
33339 @findex post-overload-choice annotation
33340 @item overload-choice
33341 When @value{GDBN} wants the user to select between various overloaded functions.
33343 @findex pre-query annotation
33344 @findex query annotation
33345 @findex post-query annotation
33347 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33349 @findex pre-prompt-for-continue annotation
33350 @findex prompt-for-continue annotation
33351 @findex post-prompt-for-continue annotation
33352 @item prompt-for-continue
33353 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33354 expect this to work well; instead use @code{set height 0} to disable
33355 prompting. This is because the counting of lines is buggy in the
33356 presence of annotations.
33361 @cindex annotations for errors, warnings and interrupts
33363 @findex quit annotation
33368 This annotation occurs right before @value{GDBN} responds to an interrupt.
33370 @findex error annotation
33375 This annotation occurs right before @value{GDBN} responds to an error.
33377 Quit and error annotations indicate that any annotations which @value{GDBN} was
33378 in the middle of may end abruptly. For example, if a
33379 @code{value-history-begin} annotation is followed by a @code{error}, one
33380 cannot expect to receive the matching @code{value-history-end}. One
33381 cannot expect not to receive it either, however; an error annotation
33382 does not necessarily mean that @value{GDBN} is immediately returning all the way
33385 @findex error-begin annotation
33386 A quit or error annotation may be preceded by
33392 Any output between that and the quit or error annotation is the error
33395 Warning messages are not yet annotated.
33396 @c If we want to change that, need to fix warning(), type_error(),
33397 @c range_error(), and possibly other places.
33400 @section Invalidation Notices
33402 @cindex annotations for invalidation messages
33403 The following annotations say that certain pieces of state may have
33407 @findex frames-invalid annotation
33408 @item ^Z^Zframes-invalid
33410 The frames (for example, output from the @code{backtrace} command) may
33413 @findex breakpoints-invalid annotation
33414 @item ^Z^Zbreakpoints-invalid
33416 The breakpoints may have changed. For example, the user just added or
33417 deleted a breakpoint.
33420 @node Annotations for Running
33421 @section Running the Program
33422 @cindex annotations for running programs
33424 @findex starting annotation
33425 @findex stopping annotation
33426 When the program starts executing due to a @value{GDBN} command such as
33427 @code{step} or @code{continue},
33433 is output. When the program stops,
33439 is output. Before the @code{stopped} annotation, a variety of
33440 annotations describe how the program stopped.
33443 @findex exited annotation
33444 @item ^Z^Zexited @var{exit-status}
33445 The program exited, and @var{exit-status} is the exit status (zero for
33446 successful exit, otherwise nonzero).
33448 @findex signalled annotation
33449 @findex signal-name annotation
33450 @findex signal-name-end annotation
33451 @findex signal-string annotation
33452 @findex signal-string-end annotation
33453 @item ^Z^Zsignalled
33454 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33455 annotation continues:
33461 ^Z^Zsignal-name-end
33465 ^Z^Zsignal-string-end
33470 where @var{name} is the name of the signal, such as @code{SIGILL} or
33471 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33472 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33473 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33474 user's benefit and have no particular format.
33476 @findex signal annotation
33478 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33479 just saying that the program received the signal, not that it was
33480 terminated with it.
33482 @findex breakpoint annotation
33483 @item ^Z^Zbreakpoint @var{number}
33484 The program hit breakpoint number @var{number}.
33486 @findex watchpoint annotation
33487 @item ^Z^Zwatchpoint @var{number}
33488 The program hit watchpoint number @var{number}.
33491 @node Source Annotations
33492 @section Displaying Source
33493 @cindex annotations for source display
33495 @findex source annotation
33496 The following annotation is used instead of displaying source code:
33499 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33502 where @var{filename} is an absolute file name indicating which source
33503 file, @var{line} is the line number within that file (where 1 is the
33504 first line in the file), @var{character} is the character position
33505 within the file (where 0 is the first character in the file) (for most
33506 debug formats this will necessarily point to the beginning of a line),
33507 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33508 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33509 @var{addr} is the address in the target program associated with the
33510 source which is being displayed. The @var{addr} is in the form @samp{0x}
33511 followed by one or more lowercase hex digits (note that this does not
33512 depend on the language).
33514 @node JIT Interface
33515 @chapter JIT Compilation Interface
33516 @cindex just-in-time compilation
33517 @cindex JIT compilation interface
33519 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33520 interface. A JIT compiler is a program or library that generates native
33521 executable code at runtime and executes it, usually in order to achieve good
33522 performance while maintaining platform independence.
33524 Programs that use JIT compilation are normally difficult to debug because
33525 portions of their code are generated at runtime, instead of being loaded from
33526 object files, which is where @value{GDBN} normally finds the program's symbols
33527 and debug information. In order to debug programs that use JIT compilation,
33528 @value{GDBN} has an interface that allows the program to register in-memory
33529 symbol files with @value{GDBN} at runtime.
33531 If you are using @value{GDBN} to debug a program that uses this interface, then
33532 it should work transparently so long as you have not stripped the binary. If
33533 you are developing a JIT compiler, then the interface is documented in the rest
33534 of this chapter. At this time, the only known client of this interface is the
33537 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33538 JIT compiler communicates with @value{GDBN} by writing data into a global
33539 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33540 attaches, it reads a linked list of symbol files from the global variable to
33541 find existing code, and puts a breakpoint in the function so that it can find
33542 out about additional code.
33545 * Declarations:: Relevant C struct declarations
33546 * Registering Code:: Steps to register code
33547 * Unregistering Code:: Steps to unregister code
33548 * Custom Debug Info:: Emit debug information in a custom format
33552 @section JIT Declarations
33554 These are the relevant struct declarations that a C program should include to
33555 implement the interface:
33565 struct jit_code_entry
33567 struct jit_code_entry *next_entry;
33568 struct jit_code_entry *prev_entry;
33569 const char *symfile_addr;
33570 uint64_t symfile_size;
33573 struct jit_descriptor
33576 /* This type should be jit_actions_t, but we use uint32_t
33577 to be explicit about the bitwidth. */
33578 uint32_t action_flag;
33579 struct jit_code_entry *relevant_entry;
33580 struct jit_code_entry *first_entry;
33583 /* GDB puts a breakpoint in this function. */
33584 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33586 /* Make sure to specify the version statically, because the
33587 debugger may check the version before we can set it. */
33588 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33591 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33592 modifications to this global data properly, which can easily be done by putting
33593 a global mutex around modifications to these structures.
33595 @node Registering Code
33596 @section Registering Code
33598 To register code with @value{GDBN}, the JIT should follow this protocol:
33602 Generate an object file in memory with symbols and other desired debug
33603 information. The file must include the virtual addresses of the sections.
33606 Create a code entry for the file, which gives the start and size of the symbol
33610 Add it to the linked list in the JIT descriptor.
33613 Point the relevant_entry field of the descriptor at the entry.
33616 Set @code{action_flag} to @code{JIT_REGISTER} and call
33617 @code{__jit_debug_register_code}.
33620 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33621 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33622 new code. However, the linked list must still be maintained in order to allow
33623 @value{GDBN} to attach to a running process and still find the symbol files.
33625 @node Unregistering Code
33626 @section Unregistering Code
33628 If code is freed, then the JIT should use the following protocol:
33632 Remove the code entry corresponding to the code from the linked list.
33635 Point the @code{relevant_entry} field of the descriptor at the code entry.
33638 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33639 @code{__jit_debug_register_code}.
33642 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33643 and the JIT will leak the memory used for the associated symbol files.
33645 @node Custom Debug Info
33646 @section Custom Debug Info
33647 @cindex custom JIT debug info
33648 @cindex JIT debug info reader
33650 Generating debug information in platform-native file formats (like ELF
33651 or COFF) may be an overkill for JIT compilers; especially if all the
33652 debug info is used for is displaying a meaningful backtrace. The
33653 issue can be resolved by having the JIT writers decide on a debug info
33654 format and also provide a reader that parses the debug info generated
33655 by the JIT compiler. This section gives a brief overview on writing
33656 such a parser. More specific details can be found in the source file
33657 @file{gdb/jit-reader.in}, which is also installed as a header at
33658 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33660 The reader is implemented as a shared object (so this functionality is
33661 not available on platforms which don't allow loading shared objects at
33662 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33663 @code{jit-reader-unload} are provided, to be used to load and unload
33664 the readers from a preconfigured directory. Once loaded, the shared
33665 object is used the parse the debug information emitted by the JIT
33669 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33670 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33673 @node Using JIT Debug Info Readers
33674 @subsection Using JIT Debug Info Readers
33675 @kindex jit-reader-load
33676 @kindex jit-reader-unload
33678 Readers can be loaded and unloaded using the @code{jit-reader-load}
33679 and @code{jit-reader-unload} commands.
33682 @item jit-reader-load @var{reader}
33683 Load the JIT reader named @var{reader}, which is a shared
33684 object specified as either an absolute or a relative file name. In
33685 the latter case, @value{GDBN} will try to load the reader from a
33686 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33687 system (here @var{libdir} is the system library directory, often
33688 @file{/usr/local/lib}).
33690 Only one reader can be active at a time; trying to load a second
33691 reader when one is already loaded will result in @value{GDBN}
33692 reporting an error. A new JIT reader can be loaded by first unloading
33693 the current one using @code{jit-reader-unload} and then invoking
33694 @code{jit-reader-load}.
33696 @item jit-reader-unload
33697 Unload the currently loaded JIT reader.
33701 @node Writing JIT Debug Info Readers
33702 @subsection Writing JIT Debug Info Readers
33703 @cindex writing JIT debug info readers
33705 As mentioned, a reader is essentially a shared object conforming to a
33706 certain ABI. This ABI is described in @file{jit-reader.h}.
33708 @file{jit-reader.h} defines the structures, macros and functions
33709 required to write a reader. It is installed (along with
33710 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33711 the system include directory.
33713 Readers need to be released under a GPL compatible license. A reader
33714 can be declared as released under such a license by placing the macro
33715 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33717 The entry point for readers is the symbol @code{gdb_init_reader},
33718 which is expected to be a function with the prototype
33720 @findex gdb_init_reader
33722 extern struct gdb_reader_funcs *gdb_init_reader (void);
33725 @cindex @code{struct gdb_reader_funcs}
33727 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33728 functions. These functions are executed to read the debug info
33729 generated by the JIT compiler (@code{read}), to unwind stack frames
33730 (@code{unwind}) and to create canonical frame IDs
33731 (@code{get_Frame_id}). It also has a callback that is called when the
33732 reader is being unloaded (@code{destroy}). The struct looks like this
33735 struct gdb_reader_funcs
33737 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33738 int reader_version;
33740 /* For use by the reader. */
33743 gdb_read_debug_info *read;
33744 gdb_unwind_frame *unwind;
33745 gdb_get_frame_id *get_frame_id;
33746 gdb_destroy_reader *destroy;
33750 @cindex @code{struct gdb_symbol_callbacks}
33751 @cindex @code{struct gdb_unwind_callbacks}
33753 The callbacks are provided with another set of callbacks by
33754 @value{GDBN} to do their job. For @code{read}, these callbacks are
33755 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33756 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33757 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33758 files and new symbol tables inside those object files. @code{struct
33759 gdb_unwind_callbacks} has callbacks to read registers off the current
33760 frame and to write out the values of the registers in the previous
33761 frame. Both have a callback (@code{target_read}) to read bytes off the
33762 target's address space.
33764 @node In-Process Agent
33765 @chapter In-Process Agent
33766 @cindex debugging agent
33767 The traditional debugging model is conceptually low-speed, but works fine,
33768 because most bugs can be reproduced in debugging-mode execution. However,
33769 as multi-core or many-core processors are becoming mainstream, and
33770 multi-threaded programs become more and more popular, there should be more
33771 and more bugs that only manifest themselves at normal-mode execution, for
33772 example, thread races, because debugger's interference with the program's
33773 timing may conceal the bugs. On the other hand, in some applications,
33774 it is not feasible for the debugger to interrupt the program's execution
33775 long enough for the developer to learn anything helpful about its behavior.
33776 If the program's correctness depends on its real-time behavior, delays
33777 introduced by a debugger might cause the program to fail, even when the
33778 code itself is correct. It is useful to be able to observe the program's
33779 behavior without interrupting it.
33781 Therefore, traditional debugging model is too intrusive to reproduce
33782 some bugs. In order to reduce the interference with the program, we can
33783 reduce the number of operations performed by debugger. The
33784 @dfn{In-Process Agent}, a shared library, is running within the same
33785 process with inferior, and is able to perform some debugging operations
33786 itself. As a result, debugger is only involved when necessary, and
33787 performance of debugging can be improved accordingly. Note that
33788 interference with program can be reduced but can't be removed completely,
33789 because the in-process agent will still stop or slow down the program.
33791 The in-process agent can interpret and execute Agent Expressions
33792 (@pxref{Agent Expressions}) during performing debugging operations. The
33793 agent expressions can be used for different purposes, such as collecting
33794 data in tracepoints, and condition evaluation in breakpoints.
33796 @anchor{Control Agent}
33797 You can control whether the in-process agent is used as an aid for
33798 debugging with the following commands:
33801 @kindex set agent on
33803 Causes the in-process agent to perform some operations on behalf of the
33804 debugger. Just which operations requested by the user will be done
33805 by the in-process agent depends on the its capabilities. For example,
33806 if you request to evaluate breakpoint conditions in the in-process agent,
33807 and the in-process agent has such capability as well, then breakpoint
33808 conditions will be evaluated in the in-process agent.
33810 @kindex set agent off
33811 @item set agent off
33812 Disables execution of debugging operations by the in-process agent. All
33813 of the operations will be performed by @value{GDBN}.
33817 Display the current setting of execution of debugging operations by
33818 the in-process agent.
33822 * In-Process Agent Protocol::
33825 @node In-Process Agent Protocol
33826 @section In-Process Agent Protocol
33827 @cindex in-process agent protocol
33829 The in-process agent is able to communicate with both @value{GDBN} and
33830 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33831 used for communications between @value{GDBN} or GDBserver and the IPA.
33832 In general, @value{GDBN} or GDBserver sends commands
33833 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33834 in-process agent replies back with the return result of the command, or
33835 some other information. The data sent to in-process agent is composed
33836 of primitive data types, such as 4-byte or 8-byte type, and composite
33837 types, which are called objects (@pxref{IPA Protocol Objects}).
33840 * IPA Protocol Objects::
33841 * IPA Protocol Commands::
33844 @node IPA Protocol Objects
33845 @subsection IPA Protocol Objects
33846 @cindex ipa protocol objects
33848 The commands sent to and results received from agent may contain some
33849 complex data types called @dfn{objects}.
33851 The in-process agent is running on the same machine with @value{GDBN}
33852 or GDBserver, so it doesn't have to handle as much differences between
33853 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33854 However, there are still some differences of two ends in two processes:
33858 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33859 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33861 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33862 GDBserver is compiled with one, and in-process agent is compiled with
33866 Here are the IPA Protocol Objects:
33870 agent expression object. It represents an agent expression
33871 (@pxref{Agent Expressions}).
33872 @anchor{agent expression object}
33874 tracepoint action object. It represents a tracepoint action
33875 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33876 memory, static trace data and to evaluate expression.
33877 @anchor{tracepoint action object}
33879 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33880 @anchor{tracepoint object}
33884 The following table describes important attributes of each IPA protocol
33887 @multitable @columnfractions .30 .20 .50
33888 @headitem Name @tab Size @tab Description
33889 @item @emph{agent expression object} @tab @tab
33890 @item length @tab 4 @tab length of bytes code
33891 @item byte code @tab @var{length} @tab contents of byte code
33892 @item @emph{tracepoint action for collecting memory} @tab @tab
33893 @item 'M' @tab 1 @tab type of tracepoint action
33894 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33895 address of the lowest byte to collect, otherwise @var{addr} is the offset
33896 of @var{basereg} for memory collecting.
33897 @item len @tab 8 @tab length of memory for collecting
33898 @item basereg @tab 4 @tab the register number containing the starting
33899 memory address for collecting.
33900 @item @emph{tracepoint action for collecting registers} @tab @tab
33901 @item 'R' @tab 1 @tab type of tracepoint action
33902 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33903 @item 'L' @tab 1 @tab type of tracepoint action
33904 @item @emph{tracepoint action for expression evaluation} @tab @tab
33905 @item 'X' @tab 1 @tab type of tracepoint action
33906 @item agent expression @tab length of @tab @ref{agent expression object}
33907 @item @emph{tracepoint object} @tab @tab
33908 @item number @tab 4 @tab number of tracepoint
33909 @item address @tab 8 @tab address of tracepoint inserted on
33910 @item type @tab 4 @tab type of tracepoint
33911 @item enabled @tab 1 @tab enable or disable of tracepoint
33912 @item step_count @tab 8 @tab step
33913 @item pass_count @tab 8 @tab pass
33914 @item numactions @tab 4 @tab number of tracepoint actions
33915 @item hit count @tab 8 @tab hit count
33916 @item trace frame usage @tab 8 @tab trace frame usage
33917 @item compiled_cond @tab 8 @tab compiled condition
33918 @item orig_size @tab 8 @tab orig size
33919 @item condition @tab 4 if condition is NULL otherwise length of
33920 @ref{agent expression object}
33921 @tab zero if condition is NULL, otherwise is
33922 @ref{agent expression object}
33923 @item actions @tab variable
33924 @tab numactions number of @ref{tracepoint action object}
33927 @node IPA Protocol Commands
33928 @subsection IPA Protocol Commands
33929 @cindex ipa protocol commands
33931 The spaces in each command are delimiters to ease reading this commands
33932 specification. They don't exist in real commands.
33936 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33937 Installs a new fast tracepoint described by @var{tracepoint_object}
33938 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33939 head of @dfn{jumppad}, which is used to jump to data collection routine
33944 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33945 @var{target_address} is address of tracepoint in the inferior.
33946 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33947 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33948 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33949 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33956 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33957 is about to kill inferiors.
33965 @item probe_marker_at:@var{address}
33966 Asks in-process agent to probe the marker at @var{address}.
33973 @item unprobe_marker_at:@var{address}
33974 Asks in-process agent to unprobe the marker at @var{address}.
33978 @chapter Reporting Bugs in @value{GDBN}
33979 @cindex bugs in @value{GDBN}
33980 @cindex reporting bugs in @value{GDBN}
33982 Your bug reports play an essential role in making @value{GDBN} reliable.
33984 Reporting a bug may help you by bringing a solution to your problem, or it
33985 may not. But in any case the principal function of a bug report is to help
33986 the entire community by making the next version of @value{GDBN} work better. Bug
33987 reports are your contribution to the maintenance of @value{GDBN}.
33989 In order for a bug report to serve its purpose, you must include the
33990 information that enables us to fix the bug.
33993 * Bug Criteria:: Have you found a bug?
33994 * Bug Reporting:: How to report bugs
33998 @section Have You Found a Bug?
33999 @cindex bug criteria
34001 If you are not sure whether you have found a bug, here are some guidelines:
34004 @cindex fatal signal
34005 @cindex debugger crash
34006 @cindex crash of debugger
34008 If the debugger gets a fatal signal, for any input whatever, that is a
34009 @value{GDBN} bug. Reliable debuggers never crash.
34011 @cindex error on valid input
34013 If @value{GDBN} produces an error message for valid input, that is a
34014 bug. (Note that if you're cross debugging, the problem may also be
34015 somewhere in the connection to the target.)
34017 @cindex invalid input
34019 If @value{GDBN} does not produce an error message for invalid input,
34020 that is a bug. However, you should note that your idea of
34021 ``invalid input'' might be our idea of ``an extension'' or ``support
34022 for traditional practice''.
34025 If you are an experienced user of debugging tools, your suggestions
34026 for improvement of @value{GDBN} are welcome in any case.
34029 @node Bug Reporting
34030 @section How to Report Bugs
34031 @cindex bug reports
34032 @cindex @value{GDBN} bugs, reporting
34034 A number of companies and individuals offer support for @sc{gnu} products.
34035 If you obtained @value{GDBN} from a support organization, we recommend you
34036 contact that organization first.
34038 You can find contact information for many support companies and
34039 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34041 @c should add a web page ref...
34044 @ifset BUGURL_DEFAULT
34045 In any event, we also recommend that you submit bug reports for
34046 @value{GDBN}. The preferred method is to submit them directly using
34047 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34048 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34051 @strong{Do not send bug reports to @samp{info-gdb}, or to
34052 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34053 not want to receive bug reports. Those that do have arranged to receive
34056 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34057 serves as a repeater. The mailing list and the newsgroup carry exactly
34058 the same messages. Often people think of posting bug reports to the
34059 newsgroup instead of mailing them. This appears to work, but it has one
34060 problem which can be crucial: a newsgroup posting often lacks a mail
34061 path back to the sender. Thus, if we need to ask for more information,
34062 we may be unable to reach you. For this reason, it is better to send
34063 bug reports to the mailing list.
34065 @ifclear BUGURL_DEFAULT
34066 In any event, we also recommend that you submit bug reports for
34067 @value{GDBN} to @value{BUGURL}.
34071 The fundamental principle of reporting bugs usefully is this:
34072 @strong{report all the facts}. If you are not sure whether to state a
34073 fact or leave it out, state it!
34075 Often people omit facts because they think they know what causes the
34076 problem and assume that some details do not matter. Thus, you might
34077 assume that the name of the variable you use in an example does not matter.
34078 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34079 stray memory reference which happens to fetch from the location where that
34080 name is stored in memory; perhaps, if the name were different, the contents
34081 of that location would fool the debugger into doing the right thing despite
34082 the bug. Play it safe and give a specific, complete example. That is the
34083 easiest thing for you to do, and the most helpful.
34085 Keep in mind that the purpose of a bug report is to enable us to fix the
34086 bug. It may be that the bug has been reported previously, but neither
34087 you nor we can know that unless your bug report is complete and
34090 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34091 bell?'' Those bug reports are useless, and we urge everyone to
34092 @emph{refuse to respond to them} except to chide the sender to report
34095 To enable us to fix the bug, you should include all these things:
34099 The version of @value{GDBN}. @value{GDBN} announces it if you start
34100 with no arguments; you can also print it at any time using @code{show
34103 Without this, we will not know whether there is any point in looking for
34104 the bug in the current version of @value{GDBN}.
34107 The type of machine you are using, and the operating system name and
34111 The details of the @value{GDBN} build-time configuration.
34112 @value{GDBN} shows these details if you invoke it with the
34113 @option{--configuration} command-line option, or if you type
34114 @code{show configuration} at @value{GDBN}'s prompt.
34117 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34118 ``@value{GCC}--2.8.1''.
34121 What compiler (and its version) was used to compile the program you are
34122 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34123 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34124 to get this information; for other compilers, see the documentation for
34128 The command arguments you gave the compiler to compile your example and
34129 observe the bug. For example, did you use @samp{-O}? To guarantee
34130 you will not omit something important, list them all. A copy of the
34131 Makefile (or the output from make) is sufficient.
34133 If we were to try to guess the arguments, we would probably guess wrong
34134 and then we might not encounter the bug.
34137 A complete input script, and all necessary source files, that will
34141 A description of what behavior you observe that you believe is
34142 incorrect. For example, ``It gets a fatal signal.''
34144 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34145 will certainly notice it. But if the bug is incorrect output, we might
34146 not notice unless it is glaringly wrong. You might as well not give us
34147 a chance to make a mistake.
34149 Even if the problem you experience is a fatal signal, you should still
34150 say so explicitly. Suppose something strange is going on, such as, your
34151 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34152 the C library on your system. (This has happened!) Your copy might
34153 crash and ours would not. If you told us to expect a crash, then when
34154 ours fails to crash, we would know that the bug was not happening for
34155 us. If you had not told us to expect a crash, then we would not be able
34156 to draw any conclusion from our observations.
34159 @cindex recording a session script
34160 To collect all this information, you can use a session recording program
34161 such as @command{script}, which is available on many Unix systems.
34162 Just run your @value{GDBN} session inside @command{script} and then
34163 include the @file{typescript} file with your bug report.
34165 Another way to record a @value{GDBN} session is to run @value{GDBN}
34166 inside Emacs and then save the entire buffer to a file.
34169 If you wish to suggest changes to the @value{GDBN} source, send us context
34170 diffs. If you even discuss something in the @value{GDBN} source, refer to
34171 it by context, not by line number.
34173 The line numbers in our development sources will not match those in your
34174 sources. Your line numbers would convey no useful information to us.
34178 Here are some things that are not necessary:
34182 A description of the envelope of the bug.
34184 Often people who encounter a bug spend a lot of time investigating
34185 which changes to the input file will make the bug go away and which
34186 changes will not affect it.
34188 This is often time consuming and not very useful, because the way we
34189 will find the bug is by running a single example under the debugger
34190 with breakpoints, not by pure deduction from a series of examples.
34191 We recommend that you save your time for something else.
34193 Of course, if you can find a simpler example to report @emph{instead}
34194 of the original one, that is a convenience for us. Errors in the
34195 output will be easier to spot, running under the debugger will take
34196 less time, and so on.
34198 However, simplification is not vital; if you do not want to do this,
34199 report the bug anyway and send us the entire test case you used.
34202 A patch for the bug.
34204 A patch for the bug does help us if it is a good one. But do not omit
34205 the necessary information, such as the test case, on the assumption that
34206 a patch is all we need. We might see problems with your patch and decide
34207 to fix the problem another way, or we might not understand it at all.
34209 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34210 construct an example that will make the program follow a certain path
34211 through the code. If you do not send us the example, we will not be able
34212 to construct one, so we will not be able to verify that the bug is fixed.
34214 And if we cannot understand what bug you are trying to fix, or why your
34215 patch should be an improvement, we will not install it. A test case will
34216 help us to understand.
34219 A guess about what the bug is or what it depends on.
34221 Such guesses are usually wrong. Even we cannot guess right about such
34222 things without first using the debugger to find the facts.
34225 @c The readline documentation is distributed with the readline code
34226 @c and consists of the two following files:
34229 @c Use -I with makeinfo to point to the appropriate directory,
34230 @c environment var TEXINPUTS with TeX.
34231 @ifclear SYSTEM_READLINE
34232 @include rluser.texi
34233 @include hsuser.texi
34237 @appendix In Memoriam
34239 The @value{GDBN} project mourns the loss of the following long-time
34244 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34245 to Free Software in general. Outside of @value{GDBN}, he was known in
34246 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34248 @item Michael Snyder
34249 Michael was one of the Global Maintainers of the @value{GDBN} project,
34250 with contributions recorded as early as 1996, until 2011. In addition
34251 to his day to day participation, he was a large driving force behind
34252 adding Reverse Debugging to @value{GDBN}.
34255 Beyond their technical contributions to the project, they were also
34256 enjoyable members of the Free Software Community. We will miss them.
34258 @node Formatting Documentation
34259 @appendix Formatting Documentation
34261 @cindex @value{GDBN} reference card
34262 @cindex reference card
34263 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34264 for printing with PostScript or Ghostscript, in the @file{gdb}
34265 subdirectory of the main source directory@footnote{In
34266 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34267 release.}. If you can use PostScript or Ghostscript with your printer,
34268 you can print the reference card immediately with @file{refcard.ps}.
34270 The release also includes the source for the reference card. You
34271 can format it, using @TeX{}, by typing:
34277 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34278 mode on US ``letter'' size paper;
34279 that is, on a sheet 11 inches wide by 8.5 inches
34280 high. You will need to specify this form of printing as an option to
34281 your @sc{dvi} output program.
34283 @cindex documentation
34285 All the documentation for @value{GDBN} comes as part of the machine-readable
34286 distribution. The documentation is written in Texinfo format, which is
34287 a documentation system that uses a single source file to produce both
34288 on-line information and a printed manual. You can use one of the Info
34289 formatting commands to create the on-line version of the documentation
34290 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34292 @value{GDBN} includes an already formatted copy of the on-line Info
34293 version of this manual in the @file{gdb} subdirectory. The main Info
34294 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34295 subordinate files matching @samp{gdb.info*} in the same directory. If
34296 necessary, you can print out these files, or read them with any editor;
34297 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34298 Emacs or the standalone @code{info} program, available as part of the
34299 @sc{gnu} Texinfo distribution.
34301 If you want to format these Info files yourself, you need one of the
34302 Info formatting programs, such as @code{texinfo-format-buffer} or
34305 If you have @code{makeinfo} installed, and are in the top level
34306 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34307 version @value{GDBVN}), you can make the Info file by typing:
34314 If you want to typeset and print copies of this manual, you need @TeX{},
34315 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34316 Texinfo definitions file.
34318 @TeX{} is a typesetting program; it does not print files directly, but
34319 produces output files called @sc{dvi} files. To print a typeset
34320 document, you need a program to print @sc{dvi} files. If your system
34321 has @TeX{} installed, chances are it has such a program. The precise
34322 command to use depends on your system; @kbd{lpr -d} is common; another
34323 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34324 require a file name without any extension or a @samp{.dvi} extension.
34326 @TeX{} also requires a macro definitions file called
34327 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34328 written in Texinfo format. On its own, @TeX{} cannot either read or
34329 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34330 and is located in the @file{gdb-@var{version-number}/texinfo}
34333 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34334 typeset and print this manual. First switch to the @file{gdb}
34335 subdirectory of the main source directory (for example, to
34336 @file{gdb-@value{GDBVN}/gdb}) and type:
34342 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34344 @node Installing GDB
34345 @appendix Installing @value{GDBN}
34346 @cindex installation
34349 * Requirements:: Requirements for building @value{GDBN}
34350 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34351 * Separate Objdir:: Compiling @value{GDBN} in another directory
34352 * Config Names:: Specifying names for hosts and targets
34353 * Configure Options:: Summary of options for configure
34354 * System-wide configuration:: Having a system-wide init file
34358 @section Requirements for Building @value{GDBN}
34359 @cindex building @value{GDBN}, requirements for
34361 Building @value{GDBN} requires various tools and packages to be available.
34362 Other packages will be used only if they are found.
34364 @heading Tools/Packages Necessary for Building @value{GDBN}
34366 @item ISO C90 compiler
34367 @value{GDBN} is written in ISO C90. It should be buildable with any
34368 working C90 compiler, e.g.@: GCC.
34372 @heading Tools/Packages Optional for Building @value{GDBN}
34376 @value{GDBN} can use the Expat XML parsing library. This library may be
34377 included with your operating system distribution; if it is not, you
34378 can get the latest version from @url{http://expat.sourceforge.net}.
34379 The @file{configure} script will search for this library in several
34380 standard locations; if it is installed in an unusual path, you can
34381 use the @option{--with-libexpat-prefix} option to specify its location.
34387 Remote protocol memory maps (@pxref{Memory Map Format})
34389 Target descriptions (@pxref{Target Descriptions})
34391 Remote shared library lists (@xref{Library List Format},
34392 or alternatively @pxref{Library List Format for SVR4 Targets})
34394 MS-Windows shared libraries (@pxref{Shared Libraries})
34396 Traceframe info (@pxref{Traceframe Info Format})
34398 Branch trace (@pxref{Branch Trace Format},
34399 @pxref{Branch Trace Configuration Format})
34404 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
34405 library. This library may be included with your operating system
34406 distribution; if it is not, you can get the latest version from
34407 @url{http://www.mpfr.org}. The @file{configure} script will search
34408 for this library in several standard locations; if it is installed
34409 in an unusual path, you can use the @option{--with-libmpfr-prefix}
34410 option to specify its location.
34412 GNU MPFR is used to emulate target floating-point arithmetic during
34413 expression evaluation when the target uses different floating-point
34414 formats than the host. If GNU MPFR it is not available, @value{GDBN}
34415 will fall back to using host floating-point arithmetic.
34418 @cindex compressed debug sections
34419 @value{GDBN} will use the @samp{zlib} library, if available, to read
34420 compressed debug sections. Some linkers, such as GNU gold, are capable
34421 of producing binaries with compressed debug sections. If @value{GDBN}
34422 is compiled with @samp{zlib}, it will be able to read the debug
34423 information in such binaries.
34425 The @samp{zlib} library is likely included with your operating system
34426 distribution; if it is not, you can get the latest version from
34427 @url{http://zlib.net}.
34430 @value{GDBN}'s features related to character sets (@pxref{Character
34431 Sets}) require a functioning @code{iconv} implementation. If you are
34432 on a GNU system, then this is provided by the GNU C Library. Some
34433 other systems also provide a working @code{iconv}.
34435 If @value{GDBN} is using the @code{iconv} program which is installed
34436 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34437 This is done with @option{--with-iconv-bin} which specifies the
34438 directory that contains the @code{iconv} program.
34440 On systems without @code{iconv}, you can install GNU Libiconv. If you
34441 have previously installed Libiconv, you can use the
34442 @option{--with-libiconv-prefix} option to configure.
34444 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34445 arrange to build Libiconv if a directory named @file{libiconv} appears
34446 in the top-most source directory. If Libiconv is built this way, and
34447 if the operating system does not provide a suitable @code{iconv}
34448 implementation, then the just-built library will automatically be used
34449 by @value{GDBN}. One easy way to set this up is to download GNU
34450 Libiconv, unpack it, and then rename the directory holding the
34451 Libiconv source code to @samp{libiconv}.
34454 @node Running Configure
34455 @section Invoking the @value{GDBN} @file{configure} Script
34456 @cindex configuring @value{GDBN}
34457 @value{GDBN} comes with a @file{configure} script that automates the process
34458 of preparing @value{GDBN} for installation; you can then use @code{make} to
34459 build the @code{gdb} program.
34461 @c irrelevant in info file; it's as current as the code it lives with.
34462 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34463 look at the @file{README} file in the sources; we may have improved the
34464 installation procedures since publishing this manual.}
34467 The @value{GDBN} distribution includes all the source code you need for
34468 @value{GDBN} in a single directory, whose name is usually composed by
34469 appending the version number to @samp{gdb}.
34471 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34472 @file{gdb-@value{GDBVN}} directory. That directory contains:
34475 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34476 script for configuring @value{GDBN} and all its supporting libraries
34478 @item gdb-@value{GDBVN}/gdb
34479 the source specific to @value{GDBN} itself
34481 @item gdb-@value{GDBVN}/bfd
34482 source for the Binary File Descriptor library
34484 @item gdb-@value{GDBVN}/include
34485 @sc{gnu} include files
34487 @item gdb-@value{GDBVN}/libiberty
34488 source for the @samp{-liberty} free software library
34490 @item gdb-@value{GDBVN}/opcodes
34491 source for the library of opcode tables and disassemblers
34493 @item gdb-@value{GDBVN}/readline
34494 source for the @sc{gnu} command-line interface
34496 @item gdb-@value{GDBVN}/glob
34497 source for the @sc{gnu} filename pattern-matching subroutine
34499 @item gdb-@value{GDBVN}/mmalloc
34500 source for the @sc{gnu} memory-mapped malloc package
34503 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34504 from the @file{gdb-@var{version-number}} source directory, which in
34505 this example is the @file{gdb-@value{GDBVN}} directory.
34507 First switch to the @file{gdb-@var{version-number}} source directory
34508 if you are not already in it; then run @file{configure}. Pass the
34509 identifier for the platform on which @value{GDBN} will run as an
34515 cd gdb-@value{GDBVN}
34516 ./configure @var{host}
34521 where @var{host} is an identifier such as @samp{sun4} or
34522 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34523 (You can often leave off @var{host}; @file{configure} tries to guess the
34524 correct value by examining your system.)
34526 Running @samp{configure @var{host}} and then running @code{make} builds the
34527 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34528 libraries, then @code{gdb} itself. The configured source files, and the
34529 binaries, are left in the corresponding source directories.
34532 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34533 system does not recognize this automatically when you run a different
34534 shell, you may need to run @code{sh} on it explicitly:
34537 sh configure @var{host}
34540 If you run @file{configure} from a directory that contains source
34541 directories for multiple libraries or programs, such as the
34542 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34544 creates configuration files for every directory level underneath (unless
34545 you tell it not to, with the @samp{--norecursion} option).
34547 You should run the @file{configure} script from the top directory in the
34548 source tree, the @file{gdb-@var{version-number}} directory. If you run
34549 @file{configure} from one of the subdirectories, you will configure only
34550 that subdirectory. That is usually not what you want. In particular,
34551 if you run the first @file{configure} from the @file{gdb} subdirectory
34552 of the @file{gdb-@var{version-number}} directory, you will omit the
34553 configuration of @file{bfd}, @file{readline}, and other sibling
34554 directories of the @file{gdb} subdirectory. This leads to build errors
34555 about missing include files such as @file{bfd/bfd.h}.
34557 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34558 However, you should make sure that the shell on your path (named by
34559 the @samp{SHELL} environment variable) is publicly readable. Remember
34560 that @value{GDBN} uses the shell to start your program---some systems refuse to
34561 let @value{GDBN} debug child processes whose programs are not readable.
34563 @node Separate Objdir
34564 @section Compiling @value{GDBN} in Another Directory
34566 If you want to run @value{GDBN} versions for several host or target machines,
34567 you need a different @code{gdb} compiled for each combination of
34568 host and target. @file{configure} is designed to make this easy by
34569 allowing you to generate each configuration in a separate subdirectory,
34570 rather than in the source directory. If your @code{make} program
34571 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34572 @code{make} in each of these directories builds the @code{gdb}
34573 program specified there.
34575 To build @code{gdb} in a separate directory, run @file{configure}
34576 with the @samp{--srcdir} option to specify where to find the source.
34577 (You also need to specify a path to find @file{configure}
34578 itself from your working directory. If the path to @file{configure}
34579 would be the same as the argument to @samp{--srcdir}, you can leave out
34580 the @samp{--srcdir} option; it is assumed.)
34582 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34583 separate directory for a Sun 4 like this:
34587 cd gdb-@value{GDBVN}
34590 ../gdb-@value{GDBVN}/configure sun4
34595 When @file{configure} builds a configuration using a remote source
34596 directory, it creates a tree for the binaries with the same structure
34597 (and using the same names) as the tree under the source directory. In
34598 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34599 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34600 @file{gdb-sun4/gdb}.
34602 Make sure that your path to the @file{configure} script has just one
34603 instance of @file{gdb} in it. If your path to @file{configure} looks
34604 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34605 one subdirectory of @value{GDBN}, not the whole package. This leads to
34606 build errors about missing include files such as @file{bfd/bfd.h}.
34608 One popular reason to build several @value{GDBN} configurations in separate
34609 directories is to configure @value{GDBN} for cross-compiling (where
34610 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34611 programs that run on another machine---the @dfn{target}).
34612 You specify a cross-debugging target by
34613 giving the @samp{--target=@var{target}} option to @file{configure}.
34615 When you run @code{make} to build a program or library, you must run
34616 it in a configured directory---whatever directory you were in when you
34617 called @file{configure} (or one of its subdirectories).
34619 The @code{Makefile} that @file{configure} generates in each source
34620 directory also runs recursively. If you type @code{make} in a source
34621 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34622 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34623 will build all the required libraries, and then build GDB.
34625 When you have multiple hosts or targets configured in separate
34626 directories, you can run @code{make} on them in parallel (for example,
34627 if they are NFS-mounted on each of the hosts); they will not interfere
34631 @section Specifying Names for Hosts and Targets
34633 The specifications used for hosts and targets in the @file{configure}
34634 script are based on a three-part naming scheme, but some short predefined
34635 aliases are also supported. The full naming scheme encodes three pieces
34636 of information in the following pattern:
34639 @var{architecture}-@var{vendor}-@var{os}
34642 For example, you can use the alias @code{sun4} as a @var{host} argument,
34643 or as the value for @var{target} in a @code{--target=@var{target}}
34644 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34646 The @file{configure} script accompanying @value{GDBN} does not provide
34647 any query facility to list all supported host and target names or
34648 aliases. @file{configure} calls the Bourne shell script
34649 @code{config.sub} to map abbreviations to full names; you can read the
34650 script, if you wish, or you can use it to test your guesses on
34651 abbreviations---for example:
34654 % sh config.sub i386-linux
34656 % sh config.sub alpha-linux
34657 alpha-unknown-linux-gnu
34658 % sh config.sub hp9k700
34660 % sh config.sub sun4
34661 sparc-sun-sunos4.1.1
34662 % sh config.sub sun3
34663 m68k-sun-sunos4.1.1
34664 % sh config.sub i986v
34665 Invalid configuration `i986v': machine `i986v' not recognized
34669 @code{config.sub} is also distributed in the @value{GDBN} source
34670 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34672 @node Configure Options
34673 @section @file{configure} Options
34675 Here is a summary of the @file{configure} options and arguments that
34676 are most often useful for building @value{GDBN}. @file{configure} also has
34677 several other options not listed here. @inforef{What Configure
34678 Does,,configure.info}, for a full explanation of @file{configure}.
34681 configure @r{[}--help@r{]}
34682 @r{[}--prefix=@var{dir}@r{]}
34683 @r{[}--exec-prefix=@var{dir}@r{]}
34684 @r{[}--srcdir=@var{dirname}@r{]}
34685 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34686 @r{[}--target=@var{target}@r{]}
34691 You may introduce options with a single @samp{-} rather than
34692 @samp{--} if you prefer; but you may abbreviate option names if you use
34697 Display a quick summary of how to invoke @file{configure}.
34699 @item --prefix=@var{dir}
34700 Configure the source to install programs and files under directory
34703 @item --exec-prefix=@var{dir}
34704 Configure the source to install programs under directory
34707 @c avoid splitting the warning from the explanation:
34709 @item --srcdir=@var{dirname}
34710 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34711 @code{make} that implements the @code{VPATH} feature.}@*
34712 Use this option to make configurations in directories separate from the
34713 @value{GDBN} source directories. Among other things, you can use this to
34714 build (or maintain) several configurations simultaneously, in separate
34715 directories. @file{configure} writes configuration-specific files in
34716 the current directory, but arranges for them to use the source in the
34717 directory @var{dirname}. @file{configure} creates directories under
34718 the working directory in parallel to the source directories below
34721 @item --norecursion
34722 Configure only the directory level where @file{configure} is executed; do not
34723 propagate configuration to subdirectories.
34725 @item --target=@var{target}
34726 Configure @value{GDBN} for cross-debugging programs running on the specified
34727 @var{target}. Without this option, @value{GDBN} is configured to debug
34728 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34730 There is no convenient way to generate a list of all available targets.
34732 @item @var{host} @dots{}
34733 Configure @value{GDBN} to run on the specified @var{host}.
34735 There is no convenient way to generate a list of all available hosts.
34738 There are many other options available as well, but they are generally
34739 needed for special purposes only.
34741 @node System-wide configuration
34742 @section System-wide configuration and settings
34743 @cindex system-wide init file
34745 @value{GDBN} can be configured to have a system-wide init file;
34746 this file will be read and executed at startup (@pxref{Startup, , What
34747 @value{GDBN} does during startup}).
34749 Here is the corresponding configure option:
34752 @item --with-system-gdbinit=@var{file}
34753 Specify that the default location of the system-wide init file is
34757 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34758 it may be subject to relocation. Two possible cases:
34762 If the default location of this init file contains @file{$prefix},
34763 it will be subject to relocation. Suppose that the configure options
34764 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34765 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34766 init file is looked for as @file{$install/etc/gdbinit} instead of
34767 @file{$prefix/etc/gdbinit}.
34770 By contrast, if the default location does not contain the prefix,
34771 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34772 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34773 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34774 wherever @value{GDBN} is installed.
34777 If the configured location of the system-wide init file (as given by the
34778 @option{--with-system-gdbinit} option at configure time) is in the
34779 data-directory (as specified by @option{--with-gdb-datadir} at configure
34780 time) or in one of its subdirectories, then @value{GDBN} will look for the
34781 system-wide init file in the directory specified by the
34782 @option{--data-directory} command-line option.
34783 Note that the system-wide init file is only read once, during @value{GDBN}
34784 initialization. If the data-directory is changed after @value{GDBN} has
34785 started with the @code{set data-directory} command, the file will not be
34789 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34792 @node System-wide Configuration Scripts
34793 @subsection Installed System-wide Configuration Scripts
34794 @cindex system-wide configuration scripts
34796 The @file{system-gdbinit} directory, located inside the data-directory
34797 (as specified by @option{--with-gdb-datadir} at configure time) contains
34798 a number of scripts which can be used as system-wide init files. To
34799 automatically source those scripts at startup, @value{GDBN} should be
34800 configured with @option{--with-system-gdbinit}. Otherwise, any user
34801 should be able to source them by hand as needed.
34803 The following scripts are currently available:
34806 @item @file{elinos.py}
34808 @cindex ELinOS system-wide configuration script
34809 This script is useful when debugging a program on an ELinOS target.
34810 It takes advantage of the environment variables defined in a standard
34811 ELinOS environment in order to determine the location of the system
34812 shared libraries, and then sets the @samp{solib-absolute-prefix}
34813 and @samp{solib-search-path} variables appropriately.
34815 @item @file{wrs-linux.py}
34816 @pindex wrs-linux.py
34817 @cindex Wind River Linux system-wide configuration script
34818 This script is useful when debugging a program on a target running
34819 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34820 the host-side sysroot used by the target system.
34824 @node Maintenance Commands
34825 @appendix Maintenance Commands
34826 @cindex maintenance commands
34827 @cindex internal commands
34829 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34830 includes a number of commands intended for @value{GDBN} developers,
34831 that are not documented elsewhere in this manual. These commands are
34832 provided here for reference. (For commands that turn on debugging
34833 messages, see @ref{Debugging Output}.)
34836 @kindex maint agent
34837 @kindex maint agent-eval
34838 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34839 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34840 Translate the given @var{expression} into remote agent bytecodes.
34841 This command is useful for debugging the Agent Expression mechanism
34842 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34843 expression useful for data collection, such as by tracepoints, while
34844 @samp{maint agent-eval} produces an expression that evaluates directly
34845 to a result. For instance, a collection expression for @code{globa +
34846 globb} will include bytecodes to record four bytes of memory at each
34847 of the addresses of @code{globa} and @code{globb}, while discarding
34848 the result of the addition, while an evaluation expression will do the
34849 addition and return the sum.
34850 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34851 If not, generate remote agent bytecode for current frame PC address.
34853 @kindex maint agent-printf
34854 @item maint agent-printf @var{format},@var{expr},...
34855 Translate the given format string and list of argument expressions
34856 into remote agent bytecodes and display them as a disassembled list.
34857 This command is useful for debugging the agent version of dynamic
34858 printf (@pxref{Dynamic Printf}).
34860 @kindex maint info breakpoints
34861 @item @anchor{maint info breakpoints}maint info breakpoints
34862 Using the same format as @samp{info breakpoints}, display both the
34863 breakpoints you've set explicitly, and those @value{GDBN} is using for
34864 internal purposes. Internal breakpoints are shown with negative
34865 breakpoint numbers. The type column identifies what kind of breakpoint
34870 Normal, explicitly set breakpoint.
34873 Normal, explicitly set watchpoint.
34876 Internal breakpoint, used to handle correctly stepping through
34877 @code{longjmp} calls.
34879 @item longjmp resume
34880 Internal breakpoint at the target of a @code{longjmp}.
34883 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34886 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34889 Shared library events.
34893 @kindex maint info btrace
34894 @item maint info btrace
34895 Pint information about raw branch tracing data.
34897 @kindex maint btrace packet-history
34898 @item maint btrace packet-history
34899 Print the raw branch trace packets that are used to compute the
34900 execution history for the @samp{record btrace} command. Both the
34901 information and the format in which it is printed depend on the btrace
34906 For the BTS recording format, print a list of blocks of sequential
34907 code. For each block, the following information is printed:
34911 Newer blocks have higher numbers. The oldest block has number zero.
34912 @item Lowest @samp{PC}
34913 @item Highest @samp{PC}
34917 For the Intel Processor Trace recording format, print a list of
34918 Intel Processor Trace packets. For each packet, the following
34919 information is printed:
34922 @item Packet number
34923 Newer packets have higher numbers. The oldest packet has number zero.
34925 The packet's offset in the trace stream.
34926 @item Packet opcode and payload
34930 @kindex maint btrace clear-packet-history
34931 @item maint btrace clear-packet-history
34932 Discards the cached packet history printed by the @samp{maint btrace
34933 packet-history} command. The history will be computed again when
34936 @kindex maint btrace clear
34937 @item maint btrace clear
34938 Discard the branch trace data. The data will be fetched anew and the
34939 branch trace will be recomputed when needed.
34941 This implicitly truncates the branch trace to a single branch trace
34942 buffer. When updating branch trace incrementally, the branch trace
34943 available to @value{GDBN} may be bigger than a single branch trace
34946 @kindex maint set btrace pt skip-pad
34947 @item maint set btrace pt skip-pad
34948 @kindex maint show btrace pt skip-pad
34949 @item maint show btrace pt skip-pad
34950 Control whether @value{GDBN} will skip PAD packets when computing the
34953 @kindex set displaced-stepping
34954 @kindex show displaced-stepping
34955 @cindex displaced stepping support
34956 @cindex out-of-line single-stepping
34957 @item set displaced-stepping
34958 @itemx show displaced-stepping
34959 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34960 if the target supports it. Displaced stepping is a way to single-step
34961 over breakpoints without removing them from the inferior, by executing
34962 an out-of-line copy of the instruction that was originally at the
34963 breakpoint location. It is also known as out-of-line single-stepping.
34966 @item set displaced-stepping on
34967 If the target architecture supports it, @value{GDBN} will use
34968 displaced stepping to step over breakpoints.
34970 @item set displaced-stepping off
34971 @value{GDBN} will not use displaced stepping to step over breakpoints,
34972 even if such is supported by the target architecture.
34974 @cindex non-stop mode, and @samp{set displaced-stepping}
34975 @item set displaced-stepping auto
34976 This is the default mode. @value{GDBN} will use displaced stepping
34977 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34978 architecture supports displaced stepping.
34981 @kindex maint check-psymtabs
34982 @item maint check-psymtabs
34983 Check the consistency of currently expanded psymtabs versus symtabs.
34984 Use this to check, for example, whether a symbol is in one but not the other.
34986 @kindex maint check-symtabs
34987 @item maint check-symtabs
34988 Check the consistency of currently expanded symtabs.
34990 @kindex maint expand-symtabs
34991 @item maint expand-symtabs [@var{regexp}]
34992 Expand symbol tables.
34993 If @var{regexp} is specified, only expand symbol tables for file
34994 names matching @var{regexp}.
34996 @kindex maint set catch-demangler-crashes
34997 @kindex maint show catch-demangler-crashes
34998 @cindex demangler crashes
34999 @item maint set catch-demangler-crashes [on|off]
35000 @itemx maint show catch-demangler-crashes
35001 Control whether @value{GDBN} should attempt to catch crashes in the
35002 symbol name demangler. The default is to attempt to catch crashes.
35003 If enabled, the first time a crash is caught, a core file is created,
35004 the offending symbol is displayed and the user is presented with the
35005 option to terminate the current session.
35007 @kindex maint cplus first_component
35008 @item maint cplus first_component @var{name}
35009 Print the first C@t{++} class/namespace component of @var{name}.
35011 @kindex maint cplus namespace
35012 @item maint cplus namespace
35013 Print the list of possible C@t{++} namespaces.
35015 @kindex maint deprecate
35016 @kindex maint undeprecate
35017 @cindex deprecated commands
35018 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35019 @itemx maint undeprecate @var{command}
35020 Deprecate or undeprecate the named @var{command}. Deprecated commands
35021 cause @value{GDBN} to issue a warning when you use them. The optional
35022 argument @var{replacement} says which newer command should be used in
35023 favor of the deprecated one; if it is given, @value{GDBN} will mention
35024 the replacement as part of the warning.
35026 @kindex maint dump-me
35027 @item maint dump-me
35028 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35029 Cause a fatal signal in the debugger and force it to dump its core.
35030 This is supported only on systems which support aborting a program
35031 with the @code{SIGQUIT} signal.
35033 @kindex maint internal-error
35034 @kindex maint internal-warning
35035 @kindex maint demangler-warning
35036 @cindex demangler crashes
35037 @item maint internal-error @r{[}@var{message-text}@r{]}
35038 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35039 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35041 Cause @value{GDBN} to call the internal function @code{internal_error},
35042 @code{internal_warning} or @code{demangler_warning} and hence behave
35043 as though an internal problem has been detected. In addition to
35044 reporting the internal problem, these functions give the user the
35045 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35046 and @code{internal_warning}) create a core file of the current
35047 @value{GDBN} session.
35049 These commands take an optional parameter @var{message-text} that is
35050 used as the text of the error or warning message.
35052 Here's an example of using @code{internal-error}:
35055 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35056 @dots{}/maint.c:121: internal-error: testing, 1, 2
35057 A problem internal to GDB has been detected. Further
35058 debugging may prove unreliable.
35059 Quit this debugging session? (y or n) @kbd{n}
35060 Create a core file? (y or n) @kbd{n}
35064 @cindex @value{GDBN} internal error
35065 @cindex internal errors, control of @value{GDBN} behavior
35066 @cindex demangler crashes
35068 @kindex maint set internal-error
35069 @kindex maint show internal-error
35070 @kindex maint set internal-warning
35071 @kindex maint show internal-warning
35072 @kindex maint set demangler-warning
35073 @kindex maint show demangler-warning
35074 @item maint set internal-error @var{action} [ask|yes|no]
35075 @itemx maint show internal-error @var{action}
35076 @itemx maint set internal-warning @var{action} [ask|yes|no]
35077 @itemx maint show internal-warning @var{action}
35078 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35079 @itemx maint show demangler-warning @var{action}
35080 When @value{GDBN} reports an internal problem (error or warning) it
35081 gives the user the opportunity to both quit @value{GDBN} and create a
35082 core file of the current @value{GDBN} session. These commands let you
35083 override the default behaviour for each particular @var{action},
35084 described in the table below.
35088 You can specify that @value{GDBN} should always (yes) or never (no)
35089 quit. The default is to ask the user what to do.
35092 You can specify that @value{GDBN} should always (yes) or never (no)
35093 create a core file. The default is to ask the user what to do. Note
35094 that there is no @code{corefile} option for @code{demangler-warning}:
35095 demangler warnings always create a core file and this cannot be
35099 @kindex maint packet
35100 @item maint packet @var{text}
35101 If @value{GDBN} is talking to an inferior via the serial protocol,
35102 then this command sends the string @var{text} to the inferior, and
35103 displays the response packet. @value{GDBN} supplies the initial
35104 @samp{$} character, the terminating @samp{#} character, and the
35107 @kindex maint print architecture
35108 @item maint print architecture @r{[}@var{file}@r{]}
35109 Print the entire architecture configuration. The optional argument
35110 @var{file} names the file where the output goes.
35112 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35113 @item maint print c-tdesc
35114 Print the target description (@pxref{Target Descriptions}) as
35115 a C source file. By default, the target description is for the current
35116 target, but if the optional argument @var{file} is provided, that file
35117 is used to produce the description. The @var{file} should be an XML
35118 document, of the form described in @ref{Target Description Format}.
35119 The created source file is built into @value{GDBN} when @value{GDBN} is
35120 built again. This command is used by developers after they add or
35121 modify XML target descriptions.
35123 @kindex maint check xml-descriptions
35124 @item maint check xml-descriptions @var{dir}
35125 Check that the target descriptions dynamically created by @value{GDBN}
35126 equal the descriptions created from XML files found in @var{dir}.
35128 @kindex maint print dummy-frames
35129 @item maint print dummy-frames
35130 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35133 (@value{GDBP}) @kbd{b add}
35135 (@value{GDBP}) @kbd{print add(2,3)}
35136 Breakpoint 2, add (a=2, b=3) at @dots{}
35138 The program being debugged stopped while in a function called from GDB.
35140 (@value{GDBP}) @kbd{maint print dummy-frames}
35141 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35145 Takes an optional file parameter.
35147 @kindex maint print registers
35148 @kindex maint print raw-registers
35149 @kindex maint print cooked-registers
35150 @kindex maint print register-groups
35151 @kindex maint print remote-registers
35152 @item maint print registers @r{[}@var{file}@r{]}
35153 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35154 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35155 @itemx maint print register-groups @r{[}@var{file}@r{]}
35156 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35157 Print @value{GDBN}'s internal register data structures.
35159 The command @code{maint print raw-registers} includes the contents of
35160 the raw register cache; the command @code{maint print
35161 cooked-registers} includes the (cooked) value of all registers,
35162 including registers which aren't available on the target nor visible
35163 to user; the command @code{maint print register-groups} includes the
35164 groups that each register is a member of; and the command @code{maint
35165 print remote-registers} includes the remote target's register numbers
35166 and offsets in the `G' packets.
35168 These commands take an optional parameter, a file name to which to
35169 write the information.
35171 @kindex maint print reggroups
35172 @item maint print reggroups @r{[}@var{file}@r{]}
35173 Print @value{GDBN}'s internal register group data structures. The
35174 optional argument @var{file} tells to what file to write the
35177 The register groups info looks like this:
35180 (@value{GDBP}) @kbd{maint print reggroups}
35193 This command forces @value{GDBN} to flush its internal register cache.
35195 @kindex maint print objfiles
35196 @cindex info for known object files
35197 @item maint print objfiles @r{[}@var{regexp}@r{]}
35198 Print a dump of all known object files.
35199 If @var{regexp} is specified, only print object files whose names
35200 match @var{regexp}. For each object file, this command prints its name,
35201 address in memory, and all of its psymtabs and symtabs.
35203 @kindex maint print user-registers
35204 @cindex user registers
35205 @item maint print user-registers
35206 List all currently available @dfn{user registers}. User registers
35207 typically provide alternate names for actual hardware registers. They
35208 include the four ``standard'' registers @code{$fp}, @code{$pc},
35209 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35210 registers can be used in expressions in the same way as the canonical
35211 register names, but only the latter are listed by the @code{info
35212 registers} and @code{maint print registers} commands.
35214 @kindex maint print section-scripts
35215 @cindex info for known .debug_gdb_scripts-loaded scripts
35216 @item maint print section-scripts [@var{regexp}]
35217 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35218 If @var{regexp} is specified, only print scripts loaded by object files
35219 matching @var{regexp}.
35220 For each script, this command prints its name as specified in the objfile,
35221 and the full path if known.
35222 @xref{dotdebug_gdb_scripts section}.
35224 @kindex maint print statistics
35225 @cindex bcache statistics
35226 @item maint print statistics
35227 This command prints, for each object file in the program, various data
35228 about that object file followed by the byte cache (@dfn{bcache})
35229 statistics for the object file. The objfile data includes the number
35230 of minimal, partial, full, and stabs symbols, the number of types
35231 defined by the objfile, the number of as yet unexpanded psym tables,
35232 the number of line tables and string tables, and the amount of memory
35233 used by the various tables. The bcache statistics include the counts,
35234 sizes, and counts of duplicates of all and unique objects, max,
35235 average, and median entry size, total memory used and its overhead and
35236 savings, and various measures of the hash table size and chain
35239 @kindex maint print target-stack
35240 @cindex target stack description
35241 @item maint print target-stack
35242 A @dfn{target} is an interface between the debugger and a particular
35243 kind of file or process. Targets can be stacked in @dfn{strata},
35244 so that more than one target can potentially respond to a request.
35245 In particular, memory accesses will walk down the stack of targets
35246 until they find a target that is interested in handling that particular
35249 This command prints a short description of each layer that was pushed on
35250 the @dfn{target stack}, starting from the top layer down to the bottom one.
35252 @kindex maint print type
35253 @cindex type chain of a data type
35254 @item maint print type @var{expr}
35255 Print the type chain for a type specified by @var{expr}. The argument
35256 can be either a type name or a symbol. If it is a symbol, the type of
35257 that symbol is described. The type chain produced by this command is
35258 a recursive definition of the data type as stored in @value{GDBN}'s
35259 data structures, including its flags and contained types.
35261 @kindex maint selftest
35263 @item maint selftest @r{[}@var{filter}@r{]}
35264 Run any self tests that were compiled in to @value{GDBN}. This will
35265 print a message showing how many tests were run, and how many failed.
35266 If a @var{filter} is passed, only the tests with @var{filter} in their
35269 @kindex "maint info selftests"
35271 @item maint info selftests
35272 List the selftests compiled in to @value{GDBN}.
35274 @kindex maint set dwarf always-disassemble
35275 @kindex maint show dwarf always-disassemble
35276 @item maint set dwarf always-disassemble
35277 @item maint show dwarf always-disassemble
35278 Control the behavior of @code{info address} when using DWARF debugging
35281 The default is @code{off}, which means that @value{GDBN} should try to
35282 describe a variable's location in an easily readable format. When
35283 @code{on}, @value{GDBN} will instead display the DWARF location
35284 expression in an assembly-like format. Note that some locations are
35285 too complex for @value{GDBN} to describe simply; in this case you will
35286 always see the disassembly form.
35288 Here is an example of the resulting disassembly:
35291 (gdb) info addr argc
35292 Symbol "argc" is a complex DWARF expression:
35296 For more information on these expressions, see
35297 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35299 @kindex maint set dwarf max-cache-age
35300 @kindex maint show dwarf max-cache-age
35301 @item maint set dwarf max-cache-age
35302 @itemx maint show dwarf max-cache-age
35303 Control the DWARF compilation unit cache.
35305 @cindex DWARF compilation units cache
35306 In object files with inter-compilation-unit references, such as those
35307 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35308 reader needs to frequently refer to previously read compilation units.
35309 This setting controls how long a compilation unit will remain in the
35310 cache if it is not referenced. A higher limit means that cached
35311 compilation units will be stored in memory longer, and more total
35312 memory will be used. Setting it to zero disables caching, which will
35313 slow down @value{GDBN} startup, but reduce memory consumption.
35315 @kindex maint set profile
35316 @kindex maint show profile
35317 @cindex profiling GDB
35318 @item maint set profile
35319 @itemx maint show profile
35320 Control profiling of @value{GDBN}.
35322 Profiling will be disabled until you use the @samp{maint set profile}
35323 command to enable it. When you enable profiling, the system will begin
35324 collecting timing and execution count data; when you disable profiling or
35325 exit @value{GDBN}, the results will be written to a log file. Remember that
35326 if you use profiling, @value{GDBN} will overwrite the profiling log file
35327 (often called @file{gmon.out}). If you have a record of important profiling
35328 data in a @file{gmon.out} file, be sure to move it to a safe location.
35330 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35331 compiled with the @samp{-pg} compiler option.
35333 @kindex maint set show-debug-regs
35334 @kindex maint show show-debug-regs
35335 @cindex hardware debug registers
35336 @item maint set show-debug-regs
35337 @itemx maint show show-debug-regs
35338 Control whether to show variables that mirror the hardware debug
35339 registers. Use @code{on} to enable, @code{off} to disable. If
35340 enabled, the debug registers values are shown when @value{GDBN} inserts or
35341 removes a hardware breakpoint or watchpoint, and when the inferior
35342 triggers a hardware-assisted breakpoint or watchpoint.
35344 @kindex maint set show-all-tib
35345 @kindex maint show show-all-tib
35346 @item maint set show-all-tib
35347 @itemx maint show show-all-tib
35348 Control whether to show all non zero areas within a 1k block starting
35349 at thread local base, when using the @samp{info w32 thread-information-block}
35352 @kindex maint set target-async
35353 @kindex maint show target-async
35354 @item maint set target-async
35355 @itemx maint show target-async
35356 This controls whether @value{GDBN} targets operate in synchronous or
35357 asynchronous mode (@pxref{Background Execution}). Normally the
35358 default is asynchronous, if it is available; but this can be changed
35359 to more easily debug problems occurring only in synchronous mode.
35361 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35362 @kindex maint show target-non-stop
35363 @item maint set target-non-stop
35364 @itemx maint show target-non-stop
35366 This controls whether @value{GDBN} targets always operate in non-stop
35367 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35368 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35369 if supported by the target.
35372 @item maint set target-non-stop auto
35373 This is the default mode. @value{GDBN} controls the target in
35374 non-stop mode if the target supports it.
35376 @item maint set target-non-stop on
35377 @value{GDBN} controls the target in non-stop mode even if the target
35378 does not indicate support.
35380 @item maint set target-non-stop off
35381 @value{GDBN} does not control the target in non-stop mode even if the
35382 target supports it.
35385 @kindex maint set per-command
35386 @kindex maint show per-command
35387 @item maint set per-command
35388 @itemx maint show per-command
35389 @cindex resources used by commands
35391 @value{GDBN} can display the resources used by each command.
35392 This is useful in debugging performance problems.
35395 @item maint set per-command space [on|off]
35396 @itemx maint show per-command space
35397 Enable or disable the printing of the memory used by GDB for each command.
35398 If enabled, @value{GDBN} will display how much memory each command
35399 took, following the command's own output.
35400 This can also be requested by invoking @value{GDBN} with the
35401 @option{--statistics} command-line switch (@pxref{Mode Options}).
35403 @item maint set per-command time [on|off]
35404 @itemx maint show per-command time
35405 Enable or disable the printing of the execution time of @value{GDBN}
35407 If enabled, @value{GDBN} will display how much time it
35408 took to execute each command, following the command's own output.
35409 Both CPU time and wallclock time are printed.
35410 Printing both is useful when trying to determine whether the cost is
35411 CPU or, e.g., disk/network latency.
35412 Note that the CPU time printed is for @value{GDBN} only, it does not include
35413 the execution time of the inferior because there's no mechanism currently
35414 to compute how much time was spent by @value{GDBN} and how much time was
35415 spent by the program been debugged.
35416 This can also be requested by invoking @value{GDBN} with the
35417 @option{--statistics} command-line switch (@pxref{Mode Options}).
35419 @item maint set per-command symtab [on|off]
35420 @itemx maint show per-command symtab
35421 Enable or disable the printing of basic symbol table statistics
35423 If enabled, @value{GDBN} will display the following information:
35427 number of symbol tables
35429 number of primary symbol tables
35431 number of blocks in the blockvector
35435 @kindex maint space
35436 @cindex memory used by commands
35437 @item maint space @var{value}
35438 An alias for @code{maint set per-command space}.
35439 A non-zero value enables it, zero disables it.
35442 @cindex time of command execution
35443 @item maint time @var{value}
35444 An alias for @code{maint set per-command time}.
35445 A non-zero value enables it, zero disables it.
35447 @kindex maint translate-address
35448 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35449 Find the symbol stored at the location specified by the address
35450 @var{addr} and an optional section name @var{section}. If found,
35451 @value{GDBN} prints the name of the closest symbol and an offset from
35452 the symbol's location to the specified address. This is similar to
35453 the @code{info address} command (@pxref{Symbols}), except that this
35454 command also allows to find symbols in other sections.
35456 If section was not specified, the section in which the symbol was found
35457 is also printed. For dynamically linked executables, the name of
35458 executable or shared library containing the symbol is printed as well.
35462 The following command is useful for non-interactive invocations of
35463 @value{GDBN}, such as in the test suite.
35466 @item set watchdog @var{nsec}
35467 @kindex set watchdog
35468 @cindex watchdog timer
35469 @cindex timeout for commands
35470 Set the maximum number of seconds @value{GDBN} will wait for the
35471 target operation to finish. If this time expires, @value{GDBN}
35472 reports and error and the command is aborted.
35474 @item show watchdog
35475 Show the current setting of the target wait timeout.
35478 @node Remote Protocol
35479 @appendix @value{GDBN} Remote Serial Protocol
35484 * Stop Reply Packets::
35485 * General Query Packets::
35486 * Architecture-Specific Protocol Details::
35487 * Tracepoint Packets::
35488 * Host I/O Packets::
35490 * Notification Packets::
35491 * Remote Non-Stop::
35492 * Packet Acknowledgment::
35494 * File-I/O Remote Protocol Extension::
35495 * Library List Format::
35496 * Library List Format for SVR4 Targets::
35497 * Memory Map Format::
35498 * Thread List Format::
35499 * Traceframe Info Format::
35500 * Branch Trace Format::
35501 * Branch Trace Configuration Format::
35507 There may be occasions when you need to know something about the
35508 protocol---for example, if there is only one serial port to your target
35509 machine, you might want your program to do something special if it
35510 recognizes a packet meant for @value{GDBN}.
35512 In the examples below, @samp{->} and @samp{<-} are used to indicate
35513 transmitted and received data, respectively.
35515 @cindex protocol, @value{GDBN} remote serial
35516 @cindex serial protocol, @value{GDBN} remote
35517 @cindex remote serial protocol
35518 All @value{GDBN} commands and responses (other than acknowledgments
35519 and notifications, see @ref{Notification Packets}) are sent as a
35520 @var{packet}. A @var{packet} is introduced with the character
35521 @samp{$}, the actual @var{packet-data}, and the terminating character
35522 @samp{#} followed by a two-digit @var{checksum}:
35525 @code{$}@var{packet-data}@code{#}@var{checksum}
35529 @cindex checksum, for @value{GDBN} remote
35531 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35532 characters between the leading @samp{$} and the trailing @samp{#} (an
35533 eight bit unsigned checksum).
35535 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35536 specification also included an optional two-digit @var{sequence-id}:
35539 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35542 @cindex sequence-id, for @value{GDBN} remote
35544 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35545 has never output @var{sequence-id}s. Stubs that handle packets added
35546 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35548 When either the host or the target machine receives a packet, the first
35549 response expected is an acknowledgment: either @samp{+} (to indicate
35550 the package was received correctly) or @samp{-} (to request
35554 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35559 The @samp{+}/@samp{-} acknowledgments can be disabled
35560 once a connection is established.
35561 @xref{Packet Acknowledgment}, for details.
35563 The host (@value{GDBN}) sends @var{command}s, and the target (the
35564 debugging stub incorporated in your program) sends a @var{response}. In
35565 the case of step and continue @var{command}s, the response is only sent
35566 when the operation has completed, and the target has again stopped all
35567 threads in all attached processes. This is the default all-stop mode
35568 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35569 execution mode; see @ref{Remote Non-Stop}, for details.
35571 @var{packet-data} consists of a sequence of characters with the
35572 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35575 @cindex remote protocol, field separator
35576 Fields within the packet should be separated using @samp{,} @samp{;} or
35577 @samp{:}. Except where otherwise noted all numbers are represented in
35578 @sc{hex} with leading zeros suppressed.
35580 Implementors should note that prior to @value{GDBN} 5.0, the character
35581 @samp{:} could not appear as the third character in a packet (as it
35582 would potentially conflict with the @var{sequence-id}).
35584 @cindex remote protocol, binary data
35585 @anchor{Binary Data}
35586 Binary data in most packets is encoded either as two hexadecimal
35587 digits per byte of binary data. This allowed the traditional remote
35588 protocol to work over connections which were only seven-bit clean.
35589 Some packets designed more recently assume an eight-bit clean
35590 connection, and use a more efficient encoding to send and receive
35593 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35594 as an escape character. Any escaped byte is transmitted as the escape
35595 character followed by the original character XORed with @code{0x20}.
35596 For example, the byte @code{0x7d} would be transmitted as the two
35597 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35598 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35599 @samp{@}}) must always be escaped. Responses sent by the stub
35600 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35601 is not interpreted as the start of a run-length encoded sequence
35604 Response @var{data} can be run-length encoded to save space.
35605 Run-length encoding replaces runs of identical characters with one
35606 instance of the repeated character, followed by a @samp{*} and a
35607 repeat count. The repeat count is itself sent encoded, to avoid
35608 binary characters in @var{data}: a value of @var{n} is sent as
35609 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35610 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35611 code 32) for a repeat count of 3. (This is because run-length
35612 encoding starts to win for counts 3 or more.) Thus, for example,
35613 @samp{0* } is a run-length encoding of ``0000'': the space character
35614 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35617 The printable characters @samp{#} and @samp{$} or with a numeric value
35618 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35619 seven repeats (@samp{$}) can be expanded using a repeat count of only
35620 five (@samp{"}). For example, @samp{00000000} can be encoded as
35623 The error response returned for some packets includes a two character
35624 error number. That number is not well defined.
35626 @cindex empty response, for unsupported packets
35627 For any @var{command} not supported by the stub, an empty response
35628 (@samp{$#00}) should be returned. That way it is possible to extend the
35629 protocol. A newer @value{GDBN} can tell if a packet is supported based
35632 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35633 commands for register access, and the @samp{m} and @samp{M} commands
35634 for memory access. Stubs that only control single-threaded targets
35635 can implement run control with the @samp{c} (continue), and @samp{s}
35636 (step) commands. Stubs that support multi-threading targets should
35637 support the @samp{vCont} command. All other commands are optional.
35642 The following table provides a complete list of all currently defined
35643 @var{command}s and their corresponding response @var{data}.
35644 @xref{File-I/O Remote Protocol Extension}, for details about the File
35645 I/O extension of the remote protocol.
35647 Each packet's description has a template showing the packet's overall
35648 syntax, followed by an explanation of the packet's meaning. We
35649 include spaces in some of the templates for clarity; these are not
35650 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35651 separate its components. For example, a template like @samp{foo
35652 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35653 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35654 @var{baz}. @value{GDBN} does not transmit a space character between the
35655 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35658 @cindex @var{thread-id}, in remote protocol
35659 @anchor{thread-id syntax}
35660 Several packets and replies include a @var{thread-id} field to identify
35661 a thread. Normally these are positive numbers with a target-specific
35662 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35663 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35666 In addition, the remote protocol supports a multiprocess feature in
35667 which the @var{thread-id} syntax is extended to optionally include both
35668 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35669 The @var{pid} (process) and @var{tid} (thread) components each have the
35670 format described above: a positive number with target-specific
35671 interpretation formatted as a big-endian hex string, literal @samp{-1}
35672 to indicate all processes or threads (respectively), or @samp{0} to
35673 indicate an arbitrary process or thread. Specifying just a process, as
35674 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35675 error to specify all processes but a specific thread, such as
35676 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35677 for those packets and replies explicitly documented to include a process
35678 ID, rather than a @var{thread-id}.
35680 The multiprocess @var{thread-id} syntax extensions are only used if both
35681 @value{GDBN} and the stub report support for the @samp{multiprocess}
35682 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35685 Note that all packet forms beginning with an upper- or lower-case
35686 letter, other than those described here, are reserved for future use.
35688 Here are the packet descriptions.
35693 @cindex @samp{!} packet
35694 @anchor{extended mode}
35695 Enable extended mode. In extended mode, the remote server is made
35696 persistent. The @samp{R} packet is used to restart the program being
35702 The remote target both supports and has enabled extended mode.
35706 @cindex @samp{?} packet
35708 Indicate the reason the target halted. The reply is the same as for
35709 step and continue. This packet has a special interpretation when the
35710 target is in non-stop mode; see @ref{Remote Non-Stop}.
35713 @xref{Stop Reply Packets}, for the reply specifications.
35715 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35716 @cindex @samp{A} packet
35717 Initialized @code{argv[]} array passed into program. @var{arglen}
35718 specifies the number of bytes in the hex encoded byte stream
35719 @var{arg}. See @code{gdbserver} for more details.
35724 The arguments were set.
35730 @cindex @samp{b} packet
35731 (Don't use this packet; its behavior is not well-defined.)
35732 Change the serial line speed to @var{baud}.
35734 JTC: @emph{When does the transport layer state change? When it's
35735 received, or after the ACK is transmitted. In either case, there are
35736 problems if the command or the acknowledgment packet is dropped.}
35738 Stan: @emph{If people really wanted to add something like this, and get
35739 it working for the first time, they ought to modify ser-unix.c to send
35740 some kind of out-of-band message to a specially-setup stub and have the
35741 switch happen "in between" packets, so that from remote protocol's point
35742 of view, nothing actually happened.}
35744 @item B @var{addr},@var{mode}
35745 @cindex @samp{B} packet
35746 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35747 breakpoint at @var{addr}.
35749 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35750 (@pxref{insert breakpoint or watchpoint packet}).
35752 @cindex @samp{bc} packet
35755 Backward continue. Execute the target system in reverse. No parameter.
35756 @xref{Reverse Execution}, for more information.
35759 @xref{Stop Reply Packets}, for the reply specifications.
35761 @cindex @samp{bs} packet
35764 Backward single step. Execute one instruction in reverse. No parameter.
35765 @xref{Reverse Execution}, for more information.
35768 @xref{Stop Reply Packets}, for the reply specifications.
35770 @item c @r{[}@var{addr}@r{]}
35771 @cindex @samp{c} packet
35772 Continue at @var{addr}, which is the address to resume. If @var{addr}
35773 is omitted, resume at current address.
35775 This packet is deprecated for multi-threading support. @xref{vCont
35779 @xref{Stop Reply Packets}, for the reply specifications.
35781 @item C @var{sig}@r{[};@var{addr}@r{]}
35782 @cindex @samp{C} packet
35783 Continue with signal @var{sig} (hex signal number). If
35784 @samp{;@var{addr}} is omitted, resume at same address.
35786 This packet is deprecated for multi-threading support. @xref{vCont
35790 @xref{Stop Reply Packets}, for the reply specifications.
35793 @cindex @samp{d} packet
35796 Don't use this packet; instead, define a general set packet
35797 (@pxref{General Query Packets}).
35801 @cindex @samp{D} packet
35802 The first form of the packet is used to detach @value{GDBN} from the
35803 remote system. It is sent to the remote target
35804 before @value{GDBN} disconnects via the @code{detach} command.
35806 The second form, including a process ID, is used when multiprocess
35807 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35808 detach only a specific process. The @var{pid} is specified as a
35809 big-endian hex string.
35819 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35820 @cindex @samp{F} packet
35821 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35822 This is part of the File-I/O protocol extension. @xref{File-I/O
35823 Remote Protocol Extension}, for the specification.
35826 @anchor{read registers packet}
35827 @cindex @samp{g} packet
35828 Read general registers.
35832 @item @var{XX@dots{}}
35833 Each byte of register data is described by two hex digits. The bytes
35834 with the register are transmitted in target byte order. The size of
35835 each register and their position within the @samp{g} packet are
35836 determined by the @value{GDBN} internal gdbarch functions
35837 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35839 When reading registers from a trace frame (@pxref{Analyze Collected
35840 Data,,Using the Collected Data}), the stub may also return a string of
35841 literal @samp{x}'s in place of the register data digits, to indicate
35842 that the corresponding register has not been collected, thus its value
35843 is unavailable. For example, for an architecture with 4 registers of
35844 4 bytes each, the following reply indicates to @value{GDBN} that
35845 registers 0 and 2 have not been collected, while registers 1 and 3
35846 have been collected, and both have zero value:
35850 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35857 @item G @var{XX@dots{}}
35858 @cindex @samp{G} packet
35859 Write general registers. @xref{read registers packet}, for a
35860 description of the @var{XX@dots{}} data.
35870 @item H @var{op} @var{thread-id}
35871 @cindex @samp{H} packet
35872 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35873 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35874 should be @samp{c} for step and continue operations (note that this
35875 is deprecated, supporting the @samp{vCont} command is a better
35876 option), and @samp{g} for other operations. The thread designator
35877 @var{thread-id} has the format and interpretation described in
35878 @ref{thread-id syntax}.
35889 @c 'H': How restrictive (or permissive) is the thread model. If a
35890 @c thread is selected and stopped, are other threads allowed
35891 @c to continue to execute? As I mentioned above, I think the
35892 @c semantics of each command when a thread is selected must be
35893 @c described. For example:
35895 @c 'g': If the stub supports threads and a specific thread is
35896 @c selected, returns the register block from that thread;
35897 @c otherwise returns current registers.
35899 @c 'G' If the stub supports threads and a specific thread is
35900 @c selected, sets the registers of the register block of
35901 @c that thread; otherwise sets current registers.
35903 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35904 @anchor{cycle step packet}
35905 @cindex @samp{i} packet
35906 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35907 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35908 step starting at that address.
35911 @cindex @samp{I} packet
35912 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35916 @cindex @samp{k} packet
35919 The exact effect of this packet is not specified.
35921 For a bare-metal target, it may power cycle or reset the target
35922 system. For that reason, the @samp{k} packet has no reply.
35924 For a single-process target, it may kill that process if possible.
35926 A multiple-process target may choose to kill just one process, or all
35927 that are under @value{GDBN}'s control. For more precise control, use
35928 the vKill packet (@pxref{vKill packet}).
35930 If the target system immediately closes the connection in response to
35931 @samp{k}, @value{GDBN} does not consider the lack of packet
35932 acknowledgment to be an error, and assumes the kill was successful.
35934 If connected using @kbd{target extended-remote}, and the target does
35935 not close the connection in response to a kill request, @value{GDBN}
35936 probes the target state as if a new connection was opened
35937 (@pxref{? packet}).
35939 @item m @var{addr},@var{length}
35940 @cindex @samp{m} packet
35941 Read @var{length} addressable memory units starting at address @var{addr}
35942 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35943 any particular boundary.
35945 The stub need not use any particular size or alignment when gathering
35946 data from memory for the response; even if @var{addr} is word-aligned
35947 and @var{length} is a multiple of the word size, the stub is free to
35948 use byte accesses, or not. For this reason, this packet may not be
35949 suitable for accessing memory-mapped I/O devices.
35950 @cindex alignment of remote memory accesses
35951 @cindex size of remote memory accesses
35952 @cindex memory, alignment and size of remote accesses
35956 @item @var{XX@dots{}}
35957 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35958 The reply may contain fewer addressable memory units than requested if the
35959 server was able to read only part of the region of memory.
35964 @item M @var{addr},@var{length}:@var{XX@dots{}}
35965 @cindex @samp{M} packet
35966 Write @var{length} addressable memory units starting at address @var{addr}
35967 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35968 byte is transmitted as a two-digit hexadecimal number.
35975 for an error (this includes the case where only part of the data was
35980 @cindex @samp{p} packet
35981 Read the value of register @var{n}; @var{n} is in hex.
35982 @xref{read registers packet}, for a description of how the returned
35983 register value is encoded.
35987 @item @var{XX@dots{}}
35988 the register's value
35992 Indicating an unrecognized @var{query}.
35995 @item P @var{n@dots{}}=@var{r@dots{}}
35996 @anchor{write register packet}
35997 @cindex @samp{P} packet
35998 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35999 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36000 digits for each byte in the register (target byte order).
36010 @item q @var{name} @var{params}@dots{}
36011 @itemx Q @var{name} @var{params}@dots{}
36012 @cindex @samp{q} packet
36013 @cindex @samp{Q} packet
36014 General query (@samp{q}) and set (@samp{Q}). These packets are
36015 described fully in @ref{General Query Packets}.
36018 @cindex @samp{r} packet
36019 Reset the entire system.
36021 Don't use this packet; use the @samp{R} packet instead.
36024 @cindex @samp{R} packet
36025 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36026 This packet is only available in extended mode (@pxref{extended mode}).
36028 The @samp{R} packet has no reply.
36030 @item s @r{[}@var{addr}@r{]}
36031 @cindex @samp{s} packet
36032 Single step, resuming at @var{addr}. If
36033 @var{addr} is omitted, resume at same address.
36035 This packet is deprecated for multi-threading support. @xref{vCont
36039 @xref{Stop Reply Packets}, for the reply specifications.
36041 @item S @var{sig}@r{[};@var{addr}@r{]}
36042 @anchor{step with signal packet}
36043 @cindex @samp{S} packet
36044 Step with signal. This is analogous to the @samp{C} packet, but
36045 requests a single-step, rather than a normal resumption of execution.
36047 This packet is deprecated for multi-threading support. @xref{vCont
36051 @xref{Stop Reply Packets}, for the reply specifications.
36053 @item t @var{addr}:@var{PP},@var{MM}
36054 @cindex @samp{t} packet
36055 Search backwards starting at address @var{addr} for a match with pattern
36056 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36057 There must be at least 3 digits in @var{addr}.
36059 @item T @var{thread-id}
36060 @cindex @samp{T} packet
36061 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36066 thread is still alive
36072 Packets starting with @samp{v} are identified by a multi-letter name,
36073 up to the first @samp{;} or @samp{?} (or the end of the packet).
36075 @item vAttach;@var{pid}
36076 @cindex @samp{vAttach} packet
36077 Attach to a new process with the specified process ID @var{pid}.
36078 The process ID is a
36079 hexadecimal integer identifying the process. In all-stop mode, all
36080 threads in the attached process are stopped; in non-stop mode, it may be
36081 attached without being stopped if that is supported by the target.
36083 @c In non-stop mode, on a successful vAttach, the stub should set the
36084 @c current thread to a thread of the newly-attached process. After
36085 @c attaching, GDB queries for the attached process's thread ID with qC.
36086 @c Also note that, from a user perspective, whether or not the
36087 @c target is stopped on attach in non-stop mode depends on whether you
36088 @c use the foreground or background version of the attach command, not
36089 @c on what vAttach does; GDB does the right thing with respect to either
36090 @c stopping or restarting threads.
36092 This packet is only available in extended mode (@pxref{extended mode}).
36098 @item @r{Any stop packet}
36099 for success in all-stop mode (@pxref{Stop Reply Packets})
36101 for success in non-stop mode (@pxref{Remote Non-Stop})
36104 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36105 @cindex @samp{vCont} packet
36106 @anchor{vCont packet}
36107 Resume the inferior, specifying different actions for each thread.
36109 For each inferior thread, the leftmost action with a matching
36110 @var{thread-id} is applied. Threads that don't match any action
36111 remain in their current state. Thread IDs are specified using the
36112 syntax described in @ref{thread-id syntax}. If multiprocess
36113 extensions (@pxref{multiprocess extensions}) are supported, actions
36114 can be specified to match all threads in a process by using the
36115 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36116 @var{thread-id} matches all threads. Specifying no actions is an
36119 Currently supported actions are:
36125 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36129 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36132 @item r @var{start},@var{end}
36133 Step once, and then keep stepping as long as the thread stops at
36134 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36135 The remote stub reports a stop reply when either the thread goes out
36136 of the range or is stopped due to an unrelated reason, such as hitting
36137 a breakpoint. @xref{range stepping}.
36139 If the range is empty (@var{start} == @var{end}), then the action
36140 becomes equivalent to the @samp{s} action. In other words,
36141 single-step once, and report the stop (even if the stepped instruction
36142 jumps to @var{start}).
36144 (A stop reply may be sent at any point even if the PC is still within
36145 the stepping range; for example, it is valid to implement this packet
36146 in a degenerate way as a single instruction step operation.)
36150 The optional argument @var{addr} normally associated with the
36151 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36152 not supported in @samp{vCont}.
36154 The @samp{t} action is only relevant in non-stop mode
36155 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36156 A stop reply should be generated for any affected thread not already stopped.
36157 When a thread is stopped by means of a @samp{t} action,
36158 the corresponding stop reply should indicate that the thread has stopped with
36159 signal @samp{0}, regardless of whether the target uses some other signal
36160 as an implementation detail.
36162 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36163 @samp{r} actions for threads that are already running. Conversely,
36164 the server must ignore @samp{t} actions for threads that are already
36167 @emph{Note:} In non-stop mode, a thread is considered running until
36168 @value{GDBN} acknowleges an asynchronous stop notification for it with
36169 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36171 The stub must support @samp{vCont} if it reports support for
36172 multiprocess extensions (@pxref{multiprocess extensions}).
36175 @xref{Stop Reply Packets}, for the reply specifications.
36178 @cindex @samp{vCont?} packet
36179 Request a list of actions supported by the @samp{vCont} packet.
36183 @item vCont@r{[};@var{action}@dots{}@r{]}
36184 The @samp{vCont} packet is supported. Each @var{action} is a supported
36185 command in the @samp{vCont} packet.
36187 The @samp{vCont} packet is not supported.
36190 @anchor{vCtrlC packet}
36192 @cindex @samp{vCtrlC} packet
36193 Interrupt remote target as if a control-C was pressed on the remote
36194 terminal. This is the equivalent to reacting to the @code{^C}
36195 (@samp{\003}, the control-C character) character in all-stop mode
36196 while the target is running, except this works in non-stop mode.
36197 @xref{interrupting remote targets}, for more info on the all-stop
36208 @item vFile:@var{operation}:@var{parameter}@dots{}
36209 @cindex @samp{vFile} packet
36210 Perform a file operation on the target system. For details,
36211 see @ref{Host I/O Packets}.
36213 @item vFlashErase:@var{addr},@var{length}
36214 @cindex @samp{vFlashErase} packet
36215 Direct the stub to erase @var{length} bytes of flash starting at
36216 @var{addr}. The region may enclose any number of flash blocks, but
36217 its start and end must fall on block boundaries, as indicated by the
36218 flash block size appearing in the memory map (@pxref{Memory Map
36219 Format}). @value{GDBN} groups flash memory programming operations
36220 together, and sends a @samp{vFlashDone} request after each group; the
36221 stub is allowed to delay erase operation until the @samp{vFlashDone}
36222 packet is received.
36232 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36233 @cindex @samp{vFlashWrite} packet
36234 Direct the stub to write data to flash address @var{addr}. The data
36235 is passed in binary form using the same encoding as for the @samp{X}
36236 packet (@pxref{Binary Data}). The memory ranges specified by
36237 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36238 not overlap, and must appear in order of increasing addresses
36239 (although @samp{vFlashErase} packets for higher addresses may already
36240 have been received; the ordering is guaranteed only between
36241 @samp{vFlashWrite} packets). If a packet writes to an address that was
36242 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36243 target-specific method, the results are unpredictable.
36251 for vFlashWrite addressing non-flash memory
36257 @cindex @samp{vFlashDone} packet
36258 Indicate to the stub that flash programming operation is finished.
36259 The stub is permitted to delay or batch the effects of a group of
36260 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36261 @samp{vFlashDone} packet is received. The contents of the affected
36262 regions of flash memory are unpredictable until the @samp{vFlashDone}
36263 request is completed.
36265 @item vKill;@var{pid}
36266 @cindex @samp{vKill} packet
36267 @anchor{vKill packet}
36268 Kill the process with the specified process ID @var{pid}, which is a
36269 hexadecimal integer identifying the process. This packet is used in
36270 preference to @samp{k} when multiprocess protocol extensions are
36271 supported; see @ref{multiprocess extensions}.
36281 @item vMustReplyEmpty
36282 @cindex @samp{vMustReplyEmpty} packet
36283 The correct reply to an unknown @samp{v} packet is to return the empty
36284 string, however, some older versions of @command{gdbserver} would
36285 incorrectly return @samp{OK} for unknown @samp{v} packets.
36287 The @samp{vMustReplyEmpty} is used as a feature test to check how
36288 @command{gdbserver} handles unknown packets, it is important that this
36289 packet be handled in the same way as other unknown @samp{v} packets.
36290 If this packet is handled differently to other unknown @samp{v}
36291 packets then it is possile that @value{GDBN} may run into problems in
36292 other areas, specifically around use of @samp{vFile:setfs:}.
36294 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36295 @cindex @samp{vRun} packet
36296 Run the program @var{filename}, passing it each @var{argument} on its
36297 command line. The file and arguments are hex-encoded strings. If
36298 @var{filename} is an empty string, the stub may use a default program
36299 (e.g.@: the last program run). The program is created in the stopped
36302 @c FIXME: What about non-stop mode?
36304 This packet is only available in extended mode (@pxref{extended mode}).
36310 @item @r{Any stop packet}
36311 for success (@pxref{Stop Reply Packets})
36315 @cindex @samp{vStopped} packet
36316 @xref{Notification Packets}.
36318 @item X @var{addr},@var{length}:@var{XX@dots{}}
36320 @cindex @samp{X} packet
36321 Write data to memory, where the data is transmitted in binary.
36322 Memory is specified by its address @var{addr} and number of addressable memory
36323 units @var{length} (@pxref{addressable memory unit});
36324 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36334 @item z @var{type},@var{addr},@var{kind}
36335 @itemx Z @var{type},@var{addr},@var{kind}
36336 @anchor{insert breakpoint or watchpoint packet}
36337 @cindex @samp{z} packet
36338 @cindex @samp{Z} packets
36339 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36340 watchpoint starting at address @var{address} of kind @var{kind}.
36342 Each breakpoint and watchpoint packet @var{type} is documented
36345 @emph{Implementation notes: A remote target shall return an empty string
36346 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36347 remote target shall support either both or neither of a given
36348 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36349 avoid potential problems with duplicate packets, the operations should
36350 be implemented in an idempotent way.}
36352 @item z0,@var{addr},@var{kind}
36353 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36354 @cindex @samp{z0} packet
36355 @cindex @samp{Z0} packet
36356 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36357 @var{addr} of type @var{kind}.
36359 A software breakpoint is implemented by replacing the instruction at
36360 @var{addr} with a software breakpoint or trap instruction. The
36361 @var{kind} is target-specific and typically indicates the size of the
36362 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36363 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36364 architectures have additional meanings for @var{kind}
36365 (@pxref{Architecture-Specific Protocol Details}); if no
36366 architecture-specific value is being used, it should be @samp{0}.
36367 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36368 conditional expressions in bytecode form that should be evaluated on
36369 the target's side. These are the conditions that should be taken into
36370 consideration when deciding if the breakpoint trigger should be
36371 reported back to @value{GDBN}.
36373 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36374 for how to best report a software breakpoint event to @value{GDBN}.
36376 The @var{cond_list} parameter is comprised of a series of expressions,
36377 concatenated without separators. Each expression has the following form:
36381 @item X @var{len},@var{expr}
36382 @var{len} is the length of the bytecode expression and @var{expr} is the
36383 actual conditional expression in bytecode form.
36387 The optional @var{cmd_list} parameter introduces commands that may be
36388 run on the target, rather than being reported back to @value{GDBN}.
36389 The parameter starts with a numeric flag @var{persist}; if the flag is
36390 nonzero, then the breakpoint may remain active and the commands
36391 continue to be run even when @value{GDBN} disconnects from the target.
36392 Following this flag is a series of expressions concatenated with no
36393 separators. Each expression has the following form:
36397 @item X @var{len},@var{expr}
36398 @var{len} is the length of the bytecode expression and @var{expr} is the
36399 actual commands expression in bytecode form.
36403 @emph{Implementation note: It is possible for a target to copy or move
36404 code that contains software breakpoints (e.g., when implementing
36405 overlays). The behavior of this packet, in the presence of such a
36406 target, is not defined.}
36418 @item z1,@var{addr},@var{kind}
36419 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36420 @cindex @samp{z1} packet
36421 @cindex @samp{Z1} packet
36422 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36423 address @var{addr}.
36425 A hardware breakpoint is implemented using a mechanism that is not
36426 dependent on being able to modify the target's memory. The
36427 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36428 same meaning as in @samp{Z0} packets.
36430 @emph{Implementation note: A hardware breakpoint is not affected by code
36443 @item z2,@var{addr},@var{kind}
36444 @itemx Z2,@var{addr},@var{kind}
36445 @cindex @samp{z2} packet
36446 @cindex @samp{Z2} packet
36447 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36448 The number of bytes to watch is specified by @var{kind}.
36460 @item z3,@var{addr},@var{kind}
36461 @itemx Z3,@var{addr},@var{kind}
36462 @cindex @samp{z3} packet
36463 @cindex @samp{Z3} packet
36464 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36465 The number of bytes to watch is specified by @var{kind}.
36477 @item z4,@var{addr},@var{kind}
36478 @itemx Z4,@var{addr},@var{kind}
36479 @cindex @samp{z4} packet
36480 @cindex @samp{Z4} packet
36481 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36482 The number of bytes to watch is specified by @var{kind}.
36496 @node Stop Reply Packets
36497 @section Stop Reply Packets
36498 @cindex stop reply packets
36500 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36501 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36502 receive any of the below as a reply. Except for @samp{?}
36503 and @samp{vStopped}, that reply is only returned
36504 when the target halts. In the below the exact meaning of @dfn{signal
36505 number} is defined by the header @file{include/gdb/signals.h} in the
36506 @value{GDBN} source code.
36508 In non-stop mode, the server will simply reply @samp{OK} to commands
36509 such as @samp{vCont}; any stop will be the subject of a future
36510 notification. @xref{Remote Non-Stop}.
36512 As in the description of request packets, we include spaces in the
36513 reply templates for clarity; these are not part of the reply packet's
36514 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36520 The program received signal number @var{AA} (a two-digit hexadecimal
36521 number). This is equivalent to a @samp{T} response with no
36522 @var{n}:@var{r} pairs.
36524 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36525 @cindex @samp{T} packet reply
36526 The program received signal number @var{AA} (a two-digit hexadecimal
36527 number). This is equivalent to an @samp{S} response, except that the
36528 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36529 and other information directly in the stop reply packet, reducing
36530 round-trip latency. Single-step and breakpoint traps are reported
36531 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36535 If @var{n} is a hexadecimal number, it is a register number, and the
36536 corresponding @var{r} gives that register's value. The data @var{r} is a
36537 series of bytes in target byte order, with each byte given by a
36538 two-digit hex number.
36541 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36542 the stopped thread, as specified in @ref{thread-id syntax}.
36545 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36546 the core on which the stop event was detected.
36549 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36550 specific event that stopped the target. The currently defined stop
36551 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36552 signal. At most one stop reason should be present.
36555 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36556 and go on to the next; this allows us to extend the protocol in the
36560 The currently defined stop reasons are:
36566 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36569 @item syscall_entry
36570 @itemx syscall_return
36571 The packet indicates a syscall entry or return, and @var{r} is the
36572 syscall number, in hex.
36574 @cindex shared library events, remote reply
36576 The packet indicates that the loaded libraries have changed.
36577 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36578 list of loaded libraries. The @var{r} part is ignored.
36580 @cindex replay log events, remote reply
36582 The packet indicates that the target cannot continue replaying
36583 logged execution events, because it has reached the end (or the
36584 beginning when executing backward) of the log. The value of @var{r}
36585 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36586 for more information.
36589 @anchor{swbreak stop reason}
36590 The packet indicates a software breakpoint instruction was executed,
36591 irrespective of whether it was @value{GDBN} that planted the
36592 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36593 part must be left empty.
36595 On some architectures, such as x86, at the architecture level, when a
36596 breakpoint instruction executes the program counter points at the
36597 breakpoint address plus an offset. On such targets, the stub is
36598 responsible for adjusting the PC to point back at the breakpoint
36601 This packet should not be sent by default; older @value{GDBN} versions
36602 did not support it. @value{GDBN} requests it, by supplying an
36603 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36604 remote stub must also supply the appropriate @samp{qSupported} feature
36605 indicating support.
36607 This packet is required for correct non-stop mode operation.
36610 The packet indicates the target stopped for a hardware breakpoint.
36611 The @var{r} part must be left empty.
36613 The same remarks about @samp{qSupported} and non-stop mode above
36616 @cindex fork events, remote reply
36618 The packet indicates that @code{fork} was called, and @var{r}
36619 is the thread ID of the new child process. Refer to
36620 @ref{thread-id syntax} for the format of the @var{thread-id}
36621 field. This packet is only applicable to targets that support
36624 This packet should not be sent by default; older @value{GDBN} versions
36625 did not support it. @value{GDBN} requests it, by supplying an
36626 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36627 remote stub must also supply the appropriate @samp{qSupported} feature
36628 indicating support.
36630 @cindex vfork events, remote reply
36632 The packet indicates that @code{vfork} was called, and @var{r}
36633 is the thread ID of the new child process. Refer to
36634 @ref{thread-id syntax} for the format of the @var{thread-id}
36635 field. This packet is only applicable to targets that support
36638 This packet should not be sent by default; older @value{GDBN} versions
36639 did not support it. @value{GDBN} requests it, by supplying an
36640 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36641 remote stub must also supply the appropriate @samp{qSupported} feature
36642 indicating support.
36644 @cindex vforkdone events, remote reply
36646 The packet indicates that a child process created by a vfork
36647 has either called @code{exec} or terminated, so that the
36648 address spaces of the parent and child process are no longer
36649 shared. The @var{r} part is ignored. This packet is only
36650 applicable to targets that support vforkdone events.
36652 This packet should not be sent by default; older @value{GDBN} versions
36653 did not support it. @value{GDBN} requests it, by supplying an
36654 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36655 remote stub must also supply the appropriate @samp{qSupported} feature
36656 indicating support.
36658 @cindex exec events, remote reply
36660 The packet indicates that @code{execve} was called, and @var{r}
36661 is the absolute pathname of the file that was executed, in hex.
36662 This packet is only applicable to targets that support exec events.
36664 This packet should not be sent by default; older @value{GDBN} versions
36665 did not support it. @value{GDBN} requests it, by supplying an
36666 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36667 remote stub must also supply the appropriate @samp{qSupported} feature
36668 indicating support.
36670 @cindex thread create event, remote reply
36671 @anchor{thread create event}
36673 The packet indicates that the thread was just created. The new thread
36674 is stopped until @value{GDBN} sets it running with a resumption packet
36675 (@pxref{vCont packet}). This packet should not be sent by default;
36676 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36677 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36678 @var{r} part is ignored.
36683 @itemx W @var{AA} ; process:@var{pid}
36684 The process exited, and @var{AA} is the exit status. This is only
36685 applicable to certain targets.
36687 The second form of the response, including the process ID of the
36688 exited process, can be used only when @value{GDBN} has reported
36689 support for multiprocess protocol extensions; see @ref{multiprocess
36690 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36694 @itemx X @var{AA} ; process:@var{pid}
36695 The process terminated with signal @var{AA}.
36697 The second form of the response, including the process ID of the
36698 terminated process, can be used only when @value{GDBN} has reported
36699 support for multiprocess protocol extensions; see @ref{multiprocess
36700 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36703 @anchor{thread exit event}
36704 @cindex thread exit event, remote reply
36705 @item w @var{AA} ; @var{tid}
36707 The thread exited, and @var{AA} is the exit status. This response
36708 should not be sent by default; @value{GDBN} requests it with the
36709 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36710 @var{AA} is formatted as a big-endian hex string.
36713 There are no resumed threads left in the target. In other words, even
36714 though the process is alive, the last resumed thread has exited. For
36715 example, say the target process has two threads: thread 1 and thread
36716 2. The client leaves thread 1 stopped, and resumes thread 2, which
36717 subsequently exits. At this point, even though the process is still
36718 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36719 executing either. The @samp{N} stop reply thus informs the client
36720 that it can stop waiting for stop replies. This packet should not be
36721 sent by default; older @value{GDBN} versions did not support it.
36722 @value{GDBN} requests it, by supplying an appropriate
36723 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36724 also supply the appropriate @samp{qSupported} feature indicating
36727 @item O @var{XX}@dots{}
36728 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36729 written as the program's console output. This can happen at any time
36730 while the program is running and the debugger should continue to wait
36731 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36733 @item F @var{call-id},@var{parameter}@dots{}
36734 @var{call-id} is the identifier which says which host system call should
36735 be called. This is just the name of the function. Translation into the
36736 correct system call is only applicable as it's defined in @value{GDBN}.
36737 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36740 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36741 this very system call.
36743 The target replies with this packet when it expects @value{GDBN} to
36744 call a host system call on behalf of the target. @value{GDBN} replies
36745 with an appropriate @samp{F} packet and keeps up waiting for the next
36746 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36747 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36748 Protocol Extension}, for more details.
36752 @node General Query Packets
36753 @section General Query Packets
36754 @cindex remote query requests
36756 Packets starting with @samp{q} are @dfn{general query packets};
36757 packets starting with @samp{Q} are @dfn{general set packets}. General
36758 query and set packets are a semi-unified form for retrieving and
36759 sending information to and from the stub.
36761 The initial letter of a query or set packet is followed by a name
36762 indicating what sort of thing the packet applies to. For example,
36763 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36764 definitions with the stub. These packet names follow some
36769 The name must not contain commas, colons or semicolons.
36771 Most @value{GDBN} query and set packets have a leading upper case
36774 The names of custom vendor packets should use a company prefix, in
36775 lower case, followed by a period. For example, packets designed at
36776 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36777 foos) or @samp{Qacme.bar} (for setting bars).
36780 The name of a query or set packet should be separated from any
36781 parameters by a @samp{:}; the parameters themselves should be
36782 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36783 full packet name, and check for a separator or the end of the packet,
36784 in case two packet names share a common prefix. New packets should not begin
36785 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36786 packets predate these conventions, and have arguments without any terminator
36787 for the packet name; we suspect they are in widespread use in places that
36788 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36789 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36792 Like the descriptions of the other packets, each description here
36793 has a template showing the packet's overall syntax, followed by an
36794 explanation of the packet's meaning. We include spaces in some of the
36795 templates for clarity; these are not part of the packet's syntax. No
36796 @value{GDBN} packet uses spaces to separate its components.
36798 Here are the currently defined query and set packets:
36804 Turn on or off the agent as a helper to perform some debugging operations
36805 delegated from @value{GDBN} (@pxref{Control Agent}).
36807 @item QAllow:@var{op}:@var{val}@dots{}
36808 @cindex @samp{QAllow} packet
36809 Specify which operations @value{GDBN} expects to request of the
36810 target, as a semicolon-separated list of operation name and value
36811 pairs. Possible values for @var{op} include @samp{WriteReg},
36812 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36813 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36814 indicating that @value{GDBN} will not request the operation, or 1,
36815 indicating that it may. (The target can then use this to set up its
36816 own internals optimally, for instance if the debugger never expects to
36817 insert breakpoints, it may not need to install its own trap handler.)
36820 @cindex current thread, remote request
36821 @cindex @samp{qC} packet
36822 Return the current thread ID.
36826 @item QC @var{thread-id}
36827 Where @var{thread-id} is a thread ID as documented in
36828 @ref{thread-id syntax}.
36829 @item @r{(anything else)}
36830 Any other reply implies the old thread ID.
36833 @item qCRC:@var{addr},@var{length}
36834 @cindex CRC of memory block, remote request
36835 @cindex @samp{qCRC} packet
36836 @anchor{qCRC packet}
36837 Compute the CRC checksum of a block of memory using CRC-32 defined in
36838 IEEE 802.3. The CRC is computed byte at a time, taking the most
36839 significant bit of each byte first. The initial pattern code
36840 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36842 @emph{Note:} This is the same CRC used in validating separate debug
36843 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36844 Files}). However the algorithm is slightly different. When validating
36845 separate debug files, the CRC is computed taking the @emph{least}
36846 significant bit of each byte first, and the final result is inverted to
36847 detect trailing zeros.
36852 An error (such as memory fault)
36853 @item C @var{crc32}
36854 The specified memory region's checksum is @var{crc32}.
36857 @item QDisableRandomization:@var{value}
36858 @cindex disable address space randomization, remote request
36859 @cindex @samp{QDisableRandomization} packet
36860 Some target operating systems will randomize the virtual address space
36861 of the inferior process as a security feature, but provide a feature
36862 to disable such randomization, e.g.@: to allow for a more deterministic
36863 debugging experience. On such systems, this packet with a @var{value}
36864 of 1 directs the target to disable address space randomization for
36865 processes subsequently started via @samp{vRun} packets, while a packet
36866 with a @var{value} of 0 tells the target to enable address space
36869 This packet is only available in extended mode (@pxref{extended mode}).
36874 The request succeeded.
36877 An error occurred. The error number @var{nn} is given as hex digits.
36880 An empty reply indicates that @samp{QDisableRandomization} is not supported
36884 This packet is not probed by default; the remote stub must request it,
36885 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36886 This should only be done on targets that actually support disabling
36887 address space randomization.
36889 @item QStartupWithShell:@var{value}
36890 @cindex startup with shell, remote request
36891 @cindex @samp{QStartupWithShell} packet
36892 On UNIX-like targets, it is possible to start the inferior using a
36893 shell program. This is the default behavior on both @value{GDBN} and
36894 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
36895 used to inform @command{gdbserver} whether it should start the
36896 inferior using a shell or not.
36898 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
36899 to start the inferior. If @var{value} is @samp{1},
36900 @command{gdbserver} will use a shell to start the inferior. All other
36901 values are considered an error.
36903 This packet is only available in extended mode (@pxref{extended
36909 The request succeeded.
36912 An error occurred. The error number @var{nn} is given as hex digits.
36915 This packet is not probed by default; the remote stub must request it,
36916 by supplying an appropriate @samp{qSupported} response
36917 (@pxref{qSupported}). This should only be done on targets that
36918 actually support starting the inferior using a shell.
36920 Use of this packet is controlled by the @code{set startup-with-shell}
36921 command; @pxref{set startup-with-shell}.
36923 @item QEnvironmentHexEncoded:@var{hex-value}
36924 @anchor{QEnvironmentHexEncoded}
36925 @cindex set environment variable, remote request
36926 @cindex @samp{QEnvironmentHexEncoded} packet
36927 On UNIX-like targets, it is possible to set environment variables that
36928 will be passed to the inferior during the startup process. This
36929 packet is used to inform @command{gdbserver} of an environment
36930 variable that has been defined by the user on @value{GDBN} (@pxref{set
36933 The packet is composed by @var{hex-value}, an hex encoded
36934 representation of the @var{name=value} format representing an
36935 environment variable. The name of the environment variable is
36936 represented by @var{name}, and the value to be assigned to the
36937 environment variable is represented by @var{value}. If the variable
36938 has no value (i.e., the value is @code{null}), then @var{value} will
36941 This packet is only available in extended mode (@pxref{extended
36947 The request succeeded.
36950 This packet is not probed by default; the remote stub must request it,
36951 by supplying an appropriate @samp{qSupported} response
36952 (@pxref{qSupported}). This should only be done on targets that
36953 actually support passing environment variables to the starting
36956 This packet is related to the @code{set environment} command;
36957 @pxref{set environment}.
36959 @item QEnvironmentUnset:@var{hex-value}
36960 @anchor{QEnvironmentUnset}
36961 @cindex unset environment variable, remote request
36962 @cindex @samp{QEnvironmentUnset} packet
36963 On UNIX-like targets, it is possible to unset environment variables
36964 before starting the inferior in the remote target. This packet is
36965 used to inform @command{gdbserver} of an environment variable that has
36966 been unset by the user on @value{GDBN} (@pxref{unset environment}).
36968 The packet is composed by @var{hex-value}, an hex encoded
36969 representation of the name of the environment variable to be unset.
36971 This packet is only available in extended mode (@pxref{extended
36977 The request succeeded.
36980 This packet is not probed by default; the remote stub must request it,
36981 by supplying an appropriate @samp{qSupported} response
36982 (@pxref{qSupported}). This should only be done on targets that
36983 actually support passing environment variables to the starting
36986 This packet is related to the @code{unset environment} command;
36987 @pxref{unset environment}.
36989 @item QEnvironmentReset
36990 @anchor{QEnvironmentReset}
36991 @cindex reset environment, remote request
36992 @cindex @samp{QEnvironmentReset} packet
36993 On UNIX-like targets, this packet is used to reset the state of
36994 environment variables in the remote target before starting the
36995 inferior. In this context, reset means unsetting all environment
36996 variables that were previously set by the user (i.e., were not
36997 initially present in the environment). It is sent to
36998 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
36999 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
37000 (@pxref{QEnvironmentUnset}) packets.
37002 This packet is only available in extended mode (@pxref{extended
37008 The request succeeded.
37011 This packet is not probed by default; the remote stub must request it,
37012 by supplying an appropriate @samp{qSupported} response
37013 (@pxref{qSupported}). This should only be done on targets that
37014 actually support passing environment variables to the starting
37017 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
37018 @anchor{QSetWorkingDir packet}
37019 @cindex set working directory, remote request
37020 @cindex @samp{QSetWorkingDir} packet
37021 This packet is used to inform the remote server of the intended
37022 current working directory for programs that are going to be executed.
37024 The packet is composed by @var{directory}, an hex encoded
37025 representation of the directory that the remote inferior will use as
37026 its current working directory. If @var{directory} is an empty string,
37027 the remote server should reset the inferior's current working
37028 directory to its original, empty value.
37030 This packet is only available in extended mode (@pxref{extended
37036 The request succeeded.
37040 @itemx qsThreadInfo
37041 @cindex list active threads, remote request
37042 @cindex @samp{qfThreadInfo} packet
37043 @cindex @samp{qsThreadInfo} packet
37044 Obtain a list of all active thread IDs from the target (OS). Since there
37045 may be too many active threads to fit into one reply packet, this query
37046 works iteratively: it may require more than one query/reply sequence to
37047 obtain the entire list of threads. The first query of the sequence will
37048 be the @samp{qfThreadInfo} query; subsequent queries in the
37049 sequence will be the @samp{qsThreadInfo} query.
37051 NOTE: This packet replaces the @samp{qL} query (see below).
37055 @item m @var{thread-id}
37057 @item m @var{thread-id},@var{thread-id}@dots{}
37058 a comma-separated list of thread IDs
37060 (lower case letter @samp{L}) denotes end of list.
37063 In response to each query, the target will reply with a list of one or
37064 more thread IDs, separated by commas.
37065 @value{GDBN} will respond to each reply with a request for more thread
37066 ids (using the @samp{qs} form of the query), until the target responds
37067 with @samp{l} (lower-case ell, for @dfn{last}).
37068 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37071 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37072 initial connection with the remote target, and the very first thread ID
37073 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37074 message. Therefore, the stub should ensure that the first thread ID in
37075 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37077 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37078 @cindex get thread-local storage address, remote request
37079 @cindex @samp{qGetTLSAddr} packet
37080 Fetch the address associated with thread local storage specified
37081 by @var{thread-id}, @var{offset}, and @var{lm}.
37083 @var{thread-id} is the thread ID associated with the
37084 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37086 @var{offset} is the (big endian, hex encoded) offset associated with the
37087 thread local variable. (This offset is obtained from the debug
37088 information associated with the variable.)
37090 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37091 load module associated with the thread local storage. For example,
37092 a @sc{gnu}/Linux system will pass the link map address of the shared
37093 object associated with the thread local storage under consideration.
37094 Other operating environments may choose to represent the load module
37095 differently, so the precise meaning of this parameter will vary.
37099 @item @var{XX}@dots{}
37100 Hex encoded (big endian) bytes representing the address of the thread
37101 local storage requested.
37104 An error occurred. The error number @var{nn} is given as hex digits.
37107 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37110 @item qGetTIBAddr:@var{thread-id}
37111 @cindex get thread information block address
37112 @cindex @samp{qGetTIBAddr} packet
37113 Fetch address of the Windows OS specific Thread Information Block.
37115 @var{thread-id} is the thread ID associated with the thread.
37119 @item @var{XX}@dots{}
37120 Hex encoded (big endian) bytes representing the linear address of the
37121 thread information block.
37124 An error occured. This means that either the thread was not found, or the
37125 address could not be retrieved.
37128 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37131 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37132 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37133 digit) is one to indicate the first query and zero to indicate a
37134 subsequent query; @var{threadcount} (two hex digits) is the maximum
37135 number of threads the response packet can contain; and @var{nextthread}
37136 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37137 returned in the response as @var{argthread}.
37139 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37143 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37144 Where: @var{count} (two hex digits) is the number of threads being
37145 returned; @var{done} (one hex digit) is zero to indicate more threads
37146 and one indicates no further threads; @var{argthreadid} (eight hex
37147 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37148 is a sequence of thread IDs, @var{threadid} (eight hex
37149 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37153 @cindex section offsets, remote request
37154 @cindex @samp{qOffsets} packet
37155 Get section offsets that the target used when relocating the downloaded
37160 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37161 Relocate the @code{Text} section by @var{xxx} from its original address.
37162 Relocate the @code{Data} section by @var{yyy} from its original address.
37163 If the object file format provides segment information (e.g.@: @sc{elf}
37164 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37165 segments by the supplied offsets.
37167 @emph{Note: while a @code{Bss} offset may be included in the response,
37168 @value{GDBN} ignores this and instead applies the @code{Data} offset
37169 to the @code{Bss} section.}
37171 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37172 Relocate the first segment of the object file, which conventionally
37173 contains program code, to a starting address of @var{xxx}. If
37174 @samp{DataSeg} is specified, relocate the second segment, which
37175 conventionally contains modifiable data, to a starting address of
37176 @var{yyy}. @value{GDBN} will report an error if the object file
37177 does not contain segment information, or does not contain at least
37178 as many segments as mentioned in the reply. Extra segments are
37179 kept at fixed offsets relative to the last relocated segment.
37182 @item qP @var{mode} @var{thread-id}
37183 @cindex thread information, remote request
37184 @cindex @samp{qP} packet
37185 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37186 encoded 32 bit mode; @var{thread-id} is a thread ID
37187 (@pxref{thread-id syntax}).
37189 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37192 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37196 @cindex non-stop mode, remote request
37197 @cindex @samp{QNonStop} packet
37199 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37200 @xref{Remote Non-Stop}, for more information.
37205 The request succeeded.
37208 An error occurred. The error number @var{nn} is given as hex digits.
37211 An empty reply indicates that @samp{QNonStop} is not supported by
37215 This packet is not probed by default; the remote stub must request it,
37216 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37217 Use of this packet is controlled by the @code{set non-stop} command;
37218 @pxref{Non-Stop Mode}.
37220 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37221 @itemx QCatchSyscalls:0
37222 @cindex catch syscalls from inferior, remote request
37223 @cindex @samp{QCatchSyscalls} packet
37224 @anchor{QCatchSyscalls}
37225 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37226 catching syscalls from the inferior process.
37228 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37229 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37230 is listed, every system call should be reported.
37232 Note that if a syscall not in the list is reported, @value{GDBN} will
37233 still filter the event according to its own list from all corresponding
37234 @code{catch syscall} commands. However, it is more efficient to only
37235 report the requested syscalls.
37237 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37238 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37240 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37241 kept for the new process too. On targets where exec may affect syscall
37242 numbers, for example with exec between 32 and 64-bit processes, the
37243 client should send a new packet with the new syscall list.
37248 The request succeeded.
37251 An error occurred. @var{nn} are hex digits.
37254 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37258 Use of this packet is controlled by the @code{set remote catch-syscalls}
37259 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37260 This packet is not probed by default; the remote stub must request it,
37261 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37263 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37264 @cindex pass signals to inferior, remote request
37265 @cindex @samp{QPassSignals} packet
37266 @anchor{QPassSignals}
37267 Each listed @var{signal} should be passed directly to the inferior process.
37268 Signals are numbered identically to continue packets and stop replies
37269 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37270 strictly greater than the previous item. These signals do not need to stop
37271 the inferior, or be reported to @value{GDBN}. All other signals should be
37272 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37273 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37274 new list. This packet improves performance when using @samp{handle
37275 @var{signal} nostop noprint pass}.
37280 The request succeeded.
37283 An error occurred. The error number @var{nn} is given as hex digits.
37286 An empty reply indicates that @samp{QPassSignals} is not supported by
37290 Use of this packet is controlled by the @code{set remote pass-signals}
37291 command (@pxref{Remote Configuration, set remote pass-signals}).
37292 This packet is not probed by default; the remote stub must request it,
37293 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37295 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37296 @cindex signals the inferior may see, remote request
37297 @cindex @samp{QProgramSignals} packet
37298 @anchor{QProgramSignals}
37299 Each listed @var{signal} may be delivered to the inferior process.
37300 Others should be silently discarded.
37302 In some cases, the remote stub may need to decide whether to deliver a
37303 signal to the program or not without @value{GDBN} involvement. One
37304 example of that is while detaching --- the program's threads may have
37305 stopped for signals that haven't yet had a chance of being reported to
37306 @value{GDBN}, and so the remote stub can use the signal list specified
37307 by this packet to know whether to deliver or ignore those pending
37310 This does not influence whether to deliver a signal as requested by a
37311 resumption packet (@pxref{vCont packet}).
37313 Signals are numbered identically to continue packets and stop replies
37314 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37315 strictly greater than the previous item. Multiple
37316 @samp{QProgramSignals} packets do not combine; any earlier
37317 @samp{QProgramSignals} list is completely replaced by the new list.
37322 The request succeeded.
37325 An error occurred. The error number @var{nn} is given as hex digits.
37328 An empty reply indicates that @samp{QProgramSignals} is not supported
37332 Use of this packet is controlled by the @code{set remote program-signals}
37333 command (@pxref{Remote Configuration, set remote program-signals}).
37334 This packet is not probed by default; the remote stub must request it,
37335 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37337 @anchor{QThreadEvents}
37338 @item QThreadEvents:1
37339 @itemx QThreadEvents:0
37340 @cindex thread create/exit events, remote request
37341 @cindex @samp{QThreadEvents} packet
37343 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37344 reporting of thread create and exit events. @xref{thread create
37345 event}, for the reply specifications. For example, this is used in
37346 non-stop mode when @value{GDBN} stops a set of threads and
37347 synchronously waits for the their corresponding stop replies. Without
37348 exit events, if one of the threads exits, @value{GDBN} would hang
37349 forever not knowing that it should no longer expect a stop for that
37350 same thread. @value{GDBN} does not enable this feature unless the
37351 stub reports that it supports it by including @samp{QThreadEvents+} in
37352 its @samp{qSupported} reply.
37357 The request succeeded.
37360 An error occurred. The error number @var{nn} is given as hex digits.
37363 An empty reply indicates that @samp{QThreadEvents} is not supported by
37367 Use of this packet is controlled by the @code{set remote thread-events}
37368 command (@pxref{Remote Configuration, set remote thread-events}).
37370 @item qRcmd,@var{command}
37371 @cindex execute remote command, remote request
37372 @cindex @samp{qRcmd} packet
37373 @var{command} (hex encoded) is passed to the local interpreter for
37374 execution. Invalid commands should be reported using the output
37375 string. Before the final result packet, the target may also respond
37376 with a number of intermediate @samp{O@var{output}} console output
37377 packets. @emph{Implementors should note that providing access to a
37378 stubs's interpreter may have security implications}.
37383 A command response with no output.
37385 A command response with the hex encoded output string @var{OUTPUT}.
37387 Indicate a badly formed request.
37389 An empty reply indicates that @samp{qRcmd} is not recognized.
37392 (Note that the @code{qRcmd} packet's name is separated from the
37393 command by a @samp{,}, not a @samp{:}, contrary to the naming
37394 conventions above. Please don't use this packet as a model for new
37397 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37398 @cindex searching memory, in remote debugging
37400 @cindex @samp{qSearch:memory} packet
37402 @cindex @samp{qSearch memory} packet
37403 @anchor{qSearch memory}
37404 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37405 Both @var{address} and @var{length} are encoded in hex;
37406 @var{search-pattern} is a sequence of bytes, also hex encoded.
37411 The pattern was not found.
37413 The pattern was found at @var{address}.
37415 A badly formed request or an error was encountered while searching memory.
37417 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37420 @item QStartNoAckMode
37421 @cindex @samp{QStartNoAckMode} packet
37422 @anchor{QStartNoAckMode}
37423 Request that the remote stub disable the normal @samp{+}/@samp{-}
37424 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37429 The stub has switched to no-acknowledgment mode.
37430 @value{GDBN} acknowledges this reponse,
37431 but neither the stub nor @value{GDBN} shall send or expect further
37432 @samp{+}/@samp{-} acknowledgments in the current connection.
37434 An empty reply indicates that the stub does not support no-acknowledgment mode.
37437 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37438 @cindex supported packets, remote query
37439 @cindex features of the remote protocol
37440 @cindex @samp{qSupported} packet
37441 @anchor{qSupported}
37442 Tell the remote stub about features supported by @value{GDBN}, and
37443 query the stub for features it supports. This packet allows
37444 @value{GDBN} and the remote stub to take advantage of each others'
37445 features. @samp{qSupported} also consolidates multiple feature probes
37446 at startup, to improve @value{GDBN} performance---a single larger
37447 packet performs better than multiple smaller probe packets on
37448 high-latency links. Some features may enable behavior which must not
37449 be on by default, e.g.@: because it would confuse older clients or
37450 stubs. Other features may describe packets which could be
37451 automatically probed for, but are not. These features must be
37452 reported before @value{GDBN} will use them. This ``default
37453 unsupported'' behavior is not appropriate for all packets, but it
37454 helps to keep the initial connection time under control with new
37455 versions of @value{GDBN} which support increasing numbers of packets.
37459 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37460 The stub supports or does not support each returned @var{stubfeature},
37461 depending on the form of each @var{stubfeature} (see below for the
37464 An empty reply indicates that @samp{qSupported} is not recognized,
37465 or that no features needed to be reported to @value{GDBN}.
37468 The allowed forms for each feature (either a @var{gdbfeature} in the
37469 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37473 @item @var{name}=@var{value}
37474 The remote protocol feature @var{name} is supported, and associated
37475 with the specified @var{value}. The format of @var{value} depends
37476 on the feature, but it must not include a semicolon.
37478 The remote protocol feature @var{name} is supported, and does not
37479 need an associated value.
37481 The remote protocol feature @var{name} is not supported.
37483 The remote protocol feature @var{name} may be supported, and
37484 @value{GDBN} should auto-detect support in some other way when it is
37485 needed. This form will not be used for @var{gdbfeature} notifications,
37486 but may be used for @var{stubfeature} responses.
37489 Whenever the stub receives a @samp{qSupported} request, the
37490 supplied set of @value{GDBN} features should override any previous
37491 request. This allows @value{GDBN} to put the stub in a known
37492 state, even if the stub had previously been communicating with
37493 a different version of @value{GDBN}.
37495 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37500 This feature indicates whether @value{GDBN} supports multiprocess
37501 extensions to the remote protocol. @value{GDBN} does not use such
37502 extensions unless the stub also reports that it supports them by
37503 including @samp{multiprocess+} in its @samp{qSupported} reply.
37504 @xref{multiprocess extensions}, for details.
37507 This feature indicates that @value{GDBN} supports the XML target
37508 description. If the stub sees @samp{xmlRegisters=} with target
37509 specific strings separated by a comma, it will report register
37513 This feature indicates whether @value{GDBN} supports the
37514 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37515 instruction reply packet}).
37518 This feature indicates whether @value{GDBN} supports the swbreak stop
37519 reason in stop replies. @xref{swbreak stop reason}, for details.
37522 This feature indicates whether @value{GDBN} supports the hwbreak stop
37523 reason in stop replies. @xref{swbreak stop reason}, for details.
37526 This feature indicates whether @value{GDBN} supports fork event
37527 extensions to the remote protocol. @value{GDBN} does not use such
37528 extensions unless the stub also reports that it supports them by
37529 including @samp{fork-events+} in its @samp{qSupported} reply.
37532 This feature indicates whether @value{GDBN} supports vfork event
37533 extensions to the remote protocol. @value{GDBN} does not use such
37534 extensions unless the stub also reports that it supports them by
37535 including @samp{vfork-events+} in its @samp{qSupported} reply.
37538 This feature indicates whether @value{GDBN} supports exec event
37539 extensions to the remote protocol. @value{GDBN} does not use such
37540 extensions unless the stub also reports that it supports them by
37541 including @samp{exec-events+} in its @samp{qSupported} reply.
37543 @item vContSupported
37544 This feature indicates whether @value{GDBN} wants to know the
37545 supported actions in the reply to @samp{vCont?} packet.
37548 Stubs should ignore any unknown values for
37549 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37550 packet supports receiving packets of unlimited length (earlier
37551 versions of @value{GDBN} may reject overly long responses). Additional values
37552 for @var{gdbfeature} may be defined in the future to let the stub take
37553 advantage of new features in @value{GDBN}, e.g.@: incompatible
37554 improvements in the remote protocol---the @samp{multiprocess} feature is
37555 an example of such a feature. The stub's reply should be independent
37556 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37557 describes all the features it supports, and then the stub replies with
37558 all the features it supports.
37560 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37561 responses, as long as each response uses one of the standard forms.
37563 Some features are flags. A stub which supports a flag feature
37564 should respond with a @samp{+} form response. Other features
37565 require values, and the stub should respond with an @samp{=}
37568 Each feature has a default value, which @value{GDBN} will use if
37569 @samp{qSupported} is not available or if the feature is not mentioned
37570 in the @samp{qSupported} response. The default values are fixed; a
37571 stub is free to omit any feature responses that match the defaults.
37573 Not all features can be probed, but for those which can, the probing
37574 mechanism is useful: in some cases, a stub's internal
37575 architecture may not allow the protocol layer to know some information
37576 about the underlying target in advance. This is especially common in
37577 stubs which may be configured for multiple targets.
37579 These are the currently defined stub features and their properties:
37581 @multitable @columnfractions 0.35 0.2 0.12 0.2
37582 @c NOTE: The first row should be @headitem, but we do not yet require
37583 @c a new enough version of Texinfo (4.7) to use @headitem.
37585 @tab Value Required
37589 @item @samp{PacketSize}
37594 @item @samp{qXfer:auxv:read}
37599 @item @samp{qXfer:btrace:read}
37604 @item @samp{qXfer:btrace-conf:read}
37609 @item @samp{qXfer:exec-file:read}
37614 @item @samp{qXfer:features:read}
37619 @item @samp{qXfer:libraries:read}
37624 @item @samp{qXfer:libraries-svr4:read}
37629 @item @samp{augmented-libraries-svr4-read}
37634 @item @samp{qXfer:memory-map:read}
37639 @item @samp{qXfer:sdata:read}
37644 @item @samp{qXfer:spu:read}
37649 @item @samp{qXfer:spu:write}
37654 @item @samp{qXfer:siginfo:read}
37659 @item @samp{qXfer:siginfo:write}
37664 @item @samp{qXfer:threads:read}
37669 @item @samp{qXfer:traceframe-info:read}
37674 @item @samp{qXfer:uib:read}
37679 @item @samp{qXfer:fdpic:read}
37684 @item @samp{Qbtrace:off}
37689 @item @samp{Qbtrace:bts}
37694 @item @samp{Qbtrace:pt}
37699 @item @samp{Qbtrace-conf:bts:size}
37704 @item @samp{Qbtrace-conf:pt:size}
37709 @item @samp{QNonStop}
37714 @item @samp{QCatchSyscalls}
37719 @item @samp{QPassSignals}
37724 @item @samp{QStartNoAckMode}
37729 @item @samp{multiprocess}
37734 @item @samp{ConditionalBreakpoints}
37739 @item @samp{ConditionalTracepoints}
37744 @item @samp{ReverseContinue}
37749 @item @samp{ReverseStep}
37754 @item @samp{TracepointSource}
37759 @item @samp{QAgent}
37764 @item @samp{QAllow}
37769 @item @samp{QDisableRandomization}
37774 @item @samp{EnableDisableTracepoints}
37779 @item @samp{QTBuffer:size}
37784 @item @samp{tracenz}
37789 @item @samp{BreakpointCommands}
37794 @item @samp{swbreak}
37799 @item @samp{hwbreak}
37804 @item @samp{fork-events}
37809 @item @samp{vfork-events}
37814 @item @samp{exec-events}
37819 @item @samp{QThreadEvents}
37824 @item @samp{no-resumed}
37831 These are the currently defined stub features, in more detail:
37834 @cindex packet size, remote protocol
37835 @item PacketSize=@var{bytes}
37836 The remote stub can accept packets up to at least @var{bytes} in
37837 length. @value{GDBN} will send packets up to this size for bulk
37838 transfers, and will never send larger packets. This is a limit on the
37839 data characters in the packet, including the frame and checksum.
37840 There is no trailing NUL byte in a remote protocol packet; if the stub
37841 stores packets in a NUL-terminated format, it should allow an extra
37842 byte in its buffer for the NUL. If this stub feature is not supported,
37843 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37845 @item qXfer:auxv:read
37846 The remote stub understands the @samp{qXfer:auxv:read} packet
37847 (@pxref{qXfer auxiliary vector read}).
37849 @item qXfer:btrace:read
37850 The remote stub understands the @samp{qXfer:btrace:read}
37851 packet (@pxref{qXfer btrace read}).
37853 @item qXfer:btrace-conf:read
37854 The remote stub understands the @samp{qXfer:btrace-conf:read}
37855 packet (@pxref{qXfer btrace-conf read}).
37857 @item qXfer:exec-file:read
37858 The remote stub understands the @samp{qXfer:exec-file:read} packet
37859 (@pxref{qXfer executable filename read}).
37861 @item qXfer:features:read
37862 The remote stub understands the @samp{qXfer:features:read} packet
37863 (@pxref{qXfer target description read}).
37865 @item qXfer:libraries:read
37866 The remote stub understands the @samp{qXfer:libraries:read} packet
37867 (@pxref{qXfer library list read}).
37869 @item qXfer:libraries-svr4:read
37870 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37871 (@pxref{qXfer svr4 library list read}).
37873 @item augmented-libraries-svr4-read
37874 The remote stub understands the augmented form of the
37875 @samp{qXfer:libraries-svr4:read} packet
37876 (@pxref{qXfer svr4 library list read}).
37878 @item qXfer:memory-map:read
37879 The remote stub understands the @samp{qXfer:memory-map:read} packet
37880 (@pxref{qXfer memory map read}).
37882 @item qXfer:sdata:read
37883 The remote stub understands the @samp{qXfer:sdata:read} packet
37884 (@pxref{qXfer sdata read}).
37886 @item qXfer:spu:read
37887 The remote stub understands the @samp{qXfer:spu:read} packet
37888 (@pxref{qXfer spu read}).
37890 @item qXfer:spu:write
37891 The remote stub understands the @samp{qXfer:spu:write} packet
37892 (@pxref{qXfer spu write}).
37894 @item qXfer:siginfo:read
37895 The remote stub understands the @samp{qXfer:siginfo:read} packet
37896 (@pxref{qXfer siginfo read}).
37898 @item qXfer:siginfo:write
37899 The remote stub understands the @samp{qXfer:siginfo:write} packet
37900 (@pxref{qXfer siginfo write}).
37902 @item qXfer:threads:read
37903 The remote stub understands the @samp{qXfer:threads:read} packet
37904 (@pxref{qXfer threads read}).
37906 @item qXfer:traceframe-info:read
37907 The remote stub understands the @samp{qXfer:traceframe-info:read}
37908 packet (@pxref{qXfer traceframe info read}).
37910 @item qXfer:uib:read
37911 The remote stub understands the @samp{qXfer:uib:read}
37912 packet (@pxref{qXfer unwind info block}).
37914 @item qXfer:fdpic:read
37915 The remote stub understands the @samp{qXfer:fdpic:read}
37916 packet (@pxref{qXfer fdpic loadmap read}).
37919 The remote stub understands the @samp{QNonStop} packet
37920 (@pxref{QNonStop}).
37922 @item QCatchSyscalls
37923 The remote stub understands the @samp{QCatchSyscalls} packet
37924 (@pxref{QCatchSyscalls}).
37927 The remote stub understands the @samp{QPassSignals} packet
37928 (@pxref{QPassSignals}).
37930 @item QStartNoAckMode
37931 The remote stub understands the @samp{QStartNoAckMode} packet and
37932 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37935 @anchor{multiprocess extensions}
37936 @cindex multiprocess extensions, in remote protocol
37937 The remote stub understands the multiprocess extensions to the remote
37938 protocol syntax. The multiprocess extensions affect the syntax of
37939 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37940 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37941 replies. Note that reporting this feature indicates support for the
37942 syntactic extensions only, not that the stub necessarily supports
37943 debugging of more than one process at a time. The stub must not use
37944 multiprocess extensions in packet replies unless @value{GDBN} has also
37945 indicated it supports them in its @samp{qSupported} request.
37947 @item qXfer:osdata:read
37948 The remote stub understands the @samp{qXfer:osdata:read} packet
37949 ((@pxref{qXfer osdata read}).
37951 @item ConditionalBreakpoints
37952 The target accepts and implements evaluation of conditional expressions
37953 defined for breakpoints. The target will only report breakpoint triggers
37954 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37956 @item ConditionalTracepoints
37957 The remote stub accepts and implements conditional expressions defined
37958 for tracepoints (@pxref{Tracepoint Conditions}).
37960 @item ReverseContinue
37961 The remote stub accepts and implements the reverse continue packet
37965 The remote stub accepts and implements the reverse step packet
37968 @item TracepointSource
37969 The remote stub understands the @samp{QTDPsrc} packet that supplies
37970 the source form of tracepoint definitions.
37973 The remote stub understands the @samp{QAgent} packet.
37976 The remote stub understands the @samp{QAllow} packet.
37978 @item QDisableRandomization
37979 The remote stub understands the @samp{QDisableRandomization} packet.
37981 @item StaticTracepoint
37982 @cindex static tracepoints, in remote protocol
37983 The remote stub supports static tracepoints.
37985 @item InstallInTrace
37986 @anchor{install tracepoint in tracing}
37987 The remote stub supports installing tracepoint in tracing.
37989 @item EnableDisableTracepoints
37990 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37991 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37992 to be enabled and disabled while a trace experiment is running.
37994 @item QTBuffer:size
37995 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37996 packet that allows to change the size of the trace buffer.
37999 @cindex string tracing, in remote protocol
38000 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
38001 See @ref{Bytecode Descriptions} for details about the bytecode.
38003 @item BreakpointCommands
38004 @cindex breakpoint commands, in remote protocol
38005 The remote stub supports running a breakpoint's command list itself,
38006 rather than reporting the hit to @value{GDBN}.
38009 The remote stub understands the @samp{Qbtrace:off} packet.
38012 The remote stub understands the @samp{Qbtrace:bts} packet.
38015 The remote stub understands the @samp{Qbtrace:pt} packet.
38017 @item Qbtrace-conf:bts:size
38018 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38020 @item Qbtrace-conf:pt:size
38021 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38024 The remote stub reports the @samp{swbreak} stop reason for memory
38028 The remote stub reports the @samp{hwbreak} stop reason for hardware
38032 The remote stub reports the @samp{fork} stop reason for fork events.
38035 The remote stub reports the @samp{vfork} stop reason for vfork events
38036 and vforkdone events.
38039 The remote stub reports the @samp{exec} stop reason for exec events.
38041 @item vContSupported
38042 The remote stub reports the supported actions in the reply to
38043 @samp{vCont?} packet.
38045 @item QThreadEvents
38046 The remote stub understands the @samp{QThreadEvents} packet.
38049 The remote stub reports the @samp{N} stop reply.
38054 @cindex symbol lookup, remote request
38055 @cindex @samp{qSymbol} packet
38056 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38057 requests. Accept requests from the target for the values of symbols.
38062 The target does not need to look up any (more) symbols.
38063 @item qSymbol:@var{sym_name}
38064 The target requests the value of symbol @var{sym_name} (hex encoded).
38065 @value{GDBN} may provide the value by using the
38066 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38070 @item qSymbol:@var{sym_value}:@var{sym_name}
38071 Set the value of @var{sym_name} to @var{sym_value}.
38073 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38074 target has previously requested.
38076 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38077 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38083 The target does not need to look up any (more) symbols.
38084 @item qSymbol:@var{sym_name}
38085 The target requests the value of a new symbol @var{sym_name} (hex
38086 encoded). @value{GDBN} will continue to supply the values of symbols
38087 (if available), until the target ceases to request them.
38092 @itemx QTDisconnected
38099 @itemx qTMinFTPILen
38101 @xref{Tracepoint Packets}.
38103 @item qThreadExtraInfo,@var{thread-id}
38104 @cindex thread attributes info, remote request
38105 @cindex @samp{qThreadExtraInfo} packet
38106 Obtain from the target OS a printable string description of thread
38107 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38108 for the forms of @var{thread-id}. This
38109 string may contain anything that the target OS thinks is interesting
38110 for @value{GDBN} to tell the user about the thread. The string is
38111 displayed in @value{GDBN}'s @code{info threads} display. Some
38112 examples of possible thread extra info strings are @samp{Runnable}, or
38113 @samp{Blocked on Mutex}.
38117 @item @var{XX}@dots{}
38118 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38119 comprising the printable string containing the extra information about
38120 the thread's attributes.
38123 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38124 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38125 conventions above. Please don't use this packet as a model for new
38144 @xref{Tracepoint Packets}.
38146 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38147 @cindex read special object, remote request
38148 @cindex @samp{qXfer} packet
38149 @anchor{qXfer read}
38150 Read uninterpreted bytes from the target's special data area
38151 identified by the keyword @var{object}. Request @var{length} bytes
38152 starting at @var{offset} bytes into the data. The content and
38153 encoding of @var{annex} is specific to @var{object}; it can supply
38154 additional details about what data to access.
38159 Data @var{data} (@pxref{Binary Data}) has been read from the
38160 target. There may be more data at a higher address (although
38161 it is permitted to return @samp{m} even for the last valid
38162 block of data, as long as at least one byte of data was read).
38163 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38167 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38168 There is no more data to be read. It is possible for @var{data} to
38169 have fewer bytes than the @var{length} in the request.
38172 The @var{offset} in the request is at the end of the data.
38173 There is no more data to be read.
38176 The request was malformed, or @var{annex} was invalid.
38179 The offset was invalid, or there was an error encountered reading the data.
38180 The @var{nn} part is a hex-encoded @code{errno} value.
38183 An empty reply indicates the @var{object} string was not recognized by
38184 the stub, or that the object does not support reading.
38187 Here are the specific requests of this form defined so far. All the
38188 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38189 formats, listed above.
38192 @item qXfer:auxv:read::@var{offset},@var{length}
38193 @anchor{qXfer auxiliary vector read}
38194 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38195 auxiliary vector}. Note @var{annex} must be empty.
38197 This packet is not probed by default; the remote stub must request it,
38198 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38200 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38201 @anchor{qXfer btrace read}
38203 Return a description of the current branch trace.
38204 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38205 packet may have one of the following values:
38209 Returns all available branch trace.
38212 Returns all available branch trace if the branch trace changed since
38213 the last read request.
38216 Returns the new branch trace since the last read request. Adds a new
38217 block to the end of the trace that begins at zero and ends at the source
38218 location of the first branch in the trace buffer. This extra block is
38219 used to stitch traces together.
38221 If the trace buffer overflowed, returns an error indicating the overflow.
38224 This packet is not probed by default; the remote stub must request it
38225 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38227 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38228 @anchor{qXfer btrace-conf read}
38230 Return a description of the current branch trace configuration.
38231 @xref{Branch Trace Configuration Format}.
38233 This packet is not probed by default; the remote stub must request it
38234 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38236 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38237 @anchor{qXfer executable filename read}
38238 Return the full absolute name of the file that was executed to create
38239 a process running on the remote system. The annex specifies the
38240 numeric process ID of the process to query, encoded as a hexadecimal
38241 number. If the annex part is empty the remote stub should return the
38242 filename corresponding to the currently executing process.
38244 This packet is not probed by default; the remote stub must request it,
38245 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38247 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38248 @anchor{qXfer target description read}
38249 Access the @dfn{target description}. @xref{Target Descriptions}. The
38250 annex specifies which XML document to access. The main description is
38251 always loaded from the @samp{target.xml} annex.
38253 This packet is not probed by default; the remote stub must request it,
38254 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38256 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38257 @anchor{qXfer library list read}
38258 Access the target's list of loaded libraries. @xref{Library List Format}.
38259 The annex part of the generic @samp{qXfer} packet must be empty
38260 (@pxref{qXfer read}).
38262 Targets which maintain a list of libraries in the program's memory do
38263 not need to implement this packet; it is designed for platforms where
38264 the operating system manages the list of loaded libraries.
38266 This packet is not probed by default; the remote stub must request it,
38267 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38269 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38270 @anchor{qXfer svr4 library list read}
38271 Access the target's list of loaded libraries when the target is an SVR4
38272 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38273 of the generic @samp{qXfer} packet must be empty unless the remote
38274 stub indicated it supports the augmented form of this packet
38275 by supplying an appropriate @samp{qSupported} response
38276 (@pxref{qXfer read}, @ref{qSupported}).
38278 This packet is optional for better performance on SVR4 targets.
38279 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38281 This packet is not probed by default; the remote stub must request it,
38282 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38284 If the remote stub indicates it supports the augmented form of this
38285 packet then the annex part of the generic @samp{qXfer} packet may
38286 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38287 arguments. The currently supported arguments are:
38290 @item start=@var{address}
38291 A hexadecimal number specifying the address of the @samp{struct
38292 link_map} to start reading the library list from. If unset or zero
38293 then the first @samp{struct link_map} in the library list will be
38294 chosen as the starting point.
38296 @item prev=@var{address}
38297 A hexadecimal number specifying the address of the @samp{struct
38298 link_map} immediately preceding the @samp{struct link_map}
38299 specified by the @samp{start} argument. If unset or zero then
38300 the remote stub will expect that no @samp{struct link_map}
38301 exists prior to the starting point.
38305 Arguments that are not understood by the remote stub will be silently
38308 @item qXfer:memory-map:read::@var{offset},@var{length}
38309 @anchor{qXfer memory map read}
38310 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38311 annex part of the generic @samp{qXfer} packet must be empty
38312 (@pxref{qXfer read}).
38314 This packet is not probed by default; the remote stub must request it,
38315 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38317 @item qXfer:sdata:read::@var{offset},@var{length}
38318 @anchor{qXfer sdata read}
38320 Read contents of the extra collected static tracepoint marker
38321 information. The annex part of the generic @samp{qXfer} packet must
38322 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38325 This packet is not probed by default; the remote stub must request it,
38326 by supplying an appropriate @samp{qSupported} response
38327 (@pxref{qSupported}).
38329 @item qXfer:siginfo:read::@var{offset},@var{length}
38330 @anchor{qXfer siginfo read}
38331 Read contents of the extra signal information on the target
38332 system. The annex part of the generic @samp{qXfer} packet must be
38333 empty (@pxref{qXfer read}).
38335 This packet is not probed by default; the remote stub must request it,
38336 by supplying an appropriate @samp{qSupported} response
38337 (@pxref{qSupported}).
38339 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38340 @anchor{qXfer spu read}
38341 Read contents of an @code{spufs} file on the target system. The
38342 annex specifies which file to read; it must be of the form
38343 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38344 in the target process, and @var{name} identifes the @code{spufs} file
38345 in that context to be accessed.
38347 This packet is not probed by default; the remote stub must request it,
38348 by supplying an appropriate @samp{qSupported} response
38349 (@pxref{qSupported}).
38351 @item qXfer:threads:read::@var{offset},@var{length}
38352 @anchor{qXfer threads read}
38353 Access the list of threads on target. @xref{Thread List Format}. The
38354 annex part of the generic @samp{qXfer} packet must be empty
38355 (@pxref{qXfer read}).
38357 This packet is not probed by default; the remote stub must request it,
38358 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38360 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38361 @anchor{qXfer traceframe info read}
38363 Return a description of the current traceframe's contents.
38364 @xref{Traceframe Info Format}. The annex part of the generic
38365 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38367 This packet is not probed by default; the remote stub must request it,
38368 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38370 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38371 @anchor{qXfer unwind info block}
38373 Return the unwind information block for @var{pc}. This packet is used
38374 on OpenVMS/ia64 to ask the kernel unwind information.
38376 This packet is not probed by default.
38378 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38379 @anchor{qXfer fdpic loadmap read}
38380 Read contents of @code{loadmap}s on the target system. The
38381 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38382 executable @code{loadmap} or interpreter @code{loadmap} to read.
38384 This packet is not probed by default; the remote stub must request it,
38385 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38387 @item qXfer:osdata:read::@var{offset},@var{length}
38388 @anchor{qXfer osdata read}
38389 Access the target's @dfn{operating system information}.
38390 @xref{Operating System Information}.
38394 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38395 @cindex write data into object, remote request
38396 @anchor{qXfer write}
38397 Write uninterpreted bytes into the target's special data area
38398 identified by the keyword @var{object}, starting at @var{offset} bytes
38399 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38400 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38401 is specific to @var{object}; it can supply additional details about what data
38407 @var{nn} (hex encoded) is the number of bytes written.
38408 This may be fewer bytes than supplied in the request.
38411 The request was malformed, or @var{annex} was invalid.
38414 The offset was invalid, or there was an error encountered writing the data.
38415 The @var{nn} part is a hex-encoded @code{errno} value.
38418 An empty reply indicates the @var{object} string was not
38419 recognized by the stub, or that the object does not support writing.
38422 Here are the specific requests of this form defined so far. All the
38423 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38424 formats, listed above.
38427 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38428 @anchor{qXfer siginfo write}
38429 Write @var{data} to the extra signal information on the target system.
38430 The annex part of the generic @samp{qXfer} packet must be
38431 empty (@pxref{qXfer write}).
38433 This packet is not probed by default; the remote stub must request it,
38434 by supplying an appropriate @samp{qSupported} response
38435 (@pxref{qSupported}).
38437 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38438 @anchor{qXfer spu write}
38439 Write @var{data} to an @code{spufs} file on the target system. The
38440 annex specifies which file to write; it must be of the form
38441 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38442 in the target process, and @var{name} identifes the @code{spufs} file
38443 in that context to be accessed.
38445 This packet is not probed by default; the remote stub must request it,
38446 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38449 @item qXfer:@var{object}:@var{operation}:@dots{}
38450 Requests of this form may be added in the future. When a stub does
38451 not recognize the @var{object} keyword, or its support for
38452 @var{object} does not recognize the @var{operation} keyword, the stub
38453 must respond with an empty packet.
38455 @item qAttached:@var{pid}
38456 @cindex query attached, remote request
38457 @cindex @samp{qAttached} packet
38458 Return an indication of whether the remote server attached to an
38459 existing process or created a new process. When the multiprocess
38460 protocol extensions are supported (@pxref{multiprocess extensions}),
38461 @var{pid} is an integer in hexadecimal format identifying the target
38462 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38463 the query packet will be simplified as @samp{qAttached}.
38465 This query is used, for example, to know whether the remote process
38466 should be detached or killed when a @value{GDBN} session is ended with
38467 the @code{quit} command.
38472 The remote server attached to an existing process.
38474 The remote server created a new process.
38476 A badly formed request or an error was encountered.
38480 Enable branch tracing for the current thread using Branch Trace Store.
38485 Branch tracing has been enabled.
38487 A badly formed request or an error was encountered.
38491 Enable branch tracing for the current thread using Intel Processor Trace.
38496 Branch tracing has been enabled.
38498 A badly formed request or an error was encountered.
38502 Disable branch tracing for the current thread.
38507 Branch tracing has been disabled.
38509 A badly formed request or an error was encountered.
38512 @item Qbtrace-conf:bts:size=@var{value}
38513 Set the requested ring buffer size for new threads that use the
38514 btrace recording method in bts format.
38519 The ring buffer size has been set.
38521 A badly formed request or an error was encountered.
38524 @item Qbtrace-conf:pt:size=@var{value}
38525 Set the requested ring buffer size for new threads that use the
38526 btrace recording method in pt format.
38531 The ring buffer size has been set.
38533 A badly formed request or an error was encountered.
38538 @node Architecture-Specific Protocol Details
38539 @section Architecture-Specific Protocol Details
38541 This section describes how the remote protocol is applied to specific
38542 target architectures. Also see @ref{Standard Target Features}, for
38543 details of XML target descriptions for each architecture.
38546 * ARM-Specific Protocol Details::
38547 * MIPS-Specific Protocol Details::
38550 @node ARM-Specific Protocol Details
38551 @subsection @acronym{ARM}-specific Protocol Details
38554 * ARM Breakpoint Kinds::
38557 @node ARM Breakpoint Kinds
38558 @subsubsection @acronym{ARM} Breakpoint Kinds
38559 @cindex breakpoint kinds, @acronym{ARM}
38561 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38566 16-bit Thumb mode breakpoint.
38569 32-bit Thumb mode (Thumb-2) breakpoint.
38572 32-bit @acronym{ARM} mode breakpoint.
38576 @node MIPS-Specific Protocol Details
38577 @subsection @acronym{MIPS}-specific Protocol Details
38580 * MIPS Register packet Format::
38581 * MIPS Breakpoint Kinds::
38584 @node MIPS Register packet Format
38585 @subsubsection @acronym{MIPS} Register Packet Format
38586 @cindex register packet format, @acronym{MIPS}
38588 The following @code{g}/@code{G} packets have previously been defined.
38589 In the below, some thirty-two bit registers are transferred as
38590 sixty-four bits. Those registers should be zero/sign extended (which?)
38591 to fill the space allocated. Register bytes are transferred in target
38592 byte order. The two nibbles within a register byte are transferred
38593 most-significant -- least-significant.
38598 All registers are transferred as thirty-two bit quantities in the order:
38599 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38600 registers; fsr; fir; fp.
38603 All registers are transferred as sixty-four bit quantities (including
38604 thirty-two bit registers such as @code{sr}). The ordering is the same
38609 @node MIPS Breakpoint Kinds
38610 @subsubsection @acronym{MIPS} Breakpoint Kinds
38611 @cindex breakpoint kinds, @acronym{MIPS}
38613 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38618 16-bit @acronym{MIPS16} mode breakpoint.
38621 16-bit @acronym{microMIPS} mode breakpoint.
38624 32-bit standard @acronym{MIPS} mode breakpoint.
38627 32-bit @acronym{microMIPS} mode breakpoint.
38631 @node Tracepoint Packets
38632 @section Tracepoint Packets
38633 @cindex tracepoint packets
38634 @cindex packets, tracepoint
38636 Here we describe the packets @value{GDBN} uses to implement
38637 tracepoints (@pxref{Tracepoints}).
38641 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38642 @cindex @samp{QTDP} packet
38643 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38644 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38645 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38646 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38647 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38648 the number of bytes that the target should copy elsewhere to make room
38649 for the tracepoint. If an @samp{X} is present, it introduces a
38650 tracepoint condition, which consists of a hexadecimal length, followed
38651 by a comma and hex-encoded bytes, in a manner similar to action
38652 encodings as described below. If the trailing @samp{-} is present,
38653 further @samp{QTDP} packets will follow to specify this tracepoint's
38659 The packet was understood and carried out.
38661 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38663 The packet was not recognized.
38666 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38667 Define actions to be taken when a tracepoint is hit. The @var{n} and
38668 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38669 this tracepoint. This packet may only be sent immediately after
38670 another @samp{QTDP} packet that ended with a @samp{-}. If the
38671 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38672 specifying more actions for this tracepoint.
38674 In the series of action packets for a given tracepoint, at most one
38675 can have an @samp{S} before its first @var{action}. If such a packet
38676 is sent, it and the following packets define ``while-stepping''
38677 actions. Any prior packets define ordinary actions --- that is, those
38678 taken when the tracepoint is first hit. If no action packet has an
38679 @samp{S}, then all the packets in the series specify ordinary
38680 tracepoint actions.
38682 The @samp{@var{action}@dots{}} portion of the packet is a series of
38683 actions, concatenated without separators. Each action has one of the
38689 Collect the registers whose bits are set in @var{mask},
38690 a hexadecimal number whose @var{i}'th bit is set if register number
38691 @var{i} should be collected. (The least significant bit is numbered
38692 zero.) Note that @var{mask} may be any number of digits long; it may
38693 not fit in a 32-bit word.
38695 @item M @var{basereg},@var{offset},@var{len}
38696 Collect @var{len} bytes of memory starting at the address in register
38697 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38698 @samp{-1}, then the range has a fixed address: @var{offset} is the
38699 address of the lowest byte to collect. The @var{basereg},
38700 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38701 values (the @samp{-1} value for @var{basereg} is a special case).
38703 @item X @var{len},@var{expr}
38704 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38705 it directs. The agent expression @var{expr} is as described in
38706 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38707 two-digit hex number in the packet; @var{len} is the number of bytes
38708 in the expression (and thus one-half the number of hex digits in the
38713 Any number of actions may be packed together in a single @samp{QTDP}
38714 packet, as long as the packet does not exceed the maximum packet
38715 length (400 bytes, for many stubs). There may be only one @samp{R}
38716 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38717 actions. Any registers referred to by @samp{M} and @samp{X} actions
38718 must be collected by a preceding @samp{R} action. (The
38719 ``while-stepping'' actions are treated as if they were attached to a
38720 separate tracepoint, as far as these restrictions are concerned.)
38725 The packet was understood and carried out.
38727 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38729 The packet was not recognized.
38732 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38733 @cindex @samp{QTDPsrc} packet
38734 Specify a source string of tracepoint @var{n} at address @var{addr}.
38735 This is useful to get accurate reproduction of the tracepoints
38736 originally downloaded at the beginning of the trace run. The @var{type}
38737 is the name of the tracepoint part, such as @samp{cond} for the
38738 tracepoint's conditional expression (see below for a list of types), while
38739 @var{bytes} is the string, encoded in hexadecimal.
38741 @var{start} is the offset of the @var{bytes} within the overall source
38742 string, while @var{slen} is the total length of the source string.
38743 This is intended for handling source strings that are longer than will
38744 fit in a single packet.
38745 @c Add detailed example when this info is moved into a dedicated
38746 @c tracepoint descriptions section.
38748 The available string types are @samp{at} for the location,
38749 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38750 @value{GDBN} sends a separate packet for each command in the action
38751 list, in the same order in which the commands are stored in the list.
38753 The target does not need to do anything with source strings except
38754 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38757 Although this packet is optional, and @value{GDBN} will only send it
38758 if the target replies with @samp{TracepointSource} @xref{General
38759 Query Packets}, it makes both disconnected tracing and trace files
38760 much easier to use. Otherwise the user must be careful that the
38761 tracepoints in effect while looking at trace frames are identical to
38762 the ones in effect during the trace run; even a small discrepancy
38763 could cause @samp{tdump} not to work, or a particular trace frame not
38766 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38767 @cindex define trace state variable, remote request
38768 @cindex @samp{QTDV} packet
38769 Create a new trace state variable, number @var{n}, with an initial
38770 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38771 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38772 the option of not using this packet for initial values of zero; the
38773 target should simply create the trace state variables as they are
38774 mentioned in expressions. The value @var{builtin} should be 1 (one)
38775 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38776 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38777 @samp{qTsV} packet had it set. The contents of @var{name} is the
38778 hex-encoded name (without the leading @samp{$}) of the trace state
38781 @item QTFrame:@var{n}
38782 @cindex @samp{QTFrame} packet
38783 Select the @var{n}'th tracepoint frame from the buffer, and use the
38784 register and memory contents recorded there to answer subsequent
38785 request packets from @value{GDBN}.
38787 A successful reply from the stub indicates that the stub has found the
38788 requested frame. The response is a series of parts, concatenated
38789 without separators, describing the frame we selected. Each part has
38790 one of the following forms:
38794 The selected frame is number @var{n} in the trace frame buffer;
38795 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38796 was no frame matching the criteria in the request packet.
38799 The selected trace frame records a hit of tracepoint number @var{t};
38800 @var{t} is a hexadecimal number.
38804 @item QTFrame:pc:@var{addr}
38805 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38806 currently selected frame whose PC is @var{addr};
38807 @var{addr} is a hexadecimal number.
38809 @item QTFrame:tdp:@var{t}
38810 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38811 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38812 is a hexadecimal number.
38814 @item QTFrame:range:@var{start}:@var{end}
38815 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38816 currently selected frame whose PC is between @var{start} (inclusive)
38817 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38820 @item QTFrame:outside:@var{start}:@var{end}
38821 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38822 frame @emph{outside} the given range of addresses (exclusive).
38825 @cindex @samp{qTMinFTPILen} packet
38826 This packet requests the minimum length of instruction at which a fast
38827 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38828 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38829 it depends on the target system being able to create trampolines in
38830 the first 64K of memory, which might or might not be possible for that
38831 system. So the reply to this packet will be 4 if it is able to
38838 The minimum instruction length is currently unknown.
38840 The minimum instruction length is @var{length}, where @var{length}
38841 is a hexadecimal number greater or equal to 1. A reply
38842 of 1 means that a fast tracepoint may be placed on any instruction
38843 regardless of size.
38845 An error has occurred.
38847 An empty reply indicates that the request is not supported by the stub.
38851 @cindex @samp{QTStart} packet
38852 Begin the tracepoint experiment. Begin collecting data from
38853 tracepoint hits in the trace frame buffer. This packet supports the
38854 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38855 instruction reply packet}).
38858 @cindex @samp{QTStop} packet
38859 End the tracepoint experiment. Stop collecting trace frames.
38861 @item QTEnable:@var{n}:@var{addr}
38863 @cindex @samp{QTEnable} packet
38864 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38865 experiment. If the tracepoint was previously disabled, then collection
38866 of data from it will resume.
38868 @item QTDisable:@var{n}:@var{addr}
38870 @cindex @samp{QTDisable} packet
38871 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38872 experiment. No more data will be collected from the tracepoint unless
38873 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38876 @cindex @samp{QTinit} packet
38877 Clear the table of tracepoints, and empty the trace frame buffer.
38879 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38880 @cindex @samp{QTro} packet
38881 Establish the given ranges of memory as ``transparent''. The stub
38882 will answer requests for these ranges from memory's current contents,
38883 if they were not collected as part of the tracepoint hit.
38885 @value{GDBN} uses this to mark read-only regions of memory, like those
38886 containing program code. Since these areas never change, they should
38887 still have the same contents they did when the tracepoint was hit, so
38888 there's no reason for the stub to refuse to provide their contents.
38890 @item QTDisconnected:@var{value}
38891 @cindex @samp{QTDisconnected} packet
38892 Set the choice to what to do with the tracing run when @value{GDBN}
38893 disconnects from the target. A @var{value} of 1 directs the target to
38894 continue the tracing run, while 0 tells the target to stop tracing if
38895 @value{GDBN} is no longer in the picture.
38898 @cindex @samp{qTStatus} packet
38899 Ask the stub if there is a trace experiment running right now.
38901 The reply has the form:
38905 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38906 @var{running} is a single digit @code{1} if the trace is presently
38907 running, or @code{0} if not. It is followed by semicolon-separated
38908 optional fields that an agent may use to report additional status.
38912 If the trace is not running, the agent may report any of several
38913 explanations as one of the optional fields:
38918 No trace has been run yet.
38920 @item tstop[:@var{text}]:0
38921 The trace was stopped by a user-originated stop command. The optional
38922 @var{text} field is a user-supplied string supplied as part of the
38923 stop command (for instance, an explanation of why the trace was
38924 stopped manually). It is hex-encoded.
38927 The trace stopped because the trace buffer filled up.
38929 @item tdisconnected:0
38930 The trace stopped because @value{GDBN} disconnected from the target.
38932 @item tpasscount:@var{tpnum}
38933 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38935 @item terror:@var{text}:@var{tpnum}
38936 The trace stopped because tracepoint @var{tpnum} had an error. The
38937 string @var{text} is available to describe the nature of the error
38938 (for instance, a divide by zero in the condition expression); it
38942 The trace stopped for some other reason.
38946 Additional optional fields supply statistical and other information.
38947 Although not required, they are extremely useful for users monitoring
38948 the progress of a trace run. If a trace has stopped, and these
38949 numbers are reported, they must reflect the state of the just-stopped
38954 @item tframes:@var{n}
38955 The number of trace frames in the buffer.
38957 @item tcreated:@var{n}
38958 The total number of trace frames created during the run. This may
38959 be larger than the trace frame count, if the buffer is circular.
38961 @item tsize:@var{n}
38962 The total size of the trace buffer, in bytes.
38964 @item tfree:@var{n}
38965 The number of bytes still unused in the buffer.
38967 @item circular:@var{n}
38968 The value of the circular trace buffer flag. @code{1} means that the
38969 trace buffer is circular and old trace frames will be discarded if
38970 necessary to make room, @code{0} means that the trace buffer is linear
38973 @item disconn:@var{n}
38974 The value of the disconnected tracing flag. @code{1} means that
38975 tracing will continue after @value{GDBN} disconnects, @code{0} means
38976 that the trace run will stop.
38980 @item qTP:@var{tp}:@var{addr}
38981 @cindex tracepoint status, remote request
38982 @cindex @samp{qTP} packet
38983 Ask the stub for the current state of tracepoint number @var{tp} at
38984 address @var{addr}.
38988 @item V@var{hits}:@var{usage}
38989 The tracepoint has been hit @var{hits} times so far during the trace
38990 run, and accounts for @var{usage} in the trace buffer. Note that
38991 @code{while-stepping} steps are not counted as separate hits, but the
38992 steps' space consumption is added into the usage number.
38996 @item qTV:@var{var}
38997 @cindex trace state variable value, remote request
38998 @cindex @samp{qTV} packet
38999 Ask the stub for the value of the trace state variable number @var{var}.
39004 The value of the variable is @var{value}. This will be the current
39005 value of the variable if the user is examining a running target, or a
39006 saved value if the variable was collected in the trace frame that the
39007 user is looking at. Note that multiple requests may result in
39008 different reply values, such as when requesting values while the
39009 program is running.
39012 The value of the variable is unknown. This would occur, for example,
39013 if the user is examining a trace frame in which the requested variable
39018 @cindex @samp{qTfP} packet
39020 @cindex @samp{qTsP} packet
39021 These packets request data about tracepoints that are being used by
39022 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39023 of data, and multiple @code{qTsP} to get additional pieces. Replies
39024 to these packets generally take the form of the @code{QTDP} packets
39025 that define tracepoints. (FIXME add detailed syntax)
39028 @cindex @samp{qTfV} packet
39030 @cindex @samp{qTsV} packet
39031 These packets request data about trace state variables that are on the
39032 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39033 and multiple @code{qTsV} to get additional variables. Replies to
39034 these packets follow the syntax of the @code{QTDV} packets that define
39035 trace state variables.
39041 @cindex @samp{qTfSTM} packet
39042 @cindex @samp{qTsSTM} packet
39043 These packets request data about static tracepoint markers that exist
39044 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39045 first piece of data, and multiple @code{qTsSTM} to get additional
39046 pieces. Replies to these packets take the following form:
39050 @item m @var{address}:@var{id}:@var{extra}
39052 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39053 a comma-separated list of markers
39055 (lower case letter @samp{L}) denotes end of list.
39057 An error occurred. The error number @var{nn} is given as hex digits.
39059 An empty reply indicates that the request is not supported by the
39063 The @var{address} is encoded in hex;
39064 @var{id} and @var{extra} are strings encoded in hex.
39066 In response to each query, the target will reply with a list of one or
39067 more markers, separated by commas. @value{GDBN} will respond to each
39068 reply with a request for more markers (using the @samp{qs} form of the
39069 query), until the target responds with @samp{l} (lower-case ell, for
39072 @item qTSTMat:@var{address}
39074 @cindex @samp{qTSTMat} packet
39075 This packets requests data about static tracepoint markers in the
39076 target program at @var{address}. Replies to this packet follow the
39077 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39078 tracepoint markers.
39080 @item QTSave:@var{filename}
39081 @cindex @samp{QTSave} packet
39082 This packet directs the target to save trace data to the file name
39083 @var{filename} in the target's filesystem. The @var{filename} is encoded
39084 as a hex string; the interpretation of the file name (relative vs
39085 absolute, wild cards, etc) is up to the target.
39087 @item qTBuffer:@var{offset},@var{len}
39088 @cindex @samp{qTBuffer} packet
39089 Return up to @var{len} bytes of the current contents of trace buffer,
39090 starting at @var{offset}. The trace buffer is treated as if it were
39091 a contiguous collection of traceframes, as per the trace file format.
39092 The reply consists as many hex-encoded bytes as the target can deliver
39093 in a packet; it is not an error to return fewer than were asked for.
39094 A reply consisting of just @code{l} indicates that no bytes are
39097 @item QTBuffer:circular:@var{value}
39098 This packet directs the target to use a circular trace buffer if
39099 @var{value} is 1, or a linear buffer if the value is 0.
39101 @item QTBuffer:size:@var{size}
39102 @anchor{QTBuffer-size}
39103 @cindex @samp{QTBuffer size} packet
39104 This packet directs the target to make the trace buffer be of size
39105 @var{size} if possible. A value of @code{-1} tells the target to
39106 use whatever size it prefers.
39108 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39109 @cindex @samp{QTNotes} packet
39110 This packet adds optional textual notes to the trace run. Allowable
39111 types include @code{user}, @code{notes}, and @code{tstop}, the
39112 @var{text} fields are arbitrary strings, hex-encoded.
39116 @subsection Relocate instruction reply packet
39117 When installing fast tracepoints in memory, the target may need to
39118 relocate the instruction currently at the tracepoint address to a
39119 different address in memory. For most instructions, a simple copy is
39120 enough, but, for example, call instructions that implicitly push the
39121 return address on the stack, and relative branches or other
39122 PC-relative instructions require offset adjustment, so that the effect
39123 of executing the instruction at a different address is the same as if
39124 it had executed in the original location.
39126 In response to several of the tracepoint packets, the target may also
39127 respond with a number of intermediate @samp{qRelocInsn} request
39128 packets before the final result packet, to have @value{GDBN} handle
39129 this relocation operation. If a packet supports this mechanism, its
39130 documentation will explicitly say so. See for example the above
39131 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39132 format of the request is:
39135 @item qRelocInsn:@var{from};@var{to}
39137 This requests @value{GDBN} to copy instruction at address @var{from}
39138 to address @var{to}, possibly adjusted so that executing the
39139 instruction at @var{to} has the same effect as executing it at
39140 @var{from}. @value{GDBN} writes the adjusted instruction to target
39141 memory starting at @var{to}.
39146 @item qRelocInsn:@var{adjusted_size}
39147 Informs the stub the relocation is complete. The @var{adjusted_size} is
39148 the length in bytes of resulting relocated instruction sequence.
39150 A badly formed request was detected, or an error was encountered while
39151 relocating the instruction.
39154 @node Host I/O Packets
39155 @section Host I/O Packets
39156 @cindex Host I/O, remote protocol
39157 @cindex file transfer, remote protocol
39159 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39160 operations on the far side of a remote link. For example, Host I/O is
39161 used to upload and download files to a remote target with its own
39162 filesystem. Host I/O uses the same constant values and data structure
39163 layout as the target-initiated File-I/O protocol. However, the
39164 Host I/O packets are structured differently. The target-initiated
39165 protocol relies on target memory to store parameters and buffers.
39166 Host I/O requests are initiated by @value{GDBN}, and the
39167 target's memory is not involved. @xref{File-I/O Remote Protocol
39168 Extension}, for more details on the target-initiated protocol.
39170 The Host I/O request packets all encode a single operation along with
39171 its arguments. They have this format:
39175 @item vFile:@var{operation}: @var{parameter}@dots{}
39176 @var{operation} is the name of the particular request; the target
39177 should compare the entire packet name up to the second colon when checking
39178 for a supported operation. The format of @var{parameter} depends on
39179 the operation. Numbers are always passed in hexadecimal. Negative
39180 numbers have an explicit minus sign (i.e.@: two's complement is not
39181 used). Strings (e.g.@: filenames) are encoded as a series of
39182 hexadecimal bytes. The last argument to a system call may be a
39183 buffer of escaped binary data (@pxref{Binary Data}).
39187 The valid responses to Host I/O packets are:
39191 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39192 @var{result} is the integer value returned by this operation, usually
39193 non-negative for success and -1 for errors. If an error has occured,
39194 @var{errno} will be included in the result specifying a
39195 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39196 operations which return data, @var{attachment} supplies the data as a
39197 binary buffer. Binary buffers in response packets are escaped in the
39198 normal way (@pxref{Binary Data}). See the individual packet
39199 documentation for the interpretation of @var{result} and
39203 An empty response indicates that this operation is not recognized.
39207 These are the supported Host I/O operations:
39210 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39211 Open a file at @var{filename} and return a file descriptor for it, or
39212 return -1 if an error occurs. The @var{filename} is a string,
39213 @var{flags} is an integer indicating a mask of open flags
39214 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39215 of mode bits to use if the file is created (@pxref{mode_t Values}).
39216 @xref{open}, for details of the open flags and mode values.
39218 @item vFile:close: @var{fd}
39219 Close the open file corresponding to @var{fd} and return 0, or
39220 -1 if an error occurs.
39222 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39223 Read data from the open file corresponding to @var{fd}. Up to
39224 @var{count} bytes will be read from the file, starting at @var{offset}
39225 relative to the start of the file. The target may read fewer bytes;
39226 common reasons include packet size limits and an end-of-file
39227 condition. The number of bytes read is returned. Zero should only be
39228 returned for a successful read at the end of the file, or if
39229 @var{count} was zero.
39231 The data read should be returned as a binary attachment on success.
39232 If zero bytes were read, the response should include an empty binary
39233 attachment (i.e.@: a trailing semicolon). The return value is the
39234 number of target bytes read; the binary attachment may be longer if
39235 some characters were escaped.
39237 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39238 Write @var{data} (a binary buffer) to the open file corresponding
39239 to @var{fd}. Start the write at @var{offset} from the start of the
39240 file. Unlike many @code{write} system calls, there is no
39241 separate @var{count} argument; the length of @var{data} in the
39242 packet is used. @samp{vFile:write} returns the number of bytes written,
39243 which may be shorter than the length of @var{data}, or -1 if an
39246 @item vFile:fstat: @var{fd}
39247 Get information about the open file corresponding to @var{fd}.
39248 On success the information is returned as a binary attachment
39249 and the return value is the size of this attachment in bytes.
39250 If an error occurs the return value is -1. The format of the
39251 returned binary attachment is as described in @ref{struct stat}.
39253 @item vFile:unlink: @var{filename}
39254 Delete the file at @var{filename} on the target. Return 0,
39255 or -1 if an error occurs. The @var{filename} is a string.
39257 @item vFile:readlink: @var{filename}
39258 Read value of symbolic link @var{filename} on the target. Return
39259 the number of bytes read, or -1 if an error occurs.
39261 The data read should be returned as a binary attachment on success.
39262 If zero bytes were read, the response should include an empty binary
39263 attachment (i.e.@: a trailing semicolon). The return value is the
39264 number of target bytes read; the binary attachment may be longer if
39265 some characters were escaped.
39267 @item vFile:setfs: @var{pid}
39268 Select the filesystem on which @code{vFile} operations with
39269 @var{filename} arguments will operate. This is required for
39270 @value{GDBN} to be able to access files on remote targets where
39271 the remote stub does not share a common filesystem with the
39274 If @var{pid} is nonzero, select the filesystem as seen by process
39275 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39276 the remote stub. Return 0 on success, or -1 if an error occurs.
39277 If @code{vFile:setfs:} indicates success, the selected filesystem
39278 remains selected until the next successful @code{vFile:setfs:}
39284 @section Interrupts
39285 @cindex interrupts (remote protocol)
39286 @anchor{interrupting remote targets}
39288 In all-stop mode, when a program on the remote target is running,
39289 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39290 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39291 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39293 The precise meaning of @code{BREAK} is defined by the transport
39294 mechanism and may, in fact, be undefined. @value{GDBN} does not
39295 currently define a @code{BREAK} mechanism for any of the network
39296 interfaces except for TCP, in which case @value{GDBN} sends the
39297 @code{telnet} BREAK sequence.
39299 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39300 transport mechanisms. It is represented by sending the single byte
39301 @code{0x03} without any of the usual packet overhead described in
39302 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39303 transmitted as part of a packet, it is considered to be packet data
39304 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39305 (@pxref{X packet}), used for binary downloads, may include an unescaped
39306 @code{0x03} as part of its packet.
39308 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39309 When Linux kernel receives this sequence from serial port,
39310 it stops execution and connects to gdb.
39312 In non-stop mode, because packet resumptions are asynchronous
39313 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39314 command to the remote stub, even when the target is running. For that
39315 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39316 packet}) with the usual packet framing instead of the single byte
39319 Stubs are not required to recognize these interrupt mechanisms and the
39320 precise meaning associated with receipt of the interrupt is
39321 implementation defined. If the target supports debugging of multiple
39322 threads and/or processes, it should attempt to interrupt all
39323 currently-executing threads and processes.
39324 If the stub is successful at interrupting the
39325 running program, it should send one of the stop
39326 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39327 of successfully stopping the program in all-stop mode, and a stop reply
39328 for each stopped thread in non-stop mode.
39329 Interrupts received while the
39330 program is stopped are queued and the program will be interrupted when
39331 it is resumed next time.
39333 @node Notification Packets
39334 @section Notification Packets
39335 @cindex notification packets
39336 @cindex packets, notification
39338 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39339 packets that require no acknowledgment. Both the GDB and the stub
39340 may send notifications (although the only notifications defined at
39341 present are sent by the stub). Notifications carry information
39342 without incurring the round-trip latency of an acknowledgment, and so
39343 are useful for low-impact communications where occasional packet loss
39346 A notification packet has the form @samp{% @var{data} #
39347 @var{checksum}}, where @var{data} is the content of the notification,
39348 and @var{checksum} is a checksum of @var{data}, computed and formatted
39349 as for ordinary @value{GDBN} packets. A notification's @var{data}
39350 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39351 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39352 to acknowledge the notification's receipt or to report its corruption.
39354 Every notification's @var{data} begins with a name, which contains no
39355 colon characters, followed by a colon character.
39357 Recipients should silently ignore corrupted notifications and
39358 notifications they do not understand. Recipients should restart
39359 timeout periods on receipt of a well-formed notification, whether or
39360 not they understand it.
39362 Senders should only send the notifications described here when this
39363 protocol description specifies that they are permitted. In the
39364 future, we may extend the protocol to permit existing notifications in
39365 new contexts; this rule helps older senders avoid confusing newer
39368 (Older versions of @value{GDBN} ignore bytes received until they see
39369 the @samp{$} byte that begins an ordinary packet, so new stubs may
39370 transmit notifications without fear of confusing older clients. There
39371 are no notifications defined for @value{GDBN} to send at the moment, but we
39372 assume that most older stubs would ignore them, as well.)
39374 Each notification is comprised of three parts:
39376 @item @var{name}:@var{event}
39377 The notification packet is sent by the side that initiates the
39378 exchange (currently, only the stub does that), with @var{event}
39379 carrying the specific information about the notification, and
39380 @var{name} specifying the name of the notification.
39382 The acknowledge sent by the other side, usually @value{GDBN}, to
39383 acknowledge the exchange and request the event.
39386 The purpose of an asynchronous notification mechanism is to report to
39387 @value{GDBN} that something interesting happened in the remote stub.
39389 The remote stub may send notification @var{name}:@var{event}
39390 at any time, but @value{GDBN} acknowledges the notification when
39391 appropriate. The notification event is pending before @value{GDBN}
39392 acknowledges. Only one notification at a time may be pending; if
39393 additional events occur before @value{GDBN} has acknowledged the
39394 previous notification, they must be queued by the stub for later
39395 synchronous transmission in response to @var{ack} packets from
39396 @value{GDBN}. Because the notification mechanism is unreliable,
39397 the stub is permitted to resend a notification if it believes
39398 @value{GDBN} may not have received it.
39400 Specifically, notifications may appear when @value{GDBN} is not
39401 otherwise reading input from the stub, or when @value{GDBN} is
39402 expecting to read a normal synchronous response or a
39403 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39404 Notification packets are distinct from any other communication from
39405 the stub so there is no ambiguity.
39407 After receiving a notification, @value{GDBN} shall acknowledge it by
39408 sending a @var{ack} packet as a regular, synchronous request to the
39409 stub. Such acknowledgment is not required to happen immediately, as
39410 @value{GDBN} is permitted to send other, unrelated packets to the
39411 stub first, which the stub should process normally.
39413 Upon receiving a @var{ack} packet, if the stub has other queued
39414 events to report to @value{GDBN}, it shall respond by sending a
39415 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39416 packet to solicit further responses; again, it is permitted to send
39417 other, unrelated packets as well which the stub should process
39420 If the stub receives a @var{ack} packet and there are no additional
39421 @var{event} to report, the stub shall return an @samp{OK} response.
39422 At this point, @value{GDBN} has finished processing a notification
39423 and the stub has completed sending any queued events. @value{GDBN}
39424 won't accept any new notifications until the final @samp{OK} is
39425 received . If further notification events occur, the stub shall send
39426 a new notification, @value{GDBN} shall accept the notification, and
39427 the process shall be repeated.
39429 The process of asynchronous notification can be illustrated by the
39432 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39435 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39437 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39442 The following notifications are defined:
39443 @multitable @columnfractions 0.12 0.12 0.38 0.38
39452 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39453 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39454 for information on how these notifications are acknowledged by
39456 @tab Report an asynchronous stop event in non-stop mode.
39460 @node Remote Non-Stop
39461 @section Remote Protocol Support for Non-Stop Mode
39463 @value{GDBN}'s remote protocol supports non-stop debugging of
39464 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39465 supports non-stop mode, it should report that to @value{GDBN} by including
39466 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39468 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39469 establishing a new connection with the stub. Entering non-stop mode
39470 does not alter the state of any currently-running threads, but targets
39471 must stop all threads in any already-attached processes when entering
39472 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39473 probe the target state after a mode change.
39475 In non-stop mode, when an attached process encounters an event that
39476 would otherwise be reported with a stop reply, it uses the
39477 asynchronous notification mechanism (@pxref{Notification Packets}) to
39478 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39479 in all processes are stopped when a stop reply is sent, in non-stop
39480 mode only the thread reporting the stop event is stopped. That is,
39481 when reporting a @samp{S} or @samp{T} response to indicate completion
39482 of a step operation, hitting a breakpoint, or a fault, only the
39483 affected thread is stopped; any other still-running threads continue
39484 to run. When reporting a @samp{W} or @samp{X} response, all running
39485 threads belonging to other attached processes continue to run.
39487 In non-stop mode, the target shall respond to the @samp{?} packet as
39488 follows. First, any incomplete stop reply notification/@samp{vStopped}
39489 sequence in progress is abandoned. The target must begin a new
39490 sequence reporting stop events for all stopped threads, whether or not
39491 it has previously reported those events to @value{GDBN}. The first
39492 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39493 subsequent stop replies are sent as responses to @samp{vStopped} packets
39494 using the mechanism described above. The target must not send
39495 asynchronous stop reply notifications until the sequence is complete.
39496 If all threads are running when the target receives the @samp{?} packet,
39497 or if the target is not attached to any process, it shall respond
39500 If the stub supports non-stop mode, it should also support the
39501 @samp{swbreak} stop reason if software breakpoints are supported, and
39502 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39503 (@pxref{swbreak stop reason}). This is because given the asynchronous
39504 nature of non-stop mode, between the time a thread hits a breakpoint
39505 and the time the event is finally processed by @value{GDBN}, the
39506 breakpoint may have already been removed from the target. Due to
39507 this, @value{GDBN} needs to be able to tell whether a trap stop was
39508 caused by a delayed breakpoint event, which should be ignored, as
39509 opposed to a random trap signal, which should be reported to the user.
39510 Note the @samp{swbreak} feature implies that the target is responsible
39511 for adjusting the PC when a software breakpoint triggers, if
39512 necessary, such as on the x86 architecture.
39514 @node Packet Acknowledgment
39515 @section Packet Acknowledgment
39517 @cindex acknowledgment, for @value{GDBN} remote
39518 @cindex packet acknowledgment, for @value{GDBN} remote
39519 By default, when either the host or the target machine receives a packet,
39520 the first response expected is an acknowledgment: either @samp{+} (to indicate
39521 the package was received correctly) or @samp{-} (to request retransmission).
39522 This mechanism allows the @value{GDBN} remote protocol to operate over
39523 unreliable transport mechanisms, such as a serial line.
39525 In cases where the transport mechanism is itself reliable (such as a pipe or
39526 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39527 It may be desirable to disable them in that case to reduce communication
39528 overhead, or for other reasons. This can be accomplished by means of the
39529 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39531 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39532 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39533 and response format still includes the normal checksum, as described in
39534 @ref{Overview}, but the checksum may be ignored by the receiver.
39536 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39537 no-acknowledgment mode, it should report that to @value{GDBN}
39538 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39539 @pxref{qSupported}.
39540 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39541 disabled via the @code{set remote noack-packet off} command
39542 (@pxref{Remote Configuration}),
39543 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39544 Only then may the stub actually turn off packet acknowledgments.
39545 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39546 response, which can be safely ignored by the stub.
39548 Note that @code{set remote noack-packet} command only affects negotiation
39549 between @value{GDBN} and the stub when subsequent connections are made;
39550 it does not affect the protocol acknowledgment state for any current
39552 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39553 new connection is established,
39554 there is also no protocol request to re-enable the acknowledgments
39555 for the current connection, once disabled.
39560 Example sequence of a target being re-started. Notice how the restart
39561 does not get any direct output:
39566 @emph{target restarts}
39569 <- @code{T001:1234123412341234}
39573 Example sequence of a target being stepped by a single instruction:
39576 -> @code{G1445@dots{}}
39581 <- @code{T001:1234123412341234}
39585 <- @code{1455@dots{}}
39589 @node File-I/O Remote Protocol Extension
39590 @section File-I/O Remote Protocol Extension
39591 @cindex File-I/O remote protocol extension
39594 * File-I/O Overview::
39595 * Protocol Basics::
39596 * The F Request Packet::
39597 * The F Reply Packet::
39598 * The Ctrl-C Message::
39600 * List of Supported Calls::
39601 * Protocol-specific Representation of Datatypes::
39603 * File-I/O Examples::
39606 @node File-I/O Overview
39607 @subsection File-I/O Overview
39608 @cindex file-i/o overview
39610 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39611 target to use the host's file system and console I/O to perform various
39612 system calls. System calls on the target system are translated into a
39613 remote protocol packet to the host system, which then performs the needed
39614 actions and returns a response packet to the target system.
39615 This simulates file system operations even on targets that lack file systems.
39617 The protocol is defined to be independent of both the host and target systems.
39618 It uses its own internal representation of datatypes and values. Both
39619 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39620 translating the system-dependent value representations into the internal
39621 protocol representations when data is transmitted.
39623 The communication is synchronous. A system call is possible only when
39624 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39625 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39626 the target is stopped to allow deterministic access to the target's
39627 memory. Therefore File-I/O is not interruptible by target signals. On
39628 the other hand, it is possible to interrupt File-I/O by a user interrupt
39629 (@samp{Ctrl-C}) within @value{GDBN}.
39631 The target's request to perform a host system call does not finish
39632 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39633 after finishing the system call, the target returns to continuing the
39634 previous activity (continue, step). No additional continue or step
39635 request from @value{GDBN} is required.
39638 (@value{GDBP}) continue
39639 <- target requests 'system call X'
39640 target is stopped, @value{GDBN} executes system call
39641 -> @value{GDBN} returns result
39642 ... target continues, @value{GDBN} returns to wait for the target
39643 <- target hits breakpoint and sends a Txx packet
39646 The protocol only supports I/O on the console and to regular files on
39647 the host file system. Character or block special devices, pipes,
39648 named pipes, sockets or any other communication method on the host
39649 system are not supported by this protocol.
39651 File I/O is not supported in non-stop mode.
39653 @node Protocol Basics
39654 @subsection Protocol Basics
39655 @cindex protocol basics, file-i/o
39657 The File-I/O protocol uses the @code{F} packet as the request as well
39658 as reply packet. Since a File-I/O system call can only occur when
39659 @value{GDBN} is waiting for a response from the continuing or stepping target,
39660 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39661 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39662 This @code{F} packet contains all information needed to allow @value{GDBN}
39663 to call the appropriate host system call:
39667 A unique identifier for the requested system call.
39670 All parameters to the system call. Pointers are given as addresses
39671 in the target memory address space. Pointers to strings are given as
39672 pointer/length pair. Numerical values are given as they are.
39673 Numerical control flags are given in a protocol-specific representation.
39677 At this point, @value{GDBN} has to perform the following actions.
39681 If the parameters include pointer values to data needed as input to a
39682 system call, @value{GDBN} requests this data from the target with a
39683 standard @code{m} packet request. This additional communication has to be
39684 expected by the target implementation and is handled as any other @code{m}
39688 @value{GDBN} translates all value from protocol representation to host
39689 representation as needed. Datatypes are coerced into the host types.
39692 @value{GDBN} calls the system call.
39695 It then coerces datatypes back to protocol representation.
39698 If the system call is expected to return data in buffer space specified
39699 by pointer parameters to the call, the data is transmitted to the
39700 target using a @code{M} or @code{X} packet. This packet has to be expected
39701 by the target implementation and is handled as any other @code{M} or @code{X}
39706 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39707 necessary information for the target to continue. This at least contains
39714 @code{errno}, if has been changed by the system call.
39721 After having done the needed type and value coercion, the target continues
39722 the latest continue or step action.
39724 @node The F Request Packet
39725 @subsection The @code{F} Request Packet
39726 @cindex file-i/o request packet
39727 @cindex @code{F} request packet
39729 The @code{F} request packet has the following format:
39732 @item F@var{call-id},@var{parameter@dots{}}
39734 @var{call-id} is the identifier to indicate the host system call to be called.
39735 This is just the name of the function.
39737 @var{parameter@dots{}} are the parameters to the system call.
39738 Parameters are hexadecimal integer values, either the actual values in case
39739 of scalar datatypes, pointers to target buffer space in case of compound
39740 datatypes and unspecified memory areas, or pointer/length pairs in case
39741 of string parameters. These are appended to the @var{call-id} as a
39742 comma-delimited list. All values are transmitted in ASCII
39743 string representation, pointer/length pairs separated by a slash.
39749 @node The F Reply Packet
39750 @subsection The @code{F} Reply Packet
39751 @cindex file-i/o reply packet
39752 @cindex @code{F} reply packet
39754 The @code{F} reply packet has the following format:
39758 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39760 @var{retcode} is the return code of the system call as hexadecimal value.
39762 @var{errno} is the @code{errno} set by the call, in protocol-specific
39764 This parameter can be omitted if the call was successful.
39766 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39767 case, @var{errno} must be sent as well, even if the call was successful.
39768 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39775 or, if the call was interrupted before the host call has been performed:
39782 assuming 4 is the protocol-specific representation of @code{EINTR}.
39787 @node The Ctrl-C Message
39788 @subsection The @samp{Ctrl-C} Message
39789 @cindex ctrl-c message, in file-i/o protocol
39791 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39792 reply packet (@pxref{The F Reply Packet}),
39793 the target should behave as if it had
39794 gotten a break message. The meaning for the target is ``system call
39795 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39796 (as with a break message) and return to @value{GDBN} with a @code{T02}
39799 It's important for the target to know in which
39800 state the system call was interrupted. There are two possible cases:
39804 The system call hasn't been performed on the host yet.
39807 The system call on the host has been finished.
39811 These two states can be distinguished by the target by the value of the
39812 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39813 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39814 on POSIX systems. In any other case, the target may presume that the
39815 system call has been finished --- successfully or not --- and should behave
39816 as if the break message arrived right after the system call.
39818 @value{GDBN} must behave reliably. If the system call has not been called
39819 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39820 @code{errno} in the packet. If the system call on the host has been finished
39821 before the user requests a break, the full action must be finished by
39822 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39823 The @code{F} packet may only be sent when either nothing has happened
39824 or the full action has been completed.
39827 @subsection Console I/O
39828 @cindex console i/o as part of file-i/o
39830 By default and if not explicitly closed by the target system, the file
39831 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39832 on the @value{GDBN} console is handled as any other file output operation
39833 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39834 by @value{GDBN} so that after the target read request from file descriptor
39835 0 all following typing is buffered until either one of the following
39840 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39842 system call is treated as finished.
39845 The user presses @key{RET}. This is treated as end of input with a trailing
39849 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39850 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39854 If the user has typed more characters than fit in the buffer given to
39855 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39856 either another @code{read(0, @dots{})} is requested by the target, or debugging
39857 is stopped at the user's request.
39860 @node List of Supported Calls
39861 @subsection List of Supported Calls
39862 @cindex list of supported file-i/o calls
39879 @unnumberedsubsubsec open
39880 @cindex open, file-i/o system call
39885 int open(const char *pathname, int flags);
39886 int open(const char *pathname, int flags, mode_t mode);
39890 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39893 @var{flags} is the bitwise @code{OR} of the following values:
39897 If the file does not exist it will be created. The host
39898 rules apply as far as file ownership and time stamps
39902 When used with @code{O_CREAT}, if the file already exists it is
39903 an error and open() fails.
39906 If the file already exists and the open mode allows
39907 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39908 truncated to zero length.
39911 The file is opened in append mode.
39914 The file is opened for reading only.
39917 The file is opened for writing only.
39920 The file is opened for reading and writing.
39924 Other bits are silently ignored.
39928 @var{mode} is the bitwise @code{OR} of the following values:
39932 User has read permission.
39935 User has write permission.
39938 Group has read permission.
39941 Group has write permission.
39944 Others have read permission.
39947 Others have write permission.
39951 Other bits are silently ignored.
39954 @item Return value:
39955 @code{open} returns the new file descriptor or -1 if an error
39962 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39965 @var{pathname} refers to a directory.
39968 The requested access is not allowed.
39971 @var{pathname} was too long.
39974 A directory component in @var{pathname} does not exist.
39977 @var{pathname} refers to a device, pipe, named pipe or socket.
39980 @var{pathname} refers to a file on a read-only filesystem and
39981 write access was requested.
39984 @var{pathname} is an invalid pointer value.
39987 No space on device to create the file.
39990 The process already has the maximum number of files open.
39993 The limit on the total number of files open on the system
39997 The call was interrupted by the user.
40003 @unnumberedsubsubsec close
40004 @cindex close, file-i/o system call
40013 @samp{Fclose,@var{fd}}
40015 @item Return value:
40016 @code{close} returns zero on success, or -1 if an error occurred.
40022 @var{fd} isn't a valid open file descriptor.
40025 The call was interrupted by the user.
40031 @unnumberedsubsubsec read
40032 @cindex read, file-i/o system call
40037 int read(int fd, void *buf, unsigned int count);
40041 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40043 @item Return value:
40044 On success, the number of bytes read is returned.
40045 Zero indicates end of file. If count is zero, read
40046 returns zero as well. On error, -1 is returned.
40052 @var{fd} is not a valid file descriptor or is not open for
40056 @var{bufptr} is an invalid pointer value.
40059 The call was interrupted by the user.
40065 @unnumberedsubsubsec write
40066 @cindex write, file-i/o system call
40071 int write(int fd, const void *buf, unsigned int count);
40075 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40077 @item Return value:
40078 On success, the number of bytes written are returned.
40079 Zero indicates nothing was written. On error, -1
40086 @var{fd} is not a valid file descriptor or is not open for
40090 @var{bufptr} is an invalid pointer value.
40093 An attempt was made to write a file that exceeds the
40094 host-specific maximum file size allowed.
40097 No space on device to write the data.
40100 The call was interrupted by the user.
40106 @unnumberedsubsubsec lseek
40107 @cindex lseek, file-i/o system call
40112 long lseek (int fd, long offset, int flag);
40116 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40118 @var{flag} is one of:
40122 The offset is set to @var{offset} bytes.
40125 The offset is set to its current location plus @var{offset}
40129 The offset is set to the size of the file plus @var{offset}
40133 @item Return value:
40134 On success, the resulting unsigned offset in bytes from
40135 the beginning of the file is returned. Otherwise, a
40136 value of -1 is returned.
40142 @var{fd} is not a valid open file descriptor.
40145 @var{fd} is associated with the @value{GDBN} console.
40148 @var{flag} is not a proper value.
40151 The call was interrupted by the user.
40157 @unnumberedsubsubsec rename
40158 @cindex rename, file-i/o system call
40163 int rename(const char *oldpath, const char *newpath);
40167 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40169 @item Return value:
40170 On success, zero is returned. On error, -1 is returned.
40176 @var{newpath} is an existing directory, but @var{oldpath} is not a
40180 @var{newpath} is a non-empty directory.
40183 @var{oldpath} or @var{newpath} is a directory that is in use by some
40187 An attempt was made to make a directory a subdirectory
40191 A component used as a directory in @var{oldpath} or new
40192 path is not a directory. Or @var{oldpath} is a directory
40193 and @var{newpath} exists but is not a directory.
40196 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40199 No access to the file or the path of the file.
40203 @var{oldpath} or @var{newpath} was too long.
40206 A directory component in @var{oldpath} or @var{newpath} does not exist.
40209 The file is on a read-only filesystem.
40212 The device containing the file has no room for the new
40216 The call was interrupted by the user.
40222 @unnumberedsubsubsec unlink
40223 @cindex unlink, file-i/o system call
40228 int unlink(const char *pathname);
40232 @samp{Funlink,@var{pathnameptr}/@var{len}}
40234 @item Return value:
40235 On success, zero is returned. On error, -1 is returned.
40241 No access to the file or the path of the file.
40244 The system does not allow unlinking of directories.
40247 The file @var{pathname} cannot be unlinked because it's
40248 being used by another process.
40251 @var{pathnameptr} is an invalid pointer value.
40254 @var{pathname} was too long.
40257 A directory component in @var{pathname} does not exist.
40260 A component of the path is not a directory.
40263 The file is on a read-only filesystem.
40266 The call was interrupted by the user.
40272 @unnumberedsubsubsec stat/fstat
40273 @cindex fstat, file-i/o system call
40274 @cindex stat, file-i/o system call
40279 int stat(const char *pathname, struct stat *buf);
40280 int fstat(int fd, struct stat *buf);
40284 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40285 @samp{Ffstat,@var{fd},@var{bufptr}}
40287 @item Return value:
40288 On success, zero is returned. On error, -1 is returned.
40294 @var{fd} is not a valid open file.
40297 A directory component in @var{pathname} does not exist or the
40298 path is an empty string.
40301 A component of the path is not a directory.
40304 @var{pathnameptr} is an invalid pointer value.
40307 No access to the file or the path of the file.
40310 @var{pathname} was too long.
40313 The call was interrupted by the user.
40319 @unnumberedsubsubsec gettimeofday
40320 @cindex gettimeofday, file-i/o system call
40325 int gettimeofday(struct timeval *tv, void *tz);
40329 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40331 @item Return value:
40332 On success, 0 is returned, -1 otherwise.
40338 @var{tz} is a non-NULL pointer.
40341 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40347 @unnumberedsubsubsec isatty
40348 @cindex isatty, file-i/o system call
40353 int isatty(int fd);
40357 @samp{Fisatty,@var{fd}}
40359 @item Return value:
40360 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40366 The call was interrupted by the user.
40371 Note that the @code{isatty} call is treated as a special case: it returns
40372 1 to the target if the file descriptor is attached
40373 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40374 would require implementing @code{ioctl} and would be more complex than
40379 @unnumberedsubsubsec system
40380 @cindex system, file-i/o system call
40385 int system(const char *command);
40389 @samp{Fsystem,@var{commandptr}/@var{len}}
40391 @item Return value:
40392 If @var{len} is zero, the return value indicates whether a shell is
40393 available. A zero return value indicates a shell is not available.
40394 For non-zero @var{len}, the value returned is -1 on error and the
40395 return status of the command otherwise. Only the exit status of the
40396 command is returned, which is extracted from the host's @code{system}
40397 return value by calling @code{WEXITSTATUS(retval)}. In case
40398 @file{/bin/sh} could not be executed, 127 is returned.
40404 The call was interrupted by the user.
40409 @value{GDBN} takes over the full task of calling the necessary host calls
40410 to perform the @code{system} call. The return value of @code{system} on
40411 the host is simplified before it's returned
40412 to the target. Any termination signal information from the child process
40413 is discarded, and the return value consists
40414 entirely of the exit status of the called command.
40416 Due to security concerns, the @code{system} call is by default refused
40417 by @value{GDBN}. The user has to allow this call explicitly with the
40418 @code{set remote system-call-allowed 1} command.
40421 @item set remote system-call-allowed
40422 @kindex set remote system-call-allowed
40423 Control whether to allow the @code{system} calls in the File I/O
40424 protocol for the remote target. The default is zero (disabled).
40426 @item show remote system-call-allowed
40427 @kindex show remote system-call-allowed
40428 Show whether the @code{system} calls are allowed in the File I/O
40432 @node Protocol-specific Representation of Datatypes
40433 @subsection Protocol-specific Representation of Datatypes
40434 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40437 * Integral Datatypes::
40439 * Memory Transfer::
40444 @node Integral Datatypes
40445 @unnumberedsubsubsec Integral Datatypes
40446 @cindex integral datatypes, in file-i/o protocol
40448 The integral datatypes used in the system calls are @code{int},
40449 @code{unsigned int}, @code{long}, @code{unsigned long},
40450 @code{mode_t}, and @code{time_t}.
40452 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40453 implemented as 32 bit values in this protocol.
40455 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40457 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40458 in @file{limits.h}) to allow range checking on host and target.
40460 @code{time_t} datatypes are defined as seconds since the Epoch.
40462 All integral datatypes transferred as part of a memory read or write of a
40463 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40466 @node Pointer Values
40467 @unnumberedsubsubsec Pointer Values
40468 @cindex pointer values, in file-i/o protocol
40470 Pointers to target data are transmitted as they are. An exception
40471 is made for pointers to buffers for which the length isn't
40472 transmitted as part of the function call, namely strings. Strings
40473 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40480 which is a pointer to data of length 18 bytes at position 0x1aaf.
40481 The length is defined as the full string length in bytes, including
40482 the trailing null byte. For example, the string @code{"hello world"}
40483 at address 0x123456 is transmitted as
40489 @node Memory Transfer
40490 @unnumberedsubsubsec Memory Transfer
40491 @cindex memory transfer, in file-i/o protocol
40493 Structured data which is transferred using a memory read or write (for
40494 example, a @code{struct stat}) is expected to be in a protocol-specific format
40495 with all scalar multibyte datatypes being big endian. Translation to
40496 this representation needs to be done both by the target before the @code{F}
40497 packet is sent, and by @value{GDBN} before
40498 it transfers memory to the target. Transferred pointers to structured
40499 data should point to the already-coerced data at any time.
40503 @unnumberedsubsubsec struct stat
40504 @cindex struct stat, in file-i/o protocol
40506 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40507 is defined as follows:
40511 unsigned int st_dev; /* device */
40512 unsigned int st_ino; /* inode */
40513 mode_t st_mode; /* protection */
40514 unsigned int st_nlink; /* number of hard links */
40515 unsigned int st_uid; /* user ID of owner */
40516 unsigned int st_gid; /* group ID of owner */
40517 unsigned int st_rdev; /* device type (if inode device) */
40518 unsigned long st_size; /* total size, in bytes */
40519 unsigned long st_blksize; /* blocksize for filesystem I/O */
40520 unsigned long st_blocks; /* number of blocks allocated */
40521 time_t st_atime; /* time of last access */
40522 time_t st_mtime; /* time of last modification */
40523 time_t st_ctime; /* time of last change */
40527 The integral datatypes conform to the definitions given in the
40528 appropriate section (see @ref{Integral Datatypes}, for details) so this
40529 structure is of size 64 bytes.
40531 The values of several fields have a restricted meaning and/or
40537 A value of 0 represents a file, 1 the console.
40540 No valid meaning for the target. Transmitted unchanged.
40543 Valid mode bits are described in @ref{Constants}. Any other
40544 bits have currently no meaning for the target.
40549 No valid meaning for the target. Transmitted unchanged.
40554 These values have a host and file system dependent
40555 accuracy. Especially on Windows hosts, the file system may not
40556 support exact timing values.
40559 The target gets a @code{struct stat} of the above representation and is
40560 responsible for coercing it to the target representation before
40563 Note that due to size differences between the host, target, and protocol
40564 representations of @code{struct stat} members, these members could eventually
40565 get truncated on the target.
40567 @node struct timeval
40568 @unnumberedsubsubsec struct timeval
40569 @cindex struct timeval, in file-i/o protocol
40571 The buffer of type @code{struct timeval} used by the File-I/O protocol
40572 is defined as follows:
40576 time_t tv_sec; /* second */
40577 long tv_usec; /* microsecond */
40581 The integral datatypes conform to the definitions given in the
40582 appropriate section (see @ref{Integral Datatypes}, for details) so this
40583 structure is of size 8 bytes.
40586 @subsection Constants
40587 @cindex constants, in file-i/o protocol
40589 The following values are used for the constants inside of the
40590 protocol. @value{GDBN} and target are responsible for translating these
40591 values before and after the call as needed.
40602 @unnumberedsubsubsec Open Flags
40603 @cindex open flags, in file-i/o protocol
40605 All values are given in hexadecimal representation.
40617 @node mode_t Values
40618 @unnumberedsubsubsec mode_t Values
40619 @cindex mode_t values, in file-i/o protocol
40621 All values are given in octal representation.
40638 @unnumberedsubsubsec Errno Values
40639 @cindex errno values, in file-i/o protocol
40641 All values are given in decimal representation.
40666 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40667 any error value not in the list of supported error numbers.
40670 @unnumberedsubsubsec Lseek Flags
40671 @cindex lseek flags, in file-i/o protocol
40680 @unnumberedsubsubsec Limits
40681 @cindex limits, in file-i/o protocol
40683 All values are given in decimal representation.
40686 INT_MIN -2147483648
40688 UINT_MAX 4294967295
40689 LONG_MIN -9223372036854775808
40690 LONG_MAX 9223372036854775807
40691 ULONG_MAX 18446744073709551615
40694 @node File-I/O Examples
40695 @subsection File-I/O Examples
40696 @cindex file-i/o examples
40698 Example sequence of a write call, file descriptor 3, buffer is at target
40699 address 0x1234, 6 bytes should be written:
40702 <- @code{Fwrite,3,1234,6}
40703 @emph{request memory read from target}
40706 @emph{return "6 bytes written"}
40710 Example sequence of a read call, file descriptor 3, buffer is at target
40711 address 0x1234, 6 bytes should be read:
40714 <- @code{Fread,3,1234,6}
40715 @emph{request memory write to target}
40716 -> @code{X1234,6:XXXXXX}
40717 @emph{return "6 bytes read"}
40721 Example sequence of a read call, call fails on the host due to invalid
40722 file descriptor (@code{EBADF}):
40725 <- @code{Fread,3,1234,6}
40729 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40733 <- @code{Fread,3,1234,6}
40738 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40742 <- @code{Fread,3,1234,6}
40743 -> @code{X1234,6:XXXXXX}
40747 @node Library List Format
40748 @section Library List Format
40749 @cindex library list format, remote protocol
40751 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40752 same process as your application to manage libraries. In this case,
40753 @value{GDBN} can use the loader's symbol table and normal memory
40754 operations to maintain a list of shared libraries. On other
40755 platforms, the operating system manages loaded libraries.
40756 @value{GDBN} can not retrieve the list of currently loaded libraries
40757 through memory operations, so it uses the @samp{qXfer:libraries:read}
40758 packet (@pxref{qXfer library list read}) instead. The remote stub
40759 queries the target's operating system and reports which libraries
40762 The @samp{qXfer:libraries:read} packet returns an XML document which
40763 lists loaded libraries and their offsets. Each library has an
40764 associated name and one or more segment or section base addresses,
40765 which report where the library was loaded in memory.
40767 For the common case of libraries that are fully linked binaries, the
40768 library should have a list of segments. If the target supports
40769 dynamic linking of a relocatable object file, its library XML element
40770 should instead include a list of allocated sections. The segment or
40771 section bases are start addresses, not relocation offsets; they do not
40772 depend on the library's link-time base addresses.
40774 @value{GDBN} must be linked with the Expat library to support XML
40775 library lists. @xref{Expat}.
40777 A simple memory map, with one loaded library relocated by a single
40778 offset, looks like this:
40782 <library name="/lib/libc.so.6">
40783 <segment address="0x10000000"/>
40788 Another simple memory map, with one loaded library with three
40789 allocated sections (.text, .data, .bss), looks like this:
40793 <library name="sharedlib.o">
40794 <section address="0x10000000"/>
40795 <section address="0x20000000"/>
40796 <section address="0x30000000"/>
40801 The format of a library list is described by this DTD:
40804 <!-- library-list: Root element with versioning -->
40805 <!ELEMENT library-list (library)*>
40806 <!ATTLIST library-list version CDATA #FIXED "1.0">
40807 <!ELEMENT library (segment*, section*)>
40808 <!ATTLIST library name CDATA #REQUIRED>
40809 <!ELEMENT segment EMPTY>
40810 <!ATTLIST segment address CDATA #REQUIRED>
40811 <!ELEMENT section EMPTY>
40812 <!ATTLIST section address CDATA #REQUIRED>
40815 In addition, segments and section descriptors cannot be mixed within a
40816 single library element, and you must supply at least one segment or
40817 section for each library.
40819 @node Library List Format for SVR4 Targets
40820 @section Library List Format for SVR4 Targets
40821 @cindex library list format, remote protocol
40823 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40824 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40825 shared libraries. Still a special library list provided by this packet is
40826 more efficient for the @value{GDBN} remote protocol.
40828 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40829 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40830 target, the following parameters are reported:
40834 @code{name}, the absolute file name from the @code{l_name} field of
40835 @code{struct link_map}.
40837 @code{lm} with address of @code{struct link_map} used for TLS
40838 (Thread Local Storage) access.
40840 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40841 @code{struct link_map}. For prelinked libraries this is not an absolute
40842 memory address. It is a displacement of absolute memory address against
40843 address the file was prelinked to during the library load.
40845 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40848 Additionally the single @code{main-lm} attribute specifies address of
40849 @code{struct link_map} used for the main executable. This parameter is used
40850 for TLS access and its presence is optional.
40852 @value{GDBN} must be linked with the Expat library to support XML
40853 SVR4 library lists. @xref{Expat}.
40855 A simple memory map, with two loaded libraries (which do not use prelink),
40859 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40860 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40862 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40864 </library-list-svr>
40867 The format of an SVR4 library list is described by this DTD:
40870 <!-- library-list-svr4: Root element with versioning -->
40871 <!ELEMENT library-list-svr4 (library)*>
40872 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40873 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40874 <!ELEMENT library EMPTY>
40875 <!ATTLIST library name CDATA #REQUIRED>
40876 <!ATTLIST library lm CDATA #REQUIRED>
40877 <!ATTLIST library l_addr CDATA #REQUIRED>
40878 <!ATTLIST library l_ld CDATA #REQUIRED>
40881 @node Memory Map Format
40882 @section Memory Map Format
40883 @cindex memory map format
40885 To be able to write into flash memory, @value{GDBN} needs to obtain a
40886 memory map from the target. This section describes the format of the
40889 The memory map is obtained using the @samp{qXfer:memory-map:read}
40890 (@pxref{qXfer memory map read}) packet and is an XML document that
40891 lists memory regions.
40893 @value{GDBN} must be linked with the Expat library to support XML
40894 memory maps. @xref{Expat}.
40896 The top-level structure of the document is shown below:
40899 <?xml version="1.0"?>
40900 <!DOCTYPE memory-map
40901 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40902 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40908 Each region can be either:
40913 A region of RAM starting at @var{addr} and extending for @var{length}
40917 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40922 A region of read-only memory:
40925 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40930 A region of flash memory, with erasure blocks @var{blocksize}
40934 <memory type="flash" start="@var{addr}" length="@var{length}">
40935 <property name="blocksize">@var{blocksize}</property>
40941 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40942 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40943 packets to write to addresses in such ranges.
40945 The formal DTD for memory map format is given below:
40948 <!-- ................................................... -->
40949 <!-- Memory Map XML DTD ................................ -->
40950 <!-- File: memory-map.dtd .............................. -->
40951 <!-- .................................... .............. -->
40952 <!-- memory-map.dtd -->
40953 <!-- memory-map: Root element with versioning -->
40954 <!ELEMENT memory-map (memory)*>
40955 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40956 <!ELEMENT memory (property)*>
40957 <!-- memory: Specifies a memory region,
40958 and its type, or device. -->
40959 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
40960 start CDATA #REQUIRED
40961 length CDATA #REQUIRED>
40962 <!-- property: Generic attribute tag -->
40963 <!ELEMENT property (#PCDATA | property)*>
40964 <!ATTLIST property name (blocksize) #REQUIRED>
40967 @node Thread List Format
40968 @section Thread List Format
40969 @cindex thread list format
40971 To efficiently update the list of threads and their attributes,
40972 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40973 (@pxref{qXfer threads read}) and obtains the XML document with
40974 the following structure:
40977 <?xml version="1.0"?>
40979 <thread id="id" core="0" name="name">
40980 ... description ...
40985 Each @samp{thread} element must have the @samp{id} attribute that
40986 identifies the thread (@pxref{thread-id syntax}). The
40987 @samp{core} attribute, if present, specifies which processor core
40988 the thread was last executing on. The @samp{name} attribute, if
40989 present, specifies the human-readable name of the thread. The content
40990 of the of @samp{thread} element is interpreted as human-readable
40991 auxiliary information. The @samp{handle} attribute, if present,
40992 is a hex encoded representation of the thread handle.
40995 @node Traceframe Info Format
40996 @section Traceframe Info Format
40997 @cindex traceframe info format
40999 To be able to know which objects in the inferior can be examined when
41000 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41001 memory ranges, registers and trace state variables that have been
41002 collected in a traceframe.
41004 This list is obtained using the @samp{qXfer:traceframe-info:read}
41005 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41007 @value{GDBN} must be linked with the Expat library to support XML
41008 traceframe info discovery. @xref{Expat}.
41010 The top-level structure of the document is shown below:
41013 <?xml version="1.0"?>
41014 <!DOCTYPE traceframe-info
41015 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41016 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41022 Each traceframe block can be either:
41027 A region of collected memory starting at @var{addr} and extending for
41028 @var{length} bytes from there:
41031 <memory start="@var{addr}" length="@var{length}"/>
41035 A block indicating trace state variable numbered @var{number} has been
41039 <tvar id="@var{number}"/>
41044 The formal DTD for the traceframe info format is given below:
41047 <!ELEMENT traceframe-info (memory | tvar)* >
41048 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41050 <!ELEMENT memory EMPTY>
41051 <!ATTLIST memory start CDATA #REQUIRED
41052 length CDATA #REQUIRED>
41054 <!ATTLIST tvar id CDATA #REQUIRED>
41057 @node Branch Trace Format
41058 @section Branch Trace Format
41059 @cindex branch trace format
41061 In order to display the branch trace of an inferior thread,
41062 @value{GDBN} needs to obtain the list of branches. This list is
41063 represented as list of sequential code blocks that are connected via
41064 branches. The code in each block has been executed sequentially.
41066 This list is obtained using the @samp{qXfer:btrace:read}
41067 (@pxref{qXfer btrace read}) packet and is an XML document.
41069 @value{GDBN} must be linked with the Expat library to support XML
41070 traceframe info discovery. @xref{Expat}.
41072 The top-level structure of the document is shown below:
41075 <?xml version="1.0"?>
41077 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41078 "http://sourceware.org/gdb/gdb-btrace.dtd">
41087 A block of sequentially executed instructions starting at @var{begin}
41088 and ending at @var{end}:
41091 <block begin="@var{begin}" end="@var{end}"/>
41096 The formal DTD for the branch trace format is given below:
41099 <!ELEMENT btrace (block* | pt) >
41100 <!ATTLIST btrace version CDATA #FIXED "1.0">
41102 <!ELEMENT block EMPTY>
41103 <!ATTLIST block begin CDATA #REQUIRED
41104 end CDATA #REQUIRED>
41106 <!ELEMENT pt (pt-config?, raw?)>
41108 <!ELEMENT pt-config (cpu?)>
41110 <!ELEMENT cpu EMPTY>
41111 <!ATTLIST cpu vendor CDATA #REQUIRED
41112 family CDATA #REQUIRED
41113 model CDATA #REQUIRED
41114 stepping CDATA #REQUIRED>
41116 <!ELEMENT raw (#PCDATA)>
41119 @node Branch Trace Configuration Format
41120 @section Branch Trace Configuration Format
41121 @cindex branch trace configuration format
41123 For each inferior thread, @value{GDBN} can obtain the branch trace
41124 configuration using the @samp{qXfer:btrace-conf:read}
41125 (@pxref{qXfer btrace-conf read}) packet.
41127 The configuration describes the branch trace format and configuration
41128 settings for that format. The following information is described:
41132 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41135 The size of the @acronym{BTS} ring buffer in bytes.
41138 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41142 The size of the @acronym{Intel PT} ring buffer in bytes.
41146 @value{GDBN} must be linked with the Expat library to support XML
41147 branch trace configuration discovery. @xref{Expat}.
41149 The formal DTD for the branch trace configuration format is given below:
41152 <!ELEMENT btrace-conf (bts?, pt?)>
41153 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41155 <!ELEMENT bts EMPTY>
41156 <!ATTLIST bts size CDATA #IMPLIED>
41158 <!ELEMENT pt EMPTY>
41159 <!ATTLIST pt size CDATA #IMPLIED>
41162 @include agentexpr.texi
41164 @node Target Descriptions
41165 @appendix Target Descriptions
41166 @cindex target descriptions
41168 One of the challenges of using @value{GDBN} to debug embedded systems
41169 is that there are so many minor variants of each processor
41170 architecture in use. It is common practice for vendors to start with
41171 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41172 and then make changes to adapt it to a particular market niche. Some
41173 architectures have hundreds of variants, available from dozens of
41174 vendors. This leads to a number of problems:
41178 With so many different customized processors, it is difficult for
41179 the @value{GDBN} maintainers to keep up with the changes.
41181 Since individual variants may have short lifetimes or limited
41182 audiences, it may not be worthwhile to carry information about every
41183 variant in the @value{GDBN} source tree.
41185 When @value{GDBN} does support the architecture of the embedded system
41186 at hand, the task of finding the correct architecture name to give the
41187 @command{set architecture} command can be error-prone.
41190 To address these problems, the @value{GDBN} remote protocol allows a
41191 target system to not only identify itself to @value{GDBN}, but to
41192 actually describe its own features. This lets @value{GDBN} support
41193 processor variants it has never seen before --- to the extent that the
41194 descriptions are accurate, and that @value{GDBN} understands them.
41196 @value{GDBN} must be linked with the Expat library to support XML
41197 target descriptions. @xref{Expat}.
41200 * Retrieving Descriptions:: How descriptions are fetched from a target.
41201 * Target Description Format:: The contents of a target description.
41202 * Predefined Target Types:: Standard types available for target
41204 * Enum Target Types:: How to define enum target types.
41205 * Standard Target Features:: Features @value{GDBN} knows about.
41208 @node Retrieving Descriptions
41209 @section Retrieving Descriptions
41211 Target descriptions can be read from the target automatically, or
41212 specified by the user manually. The default behavior is to read the
41213 description from the target. @value{GDBN} retrieves it via the remote
41214 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41215 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41216 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41217 XML document, of the form described in @ref{Target Description
41220 Alternatively, you can specify a file to read for the target description.
41221 If a file is set, the target will not be queried. The commands to
41222 specify a file are:
41225 @cindex set tdesc filename
41226 @item set tdesc filename @var{path}
41227 Read the target description from @var{path}.
41229 @cindex unset tdesc filename
41230 @item unset tdesc filename
41231 Do not read the XML target description from a file. @value{GDBN}
41232 will use the description supplied by the current target.
41234 @cindex show tdesc filename
41235 @item show tdesc filename
41236 Show the filename to read for a target description, if any.
41240 @node Target Description Format
41241 @section Target Description Format
41242 @cindex target descriptions, XML format
41244 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41245 document which complies with the Document Type Definition provided in
41246 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41247 means you can use generally available tools like @command{xmllint} to
41248 check that your feature descriptions are well-formed and valid.
41249 However, to help people unfamiliar with XML write descriptions for
41250 their targets, we also describe the grammar here.
41252 Target descriptions can identify the architecture of the remote target
41253 and (for some architectures) provide information about custom register
41254 sets. They can also identify the OS ABI of the remote target.
41255 @value{GDBN} can use this information to autoconfigure for your
41256 target, or to warn you if you connect to an unsupported target.
41258 Here is a simple target description:
41261 <target version="1.0">
41262 <architecture>i386:x86-64</architecture>
41267 This minimal description only says that the target uses
41268 the x86-64 architecture.
41270 A target description has the following overall form, with [ ] marking
41271 optional elements and @dots{} marking repeatable elements. The elements
41272 are explained further below.
41275 <?xml version="1.0"?>
41276 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41277 <target version="1.0">
41278 @r{[}@var{architecture}@r{]}
41279 @r{[}@var{osabi}@r{]}
41280 @r{[}@var{compatible}@r{]}
41281 @r{[}@var{feature}@dots{}@r{]}
41286 The description is generally insensitive to whitespace and line
41287 breaks, under the usual common-sense rules. The XML version
41288 declaration and document type declaration can generally be omitted
41289 (@value{GDBN} does not require them), but specifying them may be
41290 useful for XML validation tools. The @samp{version} attribute for
41291 @samp{<target>} may also be omitted, but we recommend
41292 including it; if future versions of @value{GDBN} use an incompatible
41293 revision of @file{gdb-target.dtd}, they will detect and report
41294 the version mismatch.
41296 @subsection Inclusion
41297 @cindex target descriptions, inclusion
41300 @cindex <xi:include>
41303 It can sometimes be valuable to split a target description up into
41304 several different annexes, either for organizational purposes, or to
41305 share files between different possible target descriptions. You can
41306 divide a description into multiple files by replacing any element of
41307 the target description with an inclusion directive of the form:
41310 <xi:include href="@var{document}"/>
41314 When @value{GDBN} encounters an element of this form, it will retrieve
41315 the named XML @var{document}, and replace the inclusion directive with
41316 the contents of that document. If the current description was read
41317 using @samp{qXfer}, then so will be the included document;
41318 @var{document} will be interpreted as the name of an annex. If the
41319 current description was read from a file, @value{GDBN} will look for
41320 @var{document} as a file in the same directory where it found the
41321 original description.
41323 @subsection Architecture
41324 @cindex <architecture>
41326 An @samp{<architecture>} element has this form:
41329 <architecture>@var{arch}</architecture>
41332 @var{arch} is one of the architectures from the set accepted by
41333 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41336 @cindex @code{<osabi>}
41338 This optional field was introduced in @value{GDBN} version 7.0.
41339 Previous versions of @value{GDBN} ignore it.
41341 An @samp{<osabi>} element has this form:
41344 <osabi>@var{abi-name}</osabi>
41347 @var{abi-name} is an OS ABI name from the same selection accepted by
41348 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41350 @subsection Compatible Architecture
41351 @cindex @code{<compatible>}
41353 This optional field was introduced in @value{GDBN} version 7.0.
41354 Previous versions of @value{GDBN} ignore it.
41356 A @samp{<compatible>} element has this form:
41359 <compatible>@var{arch}</compatible>
41362 @var{arch} is one of the architectures from the set accepted by
41363 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41365 A @samp{<compatible>} element is used to specify that the target
41366 is able to run binaries in some other than the main target architecture
41367 given by the @samp{<architecture>} element. For example, on the
41368 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41369 or @code{powerpc:common64}, but the system is able to run binaries
41370 in the @code{spu} architecture as well. The way to describe this
41371 capability with @samp{<compatible>} is as follows:
41374 <architecture>powerpc:common</architecture>
41375 <compatible>spu</compatible>
41378 @subsection Features
41381 Each @samp{<feature>} describes some logical portion of the target
41382 system. Features are currently used to describe available CPU
41383 registers and the types of their contents. A @samp{<feature>} element
41387 <feature name="@var{name}">
41388 @r{[}@var{type}@dots{}@r{]}
41394 Each feature's name should be unique within the description. The name
41395 of a feature does not matter unless @value{GDBN} has some special
41396 knowledge of the contents of that feature; if it does, the feature
41397 should have its standard name. @xref{Standard Target Features}.
41401 Any register's value is a collection of bits which @value{GDBN} must
41402 interpret. The default interpretation is a two's complement integer,
41403 but other types can be requested by name in the register description.
41404 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41405 Target Types}), and the description can define additional composite
41408 Each type element must have an @samp{id} attribute, which gives
41409 a unique (within the containing @samp{<feature>}) name to the type.
41410 Types must be defined before they are used.
41413 Some targets offer vector registers, which can be treated as arrays
41414 of scalar elements. These types are written as @samp{<vector>} elements,
41415 specifying the array element type, @var{type}, and the number of elements,
41419 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41423 If a register's value is usefully viewed in multiple ways, define it
41424 with a union type containing the useful representations. The
41425 @samp{<union>} element contains one or more @samp{<field>} elements,
41426 each of which has a @var{name} and a @var{type}:
41429 <union id="@var{id}">
41430 <field name="@var{name}" type="@var{type}"/>
41437 If a register's value is composed from several separate values, define
41438 it with either a structure type or a flags type.
41439 A flags type may only contain bitfields.
41440 A structure type may either contain only bitfields or contain no bitfields.
41441 If the value contains only bitfields, its total size in bytes must be
41444 Non-bitfield values have a @var{name} and @var{type}.
41447 <struct id="@var{id}">
41448 <field name="@var{name}" type="@var{type}"/>
41453 Both @var{name} and @var{type} values are required.
41454 No implicit padding is added.
41456 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41459 <struct id="@var{id}" size="@var{size}">
41460 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41466 <flags id="@var{id}" size="@var{size}">
41467 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41472 The @var{name} value is required.
41473 Bitfield values may be named with the empty string, @samp{""},
41474 in which case the field is ``filler'' and its value is not printed.
41475 Not all bits need to be specified, so ``filler'' fields are optional.
41477 The @var{start} and @var{end} values are required, and @var{type}
41479 The field's @var{start} must be less than or equal to its @var{end},
41480 and zero represents the least significant bit.
41482 The default value of @var{type} is @code{bool} for single bit fields,
41483 and an unsigned integer otherwise.
41485 Which to choose? Structures or flags?
41487 Registers defined with @samp{flags} have these advantages over
41488 defining them with @samp{struct}:
41492 Arithmetic may be performed on them as if they were integers.
41494 They are printed in a more readable fashion.
41497 Registers defined with @samp{struct} have one advantage over
41498 defining them with @samp{flags}:
41502 One can fetch individual fields like in @samp{C}.
41505 (gdb) print $my_struct_reg.field3
41511 @subsection Registers
41514 Each register is represented as an element with this form:
41517 <reg name="@var{name}"
41518 bitsize="@var{size}"
41519 @r{[}regnum="@var{num}"@r{]}
41520 @r{[}save-restore="@var{save-restore}"@r{]}
41521 @r{[}type="@var{type}"@r{]}
41522 @r{[}group="@var{group}"@r{]}/>
41526 The components are as follows:
41531 The register's name; it must be unique within the target description.
41534 The register's size, in bits.
41537 The register's number. If omitted, a register's number is one greater
41538 than that of the previous register (either in the current feature or in
41539 a preceding feature); the first register in the target description
41540 defaults to zero. This register number is used to read or write
41541 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41542 packets, and registers appear in the @code{g} and @code{G} packets
41543 in order of increasing register number.
41546 Whether the register should be preserved across inferior function
41547 calls; this must be either @code{yes} or @code{no}. The default is
41548 @code{yes}, which is appropriate for most registers except for
41549 some system control registers; this is not related to the target's
41553 The type of the register. It may be a predefined type, a type
41554 defined in the current feature, or one of the special types @code{int}
41555 and @code{float}. @code{int} is an integer type of the correct size
41556 for @var{bitsize}, and @code{float} is a floating point type (in the
41557 architecture's normal floating point format) of the correct size for
41558 @var{bitsize}. The default is @code{int}.
41561 The register group to which this register belongs. It must
41562 be either @code{general}, @code{float}, or @code{vector}. If no
41563 @var{group} is specified, @value{GDBN} will not display the register
41564 in @code{info registers}.
41568 @node Predefined Target Types
41569 @section Predefined Target Types
41570 @cindex target descriptions, predefined types
41572 Type definitions in the self-description can build up composite types
41573 from basic building blocks, but can not define fundamental types. Instead,
41574 standard identifiers are provided by @value{GDBN} for the fundamental
41575 types. The currently supported types are:
41580 Boolean type, occupying a single bit.
41587 Signed integer types holding the specified number of bits.
41594 Unsigned integer types holding the specified number of bits.
41598 Pointers to unspecified code and data. The program counter and
41599 any dedicated return address register may be marked as code
41600 pointers; printing a code pointer converts it into a symbolic
41601 address. The stack pointer and any dedicated address registers
41602 may be marked as data pointers.
41605 Single precision IEEE floating point.
41608 Double precision IEEE floating point.
41611 The 12-byte extended precision format used by ARM FPA registers.
41614 The 10-byte extended precision format used by x87 registers.
41617 32bit @sc{eflags} register used by x86.
41620 32bit @sc{mxcsr} register used by x86.
41624 @node Enum Target Types
41625 @section Enum Target Types
41626 @cindex target descriptions, enum types
41628 Enum target types are useful in @samp{struct} and @samp{flags}
41629 register descriptions. @xref{Target Description Format}.
41631 Enum types have a name, size and a list of name/value pairs.
41634 <enum id="@var{id}" size="@var{size}">
41635 <evalue name="@var{name}" value="@var{value}"/>
41640 Enums must be defined before they are used.
41643 <enum id="levels_type" size="4">
41644 <evalue name="low" value="0"/>
41645 <evalue name="high" value="1"/>
41647 <flags id="flags_type" size="4">
41648 <field name="X" start="0"/>
41649 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41651 <reg name="flags" bitsize="32" type="flags_type"/>
41654 Given that description, a value of 3 for the @samp{flags} register
41655 would be printed as:
41658 (gdb) info register flags
41659 flags 0x3 [ X LEVEL=high ]
41662 @node Standard Target Features
41663 @section Standard Target Features
41664 @cindex target descriptions, standard features
41666 A target description must contain either no registers or all the
41667 target's registers. If the description contains no registers, then
41668 @value{GDBN} will assume a default register layout, selected based on
41669 the architecture. If the description contains any registers, the
41670 default layout will not be used; the standard registers must be
41671 described in the target description, in such a way that @value{GDBN}
41672 can recognize them.
41674 This is accomplished by giving specific names to feature elements
41675 which contain standard registers. @value{GDBN} will look for features
41676 with those names and verify that they contain the expected registers;
41677 if any known feature is missing required registers, or if any required
41678 feature is missing, @value{GDBN} will reject the target
41679 description. You can add additional registers to any of the
41680 standard features --- @value{GDBN} will display them just as if
41681 they were added to an unrecognized feature.
41683 This section lists the known features and their expected contents.
41684 Sample XML documents for these features are included in the
41685 @value{GDBN} source tree, in the directory @file{gdb/features}.
41687 Names recognized by @value{GDBN} should include the name of the
41688 company or organization which selected the name, and the overall
41689 architecture to which the feature applies; so e.g.@: the feature
41690 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41692 The names of registers are not case sensitive for the purpose
41693 of recognizing standard features, but @value{GDBN} will only display
41694 registers using the capitalization used in the description.
41697 * AArch64 Features::
41701 * MicroBlaze Features::
41705 * Nios II Features::
41706 * PowerPC Features::
41707 * S/390 and System z Features::
41713 @node AArch64 Features
41714 @subsection AArch64 Features
41715 @cindex target descriptions, AArch64 features
41717 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41718 targets. It should contain registers @samp{x0} through @samp{x30},
41719 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41721 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41722 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41726 @subsection ARC Features
41727 @cindex target descriptions, ARC Features
41729 ARC processors are highly configurable, so even core registers and their number
41730 are not completely predetermined. In addition flags and PC registers which are
41731 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41732 that one of the core registers features is present.
41733 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41735 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41736 targets with a normal register file. It should contain registers @samp{r0}
41737 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41738 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41739 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41740 @samp{ilink} and extension core registers are not available to read/write, when
41741 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41743 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41744 ARC HS targets with a reduced register file. It should contain registers
41745 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41746 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41747 This feature may contain register @samp{ilink} and any of extension core
41748 registers @samp{r32} through @samp{r59/acch}.
41750 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41751 targets with a normal register file. It should contain registers @samp{r0}
41752 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41753 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41754 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41755 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41756 registers are not available when debugging GNU/Linux applications. The only
41757 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41758 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41759 ARC v2, but @samp{ilink2} is optional on ARCompact.
41761 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41762 targets. It should contain registers @samp{pc} and @samp{status32}.
41765 @subsection ARM Features
41766 @cindex target descriptions, ARM features
41768 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41770 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41771 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41773 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41774 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41775 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41778 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41779 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41781 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41782 it should contain at least registers @samp{wR0} through @samp{wR15} and
41783 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41784 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41786 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41787 should contain at least registers @samp{d0} through @samp{d15}. If
41788 they are present, @samp{d16} through @samp{d31} should also be included.
41789 @value{GDBN} will synthesize the single-precision registers from
41790 halves of the double-precision registers.
41792 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41793 need to contain registers; it instructs @value{GDBN} to display the
41794 VFP double-precision registers as vectors and to synthesize the
41795 quad-precision registers from pairs of double-precision registers.
41796 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41797 be present and include 32 double-precision registers.
41799 @node i386 Features
41800 @subsection i386 Features
41801 @cindex target descriptions, i386 features
41803 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41804 targets. It should describe the following registers:
41808 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41810 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41812 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41813 @samp{fs}, @samp{gs}
41815 @samp{st0} through @samp{st7}
41817 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41818 @samp{foseg}, @samp{fooff} and @samp{fop}
41821 The register sets may be different, depending on the target.
41823 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41824 describe registers:
41828 @samp{xmm0} through @samp{xmm7} for i386
41830 @samp{xmm0} through @samp{xmm15} for amd64
41835 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41836 @samp{org.gnu.gdb.i386.sse} feature. It should
41837 describe the upper 128 bits of @sc{ymm} registers:
41841 @samp{ymm0h} through @samp{ymm7h} for i386
41843 @samp{ymm0h} through @samp{ymm15h} for amd64
41846 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41847 Memory Protection Extension (MPX). It should describe the following registers:
41851 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41853 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41856 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41857 describe a single register, @samp{orig_eax}.
41859 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
41860 describe two system registers: @samp{fs_base} and @samp{gs_base}.
41862 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41863 @samp{org.gnu.gdb.i386.avx} feature. It should
41864 describe additional @sc{xmm} registers:
41868 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41871 It should describe the upper 128 bits of additional @sc{ymm} registers:
41875 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41879 describe the upper 256 bits of @sc{zmm} registers:
41883 @samp{zmm0h} through @samp{zmm7h} for i386.
41885 @samp{zmm0h} through @samp{zmm15h} for amd64.
41889 describe the additional @sc{zmm} registers:
41893 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41896 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
41897 describe a single register, @samp{pkru}. It is a 32-bit register
41898 valid for i386 and amd64.
41900 @node MicroBlaze Features
41901 @subsection MicroBlaze Features
41902 @cindex target descriptions, MicroBlaze features
41904 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41905 targets. It should contain registers @samp{r0} through @samp{r31},
41906 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41907 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41908 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41910 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41911 If present, it should contain registers @samp{rshr} and @samp{rslr}
41913 @node MIPS Features
41914 @subsection @acronym{MIPS} Features
41915 @cindex target descriptions, @acronym{MIPS} features
41917 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41918 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41919 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41922 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41923 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41924 registers. They may be 32-bit or 64-bit depending on the target.
41926 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41927 it may be optional in a future version of @value{GDBN}. It should
41928 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41929 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41931 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41932 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41933 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41934 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41936 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41937 contain a single register, @samp{restart}, which is used by the
41938 Linux kernel to control restartable syscalls.
41940 @node M68K Features
41941 @subsection M68K Features
41942 @cindex target descriptions, M68K features
41945 @item @samp{org.gnu.gdb.m68k.core}
41946 @itemx @samp{org.gnu.gdb.coldfire.core}
41947 @itemx @samp{org.gnu.gdb.fido.core}
41948 One of those features must be always present.
41949 The feature that is present determines which flavor of m68k is
41950 used. The feature that is present should contain registers
41951 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41952 @samp{sp}, @samp{ps} and @samp{pc}.
41954 @item @samp{org.gnu.gdb.coldfire.fp}
41955 This feature is optional. If present, it should contain registers
41956 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41960 @node NDS32 Features
41961 @subsection NDS32 Features
41962 @cindex target descriptions, NDS32 features
41964 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
41965 targets. It should contain at least registers @samp{r0} through
41966 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
41969 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
41970 it should contain 64-bit double-precision floating-point registers
41971 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
41972 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
41974 @emph{Note:} The first sixteen 64-bit double-precision floating-point
41975 registers are overlapped with the thirty-two 32-bit single-precision
41976 floating-point registers. The 32-bit single-precision registers, if
41977 not being listed explicitly, will be synthesized from halves of the
41978 overlapping 64-bit double-precision registers. Listing 32-bit
41979 single-precision registers explicitly is deprecated, and the
41980 support to it could be totally removed some day.
41982 @node Nios II Features
41983 @subsection Nios II Features
41984 @cindex target descriptions, Nios II features
41986 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
41987 targets. It should contain the 32 core registers (@samp{zero},
41988 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
41989 @samp{pc}, and the 16 control registers (@samp{status} through
41992 @node PowerPC Features
41993 @subsection PowerPC Features
41994 @cindex target descriptions, PowerPC features
41996 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41997 targets. It should contain registers @samp{r0} through @samp{r31},
41998 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41999 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42001 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42002 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42004 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42005 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42008 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42009 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42010 will combine these registers with the floating point registers
42011 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42012 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42013 through @samp{vs63}, the set of vector registers for POWER7.
42015 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42016 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42017 @samp{spefscr}. SPE targets should provide 32-bit registers in
42018 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42019 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42020 these to present registers @samp{ev0} through @samp{ev31} to the
42023 @node S/390 and System z Features
42024 @subsection S/390 and System z Features
42025 @cindex target descriptions, S/390 features
42026 @cindex target descriptions, System z features
42028 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42029 System z targets. It should contain the PSW and the 16 general
42030 registers. In particular, System z targets should provide the 64-bit
42031 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42032 S/390 targets should provide the 32-bit versions of these registers.
42033 A System z target that runs in 31-bit addressing mode should provide
42034 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42035 register's upper halves @samp{r0h} through @samp{r15h}, and their
42036 lower halves @samp{r0l} through @samp{r15l}.
42038 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42039 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42042 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42043 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42045 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42046 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42047 targets and 32-bit otherwise. In addition, the feature may contain
42048 the @samp{last_break} register, whose width depends on the addressing
42049 mode, as well as the @samp{system_call} register, which is always
42052 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42053 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42054 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42056 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42057 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42058 combined by @value{GDBN} with the floating point registers @samp{f0}
42059 through @samp{f15} to present the 128-bit wide vector registers
42060 @samp{v0} through @samp{v15}. In addition, this feature should
42061 contain the 128-bit wide vector registers @samp{v16} through
42064 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42065 the 64-bit wide guarded-storage-control registers @samp{gsd},
42066 @samp{gssm}, and @samp{gsepla}.
42068 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42069 the 64-bit wide guarded-storage broadcast control registers
42070 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42072 @node Sparc Features
42073 @subsection Sparc Features
42074 @cindex target descriptions, sparc32 features
42075 @cindex target descriptions, sparc64 features
42076 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42077 targets. It should describe the following registers:
42081 @samp{g0} through @samp{g7}
42083 @samp{o0} through @samp{o7}
42085 @samp{l0} through @samp{l7}
42087 @samp{i0} through @samp{i7}
42090 They may be 32-bit or 64-bit depending on the target.
42092 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42093 targets. It should describe the following registers:
42097 @samp{f0} through @samp{f31}
42099 @samp{f32} through @samp{f62} for sparc64
42102 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42103 targets. It should describe the following registers:
42107 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42108 @samp{fsr}, and @samp{csr} for sparc32
42110 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42114 @node TIC6x Features
42115 @subsection TMS320C6x Features
42116 @cindex target descriptions, TIC6x features
42117 @cindex target descriptions, TMS320C6x features
42118 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42119 targets. It should contain registers @samp{A0} through @samp{A15},
42120 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42122 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42123 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42124 through @samp{B31}.
42126 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42127 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42129 @node Operating System Information
42130 @appendix Operating System Information
42131 @cindex operating system information
42137 Users of @value{GDBN} often wish to obtain information about the state of
42138 the operating system running on the target---for example the list of
42139 processes, or the list of open files. This section describes the
42140 mechanism that makes it possible. This mechanism is similar to the
42141 target features mechanism (@pxref{Target Descriptions}), but focuses
42142 on a different aspect of target.
42144 Operating system information is retrived from the target via the
42145 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42146 read}). The object name in the request should be @samp{osdata}, and
42147 the @var{annex} identifies the data to be fetched.
42150 @appendixsection Process list
42151 @cindex operating system information, process list
42153 When requesting the process list, the @var{annex} field in the
42154 @samp{qXfer} request should be @samp{processes}. The returned data is
42155 an XML document. The formal syntax of this document is defined in
42156 @file{gdb/features/osdata.dtd}.
42158 An example document is:
42161 <?xml version="1.0"?>
42162 <!DOCTYPE target SYSTEM "osdata.dtd">
42163 <osdata type="processes">
42165 <column name="pid">1</column>
42166 <column name="user">root</column>
42167 <column name="command">/sbin/init</column>
42168 <column name="cores">1,2,3</column>
42173 Each item should include a column whose name is @samp{pid}. The value
42174 of that column should identify the process on the target. The
42175 @samp{user} and @samp{command} columns are optional, and will be
42176 displayed by @value{GDBN}. The @samp{cores} column, if present,
42177 should contain a comma-separated list of cores that this process
42178 is running on. Target may provide additional columns,
42179 which @value{GDBN} currently ignores.
42181 @node Trace File Format
42182 @appendix Trace File Format
42183 @cindex trace file format
42185 The trace file comes in three parts: a header, a textual description
42186 section, and a trace frame section with binary data.
42188 The header has the form @code{\x7fTRACE0\n}. The first byte is
42189 @code{0x7f} so as to indicate that the file contains binary data,
42190 while the @code{0} is a version number that may have different values
42193 The description section consists of multiple lines of @sc{ascii} text
42194 separated by newline characters (@code{0xa}). The lines may include a
42195 variety of optional descriptive or context-setting information, such
42196 as tracepoint definitions or register set size. @value{GDBN} will
42197 ignore any line that it does not recognize. An empty line marks the end
42202 Specifies the size of a register block in bytes. This is equal to the
42203 size of a @code{g} packet payload in the remote protocol. @var{size}
42204 is an ascii decimal number. There should be only one such line in
42205 a single trace file.
42207 @item status @var{status}
42208 Trace status. @var{status} has the same format as a @code{qTStatus}
42209 remote packet reply. There should be only one such line in a single trace
42212 @item tp @var{payload}
42213 Tracepoint definition. The @var{payload} has the same format as
42214 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42215 may take multiple lines of definition, corresponding to the multiple
42218 @item tsv @var{payload}
42219 Trace state variable definition. The @var{payload} has the same format as
42220 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42221 may take multiple lines of definition, corresponding to the multiple
42224 @item tdesc @var{payload}
42225 Target description in XML format. The @var{payload} is a single line of
42226 the XML file. All such lines should be concatenated together to get
42227 the original XML file. This file is in the same format as @code{qXfer}
42228 @code{features} payload, and corresponds to the main @code{target.xml}
42229 file. Includes are not allowed.
42233 The trace frame section consists of a number of consecutive frames.
42234 Each frame begins with a two-byte tracepoint number, followed by a
42235 four-byte size giving the amount of data in the frame. The data in
42236 the frame consists of a number of blocks, each introduced by a
42237 character indicating its type (at least register, memory, and trace
42238 state variable). The data in this section is raw binary, not a
42239 hexadecimal or other encoding; its endianness matches the target's
42242 @c FIXME bi-arch may require endianness/arch info in description section
42245 @item R @var{bytes}
42246 Register block. The number and ordering of bytes matches that of a
42247 @code{g} packet in the remote protocol. Note that these are the
42248 actual bytes, in target order, not a hexadecimal encoding.
42250 @item M @var{address} @var{length} @var{bytes}...
42251 Memory block. This is a contiguous block of memory, at the 8-byte
42252 address @var{address}, with a 2-byte length @var{length}, followed by
42253 @var{length} bytes.
42255 @item V @var{number} @var{value}
42256 Trace state variable block. This records the 8-byte signed value
42257 @var{value} of trace state variable numbered @var{number}.
42261 Future enhancements of the trace file format may include additional types
42264 @node Index Section Format
42265 @appendix @code{.gdb_index} section format
42266 @cindex .gdb_index section format
42267 @cindex index section format
42269 This section documents the index section that is created by @code{save
42270 gdb-index} (@pxref{Index Files}). The index section is
42271 DWARF-specific; some knowledge of DWARF is assumed in this
42274 The mapped index file format is designed to be directly
42275 @code{mmap}able on any architecture. In most cases, a datum is
42276 represented using a little-endian 32-bit integer value, called an
42277 @code{offset_type}. Big endian machines must byte-swap the values
42278 before using them. Exceptions to this rule are noted. The data is
42279 laid out such that alignment is always respected.
42281 A mapped index consists of several areas, laid out in order.
42285 The file header. This is a sequence of values, of @code{offset_type}
42286 unless otherwise noted:
42290 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42291 Version 4 uses a different hashing function from versions 5 and 6.
42292 Version 6 includes symbols for inlined functions, whereas versions 4
42293 and 5 do not. Version 7 adds attributes to the CU indices in the
42294 symbol table. Version 8 specifies that symbols from DWARF type units
42295 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42296 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42298 @value{GDBN} will only read version 4, 5, or 6 indices
42299 by specifying @code{set use-deprecated-index-sections on}.
42300 GDB has a workaround for potentially broken version 7 indices so it is
42301 currently not flagged as deprecated.
42304 The offset, from the start of the file, of the CU list.
42307 The offset, from the start of the file, of the types CU list. Note
42308 that this area can be empty, in which case this offset will be equal
42309 to the next offset.
42312 The offset, from the start of the file, of the address area.
42315 The offset, from the start of the file, of the symbol table.
42318 The offset, from the start of the file, of the constant pool.
42322 The CU list. This is a sequence of pairs of 64-bit little-endian
42323 values, sorted by the CU offset. The first element in each pair is
42324 the offset of a CU in the @code{.debug_info} section. The second
42325 element in each pair is the length of that CU. References to a CU
42326 elsewhere in the map are done using a CU index, which is just the
42327 0-based index into this table. Note that if there are type CUs, then
42328 conceptually CUs and type CUs form a single list for the purposes of
42332 The types CU list. This is a sequence of triplets of 64-bit
42333 little-endian values. In a triplet, the first value is the CU offset,
42334 the second value is the type offset in the CU, and the third value is
42335 the type signature. The types CU list is not sorted.
42338 The address area. The address area consists of a sequence of address
42339 entries. Each address entry has three elements:
42343 The low address. This is a 64-bit little-endian value.
42346 The high address. This is a 64-bit little-endian value. Like
42347 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42350 The CU index. This is an @code{offset_type} value.
42354 The symbol table. This is an open-addressed hash table. The size of
42355 the hash table is always a power of 2.
42357 Each slot in the hash table consists of a pair of @code{offset_type}
42358 values. The first value is the offset of the symbol's name in the
42359 constant pool. The second value is the offset of the CU vector in the
42362 If both values are 0, then this slot in the hash table is empty. This
42363 is ok because while 0 is a valid constant pool index, it cannot be a
42364 valid index for both a string and a CU vector.
42366 The hash value for a table entry is computed by applying an
42367 iterative hash function to the symbol's name. Starting with an
42368 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42369 the string is incorporated into the hash using the formula depending on the
42374 The formula is @code{r = r * 67 + c - 113}.
42376 @item Versions 5 to 7
42377 The formula is @code{r = r * 67 + tolower (c) - 113}.
42380 The terminating @samp{\0} is not incorporated into the hash.
42382 The step size used in the hash table is computed via
42383 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42384 value, and @samp{size} is the size of the hash table. The step size
42385 is used to find the next candidate slot when handling a hash
42388 The names of C@t{++} symbols in the hash table are canonicalized. We
42389 don't currently have a simple description of the canonicalization
42390 algorithm; if you intend to create new index sections, you must read
42394 The constant pool. This is simply a bunch of bytes. It is organized
42395 so that alignment is correct: CU vectors are stored first, followed by
42398 A CU vector in the constant pool is a sequence of @code{offset_type}
42399 values. The first value is the number of CU indices in the vector.
42400 Each subsequent value is the index and symbol attributes of a CU in
42401 the CU list. This element in the hash table is used to indicate which
42402 CUs define the symbol and how the symbol is used.
42403 See below for the format of each CU index+attributes entry.
42405 A string in the constant pool is zero-terminated.
42408 Attributes were added to CU index values in @code{.gdb_index} version 7.
42409 If a symbol has multiple uses within a CU then there is one
42410 CU index+attributes value for each use.
42412 The format of each CU index+attributes entry is as follows
42418 This is the index of the CU in the CU list.
42420 These bits are reserved for future purposes and must be zero.
42422 The kind of the symbol in the CU.
42426 This value is reserved and should not be used.
42427 By reserving zero the full @code{offset_type} value is backwards compatible
42428 with previous versions of the index.
42430 The symbol is a type.
42432 The symbol is a variable or an enum value.
42434 The symbol is a function.
42436 Any other kind of symbol.
42438 These values are reserved.
42442 This bit is zero if the value is global and one if it is static.
42444 The determination of whether a symbol is global or static is complicated.
42445 The authorative reference is the file @file{dwarf2read.c} in
42446 @value{GDBN} sources.
42450 This pseudo-code describes the computation of a symbol's kind and
42451 global/static attributes in the index.
42454 is_external = get_attribute (die, DW_AT_external);
42455 language = get_attribute (cu_die, DW_AT_language);
42458 case DW_TAG_typedef:
42459 case DW_TAG_base_type:
42460 case DW_TAG_subrange_type:
42464 case DW_TAG_enumerator:
42466 is_static = language != CPLUS;
42468 case DW_TAG_subprogram:
42470 is_static = ! (is_external || language == ADA);
42472 case DW_TAG_constant:
42474 is_static = ! is_external;
42476 case DW_TAG_variable:
42478 is_static = ! is_external;
42480 case DW_TAG_namespace:
42484 case DW_TAG_class_type:
42485 case DW_TAG_interface_type:
42486 case DW_TAG_structure_type:
42487 case DW_TAG_union_type:
42488 case DW_TAG_enumeration_type:
42490 is_static = language != CPLUS;
42498 @appendix Manual pages
42502 * gdb man:: The GNU Debugger man page
42503 * gdbserver man:: Remote Server for the GNU Debugger man page
42504 * gcore man:: Generate a core file of a running program
42505 * gdbinit man:: gdbinit scripts
42511 @c man title gdb The GNU Debugger
42513 @c man begin SYNOPSIS gdb
42514 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42515 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42516 [@option{-b}@w{ }@var{bps}]
42517 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42518 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42519 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42520 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42521 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42524 @c man begin DESCRIPTION gdb
42525 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42526 going on ``inside'' another program while it executes -- or what another
42527 program was doing at the moment it crashed.
42529 @value{GDBN} can do four main kinds of things (plus other things in support of
42530 these) to help you catch bugs in the act:
42534 Start your program, specifying anything that might affect its behavior.
42537 Make your program stop on specified conditions.
42540 Examine what has happened, when your program has stopped.
42543 Change things in your program, so you can experiment with correcting the
42544 effects of one bug and go on to learn about another.
42547 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42550 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42551 commands from the terminal until you tell it to exit with the @value{GDBN}
42552 command @code{quit}. You can get online help from @value{GDBN} itself
42553 by using the command @code{help}.
42555 You can run @code{gdb} with no arguments or options; but the most
42556 usual way to start @value{GDBN} is with one argument or two, specifying an
42557 executable program as the argument:
42563 You can also start with both an executable program and a core file specified:
42569 You can, instead, specify a process ID as a second argument, if you want
42570 to debug a running process:
42578 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42579 named @file{1234}; @value{GDBN} does check for a core file first).
42580 With option @option{-p} you can omit the @var{program} filename.
42582 Here are some of the most frequently needed @value{GDBN} commands:
42584 @c pod2man highlights the right hand side of the @item lines.
42586 @item break [@var{file}:]@var{function}
42587 Set a breakpoint at @var{function} (in @var{file}).
42589 @item run [@var{arglist}]
42590 Start your program (with @var{arglist}, if specified).
42593 Backtrace: display the program stack.
42595 @item print @var{expr}
42596 Display the value of an expression.
42599 Continue running your program (after stopping, e.g. at a breakpoint).
42602 Execute next program line (after stopping); step @emph{over} any
42603 function calls in the line.
42605 @item edit [@var{file}:]@var{function}
42606 look at the program line where it is presently stopped.
42608 @item list [@var{file}:]@var{function}
42609 type the text of the program in the vicinity of where it is presently stopped.
42612 Execute next program line (after stopping); step @emph{into} any
42613 function calls in the line.
42615 @item help [@var{name}]
42616 Show information about @value{GDBN} command @var{name}, or general information
42617 about using @value{GDBN}.
42620 Exit from @value{GDBN}.
42624 For full details on @value{GDBN},
42625 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42626 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42627 as the @code{gdb} entry in the @code{info} program.
42631 @c man begin OPTIONS gdb
42632 Any arguments other than options specify an executable
42633 file and core file (or process ID); that is, the first argument
42634 encountered with no
42635 associated option flag is equivalent to a @option{-se} option, and the second,
42636 if any, is equivalent to a @option{-c} option if it's the name of a file.
42638 both long and short forms; both are shown here. The long forms are also
42639 recognized if you truncate them, so long as enough of the option is
42640 present to be unambiguous. (If you prefer, you can flag option
42641 arguments with @option{+} rather than @option{-}, though we illustrate the
42642 more usual convention.)
42644 All the options and command line arguments you give are processed
42645 in sequential order. The order makes a difference when the @option{-x}
42651 List all options, with brief explanations.
42653 @item -symbols=@var{file}
42654 @itemx -s @var{file}
42655 Read symbol table from file @var{file}.
42658 Enable writing into executable and core files.
42660 @item -exec=@var{file}
42661 @itemx -e @var{file}
42662 Use file @var{file} as the executable file to execute when
42663 appropriate, and for examining pure data in conjunction with a core
42666 @item -se=@var{file}
42667 Read symbol table from file @var{file} and use it as the executable
42670 @item -core=@var{file}
42671 @itemx -c @var{file}
42672 Use file @var{file} as a core dump to examine.
42674 @item -command=@var{file}
42675 @itemx -x @var{file}
42676 Execute @value{GDBN} commands from file @var{file}.
42678 @item -ex @var{command}
42679 Execute given @value{GDBN} @var{command}.
42681 @item -directory=@var{directory}
42682 @itemx -d @var{directory}
42683 Add @var{directory} to the path to search for source files.
42686 Do not execute commands from @file{~/.gdbinit}.
42690 Do not execute commands from any @file{.gdbinit} initialization files.
42694 ``Quiet''. Do not print the introductory and copyright messages. These
42695 messages are also suppressed in batch mode.
42698 Run in batch mode. Exit with status @code{0} after processing all the command
42699 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42700 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42701 commands in the command files.
42703 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42704 download and run a program on another computer; in order to make this
42705 more useful, the message
42708 Program exited normally.
42712 (which is ordinarily issued whenever a program running under @value{GDBN} control
42713 terminates) is not issued when running in batch mode.
42715 @item -cd=@var{directory}
42716 Run @value{GDBN} using @var{directory} as its working directory,
42717 instead of the current directory.
42721 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42722 @value{GDBN} to output the full file name and line number in a standard,
42723 recognizable fashion each time a stack frame is displayed (which
42724 includes each time the program stops). This recognizable format looks
42725 like two @samp{\032} characters, followed by the file name, line number
42726 and character position separated by colons, and a newline. The
42727 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42728 characters as a signal to display the source code for the frame.
42731 Set the line speed (baud rate or bits per second) of any serial
42732 interface used by @value{GDBN} for remote debugging.
42734 @item -tty=@var{device}
42735 Run using @var{device} for your program's standard input and output.
42739 @c man begin SEEALSO gdb
42741 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42742 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42743 documentation are properly installed at your site, the command
42750 should give you access to the complete manual.
42752 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42753 Richard M. Stallman and Roland H. Pesch, July 1991.
42757 @node gdbserver man
42758 @heading gdbserver man
42760 @c man title gdbserver Remote Server for the GNU Debugger
42762 @c man begin SYNOPSIS gdbserver
42763 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42765 gdbserver --attach @var{comm} @var{pid}
42767 gdbserver --multi @var{comm}
42771 @c man begin DESCRIPTION gdbserver
42772 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42773 than the one which is running the program being debugged.
42776 @subheading Usage (server (target) side)
42779 Usage (server (target) side):
42782 First, you need to have a copy of the program you want to debug put onto
42783 the target system. The program can be stripped to save space if needed, as
42784 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42785 the @value{GDBN} running on the host system.
42787 To use the server, you log on to the target system, and run the @command{gdbserver}
42788 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42789 your program, and (c) its arguments. The general syntax is:
42792 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42795 For example, using a serial port, you might say:
42799 @c @file would wrap it as F</dev/com1>.
42800 target> gdbserver /dev/com1 emacs foo.txt
42803 target> gdbserver @file{/dev/com1} emacs foo.txt
42807 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42808 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42809 waits patiently for the host @value{GDBN} to communicate with it.
42811 To use a TCP connection, you could say:
42814 target> gdbserver host:2345 emacs foo.txt
42817 This says pretty much the same thing as the last example, except that we are
42818 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42819 that we are expecting to see a TCP connection from @code{host} to local TCP port
42820 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42821 want for the port number as long as it does not conflict with any existing TCP
42822 ports on the target system. This same port number must be used in the host
42823 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42824 you chose a port number that conflicts with another service, @command{gdbserver} will
42825 print an error message and exit.
42827 @command{gdbserver} can also attach to running programs.
42828 This is accomplished via the @option{--attach} argument. The syntax is:
42831 target> gdbserver --attach @var{comm} @var{pid}
42834 @var{pid} is the process ID of a currently running process. It isn't
42835 necessary to point @command{gdbserver} at a binary for the running process.
42837 To start @code{gdbserver} without supplying an initial command to run
42838 or process ID to attach, use the @option{--multi} command line option.
42839 In such case you should connect using @kbd{target extended-remote} to start
42840 the program you want to debug.
42843 target> gdbserver --multi @var{comm}
42847 @subheading Usage (host side)
42853 You need an unstripped copy of the target program on your host system, since
42854 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42855 would, with the target program as the first argument. (You may need to use the
42856 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42857 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42858 new command you need to know about is @code{target remote}
42859 (or @code{target extended-remote}). Its argument is either
42860 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42861 descriptor. For example:
42865 @c @file would wrap it as F</dev/ttyb>.
42866 (gdb) target remote /dev/ttyb
42869 (gdb) target remote @file{/dev/ttyb}
42874 communicates with the server via serial line @file{/dev/ttyb}, and:
42877 (gdb) target remote the-target:2345
42881 communicates via a TCP connection to port 2345 on host `the-target', where
42882 you previously started up @command{gdbserver} with the same port number. Note that for
42883 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42884 command, otherwise you may get an error that looks something like
42885 `Connection refused'.
42887 @command{gdbserver} can also debug multiple inferiors at once,
42890 the @value{GDBN} manual in node @code{Inferiors and Programs}
42891 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42894 @ref{Inferiors and Programs}.
42896 In such case use the @code{extended-remote} @value{GDBN} command variant:
42899 (gdb) target extended-remote the-target:2345
42902 The @command{gdbserver} option @option{--multi} may or may not be used in such
42906 @c man begin OPTIONS gdbserver
42907 There are three different modes for invoking @command{gdbserver}:
42912 Debug a specific program specified by its program name:
42915 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42918 The @var{comm} parameter specifies how should the server communicate
42919 with @value{GDBN}; it is either a device name (to use a serial line),
42920 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42921 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42922 debug in @var{prog}. Any remaining arguments will be passed to the
42923 program verbatim. When the program exits, @value{GDBN} will close the
42924 connection, and @code{gdbserver} will exit.
42927 Debug a specific program by specifying the process ID of a running
42931 gdbserver --attach @var{comm} @var{pid}
42934 The @var{comm} parameter is as described above. Supply the process ID
42935 of a running program in @var{pid}; @value{GDBN} will do everything
42936 else. Like with the previous mode, when the process @var{pid} exits,
42937 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42940 Multi-process mode -- debug more than one program/process:
42943 gdbserver --multi @var{comm}
42946 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42947 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42948 close the connection when a process being debugged exits, so you can
42949 debug several processes in the same session.
42952 In each of the modes you may specify these options:
42957 List all options, with brief explanations.
42960 This option causes @command{gdbserver} to print its version number and exit.
42963 @command{gdbserver} will attach to a running program. The syntax is:
42966 target> gdbserver --attach @var{comm} @var{pid}
42969 @var{pid} is the process ID of a currently running process. It isn't
42970 necessary to point @command{gdbserver} at a binary for the running process.
42973 To start @code{gdbserver} without supplying an initial command to run
42974 or process ID to attach, use this command line option.
42975 Then you can connect using @kbd{target extended-remote} and start
42976 the program you want to debug. The syntax is:
42979 target> gdbserver --multi @var{comm}
42983 Instruct @code{gdbserver} to display extra status information about the debugging
42985 This option is intended for @code{gdbserver} development and for bug reports to
42988 @item --remote-debug
42989 Instruct @code{gdbserver} to display remote protocol debug output.
42990 This option is intended for @code{gdbserver} development and for bug reports to
42993 @item --debug-format=option1@r{[},option2,...@r{]}
42994 Instruct @code{gdbserver} to include extra information in each line
42995 of debugging output.
42996 @xref{Other Command-Line Arguments for gdbserver}.
42999 Specify a wrapper to launch programs
43000 for debugging. The option should be followed by the name of the
43001 wrapper, then any command-line arguments to pass to the wrapper, then
43002 @kbd{--} indicating the end of the wrapper arguments.
43005 By default, @command{gdbserver} keeps the listening TCP port open, so that
43006 additional connections are possible. However, if you start @code{gdbserver}
43007 with the @option{--once} option, it will stop listening for any further
43008 connection attempts after connecting to the first @value{GDBN} session.
43010 @c --disable-packet is not documented for users.
43012 @c --disable-randomization and --no-disable-randomization are superseded by
43013 @c QDisableRandomization.
43018 @c man begin SEEALSO gdbserver
43020 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43021 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43022 documentation are properly installed at your site, the command
43028 should give you access to the complete manual.
43030 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43031 Richard M. Stallman and Roland H. Pesch, July 1991.
43038 @c man title gcore Generate a core file of a running program
43041 @c man begin SYNOPSIS gcore
43042 gcore [-o @var{filename}] @var{pid}
43046 @c man begin DESCRIPTION gcore
43047 Generate a core dump of a running program with process ID @var{pid}.
43048 Produced file is equivalent to a kernel produced core file as if the process
43049 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43050 limit). Unlike after a crash, after @command{gcore} the program remains
43051 running without any change.
43054 @c man begin OPTIONS gcore
43056 @item -o @var{filename}
43057 The optional argument
43058 @var{filename} specifies the file name where to put the core dump.
43059 If not specified, the file name defaults to @file{core.@var{pid}},
43060 where @var{pid} is the running program process ID.
43064 @c man begin SEEALSO gcore
43066 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43067 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43068 documentation are properly installed at your site, the command
43075 should give you access to the complete manual.
43077 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43078 Richard M. Stallman and Roland H. Pesch, July 1991.
43085 @c man title gdbinit GDB initialization scripts
43088 @c man begin SYNOPSIS gdbinit
43089 @ifset SYSTEM_GDBINIT
43090 @value{SYSTEM_GDBINIT}
43099 @c man begin DESCRIPTION gdbinit
43100 These files contain @value{GDBN} commands to automatically execute during
43101 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43104 the @value{GDBN} manual in node @code{Sequences}
43105 -- shell command @code{info -f gdb -n Sequences}.
43111 Please read more in
43113 the @value{GDBN} manual in node @code{Startup}
43114 -- shell command @code{info -f gdb -n Startup}.
43121 @ifset SYSTEM_GDBINIT
43122 @item @value{SYSTEM_GDBINIT}
43124 @ifclear SYSTEM_GDBINIT
43125 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43127 System-wide initialization file. It is executed unless user specified
43128 @value{GDBN} option @code{-nx} or @code{-n}.
43131 the @value{GDBN} manual in node @code{System-wide configuration}
43132 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43135 @ref{System-wide configuration}.
43139 User initialization file. It is executed unless user specified
43140 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43143 Initialization file for current directory. It may need to be enabled with
43144 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43147 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43148 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43151 @ref{Init File in the Current Directory}.
43156 @c man begin SEEALSO gdbinit
43158 gdb(1), @code{info -f gdb -n Startup}
43160 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43161 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43162 documentation are properly installed at your site, the command
43168 should give you access to the complete manual.
43170 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43171 Richard M. Stallman and Roland H. Pesch, July 1991.
43177 @node GNU Free Documentation License
43178 @appendix GNU Free Documentation License
43181 @node Concept Index
43182 @unnumbered Concept Index
43186 @node Command and Variable Index
43187 @unnumbered Command, Variable, and Function Index
43192 % I think something like @@colophon should be in texinfo. In the
43194 \long\def\colophon{\hbox to0pt{}\vfill
43195 \centerline{The body of this manual is set in}
43196 \centerline{\fontname\tenrm,}
43197 \centerline{with headings in {\bf\fontname\tenbf}}
43198 \centerline{and examples in {\tt\fontname\tentt}.}
43199 \centerline{{\it\fontname\tenit\/},}
43200 \centerline{{\bf\fontname\tenbf}, and}
43201 \centerline{{\sl\fontname\tensl\/}}
43202 \centerline{are used for emphasis.}\vfill}
43204 % Blame: doc@@cygnus.com, 1991.